Sterling Infrastructure (STRL) 10-K 3 Mar 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Feb. 28, 2020	Jun. 28, 2019
Document And Entity Information
Entity Registrant Name	STERLING CONSTRUCTION CO INC
Entity Central Index Key	0000874238
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Shell Company	false
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding (in shares)		27,787,903
Entity Public Float			$ 349.1
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenues	$ 1,126,278	$ 1,037,667	$ 957,958
Cost of revenues	(1,018,484)	(927,335)	(868,866)
Gross profit	107,794	110,332	89,092
General and administrative expense	(49,200)	(48,220)	(46,552)
Intangible asset amortization	(4,695)	(2,400)	(1,799)
Acquisition related costs	(4,311)	0	0
Other operating expense, net	(11,837)	(17,101)	(14,565)
Operating income	37,751	42,611	26,176
Interest income	1,142	1,017	314
Interest expense	(16,686)	(12,350)	(9,800)
Loss on extinguishment of debt	(7,728)	0	(755)
Income before income taxes	14,479	31,278	15,935
Income tax benefit (expense)	26,216	(1,738)	(118)
Net income	40,695	29,540	15,817
Less: Net income attributable to noncontrolling interests	(794)	(4,353)	(4,200)
Net income attributable to Sterling common stockholders	$ 39,901	$ 25,187	$ 11,617
Net income (loss) per share attributable to Sterling common stockholders:
Basic (in dollars per share)	$ 1.50	$ 0.94	$ 0.44
Diluted (in dollars per share)	$ 1.47	$ 0.93	$ 0.43
Weighted average number of common shares outstanding used in computing per share amounts:
Basic (in shares)	26,671	26,903	26,274
Diluted (in shares)	27,119	27,194	26,712

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 40,695	$ 29,540	$ 15,817
Loss on interest rate swap	(209)	0	0
Total comprehensive income	40,486	29,540	15,817
Less: Comprehensive income attributable to noncontrolling interests	(794)	(4,353)	(4,200)
Comprehensive income attributable to Sterling common stockholders	$ 39,692	$ 25,187	$ 11,617

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents ($7,538 and $8,750 related to variable interest entities (“VIEs”))	$ 45,733	$ 94,095
Accounts receivable, including retainage ($24,642 and $24,108 related to VIEs)	248,247	145,026
Costs and estimated earnings in excess of billings ($8,328 and $8,180 related to VIEs)	42,555	41,542
Receivables from and equity in construction joint ventures ($7,406 and $6,984 related to VIEs)	9,196	10,720
Other current assets ($503 and $32 related to VIEs)	11,790	11,233
Total current assets	357,521	302,616
Property and equipment, net ($5,619 and $7,219 related to VIEs)	116,030	51,999
Operating lease right-of-use assets ($3,817 and $0 related to VIEs)	13,979
Goodwill ($1,501 and $1,501 related to VIEs)	191,892	85,231
Other intangibles, net	256,323	42,418
Deferred tax asset, net	26,012	0
Other non-current assets, net	183	309
Total assets	961,940	482,573
Current liabilities:
Accounts payable ($18,213 and $22,859 related to VIEs)	137,593	99,426
Billings in excess of costs and estimated earnings ($9,649 and $6,585 related to VIEs)	85,011	62,407
Current maturities of long-term debt ($39 and $174 related to VIEs)	42,473	2,899
Current portion of long-term lease obligations ($1,838 and $0 related to VIEs)	7,095
Income taxes payable	1,212	318
Accrued compensation ($1,521 and $1,566 related to VIEs)	13,727	9,448
Other current liabilities ($1,429 and $1,485 related to VIEs)	6,393	4,676
Total current liabilities	293,504	179,174
Other current liabilities ($1,429 and $1,485 related to VIEs)
Long-term debt ($2 and $1,976 related to VIEs)	390,627	79,117
Long-term lease obligations ($1,979 and $0 related to VIEs)	6,976
Members’ interest subject to mandatory redemption and undistributed earnings	49,003	49,343
Deferred taxes	0	1,450
Other long-term liabilities	619	1,229
Total liabilities	740,729	310,313
Commitments and Contingencies
Stockholders’ equity:
Common stock, par value $0.01 per share; 38,000 shares authorized, 28,290 and 27,064 shares issued, 27,772 and 26,597 shares outstanding	283	271
Additional paid in capital	251,019	233,795
Treasury Stock, at cost: 518 and 467 shares	(6,142)	(4,731)
Retained deficit	(25,033)	(64,934)
Accumulated other comprehensive loss	(209)
Total Sterling stockholders’ equity	219,918	164,401
Noncontrolling interests	1,293	7,859
Total stockholders’ equity	221,211	172,260
Total liabilities and stockholders’ equity	$ 961,940	$ 482,573

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	38,000,000	38,000,000
Common stock, shares issued (in shares)	28,290,000	27,064,000
Common Stock, shares outstanding (in shares)	27,772,000	26,597,000
Treasury stock (in shares)	518,000	467,000
Cash and cash equivalents	$ 45,733	$ 94,095
Accounts receivable, including retainage ($24,642 and $24,108 related to VIEs)	248,247	145,026
Costs and estimated earnings in excess of billings ($8,328 and $8,180 related to VIEs)	42,555	41,542
Receivables from and equity in construction joint ventures ($7,406 and $6,984 related to VIEs)	9,196	10,720
Other current assets ($503 and $32 related to VIEs)	11,790	11,233
Property and equipment, net ($5,619 and $7,219 related to VIEs)	116,030	51,999
Operating lease right-of-use assets ($3,817 and $0 related to VIEs)	13,979
Goodwill	191,892	85,231
Accounts payable ($18,213 and $22,859 related to VIEs)	137,593	99,426
Billings in excess of costs and estimated earnings ($9,649 and $6,585 related to VIEs)	85,011	62,407
Current maturities of long-term debt ($39 and $174 related to VIEs)	42,473	2,899
Current portion of long-term lease obligations ($1,838 and $0 related to VIEs)	7,095
Accrued compensation ($1,521 and $1,566 related to VIEs)	13,727	9,448
Other current liabilities ($1,429 and $1,485 related to VIEs)	6,393	4,676
Long-term debt ($2 and $1,976 related to VIEs)	390,627	79,117
Long-term lease obligations ($1,979 and $0 related to VIEs)	6,976
Variable Interest Entity, Primary Beneficiary
Cash and cash equivalents	7,538	8,750
Accounts receivable, including retainage ($24,642 and $24,108 related to VIEs)	24,642	24,108
Costs and estimated earnings in excess of billings ($8,328 and $8,180 related to VIEs)	8,328	8,180
Receivables from and equity in construction joint ventures ($7,406 and $6,984 related to VIEs)	7,406	6,984
Other current assets ($503 and $32 related to VIEs)	503	32
Property and equipment, net ($5,619 and $7,219 related to VIEs)	5,619	7,219
Operating lease right-of-use assets ($3,817 and $0 related to VIEs)	3,817
Goodwill	1,501	1,501
Accounts payable ($18,213 and $22,859 related to VIEs)	18,213	22,859
Billings in excess of costs and estimated earnings ($9,649 and $6,585 related to VIEs)	9,649	6,585
Current maturities of long-term debt ($39 and $174 related to VIEs)	39	174
Current portion of long-term lease obligations ($1,838 and $0 related to VIEs)	1,838
Accrued compensation ($1,521 and $1,566 related to VIEs)	1,521	1,566
Other current liabilities ($1,429 and $1,485 related to VIEs)	1,429	1,485
Long-term debt ($2 and $1,976 related to VIEs)	2	$ 1,976
Long-term lease obligations ($1,979 and $0 related to VIEs)	$ 1,979

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net income	$ 40,695	$ 29,540	$ 15,817
Amortization of deferred debt costs
Depreciation and amortization	20,740	16,770	16,994
Amortization of deferred debt costs	3,393	3,250	2,563
(Gain) loss on disposal of property and equipment	(527)	(580)	171
Loss on debt extinguishment	4,334	0	755
Deferred taxes	(27,398)	1,450	0
Stock-based compensation	3,788	3,064	2,843
Unrealized gain on hedge	(30)	0	0
Changes in operating assets and liabilities	(3,902)	(14,020)	(14,376)
Net cash provided by operating activities	41,093	39,474	24,767
Cash flows from investing activities:
Capital expenditures	(15,397)	(13,171)	(9,420)
Proceeds from sale of property and equipment	1,334	1,789	8,384
Net cash used in investing activities	(410,386)	(11,382)	(55,897)
Cash flows from financing activities:
Cash received from credit facility	430,000	0	85,000
Repayments of long-term debt	(87,621)	(11,555)	(4,710)
Distributions to noncontrolling interest owners	(7,360)	(1,350)	0
Purchase of treasury stock	(3,201)	(4,731)	0
Debt issuance costs	(10,688)	0	(6,871)
Other	(199)	(314)	(1,121)
Net cash provided by (used in) financing activities	320,931	(17,950)	72,298
Net change in cash and cash equivalents	(48,362)	10,142	41,168
Cash and cash equivalents at beginning of period	94,095	83,953	42,785
Cash and cash equivalents at end of period	45,733	94,095	83,953
Supplemental disclosures of cash flow information:
Cash paid during the period for interest	11,566	10,829	9,800
Cash paid during the period for income taxes	94	276	279
Non-cash items:
Share consideration given for acquisitions	16,195	0	17,601
Notes and deferred payments to sellers	10,000	0	11,588
Estimated tax basis election		0	0
Warrants issued to lenders (1,000 Warrants)	0	0	3,500
Plateau
Cash flows from investing activities:
Payments to acquire businesses, net of cash acquired	(396,323)	0	0
Tealstone
Cash flows from investing activities:
Payments to acquire businesses, net of cash acquired	$ 0	$ 0	$ (54,861)

Consolidated Statements of Ca_2

Consolidated Statements of Cash Flows (Parenthetical)	12 Months Ended
	Dec. 31, 2017shares
Statement of Cash Flows [Abstract]
Warrants issued during the period (in shares)	1,000,000

Consolidated Statement of Stock

Consolidated Statement of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid in Capital	Treasury Stock	Retained Deficit	Accumulated Other Comprehensive Loss	Total Sterling Stockholders’ Equity	Non-controlling interests
Balance (in shares) at Dec. 31, 2016		24,987
Balance at Dec. 31, 2016	$ 108,090	$ 250	$ 208,922		$ (101,738)		$ 107,434	$ 656
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	15,817				11,617		11,617	4,200
Stock-based compensation (in shares)		248
Stock-based compensation	2,843	$ 3	2,840				2,843
Stock issued for acquisition (in shares)		1,882
Stock issued for acquisition	17,061	$ 19	17,042				17,061
Distribution to owners	0						0	0
Warrants issued to lenders	3,500		3,500				3,500
Other (in shares)		66
Other	(1,122)	$ (1)	(1,121)				(1,122)	0
Balance (in shares) at Dec. 31, 2017		27,051
Balance at Dec. 31, 2017	146,189	$ 271	231,183		(90,121)		141,333	4,856
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	29,540				25,187		25,187	4,353
Stock-based compensation (in shares)		40
Stock-based compensation	3,064		3,064				3,064
Distribution to owners	(1,350)						0	(1,350)
Shares withheld for taxes (in shares)		(27)
Shares withheld for taxes	(452)		(452)				(452)
Purchase of Treasury Stock (in shares)		(467)		(467)
Purchase of Treasury Stock	(4,731)			$ (4,731)			(4,731)
Balance (in shares) at Dec. 31, 2018		26,597		467
Balance at Dec. 31, 2018	172,260	$ 271	233,795	$ (4,731)	(64,934)		164,401	7,859
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	40,695				39,901		39,901	794
Other Comprehensive Income (Loss), Net of Tax	(209)					$ (209)	(209)
Stock-based compensation (in shares)		(1)
Stock-based compensation	3,788	$ 0	3,788				3,788
Stock issued for acquisition (in shares)		1,245
Stock issued for acquisition	16,195	$ 12	16,183				16,195
Distribution to owners	(7,360)						0	(7,360)
Issuance of stock (in shares)		273		(273)
Issuance of stock	152		(2,599)	$ 2,751			152
Shares withheld for taxes (in shares)		(92)		(74)
Shares withheld for taxes	(1,109)		(148)	$ (961)			(1,109)
Purchase of Treasury Stock (in shares)		(250)		(250)
Purchase of Treasury Stock	(3,201)			$ (3,201)			(3,201)
Balance (in shares) at Dec. 31, 2019		27,772		518
Balance at Dec. 31, 2019	$ 221,211	$ 283	$ 251,019	$ (6,142)	$ (25,033)	$ (209)	$ 219,918	$ 1,293

Nature of Operations (Notes)

Nature of Operations (Notes)	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations	1. NATURE OF OPERATIONS Business Summary Sterling Construction Company, Inc., (“Sterling,” “the Company,” “we,” “our” or “us”), a Delaware corporation, is a construction company that has been involved in the construction industry since its founding in 1955. The Company operates through a variety of subsidiaries within three operating groups specializing in heavy civil, specialty services, and residential projects in the United States (the “U.S.”), primarily across the southern U.S., the Rocky Mountain states, California and Hawaii, as well as other areas with strategic construction opportunities. Heavy civil includes infrastructure and rehabilitation projects for highways, roads, bridges, airfields, ports, light rail, water, wastewater and storm drainage systems. Specialty services projects include construction site excavation and drainage, drilling and blasting for excavation, foundations for multi-family homes, parking structures and other commercial concrete projects. Residential projects include concrete foundations for single-family homes. See Note 3 - Plateau Acquisition for discussion of the acquisition of Plateau on October 2, 2019 and Note 21 - Segment Information for discussion of changes to the historical presentation of the Company’s business segments during 2019.

