Saia (SAIA) 10-K23 Feb 242023 FY Annual reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2023	Feb. 16, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Entity Registrant Name	Saia, Inc.
Entity Central Index Key	0001177702
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		26,587,167
Entity Public Float			$ 9,085,980,151
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Interactive Data Current	Yes
Entity File Number	0-49983
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	48-1229851
Document Annual Report	true
Document Transition Report	false
Entity Address, Address Line One	11465 Johns Creek Parkway
Entity Address, Address Line Two	Suite 400
Entity Address, City or Town	Johns Creek
Entity Address, State or Province	GA
Entity Address, Postal Zip Code	30097
City Area Code	770
Local Phone Number	232-5067
Title of each class	Common Stock, par value $.001 per share
Security Exchange Name	NASDAQ
Trading Symbol	SAIA
ICFR Auditor Attestation Flag	true
Auditor Name	KPMG LLP
Auditor Location	Atlanta, Georgia, United States
Auditor Firm ID	185
Documents Incorporated by Reference	Portions of the definitive Proxy Statement to be filed within 120 days of December 31, 2023, pursuant to Regulation 14A under the Securities Exchange Act of 1934 for the Annual Meeting of Stockholders to be held April 25, 2024, have been incorporated by reference into Part III of this Form 10-K.
Document Financial Statement Error Correction [Flag]	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current Assets:
Cash and cash equivalents	$ 296,215	$ 187,390
Accounts receivable, less allowances of $4,427 in 2023 and $5,804 in 2022	311,742	290,306
Prepaid expenses	32,648	22,525
Income tax receivable	1,005	23,438
Other current assets	7,084	7,227
Total current assets	648,694	530,886
Property and Equipment, at cost	2,881,800	2,478,824
Less-accumulated depreciation and amortization	1,118,492	996,204
Net property and equipment	1,763,308	1,482,620
Operating Lease Right-of-Use Assets	118,734	120,455
Goodwill and Identifiable Intangibles, net	17,296	18,149
Other Noncurrent Assets	35,533	22,600
Total assets	2,583,565	2,174,710
Current Liabilities:
Accounts payable	141,877	99,792
Wages, vacation and employees’ benefits	75,514	66,684
Claims and insurance accruals	41,641	45,481
Other current liabilities	27,094	22,684
Current portion of long-term debt	10,173	14,519
Current portion of operating lease liability	25,757	24,925
Total current liabilities	322,056	274,085
Other Liabilities:
Long-term debt, less current portion	6,315	16,489
Operating lease liability, less current portion	96,462	98,581
Deferred income taxes	155,841	145,771
Claims, insurance and other	61,397	60,443
Total other liabilities	320,015	321,284
Commitments and Contingencies (Note 3)	0	0
Stockholders’ Equity:
Preferred stock, $0.001 par value, 50,000 shares authorized, none issued and outstanding	0	0
Common stock, $0.001 par value, 100,000,000 shares authorized, 26,549,372 and 26,464,197 shares issued and outstanding at December 31, 2023 and 2022, respectively	27	26
Additional paid-in-capital	285,092	277,366
Deferred compensation trust, 69,672 and 69,982 shares of common stock at cost at December 31, 2023 and 2022, respectively	(5,679)	(5,248)
Retained earnings	1,662,054	1,307,197
Total stockholders’ equity	1,941,494	1,579,341
Total liabilities and stockholders’ equity	$ 2,583,565	$ 2,174,710

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Allowance of accounts receivable	$ 4,427	$ 5,804
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	50,000	50,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	26,549,372	26,464,197
Common stock, shares outstanding	26,549,372	26,464,197
Deferred compensation trust	69,672	69,982

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Statement [Abstract]
Operating Revenue	$ 2,881,433	$ 2,792,057	$ 2,288,704
Operating Expenses:
Salaries, wages and employees’ benefits	1,301,280	1,169,539	1,063,703
Purchased transportation	238,688	315,896	249,710
Fuel, operating expenses and supplies	563,688	558,456	381,904
Operating taxes and licenses	69,542	63,824	59,095
Claims and insurance	67,984	56,601	61,345
Depreciation and amortization	178,845	157,203	141,700
Operating losses (gains), net	910	50	(3,894)
Total operating expenses	2,420,937	2,321,569	1,953,563
Operating Income	460,496	470,488	335,141
Non-operating (Income) Expenses:
Interest expense	2,535	2,611	3,212
Interest income	(6,208)	(217)	(11)
Other, net	(2,058)	46	(833)
Non-operating (income) expenses, net	(5,731)	2,440	2,368
Income Before Income Taxes	466,227	468,048	332,773
Income Tax Expense	111,370	110,626	79,538
Net Income	$ 354,857	$ 357,422	$ 253,235
Weighted average common shares outstanding – basic	26,632	26,520	26,322
Weighted average common shares outstanding – diluted	26,763	26,674	26,707
Basic Earnings Per Share	$ 13.32	$ 13.48	$ 9.62
Diluted Earnings Per Share	$ 13.26	$ 13.40	$ 9.48

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Deferred Compensation Trust [Member]	Retained Earnings [Member]
Beginning Balance at Dec. 31, 2020	$ 961,288	$ 26	$ 267,666	$ (2,944)	$ 696,540
Beginning Balance, Shares at Dec. 31, 2020		26,236,000
Stock compensation, including options and long-term incentives	7,245		7,245
Director deferred share activity	1,458		1,458
Director deferred share activity , Shares		2,000
Exercise of stock options less shares withheld for taxes	3,678		3,678
Exercise of stock options less shares withheld for taxes, Shares		47,000
Shares issued for long-term incentive awards, net of shares withheld for taxes, Shares		52,000
Shares issued for long-term incentive awards, net of shares withheld for taxes	(6,571)		(6,571)
Purchase of shares by Deferred Compensation Trust			1,268	(1,268)
Sale of shares by Deferred Compensation Trust			(111)	111
Net Income (Loss)	253,235				253,235
Ending Balance at Dec. 31, 2021	1,220,333	$ 26	274,633	(4,101)	949,775
Ending Balance, Shares at Dec. 31, 2021		26,337,000
Stock compensation, including options and long-term incentives	7,657		7,657
Director deferred share activity	1,170		1,170
Director deferred share activity , Shares		2,000
Exercise of stock options less shares withheld for taxes	4,511		4,511
Exercise of stock options less shares withheld for taxes, Shares		62,000
Shares issued for long-term incentive awards, net of shares withheld for taxes, Shares		63,000
Shares issued for long-term incentive awards, net of shares withheld for taxes	(11,752)		(11,752)
Purchase of shares by Deferred Compensation Trust			3,254	(3,254)
Sale of shares by Deferred Compensation Trust			(2,107)	2,107
Net Income (Loss)	357,422				357,422
Ending Balance at Dec. 31, 2022	1,579,341	$ 26	277,366	(5,248)	1,307,197
Ending Balance, Shares at Dec. 31, 2022		26,464,000
Stock compensation, including options and long-term incentives	10,219		10,219
Director deferred share activity	1,417		1,417
Director deferred share activity , Shares		2,000
Exercise of stock options less shares withheld for taxes	$ 4,875		4,875
Exercise of stock options less shares withheld for taxes, Shares	34,881	35,000
Shares issued for long-term incentive awards, net of shares withheld for taxes, Shares		48,000
Shares issued for long-term incentive awards, net of shares withheld for taxes	$ (9,215)	$ (1)	(9,216)
Purchase of shares by Deferred Compensation Trust			620	(620)
Sale of shares by Deferred Compensation Trust			(189)	189
Net Income (Loss)	354,857				354,857
Ending Balance at Dec. 31, 2023	$ 1,941,494	$ 27	$ 285,092	$ (5,679)	$ 1,662,054
Ending Balance, Shares at Dec. 31, 2023		26,549,000

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating Activities:
Net income	$ 354,857	$ 357,422	$ 253,235
Noncash items included in net income:
Depreciation and amortization	178,845	157,203	141,700
Allowance for credit losses	1,955	3,074	3,559
Deferred income taxes	10,070	21,634	4,319
Loss (gain) from property disposals, net	910	50	(3,894)
Stock-based compensation	11,636	8,827	8,703
Changes in operating assets and liabilities:
Accounts receivable	(23,391)	(16,624)	(63,415)
Accounts payable	10,752	(9,523)	16,729
Change in other assets and liabilities, net	32,311	(49,037)	21,656
Net cash provided by operating activities	577,945	473,026	382,592
Investing Activities:
Acquisition of property and equipment	(439,879)	(367,429)	(285,746)
Proceeds from disposal of property and equipment	2,727	1,917	8,398
Other	(11,544)	0	(500)
Net cash used in investing activities	(448,696)	(365,512)	(277,848)
Financing Activities:
Repayment of credit and private shelf agreements	0	(1,000)	(43,175)
Borrowing of credit and private shelf agreements	0	1,000	43,175
Proceeds from stock option exercises	4,875	4,511	3,678
Shares withheld for taxes	(9,216)	(11,752)	(6,571)
Repayment of finance leases	(14,520)	(19,471)	(20,571)
Other financing activity	(1,563)	0	0
Net cash used in financing activities	(20,424)	(26,712)	(23,464)
Net Increase in Cash and Cash Equivalents	108,825	80,802	81,280
Cash and cash equivalents, beginning of year	187,390	106,588	25,308
Cash and cash equivalents, end of year	$ 296,215	$ 187,390	$ 106,588

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net Income (Loss)	$ 354,857	$ 357,422	$ 253,235

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Dec. 31, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Description of Business and Sum

