Comfort Systems USA (FIX) 10-K22 Feb 242023 FY Annual reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2023	Feb. 16, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Document Transition Report	false
Entity File Number	1-13011
Entity Registrant Name	Comfort Systems USA, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	76-0526487
Entity Address, Address Line One	675 Bering Drive
Entity Address, Address Line Two	Suite 400
Entity Address, City or Town	Houston
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77057
City Area Code	713
Local Phone Number	830-9600
Title of 12(b) Security	Common Stock, $.01 par value
Trading Symbol	FIX
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 5,750
Entity Common Stock, Shares Outstanding		35,684,609
Entity Central Index Key	0001035983
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Amendment Flag	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Auditor Name	Deloitte & Touche LLP
Auditor Firm ID	34
Auditor Location	Houston, Texas

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
CURRENT ASSETS:
Cash and cash equivalents	$ 205,150	$ 57,214
Billed accounts receivable, less allowance for credit losses of $11,926 and $10,640, respectively	1,318,926	1,024,082
Unbilled accounts receivable, less allowance for credit losses of $850 and $1,011, respectively	72,774	77,030
Other receivables, less allowance for credit losses of $522 and $510, respectively	166,319	38,369
Inventories	65,538	35,309
Prepaid expenses and other	54,309	48,456
Costs and estimated earnings in excess of billings, less allowance for credit losses of $79 and $80, respectively	28,084	27,211
Total current assets	1,911,100	1,307,671
PROPERTY AND EQUIPMENT, NET	208,568	143,949
LEASE RIGHT-OF-USE ASSET	205,712	130,666
GOODWILL	666,834	611,789
IDENTIFIABLE INTANGIBLE ASSETS, NET	280,397	273,901
DEFERRED TAX ASSETS	17,723	115,665
OTHER NONCURRENT ASSETS	15,245	13,837
Total assets	3,305,579	2,597,478
CURRENT LIABILITIES:
Current maturities of long-term debt	4,867	9,000
Accounts payable	419,962	337,385
Accrued compensation and benefits	169,136	127,765
Billings in excess of costs and estimated earnings and deferred revenue	909,538	548,293
Accrued self-insurance	27,774	27,644
Other current liabilities	189,928	120,715
Total current liabilities	1,721,205	1,170,802
LONG-TERM DEBT	39,345	247,245
LEASE LIABILITIES	188,136	111,744
DEFERRED TAX LIABILITIES	1,120
OTHER LONG-TERM LIABILITIES	77,944	67,764
Total liabilities	2,027,750	1,597,555
COMMITMENTS AND CONTINGENCIES
STOCKHOLDERS' EQUITY:
Preferred stock, $.01 par, 5,000,000 shares authorized, none issued and outstanding
Common stock, $.01 par, 102,969,912 shares authorized, 41,123,365 and 41,123,365 shares issued, respectively	411	411
Treasury stock, at cost, 5,438,625 and 5,362,224 shares, respectively	(209,807)	(187,212)
Additional paid-in capital	339,562	332,080
Retained earnings	1,147,663	854,644
Total stockholders' equity	1,277,829	999,923
Total liabilities and stockholders' equity	$ 3,305,579	$ 2,597,478

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
CONSOLIDATED BALANCE SHEETS
Billed accounts receivable, allowance for credit losses (in dollars)	$ 11,926	$ 10,640
Unbilled accounts receivable, allowance for credit losses (in dollars)	850	1,011
Other receivables, allowance for credit losses (in dollars)	522	510
Costs and estimated earnings in excess of billings, allowance for credit losses (in dollars)	$ 79	$ 80
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	102,969,912	102,969,912
Common stock, shares issued	41,123,365	41,123,365
Treasury stock, shares	5,438,625	5,362,224

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
CONSOLIDATED STATEMENTS OF OPERATIONS
REVENUE	$ 5,206,760	$ 4,140,364	$ 3,073,636
COST OF SERVICES	4,216,251	3,398,756	2,510,429
Gross profit	990,509	741,608	563,207
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES	574,423	489,344	376,309
GAIN ON SALE OF ASSETS	(2,302)	(1,585)	(1,540)
Operating income	418,388	253,849	188,438
OTHER INCOME (EXPENSE):
Interest income	3,492	46	24
Interest expense	(10,281)	(13,352)	(6,196)
Changes in the fair value of contingent earn-out obligations	(23,607)	(4,819)	7,820
Other	202	134	188
Other income (expense)	(30,194)	(17,991)	1,836
INCOME BEFORE INCOME TAXES	388,194	235,858	190,274
PROVISION (BENEFIT) FOR INCOME TAXES	64,796	(10,089)	46,926
NET INCOME	$ 323,398	$ 245,947	$ 143,348
INCOME PER SHARE:
Basic	$ 9.03	$ 6.84	$ 3.95
Diluted	$ 9.01	$ 6.82	$ 3.93
SHARES USED IN COMPUTING INCOME PER SHARE:
Basic	35,802	35,932	36,285
Diluted	35,895	36,046	36,450

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Total
BALANCE at Dec. 31, 2020	$ 411	$ (129,243)	$ 322,451	$ 502,810	$ 696,429
BALANCE (in shares) at Dec. 31, 2020	41,123,365
BALANCE (in shares) at Dec. 31, 2020		(4,935,186)
Increase (Decrease) in Stockholders' Equity
Net income				143,348	143,348
Issuance of Stock:
Issuance of shares for options exercised		$ 5,399	235		5,634
Issuance of shares for options exercised (in shares)		195,724
Issuance of restricted stock & performance stock		$ 2,681	(473)		2,208
Issuance of restricted stock & performance stock (in shares)		101,360
Shares received in lieu of tax withholding on vested stock		$ (2,363)			(2,363)
Shares received in lieu of tax withholding on vested stock (in shares)		(31,413)
Stock-based compensation			4,848		4,848
Dividends				(17,384)	(17,384)
Share repurchase		$ (27,054)			(27,054)
Share repurchase (in shares)		(362,796)
BALANCE at Dec. 31, 2021	$ 411	$ (150,580)	327,061	628,774	805,666
BALANCE (in shares) at Dec. 31, 2021	41,123,365
BALANCE (in shares) at Dec. 31, 2021		(5,032,311)
Increase (Decrease) in Stockholders' Equity
Net income				245,947	245,947
Issuance of Stock:
Issuance of shares for options exercised		$ 1,174	(88)		1,086
Issuance of shares for options exercised (in shares)		34,187
Issuance of restricted stock & performance stock		$ 3,657	(113)		3,544
Issuance of restricted stock & performance stock (in shares)		113,955
Shares received in lieu of tax withholding on vested stock		$ (3,247)			(3,247)
Shares received in lieu of tax withholding on vested stock (in shares)		(36,006)
Stock-based compensation			5,220		5,220
Dividends				(20,077)	(20,077)
Share repurchase		$ (38,216)			(38,216)
Share repurchase (in shares)		(442,049)
BALANCE at Dec. 31, 2022	$ 411	$ (187,212)	332,080	854,644	$ 999,923
BALANCE (in shares) at Dec. 31, 2022	41,123,365				41,123,365
BALANCE (in shares) at Dec. 31, 2022		(5,362,224)			5,362,224
Increase (Decrease) in Stockholders' Equity
Net income				323,398	$ 323,398
Issuance of Stock:
Issuance of shares for options exercised		$ 36	(18)		18
Issuance of shares for options exercised (in shares)		1,000
Issuance of restricted stock & performance stock		$ 3,398	1,117		4,515
Issuance of restricted stock & performance stock (in shares)		94,729
Shares received in lieu of tax withholding on vested stock		$ (4,725)			(4,725)
Shares received in lieu of tax withholding on vested stock (in shares)		(32,652)
Stock-based compensation			6,383		6,383
Dividends				(30,379)	(30,379)
Share repurchase		$ (21,304)			(21,304)
Share repurchase (in shares)		(139,478)
BALANCE at Dec. 31, 2023	$ 411	$ (209,807)	$ 339,562	$ 1,147,663	$ 1,277,829
BALANCE (in shares) at Dec. 31, 2023	41,123,365				41,123,365
BALANCE (in shares) at Dec. 31, 2023		(5,438,625)			5,438,625

CONSOLIDATED STATEMENTS OF ST_2

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY
Dividends (per share)	$ 0.85	$ 0.56	$ 0.48

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 323,398	$ 245,947	$ 143,348
Adjustments to reconcile net income to net cash provided by operating activities-
Amortization of identifiable intangible assets	43,404	47,795	40,505
Depreciation expense	38,162	33,552	28,439
Change in right-of-use assets	25,964	21,557	17,592
Bad debt expense	4,944	2,670	(1,452)
Deferred tax provision (benefit)	95,296	(94,505)	6,902
Amortization of debt financing costs	685	786	538
Gain on sale of assets	(2,302)	(1,585)	(1,540)
Changes in the fair value of contingent earn-out obligations	23,607	4,819	(7,820)
Stock-based compensation	12,939	10,532	10,593
(Increase) decrease in-
Receivables, net	(381,555)	(223,178)	(58,046)
Inventories	(29,688)	(13,495)	(5,651)
Prepaid expenses and other current assets	(11,137)	(26,238)	(8,623)
Costs and estimated earnings in excess of billings and unbilled accounts receivable	7,350	(9,643)	(17,271)
Other noncurrent assets	(152)	(995)	(1,174)
Increase (decrease) in-
Accounts payable and accrued liabilities	136,467	93,110	(5,171)
Billings in excess of costs and estimated earnings and deferred revenue	349,166	226,019	53,795
Other long-term liabilities	3,020	(15,617)	(14,813)
Net cash provided by operating activities	639,568	301,531	180,151
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(94,838)	(48,359)	(22,330)
Proceeds from sales of property and equipment	5,951	2,858	3,101
Cash paid for acquisitions, net of cash acquired	(102,261)	(49,217)	(227,493)
Payments for investments	(1,860)	(2,460)
Net cash used in investing activities	(193,008)	(97,178)	(246,722)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving credit facility	285,000	555,000	275,000
Payments on revolving credit facility	(500,000)	(560,000)	(125,000)
Payments on term loan		(120,000)	(15,000)
Payments on other debt	(12,033)	(12,256)	(15,696)
Payments on finance lease liabilities		(899)	(3,805)
Debt financing costs		(2,297)
Payments of dividends to stockholders	(30,379)	(20,077)	(17,384)
Share repurchase	(21,184)	(38,216)	(27,054)
Shares received in lieu of tax withholding	(4,725)	(3,247)	(2,363)
Proceeds from exercise of options	18	1,086	5,634
Deferred acquisition payments		(50)	(400)
Payments for contingent consideration arrangements	(15,321)	(4,959)	(3,481)
Net cash provided by (used in) financing activities	(298,624)	(205,915)	70,451
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	147,936	(1,562)	3,880
CASH AND CASH EQUIVALENTS, beginning of period	57,214	58,776	54,896
CASH AND CASH EQUIVALENTS, end of period	$ 205,150	$ 57,214	$ 58,776

Business and Organization

Business and Organization	12 Months Ended
Business and Organization	Dec. 31, 2023
Business and Organization
Business and Organization	1. Business and Organization Comfort Systems USA, Inc., a Delaware corporation, provides comprehensive mechanical and electrical contracting services, which principally includes heating, ventilation and air conditioning (“HVAC”), plumbing, electrical, piping and controls, as well as off-site construction, monitoring and fire protection. We build, install, maintain, repair and replace mechanical, electrical and plumbing (“MEP”) systems throughout the United States. Approximately 54.8% of our consolidated 2023 revenue is attributable to installation of systems in newly constructed facilities, with the remaining 45.2% attributable to renovation, expansion, maintenance, repair and replacement services in existing buildings. The terms “Comfort Systems,” “we,” “us,” or the “Company,” refer to Comfort Systems USA, Inc. or Comfort Systems USA, Inc. and its consolidated subsidiaries, as appropriate in the context.

Summary of Significant Accounti

Summary of Significant Accounting Policies and Estimates	12 Months Ended
Summary of Significant Accounting Policies and Estimates	Dec. 31, 2023
Summary of Significant Accounting Policies and Estimates
Summary of Significant Accounting Policies and Estimates	2. Summary of Significant Accounting Policies and Estimates Principles of Consolidation These financial statements are prepared in accordance with accounting principles generally accepted in the United States of America. The accompanying consolidated financial statements include our accounts and those of our subsidiaries in which we have a controlling interest. All intercompany accounts and transactions have been eliminated. Certain amounts in prior periods have been reclassified to conform to the current period presentation. The effects of the reclassifications were not material to the consolidated financial statements. Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles requires the use of estimates and assumptions by management in determining the reported amounts of assets and liabilities, revenue and expenses and disclosures regarding contingent assets and liabilities. Actual results could differ from those estimates. The most significant estimates used in our financial statements affect revenue and cost recognition for construction contracts, self-insurance accruals, accounting for income taxes, fair value accounting for acquisitions and the quantification of fair value for reporting units in connection with our goodwill impairment testing. Cash Flow Information We consider all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. Cash paid (in thousands) for: Year Ended December 31, 2023 2022 2021 Interest $ 9,862 $ 12,915 $ 6,052 Income taxes, net of refunds $ 100,254 $ 44,296 $ 52,204 Recent Accounting Pronouncements Recently Adopted Accounting Pronouncements In October 2021, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2021-08, “Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers.” This standard requires an acquirer to apply Accounting Standards Codification Topic 606 to recognize and measure contract assets and contract liabilities in a business combination. ASU 2021-08 is effective for fiscal years beginning after December 15, 2022 and interim periods within that year. We adopted this standard on January 1, 2023, and the impact on our consolidated financial statements was not material. Recent Accounting Pronouncements Not Yet Adopted In November 2023, the FASB issued ASU 2023-07, “Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures.” This standard requires entities to disclose, on an annual and interim basis, significant segment expenses that are regularly provided to the chief decision maker and included within each reported measure of segment profit and loss. ASU 2023-07 is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. We are currently evaluating the impact ASU 2023-07 will have on our disclosures; however, the standard will not have an impact on our consolidated financial position, results of operations or cash flows. In December 2023, the FASB issued ASU 2023-09, “Income Taxes (Topic 740): Improvements to Income Tax Disclosures.” This standard requires entities to disclose more detailed information in the reconciliation of their statutory tax rate to their effective tax rate. The standard also requires entities to make additional disclosures on income taxes paid as well as on certain income statement-related disclosures. ASU 2023-09 is effective for fiscal years beginning after December 15, 2024 . Early adoption is permitted. We are currently evaluating the impact ASU 2023-09 will have on our disclosures; however, the standard will not have an impact on our consolidated financial position, results of operations or cash flows. Revenue Recognition We recognize revenue over time for all of our services as we perform them because (i) control continuously transfers to that customer as work progresses, and (ii) we have the right to bill the customer as costs are incurred. The customer typically controls the work in process, as evidenced either by contractual termination clauses or by our rights to payment for work performed to date, plus a reasonable profit, for delivery of products or services that do not have an alternative use to the Company. For the reasons listed above, revenue is recognized based on the extent of progress towards completion of the performance obligation. The selection of the method to measure progress towards completion requires judgment and is based on the nature of the products or services to be provided. We generally use a cost-to-cost input method to measure our progress towards satisfaction of the performance obligation for our contracts, as it best depicts the transfer of assets to the customer that occurs as we incur costs on our contracts. Under the cost-to-cost input method, the extent of progress towards completion is measured based on the ratio of costs incurred to date to the total estimated costs at completion of the performance obligation. Revenue, including estimated fees or profits, is recorded proportionally as costs are incurred. Costs to fulfill include labor, materials, subcontractors’ costs, other direct costs and an allocation of indirect costs. For a small portion of our business in which our services are delivered in the form of service maintenance agreements for existing systems to be repaired and maintained, as opposed to constructed, our performance obligation is to maintain the customer’s mechanical system for a specific period of time. Similar to construction jobs, we recognize revenue over time; however, for service maintenance agreements in which the full cost to provide services may not be known, we generally use an input method to recognize revenue, which is based on the amount of time we have provided our services out of the total time we have been contracted to perform those services. Our revenue recognition policy is further discussed in Note 3 “Revenue from Contracts with Customers.” Accounts Receivable and Allowance for Credit Losses We are required to estimate and record the expected credit losses over the contractual life of our financial assets measured at amortized cost, including billed and unbilled accounts receivable, other receivables and contract assets. Accounts receivable include amounts from work completed in which we have billed or have an unconditional right to bill our customers. Our trade receivables are contractually due in less than a year. We estimate our credit losses using a loss-rate method for each of our identified portfolio segments. Our portfolio segments are construction, service and other. While our construction and service financial assets are often with the same subset of customers and industries, our construction financial assets will generally have a lower loss-rate than service financial assets due to lien rights, which we are more likely to have on construction jobs. These lien rights result in lower credit loss expenses on average compared to receivables that do not have lien rights. Financial assets classified as Other include receivables that are not related to our core revenue producing activities, such as receivables related to our acquisition activity from former owners, our vendor rebate program or receivables for estimated losses in excess of our insurance deductible, which are accrued with a corresponding accrued insurance liability. Loss rates for our portfolios are based on numerous factors, including our history of credit loss expense by portfolio, the financial strength of our customers and counterparties in each portfolio, the aging of our receivables, our expectation of likelihood of payment, macroeconomic trends in the U.S. and the current and forecasted nonresidential construction market trends in the U.S. In addition to the loss-rate calculations discussed above, we also record allowance for credit losses for specific receivables that are deemed to have a higher risk profile than the rest of the respective pool of receivables (e.g., when we hold concerns about a specific customer going bankrupt and no longer being able to pay the receivables due to us). Activity in our allowance for credit losses consisted of the following (in thousands): Year Ended December 31, Year Ended December 31, 2023 2022 Service Construction Other Total Service Construction Other Total Balance at beginning of year $ 5,245 $ 6,931 $ 65 $ 12,241 $ 3,294 $ 6,758 $ 58 $ 10,110 Bad debt expense 2,113 2,819 12 4,944 2,431 232 7 2,670 Deductions for uncollectible receivables written off, net of recoveries (1,658) (2,355) — (4,013) (804) (402) — (1,206) Credit allowance of acquired receivables on the acquisition date — 205 — 205 324 343 — 667 Balance at end of period $ 5,700 $ 7,600 $ 77 $ 13,377 $ 5,245 $ 6,931 $ 65 $ 12,241 Unbilled Accounts Receivable Inventories Inventories consist of parts and supplies that we purchase and hold for use in the ordinary course of business and are stated at the lower of cost or net realizable value using the average-cost method. Property and Equipment Property and equipment are stated at cost, and depreciation is computed using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are capitalized and amortized over the lesser of the expected life of the lease or the estimated useful life of the asset. Expenditures for repairs and maintenance are charged to expense when incurred. Expenditures for major renewals and betterments, which extend the useful lives of existing equipment, are capitalized and depreciated over the remaining useful life of the equipment. Upon retirement or disposition of property and equipment, the cost and related accumulated depreciation are removed from the accounts and any resulting gain or loss is recognized in “Gain on Sale of Assets” in the Consolidated Statements of Operations. Recoverability of Goodwill and Identifiable Intangible Assets Goodwill is the excess of purchase price over the fair value of the net assets of acquired businesses. We assess goodwill for impairment each year, and more frequently if circumstances suggest an impairment may have occurred. When the carrying value of a given reporting unit exceeds its fair value, a goodwill impairment loss is recorded for this difference, not to exceed the carrying amount of goodwill. The requirements for assessing whether goodwill has been impaired involve market-based information. This information, and its use in assessing goodwill, entails some degree of subjective assessment. We perform our annual impairment testing as of October 1, and any impairment charges resulting from this process are reported in the fourth quarter. We segregate our operations into reporting units based on the degree of operating and financial independence of each unit and our related management of them. We perform our annual goodwill impairment testing at the reporting unit level. We perform a goodwill impairment review for each of our operating units, as we have determined that each of our operating units are reporting units. In the evaluation of goodwill for impairment, we have the option to first assess qualitative factors to determine whether the existence of events or circumstances lead to a determination that it is more likely than not that the fair value of one of our reporting units is greater than its carrying value. If, after completing such assessment, we determine it is more likely than not that the fair value of a reporting unit is greater than its carrying amount, then there is no need to perform any further testing. If we conclude otherwise, or if we elect to perform a quantitative assessment, then we calculate the fair value of the reporting unit and compare the fair value with the carrying value of the reporting unit. We estimate the fair value of the reporting unit based on a market approach and an income approach, which utilizes discounted future cash flows. Assumptions critical to the fair value estimates under the discounted cash flow model include discount rates, cash flow projections, projected long-term growth rates and the determination of terminal values. The market approach utilizes market multiples of invested capital from comparable publicly traded companies (“public company approach”). The market multiples from invested capital include revenue, book equity plus debt and earnings before interest, provision for income taxes, depreciation and amortization (“EBITDA”). We amortize identifiable intangible assets with finite lives over their useful lives. Changes in strategy and/or market condition may result in adjustments to recorded intangible asset balances or their useful lives. Long-Lived Assets Long-lived assets are comprised principally of identifiable intangible assets, property and equipment, lease right-of-use assets and deferred tax assets. We periodically evaluate whether events and circumstances have occurred that indicate that the remaining balances of these assets may not be recoverable. We use estimates of future undiscounted cash flows, as well as other economic and business factors, to assess the recoverability of these assets. Acquisitions We recognize assets acquired and liabilities assumed in business combinations, including contingent assets and liabilities, based on fair value estimates as of the date of acquisition. Contingent Consideration Contingent Assets and Liabilities Self-Insurance Liabilities We are substantially self-insured for workers’ compensation, employer’s liability, auto liability, general liability and employee group health claims, in view of the relatively high per-incident deductibles we absorb under our insurance arrangements for these risks. Losses are estimated and accrued based upon known facts, historical trends and industry averages. Estimated losses in excess of our deductible, which have not already been paid, are included in our accrual with a corresponding receivable from our insurance carrier. Loss estimates associated with the larger and longer-developing risks, such as workers’ compensation, auto liability and general liability, are reviewed by a third-party actuary quarterly. Our self-insurance arrangements are further discussed in Note 13 “Commitments and Contingencies.” Warranty Costs We typically warrant labor for the first year after installation on new MEP systems that we build and install, and we pass through to the customer manufacturers’ warranties on equipment. We generally warrant labor for thirty days after servicing existing MEP systems. A reserve for warranty costs is estimated and recorded based upon the historical level of warranty claims and management’s estimate of future costs. Income Taxes We conduct business throughout the United States in virtually all fifty states. Our effective tax rate changes based upon our relative profitability, or lack thereof, in the federal and various state jurisdictions with differing tax rates and rules. In addition, discrete items such as tax law changes, judgments and legal structures, can impact our effective tax rate. These items can also include the tax treatment for impairment of goodwill and other intangible assets, changes in fair value of acquisition-related assets and liabilities, uncertain tax positions, and accounting for losses associated with underperforming operations. Income taxes are provided for under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, we determine deferred tax assets and liabilities based on the differences between the financial statement and tax basis of assets and liabilities by using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in the provision for income taxes in the period that includes the enactment date. We recognize deferred tax assets to the extent that we believe that these assets are more likely than not to be realized. In making such a determination, we consider all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, taxable income in prior carryback years and tax planning strategies. Management’s judgment is required in considering the relative weight of negative and positive evidence. We record uncertain tax positions based on a two-step process in which (i) we determine whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (ii) for those tax positions that meet the more-likely-than-not recognition threshold, we recognize the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the relevant taxing authority. To the extent interest and penalties may be assessed by taxing authorities on any underpayment of income taxes, such amounts are accrued and classified as a component in the provision for income taxes in our Consolidated Statements of Operations. Concentrations of Credit Risk We provide services in a broad range of geographic regions. Our credit risk primarily consists of receivables from a variety of customers, including general contractors, property owners and developers, and commercial and industrial companies. We are subject to potential credit risk related to changes in business and economic factors throughout the United States within the nonresidential construction industry. However, we are entitled to payment for work performed and have certain lien rights related to that work. Further, we believe that our contract acceptance, billing and collection policies are adequate to manage potential credit risk. We regularly review our accounts receivable and estimate an allowance for credit losses. We have a diverse customer base, with our top customer representing 14% of consolidated 2023 revenue. Financial Instruments Our financial instruments consist of cash and cash equivalents, accounts receivable, other receivables, accounts payable and life insurance policies, for which we deem the carrying values approximate their fair value due to the short-term nature of these instruments, as well as notes to former owners and a revolving credit facility. Investments We have a $4.3 million investment in a construction focused technology fund with a fair value that is not readily determinable and is recorded at cost. This investment is included in “Other Noncurrent Assets” in our Consolidated Balance Sheet and is reviewed quarterly for impairment. We did not recognize any impairments in the current year related to this investment.