Summary of Business and Signifi

Summary of Business and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Summary of Business and Significant Accounting Policies	2. BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation Presentation Basis— The accompanying Consolidated Financial Statements are presented in accordance with accounting policies generally accepted in the United States (“GAAP”) and reflect all wholly owned subsidiaries and those entities the Company is required to consolidate. See the “Consolidated 50% Owned Subsidiaries” and “Construction Joint Ventures” section of this Note for further discussion of the Company’s consolidation policy for those entities that are not wholly owned. In the opinion of management, all adjustments, consisting only of normal recurring adjustments, considered necessary for a fair presentation have been included. All significant intercompany accounts and transactions have been eliminated in consolidation. Values presented within tables (excluding per share data) are in thousands. Reclassifications have been made to historical financial data in the Consolidated Financial Statements to conform to the current year presentation. See Note 21 - Segment Information for discussion of changes to the historical presentation of the Company’s business segments during 2019. Estimates and Judgments— The preparation of the accompanying Consolidated Financial Statements in conformity with GAAP requires management to make estimates and judgments that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Certain accounting estimates of the Company require a higher degree of judgment than others in their application. These include the recognition of revenue and earnings from construction contracts over time, the valuation of long-lived assets, goodwill, income taxes, and purchase accounting estimates, including goodwill and other intangible assets. Management continually evaluates all of its estimates and judgments based on available information and experience; however, actual results could differ from these estimates. Significant Accounting Policies Revenue Recognition— Our revenue is derived from long-term contracts for customers in our heavy civil and specialty services business segments, as well as short-term projects for customers in our residential business segment. Accounting treatment for these contracts in accordance with ASU 2014-09 (Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers ) , is as follows: • Performance Obligations Satisfied Over Time (Heavy Civil and Specialty Services) Recognition of Performance Obligations— A performance obligation is a promise in a contract to transfer a distinct good or service to the customer, and is the unit of account in the new revenue standard. The contract transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. Heavy civil projects typically span between 12 to 36 months , and specialty services projects are between 6 to 24 months . The majority of our contracts have a single performance obligation as the promise to transfer the individual goods or services is not separately identifiable from other promises in the contracts and, therefore, not distinct. Some contracts have multiple performance obligations, most commonly due to the contract covering multiple phases of the project life cycle (design and construction). Revenues are recognized as our obligations are satisfied over time, using the ratio of project costs incurred to estimated total costs for each contract because of the continuous transfer of control to the customer as all of the work is performed at the customer’s site and, therefore, the customer controls the asset as it is being constructed. This continuous transfer of control to the customer is further supported by clauses in the contract that allow the customer to unilaterally terminate the contract for convenience, pay the Company for costs incurred plus a reasonable profit and take control of any work in process. This cost-to-cost measure is used because management considers it to be the best available measure of progress on these contracts. Contract costs include all direct material, labor, subcontract and other costs and those indirect costs determined to relate to contract performance, such as indirect salaries and wages, equipment repairs and depreciation, insurance and payroll taxes. Items excluded from cost-to-cost— Pre-contract costs are generally not material and are charged to expense as incurred, but in certain cases pre-contract recognition may be deferred if specific probability criteria are met. Provisions for estimated losses on uncompleted contracts are made in the period in which such losses are determined. Remaining Performance Obligations (“RPOs”)— RPOs represent the amount of revenues we expect to recognize in the future from our contract commitments on projects and are hereafter referred to as “Backlog”. Backlog includes the entire expected revenue values for joint ventures we consolidate and our proportionate value for those we proportionately consolidate. Backlog may not be indicative of future operating results, and projects included in Backlog may be canceled, modified or otherwise altered by customers. See Note 4 - Revenue from Customers , for further discussion. Variable Consideration— Contract modifications through change orders, claims and incentives are routine in the performance of the Company’s contracts to account for changes in the contract specifications or requirements. In most instances, contract modifications are not distinct from the existing contract due to the significant integration service provided in the contract and are accounted for as a modification of the existing contract and performance obligation. Either the Company or its customers may initiate change orders, which may include changes in specifications or designs, manner of performance, facilities, equipment, materials, sites and period of completion of the work. Change orders that are unapproved as to both price and scope are evaluated as claims. The Company considers claims to be amounts in excess of approved contract prices that the Company seeks to collect from its customers or others for customer-caused delays, errors in specifications and designs, contract terminations, change orders that are either in dispute or are unapproved as to both scope and price, or other causes of unanticipated additional contract costs. The Company estimates variable consideration for a performance obligation at the most likely amount to which the Company expects to be entitled (or the most likely amount the Company expects to incur in the case of liquidated damages), utilizing estimation methods that best predict the amount of consideration to which the Company will be entitled (or will be incurred in the case of liquidated damages). The Company includes variable consideration in the estimated transaction price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur or when the uncertainty associated with the variable consideration is resolved. The Company’s estimates of variable consideration and determination of whether to include estimated amounts in transaction price are based largely on an assessment of its anticipated performance and all information (historical, current and forecasted) that is reasonably available to the Company. The effect of variable consideration on the transaction price of a performance obligation is recognized as an adjustment to revenue on a cumulative catch-up basis. To the extent unapproved change orders and claims reflected in transaction price (or excluded from transaction price in the case of liquidated damages) are not resolved in the Company’s favor, or to the extent incentives reflected in transaction price are not earned, there could be reductions in, or reversals of, previously recognized revenue. • Performance Obligations Satisfied at a Point-in-Time (Residential) Revenue for our residential contracts is recognized at a point in time and utilizes an output measure for performance based on the completion of a unit of work (e.g. completion of concrete foundation). The time from starting construction to completion is typically two weeks or less. Upon fulfillment of the performance obligation, the customer is provided an invoice (or equivalent) demonstrating transfer of control to the customer. Receivables, including Retainage— Receivables are generally based on amounts billed to the customer in accordance with contractual provisions. Many of the contracts under which the Company performs work also contain retainage provisions. Retainage refers to that portion of our billings held for payment by the customer pending satisfactory completion of the project. Unless reserved, the Company assumes that all amounts retained by customers under such provisions are fully collectible. Retainage on active contracts is classified as a current asset regardless of the term of the contract and is generally collected within one year of the completion of a contract. At December 31, 2019 and 2018 , receivables included $79,400 and $47,400 of retainage. We anticipate collecting approximately 75% of our December 31, 2019 of retainage in 2020 . Receivables are written off based on individual credit evaluation and specific circumstances of the customer, when such treatment is warranted. The Company performs a review of outstanding receivables, historical collection information and existing economic conditions to determine if there are potential uncollectible receivables. At December 31, 2019 and 2018 , our allowance for doubtful accounts against contracts receivable was minimal. As is customary, we have agreed to indemnify our bonding company for all losses incurred by it in connection with bonds that are issued, and we have granted our bonding company a security interest in certain assets, including accounts receivable, as collateral for such obligation. Contracts in Progress— The timing of revenue recognition, billings and costs incurred results in billed accounts receivable and costs and estimated earnings in excess of billings on uncompleted contracts (contract assets) on the Consolidated Balance Sheet. For performance obligations satisfied over time, amounts are billed as work progresses in accordance with agreed-upon contractual terms, either at periodic intervals (e.g., biweekly or monthly) or upon achievement of contractual milestones. Typically, Sterling bills for advances or deposits from its customers, before revenue is recognized, resulting in billings in excess of costs and estimated earnings on uncompleted contracts (contract liabilities). However, the Company occasionally bills subsequent to revenue recognition, resulting in contract assets. These assets and liabilities are reported on the Consolidated Balance Sheet on a contract-by-contract basis at the end of each reporting period. Consolidated 50% Owned Subsidiaries— The Company has 50% ownership interests in two subsidiaries that it fully consolidates as a result of its exercise of control of the entities. The results attributable to the 50% portions that the Company does not own are eliminated within “Other operating expense, net” within the Consolidated Statements of Operations and an associated liability is established within “Members’ interest subject to mandatory redemption and undistributed earnings” within the Consolidated Balance Sheets. These subsidiaries also have individual mandatory redemption provisions which, under circumstances that are certain to occur, obligate the Company to purchase the remaining 50% interests. These purchase obligations are also recorded in “Members’ interest subject to mandatory redemption and undistributed earnings” on the Consolidated Balance Sheets. Construction Joint Ventures— In the ordinary course of business, the Company executes specific projects and conducts certain operations through joint venture arrangements (referred to as “joint ventures”). The Company has various ownership interests in these joint ventures, with such ownership typically proportionate to the Company’s decision making and distribution rights. Each joint venture is assessed at inception and on an ongoing basis as to whether it qualifies as a Variable Interest Entity (“VIE”) under the consolidations guidance in ASC Topic 810. If at any time a joint venture qualifies as a VIE, the Company performs a qualitative assessment to determine whether the Company is the primary beneficiary of the VIE and therefore needs to consolidate the VIE. If the Company determines it is not the primary beneficiary of the VIE or only has the ability to significantly influence, rather than control the joint venture, it is not consolidated. The Company accounts for unconsolidated joint ventures using a pro-rata basis in the Consolidated Statements of Operations and as a single line item (“Receivables from and equity in construction joint ventures”) in the Consolidated Balance Sheets. This method is a permissible modification of the equity method of accounting which is a common practice in the construction industry. Cash and Restricted cash— Our cash is comprised of highly liquid investments with maturities of three months or less. Restricted cash of approximately $4,800 and $3,900 is included in “Other current assets” on the Consolidated Balance Sheets at December 31, 2019 and 2018 . This primarily represents cash deposited by the Company into separate accounts and designated as collateral for standby letters of credit in the same amount in accordance with contractual agreements. Property and equipment— Property and equipment are recorded at cost and depreciated on a straight-line basis over their estimated useful lives, including buildings and improvements ( 5 to 39 years) and plant and field equipment ( 5 to 20 years). Renewals and betterments that substantially extend the useful life of an asset are capitalized and depreciated. Leasehold improvements are depreciated over the lesser of the useful life of the asset or the applicable lease term. See Note 7 - Property and Equipment for disclosure of the components of property and equipment. Lease Arrangements— In the ordinary course of business, the Company enters into a variety of lease arrangements, including operating, finance and capital leases. • Operating & Finance Leases— Effective January 1, 2019, the Company determines if an arrangement is a lease at inception. The operating lease right-of-use (“ROU”) assets are included within the Company’s non-current assets and lease liabilities are included in current or non-current liabilities on the Company’s Consolidated Balance Sheets. Finance leases are included in “Property and equipment”, “Current maturities of long-term debt”, and “Long-term debt” on the Company’s Consolidated Balance Sheets. ROU assets represent the Company’s right to use, or control the use of, a specified asset for the lease term. Lease liabilities are the Company’s obligation to make lease payments arising from a lease, and are measured on a discounted basis. Operating lease ROU assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term on the commencement date. As most of the Company’s leases do not provide an implicit rate, the Company’s incremental borrowing rate was used based on the information available on the commencement date in determining the present value of lease payments. For future leases, the implied rate in the lease will be used to determine the present value. The operating lease ROU asset includes any lease payments made and initial direct costs incurred and excludes lease incentives. The lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for minimum lease payments continues to be recognized on a straight-line basis over the lease term. • Capital Leases— The Company accounts for capital leases, which transfer substantially all the benefits and risks incident to the ownership of the leased property to the Company, as the acquisition of an asset and the incurrence of an obligation. Under this method of accounting, the recorded value of the leased asset is amortized principally using the straight-line method over its estimated useful life and the obligation, including interest thereon, is reduced through payments over the life of the lease. Depreciation expense on equipment subject to capital leases and the related accumulated depreciation is included with that of owned equipment. Capital leases are recorded in “Long-term debt, net of current maturities” and “Current maturities of long-term debt,” as applicable, in our Consolidated Balance Sheets. Goodwill— Goodwill represents the excess of the cost of companies acquired over the fair value of their net assets at the dates of acquisition. Goodwill is not amortized, but instead is reviewed for impairment at least annually at a reporting unit level, absent any interim indicators of impairment. Interim testing for impairment is performed if indicators of potential impairment exist. We perform our annual impairment assessment during the fourth quarter of each year. We identify a potential impairment by comparing the fair value of the applicable reporting unit to its net book value, including goodwill. To determine the fair value of our reporting units and test for impairment, we utilize an income approach (discounted cash flow method) as we believe this is the most direct approach to incorporate the specific economic attributes and risk profiles of our reporting units into our valuation model. We generally do not utilize a market approach, given the lack of relevant information generated by market transactions involving comparable businesses. However, to the extent market indicators of fair value become available, we consider such market indicators in our discounted cash flow analysis and determination of fair value. Refer to Note 3 - Plateau Acquisition and Note 8 - Goodwill and Other Intangible Assets for our disclosure regarding goodwill impairment testing. Evaluating Impairment of Other Intangible Assets and Other Long-Lived Assets— Our finite-lived intangible assets are amortized over their estimated remaining useful economic lives. Our project-related intangible assets are amortized as the applicable projects progress, customer relationships are amortized utilizing an accelerated method based on the pattern of cash flows expected to be realized, taking into consideration expected revenues and customer attrition, and our other intangibles are amortized utilizing a straight-line method. When events or changes in circumstances indicate that finite-lived intangible and other long-lived assets may be impaired, an evaluation is performed. If the asset or asset group fails the recoverability test, we will perform a fair value measurement to determine and record an impairment charge. See Note 8 - Goodwill and Other Intangible Assets for further discussion. Federal and State Income Taxes— We determine deferred income tax assets and liabilities using the balance sheet method. Under this method, the net deferred tax asset or liability is determined based on the tax effects of the temporary differences between the book and tax bases of the various balance sheet assets and liabilities and gives current recognition to changes in tax rates and laws. Valuation allowances are established when necessary to reduce deferred tax assets to the amount expected to be realized. We recognize the financial statement benefit of a tax position only after determining the relevant tax authority would more likely than not sustain the position following an audit. For tax positions meeting the more likely than not threshold, the amount recognized in the financial statements is the largest benefit that has a greater than 50 percent likelihood of being realized upon ultimate settlement with the relevant tax authority. Refer to Note 13 - Income Taxes for further information regarding our federal and state income taxes. Recently Adopted Accounting Pronouncements Leases— In February 2016, the Financial Accounting Standards Board (“FASB”) issued its new lease accounting guidance in ASU 2016-2, “Leases” (ASC 842). Under the new guidance, lessees are required to recognize all leases (with the exception of short-term leases) on the balance sheet. The Company adopted ASC 842 effective January 1, 2019 using the modified retrospective method. The new guidance has been applied to leases that exist or were entered into on or after January 1, 2019 without adjusting comparative periods in the financial statements. As an accounting policy, the Company has elected not to apply the recognition requirements to short-term leases (leases with terms of 12 months or less). Instead, the Company recognizes the lease payments in the Consolidated Statement of Operations on a straight-line basis over the lease term and variable lease payments in the period in which the obligation for those payments is incurred. The Company has elected to utilize the package of practical expedients that allows entities to not reassess (1) the classification of leases existing at the date of adoption, (2) the initial direct costs for any existing leases, and (3) whether any expired or existing contracts are or contain leases. At January 1, 2019, the Company recorded “Operating lease right-of-use assets”, “Current portion of long-term lease obligations” and “Long-term lease obligations” of $13,600 , $6,200 and $7,400 , respectively on its Consolidated Balance Sheet, related to its existing operating leases. The adoption of this standard did not have a material impact on the Company’s Consolidated Statements of Operations. As of December 31, 2019 , the weighted average remaining lease terms for the Company’s various operating leases extends out over the next 2.5 years . The weighted average discount rate used to determine the present value of the Company’s operating leases’ future payments was approximately 6.0% . Refer to Note 10 - Lease Obligations for further information regarding leases. Recently Issued Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13 to add the guidance in ASC 326 on the impairment of financial instruments. The ASU introduces an impairment model (known as the current expected credit loss (CECL) model) that is based on expected losses rather than incurred losses. Under the new guidance, an entity recognizes as an allowance its estimate of expected credit losses, which the FASB believes will result in more timely recognition of such losses. The ASU is also intended to reduce the complexity of U.S. GAAP by decreasing the number of credit impairment models that entities use to account for debt instruments. The amendments in the ASU are effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. The Company expects to adopt this guidance as required and does not expect a material impact to the Company’s Consolidated Financial Statements.

Plateau Acquisition

Plateau Acquisition	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Plateau Acquisition	3. PLATEAU ACQUISITION General— On October 2, 2019, pursuant to the Equity Purchase Agreement with Greg K. Rogers, Philip T. Travis, as trustee of the Lorin L. Rogers 2018 Trust, Kimberlin Rogers 2018 Trust, Gregory K. Rogers 2018 Trust and Mary A. Rogers 2018 Trust, LK Gregory Construction, Inc., Plateau Excavation, Inc. and DeWitt Excavation, LLC (collectively “Plateau”), Sterling consummated the acquisition (the “Plateau Acquisition”) of all of the issued and outstanding shares of capital stock of LK Gregory Construction, Inc. and Plateau Excavation, Inc., and all of the issued and outstanding equity interests in DeWitt Excavation, LLC. Plateau is engaged in the business of surveying, clearing and grubbing, erosion control, grading, grassing, site excavation, storm drainage, sanitary sewer and water main installation, drilling and blasting, curb and gutter, paving, concrete work and landfill services, in each case to general contractors and developers engaged in construction services, and engineering services relating thereto. Acquisition Accounting— The Plateau Acquisition is accounted for using the acquisition method of accounting in accordance with ASC Topic 805, Business Combinations . Purchase Consideration— Sterling completed the Plateau Acquisition for a purchase price of $427,659 , net of cash acquired, detailed as follows: Cash consideration transferred, net of $2,425 of cash acquired $ 375,000 Target working capital adjustment 21,323 Equity consideration transferred (1,245 shares at $13.01 per share (1) ) 16,195 Note payable to seller (See Note 9 - Debt) 10,000 Estimated tax basis election 5,141 Total consideration $ 427,659 (1) Sterling’s closing stock price on October 1, 2019 Preliminary Purchase Price Allocation— The aggregate purchase price noted above was allocated to the assets and liabilities acquired based upon their estimated fair values at the acquisition closing date, which were based, in part, upon external preliminary appraisal and valuation of certain assets, including specifically identified intangible assets. The excess of the purchase price over the preliminary estimated fair value of the net tangible and identifiable intangible assets acquired totaling $106,661 , was recorded as goodwill. The following table summarizes our purchase price allocation at the acquisition closing date, net of cash acquired: Net tangible assets: Accounts receivable, including retainage $ 81,921 Costs and estimated earnings in excess of billings 974 Other current assets 249 Property and equipment, net 65,492 Other non-current assets, net 10 Accounts payable (22,039 ) Billings in excess of costs and estimated earnings (16,540 ) Other current liabilities (7,669 ) Total net tangible assets 102,398 Preliminary identifiable intangible assets 218,600 Goodwill 106,661 Total consideration transferred $ 427,659 The purchase price allocation above is subject to further change when additional information is obtained. We have not finalized our assessment of the fair values primarily for intangible assets and property and equipment. We intend to finalize the purchase price allocation as soon as practicable within the measurement period, but in no event later than one year following the closing date of the Plateau Acquisition. Our final purchase price allocation may result in additional adjustments to various other assets and liabilities, including the residual amount allocated to goodwill during the measurement period. Identifiable Intangible Assets — Intangible assets identified as part of the Plateau Acquisition are reflected in the table below and are recorded at their estimated fair value, as determined by the Company’s management, based on available information which includes a preliminary valuation from external experts. The estimated useful lives for intangible assets were determined based upon the remaining useful economic lives of the intangible assets that are expected to contribute directly or indirectly to future cash flows. Weighted Average Life (Years) October 2, 2019 Fair Value Customer relationships 25 $ 191,800 Trade name 25 24,800 Non-compete agreements 5 2,000 Total $ 218,600 Acquired Backlog — Plateau backlog totaled approximately $159,000 at the Plateau Acquisition closing date. Impact of the Acquisition on Statements of Operations — From October 2, 2019 (the Plateau Acquisition closing date), through December 31, 2019 , revenue and income from operations (net of acquisition related costs) associated with the Acquisition totaled $84,637 and $10,921 , respectively. Supplemental Pro Forma Information (Unaudited) — The following unaudited pro forma combined financial information (“the pro forma financial information”) gives effect to the Plateau Acquisition, accounted for as a business combination using the purchase method of accounting. The pro forma financial information reflects the Plateau Acquisition and related events as if they occurred at the beginning of the period, and gives effect to pro forma events that are: directly attributable to the acquisition, factually supportable and expected to have a continuing impact on the combined results of Sterling and Plateau following the Plateau Acquisition. The pro forma financial information includes adjustments to: (1) exclude transaction costs that were included in historical results and are expected to be non-recurring, (2) include additional intangibles amortization and net interest expense associated with the Plateau Acquisition and (3) include the pro forma results of Plateau for the years ended December 31, 2019 and 2018 . This pro forma financial information has been presented for illustrative purposes only and is not necessarily indicative of the operating results that would have been achieved had the pro forma events taken place on the dates indicated. Further, the pro forma financial information does not purport to project the future operating results of the combined company following the Plateau Acquisition. Years Ended December 31, 2019 2018 Pro forma revenue $ 1,358,736 $ 1,326,854 Pro forma net income attributable to Sterling $ 90,408 $ 54,282

Revenue from Customers

Revenue from Customers	12 Months Ended
	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Revenue from Customers	4. REVENUE FROM CUSTOMERS Backlog The Company had the following backlog, by segment: December 31, 2019 2018 Heavy Civil Backlog $ 834,049 $ 780,706 Specialty Services Backlog 233,976 70,019 Total Heavy Civil and Specialty Services Backlog $ 1,068,025 $ 850,725 The Company expects to recognize approximately 70% of its backlog as revenue during the next twelve months , and the balance thereafter. Revenue Disaggregation The following tables present the Company’s revenue disaggregated by major end market and contract type: Years Ended December 31, Revenue by major end market 2019 2018 2017 Heavy Highway $ 483,175 $ 513,376 $ 579,157 Aviation 141,371 111,824 77,399 Water Containment and Treatment 65,795 66,928 59,593 Other 69,984 73,510 85,503 Heavy Civil Revenue $ 760,325 $ 765,638 $ 801,652 Land Development $ 84,637 $ — $ — Commercial 128,187 120,333 48,314 Specialty Services Revenue $ 212,824 $ 120,333 $ 48,314 Residential Revenue $ 153,129 $ 151,696 $ 107,992 Revenues $ 1,126,278 $ 1,037,667 $ 957,958 Revenue by contract type Fixed-Unit Price $ 708,638 $ 733,047 $ 755,840 Lump Sum 262,237 146,874 57,823 Residential and Other 155,403 157,746 144,295 Revenues $ 1,126,278 $ 1,037,667 $ 957,958 Each of these contract types presents advantages and disadvantages. Typically, the Company assumes more risk with lump-sum contracts. However, these types of contracts offer additional profits if the work is completed for less than originally estimated. Under fixed-unit price contracts, the Company’s profit may vary if actual labor-hour costs vary significantly from the negotiated rates. Also, because some contracts can provide little or no fee for managing material costs, the components of contract cost can impact profitability. Variable Consideration The Company has projects that it is in the process of negotiating, or awaiting final approval of, unapproved change orders and claims with its customers. The Company is proceeding with its contractual rights to recoup additional costs incurred from its customers based on completing work associated with change orders, including change orders with pending change order pricing, or claims related to significant changes in scope which resulted in substantial delays and additional costs in completing the work. Unapproved change order and claim information has been provided to the Company’s customers and negotiations with the customers are ongoing. If additional progress with an acceptable resolution is not reached, legal action will be taken. Based upon the Company’s review of the provisions of its contracts, specific costs incurred and other related evidence supporting the unapproved change orders and claims, together in some cases as necessary with the views of the Company’s outside claim consultants, the Company concluded it was appropriate to include in project price amounts of $3,000 and $9,300 , at December 31, 2019 and 2018 , respectively. Provisions for estimated losses on uncompleted contracts are made in the period in which such losses are determined. Contract Estimates Accounting for long-term contracts and programs involves the use of various techniques to estimate total contract revenue and costs. For long-term contracts, the Company estimates the profit on a contract as the difference between the total estimated revenue and expected costs to complete a contract and recognizes such profit over the life of the contract. Contract estimates are based on various assumptions to project the outcome of future events that often span several years. These assumptions include labor productivity and availability, the complexity of the work to be performed, the cost and availability of materials and the performance of subcontractors. Changes in job performance, job conditions and estimated profitability, including those changes arising from contract penalty provisions and final contract settlements may result in revisions to costs and income and are recognized in the period in which the revisions are determined. In December 2019, Sterling was able to come to an interim agreement related to a 2014 project involving the construction of three separate bridges in Texas that had suffered from significant schedule delays and cost overruns due to major owner design flaws. This agreement enabled Sterling to recover approximately $17,000 in costs to date related to these delays and defined a better dispute resolution process along with agreed upon rates for future work if there are further delays. As part of this agreement, Sterling agreed to work on all three bridges simultaneously (versus doing one at a time) to accelerate the final completion schedule. This revised schedule has significantly increased the amount of labor, equipment and infrastructure required to complete the project under the new terms of the agreement and resulted in a reduction of gross profit in the quarter of $10,200 . Changes in estimated revenues and gross margin resulted in a net decrease of $9,044 for the year ended December 31, 2019 , and net increases of $7,098 and $923 for the years ended December 31, 2018 and 2017 respectively, included in “Operating income” on the Consolidated Statements of Operations. The 2019 decrease primarily related to the aforementioned bridge project in Texas.