Description of Business and Summary of Accounting Policies	12 Months Ended
Description of Business and Summary of Accounting Policies	Dec. 31, 2023
Accounting Policies [Abstract]
Description of Business and Summary of Accounting Policies	1. Description of Business and Summary of Accounting Policies Description of Business Saia, Inc., and its subsidiaries (Saia or the Company), is headquartered in Johns Creek, Georgia. Saia is a leading, less-than-truckload (LTL) motor carrier with more than 97 % of its revenue derived from transporting LTL shipments for customers. In addition to the core LTL services provided in 45 states, the Company also offers customers a wide range of other value-added services, including non-asset truckload, expedited transportation and logistics services across the United States. The chief operating decision maker is the Chief Executive Officer who regularly reviews the operating results of the Company's single operating segment. Basis of Presentation The accompanying consolidated financial statements include the accounts of Saia, Inc. and its wholly-owned subsidiaries. All significant intercompany accounts and transactions have been eliminated in the consolidated financial statements. Use of Estimates The preparation of our consolidated financial statements in conformity with U.S. generally accepted accounting principles requires the use of estimates and assumptions that affect the reported amounts of assets and liabilities and the reported amounts of revenues and expenses. Management makes its best estimate of the ultimate outcome for these items based on historical trends and other information available when the financial statements are prepared. Changes in estimates are recognized in accordance with the accounting rules for the estimate, which is typically in the period when new information becomes available to management. Areas where the nature of the estimate makes it reasonably possible that actual results could materially differ from amounts estimated include: revenue reserves; self-insurance accruals; long-term incentive compensation; tax liabilities; loss contingencies; litigation claims; and impairment assessments on long-lived assets and goodwill. Recently Issued Accounting Pronouncements In November 2023, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2023-07, “ Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. ” Under this ASU, interim and annual segment disclosures are expanded primarily through enhanced disclosures about significant segment expenses and information used to assess segment performance. Additionally, the standard requires all entities with a single reportable segment to apply all segment disclosure requirements. This standard is effective for annual reporting periods beginning after December 15, 2023 and interim reporting periods beginning after December 15, 2024. The Company is currently evaluating the impact of this standard on its consolidated financial statements and related disclosures. In December 2023, the FASB issued ASU No. 2023-09, “ Income Taxes (Topic 326): Improvements to Income Tax Disclosures. ” Under this ASU income tax disclosures are expanded primarily by requiring the disaggregation of the rate reconciliation and income taxes paid disclosures. This standard is effective for annual reporting periods beginning after December 15, 2024. The Company is currently evaluating the impact of this standard on its consolidated financial statements and related disclosures. Summary of Accounting Policies Significant accounting policies and practices used in the preparation of the accompanying consolidated financial statements are as follows: Cash and Cash Equivalents: Cash and cash equivalents includes cash on hand and short term marketable securities with original maturities of three months or less. Spare Parts, Fuel and Operating Supplies: Spare parts, fuel and operating supplies on hand are carried at average cost and are included in other current assets on the accompanying consolidated balance sheets. Property and Equipment: Property and equipment are carried at cost less accumulated depreciation. Replacements and improvements that extend the useful life of an asset are capitalized, while repairs and maintenance that do not improve or extend the lives of the respective assets are charged to expense as incurred. The Company evaluates long-lived assets for impairment whenever events or changes in circumstances indicate the carrying value of assets may not be recoverable. Depreciation is computed using the straight-line method, except for tractors (included in revenue equipment) for which the declining-balance method is used. The following service lives are used to compute depreciation: Years Structures 20 to 25 Revenue equipment 6 to 14 Technology equipment and software 3 to 5 Other 3 to 10 At December 31, property and equipment consisted of the following (in thousands): 2023 2022 Land $ 272,633 $ 191,057 Structures 813,146 638,180 Revenue equipment 1,470,913 1,340,761 Technology equipment and software 176,854 187,333 Other 148,254 121,493 Total property and equipment, at cost $ 2,881,800 $ 2,478,824 The Company’s investment in technology equipment and software consists primarily of systems to support customer service, maintenance and freight management. Depreciation and amortization expense (including amortization of assets under finance leases) was $ 177.9 million, $ 156.2 million and $ 140.5 million for the years ended December 31, 2023, 2022 and 2021, respectively. At December 31, 2023, trailers acquired under finance leases had a gross carrying value of $ 137.4 million and accumulated amortization of $ 67.7 million. At December 31, 2022, trailers acquired under finance leases had a gross carrying value of $ 137.9 million and accumulated amortization of $ 58.7 million. Claims and Insurance Accruals: The Company maintains a significant amount of insurance coverage with third-party insurance carriers that provides various levels of protection for covered risk exposure, including in the areas of workers’ compensation, bodily injury and property damage, casualty, cargo loss and damage and group health, with coverage limits and retention and deductible amounts that vary based on policy periods and claim type. Claims and insurance accruals related to workers’ compensation, bodily injury and property damage, casualty, cargo loss and damage and group health are established by management based on estimates of losses that the Company will ultimately incur on reported claims and on claims that have been incurred but not yet reported. Accruals are calculated on reported claims based on an evaluation of the nature and severity of the claim, historical loss experience and on legal, economic and other factors. Actuarial analysis is also used in calculating the accruals for workers’ compensation and bodily injury and property damage claims. Income Taxes: Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period enacted. As required by FASB Accounting Standards Codification (ASC) Topic 740, Income Taxes , the Company defines the threshold for recognizing the benefits of tax-filing positions in the financial statements as “more-likely-than-not” to be sustained by the tax authority. Revenue Recognition: The Company’s revenues are derived primarily from the transportation of freight as it satisfies performance obligations that arise from contracts with its customers. The Company’s performance obligations arise when it receives a bill of lading (BOL) to transport a customer's commodities at negotiated prices contained in either a transportation services agreement or a publicly disclosed tariff rate. Once a BOL is received and accepted, a legally-enforceable contract is formed whereby the parties are committed to perform and the rights of the parties, shipping terms and conditions, and payment terms have been identified. Each shipment represents a distinct service that is a separately identified performance obligation. The typical transit time to complete a shipment is from one to five days . Billing for transportation services normally occurs after completion of the service and payment is generally due within 30 days after the invoice date. The Company recognizes revenue related to the Company’s LTL, non-asset truckload and expedited transportation services over the transit time of the shipment as it moves from origin to destination based on the transit status at the end of each reporting period. Key estimates included in the recognition and measurement of revenue and related accounts receivable are as follows: • Revenue associated with shipments in transit is recognized ratably over transit time; and • Adjustments to revenue for billing adjustments and collectability. The portion of the gross invoice related to interline transportation services that involve the services of another party, such as another LTL service provider, is not recorded in the Company’s revenues. Revenue from logistics services is recognized as the services are provided. Credit Risk: The Company routinely grants credit to its customers. The risk of significant loss in trade receivables is substantially mitigated by the Company’s credit evaluation process, short collection terms, low revenue per transaction and services performed for a large number of customers, with no single customer representing more than 5 percent of accounts receivable at year-end. Allowances for potential credit losses are based on historical loss experience, current economic environment, expected trends and customer specific factors. Stock-Based Compensation: The Company has various stock-based compensation plans for its employees and non-employee directors. The Company stock-based compensation includes awards of stock options, restricted stock awards, and stock-based performance unit awards, all of which are accounted for under FASB ASC Topic 718, Compensation-Stock Compensation . Stock options granted to employees are valued using a Black-Scholes-Merton model with the expense amortized over the three-year vesting period. Restricted stock is valued based on the fair market value of the Company's common stock at the date of grant and the expense is amortized over the three to five year vesting period. Stock-based performance unit awards are valued using a Monte Carlo model and the expense is amortized over the three-year vesting period. Intangible Assets: The Company tests goodwill for impairment annually and whenever events or changes in circumstance indicate that impairment may have occurred. The Company first performs a qualitative assessment to determine whether it is necessary to perform a quantitative assessment. The Company is not required to estimate the fair value of a reporting unit unless the Company determines, based on qualitative assessment, that it is more likely than not that its fair value is less than its carrying amount. Purchased intangible assets subject to amortization are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Advertising: The costs of advertising are expensed as incurred. Advertising costs charged to expense were $ 2.9 million, $ 7.2 million, and $ 5.7 million in 2023, 2022 and 2021 , respectively. Financial Instruments: The carrying amounts of financial instruments including cash and cash equivalents, accounts receivable and accounts payable approximated fair value as of December 31, 2023 and 2022 , because of the relatively short maturity of these instruments. See Note 2 for fair value disclosures related to debt.

Debt and Financing Arrangements

Debt and Financing Arrangements	12 Months Ended
Debt and Financing Arrangements	Dec. 31, 2023
Debt Disclosure [Abstract]
Debt and Financing Arrangements	2. Debt and Financing Arrangements At December 31, debt consisted of the following (in thousands): December 31, 2023 December 31, 2022 Credit and Private Shelf Agreements, described below $ — $ — Finance Leases, described below 16,488 31,008 Total debt 16,488 31,008 Less: current portion of long-term debt 10,173 14,519 Long-term debt, less current portion $ 6,315 $ 16,489 The Company's liquidity needs arise primarily from capital investment in new equipment, land and structures, information technology and letters of credit required under insurance programs, as well as funding working capital requirements. The Company is party to a credit agreement with a group of banks as well as a private shelf debt agreement to fund capital investments, letters of credit and working capital needs. Credit Agreements At December 31, 2022 the Company was party to a credit agreement with a banking group that provided for a $ 300 million line of credit with a term ending February 2024 . This credit agreement also had an accordion feature that allowed for an additional $ 100 million availability, subject to certain conditions and availability of lender commitments. This credit agreement provided for a pledge by the Company of certain land and structures, accounts receivable and other assets to secure indebtedness under this agreement. On February 3, 2023, the Company entered into a new unsecured credit agreement with a banking group (the 2023 Credit Agreement) and terminated its previous credit agreement. The 2023 Credit Agreement maintains the amount of the previous line of credit of $ 300 million and extends the term until February 2028. The 2023 Credit Agreement contains an accordion feature that allows the Company to increase the size of the facility by up to $ 150 million, subject to certain conditions and availability of lender commitments. Borrowings under the 2023 Credit Agreement bear interest at the Company’s election at a variable rate equal to (a) one, three or six month term SOFR (the forward-looking secured overnight financing rate) plus 0.10 %, or (b) an alternate base rate, in each case plus an applicable margin. The applicable margin will be between 1.00 % and 1.75 % per annum for term SOFR loans and between 0.00 % and 0.75 % per annum for alternate base rate loans, in each case based on the Company’s consolidated net lease adjusted leverage ratio. The Company also accrues fees based on the daily unused portion of the credit facility, which will be between 0.0125 % and 0.025 % based on the Company’s consolidated net lease adjusted leverage ratio. Under the 2023 Credit Agreement, the Company is subject to a maximum consolidated net lease adjusted leverage ratio of less than 3.50 to 1.00 with the potential to be temporarily increased in the event the Company makes an acquisition that meets certain criteria. The 2023 Credit Agreement contains certain customary representations and warranties, affirmative and negative covenants and provisions relating to events of default. Under the 2023 Credit Agreement, if an event of default occurs, the banks will be entitled to take various actions, including the acceleration of amounts due. At December 31, 2023 and 2022, the Company had no outstanding borrowings and outstanding letters of credit of $ 32.1 million and $ 31.2 million, respectively, under the credit agreements. Private Shelf Agreement On November 9, 2023, the Company entered into a $ 350 million uncommitted Private Shelf Agreement (the Shelf Agreement), by and among the Company, PGIM, Inc. (Prudential), and certain affiliates and managed accounts of Prudential (the Note Purchasers) which allows the Company, from time to time, to offer for sale to Prudential and its affiliates, in one or a series of transactions, senior notes of the Company, through November 9, 2026. Pursuant to the Shelf Agreement, the Company agreed to sell up to $ 100 million aggregate principal amount of senior notes (the Initial Notes) to the Note Purchasers. The Initial Notes will bear interest at 6.09 % per annum and will mature five years after the date on which the Initial Notes are issued, unless repaid earlier by the Company. The funding date for the Initial Notes may occur at any time on or prior to August 2, 2024. The Initial Notes will be senior unsecured obligations and rank pari passu with borrowings under the 2023 Credit Agreement or other senior promissory notes issued pursuant to the Shelf Agreement. Additional notes issued under the Shelf Agreement, if any, would bear interest at a rate per annum, and would have such other terms, as would be set forth in a confirmation of acceptance executed by the parties prior to the closing of the applicable sale transaction. The Shelf Agreement requires that the Company maintain a consolidated net lease adjusted leverage ratio of less than 3.50 to 1.00, with limited exceptions. The Shelf Agreement also contains certain customary representations and warranties, affirmative and negative covenants and provisions related to events of default. Upon the occurrence and continuance of an event of default, the holders of notes issued under the Shelf Agreement may require immediate payment of all amounts owing under such notes. At December 31, 2023 , the Company had no outstanding borrowings under the Shelf Agreement. Finance Leases The Company is obligated under finance leases with seven-year terms which include obligations collateralized by revenue equipment totaling $ 16.5 million and $ 31.0 million as of December 31, 2023 and 2022, respectively. Amortization of assets held under the finance leases is included in depreciation and amortization expense. The estimated fair value of the finance leases at December 31, 2023 and 2022 is $ 16.1 million and $ 31.2 million, respectively, which is based on current market interest rates for similar types of financial instruments, reflective of Level 2 inputs. Other The Company paid cash for interest of $ 1.6 million, $ 2.3 million, and $ 3.0 million for the years ended December 31, 2023, 2022 and 2021 , respectively.

