ONEOK (OKE) 10-K23 Feb 212020 FY Annual reportFinancial data

Company Profile

Document And Entity Information

Document And Entity Information - USD ($) $ in Billions	12 Months Ended
Document And Entity Information - USD ($) $ in Billions	Dec. 31, 2020	Feb. 16, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	001-13643
Entity Registrant Name	ONEOK, Inc.
Entity Incorporation, State or Country Code	OK
Entity Tax Identification Number	73-1520922
Entity Address, Address Line One	100 West Fifth Street,
Entity Address, City or Town	Tulsa,
Entity Address, State or Province	OK
Entity Address, Postal Zip Code	74103
City Area Code	918
Local Phone Number	588-7000
Title of 12(b) Security	Common stock, par value of $0.01
Trading Symbol	OKE
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 14.5
Entity Common Stock, Shares Outstanding		444,983,595
Documents Incorporated by Reference	Portions of the definitive proxy statement to be delivered to shareholders in connection with the Annual Meeting of Shareholders to be held May 26, 2021, are incorporated by reference in Part III.
Entity Central Index Key	0001039684
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues
Revenues	$ 8,542,242	$ 10,164,367	$ 12,593,196
Cost of sales and fuel (exclusive of items shown separately below)	5,110,146	6,788,040	9,422,708
Operations and maintenance	761,176	863,708	803,146
Depreciation and amortization	578,662	476,535	428,557
Impairment charges (Note A)	607,200	0	0
General taxes	125,028	119,156	103,922
(Gain) loss on sale of assets	(1,327)	2,575	(601)
Operating income	1,361,357	1,914,353	1,835,464
Equity in net earnings from investments (Note M)	143,241	154,541	158,383
Impairment of equity investments (Note A)	(37,730)	0	0
Allowance for equity funds used during construction	23,662	64,815	7,962
Other income	43,745	27,058	674
Other expense	(19,073)	(18,003)	(14,928)
Interest expense (net of capitalized interest of $75,436, $107,275 and $28,062, respectively)	(712,886)	(491,773)	(469,620)
Income before income taxes	802,316	1,650,991	1,517,935
Income taxes (Note L)	(189,507)	(372,414)	(362,903)
Net income	612,809	1,278,577	1,155,032
Less: Net income attributable to noncontrolling interests	0	0	3,329
Net income attributable to ONEOK	612,809	1,278,577	1,151,703
Less: Preferred stock dividends	1,100	1,100	1,100
Net income available to common shareholders	$ 611,709	$ 1,277,477	$ 1,150,603
Basic EPS (Note I)	$ 1.42	$ 3.09	$ 2.80
Diluted EPS (Note I)	$ 1.42	$ 3.07	$ 2.78
Average shares (thousands)
Basic	431,105	413,560	411,485
Diluted	431,782	415,444	414,195
Commodity Sales
Revenues
Revenues	$ 7,255,259	$ 8,916,047	$ 11,395,642
Services
Revenues
Revenues	$ 1,286,983	$ 1,248,320	$ 1,197,554

CONSOLIDATED STATEMENTS OF IN_2

CONSOLIDATED STATEMENTS OF INCOME CONSOLIDATED STATEMENT OF INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Interest expense (net of capitalized interest)	$ 75,436	$ 107,275	$ 28,062

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net income	$ 612,809	$ 1,278,577	$ 1,155,032
Other comprehensive income (loss), net of tax
Change in fair value of derivatives, net of tax of $49,292, $44,149 and $1,694, respectively	(165,023)	(147,803)	(5,673)
Derivative amounts reclassified to net income, net of tax of $(6,313), $6,058 and $(11,013), respectively	21,097	(21,057)	36,870
Change in retirement and other postretirement benefit plan obligations, net of tax of $7,812, $2,910 and $(1,425), respectively	(26,154)	(9,696)	4,771
Other comprehensive income (loss) of unconsolidated affiliates, net of tax of $2,201, $2,152 and $(724), respectively	(7,369)	(7,205)	2,424
Total other comprehensive income (loss), net of tax	(177,449)	(185,761)	38,392
Comprehensive income	435,360	1,092,816	1,193,424
Less: Comprehensive income attributable to noncontrolling interests	0	0	3,329
Comprehensive income attributable to ONEOK	$ 435,360	$ 1,092,816	$ 1,190,095

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in fair value of derivatives, tax	$ 49,292	$ 44,149	$ 1,694
Derivative amounts reclassified to net income, tax	6,313	(6,058)	11,013
Change in retirement and other postretirement benefit plan obligations, tax	7,812	2,910	(1,425)
Other comprehensive income (loss) of unconsolidated affiliates, tax	$ (2,201)	$ (2,152)	$ 724

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 524,496	$ 20,958
Accounts receivable, net	829,796	835,121
Materials and supplies	143,178	201,749
NGLs and natural gas in storage	227,810	304,926
Commodity imbalances	11,959	25,267
Other current assets	132,536	82,313
Total current assets	1,869,775	1,470,334
Property, plant and equipment
Property, plant and equipment	23,072,935	22,051,492
Accumulated depreciation and amortization	3,918,007	3,702,807
Net property, plant and equipment (Note D)	19,154,928	18,348,685
Investments and other assets
Investments in unconsolidated affiliates (Note M)	805,032	861,844
Goodwill and intangible assets (Note E)	773,723	957,833
Other assets	475,296	173,425
Total investments and other assets	2,054,051	1,993,102
Total assets	23,078,754	21,812,121
Current liabilities
Current maturities of long-term debt (Note F)	7,650	7,650
Short-term borrowings (Note F)	0	220,000
Accounts payable	719,302	1,209,900
Commodity imbalances	186,372	104,480
Accrued taxes	89,428	75,422
Accrued interest	245,153	190,750
Operating lease liability (Note O)	13,610	1,883
Other current liabilities	83,032	210,213
Total current liabilities	1,344,547	2,020,298
Long-term debt, excluding current maturities (Note F)	14,228,421	12,479,757
Deferred credits and other liabilities
Deferred income taxes (Note L)	669,697	536,063
Operating lease liability (Note O)	87,610	13,509
Other deferred credits	706,081	536,543
Total deferred credits and other liabilities	1,463,388	1,086,115
Commitments and contingencies (Note N)
Equity (Note G)
Preferred stock, $0.01 par value: authorized and issued 20,000 shares at December 31, 2020, and at December 31, 2019	0	0
Common stock, $0.01 par value: authorized 1,200,000,000 shares; issued 474,916,234 shares and outstanding 444,872,383 shares at December 31, 2020; issued 445,016,234 shares and outstanding 413,239,050 shares at December 31, 2019	4,749	4,450
Paid-in capital	7,353,396	7,403,895
Accumulated other comprehensive loss (Note H)	(551,449)	(374,000)
Retained earnings	0	0
Treasury stock, at cost: 30,043,851 shares at December 31, 2020, and 31,777,184 shares at December 31, 2019	(764,298)	(808,394)
Total equity	6,042,398	6,225,951
Total liabilities and equity	$ 23,078,754	$ 21,812,121

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Equity (Note G)
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Shares Issued	20,000	20,000
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	1,200,000,000	1,200,000,000
Common Stock, Shares, Issued	474,916,234	445,016,234
Common Stock, Shares, Outstanding	444,872,383	413,239,050
Treasury Stock, Shares	30,043,851	31,777,184

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating activities
Net income	$ 612,809	$ 1,278,577	$ 1,155,032
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	578,662	476,535	428,557
Impairment charges	644,930	0	0
Equity in net earnings from investments	(143,241)	(154,541)	(158,383)
Distributions received from unconsolidated affiliates	144,352	163,476	170,528
Deferred income tax expense	186,730	372,729	361,010
Other, net	35,327	(26,101)	23,570
Changes in assets and liabilities:
Accounts receivable	(1,297)	(19,688)	383,993
NGLs and natural gas in storage	77,116	(8,259)	38,456
Accounts payable	(80,257)	(62,946)	(320,132)
Commodity imbalances	95,200	(1,934)	(44,302)
Accrued interest	54,403	29,373	26,068
Risk-management assets and liabilities	(187,458)	(86,268)	117,717
Other assets and liabilities, net	118,208	14,174	4,605
Cash provided by operating activities	1,899,068	1,946,779	2,186,719
Investing activities
Capital expenditures (less allowance for equity funds used during construction)	(2,195,381)	(3,848,349)	(2,141,475)
Distributions received from unconsolidated affiliates in excess of cumulative earnings	31,808	94,168	26,757
Other, net	(106,956)	(14,577)	(170)
Cash used in investing activities	(2,270,529)	(3,768,758)	(2,114,888)
Financing activities
Dividends paid	(1,605,366)	(1,457,628)	(1,335,058)
Distributions to noncontrolling interests	0	0	(3,500)
Borrowing (repayment) of short-term borrowings, net	(220,000)	220,000	(614,673)
Issuance of long-term debt, net of discounts	3,244,777	4,185,435	1,795,773
Debt financing costs	(28,247)	(29,747)	(13,441)
Repayment of long-term debt	(1,457,222)	(1,057,348)	(932,650)
Issuance of common stock	969,759	29,040	1,203,981
Acquisition of noncontrolling interests	0	0	(195,000)
Other, net	(28,702)	(58,790)	(2,481)
Cash provided by (used in) financing activities	874,999	1,830,962	(97,049)
Change in cash and cash equivalents	503,538	8,983	(25,218)
Cash and cash equivalents at beginning of period	20,958	11,975	37,193
Cash and cash equivalents at end of period	524,496	20,958	11,975
Supplemental cash flow information:
Cash paid for interest, net of amounts capitalized	760,984	435,165	418,244
Cash paid for income taxes, net of refunds	$ 342	$ 2,690	$ 2,225

CONSOLIDATED STATEMENT OF CHANG

CONSOLIDATED STATEMENT OF CHANGES IN EQUITY - USD ($) $ in Thousands	Total	Common Stock	Preferred Stock	Accumulated Other Comprehensive Loss	Retained Earnings	Paid-in Capital	Treasury Stock	Noncontrolling Interests in Consolidated Subsidiaries
Shares, issued, beginning balance at Dec. 31, 2017		423,166,234	20,000
Total equity, beginning balance at Dec. 31, 2017	$ 5,685,352	$ 4,232	$ 0	$ (188,530)	$ 0	$ 6,588,878	$ (876,713)	$ 157,485
Net income	1,155,032	0	0	0	1,151,703	0	0	3,329
Other comprehensive income (loss)	$ 38,392	0	0	38,392	0	0	0	0
Preferred stock dividends paid (in dollars per share)	$ 55
Preferred stock dividends	$ (1,100)	$ 0	0	0	(1,100)	0	0	0
Common Stock Issued During Period, Shares, Other		21,850,000
Common Stock Issued During Period, Value, Other	$ 1,208,446	$ 218	0	0	0	1,183,321	24,907	0
Common stock dividends paid (in dollars per share)	$ 3.245
Common Stock Dividends	$ (1,335,211)	0	0	0	(1,190,406)	(144,805)	0	0
Distributions to noncontrolling interests	(3,500)	0	0	0	0	0	0	(3,500)
Contributions from noncontrolling interests	16,449	$ 0	0	0	0	0	0	16,449
Common Stock Issued During Period, Shares, Acquisitions		0
Acquisition of noncontrolling interests (Note G)	(195,000)	$ 0	0	0	0	(21,220)	0	(173,780)
Other, net	8,964	$ 0	$ 0	0	0	8,964	0	0
Shares, issued, ending balance at Dec. 31, 2018		445,016,234	20,000
Total equity, ending balance at Dec. 31, 2018	6,579,543	$ 4,450	$ 0	(188,239)	0	7,615,138	(851,806)	0
Cumulative effect adjustment for adoption of ASUs	1,719	0	0	(38,101)	39,803	0	0	17
Net income	1,278,577	0	0	0	1,278,577	0	0	0
Other comprehensive income (loss)	$ (185,761)	0	0	(185,761)	0	0	0	0
Preferred stock dividends paid (in dollars per share)	$ 55
Preferred stock dividends	$ (1,100)	$ 0	0	0	(1,100)	0	0	0
Common Stock Issued During Period, Shares, Other		0
Common Stock Issued During Period, Value, Other	$ 35,745	$ 0	0	0	0	(7,667)	43,412	0
Common stock dividends paid (in dollars per share)	$ 3.53
Common Stock Dividends	$ (1,457,831)	0	0	0	(1,277,410)	(180,421)	0	0
Other, net	(23,155)	$ 0	$ 0	0	0	(23,155)	0	0
Shares, issued, ending balance at Dec. 31, 2019		445,016,234	20,000
Total equity, ending balance at Dec. 31, 2019	6,225,951	$ 4,450	$ 0	(374,000)	0	7,403,895	(808,394)	0
Cumulative effect adjustment for adoption of ASUs	(67)	0	0	0	(67)	0	0	0
Net income	612,809	0	0	0	612,809	0	0	0
Other comprehensive income (loss)	$ (177,449)	0	0	(177,449)	0	0	0	0
Preferred stock dividends paid (in dollars per share)	$ 55
Preferred stock dividends	$ (1,100)	$ 0	0	0	(550)	(550)	0	0
Common Stock Issued During Period, Shares, Other		29,900,000
Common Stock Issued During Period, Value, Other	$ 978,868	$ 299	0	0	0	934,473	44,096	0
Common stock dividends paid (in dollars per share)	$ 3.74
Common Stock Dividends	$ (1,605,000)	0	0	0	(612,259)	(992,741)	0	0
Other, net	8,319	$ 0	$ 0	0	0	8,319	0	0
Shares, issued, ending balance at Dec. 31, 2020		474,916,234	20,000
Total equity, ending balance at Dec. 31, 2020	$ 6,042,398	$ 4,749	$ 0	$ (551,449)	$ 0	$ 7,353,396	$ (764,298)	$ 0

CONSOLIDATED STATEMENT OF CHA_2

CONSOLIDATED STATEMENT OF CHANGES IN EQUITY CONSOLIDATED STATEMENT OF CHANGES IN EQUITY (Parenthetical) - $ / shares	3 Months Ended												12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Stockholders' Equity [Abstract]
Preferred stock dividends paid (in dollars per share)													$ 55	$ 55	$ 55
Common stock dividends paid (in dollars per share)	$ 0.935	$ 0.935	$ 0.935	$ 0.935	$ 0.915	$ 0.890	$ 0.865	$ 0.860	$ 0.855	$ 0.825	$ 0.795	$ 0.770	$ 3.74	$ 3.53	$ 3.245

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Notes)	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Notes)	Dec. 31, 2020
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Organization and Nature of Operations - We are a corporation incorporated under the laws of the state of Oklahoma. Our Natural Gas Gathering and Processing segment provides midstream services to producers in North Dakota, Montana, Wyoming, Kansas and Oklahoma. Raw natural gas is typically gathered at the wellhead, compressed and transported through pipelines to our processing facilities. Processed natural gas, usually referred to as residue natural gas, is then recompressed and delivered to natural gas pipelines, storage facilities and end users. The NGLs separated from the raw natural gas are sold and delivered through NGL pipelines to fractionation facilities for further processing. Our Natural Gas Liquids segment owns and operates facilities that gather, fractionate, treat and distribute NGLs and store NGL products, primarily in Oklahoma, Kansas, Texas, New Mexico and the Rocky Mountain region, which includes the Williston, Powder River and DJ Basins. We provide midstream services to producers of NGLs and deliver those products to the two primary market centers, one in the Mid-Continent in Conway, Kansas, and the other in the Gulf Coast in Mont Belvieu, Texas. We own or have an ownership interest in FERC-regulated NGL gathering and distribution pipelines in Oklahoma, Kansas, Texas, New Mexico, Montana, North Dakota, Wyoming and Colorado, and terminal and storage facilities in Kansas, Missouri, Nebraska, Iowa and Illinois. We have a 50% ownership interest in Overland Pass Pipeline Company, which operates an interstate NGL pipeline originating in Wyoming and Colorado and terminating in Kansas. The majority of the pipeline-connected natural gas processing plants in the Williston Basin, Oklahoma, Kansas and the Texas Panhandle are connected to our NGL gathering systems. We lease rail cars and own and operate truck- and rail-loading and -unloading facilities connected to our NGL fractionation, storage and pipeline assets. We also own FERC-regulated NGL distribution pipelines in Kansas, Missouri, Nebraska, Iowa, Illinois and Indiana that connect our Mid-Continent assets with Midwest markets, including Chicago, Illinois. A portion of our ONEOK North System transports refined products, including unleaded gasoline and diesel, from Kansas to Iowa. Our Natural Gas Pipelines segment, through its wholly owned assets, provides intrastate and interstate transportation and storage services to end users. We have 50% ownership interests in Northern Border Pipeline and Roadrunner, which provide transportation services to various end users. Our interstate pipelines are regulated by the FERC and are located in North Dakota, Minnesota, Wisconsin, Illinois, Indiana, Kentucky, Tennessee, Oklahoma, Texas and New Mexico. Our intrastate natural gas pipeline and storage assets are located in Oklahoma, Kansas and Texas. Our assets connect major natural gas producing basins and market hubs with end-use customers. Consolidation - Our Consolidated Financial Statements include our accounts and the accounts of our subsidiaries over which we have control or are the primary beneficiary. All intercompany balances and transactions have been eliminated in consolidation. Investments in unconsolidated affiliates are accounted for using the equity method if we have the ability to exercise significant influence over operating and financial policies of our investee. Under this method, an investment is carried at its acquisition cost and adjusted each period for contributions made, distributions received and our share of the investee’s comprehensive income. For the investments we account for under the equity method, the premium or excess cost over underlying fair value of net assets is referred to as equity-method goodwill. Impairment of equity investments is recorded when the impairments are other than temporary. These amounts are recorded as investments in unconsolidated affiliates on our accompanying Consolidated Balance Sheets. See Note M for disclosures of our unconsolidated affiliates. Distributions paid to us from our unconsolidated affiliates are classified as operating activities on our Consolidated Statements of Cash Flows until the cumulative distributions exceed our proportionate share of income from the unconsolidated affiliate since the date of our initial investment. The amount of cumulative distributions paid to us that exceeds our cumulative proportionate share of income in each period represents a return of investment and is classified as an investing activity on our Consolidated Statements of Cash Flows. Use of Estimates - The preparation of our Consolidated Financial Statements and related disclosures in accordance with GAAP requires us to make estimates and assumptions with respect to values or conditions that cannot be known with certainty that affect the reported amounts on our Consolidated Financial Statements. Items that may be estimated include, but are not limited to, the economic useful life of assets, fair value of assets, liabilities and equity-method investments, obligations under employee benefit plans, provisions for uncollectible accounts receivable, expenses for services received but for which no invoice has been received, provision for income taxes, including any deferred tax valuation allowances, the results of litigation and various other recorded or disclosed amounts. In addition, a portion of our revenues and cost of sales and fuel are recorded based on current month prices and estimated volumes. The estimates are reversed in the following month when we record actual volumes and prices. We evaluate our estimates on an ongoing basis using historical experience, consultation with experts and other methods we consider reasonable based on the particular circumstances. Nevertheless, actual results may differ significantly from the estimates. Any effects on our financial position or results of operations from revisions to these estimates are recorded in the period when the facts that give rise to the revision become known. Fair Value Measurements - For our fair value measurements, we utilize market prices, third-party pricing services, present value methods and standard option valuation models to determine the price we would receive from the sale of an asset or the transfer of a liability in an orderly transaction at the measurement date. We measure the fair value of a group of financial assets and liabilities consistent with how a market participant would price the net risk exposure at the measurement date. Many of the contracts in our derivative portfolio are executed in liquid markets where price transparency exists. Our financial commodity derivatives are generally settled through a NYMEX or ICE clearing broker account with daily margin requirements. We validate our valuation inputs with third-party information and settlement prices from other sources, where available. We compute the fair value of our derivative portfolio by discounting the projected future cash flows from our derivative assets and liabilities to present value using interest-rate yields to calculate present-value discount factors derived from the implied forward LIBOR yield curve. The fair value of our forward-starting interest-rate swaps is determined using financial models that incorporate the implied forward LIBOR yield curve for the same period as the future interest-rate swap settlements. We consider current market data in evaluating counterparties’, as well as our own, nonperformance risk, net of collateral, by using counterparty-specific bond yields. Although we use our best estimates to determine the fair value of the derivative contracts we have executed, the ultimate market prices realized could differ materially from our estimates. Fair Value Hierarchy - At each balance sheet date, we utilize a fair value hierarchy to classify fair value amounts recognized or disclosed in our financial statements based on the observability of inputs used to estimate such fair value. The levels of the hierarchy are described below: • Level 1 - fair value measurements are based on unadjusted quoted prices for identical securities in active markets. These balances are composed predominantly of exchange-traded derivative contracts for natural gas and crude oil. • Level 2 - fair value measurements are based on significant observable pricing inputs, including quoted prices for similar assets and liabilities in active markets and inputs from third-party pricing services supported with corroborative evidence. These balances are composed of over-the-counter interest-rate derivatives. • Level 3 - fair value measurements are based on inputs that may include one or more unobservable inputs, including internally developed commodity price curves that incorporate market data from broker quotes and third-party pricing services. These balances are composed predominantly of exchange-cleared and over-the-counter derivatives to hedge NGL price risk and natural gas basis risk between various transaction locations and the NYMEX Henry Hub. Our commodity derivatives are generally valued using forward quotes provided by third-party pricing services that are validated with other market data. We believe any measurement uncertainty at December 31, 2020, is immaterial as our Level 3 fair value measurements are based on unadjusted pricing information from broker quotes and third-party pricing services. We do not believe that our Level 3 fair value estimates have a material impact on our results of operations, as our derivatives are primarily accounted for as hedges. Determining the appropriate classification of our fair value measurements within the fair value hierarchy requires management’s judgment regarding the degree to which market data is observable or corroborated by observable market data. We categorize derivatives for which fair value is determined using multiple inputs within a single level, based on the lowest level input that is significant to the fair value measurement in its entirety. See Note B for our fair value measurements disclosures. Cash and Cash Equivalents - Cash equivalents consist of highly liquid investments, which are readily convertible into cash and have original maturities of three months or less. Revenue Recognition - Revenues are recognized when control of the promised goods or services is transferred to our customers in an amount that reflects the consideration we expect to be entitled to receive in exchange for those goods or services. Our payment terms vary by customer and contract type, including requiring payment before products or services are delivered to certain customers. However, the term between customer prepayments, completion of our performance obligations, invoicing and receipt of payment due is not significant. Upon adoption of Topic 606 in January 2018, we determined that certain Natural Gas Gathering and Processing segment fee with POP contracts and Natural Gas Liquids segment exchange services contracts that include the purchase of commodities are supplier contracts. Contractual fees in these identified contracts are recorded as a reduction of the commodity purchase price in cost of sales and fuel. In 2017 and prior periods, these fees were recorded as services revenue. Performance Obligations and Revenue Sources - Revenue sources are disaggregated in Note Q and are derived from commodity sales and services revenues, as described below: Commodity Sales (all segments) - We contract to deliver residue natural gas, condensate, unfractionated NGLs and/or NGL products to customers at a specified delivery point. Our sales agreements may be daily or longer-term contracts for a specified volume. We consider the sale and delivery of each unit of a commodity an individual performance obligation as the customer is expected to control, accept and benefit from each unit individually. We record revenue when the commodity is delivered to the customer as this represents the point in time when control of the product is transferred to the customer. Revenue is recorded based on the contracted selling price, which is generally index-based and settled monthly. Services Gathering only contracts ( Natural Gas Gathering and Processing segment ) - Under this type of contract, we charge fees for providing midstream services, which include gathering and treating our customer’s natural gas. Our performance obligation begins with delivery of raw natural gas to our system. This service is treated as one performance obligation that is satisfied over time. We use the output method based on delivery of product to our system as the measure of progress, as our services are performed simultaneously. Fee with POP contracts with producer take-in-kind rights ( Natural Gas Gathering and Processing segment ) - Under this type of contract, we do not control the stream of unprocessed natural gas that we receive at the wellhead due to the producer’s take-in-kind rights. We purchase a portion of the raw natural gas stream, charge fees for providing midstream services, which include gathering, treating, compressing and processing our customer’s natural gas. After performing these services, we return primarily the residue natural gas to the producer, sell the remaining commodities and remit a portion of the commodity sales proceeds to the producer less our contractual fees. Our performance obligation begins with delivery of raw natural gas to our system. This service is treated as one performance obligation that is satisfied over time. We use the output method based on delivery of product to our system as the measure of progress, as our services are performed simultaneously. Transportation and exchange contracts ( Natural Gas Liquids segment ) - Under this type of contract, we charge fees for providing midstream services, which may include a bundled combination of gathering, transporting and/or fractionation of our customer’s NGLs. Our performance obligation begins with delivery of unfractionated NGLs or NGL products to our system. These services represent a series of distinct services that are treated as one performance obligation that is satisfied over time. We use the output method based on delivery of product to our system as the measure of progress, as our services are performed simultaneously. For transportation services under a tariff on our NGL transportation pipelines, fees are recorded upon redelivery to our customer at the completion of the transportation services. Storage contracts ( Natural Gas Liquids and Natural Gas Pipelines segments ) - We reserve a stated storage capacity and inject/withdraw/store commodities for our customer. The capacity reservation and injection/withdrawal/storage services are considered a bundled service, as we integrate them into one stand-ready obligation provided on a daily basis over the life of the agreement and satisfied over time. Fixed capacity reservation fees are allocated and evenly recognized in revenue. Capacity reservation fees that vary based on a stated or implied economic index and correspond with the costs to provide our services are recognized in revenue as invoiced to our customers. For contracts that do not include a capacity reservation, transportation, injection and withdrawal fees are recognized in revenue as those services are provided and are dependent on the volume transported, injected or withdrawn by our customer, which is at our customer’s discretion. We use the output method based on the passage of time to measure satisfaction of the performance obligation associated with our daily stand-ready services. Firm service transportation contracts ( Natural Gas Pipelines segment ) - We reserve a stated transportation capacity and transport commodities for our customer. The capacity reservation and transportation services are considered a bundled service, as we integrate them into one stand-ready obligation provided on a daily basis over the life of the agreement and satisfied over time. Fixed capacity reservation fees are allocated and evenly recognized in revenue. Capacity reservation fees that vary based on a stated or implied economic index and correspond with the costs to provide our services are recognized in revenue based on a daily effective fee rate. If the capacity reservation fees vary solely as a contract feature, contract assets or liabilities are recorded for the difference between the amount recorded in revenue and the amount billed to the customer. Transportation fees are recognized in revenue as those services are provided and are dependent on the volume transported by our customer, which is at our customer’s discretion. We use the output method based on the passage of time to measure satisfaction of the performance obligation associated with our daily stand-ready services. Interruptible transportation contracts ( Natural Gas Pipelines segment ) - We agree to transport natural gas on our pipelines between the customer’s specified nomination and delivery points if capacity is available after satisfying firm transportation service obligations. The transaction price is based on the transportation fees times the volumes transported. We use the output method based on delivery of product to the customer to measure satisfaction of the performance obligation. The total consideration for delivered volumes is recorded in revenue at the time of delivery, when the customer obtains control. See Note P for our revenue disclosures. Contract Assets and Contract Liabilities - Contract assets and contract liabilities are recorded when the amount of revenue recognized from a contract with a customer differs from the amount billed to the customer and recorded in accounts receivable. Our contract asset balances at the beginning and end of the period primarily relate to our firm service transportation contracts with tiered rates. Our contract liabilities primarily represent deferred revenue on contributions in aid of construction received from customers for which revenue is recognized over the contract periods, which range from 5 to 10 years, and deferred revenue on NGL storage contracts for which revenue is recognized over a one-year term. Cost of Sales and Fuel - Cost of sales and fuel primarily includes (i) the cost of purchased commodities, including NGLs, natural gas and condensate, (ii) fees incurred for third-party transportation, fractionation and storage of commodities, (iii) fuel and power costs incurred to operate our own facilities that gather, process, transport and store commodities, and (iv) an offset from the contractual fees deducted from the cost of purchased commodities under the contract types below: Fee with POP contracts with no producer take-in-kind rights (Natural Gas Gathering and Processing segment ) - We purchase raw natural gas and charge contractual fees for providing midstream services, which include gathering, treating, compressing and processing the producer’s natural gas. After performing these services, we sell the commodities and return a portion of the commodity sales proceeds to the producer less our contractual fees. Purchase with fee ( Natural Gas Liquids segment ) - Under this type of contract, we purchase raw, unfractionated NGLs at an index price and charge fees for providing midstream services, which may include a bundled combination of gathering, transporting and/or fractionation of our customer’s NGLs. Operations and Maintenance - Operations and maintenance primarily includes (i) payroll and benefit costs, (ii) third-party costs for operations, maintenance and integrity management, regulatory compliance and environmental and safety, and (iii) other business-related service costs. Accounts Receivable - Accounts receivable represent valid claims against nonaffiliated customers for products sold or services rendered. Upon adoption of ASU 2016-13 in January 2020, we present accounts receivable net of an allowance for credit losses to reflect the net amount expected to be collected. We assess the creditworthiness of our counterparties on an ongoing basis and require security, including prepayments and other forms of collateral, when appropriate. Outstanding customer receivables are reviewed regularly for possible nonpayment indicators, and allowances for credit losses are recorded based upon management’s estimate of collectability, current conditions and supportable forecasts at each balance sheet date. At December 31, 2020, our allowance for credit losses was not material. See “Recently Issued Accounting Standards Update” table below for more information. Inventory - The values of current NGLs and natural gas in storage are determined using the lower of weighted-average cost or net realizable value. Noncurrent NGLs and natural gas are classified as property and valued at cost. Materials and supplies are valued at average cost. Certain large equipment inventory, which will ultimately be capitalized to property, plant and equipment when utilized, is included in other assets in our Consolidated Balance Sheets and is valued at weighted-average cost. Commodity Imbalances - Commodity imbalances represent amounts payable or receivable for NGL exchange contracts and natural gas pipeline imbalances and are valued at market prices. Under the majority of our NGL exchange agreements, we physically receive volumes of unfractionated NGLs, including the risk of loss and legal title to such volumes, from the exchange counterparty. In turn, we deliver NGL products back to the customer and charge them gathering, transportation and fractionation fees. To the extent that the volumes we receive under such agreements differ from those we deliver, we record a net exchange receivable or payable position with the counterparties. These net exchange receivables and payables are generally settled with movements of NGL products rather than with cash. Natural gas pipeline imbalances are settled in cash or in-kind, subject to the terms of the pipelines’ tariffs or by agreement. Derivatives and Risk Management - We utilize derivatives to reduce our market-risk exposure to commodity price and interest-rate fluctuations and to achieve more predictable cash flows. We record all derivative instruments at fair value, with the exception of normal purchases and normal sales transactions that are expected to result in physical delivery. Commodity price and interest-rate volatility may have a significant impact on the fair value of derivative instruments as of a given date. The accounting for changes in the fair value of a derivative instrument depends on whether it has been designated and qualifies as part of a hedging relationship and, if so, the reason for holding it. The table below summarizes the various ways in which we account for our derivative instruments and the impact on our Consolidated Financial Statements: Recognition and Measurement Accounting Treatment Balance Sheet Income Statement Normal purchases and - Fair value not recorded - Change in fair value not recognized in earnings Mark-to-market - Recorded at fair value - Change in fair value recognized in earnings Cash flow hedge - The gain or loss on the - The gain or loss on the derivative instrument is reclassified out of accumulated other comprehensive income (loss) into earnings when the forecasted transaction affects earnings Fair value hedge - Recorded at fair value - The gain or loss on the derivative instrument is - Change in fair value of the hedged item is - Change in fair value of the hedged item is To reduce our exposure to fluctuations in natural gas, NGLs and condensate prices, we periodically enter into futures, forward purchases and sales, options or swap transactions in order to hedge anticipated purchases and sales of natural gas, NGLs and condensate. Interest-rate swaps are used from time to time to manage interest-rate risk. Under certain conditions, we designate our derivative instruments as a hedge of exposure to changes in fair values or cash flows. We formally document all relationships between hedging instruments and hedged items, as well as risk-management objectives and strategies for undertaking various hedge transactions, and methods for assessing and testing correlation and hedge effectiveness. We specifically identify the forecasted transaction that has been designated as the hedged item in a cash flow hedge relationship. We assess hedging relationships at the inception of the hedge and on an ongoing basis to determine whether the hedging relationship is, and is expected to remain, highly effective. We also document our normal purchases and normal sales transactions that we expect to result in physical delivery and that we elect to exempt from derivative accounting treatment. The realized revenues and purchase costs of our derivative instruments not considered held for trading purposes and derivatives that qualify as normal purchases or normal sales that are expected to result in physical delivery are reported on a gross basis. Cash flows from futures, forwards, options and swaps that are accounted for as hedges are included in the same category as the cash flows from the related hedged items in our Consolidated Statements of Cash Flows. See Notes B and C for disclosures of our fair value measurements and risk-management and hedging activities, respectively. Property, Plant and Equipment - Our properties are stated at cost, including AFUDC and capitalized interest. In some cases, the cost of regulated property retired or sold, plus removal costs, less salvage, is charged to accumulated depreciation. Gains and losses from sales or transfers of nonregulated properties or an entire operating unit or system of our regulated properties are recognized in income. Maintenance and repairs are charged directly to expense. The interest portion of AFUDC and capitalized interest represent the cost of borrowed funds used to finance construction activities for regulated and nonregulated projects, respectively. We capitalize interest costs during the construction or upgrade of qualifying assets. These costs are recorded as a reduction to interest expense. The equity portion of AFUDC represents the capitalization of the estimated average cost of equity used during the construction of major projects and is recorded in the cost of our regulated properties and as a credit to the allowance for equity funds used during construction. Our properties are depreciated using the straight-line method over their estimated useful lives. Generally, we apply composite depreciation rates to functional groups of property having similar economic circumstances. We periodically conduct depreciation studies to assess the economic lives of our assets. For our regulated assets, these depreciation studies are completed as a part of our rate proceedings or tariff filings, and the changes in economic lives, if applicable, are implemented prospectively when the new rates are approved. For our nonregulated assets, if it is determined that the estimated economic life changes, the changes are made prospectively. Changes in the estimated economic lives of our property, plant and equipment could have a material effect on our financial position or results of operations. Property, plant and equipment on our Consolidated Balance Sheets includes construction work in process for capital projects that have not yet been placed in service and therefore are not being depreciated. Assets are transferred out of construction work in process when they are substantially complete and ready for their intended use. See Note D for our property, plant and equipment disclosures. Impairment of Goodwill and Long-Lived Assets, Including Intangible Assets - We assess our goodwill for impairment at least annually as of July 1, unless events or changes in circumstances indicate an impairment may have occurred before that time. At July 1, 2020, we assessed qualitative factors subsequent to our first quarter 2020 impairment charges discussed below to determine whether it was more likely than not that the fair value of our Natural Gas Liquids and Natural Gas Pipelines reporting units were less than their carrying amount. After assessing qualitative factors (including macroeconomic conditions, industry and market considerations, cost factors and overall financial performance), we determined that it was more likely than not that the fair value of our Natural Gas Liquids and Natural Gas Pipelines reporting units were not less than their respective carrying value, no further testing was necessary and goodwill was not considered impaired. At July 1, 2020, there was no remaining goodwill associated with our Natural Gas Gathering and Processing reporting unit. Late in the first quarter 2020, we experienced a significant decline in our share price and market capitalization as the energy industry experienced historic events that led to a simultaneous demand and supply disruption. The World Health Organization declared COVID-19 a global pandemic and recommended containment and mitigation measures worldwide, which contributed to a massive economic slowdown and decreased demand for crude oil, natural gas and NGLs. In addition, Saudi Arabia and Russia increased production of crude oil as the two countries competed for market share. As a result, the global supply of crude oil significantly exceeded demand and led to a collapse in crude oil prices. Due to the impact of these events, we performed a Step 1 analysis in the first quarter 2020 to test our goodwill for impairment and evaluated certain long-lived asset groups and equity investments for impairment. Goodwill - In the Step 1 analysis, an assessment is made by comparing the fair value of a reporting unit with its carrying amount, including goodwill. If the carrying value of a reporting unit exceeds its fair value, an impairment loss is recognized in an amount equal to that excess, limited to the total amount of goodwill allocated to that reporting unit. In January 2020, we adopted ASU 2017-04 in which the requirement to calculate the implied fair value of goodwill under the two-step impairment test was eliminated. To estimate the fair value of our reporting units, we use two generally accepted valuation approaches, an income approach and a market approach, using assumptions consistent with a market participant’s perspective. Under the income approach, we use anticipated cash flows over a period of years plus a terminal value and discount these amounts to their present value using appropriate discount rates. Under the market approach, we apply EBITDA multiples to forecasted EBITDA. The multiples used are consistent with historical asset transactions. The forecasted cash flows are based on average forecasted cash flows for a reporting unit over a period of years. Based on the results of our impairment test, we concluded that the carrying value of the Natural Gas Gathering and Processing reporting unit exceeded its estimated fair value, resulting in a noncash impairment charge of $153.4 million, which is included within impairment charges in our Consolidated Statement of Income for the year ended December 31, 2020. The estimated fair value of our Natural Gas Liquids and Natural Gas Pipelines reporting units substantially exceeded their respective carrying values. Long-lived assets - We assess our long-lived assets for impairment whenever events or changes in circumstances indicate that an asset’s carrying amount may not be recoverable. An impairment is indicated if the carrying amount of a long-lived asset exceeds the sum of the undiscounted future cash flows expected to result from the use and eventual disposition of the asset. If an impairment is indicated, we record an impairment loss equal to the difference between the carrying value and the fair value of the long-lived asset. In 2020, we evaluated our Natural Gas Gathering and Processing segment asset groups and determined that the carrying value of certain long-lived asset groups in the Powder River Basin, western Oklahoma and Kansas were not recoverable and exceeded their estimated fair value. We recorded noncash impairment charges of $382.2 million, which includes a natural gas processing plant and infrastructure in the Powder River Basin and its related supply contracts and natural gas processing plants and infrastructure in western Oklahoma and Kansas. In our Natural Gas Liquids segment, we recorded noncash impairment charges of $71.6 million related primarily to certain inactive assets, as our expectation for future use of the assets changed. These charges are included within impairment charges in our Consolidated Statement of Income for the year ended December 31, 2020. Investments i