Cash and Cash Equivalents

Cash and Cash Equivalents	12 Months Ended
	Dec. 31, 2019
Cash and Cash Equivalents [Abstract]
Cash and Cash Equivalents	5. CASH AND CASH EQUIVALENTS The Company considers all highly liquid investments with original or remaining maturities of three months or less at the time of purchase to be cash equivalents. Cash and cash equivalents include cash balances held by our consolidated 50% owned subsidiaries and our majority owned construction joint ventures. At December 31, 2019 and 2018 , cash and cash equivalents included $13.3 million and $31.1 million, respectively, attributable to our consolidated 50% owned subsidiaries. At December 31, 2019 and 2018, cash and cash equivalents included $3.1 million and $18.9 million, respectively, attributable to our majority owned construction joint ventures. Majority owned construction joint ventures and consolidated 50% owned subsidiaries cash balances are limited to joint venture activities and are not available for other projects, general cash needs or distribution to Sterling without approval of the board of directors, or equivalent body, of the respective joint ventures. Restricted cash of approximately $3.9 million and $3.6 million is included in “Other current assets” on the consolidated balance sheet as of December 31, 2019 and 2018. This represents $0.0 million and $3.0 million of cash deposited by the Company into a separate account and designated as collateral for a standby letter of credit in the same amount in accordance with contractual agreements, respectively. In addition, the December 31, 2018 balance includes approximately $0.6 million of cash deposited by a customer, for the benefit of the Company, in an escrow account which was released upon completion of the job. The Company holds cash on deposit in U.S. banks, at times, in excess of federally insured limits. Management believes that the risk associated with keeping cash deposits in excess of federal deposit insurance is not material.

Consolidated 50% Owned Subsidia

Consolidated 50% Owned Subsidiaries, including Variable Interest Entities ("VIE")	12 Months Ended
	Dec. 31, 2019
Noncontrolling Interest [Abstract]
Consolidated 50% Owned Subsidiaries, including Variable Interest Entities (VIE)	5. CONSOLIDATED 50% OWNED SUBSIDIARIES The Company has 50% ownership interests in two subsidiaries (“Myers” and “RHB”) that it fully consolidates as a result of its exercise of control over the entities. The earnings attributable to the 50% portions the Company does not own were $9,800 , $15,100 and $11,500 for 2019 , 2018 and 2017 , respectively, and are eliminated within “Other operating expense, net” in the Consolidated Statements of Operations. Any undistributed earnings for partners are included in “Members’ interest subject to mandatory redemption and undistributed earnings” within the Consolidated Balance Sheets and are mandatorily payable at the time of the noncontrolling owners’ death or permanent disability. The Company has purchased two separate $20,000 death and permanent total disability insurance policies to mitigate the Company’s cash draw if such events were to occur. These two subsidiaries also have individual mandatory redemption provisions which, under circumstances outlined in the partner agreements, are certain to occur and obligate the Company to purchase each partner’s remaining 50% interests for $20,000 ( $40,000 in the aggregate). These purchase obligations are also recorded in “Members’ interest subject to mandatory redemption and undistributed earnings” on the Consolidated Balance Sheets. The liability consists of the following: As of December 31, 2019 2018 Members’ interest subject to mandatory redemption $ 40,000 $ 40,000 Net accumulated earnings 9,003 9,343 Total liability $ 49,003 $ 49,343 The Company must determine whether any of its entities, including these two 50% owned subsidiaries, in which it participates, is a variable interest entity (“VIE”). The Company determined Myers is a VIE, as the Company is the primary beneficiary, as pursuant to the terms of the Myers Operating Agreement the Company is exposed to the majority of potential losses of the partnership. Summary financial information for Myers is as follows: Years Ended December 31, 2019 2018 2017 Revenues $ 205,615 $ 193,677 $ 181,589 Operating income $ 6,372 $ 8,819 $ 9,069 Net income attributable to Sterling common stockholders $ 3,196 $ 4,415 $ 4,531

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Financial Instruments	11. FINANCIAL INSTRUMENTS Derivatives Interest Rate Derivative —On December 5, 2019 , the Company entered into a three year interest rate swap agreement with Bank of America in order to mitigate exposure to the market risk associated with the variable interest on the $400,000 term loan. The Company has designated its interest rate swap agreement as a cash flow hedging derivative. To the extent the derivative instrument is effective and the documentation requirements have been met, changes in fair value are recognized in other comprehensive income until the underlying hedged item is recognized in earnings. As of December 31, 2019 , the notional value of the swap contract was $350,000 and the fair value of the swap contract was loss of $243 . We utilized Level 2 inputs in the fair value hierarchy of valuation techniques to determine the fair value of the swap contract. Financial Instruments Disclosures Fair Value —Financial instruments are required to be categorized within a valuation hierarchy based upon the lowest level of input that is significant to the fair value measurement. The three levels of the valuation hierarchy are as follows: • Level 1—Fair value is based on quoted prices in active markets. • Level 2—Fair value is based on internally developed models that use, as their basis, readily observable market parameters. Our derivative positions are classified within level 2 of the valuation hierarchy as they are valued using quoted market prices for similar assets and liabilities in active markets. These level 2 derivatives are valued utilizing an income approach, which discounts future cash flow based on current market expectations and adjusts for credit risk. • Level 3—Fair value is based on internally developed models that use, as their basis, significant unobservable market parameters. The Company did not have any level 3 classifications at December 31, 2019 . The following table presents the fair value of the interest rate derivative by valuation hierarchy and balance sheet classification: December 31, 2019 Level 1 Level 2 Level 3 Total Derivative Assets Other current assets $ — $ 216 $ — $ 216 Other non-current assets — — — — Total assets at fair value $ — $ 216 $ — $ 216 Derivative Liabilities Other current liabilities $ — $ (61 ) $ — $ (61 ) Other non-current liabilities — (398 ) — (398 ) Total liabilities at fair value $ — $ (459 ) $ — $ (459 ) The carrying values of the Company's cash and cash equivalents (primarily consisting of bank deposits), accounts receivable and accounts payable approximate their fair values because of the short-term nature of these instruments. At December 31, 2019 , the fair value of the term loan, based upon the current market rates for debt with similar credit risk and maturities, approximated its carrying value as interest is based on LIBOR plus an applicable margin. Derivatives Disclosures AOCI/Other —The following table presents the total value recognized in other comprehensive income (“OCI”) and reclassified from AOCI to interest expense during 2019 for derivatives designated as cash flow hedges: Gain (Loss) Recognized in OCI Gain (Loss) Reclassified from AOCI into Earnings (1) Interest rate cash flow hedge (273 ) 30 (1) Net unrealized gains totaling $135 are anticipated to be reclassified from AOCI into interest expense during the next 12 months due to settlement of the associated underlying obligations.

Stock Incentive Plan

Stock Incentive Plan	12 Months Ended
	Dec. 31, 2019
Stockholders' Equity Note [Abstract]
Stock Incentive Plan	15. STOCK INCENTIVE PLAN General —The Company has equity-based incentive plans (the “Stock Incentive Plans”) administered by the Compensation and Talent Development Committee of the Board of Directors. Under the Stock Incentive Plans, the Company can issue shares to employees and directors in the form of restricted stock awards (“RSAs”), restricted stock units (“RSUs”), and performance based units (“PSUs”). Compensation expense recognized related to the Company’s Stock Incentive Plans was $3,761 , $3,064 and $2,843 for 2019 , 2018 and 2017 , respectively. At December 31, 2019 , 133 authorized shares remained available under our Stock Incentive Plans for future grants, assuming PSU vestings occur at maximum payout with vesting dates through 2024. During 2019, the Company implemented an Employee Stock Purchase Plan (“ESPP”). Under the ESPP, employees may make quarterly purchases of shares at a discount through regular payroll deductions for up to 15% of their compensation ( $25 maximum per year). The shares are purchased at 85% of the closing price per share on the last trading day of the calendar quarter. Included within total stock-based compensation expense for 2019 is $27 of expense related to the ESPP. ESPP expense, represents the difference between the fair value on the date of purchase and the price paid. At December 31, 2019 , 787 authorized shares remained available for issuance under the ESPP. Total equity-based compensation expense recognized related to the Company’s Stock Incentive Plans was $3,788 , $3,064 and $2,843 for 2019 , 2018 , and 2017 , respectively, primarily recognized within general and administrative expenses. At December 31, 2019 , there was $16,300 of unrecognized compensation cost related to equity-based grants, which is expected to be recognized over a weighted-average period of 3.2 years. The Company recognizes forfeitures as they occur, rather than estimating expected forfeitures. RSAs —The Company’s RSA awards may not be sold or otherwise transferred until certain restrictions have lapsed, which is generally over a three -year graded vesting period for employees and over one year for Directors. The total initial fair value for these awards is determined based upon the market price of our stock at the grant date, and is expensed on a straight-line basis over the vesting period. During 2019 , we recognized $1,092 of compensation expense, primarily within “General and administrative expense”. The following table presents employee and director RSA activity: Number of Shares Weighted Average Employee’s RSAs Balance at December 31, 2018 147 11.16 Granted 52 12.06 Vested (114 ) 11.04 Forfeited (2 ) 9.64 Balance at December 31, 2019 83 11.91 Director’s RSAs Balance at December 31, 2018 42 11.67 Granted 52 12.06 Vested (52 ) $ 11.69 Forfeited — — Balance at December 31, 2019 42 12.12 During 2018 , 49 RSAs were granted with a weighted-average grant-date fair value per share of $11.64 . During 2017 , 217 RSAs were granted with a weighted-average grant-date fair value per share of $10.69 . The total fair value of RSAs that vested during 2019 , 2018 and 2017 was $1,261 , $1,107 and $3,117 , respectively. RSUs —The Company’s RSU awards may not be sold or otherwise transferred until certain restrictions have lapsed, which is generally over a three -year graded vesting period. The total initial fair value for these awards is determined based upon the market price of our stock at the grant date, and is expensed on a straight-line basis over the vesting period. During 2019 , we recognized $1,573 of compensation expense, primarily within selling and administrative expense. The following table presents RSU activity: Number of Shares Weighted Average Nonvested RSUs Balance at December 31, 2018 217 12.40 Granted 261 12.14 Vested (120 ) 14.30 Forfeited (14 ) 16.14 Balance at December 31, 2019 344 13.78 During 2018 , 248 RSUs were granted with a weighted-average grant-date fair value per share of $16.08 . During 2017 , there were no t any RSUs granted. The total fair value of RSUs that vested during 2019 and 2018 were $1,709 and $392 , respectively. There were no RSUs vested in 2017 . PSUs —The Company’s performance-based share awards are subject to the achievement of specified financial based performance targets and are generally based upon EPS and vest over three years . The total initial fair value for these awards is determined based upon the market price of our stock at the grant date applied to the total number of shares. This fair value is expensed and adjusted over the vesting period based on the level of payout expected to be achieved. As a result of financial performance conditions met during 2019 , we recognized $1,096 of compensation expense. During 2019 and 2018 , PSU shares totaling 310 and 890 , respectively, were granted with a weighted-average grant-date fair value per share of $11.81 and $11.64 , respectively. There were no PSUs granted in 2017 . During 2019 , upon vesting and achievement of certain performance goals, we distributed 63 PSUs with a weighted-average grant-date fair value per share of $ 15.15 . The total fair value of PSU awards that vested during 2019 was $948 . There were no PSUs awarded in 2018 and 2017 . Share Repurchases for Tax Withholdings —Upon the vesting of shares, the Company allows employees to withhold shares to satisfy tax withholding requirements. For RSA vestings, the shares repurchased by the Company are considered constructively received and are retired thereafter. The Company repurchased 17 , 28 and 66 shares for taxes withheld on RSA vestings for $255 , $361 and $1,075 during 2019 , 2018 and 2017 , respectively. For RSU and PSU vestings, the employee is issued shares net of the requested tax withholding, and the Company transfers the withheld shares to Treasury Stock. The Company withheld 74 and 8 shares for taxes on RSU and PSU vestings for $964 and $92 during 2019 and 2018 , respectively. There were no shares withheld for taxes on RSU and PSU vestings in 2017 . Warrants —On April 3, 2017, the Company issued warrants (the “Warrants”) to the lenders under the Oaktree Facility (the “Holders”) pursuant to which such holders have the right to purchase, for a period of 5 years from the date of issuance, up to an aggregate of 1,000 shares of the Company’s common stock (the “Warrant Shares”) at an initial exercise price of $10.25 per share, subject to adjustment for stock splits, combinations and similar recapitalization events and weighted-average anti-dilution upon the issuance by the Company of shares of common stock or rights, options or convertible securities exercisable for common stock in the future at a price below the exercise price of the Warrants. The Company valued these Warrants using the Black-Scholes model, which is a type 3 fair value measurement. The key assumptions used in the Black-Scholes Model and fair value output are summarized in the table below: April 3, 2017 Stock price at grant date $ 8.88 Exercise option price $ 10.25 Expected term of warrants (in years) 5 Expected volatility rate 48.29 % Risk-free rate 1.88 % Expected dividend yield — % Total fair value $ 3,500

Stockholders' Equity (Notes)

Stockholders' Equity (Notes)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Stockholders' Equity	14. STOCKHOLDERS' EQUITY General —Holders of common stock are entitled to one vote for each share on all matters voted upon by the stockholders, including the election of directors and do not have cumulative voting rights. Holders of common stock are entitled to share ratably in net assets upon any dissolution or liquidation after payment of provision for all liabilities and any preferential liquidation rights of our preferred stock then outstanding. Common stock shares are not subject to any redemption provisions and are not convertible into any other shares of capital stock. The rights, preferences and privileges of holders of common stock are subject to those of the holders of any shares of preferred stock that may be issued in the future. The Board of Directors may authorize the issuance of one or more classes or series of preferred stock without stockholder approval and may establish the voting powers, designations, preferences and rights and restrictions of such shares. No preferred shares have been issued. Treasury Stock —On November 2, 2018, the Board of Directors approved a plan that authorized stock repurchases of up to 2,000 shares of the Company’s common stock. Under the plan, the Company may repurchase its common stock in the open market or through privately negotiated transactions at such times and at such prices as determined to be in the Company’s best interest. The Company accounts for the repurchase of treasury shares under the cost method. This repurchase program expires on June 30, 2020 and may be modified, extended or terminated by the Board at any time. As mentioned in Note 9 - Debt , the Company’s Credit Agreement entered into on October 2, 2019 contains various usual and customary covenants including one that limits the repurchase of common shares. The Company repurchased 250 and 467 shares of its common stock during fiscal years 2019 and 2018 , respectively. See Note 15 - Stock Incentive Plan , for a discussion of share repurchases transferred into treasury stock resulting from tax withholding requirements under our stock incentive plan. AOCI —The following tables presents changes in AOCI, net of tax, and reclassifications of AOCI into earnings, net of tax: Unrealized Fair Value of Swap (Cash Flow Hedge) Balance at December 31, 2018 $ — OCI before reclassifications (186 ) Amounts reclassified from AOCI (23 ) Net OCI (209 ) Balance at December 31, 2019 $ (209 ) Amount Reclassified from AOCI (1) Interest rate derivatives (interest expense) $ (30 ) Tax 7 Total net of tax $ (23 ) (1) See Note 11 - Financial Instruments for further discussion of our cash flow hedges, including the total value reclassified from AOCI to earnings. Stock Offerings —On October 2, 2019 , in connection with the Plateau Acquisition, the Company issued 1,245 shares of the Company’s stock as consideration paid to the Plateau sellers. The value of the shares issued was $16,195 based on Sterling’s closing stock price on October 1, 2019. See Note 3 - Plateau Acquisition for further discussion of the Plateau Acquisition purchase consideration. On April 3, 2017, in connection with the Tealstone Acquisition, the Company issued 1,882 shares of the Company’s stock as consideration paid to the Tealstone sellers. The value of the shares issued was $17,061 based on the average fair value of the shares on the date of acquisition.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information (Notes)	12 Months Ended
	Dec. 31, 2019
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	18. SUPPLEMENTAL CASH FLOW INFORMATION Operating assets and liabilities The following table summarizes the changes in the components of operating assets and liabilities: Twelve Months Ended December 31, 2019 2018 2017 Accounts receivable, including retainage $ (21,300 ) $ (11,094 ) $ (29,923 ) Contracts in progress, net 6,023 (4,397 ) (3,492 ) Receivables from and equity in construction joint ventures 1,524 659 (4,250 ) Other current and non-current assets 43 924 929 Accounts payable 10,987 1,969 13,579 Accrued compensation and other liabilities (839 ) (4,038 ) 6,625 Members' interest subject to mandatory redemption and undistributed earnings (340 ) 1,957 2,156 Changes in operating assets and liabilities $ (3,902 ) $ (14,020 ) $ (14,376 )

Construction Joint Ventures

Construction Joint Ventures	12 Months Ended
	Dec. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Construction Joint Ventures	6. CONSTRUCTION JOINT VENTURES The Company participates in joint ventures with other major construction companies and other partners, typically for large, technically complex projects, including design-build projects, when it is desirable to share risk and resources in order to seek a competitive advantage. Joint venture partners typically provide independently prepared estimates, furnish employees and equipment, enhance bonding capacity and often also bring local knowledge and expertise. These projects generally have joint and several liability. The Company selects its joint venture partners based on its analysis of their construction and financial capabilities, expertise in the type of work to be performed and past working relationships with the Company, among other criteria. Joint ventures with a controlling interest —For these joint ventures, the equity held by the remaining owners and their portions of net income (loss) are reflected in the Consolidated Balance Sheets line item “Noncontrolling interests” in “Stockholders’ equity” and the Consolidated Statements of Operations line item “Net income attributable to noncontrolling interests,” respectively. The following table summarizes the changes in the noncontrolling owners’ interests in subsidiaries and consolidated joint ventures: Years Ended December 31, 2019 2018 2017 Balance, beginning of period $ 7,859 $ 4,856 $ 656 Net income attributable to noncontrolling interest included in equity 794 4,353 4,200 Distributions to noncontrolling interest owners (7,360 ) (1,350 ) — Balance, end of period $ 1,293 $ 7,859 $ 4,856 Joint ventures with a noncontrolling interest —Where the Company has a noncontrolling joint interest in a venture, the Company accounts for its share of the operations of such construction joint ventures on a pro-rata basis using proportionate consolidation on its Consolidated Statements of Operations and as a single line item in “Receivables from and equity in construction joint ventures” in the Consolidated Balance Sheets. This method is an acceptable modification of the equity method of accounting which is a common practice in the construction industry. Condensed combined financial amounts of joint ventures in which the Company has a noncontrolling interest and the Company’s share of such amounts which are included in the Company’s Consolidated Financial Statements are shown below: Generally, each construction joint venture is formed to accomplish a specific project and is jointly controlled by the joint venture partners. The joint venture agreements typically provide that our interests in any profits and assets, and our respective share in any losses and liabilities that may result from the performance of the contract are limited to our stated percentage interest in the venture. We have no significant commitments beyond completion of the contract with the customer. Joint venture contracts with project owners typically impose joint and several liability on the joint venture partners. Although our agreements with our joint venture partners provide that each party will assume and pay its share of any losses resulting from a project, if one of our partners is unable to pay its share, we would be fully liable under our contract with the project owner. Circumstances that could lead to a loss under these guarantee arrangements include a partner’s inability to contribute additional funds to the venture in the event that the project incurs a loss or additional costs that we could incur should the partner fail to provide the services and resources toward project completion that had been committed to in the joint venture agreement. Historically, the Company has not incurred a liability related to the nonperformance of a joint venture partner. Under a joint venture agreement, one partner is typically designated as the sponsor or manager. The sponsoring partner typically provides all administrative, accounting and most of the project management support for the project and generally receives a fee from the joint venture for these services. We have been designated as the sponsoring partner in certain of our current joint venture projects and are a non-sponsoring partner in others. The Company must determine whether each joint venture in which it participates is a variable interest entity. This determination focuses on identifying which joint venture partner, if any, has the power to direct the activities of a joint venture and the obligation to absorb losses of the joint venture or the right to receive benefits from the joint venture in excess of their ownership interests and could have the effect of requiring us to consolidate joint ventures in which we have a noncontrolling variable interest. The Company determined that the joint venture between RLW ( 51% owner) and SEMA Construction Inc (“SEMA”) ( 49% owner) is a VIE as the Company is the primary beneficiary, as pursuant to the terms of the SEMA Operating Agreement the Company is exposed to the majority of potential losses of the partnership. At December 31, 2018 and 2017 we had no participation in a joint venture where we have a material non-majority variable interest. Summary financial information for SEMA is as follows: Year Ended December 31, 2019 Revenues $ 6,903 Operating income $ 467 Net income attributable to Sterling common stockholders $ 471 Where we are a noncontrolling venture partner, we account for our share of the operations of such construction joint ventures on a pro-rata basis using proportionate consolidation on our Consolidated Statements of Operations and as a single line item in “ Receivables from and equity in construction joint ventures ” in the Consolidated Balance Sheets. This method is an acceptable modification of the equity method of accounting which is a common practice in the construction industry. Combined financial amounts of joint ventures in which the Company has a noncontrolling interest and the Company’s share of such amounts which are included in the Company’s Consolidated Financial Statements are shown below: As of December 31, 2019 2018 Current assets $ 92,710 $ 64,815 Current liabilities $ (86,705 ) $ (74,543 ) Sterling’s receivables from and equity in construction joint ventures $ 9,196 $ 10,720 Years Ended December 31, 2019 2018 2017 Revenues $ 158,291 $ 115,441 $ 93,848 Income before tax $ 20,449 $ 8,097 $ 7,827 Sterling’s noncontrolling interest: Revenues $ 76,419 $ 55,134 $ 44,948 Income before tax $ 8,170 $ 4,104 $ 3,847 The caption “ Receivables from and equity in construction joint ventures ,” includes undistributed earnings and receivables owed to the Company. Undistributed earnings are typically released to the joint venture partners after the customer accepts the project as completed and any warranty period, if any, has passed.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Property and Equipment	7. PROPERTY AND EQUIPMENT Property and equipment are summarized as follows: As of December 31, 2019 2018 Construction and transportation equipment $ 217,945 $ 144,630 Buildings and improvements 14,641 11,072 Land 3,891 2,720 Office equipment 2,767 2,711 Total property and equipment 239,244 161,133 Less accumulated depreciation (123,214 ) (109,134 ) Total property and equipment, net $ 116,030 $ 51,999 Depreciation Expense— Depreciation expense is primarily included within cost of revenues and was approximately $15,900 , $14,200 and $15,100 for 2019 , 2018 and 2017 , respectively.