Commitments, Contingencies and

Commitments, Contingencies and Uncertainties	12 Months Ended
Commitments, Contingencies and Uncertainties	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments, Contingencies and Uncertainties	3. Commitments, Contingencies and Uncertainties The Company has contractual obligations and commitments in the form of finance leases, operating leases and purchase commitments. At December 31, 2023, the Company was committed under non-cancellable operating lease agreements requiring minimum annual rentals payable as follows (in thousands): Amount 2024 $ 31,218 2025 28,830 2026 21,977 2027 19,180 2028 16,273 Thereafter 25,100 Total $ 142,578 Rent expense was $ 37.2 million, $ 33.4 million, and $ 31.6 million for the years ended December 31, 2023, 2022 and 2021, respectively. Management expects that in the normal course of business, leases will be renewed or replaced as they expire. Finance and operating leases are discussed further in Note 4. Purchase commitments related to capital expenditures were $ 306.6 million at December 31, 2023 . These commitments include a commitment to purchase 17 terminals from Yellow Corporation for $ 235.7 million. In addition to this, the Company was committed to a purchase price of $ 7.9 million related to the acquisition of 11 terminal leases. See Note 12 for additional information on these transactions. As of December 31, 2023 and 2022, the Company had $ 50.9 million and $ 19.5 million, respectively, of capital expenditures accrued for in accounts payable. Other The Company is subject to legal proceedings that arise in the ordinary course of its business. Management believes that adequate provisions for resolution of all contingencies, claims and pending litigation have been made for probable and estimable losses and that the ultimate outcome of these actions will not have a material adverse effect on its financial condition but could have a material adverse effect on its results of operations in a given quarter or annual period.

Leases

Leases	12 Months Ended
Leases	Dec. 31, 2023
Leases [Abstract]
Leases	4. Leases The Company’s leases include, but are not limited to, real estate, including terminals and general office buildings, trailers, corporate fleet vehicles and other equipment. Leases with an initial term of 12 months or less are not recorded on the consolidated balance sheet; the Company recognizes lease expense for these leases on a straight-line basis over the lease term. As of December 31, 2023 and 2022, approximately $ 38.6 million and $ 60.5 million , respectively, of finance leased assets, net of amortization, were included in property and equipment . Accumulated amortization for these assets totaled $ 31.2 million and $ 43.8 million as of the same periods ended. A summary of the lease costs for the years ended December 31, 2023 and 2022 follows (in thousands): 2023 2022 Finance lease cost: Amortization of right-of-use assets $ 5,693 $ 8,276 Interest on lease liabilities 883 1,476 Operating lease cost (includes variable and sublease costs as they are immaterial) 34,522 30,919 Short-term lease cost 16,303 19,387 Total lease cost $ 57,401 $ 60,058 Other Information Right-of-use assets obtained in exchange for new finance lease liabilities — — Right-of-use assets obtained in exchange for new operating lease liabilities 27,026 39,122 The discount rate used in the Company's calculation of its right-of-use assets and corresponding lease liabilities was determined based on the stated rate within each contract when available, or its incremental borrowing rate, which approximates the rate at which the Company could borrow, on a collateralized basis, over the term of a lease. Supplemental cash flow and balance sheet information related to leases was as follows (in thousands, except where noted): 2023 2022 Cash paid for amounts included in the measurement of lease liabilities Operating cash outflows from finance leases $ 890 $ 1,484 Operating cash outflows from operating leases 35,339 31,043 Financing cash outflows from finance leases 14,520 19,471 Weighted-average remaining lease term - finance leases (years) 1.2 1.8 Weighted-average remaining lease term - operating leases (years) 5.4 5.2 Weighted-average discount rate - finance leases 4.0 % 3.7 % Weighted-average discount rate - operating leases 5.4 % 5.1 % As of December 31, 2023, maturities of lease liabilities were as follows (in thousands): Operating Leases Finance Leases Maturity of Lease Liabilities 2024 $ 31,218 $ 10,605 2025 28,830 5,453 2026 21,977 995 2027 19,180 - 2028 16,273 - Thereafter 25,100 - Total lease payments 142,578 17,053 Less: Interest 20,359 565 Present value of lease liabilities $ 122,219 $ 16,488

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
Goodwill and Other Intangible Assets	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	5. Goodwill and Other Intangible Assets There was no change to the carrying amount of goodwill of $ 12.1 million for fiscal years ending December 31, 2023, 2022 and 2021, respectively. The gross amounts and accumulated amortization of identifiable intangible assets are as follows (in thousands): December 31, 2023 December 31, 2022 Gross Amount Accumulated Amortization Gross Amount Accumulated Amortization Amortizable intangible assets: Customer relationships (useful life of 6 - 15 years) $ 19,000 $ 14,417 $ 19,000 $ 13,664 Trademarks (useful life of 15 years) 1,500 892 1,500 792 Total $ 20,500 $ 15,309 $ 20,500 $ 14,456 Amortization expense for intangible assets was $ 0.9 million for 2023 , $ 1.0 million in 2022 and $ 1.2 million in 2021 . Estimated amortization expense for the next five years is as follows (in thousands): Amount 2024 $ 853 2025 853 2026 853 2027 853 2028 853