Revenue from Contracts with Cus

Revenue from Contracts with Customers	12 Months Ended
Revenue from Contracts with Customers	Dec. 31, 2023
Revenue from Contracts with Customers
Revenue from Contracts with Customers	3. Revenue from Contracts with Customers Revenue is recognized when control of the promised goods or services is transferred to our customers, in an amount that reflects the consideration to which we expect to be entitled in exchange for those goods or services. Sales-based taxes are excluded from revenue. We provide mechanical and electrical contracting services. Our mechanical segment principally includes HVAC, plumbing, piping and controls, as well as off‑site construction, monitoring and fire protection. Our electrical segment includes installation and servicing of electrical systems. We build, install, maintain, repair and replace products and systems throughout the United States. All of our revenue is recognized over time as we deliver goods and services to our customers. Revenue can be earned based on an agreed-upon fixed price or based on actual costs incurred, marked up at an agreed-upon percentage. For fixed price agreements, we use the cost-to-cost input method of accounting under which contract revenue recognizable at any time during the life of a contract is determined by multiplying expected total contract revenue by the percentage of contract costs incurred at any time to total estimated contract costs. More specifically, as part of the negotiation and bidding process to obtain installation contracts, we estimate our contract costs, which include all direct materials, labor and subcontract costs and indirect costs related to contract performance, such as indirect labor, supplies, tools, repairs and depreciation costs. These contract costs are included in our results of operations under the caption “Cost of Services.” Then, as we perform under those contracts, we measure costs incurred, compare them to total estimated costs to complete the contract and recognize a corresponding proportion of contract revenue. Labor costs are considered to be incurred as the work is performed. Subcontractor labor is recognized as the work is performed. Non‑labor project costs consist of purchased equipment, prefabricated materials and other materials. Purchased equipment on our projects is substantially produced to job specifications, normally installed shortly after receipt and is a value-added element to our work. Prefabricated materials, such as ductwork and piping, are generally performed at our shops and recognized as contract costs when fabricated for the unique specifications of the job. Other materials costs are generally recorded when delivered to the work site. This measurement and comparison process requires updates to the estimate of total costs to complete the contract, and these updates may include subjective assessments and judgments. We account for a contract when: (i) it has approval and commitment from both parties, (ii) the rights of the parties are identified, (iii) payment terms are identified, (iv) the contract has commercial substance, and (v) collectability of consideration is probable. We consider the start of a project to be when the above criteria have been met and we either have written authorization from the customer to proceed or an executed contract. Selling, marketing and estimation costs incurred in relation to selling contracts are expensed as incurred. On rare occasions, we may incur significant expenses related to selling a contract that we only incurred because we sold that contract. If this occurs, we capitalize that cost and amortize it on a completion percentage basis over the life of the contract. We do not currently have any capitalized selling, marketing, or estimation costs in our Consolidated Balance Sheet and did not incur any impairment loss on such costs in the current year. We generally do not incur significant incremental costs related to obtaining or fulfilling a contract prior to the start of a project. On rare occasions, when significant pre contract costs are incurred, they are capitalized and amortized over the life of the contract using a cost-to-cost input method to measure progress towards contract completion. We do not currently have any capitalized obtainment or fulfillment costs in our Consolidated Balance Sheet and have not incurred any impairment loss on such costs in the current year. Project contracts typically provide for a schedule of billings or invoices to the customer based on our job-to-date completion percentage of specific tasks inherent in the fulfillment of our performance obligation(s). The schedules for such billings usually do not precisely match the schedule on which costs are incurred. As a result, contract revenue recognized in our Consolidated Statement of Operations can, and usually does, differ from amounts that can be billed or invoiced to the customer at any point during the contract. Amounts by which cumulative contract revenue recognized on a contract as of a given date exceed cumulative billings and unbilled receivables to the customer under the contract are reflected as a current asset in our Consolidated Balance Sheet under the caption “Costs and Estimated Earnings in Excess of Billings.” Amounts by which cumulative billings to the customer under a contract as of a given date exceed cumulative contract revenue recognized on the contract are reflected as a current liability in our Consolidated Balance Sheet under the caption “Billings in Excess of Costs and Estimated Earnings and Deferred Revenue.” Accounts receivable include amounts billed to customers under retention or retainage provisions in construction contracts. Such provisions are standard in our industry and usually allow for a small portion of progress billings or the contract price to be withheld by the customer until after we have completed work on the project, typically for a period of six months. Based on our experience with similar contracts in recent years, the majority of our billings for such retention balances at each Balance Sheet date are finalized and collected within the subsequent year. Retention balances at December 31, 2023 and 2022 were $245.0 million and $193.6 million, respectively, and are included in accounts receivable. Accounts payable at December 31, 2023 and 2022 included $32.9 million and $29.8 million of retainage under terms of contracts with subcontractors, respectively. The majority of the retention balances at each Balance Sheet date are finalized and paid within the subsequent year. The cost-to-cost input method of accounting is also affected by changes in job performance, job conditions, and final contract settlements. These factors may result in revisions to estimated costs and, therefore, revenue. Such revisions are frequently based on further estimates and subjective assessments. The effects of these revisions are recognized in the period in which revisions are determined. When such revisions lead to a conclusion that a loss will be recognized on a contract, the full amount of the estimated ultimate loss is recognized in the period such conclusion is reached, regardless of the completion percentage of the contract. Revisions to project costs and conditions can give rise to change orders under which there is an agreement between the customer and us that the customer pays an additional or reduced contract price. Revisions can also result in claims we might make against the customer to recover project variances that have not been satisfactorily addressed through change orders with the customer. The amount of revenue associated with unapproved change orders and claims was immaterial for the year ended December 31, 2023. Variations from estimated project costs could have a significant impact on our operating results, depending on project size, and the recoverability of the variation from change orders collected from customers. We typically invoice our customers with payment terms of net due in 30 days. It is common in the construction industry for a contract to specify more lenient payment terms allowing the customer 45 30 A performance obligation is a promise in a contract to transfer a distinct good or service to the customer. A contract’s transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. To determine the proper revenue recognition method for contracts, we evaluate whether two or more contracts should be combined and accounted for as one performance obligation and whether the combined or single contract should be accounted for as more than one performance obligation. This evaluation requires significant judgment and the decision to combine a group of contracts or separate the combined or single contract into multiple performance obligations could change the amount of revenue and profit recorded in a given period. For most of our contracts, the customer contracts with us to provide a significant service of integrating a complex set of tasks and components into a single project or capability (even if that single project results in the delivery of multiple units). Hence, the entire contract is accounted for as one performance obligation. Less commonly, however, we may promise to provide distinct goods or services within a contract, in which case we separate the contract into more than one performance obligation. If a contract is separated into more than one performance obligation, we allocate the total transaction price to each performance obligation in an amount based on the estimated relative standalone selling prices of the promised goods or services underlying each performance obligation. We infrequently sell standard products with observable standalone sales. In such cases, the observable standalone sales are used to determine the standalone selling price. More frequently, we sell a customized, customer-specific solution, and, in these cases, we typically use the expected cost plus a margin approach to estimate the standalone selling price of each performance obligation. We recognize revenue over time for all of our services as we perform them because (i) control continuously transfers to that customer as work progresses, and (ii) we have the right to bill the customer as costs are incurred. The customer typically controls the work in process, as evidenced either by contractual termination clauses or by our rights to payment for work performed to date plus a reasonable profit to deliver products or services that do not have an alternative use to the Company. Due to the nature of the work required to be performed on many of our performance obligations, the estimation of total revenue and cost at completion (the process described below in more detail) is complex, subject to many variables and requires significant judgment. The consideration to which we are entitled on our long-term contracts may include both fixed and variable amounts. Variable amounts can either increase or decrease the transaction price. A common example of variable amounts that can either increase or decrease contract value are pending change orders that represent contract modifications for which a change in scope has been authorized or acknowledged by our customer, but the final adjustment to contract price is yet to be negotiated. Other examples of positive variable revenue include amounts awarded upon achievement of certain performance metrics, program milestones or cost of completion date targets and can be based upon customer discretion. Variable amounts can result in a deduction from contract revenue if we fail to meet stated performance requirements, such as complying with the construction schedule. We include estimated amounts of variable consideration in the contract price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved. Our estimates of variable consideration and determinatio Contracts are often modified to account for changes in contract specifications and requirements. We consider contract modifications to exist when the modification either creates new, or changes the existing, enforceable rights and obligations. Most of our contract modifications are for goods or services that are not distinct from the existing performance obligation(s). The effect of a contract modification on the transaction price, and our measure of progress for the performance obligation to which it relates, is recognized as an adjustment to revenue (either as an increase or decrease) on a cumulative catch-up basis. We have a Company-wide policy requiring periodic review of the Estimate at Completion in which management reviews the progress and execution of our performance obligations and estimated remaining obligations. As part of this process, management reviews information including, but not limited to, any outstanding key contract matters, progress towards completion and the related program schedule, identified risks and opportunities and the related changes in estimates of revenue and costs. The risks and opportunities include management's judgment about the ability and cost to achieve the schedule (e.g., the number and type of milestone events), technical requirements (e.g., a newly developed product versus a mature product) and other contract requirements. Management must make assumptions and estimates regarding labor productivity and availability, the complexity of the work to be performed, the availability of materials, the length of time to complete the performance obligation (e.g., to estimate increases in wages and prices for materials and related support cost allocations), execution by our subcontractors, the availability and timing of funding from our customer, and overhead cost rates, among other variables. Based on this analysis, any adjustments to revenue, cost of services, and the related impact to operating income are recognized as necessary in the quarter when they become known. These adjustments may result from positive program performance if we determine we will be successful in mitigating risks surrounding the technical, schedule and cost aspects of those performance obligations or realizing related opportunities and may result in an increase in operating income during the performance of individual performance obligations. Likewise, if we determine we will not be successful in mitigating these risks or realizing related opportunities, these adjustments may result in a decrease in operating income. Changes in estimates of revenue, cost of services and the related impact to operating income are recognized quarterly on a cumulative catch-up basis, meaning we recognize in the current period the cumulative effect of the changes on current and prior periods based on our progress towards complete satisfaction of a performance obligation. A significant change in one or more of these estimates could affect the profitability of one or more of our performance obligations. For projects in which estimates of total costs to be incurred on a performance obligation exceed total estimates of revenue to be earned, a provision for the entire loss on the performance obligation is recognized in the period the loss is determined. The Company typically does not incur any returns, refunds, or similar obligations after the completion of the performance obligation since any deficiencies are corrected during the course of the work or are included as a modification to revenue. The Company does offer an industry standard warranty on our work, which is most commonly for a one-year period. The vendors providing the equipment and materials are responsible for any failures in their product unless installed incorrectly. We include an estimated amount to cover estimated warranty expense in our Cost of Services and record a liability in our Consolidated Balance Sheet to cover our current estimated outstanding warranty obligations. During the years ended December 31, 2023, December 31, 2022 and December 31, 2021, net revenue recognized from our performance obligations partially satisfied in previous periods was not material. Disaggregation of Revenue Our consolidated 2023 revenue was derived from contracts to provide service activities in the mechanical and electrical segments we serve. Refer to Note 16 “Segment Information” for additional information on our reportable segments. We disaggregate our revenue from contracts with customers by activity, customer type and service provided, as we believe it best depicts how the nature, amount, timing and uncertainty of our revenue and cash flows are affected by economic factors. See details in the following tables (dollars in thousands): Year Ended December 31, Revenue by Service Provided 2023 2022 2021 Mechanical Segment $ 3,946,022 75.8 % $ 3,178,475 76.8 % $ 2,542,623 82.7 % Electrical Segment 1,260,738 24.2 % 961,889 23.2 % 531,013 17.3 % Total $ 5,206,760 100.0 % $ 4,140,364 100.0 % $ 3,073,636 100.0 % Year Ended December 31, Revenue by Type of Customer 2023 2022 2021 Manufacturing $ 1,751,684 33.6 % $ 1,426,962 34.5 % $ 970,986 31.6 % Technology 1,114,382 21.4 % 546,290 13.2 % 385,702 12.5 % Healthcare 554,906 10.6 % 584,023 14.1 % 417,901 13.6 % Education 493,982 9.5 % 445,638 10.8 % 390,251 12.7 % Office Buildings 400,754 7.7 % 349,235 8.4 % 308,799 10.1 % Retail, Restaurants and Entertainment 310,381 6.0 % 311,697 7.5 % 213,386 6.9 % Government 301,837 5.8 % 255,314 6.2 % 174,813 5.7 % Multi-Family and Residential 181,780 3.5 % 126,339 3.0 % 112,779 3.7 % Other 97,054 1.9 % 94,866 2.3 % 99,019 3.2 % Total $ 5,206,760 100.0 % $ 4,140,364 100.0 % $ 3,073,636 100.0 % Year Ended December 31, Revenue by Activity Type 2023 2022 2021 New Construction $ 2,853,239 54.8 % $ 2,011,992 48.6 % $ 1,421,784 46.3 % Existing Building Construction 1,337,023 25.6 % 1,210,512 29.2 % 963,461 31.3 % Service Projects 446,151 8.6 % 382,155 9.2 % 278,582 9.1 % Service Calls, Maintenance and Monitoring 570,347 11.0 % 535,705 13.0 % 409,809 13.3 % Total $ 5,206,760 100.0 % $ 4,140,364 100.0 % $ 3,073,636 100.0 % Contract Assets and Liabilities Contract assets include unbilled amounts typically resulting from sales under long term contracts when the cost-to-cost method of revenue recognition is used, revenue recognized exceeds the amount billed to the customer and right to payment is conditional or subject to completing a milestone, such as a phase of the project. Contract assets are not considered to have a significant financing component, as they are intended to protect the customer in the event that we do not perform our obligations under the contract. Contract liabilities consist of advance payments and billings in excess of revenue recognized. Advanced payments from customers related to work not yet started are classified as deferred revenue. Contract liabilities are not considered to have a significant financing component, as they are used to meet working capital requirements that are generally higher in the early stages of a contract and are intended to protect us from the other party failing to meet its obligations under the contract. Our contract assets and liabilities are reported in a net position on a contract-by-contract basis at the end of each reporting period. Contract assets and liabilities in the Consolidated Balance Sheet consisted of the following amounts as of December 31, 2023 and December 31, 2022 (in thousands): December 31, 2023 December 31, 2022 Contract assets: Costs and estimated earnings in excess of billings, less allowance for credit losses $ 28,084 $ 27,211 Contract liabilities: Billings in excess of costs and estimated earnings and deferred revenue $ 909,538 $ 548,293 Contract assets and liabilities fluctuate year to year based on various factors, including, but not limited to, the variability in billing and payment terms of customers and changes in the number and size of projects in progress at period end. Contract assets and contract liabilities increased from December 31, 2022 to December 31, 2023 by approximately $0.9 million and $361.2 million, respectively. The increase in contract assets was primarily due to an increase of $4.1 million as a result of the acquisitions of Eldeco, Inc. (“Eldeco”) and DECCO, Inc. (“DECCO”). This increase was substantially offset by a decrease of $3.2 million due to the timing of billings and related costs and estimated earnings in excess of billings at December 31, 2023 as compared to December 31, 2022. The increase in contract liabilities was driven by an increase of $349.1 million related to an increase in billings in excess of costs recognized on our performance obligations, primarily from projects within the technology sector. Additionally, there was an increase of $12.1 million as a result of the Eldeco and DECCO acquisitions. During the years ended December 31, 2023 and 2022, we recognized revenue of $500.6 million and $286.5 million related to our contract liabilities at January 1, 2023 and January 1, 2022, respectively. We did not have any impairment losses recognized on our receivables or contract assets in 2023 and 2022. Remaining Performance Obligations Remaining construction performance obligations represent the remaining transaction price of firm orders for which work has not been performed and exclude unexercised contract options. As of December 31, 2023, the aggregate amount of the transaction price allocated to remaining performance obligations was $5.16 billion. The Company expects to recognize revenue on approximately 65-75% of the remaining performance obligations over the next 12 months, with the remaining recognized thereafter. Our service maintenance agreements are generally one-year renewable agreements. We have adopted the practical expedient that allows us to not include service maintenance contracts with a total term of one year or less; therefore, we do not report unfulfilled performance obligations for service maintenance agreements.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
Fair Value Measurements	Dec. 31, 2023
Fair Value Measurements
Fair Value Measurements	4. Fair Value Measurements Interest Rate Risk Management and Derivative Instruments In April 2020, we entered into interest rate swap agreements to reduce our exposure to variable interest rates on our revolving credit facility. The interest rate swap agreements terminated on September 30, 2022. At times, we use derivative instruments to manage exposure to market risk, including interest rate risk. Unsettled amounts under our interest rate swaps, if any, are recorded in the Consolidated Balance Sheet at fair value in “Other Receivables” or “Other Current Liabilities.” Gains and losses on our interest rate swaps are recorded in the Consolidated Statement of Operations in “Interest Expense.” For the years ended December 31, 2022 and 2021, we recognized a net gain of $0.3 million and a net loss of $0.5 million, respectively, related to our interest rate swaps. We currently do not have any derivatives that are accounted for as hedges under ASC 815. Fair Value Measurement We classify and disclose assets and liabilities carried at fair value in one of the following three categories: ● Level 1—quoted prices in active markets for identical assets and liabilities; ● Level 2—observable market-based inputs or unobservable inputs that are corroborated by market data; and ● Level 3—significant unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions. The following table summarizes the fair values, and levels within the fair value hierarchy in which the fair value measurements are included, for assets and liabilities measured on a recurring basis as of December 31, 2023 and 2022 (in thousands): Fair Value Measurements at December 31, 2023 Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 205,150 $ — $ — $ 205,150 Life insurance—cash surrender value $ — $ 7,473 $ — $ 7,473 Contingent earn-out obligations $ — $ — $ 44,222 $ 44,222 Fair Value Measurements at December 31, 2022 Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 57,214 $ — $ — $ 57,214 Life insurance—cash surrender value $ — $ 9,315 $ — $ 9,315 Contingent earn-out obligations $ — $ — $ 32,317 $ 32,317 Cash and cash equivalents consist primarily of highly rated money market funds at a variety of well-known institutions with original maturities of three months or less. The original cost of these assets approximates fair value due to their short-term maturity. We believe the carrying value of our debt associated with our revolving credit facility approximates its fair value due to the variable rate on such debt. We believe the carrying values of our notes to former owners approximate their fair values due to the relatively short remaining terms on these notes. We have life insurance policies covering 131 employees with a combined face value of $87.8 million. The policies are invested in several investment vehicles, and the fair value measurement of the cash surrender balance associated with these policies is determined using Level 2 inputs within the fair value hierarchy and will vary with investment performance. The cash surrender value of these policies is included in “Other Noncurrent Assets” in our Consolidated Balance Sheets. We value contingent earn-out obligations using a probability weighted discounted cash flow method. This fair value measurement is based on significant unobservable inputs in the market and thus represents a Level 3 measurement within the fair value hierarchy. This analysis reflects the contractual terms of the purchase agreements (e.g., minimum and maximum payments, length of earn-out periods, manner of calculating any amounts due, etc.) and utilizes assumptions with regard to future cash flows and operating income, probabilities of achieving such future cash flows and operating income and a weighted average cost of capital. Significant changes in any of these assumptions could result in a significantly higher or lower potential liability. The contingent earn-out obligations are measured at fair value each reporting period, and changes in estimates of fair value are recognized in earnings. As of December 31, 2023, cash flows were discounted using a weighted average cost of capital ranging from 15.0% - 16.0%. The table below presents a reconciliation of the fair value of our contingent earn-out obligations that use significant unobservable inputs (Level 3) (in thousands): Year Ended Year Ended December 31, 2023 December 31, 2022 Balance at beginning of year $ 32,317 $ 34,114 Issuances 4,315 — Settlements (16,017) (6,616) Adjustments to fair value 23,607 4,819 Balance at end of year $ 44,222 $ 32,317