Goodwill and Other Intangibles

Goodwill and Other Intangibles	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangbiles	8. GOODWILL AND OTHER INTANGIBLE ASSETS Goodwill Reporting Units— In combination with the completion of the Plateau Acquisition during the fourth quarter of 2019, the Company realigned its operating segments and reporting units to reflect management’s present oversight of the business. The Company’s reporting units now consist of its heavy civil, specialty services and residential operating groups. The specialty services operating segment was added and includes the newly acquired Plateau operations and its associated goodwill. Goodwill is not amortized, but instead is reviewed for impairment at least annually during the fourth quarter of each year at the reporting level, absent any interim indicators of impairment or other factors requiring an assessment. Annual Impairment Assessment— For our 2019 annual impairment test of the heavy civil and residential reporting units, we performed a qualitative assessment, using information as of October 1. Under current guidance, we are permitted to first assess qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform a quantitative goodwill impairment test. We determined there were no factors indicating the need to perform a quantitative goodwill impairment test and concluded that it is more likely than not the fair value of our reporting units is greater than their carrying value and thus there was no impairment to goodwill. Due to the proximity of the timing of the Plateau Acquisition, its purchase price and associated carrying value included in the specialty services reporting unit approximated its fair value. Other adjustments to our reporting units resulting from the realignment were not material. In addition to our annual review, we assess the impairment of goodwill whenever events or changes in circumstances indicate that the carrying value of a reporting unit may be greater than fair value. Factors that could trigger an interim impairment review include, but are not limited to, significant adverse changes in the business climate which may be indicated by a decline in our market capitalization or decline in operating results. No impairments were recorded to our goodwill during the years ended December 31, 2019 , 2018 or 2017 . No such events or changes occurred between the testing date and year end to trigger a subsequent impairment review. At December 31, 2019 and 2018 , we had goodwill with a carrying amount of $191,892 and $85,231 , respectively, with the increase attributable to the Plateau Acquisition. See Note 3 - Plateau Acquisition for further information regarding goodwill from the acquisition. The following table presents goodwill by reportable segment: December 31, December 31, Goodwill Heavy Civil $ 54,806 $ 54,806 Specialty Services 106,661 — Residential 30,425 30,425 Total Goodwill $ 191,892 $ 85,231 Other Intangible Assets The following table presents our acquired finite-lived intangible assets, including the weighted-average useful lives for each major intangible asset category and in total: December 31, 2019 December 31, 2018 Weighted Gross Gross Customer relationships 25 $ 232,623 $ (6,911 ) $ 40,823 $ (3,159 ) Trade name 23 30,107 (1,692 ) 5,307 (919 ) Non-compete agreements 5 2,487 (291 ) 487 (121 ) Total 24 $ 265,217 $ (8,894 ) $ 46,617 $ (4,199 ) During the year ended December 31, 2019 , 2018 and 2017 , we have amortized approximately $4,700 , $2,400 , and $1,800 respectively. Amortization expense is anticipated to be approximately $11,500 , $11,500 , $11,300 , $11,200 , and $10,900 for 2020 , 2021 , 2022 , 2023 and 2024 , respectively. See Note 3 - Plateau Acquisition for further information regarding intangibles from the acquisition.

Debt

Debt	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Debt	9. DEBT The Company’s outstanding debt was as follows: As of December 31, 2019 2018 Credit Facility $ 420,000 $ — Oaktree Facility — 74,571 Note payable to seller, Plateau Acquisition 10,000 — Notes and deferred payments to sellers, Tealstone Acquisition 12,230 13,572 Notes payable for transportation and construction equipment and other 805 612 Total debt 443,035 88,755 Less - Current maturities of long-term debt (42,473 ) (2,899 ) Less - Unamortized debt issuance costs (9,935 ) (6,739 ) Total long-term debt $ 390,627 $ 79,117 Credit Facility —On October 2, 2019, the Company, as borrower, and certain of its subsidiaries, as guarantors, entered into a Credit Agreement (the “Credit Agreement”) with BMO Harris Bank N.A., as administrative agent (the “Agent”), Bank of America, N.A., as syndication agent, and BMO Capital Markets Corp. and BofA Securities, Inc., as joint lead arrangers and joint book runners. The Credit Agreement provides the Company with senior secured debt financing in an amount up to $475,000 in the aggregate, consisting of (i) a senior secured first lien revolving credit facility (the “Revolving Credit Facility”) in an aggregate principal amount of $75,000 (with a $75,000 limit for the issuance of letters of credit and a $15,000 sublimit for swing line loans) and (ii) a senior secured first lien term loan facility (the “Term Loan Facility”) in the amount of $400,000 (collectively, the “Credit Facility”). The obligations under the Credit Facility are secured by substantially all assets of the Company and the subsidiary guarantors, subject to certain permitted liens and interests of other parties. The Credit Facility will mature on October 2, 2024. The Company obtained the Credit Facility in order to facilitate the transactions contemplated by the Plateau Acquisition, including refinancing existing indebtedness of the Company, finance capital expenditures, finance working capital, finance acquisitions permitted under the Credit Agreement, finance other general corporate purposes and fund certain fees and expenses associated with the closing of the Credit Facility and the Plateau Acquisition. On December 2, 2019, the Credit Agreement was amended to modify (i) the applicable margins with respect to Base Rate and LIBOR borrowings under the Credit Facility, (ii) the required amounts of mandatory prepayments of the Credit Facility with excess cash flow, (iii) the amounts of scheduled principal payments quarterly and at maturity on the Term Loan Facility, and (iv) the applications of partial prepayments of the Term Loan Facility on a ratable, weighted basis among all remaining scheduled principal payments on the Term Loan Facility. The modifications in (i)-(iii) mentioned above were pursuant to the customary “market flex” rights contained in the fee letter related to the Credit Agreement. The Revolving Credit Facility bears interest at either the Base Rate plus a margin ( 4.75% and 3.50% per annum, respectively at December 31, 2019 ), or one-, two-, three-, six- or, if available, twelve-month LIBOR plus an applicable margin ( 1.74% and 4.50% per annum, respectively at December 31, 2019 , using a one-month LIBOR rate), at the Company’s election. In addition to interest on debt borrowings, we are assessed quarterly commitment fees on the unutilized portion of the facility as well as letter of credit fees on outstanding instruments. Interest under the Revolving Credit Facility is payable (i) with respect to LIBOR borrowings, on the last day of each applicable interest period (one, two, three, six or twelve months), unless the applicable interest period is longer than three months, then on each day occurring every three months after the commencement of such interest period, and on the maturity date, and (ii) with respect to Base Rate borrowings, on the last day of every calendar quarter and on the maturity date. At December 31, 2019 , we had $20,000 of outstanding borrowings under the facility, providing $55,000 of available capacity. During 2019 , our weighted average interest rate on borrowings under the facility was approximately 5.73% . The Revolving Credit Facility may be repaid in whole or in part at any time, with final payment of all principal and interest then outstanding due on October 2, 2024. Interest under the Term Loan Facility is payable at the same frequencies and bears interest at the same rate options as the Revolving Credit Facility. In connection with entering into the Credit Facility, on December 5, 2019 we entered into an interest rate swap to hedge against $350,000 of the outstanding Term Loan Facility, which resulted in a weighted average interest rate of approximately 5.70% per annum during 2019 . At December 31, 2019 , we had $400,000 of outstanding borrowings under the facility. Quarterly principal payments on the Term Loan Facility total $30,000 , $50,000 , $50,000 , $50,000 and $220,000 for each of the years ending 2020 , 2021 , 2022 , 2023 , and 2024 , respectively. A final payment of all principal and interest then outstanding on the Term Loan Facility is due on October 2, 2024. The Credit Agreement contains various affirmative and negative covenants that may, subject to certain exceptions, restrict the ability of us and our subsidiaries to, among other things, grant liens, incur additional indebtedness, make loans, advances or other investments, make non-ordinary course asset sales, declare or pay dividends or make other distributions with respect to equity interests, purchase, redeem or otherwise acquire or retire capital stock or other equity interests, or merge or consolidate with any other person, among various other things. In addition, the Company is required to maintain the following financial covenants: • a Total Leverage Ratio (as defined in the Credit Agreement) at the last day of each fiscal quarter not to be greater than 4.00 to 1.00 ending on December 31, 2019 through and including June 30, 2020, 3.75 to 1.00 ending on September 30, 2020, 3.50 to 1.00 ending on December 31, 2020 through and including March 31, 2021, 3.25 to 1.00 ending on June 30, 2021 through and including September 30, 2021, and 3.00 to 1.00 ending on December 31, 2021 and thereafter; and • a Fixed Charge Coverage Ratio (as defined in the Credit Agreement) of not less than 1.20 to 1.00 as of the last day of each fiscal quarter of the Company, commencing with the fiscal quarter ending December 31, 2019. Debt issuance costs —The Company incurred $10,688 of fees relating to the establishment of the Credit Facility. The costs associated with the Term Loan Facility and Revolving Credit Facility are reflected on the Balance Sheets as a direct reduction from the related debt liability and amortized over the terms of the respective facilities. Oaktree Facility —On October 2, 2019, concurrently with the Company’s entry into the Credit Agreement, the Company terminated the Loan and Security Agreement, dated April 3, 2017, with Wilmington Trust, National Association, as agent, and the lenders party thereto (the “Oaktree Facility”), which provided for a $85,000 term loan. The Company used a portion of the proceeds of the Credit Agreement to pay in full all outstanding borrowings of $67,100 under the Oaktree Facility. Interest on the Oaktree Facility was equal to the one-, two-, three- or six-month LIBOR, plus 8.75% per annum. Debt extinguishment costs —As part of the replacement of the Oaktree Facility, $7,728 in debt extinguishment costs were expensed and included as a “ Loss on extinguishment of debt ” on the Company’s Statement of Operations for the year ended December 31, 2019 . Debt extinguishment costs primarily consist of a prepayment premium of $3,394 (which amount is equal to 5% of the aggregate principal amount, including any interest and fees, of the Oaktree Facility repaid) and the write-off of the Oaktree Facility unamortized debt issuance costs of $4,334 . Note Payable to Seller, Plateau Acquisition —As part of the Plateau Acquisition, the Company issued a $10,000 subordinated promissory note to one of the Plateau sellers that bears interest at 8% with interest payments due quarterly beginning January 1, 2020. The subordinated promissory note has no scheduled payments, however, it may be repaid in whole or in part at any time, subject to certain payment restrictions under a subordination agreement with the Agent under our Credit Agreement, without premium or penalty, with final payment of all principal and interest then outstanding due on April 2, 2025. At inception, the subordinated promissory note’s interest rate approximated market. Notes and deferred Payments to Sellers, Tealstone Acquisition— At December 31, 2019 the Company had $12,230 outstanding, net of debt discounts, of the combined promissory notes and deferred cash payments issued as part of the Tealstone Acquisition. During the year ended December 31, 2019 , the Company paid approximately $2,400 of the deferred cash payments. The remaining principal amounts of $5,000 of promissory notes and $7,500 of deferred cash payments are due on April 3, 2020. Accreted interest for the period was approximately $1,100 and $1,200 for the years ended December 31, 2019 and 2018 , respectively, and was recorded as interest expense. Notes Payable for Transportation and Construction Equipment —The Company has purchased and financed various construction and transportation equipment to enhance the Company’s fleet of equipment. The total long-term notes payable related to the purchase of financed equipment was $805 and $612 at December 31, 2019 and 2018 , respectively. The purchases have payment terms ranging from 3 to 5 years and the associated interest rates range from 2.99% to 6.92% . Compliance and other —As of December 31, 2019 , we were in compliance with all of our restrictive and financial covenants. The Company’s debt is recorded at its carrying amount in the Consolidated Balance Sheets. As of December 31, 2019 and 2018 , the carrying values of our debt outstanding approximated the fair values.

Lease Obligations

Lease Obligations	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Lease Obligations	10. LEASE OBLIGATIONS The Company has operating and finance leases primarily for construction and transportation equipment, as well as office space. The Company’s leases have remaining lease terms of 1 month to 5 years , some of which include options to extend the leases for up to 10 years . The components of lease expense are as follows: Twelve Months Ended December 31, 2019 Operating lease cost $ 8,594 Short-term lease cost $ 18,032 Finance lease cost: Amortization of right-of-use assets $ 213 Interest on lease liabilities 20 Total finance lease cost $ 233 Supplemental cash flow information related to leases is as follows: Twelve Months Ended December 31, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 8,127 Operating cash flows from finance leases $ 20 Financing cash flows from finance leases $ 213 Right-of-use assets obtained in exchange for lease obligations (non-cash): Operating leases $ 8,955 Finance leases $ 816 Supplemental balance sheet information related to leases was as follows: December 31, 2019 Operating Leases Operating lease right-of-use assets $ 13,979 Current portion of long-term lease obligations $ 7,095 Long-term lease obligations 6,976 Total operating lease liabilities $ 14,071 Finance Leases Property and equipment, at cost $ 1,479 Accumulated depreciation (482 ) Property and equipment, net $ 997 Current maturities of long-term debt $ 204 Long-term debt 560 Total finance lease liabilities $ 764 Weighted Average Remaining Lease Term Operating leases 2.5 Finance leases 4.0 Weighted Average Discount Rate Operating leases 6.0 % Finance leases 4.2 % Maturities of lease liabilities are as follows: Operating Leases Finance Leases Year Ending December 31, 2020 $ 6,813 $ 233 2021 5,180 208 2022 2,858 161 2023 784 154 2024 45 77 Thereafter — — Total lease payments $ 15,680 $ 833 Less imputed interest (1,609 ) (69 ) Total $ 14,071 $ 764
Lease Obligations	10. LEASE OBLIGATIONS The Company has operating and finance leases primarily for construction and transportation equipment, as well as office space. The Company’s leases have remaining lease terms of 1 month to 5 years , some of which include options to extend the leases for up to 10 years . The components of lease expense are as follows: Twelve Months Ended December 31, 2019 Operating lease cost $ 8,594 Short-term lease cost $ 18,032 Finance lease cost: Amortization of right-of-use assets $ 213 Interest on lease liabilities 20 Total finance lease cost $ 233 Supplemental cash flow information related to leases is as follows: Twelve Months Ended December 31, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 8,127 Operating cash flows from finance leases $ 20 Financing cash flows from finance leases $ 213 Right-of-use assets obtained in exchange for lease obligations (non-cash): Operating leases $ 8,955 Finance leases $ 816 Supplemental balance sheet information related to leases was as follows: December 31, 2019 Operating Leases Operating lease right-of-use assets $ 13,979 Current portion of long-term lease obligations $ 7,095 Long-term lease obligations 6,976 Total operating lease liabilities $ 14,071 Finance Leases Property and equipment, at cost $ 1,479 Accumulated depreciation (482 ) Property and equipment, net $ 997 Current maturities of long-term debt $ 204 Long-term debt 560 Total finance lease liabilities $ 764 Weighted Average Remaining Lease Term Operating leases 2.5 Finance leases 4.0 Weighted Average Discount Rate Operating leases 6.0 % Finance leases 4.2 % Maturities of lease liabilities are as follows: Operating Leases Finance Leases Year Ending December 31, 2020 $ 6,813 $ 233 2021 5,180 208 2022 2,858 161 2023 784 154 2024 45 77 Thereafter — — Total lease payments $ 15,680 $ 833 Less imputed interest (1,609 ) (69 ) Total $ 14,071 $ 764

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies Disclosure	12. COMMITMENTS AND CONTINGENCIES Insurance The Company carries insurance policies to cover various risks, primarily general liability, automobile liability, workers’ compensation and employee medical expenses under which we are liable to reimburse the insurance company for a portion of each claim paid. Property and Casualty— Payments for general liability and workers’ compensation claim amounts generally range from the first $2 to $250 per occurrence for Workers’ Compensation, and $25 per occurrence for General Liability. We accrue for probable losses, both reported and unreported, that are reasonably estimable using actuarial methods based on historic trends, modified, if necessary, by recent events. Changes in our loss assumptions caused by changes in actual experience would affect our assessment of the ultimate liability and could have an effect on our operating results and financial position for payments up to $275 per occurrence collective for general liability and workers’ compensation, with a maximum aggregate liability of $4,000 combined casualty losses per year. The Company also maintains commercial insurance coverage in excess of the limits of our primary commercial automobile, general liability and employers liability policies, in the amount of $75,000 . The Company also maintains guaranteed cost program for Workers’ Compensation, General Liability, and Automobile Liability. Utilizing internal actuarial models, the insurance carriers established, and applied to the exposure base, a fixed rate to ascertain the premium cost to the Company. These premium costs are auditable at the conclusion of the policy term to account for discrepancies in the estimated and actual policy exposure, however not for any losses incurred during the policy term. The guaranteed cost program maintained by the Company does carry a deductible, however in a small enough amount as to expose the Company to unsubstantial and immaterial risk for any one loss incurred. Medical— The Company maintains fully insured and self-insured medical benefit plans, which provides medical benefits to employees electing coverage under the plans. Under its self-insured plans, the Company has stop-loss coverage to limit the exposure arising from these claims. Self-insured claims filed and claims incurred but not reported are accrued based upon management’s estimates of the ultimate cost of claims incurred using actuarial assumptions followed in the insurance industry and historical experience. Although management believes it has the ability to reasonably estimate losses related to claims, it is possible that actual results could differ from recorded self-insured liabilities. Guarantees The Company obtains bonding on construction contracts through Travelers Casualty and Surety Company of America (“Travelers”). As is customary in the construction industry, the Company indemnifies Travelers for any losses incurred by it in connection with bonds that are issued. The Company has granted Travelers a security interest in accounts receivable and contract rights for that obligation. The Company typically indemnifies contract owners for claims arising during the construction process and carries insurance coverage for such claims, which in the past have not been material. The Company’s Certificate of Incorporation provides for indemnification of its officers and directors. The Company has a directors and officers insurance policy that limits their exposure to litigation against them in their capacities as such. Litigation The Company is the subject of certain other claims and lawsuits occurring in the normal course of business. Management, after consultation with legal counsel, does not believe that the outcome of these other actions will have a material impact on the financial statements of the Company. There are no significant unresolved legal issues as of December 31, 2019 and 2018 . Purchase Commitments To manage the risk of changes in material prices and subcontracting costs used in tendering bids for construction contracts, most of the time, we obtain firm quotations from suppliers and subcontractors before submitting a bid. These quotations do not include any quantity guarantees. As soon as we are advised that our bid is the lowest, we enter into firm contracts with most of our materials suppliers and sub-contractors, thereby mitigating the risk of future price variations affecting the contract costs. Earn-out Liabilities The Company has earn-out agreements with JBC’s and Tealstone’s former owners. The JBC earn-out performance period ended December 31, 2017. The JBC earn-out liability was determined based on its performance against established benchmarks. In 2017, JBC’s actual performance surpassed the benchmarks which resulted in an earn-out expense of $1,300 , recorded in “Other operating expense, net” on the Consolidated Statements of Operations. The earn-out agreement with Tealstone’s former owners extends through March 31, 2021 and is subject to a maximum earn-out of $15,000 over that period. The initial annual performance period for the Tealstone earn-out ended March 31, 2018. The Tealstone earn-out liability is determined based on the Company’s net income performance against established benchmarks. In 2019 , 2018 , and 2017 we recorded an earn-out obligation of $2,000 , $1,900 , and $400 , respectively, recorded in “Other operating expense, net” on the Consolidated Statements of Operations. This liability is included in other current liabilities on the accompanying Consolidated Balance Sheets.