FAIR VALUE MEASUREMENTS (Notes)

FAIR VALUE MEASUREMENTS (Notes)	12 Months Ended
FAIR VALUE MEASUREMENTS (Notes)	Dec. 31, 2020
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS Recurring Fair Value Measurements - The following tables set forth our recurring fair value measurements for the periods indicated: December 31, 2020 Level 1 Level 2 Level 3 Total - Gross Netting (a) Total - Net ( Thousands of dollars ) Derivative assets Commodity contracts Financial contracts $ 6,697 $ — $ 103,801 $ 110,498 $ (110,498) $ — Total derivative assets $ 6,697 $ — $ 103,801 $ 110,498 $ (110,498) $ — Derivative liabilities Commodity contracts Financial contracts $ (10,489) $ — $ (135,122) $ (145,611) $ 145,611 $ — Interest-rate contracts — (203,407) — (203,407) — (203,407) Total derivative liabilities $ (10,489) $ (203,407) $ (135,122) $ (349,018) $ 145,611 $ (203,407) (a) - Derivative assets and liabilities are presented in our Consolidated Balance Sheet on a net basis. We net derivative assets and liabilities when a legally enforceable master-netting arrangement exists between the counterparty to a derivative contract and us. At December 31, 2020, we held no cash and posted $63.1 million of cash with various counterparties, including $35.1 million of cash collateral that is offsetting derivative net liability positions under master-netting arrangements in the table above. The remaining $28.0 million of cash collateral in excess of derivative net liability positions is included in other current assets in our Consolidated Balance Sheet. December 31, 2019 Level 1 Level 2 Level 3 Total - Gross Netting (a) Total - Net ( Thousands of dollars ) Derivative assets Commodity contracts Financial contracts $ 10,892 $ — $ 55,557 $ 66,449 $ (28,588) $ 37,861 Interest-rate contracts — 581 — 581 — 581 Total derivative assets $ 10,892 $ 581 $ 55,557 $ 67,030 $ (28,588) $ 38,442 Derivative liabilities Commodity contracts Financial contracts $ (4,811) $ — $ (24,785) $ (29,596) $ 28,588 $ (1,008) Interest-rate contracts — (201,941) — (201,941) — (201,941) Total derivative liabilities $ (4,811) $ (201,941) $ (24,785) $ (231,537) $ 28,588 $ (202,949) (a) - Derivative assets and liabilities are presented in our Consolidated Balance Sheet on a net basis. We net derivative assets and liabilities when a legally enforceable master-netting arrangement exists between the counterparty to a derivative contract and us. At December 31, 2019, we held no cash and posted $8.8 million of cash with various counterparties, which is included in other current assets in our Consolidated Balance Sheet. The following table sets forth a reconciliation of our Level 3 fair value measurements for the periods indicated: Years Ended December 31, Derivative Assets (Liabilities) 2020 2019 ( Thousands of dollars ) Net assets at beginning of period $ 30,772 $ 40,484 Total changes in fair value: Settlements included in net income (a) (31,660) (40,344) New Level 3 derivatives included in other comprehensive loss (b) (36,568) 30,627 Unrealized change included in other comprehensive loss (b) 6,135 5 Net assets (liabilities) at end of period $ (31,321) $ 30,772 (a) - Included in commodity sales revenues/cost of sales and fuel in our Consolidated Statements of Income. (b) - Included in change in fair value of derivatives in our Consolidated Statements of Comprehensive Income. During the years ended December 31, 2020 and 2019, there were no transfers in or out of Level 3 of the fair value hierarchy. Other Financial Instruments - The approximate fair value of cash and cash equivalents, accounts receivable, accounts payable and short-term borrowings is equal to book value due to the short-term nature of these items. Our cash and cash equivalents are composed of bank and money market accounts and are classified as Level 1. Our short-term borrowings are classified as Level 2 since the estimated fair value of the short-term borrowings can be determined using information available in the commercial paper market. The estimated fair value of our consolidated long-term debt, including current maturities, was $16.3 billion and $13.8 billion at December 31, 2020 and 2019, respectively. The book value of our consolidated long-term debt, including current maturities, was $14.2 billion and $12.5 billion at December 31, 2020 and 2019, respectively. The estimated fair value of the aggregate senior notes outstanding was determined using quoted market prices for similar issues with similar terms and maturities. The estimated fair value of our consolidated long-term debt is classified as Level 2. Nonrecurring Fair Value Measurements - In 2020, we incurred noncash impairment charges for certain long-lived assets and equity investments. The valuation of these assets and investments required the use of significant unobservable inputs. To estimate the fair value, we used two generally accepted valuation approaches, an income approach and a market approach. Under the income approach, our discounted cash flow analysis included the following inputs that are not readily available: a discount rate reflective of industry cost of capital, our estimated contract rates, volumes, operating margins, operating and maintenance costs and capital expenditures. Under the market approach, our inputs included EBITDA multiples, which were estimated from recent peer acquisition transactions, and forecasted EBITDA, which incorporates inputs similar to those used under the income approach. The estimated fair value of these assets is classified as Level 3. See Note A for additional information about our impairment charges.

RISK MANAGEMENT AND HEDGING ACT

RISK MANAGEMENT AND HEDGING ACTIVITIES USING DERIVATIVES (Notes)	12 Months Ended
	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
RISK MANAGEMENT AND HEDGING ACTIVITIES USING DERIVATIVES	RISK-MANAGEMENT AND HEDGING ACTIVITIES USING DERIVATIVES Risk-management Activities - We are sensitive to changes in natural gas, crude oil and NGL prices, principally as a result of contractual terms under which these commodities are processed, purchased and sold. We are also subject to the risk of interest-rate fluctuation in the normal course of business. We use physical-forward purchases and sales and financial derivatives to secure a certain price for a portion of our natural gas, condensate and NGL products; to reduce our exposure to commodity price and interest-rate fluctuations; and to achieve more predictable cash flows. We follow established policies and procedures to assess risk and approve, monitor and report our risk-management activities. We have not used these instruments for trading purposes. Commodity price risk - Commodity price risk refers to the risk of loss in cash flows and future earnings arising from adverse changes in the price of natural gas, NGLs and condensate. We may use the following commodity derivative instruments to reduce the near-term commodity price risk associated with a portion of the forecasted sales of these commodities: • Futures contracts - Standardized contracts to purchase or sell natural gas and crude oil for future delivery or settlement under the provisions of exchange regulations; • Forward contracts - Nonstandardized commitments between two parties to purchase or sell natural gas, crude oil or NGLs for future physical delivery. These contracts are typically nontransferable and can only be canceled with the consent of both parties; • Swaps - Exchange of one or more payments based on the value of one or more commodities. These instruments transfer the financial risk associated with a future change in value between the counterparties of the transaction, without also conveying ownership interest in the asset or liability; and • Options - Contractual agreements that give the holder the right, but not the obligation, to buy or sell a fixed quantity of a commodity at a fixed price within a specified period of time. Options may either be standardized and exchange-traded or customized and nonexchange-traded. We may also use other instruments, including collars, to mitigate commodity price risk. A collar is a combination of a purchased put option and a sold call option, which places a floor and a ceiling price for commodity sales being hedged. In our Natural Gas Gathering and Processing segment, we are exposed to commodity price risk as a result of retaining a portion of the commodity sales proceeds associated with our fee with POP contracts. Under certain fee with POP contracts, our fees and POP percentage may increase or decrease if production volumes, delivery pressures or commodity prices change relative to specified thresholds. In certain commodity price environments, our contractual fees on these certain fee with POP contracts may decrease, which impacts the average fee rate in our Natural Gas Gathering and Processing segment. We also are exposed to basis risk between the various production and market locations where we buy and sell commodities. As part of our hedging strategy, we use the previously described commodity derivative financial instruments and physical-forward contracts to reduce the impact of price fluctuations related to natural gas, NGLs and condensate. In our Natural Gas Liquids segment, we are primarily exposed to commodity price risk resulting from the relative values of the various NGL products to each other, the value of NGLs in storage and the relative value of NGLs to natural gas. We are also exposed to location price differential risk as a result of the relative value of NGL purchases at one location and sales at another location, primarily related to our optimization and marketing business. As part of our hedging strategy, we utilize physical-forward contracts and commodity derivative financial instruments to reduce the impact of price fluctuations related to NGLs. In our Natural Gas Pipelines segment, we are primarily exposed to commodity price risk on our intrastate pipelines because they consume natural gas in operations and retain natural gas from our customers for operations or as part of our fee for services provided. When the amount consumed in operations differs from the amount provided by our customers, our pipelines must buy or sell natural gas, or store or use natural gas inventory, which can expose this segment to commodity price risk depending on the regulatory treatment for this activity. To the extent that commodity price risk in our Natural Gas Pipelines segment is not mitigated by fuel cost-recovery mechanisms, we may use physical-forward sales or purchases to reduce the impact of natural gas price fluctuations. At December 31, 2020 and 2019, there were no financial derivative instruments with respect to our natural gas pipeline operations. Interest-rate risk - We manage interest-rate risk through the use of fixed-rate debt, floating-rate debt and interest-rate swaps. Interest-rate swaps are agreements to exchange interest payments at some future point based on specified notional amounts. In 2020, we settled $750 million of our forward-starting interest-rate swaps related to our underwritten public offerings of $1.75 billion senior unsecured notes resulting in a loss of $152.5 million, which is included in accumulated other comprehensive loss and amortized to interest expense over the term of the related debt. We also settled the remaining $1.3 billion of our interest-rate swaps used to hedge our LIBOR-based interest payments resulting in a loss of $48.3 million, which was recognized into interest expense upon repayment of the remaining balance of our $1.5 Billion Term Loan Agreement. At December 31, 2020, and December 31, 2019, we had forward-starting interest-rate swaps with notional amounts totaling $1.1 billion and $1.8 billion, respectively, to hedge the variability of interest payments on a portion of our forecasted debt issuances. At December 31, 2019, we had interest-rate swaps with notional amounts totaling $1.3 billion to hedge the variability of our LIBOR-based interest payments, all of which have settled as of December 31, 2020. All of our interest-rate swaps are designated as cash flow hedges. Fair Values of Derivative Instruments - See Note A for a discussion of the inputs associated with our fair value measurements. The following table sets forth the fair values of our derivative instruments presented on a gross basis for the periods indicated: December 31, 2020 December 31, 2019 Location in our Consolidated Balance Sheets Assets (Liabilities) Assets (Liabilities) ( Thousands of dollars ) Derivatives designated as hedging instruments Commodity contracts (a) Financial contracts (b) Other current assets $ 107,461 $ (142,573) $ 64,858 $ (26,997) Other deferred credits — — 1,591 (2,599) Interest-rate contracts Other current liabilities — — — (90,161) Other assets/other deferred credits — (203,407) 581 (111,780) Total derivatives designated as hedging instruments 107,461 (345,980) 67,030 (231,537) Derivatives not designated as hedging instruments Commodity contracts (a) Financial contracts (b) 3,037 (3,038) — — Total derivatives not designated as hedging instruments 3,037 (3,038) — — Total derivatives $ 110,498 $ (349,018) $ 67,030 $ (231,537) (a) - Derivative assets and liabilities are presented in our Consolidated Balance Sheets on a net basis when a legally enforceable master-netting arrangement exists between the counterparty to a derivative contract and us. (b) - At December 31, 2020, our derivative net liability positions under master-netting arrangements for financial contracts were fully offset by $35.1 million of cash collateral. Notional Quantities for Derivative Instruments - The following table sets forth the notional quantities for derivative instruments held for the periods indicated: December 31, 2020 December 31, 2019 Contract Net Purchased/Payor Derivatives designated as hedging instruments: (a) Cash flow hedges Fixed price -Natural gas ( Bcf ) Futures (43.3) (59.0) -Crude oil and NGLs ( MMBbl ) Futures (4.6) (9.5) Basis -Natural gas ( Bcf ) Futures (43.3) (59.0) Interest-rate contracts ( Billions of dollars ) Swaps $ 1.1 $ 3.1 (a) - Notional amounts for derivatives not designated as hedging instruments are excluded from the table above due to fully offsetting notional quantities of 0.8 Bcf for crude oil and NGLs fixed priced derivative instruments for the year ended December 31, 2020. Cash Flow Hedges - The following table sets forth the unrealized change in fair value of cash flow hedges in other comprehensive income (loss) for the periods indicated: Years Ended December 31, 2020 2019 2018 ( Thousands of dollars ) Commodity contracts $ (5,699) $ 38,819 $ 53,217 Interest-rate contracts (208,616) (230,771) (60,584) Total unrealized change in fair value of cash flow hedges in other comprehensive income (loss) $ (214,315) $ (191,952) $ (7,367) The following table sets forth the effect of cash flow hedges on net income for the periods indicated: Derivatives in Cash Flow Location of Gain (Loss) Reclassified from Years Ended December 31, 2020 2019 2018 ( Thousands of dollars ) Commodity contracts Commodity sales revenues $ 85,436 $ 94,547 $ (37,596) Cost of sales and fuel (19,170) (44,202) 8,000 Interest-rate contracts (a) Interest expense (93,676) (23,230) (18,287) Total change in fair value of cash flow hedges reclassified from accumulated other comprehensive loss into net income on derivatives $ (27,410) $ 27,115 $ (47,883) (a) - The year ended December 31, 2020, includes a loss of $48.3 million on the settlement of our remaining $1.3 billion interest-rate swaps used to hedge our LIBOR-based interest payments. Credit Risk - We monitor the creditworthiness of our counterparties and compliance with policies and limits established by our Risk Oversight and Strategy Committee. We maintain credit policies with regard to our counterparties that we believe minimize overall credit risk. These policies include an evaluation of potential counterparties’ financial condition (including credit ratings, bond yields and credit default swap rates), collateral requirements under certain circumstances and the use of standardized master-netting agreements that allow us to net the positive and negative exposures associated with a single counterparty. We use internally developed credit ratings for counterparties that do not have a credit rating. Our financial commodity derivatives are generally settled through a NYMEX or ICE clearing broker account with daily margin requirements. However, we may enter into financial derivative instruments that contain provisions that require us to maintain an investment-grade credit rating from S&P, Fitch and/or Moody’s. If our credit ratings on our senior unsecured long-term debt were to decline below investment grade, the counterparties to the derivative instruments could request collateralization on derivative instruments in net liability positions. There were no financial derivative instruments with contingent features related to credit risk at December 31, 2020. The counterparties to our derivative contracts typically consist of major energy companies, financial institutions and commercial and industrial end users. This concentration of counterparties may affect our overall exposure to credit risk, either positively or negatively, in that the counterparties may be affected similarly by changes in economic, regulatory or other conditions. Based on our policies, exposures, credit and other reserves, we do not anticipate a material adverse effect on our financial position or results of operations as a result of counterparty nonperformance. At December 31, 2020, the credit exposure from our derivative assets is with investment-grade companies in the financial services sector.

PROPERTY, PLANT AND EQUIPMENT (

PROPERTY, PLANT AND EQUIPMENT (Notes)	12 Months Ended
PROPERTY, PLANT AND EQUIPMENT (Notes)	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND EQUIPMENT	PROPERTY, PLANT AND EQUIPMENT The following table sets forth our property, plant and equipment by property type, for the periods indicated: Estimated Useful December 31, December 31, ( Thousands of dollars ) Nonregulated Gathering pipelines and related equipment 5 to 40 $ 4,143,752 $ 4,316,936 Processing and fractionation and related equipment 3 to 40 5,084,802 4,439,332 Storage and related equipment 3 to 54 798,785 684,635 Transmission pipelines and related equipment 5 to 54 810,434 797,678 General plant and other 2 to 60 647,675 610,013 Construction work in process — 1,265,736 1,645,663 Regulated Storage and related equipment 5 to 25 9,180 9,180 Natural gas transmission pipelines and related equipment 5 to 77 1,569,268 1,552,546 NGL transmission pipelines and related equipment 5 to 88 8,423,544 6,126,056 General plant and other 2 to 50 72,535 66,507 Construction work in process — 247,224 1,802,946 Property, plant and equipment 23,072,935 22,051,492 Accumulated depreciation and amortization - nonregulated (2,514,328) (2,471,649) Accumulated depreciation and amortization - regulated (1,403,679) (1,231,158) Net property, plant and equipment $ 19,154,928 $ 18,348,685 The average depreciation rates for our regulated property are set forth, by segment, in the following table for the periods indicated: Years Ended December 31, 2020 2019 2018 Natural Gas Liquids 2.2% 2.0% 1.9% Natural Gas Pipelines 2.1% 2.1% 2.1% We incurred costs for construction work in process that had not been paid at December 31, 2020, 2019 and 2018, of $151.7 million, $544.8 million and $388.3 million, respectively. Such amounts are not included in capital expenditures (less AFUDC and capitalized interest) on the Consolidated Statements of Cash Flows. Impairment Charges - In 2020, we evaluated our Natural Gas Gathering and Processing segment asset groups and determined that the carrying value of certain long-lived asset groups in the Powder River Basin, western Oklahoma and Kansas were not recoverable and exceeded their estimated fair value. As a result, we recorded noncash impairment charges of $362.3 million, which includes a natural gas processing plant and infrastructure in the Powder River Basin and its related supply contracts and natural gas processing plants and infrastructure in western Oklahoma and Kansas. In our Natural Gas Liquids segment, we recorded noncash impairment charges of $71.6 million related primarily to certain inactive assets, as our expectation for future use of the assets changed. These charges are included within impairment charges in our Consolidated Statement of Income for the year ended December 31, 2020. For additional information on our impairment charges, see Note A.

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Notes)	12 Months Ended
GOODWILL AND INTANGIBLE ASSETS (Notes)	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND INTANGIBLE ASSETS	GOODWILL AND INTANGIBLE ASSETS Goodwill - The following table sets forth our goodwill, by segment, for the periods indicated: December 31, December 31, ( Thousands of dollars ) Natural Gas Gathering and Processing $ — $ 153,404 Natural Gas Liquids 371,217 371,217 Natural Gas Pipelines 156,375 156,375 Total goodwill $ 527,592 $ 680,996 Impairment Charges - Based on the results of our goodwill impairment test in the first quarter 2020, we concluded that the carrying value of the Natural Gas Gathering and Processing reporting unit exceeded its estimated fair value, resulting in a noncash impairment charge of $153.4 million, which is included within impairment charges in our Consolidated Statement of Income for the year ended December 31, 2020. For additional information on our impairment charges, see Note A. Intangible Assets - Our intangible assets relate primarily to contracts acquired through acquisitions in our Natural Gas Liquids and Natural Gas Gathering and Processing segments, which are being amortized over periods of 15 to 40 years. Amortization expense for intangible assets was $10.8 million in 2020 and $11.9 million in 2019 and 2018, and the aggregate amortization expense for each of the next five years is estimated to be $10.4 million. The following table reflects the gross carrying amount and accumulated amortization of intangible assets for the periods presented: December 31, December 31, ( Thousands of dollars ) Gross intangible assets $ 381,435 $ 414,345 Accumulated amortization (135,304) (137,508) Net intangible assets $ 246,131 $ 276,837 Impairment Charges - In our Natural Gas Gathering and Processing segment, we recorded noncash impairment charges to intangible assets of $19.9 million related to supply contracts associated with our natural gas processing plant in the Powder River Basin, which was also impaired. These charges are included within impairment charges in our Consolidated Statement of Income for the year ended December 31, 2020. For additional information on our impairment charges, see Note A.

DEBT (Notes)

DEBT (Notes)	12 Months Ended
DEBT (Notes)	Dec. 31, 2020
Long-term Debt, Unclassified [Abstract]
DEBT	DEBT The following table sets forth our consolidated debt for the periods indicated: December 31, December 31, (Thousands of dollars) Commercial paper outstanding, bearing a weighted-average interest rate of 2.16% as of December 31, 2019 $ — $ 220,000 Senior unsecured obligations: $1,500,000 term loan at 2.70% as of December 31, 2019, due November 2021 — 1,250,000 $700,000 at 4.25% due February 2022 541,877 547,397 $900,000 at 3.375% due October 2022 895,814 900,000 $425,000 at 5.0% due September 2023 425,000 425,000 $500,000 at 7.5% due September 2023 500,000 500,000 $500,000 at 2.75% due September 2024 500,000 500,000 $500,000 at 4.9% due March 2025 500,000 500,000 $400,000 at 2.2% due September 2025 387,000 — $600,000 at 5.85% due January 2026 600,000 — $500,000 at 4.0% due July 2027 500,000 500,000 $800,000 at 4.55% due July 2028 800,000 800,000 $100,000 at 6.875% due September 2028 100,000 100,000 $700,000 at 4.35% due March 2029 700,000 700,000 $750,000 at 3.4% due September 2029 714,251 750,000 $850,000 at 3.1% due March 2030 780,093 — $600,000 at 6.35% due January 2031 600,000 — $400,000 at 6.0% due June 2035 400,000 400,000 $600,000 at 6.65% due October 2036 600,000 600,000 $600,000 at 6.85% due October 2037 600,000 600,000 $650,000 at 6.125% due February 2041 650,000 650,000 $400,000 at 6.2% due September 2043 400,000 400,000 $700,000 at 4.95% due July 2047 689,006 700,000 $1,000,000 at 5.2% due July 2048 1,000,000 1,000,000 $750,000 at 4.45% due September 2049 713,676 750,000 $500,000 at 4.5% due March 2050 451,270 — $300,000 at 7.15% due January 2051 300,000 — Guardian Pipeline Weighted average 7.85% due December 2022 13,657 21,307 Total debt 14,361,644 12,813,704 Unamortized portion of terminated swaps 13,314 15,032 Unamortized debt issuance costs and discounts (138,887) (121,329) Current maturities of long-term debt (7,650) (7,650) Short-term borrowings (a) — (220,000) Long-term debt $ 14,228,421 $ 12,479,757 (a) - Individual issuances of commercial paper under our commercial paper program generally mature in 90 days or less. $2.5 Billion Credit Agreement - In May 2019, we extended the term of our $2.5 Billion Credit Agreement by one year to June 2024. Our $2.5 Billion Credit Agreement is a revolving credit facility and contains certain financial, operational and legal covenants. Among other things, these covenants include maintaining a ratio of indebtedness to adjusted EBITDA (EBITDA, as defined in our $2.5 Billion Credit Agreement, adjusted for all noncash charges and increased for projected EBITDA from certain lender-approved capital expansion projects). In June 2020, we amended our $2.5 Billion Credit Agreement by, among other things, modifying the leverage ratio so that we may net up to $700 million of cash on hand against our consolidated indebtedness for purposes of calculating the ratio’s numerator for the fiscal quarters ending June 30, 2020, September 30, 2020, and December 31, 2020. In October 2020, we acquired additional interest in one of our equity investments and a related asset for $27 million, which allowed us to elect an acquisition adjustment period under our $2.5 Billion Credit Agreement and, as a result, increased our leverage ratio covenant to 5.5 to 1 for the fourth quarter 2020 and the two following quarters. Thereafter, the covenant will decrease to 5.0 to 1. Our $2.5 Billion Credit Agreement includes a $100 million sublimit for the issuance of standby letters of credit and a $200 million sublimit for swingline loans. Under the terms of our $2.5 Billion Credit Agreement, we may request an increase in the size of the facility to an aggregate of $3.5 billion by either commitments from new lenders or increased commitments from existing lenders. Our $2.5 Billion Credit Agreement contains provisions for an applicable margin rate and an annual facility fee, both of which adjust with changes in our credit ratings. Based on our current credit ratings, borrowings, if any, will accrue at LIBOR, or alternate benchmark rate, plus 110 basis points, and the annual facility fee is 15 basis points. At December 31, 2020, our ratio of indebtedness to adjusted EBITDA was 4.6 to 1, and we were in compliance with all covenants under our $2.5 Billion Credit Agreement. At December 31, 2020 and 2019, we had letters of credit issued totaling $7.7 million and $4.7 million, respectively, and no borrowings outstanding under our $2.5 Billion Credit Agreement. Senior Unsecured Obligations - All notes are senior unsecured obligations, ranking equally in right of payment with all of our existing and future unsecured senior indebtedness, and are structurally subordinate to any of the existing and future debt and other liabilities of any non-guarantor subsidiaries. Issuances - In May 2020, we completed an underwritten public offering of $1.5 billion senior unsecured notes consisting of $600 million, 5.85% senior notes due 2026; $600 million, 6.35% senior notes due 2031; and $300 million, 7.15% senior notes due 2051. The net proceeds, after deducting underwriting discounts, commissions and offering expenses, were $1.48 billion. A portion of the proceeds was used to repay the outstanding borrowings under our $1.5 Billion Term Loan Agreement. The remainder was used for general corporate purposes. In March 2020, we completed an underwritten public offering of $1.75 billion senior unsecured notes consisting of $400 million, 2.2% senior notes due 2025; $850 million, 3.1% senior notes due 2030; and $500 million, 4.5% senior notes due 2050. The net proceeds, after deducting underwriting discounts, commissions and offering expenses, were $1.73 billion. A portion of the proceeds was used to pay all outstanding amounts under our commercial paper program. The remainder was used for general corporate purposes, which included repayment of other existing indebtedness and funding capital expenditures. In August 2019, we completed an underwritten public offering of $2.0 billion senior unsecured notes consisting of $500 million, 2.75% senior notes due 2024; $750 million, 3.4% senior notes due 2029; and $750 million, 4.45% senior notes due 2049. The net proceeds, after deducting underwriting discounts, commissions and offering expenses, were $1.97 billion. The proceeds were used for general corporate purposes, including repayment of existing indebtedness and funding capital expenditures. In March 2019, we completed an underwritten public offering of $1.25 billion senior unsecured notes consisting of $700 million, 4.35% senior notes due 2029 and an additional issuance of $550 million of our existing 5.2% senior notes due 2048. The net proceeds, after deducting underwriting discounts, commissions and offering expenses, and exclusive of accrued interest, were $1.23 billion. The proceeds were used for general corporate purposes, including repayment of existing indebtedness and funding capital expenditures. In November 2018, we entered into our $1.5 Billion Term Loan Agreement with a syndicate of banks, which was fully drawn as of June 30, 2019. The proceeds were used for general corporate purposes, including repayment of existing indebtedness and funding capital expenditures. In July 2018, we completed an underwritten public offering of $1.25 billion senior unsecured notes consisting of $800 million, 4.55% senior notes due 2028 and $450 million, 5.2% senior notes due 2048. The net proceeds, after deducting underwriting discounts, commissions and offering expenses, were $1.23 billion. The proceeds were used for general corporate purposes, which included repayment of existing indebtedness and funding capital expenditures. Repayments - In May 2020, we repaid the remaining $1.25 billion of our $1.5 Billion Term Loan Agreement with cash on hand from our May 2020 public offering of $1.5 billion senior unsecured notes. In 2020, we repurchased in the open market outstanding principal of certain of our senior notes in the amount of $224.4 million for an aggregate repurchase price of $199.6 million with cash on hand. In connection with these open market repurchases, we recognized $22.3 million of net gains on extinguishment of debt, which is included in other income in our Consolidated Statement of Income for the year ended December 31, 2020. In September 2019, we redeemed our $300 million, 3.8% senior notes due March 2020 at a redemption price of $308.0 million, including the outstanding principal, plus accrued and unpaid interest, with cash on hand from our public offering of $2.0 billion senior unsecured notes in August 2019. In connection with this early redemption, we incurred a $2.7 million loss on extinguishment of debt, which is included in other expense in our Consolidated Statements of Income for the year ended December 31, 2019. In August 2019, we repaid $250 million of our $1.5 Billion Term Loan agreement with cash on hand. In March 2019, we repaid our $500 million, 8.625% senior notes at maturity with a combination of cash on hand and short-term borrowings. In 2018, we repaid our $425 million, 3.2% senior notes due September 2018 with cash on hand and the remaining $500 million of the ONEOK Partners Term Loan Agreement due 2019 with a combination of cash on hand and short-term borrowings. The aggregate maturities of long-term debt outstanding as of December 31, 2020, for the years 2021 through 2025 are shown below: Senior Guardian Total (Millions of dollars) 2021 $ — $ 7.7 $ 7.7 2022 $ 1,437.7 $ 6.0 $ 1,443.7 2023 $ 925.0 $ — $ 925.0 2024 $ 500.0 $ — $ 500.0 2025 $ 887.0 $ — $ 887.0 Covenants - Our senior notes are governed by indentures containing covenants, including among other provisions, limitations on our ability to place liens on our property or assets and to sell and leaseback our property. The indentures governing our 6.875% senior notes due 2028 include an event of default upon acceleration of other indebtedness of $15 million or more, and the indentures governing the remainder of our senior notes include an event of default upon the acceleration of other indebtedness of $100 million or more. Such events of default would entitle the trustee or the holders of 25% in aggregate principal amount of the outstanding senior notes to declare those senior notes immediately due and payable in full. The indenture for the 7.5% notes due 2023 also contains a provision that allows the holders of the notes to require ONEOK to offer to repurchase all or any part of their notes if a change of control and a credit rating downgrade occur at a purchase price of 101% of the principal amount, plus accrued and unpaid interest, if any. We may redeem our senior notes, in whole or in part, at any time prior to their maturity at a redemption price equal to the principal amount, plus accrued and unpaid interest and a make-whole premium. We may redeem the balance of our senior notes due 2022, 2023, 2024, 2025, 2026, 2027, 2028 (4.55%), 2029, 2030, 2031, 2041, 2043, 2047, 2048, 2049, 2050 and 2051 at a redemption price equal to the principal amount, plus accrued and unpaid interest, starting one to six months before the maturity date as stipulated in the respective contract terms. Our senior notes are senior unsecured obligations, ranking equally in right of payment with all of our existing and future unsecured senior indebtedness. Guardian Pipeline Senior Notes - These senior notes were issued under a master shelf agreement dated November 8, 2001, with certain financial institutions. Principal payments are due quarterly through 2022. Guardian Pipeline’s senior notes contain financial covenants that require the maintenance of certain financial ratios as defined in the master shelf agreement based on Guardian Pipeline’s financial position and results of operations. Upon any breach of these covenants, all amounts outstanding under the master shelf agreement may become due and payable immediately. At December 31, 2020, Guardian Pipeline was in compliance with its financial covenants. Other - We amortize premiums, discounts and expenses incurred in connection with the issuance of long-term debt consistent with the terms of the respective debt instrument. Debt Guarantees - ONEOK, ONEOK Partners and the Intermediate Partnership have cross guarantees in place for our and ONEOK Partners’ indebtedness.