Acquisitions

Acquisitions	12 Months Ended
Acquisitions	Dec. 31, 2023
Acquisitions
Acquisitions	5. Acquisitions On October 2, 2023, we acquired all of the issued and outstanding equity interests of DECCO, Inc. (“DECCO”), headquartered in Nashua, New Hampshire, for a total preliminary purchase price of $59.8 million, which included $48.8 million of cash paid on the closing date, $7.0 million in notes payable to the former owners, an earn-out that will be paid if certain financial targets are met after the acquisition date and a working capital adjustment. DECCO operates in the Northeastern United States and performs mechanical and plumbing services with specialties in piping systems, steam, power, biotechnical processes and conveying systems, in addition to turnkey tool and equipment installation, critical equipment handling services and associated maintenance and support services. As a result of the acquisition, DECCO is a wholly owned subsidiary of the Company reported in our mechanical segment. The goodwill recognized as a result of the DECCO acquisition is not deductible for tax purposes. On February 1, 2023, we acquired all of the issued and outstanding shares of capital stock of Eldeco, Inc. (“Eldeco”), headquartered in South Carolina, for a total purchase price of $74.0 million, which included $60.8 million of cash paid on the closing date, $8.0 million in notes payable to the former owners, an earn-out that will be paid if certain financial targets are met after the acquisition date and a working capital adjustment. Eldeco performs electrical design and construction services in the Southeastern region of the United States. As a result of the acquisition, Eldeco is a wholly owned subsidiary of the Company reported in our electrical segment. The goodwill recognized as a result of the Eldeco acquisition is deductible for tax purposes. On April 1, 2022, we acquired Atlantic Electric, LLC and its related subsidiary (“Atlantic”), headquartered in Charleston, South Carolina, and with operations in South Carolina and Western North Carolina, for a total purchase price of $48.1 million, which included $34.1 million of cash paid on the closing date, $5.3 million in notes payable to former owners and a working capital adjustment. Atlantic performs electrical contracting for customers in various South Carolina markets, as well as installation of airport runway lighting in the Southeast. As a result of the acquisition, Atlantic is a wholly owned subsidiary of the Company reported in our electrical segment. The results of operations of acquisitions are included in our consolidated financial statements from their respective acquisition dates. Our Consolidated Balance Sheet includes preliminary allocations of the purchase price to the assets acquired and liabilities assumed for the applicable acquisitions pending the completion of the final valuation of intangible assets and accrued liabilities. The acquisitions completed in the current and prior year were not material, individually or in the aggregate. Additional contingent purchase price (“earn-out”) has been or will be paid if certain acquisitions achieve predetermined profitability targets. Such earn-outs, when they are not subject to the continued employment of the sellers, are estimated as of the purchase date and included as part of the consideration paid for the acquisition. If we have an earn-out under which continued employment is a condition to receipt of payment, then the earn-out is recorded as compensation expense over the period earned.

Goodwill and Identifiable Intan

Goodwill and Identifiable Intangible Assets, Net	12 Months Ended
Goodwill and Identifiable Intangible Assets, Net	Dec. 31, 2023
Goodwill and Identifiable Intangible Assets, Net
Goodwill and Identifiable Intangible Assets, Net	6. Goodwill and Identifiable Intangible Assets, Net Goodwill The changes in the carrying amount of goodwill are as follows (in thousands): Mechanical Segment Electrical Segment Total Balance at December 31, 2021 $ 361,320 $ 230,794 $ 592,114 Acquisitions and purchase price adjustments (See Note 5) 2,609 17,066 19,675 Balance at December 31, 2022 363,929 247,860 611,789 Acquisitions and purchase price adjustments (See Note 5) 29,347 25,698 55,045 Balance at December 31, 2023 $ 393,276 $ 273,558 $ 666,834 The aggregate goodwill balance as of December 31, 2023 and 2022 includes $116.6 million of accumulated impairment charges, all of which relate to the mechanical segment. During our annual impairment testing on October 1, 2023, we performed a qualitative assessment for each reporting unit, which considered various factors, including changes in the carrying value of the reporting unit, forecasted operating results, long-term growth rates and discount rates. Additionally, we considered qualitative key events and circumstances (i.e., macroeconomic environment, industry and market specific conditions, cost factors and events specific to the reporting unit, etc.). Based on this assessment, we concluded that it was more likely than not that the fair value of each reporting unit was greater than its carrying value. Accordingly, no further testing was required. For the years ended December 31, 2023, 2022 and 2021, no impairment of our goodwill or other intangible assets was recorded. There are significant inherent uncertainties and management judgment involved in estimating the fair value of each reporting unit. While we believe we have made reasonable estimates and assumptions to estimate the fair value of our reporting units, it is possible that a material change could occur. If actual results are not consistent with our current estimates and assumptions, or the current economic outlook worsens, goodwill impairment charges may be recorded in future periods. Identifiable Intangible Assets, Net Identifiable intangible assets consist of the following (dollars in thousands): Weighted-Average December 31, 2023 December 31, 2022 Remaining Useful Lives Gross Book Accumulated Gross Book Accumulated in Years Value Amortization Value Amortization Customer Relationships 6.4 $ 376,621 $ (193,338) $ 340,721 $ (161,049) Backlog 0.6 5,900 (4,331) 3,200 (2,361) Trade Names 17.6 129,661 (34,116) 121,561 (28,171) Total $ 512,182 $ (231,785) $ 465,482 $ (191,581) The amounts attributable to customer relationships and trade names are amortized to “Selling, General and Administrative Expenses” based upon the estimated consumption of their economic benefits, or under a shorter period of time using the straight-line method if the pattern of economic benefit cannot be reliably estimated. Our intangible assets related to customer relationships and trade names are amortized over periods from one backlog period. Amortization expense for the years ended December 31, 2023, 2022 and 2021 was $43.4 million, $47.8 million and $40.5 million, respectively. As of December 31, 2023, future amortization expense of identifiable intangible assets was as follows (in thousands): Year ending December 31— 2024 $ 39,851 2025 36,095 2026 35,251 2027 33,269 2028 33,109 Thereafter 102,822 Total $ 280,397

Property and Equipment

Property and Equipment	12 Months Ended
Property and Equipment	Dec. 31, 2023
Property and Equipment
Property and Equipment	7. Property and Equipment Property and equipment consist of the following (dollars in thousands): Estimated Useful Lives December 31, in Years 2023 2022 Land — $ 8,437 $ 6,792 Transportation equipment 1 - 7 188,073 153,587 Machinery and equipment 1 - 20 77,142 56,357 Computer and telephone equipment 1 - 10 29,052 23,551 Buildings and leasehold improvements 1 - 40 101,568 80,275 Furniture and fixtures 1 - 17 8,600 6,270 Construction in progress — 12,645 6,717 425,517 333,549 Less—Accumulated depreciation (216,949) (189,600) Property and equipment, net $ 208,568 $ 143,949 Depreciation expense for the years ended December 31, 2023, 2022 and 2021 was $38.2 million, $33.6 million and $28.4 million, respectively.

Detail of Other Current Liabili

Detail of Other Current Liabilities	12 Months Ended
Detail of Other Current Liabilities	Dec. 31, 2023
Detail of Other Current Liabilities
Detail of Other Current Liabilities	8. Detail of Other Current Liabilities Other current liabilities consist of the following (in thousands): December 31, 2023 2022 Accrued warranty costs $ 11,650 $ 9,429 Current lease liability 24,426 21,151 Accrued job losses 5,458 3,650 Accrued sales and use tax 6,592 5,335 Liabilities due to former owners 49,024 31,510 Other current liabilities 92,778 49,640 $ 189,928 $ 120,715

Debt Obligations

Debt Obligations	12 Months Ended
Debt Obligations	Dec. 31, 2023
Debt Obligations
Debt Obligations	9. Debt Obligations Debt obligations consist of the following (in thousands): December 31, 2023 2022 Revolving credit facility $ — $ 215,000 Notes to former owners 44,070 41,040 Other debt 142 205 Total debt 44,212 256,245 Less—current portion (4,867) (9,000) Total long-term portion of debt $ 39,345 $ 247,245 At December 31, 2023, future principal payments of debt are as follows (in thousands): Year ending December 31— 2024 $ 4,867 2025 21,701 2026 14,144 2027 3,500 $ 44,212 Year Ended December 31, 2023 2022 2021 Interest expense on notes to former owners $ 1,365 $ 1,139 $ 1,052 Interest expense on borrowings and unused commitment fees 7,507 10,955 3,371 Interest expense (income) on interest rate swaps — (332) 499 Interest expense on finance leases — 4 57 Letter of credit fees 724 800 679 Amortization of debt financing costs 685 786 538 Total $ 10,281 $ 13,352 $ 6,196 Revolving Credit Facility On May 25, 2022, we amended our senior credit facility (as amended, the “Facility”) arranged by Wells Fargo Bank, National Association, as administrative agent, and provided by a syndicate of banks, increasing our borrowing capacity to $850 million. As amended, the Facility is composed of a revolving credit line guaranteed by certain of our subsidiaries, in the amount of $850.0 million. The amended Facility also provides for an accordion or increase option not to exceed the greater of (a) $250 million and (b) 1.0x Credit Facility Adjusted EBITDA (as defined below), as well as a sublimit of up to $175.0 million issuable in the form of letters of credit. The Facility expires in July 2027 and is secured by a first lien on substantially all of our personal property except for assets related to projects subject to surety bonds and the equity of, and assets held by, certain unrestricted subsidiaries and our wholly owned captive insurance company, and a second lien on our assets related to projects subject to surety bonds. In 2022, we incurred approximately $2.3 million in financing and professional costs in connection with the amendment to the Facility, which, combined with previously unamortized costs of $1.2 million, are being amortized on a straight-line basis as a non-cash charge to interest expense over the remaining term of the Facility. As of December 31, 2023, we had no outstanding borrowings on the revolving credit facility, $70.2 million in letters of credit outstanding and $779.8 million of credit available. Collateral A common practice in our industry is the posting of payment and performance bonds with customers. These bonds are offered by financial institutions known as sureties and provide assurance to the customer that in the event we encounter significant financial or operational difficulties, the surety will arrange for the completion of our contractual obligations and for the payment of our vendors on the projects subject to the bonds. In cooperation with our lenders, we granted our sureties a first lien on assets such as receivables, costs and estimated earnings in excess of billings, and equipment specifically identifiable to projects for which bonds are outstanding, as collateral for potential obligations under bonds. As of December 31, 2023, the book value of these assets was approximately $162.4 million. Covenants and Restrictions The Facility contains financial covenants defining various financial measures and the levels of these measures with which we must comply. Covenant compliance is assessed as of each quarter end. Credit Facility Adjusted EBITDA is defined under the Facility for financial covenant purposes as consolidated net income for the four fiscal quarters ending as of any given quarterly covenant compliance measurement date, plus the corresponding amounts for (a) interest expense; (b) provision for income taxes; (c) depreciation and amortization; (d) stock or equity compensation; (e) other non-cash charges; and (f) pre-acquisition results of acquired companies. The Facility’s principal financial covenants include: Net Leverage Ratio Interest Coverage Ratio Other Restrictions While the Facility’s financial covenants do not specifically govern capacity under the Facility, if our debt level under the Facility at a quarter-end covenant compliance measurement date were to cause us to violate the Facility’s Net Leverage Ratio covenant, our borrowing capacity under the Facility and the favorable terms that we currently have could be negatively impacted. We were in compliance with all of our financial covenants as of December 31, 2023. Interest Rates and Fees There are two interest rate options for borrowings under the Facility, the Base Rate Loan (as defined in the Facility) option and the Secured Overnight Financing Rate (“SOFR”) Loan option. Under the Base Rate Loan option, the interest rate is determined based on the highest of (a) the Federal Funds Rate (as defined in the Facility) plus 0.50%, (b) the prime lending rate established by Wells Fargo Bank, N.A., and (c) the one-month Adjusted Term SOFR (as defined in the Facility) plus 1.00%. Under the SOFR Loan option, the interest rate is determined based on Adjusted Term SOFR for a one, three, or six-month tenor at our election. Additional margins are then added to these two rates. The additional margins are determined based on our Net Leverage Ratio. These rates are floating rates determined by the broad financial markets, meaning they can and do move up and down from time to time. For illustrative purposes, the following are the respective market rates as of December 31, 2023 relating to interest options under the Facility: Base Rate Loan Option: Federal Funds Rate plus 0.50% 5.83% Wells Fargo Bank, N.A. Prime Rate 8.50% One-month SOFR plus 1.00% 6.34% SOFR Loan Option: One-month SOFR 5.34% Three-month SOFR 5.36% Six-month SOFR 5.35% Certain of our vendors require letters of credit to ensure reimbursement for amounts they are disbursing on our behalf, such as to beneficiaries under our self-funded insurance programs. We have also occasionally used letters of credit to guarantee performance under our contracts and to ensure payment to our subcontractors and vendors under those contracts. Our lenders issue such letters of credit through the Facility. A letter of credit commits the lenders to pay specified amounts to the holder of the letter of credit if the holder demonstrates that we have failed to perform specified actions. If this were to occur, we would be required to reimburse the lenders for amounts they fund to honor the letter of credit holder’s claim. Absent a claim, there is no payment or reserving of funds by us in connection with a letter of credit. However, because a claim on a letter of credit would require immediate reimbursement by us to our lenders, letters of credit are treated as a use of facility capacity just the same as actual borrowings. We have never had a claim made against a letter of credit that resulted in payments by a lender or by us and believe such a claim is unlikely in the foreseeable future. Commitment fees are payable on the portion of the revolving loan capacity not in use for borrowings or letters of credit at any given time. Letter of credit fees and commitment fees are based on the Net Leverage Ratio. Net Leverage Ratio Less than 1.00 1.00 to less than 1.75 1.75 to less than 2.50 2.50 to less than 3.00 3.00 or greater Additional Per Annum Interest Margin Added Under: Base Rate Loan Option 0.00 % 0.25 % 0.50 % 0.75 % 1.00 % SOFR Loan Option 1.00 % 1.25 % 1.50 % 1.75 % 2.00 % Letter of credit fees 1.00 % 1.25 % 1.50 % 1.75 % 2.00 % Commitment fees on any portion of the Revolving Loan capacity not in use for borrowings or letters of credit at any given time 0.15 % 0.175 % 0.20 % 0.225 % 0.25 % The weighted average interest rate applicable to the borrowings under the revolving credit facility was approximately 5.7% as of December 31, 2022. There were no outstanding borrowings on the revolving credit facility as of December 31, 2023. Notes to Former Owners As part of the consideration used to acquire eight companies, we have outstanding notes to the former owners. Together, these notes had an outstanding balance of $44.1 million as of December 31, 2023. At December 31, 2023, future principal payments of notes to former owners by maturity year are as follows (dollars in thousands): Balance at Range of Stated December 31, 2023 Interest Rates 2024 $ 4,800 2.5 % 2025 21,645 2.3 - 3.0 % 2026 14,125 2.5 - 5.5 % 2027 3,500 5.5 % Total $ 44,070