Computation of Earnings Per Sha

Computation of Earnings Per Share	12 Months Ended
Computation of Earnings Per Share	Dec. 31, 2023
Earnings Per Share [Abstract]
Computation of Earnings Per Share	6. Computation of Earnings Per Share The calculation of basic earnings per common share and diluted earnings per common share is as follows (in thousands except per share amounts): For The Years Ended December 31, 2023 2022 2021 Numerator: Net income $ 354,857 $ 357,422 $ 253,235 Denominator: Denominator for basic earnings per share–weighted 26,632 26,520 26,322 Dilutive effect of share-based awards 131 154 385 Denominator for diluted earnings per share–adjusted 26,763 26,674 26,707 Basic Earnings Per Share $ 13.32 $ 13.48 $ 9.62 Diluted Earnings Per Share $ 13.26 $ 13.40 $ 9.48 In 2023, there were 5,790 anti-dilutive options or restricted stock. In 2022, there were 22,237 anti-dilutive options or restricted stock. In 2021 , there were 19,386 anti-dilutive options or restricted stock.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2023
Equity [Abstract]
Stockholders' Equity	7. Stockholders’ Equity Deferred Compensation Plan The Saia Executive Capital Accumulation Plan (Capital Accumulation Plan) is a nonqualified deferred compensation plan for Saia executives. The Capital Accumulation Plan allows for the plan participants to invest in the Company’s common stock. Elections to invest in the Company’s common stock are irrevocable, and upon distribution, the funds invested in the Company’s common stock are paid out in Company common stock rather than cash. At December 31, 2023 and 2022, the Company’s rabbi trust, which holds the investments for the Capital Accumulation Plan, held 69,672 and 69,982 shares of the Company’s common stock, respectively, all of which were purchased on the open market. The following table summarizes the shares of the Company’s common stock that were purchased and sold by the Company’s rabbi trust: For The Years Ended December 31, 2023 2022 2021 Shares of common stock purchased 2,110 12,117 5,580 Aggregate purchase price of shares purchased $ 620,282 $ 3,253,577 $ 1,268,370 Shares of common stock sold 2,420 36,762 2,841 Aggregate sale price of shares sold $ 834,704 $ 10,370,165 $ 802,030 Company common stock held by the rabbi trust is accounted for within stockholders' equity similar to treasury stock at historical cost with the corresponding deferred compensation obligation also presented within stockholders' equity as additional paid-in capital. Directors’ Deferred Compensation Under the Company’s Directors’ Deferred Fee Plan, non-employee directors may elect to defer all or a portion of their annual fees and retainers. Such deferrals are converted into units equivalent to the value of the Company’s stock. Upon the director’s termination, death or disability, accumulated deferrals are distributed in the form of Company common stock. The Company had 100,110 and 97,381 shares reserved for issuance under the Directors’ Deferred Fee Plan at December 31, 2023 and 2022 , respectively. The shares reserved for issuance under the Directors’ Deferred Fee Plan are treated as common stock in computing basic earnings per share.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
Stock-Based Compensation	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	8. Stock-Based Compensation The stockholders of the Company approved the 2018 Omnibus Incentive Plan (the 2018 Omnibus Plan) and the Second Amended and Restated 2011 Omnibus Incentive Plan (the 2011 Omnibus Plan) to allow the Company to issue equity based compensation to help attract and retain executive, managerial, supervisory or professional employees and non-employee directors. The 2018 Omnibus Plan has 1,100,000 shares of common stock reserved. The 2011 Omnibus Plan had a total of 2,350,000 shares of common stock reserved. Following stockholder approval of the 2018 Omnibus Plan, no additional awards have been made under the 2011 Omnibus Plan. The 2018 Omnibus Plan and the 2011 Omnibus Plan provide for the grant or award of stock options; stock appreciation rights; restricted and unrestricted stock; restricted stock units; and performance unit awards. At December 31, 2023 and 2022, 391,089 shares remain reserved and unissued under the provisions of the 2011 Omnibus Plan, a portion of which are allocated to outstanding stock options described below. At December 31, 2023 and 2022, 677,500 and 765,617 shares, respectively, remain reserved and unissued under the provisions of the 2018 Omnibus Plan, a portion of which are allocated to outstanding performance unit awards, outstanding stock options and restricted stock described below. The Company has historically issued new shares to satisfy stock option exercises or other awards issued under the 2018 Omnibus Plan and 2011 Omnibus Plan. Stock option awards have been granted with an exercise price equal to the market price of the Company’s stock at the date of grant. Stock option awards granted to employees under the plans to date are non-qualified stock options, have vesting over three years , subject to earlier vesting upon a change of control and certain other events, and have a seven-year contractual term. All outstanding stock options held by non-employee directors were granted to the director while employed by Saia, and tota l 10,000 shares as of December 31, 2023. The Company grants shares of restricted stock as part of its long-term incentive plan. These shares of restricted stock vest over three years , subject to earlier vesting upon a change in control. The value of restricted stock is based on the fair market value of the Company’s common stock at the date of grant. In addition, the Company has periodically granted shares of restricted stock to certain key executives that vests 25 % after three years , 25 % after four years and the remaining 50 % after five years , assuming the executive has been in continuous service to the Company since the award date, subject to earlier vesting upon a change in control. Stock option and restricted stock compensation expense of $ 5.7 million, $ 3.9 million and $ 3.3 million, was recorded for the years ended December 31, 2023, 2022 and 2021, respectively, and is included in salaries, wages and employees’ benefits. As of December 31, 2023, there is unrecognized compensation expense of $ 6.2 million related to unvested stock options and restricted stock, which is expected to be recognized over a weighted average period of 1.6 years. The following table summarizes stock option activity for the year ended December 31, 2023 for employees: Options Weighted Average Exercise price Weighted Average Remaining Contractual Life Aggregate Intrinsic Value Outstanding at December 31, 2022 72,323 $ 155.83 4.6 $ 4,921 Exercised ( 34,881 ) 139.76 Outstanding at December 31, 2023 37,442 $ 170.79 3.8 $ 10,013 Exercisable at December 31, 2023 21,850 $ 113.98 3.0 $ 7,085 The total intrinsic value of options exercised during the years ended December 31, 2023, 2022 and 2021 was $ 7.0 million, $ 10.8 million, and $ 5.9 million, respectively. The weighted-average grant-date fair value per share of options granted during the years ended December 31, 2022 and 2021 was $ 94.36 , and $ 62.65 , respectively. There were no options granted during the year ended December 31, 2023. The following table summarizes the weighted average assumptions used in valuing options for the years ended December 31, 2022 and 2021: 2022 2021 Risk-free interest rate 1.92 % 1.19 % Expected life in years 3.5 3.5 Expected volatility 43.32 % 40.57 % Dividend rate — — The risk-free interest rate for periods within the contractual life of the option is based on a three-month average U.S. Treasury yield at the time of grant. The expected life of the options represents the period of time that options granted are expected to be outstanding. Expected volatilities are based on historical volatility of the Company’s stock. The following table summarizes restricted stock activity during the year ended December 31, 2023: Shares Weighted Average Grant-date Fair Value Restricted Stock at December 31, 2022 48,240 $ 177.89 Granted 20,056 329.32 Vested ( 16,340 ) 101.30 Forfeited — — Restricted Stock at December 31, 2023 51,956 $ 260.43 The total fair value of restricted stock that vested during the years ended December 31, 2023, 2022, and 2021 were $ 1.7 million, $ 2.1 million and $ 1.4 million, respectively. Performance Unit Awards The Company grants performance unit awards to executives as part of the Company’s long term incentive plan. The criteria for payout of the awards is based on a comparison over the three-year performance period of these awards of the total stockholder return (TSR) of the Company’s common stock compared to the TSR of the companies in a peer group established by the Compensation Committee. The stock-based awards are accounted for in accordance with ASC Topic 718 with the expense amortized over the three-year vesting period based on the fair value of the awards at the grant date using the Monte Carlo method. Operating results include expense for the performance unit awards of $ 4.5 million in 2023, $ 3.8 million in 2022 and $ 4.0 million in 2021. Shares earned under the performance unit awards are issued in the first quarter of the year following the end of the performance period. There was an issuance of 25,716 shares for the January 2021 - December 2023 performance period in February 2024, 63,188 shares for the January 2020 - December 2022 performance period in February 2023, and 78,710 shares for the January 2019 - December 2021 performance period in February 2022. At December 31, 2023, performance unit awards are outstanding for a maximum of 25,020 shares for the January 2022 – December 2024 performance period and for a maximum of 28,532 shares for the January 2023 – December 2025 performance period. As of December 31, 2023, there is unrecognized compensation expense of $ 5.9 million related to unvested performance unit awards, which is expected to be recognized over a weighted average period of 1.8 years. The following table summarizes performance unit awards during the year ended December 31, 2023: Shares Weighted Average Grant-date Fair Value Performance Unit Awards at December 31, 2022 57,431 $ 207.32 Granted 14,266 429.55 Added by performance factor 31,594 132.81 Vested ( 63,188 ) 132.81 Forfeited — — Performance Unit Awards at December 31, 2023 40,103 $ 345.08 The total fair value of performance unit awards shares that vested during the years ended December 31, 2023, 2022, and 2021 were $ 4.2 million, $ 3.6 million and $ 3.0 million, respectively. Director Awards The 2018 Omnibus Plan provides for an annual grant to each non-employee director of shares of Saia stock with a value not to exceed $ 500,000 with the number of shares to be determined each year by the Compensation Committee. For 2023, 2022 and 2021 each non-employee director was granted 379 , 396 and 548 shares, respectively, of Saia stock under the 2018 Omnibus Plan. These shares vest in one year from grant, subject to accelerated vesting upon leaving the Board (other than for cause) or a change in control. Under the Director’s Deferred Fee Plan, non-employee directors may defer all or a portion of annual fees and awards earned. The deferrals are converted into phantom stock units equivalent to the value of Company common stock. Upon the director’s termination, death or disability, accumulated deferrals are distributed in the form of Company common stock in accordance with elections made by the directors. Non-employee directors were issued 2,729 ; 3,272 ; and 3,929 units equivalent to shares in the Company's common stock under the Directors' Deferred Fee Plan during the years ended December 31, 2023, 2022 and 2021 , respectively.

Employee Benefits

Employee Benefits	12 Months Ended
Employee Benefits	Dec. 31, 2023
Retirement Benefits [Abstract]
Employee Benefits	9. Employee Benefits Defined Contribution Plans The Company sponsors defined contribution plans, principally consisting of contributory 401(k) savings plans and noncontributory profit sharing plans. The Company’s contributions to the 401(k) savings plans consist of a matching percentage of employee contributions up to certain maximum limits. The Company match has historically been 50 percent of the first six percent of an eligible employee’s contributions. The Company’s total contributions to the 401(k) savings plans included in salaries, wages and employees' benefits for the years ended December 31, 2023, 2022 and 2021, were $ 15.2 million, $ 14.0 million, and $ 12.4 million, respectively. Cash Incentive Awards The Company provides cash incentive awards to certain salaried employees which are based primarily on actual operating results achieved for the year, compared to targeted operating results. Operating results include cash incentive awards of $ 38.8 million, $ 32.6 million, and $ 36.4 million in 2023, 2022 and 2021, respectively. Included in these amounts are also incentives that are based on other targets specifically associated with the respective employees' positions. Employee Stock Purchase Plan In January 2003, the Company adopted the Employee Stock Purchase Plan of Saia, Inc. (the ESPP) allowing eligible employees to purchase common stock of the Company at current market prices through payroll deductions of up to 10 percent of annual wages. In 2015, the Company amended the ESPP to allow highly compensated employees as defined by Section 401(a)(17) of the Internal Revenue Code to make payroll deductions of up to 20 percent of annual wages. The custodian uses the funds to purchase the Company’s common stock at current market prices. The custodian purchased 1,420 , 2,158 and 2,516 shares in the open market during 2023, 2022 and 2021 , respectively.