EQUITY EQUITY (Notes)

EQUITY EQUITY (Notes)	12 Months Ended
EQUITY EQUITY (Notes)	Dec. 31, 2020
Equity [Abstract]
EQUITY	EQUITY Noncontrolling Interests - In July 2018, we acquired the remaining 20% interest in West Texas LPG Pipeline Limited Partnership for $195 million with cash on hand. We are now the sole owner of ONEOK West Texas NGL, formerly known as West Texas LPG. Series A and B Convertible Preferred Stock - There are no shares of Series A or Series B Preferred Stock currently issued or outstanding. Equity Issuances - In July 2020, we established an “at-the-market” equity program for the offer and sale from time to time of our common stock up to an aggregate offering price of $1.0 billion. The program allows us to offer and sell common stock at prices we deem appropriate through a sales agent, in forward sales transactions through a forward seller or directly to one or more of the program’s managers acting as principals. Sales of our common stock may be made by means of ordinary brokers’ transactions on the NYSE, in block transactions or as otherwise agreed to between us and the sales agent. We are under no obligation to offer and sell common stock under the program. No shares have been sold through our “at-the-market” program as of the date of this report. In June 2020, we completed an underwritten public offering of 29.9 million shares of our common stock at a public offering price of $32.00 per share, generating net proceeds, after deducting underwriting discounts, commissions and offering expenses, of $937.0 million. A portion of the proceeds was, and we anticipate the remainder will be, used for general corporate purposes, including repayment of existing indebtedness and funding capital expenditures. In January 2018, we completed an underwritten public offering of 21.9 million shares of our common stock at a public offering price of $54.50 per share, generating net proceeds of $1.2 billion. We used the net proceeds from this offering to fund capital expenditures and for general corporate purposes, which included repaying a portion of our outstanding indebtedness. Dividends - Holders of our common stock share equally in any dividend declared by our Board of Directors, subject to the rights of the holders of outstanding Series E Preferred Stock. Dividends paid totaled $1.6 billion, $1.5 billion and $1.3 billion for 2020, 2019 and 2018, respectively. In addition to the increase in dividends paid per share outlined in the table below, dividends paid increased due to the increase in number of shares outstanding as a result of our equity issuances. The following table sets forth the quarterly dividends per share paid on our common stock in the periods indicated: Years Ended December 31, 2020 2019 2018 First Quarter $ 0.935 $ 0.860 $ 0.770 Second Quarter 0.935 0.865 0.795 Third Quarter 0.935 0.890 0.825 Fourth Quarter 0.935 0.915 0.855 Total $ 3.74 $ 3.53 $ 3.245 Additionally, in February 2021, we maintained and paid a quarterly dividend of $0.935 per share ($3.74 per share on an annualized basis), which was paid to shareholders of record as of February 1, 2021.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Notes)	12 Months Ended
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Notes)	Dec. 31, 2020
ACCUMULATED OTHER COMPREHENSIVE LOSS	ACCUMULATED OTHER COMPREHENSIVE LOSS The following table sets forth the balance in accumulated other comprehensive loss for the periods indicated: Risk- Retirement and Other Risk- Accumulated ( Thousands of dollars ) January 1, 2019 $ (64,660) $ (121,785) $ (1,794) $ (188,239) Other comprehensive loss before reclassifications (147,803) (19,490) (7,275) (174,568) Amounts reclassified to net income (c) (21,057) 9,794 70 (11,193) Other comprehensive loss (168,860) (9,696) (7,205) (185,761) December 31, 2019 (233,520) (131,481) (8,999) (374,000) Other comprehensive loss before reclassifications (165,023) (40,341) (8,635) (213,999) Amounts reclassified to net income (c) 21,097 14,187 1,266 36,550 Other comprehensive loss (143,926) (26,154) (7,369) (177,449) December 31, 2020 $ (377,446) $ (157,635) $ (16,368) $ (551,449) (a) - All amounts are presented net of tax. (b) - Includes amounts related to supplemental executive retirement plan. (c) - See Note C for details of amounts reclassified to net income for risk-management assets/liabilities and Note K for retirement and other postretirement benefit plan obligations. The following table sets forth information about the balance of accumulated other comprehensive loss at December 31, 2020, representing unrealized gains (losses) related to risk-management assets and liabilities: Risk- ( Thousands of dollars ) Commodity derivative instruments expected to be realized within the next 24 months (b) $ (27,303) Settled interest-rate swaps to be recognized over the life of the long-term, fixed-rate debt (c) (193,519) Interest-rate swaps with future settlement dates expected to be amortized over the life of long-term debt (156,624) Accumulated other comprehensive loss at December 31, 2020 $ (377,446) (a) - All amounts are presented net of tax. (b) - Based on December 31, 2020, commodity prices, we expect $27.0 million in net losses, net of tax, over the next 12 months and $0.3 million in net losses, net of tax, thereafter. (c) - We expect net losses of $30.5 million, net of tax, will be reclassified into earnings during the next 12 months.

EARNINGS PER SHARE EARNINGS PER

EARNINGS PER SHARE EARNINGS PER SHARE (Notes)	12 Months Ended
EARNINGS PER SHARE EARNINGS PER SHARE (Notes)	Dec. 31, 2020
Earnings Per Share [Abstract]
Earnings Per Share [Text Block]	EARNINGS PER SHARE The following tables set forth the computation of basic and diluted EPS for the periods indicated: Year Ended December 31, 2020 Income Shares Per Share ( Thousands, except per share amounts ) Basic EPS Net income available for common stock $ 611,709 431,105 $ 1.42 Diluted EPS Effect of dilutive securities — 677 Net income available for common stock and common stock equivalents $ 611,709 431,782 $ 1.42 Year Ended December 31, 2019 Income Shares Per Share ( Thousands, except per share amounts ) Basic EPS Net income available for common stock $ 1,277,477 413,560 $ 3.09 Diluted EPS Effect of dilutive securities — 1,884 Net income available for common stock and common stock equivalents $ 1,277,477 415,444 $ 3.07 Year Ended December 31, 2018 Income Shares Per Share ( Thousands, except per share amounts ) Basic EPS Net income attributable to ONEOK available for common stock $ 1,150,603 411,485 $ 2.80 Diluted EPS Effect of dilutive securities — 2,710 Net income attributable to ONEOK available for common stock and common stock equivalents $ 1,150,603 414,195 $ 2.78

SHARE-BASED PAYMENTS SHARE-BASE

SHARE-BASED PAYMENTS SHARE-BASED PAYMENTS (Notes)	12 Months Ended
SHARE-BASED PAYMENTS SHARE-BASED PAYMENTS (Notes)	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
SHARE-BASED PAYMENTS	SHARE-BASED PAYMENTS Our Equity Compensation Plan (ECP) and Long-Term Incentive Plan (LTIP) historically provided for the granting of stock-based compensation, including incentive stock options, nonstatutory stock options, stock bonus awards, restricted stock unit awards and performance unit awards to eligible employees and the granting of stock awards to non-employee directors. The ECP was terminated immediately following the issuance of new awards in February 2018. The awards issued prior to the termination remain subject to the terms of the ECP and the applicable award agreement. Similarly, the LTIP was terminated in May 2018, and the awards issued under the LTIP prior to the termination date remain subject to the terms of the LTIP and the applicable award agreement. In May 2018, our shareholders approved the ONEOK, Inc. Equity Incentive Plan (EIP), which has been used for all new equity awards since such date. We have reserved 8.5 million shares of common stock for issuance under the EIP and at December 31, 2020, we had 6.9 million shares available for issuance under the plan. This calculation of available shares reflects shares issued and estimated shares expected to be issued upon vesting of outstanding awards granted under the EIP, excluding estimated forfeitures expected to be returned to the plan. Restricted Stock Units - We have granted restricted stock units to key employees that vest at the end of a three Restricted stock unit awards accrue dividend equivalents in the form of additional restricted stock units prior to vesting. Compensation expense is recognized on a straight-line basis over the vesting period of the award. Performance Unit Awards - We have granted performance unit awards to key employees that vest at the end of a three Stock Compensation for Non-Employee Directors The EIP provides for the granting of nonstatutory stock options and stock bonus awards to non-employee directors, including performance unit awards and restricted stock unit awards. Under the EIP, awards may be granted by the Executive Compensation Committee at any time, until grants have been made for all shares authorized under the EIP. The maximum number of shares of common stock and cash-based awards that can be issued to a participant under the EIP during any year is limited to $0.8 million in value as of the grant date. No performance unit awards or restricted stock unit awards have been made to non-employee directors, and there are no options outstanding. General For all awards outstanding, we used a 3% forfeiture rate based on historical forfeitures under our share-based payment plans. We currently use treasury stock to satisfy our share-based payment obligations. Compensation expense for our share-based payment plans was $29.4 million, $46.5 million and $33.2 million during 2020, 2019 and 2018, respectively, before related tax benefits of $14.1 million, $31.7 million and $12.2 million, respectively. Restricted Stock Unit Activity As of December 31, 2020, we had $16.7 million of total unrecognized compensation cost related to our nonvested restricted stock unit awards, which is expected to be recognized over a weighted-average period of 1.8 years. The following tables set forth activity and various statistics for our restricted stock unit awards: Number of Weighted Nonvested December 31, 2019 698,990 $ 54.05 Granted 216,392 $ 76.49 Released to participants (240,576) $ 46.58 Forfeited (28,519) $ 65.20 Nonvested December 31, 2020 646,287 $ 63.85 2020 2019 2018 Weighted-average grant date fair value (per share) $ 76.49 $ 58.07 $ 46.94 Fair value of units granted (thousands of dollars) $ 16,552 $ 15,238 $ 13,907 Grant date fair value of units vested (thousands of dollars) $ 11,204 $ 10,691 $ 9,552 Performance Unit Activity As of December 31, 2020, we had $25.0 million of total unrecognized compensation cost related to the nonvested performance unit awards, which is expected to be recognized over a weighted-average period of 1.8 years. The following tables set forth activity and various statistics related to the performance unit awards and the assumptions used in the valuations at the respective grant dates: Number of Weighted Nonvested December 31, 2019 937,821 $ 66.67 Granted 283,029 $ 88.43 Released to participants (300,423) $ 58.99 Forfeited (86,181) $ 74.83 Nonvested December 31, 2020 834,246 $ 75.96 2020 2019 2018 Volatility (a) 21.70% 27.10% 39.20% Dividend yield 4.87% 5.05% 5.49% Risk-free interest rate 1.39% 2.47% 2.44% (a) - Volatility was based on historical volatility over three years using daily stock price observations. 2020 2019 2018 Weighted-average grant date fair value (per share) $ 88.43 $ 68.02 $ 59.57 Fair value of units granted (thousands of dollars) $ 25,028 $ 23,020 $ 22,081 Grant date fair value of units vested (thousands of dollars) $ 17,722 $ 15,018 $ 12,545 Employee Stock Purchase Plan We have reserved a total of 11.6 million shares of common stock for issuance under our Employee Stock Purchase Plan (the ESPP). Subject to certain exclusions, all employees are eligible to participate in the ESPP. Employees can choose to have up to 10% of their base pay withheld from each paycheck during the offering period to purchase our common stock, subject to terms and limitations of the plan. The purchase price of the stock is 85% of the lower of its grant date or exercise date market price. Approximately 68%, 62% and 60% of employees participated in the plan in 2020, 2019 and 2018, respectively. Under the plan, we sold 359,977 shares at a weighted average of $27.78 per share in 2020, 171,590 shares at a weighted average of $51.24 per share in 2019 and 165,877 shares at a weighted average of $45.53 per share in 2018. Employee Stock Award Program Under our Employee Stock Award Program, we issue, for no monetary consideration, to all eligible employees one share of our common stock when the per-share closing price of our common stock on the NYSE is at or above each one dollar increment above its previous high closing price. The total number of shares of our common stock available for issuance under this program is 900,000. Shares issued to employees under this program during 2020, 2019 and 2018 totaled 2,871, 14,022 and 2,553, respectively. Compensation expense related to the Employee Stock Award Program was $0.2 million, $1.0 million and $0.2 million for 2020, 2019 and 2018, respectively. As of the date of this report, the next award will be issued when our common stock closes at or above $78. Deferred Compensation Plan for Non-Employee Directors Our Deferred Compensation Plan for Non-Employee Directors provides our non-employee directors the option to defer all or a portion of their compensation for their service on our Board of Directors. Under the plan, directors may elect either a cash deferral option or a phantom stock option. Under the cash deferral option, directors may elect to defer the receipt of all or a portion of their annual retainer fees, which will be credited with interest during the deferral period. Under the phantom stock option, directors may defer all or a portion of their annual retainer fees and receive such fees on a deferred basis in the form of shares of common stock under our EIP, which earn the equivalent of dividends declared on our common stock. Shares are distributed to non-employee directors at the fair market value of our common stock at the date of distribution.

INCOME TAXES (Notes)

INCOME TAXES (Notes)	12 Months Ended
INCOME TAXES (Notes)	Dec. 31, 2020
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The following table sets forth our provision for income taxes for the periods indicated: Years Ended December 31, 2020 2019 2018 ( Thousands of dollars ) Current tax expense (benefit) Federal $ 980 $ (1,278) $ 260 State 1,797 963 1,633 Total current tax expense (benefit) 2,777 (315) 1,893 Deferred tax expense Federal 154,068 327,806 319,551 State 32,662 44,923 41,459 Total deferred tax expense 186,730 372,729 361,010 Total provision for income taxes $ 189,507 $ 372,414 $ 362,903 The following table is a reconciliation of our income tax provision for the periods indicated: Years Ended December 31, 2020 2019 2018 ( Thousands of dollars ) Income before income taxes $ 802,316 $ 1,650,991 $ 1,517,935 Less: Net income attributable to noncontrolling interests — — 3,329 Net income attributable to ONEOK before income taxes 802,316 1,650,991 1,514,606 Federal statutory income tax rate 21.0 % 21.0 % 21.0 % Provision for federal income taxes 168,486 346,708 318,067 State income taxes, net of federal benefit 13,580 34,545 38,668 Deferred tax rate change, inclusive of valuation allowance 20,879 11,340 5,552 Excess tax benefits from share-based compensation (7,380) (20,983) (4,644) Other, net (6,058) 804 5,260 Income tax provision $ 189,507 $ 372,414 $ 362,903 The following table sets forth the tax effects of temporary differences that gave rise to significant portions of the deferred tax assets and liabilities for the periods indicated: December 31, December 31, Deferred tax assets ( Thousands of dollars ) Employee benefits and other accrued liabilities $ 96,741 $ 99,510 Federal net operating loss 1,473,093 858,030 State net operating loss and benefits 258,929 171,779 Derivative instruments 134,499 83,710 Other 12,894 12,769 Total deferred tax assets 1,976,156 1,225,798 Valuation allowance for state net operating loss and tax credits Carryforward expected to expire prior to utilization (121,212) (94,794) Net deferred tax assets 1,854,944 1,131,004 Deferred tax liabilities Excess of tax over book depreciation 87,021 84,631 Investment in partnerships (a) 2,437,620 1,582,436 Total deferred tax liabilities 2,524,641 1,667,067 Net deferred tax assets (liabilities) $ (669,697) $ (536,063) (a) Due primarily to excess of tax over book depreciation. The majority of our tax benefits relate to federal and state net operating losses and carry forward indefinitely. Due to the Tax Cuts and Jobs Act and the impact of increased expensing for capital investment, we believe that it is more likely than not that the tax benefits of certain carryforwards will not be utilized prior to their expirations; therefore, we recorded a valuation allowance of $20.9 milli on, $11.3 million and $5.6 million through net income related to these tax benefits in 2020, 2019 and 2018, respectively.

UNCONSOLIDATED AFFILIATES (Note

UNCONSOLIDATED AFFILIATES (Notes)	12 Months Ended
UNCONSOLIDATED AFFILIATES (Notes)	Dec. 31, 2020
Equity Method Investments and Joint Ventures [Abstract]
UNCONSOLIDATED AFFILIATES	UNCONSOLIDATED AFFILIATES Investments in Unconsolidated Affiliates - The following table sets forth our investments in unconsolidated affiliates for the periods indicated: Net December 31, December 31, ( Thousands of dollars ) Northern Border Pipeline 50% $ 291,987 $ 307,209 Overland Pass Pipeline 50% 409,573 417,473 Roadrunner 50% 66,794 80,816 Other (a) Various 36,678 56,346 Investments in unconsolidated affiliates (b) $ 805,032 $ 861,844 (a) - Year ended December 31, 2020, includes the impact of noncash impairment charges of $37.7 million related to the equity investments discussed below, offset partially by an acquisition of additional equity interest for $20.0 million. (b) - Equity-method goodwill (Note A) was $16.5 million and $38.8 million at December 31, 2020 and 2019, respectively. Equity in Net Earnings from Investments and Impairments - The following table sets forth our equity in net earnings (loss) from investments for the periods indicated: Years Ended December 31, 2020 2019 2018 ( Thousands of dollars ) Northern Border Pipeline $ 75,409 $ 68,871 $ 67,854 Overland Pass Pipeline 38,618 63,698 65,887 Roadrunner 29,017 26,839 22,993 Other 197 (4,867) 1,649 Equity in net earnings from investments $ 143,241 $ 154,541 $ 158,383 Impairment of equity investments $ (37,730) $ — $ — Impairment Charges - In 2020, we incurred a noncash impairment charge of $30.5 million related to our 10.2% investment in Venice Energy Services Company in our Natural Gas Gathering and Processing segment, which includes $22.3 million related to equity-method goodwill, and a $7.2 million noncash impairment charge related to our 50% investment in Chisholm Pipeline Company in our Natural Gas Liquids segment. These impairment charges are included within impairment of equity investments in our Consolidated Statement of Income for the year ended December 31, 2020. For additional information on our impairment charges, see Note A. We incurred expenses in transactions with unconsolidated affiliates of $135.4 million, $164.7 million and $153.9 million for 2020, 2019 and 2018, respectively, primarily related to Overland Pass Pipeline and Northern Border Pipeline. Accounts payable to our equity-method investees at December 31, 2020 and 2019, were $8.4 million and $13.5 million, respectively. Northern Border Pipeline - The Northern Border Pipeline partnership agreement provides that distributions to Northern Border Pipeline’s partners are to be made on a pro rata basis according to each partner’s percentage interest. The Northern Border Pipeline Management Committee determines the amount and timing of such distributions. Any changes to, or suspension of, the cash distribution policy of Northern Border Pipeline requires the unanimous approval of the Northern Border Pipeline Management Committee. Cash distributions are equal to 100% of distributable cash flow as determined from Northern Border Pipeline’s financial statements based upon EBITDA less interest expense and maintenance capital expenditures. As determined by the Northern Border Pipeline Management Committee, we received an additional distribution of $50.0 million from Northern Border Pipeline during the year ended December 31, 2019. Loans or other advances from Northern Border Pipeline to its partners or affiliates are prohibited under its credit agreement. In 2020, 2019 and 2018, we made no contributions to Northern Border Pipeline. Northern Border Pipeline entered into a settlement with shippers that was approved by the FERC in February 2018. The settlement provides for tiered rate reductions beginning January 1, 2018, that reduced tariff rates 12.5% by January 2020, compared with previous tariff rates, and requires new rates to be established by January 2024. The impact of lower tariff rates on Northern Border Pipeline’s earnings and cash distributions was not material to us. Overland Pass Pipeline - The Overland Pass Pipeline agreement provides that distributions to Overland Pass Pipeline’s members are to be made on a pro rata basis according to each member’s percentage interest. The Overland Pass Pipeline Company Management Committee determines the amount and timing of such distributions. Any changes to, or suspension of, the cash distributions from Overland Pass Pipeline requires the unanimous approval of the Overland Pass Pipeline Company Management Committee. Cash distributions are equal to 100% of available cash as defined in the limited liability company agreement. In 2020, 2019 and 2018, our contributions to Overland Pass Pipeline were not material. Roadrunner - The Roadrunner agreement provides that distributions to members are made on a pro rata basis according to each member’s ownership interest. As the operator, we have been delegated the authority to determine such distributions in accordance with, and on the frequency set forth in, the Roadrunner agreement. Cash distributions are equal to 100% of available cash, as defined in the limited liability company agreement. In 2020, 2019 and 2018, our contributions to Roadrunner were not material. We have an operating agreement with Roadrunner that provides for reimbursement or payment to us for management services and certain operating costs. Reimbursements and payments from Roadrunner included in operating income in our Consolidated Statements of Income for the years ended December 31, 2020, 2019 and 2018, were not material.

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Notes)	12 Months Ended
COMMITMENTS AND CONTINGENCIES (Notes)	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Commitments - Firm transportation and storage contracts are fixed-price contracts that provide us with firm transportation and storage capacity. The following table sets forth our firm transportation and storage contract payments for the periods indicated: Firm ( Millions of dollars ) 2021 $ 70.9 2022 60.9 2023 55.8 2024 53.4 2025 47.9 Thereafter 227.8 Total $ 516.7 Environmental Matters and Pipeline Safety - The operation of pipelines, plants and other facilities for the gathering, processing, fractionation, transportation and storage of natural gas, NGLs, condensate and other products is subject to numerous and complex laws and regulations pertaining to health, safety and the environment. As an owner and/or operator of these facilities, we must comply with laws and regulations that relate to air and water quality, hazardous and solid waste management and disposal, cultural resource protection and other environmental and safety matters. The cost of planning, designing, constructing and operating pipelines, plants and other facilities must incorporate compliance with these laws, regulations and safety standards. Failure to comply with these laws and regulations may trigger a variety of administrative, civil and potentially criminal enforcement measures, including citizen suits, which can include the assessment of monetary penalties, the imposition of remedial requirements and the issuance of injunctions or restrictions on operation or construction. Management does not believe that, based on currently known information, a material risk of noncompliance with these laws and regulations exists that will affect adversely our consolidated results of operations, financial condition or cash flows. Legal Proceedings - We are a party to various litigation matters and claims that have arisen in the normal course of our operations. While the results of these litigation matters and claims cannot be predicted with certainty, we believe the reasonably possible losses from such matters, individually and in the aggregate, are not material. Additionally, we believe the probable final outcome of such matters will not have a material adverse effect on our consolidated results of operations, financial position or cash flows.

LEASES (Notes)

LEASES (Notes)	12 Months Ended
LEASES (Notes)	Dec. 31, 2020
Leases [Abstract]
Leases of Lessee Disclosure [Text Block]	LEASESWe adopted Topic 842 using the modified retrospective method and the optional transition method to record the adoption impact through a cumulative-effect adjustment to retained earnings as of January 1, 2019. Results for reporting periods beginning after January 1, 2019, are presented under Topic 842, while prior periods are not adjusted and continue to be reported under the accounting standards in effect for those periods. We lease certain buildings, warehouses, office space, pipeline capacity, land and equipment, including pipeline equipment, rail cars and information technology equipment. Our lease payments are generally straight-line and the exercise of lease renewal options, which vary in term, is at our sole discretion. We include renewal periods in a lease term if we are reasonably certain to exercise available renewal options. We apply the short-term policy election, which allows us to exclude from recognition leases with an initial term of 12 months or less. Our lease agreements do not include any residual value guarantees or material restrictive covenants. Through ONEOK Leasing Company, L.L.C. and ONEOK Parking Company, L.L.C., we own an office building and a parking garage and lease excess space in these facilities to affiliates and others. Our consolidated lease income is not material. In December 2019, we entered into an operating lease for pipeline capacity with a lease term of 10 years that commenced January 1, 2020. In connection with this lease, we recognized an operating lease right-of-use asset and a lease liability with remaining balances of $69.0 million and $69.9 million, respectively, as of December 31, 2020. The following table sets forth information about our lease assets and liabilities included in our Consolidated Balance Sheet for the periods indicated: Leases Location in our Consolidated Balance Sheet December 31, 2020 December 31, 2019 ( Thousands of dollars ) Assets Operating leases Other assets $ 100,154 $ 15,147 Finance lease Property, plant and equipment 28,286 28,286 Finance lease Accumulated depreciation (2,451) (1,320) Total leased assets $ 125,989 $ 42,113 Liabilities Current Operating leases Operating lease liability $ 13,610 $ 1,883 Finance lease Other current liabilities 2,153 1,949 Noncurrent Operating leases Operating lease liability 87,610 13,509 Finance lease Other deferred credits 22,143 24,296 Total lease liabilities $ 125,516 $ 41,637 The following table sets forth supplemental cash flow information related to our leases: Years Ended December 31, 2020 2019 ( Thousands of dollars ) Cash paid for amounts included in the measurement of lease liabilities Operating cash flows for operating leases $ 13,245 $ 6,213 Financing cash flows for finance lease $ 1,949 $ 1,764 Right-of-use assets obtained in exchange for operating lease liabilities (noncash) $ 99,547 $ 4,097 The following table sets forth information about our lease costs for the periods indicated: Years Ended December 31, Location in our 2020 2019 ( Thousands of dollars ) Operating leases Operations and maintenance $ 17,162 $ 6,803 Finance lease Amortization of lease assets Depreciation and amortization 1,131 1,131 Interest on lease liabilities Interest expense 2,537 2,721 Total lease cost $ 20,830 $ 10,655 The following table sets forth information about our leases for the periods indicated: December 31, 2020 December 31, 2019 Weighted average remaining lease term (years) Operating leases 8.3 10.4 Finance lease 7.8 8.8 Weighted average discount rate (a) Operating leases 3.20% 4.58% Finance lease 10.00% 10.00% (a) - Our weighted-average discount rates represent the rate implicit in the lease or our incremental borrowing rate for a term equal to the remaining term of the lease. The following table sets forth the maturity of our lease liabilities as of December 31, 2020: Finance Operating ( Millions of dollars ) 2021 $ 4.5 $ 16.5 2022 4.5 15.1 2023 4.5 13.8 2024 4.5 12.5 2025 4.5 11.1 2026 and beyond 12.6 47.1 Total lease payments 35.1 116.1 Less: Interest 10.8 14.9 Present value of lease liabilities $ 24.3 $ 101.2

REVENUES (Notes)

REVENUES (Notes)	12 Months Ended
REVENUES (Notes)	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer [Text Block]	REVENUES Accounting Policies - See Note A for revenue recognition accounting policies. Contract Assets and Contract Liabilities - Our contract asset balances at the beginning and end of the years ended December 31, 2020 and 2019, are not material. The following table sets forth the changes in our contract liability balances for the periods indicated: Contract Liabilities ( Millions of dollars ) Balance at January 1, 2019 $ 31.7 Revenue recognized included in beginning balance (15.6) Net additions 41.0 Balance at December 31, 2019 (a) 57.1 Revenue recognized included in beginning balance (c) (36.1) Net additions 20.4 Balance at December 31, 2020 (b) $ 41.4 (a) - Contract liabilities of $22.2 million and $34.9 million are included in other current liabilities and other deferred credits, respectively, in our Consolidated Balance Sheet. (b) - Contract liabilities of $23.7 million and $17.7 million are included in other current liabilities and other deferred credits, respectively, in our Consolidated Balance Sheet. (c) - Includes a contract settlement of revenue previously deferred. Receivables from Customers and Revenue Disaggregation - Substantially all of the balances in accounts receivable on our Consolidated Balance Sheets at December 31, 2020 and 2019, relate to customer receivables. Revenues sources are disaggregated in Note Q. Practical Expedients - We do not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) variable consideration on contracts for which we recognize revenue at the amount to which we have the right to invoice for services performed. Transaction Price Allocated to Unsatisfied Performance Obligations - The following table presents aggregate value allocated to unsatisfied performance obligations as of December 31, 2020, and the amounts we expect to recognize in revenue in future periods, related primarily to firm transportation and storage contracts with remaining contract terms ranging from one month to 23 years: Expected Period of Recognition in Revenue ( Millions of dollars ) 2021 $ 328.2 2022 263.0 2023 235.4 2024 197.9 2025 and beyond 762.0 Total estimated transaction price allocated to unsatisfied performance obligations $ 1,786.5 The table above excludes variable consideration allocated entirely to wholly unsatisfied performance obligations, wholly unsatisfied promises to transfer distinct goods or services that are part of a single performance obligation and consideration we determine to be fully constrained. Information on the nature of the variable consideration excluded and the nature of the performance obligations to which the variable consideration relates can be found in the description of the major contract types discussed in Note A. The amounts we determined to be fully constrained relate to future sales obligations under long-term sales contracts where the transaction price is not known and minimum volume agreements, which we consider to be fully constrained until invoiced.