Leases

Leases	12 Months Ended
Leases	Dec. 31, 2023
Leases
Leases	10. Leases We lease certain facilities, vehicles and equipment primarily under noncancelable operating leases. The most significant portion of these noncancelable operating leases is for the facilities occupied by our corporate office and our operating locations. Leases with an initial term of 12 months or less are not recorded in the Consolidated Balance Sheet. We do not separate lease components from their associated non-lease components pursuant to lease accounting guidance. We have certain leases with variable payments based on an index as well as short-term leases on equipment and facilities. Variable lease expense and short-term lease expense aggregated to $53.7 million in 2023, $19.1 million in 2022 and $11.9 million in 2021. These expenses were primarily related to short-term equipment rentals. Lease right-of-use assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As most of our leases do not provide an implicit rate, we generally use our incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The weighted average discount rate for our operating leases as of December 31, 2023 and 2022 was 5.8% and 4.3%, respectively. We recognize operating lease expense, including escalating lease payments and lease incentives, on a straight-line basis over the lease term. Operating lease expense for the years ended December 31, 2023, 2022 and 2021 was $86.1 million, $46.0 million and $34.2 million, respectively. The lease terms generally range from three A majority of the Company’s real property leases are with individuals or entities with whom we have no other business relationship. However, in certain instances the Company enters into real property leases with current or former employees. Rent paid to related parties for the years ended December 31, 2023, 2022 and 2021 was approximately $7.6 million, $6.9 million and $4.9 million, respectively. If we decide to cancel or terminate a lease before the end of its term, we would typically owe the lessor the remaining lease payments under the term of the lease. Our lease agreements do not contain any material residual value guarantees or material restrictive covenants. On rare occasions, we rent or sublease certain real estate assets that we no longer use to third parties. The following table summarizes the operating lease assets and liabilities included in the Consolidated Balance Sheet as of December 31, 2023 and December 31, 2022 (in thousands): December 31, 2023 2022 Operating lease right-of-use assets $ 205,712 $ 130,666 Operating lease liabilities: Other current liabilities $ 24,426 $ 21,151 Long-term operating lease liabilities 188,136 111,744 Total operating lease liabilities $ 212,562 $ 132,895 The maturities of operating lease liabilities as of December 31, 2023 are as follows (in thousands): Year ending December 31— 2024 $ 35,653 2025 33,968 2026 30,348 2027 26,158 2028 22,448 Thereafter 148,371 Total lease payments 296,946 Less—present value discount (84,384) Present value of operating lease liabilities $ 212,562 Supplemental information related to operating leases was as follows (in thousands): Year Ended December 31, 2023 2022 Cash paid for amounts included in the measurement of operating lease liabilities $ 29,454 $ 26,740 Operating lease right-of-use assets obtained in exchange for lease liabilities $ 101,010 $ 27,467

Income Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2023
Income Taxes
Income Taxes	11. Income Taxes Provision (Benefit) for Income Taxes Our provision (benefit) for income taxes relating to continuing operations consists of the following (in thousands): December 31, 2023 2022 2021 Current tax provision (benefit)— Federal $ (34,722) $ 58,040 $ 31,283 State 4,222 26,376 8,741 Total current (30,500) 84,416 40,024 Deferred tax provision (benefit)— Federal 81,119 (80,130) 6,197 State 14,177 (14,375) 705 Total deferred 95,296 (94,505) 6,902 Provision (benefit) for income taxes $ 64,796 $ (10,089) $ 46,926 The provision (benefit) for income taxes for the years ended December 31, 2023, 2022 and 2021 resulted in effective tax rates on continuing operations of 16.7%, (4.3%) and 24.7%, respectively. The reasons for the differences between these effective tax rates and the federal statutory rates are as follows (in thousands, except percentages): December 31, 2023 2022 2021 Federal statutory rate of— 21 % 21 % 21 % Income taxes at the federal statutory rate $ 81,521 $ 49,530 $ 39,958 Increases (decreases) resulting from— Net state income taxes 14,278 9,376 7,340 Net unrecognized tax benefits 9,049 (17,922) 640 Nondeductible expenses 5,774 4,045 2,381 R&D tax credit (43,791) (51,398) — Stock-based compensation deductions (928) (872) (2,210) Other (1,107) (2,848) (1,183) Provision (benefit) for income taxes $ 64,796 $ (10,089) $ 46,926 and the resultant reduction in taxable revenue offsets the deferral of tax deductions for R&E expenditures pursuant to the Tax Cuts and Jobs Act (2017) for the 2022 tax year. We filed our 2022 federal tax return in October 2023 requesting a refund of our $107.1 million overpayment, which was not received during the year ended December 31, 2023. Deferred Tax Assets (Liabilities) Significant components of the deferred tax assets and deferred tax liabilities as reflected on the Consolidated Balance Sheets are as follows (in thousands): Year Ended December 31, 2023 2022 Deferred tax assets— Accounts receivable and allowance for credit losses $ 3,203 $ 2,530 Stock-based compensation 4,549 3,809 Accrued liabilities and expenses 44,209 34,179 Lease liabilities 51,065 32,048 Net operating loss carryforwards 5,877 5,361 Intangible assets 8,570 9,204 Research and experimental expenditures 195,444 106,002 Other 1,234 539 Subtotal 314,151 193,672 Valuation allowances (156) (379) Total deferred tax assets 313,995 193,293 Deferred tax liabilities— Property and equipment (27,049) (18,882) Lease right-of-use asset (51,058) (32,025) Long-term contracts (193,144) (1,870) Goodwill (24,452) (23,288) Other (1,689) (1,563) Total deferred tax liabilities (297,392) (77,628) Net deferred tax assets $ 16,603 $ 115,665 The deferred tax assets and deferred tax liabilities reflected above are included in the Consolidated Balance Sheets as follows (in thousands): December 31, 2023 2022 Deferred tax assets $ 17,723 $ 115,665 Deferred tax liabilities $ 1,120 $ — As of December 31, 2023, our deferred tax assets were primarily attributable to R&E expenditures, accrued liabilities and expenses, intangible assets and net operating loss (“NOL”) carryforwards. Beginning in 2022, R&E expenditures must be capitalized and amortized pursuant to the Tax Cuts and Jobs Act (2017). Of the $5.9 million deferred tax asset for NOL carryforwards, $2.5 million is related to $12.0 million of federal NOL carryforwards from the TAS Energy Inc. (“TAS”) acquisition. If not used, such carryforwards will begin to expire in 2034. Pursuant to Section 382 of the Internal Revenue Code, utilization of our federal NOL carryforwards is subject to annual limitations due to the ownership change in TAS. In general, an ownership change, as defined by Section 382, results from transactions increasing the ownership of certain stockholders or public groups in the stock of a corporation by more than 50 percentage points over a three-year period. Our management assesses the available positive and negative evidence to estimate whether sufficient future taxable income will be generated to permit the use of the existing deferred tax assets. The most significant piece of objective evidence evaluated was three years of cumulative pre-tax income in the federal jurisdiction. Management determined there is sufficient positive evidence to conclude it is more likely than not our deferred tax assets are virtually all realizable. Liabilities for Uncertain Tax Positions A reconciliation of the beginning and ending amount of unrecognized tax benefits, excluding accrued interest and penalties, is as follows (in thousands): Year Ended December 31, 2023 2022 2021 Balance at beginning of year $ 11,530 $ 29,452 $ 28,756 Additions based on tax positions related to current year 6,370 3,420 207 Additions based on tax positions related to prior years 2,723 7,427 489 Reductions for tax positions related to prior years (44) (13) — Reductions for settlements with taxing authorities — (28,756) — Balance at end of year $ 20,579 $ 11,530 $ 29,452 We are subject to taxation in the federal and various state jurisdictions. For the year ended December 31, 2022, our unrecognized tax benefits were reduced by $28.8 million due to favorable settlements with the IRS for the 2016 through 2018 tax years. As of December 31, 2023, we remain open to IRS examination for the 2020 tax year forward. State income tax returns are generally subject to examination for a period of three to four years after filing the returns. However, the state impact of any federal audit adjustments and/or amendments remains subject to examination by various states for up to one year after formal notification to the states. As of December 31, 2023, we generally remain open to examination by various state taxing authorities for the 2019 tax year forward. We believe it is reasonably possible that a reduction of up to $5.3 million in unrecognized tax benefits could occur within the next twelve months. Any reductions in our unrecognized tax benefits, due to the future recognition of those tax benefits, would affect our effective tax rates.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
Employee Benefit Plans	Dec. 31, 2023
Employee Benefit Plans
Employee Benefit Plans	12. Employee Benefit Plans We and certain of our subsidiaries sponsor various retirement plans for most full-time and some part-time employees. These plans primarily consist of defined contribution plans. The defined contribution plans generally provide for contributions up to 2.5% of covered employees’ salaries or wages. These contributions totaled $22.9 million in 2023, $19.8 million in 2022 and $16.1 million in 2021. Of these amounts, approximately $0.5 million were payable to the plans at both December 31, 2023 and 2022. Certain of our subsidiaries also participate or have participated in various multi-employer pension plans for the benefit of employees who are union members. As of December 31, 2023 and 2022, we had 7 and 12 employees, respectively, who were union members. There were no contributions made to multi-employer pension plans in 2023, 2022 or 2021. The data available from administrators of other multi-employer pension plans is not sufficient to determine the accumulated benefit obligations, nor the net assets attributable to the multi-employer plans in which our employees participate or previously participated. Certain individuals at one of our operating units are entitled to receive fixed annual payments that reach a maximum amount, as specified in the related agreements, for a 15 year period following retirement or, in some cases, the attainment of 65 years of age. We recognize the unfunded status of the plan as a non-current liability in our Consolidated Balance Sheet. Benefits vest 50% after 10 years of service, 75% after 15 years of service and are fully vested after 20 years of service. We had an unfunded benefit liability of $3.5 million and $3.7 million recorded as of December 31, 2023 and 2022, respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2023
Commitments and Contingencies
Commitments and Contingencies	13. Commitments and Contingencies Claims and Lawsuits We are subject to certain legal and regulatory claims, including lawsuits arising in the normal course of business. We maintain various insurance coverages to minimize financial risk associated with these claims. We have estimated and provided accruals for probable losses and related legal fees associated with certain litigation in the accompanying consolidated financial statements. While we cannot predict the outcome of these proceedings, in management’s opinion and based on reports of counsel, any liability arising from these matters individually and in the aggregate will not have a material effect on our operating results, cash flows or financial condition, after giving effect to provisions already recorded. In the first quarter of 2023, we recorded a pre-tax gain of $6.8 million from legal developments and settlements that primarily relate to disputes with customers regarding the outcome of completed projects as well as an obligation to perform subcontract work under two executed letters of intent for subsequent projects that we believed were not enforceable. The pre-tax gain of $6.8 million was recorded as an increase in gross profit of $6.6 million, a reduction in SG&A of $0.7 million, an increase in interest income of $1.3 million and an increase in the change in fair value of contingent earn-out obligations expense of $1.8 million in our Consolidated Statement of Operations. In 2022, we recorded a net gain of $5.1 million related to legal matters that merited changes to our assessments of the related accruals in the ordinary course of our business based on information received in 2022. The largest change resulted from favorable developments related to a dispute with a customer regarding the outcome of a completed project as well as the obligation to perform subcontract work under two executed letters of intent for subsequent projects that we believed were not enforceable. The net gain of $5.1 million was recorded primarily as an increase in gross profit in our Consolidated Statements of Operations. As of December 31, 2023, we recorded an accrual for unresolved matters, which is not material to our financial statements, based on our analysis of likely outcomes related to the respective matters; however, it is possible that the ultimate outcome and associated costs will deviate from our estimates and that, in the event of an unexpectedly adverse outcome, we may experience additional costs and expenses in future periods. Surety Many customers, particularly in connection with new construction, require us to post performance and payment bonds issued by a financial institution known as a surety. If we fail to perform under the terms of a contract or to pay subcontractors and vendors who provided goods or services under a contract, the customer may demand that the surety make payments or provide services under the bond. We must reimburse the surety for any expenses or outlays it incurs. Current market conditions for surety markets and bonding capacity are adequate, with acceptable terms and conditions. Historically, approximately 10% to 20% of our business has required bonds. While we currently have strong surety relationships to support our bonding needs, future market conditions or changes in the sureties’ assessment of our operating and financial risk could cause the sureties to decline to issue bonds for our work. If that were to occur, the alternatives include doing more business that does not require bonds, posting other forms of collateral for project performance, such as letters of credit or cash, and seeking bonding capacity from other sureties. We would likely also encounter concerns from customers, suppliers and other market participants as to our creditworthiness. While we believe our general operating and financial characteristics would enable us to ultimately respond effectively to an interruption in the availability of bonding capacity, such an interruption would likely cause our revenue and profits to decline in the near term. Self-Insurance We are substantially self-insured for workers’ compensation, employer’s liability, auto liability, general liability and employee group health claims, in view of the relatively high per-incident deductibles we absorb under our insurance arrangements for these risks. Losses are estimated and accrued based upon known facts, historical trends and industry averages. Estimated losses in excess of our deductible, which have not already been paid, are included in our accrual with a corresponding receivable from our insurance carrier. Loss estimates associated with the larger and longer-developing risks, such as workers’ compensation, auto liability and general liability, are reviewed by a third-party actuary quarterly. Our self-insurance arrangements as of December 31, 2023 were as follows: Workers’ Compensation— Employer’s Liability— General Liability— Auto Liability— Employee Medical— each plan Our $250.0 million of aggregate excess loss coverage above applicable per-incident deductibles represents one policy limit that applies to all lines of risk; we do not have a separate $250.0 million of excess loss coverage for each of general liability, employer’s liability and auto liability.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2023
Stockholders' Equity
Stockholders' Equity	14. Stockholders’ Equity Stock Incentive Plans In May 2017, our stockholders approved our 2017 Omnibus Incentive Plan (the “2017 Plan”), which provides for the granting of incentive or non-qualified stock options, stock appreciation rights, restricted or deferred stock, dividend equivalents or other incentive awards to directors, employees, or consultants. The number of shares authorized and reserved for issuance under the 2017 Plan is 2.9 million shares. As of December 31, 2023, there were 1.5 million shares available for issuance under this plan. The 2017 Plan will expire in May 2027. We have outstanding and exercisable stock options under our 2012 Equity Incentive Plan, which was superseded by the 2017 Plan. Share Repurchase Program On March 29, 2007, our Board of Directors (the “Board”) approved a stock repurchase program to acquire up to 1.0 million shares of our outstanding common stock. Subsequently, the Board has from time to time increased the number of shares that may be acquired under the program and approved extensions of the program. On May 17, 2022, the Board approved an extension to the program by increasing the shares authorized for repurchase by 0.7 million shares. Since the inception of the repurchase program, the Board has approved 10.9 million shares to be repurchased. As of December 31, 2023, we have repurchased a cumulative total of 10.3 million shares at an average price of $26.27 per share under the repurchase program. The share repurchases will be made from time to time at our discretion in the open market or privately negotiated transactions as permitted by securities laws and other legal requirements, and subject to market conditions and other factors. The Board may modify, suspend, extend or terminate the program at any time. During the year ended December 31, 2023, we repurchased 0.1 million shares for approximately $21.3 million at an average price of $152.75 per share. Earnings Per Share Basic earnings per share (“EPS”) is computed by dividing net income by the weighted average number of shares of common stock outstanding during the year. Diluted EPS is computed considering the dilutive effect of stock options, restricted stock, restricted stock units and performance stock units. The vesting of unvested, contingently issuable performance stock units is based on the achievement of certain earnings per share targets and total shareholder return. These shares are considered contingently issuable shares for purposes of calculating diluted earnings per share. These shares are not included in the diluted earnings per share denominator until the performance criteria are met, if it is assumed that the end of the reporting period was the end of the contingency period. Unvested restricted stock, restricted stock units and performance stock units are included in diluted earnings per share, weighted outstanding until the shares and units vest. Upon vesting, the vested restricted stock, restricted stock units and performance stock units are included in basic earnings per share weighted outstanding from the vesting date. There were zero anti-dilutive stock options excluded from the calculation of diluted EPS for the years ended December 31, 2023, 2022 and 2021. The following table reconciles the number of shares outstanding with the number of shares used in computing basic and diluted earnings per share for each of the periods presented (in thousands): Year Ended December 31, 2023 2022 2021 Common shares outstanding, end of period 35,685 35,761 36,091 Effect of using weighted average common shares outstanding 117 171 194 Shares used in computing earnings per share—basic 35,802 35,932 36,285 Effect of shares issuable under stock option plans based on the treasury stock method 26 36 89 Effect of restricted and contingently issuable shares 67 78 76 Shares used in computing earnings per share—diluted 35,895 36,046 36,450

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
Stock-Based Compensation	Dec. 31, 2023
Stock-Based Compensation
Stock-Based Compensation	15. Stock-Based Compensation Grants of restricted stock and restricted stock units and performance share units have been determined and administered by the compensation committee of the Board of Directors. Total stock-based compensation expense was $12.9 million, $10.5 million and $10.6 million for the years ended December 31, 2023, 2022 and 2021, respectively. Stock-based compensation expense is recognized using the straight-line method over the vesting period and generally vests over a three-year vesting period. Certain awards provide for accelerated vesting when the sum of an employee's age and years of service is at least 75. We recognize forfeitures as they occur. Total income tax benefit recognized for stock-based compensation arrangements was $2.7 million, $2.2 million and $2.2 million for each of the years ended December 31, 2023, 2022 and 2021. We generally issue treasury shares for stock options and restricted stock, unless treasury shares are not available. Upon the vesting of restricted shares, we have allowed the holder to elect to surrender an amount of shares to meet their statutory tax withholding requirements. These shares are accounted for as treasury stock based upon the value of the stock on the date of vesting. Restricted Stock and Restricted Stock Units The following table summarizes activity under our restricted stock plans (shares in thousands): Year Ended December 31, 2023 Weighted- Average Grant Restricted Stock and Restricted Stock Units Shares Date Fair Value Unvested at beginning of year 104 $ 76.39 Granted 72 $ 164.47 Vested (63) $ 79.32 Forfeited — $ — Unvested at end of year 113 $ 130.83 Approximately $7.5 million of compensation expense related to restricted stock and restricted stock units will be recognized over a weighted-average period of 2.6 years. We determine the fair value of restricted stock and restricted stock units based on the quoted price of our stock at the date of grant. The weighted-average grant date fair value per share of restricted stock shares and units awarded during 2023, 2022 and 2021 was $164.47, $90.17 and $76.73, respectively. The fair value of restricted stock vested during the years ended December 31, 2023, 2022 and 2021 was $9.3 million, $6.6 million and $5.5 million, respectively. Performance Stock Units Under the 2017 Plan, we granted dollar-denominated performance vesting restricted stock units (“PSUs”), which cliff vest at the end of a three-year performance period. The PSUs are subject to two performance measures; 50% of the PSUs are based on the annual performance of our stock price relative to a group of our peers (total shareholder return) and 50% of the PSUs are measured based on meeting or exceeding a pre-determined annual earnings per share target as set by our Board of Directors (EPS). Depending on the Company’s performance in relation to the established performance measures, the awards may vest at zero to a maximum of 2.0 times the dollar-denominated award granted at target. Upon achievement of the necessary performance metrics, the award will be determined in dollars and may be settled in cash or stock based on the market price of the Company’s common stock at the end of the performance period, at our discretion. Compensation expense for dollar-denominated performance units will ultimately be equal to the final dollar value awarded to the grantee upon vesting, settled either in cash or stock. However, throughout the performance period we must record and accrue expense based on an estimate of that future payout. For units determined by EPS performance, the awards are evaluated quarterly against established targets in order to estimate the liability throughout the vesting period. For units determined by total shareholder return performance, a Monte Carlo simulation model is used to estimate accruals throughout the vesting period. The model simulates our total shareholder return and compares it against our peer group over the three-year performance period to produce a predicted distribution of relative share performance. This is applied to the reward criteria to give an expected value of the total shareholder return element. The calculated fair market value as of December 31, 2023 was $15.0 million. Of this amount, $5.4 million relates to the PSUs granted in 2021 whose performance period ended December 31, 2023. These awards will be settled within the upcoming year either in cash or stock. The fair value of performance stock units vested during the years ended December 31, 2023, 2022, and 2021 was $4.5 million, $3.5 million and $2.2 million, respectively. The expense related to performance stock units for the years ended December 31, 2023, 2022 and 2021 was $6.6 million, $5.3 million and $5.7 million, respectively. At the December 31, 2023 calculated fair market value, approximately $2.1 million of compensation expense related to performance stock units will be recognized over a weighted-average period of 1.4 years. We estimated the fair value of the total shareholder return portion of the PSUs as of December 31, 2023, 2022, and 2021 using a Monte Carlo simulation model with the following assumptions: December 31, 2023 2023 PSU Grant 2022 PSU Grant Risk-free interest rate 4.2 % 4.7 % Dividend yield 0.5 % 0.5 % Volatility 35.0 % 35.1 % Look-back period (in years) 2.0 1.0 December 31, 2022 2022 PSU Grant 2021 PSU Grant Risk-free interest rate 4.4 % 4.7 % Dividend yield 0.5 % 0.5 % Volatility 33.5 % 35.1 % Look-back period (in years) 2.0 1.0 December 31, 2021 2021 PSU Grant 2020 PSU Grant Risk-free interest rate 0.7 % 0.4 % Dividend yield 0.5 % 0.5 % Volatility 50.1 % 31.8 % Look-back period (in years) 2.0 1.0 The look-back period reflects the remaining performance period as of the respective year-end dates. The risk-free interest rate for the remaining performance period is based on U.S. Treasury rates as of the respective year-end dates. The assumption for the expected volatility reflects the daily annualized historical volatility on the Company’s dividend adjusted close stock prices measured over the look-back period. The dividend yield assumption is based on the annualized most recent quarterly dividend divided by the stock price on the respective year-end dates.