Income Taxes and Deferred Tax A

Income Taxes and Deferred Tax Asset/Liability	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	13. INCOME TAXES Provision For Income Taxes The Company and its subsidiaries are based in the U.S. and file federal and various state income tax returns. The components of the provision for income taxes were as follows: Years Ended December 31, 2019 2018 2017 Current tax expense $ 1,182 $ 288 $ 118 Deferred tax (benefit) expense (27,398 ) 1,450 — Income tax (benefit) expense $ (26,216 ) $ 1,738 $ 118 Due to the net operating loss carryforwards described below, the Company has not had current federal tax expense for any of the years presented. The Company has incurred current expense in states in which the Company does not have net operating loss carry forwards. Effective Tax Rate The items comprising the difference between income taxes computed at the U.S. federal statutory rates in effect for 2019, 2018 an 2017 and our effective tax rates were as follows: Years Ended December 31, 2019 2018 2017 Amount % Amount % Amount % Tax expense (recovery) at the U.S. federal statutory rate $ 3,041 21.0 % $ 6,568 21.0 % $ 5,577 35.0 % State tax based on income, net of refunds and federal benefits 1,670 11.5 364 1.2 (264 ) (1.7 ) Taxes on subsidiaries’ and joint ventures’ earnings allocated to noncontrolling interests owners (2,241 ) (15.5 ) (4,097 ) (13.1 ) (5,504 ) (34.5 ) Valuation allowance (29,375 ) (202.9 ) (1,013 ) (3.3 ) (18,006 ) (113.0 ) Tax credits (397 ) (2.7 ) (286 ) (0.9 ) (349 ) (2.2 ) Tax rate change — — (281 ) (0.9 ) 19,545 122.7 Return to provision 48 0.3 21 0.1 (62 ) (0.4 ) Earn-out liability — — — — 460 2.9 Equity compensation 805 5.6 26 0.1 (1,371 ) (8.6 ) Other permanent differences 233 1.6 436 1.4 92 0.6 Income tax (benefit) expense $ (26,216 ) (181.1 )% $ 1,738 5.6 % $ 118 0.8 % The decrease from the U.S. federal statutory rate in 2019 was primarily a result of the reversal of the valuation allowance on our net deferred tax assets. The 2018 effective income rate varied from the statutory rate primarily as a result of a change in the valuation allowance on our net deferred tax assets exclusive of deferred tax liabilities on indefinite lived assets and net income attributable to noncontrolling interest owners, which is taxable to those owners rather than the Company. The 2017 effective income rate varied from the statutory rate primarily as a result of the change in federal tax rate under the U.S. government Tax Cuts and Jobs Act (the “Act”), offset by a change in the valuation allowance, net income attributable to noncontrolling interest owners, and equity compensation. The Act was enacted on December 22, 2017 and resulted in the U.S. federal corporate tax rate decreasing from 35 percent in 2017 to 21 percent thereafter and primarily resulted in a reduction in the value of deferred tax assets by $19,300 and corresponding reduction in valuation allowance in 2017. Deferred Tax Assets and Liabilities The components of deferred tax assets and liabilities were as follows: Long Term As of December 31, 2019 2018 Assets related to: Accrued compensation and other $ 3,981 $ 3,707 Goodwill — — Noncontrolling interests 1,812 1,687 Deferred revenue 922 232 Members interest liabilities 11,328 11,570 Right of use liabilities 3,253 — Net operating loss carryforwards 19,801 22,818 Total deferred tax assets 41,097 40,014 Valuation allowance for deferred tax assets — (31,718 ) Net deferred tax assets $ 41,097 $ 8,296 Liabilities related to: Depreciation of property and equipment (7,911 ) (7,709 ) Right of use assets (3,232 ) — Amortization of tax basis goodwill (3,091 ) (1,450 ) Other (851 ) (587 ) Net deferred tax liabilities $ (15,085 ) $ (9,746 ) Net total deferred tax asset (liability) $ 26,012 $ (1,450 ) Net Operating Loss— We have federal and state net operating loss (“NOL”) carryforwards of $83,270 and $44,857 , respectively, which expire at various dates in the next 18 years for U.S. federal income tax and in the next 8 to 18 years for the various state jurisdictions where we operate. Such NOL carryforwards expire beginning in 2028 through 2038. Valuation Allowance— The Company performs an analysis at the end of each reporting period to determine whether it is more likely than not deferred tax assets will be realized in future years. In performing its assessments in prior periods, a full valuation allowance was recorded as a result of objective negative evidence which included historical losses from 2013 to 2016 and the first quarter of 2017 and associated limits on ability to consider other subjective evidence such as projections for future growth. During 2019, the Company achieved eleven of the last twelve consecutive quarters of pre-tax income and is projecting sufficient future taxable income to be available to utilize all NOLs prior to their expiration. Deferred tax liabilities were a consideration in the analysis of whether to apply a valuation allowance because taxable temporary differences may be used as a source of taxable income to support the realization of deferred tax assets. A deferred tax liability that relates to an asset with an indefinite life, such as goodwill, may not be considered a source of income and should not be netted against deferred tax assets for valuation allowance purposes. As a result of this analysis, the Company now believes sufficient positive evidence outweighs any negative evidence and therefore released the full valuation allowance in the fourth quarter of 2019, resulting in $29,375 being recorded as a reduction to income tax expense. Uncertain Tax Positions As a result of the Company’s analysis, management has determined that the Company does not have any material uncertain tax positions. The Company’s U.S. federal income tax returns for 2016 and later years are open and subject to examination by the I.R.S. In addition, the Company’s state income tax returns for 2015 and later years are open and subject to examination.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Earnings Per Share	16. EARNINGS PER SHARE Basic net income per share attributable to Sterling common stockholders is computed by dividing net income attributable to Sterling common stockholders by the weighted average number of common shares outstanding during the period. Diluted net income per common share attributable to Sterling common stockholders is the same as basic net income per share attributable to Sterling common stockholders but includes dilutive unvested stock awards and warrants using the treasury stock method. The following table reconciles the numerators and denominators of the basic and diluted per common share computations for net income attributable to Sterling common stockholders: Years Ended December 31, Numerator: 2019 2018 2017 Net income attributable to Sterling common stockholders $ 39,901 $ 25,187 $ 11,617 Denominator: Weighted average common shares outstanding — basic 26,671 26,903 26,274 Shares for dilutive unvested stock 448 291 438 Weighted average common shares outstanding and assumed conversions— diluted 27,119 27,194 26,712 Basic net income per share attributable to Sterling common stockholders $ 1.50 $ 0.94 $ 0.44 Diluted net income per share attributable to Sterling common stockholders $ 1.47 $ 0.93 $ 0.43

Retirement Benefits

Retirement Benefits	12 Months Ended
	Dec. 31, 2019
Defined Benefit Plan [Abstract]
Employee Benefit Plans	17. RETIREMENT BENEFITS Defined Contribution Plans The Company maintains a defined contribution profit-sharing plan (401(k) plan) covering substantially all non-union persons employed by the Company, whereby employees may contribute a percentage of compensation, limited to maximum allowed amounts under the Internal Revenue Code. The 401(k) plan provides for a discretionary employer contribution and is determined annually by the Company’s board of directors. With the acquisition of Plateau, the Company made matching contributions for the year ended December 31, 2019 of $2,800 , and $2,700 and $2,300 for the years ended December 31, 2018 and 2017 , respectively. Multi-Employer Pension Plans As of December 31, 2019 , the Company had approximately 2,800 employees, including 2,400 field personnel. We had 400 employees, or 17% of total employees, that were union members covered by collective bargaining agreements. The Company contributes to a number of multi-employer defined benefit pension plans under the terms of collective-bargaining agreements that cover its union-represented employees. The risks of participating in these multi-employer plans are different from single-employer plans in the following aspects: • Assets contributed to the multi-employer plan by one employer may be used to provide benefits to employees of other participating employers. If a participating employer stops contributing to the plan, the unfunded obligations of the plan may be borne by the remaining participating employers. • If the Company chooses to stop participating in some of its multi-employer plans, the Company may be required to pay those plans an amount based on the underfunded status of the plan, referred to as a withdrawal liability. The following table presents our participation in these plans: Pension Plan Employer Pension Protection Act (“PPA”) Certified Zone Status (1) FIP / RP Status Pending/Implemented (2) Contributions Surcharge Imposed Expiration Date of Collective Bargaining Agreement (3) Pension Trust Fund Identification Number 2019 2018 2019 2018 2017 Pension Trust Fund for Operating Engineers Pension Plan 94-6090764 Yellow Red Yes $ 2,314 $ 1,932 $ 2,477 No Various Laborers Pension Trust for Northern California 94-6277608 Green Yellow Yes 857 880 953 No Various Carpenter Funds Administrative Office 94-6050970 Red Red Yes 547 748 727 No Various Cement Mason Pension Trust Fund For Northern California 94-6277669 Yellow Yellow Yes 320 504 423 No Various All other funds (4) 7,144 7,283 8,006 Total Contributions: $ 11,182 $ 11,347 $ 12,586 (1) The most recent PPA zone status available in 2019 and 2018 is for the plan’s year-end during 2018 and 2017 , respectively. The zone status is based on information that we received from the plan and is certified by the plan’s actuary. Among other factors, plans in the red zone are generally less than 65 percent funded, plans in the orange zone are less than 80 percent funded and have an Accumulated Funding Deficiency in the current year or projected into the next six years, plans in the yellow zone are less than 80 percent funded and plans in the green zone are at least 80 percent funded. (2) Indicates whether the plan has a financial improvement plan (“FIP”) or a rehabilitation plan (“RP”) which is either pending or has been implemented. (3) Lists the expiration date(s) of the collective-bargaining agreement(s) to which the plans are subject. (4) These funds include multi-employer plans for pensions and other employee benefits. The total individually insignificant multi-employer pension costs contributed were $829 , $1,300 and $1,500 for 2019 , 2018 and 2017 , respectively, and are included in the contributions to all other funds along with contributions to other types of benefit plans. Other employee benefits include certain coverage for medical, prescription drug, dental, vision, life and accidental death and dismemberment, disability and other benefit costs. We currently have no intention of withdrawing from any of the multi-employer pension plans in which we participate.

Concentration of Risk and Enter

Concentration of Risk and Enterprise Wide Disclosures	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Concentration of Risk and Enterprise Wide Disclosures	19. CONCENTRATION OF RISK AND ENTERPRISE WIDE DISCLOSURES The following table shows contract revenues generated from customers that accounted for more than 10% of the Company’s consolidated revenues: Years Ended December 31, 2019 2018 2017 Amount % Amount % Amount % Utah Department of Transportation (“UDOT”) $ 135,496 12.0 % $ 153,276 14.8 % $ 140,529 14.7 % Texas Department of Transportation (“TXDOT”) * * * * 103,236 10.8 % *Represents less than 10% of revenues At December 31, 2019 , The Conlan Company accounted for 11% of the Company’s outstanding contract receivables with a receivable balance of $18,700 . There were no individual customers accounting for greater than 10% of the Company’s outstanding contract receivables December 31, 2018 . The Company’s revenue and receivables are entirely derived from the construction of U.S. projects and all of the Company’s assets are held domestically within the U.S.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2019
Related Party Transactions [Abstract]
Related Party Transactions	20. RELATED PARTY TRANSACTIONS The Company has limited related party transactions. The most significant transactions relate to the Company’s Ralph L. Wadsworth Construction (“RLW”) subsidiary and its executive management who own or have an ownership interest in certain real estate and other companies. RLW has historically performed construction contracts, leased properties, or has provided professional and other services for entities owned by the executive managers of RLW. The total RLW related party revenue related to construction contracts totaled $6,400 , $15,300 and $700 in 2019 , 2018 and 2017 , respectively. RLW leases its main office and equipment maintenance shop for its Utah operations for an annual cost of approximately $800 . The office and shop leases expire in 2022. RLW had no other miscellaneous related party transactions in 2019 , 2018 , and 2017 . The Company had other individually insignificant miscellaneous transactions with related parties including facility and equipment leases from executive management who own or have an ownership interest in real estate and equipment companies that totaled $300 , $300 and $200 during 2019 , 2018 and 2017 , respectively.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Segment Information	21. SEGMENT INFORMATION The Company’s internal and public segment reporting are aligned based upon the services offered by its operating groups, which represent the reportable segments. Due to the October 2, 2019 acquisition of Plateau, the Company realigned its operating groups to reflect management’s present oversight of operations. After realignment, the Company’s operations consist of three reportable segments: Heavy Civil , Specialty Services and Residential , with our commercial business reclassified from the Heavy Civil operating group into our newly formed Specialty Services operating group. The segment information for the prior periods presented has been recast to conform to the current presentation. The Company’s Chief Operating Decision Maker evaluates the performance of the operating groups based upon revenue and income from operations. Each operating group’s income from operations reflects corporate costs, allocated based primarily upon revenue. The following table presents total revenue, depreciation and amortization, and income from operations by reportable segment for the years ended December 31, 2019 , 2018 and 2017 : Years Ended December 31, 2019 2018 2017 Revenue Heavy Civil $ 760,325 $ 765,638 $ 801,652 Specialty Services 212,824 120,333 48,314 Residential 153,129 151,696 107,992 Total Revenue $ 1,126,278 $ 1,037,667 $ 957,958 Depreciation and Amortization Heavy Civil $ 12,839 $ 13,492 $ 14,789 Specialty Services 6,059 1,439 815 Residential 1,842 1,839 1,390 Total Depreciation and Amortization $ 20,740 $ 16,770 $ 16,994 Operating Income Heavy Civil $ 3,316 $ 17,044 $ 8,246 Specialty Services 18,207 4,629 2,284 Residential 20,539 20,938 15,646 Subtotal 42,062 42,611 26,176 Acquisition related costs (4,311 ) — — Total Operating Income $ 37,751 $ 42,611 $ 26,176 The following table presents total assets by reportable segment at December 31, 2019 and 2018 : December 31, December 31, Assets Heavy Civil $ 287,779 $ 318,586 Specialty Services 587,642 76,170 Residential 86,519 87,817 Total Assets $ 961,940 $ 482,573

Quarterly Financial Information

Quarterly Financial Information	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information	22. QUARTERLY FINANCIAL INFORMATION The following table summarizes the unaudited quarterly results of operations for 2019 and 2018 : 2019 Quarters Ended (unaudited) March 31 June 30 September 30 December 31 Revenues $ 223,949 $ 264,086 $ 291,699 $ 346,544 Gross profit 19,503 25,496 29,216 33,579 Income (loss) before income taxes 2,024 8,571 9,422 (5,538 ) Net income attributable to Sterling common stockholders $ 1,815 $ 7,828 $ 7,957 $ 22,301 Net income per share attributable to Sterling common stockholders: Basic $ 0.07 $ 0.30 $ 0.30 $ 0.81 Diluted $ 0.07 $ 0.29 $ 0.30 $ 0.79 2018 Quarters Ended (unaudited) March 31 June 30 September 30 December 31 Revenues $ 222,492 $ 268,734 $ 291,266 $ 255,175 Gross profit $ 19,834 $ 31,046 $ 31,279 $ 28,173 Income before income taxes $ 3,721 $ 9,238 $ 11,581 $ 6,738 Net income attributable to Sterling common stockholders $ 2,489 $ 8,174 $ 8,917 $ 5,607 Net income per share attributable to Sterling common stockholders: Basic $ 0.09 $ 0.30 $ 0.33 $ 0.22 Diluted $ 0.09 $ 0.30 $ 0.33 $ 0.21 The Company’s operating revenues tend to be somewhat higher in the summer months which are typically due to holiday schedules and warmer and dryer weather conditions. Our second and third quarter revenues and results of operations typically reflect these seasonal trends. However, from time to time, the Company’s operating results are significantly affected by certain transactions or events that management believes are not indicative or representative of our results. As of October 2, 2019, Plateau’s results are included in the results for the remainder of 2019. As discussed in Note 21 - Segment Information , during the fourth quarter 2019, the Company realigned the operating groups to reflect the present management oversight of operations. Due to the aforementioned realignment, part the 2019 and 2018 results for our commercial business were reclassified from the Heavy Civil operating group into our newly formed Specialty Services operating group. The following tables represent our 2019 and 2018 quarterly revenue and income from operations adjusted to reflect our operating group realignment and to conform to our 2019 presentation: 2019 Quarters Ended (unaudited) March 31 June 30 September 30 December 31 Total Revenue Heavy Civil $ 150,505 $ 200,236 $ 218,894 $ 190,690 $ 760,325 Specialty Services 30,679 27,894 32,863 121,388 212,824 Residential 42,765 35,956 39,942 34,466 153,129 Total Revenue $ 223,949 $ 264,086 $ 291,699 $ 346,544 $ 1,126,278 Operating Income Heavy Civil $ (2,147 ) $ 5,747 $ 7,420 $ (7,704 ) $ 3,316 Specialty Services 1,048 865 1,371 14,923 18,207 Residential 5,819 4,834 5,220 4,666 20,539 Subtotal 4,720 11,446 14,011 11,885 42,062 Acquisition related costs — (262 ) (1,896 ) (2,153 ) (4,311 ) Total Operating Income $ 4,720 $ 11,184 $ 12,115 $ 9,732 $ 37,751 2018 Quarters Ended (unaudited) March 31 June 30 September 30 December 31 Total Revenue Heavy Civil $ 158,722 $ 194,174 $ 222,299 $ 190,443 $ 765,638 Specialty Services 28,519 29,109 32,245 30,460 120,333 Residential 35,251 45,451 36,722 34,272 151,696 Total Revenue $ 222,492 $ 268,734 $ 291,266 $ 255,175 $ 1,037,667 Operating Income Heavy Civil $ 1,092 $ 4,322 $ 7,385 $ 4,245 $ 17,044 Specialty Services 519 1,480 1,647 983 4,629 Residential 5,068 6,347 5,341 4,182 20,938 Total Operating Income $ 6,679 $ 12,149 $ 14,373 $ 9,410 $ 42,611