SEGMENTS (Notes)

SEGMENTS (Notes)	12 Months Ended
SEGMENTS (Notes)	Dec. 31, 2020
Segment Reporting, Disclosure of Entity's Reportable Segments [Abstract]
SEGMENTS	SEGMENTS Segment Descriptions - Our operations are divided into three reportable business segments, as follows: • our Natural Gas Gathering and Processing segment gathers, treats and processes natural gas; • our Natural Gas Liquids segment gathers, treats, fractionates and transports NGLs and stores, markets and distributes NGL products; and • our Natural Gas Pipelines segment transports and stores natural gas via regulated intrastate and interstate natural gas transmission pipelines and natural gas storage facilities. Other and eliminations consist of corporate costs, the operating and leasing activities of our headquarters building and related parking facility and eliminations necessary to reconcile our reportable segments to our Consolidated Financial Statements. Accounting Policies - The accounting policies of the segments are described in Note A. For each of the years ended December 31, 2020, 2019 and 2018, we had no single customer from which we received 10% or more of our consolidated revenues. Operating Segment Information - The following tables set forth certain selected financial information for our operating segments for the periods indicated: Year Ended December 31, 2020 Natural Gas Natural Gas Natural Gas Total ( Thousands of dollars ) NGL and condensate sales $ 889,388 $ 6,409,332 $ — $ 7,298,720 Residue natural gas sales 771,486 — 8,693 780,179 Gathering, processing and exchange services revenue 141,943 488,574 — 630,517 Transportation and storage revenue — 182,915 470,097 653,012 Other 17,304 9,192 1,192 27,688 Total revenues (c) 1,820,121 7,090,013 479,982 9,390,116 Cost of sales and fuel (exclusive of depreciation and operating costs) (843,976) (5,108,558) (6,809) (5,959,343) Operating costs (326,938) (412,900) (141,713) (881,551) Equity in net earnings (loss) from investments (1,123) 39,938 104,426 143,241 Noncash compensation expense and other 1,952 8,748 1,540 12,240 Segment adjusted EBITDA $ 650,036 $ 1,617,241 $ 437,426 $ 2,704,703 Depreciation and amortization $ (247,010) $ (271,900) $ (55,739) $ (574,649) Impairment charges $ (566,145) $ (78,785) $ — $ (644,930) Investments in unconsolidated affiliates $ 22,757 $ 423,494 $ 358,781 $ 805,032 Total assets $ 6,499,908 $ 13,636,109 $ 2,100,213 $ 22,236,230 Capital expenditures $ 446,142 $ 1,655,759 $ 71,918 $ 2,173,819 (a) - Our Natural Gas Liquids segment has regulated and nonregulated operations. Our Natural Gas Liquids segment’s regulated operations had revenues of $2.0 billion, of which $1.8 billion related to sales within the segment, and cost of sales and fuel of $520.6 million. (b) - Our Natural Gas Pipelines segment has regulated and nonregulated operations. Our Natural Gas Pipelines segment’s regulated operations had revenues of $298.5 million and cost of sales and fuel of $30.4 million. (c) - Intersegment revenues are primarily commodity sales which are based on the contracted selling price, which is generally index-based and settled monthly, and for the Natural Gas Gathering and Processing segment totaled $865.6 million. Intersegment revenues for the Natural Gas Liquids and Natural Gas Pipelines segments were not material. Year Ended December 31, 2020 Total Other and Total ( Thousands of dollars ) Reconciliations of total segments to consolidated NGL and condensate sales $ 7,298,720 $ (820,851) $ 6,477,869 Residue natural gas sales 780,179 (10,860) 769,319 Gathering, processing and exchange services revenue 630,517 — 630,517 Transportation and storage revenue 653,012 (14,599) 638,413 Other 27,688 (1,564) 26,124 Total revenues (a) $ 9,390,116 $ (847,874) $ 8,542,242 Cost of sales and fuel (exclusive of depreciation and operating costs) $ (5,959,343) $ 849,197 $ (5,110,146) Operating costs $ (881,551) $ (4,653) $ (886,204) Depreciation and amortization $ (574,649) $ (4,013) $ (578,662) Impairment charges $ (644,930) $ — $ (644,930) Equity in net earnings from investments $ 143,241 $ — $ 143,241 Investments in unconsolidated affiliates $ 805,032 $ — $ 805,032 Total assets $ 22,236,230 $ 842,524 $ 23,078,754 Capital expenditures $ 2,173,819 $ 21,562 $ 2,195,381 (a) - Noncustomer revenue for the year ended December 31, 2020, totaled $65.8 million related primarily to gains from derivatives on commodity contracts. Year Ended December 31, 2019 Natural Gas Natural Gas Natural Gas Total ( Thousands of dollars ) NGL and condensate sales $ 1,224,378 $ 7,910,833 $ — $ 9,135,211 Residue natural gas sales 966,149 — 1,244 967,393 Gathering, processing and exchange services revenue 164,299 414,238 — 578,537 Transportation and storage revenue — 197,483 466,266 663,749 Other 13,813 9,962 4,477 28,252 Total revenues (c) 2,368,639 8,532,516 471,987 11,373,142 Cost of sales and fuel (exclusive of depreciation and operating costs) (1,302,310) (6,690,918) (4,628) (7,997,856) Operating costs (368,352) (456,892) (157,230) (982,474) Equity in net earnings (loss) from investments (6,292) 65,123 95,710 154,541 Noncash compensation expense and other 10,965 15,936 2,977 29,878 Segment adjusted EBITDA $ 702,650 $ 1,465,765 $ 408,816 $ 2,577,231 Depreciation and amortization $ (219,519) $ (196,132) $ (57,250) $ (472,901) Investments in unconsolidated affiliates $ 34,426 $ 439,393 $ 388,025 $ 861,844 Total assets $ 6,795,744 $ 12,551,476 $ 2,094,072 $ 21,441,292 Capital expenditures $ 926,489 $ 2,796,604 $ 99,221 $ 3,822,314 (a) - Our Natural Gas Liquids segment has regulated and nonregulated operations. Our Natural Gas Liquids segment’s regulated operations had revenues of $1.4 billion, of which $1.2 billion related to revenues within the segment, and cost of sales and fuel of $496.8 million. (b) - Our Natural Gas Pipelines segment has regulated and nonregulated operations. Our Natural Gas Pipelines segment’s regulated operations had revenues of $285.3 million and cost of sales and fuel of $20.0 million. (c) - Intersegment revenues are primarily commodity sales which are based on the contracted selling price, which is generally index-based and settled monthly, and for the Natural Gas Gathering and Processing segment totaled $1.2 billion. Intersegment revenues for the Natural Gas Liquids and Natural Gas Pipelines segments were not material. Year Ended December 31, 2019 Total Other and Total ( Thousands of dollars ) Reconciliations of total segments to consolidated NGL and condensate sales $ 9,135,211 $ (1,190,424) $ 7,944,787 Residue natural gas sales 967,393 (1,418) 965,975 Gathering, processing and exchange services revenue 578,537 — 578,537 Transportation and storage revenue 663,749 (15,646) 648,103 Other 28,252 (1,287) 26,965 Total revenues (a) $ 11,373,142 $ (1,208,775) $ 10,164,367 Cost of sales and fuel (exclusive of depreciation and operating costs) $ (7,997,856) $ 1,209,816 $ (6,788,040) Operating costs $ (982,474) $ (390) $ (982,864) Depreciation and amortization $ (472,901) $ (3,634) $ (476,535) Equity in net earnings from investments $ 154,541 $ — $ 154,541 Investments in unconsolidated affiliates $ 861,844 $ — $ 861,844 Total assets $ 21,441,292 $ 370,829 $ 21,812,121 Capital expenditures $ 3,822,314 $ 26,035 $ 3,848,349 (a) - Noncustomer revenue for the year ended December 31, 2019, totaled $139.6 million related primarily to gains from derivatives on commodity contracts. Year Ended December 31, 2018 Natural Gas Natural Gas Natural Gas Total ( Thousands of dollars ) NGL and condensate sales $ 1,775,991 $ 10,319,847 $ — $ 12,095,838 Residue natural gas sales 1,084,162 — 9,772 1,093,934 Gathering, processing and exchange services revenue 163,194 404,897 — 568,091 Transportation and storage revenue — 199,018 414,969 613,987 Other 11,230 10,816 6,994 29,040 Total revenues (c) 3,034,577 10,934,578 431,735 14,400,890 Cost of sales and fuel (exclusive of depreciation and operating costs) (2,041,448) (9,176,813) (15,984) (11,234,245) Operating costs (368,939) (394,115) (144,259) (907,313) Equity in net earnings from investments 410 67,126 90,847 158,383 Noncash compensation expense and other 7,007 9,829 3,912 20,748 Segment adjusted EBITDA $ 631,607 $ 1,440,605 $ 366,251 $ 2,438,463 Depreciation and amortization $ (196,090) $ (174,007) $ (55,118) $ (425,215) Investments in unconsolidated affiliates $ 42,630 $ 451,040 $ 475,480 $ 969,150 Total assets $ 6,078,473 $ 9,663,640 $ 2,131,669 $ 17,873,782 Capital expenditures $ 694,611 $ 1,306,341 $ 119,185 $ 2,120,137 (a) - Our Natural Gas Liquids segment has regulated and nonregulated operations. Our Natural Gas Liquids segment’s regulated operations had revenues of $1.2 billion, of which $1.1 billion related to revenues within the segment, and cost of sales and fuel of $506.0 million. (b) - Our Natural Gas Pipelines segment has regulated and nonregulated operations. Our Natural Gas Pipelines segment’s regulated operations had revenues of $266.6 million and cost of sales and fuel of $26.0 million. (c) - Intersegment revenues are primarily commodity sales which are based on the contracted selling price, which is generally index-based and settled monthly, and for the Natural Gas Gathering and Processing segment totaled $1.8 billion. Intersegment revenues for the Natural Gas Liquids and Natural Gas Pipelines segments were not material. Year Ended December 31, 2018 Total Other and Total (Thousands of dollars) Reconciliations of total segments to consolidated NGL and condensate sales $ 12,095,838 $ (1,794,342) $ 10,301,496 Residue natural gas sales 1,093,934 (2,832) 1,091,102 Gathering, processing and exchange services revenue 568,091 (21) 568,070 Transportation and storage revenue 613,987 (10,550) 603,437 Other 29,040 51 29,091 Total revenues (a) $ 14,400,890 $ (1,807,694) $ 12,593,196 Cost of sales and fuel (exclusive of depreciation and operating costs) $ (11,234,245) $ 1,811,537 $ (9,422,708) Operating costs $ (907,313) $ 245 $ (907,068) Depreciation and amortization $ (425,215) $ (3,342) $ (428,557) Equity in net earnings from investments $ 158,383 $ — $ 158,383 Investments in unconsolidated affiliates $ 969,150 $ — $ 969,150 Total assets $ 17,873,782 $ 357,889 $ 18,231,671 Capital expenditures $ 2,120,137 $ 21,338 $ 2,141,475 (a) - Noncustomer revenue for the year ended December 31, 2018, totaled $(16.2) million related primarily to losses from derivatives on commodity contract s. Years Ended December 31, 2020 2019 2018 Reconciliation of net income to total segment adjusted EBITDA ( Thousands of dollars ) Net income $ 612,809 $ 1,278,577 $ 1,155,032 Add: Interest expense, net of capitalized interest 712,886 491,773 469,620 Depreciation and amortization 578,662 476,535 428,557 Income tax expense 189,507 372,414 362,903 Impairment charges 644,930 — — Noncash compensation expense 8,540 26,699 37,954 Other corporate costs and equity AFUDC (a) (42,631) (68,767) (15,603) Total segment adjusted EBITDA $ 2,704,703 $ 2,577,231 $ 2,438,463 (a) - The year ended December 31, 2020, includes corporate net gains of $22.3 million on extinguishment of debt related to open market repurchases. The year ended December 31, 2019, includes higher equity AFUDC related to our capital-growth projects compared with 2020 and 2018.

QUARTERLY FINANCIAL DATA (UNAUD

QUARTERLY FINANCIAL DATA (UNAUDITED) (Notes)	12 Months Ended
QUARTERLY FINANCIAL DATA (UNAUDITED) (Notes)	Dec. 31, 2020
Quarterly Financial Data [Abstract]
QUARTERLY FINANCIAL DATA (UNAUDITED)	QUARTERLY FINANCIAL DATA (UNAUDITED) Year Ended December 31, 2020 First Second Third Fourth ( Thousands of dollars, except per share amounts ) Total revenues $ 2,136,672 $ 1,660,729 $ 2,174,264 $ 2,570,577 Operating income (loss) $ (83,469) $ 355,730 $ 550,433 $ 538,663 Net income (loss) $ (141,857) $ 134,321 $ 312,316 $ 308,029 Net income (loss) available to common shareholders $ (142,132) $ 134,046 $ 312,041 $ 307,754 Earnings (loss) per share total Basic $ (0.34) $ 0.32 $ 0.70 $ 0.69 Diluted $ (0.34) $ 0.32 $ 0.70 $ 0.69 (a) - Due to historic events as a result of COVID-19 impacting supply, demand and commodity prices, we evaluated our goodwill, certain long-lived asset groups and equity investments for impairment and recorded $641.8 million in impairment charges. (b) - In the second quarter 2020, due to the commodity price environment and continued global and regional economic disruptions due primarily to COVID-19, many of our crude oil and natural gas producers curtailed production, which significantly reduced volumes on our system. (c) - In the third quarter 2020, many of our producers reversed curtailments, bringing volumes back to pre-COVID-19 levels as prices and demand improved from second quarter 2020 lows and remained stable. Year Ended December 31, 2019 First Second Third Fourth ( Thousands of dollars except per share amounts ) Total revenues $ 2,779,958 $ 2,457,575 $ 2,263,228 $ 2,663,606 Operating income $ 468,742 $ 476,146 $ 482,151 $ 487,314 Net income $ 337,208 $ 311,963 $ 309,155 $ 320,251 Net income available to common shareholders $ 336,933 $ 311,688 $ 308,880 $ 319,976 EPS total Basic $ 0.82 $ 0.75 $ 0.75 $ 0.77 Diluted $ 0.81 $ 0.75 $ 0.74 $ 0.77

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	Dec. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Consolidation	Consolidation - Our Consolidated Financial Statements include our accounts and the accounts of our subsidiaries over which we have control or are the primary beneficiary. All intercompany balances and transactions have been eliminated in consolidation. Investments in unconsolidated affiliates are accounted for using the equity method if we have the ability to exercise significant influence over operating and financial policies of our investee. Under this method, an investment is carried at its acquisition cost and adjusted each period for contributions made, distributions received and our share of the investee’s comprehensive income. For the investments we account for under the equity method, the premium or excess cost over underlying fair value of net assets is referred to as equity-method goodwill. Impairment of equity investments is recorded when the impairments are other than temporary. These amounts are recorded as investments in unconsolidated affiliates on our accompanying Consolidated Balance Sheets. See Note M for disclosures of our unconsolidated affiliates. Distributions paid to us from our unconsolidated affiliates are classified as operating activities on our Consolidated Statements of Cash Flows until the cumulative distributions exceed our proportionate share of income from the unconsolidated affiliate since the date of our initial investment. The amount of cumulative distributions paid to us that exceeds our cumulative proportionate share of income in each period represents a return of investment and is classified as an investing activity on our Consolidated Statements of Cash Flows.
Use of Estimates	Use of Estimates - The preparation of our Consolidated Financial Statements and related disclosures in accordance with GAAP requires us to make estimates and assumptions with respect to values or conditions that cannot be known with certainty that affect the reported amounts on our Consolidated Financial Statements. Items that may be estimated include, but are not limited to, the economic useful life of assets, fair value of assets, liabilities and equity-method investments, obligations under employee benefit plans, provisions for uncollectible accounts receivable, expenses for services received but for which no invoice has been received, provision for income taxes, including any deferred tax valuation allowances, the results of litigation and various other recorded or disclosed amounts. In addition, a portion of our revenues and cost of sales and fuel are recorded based on current month prices and estimated volumes. The estimates are reversed in the following month when we record actual volumes and prices. We evaluate our estimates on an ongoing basis using historical experience, consultation with experts and other methods we consider reasonable based on the particular circumstances. Nevertheless, actual results may differ significantly from the estimates. Any effects on our financial position or results of operations from revisions to these estimates are recorded in the period when the facts that give rise to the revision become known.
Fair Value Measurements	Fair Value Measurements - For our fair value measurements, we utilize market prices, third-party pricing services, present value methods and standard option valuation models to determine the price we would receive from the sale of an asset or the transfer of a liability in an orderly transaction at the measurement date. We measure the fair value of a group of financial assets and liabilities consistent with how a market participant would price the net risk exposure at the measurement date. Many of the contracts in our derivative portfolio are executed in liquid markets where price transparency exists. Our financial commodity derivatives are generally settled through a NYMEX or ICE clearing broker account with daily margin requirements. We validate our valuation inputs with third-party information and settlement prices from other sources, where available. We compute the fair value of our derivative portfolio by discounting the projected future cash flows from our derivative assets and liabilities to present value using interest-rate yields to calculate present-value discount factors derived from the implied forward LIBOR yield curve. The fair value of our forward-starting interest-rate swaps is determined using financial models that incorporate the implied forward LIBOR yield curve for the same period as the future interest-rate swap settlements. We consider current market data in evaluating counterparties’, as well as our own, nonperformance risk, net of collateral, by using counterparty-specific bond yields. Although we use our best estimates to determine the fair value of the derivative contracts we have executed, the ultimate market prices realized could differ materially from our estimates. Fair Value Hierarchy - At each balance sheet date, we utilize a fair value hierarchy to classify fair value amounts recognized or disclosed in our financial statements based on the observability of inputs used to estimate such fair value. The levels of the hierarchy are described below: • Level 1 - fair value measurements are based on unadjusted quoted prices for identical securities in active markets. These balances are composed predominantly of exchange-traded derivative contracts for natural gas and crude oil. • Level 2 - fair value measurements are based on significant observable pricing inputs, including quoted prices for similar assets and liabilities in active markets and inputs from third-party pricing services supported with corroborative evidence. These balances are composed of over-the-counter interest-rate derivatives. • Level 3 - fair value measurements are based on inputs that may include one or more unobservable inputs, including internally developed commodity price curves that incorporate market data from broker quotes and third-party pricing services. These balances are composed predominantly of exchange-cleared and over-the-counter derivatives to hedge NGL price risk and natural gas basis risk between various transaction locations and the NYMEX Henry Hub. Our commodity derivatives are generally valued using forward quotes provided by third-party pricing services that are validated with other market data. We believe any measurement uncertainty at December 31, 2020, is immaterial as our Level 3 fair value measurements are based on unadjusted pricing information from broker quotes and third-party pricing services. We do not believe that our Level 3 fair value estimates have a material impact on our results of operations, as our derivatives are primarily accounted for as hedges. Determining the appropriate classification of our fair value measurements within the fair value hierarchy requires management’s judgment regarding the degree to which market data is observable or corroborated by observable market data. We categorize derivatives for which fair value is determined using multiple inputs within a single level, based on the lowest level input that is significant to the fair value measurement in its entirety. See Note B for our fair value measurements disclosures. Nonrecurring Fair Value Measurements - In 2020, we incurred noncash impairment charges for certain long-lived assets and equity investments. The valuation of these assets and investments required the use of significant unobservable inputs. To estimate the fair value, we used two generally accepted valuation approaches, an income approach and a market approach. Under the income approach, our discounted cash flow analysis included the following inputs that are not readily available: a discount rate reflective of industry cost of capital, our estimated contract rates, volumes, operating margins, operating and maintenance costs and capital expenditures. Under the market approach, our inputs included EBITDA multiples, which were estimated from recent peer acquisition transactions, and forecasted EBITDA, which incorporates inputs similar to those used under the income approach. The estimated fair value of these assets is classified as Level 3. See Note A for additional information about our impairment charges.
Cash and Cash Equivalents	Cash and Cash Equivalents - Cash equivalents consist of highly liquid investments, which are readily convertible into cash and have original maturities of three months or less.
Revenue from Contract with Customer [Policy Text Block]	Revenue Recognition - Revenues are recognized when control of the promised goods or services is transferred to our customers in an amount that reflects the consideration we expect to be entitled to receive in exchange for those goods or services. Our payment terms vary by customer and contract type, including requiring payment before products or services are delivered to certain customers. However, the term between customer prepayments, completion of our performance obligations, invoicing and receipt of payment due is not significant. Upon adoption of Topic 606 in January 2018, we determined that certain Natural Gas Gathering and Processing segment fee with POP contracts and Natural Gas Liquids segment exchange services contracts that include the purchase of commodities are supplier contracts. Contractual fees in these identified contracts are recorded as a reduction of the commodity purchase price in cost of sales and fuel. In 2017 and prior periods, these fees were recorded as services revenue. Performance Obligations and Revenue Sources - Revenue sources are disaggregated in Note Q and are derived from commodity sales and services revenues, as described below: Commodity Sales (all segments) - We contract to deliver residue natural gas, condensate, unfractionated NGLs and/or NGL products to customers at a specified delivery point. Our sales agreements may be daily or longer-term contracts for a specified volume. We consider the sale and delivery of each unit of a commodity an individual performance obligation as the customer is expected to control, accept and benefit from each unit individually. We record revenue when the commodity is delivered to the customer as this represents the point in time when control of the product is transferred to the customer. Revenue is recorded based on the contracted selling price, which is generally index-based and settled monthly. Services Gathering only contracts ( Natural Gas Gathering and Processing segment ) - Under this type of contract, we charge fees for providing midstream services, which include gathering and treating our customer’s natural gas. Our performance obligation begins with delivery of raw natural gas to our system. This service is treated as one performance obligation that is satisfied over time. We use the output method based on delivery of product to our system as the measure of progress, as our services are performed simultaneously. Fee with POP contracts with producer take-in-kind rights ( Natural Gas Gathering and Processing segment ) - Under this type of contract, we do not control the stream of unprocessed natural gas that we receive at the wellhead due to the producer’s take-in-kind rights. We purchase a portion of the raw natural gas stream, charge fees for providing midstream services, which include gathering, treating, compressing and processing our customer’s natural gas. After performing these services, we return primarily the residue natural gas to the producer, sell the remaining commodities and remit a portion of the commodity sales proceeds to the producer less our contractual fees. Our performance obligation begins with delivery of raw natural gas to our system. This service is treated as one performance obligation that is satisfied over time. We use the output method based on delivery of product to our system as the measure of progress, as our services are performed simultaneously. Transportation and exchange contracts ( Natural Gas Liquids segment ) - Under this type of contract, we charge fees for providing midstream services, which may include a bundled combination of gathering, transporting and/or fractionation of our customer’s NGLs. Our performance obligation begins with delivery of unfractionated NGLs or NGL products to our system. These services represent a series of distinct services that are treated as one performance obligation that is satisfied over time. We use the output method based on delivery of product to our system as the measure of progress, as our services are performed simultaneously. For transportation services under a tariff on our NGL transportation pipelines, fees are recorded upon redelivery to our customer at the completion of the transportation services. Storage contracts ( Natural Gas Liquids and Natural Gas Pipelines segments ) - We reserve a stated storage capacity and inject/withdraw/store commodities for our customer. The capacity reservation and injection/withdrawal/storage services are considered a bundled service, as we integrate them into one stand-ready obligation provided on a daily basis over the life of the agreement and satisfied over time. Fixed capacity reservation fees are allocated and evenly recognized in revenue. Capacity reservation fees that vary based on a stated or implied economic index and correspond with the costs to provide our services are recognized in revenue as invoiced to our customers. For contracts that do not include a capacity reservation, transportation, injection and withdrawal fees are recognized in revenue as those services are provided and are dependent on the volume transported, injected or withdrawn by our customer, which is at our customer’s discretion. We use the output method based on the passage of time to measure satisfaction of the performance obligation associated with our daily stand-ready services. Firm service transportation contracts ( Natural Gas Pipelines segment ) - We reserve a stated transportation capacity and transport commodities for our customer. The capacity reservation and transportation services are considered a bundled service, as we integrate them into one stand-ready obligation provided on a daily basis over the life of the agreement and satisfied over time. Fixed capacity reservation fees are allocated and evenly recognized in revenue. Capacity reservation fees that vary based on a stated or implied economic index and correspond with the costs to provide our services are recognized in revenue based on a daily effective fee rate. If the capacity reservation fees vary solely as a contract feature, contract assets or liabilities are recorded for the difference between the amount recorded in revenue and the amount billed to the customer. Transportation fees are recognized in revenue as those services are provided and are dependent on the volume transported by our customer, which is at our customer’s discretion. We use the output method based on the passage of time to measure satisfaction of the performance obligation associated with our daily stand-ready services. Interruptible transportation contracts ( Natural Gas Pipelines segment ) - We agree to transport natural gas on our pipelines between the customer’s specified nomination and delivery points if capacity is available after satisfying firm transportation service obligations. The transaction price is based on the transportation fees times the volumes transported. We use the output method based on delivery of product to the customer to measure satisfaction of the performance obligation. The total consideration for delivered volumes is recorded in revenue at the time of delivery, when the customer obtains control. See Note P for our revenue disclosures.
Cost of Sales and Fuel	Cost of Sales and Fuel - Cost of sales and fuel primarily includes (i) the cost of purchased commodities, including NGLs, natural gas and condensate, (ii) fees incurred for third-party transportation, fractionation and storage of commodities, (iii) fuel and power costs incurred to operate our own facilities that gather, process, transport and store commodities, and (iv) an offset from the contractual fees deducted from the cost of purchased commodities under the contract types below: Fee with POP contracts with no producer take-in-kind rights (Natural Gas Gathering and Processing segment ) - We purchase raw natural gas and charge contractual fees for providing midstream services, which include gathering, treating, compressing and processing the producer’s natural gas. After performing these services, we sell the commodities and return a portion of the commodity sales proceeds to the producer less our contractual fees. Purchase with fee ( Natural Gas Liquids segment ) -
Inventory	Inventory - The values of current NGLs and natural gas in storage are determined using the lower of weighted-average cost or net realizable value. Noncurrent NGLs and natural gas are classified as property and valued at cost. Materials and supplies are valued at average cost. Certain large equipment inventory, which will ultimately be capitalized to property, plant and equipment when utilized, is included in other assets in our Consolidated Balance Sheets and is valued at weighted-average cost.
Derivatives and Risk Management	Derivatives and Risk Management - We utilize derivatives to reduce our market-risk exposure to commodity price and interest-rate fluctuations and to achieve more predictable cash flows. We record all derivative instruments at fair value, with the exception of normal purchases and normal sales transactions that are expected to result in physical delivery. Commodity price and interest-rate volatility may have a significant impact on the fair value of derivative instruments as of a given date. The accounting for changes in the fair value of a derivative instrument depends on whether it has been designated and qualifies as part of a hedging relationship and, if so, the reason for holding it. The table below summarizes the various ways in which we account for our derivative instruments and the impact on our Consolidated Financial Statements: Recognition and Measurement Accounting Treatment Balance Sheet Income Statement Normal purchases and - Fair value not recorded - Change in fair value not recognized in earnings Mark-to-market - Recorded at fair value - Change in fair value recognized in earnings Cash flow hedge - The gain or loss on the - The gain or loss on the derivative instrument is reclassified out of accumulated other comprehensive income (loss) into earnings when the forecasted transaction affects earnings Fair value hedge - Recorded at fair value - The gain or loss on the derivative instrument is - Change in fair value of the hedged item is - Change in fair value of the hedged item is To reduce our exposure to fluctuations in natural gas, NGLs and condensate prices, we periodically enter into futures, forward purchases and sales, options or swap transactions in order to hedge anticipated purchases and sales of natural gas, NGLs and condensate. Interest-rate swaps are used from time to time to manage interest-rate risk. Under certain conditions, we designate our derivative instruments as a hedge of exposure to changes in fair values or cash flows. We formally document all relationships between hedging instruments and hedged items, as well as risk-management objectives and strategies for undertaking various hedge transactions, and methods for assessing and testing correlation and hedge effectiveness. We specifically identify the forecasted transaction that has been designated as the hedged item in a cash flow hedge relationship. We assess hedging relationships at the inception of the hedge and on an ongoing basis to determine whether the hedging relationship is, and is expected to remain, highly effective. We also document our normal purchases and normal sales transactions that we expect to result in physical delivery and that we elect to exempt from derivative accounting treatment. The realized revenues and purchase costs of our derivative instruments not considered held for trading purposes and derivatives that qualify as normal purchases or normal sales that are expected to result in physical delivery are reported on a gross basis. Cash flows from futures, forwards, options and swaps that are accounted for as hedges are included in the same category as the cash flows from the related hedged items in our Consolidated Statements of Cash Flows. See Notes B and C for disclosures of our fair value measurements and risk-management and hedging activities, respectively.
Property, Plant and Equipment	Property, Plant and Equipment - Our properties are stated at cost, including AFUDC and capitalized interest. In some cases, the cost of regulated property retired or sold, plus removal costs, less salvage, is charged to accumulated depreciation. Gains and losses from sales or transfers of nonregulated properties or an entire operating unit or system of our regulated properties are recognized in income. Maintenance and repairs are charged directly to expense. The interest portion of AFUDC and capitalized interest represent the cost of borrowed funds used to finance construction activities for regulated and nonregulated projects, respectively. We capitalize interest costs during the construction or upgrade of qualifying assets. These costs are recorded as a reduction to interest expense. The equity portion of AFUDC represents the capitalization of the estimated average cost of equity used during the construction of major projects and is recorded in the cost of our regulated properties and as a credit to the allowance for equity funds used during construction. Our properties are depreciated using the straight-line method over their estimated useful lives. Generally, we apply composite depreciation rates to functional groups of property having similar economic circumstances. We periodically conduct depreciation studies to assess the economic lives of our assets. For our regulated assets, these depreciation studies are completed as a part of our rate proceedings or tariff filings, and the changes in economic lives, if applicable, are implemented prospectively when the new rates are approved. For our nonregulated assets, if it is determined that the estimated economic life changes, the changes are made prospectively. Changes in the estimated economic lives of our property, plant and equipment could have a material effect on our financial position or results of operations. Property, plant and equipment on our Consolidated Balance Sheets includes construction work in process for capital projects that have not yet been placed in service and therefore are not being depreciated. Assets are transferred out of construction work in process when they are substantially complete and ready for their intended use. See Note D for our property, plant and equipment disclosures.
Impairment of Goodwill and Long-Lived Assets, including Intangible Assets	Impairment of Goodwill and Long-Lived Assets, Including Intangible Assets - We assess our goodwill for impairment at least annually as of July 1, unless events or changes in circumstances indicate an impairment may have occurred before that time. At July 1, 2020, we assessed qualitative factors subsequent to our first quarter 2020 impairment charges discussed below to determine whether it was more likely than not that the fair value of our Natural Gas Liquids and Natural Gas Pipelines reporting units were less than their carrying amount. After assessing qualitative factors (including macroeconomic conditions, industry and market considerations, cost factors and overall financial performance), we determined that it was more likely than not that the fair value of our Natural Gas Liquids and Natural Gas Pipelines reporting units were not less than their respective carrying value, no further testing was necessary and goodwill was not considered impaired. At July 1, 2020, there was no remaining goodwill associated with our Natural Gas Gathering and Processing reporting unit. Late in the first quarter 2020, we experienced a significant decline in our share price and market capitalization as the energy industry experienced historic events that led to a simultaneous demand and supply disruption. The World Health Organization declared COVID-19 a global pandemic and recommended containment and mitigation measures worldwide, which contributed to a massive economic slowdown and decreased demand for crude oil, natural gas and NGLs. In addition, Saudi Arabia and Russia increased production of crude oil as the two countries competed for market share. As a result, the global supply of crude oil significantly exceeded demand and led to a collapse in crude oil prices. Due to the impact of these events, we performed a Step 1 analysis in the first quarter 2020 to test our goodwill for impairment and evaluated certain long-lived asset groups and equity investments for impairment. Goodwill - In the Step 1 analysis, an assessment is made by comparing the fair value of a reporting unit with its carrying amount, including goodwill. If the carrying value of a reporting unit exceeds its fair value, an impairment loss is recognized in an amount equal to that excess, limited to the total amount of goodwill allocated to that reporting unit. In January 2020, we adopted ASU 2017-04 in which the requirement to calculate the implied fair value of goodwill under the two-step impairment test was eliminated. To estimate the fair value of our reporting units, we use two generally accepted valuation approaches, an income approach and a market approach, using assumptions consistent with a market participant’s perspective. Under the income approach, we use anticipated cash flows over a period of years plus a terminal value and discount these amounts to their present value using appropriate discount rates. Under the market approach, we apply EBITDA multiples to forecasted EBITDA. The multiples used are consistent with historical asset transactions. The forecasted cash flows are based on average forecasted cash flows for a reporting unit over a period of years. Based on the results of our impairment test, we concluded that the carrying value of the Natural Gas Gathering and Processing reporting unit exceeded its estimated fair value, resulting in a noncash impairment charge of $153.4 million, which is included within impairment charges in our Consolidated Statement of Income for the year ended December 31, 2020. The estimated fair value of our Natural Gas Liquids and Natural Gas Pipelines reporting units substantially exceeded their respective carrying values. Long-lived assets - We assess our long-lived assets for impairment whenever events or changes in circumstances indicate that an asset’s carrying amount may not be recoverable. An impairment is indicated if the carrying amount of a long-lived asset exceeds the sum of the undiscounted future cash flows expected to result from the use and eventual disposition of the asset. If an impairment is indicated, we record an impairment loss equal to the difference between the carrying value and the fair value of the long-lived asset. In 2020, we evaluated our Natural Gas Gathering and Processing segment asset groups and determined that the carrying value of certain long-lived asset groups in the Powder River Basin, western Oklahoma and Kansas were not recoverable and exceeded their estimated fair value. We recorded noncash impairment charges of $382.2 million, which includes a natural gas processing plant and infrastructure in the Powder River Basin and its related supply contracts and natural gas processing plants and infrastructure in western Oklahoma and Kansas. In our Natural Gas Liquids segment, we recorded noncash impairment charges of $71.6 million related primarily to certain inactive assets, as our expectation for future use of the assets changed. These charges are included within impairment charges in our Consolidated Statement of Income for the year ended December 31, 2020. Investments in unconsolidated affiliates - The impairment test for equity-method investments considers whether the fair value of the equity investment as a whole, not the underlying net assets, has declined and whether that decline is other than temporary. Therefore, we periodically evaluate the amount at which we carry our equity-method investments to determine whether current events or circumstances warrant adjustments to our carrying values. In 2020, we evaluated our investments in unconsolidated affiliates and concluded that the carrying value of our 10.2% investment in Venice Energy Services Company in our Natural Gas Gathering and Processing segment exceeded its estimated fair value, resulting in a noncash impairment charge of $30.5 million, which includes an impairment to our equity-method goodwill of $22.3 million. We also concluded that the carrying value of our 50% investment in Chisholm Pipeline Company in our Natural Gas Liquids segment exceeded its estimated fair value, resulting in a noncash impairment charge of $7.2 million. These impairment charges are included within impairment of equity investments in our Consolidated Statement of Income for the year ended December 31, 2020. See Notes D, E and M for our long-lived assets, goodwill and intangible assets and investments in unconsolidated affiliates disclosures, respectively.
Regulation	Regulation - Depending on the specific service provided, our natural gas transmission pipelines, NGL pipelines and certain natural gas storage facilities are subject to rate regulation and/or accounting requirements by one or more of the FERC, OCC, KCC and RRC. Accordingly, portions of our Natural Gas Liquids and Natural Gas Pipelines segments follow the accounting and reporting guidance for regulated operations. In our Consolidated Financial Statements and our Notes to Consolidated Financial Statements, regulated operations are defined pursuant to Financial Accounting Standards Board’s (FASB) ASC 980, Regulated Operations. During the rate-making process for certain of our assets, regulatory authorities set the framework for what we can charge customers for our services and establish the manner that our costs are accounted for, including allowing us to defer recognition of certain costs and permitting recovery of the amounts through rates over time as opposed to expensing such costs as incurred. Certain examples of types of regulatory guidance include costs for fuel and losses, acquisition costs, contributions in aid of construction, charges for depreciation, and gains or losses on disposition of assets. This allows us to stabilize rates over time rather than passing such costs on to the customer for immediate recovery. Actions by regulatory authorities could have an effect on the amounts we may charge our customers. Any difference in the amount recoverable and the amount deferred is recorded as income or expense at the time of the regulatory action. A write-off of regulatory assets and costs not recovered may be required if all or a portion of the regulated operations have rates that are no longer (i) established by independent, third-party regulators and (ii) set at levels that will recover our costs when considering the demand and competition for our services.
Retirement and Other Postretirement Employee Benefits	Retirement and Other Postretirement Employee Benefits - We have defined benefit retirement plans covering certain employees and former employees. We sponsor welfare plans that provide postretirement medical and life insurance benefits to certain employees hired prior to 2017 who retire with at least five years of service. The expense and liability related to these plans is calculated using statistical and other factors that attempt to anticipate future events. These factors include assumptions about the discount rate, expected return on plan assets, rate of future compensation increases, mortality and employment length. In determining the projected benefit obligations and costs, assumptions can change from period to period and may result in changes in the costs and liabilities we recognize. See Note K for our retirement and other postretirement employee benefits disclosures.
Income Taxes	Income Taxes - Deferred income taxes are provided for the difference between the financial statement and income tax basis of assets and liabilities and carryforward items based on income tax laws and rates existing at the time the temporary differences are expected to reverse. Generally, the effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date of the rate change. We utilize a more-likely-than-not recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position that is taken or expected to be taken in a tax return. We reflect penalties and interest as part of income tax expense as they become applicable for tax provisions that do not meet the more-likely-than-not recognition threshold and measurement attribute. During 2020, 2019 and 2018, we had no uncertain tax positions that required the establishment of a material reserve. We utilize the “with-and-without” approach for intra-period tax allocation for purposes of allocating total tax expense (or benefit) for the year among the various financial statement components. We file numerous consolidated and separate income tax returns with federal tax authorities of the United States along with the tax authorities of several states. We are not under any United States federal audits or statute waivers at this time. See Note L for our income taxes disclosures.
Asset Retirement Obligations	Asset Retirement Obligations - Asset retirement obligations represent legal obligations associated with the retirement of long-lived assets that result from the acquisition, construction, development and/or normal use of the asset. Certain of our natural gas gathering and processing, NGL and natural gas pipeline facilities are subject to agreements or regulations that give rise to our asset retirement obligations for removal or other disposition costs associated with retiring the assets in place upon the discontinued use of the assets. We recognize the fair value of a liability for an asset retirement obligation in the period when it is incurred if a reasonable estimate of the fair value can be made. We are not able to estimate reasonably the fair value of the asset retirement obligations for portions of our assets, primarily certain pipeline assets, because the settlement dates are indeterminable given our expected continued use of the assets with proper maintenance. We expect our pipeline assets, for which we are unable to estimate reasonably the fair value of the asset retirement obligation, will continue in operation as long as supply and demand for natural gas and NGLs exist. Based on the widespread use of natural gas for heating and cooking activities for residential users and electric-power generation for commercial users, as well as use of NGLs by the petrochemical industry, we expect supply and demand to exist for the foreseeable future. For our assets that we are able to make an estimate, the fair value of the liability is added to the carrying amount of the associated asset, and this additional carrying amount is depreciated over the life of the asset. The liability is accreted at the end of each period through charges to operating expense. If the obligation is settled for an amount other than the carrying amount of the liability, we will recognize a gain or loss on settlement. The depreciation and accretion expense are immaterial to our Consolidated Financial Statements.
Contingencies	Contingencies - Our accounting for contingencies covers a variety of business activities, including contingencies for legal and environmental exposures. We accrue these contingencies when our assessments indicate that it is probable that a liability has been incurred or an asset will not be recovered and an amount can be estimated reasonably. We expense legal fees as incurred and base our legal liability estimates on currently available facts and our estimates of the ultimate outcome or resolution. Accruals for estimated losses from environmental remediation obligations generally are recognized no later than completion of a remediation feasibility study. Recoveries of environmental remediation costs from other parties are recorded as assets when their receipt is deemed probable. Our expenditures for environmental evaluation, mitigation, remediation and compliance to date have not been significant in relation to our financial position or results of operations, and our expenditures related to environmental matters had no significant effect on earnings or cash flows during 2020, 2019 and 2018. Actual results may differ from our estimates resulting in an impact, positive or negative, on earnings. See Note N for additional discussion of contingencies.
Share-Based Payments	Share-Based Payments - We expense the fair value of share-based payments net of estimated forfeitures. We estimate forfeiture rates based on historical forfeitures under our share-based payment plans. See Note J for our share-based payments disclosures.
Earnings per Common Share	Earnings per Common Share - Basic EPS is calculated based on the daily weighted-average number of shares of common stock outstanding during the period, vested restricted and performance units that have been deferred and share awards deferred under the compensation plan for non-employee directors. Diluted EPS is calculated based on the daily weighted-average number of shares of common stock outstanding during the period plus potentially dilutive components. The dilutive components are calculated based on the dilutive effect for each quarter. For fiscal-year periods, the dilutive components for each quarter are averaged to arrive at the fiscal year-to-date dilutive component. See Note I for our EPS disclosures.
Segment Reporting, Policy [Policy Text Block]	Segment Reporting - Our chief operating decision-maker reviews the financial performance of each of our three segments, as well as our financial performance as a whole, on a regular basis. Adjusted EBITDA by segment is utilized in this evaluation. We believe this financial measure is useful to investors because it and similar measures are used by many companies in our industry as a measurement of financial performance and are commonly employed by financial analysts and others to evaluate our financial performance and to compare financial performance among companies in our industry. Adjusted EBITDA for each segment is defined as net income adjusted for interest expense, depreciation and amortization, noncash impairment charges, income taxes, allowance for equity funds used during construction, noncash compensation expense, and other noncash items. This calculation may not be comparable with similarly titled measures of other companies. See Note Q for our segments disclosures.
New Accounting Pronouncements	Except as discussed below, there have been no new accounting pronouncements that have become effective or have been issued that are of significance or potential significance to us. The following table provides a brief description of recently adopted accounting pronouncements and our analysis of the effects on our financial statements: Standard Description Date of Adoption Effect on the Financial Statements or Other Significant Matters Standards that were adopted as of December 31, 2020 ASU 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments” The standard requires a financial asset (or a group of financial assets) measured at amortized cost basis to be presented net of the allowance for credit losses to reflect the net carrying value at the amount expected to be collected on the financial asset; and the initial allowance for credit losses for purchased financial assets, including available-for-sale debt securities, to be added to the purchase price rather than being reported as a credit loss expense. First quarter 2020 The impact of adopting this standard was not material. ASU 2017-04, “Intangibles- Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment” The standard simplifies the subsequent measurement of goodwill by eliminating the requirement to calculate the implied fair value of goodwill under step 2. Instead, an entity will recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value. The standard does not change step zero or step 1 assessments. First quarter 2020 We adopted and implemented this standard prior to recording noncash impairment charges related to our goodwill, as described above. ASU 2020-04, “Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting” The standard provides optional expedients and exceptions for applying U.S. GAAP to contracts, hedging relationships and other transactions affected by reference rate reform if certain criteria are met. First quarter 2020 The impact of adopting this standard was not material. Standards that are not yet adopted as of December 31, 2020 ASU 2019-12, “Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes” The standard simplifies certain concepts in Topic 740, Income Taxes. First quarter 2021 We adopted this standard in January 2021, and the impact of adopting this standard was not material.
Operations and Maintenance	Operations and Maintenance - Operations and maintenance primarily includes (i) payroll and benefit costs, (ii) third-party costs for operations, maintenance and integrity management, regulatory compliance and environmental and safety, and (iii) other business-related service costs.
Accounts Receivable	Accounts Receivable - Accounts receivable represent valid claims against nonaffiliated customers for products sold or services rendered. Upon adoption of ASU 2016-13 in January 2020, we present accounts receivable net of an allowance for credit losses to reflect the net amount expected to be collected. We assess the creditworthiness of our counterparties on an ongoing basis and require security, including prepayments and other forms of collateral, when appropriate. Outstanding customer receivables are reviewed regularly for possible nonpayment indicators, and allowances for credit losses are recorded based upon management’s estimate of collectability, current conditions and supportable forecasts at each balance sheet date. At December 31, 2020, our allowance for credit losses was not material. See “Recently Issued Accounting Standards Update” table below for more information.
Commodity Imbalances	Commodity Imbalances - Commodity imbalances represent amounts payable or receivable for NGL exchange contracts and natural gas pipeline imbalances and are valued at market prices. Under the majority of our NGL exchange agreements, we physically receive volumes of unfractionated NGLs, including the risk of loss and legal title to such volumes, from the exchange counterparty. In turn, we deliver NGL products back to the customer and charge them gathering, transportation and fractionation fees. To the extent that the volumes we receive under such agreements differ from those we deliver, we record a net exchange receivable or payable position with the counterparties. These net exchange receivables and payables are generally settled with movements of NGL products rather than with cash. Natural gas pipeline imbalances are settled in cash or in-kind, subject to the terms of the pipelines’ tariffs or by agreement.