Segment Information

Segment Information	12 Months Ended
Segment Information	Dec. 31, 2023
Segment Information
Segment Information	16. Segment Information Mechanical Segment Electrical Segment Corporate Consolidated Total Assets at December 31, 2023 $ 2,180,021 $ 901,025 $ 224,533 $ 3,305,579 Total Assets at December 31, 2022 $ 1,741,135 $ 790,040 $ 66,303 $ 2,597,478 Year Ended December 31, 2023 Mechanical Segment Electrical Segment Corporate Consolidated Revenue $ 3,946,022 $ 1,260,738 $ — $ 5,206,760 Gross Profit $ 750,106 $ 240,403 $ — $ 990,509 Capital Expenditures $ 82,449 $ 9,600 $ 2,789 $ 94,838 Year Ended December 31, 2022 Mechanical Segment Electrical Segment Corporate Consolidated Revenue $ 3,178,475 $ 961,889 $ — $ 4,140,364 Gross Profit $ 580,619 $ 160,989 $ — $ 741,608 Capital Expenditures $ 43,532 $ 4,101 $ 726 $ 48,359 Year Ended December 31, 2021 Mechanical Segment Electrical Segment Corporate Consolidated Revenue $ 2,542,623 $ 531,013 $ — $ 3,073,636 Gross Profit $ 486,346 $ 76,861 $ — $ 563,207 Capital Expenditures $ 19,408 $ 2,413 $ 509 $ 22,330

Subsequent Events

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2023
Subsequent Event.
Subsequent Events	17. Subsequent Events

Summary of Significant Accoun_2

Summary of Significant Accounting Policies and Estimates (Policies)	12 Months Ended
	Dec. 31, 2023
Summary of Significant Accounting Policies and Estimates
Principles of Consolidation	Principles of Consolidation These financial statements are prepared in accordance with accounting principles generally accepted in the United States of America. The accompanying consolidated financial statements include our accounts and those of our subsidiaries in which we have a controlling interest. All intercompany accounts and transactions have been eliminated. Certain amounts in prior periods have been reclassified to conform to the current period presentation. The effects of the reclassifications were not material to the consolidated financial statements.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles requires the use of estimates and assumptions by management in determining the reported amounts of assets and liabilities, revenue and expenses and disclosures regarding contingent assets and liabilities. Actual results could differ from those estimates. The most significant estimates used in our financial statements affect revenue and cost recognition for construction contracts, self-insurance accruals, accounting for income taxes, fair value accounting for acquisitions and the quantification of fair value for reporting units in connection with our goodwill impairment testing.
Cash Flow Information	Cash Flow Information We consider all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. Cash paid (in thousands) for: Year Ended December 31, 2023 2022 2021 Interest $ 9,862 $ 12,915 $ 6,052 Income taxes, net of refunds $ 100,254 $ 44,296 $ 52,204
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Adopted Accounting Pronouncements In October 2021, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2021-08, “Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers.” This standard requires an acquirer to apply Accounting Standards Codification Topic 606 to recognize and measure contract assets and contract liabilities in a business combination. ASU 2021-08 is effective for fiscal years beginning after December 15, 2022 and interim periods within that year. We adopted this standard on January 1, 2023, and the impact on our consolidated financial statements was not material. Recent Accounting Pronouncements Not Yet Adopted In November 2023, the FASB issued ASU 2023-07, “Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures.” This standard requires entities to disclose, on an annual and interim basis, significant segment expenses that are regularly provided to the chief decision maker and included within each reported measure of segment profit and loss. ASU 2023-07 is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. We are currently evaluating the impact ASU 2023-07 will have on our disclosures; however, the standard will not have an impact on our consolidated financial position, results of operations or cash flows. In December 2023, the FASB issued ASU 2023-09, “Income Taxes (Topic 740): Improvements to Income Tax Disclosures.” This standard requires entities to disclose more detailed information in the reconciliation of their statutory tax rate to their effective tax rate. The standard also requires entities to make additional disclosures on income taxes paid as well as on certain income statement-related disclosures. ASU 2023-09 is effective for fiscal years beginning after December 15, 2024 . Early adoption is permitted. We are currently evaluating the impact ASU 2023-09 will have on our disclosures; however, the standard will not have an impact on our consolidated financial position, results of operations or cash flows.
Revenue Recognition	Revenue Recognition We recognize revenue over time for all of our services as we perform them because (i) control continuously transfers to that customer as work progresses, and (ii) we have the right to bill the customer as costs are incurred. The customer typically controls the work in process, as evidenced either by contractual termination clauses or by our rights to payment for work performed to date, plus a reasonable profit, for delivery of products or services that do not have an alternative use to the Company. For the reasons listed above, revenue is recognized based on the extent of progress towards completion of the performance obligation. The selection of the method to measure progress towards completion requires judgment and is based on the nature of the products or services to be provided. We generally use a cost-to-cost input method to measure our progress towards satisfaction of the performance obligation for our contracts, as it best depicts the transfer of assets to the customer that occurs as we incur costs on our contracts. Under the cost-to-cost input method, the extent of progress towards completion is measured based on the ratio of costs incurred to date to the total estimated costs at completion of the performance obligation. Revenue, including estimated fees or profits, is recorded proportionally as costs are incurred. Costs to fulfill include labor, materials, subcontractors’ costs, other direct costs and an allocation of indirect costs. For a small portion of our business in which our services are delivered in the form of service maintenance agreements for existing systems to be repaired and maintained, as opposed to constructed, our performance obligation is to maintain the customer’s mechanical system for a specific period of time. Similar to construction jobs, we recognize revenue over time; however, for service maintenance agreements in which the full cost to provide services may not be known, we generally use an input method to recognize revenue, which is based on the amount of time we have provided our services out of the total time we have been contracted to perform those services. Our revenue recognition policy is further discussed in Note 3 “Revenue from Contracts with Customers.”
Accounts Receivable and Allowance for Credit Losses	Accounts Receivable and Allowance for Credit Losses We are required to estimate and record the expected credit losses over the contractual life of our financial assets measured at amortized cost, including billed and unbilled accounts receivable, other receivables and contract assets. Accounts receivable include amounts from work completed in which we have billed or have an unconditional right to bill our customers. Our trade receivables are contractually due in less than a year. We estimate our credit losses using a loss-rate method for each of our identified portfolio segments. Our portfolio segments are construction, service and other. While our construction and service financial assets are often with the same subset of customers and industries, our construction financial assets will generally have a lower loss-rate than service financial assets due to lien rights, which we are more likely to have on construction jobs. These lien rights result in lower credit loss expenses on average compared to receivables that do not have lien rights. Financial assets classified as Other include receivables that are not related to our core revenue producing activities, such as receivables related to our acquisition activity from former owners, our vendor rebate program or receivables for estimated losses in excess of our insurance deductible, which are accrued with a corresponding accrued insurance liability. Loss rates for our portfolios are based on numerous factors, including our history of credit loss expense by portfolio, the financial strength of our customers and counterparties in each portfolio, the aging of our receivables, our expectation of likelihood of payment, macroeconomic trends in the U.S. and the current and forecasted nonresidential construction market trends in the U.S. In addition to the loss-rate calculations discussed above, we also record allowance for credit losses for specific receivables that are deemed to have a higher risk profile than the rest of the respective pool of receivables (e.g., when we hold concerns about a specific customer going bankrupt and no longer being able to pay the receivables due to us). Activity in our allowance for credit losses consisted of the following (in thousands): Year Ended December 31, Year Ended December 31, 2023 2022 Service Construction Other Total Service Construction Other Total Balance at beginning of year $ 5,245 $ 6,931 $ 65 $ 12,241 $ 3,294 $ 6,758 $ 58 $ 10,110 Bad debt expense 2,113 2,819 12 4,944 2,431 232 7 2,670 Deductions for uncollectible receivables written off, net of recoveries (1,658) (2,355) — (4,013) (804) (402) — (1,206) Credit allowance of acquired receivables on the acquisition date — 205 — 205 324 343 — 667 Balance at end of period $ 5,700 $ 7,600 $ 77 $ 13,377 $ 5,245 $ 6,931 $ 65 $ 12,241
Unbilled Accounts Receivable	Unbilled Accounts Receivable
Inventories	Inventories Inventories consist of parts and supplies that we purchase and hold for use in the ordinary course of business and are stated at the lower of cost or net realizable value using the average-cost method.
Property and Equipment	Property and Equipment Property and equipment are stated at cost, and depreciation is computed using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are capitalized and amortized over the lesser of the expected life of the lease or the estimated useful life of the asset. Expenditures for repairs and maintenance are charged to expense when incurred. Expenditures for major renewals and betterments, which extend the useful lives of existing equipment, are capitalized and depreciated over the remaining useful life of the equipment. Upon retirement or disposition of property and equipment, the cost and related accumulated depreciation are removed from the accounts and any resulting gain or loss is recognized in “Gain on Sale of Assets” in the Consolidated Statements of Operations.
Recoverability of Goodwill and Identifiable Intangible Assets	Recoverability of Goodwill and Identifiable Intangible Assets Goodwill is the excess of purchase price over the fair value of the net assets of acquired businesses. We assess goodwill for impairment each year, and more frequently if circumstances suggest an impairment may have occurred. When the carrying value of a given reporting unit exceeds its fair value, a goodwill impairment loss is recorded for this difference, not to exceed the carrying amount of goodwill. The requirements for assessing whether goodwill has been impaired involve market-based information. This information, and its use in assessing goodwill, entails some degree of subjective assessment. We perform our annual impairment testing as of October 1, and any impairment charges resulting from this process are reported in the fourth quarter. We segregate our operations into reporting units based on the degree of operating and financial independence of each unit and our related management of them. We perform our annual goodwill impairment testing at the reporting unit level. We perform a goodwill impairment review for each of our operating units, as we have determined that each of our operating units are reporting units. In the evaluation of goodwill for impairment, we have the option to first assess qualitative factors to determine whether the existence of events or circumstances lead to a determination that it is more likely than not that the fair value of one of our reporting units is greater than its carrying value. If, after completing such assessment, we determine it is more likely than not that the fair value of a reporting unit is greater than its carrying amount, then there is no need to perform any further testing. If we conclude otherwise, or if we elect to perform a quantitative assessment, then we calculate the fair value of the reporting unit and compare the fair value with the carrying value of the reporting unit. We estimate the fair value of the reporting unit based on a market approach and an income approach, which utilizes discounted future cash flows. Assumptions critical to the fair value estimates under the discounted cash flow model include discount rates, cash flow projections, projected long-term growth rates and the determination of terminal values. The market approach utilizes market multiples of invested capital from comparable publicly traded companies (“public company approach”). The market multiples from invested capital include revenue, book equity plus debt and earnings before interest, provision for income taxes, depreciation and amortization (“EBITDA”). We amortize identifiable intangible assets with finite lives over their useful lives. Changes in strategy and/or market condition may result in adjustments to recorded intangible asset balances or their useful lives.
Long-Lived Assets	Long-Lived Assets Long-lived assets are comprised principally of identifiable intangible assets, property and equipment, lease right-of-use assets and deferred tax assets. We periodically evaluate whether events and circumstances have occurred that indicate that the remaining balances of these assets may not be recoverable. We use estimates of future undiscounted cash flows, as well as other economic and business factors, to assess the recoverability of these assets.
Acquisitions	Acquisitions We recognize assets acquired and liabilities assumed in business combinations, including contingent assets and liabilities, based on fair value estimates as of the date of acquisition. Contingent Consideration Contingent Assets and Liabilities
Self-Insurance Liabilities	Self-Insurance Liabilities We are substantially self-insured for workers’ compensation, employer’s liability, auto liability, general liability and employee group health claims, in view of the relatively high per-incident deductibles we absorb under our insurance arrangements for these risks. Losses are estimated and accrued based upon known facts, historical trends and industry averages. Estimated losses in excess of our deductible, which have not already been paid, are included in our accrual with a corresponding receivable from our insurance carrier. Loss estimates associated with the larger and longer-developing risks, such as workers’ compensation, auto liability and general liability, are reviewed by a third-party actuary quarterly. Our self-insurance arrangements are further discussed in Note 13 “Commitments and Contingencies.”
Warranty Costs	Warranty Costs We typically warrant labor for the first year after installation on new MEP systems that we build and install, and we pass through to the customer manufacturers’ warranties on equipment. We generally warrant labor for thirty days after servicing existing MEP systems. A reserve for warranty costs is estimated and recorded based upon the historical level of warranty claims and management’s estimate of future costs.
Income Taxes	Income Taxes We conduct business throughout the United States in virtually all fifty states. Our effective tax rate changes based upon our relative profitability, or lack thereof, in the federal and various state jurisdictions with differing tax rates and rules. In addition, discrete items such as tax law changes, judgments and legal structures, can impact our effective tax rate. These items can also include the tax treatment for impairment of goodwill and other intangible assets, changes in fair value of acquisition-related assets and liabilities, uncertain tax positions, and accounting for losses associated with underperforming operations. Income taxes are provided for under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, we determine deferred tax assets and liabilities based on the differences between the financial statement and tax basis of assets and liabilities by using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in the provision for income taxes in the period that includes the enactment date. We recognize deferred tax assets to the extent that we believe that these assets are more likely than not to be realized. In making such a determination, we consider all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, taxable income in prior carryback years and tax planning strategies. Management’s judgment is required in considering the relative weight of negative and positive evidence. We record uncertain tax positions based on a two-step process in which (i) we determine whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (ii) for those tax positions that meet the more-likely-than-not recognition threshold, we recognize the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the relevant taxing authority. To the extent interest and penalties may be assessed by taxing authorities on any underpayment of income taxes, such amounts are accrued and classified as a component in the provision for income taxes in our Consolidated Statements of Operations.
Concentrations of Credit Risk	Concentrations of Credit Risk We provide services in a broad range of geographic regions. Our credit risk primarily consists of receivables from a variety of customers, including general contractors, property owners and developers, and commercial and industrial companies. We are subject to potential credit risk related to changes in business and economic factors throughout the United States within the nonresidential construction industry. However, we are entitled to payment for work performed and have certain lien rights related to that work. Further, we believe that our contract acceptance, billing and collection policies are adequate to manage potential credit risk. We regularly review our accounts receivable and estimate an allowance for credit losses. We have a diverse customer base, with our top customer representing 14% of consolidated 2023 revenue.
Financial Instruments	Financial Instruments Our financial instruments consist of cash and cash equivalents, accounts receivable, other receivables, accounts payable and life insurance policies, for which we deem the carrying values approximate their fair value due to the short-term nature of these instruments, as well as notes to former owners and a revolving credit facility.
Investments	Investments We have a $4.3 million investment in a construction focused technology fund with a fair value that is not readily determinable and is recorded at cost. This investment is included in “Other Noncurrent Assets” in our Consolidated Balance Sheet and is reviewed quarterly for impairment. We did not recognize any impairments in the current year related to this investment.
Leases	We lease certain facilities, vehicles and equipment primarily under noncancelable operating leases. The most significant portion of these noncancelable operating leases is for the facilities occupied by our corporate office and our operating locations. Leases with an initial term of 12 months or less are not recorded in the Consolidated Balance Sheet. We do not separate lease components from their associated non-lease components pursuant to lease accounting guidance. We have certain leases with variable payments based on an index as well as short-term leases on equipment and facilities. Variable lease expense and short-term lease expense aggregated to $53.7 million in 2023, $19.1 million in 2022 and $11.9 million in 2021. These expenses were primarily related to short-term equipment rentals. Lease right-of-use assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As most of our leases do not provide an implicit rate, we generally use our incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The weighted average discount rate for our operating leases as of December 31, 2023 and 2022 was 5.8% and 4.3%, respectively. We recognize operating lease expense, including escalating lease payments and lease incentives, on a straight-line basis over the lease term. Operating lease expense for the years ended December 31, 2023, 2022 and 2021 was $86.1 million, $46.0 million and $34.2 million, respectively. The lease terms generally range from three A majority of the Company’s real property leases are with individuals or entities with whom we have no other business relationship. However, in certain instances the Company enters into real property leases with current or former employees. Rent paid to related parties for the years ended December 31, 2023, 2022 and 2021 was approximately $7.6 million, $6.9 million and $4.9 million, respectively. If we decide to cancel or terminate a lease before the end of its term, we would typically owe the lessor the remaining lease payments under the term of the lease. Our lease agreements do not contain any material residual value guarantees or material restrictive covenants. On rare occasions, we rent or sublease certain real estate assets that we no longer use to third parties. The following table summarizes the operating lease assets and liabilities included in the Consolidated Balance Sheet as of December 31, 2023 and December 31, 2022 (in thousands): December 31, 2023 2022 Operating lease right-of-use assets $ 205,712 $ 130,666 Operating lease liabilities: Other current liabilities $ 24,426 $ 21,151 Long-term operating lease liabilities 188,136 111,744 Total operating lease liabilities $ 212,562 $ 132,895 The maturities of operating lease liabilities as of December 31, 2023 are as follows (in thousands): Year ending December 31— 2024 $ 35,653 2025 33,968 2026 30,348 2027 26,158 2028 22,448 Thereafter 148,371 Total lease payments 296,946 Less—present value discount (84,384) Present value of operating lease liabilities $ 212,562 Supplemental information related to operating leases was as follows (in thousands): Year Ended December 31, 2023 2022 Cash paid for amounts included in the measurement of operating lease liabilities $ 29,454 $ 26,740 Operating lease right-of-use assets obtained in exchange for lease liabilities $ 101,010 $ 27,467