Summary of Business and Signi_2

Summary of Business and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Principles of Consolidation	Presentation Basis— The accompanying Consolidated Financial Statements are presented in accordance with accounting policies generally accepted in the United States (“GAAP”) and reflect all wholly owned subsidiaries and those entities the Company is required to consolidate. See the “Consolidated 50% Owned Subsidiaries” and “Construction Joint Ventures” section of this Note for further discussion of the Company’s consolidation policy for those entities that are not wholly owned. In the opinion of management, all adjustments, consisting only of normal recurring adjustments, considered necessary for a fair presentation have been included. All significant intercompany accounts and transactions have been eliminated in consolidation. Values presented within tables (excluding per share data) are in thousands. Reclassifications have been made to historical financial data in the Consolidated Financial Statements to conform to the current year presentation.
Use of Estimates	Estimates and Judgments— The preparation of the accompanying Consolidated Financial Statements in conformity with GAAP requires management to make estimates and judgments that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Certain accounting estimates of the Company require a higher degree of judgment than others in their application. These include the recognition of revenue and earnings from construction contracts over time, the valuation of long-lived assets, goodwill, income taxes, and purchase accounting estimates, including goodwill and other intangible assets. Management continually evaluates all of its estimates and judgments based on available information and experience; however, actual results could differ from these estimates.
Revenue Recognition	Revenue Recognition— Our revenue is derived from long-term contracts for customers in our heavy civil and specialty services business segments, as well as short-term projects for customers in our residential business segment. Accounting treatment for these contracts in accordance with ASU 2014-09 (Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers ) , is as follows: • Performance Obligations Satisfied Over Time (Heavy Civil and Specialty Services) Recognition of Performance Obligations— A performance obligation is a promise in a contract to transfer a distinct good or service to the customer, and is the unit of account in the new revenue standard. The contract transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. Heavy civil projects typically span between 12 to 36 months , and specialty services projects are between 6 to 24 months . The majority of our contracts have a single performance obligation as the promise to transfer the individual goods or services is not separately identifiable from other promises in the contracts and, therefore, not distinct. Some contracts have multiple performance obligations, most commonly due to the contract covering multiple phases of the project life cycle (design and construction). Revenues are recognized as our obligations are satisfied over time, using the ratio of project costs incurred to estimated total costs for each contract because of the continuous transfer of control to the customer as all of the work is performed at the customer’s site and, therefore, the customer controls the asset as it is being constructed. This continuous transfer of control to the customer is further supported by clauses in the contract that allow the customer to unilaterally terminate the contract for convenience, pay the Company for costs incurred plus a reasonable profit and take control of any work in process. This cost-to-cost measure is used because management considers it to be the best available measure of progress on these contracts. Contract costs include all direct material, labor, subcontract and other costs and those indirect costs determined to relate to contract performance, such as indirect salaries and wages, equipment repairs and depreciation, insurance and payroll taxes. Items excluded from cost-to-cost— Pre-contract costs are generally not material and are charged to expense as incurred, but in certain cases pre-contract recognition may be deferred if specific probability criteria are met. Provisions for estimated losses on uncompleted contracts are made in the period in which such losses are determined. Remaining Performance Obligations (“RPOs”)— RPOs represent the amount of revenues we expect to recognize in the future from our contract commitments on projects and are hereafter referred to as “Backlog”. Backlog includes the entire expected revenue values for joint ventures we consolidate and our proportionate value for those we proportionately consolidate. Backlog may not be indicative of future operating results, and projects included in Backlog may be canceled, modified or otherwise altered by customers. See Note 4 - Revenue from Customers , for further discussion. Variable Consideration— Contract modifications through change orders, claims and incentives are routine in the performance of the Company’s contracts to account for changes in the contract specifications or requirements. In most instances, contract modifications are not distinct from the existing contract due to the significant integration service provided in the contract and are accounted for as a modification of the existing contract and performance obligation. Either the Company or its customers may initiate change orders, which may include changes in specifications or designs, manner of performance, facilities, equipment, materials, sites and period of completion of the work. Change orders that are unapproved as to both price and scope are evaluated as claims. The Company considers claims to be amounts in excess of approved contract prices that the Company seeks to collect from its customers or others for customer-caused delays, errors in specifications and designs, contract terminations, change orders that are either in dispute or are unapproved as to both scope and price, or other causes of unanticipated additional contract costs. The Company estimates variable consideration for a performance obligation at the most likely amount to which the Company expects to be entitled (or the most likely amount the Company expects to incur in the case of liquidated damages), utilizing estimation methods that best predict the amount of consideration to which the Company will be entitled (or will be incurred in the case of liquidated damages). The Company includes variable consideration in the estimated transaction price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur or when the uncertainty associated with the variable consideration is resolved. The Company’s estimates of variable consideration and determination of whether to include estimated amounts in transaction price are based largely on an assessment of its anticipated performance and all information (historical, current and forecasted) that is reasonably available to the Company. The effect of variable consideration on the transaction price of a performance obligation is recognized as an adjustment to revenue on a cumulative catch-up basis. To the extent unapproved change orders and claims reflected in transaction price (or excluded from transaction price in the case of liquidated damages) are not resolved in the Company’s favor, or to the extent incentives reflected in transaction price are not earned, there could be reductions in, or reversals of, previously recognized revenue. • Performance Obligations Satisfied at a Point-in-Time (Residential) Revenue for our residential contracts is recognized at a point in time and utilizes an output measure for performance based on the completion of a unit of work (e.g. completion of concrete foundation). The time from starting construction to completion is typically two weeks or less. Upon fulfillment of the performance obligation, the customer is provided an invoice (or equivalent) demonstrating transfer of control to the customer. Contracts in Progress— The timing of revenue recognition, billings and costs incurred results in billed accounts receivable and costs and estimated earnings in excess of billings on uncompleted contracts (contract assets) on the Consolidated Balance Sheet. For performance obligations satisfied over time, amounts are billed as work progresses in accordance with agreed-upon contractual terms, either at periodic intervals (e.g., biweekly or monthly) or upon achievement of contractual milestones. Typically, Sterling bills for advances or deposits from its customers, before revenue is recognized, resulting in billings in excess of costs and estimated earnings on uncompleted contracts (contract liabilities). However, the Company occasionally bills subsequent to revenue recognition, resulting in contract assets. These assets and liabilities are reported on the Consolidated Balance Sheet on a contract-by-contract basis at the end of each reporting period.
Receivables, including Retainage	Receivables, including Retainage— Receivables are generally based on amounts billed to the customer in accordance with contractual provisions. Many of the contracts under which the Company performs work also contain retainage provisions. Retainage refers to that portion of our billings held for payment by the customer pending satisfactory completion of the project. Unless reserved, the Company assumes that all amounts retained by customers under such provisions are fully collectible. Retainage on active contracts is classified as a current asset regardless of the term of the contract and is generally collected within one year of the completion of a contract. At December 31, 2019 and 2018 , receivables included $79,400 and $47,400 of retainage. We anticipate collecting approximately 75% of our December 31, 2019 of retainage in 2020 . Receivables are written off based on individual credit evaluation and specific circumstances of the customer, when such treatment is warranted. The Company performs a review of outstanding receivables, historical collection information and existing economic conditions to determine if there are potential uncollectible receivables. At December 31, 2019 and 2018 , our allowance for doubtful accounts against contracts receivable was minimal. As is customary, we have agreed to indemnify our bonding company for all losses incurred by it in connection with bonds that are issued, and we have granted our bonding company a security interest in certain assets, including accounts receivable, as collateral for such obligation.
Property and equipment	Property and equipment— Property and equipment are recorded at cost and depreciated on a straight-line basis over their estimated useful lives, including buildings and improvements ( 5 to 39 years) and plant and field equipment ( 5 to 20 years). Renewals and betterments that substantially extend the useful life of an asset are capitalized and depreciated. Leasehold improvements are depreciated over the lesser of the useful life of the asset or the applicable lease term.
Leases and Equipment under Capital Leases	Lease Arrangements— In the ordinary course of business, the Company enters into a variety of lease arrangements, including operating, finance and capital leases. • Operating & Finance Leases— Effective January 1, 2019, the Company determines if an arrangement is a lease at inception. The operating lease right-of-use (“ROU”) assets are included within the Company’s non-current assets and lease liabilities are included in current or non-current liabilities on the Company’s Consolidated Balance Sheets. Finance leases are included in “Property and equipment”, “Current maturities of long-term debt”, and “Long-term debt” on the Company’s Consolidated Balance Sheets. ROU assets represent the Company’s right to use, or control the use of, a specified asset for the lease term. Lease liabilities are the Company’s obligation to make lease payments arising from a lease, and are measured on a discounted basis. Operating lease ROU assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term on the commencement date. As most of the Company’s leases do not provide an implicit rate, the Company’s incremental borrowing rate was used based on the information available on the commencement date in determining the present value of lease payments. For future leases, the implied rate in the lease will be used to determine the present value. The operating lease ROU asset includes any lease payments made and initial direct costs incurred and excludes lease incentives. The lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for minimum lease payments continues to be recognized on a straight-line basis over the lease term. • Capital Leases— The Company accounts for capital leases, which transfer substantially all the benefits and risks incident to the ownership of the leased property to the Company, as the acquisition of an asset and the incurrence of an obligation. Under this method of accounting, the recorded value of the leased asset is amortized principally using the straight-line method over its estimated useful life and the obligation, including interest thereon, is reduced through payments over the life of the lease. Depreciation expense on equipment subject to capital leases and the related accumulated depreciation is included with that of owned equipment. Capital leases are recorded in “Long-term debt, net of current maturities” and “Current maturities of long-term debt,” as applicable, in our Consolidated Balance Sheets.
Goodwill and Intangibles	Goodwill— Goodwill represents the excess of the cost of companies acquired over the fair value of their net assets at the dates of acquisition. Goodwill is not amortized, but instead is reviewed for impairment at least annually at a reporting unit level, absent any interim indicators of impairment. Interim testing for impairment is performed if indicators of potential impairment exist. We perform our annual impairment assessment during the fourth quarter of each year. We identify a potential impairment by comparing the fair value of the applicable reporting unit to its net book value, including goodwill. To determine the fair value of our reporting units and test for impairment, we utilize an income approach (discounted cash flow method) as we believe this is the most direct approach to incorporate the specific economic attributes and risk profiles of our reporting units into our valuation model. We generally do not utilize a market approach, given the lack of relevant information generated by market transactions involving comparable businesses. However, to the extent market indicators of fair value become available, we consider such market indicators in our discounted cash flow analysis and determination of fair value.
Evaluating Impairment of Long-Lived Assets	Evaluating Impairment of Other Intangible Assets and Other Long-Lived Assets— Our finite-lived intangible assets are amortized over their estimated remaining useful economic lives. Our project-related intangible assets are amortized as the applicable projects progress, customer relationships are amortized utilizing an accelerated method based on the pattern of cash flows expected to be realized, taking into consideration expected revenues and customer attrition, and our other intangibles are amortized utilizing a straight-line method. When events or changes in circumstances indicate that finite-lived intangible and other long-lived assets may be impaired, an evaluation is performed. If the asset or asset group fails the recoverability test, we will perform a fair value measurement to determine and record an impairment charge.
Federal and State Income Taxes	Federal and State Income Taxes— We determine deferred income tax assets and liabilities using the balance sheet method. Under this method, the net deferred tax asset or liability is determined based on the tax effects of the temporary differences between the book and tax bases of the various balance sheet assets and liabilities and gives current recognition to changes in tax rates and laws. Valuation allowances are established when necessary to reduce deferred tax assets to the amount expected to be realized. We recognize the financial statement benefit of a tax position only after determining the relevant tax authority would more likely than not sustain the position following an audit. For tax positions meeting the more likely than not threshold, the amount recognized in the financial statements is the largest benefit that has a greater than 50 percent likelihood of being realized upon ultimate settlement with the relevant tax authority.
Recently Adopted and Issued Accounting Pronouncements	Recently Adopted Accounting Pronouncements Leases— In February 2016, the Financial Accounting Standards Board (“FASB”) issued its new lease accounting guidance in ASU 2016-2, “Leases” (ASC 842). Under the new guidance, lessees are required to recognize all leases (with the exception of short-term leases) on the balance sheet. The Company adopted ASC 842 effective January 1, 2019 using the modified retrospective method. The new guidance has been applied to leases that exist or were entered into on or after January 1, 2019 without adjusting comparative periods in the financial statements. As an accounting policy, the Company has elected not to apply the recognition requirements to short-term leases (leases with terms of 12 months or less). Instead, the Company recognizes the lease payments in the Consolidated Statement of Operations on a straight-line basis over the lease term and variable lease payments in the period in which the obligation for those payments is incurred. The Company has elected to utilize the package of practical expedients that allows entities to not reassess (1) the classification of leases existing at the date of adoption, (2) the initial direct costs for any existing leases, and (3) whether any expired or existing contracts are or contain leases. At January 1, 2019, the Company recorded “Operating lease right-of-use assets”, “Current portion of long-term lease obligations” and “Long-term lease obligations” of $13,600 , $6,200 and $7,400 , respectively on its Consolidated Balance Sheet, related to its existing operating leases. The adoption of this standard did not have a material impact on the Company’s Consolidated Statements of Operations. As of December 31, 2019 , the weighted average remaining lease terms for the Company’s various operating leases extends out over the next 2.5 years . The weighted average discount rate used to determine the present value of the Company’s operating leases’ future payments was approximately 6.0% . Refer to Note 10 - Lease Obligations for further information regarding leases. Recently Issued Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13 to add the guidance in ASC 326 on the impairment of financial instruments. The ASU introduces an impairment model (known as the current expected credit loss (CECL) model) that is based on expected losses rather than incurred losses. Under the new guidance, an entity recognizes as an allowance its estimate of expected credit losses, which the FASB believes will result in more timely recognition of such losses. The ASU is also intended to reduce the complexity of U.S. GAAP by decreasing the number of credit impairment models that entities use to account for debt instruments. The amendments in the ASU are effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. The Company expects to adopt this guidance as required and does not expect a material impact to the Company’s Consolidated Financial Statements.

Plateau Acquisition (Tables)

Plateau Acquisition (Tables)	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Summary of Fair Value Consideration Transferred	Cash consideration transferred, net of $2,425 of cash acquired $ 375,000 Target working capital adjustment 21,323 Equity consideration transferred (1,245 shares at $13.01 per share (1) ) 16,195 Note payable to seller (See Note 9 - Debt) 10,000 Estimated tax basis election 5,141 Total consideration $ 427,659 (1) Sterling’s closing stock price on October 1, 2019
Summary of Preliminary Purchase Price Allocation	The following table summarizes our purchase price allocation at the acquisition closing date, net of cash acquired: Net tangible assets: Accounts receivable, including retainage $ 81,921 Costs and estimated earnings in excess of billings 974 Other current assets 249 Property and equipment, net 65,492 Other non-current assets, net 10 Accounts payable (22,039 ) Billings in excess of costs and estimated earnings (16,540 ) Other current liabilities (7,669 ) Total net tangible assets 102,398 Preliminary identifiable intangible assets 218,600 Goodwill 106,661 Total consideration transferred $ 427,659
Schedule of Identifiable Intangible Assets Acquired	Weighted Average Life (Years) October 2, 2019 Fair Value Customer relationships 25 $ 191,800 Trade name 25 24,800 Non-compete agreements 5 2,000 Total $ 218,600
Summary of Proforma Information	Years Ended December 31, 2019 2018 Pro forma revenue $ 1,358,736 $ 1,326,854 Pro forma net income attributable to Sterling $ 90,408 $ 54,282

Revenue from Customers (Tables)

Revenue from Customers (Tables)	12 Months Ended
	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Schedule of Backlog By Segment	The Company had the following backlog, by segment: December 31, 2019 2018 Heavy Civil Backlog $ 834,049 $ 780,706 Specialty Services Backlog 233,976 70,019 Total Heavy Civil and Specialty Services Backlog $ 1,068,025 $ 850,725
Disaggregation of Revenue	The following tables present the Company’s revenue disaggregated by major end market and contract type: Years Ended December 31, Revenue by major end market 2019 2018 2017 Heavy Highway $ 483,175 $ 513,376 $ 579,157 Aviation 141,371 111,824 77,399 Water Containment and Treatment 65,795 66,928 59,593 Other 69,984 73,510 85,503 Heavy Civil Revenue $ 760,325 $ 765,638 $ 801,652 Land Development $ 84,637 $ — $ — Commercial 128,187 120,333 48,314 Specialty Services Revenue $ 212,824 $ 120,333 $ 48,314 Residential Revenue $ 153,129 $ 151,696 $ 107,992 Revenues $ 1,126,278 $ 1,037,667 $ 957,958 Revenue by contract type Fixed-Unit Price $ 708,638 $ 733,047 $ 755,840 Lump Sum 262,237 146,874 57,823 Residential and Other 155,403 157,746 144,295 Revenues $ 1,126,278 $ 1,037,667 $ 957,958

Consolidated 50% Owned Subsid_2

Consolidated 50% Owned Subsidiaries, including Variable Interest Entities ("VIE") (Tables)	12 Months Ended
	Dec. 31, 2019
Noncontrolling Interest [Abstract]
Schedule of Components of Agreement Obligation	The Company has 50% ownership interests in two subsidiaries (“Myers” and “RHB”) that it fully consolidates as a result of its exercise of control over the entities. The earnings attributable to the 50% portions the Company does not own were $9,800 , $15,100 and $11,500 for 2019 , 2018 and 2017 , respectively, and are eliminated within “Other operating expense, net” in the Consolidated Statements of Operations. Any undistributed earnings for partners are included in “Members’ interest subject to mandatory redemption and undistributed earnings” within the Consolidated Balance Sheets and are mandatorily payable at the time of the noncontrolling owners’ death or permanent disability. The Company has purchased two separate $20,000 death and permanent total disability insurance policies to mitigate the Company’s cash draw if such events were to occur. These two subsidiaries also have individual mandatory redemption provisions which, under circumstances outlined in the partner agreements, are certain to occur and obligate the Company to purchase each partner’s remaining 50% interests for $20,000 ( $40,000 in the aggregate). These purchase obligations are also recorded in “Members’ interest subject to mandatory redemption and undistributed earnings” on the Consolidated Balance Sheets. The liability consists of the following: As of December 31, 2019 2018 Members’ interest subject to mandatory redemption $ 40,000 $ 40,000 Net accumulated earnings 9,003 9,343 Total liability $ 49,003 $ 49,343
Condensed Income Statement	Years Ended December 31, 2019 2018 2017 Revenues $ 205,615 $ 193,677 $ 181,589 Operating income $ 6,372 $ 8,819 $ 9,069 Net income attributable to Sterling common stockholders $ 3,196 $ 4,415 $ 4,531 Years Ended December 31, 2019 2018 2017 Revenues $ 158,291 $ 115,441 $ 93,848 Income before tax $ 20,449 $ 8,097 $ 7,827 Sterling’s noncontrolling interest: Revenues $ 76,419 $ 55,134 $ 44,948 Income before tax $ 8,170 $ 4,104 $ 3,847 Summary financial information for SEMA is as follows: Year Ended December 31, 2019 Revenues $ 6,903 Operating income $ 467 Net income attributable to Sterling common stockholders $ 471

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Liabilities at Fair Value	The following table presents the fair value of the interest rate derivative by valuation hierarchy and balance sheet classification: December 31, 2019 Level 1 Level 2 Level 3 Total Derivative Assets Other current assets $ — $ 216 $ — $ 216 Other non-current assets — — — — Total assets at fair value $ — $ 216 $ — $ 216 Derivative Liabilities Other current liabilities $ — $ (61 ) $ — $ (61 ) Other non-current liabilities — (398 ) — (398 ) Total liabilities at fair value $ — $ (459 ) $ — $ (459 )
Schedule of Derivative Assets at Fair Value	The following table presents the fair value of the interest rate derivative by valuation hierarchy and balance sheet classification: December 31, 2019 Level 1 Level 2 Level 3 Total Derivative Assets Other current assets $ — $ 216 $ — $ 216 Other non-current assets — — — — Total assets at fair value $ — $ 216 $ — $ 216 Derivative Liabilities Other current liabilities $ — $ (61 ) $ — $ (61 ) Other non-current liabilities — (398 ) — (398 ) Total liabilities at fair value $ — $ (459 ) $ — $ (459 )
Schedule of Changes in AOCI	The following table presents the total value recognized in other comprehensive income (“OCI”) and reclassified from AOCI to interest expense during 2019 for derivatives designated as cash flow hedges: Gain (Loss) Recognized in OCI Gain (Loss) Reclassified from AOCI into Earnings (1) Interest rate cash flow hedge (273 ) 30 (1) Net unrealized gains totaling $135 are anticipated to be reclassified from AOCI into interest expense during the next 12 months due to settlement of the associated underlying obligations. AOCI —The following tables presents changes in AOCI, net of tax, and reclassifications of AOCI into earnings, net of tax: Unrealized Fair Value of Swap (Cash Flow Hedge) Balance at December 31, 2018 $ — OCI before reclassifications (186 ) Amounts reclassified from AOCI (23 ) Net OCI (209 ) Balance at December 31, 2019 $ (209 ) Amount Reclassified from AOCI (1) Interest rate derivatives (interest expense) $ (30 ) Tax 7 Total net of tax $ (23 ) (1) See Note 11 - Financial Instruments for further discussion of our cash flow hedges, including the total value reclassified from AOCI to earnings.