Fair Value Measures and Disclos

Fair Value Measures and Disclosures (Policies)	12 Months Ended
Fair Value Measures and Disclosures (Policies)	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements - For our fair value measurements, we utilize market prices, third-party pricing services, present value methods and standard option valuation models to determine the price we would receive from the sale of an asset or the transfer of a liability in an orderly transaction at the measurement date. We measure the fair value of a group of financial assets and liabilities consistent with how a market participant would price the net risk exposure at the measurement date. Many of the contracts in our derivative portfolio are executed in liquid markets where price transparency exists. Our financial commodity derivatives are generally settled through a NYMEX or ICE clearing broker account with daily margin requirements. We validate our valuation inputs with third-party information and settlement prices from other sources, where available. We compute the fair value of our derivative portfolio by discounting the projected future cash flows from our derivative assets and liabilities to present value using interest-rate yields to calculate present-value discount factors derived from the implied forward LIBOR yield curve. The fair value of our forward-starting interest-rate swaps is determined using financial models that incorporate the implied forward LIBOR yield curve for the same period as the future interest-rate swap settlements. We consider current market data in evaluating counterparties’, as well as our own, nonperformance risk, net of collateral, by using counterparty-specific bond yields. Although we use our best estimates to determine the fair value of the derivative contracts we have executed, the ultimate market prices realized could differ materially from our estimates. Fair Value Hierarchy - At each balance sheet date, we utilize a fair value hierarchy to classify fair value amounts recognized or disclosed in our financial statements based on the observability of inputs used to estimate such fair value. The levels of the hierarchy are described below: • Level 1 - fair value measurements are based on unadjusted quoted prices for identical securities in active markets. These balances are composed predominantly of exchange-traded derivative contracts for natural gas and crude oil. • Level 2 - fair value measurements are based on significant observable pricing inputs, including quoted prices for similar assets and liabilities in active markets and inputs from third-party pricing services supported with corroborative evidence. These balances are composed of over-the-counter interest-rate derivatives. • Level 3 - fair value measurements are based on inputs that may include one or more unobservable inputs, including internally developed commodity price curves that incorporate market data from broker quotes and third-party pricing services. These balances are composed predominantly of exchange-cleared and over-the-counter derivatives to hedge NGL price risk and natural gas basis risk between various transaction locations and the NYMEX Henry Hub. Our commodity derivatives are generally valued using forward quotes provided by third-party pricing services that are validated with other market data. We believe any measurement uncertainty at December 31, 2020, is immaterial as our Level 3 fair value measurements are based on unadjusted pricing information from broker quotes and third-party pricing services. We do not believe that our Level 3 fair value estimates have a material impact on our results of operations, as our derivatives are primarily accounted for as hedges. Determining the appropriate classification of our fair value measurements within the fair value hierarchy requires management’s judgment regarding the degree to which market data is observable or corroborated by observable market data. We categorize derivatives for which fair value is determined using multiple inputs within a single level, based on the lowest level input that is significant to the fair value measurement in its entirety. See Note B for our fair value measurements disclosures. Nonrecurring Fair Value Measurements - In 2020, we incurred noncash impairment charges for certain long-lived assets and equity investments. The valuation of these assets and investments required the use of significant unobservable inputs. To estimate the fair value, we used two generally accepted valuation approaches, an income approach and a market approach. Under the income approach, our discounted cash flow analysis included the following inputs that are not readily available: a discount rate reflective of industry cost of capital, our estimated contract rates, volumes, operating margins, operating and maintenance costs and capital expenditures. Under the market approach, our inputs included EBITDA multiples, which were estimated from recent peer acquisition transactions, and forecasted EBITDA, which incorporates inputs similar to those used under the income approach. The estimated fair value of these assets is classified as Level 3. See Note A for additional information about our impairment charges.

DEBT DEBT (Policies)

DEBT DEBT (Policies)	12 Months Ended
DEBT DEBT (Policies)	Dec. 31, 2020
Debt Instrument [Line Items]
Debt Policy	We amortize premiums, discounts and expenses incurred in connection with the issuance of long-term debt consistent with the terms of the respective debt instrument.

EMPLOYEE BENEFIT PLANS EMPLOYEE

EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS (Policies)	12 Months Ended
EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS (Policies)	Dec. 31, 2020
Defined Benefit Plan [Abstract]
Investment, Policy [Policy Text Block]	Plan Assets - Our investment strategy is to invest plan assets in accordance with sound investment practices that emphasize long-term fundamentals. The goal of this strategy is to maximize investment returns while managing risk in order to meet the plan’s current and projected financial obligations. The investment allocation for our other postretirement benefit plans is to target a diversified mix of approximately 30% fixed income and 70% equity securities. The investment allocation for our defined benefit pension plan follows a glide path approach of liability-driven investing that shifts a higher portfolio weighting to fixed income as the plan’s funded status increases. The purpose of liability-driven investing is to structure the asset portfolio to more closely resemble the pension liability and thereby more effectively hedge against changes in the liability. The plan’s current investments include a diverse blend of various domestic and international equities, investments in various classes of debt securities, real estate and hedge funds. The target allocation for the assets of our retirement plan as of December 31, 2020, is as follows: Domestic and international equities 42 % Long duration fixed income 30 % Return-seeking credit 11 % Hedge funds 10 % Real estate funds 7 % Total 100 % As part of our risk management for the plans, minimums and maximums have been set for each of the asset classes listed above.
Pension and Other Postretirement Plans, Policy [Policy Text Block]	Retirement and Other Postretirement Employee Benefits - We have defined benefit retirement plans covering certain employees and former employees. We sponsor welfare plans that provide postretirement medical and life insurance benefits to certain employees hired prior to 2017 who retire with at least five years of service. The expense and liability related to these plans is calculated using statistical and other factors that attempt to anticipate future events. These factors include assumptions about the discount rate, expected return on plan assets, rate of future compensation increases, mortality and employment length. In determining the projected benefit obligations and costs, assumptions can change from period to period and may result in changes in the costs and liabilities we recognize. See Note K for our retirement and other postretirement employee benefits disclosures.

LEASES (Policies)

LEASES (Policies)	12 Months Ended
LEASES (Policies)	Dec. 31, 2020
Leases [Abstract]
Lessee, Leases [Policy Text Block]	We lease certain buildings, warehouses, office space, pipeline capacity, land and equipment, including pipeline equipment, rail cars and information technology equipment. Our lease payments are generally straight-line and the exercise of lease renewal options, which vary in term, is at our sole discretion. We include renewal periods in a lease term if we are reasonably certain to exercise available renewal options. We apply the short-term policy election, which allows us to exclude from recognition leases with an initial term of 12 months or less. Our lease agreements do not include any residual value guarantees or material restrictive covenants.

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	12 Months Ended
FAIR VALUE MEASUREMENTS (Tables)	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Recurring Fair Value Measurements	The following tables set forth our recurring fair value measurements for the periods indicated: December 31, 2020 Level 1 Level 2 Level 3 Total - Gross Netting (a) Total - Net ( Thousands of dollars ) Derivative assets Commodity contracts Financial contracts $ 6,697 $ — $ 103,801 $ 110,498 $ (110,498) $ — Total derivative assets $ 6,697 $ — $ 103,801 $ 110,498 $ (110,498) $ — Derivative liabilities Commodity contracts Financial contracts $ (10,489) $ — $ (135,122) $ (145,611) $ 145,611 $ — Interest-rate contracts — (203,407) — (203,407) — (203,407) Total derivative liabilities $ (10,489) $ (203,407) $ (135,122) $ (349,018) $ 145,611 $ (203,407) (a) - Derivative assets and liabilities are presented in our Consolidated Balance Sheet on a net basis. We net derivative assets and liabilities when a legally enforceable master-netting arrangement exists between the counterparty to a derivative contract and us. At December 31, 2020, we held no cash and posted $63.1 million of cash with various counterparties, including $35.1 million of cash collateral that is offsetting derivative net liability positions under master-netting arrangements in the table above. The remaining $28.0 million of cash collateral in excess of derivative net liability positions is included in other current assets in our Consolidated Balance Sheet. December 31, 2019 Level 1 Level 2 Level 3 Total - Gross Netting (a) Total - Net ( Thousands of dollars ) Derivative assets Commodity contracts Financial contracts $ 10,892 $ — $ 55,557 $ 66,449 $ (28,588) $ 37,861 Interest-rate contracts — 581 — 581 — 581 Total derivative assets $ 10,892 $ 581 $ 55,557 $ 67,030 $ (28,588) $ 38,442 Derivative liabilities Commodity contracts Financial contracts $ (4,811) $ — $ (24,785) $ (29,596) $ 28,588 $ (1,008) Interest-rate contracts — (201,941) — (201,941) — (201,941) Total derivative liabilities $ (4,811) $ (201,941) $ (24,785) $ (231,537) $ 28,588 $ (202,949) (a) - Derivative assets and liabilities are presented in our Consolidated Balance Sheet on a net basis. We net derivative assets and liabilities when a legally enforceable master-netting arrangement exists between the counterparty to a derivative contract and us. At December 31, 2019, we held no cash and posted $8.8 million of cash with various counterparties, which is included in other current assets in our Consolidated Balance Sheet.
Reconciliation of Level 3 Fair Value Measurements	The following table sets forth a reconciliation of our Level 3 fair value measurements for the periods indicated: Years Ended December 31, Derivative Assets (Liabilities) 2020 2019 ( Thousands of dollars ) Net assets at beginning of period $ 30,772 $ 40,484 Total changes in fair value: Settlements included in net income (a) (31,660) (40,344) New Level 3 derivatives included in other comprehensive loss (b) (36,568) 30,627 Unrealized change included in other comprehensive loss (b) 6,135 5 Net assets (liabilities) at end of period $ (31,321) $ 30,772 (a) - Included in commodity sales revenues/cost of sales and fuel in our Consolidated Statements of Income. (b) - Included in change in fair value of derivatives in our Consolidated Statements of Comprehensive Income.

RISK MANAGEMENT AND HEDGING A_2

RISK MANAGEMENT AND HEDGING ACTIVITIES USING DERIVATIVES (Tables)	12 Months Ended
	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fair Value of Derivatives	The following table sets forth the fair values of our derivative instruments presented on a gross basis for the periods indicated: December 31, 2020 December 31, 2019 Location in our Consolidated Balance Sheets Assets (Liabilities) Assets (Liabilities) ( Thousands of dollars ) Derivatives designated as hedging instruments Commodity contracts (a) Financial contracts (b) Other current assets $ 107,461 $ (142,573) $ 64,858 $ (26,997) Other deferred credits — — 1,591 (2,599) Interest-rate contracts Other current liabilities — — — (90,161) Other assets/other deferred credits — (203,407) 581 (111,780) Total derivatives designated as hedging instruments 107,461 (345,980) 67,030 (231,537) Derivatives not designated as hedging instruments Commodity contracts (a) Financial contracts (b) 3,037 (3,038) — — Total derivatives not designated as hedging instruments 3,037 (3,038) — — Total derivatives $ 110,498 $ (349,018) $ 67,030 $ (231,537) (a) - Derivative assets and liabilities are presented in our Consolidated Balance Sheets on a net basis when a legally enforceable master-netting arrangement exists between the counterparty to a derivative contract and us. (b) - At December 31, 2020, our derivative net liability positions under master-netting arrangements for financial contracts were fully offset by $35.1 million of cash collateral.
Notional Amounts of Derivative Instruments	The following table sets forth the notional quantities for derivative instruments held for the periods indicated: December 31, 2020 December 31, 2019 Contract Net Purchased/Payor Derivatives designated as hedging instruments: (a) Cash flow hedges Fixed price -Natural gas ( Bcf ) Futures (43.3) (59.0) -Crude oil and NGLs ( MMBbl ) Futures (4.6) (9.5) Basis -Natural gas ( Bcf ) Futures (43.3) (59.0) Interest-rate contracts ( Billions of dollars ) Swaps $ 1.1 $ 3.1
Schedule of Cash Flow Hedging Instruments Effect on Comprehensive Income (Loss)	The following table sets forth the unrealized change in fair value of cash flow hedges in other comprehensive income (loss) for the periods indicated: Years Ended December 31, 2020 2019 2018 ( Thousands of dollars ) Commodity contracts $ (5,699) $ 38,819 $ 53,217 Interest-rate contracts (208,616) (230,771) (60,584) Total unrealized change in fair value of cash flow hedges in other comprehensive income (loss) $ (214,315) $ (191,952) $ (7,367)
Schedule of Cash Flow Hedging Instruments Effect on Income	The following table sets forth the effect of cash flow hedges on net income for the periods indicated: Derivatives in Cash Flow Location of Gain (Loss) Reclassified from Years Ended December 31, 2020 2019 2018 ( Thousands of dollars ) Commodity contracts Commodity sales revenues $ 85,436 $ 94,547 $ (37,596) Cost of sales and fuel (19,170) (44,202) 8,000 Interest-rate contracts (a) Interest expense (93,676) (23,230) (18,287) Total change in fair value of cash flow hedges reclassified from accumulated other comprehensive loss into net income on derivatives $ (27,410) $ 27,115 $ (47,883) (a) - The year ended December 31, 2020, includes a loss of $48.3 million on the settlement of our remaining $1.3 billion interest-rate swaps used to hedge our LIBOR-based interest payments.

PROPERTY, PLANT AND EQUIPMENT_2

PROPERTY, PLANT AND EQUIPMENT (Tables)	12 Months Ended
PROPERTY, PLANT AND EQUIPMENT (Tables)	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment by Property Type	The following table sets forth our property, plant and equipment by property type, for the periods indicated: Estimated Useful December 31, December 31, ( Thousands of dollars ) Nonregulated Gathering pipelines and related equipment 5 to 40 $ 4,143,752 $ 4,316,936 Processing and fractionation and related equipment 3 to 40 5,084,802 4,439,332 Storage and related equipment 3 to 54 798,785 684,635 Transmission pipelines and related equipment 5 to 54 810,434 797,678 General plant and other 2 to 60 647,675 610,013 Construction work in process — 1,265,736 1,645,663 Regulated Storage and related equipment 5 to 25 9,180 9,180 Natural gas transmission pipelines and related equipment 5 to 77 1,569,268 1,552,546 NGL transmission pipelines and related equipment 5 to 88 8,423,544 6,126,056 General plant and other 2 to 50 72,535 66,507 Construction work in process — 247,224 1,802,946 Property, plant and equipment 23,072,935 22,051,492 Accumulated depreciation and amortization - nonregulated (2,514,328) (2,471,649) Accumulated depreciation and amortization - regulated (1,403,679) (1,231,158) Net property, plant and equipment $ 19,154,928 $ 18,348,685
Average Depreciation Rates for Regulated Property	The average depreciation rates for our regulated property are set forth, by segment, in the following table for the periods indicated: Years Ended December 31, 2020 2019 2018 Natural Gas Liquids 2.2% 2.0% 1.9% Natural Gas Pipelines 2.1% 2.1% 2.1%

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS (Tables)	12 Months Ended
GOODWILL AND INTANGIBLE ASSETS (Tables)	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill by Segment	The following table sets forth our goodwill, by segment, for the periods indicated: December 31, December 31, ( Thousands of dollars ) Natural Gas Gathering and Processing $ — $ 153,404 Natural Gas Liquids 371,217 371,217 Natural Gas Pipelines 156,375 156,375 Total goodwill $ 527,592 $ 680,996
Gross Carrying Amount and Accumulated Amortization of Intangible Assets	The following table reflects the gross carrying amount and accumulated amortization of intangible assets for the periods presented: December 31, December 31, ( Thousands of dollars ) Gross intangible assets $ 381,435 $ 414,345 Accumulated amortization (135,304) (137,508) Net intangible assets $ 246,131 $ 276,837

DEBT (Tables)

DEBT (Tables)	12 Months Ended
DEBT (Tables)	Dec. 31, 2020
Long-term Debt, Unclassified [Abstract]
Debt	The following table sets forth our consolidated debt for the periods indicated: December 31, December 31, (Thousands of dollars) Commercial paper outstanding, bearing a weighted-average interest rate of 2.16% as of December 31, 2019 $ — $ 220,000 Senior unsecured obligations: $1,500,000 term loan at 2.70% as of December 31, 2019, due November 2021 — 1,250,000 $700,000 at 4.25% due February 2022 541,877 547,397 $900,000 at 3.375% due October 2022 895,814 900,000 $425,000 at 5.0% due September 2023 425,000 425,000 $500,000 at 7.5% due September 2023 500,000 500,000 $500,000 at 2.75% due September 2024 500,000 500,000 $500,000 at 4.9% due March 2025 500,000 500,000 $400,000 at 2.2% due September 2025 387,000 — $600,000 at 5.85% due January 2026 600,000 — $500,000 at 4.0% due July 2027 500,000 500,000 $800,000 at 4.55% due July 2028 800,000 800,000 $100,000 at 6.875% due September 2028 100,000 100,000 $700,000 at 4.35% due March 2029 700,000 700,000 $750,000 at 3.4% due September 2029 714,251 750,000 $850,000 at 3.1% due March 2030 780,093 — $600,000 at 6.35% due January 2031 600,000 — $400,000 at 6.0% due June 2035 400,000 400,000 $600,000 at 6.65% due October 2036 600,000 600,000 $600,000 at 6.85% due October 2037 600,000 600,000 $650,000 at 6.125% due February 2041 650,000 650,000 $400,000 at 6.2% due September 2043 400,000 400,000 $700,000 at 4.95% due July 2047 689,006 700,000 $1,000,000 at 5.2% due July 2048 1,000,000 1,000,000 $750,000 at 4.45% due September 2049 713,676 750,000 $500,000 at 4.5% due March 2050 451,270 — $300,000 at 7.15% due January 2051 300,000 — Guardian Pipeline Weighted average 7.85% due December 2022 13,657 21,307 Total debt 14,361,644 12,813,704 Unamortized portion of terminated swaps 13,314 15,032 Unamortized debt issuance costs and discounts (138,887) (121,329) Current maturities of long-term debt (7,650) (7,650) Short-term borrowings (a) — (220,000) Long-term debt $ 14,228,421 $ 12,479,757 (a) - Individual issuances of commercial paper under our commercial paper program generally mature in 90 days or less.
Aggregate maturities of long-term debt outstanding	The aggregate maturities of long-term debt outstanding as of December 31, 2020, for the years 2021 through 2025 are shown below: Senior Guardian Total (Millions of dollars) 2021 $ — $ 7.7 $ 7.7 2022 $ 1,437.7 $ 6.0 $ 1,443.7 2023 $ 925.0 $ — $ 925.0 2024 $ 500.0 $ — $ 500.0 2025 $ 887.0 $ — $ 887.0

EQUITY EQUITY (Tables)

EQUITY EQUITY (Tables)	12 Months Ended
EQUITY EQUITY (Tables)	Dec. 31, 2020
Equity [Abstract]
Quarterly dividends per share paid on common stock	The following table sets forth the quarterly dividends per share paid on our common stock in the periods indicated: Years Ended December 31, 2020 2019 2018 First Quarter $ 0.935 $ 0.860 $ 0.770 Second Quarter 0.935 0.865 0.795 Third Quarter 0.935 0.890 0.825 Fourth Quarter 0.935 0.915 0.855 Total $ 3.74 $ 3.53 $ 3.245

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)	12 Months Ended
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)	Dec. 31, 2020
Accumulated Other Comprehensive Loss	The following table sets forth the balance in accumulated other comprehensive loss for the periods indicated: Risk- Retirement and Other Risk- Accumulated ( Thousands of dollars ) January 1, 2019 $ (64,660) $ (121,785) $ (1,794) $ (188,239) Other comprehensive loss before reclassifications (147,803) (19,490) (7,275) (174,568) Amounts reclassified to net income (c) (21,057) 9,794 70 (11,193) Other comprehensive loss (168,860) (9,696) (7,205) (185,761) December 31, 2019 (233,520) (131,481) (8,999) (374,000) Other comprehensive loss before reclassifications (165,023) (40,341) (8,635) (213,999) Amounts reclassified to net income (c) 21,097 14,187 1,266 36,550 Other comprehensive loss (143,926) (26,154) (7,369) (177,449) December 31, 2020 $ (377,446) $ (157,635) $ (16,368) $ (551,449) (a) - All amounts are presented net of tax. (b) - Includes amounts related to supplemental executive retirement plan. (c) - See Note C for details of amounts reclassified to net income for risk-management assets/liabilities and Note K for retirement and other postretirement benefit plan obligations.
Schedule of Accumulated Other Comprehensive Loss for Risk-Management Assets/Liabilities [Table Text Block]	The following table sets forth information about the balance of accumulated other comprehensive loss at December 31, 2020, representing unrealized gains (losses) related to risk-management assets and liabilities: Risk- ( Thousands of dollars ) Commodity derivative instruments expected to be realized within the next 24 months (b) $ (27,303) Settled interest-rate swaps to be recognized over the life of the long-term, fixed-rate debt (c) (193,519) Interest-rate swaps with future settlement dates expected to be amortized over the life of long-term debt (156,624) Accumulated other comprehensive loss at December 31, 2020 $ (377,446) (a) - All amounts are presented net of tax. (b) - Based on December 31, 2020, commodity prices, we expect $27.0 million in net losses, net of tax, over the next 12 months and $0.3 million in net losses, net of tax, thereafter. (c) - We expect net losses of $30.5 million, net of tax, will be reclassified into earnings during the next 12 months.

EARNINGS PER SHARE EARNINGS P_2

EARNINGS PER SHARE EARNINGS PER SHARE (Tables)	12 Months Ended
EARNINGS PER SHARE EARNINGS PER SHARE (Tables)	Dec. 31, 2020
Earnings Per Share [Abstract]
Earnings Per Share	The following tables set forth the computation of basic and diluted EPS for the periods indicated: Year Ended December 31, 2020 Income Shares Per Share ( Thousands, except per share amounts ) Basic EPS Net income available for common stock $ 611,709 431,105 $ 1.42 Diluted EPS Effect of dilutive securities — 677 Net income available for common stock and common stock equivalents $ 611,709 431,782 $ 1.42 Year Ended December 31, 2019 Income Shares Per Share ( Thousands, except per share amounts ) Basic EPS Net income available for common stock $ 1,277,477 413,560 $ 3.09 Diluted EPS Effect of dilutive securities — 1,884 Net income available for common stock and common stock equivalents $ 1,277,477 415,444 $ 3.07 Year Ended December 31, 2018 Income Shares Per Share ( Thousands, except per share amounts ) Basic EPS Net income attributable to ONEOK available for common stock $ 1,150,603 411,485 $ 2.80 Diluted EPS Effect of dilutive securities — 2,710 Net income attributable to ONEOK available for common stock and common stock equivalents $ 1,150,603 414,195 $ 2.78

SHARE-BASED PAYMENTS SHARE-BA_2

SHARE-BASED PAYMENTS SHARE-BASED PAYMENTS (Tables)	12 Months Ended
SHARE-BASED PAYMENTS SHARE-BASED PAYMENTS (Tables)	Dec. 31, 2020
Restricted Stock Units Activity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Compensation, Activity	The following tables set forth activity and various statistics for our restricted stock unit awards: Number of Weighted Nonvested December 31, 2019 698,990 $ 54.05 Granted 216,392 $ 76.49 Released to participants (240,576) $ 46.58 Forfeited (28,519) $ 65.20 Nonvested December 31, 2020 646,287 $ 63.85 2020 2019 2018 Weighted-average grant date fair value (per share) $ 76.49 $ 58.07 $ 46.94 Fair value of units granted (thousands of dollars) $ 16,552 $ 15,238 $ 13,907 Grant date fair value of units vested (thousands of dollars) $ 11,204 $ 10,691 $ 9,552
Performance-Unit Activity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Compensation, Activity	The following tables set forth activity and various statistics related to the performance unit awards and the assumptions used in the valuations at the respective grant dates: Number of Weighted Nonvested December 31, 2019 937,821 $ 66.67 Granted 283,029 $ 88.43 Released to participants (300,423) $ 58.99 Forfeited (86,181) $ 74.83 Nonvested December 31, 2020 834,246 $ 75.96 2020 2019 2018 Volatility (a) 21.70% 27.10% 39.20% Dividend yield 4.87% 5.05% 5.49% Risk-free interest rate 1.39% 2.47% 2.44% (a) - Volatility was based on historical volatility over three years using daily stock price observations. 2020 2019 2018 Weighted-average grant date fair value (per share) $ 88.43 $ 68.02 $ 59.57 Fair value of units granted (thousands of dollars) $ 25,028 $ 23,020 $ 22,081 Grant date fair value of units vested (thousands of dollars) $ 17,722 $ 15,018 $ 12,545