Summary of Significant Accoun_3

Summary of Significant Accounting Policies and Estimates (Tables)	12 Months Ended
	Dec. 31, 2023
Summary of Significant Accounting Policies and Estimates
Schedule of cash paid	Cash paid (in thousands) for: Year Ended December 31, 2023 2022 2021 Interest $ 9,862 $ 12,915 $ 6,052 Income taxes, net of refunds $ 100,254 $ 44,296 $ 52,204
Schedule of activity in allowance for credit losses	Activity in our allowance for credit losses consisted of the following (in thousands): Year Ended December 31, Year Ended December 31, 2023 2022 Service Construction Other Total Service Construction Other Total Balance at beginning of year $ 5,245 $ 6,931 $ 65 $ 12,241 $ 3,294 $ 6,758 $ 58 $ 10,110 Bad debt expense 2,113 2,819 12 4,944 2,431 232 7 2,670 Deductions for uncollectible receivables written off, net of recoveries (1,658) (2,355) — (4,013) (804) (402) — (1,206) Credit allowance of acquired receivables on the acquisition date — 205 — 205 324 343 — 667 Balance at end of period $ 5,700 $ 7,600 $ 77 $ 13,377 $ 5,245 $ 6,931 $ 65 $ 12,241

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	12 Months Ended
Revenue from Contracts with Customers (Tables)	Dec. 31, 2023
Revenue from Contracts with Customers
Schedule of disaggregation of revenue	Our consolidated 2023 revenue was derived from contracts to provide service activities in the mechanical and electrical segments we serve. Refer to Note 16 “Segment Information” for additional information on our reportable segments. We disaggregate our revenue from contracts with customers by activity, customer type and service provided, as we believe it best depicts how the nature, amount, timing and uncertainty of our revenue and cash flows are affected by economic factors. See details in the following tables (dollars in thousands): Year Ended December 31, Revenue by Service Provided 2023 2022 2021 Mechanical Segment $ 3,946,022 75.8 % $ 3,178,475 76.8 % $ 2,542,623 82.7 % Electrical Segment 1,260,738 24.2 % 961,889 23.2 % 531,013 17.3 % Total $ 5,206,760 100.0 % $ 4,140,364 100.0 % $ 3,073,636 100.0 % Year Ended December 31, Revenue by Type of Customer 2023 2022 2021 Manufacturing $ 1,751,684 33.6 % $ 1,426,962 34.5 % $ 970,986 31.6 % Technology 1,114,382 21.4 % 546,290 13.2 % 385,702 12.5 % Healthcare 554,906 10.6 % 584,023 14.1 % 417,901 13.6 % Education 493,982 9.5 % 445,638 10.8 % 390,251 12.7 % Office Buildings 400,754 7.7 % 349,235 8.4 % 308,799 10.1 % Retail, Restaurants and Entertainment 310,381 6.0 % 311,697 7.5 % 213,386 6.9 % Government 301,837 5.8 % 255,314 6.2 % 174,813 5.7 % Multi-Family and Residential 181,780 3.5 % 126,339 3.0 % 112,779 3.7 % Other 97,054 1.9 % 94,866 2.3 % 99,019 3.2 % Total $ 5,206,760 100.0 % $ 4,140,364 100.0 % $ 3,073,636 100.0 % Year Ended December 31, Revenue by Activity Type 2023 2022 2021 New Construction $ 2,853,239 54.8 % $ 2,011,992 48.6 % $ 1,421,784 46.3 % Existing Building Construction 1,337,023 25.6 % 1,210,512 29.2 % 963,461 31.3 % Service Projects 446,151 8.6 % 382,155 9.2 % 278,582 9.1 % Service Calls, Maintenance and Monitoring 570,347 11.0 % 535,705 13.0 % 409,809 13.3 % Total $ 5,206,760 100.0 % $ 4,140,364 100.0 % $ 3,073,636 100.0 %
Schedule of contract assets and liabilities	Contract assets and liabilities in the Consolidated Balance Sheet consisted of the following amounts as of December 31, 2023 and December 31, 2022 (in thousands): December 31, 2023 December 31, 2022 Contract assets: Costs and estimated earnings in excess of billings, less allowance for credit losses $ 28,084 $ 27,211 Contract liabilities: Billings in excess of costs and estimated earnings and deferred revenue $ 909,538 $ 548,293

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
Fair Value Measurements (Tables)	Dec. 31, 2023
Fair Value Measurements
Summary of fair values and levels within the fair value hierarchy in which the fair value measurements fall for assets and liabilities measured on a recurring basis	The following table summarizes the fair values, and levels within the fair value hierarchy in which the fair value measurements are included, for assets and liabilities measured on a recurring basis as of December 31, 2023 and 2022 (in thousands): Fair Value Measurements at December 31, 2023 Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 205,150 $ — $ — $ 205,150 Life insurance—cash surrender value $ — $ 7,473 $ — $ 7,473 Contingent earn-out obligations $ — $ — $ 44,222 $ 44,222 Fair Value Measurements at December 31, 2022 Level 1 Level 2 Level 3 Total Cash and cash equivalents $ 57,214 $ — $ — $ 57,214 Life insurance—cash surrender value $ — $ 9,315 $ — $ 9,315 Contingent earn-out obligations $ — $ — $ 32,317 $ 32,317
Schedule of reconciliation of the fair value of contingent earn-out obligations that use significant unobservable inputs (Level 3)	The table below presents a reconciliation of the fair value of our contingent earn-out obligations that use significant unobservable inputs (Level 3) (in thousands): Year Ended Year Ended December 31, 2023 December 31, 2022 Balance at beginning of year $ 32,317 $ 34,114 Issuances 4,315 — Settlements (16,017) (6,616) Adjustments to fair value 23,607 4,819 Balance at end of year $ 44,222 $ 32,317

Goodwill and Identifiable Int_2

Goodwill and Identifiable Intangible Assets, Net (Tables)	12 Months Ended
Goodwill and Identifiable Intangible Assets, Net (Tables)	Dec. 31, 2023
Goodwill and Identifiable Intangible Assets, Net
Schedule of changes in the carrying amount of goodwill	The changes in the carrying amount of goodwill are as follows (in thousands): Mechanical Segment Electrical Segment Total Balance at December 31, 2021 $ 361,320 $ 230,794 $ 592,114 Acquisitions and purchase price adjustments (See Note 5) 2,609 17,066 19,675 Balance at December 31, 2022 363,929 247,860 611,789 Acquisitions and purchase price adjustments (See Note 5) 29,347 25,698 55,045 Balance at December 31, 2023 $ 393,276 $ 273,558 $ 666,834
Schedule of components of identifiable intangible assets	Identifiable intangible assets consist of the following (dollars in thousands): Weighted-Average December 31, 2023 December 31, 2022 Remaining Useful Lives Gross Book Accumulated Gross Book Accumulated in Years Value Amortization Value Amortization Customer Relationships 6.4 $ 376,621 $ (193,338) $ 340,721 $ (161,049) Backlog 0.6 5,900 (4,331) 3,200 (2,361) Trade Names 17.6 129,661 (34,116) 121,561 (28,171) Total $ 512,182 $ (231,785) $ 465,482 $ (191,581)
Schedule of future amortization expense of identifiable intangible assets	As of December 31, 2023, future amortization expense of identifiable intangible assets was as follows (in thousands): Year ending December 31— 2024 $ 39,851 2025 36,095 2026 35,251 2027 33,269 2028 33,109 Thereafter 102,822 Total $ 280,397

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
Property and Equipment (Tables)	Dec. 31, 2023
Property and Equipment
Schedule of components of property and equipment	Property and equipment consist of the following (dollars in thousands): Estimated Useful Lives December 31, in Years 2023 2022 Land — $ 8,437 $ 6,792 Transportation equipment 1 - 7 188,073 153,587 Machinery and equipment 1 - 20 77,142 56,357 Computer and telephone equipment 1 - 10 29,052 23,551 Buildings and leasehold improvements 1 - 40 101,568 80,275 Furniture and fixtures 1 - 17 8,600 6,270 Construction in progress — 12,645 6,717 425,517 333,549 Less—Accumulated depreciation (216,949) (189,600) Property and equipment, net $ 208,568 $ 143,949

Detail of Other Current Liabi_2

Detail of Other Current Liabilities (Tables)	12 Months Ended
Detail of Other Current Liabilities (Tables)	Dec. 31, 2023
Detail of Other Current Liabilities
Schedule of other current liabilities	Other current liabilities consist of the following (in thousands): December 31, 2023 2022 Accrued warranty costs $ 11,650 $ 9,429 Current lease liability 24,426 21,151 Accrued job losses 5,458 3,650 Accrued sales and use tax 6,592 5,335 Liabilities due to former owners 49,024 31,510 Other current liabilities 92,778 49,640 $ 189,928 $ 120,715

Debt Obligations (Tables)

Debt Obligations (Tables)	12 Months Ended
Debt Obligations (Tables)	Dec. 31, 2023
Schedule of components of debt obligations	Debt obligations consist of the following (in thousands): December 31, 2023 2022 Revolving credit facility $ — $ 215,000 Notes to former owners 44,070 41,040 Other debt 142 205 Total debt 44,212 256,245 Less—current portion (4,867) (9,000) Total long-term portion of debt $ 39,345 $ 247,245
Schedule of future principal payments of notes to former owners	At December 31, 2023, future principal payments of debt are as follows (in thousands): Year ending December 31— 2024 $ 4,867 2025 21,701 2026 14,144 2027 3,500 $ 44,212
Schedule of interest expense	Year Ended December 31, 2023 2022 2021 Interest expense on notes to former owners $ 1,365 $ 1,139 $ 1,052 Interest expense on borrowings and unused commitment fees 7,507 10,955 3,371 Interest expense (income) on interest rate swaps — (332) 499 Interest expense on finance leases — 4 57 Letter of credit fees 724 800 679 Amortization of debt financing costs 685 786 538 Total $ 10,281 $ 13,352 $ 6,196
Schedule of market rates relating to interest options under the Facility	Base Rate Loan Option: Federal Funds Rate plus 0.50% 5.83% Wells Fargo Bank, N.A. Prime Rate 8.50% One-month SOFR plus 1.00% 6.34% SOFR Loan Option: One-month SOFR 5.34% Three-month SOFR 5.36% Six-month SOFR 5.35%
Summary of additional margins	Net Leverage Ratio Less than 1.00 1.00 to less than 1.75 1.75 to less than 2.50 2.50 to less than 3.00 3.00 or greater Additional Per Annum Interest Margin Added Under: Base Rate Loan Option 0.00 % 0.25 % 0.50 % 0.75 % 1.00 % SOFR Loan Option 1.00 % 1.25 % 1.50 % 1.75 % 2.00 % Letter of credit fees 1.00 % 1.25 % 1.50 % 1.75 % 2.00 % Commitment fees on any portion of the Revolving Loan capacity not in use for borrowings or letters of credit at any given time 0.15 % 0.175 % 0.20 % 0.225 % 0.25 %
Notes to Former Owners
Schedule of future principal payments of notes to former owners	At December 31, 2023, future principal payments of notes to former owners by maturity year are as follows (dollars in thousands): Balance at Range of Stated December 31, 2023 Interest Rates 2024 $ 4,800 2.5 % 2025 21,645 2.3 - 3.0 % 2026 14,125 2.5 - 5.5 % 2027 3,500 5.5 % Total $ 44,070

Leases (Tables)

Leases (Tables)	12 Months Ended
Leases (Tables)	Dec. 31, 2023
Leases
Schedule of operating lease assets and liabilities	The following table summarizes the operating lease assets and liabilities included in the Consolidated Balance Sheet as of December 31, 2023 and December 31, 2022 (in thousands): December 31, 2023 2022 Operating lease right-of-use assets $ 205,712 $ 130,666 Operating lease liabilities: Other current liabilities $ 24,426 $ 21,151 Long-term operating lease liabilities 188,136 111,744 Total operating lease liabilities $ 212,562 $ 132,895
Schedule of maturities of lease liabilities	December 31, 2023 2022 Operating lease right-of-use assets $ 205,712 $ 130,666 Operating lease liabilities: Other current liabilities $ 24,426 $ 21,151 Long-term operating lease liabilities 188,136 111,744 Total operating lease liabilities $ 212,562 $ 132,895
Schedule of supplemental information related to leases	Supplemental information related to operating leases was as follows (in thousands): Year Ended December 31, 2023 2022 Cash paid for amounts included in the measurement of operating lease liabilities $ 29,454 $ 26,740 Operating lease right-of-use assets obtained in exchange for lease liabilities $ 101,010 $ 27,467

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2023
Income Taxes
Schedule of provision for income taxes relating to continuing operations	Our provision (benefit) for income taxes relating to continuing operations consists of the following (in thousands): December 31, 2023 2022 2021 Current tax provision (benefit)— Federal $ (34,722) $ 58,040 $ 31,283 State 4,222 26,376 8,741 Total current (30,500) 84,416 40,024 Deferred tax provision (benefit)— Federal 81,119 (80,130) 6,197 State 14,177 (14,375) 705 Total deferred 95,296 (94,505) 6,902 Provision (benefit) for income taxes $ 64,796 $ (10,089) $ 46,926
Schedule of difference in income taxes provided for and the amounts determined by applying the federal statutory tax rate to income before income taxes results	The provision (benefit) for income taxes for the years ended December 31, 2023, 2022 and 2021 resulted in effective tax rates on continuing operations of 16.7%, (4.3%) and 24.7%, respectively. The reasons for the differences between these effective tax rates and the federal statutory rates are as follows (in thousands, except percentages): December 31, 2023 2022 2021 Federal statutory rate of— 21 % 21 % 21 % Income taxes at the federal statutory rate $ 81,521 $ 49,530 $ 39,958 Increases (decreases) resulting from— Net state income taxes 14,278 9,376 7,340 Net unrecognized tax benefits 9,049 (17,922) 640 Nondeductible expenses 5,774 4,045 2,381 R&D tax credit (43,791) (51,398) — Stock-based compensation deductions (928) (872) (2,210) Other (1,107) (2,848) (1,183) Provision (benefit) for income taxes $ 64,796 $ (10,089) $ 46,926
Schedule of significant components of the net deferred tax assets and net deferred tax liabilities as reflected on the Consolidated Balance Sheets	Significant components of the deferred tax assets and deferred tax liabilities as reflected on the Consolidated Balance Sheets are as follows (in thousands): Year Ended December 31, 2023 2022 Deferred tax assets— Accounts receivable and allowance for credit losses $ 3,203 $ 2,530 Stock-based compensation 4,549 3,809 Accrued liabilities and expenses 44,209 34,179 Lease liabilities 51,065 32,048 Net operating loss carryforwards 5,877 5,361 Intangible assets 8,570 9,204 Research and experimental expenditures 195,444 106,002 Other 1,234 539 Subtotal 314,151 193,672 Valuation allowances (156) (379) Total deferred tax assets 313,995 193,293 Deferred tax liabilities— Property and equipment (27,049) (18,882) Lease right-of-use asset (51,058) (32,025) Long-term contracts (193,144) (1,870) Goodwill (24,452) (23,288) Other (1,689) (1,563) Total deferred tax liabilities (297,392) (77,628) Net deferred tax assets $ 16,603 $ 115,665
Schedule of deferred income tax assets and liabilities included in the consolidated balance sheets	The deferred tax assets and deferred tax liabilities reflected above are included in the Consolidated Balance Sheets as follows (in thousands): December 31, 2023 2022 Deferred tax assets $ 17,723 $ 115,665 Deferred tax liabilities $ 1,120 $ —
Schedule of reconciliation of the beginning and ending amount of unrecognized tax benefits, excluding accrued interest and penalties	A reconciliation of the beginning and ending amount of unrecognized tax benefits, excluding accrued interest and penalties, is as follows (in thousands): Year Ended December 31, 2023 2022 2021 Balance at beginning of year $ 11,530 $ 29,452 $ 28,756 Additions based on tax positions related to current year 6,370 3,420 207 Additions based on tax positions related to prior years 2,723 7,427 489 Reductions for tax positions related to prior years (44) (13) — Reductions for settlements with taxing authorities — (28,756) — Balance at end of year $ 20,579 $ 11,530 $ 29,452

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
Stockholders' Equity (Tables)	Dec. 31, 2023
Stockholders' Equity
Reconciliation of number of shares outstanding with the number of shares used in computing basic and diluted earnings per share	The following table reconciles the number of shares outstanding with the number of shares used in computing basic and diluted earnings per share for each of the periods presented (in thousands): Year Ended December 31, 2023 2022 2021 Common shares outstanding, end of period 35,685 35,761 36,091 Effect of using weighted average common shares outstanding 117 171 194 Shares used in computing earnings per share—basic 35,802 35,932 36,285 Effect of shares issuable under stock option plans based on the treasury stock method 26 36 89 Effect of restricted and contingently issuable shares 67 78 76 Shares used in computing earnings per share—diluted 35,895 36,046 36,450

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
Stock-Based Compensation (Tables)	Dec. 31, 2023
Restricted Stock
Summary of information about nonvested stock option awards and changes	The following table summarizes activity under our restricted stock plans (shares in thousands): Year Ended December 31, 2023 Weighted- Average Grant Restricted Stock and Restricted Stock Units Shares Date Fair Value Unvested at beginning of year 104 $ 76.39 Granted 72 $ 164.47 Vested (63) $ 79.32 Forfeited — $ — Unvested at end of year 113 $ 130.83
Performance Stock Units
Schedule of fair values of the total shareholder return portion	December 31, 2023 2023 PSU Grant 2022 PSU Grant Risk-free interest rate 4.2 % 4.7 % Dividend yield 0.5 % 0.5 % Volatility 35.0 % 35.1 % Look-back period (in years) 2.0 1.0 December 31, 2022 2022 PSU Grant 2021 PSU Grant Risk-free interest rate 4.4 % 4.7 % Dividend yield 0.5 % 0.5 % Volatility 33.5 % 35.1 % Look-back period (in years) 2.0 1.0 December 31, 2021 2021 PSU Grant 2020 PSU Grant Risk-free interest rate 0.7 % 0.4 % Dividend yield 0.5 % 0.5 % Volatility 50.1 % 31.8 % Look-back period (in years) 2.0 1.0

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
Segment Information (Tables)	Dec. 31, 2023
Segment Information
Summary of information about reportable segments	Mechanical Segment Electrical Segment Corporate Consolidated Total Assets at December 31, 2023 $ 2,180,021 $ 901,025 $ 224,533 $ 3,305,579 Total Assets at December 31, 2022 $ 1,741,135 $ 790,040 $ 66,303 $ 2,597,478 Year Ended December 31, 2023 Mechanical Segment Electrical Segment Corporate Consolidated Revenue $ 3,946,022 $ 1,260,738 $ — $ 5,206,760 Gross Profit $ 750,106 $ 240,403 $ — $ 990,509 Capital Expenditures $ 82,449 $ 9,600 $ 2,789 $ 94,838 Year Ended December 31, 2022 Mechanical Segment Electrical Segment Corporate Consolidated Revenue $ 3,178,475 $ 961,889 $ — $ 4,140,364 Gross Profit $ 580,619 $ 160,989 $ — $ 741,608 Capital Expenditures $ 43,532 $ 4,101 $ 726 $ 48,359 Year Ended December 31, 2021 Mechanical Segment Electrical Segment Corporate Consolidated Revenue $ 2,542,623 $ 531,013 $ — $ 3,073,636 Gross Profit $ 486,346 $ 76,861 $ — $ 563,207 Capital Expenditures $ 19,408 $ 2,413 $ 509 $ 22,330

Business and Organization (Deta

Business and Organization (Details)	12 Months Ended
Business and Organization (Details)	Dec. 31, 2023
Installation of systems in newly constructed facilities
Business and Organization
Percentage of revenue attributable to services	54.80%
Maintenance, repair and replacement services
Business and Organization
Percentage of revenue attributable to services	45.20%