Stock Incentive Plan (Tables)

Stock Incentive Plan (Tables)	12 Months Ended
	Dec. 31, 2019
Stockholders' Equity Note [Abstract]
Schedule of Share-based Compensation, Restricted Stock Units Award Activity	Number of Shares Weighted Average Nonvested RSUs Balance at December 31, 2018 217 12.40 Granted 261 12.14 Vested (120 ) 14.30 Forfeited (14 ) 16.14 Balance at December 31, 2019 344 13.78 The following table presents employee and director RSA activity: Number of Shares Weighted Average Employee’s RSAs Balance at December 31, 2018 147 11.16 Granted 52 12.06 Vested (114 ) 11.04 Forfeited (2 ) 9.64 Balance at December 31, 2019 83 11.91 Director’s RSAs Balance at December 31, 2018 42 11.67 Granted 52 12.06 Vested (52 ) $ 11.69 Forfeited — — Balance at December 31, 2019 42 12.12
Schedule of Fair Value Assumptions And Fair Value Ouput of Warrants	The Company valued these Warrants using the Black-Scholes model, which is a type 3 fair value measurement. The key assumptions used in the Black-Scholes Model and fair value output are summarized in the table below: April 3, 2017 Stock price at grant date $ 8.88 Exercise option price $ 10.25 Expected term of warrants (in years) 5 Expected volatility rate 48.29 % Risk-free rate 1.88 % Expected dividend yield — % Total fair value $ 3,500

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Schedule of Changes in AOCI	The following table presents the total value recognized in other comprehensive income (“OCI”) and reclassified from AOCI to interest expense during 2019 for derivatives designated as cash flow hedges: Gain (Loss) Recognized in OCI Gain (Loss) Reclassified from AOCI into Earnings (1) Interest rate cash flow hedge (273 ) 30 (1) Net unrealized gains totaling $135 are anticipated to be reclassified from AOCI into interest expense during the next 12 months due to settlement of the associated underlying obligations. AOCI —The following tables presents changes in AOCI, net of tax, and reclassifications of AOCI into earnings, net of tax: Unrealized Fair Value of Swap (Cash Flow Hedge) Balance at December 31, 2018 $ — OCI before reclassifications (186 ) Amounts reclassified from AOCI (23 ) Net OCI (209 ) Balance at December 31, 2019 $ (209 ) Amount Reclassified from AOCI (1) Interest rate derivatives (interest expense) $ (30 ) Tax 7 Total net of tax $ (23 ) (1) See Note 11 - Financial Instruments for further discussion of our cash flow hedges, including the total value reclassified from AOCI to earnings.

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2019
Supplemental Cash Flow Elements [Abstract]
Schedule of Supplemental Cash Flow	The following table summarizes the changes in the components of operating assets and liabilities: Twelve Months Ended December 31, 2019 2018 2017 Accounts receivable, including retainage $ (21,300 ) $ (11,094 ) $ (29,923 ) Contracts in progress, net 6,023 (4,397 ) (3,492 ) Receivables from and equity in construction joint ventures 1,524 659 (4,250 ) Other current and non-current assets 43 924 929 Accounts payable 10,987 1,969 13,579 Accrued compensation and other liabilities (839 ) (4,038 ) 6,625 Members' interest subject to mandatory redemption and undistributed earnings (340 ) 1,957 2,156 Changes in operating assets and liabilities $ (3,902 ) $ (14,020 ) $ (14,376 )

Construction Joint Ventures (Ta

Construction Joint Ventures (Tables)	12 Months Ended
	Dec. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Change in Non-controlling Interest	The following table summarizes the changes in the noncontrolling owners’ interests in subsidiaries and consolidated joint ventures: Years Ended December 31, 2019 2018 2017 Balance, beginning of period $ 7,859 $ 4,856 $ 656 Net income attributable to noncontrolling interest included in equity 794 4,353 4,200 Distributions to noncontrolling interest owners (7,360 ) (1,350 ) — Balance, end of period $ 1,293 $ 7,859 $ 4,856
Condensed Balance Sheet	Combined financial amounts of joint ventures in which the Company has a noncontrolling interest and the Company’s share of such amounts which are included in the Company’s Consolidated Financial Statements are shown below: As of December 31, 2019 2018 Current assets $ 92,710 $ 64,815 Current liabilities $ (86,705 ) $ (74,543 ) Sterling’s receivables from and equity in construction joint ventures $ 9,196 $ 10,720
Condensed Income Statement	Years Ended December 31, 2019 2018 2017 Revenues $ 205,615 $ 193,677 $ 181,589 Operating income $ 6,372 $ 8,819 $ 9,069 Net income attributable to Sterling common stockholders $ 3,196 $ 4,415 $ 4,531 Years Ended December 31, 2019 2018 2017 Revenues $ 158,291 $ 115,441 $ 93,848 Income before tax $ 20,449 $ 8,097 $ 7,827 Sterling’s noncontrolling interest: Revenues $ 76,419 $ 55,134 $ 44,948 Income before tax $ 8,170 $ 4,104 $ 3,847 Summary financial information for SEMA is as follows: Year Ended December 31, 2019 Revenues $ 6,903 Operating income $ 467 Net income attributable to Sterling common stockholders $ 471

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Summary of Property and Equipment	Property and equipment are summarized as follows: As of December 31, 2019 2018 Construction and transportation equipment $ 217,945 $ 144,630 Buildings and improvements 14,641 11,072 Land 3,891 2,720 Office equipment 2,767 2,711 Total property and equipment 239,244 161,133 Less accumulated depreciation (123,214 ) (109,134 ) Total property and equipment, net $ 116,030 $ 51,999

Goodwill and Other Intangibles

Goodwill and Other Intangibles (Tables)	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The following table presents goodwill by reportable segment: December 31, December 31, Goodwill Heavy Civil $ 54,806 $ 54,806 Specialty Services 106,661 — Residential 30,425 30,425 Total Goodwill $ 191,892 $ 85,231
Schedule of Finite-Lived Intangible Assets	The following table presents our acquired finite-lived intangible assets, including the weighted-average useful lives for each major intangible asset category and in total: December 31, 2019 December 31, 2018 Weighted Gross Gross Customer relationships 25 $ 232,623 $ (6,911 ) $ 40,823 $ (3,159 ) Trade name 23 30,107 (1,692 ) 5,307 (919 ) Non-compete agreements 5 2,487 (291 ) 487 (121 ) Total 24 $ 265,217 $ (8,894 ) $ 46,617 $ (4,199 )

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	The Company’s outstanding debt was as follows: As of December 31, 2019 2018 Credit Facility $ 420,000 $ — Oaktree Facility — 74,571 Note payable to seller, Plateau Acquisition 10,000 — Notes and deferred payments to sellers, Tealstone Acquisition 12,230 13,572 Notes payable for transportation and construction equipment and other 805 612 Total debt 443,035 88,755 Less - Current maturities of long-term debt (42,473 ) (2,899 ) Less - Unamortized debt issuance costs (9,935 ) (6,739 ) Total long-term debt $ 390,627 $ 79,117

Lease Obligations (Tables)

Lease Obligations (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Schedule of Lease Costs	The components of lease expense are as follows: Twelve Months Ended December 31, 2019 Operating lease cost $ 8,594 Short-term lease cost $ 18,032 Finance lease cost: Amortization of right-of-use assets $ 213 Interest on lease liabilities 20 Total finance lease cost $ 233 Supplemental cash flow information related to leases is as follows: Twelve Months Ended December 31, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 8,127 Operating cash flows from finance leases $ 20 Financing cash flows from finance leases $ 213 Right-of-use assets obtained in exchange for lease obligations (non-cash): Operating leases $ 8,955 Finance leases $ 816 Supplemental balance sheet information related to leases was as follows: December 31, 2019 Operating Leases Operating lease right-of-use assets $ 13,979 Current portion of long-term lease obligations $ 7,095 Long-term lease obligations 6,976 Total operating lease liabilities $ 14,071 Finance Leases Property and equipment, at cost $ 1,479 Accumulated depreciation (482 ) Property and equipment, net $ 997 Current maturities of long-term debt $ 204 Long-term debt 560 Total finance lease liabilities $ 764 Weighted Average Remaining Lease Term Operating leases 2.5 Finance leases 4.0 Weighted Average Discount Rate Operating leases 6.0 % Finance leases 4.2 %
Maturities of Finance Lease Liabilities	Maturities of lease liabilities are as follows: Operating Leases Finance Leases Year Ending December 31, 2020 $ 6,813 $ 233 2021 5,180 208 2022 2,858 161 2023 784 154 2024 45 77 Thereafter — — Total lease payments $ 15,680 $ 833 Less imputed interest (1,609 ) (69 ) Total $ 14,071 $ 764
Maturities of Operating Lease Liabilities	Maturities of lease liabilities are as follows: Operating Leases Finance Leases Year Ending December 31, 2020 $ 6,813 $ 233 2021 5,180 208 2022 2,858 161 2023 784 154 2024 45 77 Thereafter — — Total lease payments $ 15,680 $ 833 Less imputed interest (1,609 ) (69 ) Total $ 14,071 $ 764

Income Taxes and Deferred Tax_2

Income Taxes and Deferred Tax Asset/Liability (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit)	Years Ended December 31, 2019 2018 2017 Current tax expense $ 1,182 $ 288 $ 118 Deferred tax (benefit) expense (27,398 ) 1,450 — Income tax (benefit) expense $ (26,216 ) $ 1,738 $ 118
Schedule of Effective Income Tax Rate Reconciliation	Years Ended December 31, 2019 2018 2017 Amount % Amount % Amount % Tax expense (recovery) at the U.S. federal statutory rate $ 3,041 21.0 % $ 6,568 21.0 % $ 5,577 35.0 % State tax based on income, net of refunds and federal benefits 1,670 11.5 364 1.2 (264 ) (1.7 ) Taxes on subsidiaries’ and joint ventures’ earnings allocated to noncontrolling interests owners (2,241 ) (15.5 ) (4,097 ) (13.1 ) (5,504 ) (34.5 ) Valuation allowance (29,375 ) (202.9 ) (1,013 ) (3.3 ) (18,006 ) (113.0 ) Tax credits (397 ) (2.7 ) (286 ) (0.9 ) (349 ) (2.2 ) Tax rate change — — (281 ) (0.9 ) 19,545 122.7 Return to provision 48 0.3 21 0.1 (62 ) (0.4 ) Earn-out liability — — — — 460 2.9 Equity compensation 805 5.6 26 0.1 (1,371 ) (8.6 ) Other permanent differences 233 1.6 436 1.4 92 0.6 Income tax (benefit) expense $ (26,216 ) (181.1 )% $ 1,738 5.6 % $ 118 0.8 %
Schedule of Deferred Tax Assets and Liabilities	The components of deferred tax assets and liabilities were as follows: Long Term As of December 31, 2019 2018 Assets related to: Accrued compensation and other $ 3,981 $ 3,707 Goodwill — — Noncontrolling interests 1,812 1,687 Deferred revenue 922 232 Members interest liabilities 11,328 11,570 Right of use liabilities 3,253 — Net operating loss carryforwards 19,801 22,818 Total deferred tax assets 41,097 40,014 Valuation allowance for deferred tax assets — (31,718 ) Net deferred tax assets $ 41,097 $ 8,296 Liabilities related to: Depreciation of property and equipment (7,911 ) (7,709 ) Right of use assets (3,232 ) — Amortization of tax basis goodwill (3,091 ) (1,450 ) Other (851 ) (587 ) Net deferred tax liabilities $ (15,085 ) $ (9,746 ) Net total deferred tax asset (liability) $ 26,012 $ (1,450 )

Net Income (Loss) Per Share Att

Net Income (Loss) Per Share Attributable to Sterling Common Stockholders (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table reconciles the numerators and denominators of the basic and diluted per common share computations for net income attributable to Sterling common stockholders: Years Ended December 31, Numerator: 2019 2018 2017 Net income attributable to Sterling common stockholders $ 39,901 $ 25,187 $ 11,617 Denominator: Weighted average common shares outstanding — basic 26,671 26,903 26,274 Shares for dilutive unvested stock 448 291 438 Weighted average common shares outstanding and assumed conversions— diluted 27,119 27,194 26,712 Basic net income per share attributable to Sterling common stockholders $ 1.50 $ 0.94 $ 0.44 Diluted net income per share attributable to Sterling common stockholders $ 1.47 $ 0.93 $ 0.43

Retirement Benefits (Tables)

Retirement Benefits (Tables)	12 Months Ended
	Dec. 31, 2019
Defined Benefit Plan [Abstract]
Schedule of Defined Contribution Plan	The following table presents our participation in these plans: Pension Plan Employer Pension Protection Act (“PPA”) Certified Zone Status (1) FIP / RP Status Pending/Implemented (2) Contributions Surcharge Imposed Expiration Date of Collective Bargaining Agreement (3) Pension Trust Fund Identification Number 2019 2018 2019 2018 2017 Pension Trust Fund for Operating Engineers Pension Plan 94-6090764 Yellow Red Yes $ 2,314 $ 1,932 $ 2,477 No Various Laborers Pension Trust for Northern California 94-6277608 Green Yellow Yes 857 880 953 No Various Carpenter Funds Administrative Office 94-6050970 Red Red Yes 547 748 727 No Various Cement Mason Pension Trust Fund For Northern California 94-6277669 Yellow Yellow Yes 320 504 423 No Various All other funds (4) 7,144 7,283 8,006 Total Contributions: $ 11,182 $ 11,347 $ 12,586 (1) The most recent PPA zone status available in 2019 and 2018 is for the plan’s year-end during 2018 and 2017 , respectively. The zone status is based on information that we received from the plan and is certified by the plan’s actuary. Among other factors, plans in the red zone are generally less than 65 percent funded, plans in the orange zone are less than 80 percent funded and have an Accumulated Funding Deficiency in the current year or projected into the next six years, plans in the yellow zone are less than 80 percent funded and plans in the green zone are at least 80 percent funded. (2) Indicates whether the plan has a financial improvement plan (“FIP”) or a rehabilitation plan (“RP”) which is either pending or has been implemented. (3) Lists the expiration date(s) of the collective-bargaining agreement(s) to which the plans are subject. (4) These funds include multi-employer plans for pensions and other employee benefits. The total individually insignificant multi-employer pension costs contributed were $829 , $1,300 and $1,500 for 2019 , 2018 and 2017 , respectively, and are included in the contributions to all other funds along with contributions to other types of benefit plans. Other employee benefits include certain coverage for medical, prescription drug, dental, vision, life and accidental death and dismemberment, disability and other benefit costs.