Income Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	10. Income Taxes The income tax provision consists of the following (in thousands): 2023 2022 2021 Current: U.S. federal $ 82,802 $ 68,934 $ 62,222 State 18,498 20,058 12,997 Total current income tax provision 101,300 88,992 75,219 Deferred: U.S. federal 10,345 21,440 3,915 State ( 275 ) 194 404 Total deferred income tax provision 10,070 21,634 4,319 Total income tax provision $ 111,370 $ 110,626 $ 79,538 A reconciliation between income taxes at the federal statutory rate (21 percent) and the actual income tax provision is as follows (in thousands): 2023 2022 2021 Provision at federal statutory rate $ 97,908 $ 98,290 $ 69,856 State income taxes, net of federal benefit 15,580 16,274 11,435 Tax credits ( 1,181 ) ( 1,355 ) ( 1,754 ) Excess tax benefit on stock compensation ( 1,004 ) ( 1,578 ) ( 793 ) Other, net 67 ( 1,005 ) 794 Total provision $ 111,370 $ 110,626 $ 79,538 Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Deferred tax (liabilities) assets are comprised of the following at December 31 (in thousands): 2023 2022 Depreciation $ ( 196,494 ) $ ( 183,276 ) Leases ( 29,361 ) ( 30,886 ) Other ( 6,022 ) ( 5,471 ) Gross deferred tax liabilities ( 231,877 ) ( 219,633 ) Allowance for credit losses 1,097 1,435 Equity-based compensation 4,834 4,089 Employee benefits 12,014 9,988 Leases 30,227 30,578 Claims and insurance 21,597 22,137 Other 6,982 6,377 Gross deferred tax assets 76,751 74,604 Valuation Allowance ( 715 ) ( 742 ) Net deferred tax assets 76,036 73,862 Net deferred tax liability $ ( 155,841 ) $ ( 145,771 ) The Company and its subsidiaries file income tax returns in the U.S. federal jurisdiction and various state jurisdictions. For the U.S. federal jurisdiction, tax years 2020 - 2023 remain open to examination. The expiration of the statute of limitations related to the various state income tax returns that the Company files varies by state. In general, tax years 2014 - 2023 remain open to examination by the various state and local jurisdictions. A reconciliation of the beginning and ending total amounts of gross unrecognized tax benefits is as follows (in thousands): 2023 2022 Gross unrecognized tax benefits at beginning of year $ 3,867 $ 1,370 Gross increases in tax positions for prior years 2 1,779 Gross increases in tax positions for current year 1,077 1,005 Settlements — — Lapse of statute of limitations ( 254 ) ( 287 ) Gross unrecognized tax benefits at end of year $ 4,692 $ 3,867 The Company recognizes interest and penalties related to uncertain tax positions as a component of income tax expense. The total amount of unrecognized tax benefits, which is recorded within claims, insurance and other liabilities on the consolidated balance sheets, that would affect the Company’s effective tax rate if recognized is $ 4.7 million and $ 3.9 million as of December 31, 2023 and 2022, respectively. The Company paid cash for income taxes of $ 72.8 million, $ 115.3 million, and $ 81.6 million in 2023, 2022 and 2021, respectively. The Company does not anticipate total unrecognized tax benefits will significantly change during the next twelve months due to the settlements of audits and the expiration of statutes of limitations.

Valuation and Qualifying Accoun

Valuation and Qualifying Accounts	12 Months Ended
Valuation and Qualifying Accounts	Dec. 31, 2023
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Valuation and Qualifying Accounts	11. Valuation and Qualifying Accounts The following is a rollforward of the allowance for credit losses for receivables (in thousands): Additions Balance, beginning of period Charged to costs and expenses Charged to other accounts Deductions(1) Balance, end of period For the period ended December 31, 2023 5,804 1,955 $ — $ ( 3,332 ) $ 4,427 For the period ended December 31, 2022 5,530 3,074 — ( 2,800 ) 5,804 For the period ended December 31, 2021 5,666 3,559 — ( 3,695 ) 5,530 (1) Primarily uncollectible accounts written off — net of recoveries.

Subsequent Events

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2023
Subsequent Events [Abstract]
Subsequent Events [Text Block]	Subsequent Events On January 17, 2024 , the Company completed the purchase of 17 freight terminals of Yellow Corporation for an aggregate purchase price of $ 235.7 million in cash. In addition, on January 17, 2024 , the Company completed the acquisition of Yellow Corporation’s interests in leases for 11 freight terminals for an aggregate purchase price of $ 7.9 million in cash, plus the assumption of certain liabilities under the leases and the payment of cure costs.

Description of Business and S_2

Description of Business and Summary of Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Description of Business	Description of Business Saia, Inc., and its subsidiaries (Saia or the Company), is headquartered in Johns Creek, Georgia. Saia is a leading, less-than-truckload (LTL) motor carrier with more than 97 % of its revenue derived from transporting LTL shipments for customers. In addition to the core LTL services provided in 45 states, the Company also offers customers a wide range of other value-added services, including non-asset truckload, expedited transportation and logistics services across the United States. The chief operating decision maker is the Chief Executive Officer who regularly reviews the operating results of the Company's single operating segment.
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements include the accounts of Saia, Inc. and its wholly-owned subsidiaries. All significant intercompany accounts and transactions have been eliminated in the consolidated financial statements.
Use of Estimates	Use of Estimates The preparation of our consolidated financial statements in conformity with U.S. generally accepted accounting principles requires the use of estimates and assumptions that affect the reported amounts of assets and liabilities and the reported amounts of revenues and expenses. Management makes its best estimate of the ultimate outcome for these items based on historical trends and other information available when the financial statements are prepared. Changes in estimates are recognized in accordance with the accounting rules for the estimate, which is typically in the period when new information becomes available to management. Areas where the nature of the estimate makes it reasonably possible that actual results could materially differ from amounts estimated include: revenue reserves; self-insurance accruals; long-term incentive compensation; tax liabilities; loss contingencies; litigation claims; and impairment assessments on long-lived assets and goodwill.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In November 2023, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2023-07, “ Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. ” Under this ASU, interim and annual segment disclosures are expanded primarily through enhanced disclosures about significant segment expenses and information used to assess segment performance. Additionally, the standard requires all entities with a single reportable segment to apply all segment disclosure requirements. This standard is effective for annual reporting periods beginning after December 15, 2023 and interim reporting periods beginning after December 15, 2024. The Company is currently evaluating the impact of this standard on its consolidated financial statements and related disclosures. In December 2023, the FASB issued ASU No. 2023-09, “ Income Taxes (Topic 326): Improvements to Income Tax Disclosures. ” Under this ASU income tax disclosures are expanded primarily by requiring the disaggregation of the rate reconciliation and income taxes paid disclosures. This standard is effective for annual reporting periods beginning after December 15, 2024. The Company is currently evaluating the impact of this standard on its consolidated financial statements and related disclosures.
Cash and Cash Equivalents and Checks Outstanding	Cash and Cash Equivalents: Cash and cash equivalents includes cash on hand and short term marketable securities with original maturities of three months or less.
Parts, fuel and operating supplies	Spare Parts, Fuel and Operating Supplies: Spare parts, fuel and operating supplies on hand are carried at average cost and are included in other current assets on the accompanying consolidated balance sheets.
Property and Equipment Including Repairs and Maintenance	Property and Equipment: Property and equipment are carried at cost less accumulated depreciation. Replacements and improvements that extend the useful life of an asset are capitalized, while repairs and maintenance that do not improve or extend the lives of the respective assets are charged to expense as incurred. The Company evaluates long-lived assets for impairment whenever events or changes in circumstances indicate the carrying value of assets may not be recoverable. Depreciation is computed using the straight-line method, except for tractors (included in revenue equipment) for which the declining-balance method is used. The following service lives are used to compute depreciation: Years Structures 20 to 25 Revenue equipment 6 to 14 Technology equipment and software 3 to 5 Other 3 to 10 At December 31, property and equipment consisted of the following (in thousands): 2023 2022 Land $ 272,633 $ 191,057 Structures 813,146 638,180 Revenue equipment 1,470,913 1,340,761 Technology equipment and software 176,854 187,333 Other 148,254 121,493 Total property and equipment, at cost $ 2,881,800 $ 2,478,824 The Company’s investment in technology equipment and software consists primarily of systems to support customer service, maintenance and freight management. Depreciation and amortization expense (including amortization of assets under finance leases) was $ 177.9 million, $ 156.2 million and $ 140.5 million for the years ended December 31, 2023, 2022 and 2021, respectively. At December 31, 2023, trailers acquired under finance leases had a gross carrying value of $ 137.4 million and accumulated amortization of $ 67.7 million. At December 31, 2022, trailers acquired under finance leases had a gross carrying value of $ 137.9 million and accumulated amortization of $ 58.7 million.
Claims and Insurance Accruals	Claims and Insurance Accruals: The Company maintains a significant amount of insurance coverage with third-party insurance carriers that provides various levels of protection for covered risk exposure, including in the areas of workers’ compensation, bodily injury and property damage, casualty, cargo loss and damage and group health, with coverage limits and retention and deductible amounts that vary based on policy periods and claim type. Claims and insurance accruals related to workers’ compensation, bodily injury and property damage, casualty, cargo loss and damage and group health are established by management based on estimates of losses that the Company will ultimately incur on reported claims and on claims that have been incurred but not yet reported. Accruals are calculated on reported claims based on an evaluation of the nature and severity of the claim, historical loss experience and on legal, economic and other factors. Actuarial analysis is also used in calculating the accruals for workers’ compensation and bodily injury and property damage claims.
Income Taxes	Income Taxes: Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period enacted. As required by FASB Accounting Standards Codification (ASC) Topic 740, Income Taxes , the Company defines the threshold for recognizing the benefits of tax-filing positions in the financial statements as “more-likely-than-not” to be sustained by the tax authority.
Revenue Recognition	Revenue Recognition: The Company’s revenues are derived primarily from the transportation of freight as it satisfies performance obligations that arise from contracts with its customers. The Company’s performance obligations arise when it receives a bill of lading (BOL) to transport a customer's commodities at negotiated prices contained in either a transportation services agreement or a publicly disclosed tariff rate. Once a BOL is received and accepted, a legally-enforceable contract is formed whereby the parties are committed to perform and the rights of the parties, shipping terms and conditions, and payment terms have been identified. Each shipment represents a distinct service that is a separately identified performance obligation. The typical transit time to complete a shipment is from one to five days . Billing for transportation services normally occurs after completion of the service and payment is generally due within 30 days after the invoice date. The Company recognizes revenue related to the Company’s LTL, non-asset truckload and expedited transportation services over the transit time of the shipment as it moves from origin to destination based on the transit status at the end of each reporting period. Key estimates included in the recognition and measurement of revenue and related accounts receivable are as follows: • Revenue associated with shipments in transit is recognized ratably over transit time; and • Adjustments to revenue for billing adjustments and collectability. The portion of the gross invoice related to interline transportation services that involve the services of another party, such as another LTL service provider, is not recorded in the Company’s revenues. Revenue from logistics services is recognized as the services are provided.
Credit Risk	Credit Risk: The Company routinely grants credit to its customers. The risk of significant loss in trade receivables is substantially mitigated by the Company’s credit evaluation process, short collection terms, low revenue per transaction and services performed for a large number of customers, with no single customer representing more than 5 percent of accounts receivable at year-end. Allowances for potential credit losses are based on historical loss experience, current economic environment, expected trends and customer specific factors.
Stock-Based Compensation	Stock-Based Compensation: The Company has various stock-based compensation plans for its employees and non-employee directors. The Company stock-based compensation includes awards of stock options, restricted stock awards, and stock-based performance unit awards, all of which are accounted for under FASB ASC Topic 718, Compensation-Stock Compensation . Stock options granted to employees are valued using a Black-Scholes-Merton model with the expense amortized over the three-year vesting period. Restricted stock is valued based on the fair market value of the Company's common stock at the date of grant and the expense is amortized over the three to five year vesting period. Stock-based performance unit awards are valued using a Monte Carlo model and the expense is amortized over the three-year vesting period.
Intangible Assets	Intangible Assets: The Company tests goodwill for impairment annually and whenever events or changes in circumstance indicate that impairment may have occurred. The Company first performs a qualitative assessment to determine whether it is necessary to perform a quantitative assessment. The Company is not required to estimate the fair value of a reporting unit unless the Company determines, based on qualitative assessment, that it is more likely than not that its fair value is less than its carrying amount. Purchased intangible assets subject to amortization are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable.
Advertising	Advertising: The costs of advertising are expensed as incurred. Advertising costs charged to expense were $ 2.9 million, $ 7.2 million, and $ 5.7 million in 2023, 2022 and 2021 , respectively.
Financial Instruments	Financial Instruments: The carrying amounts of financial instruments including cash and cash equivalents, accounts receivable and accounts payable approximated fair value as of December 31, 2023 and 2022 , because of the relatively short maturity of these instruments. See Note 2 for fair value disclosures related to debt.