EMPLOYEE BENEFIT PLANS EMPLOY_2

EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS (Tables)	12 Months Ended
EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS (Tables)	Dec. 31, 2020
Defined Benefit Plan [Abstract]
Pension and postretirement benefit plans obligations and fair value of plan assets	The following table sets forth our retirement and other postretirement benefit plans benefit obligations and fair value of plan assets for the periods indicated: Retirement Benefits Other Postretirement Benefits December 31, December 31, 2020 2019 2020 2019 Change in benefit obligation ( Thousands of dollars ) Benefit obligation, beginning of period $ 534,849 $ 466,994 $ 52,309 $ 46,840 Service cost 8,154 7,825 460 468 Interest cost 18,318 20,528 1,771 2,038 Plan participants’ contributions — — 1,032 1,142 Actuarial loss 37,951 55,954 2,860 5,101 Benefits paid (16,200) (16,452) (3,917) (3,280) Benefit obligation, end of period 583,072 534,849 54,515 52,309 Change in plan assets Fair value of plan assets, beginning of period 346,792 290,684 39,060 30,800 Actual return on plan assets (a) 36,400 58,060 (15,699) 8,087 Employer contributions 12,100 14,500 — 2,000 Plan participants’ contributions — — 1,032 1,142 Benefits paid (16,200) (16,452) (3,519) (2,969) Fair value of plan assets, end of period 379,092 346,792 20,874 39,060 Balance at December 31 $ (203,980) $ (188,057) $ (33,641) $ (13,249) Current liabilities $ (4,679) $ (4,616) $ — $ — Noncurrent liabilities (199,301) (183,441) (33,641) (13,249) Balance at December 31 $ (203,980) $ (188,057) $ (33,641) $ (13,249) (a) - Other Postretirement Benefits for the year ended December 31, 2020, includes a $13.2 million tax loss incurred from the exit of an investment in an insurance contract.
Components of net periodic benefit cost for pension and postretirement benefit plans	The following table sets forth the components of net periodic benefit cost for our retirement and other postretirement benefit plans for the periods indicated: Retirement Benefits Other Postretirement Benefits Years Ended December 31, Years Ended December 31, 2020 2019 2018 2020 2019 2018 ( Thousands of dollars ) Components of net periodic benefit cost Service cost $ 8,154 $ 7,825 $ 7,339 $ 460 $ 468 $ 845 Interest cost 18,318 20,528 17,659 1,771 2,038 2,108 Expected return on plan assets (24,964) (23,600) (23,917) (2,894) (2,285) (2,690) Amortization of prior service cost (credit) 114 — — — (227) (1,662) Amortization of net loss 18,306 12,649 17,060 5 297 1,338 Net periodic benefit cost (income) $ 19,928 $ 17,402 $ 18,141 $ (658) $ 291 $ (61)
Amounts recognized in other comprehensive income (loss)	The following table sets forth the amounts recognized in other comprehensive income (loss) related to our retirement and other postretirement benefits for the periods indicated: Retirement Benefits Other Postretirement Benefits Years Ended December 31, Years Ended December 31, 2020 2019 2018 2020 2019 2018 ( Thousands of dollars ) Net gain (loss) (a) $ (31,016) $ (25,389) $ (16,351) $ (21,453) $ 700 $ 6,545 Prior service cost — (601) — — — — Amortization of prior service cost (credit) (b) 114 — — — (227) (1,662) Amortization of net loss (b) 18,306 12,649 17,060 5 297 1,338 Deferred income taxes (c) 2,897 3,068 (18,928) 4,933 (177) (2,831) Total recognized in other comprehensive income (loss) $ (9,699) $ (10,273) $ (18,219) $ (16,515) $ 593 $ 3,390 (a) - Other Postretirement Benefits for the year ended December 31, 2020, includes a $13.2 million tax loss incurred from the exit of an investment in an insurance contract. (b) - These components are recognized in accumulated other comprehensive loss and are reclassified to other expense in our Consolidated Statements of Income, with related income tax benefits of $4.2 million, $2.9 million and $3.8 million reclassified to income tax expense for the years ended December 31, 2020, 2019, and 2018, respectively. (c) - Year ended December 31, 2018, includes the impact of adopting ASU 2018-02, “Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.”
Amounts in accumulated other comprehensive income (loss)	The table below sets forth the amounts in accumulated other comprehensive loss that had not yet been recognized as components of net periodic benefit expense for the periods indicated: Retirement Benefits Other Postretirement Benefits December 31, December 31, 2020 2019 2020 2019 ( Thousands of dollars ) Prior service cost $ (487) $ (601) $ — $ — Accumulated loss (a) (185,662) (172,952) (25,558) (4,110) Accumulated other comprehensive loss (186,149) (173,553) (25,558) (4,110) Deferred income taxes 49,251 46,354 6,322 1,389 Accumulated other comprehensive loss, net of tax $ (136,898) $ (127,199) $ (19,236) $ (2,721) (a) - Other Postretirement Benefits for the year ended December 31, 2020, includes a $13.2 million tax loss incurred from the exit of an investment in an insurance contract.
Weighted-average assumptions used to determine benefit obligations and net periodic benefit costs	The following table sets forth the weighted-average assumptions used to determine benefit obligations for retirement and other postretirement benefits for the periods indicated: Retirement Benefits Other Postretirement Benefits December 31, December 31, 2020 2019 2020 2019 Discount rate 3.00% 3.50% 2.75% 3.50% Compensation increase rate 3.60% 3.70% NA NA The following table sets forth the weighted-average assumptions used to determine net periodic benefit costs for the periods indicated: Years Ended December 31, 2020 2019 2018 Discount rate - retirement plans 3.50% 4.50% 3.75% Discount rate - other postretirement plans 3.50% 4.50% 3.75% Expected long-term return on plan assets 7.50% 7.50% 8.00% Compensation increase rate 3.70% 3.65% 3.00%
Assumed health care cost trend rates	The following table sets forth the assumed health care cost-trend rates for the periods indicated: 2020 2019 Health care cost-trend rate assumed for next year 6.50% 7.00% Rate to which the cost-trend rate is assumed to decline (the ultimate trend rate) 5.00% 5.00% Year that the rate reaches the ultimate trend rate 2024 2024
Schedule of allocation of plan assets	Our investment strategy is to invest plan assets in accordance with sound investment practices that emphasize long-term fundamentals. The goal of this strategy is to maximize investment returns while managing risk in order to meet the plan’s current and projected financial obligations. The investment allocation for our other postretirement benefit plans is to target a diversified mix of approximately 30% fixed income and 70% equity securities. The investment allocation for our defined benefit pension plan follows a glide path approach of liability-driven investing that shifts a higher portfolio weighting to fixed income as the plan’s funded status increases. The purpose of liability-driven investing is to structure the asset portfolio to more closely resemble the pension liability and thereby more effectively hedge against changes in the liability. The plan’s current investments include a diverse blend of various domestic and international equities, investments in various classes of debt securities, real estate and hedge funds. The target allocation for the assets of our retirement plan as of December 31, 2020, is as follows: Domestic and international equities 42 % Long duration fixed income 30 % Return-seeking credit 11 % Hedge funds 10 % Real estate funds 7 % Total 100 % As part of our risk management for the plans, minimums and maximums have been set for each of the asset classes listed above. The following tables set forth the plan assets by fair value category as of the measurement date for our defined benefit pension and other postretirement benefit plans: Pension Benefits December 31, 2020 Asset Category Level 1 Level 2 Level 3 Subtotal Measured at NAV (d) Total ( Thousands of dollars ) Investments: Equity securities (a) $ 43 $ — $ — $ 43 $ 164,099 $ 164,142 Real estate funds — — — — 24,134 24,134 Government obligations — — — — 45,237 45,237 Corporate obligations (b) — — — — 101,626 101,626 Common/collective trusts — 4,890 — 4,890 — 4,890 Other investments (c) — — — — 39,063 39,063 Fair value of plan assets $ 43 $ 4,890 $ — $ 4,933 $ 374,159 $ 379,092 (a) - This category represents securities of the respective market sector from diverse industries. (b) - This category represents bonds from diverse industries. (c) - This category repre sen ts alternative investments in limited partnerships, which can be redeemed with a 30-day notice with no further restrictions. There are no u nfunded capital commitments. (d) - Plan asset investments measured at fair value using the net asset value per share. Pension Benefits December 31, 2019 Asset Category Level 1 Level 2 Level 3 Subtotal Measured at NAV (d) Total ( Thousands of dollars ) Investments: Equity securities (a) $ 47 $ — $ — $ 47 $ 149,985 $ 150,032 Real estate funds — — — — 23,885 23,885 Government obligations — — — — 50,708 50,708 Corporate obligations (b) — — — — 85,898 85,898 Common/collective trusts — 3,263 — 3,263 — 3,263 Cash 63 — — 63 — 63 Other investments (c) — — — — 32,943 32,943 Fair value of plan assets $ 110 $ 3,263 $ — $ 3,373 $ 343,419 $ 346,792 (a) - This category represents securities of the respective market sector from diverse industries. (b) - This category represents bonds from diverse industries. (c) - This category represents alternative investments in limited partnerships, which can be redeemed with a 30-day notice with no further restrictions. There are no unfunded capital commitments. (d) - Plan asset investments measured at fair value using the net asset value per share. Other Postretirement Benefits December 31, 2020 Asset Category Level 1 Level 2 Level 3 Total ( Thousands of dollars ) Investments: Equity securities (a) (b) $ 15,116 $ — $ — $ 15,116 Money market funds — 808 — 808 Municipal obligations (b) 4,950 — — 4,950 Fair value of plan assets $ 20,066 $ 808 $ — $ 20,874 (a) - This category represents securities of the respective market sector from diverse industries. (b) - Net proceeds of $16.2 million from the exit of an investment in an insurance contract were reinvested in various equity securities and municipal obligations. Other Postretirement Benefits December 31, 2019 Asset Category Level 1 Level 2 Level 3 Total ( Thousands of dollars ) Investments: Equity securities (a) $ 2,043 $ — $ — $ 2,043 Money market funds — 2,428 — 2,428 Insurance and group annuity contracts — 34,589 — 34,589 Fair value of plan assets $ 2,043 $ 37,017 $ — $ 39,060 (a) - This category represents securities of the respective market sector from diverse industries.
Pension benefits and postretirement benefit payments expected to be paid	The following table sets forth the defined benefit pension and other postretirement benefits payments expected to be paid in 2021 through 2030: Pension Other Postretirement Benefits to be paid in: ( Thousands of dollars ) 2021 $ 19,460 $ 3,297 2022 $ 20,325 $ 3,408 2023 $ 21,216 $ 3,371 2024 $ 22,234 $ 3,335 2025 $ 23,260 $ 3,322 2026 through 2030 $ 127,038 $ 15,848

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
INCOME TAXES (Tables)	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Provision for Income Taxes	The following table sets forth our provision for income taxes for the periods indicated: Years Ended December 31, 2020 2019 2018 ( Thousands of dollars ) Current tax expense (benefit) Federal $ 980 $ (1,278) $ 260 State 1,797 963 1,633 Total current tax expense (benefit) 2,777 (315) 1,893 Deferred tax expense Federal 154,068 327,806 319,551 State 32,662 44,923 41,459 Total deferred tax expense 186,730 372,729 361,010 Total provision for income taxes $ 189,507 $ 372,414 $ 362,903
Reconciliation of Income Tax Provision	The following table is a reconciliation of our income tax provision for the periods indicated: Years Ended December 31, 2020 2019 2018 ( Thousands of dollars ) Income before income taxes $ 802,316 $ 1,650,991 $ 1,517,935 Less: Net income attributable to noncontrolling interests — — 3,329 Net income attributable to ONEOK before income taxes 802,316 1,650,991 1,514,606 Federal statutory income tax rate 21.0 % 21.0 % 21.0 % Provision for federal income taxes 168,486 346,708 318,067 State income taxes, net of federal benefit 13,580 34,545 38,668 Deferred tax rate change, inclusive of valuation allowance 20,879 11,340 5,552 Excess tax benefits from share-based compensation (7,380) (20,983) (4,644) Other, net (6,058) 804 5,260 Income tax provision $ 189,507 $ 372,414 $ 362,903
Schedule of Deferred Tax Assets and Liabilities	The following table sets forth the tax effects of temporary differences that gave rise to significant portions of the deferred tax assets and liabilities for the periods indicated: December 31, December 31, Deferred tax assets ( Thousands of dollars ) Employee benefits and other accrued liabilities $ 96,741 $ 99,510 Federal net operating loss 1,473,093 858,030 State net operating loss and benefits 258,929 171,779 Derivative instruments 134,499 83,710 Other 12,894 12,769 Total deferred tax assets 1,976,156 1,225,798 Valuation allowance for state net operating loss and tax credits Carryforward expected to expire prior to utilization (121,212) (94,794) Net deferred tax assets 1,854,944 1,131,004 Deferred tax liabilities Excess of tax over book depreciation 87,021 84,631 Investment in partnerships (a) 2,437,620 1,582,436 Total deferred tax liabilities 2,524,641 1,667,067 Net deferred tax assets (liabilities) $ (669,697) $ (536,063) (a) Due primarily to excess of tax over book depreciation.

UNCONSOLIDATED AFFILIATES (Tabl

UNCONSOLIDATED AFFILIATES (Tables)	12 Months Ended
UNCONSOLIDATED AFFILIATES (Tables)	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Schedule of Equity Method Investments	The following table sets forth our investments in unconsolidated affiliates for the periods indicated: Net December 31, December 31, ( Thousands of dollars ) Northern Border Pipeline 50% $ 291,987 $ 307,209 Overland Pass Pipeline 50% 409,573 417,473 Roadrunner 50% 66,794 80,816 Other (a) Various 36,678 56,346 Investments in unconsolidated affiliates (b) $ 805,032 $ 861,844 (a) - Year ended December 31, 2020, includes the impact of noncash impairment charges of $37.7 million related to the equity investments discussed below, offset partially by an acquisition of additional equity interest for $20.0 million. (b) - Equity-method goodwill (Note A) was $16.5 million and $38.8 million at December 31, 2020 and 2019, respectively.
Equity In Net Earnings From Investments
Schedule of Equity Method Investments [Line Items]
Schedule of Equity Method Investments	The following table sets forth our equity in net earnings (loss) from investments for the periods indicated: Years Ended December 31, 2020 2019 2018 ( Thousands of dollars ) Northern Border Pipeline $ 75,409 $ 68,871 $ 67,854 Overland Pass Pipeline 38,618 63,698 65,887 Roadrunner 29,017 26,839 22,993 Other 197 (4,867) 1,649 Equity in net earnings from investments $ 143,241 $ 154,541 $ 158,383 Impairment of equity investments $ (37,730) $ — $ —

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES (Tables)	12 Months Ended
COMMITMENTS AND CONTINGENCIES (Tables)	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Rental Payments for Firm Transportation, Storage Contracts and Capital Leases	The following table sets forth our firm transportation and storage contract payments for the periods indicated: Firm ( Millions of dollars ) 2021 $ 70.9 2022 60.9 2023 55.8 2024 53.4 2025 47.9 Thereafter 227.8 Total $ 516.7

LEASES (Tables)

LEASES (Tables)	12 Months Ended
LEASES (Tables)	Dec. 31, 2020
Leases [Abstract]
Lessee, Operating Lease, Liability, Maturity [Table Text Block]	The following table sets forth the maturity of our lease liabilities as of December 31, 2020: Finance Operating ( Millions of dollars ) 2021 $ 4.5 $ 16.5 2022 4.5 15.1 2023 4.5 13.8 2024 4.5 12.5 2025 4.5 11.1 2026 and beyond 12.6 47.1 Total lease payments 35.1 116.1 Less: Interest 10.8 14.9 Present value of lease liabilities $ 24.3 $ 101.2
LeaseAssetsAndLiabilitiesInBalanceSheet [Table Text Block]	The following table sets forth information about our lease assets and liabilities included in our Consolidated Balance Sheet for the periods indicated: Leases Location in our Consolidated Balance Sheet December 31, 2020 December 31, 2019 ( Thousands of dollars ) Assets Operating leases Other assets $ 100,154 $ 15,147 Finance lease Property, plant and equipment 28,286 28,286 Finance lease Accumulated depreciation (2,451) (1,320) Total leased assets $ 125,989 $ 42,113 Liabilities Current Operating leases Operating lease liability $ 13,610 $ 1,883 Finance lease Other current liabilities 2,153 1,949 Noncurrent Operating leases Operating lease liability 87,610 13,509 Finance lease Other deferred credits 22,143 24,296 Total lease liabilities $ 125,516 $ 41,637 The following table sets forth supplemental cash flow information related to our leases: Years Ended December 31, 2020 2019 ( Thousands of dollars ) Cash paid for amounts included in the measurement of lease liabilities Operating cash flows for operating leases $ 13,245 $ 6,213 Financing cash flows for finance lease $ 1,949 $ 1,764 Right-of-use assets obtained in exchange for operating lease liabilities (noncash) $ 99,547 $ 4,097
Lease, Cost [Table Text Block]	The following table sets forth information about our lease costs for the periods indicated: Years Ended December 31, Location in our 2020 2019 ( Thousands of dollars ) Operating leases Operations and maintenance $ 17,162 $ 6,803 Finance lease Amortization of lease assets Depreciation and amortization 1,131 1,131 Interest on lease liabilities Interest expense 2,537 2,721 Total lease cost $ 20,830 $ 10,655 The following table sets forth information about our leases for the periods indicated: December 31, 2020 December 31, 2019 Weighted average remaining lease term (years) Operating leases 8.3 10.4 Finance lease 7.8 8.8 Weighted average discount rate (a) Operating leases 3.20% 4.58% Finance lease 10.00% 10.00% (a) - Our weighted-average discount rates represent the rate implicit in the lease or our incremental borrowing rate for a term equal to the remaining term of the lease.
Finance Lease, Liability, Maturity [Table Text Block]	The following table sets forth the maturity of our lease liabilities as of December 31, 2020: Finance Operating ( Millions of dollars ) 2021 $ 4.5 $ 16.5 2022 4.5 15.1 2023 4.5 13.8 2024 4.5 12.5 2025 4.5 11.1 2026 and beyond 12.6 47.1 Total lease payments 35.1 116.1 Less: Interest 10.8 14.9 Present value of lease liabilities $ 24.3 $ 101.2

REVENUES (Tables)

REVENUES (Tables)	12 Months Ended
REVENUES (Tables)	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Contract with Customer, Asset and Liability [Table Text Block]	The following table sets forth the changes in our contract liability balances for the periods indicated: Contract Liabilities ( Millions of dollars ) Balance at January 1, 2019 $ 31.7 Revenue recognized included in beginning balance (15.6) Net additions 41.0 Balance at December 31, 2019 (a) 57.1 Revenue recognized included in beginning balance (c) (36.1) Net additions 20.4 Balance at December 31, 2020 (b) $ 41.4 (a) - Contract liabilities of $22.2 million and $34.9 million are included in other current liabilities and other deferred credits, respectively, in our Consolidated Balance Sheet. (b) - Contract liabilities of $23.7 million and $17.7 million are included in other current liabilities and other deferred credits, respectively, in our Consolidated Balance Sheet. (c) - Includes a contract settlement of revenue previously deferred.
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table Text Block]	The following table presents aggregate value allocated to unsatisfied performance obligations as of December 31, 2020, and the amounts we expect to recognize in revenue in future periods, related primarily to firm transportation and storage contracts with remaining contract terms ranging from one month to 23 years: Expected Period of Recognition in Revenue ( Millions of dollars ) 2021 $ 328.2 2022 263.0 2023 235.4 2024 197.9 2025 and beyond 762.0 Total estimated transaction price allocated to unsatisfied performance obligations $ 1,786.5

SEGMENTS (Tables)

SEGMENTS (Tables)	12 Months Ended
SEGMENTS (Tables)	Dec. 31, 2020
Segment Reporting, Disclosure of Entity's Reportable Segments [Abstract]
Segments	The following tables set forth certain selected financial information for our operating segments for the periods indicated: Year Ended December 31, 2020 Natural Gas Natural Gas Natural Gas Total ( Thousands of dollars ) NGL and condensate sales $ 889,388 $ 6,409,332 $ — $ 7,298,720 Residue natural gas sales 771,486 — 8,693 780,179 Gathering, processing and exchange services revenue 141,943 488,574 — 630,517 Transportation and storage revenue — 182,915 470,097 653,012 Other 17,304 9,192 1,192 27,688 Total revenues (c) 1,820,121 7,090,013 479,982 9,390,116 Cost of sales and fuel (exclusive of depreciation and operating costs) (843,976) (5,108,558) (6,809) (5,959,343) Operating costs (326,938) (412,900) (141,713) (881,551) Equity in net earnings (loss) from investments (1,123) 39,938 104,426 143,241 Noncash compensation expense and other 1,952 8,748 1,540 12,240 Segment adjusted EBITDA $ 650,036 $ 1,617,241 $ 437,426 $ 2,704,703 Depreciation and amortization $ (247,010) $ (271,900) $ (55,739) $ (574,649) Impairment charges $ (566,145) $ (78,785) $ — $ (644,930) Investments in unconsolidated affiliates $ 22,757 $ 423,494 $ 358,781 $ 805,032 Total assets $ 6,499,908 $ 13,636,109 $ 2,100,213 $ 22,236,230 Capital expenditures $ 446,142 $ 1,655,759 $ 71,918 $ 2,173,819 (a) - Our Natural Gas Liquids segment has regulated and nonregulated operations. Our Natural Gas Liquids segment’s regulated operations had revenues of $2.0 billion, of which $1.8 billion related to sales within the segment, and cost of sales and fuel of $520.6 million. (b) - Our Natural Gas Pipelines segment has regulated and nonregulated operations. Our Natural Gas Pipelines segment’s regulated operations had revenues of $298.5 million and cost of sales and fuel of $30.4 million. (c) - Intersegment revenues are primarily commodity sales which are based on the contracted selling price, which is generally index-based and settled monthly, and for the Natural Gas Gathering and Processing segment totaled $865.6 million. Intersegment revenues for the Natural Gas Liquids and Natural Gas Pipelines segments were not material. Year Ended December 31, 2020 Total Other and Total ( Thousands of dollars ) Reconciliations of total segments to consolidated NGL and condensate sales $ 7,298,720 $ (820,851) $ 6,477,869 Residue natural gas sales 780,179 (10,860) 769,319 Gathering, processing and exchange services revenue 630,517 — 630,517 Transportation and storage revenue 653,012 (14,599) 638,413 Other 27,688 (1,564) 26,124 Total revenues (a) $ 9,390,116 $ (847,874) $ 8,542,242 Cost of sales and fuel (exclusive of depreciation and operating costs) $ (5,959,343) $ 849,197 $ (5,110,146) Operating costs $ (881,551) $ (4,653) $ (886,204) Depreciation and amortization $ (574,649) $ (4,013) $ (578,662) Impairment charges $ (644,930) $ — $ (644,930) Equity in net earnings from investments $ 143,241 $ — $ 143,241 Investments in unconsolidated affiliates $ 805,032 $ — $ 805,032 Total assets $ 22,236,230 $ 842,524 $ 23,078,754 Capital expenditures $ 2,173,819 $ 21,562 $ 2,195,381 (a) - Noncustomer revenue for the year ended December 31, 2020, totaled $65.8 million related primarily to gains from derivatives on commodity contracts. Year Ended December 31, 2019 Natural Gas Natural Gas Natural Gas Total ( Thousands of dollars ) NGL and condensate sales $ 1,224,378 $ 7,910,833 $ — $ 9,135,211 Residue natural gas sales 966,149 — 1,244 967,393 Gathering, processing and exchange services revenue 164,299 414,238 — 578,537 Transportation and storage revenue — 197,483 466,266 663,749 Other 13,813 9,962 4,477 28,252 Total revenues (c) 2,368,639 8,532,516 471,987 11,373,142 Cost of sales and fuel (exclusive of depreciation and operating costs) (1,302,310) (6,690,918) (4,628) (7,997,856) Operating costs (368,352) (456,892) (157,230) (982,474) Equity in net earnings (loss) from investments (6,292) 65,123 95,710 154,541 Noncash compensation expense and other 10,965 15,936 2,977 29,878 Segment adjusted EBITDA $ 702,650 $ 1,465,765 $ 408,816 $ 2,577,231 Depreciation and amortization $ (219,519) $ (196,132) $ (57,250) $ (472,901) Investments in unconsolidated affiliates $ 34,426 $ 439,393 $ 388,025 $ 861,844 Total assets $ 6,795,744 $ 12,551,476 $ 2,094,072 $ 21,441,292 Capital expenditures $ 926,489 $ 2,796,604 $ 99,221 $ 3,822,314 (a) - Our Natural Gas Liquids segment has regulated and nonregulated operations. Our Natural Gas Liquids segment’s regulated operations had revenues of $1.4 billion, of which $1.2 billion related to revenues within the segment, and cost of sales and fuel of $496.8 million. (b) - Our Natural Gas Pipelines segment has regulated and nonregulated operations. Our Natural Gas Pipelines segment’s regulated operations had revenues of $285.3 million and cost of sales and fuel of $20.0 million. (c) - Intersegment revenues are primarily commodity sales which are based on the contracted selling price, which is generally index-based and settled monthly, and for the Natural Gas Gathering and Processing segment totaled $1.2 billion. Intersegment revenues for the Natural Gas Liquids and Natural Gas Pipelines segments were not material. Year Ended December 31, 2019 Total Other and Total ( Thousands of dollars ) Reconciliations of total segments to consolidated NGL and condensate sales $ 9,135,211 $ (1,190,424) $ 7,944,787 Residue natural gas sales 967,393 (1,418) 965,975 Gathering, processing and exchange services revenue 578,537 — 578,537 Transportation and storage revenue 663,749 (15,646) 648,103 Other 28,252 (1,287) 26,965 Total revenues (a) $ 11,373,142 $ (1,208,775) $ 10,164,367 Cost of sales and fuel (exclusive of depreciation and operating costs) $ (7,997,856) $ 1,209,816 $ (6,788,040) Operating costs $ (982,474) $ (390) $ (982,864) Depreciation and amortization $ (472,901) $ (3,634) $ (476,535) Equity in net earnings from investments $ 154,541 $ — $ 154,541 Investments in unconsolidated affiliates $ 861,844 $ — $ 861,844 Total assets $ 21,441,292 $ 370,829 $ 21,812,121 Capital expenditures $ 3,822,314 $ 26,035 $ 3,848,349 (a) - Noncustomer revenue for the year ended December 31, 2019, totaled $139.6 million related primarily to gains from derivatives on commodity contracts. Year Ended December 31, 2018 Natural Gas Natural Gas Natural Gas Total ( Thousands of dollars ) NGL and condensate sales $ 1,775,991 $ 10,319,847 $ — $ 12,095,838 Residue natural gas sales 1,084,162 — 9,772 1,093,934 Gathering, processing and exchange services revenue 163,194 404,897 — 568,091 Transportation and storage revenue — 199,018 414,969 613,987 Other 11,230 10,816 6,994 29,040 Total revenues (c) 3,034,577 10,934,578 431,735 14,400,890 Cost of sales and fuel (exclusive of depreciation and operating costs) (2,041,448) (9,176,813) (15,984) (11,234,245) Operating costs (368,939) (394,115) (144,259) (907,313) Equity in net earnings from investments 410 67,126 90,847 158,383 Noncash compensation expense and other 7,007 9,829 3,912 20,748 Segment adjusted EBITDA $ 631,607 $ 1,440,605 $ 366,251 $ 2,438,463 Depreciation and amortization $ (196,090) $ (174,007) $ (55,118) $ (425,215) Investments in unconsolidated affiliates $ 42,630 $ 451,040 $ 475,480 $ 969,150 Total assets $ 6,078,473 $ 9,663,640 $ 2,131,669 $ 17,873,782 Capital expenditures $ 694,611 $ 1,306,341 $ 119,185 $ 2,120,137 (a) - Our Natural Gas Liquids segment has regulated and nonregulated operations. Our Natural Gas Liquids segment’s regulated operations had revenues of $1.2 billion, of which $1.1 billion related to revenues within the segment, and cost of sales and fuel of $506.0 million. (b) - Our Natural Gas Pipelines segment has regulated and nonregulated operations. Our Natural Gas Pipelines segment’s regulated operations had revenues of $266.6 million and cost of sales and fuel of $26.0 million. (c) - Intersegment revenues are primarily commodity sales which are based on the contracted selling price, which is generally index-based and settled monthly, and for the Natural Gas Gathering and Processing segment totaled $1.8 billion. Intersegment revenues for the Natural Gas Liquids and Natural Gas Pipelines segments were not material. Year Ended December 31, 2018 Total Other and Total (Thousands of dollars) Reconciliations of total segments to consolidated NGL and condensate sales $ 12,095,838 $ (1,794,342) $ 10,301,496 Residue natural gas sales 1,093,934 (2,832) 1,091,102 Gathering, processing and exchange services revenue 568,091 (21) 568,070 Transportation and storage revenue 613,987 (10,550) 603,437 Other 29,040 51 29,091 Total revenues (a) $ 14,400,890 $ (1,807,694) $ 12,593,196 Cost of sales and fuel (exclusive of depreciation and operating costs) $ (11,234,245) $ 1,811,537 $ (9,422,708) Operating costs $ (907,313) $ 245 $ (907,068) Depreciation and amortization $ (425,215) $ (3,342) $ (428,557) Equity in net earnings from investments $ 158,383 $ — $ 158,383 Investments in unconsolidated affiliates $ 969,150 $ — $ 969,150 Total assets $ 17,873,782 $ 357,889 $ 18,231,671 Capital expenditures $ 2,120,137 $ 21,338 $ 2,141,475 (a) - Noncustomer revenue for the year ended December 31, 2018, totaled $(16.2) million related primarily to losses from derivatives on commodity contract s. Years Ended December 31, 2020 2019 2018 Reconciliation of net income to total segment adjusted EBITDA ( Thousands of dollars ) Net income $ 612,809 $ 1,278,577 $ 1,155,032 Add: Interest expense, net of capitalized interest 712,886 491,773 469,620 Depreciation and amortization 578,662 476,535 428,557 Income tax expense 189,507 372,414 362,903 Impairment charges 644,930 — — Noncash compensation expense 8,540 26,699 37,954 Other corporate costs and equity AFUDC (a) (42,631) (68,767) (15,603) Total segment adjusted EBITDA $ 2,704,703 $ 2,577,231 $ 2,438,463 (a) - The year ended December 31, 2020, includes corporate net gains of $22.3 million on extinguishment of debt related to open market repurchases. The year ended December 31, 2019, includes higher equity AFUDC related to our capital-growth projects compared with 2020 and 2018.

QUARTERLY FINANCIAL DATA (UNA_2

QUARTERLY FINANCIAL DATA (UNAUDITED) (Tables)	12 Months Ended
QUARTERLY FINANCIAL DATA (UNAUDITED) (Tables)	Dec. 31, 2020	Dec. 31, 2019
Quarterly Financial Data [Abstract]
Quarterly Financial Data	Year Ended December 31, 2020 First Second Third Fourth ( Thousands of dollars, except per share amounts ) Total revenues $ 2,136,672 $ 1,660,729 $ 2,174,264 $ 2,570,577 Operating income (loss) $ (83,469) $ 355,730 $ 550,433 $ 538,663 Net income (loss) $ (141,857) $ 134,321 $ 312,316 $ 308,029 Net income (loss) available to common shareholders $ (142,132) $ 134,046 $ 312,041 $ 307,754 Earnings (loss) per share total Basic $ (0.34) $ 0.32 $ 0.70 $ 0.69 Diluted $ (0.34) $ 0.32 $ 0.70 $ 0.69 (a) - Due to historic events as a result of COVID-19 impacting supply, demand and commodity prices, we evaluated our goodwill, certain long-lived asset groups and equity investments for impairment and recorded $641.8 million in impairment charges. (b) - In the second quarter 2020, due to the commodity price environment and continued global and regional economic disruptions due primarily to COVID-19, many of our crude oil and natural gas producers curtailed production, which significantly reduced volumes on our system. (c) - In the third quarter 2020, many of our producers reversed curtailments, bringing volumes back to pre-COVID-19 levels as prices and demand improved from second quarter 2020 lows and remained stable.	Year Ended December 31, 2019 First Second Third Fourth ( Thousands of dollars except per share amounts ) Total revenues $ 2,779,958 $ 2,457,575 $ 2,263,228 $ 2,663,606 Operating income $ 468,742 $ 476,146 $ 482,151 $ 487,314 Net income $ 337,208 $ 311,963 $ 309,155 $ 320,251 Net income available to common shareholders $ 336,933 $ 311,688 $ 308,880 $ 319,976 EPS total Basic $ 0.82 $ 0.75 $ 0.75 $ 0.77 Diluted $ 0.81 $ 0.75 $ 0.74 $ 0.77

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Entity [Line Items]
Contract Liabilities, Contract Term	5 to 10 years
Number Of Years Of Service Employees Must Work To Be Entitled To Postretirement Medical And Life Insurance Benefits				5 years
Impairment of equity investments	$ 37,730	$ 0	$ 0
Natural Gas Gathering And Processing
Entity [Line Items]
Impairment charges	362,300
Goodwill, Impairment Loss	153,400
Impairment charges - long lived and other assets	382,200
Natural Gas Liquids
Entity [Line Items]
Impairment charges	$ 71,600
Venice Energy Services Company [Member] \| Natural Gas Gathering And Processing
Entity [Line Items]
Net ownership percentage	10.20%
Impairment of equity investments	$ 30,500
Impairment of equity investments - goodwill	$ 22,300
Chisholm Pipeline Company [Member] \| Natural Gas Liquids
Entity [Line Items]
Net ownership percentage	50.00%
Impairment of equity investments	$ 7,200
Northern Border Pipeline [Member]
Entity [Line Items]
Net ownership percentage	50.00%
Northern Border Pipeline [Member] \| Natural Gas Pipelines
Entity [Line Items]
Net ownership percentage	50.00%
Roadrunner Gas Transmission [Member]
Entity [Line Items]
Net ownership percentage	50.00%
Roadrunner Gas Transmission [Member] \| Natural Gas Pipelines
Entity [Line Items]
Net ownership percentage	50.00%
Overland Pass Pipeline Company [Member]
Entity [Line Items]
Net ownership percentage	50.00%
Overland Pass Pipeline Company [Member] \| Natural Gas Liquids
Entity [Line Items]
Net ownership percentage	50.00%

FAIR VALUE MEASUREMENTS - Part

FAIR VALUE MEASUREMENTS - Part 1 (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash held - offsetting derivative net asset positions under master-netting arrangements	$ 0	$ 0
Cash posted - total	63,100	8,800
Cash posted - offsetting derivative net liability positions under master-netting arrangements	35,100
Cash posted - remaining in excess of derivative net liability positions included in consolidated Balance Sheets	28,000
Long-term Debt, Fair Value	16,300,000	13,800,000
Long-term Debt	14,200,000	12,500,000
Fair Value, Recurring [Member] \| Gross Fair Value Measurement [Member]
Derivative assets
Derivative asset, fair value, gross	110,498	67,030
Derivative Liabilities
Derivative liability, fair value, gross	(349,018)	(231,537)
Fair Value, Recurring [Member] \| Gross Fair Value Measurement [Member] \| Financial contracts
Derivative assets
Derivative asset, fair value, gross	110,498	66,449
Derivative Liabilities
Derivative liability, fair value, gross	(145,611)	(29,596)
Fair Value, Recurring [Member] \| Gross Fair Value Measurement [Member] \| Interest Rate Contracts
Derivative assets
Interest-rate contracts		581
Derivative Liabilities
Interest-rate contracts	(203,407)	(201,941)
Fair Value, Recurring [Member]
Derivative assets
Derivative assets	0	38,442
Derivative assets netting	(110,498)	(28,588)
Derivative Liabilities
Derivative liabilities	(203,407)	(202,949)
Derivative liabilities netting	145,611	28,588
Fair Value, Recurring [Member] \| Financial contracts
Derivative assets
Derivative assets	0	37,861
Derivative assets netting	(110,498)	(28,588)
Derivative Liabilities
Derivative liabilities	0	(1,008)
Derivative liabilities netting	145,611	28,588
Fair Value, Recurring [Member] \| Interest Rate Contracts
Derivative assets
Interest-rate contracts		581
Derivative assets netting		0
Derivative Liabilities
Interest-rate contracts	(203,407)	(201,941)
Derivative liabilities netting	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Derivative assets
Derivative asset, fair value, gross	6,697	10,892
Derivative Liabilities
Derivative liability, fair value, gross	(10,489)	(4,811)
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Financial contracts
Derivative assets
Derivative asset, fair value, gross	6,697	10,892
Derivative Liabilities
Derivative liability, fair value, gross	(10,489)	(4,811)
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Interest Rate Contracts
Derivative assets
Interest-rate contracts		0
Derivative Liabilities
Interest-rate contracts	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Derivative assets
Derivative asset, fair value, gross	0	581
Derivative Liabilities
Derivative liability, fair value, gross	(203,407)	(201,941)
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Financial contracts
Derivative assets
Derivative asset, fair value, gross	0	0
Derivative Liabilities
Derivative liability, fair value, gross	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Interest Rate Contracts
Derivative assets
Interest-rate contracts		581
Derivative Liabilities
Interest-rate contracts	(203,407)	(201,941)
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Derivative assets
Derivative asset, fair value, gross	103,801	55,557
Derivative Liabilities
Derivative liability, fair value, gross	(135,122)	(24,785)
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Financial contracts
Derivative assets
Derivative asset, fair value, gross	103,801	55,557
Derivative Liabilities
Derivative liability, fair value, gross	(135,122)	(24,785)
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Interest Rate Contracts
Derivative assets
Interest-rate contracts		0
Derivative Liabilities
Interest-rate contracts	$ 0	$ 0