Summary of Significant Accoun_4

Summary of Significant Accounting Policies and Estimates - Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash paid for:
Interest	$ 9,862	$ 12,915	$ 6,052
Income taxes, net of refunds	$ 100,254	$ 44,296	$ 52,204

Summary of Significant Accoun_5

Summary of Significant Accounting Policies and Estimates - Allowance for Credit Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at beginning of year	$ 12,241	$ 10,110
Bad debt expense (benefit)	4,944	2,670	$ (1,452)
Deductions for uncollectible receivables written off, net of recoveries	(4,013)	(1,206)
Credit allowance of acquired receivables on the acquisition date	205	667
Balance at end of period	13,377	12,241	10,110
Service
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at beginning of year	5,245	3,294
Bad debt expense (benefit)	2,113	2,431
Deductions for uncollectible receivables written off, net of recoveries	(1,658)	(804)
Credit allowance of acquired receivables on the acquisition date		324
Balance at end of period	5,700	5,245	3,294
Construction
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at beginning of year	6,931	6,758
Bad debt expense (benefit)	2,819	232
Deductions for uncollectible receivables written off, net of recoveries	(2,355)	(402)
Credit allowance of acquired receivables on the acquisition date	205	343
Balance at end of period	7,600	6,931	6,758
Other.
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at beginning of year	65	58
Bad debt expense (benefit)	12	7
Balance at end of period	$ 77	$ 65	$ 58

Summary of Significant Accoun_6

Summary of Significant Accounting Policies and Estimates - Risk (Details)	12 Months Ended
	Dec. 31, 2023
Warranty Costs
Labor warranty period after servicing of existing MEP system	30 days
Revenue \| Customer concentration \| Minimum
Warranty Costs
Single customer, percentage of revenue	14%

Summary of Significant Accoun_7

Summary of Significant Accounting Policies and Estimates - Investments (Details) $ in Millions	Dec. 31, 2023 USD ($)
Summary of Significant Accounting Policies and Estimates
Investment fair value	$ 4.3

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Revenue Recognition (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Contracts in progress
Less-Unbilled accounts receivable	$ (72,774)	$ (77,030)
Less-Unbilled accounts receivable credit allowance	(850)	(1,011)
Costs and estimated earnings in excess of billings, less allowance for credit losses	28,084	27,211
Plus-Costs and estimated earnings in excess of billings credit allowance	79	80
Billings in excess of costs and estimated earnings	$ (909,538)	(548,293)
Period during which progress billings or contract price can be withheld until completion of work	6 months
Retention receivable	$ 245,000	193,600
Retention payable	$ 32,900	$ 29,800
Revenue, Performance Obligation, Description of Payment Terms	We typically invoice our customers with payment terms of net due in 30 days
Receivable payment terms (in days)	30 days
Minimum
Contracts in progress
Receivable payment terms (in days)	45 days
Payments received term (in days)	30 days
Maximum
Contracts in progress
Receivable payment terms (in days)	60 days
Payments received term (in days)	90 days

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue
Revenue	$ 5,206,760	$ 4,140,364	$ 3,073,636
Percentage of revenue from contract with customer (as a percent)	100%	100%	100%
Manufacturing
Disaggregation of Revenue
Revenue	$ 1,751,684	$ 1,426,962	$ 970,986
Percentage of revenue from contract with customer (as a percent)	33.60%	34.50%	31.60%
Technology
Disaggregation of Revenue
Revenue	$ 1,114,382	$ 546,290	$ 385,702
Percentage of revenue from contract with customer (as a percent)	21.40%	13.20%	12.50%
Healthcare
Disaggregation of Revenue
Revenue	$ 554,906	$ 584,023	$ 417,901
Percentage of revenue from contract with customer (as a percent)	10.60%	14.10%	13.60%
Education
Disaggregation of Revenue
Revenue	$ 493,982	$ 445,638	$ 390,251
Percentage of revenue from contract with customer (as a percent)	9.50%	10.80%	12.70%
Office Buildings
Disaggregation of Revenue
Revenue	$ 400,754	$ 349,235	$ 308,799
Percentage of revenue from contract with customer (as a percent)	7.70%	8.40%	10.10%
Retail, Restaurants and Entertainment
Disaggregation of Revenue
Revenue	$ 310,381	$ 311,697	$ 213,386
Percentage of revenue from contract with customer (as a percent)	6%	7.50%	6.90%
Government
Disaggregation of Revenue
Revenue	$ 301,837	$ 255,314	$ 174,813
Percentage of revenue from contract with customer (as a percent)	5.80%	6.20%	5.70%
Multi-Family and Residential
Disaggregation of Revenue
Revenue	$ 181,780	$ 126,339	$ 112,779
Percentage of revenue from contract with customer (as a percent)	3.50%	3%	3.70%
Other
Disaggregation of Revenue
Revenue	$ 97,054	$ 94,866	$ 99,019
Percentage of revenue from contract with customer (as a percent)	1.90%	2.30%	3.20%
New Construction
Disaggregation of Revenue
Revenue	$ 2,853,239	$ 2,011,992	$ 1,421,784
Percentage of revenue from contract with customer (as a percent)	54.80%	48.60%	46.30%
Existing Building Construction
Disaggregation of Revenue
Revenue	$ 1,337,023	$ 1,210,512	$ 963,461
Percentage of revenue from contract with customer (as a percent)	25.60%	29.20%	31.30%
Service Projects
Disaggregation of Revenue
Revenue	$ 446,151	$ 382,155	$ 278,582
Percentage of revenue from contract with customer (as a percent)	8.60%	9.20%	9.10%
Service Calls, Maintenance and Monitoring
Disaggregation of Revenue
Revenue	$ 570,347	$ 535,705	$ 409,809
Percentage of revenue from contract with customer (as a percent)	11%	13%	13.30%
Mechanical Segment
Disaggregation of Revenue
Revenue	$ 3,946,022	$ 3,178,475	$ 2,542,623
Percentage of revenue from contract with customer (as a percent)	75.80%	76.80%	82.70%
Electrical Segment
Disaggregation of Revenue
Revenue	$ 1,260,738	$ 961,889	$ 531,013
Percentage of revenue from contract with customer (as a percent)	24.20%	23.20%	17.30%

Revenue from Contracts with C_5

Revenue from Contracts with Customers - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Contract Assets
Costs and estimated earnings in excess of billings, less allowance for credit losses	$ 28,084	$ 27,211
Contract Liabilities
Billings in excess of costs and estimated earnings and deferred revenue	909,538	548,293
Contract assets	900
Contract liabilities	361,200
Increase in contract assets	4,100
Billings and related costs	3,200
Increase in billings in excess of costs	349,100
Consideration of Eldeco and DECCO acquisitions	12,100
Revenue related to our contract liabilities	$ 500,600	$ 286,500

Revenue from Contracts with C_6

Revenue from Contracts with Customers - Remaining Performance Obligations (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Remaining Performance Obligations
The term of the renewable service maintenance agreements (in years)	1 year
Practical Expedient	true
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Remaining Performance Obligations
Remaining performance obligations	$ 5,160
Expected timing of performance obligations	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01 \| Minimum
Remaining Performance Obligations
Expected percentage of remaining performance obligations	65%
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01 \| Maximum
Remaining Performance Obligations
Expected percentage of remaining performance obligations	75%

Fair Value Measurements (Detail

Fair Value Measurements (Details) $ in Thousands	12 Months Ended
Fair Value Measurements (Details) $ in Thousands	Dec. 31, 2023 USD ($) employee	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Fair Value Measurements
Number of employees covered under life insurance policies \| employee	131
Combined face value of life insurance policies	$ 87,800
Reconciliation of the fair value of contingent earn-out obligations that use significant unobservable inputs (Level 3)
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability
Minimum
Fair Value Measurements
Weighted average cost of capital	15%
Maximum
Fair Value Measurements
Weighted average cost of capital	16%
Contingent earn-out obligations
Fair Value Measurements
Contingent earn-out obligations	$ 44,222	$ 32,317	$ 34,114
Reconciliation of the fair value of contingent earn-out obligations that use significant unobservable inputs (Level 3)
Balance at beginning of year	32,317	34,114
Issuances	4,315
Settlements	(16,017)	(6,616)
Adjustments to fair value	(23,607)	(4,819)
Balance at end of year	44,222	32,317	34,114
Recurring basis \| Total
Fair Value Measurements
Cash and cash equivalents	205,150	57,214
Life insurance-cash surrender value	7,473	9,315
Contingent earn-out obligations	44,222	32,317
Reconciliation of the fair value of contingent earn-out obligations that use significant unobservable inputs (Level 3)
Balance at beginning of year	32,317
Balance at end of year	44,222	32,317
Recurring basis \| Quoted Market Prices In Active Markets for Identical Assets (Level 1)
Fair Value Measurements
Cash and cash equivalents	205,150	57,214
Recurring basis \| Significant Other Observable Inputs (Level 2)
Fair Value Measurements
Life insurance-cash surrender value	7,473	9,315
Recurring basis \| Significant Unobservable Inputs (Level 3)
Fair Value Measurements
Contingent earn-out obligations	44,222	32,317
Reconciliation of the fair value of contingent earn-out obligations that use significant unobservable inputs (Level 3)
Balance at beginning of year	32,317
Balance at end of year	$ 44,222	32,317
Interest Rate Swap
Fair Value Measurements
Net gain (loss)		$ 300	$ (500)

Acquisitions (Details)

Acquisitions (Details) - USD ($) $ in Millions	Oct. 02, 2023	Feb. 01, 2023	Apr. 01, 2022
Atlantic
Consideration transferred:
Fair value of consideration transferred			$ 48.1
Cash paid at closing			34.1
Notes issued to former owners			$ 5.3
Eldeco Inc
Consideration transferred:
Fair value of consideration transferred		$ 74
Cash paid at closing		60.8
Notes issued to former owners		$ 8
DECCO
Consideration transferred:
Fair value of consideration transferred	$ 59.8
Cash paid at closing	48.8
Notes issued to former owners	$ 7

Goodwill and Identifiable Int_3

Goodwill and Identifiable Intangible Assets, Net - Changes in Carrying Amount of Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Changes in the carrying amount of goodwill
Balance at beginning of year	$ 611,789	$ 592,114
Acquisitions and purchase price adjustments (See Note 5)	55,045	19,675
Balance at end of period	666,834	611,789
Mechanical Segment
Changes in the carrying amount of goodwill
Balance at beginning of year	363,929	361,320
Acquisitions and purchase price adjustments (See Note 5)	29,347	2,609
Balance at end of period	393,276	363,929
Accumulated impairment charges	116,600	116,600
Electrical Segment
Changes in the carrying amount of goodwill
Balance at beginning of year	247,860	230,794
Acquisitions and purchase price adjustments (See Note 5)	25,698	17,066
Balance at end of period	$ 273,558	$ 247,860

Goodwill and Identifiable Int_4

Goodwill and Identifiable Intangible Assets, Net - Identifiable Intangible Assets, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Identifiable Intangible Assets, Net
Finite-lived intangible assets acquired	$ 49,900	$ 16,900
Estimated Useful Life	10 years 2 months 12 days	10 years 9 months 18 days
Gross Book Value	$ 512,182	$ 465,482
Accumulated Amortization	(231,785)	(191,581)
Future amortization expense of identifiable intangible assets
2024	39,851
2025	36,095
2026	35,251
2027	33,269
2028	33,109
Thereafter	102,822
Total	$ 280,397
Customer Relationships
Identifiable Intangible Assets, Net
Estimated Useful Lives in Years	6 years 4 months 24 days
Gross Book Value	$ 376,621	340,721
Accumulated Amortization	$ (193,338)	(161,049)
Customer Relationships \| Minimum
Identifiable Intangible Assets, Net
Estimated Useful Lives in Years	6 years 4 months 24 days
Backlog
Identifiable Intangible Assets, Net
Estimated Useful Lives in Years	7 months 6 days
Gross Book Value	$ 5,900	3,200
Accumulated Amortization	$ (4,331)	(2,361)
Backlog \| Minimum
Identifiable Intangible Assets, Net
Estimated Useful Lives in Years	7 months 6 days
Trade Names [Member]
Identifiable Intangible Assets, Net
Estimated Useful Lives in Years	17 years 7 months 6 days
Gross Book Value	$ 129,661	121,561
Accumulated Amortization	$ (34,116)	$ (28,171)
Trade Names [Member] \| Minimum
Identifiable Intangible Assets, Net
Estimated Useful Lives in Years	17 years 7 months 6 days
Customer Relationships Noncompete Agreements and Tradenames \| Minimum
Identifiable Intangible Assets, Net
Estimated Useful Lives in Years	1 year
Customer Relationships Noncompete Agreements and Tradenames \| Maximum
Identifiable Intangible Assets, Net
Estimated Useful Lives in Years	25 years

Goodwill and Identifiable Int_5

Goodwill and Identifiable Intangible Assets, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Asset Impairment Charges [Abstract]
Impairment charges, goodwill	$ 0	$ 0	$ 0
Amortization of identifiable intangible assets	$ 43,404	$ 47,795	$ 40,505

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property and equipment
Property and equipment, gross	$ 425,517	$ 333,549
Less-Accumulated depreciation	(216,949)	(189,600)
Property and equipment, net	208,568	143,949
Depreciation expense	38,200	33,600	$ 28,400
Land
Property and equipment
Property and equipment, gross	8,437	6,792
Transportation equipment
Property and equipment
Property and equipment, gross	$ 188,073	153,587
Transportation equipment \| Minimum
Property and equipment
Estimated useful life	1 year
Transportation equipment \| Maximum
Property and equipment
Estimated useful life	7 years
Machinery and equipment
Property and equipment
Property and equipment, gross	$ 77,142	56,357
Machinery and equipment \| Minimum
Property and equipment
Estimated useful life	1 year
Machinery and equipment \| Maximum
Property and equipment
Estimated useful life	20 years
Computer and telephone equipment
Property and equipment
Property and equipment, gross	$ 29,052	23,551
Computer and telephone equipment \| Minimum
Property and equipment
Estimated useful life	1 year
Computer and telephone equipment \| Maximum
Property and equipment
Estimated useful life	10 years
Buildings and leasehold improvements
Property and equipment
Property and equipment, gross	$ 101,568	80,275
Buildings and leasehold improvements \| Minimum
Property and equipment
Estimated useful life	1 year
Buildings and leasehold improvements \| Maximum
Property and equipment
Estimated useful life	40 years
Furniture and fixtures
Property and equipment
Property and equipment, gross	$ 8,600	6,270
Furniture and fixtures \| Minimum
Property and equipment
Estimated useful life	1 year
Furniture and fixtures \| Maximum
Property and equipment
Estimated useful life	17 years
Construction in progress
Property and equipment
Property and equipment, gross	$ 12,645	$ 6,717

Detail of Other Current Liabi_3

Detail of Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Other current liabilities
Accrued warranty costs	$ 11,650	$ 9,429
Current lease liability	24,426	21,151
Accrued job losses	5,458	3,650
Accrued sales and use tax	6,592	5,335
Liabilities due to former owners	49,024	31,510
Other current liabilities	92,778	49,640
Total other current liabilities	$ 189,928	$ 120,715

Debt Obligations (Details)

Debt Obligations (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Obligations
Other debt	$ 142	$ 205
Total debt	44,212	256,245
Less-current portion	(4,867)	(9,000)
Total long-term portion of debt	39,345	247,245
Revolving Credit Facility
Debt Obligations
Revolving credit facility		215,000
Notes to Former Owners
Debt Obligations
Notes to former owners	$ 44,070	$ 41,040

Debt Obligations - Future Payme

Debt Obligations - Future Payments and Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Future principal payments of long-term debt
2024	$ 4,867
2025	21,701
2026	14,144
2027	3,500
Total debt	44,212
Interest expense
Interest expense on borrowings and unused commitment fees	7,507	$ 10,955	$ 3,371
Interest expense (income) on interest rate swaps		(332)	499
Interest expense on finance leases		4	57
Letter of credit fees	724	800	679
Amortization of debt financing costs	685	786	538
Total	10,281	13,352	6,196
Related Party
Interest expense
Interest expense on notes to former owners	$ 1,365	$ 1,139	$ 1,052

Debt Obligations - Other (Detai

Debt Obligations - Other (Details)	12 Months Ended
Debt Obligations - Other (Details)	Dec. 31, 2023 USD ($) item	Dec. 31, 2022 USD ($)	May 25, 2022 USD ($)	May 24, 2022 USD ($)
Debt Obligations
Financing and professional cost		$ 2,297,000
Asset pledged as collateral
Debt Obligations
Book value of assets	$ 162,400,000
Revolving Credit Facility
Debt Obligations
Borrowing capacity			$ 850,000,000
Outstanding borrowings	0
Letters of credit amount outstanding	70,200,000
Credit available	$ 779,800,000
Number of quarters of net earnings used for the calculation of the credit facility adjusted EBITDA \| item	4
Principal financial covenants
Number of interest rate options \| item	2
Number of quarters of Adjusted EBITDA and interest expense used for calculation of fixed charge coverage ratio \| item	4
Other disclosures
Weighted average interest rate (as a percent)		5.70%
Revolving Credit Facility \| Net Leverage Ratio, Less Than or Equal To 3.25
Principal financial covenants
Net leverage ratio used as basis for other restrictions	3.25
Revolving Credit Facility \| Net Leverage Ratio, Less Than or Equal To 2.75
Principal financial covenants
Net leverage ratio used as basis for other restrictions	2.75
Revolving Credit Facility \| Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: Less than 1.00
Debt Instrument, Interest Rate, Effective Percentage [Abstract]
Letter of credit fees (as a percent)	1%
Commitment fees payable on unused portion of the facility (as a percent)	0.15%
Revolving Credit Facility \| Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 1.00 to 1.75
Debt Instrument, Interest Rate, Effective Percentage [Abstract]
Letter of credit fees (as a percent)	1.25%
Commitment fees payable on unused portion of the facility (as a percent)	0.175%
Revolving Credit Facility \| Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 1.75 to 2.50
Debt Instrument, Interest Rate, Effective Percentage [Abstract]
Letter of credit fees (as a percent)	1.50%
Commitment fees payable on unused portion of the facility (as a percent)	0.20%
Revolving Credit Facility \| Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 2.50 to 3.00
Debt Instrument, Interest Rate, Effective Percentage [Abstract]
Letter of credit fees (as a percent)	1.75%
Commitment fees payable on unused portion of the facility (as a percent)	0.225%
Revolving Credit Facility \| Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 3.00 or Greater
Debt Instrument, Interest Rate, Effective Percentage [Abstract]
Letter of credit fees (as a percent)	2%
Commitment fees payable on unused portion of the facility (as a percent)	0.25%
Revolving Credit Facility \| Minimum
Principal financial covenants
Interest coverage ratio	3
Revolving Credit Facility \| Maximum
Principal financial covenants
Maximum cash adjustment allowed in net leverage ratio calculation	$ 100,000,000
Leverage ratio	3.50
Revolving Credit Facility \| Base rate \| Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: Less than 1.00
Debt Instrument, Interest Rate, Effective Percentage [Abstract]
Additional per annum interest margin (as a percent)	0%
Revolving Credit Facility \| Base rate \| Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 1.00 to 1.75
Debt Instrument, Interest Rate, Effective Percentage [Abstract]
Additional per annum interest margin (as a percent)	0.25%
Revolving Credit Facility \| Base rate \| Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 1.75 to 2.50
Debt Instrument, Interest Rate, Effective Percentage [Abstract]
Additional per annum interest margin (as a percent)	0.50%
Revolving Credit Facility \| Base rate \| Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 2.50 to 3.00
Debt Instrument, Interest Rate, Effective Percentage [Abstract]
Additional per annum interest margin (as a percent)	0.75%
Revolving Credit Facility \| Base rate \| Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 3.00 or Greater
Debt Instrument, Interest Rate, Effective Percentage [Abstract]
Additional per annum interest margin (as a percent)	1%
Amended senior revolving credit facility
Debt Obligations
Borrowing capacity			850,000,000
Financing and professional cost		$ 2,300,000
Unamortized costs				$ 1,200,000
Amended senior revolving credit facility \| Maximum
Debt Obligations
Line of credit borrowing capacity accordion option			$ 250,000,000
Notes to Former Owners
Other disclosures
Cumulative number of companies acquired \| item	8
Notes to former owners	$ 44,070,000	$ 41,040,000
Letter of Credit
Debt Obligations
Borrowing capacity	$ 175,000,000
Federal Funds Rate \| Revolving Credit Facility \| Base rate
Market rates relating to interest options
Market rate (as a percent)	5.83%
Debt Instrument, Interest Rate, Effective Percentage [Abstract]
Additional per annum interest margin (as a percent)	0.50%
SOFR \| Revolving Credit Facility \| Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: Less than 1.00
Debt Instrument, Interest Rate, Effective Percentage [Abstract]
Additional per annum interest margin (as a percent)	1%
SOFR \| Revolving Credit Facility \| Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 1.00 to 1.75
Debt Instrument, Interest Rate, Effective Percentage [Abstract]
Additional per annum interest margin (as a percent)	1.25%
SOFR \| Revolving Credit Facility \| Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 1.75 to 2.50
Debt Instrument, Interest Rate, Effective Percentage [Abstract]
Additional per annum interest margin (as a percent)	1.50%
SOFR \| Revolving Credit Facility \| Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 2.50 to 3.00
Debt Instrument, Interest Rate, Effective Percentage [Abstract]
Additional per annum interest margin (as a percent)	1.75%
SOFR \| Revolving Credit Facility \| Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 3.00 or Greater
Debt Instrument, Interest Rate, Effective Percentage [Abstract]
Additional per annum interest margin (as a percent)	2%
SOFR \| Revolving Credit Facility \| Base rate
Debt Instrument, Interest Rate, Effective Percentage [Abstract]
Additional per annum interest margin (as a percent)	1%
Wells Fargo Bank, N.A. Prime Rate \| Revolving Credit Facility \| Base rate
Market rates relating to interest options
Market rate (as a percent)	8.50%
One-month SOFR \| Revolving Credit Facility
Market rates relating to interest options
Variable rate basis	One-month SOFR
Market rate (as a percent)	5.34%
One-month SOFR \| Revolving Credit Facility \| Base rate
Market rates relating to interest options
Market rate (as a percent)	6.34%
Debt Instrument, Interest Rate, Effective Percentage [Abstract]
Additional per annum interest margin (as a percent)	1%
Three-month SOFR \| Revolving Credit Facility
Market rates relating to interest options
Variable rate basis	Three-month SOFR
Market rate (as a percent)	5.36%
Six-month SOFR \| Revolving Credit Facility
Market rates relating to interest options
Variable rate basis	Six-month SOFR
Market rate (as a percent)	5.35%