Description of Business and S_3

Description of Business and Summary of Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Property and Equipment, Estimated Useful Lives	Depreciation is computed using the straight-line method, except for tractors (included in revenue equipment) for which the declining-balance method is used. The following service lives are used to compute depreciation: Years Structures 20 to 25 Revenue equipment 6 to 14 Technology equipment and software 3 to 5 Other 3 to 10
Schedule of Property and Equipment	At December 31, property and equipment consisted of the following (in thousands): 2023 2022 Land $ 272,633 $ 191,057 Structures 813,146 638,180 Revenue equipment 1,470,913 1,340,761 Technology equipment and software 176,854 187,333 Other 148,254 121,493 Total property and equipment, at cost $ 2,881,800 $ 2,478,824

Debt and Financing Arrangemen_2

Debt and Financing Arrangements (Tables)	12 Months Ended
Debt and Financing Arrangements (Tables)	Dec. 31, 2023
Debt Disclosure [Abstract]
Summary of Reconciliation of Debt	At December 31, debt consisted of the following (in thousands): December 31, 2023 December 31, 2022 Credit and Private Shelf Agreements, described below $ — $ — Finance Leases, described below 16,488 31,008 Total debt 16,488 31,008 Less: current portion of long-term debt 10,173 14,519 Long-term debt, less current portion $ 6,315 $ 16,489

Commitments, Contingencies an_2

Commitments, Contingencies and Uncertainties (Tables)	12 Months Ended
Commitments, Contingencies and Uncertainties (Tables)	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Schedule of Non-Cancellable Capital And Operating Lease Agreements Requiring Minimum Annual Rentals Payable	At December 31, 2023, the Company was committed under non-cancellable operating lease agreements requiring minimum annual rentals payable as follows (in thousands): Amount 2024 $ 31,218 2025 28,830 2026 21,977 2027 19,180 2028 16,273 Thereafter 25,100 Total $ 142,578

Leases (Tables)

Leases (Tables)	12 Months Ended
Leases (Tables)	Dec. 31, 2023
Leases [Abstract]
Summary of Lease Cost and Other Information	2023 2022 Finance lease cost: Amortization of right-of-use assets $ 5,693 $ 8,276 Interest on lease liabilities 883 1,476 Operating lease cost (includes variable and sublease costs as they are immaterial) 34,522 30,919 Short-term lease cost 16,303 19,387 Total lease cost $ 57,401 $ 60,058 Other Information Right-of-use assets obtained in exchange for new finance lease liabilities — — Right-of-use assets obtained in exchange for new operating lease liabilities 27,026 39,122
Summary of Supplemental Cash Flow and Balance Sheet Information Related to Leases	The discount rate used in the Company's calculation of its right-of-use assets and corresponding lease liabilities was determined based on the stated rate within each contract when available, or its incremental borrowing rate, which approximates the rate at which the Company could borrow, on a collateralized basis, over the term of a lease. Supplemental cash flow and balance sheet information related to leases was as follows (in thousands, except where noted): 2023 2022 Cash paid for amounts included in the measurement of lease liabilities Operating cash outflows from finance leases $ 890 $ 1,484 Operating cash outflows from operating leases 35,339 31,043 Financing cash outflows from finance leases 14,520 19,471 Weighted-average remaining lease term - finance leases (years) 1.2 1.8 Weighted-average remaining lease term - operating leases (years) 5.4 5.2 Weighted-average discount rate - finance leases 4.0 % 3.7 % Weighted-average discount rate - operating leases 5.4 % 5.1 %
Summary of Maturity of Lease Liabilities	As of December 31, 2023, maturities of lease liabilities were as follows (in thousands): Operating Leases Finance Leases Maturity of Lease Liabilities 2024 $ 31,218 $ 10,605 2025 28,830 5,453 2026 21,977 995 2027 19,180 - 2028 16,273 - Thereafter 25,100 - Total lease payments 142,578 17,053 Less: Interest 20,359 565 Present value of lease liabilities $ 122,219 $ 16,488

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
Goodwill and Other Intangible Assets (Tables)	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of Gross Amounts and Accumulated Amortization of Identifiable Intangible Assets	The gross amounts and accumulated amortization of identifiable intangible assets are as follows (in thousands): December 31, 2023 December 31, 2022 Gross Amount Accumulated Amortization Gross Amount Accumulated Amortization Amortizable intangible assets: Customer relationships (useful life of 6 - 15 years) $ 19,000 $ 14,417 $ 19,000 $ 13,664 Trademarks (useful life of 15 years) 1,500 892 1,500 792 Total $ 20,500 $ 15,309 $ 20,500 $ 14,456
Summary of Estimated Amortization Expense for Next Five Years	Estimated amortization expense for the next five years is as follows (in thousands): Amount 2024 $ 853 2025 853 2026 853 2027 853 2028 853

Computation of Earnings Per S_2

Computation of Earnings Per Share (Tables)	12 Months Ended
Computation of Earnings Per Share (Tables)	Dec. 31, 2023
Earnings Per Share [Abstract]
Summary of Calculation of Basic Earnings Per Common Share and Diluted Earnings Per Common Share	The calculation of basic earnings per common share and diluted earnings per common share is as follows (in thousands except per share amounts): For The Years Ended December 31, 2023 2022 2021 Numerator: Net income $ 354,857 $ 357,422 $ 253,235 Denominator: Denominator for basic earnings per share–weighted 26,632 26,520 26,322 Dilutive effect of share-based awards 131 154 385 Denominator for diluted earnings per share–adjusted 26,763 26,674 26,707 Basic Earnings Per Share $ 13.32 $ 13.48 $ 9.62 Diluted Earnings Per Share $ 13.26 $ 13.40 $ 9.48

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
Stockholders' Equity (Tables)	Dec. 31, 2023
Equity [Abstract]
Summary of Purchase and Sale of Common Stock	The following table summarizes the shares of the Company’s common stock that were purchased and sold by the Company’s rabbi trust: For The Years Ended December 31, 2023 2022 2021 Shares of common stock purchased 2,110 12,117 5,580 Aggregate purchase price of shares purchased $ 620,282 $ 3,253,577 $ 1,268,370 Shares of common stock sold 2,420 36,762 2,841 Aggregate sale price of shares sold $ 834,704 $ 10,370,165 $ 802,030

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
Stock-Based Compensation (Tables)	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Summary of Stock Option Activity	The following table summarizes stock option activity for the year ended December 31, 2023 for employees: Options Weighted Average Exercise price Weighted Average Remaining Contractual Life Aggregate Intrinsic Value Outstanding at December 31, 2022 72,323 $ 155.83 4.6 $ 4,921 Exercised ( 34,881 ) 139.76 Outstanding at December 31, 2023 37,442 $ 170.79 3.8 $ 10,013 Exercisable at December 31, 2023 21,850 $ 113.98 3.0 $ 7,085
Summary of Weighted Average Assumptions Used In Valuing Options	The following table summarizes the weighted average assumptions used in valuing options for the years ended December 31, 2022 and 2021: 2022 2021 Risk-free interest rate 1.92 % 1.19 % Expected life in years 3.5 3.5 Expected volatility 43.32 % 40.57 % Dividend rate — —
Summary of Restricted Stock Activity	The following table summarizes restricted stock activity during the year ended December 31, 2023: Shares Weighted Average Grant-date Fair Value Restricted Stock at December 31, 2022 48,240 $ 177.89 Granted 20,056 329.32 Vested ( 16,340 ) 101.30 Forfeited — — Restricted Stock at December 31, 2023 51,956 $ 260.43
Summary of Performance Unit Awards	The following table summarizes performance unit awards during the year ended December 31, 2023: Shares Weighted Average Grant-date Fair Value Performance Unit Awards at December 31, 2022 57,431 $ 207.32 Granted 14,266 429.55 Added by performance factor 31,594 132.81 Vested ( 63,188 ) 132.81 Forfeited — — Performance Unit Awards at December 31, 2023 40,103 $ 345.08

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Summary of Income Tax Provision	The income tax provision consists of the following (in thousands): 2023 2022 2021 Current: U.S. federal $ 82,802 $ 68,934 $ 62,222 State 18,498 20,058 12,997 Total current income tax provision 101,300 88,992 75,219 Deferred: U.S. federal 10,345 21,440 3,915 State ( 275 ) 194 404 Total deferred income tax provision 10,070 21,634 4,319 Total income tax provision $ 111,370 $ 110,626 $ 79,538
Summary of Reconciliation Between Income Taxes and Effective Income Tax Provision	A reconciliation between income taxes at the federal statutory rate (21 percent) and the actual income tax provision is as follows (in thousands): 2023 2022 2021 Provision at federal statutory rate $ 97,908 $ 98,290 $ 69,856 State income taxes, net of federal benefit 15,580 16,274 11,435 Tax credits ( 1,181 ) ( 1,355 ) ( 1,754 ) Excess tax benefit on stock compensation ( 1,004 ) ( 1,578 ) ( 793 ) Other, net 67 ( 1,005 ) 794 Total provision $ 111,370 $ 110,626 $ 79,538
Summary of Deferred Tax Liabilities and Assets	Deferred tax (liabilities) assets are comprised of the following at December 31 (in thousands): 2023 2022 Depreciation $ ( 196,494 ) $ ( 183,276 ) Leases ( 29,361 ) ( 30,886 ) Other ( 6,022 ) ( 5,471 ) Gross deferred tax liabilities ( 231,877 ) ( 219,633 ) Allowance for credit losses 1,097 1,435 Equity-based compensation 4,834 4,089 Employee benefits 12,014 9,988 Leases 30,227 30,578 Claims and insurance 21,597 22,137 Other 6,982 6,377 Gross deferred tax assets 76,751 74,604 Valuation Allowance ( 715 ) ( 742 ) Net deferred tax assets 76,036 73,862 Net deferred tax liability $ ( 155,841 ) $ ( 145,771 )
Summary of Gross Unrecognized Tax Benefits	A reconciliation of the beginning and ending total amounts of gross unrecognized tax benefits is as follows (in thousands): 2023 2022 Gross unrecognized tax benefits at beginning of year $ 3,867 $ 1,370 Gross increases in tax positions for prior years 2 1,779 Gross increases in tax positions for current year 1,077 1,005 Settlements — — Lapse of statute of limitations ( 254 ) ( 287 ) Gross unrecognized tax benefits at end of year $ 4,692 $ 3,867