FAIR VALUE MEASUREMENTS - Par_2

FAIR VALUE MEASUREMENTS - Part 2 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets And Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Abstract]
Net assets (liabilities) at beginning of period	$ 30,772	$ 40,484
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Settlements	(31,660)	(40,344)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, New Level 3 Derivatives	(36,568)	30,627
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Unrealized Change Included in Other Comprehensive Income (Loss)	6,135	5
Net assets (liabilities) at end of period	(31,321)	30,772
Transfers in or out of level 3	$ 0	$ 0

RISK MANAGEMENT AND HEDGING A_3

RISK MANAGEMENT AND HEDGING ACTIVITIES USING DERIVATIVES - Part 1 (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Assets	$ 110,498	$ 67,030
(Liabilities)	(349,018)	(231,537)
Derivative, Net Liability Position, Aggregate Fair Value	0
Cash posted - offsetting derivative net liability positions under master-netting arrangements	35,100
Derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
Assets	107,461	67,030
(Liabilities)	(345,980)	(231,537)
Derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Assets	3,037	0
(Liabilities)	(3,038)	0
Natural Gas Pipelines
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	0	0
Other Current Assets [Member] \| Commodity contracts \| Financial contracts \| Derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
Assets	107,461	64,858
(Liabilities)	(142,573)	(26,997)
Other Current Assets [Member] \| Commodity contracts \| Financial contracts \| Derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Assets	3,037	0
(Liabilities)	(3,038)	0
Other Current Liabilities [Member] \| Interest Rate Contracts \| Derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
Assets	0	0
(Liabilities)	0	(90,161)
Other Deferred Credits \| Commodity contracts \| Financial contracts \| Derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
Assets	0	1,591
(Liabilities)	0	(2,599)
Other Deferred Credits \| Interest Rate Contracts \| Derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
Assets	0	581
(Liabilities)	$ (203,407)	(111,780)
Interest Rate Contracts \| LIBOR Based Interest Payments [Member] \| Cash Flow Hedging [Member] \| Forward contracts
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		$ 1,300,000

RISK MANAGEMENT AND HEDGING A_4

RISK MANAGEMENT AND HEDGING ACTIVITIES USING DERIVATIVES - Part 2 (Details) $ in Millions	3 Months Ended		12 Months Ended
	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2020USD ($)MMBblsBcf	Dec. 31, 2019USD ($)BcfMMBbls	Dec. 31, 2018USD ($)
Derivative [Line Items]
Realized Loss on Settled Interest Rate Swaps Recorded in AOCI	$ 48.3	$ 152.5	$ 48.3
Notional Amount Of Cash Flow Hedge Instruments Settled	1,300	750	1,300
Cash posted - offsetting derivative net liability positions under master-netting arrangements			$ 35.1
Derivatives designated as hedging instruments \| Futures and swaps \| Natural gas (Bcf) \| Fixed price \| Net Purchasor, Sellor
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| Bcf			(43.3)	(59)
Derivatives designated as hedging instruments \| Futures and swaps \| Natural gas (Bcf) \| Basis \| Net Purchasor, Sellor
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| Bcf			(43.3)	(59)
Derivatives designated as hedging instruments \| Futures, forwards and swaps \| Crude oils and NGLs (MMBbl) \| Fixed price \| Net Purchasor, Sellor
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| MMBbls			(4.6)	(9.5)
Derivatives designated as hedging instruments \| Interest Rate Contract \| Net Purchasor, Sellor
Derivative [Line Items]
Derivative, Notional Amount			$ 1,100	$ 3,100
Derivatives not designated as hedging instruments \| Futures, forwards and swaps \| Crude oils and NGLs (MMBbl) \| Fixed price \| Purchased/Payor
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| MMBbls			0.8
Derivatives not designated as hedging instruments \| Futures, forwards and swaps \| Crude oils and NGLs (MMBbl) \| Fixed price \| Sold/Receiver
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| MMBbls			(0.8)
Forecasted Debt Issuances [Member] \| Cash Flow Hedging [Member] \| Forward contracts \| Interest Rate Contract
Derivative [Line Items]
Derivative, Notional Amount			$ 1,100	1,800
LIBOR Based Interest Payments [Member] \| Cash Flow Hedging [Member] \| Forward contracts \| Interest Rate Contract
Derivative [Line Items]
Derivative, Notional Amount				$ 1,300
Notes Payable from Public Offering Due 2025, 2030 and 2050 [Member]
Derivative [Line Items]
Senior Notes, Noncurrent		$ 1,750
Term Loan Agreement due 2021 [Member] \| Parent Company [Member]
Derivative [Line Items]
Debt Instrument, Face Amount	$ 1,500		$ 1,500		$ 1,500

RISK MANAGEMENT AND HEDGING A_5

RISK MANAGEMENT AND HEDGING ACTIVITIES USING DERIVATIVES - Part 3 (Details) - Cash Flow Hedging [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized change in fair value of cash flow hedges in other comprehensive income (loss)	$ (214,315)	$ (191,952)	$ (7,367)
Change in fair value of cash flow hedges reclassified from accumulated other comprehensive loss into net income on derivatives	(27,410)	27,115	(47,883)
Commodity Contract
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized change in fair value of cash flow hedges in other comprehensive income (loss)	(5,699)	38,819	53,217
Commodity Contract \| Commodity sales revenues
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of cash flow hedges reclassified from accumulated other comprehensive loss into net income on derivatives	85,436	94,547	(37,596)
Commodity Contract \| Cost of sales and fuel
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of cash flow hedges reclassified from accumulated other comprehensive loss into net income on derivatives	(19,170)	(44,202)	8,000
Interest Rate Contract
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized change in fair value of cash flow hedges in other comprehensive income (loss)	(208,616)	(230,771)	(60,584)
Interest Rate Contract \| Interest expense
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of cash flow hedges reclassified from accumulated other comprehensive loss into net income on derivatives	$ (93,676)	$ (23,230)	$ (18,287)

PROPERTY, PLANT AND EQUIPMENT -

PROPERTY, PLANT AND EQUIPMENT - (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 23,072,935	$ 22,051,492
Accumulated depreciation and amortization	(3,918,007)	(3,702,807)
Net property, plant and equipment	19,154,928	18,348,685
Construction in Progress Expenditures Incurred but Not yet Paid	151,700	544,800	$ 388,300
Natural Gas Liquids
Property, Plant and Equipment [Line Items]
Impairment charges	71,600
Natural Gas Gathering And Processing
Property, Plant and Equipment [Line Items]
Impairment charges	362,300
Non-Regulated Property, Plant and Equipment [Member]
Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	(2,514,328)	(2,471,649)
Non-Regulated Property, Plant and Equipment [Member] \| Gathering pipelines and related equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 4,143,752	4,316,936
Non-Regulated Property, Plant and Equipment [Member] \| Gathering pipelines and related equipment \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Non-Regulated Property, Plant and Equipment [Member] \| Gathering pipelines and related equipment \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	40 years
Non-Regulated Property, Plant and Equipment [Member] \| Processing and fractionation and related equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 5,084,802	4,439,332
Non-Regulated Property, Plant and Equipment [Member] \| Processing and fractionation and related equipment \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Non-Regulated Property, Plant and Equipment [Member] \| Processing and fractionation and related equipment \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	40 years
Non-Regulated Property, Plant and Equipment [Member] \| Storage and related equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 798,785	684,635
Non-Regulated Property, Plant and Equipment [Member] \| Storage and related equipment \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Non-Regulated Property, Plant and Equipment [Member] \| Storage and related equipment \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	54 years
Non-Regulated Property, Plant and Equipment [Member] \| Transmission pipelines and related equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 810,434	797,678
Non-Regulated Property, Plant and Equipment [Member] \| Transmission pipelines and related equipment \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Non-Regulated Property, Plant and Equipment [Member] \| Transmission pipelines and related equipment \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	54 years
Non-Regulated Property, Plant and Equipment [Member] \| General plant and other
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 647,675	610,013
Non-Regulated Property, Plant and Equipment [Member] \| General plant and other \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	2 years
Non-Regulated Property, Plant and Equipment [Member] \| General plant and other \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	60 years
Non-Regulated Property, Plant and Equipment [Member] \| Construction work in process
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 1,265,736	1,645,663
Regulated Property Plant and Equipment [Member]
Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	$ (1,403,679)	$ (1,231,158)
Regulated Property Plant and Equipment [Member] \| Natural Gas Liquids
Property, Plant and Equipment [Line Items]
Average Depreciation Rate	2.20%	2.00%	1.90%
Regulated Property Plant and Equipment [Member] \| Natural Gas Pipelines
Property, Plant and Equipment [Line Items]
Average Depreciation Rate	2.10%	2.10%	2.10%
Regulated Property Plant and Equipment [Member] \| Storage and related equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 9,180	$ 9,180
Regulated Property Plant and Equipment [Member] \| Storage and related equipment \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Regulated Property Plant and Equipment [Member] \| Storage and related equipment \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	25 years
Regulated Property Plant and Equipment [Member] \| Natural gas transmission pipelines and related equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 1,569,268	1,552,546
Regulated Property Plant and Equipment [Member] \| Natural gas transmission pipelines and related equipment \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Regulated Property Plant and Equipment [Member] \| Natural gas transmission pipelines and related equipment \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	77 years
Regulated Property Plant and Equipment [Member] \| NGL transmission pipelines and related equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 8,423,544	6,126,056
Regulated Property Plant and Equipment [Member] \| NGL transmission pipelines and related equipment \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Regulated Property Plant and Equipment [Member] \| NGL transmission pipelines and related equipment \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	88 years
Regulated Property Plant and Equipment [Member] \| General plant and other
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 72,535	66,507
Regulated Property Plant and Equipment [Member] \| General plant and other \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	2 years
Regulated Property Plant and Equipment [Member] \| General plant and other \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	50 years
Regulated Property Plant and Equipment [Member] \| Construction work in process
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 247,224	$ 1,802,946

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Goodwill	$ 527,592	$ 680,996
Amortization expense for intangible assets	10,800	11,900	$ 11,900
Gross intangible assets and accumulated amortization [Abstract]
Gross intangible assets	381,435	414,345
Accumulated amortization	(135,304)	(137,508)
Net intangible assets	246,131	276,837
Future amortization expense for next five years [Abstract]
Future amortization expense, year one	10,400
Future amortization expense, year two	10,400
Future amortization expense, year three	10,400
Future amortization expense, year four	10,400
Future amortization expense, year five	10,400
Natural Gas Liquids [Member]
Segment Reporting Information [Line Items]
Goodwill	371,217	371,217
Natural Gas Pipelines
Segment Reporting Information [Line Items]
Goodwill	156,375	156,375
Natural Gas Gathering and Processing
Segment Reporting Information [Line Items]
Goodwill	0	$ 153,404
Goodwill, Impairment Loss	153,400
Impairment of Intangible Assets (Excluding Goodwill)	$ 19,900
Natural Gas Gathering And Processing and Natural Gas Liquids [Member] \| Minimum [Member]
Segment Reporting Information [Line Items]
Finite-Lived Intangible Asset, Useful Life	15 years
Natural Gas Gathering And Processing and Natural Gas Liquids [Member] \| Maximum [Member]
Segment Reporting Information [Line Items]
Finite-Lived Intangible Asset, Useful Life	40 years

DEBT (Details)

DEBT (Details) $ in Thousands	3 Months Ended						12 Months Ended
DEBT (Details) $ in Thousands	Dec. 31, 2020USD ($)Rate	Jun. 30, 2020USD ($)Rate	Mar. 31, 2020USD ($)Rate	Sep. 30, 2019USD ($)Rate	Mar. 31, 2019USD ($)Rate	Sep. 30, 2018USD ($)Rate	Dec. 31, 2020USD ($)Rate	Dec. 31, 2019USD ($)Rate	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
Total debt	$ 14,361,644						$ 14,361,644	$ 12,813,704
Unamortized portion of terminated swaps	(13,314)						(13,314)	(15,032)
Unamortized debt issuance costs and discounts	(138,887)						(138,887)	(121,329)
Current maturities of long-term debt	(7,650)						(7,650)	(7,650)
Short-term borrowings	0						0	(220,000)
Long-term debt	14,228,421						14,228,421	12,479,757
Letters of Credit Outstanding, Amount	7,700						7,700	4,700
Senior Note Covenant, Acceleration Of Indebtedness	$ 100,000						$ 100,000
Senior Note Covenant, Trustee Or Holders Percentage Required Upon Event Of Default	25.00%						25.00%
Long-term Debt, Repurchased Face Amount							$ 224,400
Repayments of Long-term Debt							199,600
Gain (Loss) on Extinguishment of Debt							22,300
Business Combination, Consideration Transferred	$ 27,000					$ 195,000
Long-term Debt, by Maturity [Abstract]
2021	7,700						7,700
2022	1,443,700						1,443,700
2023	925,000						925,000
2024	500,000						500,000
2025	887,000						887,000
$2.5 Billion Credit Agreement [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	2,500,000						2,500,000
Line of Credit Facility, Amount Outstanding	$ 0						$ 0	0
Indebtedness to Adjusted EBITDA Maximum	5						5
Indebtedness To Adjusted EBITDA From Acquisitions Maximum	5.5						5.5
Line of Credit Facility, Sublimit	$ 100,000						$ 100,000
Line of Credit Facility, Swingline Subfacility	200,000						200,000
Line Of Credit Facility, Option To Increase Borrowing Capacity	$ 3,500,000						$ 3,500,000
Line of Credit Facility, Annual Facility Fee							0.15%
Indebtedness To Adjusted EBITDA Current	4.6						4.6
Debt Instrument, Covenant Description							Among other things, these covenants include maintaining a ratio of indebtedness to adjusted EBITDA (EBITDA, as defined in our $2.5 Billion Credit Agreement, adjusted for all noncash charges and increased for projected EBITDA from certain lender-approved capital expansion projects). In June 2020, we amended our $2.5 Billion Credit Agreement by, among other things, modifying the leverage ratio so that we may net up to $700 million of cash on hand against our consolidated indebtedness for purposes of calculating the ratio’s numerator for the fiscal quarters ending June 30, 2020, September 30, 2020, and December 31, 2020. In October 2020, we acquired additional interest in one of our equity investments and a related asset for $27 million, which allowed us to elect an acquisition adjustment period under our $2.5 Billion Credit Agreement and, as a result, increased our leverage ratio covenant to 5.5 to 1 for the fourth quarter 2020 and the two following quarters. Thereafter, the covenant will decrease to 5.0 to 1. Our $2.5 Billion Credit Agreement includes a $100 million sublimit for the issuance of standby letters of credit and a $200 million sublimit for swingline loans. Under the terms of our $2.5 Billion Credit Agreement, we may request an increase in the size of the facility to an aggregate of $3.5 billion by either commitments from new lenders or increased commitments from existing lenders. Our $2.5 Billion Credit Agreement contains provisions for an applicable margin rate and an annual facility fee, both of which adjust with changes in our credit ratings. Based on our current credit ratings, borrowings, if any, will accrue at LIBOR, or alternate benchmark rate, plus 110 basis points, and the annual facility fee is 15 basis points. At December 31, 2020, our ratio of indebtedness to adjusted EBITDA was 4.6 to 1, and we were in compliance with all covenants under our $2.5 Billion Credit Agreement.
Maximum amount of cash allowable to net against indebtedness for leverage ratio	$ 700,000						$ 700,000
Notes Payable from Public Offering Due 2026, 2031 and 2051 [Member]
Debt Instrument [Line Items]
Senior Notes, Noncurrent		$ 1,500,000
Proceeds from Debt, Net of Issuance Costs		1,480,000
Notes Payable from Public Offering Due 2025, 2030 and 2050 [Member]
Debt Instrument [Line Items]
Senior Notes, Noncurrent			$ 1,750,000
Proceeds from Debt, Net of Issuance Costs			1,730,000
Notes Payable from Public Offering Due 2024, 2029 and 2049 [Member]
Debt Instrument [Line Items]
Senior Notes, Noncurrent				$ 2,000,000
Proceeds from Debt, Net of Issuance Costs				1,970,000
Notes Payable from Public Offering Due 2029 and 2048 [Member]
Debt Instrument [Line Items]
Senior Notes, Noncurrent					$ 1,250,000
Proceeds from Debt, Net of Issuance Costs					$ 1,230,000
Notes Payable from Public Offering Due 2028 and 2048 [Member]
Debt Instrument [Line Items]
Senior Notes, Noncurrent						1,250,000
Proceeds from Debt, Net of Issuance Costs						$ 1,230,000
Senior Notes [Member]
Long-term Debt, by Maturity [Abstract]
2021	0						0
2022	1,437,700						1,437,700
2023	925,000						925,000
2024	500,000						500,000
2025	887,000						$ 887,000
Guardian Pipeline [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant Description							Guardian Pipeline’s senior notes contain financial covenants that require the maintenance of certain financial ratios as defined in the master shelf agreement based on Guardian Pipeline’s financial position and results of operations. Upon any breach of these covenants, all amounts outstanding under the master shelf agreement may become due and payable immediately
Debt Instrument, Covenant Compliance							At December 31, 2020, Guardian Pipeline was in compliance with its financial covenants
Guardian Pipeline [Member] \| Notes Payables 1 due 2022 [Member]
Debt Instrument [Line Items]
Total debt	$ 13,657						$ 13,657	21,307
Average interest rate (in hundredths) \| Rate	7.85%						7.85%
Guardian Pipeline [Member] \| Notes Payables 1 due 2022 [Member]
Long-term Debt, by Maturity [Abstract]
2021	$ 7,700						$ 7,700
2022	6,000						6,000
2023	0						0
2024	0						0
2025	0						0
Subsidiary Issuer [Member] \| 3.2% Notes Payable due 2018
Debt Instrument [Line Items]
Interest rates (in hundredths) \| Rate						3.20%
Repayments of Long-term Debt						$ 425,000
Subsidiary Issuer [Member] \| 8.625% Notes Payables due 2019
Debt Instrument [Line Items]
Interest rates (in hundredths) \| Rate					8.625%
Repayments of Long-term Debt					$ 500,000
Subsidiary Issuer [Member] \| Term Loan Agreement due 2019
Debt Instrument [Line Items]
Repayments of Long-term Debt						500,000
Subsidiary Issuer [Member] \| 3.80% Notes Payable due 2020
Debt Instrument [Line Items]
Extinguishment of Debt, Amount				$ 300,000
Interest rates (in hundredths) \| Rate				3.80%
Debt Instrument, Redemption Price				$ 308,000
Gain (Loss) on Extinguishment of Debt				(2,700)
Subsidiary Issuer [Member] \| 3.375% Notes Payable due 2022 [Member]
Debt Instrument [Line Items]
Total debt	895,814						895,814	900,000
Debt Instrument, Face Amount	$ 900,000						$ 900,000
Interest rates (in hundredths) \| Rate	3.375%						3.375%
Subsidiary Issuer [Member] \| 5.0% Notes Payable due 2023 [Member]
Debt Instrument [Line Items]
Total debt	$ 425,000						$ 425,000	425,000
Debt Instrument, Face Amount	$ 425,000						$ 425,000
Interest rates (in hundredths) \| Rate	5.00%						5.00%
Subsidiary Issuer [Member] \| 4.9% Notes Payable due 2025 [Member]
Debt Instrument [Line Items]
Total debt	$ 500,000						$ 500,000	500,000
Debt Instrument, Face Amount	$ 500,000						$ 500,000
Interest rates (in hundredths) \| Rate	4.90%						4.90%
Subsidiary Issuer [Member] \| 6.65% Notes Payable due 2036 [Member]
Debt Instrument [Line Items]
Total debt	$ 600,000						$ 600,000	600,000
Debt Instrument, Face Amount	$ 600,000						$ 600,000
Interest rates (in hundredths) \| Rate	6.65%						6.65%
Subsidiary Issuer [Member] \| 6.85% Notes Payable due 2037 [Member]
Debt Instrument [Line Items]
Total debt	$ 600,000						$ 600,000	600,000
Debt Instrument, Face Amount	$ 600,000						$ 600,000
Interest rates (in hundredths) \| Rate	6.85%						6.85%
Subsidiary Issuer [Member] \| 6.125% Notes Payable due 2041 [Member]
Debt Instrument [Line Items]
Total debt	$ 650,000						$ 650,000	650,000
Debt Instrument, Face Amount	$ 650,000						$ 650,000
Interest rates (in hundredths) \| Rate	6.125%						6.125%
Subsidiary Issuer [Member] \| 6.2% Notes Payable due 2043 [Member]
Debt Instrument [Line Items]
Total debt	$ 400,000						$ 400,000	400,000
Debt Instrument, Face Amount	$ 400,000						$ 400,000
Interest rates (in hundredths) \| Rate	6.20%						6.20%
Parent Company
Debt Instrument [Line Items]
Commercial Paper	$ 0						$ 0	$ 220,000
Short-term Debt, Weighted Average Interest Rate, at Point in Time \| Rate								2.16%
Parent Company \| Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant Description							Our senior notes are governed by indentures containing covenants, including among other provisions, limitations on our ability to place liens on our property or assets and to sell and leaseback our property. The indentures governing our 6.875% senior notes due 2028 include an event of default upon acceleration of other indebtedness of $15 million or more, and the indentures governing the remainder of our senior notes include an event of default upon the acceleration of other indebtedness of $100 million or more. Such events of default would entitle the trustee or the holders of 25% in aggregate principal amount of the outstanding senior notes to declare those senior notes immediately due and payable in full. The indenture for the 7.5% notes due 2023 also contains a provision that allows the holders of the notes to require ONEOK to offer to repurchase all or any part of their notes if a change of control and a credit rating downgrade occur at a purchase price of 101% of the principal amount, plus accrued and unpaid interest, if any.
Debt instrument call feature							We may redeem our senior notes, in whole or in part, at any time prior to their maturity at a redemption price equal to the principal amount, plus accrued and unpaid interest and a make-whole premium. We may redeem the balance of our senior notes due 2022, 2023, 2024, 2025, 2026, 2027, 2028 (4.55%), 2029, 2030, 2031, 2041, 2043, 2047, 2048, 2049, 2050 and 2051 at a redemption price equal to the principal amount, plus accrued and unpaid interest, starting one to six months before the maturity date as stipulated in the respective contract terms. Our senior notes are senior unsecured obligations, ranking equally in right of payment with all of our existing and future unsecured senior indebtedness.
Parent Company \| Term Loan Agreement due 2021 [Member]
Debt Instrument [Line Items]
Total debt	0						$ 0	$ 1,250,000
Debt Instrument, Face Amount	1,500,000	1,500,000					1,500,000		$ 1,500,000
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate \| Rate								2.70%
Repayments of Long-term Debt		1,250,000		250,000
Parent Company \| 4.25% Notes Payable due 2022 [Member]
Debt Instrument [Line Items]
Total debt	541,877						541,877	$ 547,397
Debt Instrument, Face Amount	$ 700,000						$ 700,000
Interest rates (in hundredths) \| Rate	4.25%						4.25%
Parent Company \| 7.5% Notes Payable due 2023 [Member]
Debt Instrument [Line Items]
Total debt	$ 500,000						$ 500,000	500,000
Debt Instrument, Face Amount	$ 500,000						$ 500,000
Interest rates (in hundredths) \| Rate	7.50%						7.50%
Senior Note Covenant, Redemption Price Upon Event Of Default \| Rate	101.00%						101.00%
Parent Company \| 2.75% Notes Payable due 2024 [Member]
Debt Instrument [Line Items]
Total debt	$ 500,000						$ 500,000	500,000
Debt Instrument, Face Amount	$ 500,000			$ 500,000			$ 500,000
Interest rates (in hundredths) \| Rate	2.75%			2.75%			2.75%
Parent Company \| 2.2% Notes Payable due 2025 [Member]
Debt Instrument [Line Items]
Total debt	$ 387,000						$ 387,000	0
Debt Instrument, Face Amount	$ 400,000		$ 400,000				$ 400,000
Interest rates (in hundredths) \| Rate	2.20%		2.20%				2.20%
Parent Company \| 5.85% Notes Payable due 2026 [Member]
Debt Instrument [Line Items]
Total debt	$ 600,000						$ 600,000	0
Debt Instrument, Face Amount	$ 600,000	$ 600,000					$ 600,000
Interest rates (in hundredths) \| Rate	5.85%	5.85%					5.85%
Parent Company \| 4.0% Notes Payable due 2027 [Member]
Debt Instrument [Line Items]
Total debt	$ 500,000						$ 500,000	500,000
Debt Instrument, Face Amount	$ 500,000						$ 500,000
Interest rates (in hundredths) \| Rate	4.00%						4.00%
Parent Company \| 4.55% Notes Payable due 2028 [Member]
Debt Instrument [Line Items]
Total debt	$ 800,000						$ 800,000	800,000
Debt Instrument, Face Amount	$ 800,000					$ 800,000	$ 800,000
Interest rates (in hundredths) \| Rate	4.55%					4.55%	4.55%
Parent Company \| 6.875% Notes Payable due 2028 [Member]
Debt Instrument [Line Items]
Total debt	$ 100,000						$ 100,000	100,000
Debt Instrument, Face Amount	$ 100,000						$ 100,000
Interest rates (in hundredths) \| Rate	6.875%						6.875%
Senior Note Covenant, Acceleration Of Indebtedness	$ 15,000						$ 15,000
Parent Company \| 4.35% Notes Payable due 2029 [Member]
Debt Instrument [Line Items]
Total debt	700,000						700,000	700,000
Debt Instrument, Face Amount	$ 700,000				$ 700,000		$ 700,000
Interest rates (in hundredths) \| Rate	4.35%				4.35%		4.35%
Parent Company \| 3.4% Notes Payable due 2029 [Member]
Debt Instrument [Line Items]
Total debt	$ 714,251						$ 714,251	750,000
Debt Instrument, Face Amount	$ 750,000			$ 750,000			$ 750,000
Interest rates (in hundredths) \| Rate	3.40%			3.40%			3.40%
Parent Company \| 3.1% Notes Payable due 2030 [Member]
Debt Instrument [Line Items]
Total debt	$ 780,093						$ 780,093	0
Debt Instrument, Face Amount	$ 850,000		$ 850,000				$ 850,000
Interest rates (in hundredths) \| Rate	3.10%		3.10%				3.10%
Parent Company \| 6.35% Notes Payable due 2031 [Member]
Debt Instrument [Line Items]
Total debt	$ 600,000						$ 600,000	0
Debt Instrument, Face Amount	$ 600,000	$ 600,000					$ 600,000
Interest rates (in hundredths) \| Rate	6.35%	6.35%					6.35%
Parent Company \| 6.0% Notes Payable due 2035 [Member]
Debt Instrument [Line Items]
Total debt	$ 400,000						$ 400,000	400,000
Debt Instrument, Face Amount	$ 400,000						$ 400,000
Interest rates (in hundredths) \| Rate	6.00%						6.00%
Parent Company \| 4.95% Notes Payable due 2047 [Member]
Debt Instrument [Line Items]
Total debt	$ 689,006						$ 689,006	700,000
Debt Instrument, Face Amount	$ 700,000						$ 700,000
Interest rates (in hundredths) \| Rate	4.95%						4.95%
Parent Company \| 5.2% Notes Payable due 2048 [Member]
Debt Instrument [Line Items]
Total debt	$ 1,000,000						$ 1,000,000	1,000,000
Debt Instrument, Face Amount	$ 1,000,000					$ 450,000	$ 1,000,000
Interest rates (in hundredths) \| Rate	5.20%					5.20%	5.20%
Parent Company \| Note Payables, Additional Issuance, due 2048 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount					$ 550,000
Interest rates (in hundredths) \| Rate					5.20%
Parent Company \| 4.45% Notes Payable due 2049 [Member]
Debt Instrument [Line Items]
Total debt	$ 713,676						$ 713,676	750,000
Debt Instrument, Face Amount	$ 750,000			$ 750,000			$ 750,000
Interest rates (in hundredths) \| Rate	4.45%			4.45%			4.45%
Parent Company \| 4.5% Notes Payable due 2050 [Member]
Debt Instrument [Line Items]
Total debt	$ 451,270						$ 451,270	0
Debt Instrument, Face Amount	$ 500,000		$ 500,000				$ 500,000
Interest rates (in hundredths) \| Rate	4.50%		4.50%				4.50%
Parent Company \| 7.15% Notes Payable due 2051 [Member]
Debt Instrument [Line Items]
Total debt	$ 300,000						$ 300,000	$ 0
Debt Instrument, Face Amount	$ 300,000	$ 300,000					$ 300,000
Interest rates (in hundredths) \| Rate	7.15%	7.15%					7.15%
London Interbank Offered Rate (LIBOR) [Member] \| $2.5 Billion Credit Agreement [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate							1.10%

EQUITY EQUITY (Details)

EQUITY EQUITY (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended													12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners												20.00%
Business Combination, Consideration Transferred		$ 27,000									$ 195,000
Dividends, Per Share, Cash Paid		$ 0.935	$ 0.935	$ 0.935	$ 0.935	$ 0.915	$ 0.890	$ 0.865	$ 0.860	$ 0.855	$ 0.825	$ 0.795	$ 0.770	$ 3.74	$ 3.53	$ 3.245
Dividends, Cash														$ 1,600,000	$ 1,500,000	$ 1,300,000
Public Offering Price				$ 32									$ 54.50
Stock Issued During Period, Shares, New Issues				29,900									21,900
Stock Issued During Period, Value, New Issues				$ 937,000									$ 1,200,000
Dividends, Preferred Stock, Cash														1,100	1,100	1,100
Preferred stock dividends paid														$ 1,100	$ 1,100	$ 1,100
Issued Under Equity Agreement
Common Stock Sold Under Equity Distribution Agreement														0
Subsequent Event [Member]
Common Stock, Dividends, Per Share, Declared, Annualized	$ 3.74
Common Stock, Dividends, Per Share, Declared	$ 0.935
Preferred stock dividends paid	$ 300
Dividends Payable, Date of Record	Feb. 1, 2021
Series A Preferred Stock [Member]
Preferred Stock, Shares Outstanding		0												0
Series E Preferred Stock [Member]
Preferred Stock, Dividend Rate, Percentage														5.50%
ONEOK [Member]
Aggregate Amount Of Common Shares Available For Issuance And Sale Under Equity Distribution Agreement			$ 1,000,000

ACCUMULATED OTHER COMPREHENSI_3

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other comprehensive income (loss) before reclassification, risk-management assets/liabilities	$ (165,023)	$ (147,803)	$ (5,673)
Other comprehensive (income) loss before reclassification, retirement and other postretirement benefit plan obligations	(40,341)	(19,490)
Other comprehensive income (loss) before reclassification, risk-management assets/liabilities of unconsolidated affiliates	(8,635)	(7,275)
Other comprehensive income (loss) before reclassifications	(213,999)	(174,568)
Other comprehensive income reclassification adjustment from AOCI for risk-management assets/liabilities, net of tax	21,097	(21,057)	36,870
Other comprehensive income, retirement and other postretirement benefit plans, reclassification adjustment from AOCI, net of tax	14,187	9,794
Other comprehensive income, reclassification adjustment from AOCI for other comprehensive income attributable to unconsolidated affiliates, net of tax	1,266	70
Other comprehensive income, reclassification adjustment included in net income, net of tax	36,550	(11,193)
Other comprehensive income (loss), risk-management assets/liabilities, after reclassification adjustment, net of tax	(143,926)	(168,860)
Other comprehensive (income) loss, retirement and other postretirement benefit plans, after reclassification adjustment, net of tax	(26,154)	(9,696)	4,771
Other comprehensive income (loss), risk-management assets/liabilities of unconsolidated affiliates, net of tax	(7,369)	(7,205)
Other comprehensive income (loss), net of tax	(177,449)	(185,761)
Risk management assets/liabilities	(377,446)	(233,520)	(64,660)
Retirement and other postretirement benefit plan obligations	(157,635)	(131,481)	(121,785)
Risk-management assets/liabilities of unconsolidated affiliates	(16,368)	(8,999)	(1,794)
Accumulated other comprehensive loss	(551,449)	$ (374,000)	$ (188,239)
Cash Flow Hedging [Member] \| Commodity Contract
Unrealized gain loss on cash flow hedges net of tax accumulated other comprehensive income loss	(27,303)
Price risk cash flow hedge unrealized gain (loss) to be reclassified during next 12 months	(27,000)
Commodity cash flow hedge gain (loss) to be reclassified after next 12 months net	(300)
Cash Flow Hedging [Member] \| Interest Rate Contract
Amount of accumulated other comprehensive income (loss) attributable primarily to settled interest-rate swaps.	(193,519)
Amount of accumulated other comprehensive income (loss) attributable primarily to forward starting interest-rate swaps.	(156,624)
Interest rate cash flow hedge gain (loss) to be reclassified during next 12 months, net	$ (30,500)

EARNINGS PER SHARE EARNINGS P_3

EARNINGS PER SHARE EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Basic EPS
Net income available for common stock	$ 307,754	$ 312,041	$ 134,046	$ (142,132)	$ 319,976	$ 308,880	$ 311,688	$ 336,933	$ 611,709	$ 1,277,477	$ 1,150,603
Shares									431,105	413,560	411,485
Earnings per share, basic	$ 0.69	$ 0.70	$ 0.32	$ (0.34)	$ 0.77	$ 0.75	$ 0.75	$ 0.82	$ 1.42	$ 3.09	$ 2.80
Diluted EPS
Effect of dilutive securities									$ 0	$ 0	$ 0
Effect of dilutive securities, number of shares									677	1,884	2,710
Net income available for common stock and common stock equivalents									$ 611,709	$ 1,277,477	$ 1,150,603
Shares									431,782	415,444	414,195
Earnings per share, diluted	$ 0.69	$ 0.70	$ 0.32	$ (0.34)	$ 0.77	$ 0.74	$ 0.75	$ 0.81	$ 1.42	$ 3.07	$ 2.78