Debt Obligations - Notes to For

Debt Obligations - Notes to Former Owners (Details) - Notes to Former Owners - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Future principal payments of long-term debt
Notes issued to former owners	$ 44,070	$ 41,040
2024
Future principal payments of long-term debt
Notes issued to former owners	$ 4,800
Stated interest rate (as a percent)	2.50%
2025
Future principal payments of long-term debt
Notes issued to former owners	$ 21,645
2025 \| Minimum
Future principal payments of long-term debt
Stated interest rate (as a percent)	2.30%
2025 \| Maximum
Future principal payments of long-term debt
Stated interest rate (as a percent)	3%
2026
Future principal payments of long-term debt
Notes issued to former owners	$ 14,125
2026 \| Minimum
Future principal payments of long-term debt
Stated interest rate (as a percent)	2.50%
2026 \| Maximum
Future principal payments of long-term debt
Stated interest rate (as a percent)	5.50%
2027
Future principal payments of long-term debt
Notes issued to former owners	$ 3,500
Stated interest rate (as a percent)	5.50%

Leases (Details)

Leases (Details) $ in Millions	12 Months Ended
Leases (Details) $ in Millions	Dec. 31, 2023 USD ($) lease Option	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Leases
Variable lease expense and short-term lease expenses	$ 53.7	$ 19.1	$ 11.9
Weighted average discount rate for operating leases	5.80%	4.30%
Operating lease expense	$ 86.1	$ 46	34.2
Weighted average remaining lease term	10 years 10 months 24 days	8 years 1 month 6 days
Rent paid to related parties	$ 7.6	$ 6.9	$ 4.9
Existence of option to extend	true
Number of off-site construction real estate leases commenced \| lease	2
Minimum
Leases
Lease term for operating lease	3 years
Number of options to renew \| Option	1
Maximum
Leases
Lease term for operating lease	10 years

Leases - Summary of Operating L

Leases - Summary of Operating Lease Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Summary of lease asset and liabilities
Operating lease right-of-use assets	$ 205,712	$ 130,666
Operating lease liabilities:
Other current liabilities	$ 24,426	$ 21,151
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other Liabilities, Current	Other Liabilities, Current
Long-term operating lease liabilities	$ 188,136	$ 111,744
Total operating lease liabilities	$ 212,562	$ 132,895

Leases - Maturities of Lease Li

Leases - Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Maturities of lease liabilities:
2024	$ 35,653
2025	33,968
2026	30,348
2027	26,158
2028	22,448
Thereafter	148,371
Total Lease Payments	296,946
Less-Present Value Discount	(84,384)
Present Value of Operating Lease Liabilities	212,562	$ 132,895
Supplemental information related to leases:
Cash paid for amounts included in the measurement of operating lease liabilities	29,454	26,740
Operating lease right-of-use assets obtained in exchange for lease liabilities	$ 101,010	$ 27,467

Income Taxes - Provision (Detai

Income Taxes - Provision (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes - Provision (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current tax provision-
Federal	$ (34,722)	$ 58,040	$ 31,283
State	4,222	26,376	8,741
Total current	(30,500)	84,416	40,024
Deferred tax provision (benefit)-
Federal	81,119	(80,130)	6,197
State	14,177	(14,375)	705
Total deferred	95,296	(94,505)	6,902
Provision (benefit) for income taxes	$ 64,796	$ (10,089)	$ 46,926

Income Taxes - Reconciliation (

Income Taxes - Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Taxes
Effective tax rates on continuing operations	(16.70%)	4.30%	24.70%
Federal statutory income tax rate (as a percent)	21%	21%	21%
Income taxes at the federal statutory rate	$ 81,521	$ 49,530	$ 39,958
Increases (decreases) resulting from-
Net state income taxes	14,278	9,376	7,340
Net unrecognized tax benefits	9,049	(17,922)	640
Nondeductible expenses	5,774	4,045	2,381
R&D tax credits	(43,791)	(51,398)
Stock-based compensation deductions	(928)	(872)	(2,210)
Other	(1,107)	(2,848)	(1,183)
Provision (benefit) for income taxes	$ 64,796	$ (10,089)	$ 46,926

Income Taxes - Provision Change

Income Taxes - Provision Changes, Examination (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Oct. 31, 2023	Sep. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Taxes
Additions based on tax positions related to prior years				$ 2,723	$ 7,427	$ 489
Reduced provision for income taxes			$ 28,800		28,756
Net interest income on the tax refunds			1,600
Provision for income taxes				$ 64,796	$ (10,089)	$ 46,926
Refund claim for overpayment	$ 107,100
Total Tax Years 2019-2021
Income Taxes
R&D tax credits		$ 1,700	$ 26,800

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets-
Accounts receivable and allowance for doubtful accounts	$ 3,203	$ 2,530
Stock-based compensation	4,549	3,809
Accrued liabilities and expenses	44,209	34,179
Lease liabilities	51,065	32,048
Net operating loss carryforwards	5,877	5,361
Intangible assets	8,570	9,204
Research and experimental expenditures	195,444	106,002
Other	1,234	539
Subtotal	314,151	193,672
Valuation allowances	(156)	(379)
Total deferred tax assets	313,995	193,293
Deferred tax liabilities-
Property and equipment	(27,049)	(18,882)
Lease right-of-use asset	(51,058)	(32,025)
Long-term contracts	(193,144)	(1,870)
Goodwill	(24,452)	(23,288)
Other	(1,689)	(1,563)
Total deferred tax liabilities	(297,392)	(77,628)
Net deferred tax assets	16,603	115,665
Deferred income tax assets
Deferred tax assets	17,723	$ 115,665
Deferred tax liabilities	$ 1,120

Income Taxes - Loss Carryforwar

Income Taxes - Loss Carryforwards and Other (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2024
Operating loss carryforwards
Net operating loss carryforwards		$ 5,877	$ 5,361
Federal deferred tax assets net operating loss carryforwards		2,500
Net deferred tax assets		313,995	193,293
Reconciliation of the beginning and ending amount of unrecognized tax benefits, excluding accrued interest and penalties
Balance at beginning of year	$ 29,452	11,530	29,452	$ 28,756
Additions based on tax positions related to current year		6,370	3,420	207
Additions based on tax positions related to prior years		2,723	7,427	489
Reductions for tax positions related to prior years		(44)	(13)
Reductions for settlements with taxing authorities	(28,800)		(28,756)
Balance at end of year		20,579	11,530	29,452
Interest and penalties accrued		600	300	0
Reduced provision for income taxes	$ 28,800		$ 28,756
Federal
Operating loss carryforwards
Net operating loss carryforwards		$ 12,000
Maximum
Reconciliation of the beginning and ending amount of unrecognized tax benefits, excluding accrued interest and penalties
Decrease in unrecognized tax benefits					$ 5,300

Employee Benefit Plans (Details

Employee Benefit Plans (Details) $ in Millions	12 Months Ended
Employee Benefit Plans (Details) $ in Millions	Dec. 31, 2023 USD ($) employee	Dec. 31, 2022 USD ($) employee	Dec. 31, 2021 USD ($)
Employee Benefit Plans
Percentage of contributions of covered employees' salaries or wages	2.50%
Contribution	$ 22.9	$ 19.8	$ 16.1
Amount payable to plan	$ 0.5
Number of employees who are union members \| employee	7	12
Contributions made to multi-employer pension plans	$ 0	$ 0	$ 0
Period in which certain individuals are entitled to fixed annual payments	15 years
Maximum age under which certain individuals are entitled to fixed annual payments	65 years
Portion of benefits vesting after ten years of completed service (as a percent)	50%
Period of completed service over which 50% of benefits are vested	10 years
Portion of benefits vesting after fifteen years of completed service (as a percent)	75%
Period of completed service over which 75% of benefits are vested	15 years
Period of service over which benefits are fully vested	20 years
Unfunded benefit liability	$ 3.5	$ 3.7

Commitments and Contingencies -

Commitments and Contingencies - Other and Bonds (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Commitments and Contingencies
Gain (loss) related to settlement agreements			$ 5.1
Dispute With Customer
Commitments and Contingencies
Gain (loss) related to settlement agreements	$ 6.8
Surety \| Minimum
Surety
Percentage of business which has required bonds		10%
Surety \| Maximum
Surety
Percentage of business which has required bonds		20%
Gross Profit. \| Dispute With Customer
Commitments and Contingencies
Gain (loss) related to settlement agreements	6.6
Selling, General and Administrative Expenses \| Dispute With Customer
Commitments and Contingencies
Gain (loss) related to settlement agreements	0.7
Interest Income \| Dispute With Customer
Commitments and Contingencies
Gain (loss) related to settlement agreements	1.3
Change in Fair Value of Contingent Earn-Out Obligations \| Dispute With Customer
Commitments and Contingencies
Gain (loss) related to settlement agreements	$ 1.8

Commitments and Contingencies_2

Commitments and Contingencies - Self-Insurance (Details)	Dec. 31, 2023 USD ($) item
Self-Insurance
Amount of loss fully insured above per-incident deductible amount	$ 250,000,000
Amount of excess loss insurance covered	250,000,000
Workers Compensation
Self-Insurance
Per incident deductible amount	500,000
Amount of loss fully insured above per-incident deductible amount	500,000
Employer's Liability
Self-Insurance
Per incident deductible amount	500,000
Employer's Liability \| Maximum
Self-Insurance
Amount of excess loss insurance covered	250,000,000
General Liability
Self-Insurance
Per incident deductible amount	500,000
Amount of loss fully insured above per-incident deductible amount	9,500,000
General Liability \| Maximum
Self-Insurance
Amount of excess loss insurance covered	250,000,000
Auto Liability
Self-Insurance
Per incident deductible amount	500,000
Amount of loss fully insured above per-incident deductible amount	9,500,000
Auto Liability \| Maximum
Self-Insurance
Amount of excess loss insurance covered	$ 250,000,000
Employee Medical
Self-Insurance
Number of medical plans \| item	3
Employee Medical - Plan One
Self-Insurance
Per person, per policy deductible amount	$ 350,000
Employee Medical - Plan Two
Self-Insurance
Per person, per policy deductible amount	350,000
Employee Medical - Plan Three
Self-Insurance
Per incident deductible amount	$ 350,000

Stockholders' Equity - Incentiv

Stockholders' Equity - Incentive and Other (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	12 Months Ended			201 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2023	May 17, 2022	May 31, 2017	Mar. 29, 2007
Share Repurchase Program
Share repurchase	$ 21,184	$ 38,216	$ 27,054
Anti-dilutive securities excluded from computation of earnings per share amount (in shares)	0	0	0
2017 Omnibus Incentive Plan
Stockholders' Equity
Number of shares authorized and reserved for issuance						2.9
Number of shares available for issuance	1.5			1.5
Stock Repurchase Program 2007
Share Repurchase Program
Number of shares of outstanding common stock authorized to be acquired under a stock repurchase program	10.9			10.9			1
Additional number of shares authorized for repurchase					0.7
Share repurchase (in shares)	0.1			10.3
Share repurchase	$ 21,300
Average price (in dollars per share)	$ 152.75			$ 26.27

Stockholders' Equity - Anti-Dil

Stockholders' Equity - Anti-Dilutive Stock Options (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Stockholders' Equity
Anti-dilutive securities excluded from computation of earnings per share amount (in shares)	0	0	0

Stockholders' Equity - Number o

Stockholders' Equity - Number of Shares (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of the number of shares outstanding with the number of shares used in computing basic and diluted earnings per share
Common shares outstanding, end of period	35,685	35,761	36,091
Effect of using weighted average common shares outstanding	117	171	194
Shares used in computing earnings per share-basic	35,802	35,932	36,285
Effect of shares issuable under stock option plans based on the treasury stock method	26	36	89
Effect of restricted and contingently issuable shares	67	78	76
Shares used in computing earnings per share-diluted	35,895	36,046	36,450

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Stock-Based Compensation
Stock-based compensation expense	$ 12.9	$ 10.5	$ 10.6
Income tax benefit	$ 2.7	$ 2.2	$ 2.2
Minimum
Stock-Based Compensation
Sum of age and years of service for accelerated vesting on retirement of certain stock options and restricted stock awards	75 years
Stock Options
Stock-Based Compensation
Vesting period	3 years

Stock-Based Compensation - Fair

Stock-Based Compensation - Fair Value Assumptions (Details) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) item $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares
Additional information
Stock-based compensation expense	$ 12.9	$ 10.5	$ 10.6
Stock Options
Additional information
Vesting period	3 years
Restricted Stock Units (RSUs)
Other information
Compensation expense yet to be recognized	$ 7.5
Weighted-average period over which compensation cost will be recognized	2 years 7 months 6 days
Shares
Unvested at beginning of year (in shares) \| shares	104
Granted (in shares) \| shares	72
Vested (in shares) \| shares	(63)
Unvested at end of year (in shares) \| shares	113	104
Weighted Average Grant Date Fair Value
Unvested at beginning of year (in dollars per share) \| $ / shares	$ 76.39
Granted (in dollars per share) \| $ / shares	164.47	$ 90.17	$ 76.73
Vested (in dollars per share) \| $ / shares	79.32
Unvested at end of year (in dollars per share) \| $ / shares	130.83	76.39
Additional information
Weighted-average fair value (in dollars per share) \| $ / shares	$ 164.47	$ 90.17	$ 76.73
Aggregate intrinsic value of restricted stock vested	$ 9.3	$ 6.6	$ 5.5
Performance Stock Units
Other information
Compensation expense yet to be recognized	$ 2.1
Weighted-average period over which compensation cost will be recognized	1 year 4 months 24 days
Additional information
Fair value of shares vested	$ 4.5	3.5	2.2
Vesting period	3 years
Types of performance units \| item	2
Percentage of units measured on stock price relative to peer group	50%
Percentage of units measured on stock price based on pre determined EPS	50%
Period for which shareholder return is compared with peer group for units determined by EPS performance	3 years
Calculated fair market value	$ 15
Value of PSUs granted	5.4
Stock-based compensation expense	$ 6.6	$ 5.3	$ 5.7
Performance Stock Units \| Minimum
Additional information
Performance measures for dollar denominated award granted	0
Performance Stock Units \| Maximum
Additional information
Performance measures for dollar denominated award granted	2
2023 PSU Grant
Fair value assumptions:
Risk-free interest rate	4.20%
Dividend yield	0.50%
Volatility	35%
Look-back period (in years)	2 years
2022 PSU Grant
Fair value assumptions:
Risk-free interest rate	4.70%	4.40%
Dividend yield	0.50%	0.50%
Volatility	35.10%	33.50%
Look-back period (in years)	1 year	2 years
2021 PSU Grant
Fair value assumptions:
Risk-free interest rate		4.70%	0.70%
Dividend yield		0.50%	0.50%
Volatility		35.10%	50.10%
Look-back period (in years)		1 year	2 years
2020 PSU Grant
Fair value assumptions:
Risk-free interest rate			0.40%
Dividend yield			0.50%
Volatility			31.80%
Look-back period (in years)			1 year

Segment Information (Details)

Segment Information (Details) $ in Thousands	12 Months Ended
Segment Information (Details) $ in Thousands	Dec. 31, 2023 USD ($) customer segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Segment Information
Number of reportable segments \| segment	2
Total Assets	$ 3,305,579	$ 2,597,478
Revenue	5,206,760	4,140,364	$ 3,073,636
Gross Profit	990,509	741,608	563,207
Capital Expenditures	$ 94,838	48,359	22,330
Revenue from Contract with Customer Benchmark \| Customer concentration
Segment Information
Number of Customers \| customer	1
Revenue from Contract with Customer Benchmark \| Customer concentration \| Customer One
Segment Information
Single customer, percentage of revenue	14%
Operating \| Mechanical Segment
Segment Information
Total Assets	$ 2,180,021	1,741,135
Revenue	3,946,022	3,178,475	2,542,623
Gross Profit	750,106	580,619	486,346
Capital Expenditures	82,449	43,532	19,408
Operating \| Electrical Segment
Segment Information
Total Assets	901,025	790,040
Revenue	1,260,738	961,889	531,013
Gross Profit	240,403	160,989	76,861
Capital Expenditures	9,600	4,101	2,413
Corporate & Eliminations
Segment Information
Total Assets	224,533	66,303
Capital Expenditures	$ 2,789	$ 726	$ 509

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ in Thousands		12 Months Ended
Subsequent Events (Details) - USD ($) $ in Thousands	Feb. 01, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Subsequent Event [Line Items]
Revenues		$ 5,206,760	$ 4,140,364	$ 3,073,636
Subsequent Event \| Summit Texas \| Minimum
Subsequent Event [Line Items]
Revenues	$ 375,000
Subsequent Event \| Summit Texas \| Maximum
Subsequent Event [Line Items]
Revenues	400,000
Subsequent Event \| J&S West Jordan \| Minimum
Subsequent Event [Line Items]
Revenues	145,000
Subsequent Event \| J&S West Jordan \| Maximum
Subsequent Event [Line Items]
Revenues	$ 160,000

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)	$ 323,398	$ 245,947	$ 143,348

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