Valuation and Qualifying Acco_2

Valuation and Qualifying Accounts (Tables)	12 Months Ended
Valuation and Qualifying Accounts (Tables)	Dec. 31, 2023
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Summary of Valuation and Qualifying Accounts	The following is a rollforward of the allowance for credit losses for receivables (in thousands): Additions Balance, beginning of period Charged to costs and expenses Charged to other accounts Deductions(1) Balance, end of period For the period ended December 31, 2023 5,804 1,955 $ — $ ( 3,332 ) $ 4,427 For the period ended December 31, 2022 5,530 3,074 — ( 2,800 ) 5,804 For the period ended December 31, 2021 5,666 3,559 — ( 3,695 ) 5,530 (1) Primarily uncollectible accounts written off — net of recoveries.

Description of Business and S_4

Description of Business and Summary of Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Description of Business and Summary of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted		true		true
Change in accounting principle, accounting standards update, immaterial effect			true	true
Depreciation and amortization	$ 178,845	$ 157,203	$ 141,700
Advertising costs	$ 2,900	7,200	5,700
Credit Concentration Risk [Member] \| Accounts Receivable [Member] \| No Single Customer [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Percentage of accounts receivable	5%
Property and Equipment [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Depreciation and amortization	$ 177,900	156,200	$ 140,500
Trailers [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Assets acquired under finance lease, gross	137,400	137,900
Assets acquired under finance lease, accumulated depreciation	$ 67,700	$ 58,700
Minimum [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Percentage of revenue derived from transporting	97%
Average transit time	1 day
Minimum [Member] \| Restricted Stock [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Stock-based awards compensation expense amortization period	3 years
Maximum [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Average transit time	5 days
Maximum [Member] \| Restricted Stock [Member]
Description of Business and Summary of Significant Accounting Policies [Line Items]
Stock-based awards compensation expense amortization period	5 years

Description of Business and S_5

Description of Business and Summary of Accounting Policies - Summary of Property and Equipment, Estimated Useful Lives (Detail)	Dec. 31, 2023
Structures [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	20 years
Structures [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	25 years
Revenue Equipment [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	6 years
Revenue Equipment [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	14 years
Technology Equipment and Software [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	3 years
Technology Equipment and Software [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	5 years
Other [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	3 years
Other [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, service lives	10 years

Description of Business and S_6

Description of Business and Summary of Accounting Policies - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	$ 2,881,800	$ 2,478,824
Land [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	272,633	191,057
Structures [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	813,146	638,180
Revenue Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	1,470,913	1,340,761
Technology Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	176,854	187,333
Other [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	$ 148,254	$ 121,493

Description of Business and S_7

Description of Business and Summary of Accounting Policies - Additional Information1 (Detail)	Dec. 31, 2023
Maximum [Member] \| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2023-01-01
Description of Business and Summary of Significant Accounting Policies [Line Items]
Payment terms	30 days

Debt and Financing Arrangemen_3

Debt and Financing Arrangements - Summary of Reconciliation of Debt (Detail) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Debt Instruments [Abstract]
Credit Agreement with Banks, described below	$ 0	$ 0
Finance Leases, described below	16,488,000	31,008,000
Total debt	16,488,000	31,008,000
Less: current portion of long-term debt	10,173,000	14,519,000
Long-term debt, less current portion	$ 6,315,000	$ 16,489,000
Finance Lease, Liability, Statement of Financial Position [Extensible Enumeration]	us-gaap:FinanceLeaseLiabilityNoncurrent	us-gaap:FinanceLeaseLiabilityNoncurrent

Debt and Financing Arrangemen_4

Debt and Financing Arrangements - Additional Information (Detail) - USD ($)			12 Months Ended
	Nov. 09, 2023	Feb. 03, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Borrowing capacity under credit agreement			$ 0	$ 0
Initial Notes interest rate	6.09%
Maximum leverage ratio			3.50%
Finance lease liability			$ 16,488,000	31,008,000
Estimated fair value of the finance leases			16,100,000	31,200,000
Cash paid for interest			1,600,000	2,300,000	$ 3,000,000
Maximum [Member]
Debt Instrument [Line Items]
Letter of credit unused portion fee		0.025%
Minimum [Member]
Debt Instrument [Line Items]
Letter of credit unused portion fee		0.0125%
Base Rate Margin [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Rate margin		0.75%
Base Rate Margin [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Rate margin		0%
Secured Overnight Financing Rate [Member]
Debt Instrument [Line Items]
Rate margin		0.10%
Secured Overnight Financing Rate [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Rate margin		1.75%
Secured Overnight Financing Rate [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Rate margin		1%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Borrowing capacity under credit agreement				$ 300,000,000
Amendment line of credit facility expiration year and month				2024-02
Additional borrowing capacity under revolving credit facility				$ 100,000,000
Private Shelf Agreement [Member]
Debt Instrument [Line Items]
Uncommitted Private Shelf Agreement	$ 350,000,000
Private Shelf Agreement [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Selling of aggregate principal amount	$ 100,000,000
Twenty Twenty Three Credit Facility [Member]
Debt Instrument [Line Items]
Borrowing capacity under credit agreement		$ 300,000,000
Company Increase The Size		$ 150,000,000
Adjusted Leverage Ratio		3.50%
Existing Credit Agreement [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Borrowing capacity under credit agreement			0	0
Letter of credit facility outstanding amount			$ 32,100,000	$ 31,200,000

Commitments, Contingencies an_3

Commitments, Contingencies and Uncertainties - Schedule of Non-Cancellable Capital and Operating Lease Agreements Requiring Minimum Annual Rentals Payable (Detail) $ in Thousands	Dec. 31, 2023 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2024	$ 31,218
2025	28,830
2026	21,977
2027	19,180
2028	16,273
Thereafter	25,100
Total	$ 142,578

Commitments, Contingencies an_4

Commitments, Contingencies and Uncertainties - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Other Commitments [Line Items]
Rent expense	$ 37.2	$ 33.4	$ 31.6
Purchase commitments related to capital expenditures	306.6
Capital expenditures in accounts payable	50.9	$ 19.5
Seventeen Terminals [Member]
Other Commitments [Line Items]
Payments to Acquire Projects	235.7
Eleven Terminal [Member]
Other Commitments [Line Items]
Payments to Acquire Projects	$ 7.9

Leases - Additional Information

Leases - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Finance leased assets, net	$ 38.6	$ 60.5
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Property and Equipment, at cost	Property and Equipment, at cost
Accumulated depreciation and amortization of finance leased assets	$ 31.2	$ 43.8

Leases - Summary of Lease Cost

Leases - Summary of Lease Cost and Other Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Finance lease cost:
Amortization of right-of-use assets	$ 5,693	$ 8,276
Interest on lease liabilities	883	1,476
Operating lease cost (includes variable and sublease costs as they are immaterial)	34,522	30,919
Short-term lease cost	16,303	19,387
Total lease cost	57,401	60,058
Other Information
Right-of-use assets obtained in exchange for new finance lease liabilities	0	0
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 27,026	$ 39,122

Leases - Summary of Supplementa

Leases - Summary of Supplemental Cash Flow and Balance Sheet Information Related to Leases (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash paid for amounts included in the measurement of lease liabilities
Operating cash outflows from finance leases	$ 890	$ 1,484
Operating cash outflows from operating leases	35,339	31,043
Financing cash outflows from finance leases	$ 14,520	$ 19,471	$ 20,571
Weighted-average remaining lease term - finance leases (years)	1 year 2 months 12 days	1 year 9 months 18 days
Weighted-average remaining lease term - operating leases (years)	5 years 4 months 24 days	5 years 2 months 12 days
Weighted-average discount rate - finance leases	4%	3.70%
Weighted-average discount rate - operating leases	5.40%	5.10%

Leases - Summary of Maturity of

Leases - Summary of Maturity of Lease Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Operating Leases
2024	$ 31,218
2025	28,830
2026	21,977
2027	19,180
2028	16,273
Thereafter	25,100
Total lease payments	142,578
Less: Interest	20,359
Present value of lease liabilities	122,219
Finance Leases
2024	10,605
2025	5,453
2026	995
2027	0
2028	0
Thereafter	0
Total lease payments	17,053
Less: Interest	565
Finance Leases, described below	$ 16,488	$ 31,008
Finance Lease, Liability, Statement of Financial Position [Extensible Enumeration]	us-gaap:FinanceLeaseLiabilityNoncurrent	us-gaap:FinanceLeaseLiabilityNoncurrent

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 12.1	$ 12.1	$ 12.1
Amortization expense for intangible assets	$ 0.9	$ 1	$ 1.2

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets - Summary of Gross Amounts and Accumulated Amortization of Identifiable Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 20,500	$ 20,500
Accumulated Amortization	15,309	14,456
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Amount	19,000	19,000
Accumulated Amortization	14,417	13,664
Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Amount	1,500	1,500
Accumulated Amortization	$ 892	$ 792

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets - Summary of Gross Amounts and Accumulated Amortization of Identifiable Intangible Assets (Parenthetical) (Detail)	Dec. 31, 2023
Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, useful life	15 years
Minimum [Member] \| Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, useful life	6 years
Maximum [Member] \| Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, useful life	15 years