SHARE-BASED PAYMENTS SHARE-BA_3

SHARE-BASED PAYMENTS SHARE-BASED PAYMENTS (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	8,500,000
Number of Shares Available for Issuance	6,900,000
Maximum Value of Shares For Which Awards May Be Issued To A Participant During Any Year	$ 800
Forfeiture rate maximum (in hundredths)	3.00%
Allocated share-based compensation expense	$ 29,400	$ 46,500	$ 33,200
Tax Benefit	$ 14,100	$ 31,700	$ 12,200
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Vesting Period	3 years
Nonvested Award, Cost Not yet Recognized, Amount	$ 16,700
Nonvested Award, Cost Not yet Recognized, Period for Recognition	1 year 9 months 18 days
Nonvested, number of units	646,287	698,990
Granted, units	216,392
Released to participants, units	(240,576)
Forfeited, units	(28,519)
Nonvested, Weighted Average Grant Date Fair Value	$ 63.85	$ 54.05
Grants in Period, Weighted Average Grant Date Fair Value	76.49	$ 58.07	$ 46.94
Vested in Period, Weighted Average Grant Date Fair Value	46.58
Forfeitures, Weighted Average Grant Date Fair Value	$ 65.20
Granted in Period, Fair Value	$ 16,552	$ 15,238	$ 13,907
Vested in Period, Fair Value	$ 11,204	$ 10,691	$ 9,552
Performance-Unit Activity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Vesting Period	3 years
Nonvested Award, Cost Not yet Recognized, Amount	$ 25,000
Nonvested Award, Cost Not yet Recognized, Period for Recognition	1 year 9 months 18 days
Nonvested, number of units	834,246	937,821
Granted, units	283,029
Released to participants, units	(300,423)
Forfeited, units	(86,181)
Nonvested, Weighted Average Grant Date Fair Value	$ 75.96	$ 66.67
Grants in Period, Weighted Average Grant Date Fair Value	88.43	$ 68.02	$ 59.57
Vested in Period, Weighted Average Grant Date Fair Value	58.99
Forfeitures, Weighted Average Grant Date Fair Value	$ 74.83
Granted in Period, Fair Value	$ 25,028	$ 23,020	$ 22,081
Vested in Period, Fair Value	$ 17,722	$ 15,018	$ 12,545
Expected Volatility Rate	21.70%	27.10%	39.20%
Expected Dividend Rate	4.87%	5.05%	5.49%
Risk Free Interest Rate	1.39%	2.47%	2.44%
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	11,600,000
Maximum allowable percentage of annual base pay withheld to purchase our common stock	10.00%
Purchase price percentage of the lower of its grant date or exercise date market price	85.00%
Employee participation in the plan (in hundredths)	68.00%	62.00%	60.00%
Shares sold under the Employee Stock Purchase Plan	359,977	171,590	165,877
Weighted Average Share Price of Shares Sold Under the Employee Stock Purchase Plan (In Dollars per Share)	$ 27.78	$ 51.24	$ 45.53
Employee Stock Award Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	900,000
Allocated share-based compensation expense	$ 200	$ 1,000	$ 200
Shares Awarded Under Employee Stock Award Program	2,871	14,022	2,553
Non-employees and Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, units	0
Options, Outstanding, Number	0

EMPLOYEE BENEFIT PLANS EMPLOY_3

EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Deferred income taxes (c)		$ 7,812	$ 2,910	$ (1,425)
Total recognized in other comprehensive income (loss)		(26,154)	(9,696)	4,771
Other comprehensive income (loss), risk-management assets/liabilities of unconsolidated affiliates, net of tax		(7,369)	(7,205)
Accumulated other comprehensive loss, net of tax		$ (157,635)	$ (131,481)	$ (121,785)
Expected long-term return on plan assets		7.50%	7.50%	8.00%
Compensation increase rate		3.70%	3.65%	3.00%
Reclassification Adjustment from AOCI, Tax, Retirement and Other Postretirement Benefit Plans, Gain (Loss)		$ 4,200	$ 2,900	$ 3,800
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Obligation		583,072	534,849	466,994
Service cost		8,154	7,825	7,339
Interest cost		18,318	20,528	17,659
Plan participants’ contributions		0	0
Actuarial loss		37,951	55,954
Benefits paid		(16,200)	(16,452)
Fair value of plan assets		379,092	346,792	290,684
Actual return on plan assets (a)		36,400	58,060
Employer contributions		12,100	14,500
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant		0	0
Defined Benefit Plan, Plan Assets, Benefits Paid		(16,200)	(16,452)
Balance at December 31		(203,980)	(188,057)
Current liabilities		(4,679)	(4,616)
Noncurrent liabilities		(199,301)	(183,441)
Balance at December 31		(203,980)	(188,057)
Defined Benefit Plan, Accumulated Benefit Obligation		548,200	498,800
Expected return on plan assets		(24,964)	(23,600)	(23,917)
Amortization of prior service cost (credit)		114	0	0
Amortization of net loss		18,306	12,649	17,060
Net periodic benefit cost (income)		19,928	17,402	18,141
Net gain (loss) (a)		(31,016)	(25,389)	(16,351)
Prior service cost		0	(601)	0
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax		114	0	0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax		18,306	12,649	17,060
Deferred income taxes (c)		2,897	3,068	(18,928)
Total recognized in other comprehensive income (loss)		(9,699)	(10,273)	$ (18,219)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax		(487)	(601)
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax		(185,662)	(172,952)
Accumulated other comprehensive loss		(186,149)	(173,553)
Deferred income taxes		49,251	46,354
Accumulated other comprehensive loss, net of tax		$ (136,898)	$ (127,199)
Discount rate		3.00%	3.50%
Compensation increase rate		3.60%	3.70%
Discount Rates - Retirement and Other Postretirement Plans		3.50%	4.50%	3.75%
Domestic and international equities		42.00%
Long duration fixed income		30.00%
Return-seeking credit		11.00%
Hedge funds		10.00%
Real estate funds		7.00%
Total		100.00%
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months		$ 19,460
Defined Benefit Plan, Expected Future Benefit Payment, Year Two		20,325
Defined Benefit Plan, Expected Future Benefit Payment, Year Three		21,216
Defined Benefit Plan, Expected Future Benefit Payment, Year Four		22,234
Defined Benefit Plan, Expected Future Benefit Payment, Year Five		23,260
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter		127,038
Defined Benefit Plan, Benefit Obligation, Benefits Paid		(16,200)	$ (16,452)
Retirement Plan [Member] \| Subsequent Event [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 11,200
Retirement Plan [Member] \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		43	110
Retirement Plan [Member] \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		4,890	3,263
Retirement Plan [Member] \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Subtotal
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		4,933	3,373
Retirement Plan [Member] \| Measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		374,159	343,419
Retirement Plan [Member] \| Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		379,092	346,792
Retirement Plan [Member] \| Equity securities \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		43	47
Retirement Plan [Member] \| Equity securities \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Equity securities \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Equity securities \| Subtotal
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		43	47
Retirement Plan [Member] \| Equity securities \| Measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		164,099	149,985
Retirement Plan [Member] \| Equity securities \| Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		164,142	150,032
Retirement Plan [Member] \| Real Estate Funds [Member] \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Real Estate Funds [Member] \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Real Estate Funds [Member] \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Real Estate Funds [Member] \| Subtotal
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Real Estate Funds [Member] \| Measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		24,134	23,885
Retirement Plan [Member] \| Real Estate Funds [Member] \| Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		24,134	23,885
Retirement Plan [Member] \| Government obligations \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Government obligations \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Government obligations \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Government obligations \| Subtotal
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Government obligations \| Measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		45,237	50,708
Retirement Plan [Member] \| Government obligations \| Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		45,237	50,708
Retirement Plan [Member] \| Corporate obligations \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Corporate obligations \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Corporate obligations \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Corporate obligations \| Subtotal
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Corporate obligations \| Measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		101,626	85,898
Retirement Plan [Member] \| Corporate obligations \| Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		101,626	85,898
Retirement Plan [Member] \| Common/collective trusts \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Common/collective trusts \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		4,890	3,263
Retirement Plan [Member] \| Common/collective trusts \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Common/collective trusts \| Subtotal
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		4,890	3,263
Retirement Plan [Member] \| Common/collective trusts \| Measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Common/collective trusts \| Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		4,890	3,263
Retirement Plan [Member] \| Money market funds \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			63
Retirement Plan [Member] \| Money market funds \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			0
Retirement Plan [Member] \| Money market funds \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			0
Retirement Plan [Member] \| Money market funds \| Subtotal
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			63
Retirement Plan [Member] \| Money market funds \| Measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			0
Retirement Plan [Member] \| Money market funds \| Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			63
Retirement Plan [Member] \| Other Investments \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Other Investments \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Other Investments \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Other Investments \| Subtotal
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] \| Other Investments \| Measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		39,063	32,943
Retirement Plan [Member] \| Other Investments \| Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		39,063	32,943
Unfunded Capital Commitments		$ 0	$ 0
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Assumed Health Care Cost Trend Rate		6.50%	7.00%
Defined Benefit Plan Assumed Ultimate Health Care Cost Trend Rate		5.00%	5.00%
Minimum Number Of Years Of Service For Certain Employees To Be Eligible To Participate In Welfare Plans That Provide Postretirement Medical And Life Insurance Benefits		5 years
Benefit Obligation		$ 54,515	$ 52,309	$ 46,840
Service cost		460	468	845
Interest cost		1,771	2,038	2,108
Plan participants’ contributions		1,032	1,142
Actuarial loss		2,860	5,101
Benefits paid		(3,917)	(3,280)
Fair value of plan assets		20,874	39,060	30,800
Actual return on plan assets (a)		(15,699)	8,087
Employer contributions		0	2,000
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant		1,032	1,142
Defined Benefit Plan, Plan Assets, Benefits Paid		(3,519)	(2,969)
Balance at December 31		(33,641)	(13,249)
Current liabilities		0	0
Noncurrent liabilities		(33,641)	(13,249)
Balance at December 31		(33,641)	(13,249)
Expected return on plan assets		(2,894)	(2,285)	(2,690)
Amortization of prior service cost (credit)		0	(227)	(1,662)
Amortization of net loss		5	297	1,338
Net periodic benefit cost (income)		(658)	291	(61)
Net gain (loss) (a)		(21,453)	700	6,545
Prior service cost		0	0	0
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax		0	(227)	(1,662)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax		5	297	1,338
Deferred income taxes (c)		4,933	(177)	(2,831)
Total recognized in other comprehensive income (loss)		(16,515)	593	$ 3,390
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax		0	0
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax		(25,558)	(4,110)
Accumulated other comprehensive loss		(25,558)	(4,110)
Deferred income taxes		6,322	1,389
Accumulated other comprehensive loss, net of tax		$ (19,236)	$ (2,721)
Discount rate		2.75%	3.50%
Discount Rates - Retirement and Other Postretirement Plans		3.50%	4.50%	3.75%
Year that the rate reaches the ultimate trend rate		2024	2024
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months		$ 3,297
Defined Benefit Plan, Expected Future Benefit Payment, Year Two		3,408
Defined Benefit Plan, Expected Future Benefit Payment, Year Three		3,371
Defined Benefit Plan, Expected Future Benefit Payment, Year Four		3,335
Defined Benefit Plan, Expected Future Benefit Payment, Year Five		3,322
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter		15,848
Defined Benefit Plan, Benefit Obligation, Benefits Paid		(3,917)	$ (3,280)
Other Postretirement Benefits Plan [Member] \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		20,066	2,043
Other Postretirement Benefits Plan [Member] \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		808	37,017
Other Postretirement Benefits Plan [Member] \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Other Postretirement Benefits Plan [Member] \| Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		20,874	39,060
Other Postretirement Benefits Plan [Member] \| Equity securities \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		15,116	2,043
Other Postretirement Benefits Plan [Member] \| Equity securities \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Other Postretirement Benefits Plan [Member] \| Equity securities \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Other Postretirement Benefits Plan [Member] \| Equity securities \| Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		15,116	2,043
Other Postretirement Benefits Plan [Member] \| Money market funds \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Other Postretirement Benefits Plan [Member] \| Money market funds \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		808	2,428
Other Postretirement Benefits Plan [Member] \| Money market funds \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Other Postretirement Benefits Plan [Member] \| Money market funds \| Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		808	2,428
Other Postretirement Benefits Plan [Member] \| Insurance and group annuity contracts
Defined Benefit Plan Disclosure [Line Items]
Actual return on plan assets (a)		13,200
NetProceedsFromExitOfAnInvestmentInAnInsuranceContract		16,200
Other Postretirement Benefits Plan [Member] \| Insurance and group annuity contracts \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			0
Other Postretirement Benefits Plan [Member] \| Insurance and group annuity contracts \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			34,589
Other Postretirement Benefits Plan [Member] \| Insurance and group annuity contracts \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			0
Other Postretirement Benefits Plan [Member] \| Insurance and group annuity contracts \| Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			34,589
Other Postretirement Benefits Plan [Member] \| Municipal Bonds \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		4,950
Other Postretirement Benefits Plan [Member] \| Municipal Bonds \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Other Postretirement Benefits Plan [Member] \| Municipal Bonds \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Other Postretirement Benefits Plan [Member] \| Municipal Bonds \| Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		4,950
Supplemental Executive Retirement Plan Investments Included in Other Assets[Member]
Defined Benefit Plan Disclosure [Line Items]
Balance at December 31		$ 116,200	98,900
401(k) Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Percent of employee matched of eligible compensation		100.00%
Percentage of Each Participants Eligible Compensation		1.00%
Contributions made to the Plan		$ 27,100	$ 30,400	$ 28,000
Profit-sharing contribution [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of Each Participants Eligible Compensation		6.00%

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Thousands	12 Months Ended
INCOME TAXES (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	21.00%
Current tax expense (benefit)
Federal	$ 980	$ (1,278)	$ 260
State	1,797	963	1,633
Total current tax expense (benefit)	2,777	(315)	1,893
Deferred tax expense
Federal	154,068	327,806	319,551
State	32,662	44,923	41,459
Total deferred tax expense	186,730	372,729	361,010
Income tax expense	189,507	372,414	362,903
Income Tax Reconciliation
Income before income taxes	802,316	1,650,991	1,517,935
Net Income (Loss) Attributable to Noncontrolling Interest	0	0	3,329
Net income attributable to ONEOK before income taxes	$ 802,316	$ 1,650,991	$ 1,514,606
Federal statutory income tax rate	21.00%	21.00%	21.00%
Provision for federal income taxes	$ 168,486	$ 346,708	$ 318,067
State income taxes, net of federal benefit	13,580	34,545	38,668
Deferred tax rate change, inclusive of valuation allowance	20,879	11,340	5,552
Other, net	(6,058)	804	5,260
Effective Income Tax Rate Reconciliation, Tax Expense (Benefit), Share-based Payment Arrangement, Amount	(7,380)	(20,983)	(4,644)
Deferred tax assets
Employee benefits and other accrued liabilities	96,741	99,510
Federal net operating loss	1,473,093	858,030
State net operating loss and benefits	258,929	171,779
Derivative instruments	134,499	83,710
Other	12,894	12,769
Total deferred tax assets	1,976,156	1,225,798
Carryforward expected to expire prior to utilization	(121,212)	(94,794)
Net deferred tax assets	1,854,944	1,131,004
Deferred tax liabilities
Excess of tax over book depreciation	87,021	84,631
Investment in partnerships (a)	2,437,620	1,582,436
Total deferred tax liabilities	2,524,641	1,667,067
Net deferred tax assets (liabilities)	669,697	536,063
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	$ 20,900	$ 11,300	$ 5,600

UNCONSOLIDATED AFFILIATES (Deta

UNCONSOLIDATED AFFILIATES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates	$ 805,032	$ 861,844	$ 969,150
Equity method goodwill	16,500	38,800
Equity in net earnings from investments	143,241	154,541	158,383
Impairment of equity investments	(37,730)	0	0
Accounts Payable, Related Parties, Current	8,400	13,500
Payments to Acquire Equity Method Investments	20,000
Natural Gas Gathering And Processing
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates	22,757	34,426	42,630
Equity in net earnings from investments	(1,123)	(6,292)	410
Natural Gas Liquids [Member]
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates	423,494	439,393	451,040
Equity in net earnings from investments	39,938	65,123	67,126
Unconsolidated Affiliates [Member]
Schedule of Equity Method Investments [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	$ 135,400	164,700	153,900
Northern Border Pipeline [Member]
Schedule of Equity Method Investments [Line Items]
Net ownership percentage	50.00%
Investments in unconsolidated affiliates	$ 291,987	307,209
Equity in net earnings from investments	75,409	68,871	67,854
Payments to Acquire Equity Method Investments	$ 0	0	0
Distributions paid to us		50,000
Cash Distribution Percentage of Equity Method Investment	100.00%
Tiered Rate Reduction	12.50%
Overland Pass Pipeline Company [Member]
Schedule of Equity Method Investments [Line Items]
Net ownership percentage	50.00%
Investments in unconsolidated affiliates	$ 409,573	417,473
Equity in net earnings from investments	$ 38,618	63,698	65,887
Cash Distribution Percentage of Equity Method Investment	100.00%
Overland Pass Pipeline Company [Member] \| Natural Gas Liquids [Member]
Schedule of Equity Method Investments [Line Items]
Net ownership percentage	50.00%
Roadrunner Gas Transmission [Member]
Schedule of Equity Method Investments [Line Items]
Net ownership percentage	50.00%
Investments in unconsolidated affiliates	$ 66,794	80,816
Equity in net earnings from investments	$ 29,017	26,839	22,993
Cash Distribution Percentage of Equity Method Investment	100.00%
Other Unconsolidated Affiliates [Member]
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates	$ 36,678	56,346
Equity in net earnings from investments	$ 197	$ (4,867)	$ 1,649
Venice Energy Services Company [Member] \| Natural Gas Gathering And Processing
Schedule of Equity Method Investments [Line Items]
Net ownership percentage	10.20%
Impairment of equity investments	$ (30,500)
ImpairmentOfEquityMethodInvestmentDifferenceBetweenCarryingAmountAndUnderlyingEquity	$ (22,300)
Chisholm Pipeline Company [Member] \| Natural Gas Liquids [Member]
Schedule of Equity Method Investments [Line Items]
Net ownership percentage	50.00%
Impairment of equity investments	$ (7,200)

COMMITMENTS AND CONTINGENCIES_3

COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	Dec. 31, 2020USD ($)
Firm Transportation and Storage Contracts [Abstract]
2021	$ 70.9
2022	60.9
2023	55.8
2024	53.4
2025	47.9
Thereafter	227.8
Total	$ 516.7

LEASES (Details)

LEASES (Details) - USD ($) $ in Thousands	12 Months Ended
LEASES (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2020
Lessee, Lease, Details [Line Items]
Finance lease assets - accumulated depreciation	$ (3,918,007)	$ (3,702,807)
Operating lease liability - current	13,610	1,883
Operating lease liability - noncurrent	87,610	13,509
Operating cash flows for operating leases	13,245	6,213
Financing cash flows for finance lease	1,949	1,764
Right-of-use assets obtained in exchange for operating lease liability (noncash)	99,547	4,097
Lease remaining balance related to lease entered in December 2019 [Member]
Lessee, Lease, Details [Line Items]
Lessee, Operating Lease, Term of Contract			10 years
Operating lease assets - Other assets	69,000
Present value of operating lease liabilities	69,900
Components of Lease Cost [Member]
Lessee, Lease, Details [Line Items]
Operating leases - Operations and maintenance	17,162	6,803
Finance lease - Amortization of lease assets	1,131	1,131
Finance Lease - Interest on lease liabilities	2,537	2,721
Total lease cost	$ 20,830	$ 10,655
Weighted-Average Remaining Lease Term [Member]
Lessee, Lease, Details [Line Items]
Operating Lease, Weighted Average Remaining Lease Term	8 years 3 months 18 days	10 years 4 months 24 days
Finance Lease, Weighted Average Remaining Lease Term	7 years 9 months 18 days	8 years 9 months 18 days
Weighted-Average Discount Rate [Member]
Lessee, Lease, Details [Line Items]
Operating Lease, Weighted Average Discount Rate, Percent	3.20%	4.58%
Finance Lease, Weighted Average Discount Rate, Percent	10.00%	10.00%
Maturity of Finance Lease Liability [Member]
Lessee, Lease, Details [Line Items]
2021	$ 4,500
2022	4,500
2023	4,500
2024	4,500
2025	4,500
2026 and beyond	12,600
Total lease payments	35,100
Less: Interest	10,800
Present value of finance lease liabilities	24,300
Maturity of Operating Lease Liabilities [Member]
Lessee, Lease, Details [Line Items]
2021	16,500
2022	15,100
2023	13,800
2024	12,500
2025	11,100
2026 and beyond	47,100
Total lease payments	116,100
Less: Interest	14,900
Present value of operating lease liabilities	101,200
Lease Assets and Liabilities Included in the Consolidated Balance Sheet [Member]
Lessee, Lease, Details [Line Items]
Operating lease assets - Other assets	100,154	$ 15,147
Finance lease assets - PPE	28,286	28,286
Finance lease assets - accumulated depreciation	(2,451)	(1,320)
Total leased assets	125,989	42,113
Operating lease liability - current	13,610	1,883
Finance lease liability - current	2,153	1,949
Operating lease liability - noncurrent	87,610	13,509
Finance lease liability - other deferred credits	22,143	24,296
Total lease liabilities	$ 125,516	$ 41,637

REVENUES (Details)

REVENUES (Details) - USD ($) $ in Millions	12 Months Ended
REVENUES (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Contract with Customer, Liability [Abstract]
Contract with customer, liability	$ 41.4	$ 57.1	$ 31.7
Revenue recognized included in beginning balance	(36.1)	(15.6)
Net additions	20.4	41
Contract with customer, liability, current	23.7	22.2
Contract with customer, liability, noncurrent	17.7	$ 34.9
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 1,786.5
Revenue, Remaining Performance Obligation, Contract Term	5 to 10 years
Remaining Contract Terms [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Contract Term	one month to 23 years
2021 [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 328.2
2022 [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	263
2023 [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	235.4
2024 {Member}
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	197.9
Thereafter [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 762

SEGMENTS (Details)

SEGMENTS (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
SEGMENTS (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Segment Reporting, Disclosure of Major Customers									10	10	10
Operating costs									$ (886,204)	$ (982,864)	$ (907,068)
Equity in net earnings (loss) from investments									143,241	154,541	158,383
Depreciation and amortization									(578,662)	(476,535)	(428,557)
Impairment charges				$ (641,800)					(644,930)	0	0
Investments in unconsolidated affiliates (Note M)	$ 805,032				$ 861,844				805,032	861,844	969,150
Noncash compensation expense									8,540	26,699	37,954
Total assets	23,078,754				21,812,121				23,078,754	21,812,121	18,231,671
Capital expenditures									2,195,381	3,848,349	2,141,475
Operating income (loss)	538,663	$ 550,433	$ 355,730	(83,469)	487,314	$ 482,151	$ 476,146	$ 468,742	1,361,357	1,914,353	1,835,464
Net income	308,029	312,316	134,321	(141,857)	320,251	309,155	311,963	337,208	612,809	1,278,577	1,155,032
Interest expense, net of capitalized interest									712,886	491,773	469,620
Income tax expense									189,507	372,414	362,903
Other corporate costs and equity AFUDC									(42,631)	(68,767)	(15,603)
Revenues	2,570,577	$ 2,174,264	$ 1,660,729	$ 2,136,672	2,663,606	$ 2,263,228	$ 2,457,575	$ 2,779,958	8,542,242	10,164,367	12,593,196
Cost of sales and fuel (exclusive of depreciation and operating costs)									(5,110,146)	(6,788,040)	(9,422,708)
Gain (Loss) on Extinguishment of Debt									22,300
Natural Gas Gathering And Processing
Segment Reporting Information [Line Items]
Operating costs									(326,938)	(368,352)	(368,939)
Equity in net earnings (loss) from investments									(1,123)	(6,292)	410
Noncash compensation expense and other									1,952	10,965	7,007
Segment adjusted EBITDA									650,036	702,650	631,607
Depreciation and amortization									(247,010)	(219,519)	(196,090)
Impairment charges									(566,145)
Investments in unconsolidated affiliates (Note M)	22,757				34,426				22,757	34,426	42,630
Total assets	6,499,908				6,795,744				6,499,908	6,795,744	6,078,473
Capital expenditures									446,142	926,489	694,611
Revenues									1,820,121	2,368,639	3,034,577
Cost of sales and fuel (exclusive of depreciation and operating costs)									(843,976)	(1,302,310)	(2,041,448)
Natural Gas Gathering And Processing \| Natural Gas Gathering and Processing Intersegment [Member]
Segment Reporting Information [Line Items]
Revenues									865,600	1,200,000	1,800,000
Natural Gas Liquids
Segment Reporting Information [Line Items]
Operating costs									(412,900)	(456,892)	(394,115)
Equity in net earnings (loss) from investments									39,938	65,123	67,126
Noncash compensation expense and other									8,748	15,936	9,829
Segment adjusted EBITDA									1,617,241	1,465,765	1,440,605
Depreciation and amortization									(271,900)	(196,132)	(174,007)
Impairment charges									(78,785)
Investments in unconsolidated affiliates (Note M)	423,494				439,393				423,494	439,393	451,040
Total assets	13,636,109				12,551,476				13,636,109	12,551,476	9,663,640
Capital expenditures									1,655,759	2,796,604	1,306,341
Revenues									7,090,013	8,532,516	10,934,578
Cost of sales and fuel (exclusive of depreciation and operating costs)									(5,108,558)	(6,690,918)	(9,176,813)
Natural Gas Liquids \| Natural Gas Liquids Regulated [Member]
Segment Reporting Information [Line Items]
Revenues									2,000,000	1,400,000	1,200,000
Cost of sales and fuel (exclusive of depreciation and operating costs)									(520,600)	(496,800)	(506,000)
Natural Gas Pipelines
Segment Reporting Information [Line Items]
Operating costs									(141,713)	(157,230)	(144,259)
Equity in net earnings (loss) from investments									104,426	95,710	90,847
Noncash compensation expense and other									1,540	2,977	3,912
Segment adjusted EBITDA									437,426	408,816	366,251
Depreciation and amortization									(55,739)	(57,250)	(55,118)
Impairment charges									0
Investments in unconsolidated affiliates (Note M)	358,781				388,025				358,781	388,025	475,480
Total assets	2,100,213				2,094,072				2,100,213	2,094,072	2,131,669
Capital expenditures									71,918	99,221	119,185
Revenues									479,982	471,987	431,735
Cost of sales and fuel (exclusive of depreciation and operating costs)									(6,809)	(4,628)	(15,984)
Natural Gas Pipelines \| Natural Gas Pipelines Regulated [Member]
Segment Reporting Information [Line Items]
Revenues									298,500	285,300	266,600
Cost of sales and fuel (exclusive of depreciation and operating costs)									(30,400)	(20,000)	(26,000)
Total Segments [Member]
Segment Reporting Information [Line Items]
Operating costs									(881,551)	(982,474)	(907,313)
Equity in net earnings (loss) from investments									143,241	154,541	158,383
Noncash compensation expense and other									12,240	29,878	20,748
Segment adjusted EBITDA									2,704,703	2,577,231	2,438,463
Depreciation and amortization									(574,649)	(472,901)	(425,215)
Impairment charges									(644,930)
Investments in unconsolidated affiliates (Note M)	805,032				861,844				805,032	861,844	969,150
Total assets	22,236,230				21,441,292				22,236,230	21,441,292	17,873,782
Capital expenditures									2,173,819	3,822,314	2,120,137
Revenues									9,390,116	11,373,142	14,400,890
Cost of sales and fuel (exclusive of depreciation and operating costs)									(5,959,343)	(7,997,856)	(11,234,245)
Other and Eliminations
Segment Reporting Information [Line Items]
Operating costs									(4,653)	(390)	245
Equity in net earnings (loss) from investments									0	0	0
Depreciation and amortization									(4,013)	(3,634)	(3,342)
Impairment charges									0
Investments in unconsolidated affiliates (Note M)	0				0				0	0	0
Total assets	$ 842,524				$ 370,829				842,524	370,829	357,889
Capital expenditures									21,562	26,035	21,338
Revenues									(847,874)	(1,208,775)	(1,807,694)
Cost of sales and fuel (exclusive of depreciation and operating costs)									849,197	1,209,816	1,811,537
Operating Segments [Member] \| Natural Gas Liquids \| Natural Gas Liquids Regulated [Member]
Segment Reporting Information [Line Items]
Revenues									1,800,000	1,200,000	1,100,000
Noncustomer [Domain]
Segment Reporting Information [Line Items]
Revenues									65,800	139,600	(16,200)
NGL and Condensate Sales [Member]
Segment Reporting Information [Line Items]
Revenues									6,477,869	7,944,787	10,301,496
NGL and Condensate Sales [Member] \| Natural Gas Gathering And Processing
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									889,388	1,224,378	1,775,991
NGL and Condensate Sales [Member] \| Natural Gas Liquids
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									6,409,332	7,910,833	10,319,847
NGL and Condensate Sales [Member] \| Natural Gas Pipelines
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									0	0	0
NGL and Condensate Sales [Member] \| Total Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									7,298,720	9,135,211	12,095,838
NGL and Condensate Sales [Member] \| Other and Eliminations
Segment Reporting Information [Line Items]
Revenues									(820,851)	(1,190,424)	(1,794,342)
Residue Natural Gas Sales [Member]
Segment Reporting Information [Line Items]
Revenues									769,319	965,975	1,091,102
Residue Natural Gas Sales [Member] \| Natural Gas Gathering And Processing
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									771,486	966,149	1,084,162
Residue Natural Gas Sales [Member] \| Natural Gas Liquids
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									0	0	0
Residue Natural Gas Sales [Member] \| Natural Gas Pipelines
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									8,693	1,244	9,772
Residue Natural Gas Sales [Member] \| Total Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									780,179	967,393	1,093,934
Residue Natural Gas Sales [Member] \| Other and Eliminations
Segment Reporting Information [Line Items]
Revenues									(10,860)	(1,418)	(2,832)
Gathering and Exchange Services Revenue [Member]
Segment Reporting Information [Line Items]
Revenues									630,517	578,537	568,070
Gathering and Exchange Services Revenue [Member] \| Natural Gas Gathering And Processing
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									141,943	164,299	163,194
Gathering and Exchange Services Revenue [Member] \| Natural Gas Liquids
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									488,574	414,238	404,897
Gathering and Exchange Services Revenue [Member] \| Natural Gas Pipelines
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									0	0	0
Gathering and Exchange Services Revenue [Member] \| Total Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									630,517	578,537	568,091
Gathering and Exchange Services Revenue [Member] \| Other and Eliminations
Segment Reporting Information [Line Items]
Revenues									0	0	(21)
Transportation and Storage Revenue [Member]
Segment Reporting Information [Line Items]
Revenues									638,413	648,103	603,437
Transportation and Storage Revenue [Member] \| Natural Gas Gathering And Processing
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									0	0	0
Transportation and Storage Revenue [Member] \| Natural Gas Liquids
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									182,915	197,483	199,018
Transportation and Storage Revenue [Member] \| Natural Gas Pipelines
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									470,097	466,266	414,969
Transportation and Storage Revenue [Member] \| Total Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									653,012	663,749	613,987
Transportation and Storage Revenue [Member] \| Other and Eliminations
Segment Reporting Information [Line Items]
Revenues									(14,599)	(15,646)	(10,550)
Other [Member]
Segment Reporting Information [Line Items]
Revenues									26,124	26,965	29,091
Other [Member] \| Natural Gas Gathering And Processing
Segment Reporting Information [Line Items]
Revenues									17,304	13,813	11,230
Other [Member] \| Natural Gas Liquids
Segment Reporting Information [Line Items]
Revenues									9,192	9,962	10,816
Other [Member] \| Natural Gas Pipelines
Segment Reporting Information [Line Items]
Revenues									1,192	4,477	6,994
Other [Member] \| Total Segments [Member]
Segment Reporting Information [Line Items]
Revenues									27,688	28,252	29,040
Other [Member] \| Other and Eliminations
Segment Reporting Information [Line Items]
Revenues									$ (1,564)	$ (1,287)	$ 51

QUARTERLY FINANCIAL DATA (UNA_3

QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues	$ 2,570,577	$ 2,174,264	$ 1,660,729	$ 2,136,672	$ 2,663,606	$ 2,263,228	$ 2,457,575	$ 2,779,958	$ 8,542,242	$ 10,164,367	$ 12,593,196
Operating income (loss)	538,663	550,433	355,730	(83,469)	487,314	482,151	476,146	468,742	1,361,357	1,914,353	1,835,464
Net Income (loss)	308,029	312,316	134,321	(141,857)	320,251	309,155	311,963	337,208	612,809	1,278,577	1,155,032
Net Income (Loss) Available to Common Stockholders	$ 307,754	$ 312,041	$ 134,046	$ (142,132)	$ 319,976	$ 308,880	$ 311,688	$ 336,933	$ 611,709	$ 1,277,477	$ 1,150,603
Earnings (loss) per share - basic	$ 0.69	$ 0.70	$ 0.32	$ (0.34)	$ 0.77	$ 0.75	$ 0.75	$ 0.82	$ 1.42	$ 3.09	$ 2.80
Earnings (loss) per share - diluted	$ 0.69	$ 0.70	$ 0.32	$ (0.34)	$ 0.77	$ 0.74	$ 0.75	$ 0.81	$ 1.42	$ 3.07	$ 2.78
Impairment charges				$ 641,800					$ 644,930	$ 0	$ 0