Goodwill and Other Intangible_6

Goodwill and Other Intangible Assets - Summary of Estimated Amortization Expense for Next Five Years (Detail) $ in Thousands	Dec. 31, 2023 USD ($)
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2024	$ 853
2025	853
2026	853
2027	853
2028	$ 853

Computation of Earnings Per S_3

Computation of Earnings Per Share - Summary of Calculation of Basic Earnings Per Common Share and Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Numerator:
Net Income (Loss)	$ 354,857	$ 357,422	$ 253,235
Denominator:
Denominator for basic earnings per share–weighted average common shares	26,632	26,520	26,322
Dilutive effect of share-based awards	131	154	385
Denominator for diluted earnings per share–adjusted weighted average common shares	26,763	26,674	26,707
Basic Earnings Per Share	$ 13.32	$ 13.48	$ 9.62
Diluted Earnings Per Share	$ 13.26	$ 13.40	$ 9.48

Computation of Earnings Per S_4

Computation of Earnings Per Share - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Earnings Per Share [Abstract]
Common stock excluded from the calculation of diluted earnings per share	5,790	22,237	19,386

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Purchase and Sale of Common Stock (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Equity [Abstract]
Shares of common stock purchased	2,110	12,117	5,580
Aggregate purchase price of shares purchased	$ 620,282	$ 3,253,577	$ 1,268,370
Shares of common stock sold	2,420	36,762	2,841
Aggregate sale price of shares sold	$ 834,704	$ 10,370,165	$ 802,030

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - shares	Dec. 31, 2023	Dec. 31, 2022
Equity [Abstract]
Common stock shares held by Rabbi Trust	69,672	69,982
Shares reserved for issuance under the Directors Deferred Fee Plan	100,110	97,381

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2024	Feb. 29, 2024	Feb. 28, 2023	Feb. 28, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding stock options	37,442	72,323
Stock-based compensation	$ 11,636,000	$ 8,827,000	$ 8,703,000
Unrecognized compensation expense	$ 6,200,000
Weighted average recognition period of compensation expenses	1 year 7 months 6 days
Total intrinsic value of options exercised	$ 7,000,000	$ 10,800,000	$ 5,900,000
Weighted-average grant-date fair value per share of options granted	$ 0	$ 94.36	$ 62.65
Stock Option and Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 5,700,000	$ 3,900,000	$ 3,300,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of shares vested	$ 1,700,000	2,100,000	1,400,000
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock vesting period	3 years
Unrecognized compensation expense	$ 5,900,000
Weighted average recognition period of compensation expenses	1 year 9 months 18 days
Operating expense	$ 4,500,000	3,800,000	4,000,000
Fair value of shares vested	$ 4,200,000	$ 3,600,000	$ 3,000,000
After three years [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock vesting percentage	25%
After three years [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock vesting period	3 years
After five years [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock vesting period	50 years
After five years [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock vesting period	5 years
After four years [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock vesting percentage	25%
After four years [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock vesting period	4 years
January 2020 - December 2022 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period share issuance range						63,188
January 2019 - December 2021 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period share issuance range							78,710
January 2020 – December 2022 [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period share issuance range					25,716
Maximum [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock vesting period	5 years
Maximum [Member] \| January 2023 - December 2025 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance unit awards, outstanding	25,020
Maximum [Member] \| January 2023 - December 2025 [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance unit awards, outstanding				28,532
Minimum [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock vesting period	3 years
Non Employee Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual service	3 years
Contractual term	7 years
Restricted stock vesting period	3 years
Number of shares granted	10,000
2018 Omnibus Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved	1,100,000
Reserved and unissued shares	677,500	765,617
2018 Omnibus Incentive Plan [Member] \| Non Employee Director [Member] \| Director Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued to non employee director	379	396	548
2018 Omnibus Incentive Plan [Member] \| Non Employee Director [Member] \| Maximum [Member] \| Director Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual grant amount	$ 500,000
2011 Omnibus Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved	2,350,000
Additional grant under Plan	0
Reserved and unissued shares	391,089	391,089
Directors' Deferred Fee Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued to non employee director	2,729	3,272	3,929

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Beginning balance, options	72,323
Exercised, options	(34,881)
Ending balance, options	37,442	72,323
Exercisable, options	21,850
Beginning balance, weighted average exercise price	$ 155.83
Exercised	139.76
Ending balance, weighted average exercise price	170.79	$ 155.83
Exercisable, weighted average exercisable price	$ 113.98
Outstanding, weighted average remaining contractual life (years)	3 years 9 months 18 days	4 years 7 months 6 days
Exercisable, weighted average remaining contractual life (years)	3 years
Outstanding, aggregate intrinsic value	$ 10,013	$ 4,921
Exercisable, aggregate intrinsic value	$ 7,085

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Weighted Average Assumptions Used In Valuing Options (Detail)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share-Based Payment Arrangement [Abstract]
Risk-free interest rate	1.92%	1.19%
Expected life in years	3 years 6 months	3 years 6 months
Expected volatility	43.32%	40.57%

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Restricted Stock Activity (Detail) - Restricted Stock [Member]	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested, options beginning balance \| shares	48,240
Granted, options \| shares	20,056
Vested, options \| shares	(16,340)
Forfeited, options \| shares	0
Unvested, options ending balance \| shares	51,956
Unvested, weighted average grant date fair value beginning balance \| $ / shares	$ 177.89
Granted \| $ / shares	329.32
Vested \| $ / shares	101.3
Forfeited \| $ / shares	0
Unvested, weighted average grant date fair value ending balance \| $ / shares	$ 260.43

Stock-Based Compensation - Su_4

Stock-Based Compensation - Summary of Performance Unit Awards (Details) - Performance Shares [Member]	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Unvested, options beginning balance \| shares	57,431
Granted, options \| shares	14,266
Added by performance factor, options \| shares	31,594
Vested, options \| shares	(63,188)
Forfeited, options \| shares	0
Unvested, options ending balance \| shares	40,103
Unvested, weighted average grant date fair value beginning balance \| $ / shares	$ 207.32
Granted \| $ / shares	429.55
Added by performance factor \| $ / shares	132.81
Vested \| $ / shares	132.81
Forfeited \| $ / shares	0
Unvested, weighted average grant date fair value ending balance \| $ / shares	$ 345.08

Employee Benefits - Additional

Employee Benefits - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Shares held by the rabbi trust	69,672	69,982
Cash incentive awards	$ 38.8	$ 32.6	$ 36.4
Shares purchased by custodians	1,420	2,158	2,516
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Payroll deduction for ESPP, percent of annual wages	10%
Highly Compensated Employees [Member] \| Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Payroll deduction for ESPP, percent of annual wages	20%
401(k)Saving Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Company match of contribution	50%
Employees contribution share	6%
Contribution in operation	$ 15.2	$ 14	$ 12.4

Income Taxes - Summary of Incom

Income Taxes - Summary of Income Tax Provision (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current:
U.S. federal	$ 82,802	$ 68,934	$ 62,222
State	18,498	20,058	12,997
Total current income tax provision	101,300	88,992	75,219
Deferred:
U.S. federal	10,345	21,440	3,915
State	(275)	194	404
Total deferred income tax provision	10,070	21,634	4,319
Total provision	$ 111,370	$ 110,626	$ 79,538

Income Taxes - Summary of Recon

Income Taxes - Summary of Reconciliation Between Income Taxes and Effective Income Tax Provision (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Provision at federal statutory rate	$ 97,908	$ 98,290	$ 69,856
State income taxes, net of federal benefit	15,580	16,274	11,435
Tax credits	(1,181)	(1,355)	(1,754)
Excess tax benefit on stock compensation	(1,004)	(1,578)	(793)
Other, net	67	(1,005)	794
Total provision	$ 111,370	$ 110,626	$ 79,538

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax [Line Items]
Unrecognized tax benefits that would affect the Company's effective tax rate if recognized	$ 4.7	$ 3.9
Cash (received) paid for income taxes	$ 72.8	$ 115.3	$ 81.6
Maximum [Member]
Income Tax [Line Items]
Income tax year open for examination	2023
Maximum [Member] \| State and Local Jurisdiction [Member]
Income Tax [Line Items]
Income tax year open for examination	2023
Minimum [Member]
Income Tax [Line Items]
Income tax year open for examination	2020
Minimum [Member] \| State and Local Jurisdiction [Member]
Income Tax [Line Items]
Income tax year open for examination	2014

Income Taxes - Summary of Defer

Income Taxes - Summary of Deferred Tax Liabilities and Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Depreciation	$ (196,494)	$ (183,276)
Leases	(29,361)	(30,886)
Other	(6,022)	(5,471)
Gross deferred tax liabilities	(231,877)	(219,633)
Allowance for credit losses	1,097	1,435
Equity-based compensation	4,834	4,089
Employee benefits	12,014	9,988
Leases	30,227	30,578
Claims and insurance	21,597	22,137
Other	6,982	6,377
Gross deferred tax assets	76,751	74,604
Valuation Allowance	(715)	(742)
Net deferred tax assets	76,036	73,862
Net deferred tax liability	$ (155,841)	$ (145,771)

Income Taxes - Summary of Gross

Income Taxes - Summary of Gross Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Gross unrecognized tax benefits at beginning of year	$ 3,867	$ 1,370
Gross increases in tax positions for prior years	2	1,779
Gross increases in tax positions for current year	1,077	1,005
Settlements	0	0
Lapse of statute of limitations	(254)	(287)
Gross unrecognized tax benefits at end of year	$ 4,692	$ 3,867

Valuation and Qualifying Acco_3

Valuation and Qualifying Accounts - Summary of Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance, beginning of period		$ 5,804	$ 5,530	$ 5,666
Additions - Charged to costs and expenses		1,955	3,074	3,559
Additions - Charged to other accounts		0	0	0
Deductions	[1]	(3,332)	(2,800)	(3,695)
Balance, end of period		$ 4,427	$ 5,804	$ 5,530

[1] Primarily uncollectible accounts written off — net of recoveries.

Subsequent Events (Additional I

Subsequent Events (Additional Information) (Details) - Subsequent Event [Member] $ in Millions	Jan. 17, 2024 USD ($)
Seventeen Terminals [Member]
Subsequent Event [Line Items]
Asset Acquisition, Date of Acquisition Agreement	Jan. 17, 2024
Payments to Acquire Projects	$ 235.7
Eleven Terminal [Member]
Subsequent Event [Line Items]
Asset Acquisition, Date of Acquisition Agreement	Jan. 17, 2024
Payments to Acquire Projects	$ 7.9