Concentration of Risk and Ent_2

Concentration of Risk and Enterprise Wide Disclosures (Tables)	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Schedule of Revenue by Major Customers by Reporting Segments	The following table shows contract revenues generated from customers that accounted for more than 10% of the Company’s consolidated revenues: Years Ended December 31, 2019 2018 2017 Amount % Amount % Amount % Utah Department of Transportation (“UDOT”) $ 135,496 12.0 % $ 153,276 14.8 % $ 140,529 14.7 % Texas Department of Transportation (“TXDOT”) * * * * 103,236 10.8 % *Represents less than 10% of revenues

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	The following table presents total revenue, depreciation and amortization, and income from operations by reportable segment for the years ended December 31, 2019 , 2018 and 2017 : Years Ended December 31, 2019 2018 2017 Revenue Heavy Civil $ 760,325 $ 765,638 $ 801,652 Specialty Services 212,824 120,333 48,314 Residential 153,129 151,696 107,992 Total Revenue $ 1,126,278 $ 1,037,667 $ 957,958 Depreciation and Amortization Heavy Civil $ 12,839 $ 13,492 $ 14,789 Specialty Services 6,059 1,439 815 Residential 1,842 1,839 1,390 Total Depreciation and Amortization $ 20,740 $ 16,770 $ 16,994 Operating Income Heavy Civil $ 3,316 $ 17,044 $ 8,246 Specialty Services 18,207 4,629 2,284 Residential 20,539 20,938 15,646 Subtotal 42,062 42,611 26,176 Acquisition related costs (4,311 ) — — Total Operating Income $ 37,751 $ 42,611 $ 26,176 The following table presents total assets by reportable segment at December 31, 2019 and 2018 : December 31, December 31, Assets Heavy Civil $ 287,779 $ 318,586 Specialty Services 587,642 76,170 Residential 86,519 87,817 Total Assets $ 961,940 $ 482,573

Quarterly Financial Informati_2

Quarterly Financial Information (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information	The following table summarizes the unaudited quarterly results of operations for 2019 and 2018 : 2019 Quarters Ended (unaudited) March 31 June 30 September 30 December 31 Revenues $ 223,949 $ 264,086 $ 291,699 $ 346,544 Gross profit 19,503 25,496 29,216 33,579 Income (loss) before income taxes 2,024 8,571 9,422 (5,538 ) Net income attributable to Sterling common stockholders $ 1,815 $ 7,828 $ 7,957 $ 22,301 Net income per share attributable to Sterling common stockholders: Basic $ 0.07 $ 0.30 $ 0.30 $ 0.81 Diluted $ 0.07 $ 0.29 $ 0.30 $ 0.79 2018 Quarters Ended (unaudited) March 31 June 30 September 30 December 31 Revenues $ 222,492 $ 268,734 $ 291,266 $ 255,175 Gross profit $ 19,834 $ 31,046 $ 31,279 $ 28,173 Income before income taxes $ 3,721 $ 9,238 $ 11,581 $ 6,738 Net income attributable to Sterling common stockholders $ 2,489 $ 8,174 $ 8,917 $ 5,607 Net income per share attributable to Sterling common stockholders: Basic $ 0.09 $ 0.30 $ 0.33 $ 0.22 Diluted $ 0.09 $ 0.30 $ 0.33 $ 0.21 The following tables represent our 2019 and 2018 quarterly revenue and income from operations adjusted to reflect our operating group realignment and to conform to our 2019 presentation: 2019 Quarters Ended (unaudited) March 31 June 30 September 30 December 31 Total Revenue Heavy Civil $ 150,505 $ 200,236 $ 218,894 $ 190,690 $ 760,325 Specialty Services 30,679 27,894 32,863 121,388 212,824 Residential 42,765 35,956 39,942 34,466 153,129 Total Revenue $ 223,949 $ 264,086 $ 291,699 $ 346,544 $ 1,126,278 Operating Income Heavy Civil $ (2,147 ) $ 5,747 $ 7,420 $ (7,704 ) $ 3,316 Specialty Services 1,048 865 1,371 14,923 18,207 Residential 5,819 4,834 5,220 4,666 20,539 Subtotal 4,720 11,446 14,011 11,885 42,062 Acquisition related costs — (262 ) (1,896 ) (2,153 ) (4,311 ) Total Operating Income $ 4,720 $ 11,184 $ 12,115 $ 9,732 $ 37,751 2018 Quarters Ended (unaudited) March 31 June 30 September 30 December 31 Total Revenue Heavy Civil $ 158,722 $ 194,174 $ 222,299 $ 190,443 $ 765,638 Specialty Services 28,519 29,109 32,245 30,460 120,333 Residential 35,251 45,451 36,722 34,272 151,696 Total Revenue $ 222,492 $ 268,734 $ 291,266 $ 255,175 $ 1,037,667 Operating Income Heavy Civil $ 1,092 $ 4,322 $ 7,385 $ 4,245 $ 17,044 Specialty Services 519 1,480 1,647 983 4,629 Residential 5,068 6,347 5,341 4,182 20,938 Total Operating Income $ 6,679 $ 12,149 $ 14,373 $ 9,410 $ 42,611

Summary of Business and Signi_3

Summary of Business and Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
Consolidated ownership percentage	50.00%
Contract receivable retainage	$ 79,400		$ 47,400
Retainage rate	75.00%
Operating lease right-of-use assets	$ 13,979	$ 13,600
Operating lease liability, current	7,095	6,200
Operating lease liability, noncurrent	$ 6,976	$ 7,400
Operating leases	2 years 6 months 7 days
Operating leases	6.00%
Other Current Assets
Financing Receivable, Impaired [Line Items]
Restricted cash	$ 4,800		$ 3,900
Building and improvements | Minimum
Financing Receivable, Impaired [Line Items]
Property, plant and equipment, useful life	5 years
Building and improvements | Maximum
Financing Receivable, Impaired [Line Items]
Property, plant and equipment, useful life	39 years
Plant and field equipment | Minimum
Financing Receivable, Impaired [Line Items]
Property, plant and equipment, useful life	5 years
Plant and field equipment | Maximum
Financing Receivable, Impaired [Line Items]
Property, plant and equipment, useful life	20 years
Heavy Civil Construction | Minimum
Financing Receivable, Impaired [Line Items]
Revenue recognition, percentage of completion range	12 months
Heavy Civil Construction | Maximum
Financing Receivable, Impaired [Line Items]
Revenue recognition, percentage of completion range	36 months
Specialty Service | Minimum
Financing Receivable, Impaired [Line Items]
Revenue recognition, percentage of completion range	6 months
Specialty Service | Maximum
Financing Receivable, Impaired [Line Items]
Revenue recognition, percentage of completion range	24 months

Plateau Acquisition - Narrative

Plateau Acquisition - Narrative (Details) - USD ($) $ in Thousands	Oct. 02, 2019	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill		$ 191,892	$ 85,231
Backlog		1,068,025	$ 850,725
Plateau
Business Acquisition [Line Items]
Total consideration	$ 427,659
Goodwill	106,661
Backlog	$ 159,000
Revenue of acquiree since acquisition date, actual		84,637
Earnings of acquiree since acquisition date, actual		$ 10,921

Plateau Acquisition - Considera

Plateau Acquisition - Consideration Transferred and Purchase Price Allocation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	Oct. 02, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Oct. 01, 2019
Business Combination, Consideration Transferred [Abstract]
Share consideration given for acquisitions		$ 16,195	$ 0	$ 17,601
Estimated tax basis election	$ 5,141		0	$ 0
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Goodwill		$ 191,892	$ 85,231
Plateau
Business Combination, Consideration Transferred [Abstract]
Cash consideration transferred, net of $2,425 of cash acquired	375,000
Target working capital adjustment	21,323
Share consideration given for acquisitions	16,195
Sellers Note	10,000
Estimated tax basis election	5,141
Total consideration	427,659
Cash acquired	$ 2,425
Shares issued in acquisition of business (in shares)	1,245
Business acquisition share price					$ 13.01
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Accounts receivable, including retainage	$ 81,921
Costs and estimated earnings in excess of billings	974
Other current assets	249
Property and equipment, net	65,492
Other non-current assets, net	10
Accounts payable	(22,039)
Billings in excess of costs and estimated earnings	(16,540)
Other current liabilities	(7,669)
Total net tangible assets	102,398
Preliminary identifiable intangible assets	218,600
Goodwill	106,661
Total consideration transferred	$ 427,659

Plateau Acquisition Plateau Acq

Plateau Acquisition Plateau Acquisition - Schedule of Identifiable Intangible Assets (Details) - USD ($) $ in Thousands	Oct. 02, 2019	Dec. 31, 2019
Acquired Indefinite-lived Intangible Assets [Line Items]
Weighted Average Life		24 years
Plateau
Acquired Indefinite-lived Intangible Assets [Line Items]
October 2, 2019 Fair Value	$ 218,600
Customer relationships
Acquired Indefinite-lived Intangible Assets [Line Items]
Weighted Average Life		25 years
Customer relationships | Plateau
Acquired Indefinite-lived Intangible Assets [Line Items]
Weighted Average Life	25 years
October 2, 2019 Fair Value	$ 191,800
Trade name
Acquired Indefinite-lived Intangible Assets [Line Items]
Weighted Average Life		23 years
Trade name | Plateau
Acquired Indefinite-lived Intangible Assets [Line Items]
Weighted Average Life	25 years
October 2, 2019 Fair Value	$ 24,800
Noncompetition agreements
Acquired Indefinite-lived Intangible Assets [Line Items]
Weighted Average Life		5 years
Noncompetition agreements | Plateau
Acquired Indefinite-lived Intangible Assets [Line Items]
Weighted Average Life	5 years
October 2, 2019 Fair Value	$ 2,000

Plateau Acquisition - Supplemen

Plateau Acquisition - Supplemental Pro Forma Information (Details) - Plateau - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Pro forma revenue	$ 1,358,736	$ 1,326,854
Pro forma net loss attributable to Sterling	$ 90,408	$ 54,282

Revenue from Customers Revenue

Revenue from Customers Revenue from Customers - Backlog By Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Backlog	$ 1,068,025	$ 850,725
Heavy Civil Construction
Segment Reporting Information [Line Items]
Backlog	834,049	780,706
Specialty Service
Segment Reporting Information [Line Items]
Backlog	$ 233,976	$ 70,019

Revenue from Customers - Narrat

Revenue from Customers - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Remaining performance obligation, percentage	70.00%	70.00%
Recovery of construction costs	$ 17,000
Increase (decrease) in construction costs	10,200
Operating income (Loss)
Disaggregation of Revenue [Line Items]
Estimated construction gain (loss) before tax		$ (9,044)	$ 7,098	$ 923
Costs and Estimated Earnings in Excess of Billings
Disaggregation of Revenue [Line Items]
Provision for estimated loss on uncompleted contracts	$ 3,000	$ 3,000	$ 9,300

Revenue from Customers - Revenu

Revenue from Customers - Revenue Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 346,544	$ 291,699	$ 264,086	$ 223,949	$ 255,175	$ 291,266	$ 268,734	$ 222,492	$ 1,126,278	$ 1,037,667	$ 957,958
Heavy Civil Construction
Disaggregation of Revenue [Line Items]
Revenues	190,690	218,894	200,236	150,505	190,443	222,299	194,174	158,722	760,325	765,638	801,652
Heavy Civil Construction | Heavy Highway
Disaggregation of Revenue [Line Items]
Revenues									483,175	513,376	579,157
Heavy Civil Construction | Aviation
Disaggregation of Revenue [Line Items]
Revenues									141,371	111,824	77,399
Heavy Civil Construction | Water Containment and Treatment
Disaggregation of Revenue [Line Items]
Revenues									65,795	66,928	59,593
Heavy Civil Construction | Other Revenue
Disaggregation of Revenue [Line Items]
Revenues									69,984	73,510	85,503
Specialty Service
Disaggregation of Revenue [Line Items]
Revenues	121,388	32,863	27,894	30,679	30,460	32,245	29,109	28,519	212,824	120,333	48,314
Specialty Service | Land Development
Disaggregation of Revenue [Line Items]
Revenues									84,637	0	0
Specialty Service | Commercial
Disaggregation of Revenue [Line Items]
Revenues									128,187	120,333	48,314
Residential
Disaggregation of Revenue [Line Items]
Revenues	$ 34,466	$ 39,942	$ 35,956	$ 42,765	$ 34,272	$ 36,722	$ 45,451	$ 35,251	153,129	151,696	107,992
Fixed Unit Price
Disaggregation of Revenue [Line Items]
Revenues									708,638	733,047	755,840
Lump Sum
Disaggregation of Revenue [Line Items]
Revenues									262,237	146,874	57,823
Residential And Other
Disaggregation of Revenue [Line Items]
Revenues									$ 155,403	$ 157,746	$ 144,295

Revenue from Customers - Additi

Revenue from Customers - Additional Information (Details)	Dec. 31, 2019
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Disaggregation of Revenue [Line Items]
Expected timing of satisfaction	12 months

Consolidated 50% Owned Subsid_3

Consolidated 50% Owned Subsidiaries, including Variable Interest Entities ("VIE") - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)entity	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Noncontrolling Interest [Line Items]
Consolidated ownership percentage	50.00%
Death and permanent total disability insurance policies, per policy	$ 20,000
Members’ interest subject to mandatory redemption	$ 40,000	$ 40,000
Consolidated 50% owned subsidiaries, number of entities | entity	2
Myers
Noncontrolling Interest [Line Items]
Earnings from consolidated 50% owned subsidiaries	$ 9,800	$ 15,100	$ 11,500
Variable Interest Entity, Primary Beneficiary | Myers
Noncontrolling Interest [Line Items]
Members’ interest subject to mandatory redemption	$ 20,000

Financial Instruments - Narrati

Financial Instruments - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 05, 2019	Oct. 02, 2019
Interest Rate Swap
Derivative [Line Items]
Unrealized gain (loss) on derivatives	$ (243,000)
Secured Debt | Interest Rate Swap
Derivative [Line Items]
Derivative notional amount	$ 350,000,000	$ 350,000,000
Term Loan Facility | Revolving Credit Facility | Secured Debt
Derivative [Line Items]
Debt instrument, face amount			$ 400,000,000

Stock Incentive Plan - Narrativ

Stock Incentive Plan - Narrative (Details) - USD ($)	Apr. 03, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Subsidiary, Sale of Stock [Line Items]
Value of shares witheld for taxes		$ 1,109,000	$ 452,000
PSUs
Subsidiary, Sale of Stock [Line Items]
Total compensation cost attributable to shares awarded		$ 1,096,000
Share vesting period		3 years
Grants in the period (in shares)		310,000	890,000
Grants in the period (USD per share)		$ 11.81	$ 11.64	$ 0
Vested (in shares)		63,000	0	0
Vested (in usd per share)		$ 15.15
Fair value of shares vested in period		$ 948,000
RSUs
Subsidiary, Sale of Stock [Line Items]
Total compensation cost attributable to shares awarded		$ 1,573,000
Share vesting period		3 years
Grants in the period (in shares)		261,000	248,000	0
Grants in the period (USD per share)		$ 12.14	$ 16.08
Vested (in shares)		120,000		0
Vested (in usd per share)		$ 14.30
Fair value of shares vested in period		$ 1,709,000	$ 392,000	$ 0
RSAs
Subsidiary, Sale of Stock [Line Items]
Total compensation cost attributable to shares awarded		$ 1,092,000
Share vesting period		3 years
Grants in the period (in shares)			49,000	217,000
Grants in the period (USD per share)			$ 11.64	$ 10.69
Fair value of shares vested in period		$ 1,261,000	$ 1,107,000	$ 3,117,000
Shares withheld for taxes (in shares)		17,000	28,000	66,000
Value of shares witheld for taxes		$ 255,000	$ 361,000	$ 1,075,000
RSAs | Non Employee Director
Subsidiary, Sale of Stock [Line Items]
Grants in the period (in shares)		52,000
Grants in the period (USD per share)		$ 12.06
Vested (in shares)		52,000
Vested (in usd per share)		$ 11.69
Restricted Stock Units And Performance Stock Units
Subsidiary, Sale of Stock [Line Items]
Shares withheld for taxes (in shares)		74,000	8,000	0
Value of shares witheld for taxes		$ 964,000	$ 92,000
Warrants to the Lenders Under the Loan Agreement | Loan and Security Agreement
Subsidiary, Sale of Stock [Line Items]
Warrants, term	5 years
Warrant exercise price (USD per share)	$ 10.25
Number of warrants	1,000,000
Stock Incentive Plan
Subsidiary, Sale of Stock [Line Items]
Total compensation cost attributable to shares awarded		$ 3,788,000	3,064,000	$ 2,843,000
Number of shares available for grant (in shares)		133,000
Unrecognized compensation cost		$ 16,300,000
Weighted-average recognition period		3 years 2 months 12 days
Stock Incentive Plan | RSAs, RSUs and PSUs
Subsidiary, Sale of Stock [Line Items]
Total compensation cost attributable to shares awarded		$ 3,761,000	$ 3,064,000	$ 2,843,000
ESPP | Employee Stock
Subsidiary, Sale of Stock [Line Items]
Total compensation cost attributable to shares awarded		$ 27,000
Number of shares available for grant (in shares)		787,000
Maximum annual contribution per employee		15.00%
Maximum annual contribution amount		$ 25,000
Purchase price of common stock percent		85.00%

Stockholders' Equity - Narrativ

Stockholders' Equity - Narrative (Details) $ in Thousands	Oct. 02, 2019USD ($)shares	Apr. 03, 2017USD ($)shares	Dec. 31, 2019USD ($)voteshares	Dec. 31, 2018USD ($)shares	Dec. 31, 2017USD ($)	Nov. 02, 2018shares
Accumulated Other Comprehensive Income (Loss) [Line Items]
Share consideration given for acquisitions | $			$ 16,195	$ 0	$ 17,601
Common Stock
Accumulated Other Comprehensive Income (Loss) [Line Items]
Common stock, votes entitled per share | vote			1
Stock Repurchase Program, Number of Shares Authorized to be Repurchased						2,000,000
Stock repurchased			250,000	467,000
Plateau
Accumulated Other Comprehensive Income (Loss) [Line Items]
Shares issued in acquisition of business (in shares)	1,245,000
Share consideration given for acquisitions | $	$ 16,195
Tealstone
Accumulated Other Comprehensive Income (Loss) [Line Items]
Shares issued in acquisition of business (in shares)		1,882,000
Share consideration given for acquisitions | $		$ 17,061

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Accounts receivable, including retainage	$ (21,300)
Accounts receivable, including retainage		$ (11,094)	$ (29,923)
Contracts in progress, net	6,023	(4,397)	(3,492)
Receivables from and equity in construction joint ventures	1,524	659	(4,250)
Other current and non-current assets	43	924	929
Accounts payable	10,987	1,969	13,579
Accrued compensation and other liabilities	(839)	(4,038)	6,625
Members' interest subject to mandatory redemption and undistributed earnings	(340)	1,957	2,156
Changes in operating assets and liabilities	$ 3,902	$ 14,020	$ 14,376

Consolidated 50% Owned Subsid_4

Consolidated 50% Owned Subsidiaries, including Variable Interest Entities ("VIE") - Components of Noncontrolling Interest Subject to Mandatory Redemption (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Noncontrolling Interest [Abstract]
Members’ interest subject to mandatory redemption	$ 40,000	$ 40,000
Net accumulated earnings	9,003	9,343
Total liability	$ 49,003	$ 49,343

Financial Instruments - Fair Va

Financial Instruments - Fair Value of the Interest Rate Derivative (Details) - Fair Value, Recurring - Interest Rate Swap	Dec. 31, 2019USD ($)
Derivative Assets
Other current assets	$ 216,000
Other non-current assets	0
Total assets at fair value	216,000
Derivative Liability [Abstract]
Other current liabilities	(61,000)
Other non-current liabilities	(398,000)
Total liabilities at fair value	459,000
Level 1
Derivative Assets
Other current assets	0
Other non-current assets	0
Total assets at fair value	0
Derivative Liability [Abstract]
Other current liabilities	0
Other non-current liabilities	0
Total liabilities at fair value	0
Level 2
Derivative Assets
Other current assets	216,000
Other non-current assets	0
Total assets at fair value	216,000
Derivative Liability [Abstract]
Other current liabilities	(61,000)
Other non-current liabilities	(398,000)
Total liabilities at fair value	459,000
Level 3
Derivative Assets
Other current assets	0
Other non-current assets	0
Total assets at fair value	0
Derivative Liability [Abstract]
Other current liabilities	0
Other non-current liabilities	0
Total liabilities at fair value	$ 0

Stock Incentive Plan - Summary

Stock Incentive Plan - Summary of Award Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
RSAs
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted (in shares)		49,000	217,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Granted (in usd per share)		$ 11.64	$ 10.69
RSAs | Employee
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested (in shares)	147,000
Granted (in shares)	52,000
Vested (in shares)	(114,000)
Forfeited (in shares)	(2,000)
Nonvested (in shares)	83,000	147,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Nonvested (in usd per share)	$ 11.16
Granted (in usd per share)	12.06
Vested (in usd per share)	11.04
Forfeited (in usd per share)	9.64
Nonvested (in usd per share)	$ 11.91	$ 11.16
RSAs | Non Employee Director
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested (in shares)	42,000
Granted (in shares)	52,000
Vested (in shares)	(52,000)
Forfeited (in shares)	0
Nonvested (in shares)	42,000	42,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Nonvested (in usd per share)	$ 11.67
Granted (in usd per share)	12.06
Vested (in usd per share)	11.69
Forfeited (in usd per share)	0
Nonvested (in usd per share)	$ 12.12	$ 11.67
RSUs
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested (in shares)	217,000
Granted (in shares)	261,000	248,000	0
Vested (in shares)	(120,000)		0
Forfeited (in shares)	(14,000)
Nonvested (in shares)	344,000	217,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Nonvested (in usd per share)	$ 12.40
Granted (in usd per share)	12.14	$ 16.08
Vested (in usd per share)	14.30
Forfeited (in usd per share)	16.14
Nonvested (in usd per share)	$ 13.78	$ 12.40

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Changes in AOCI and Reclassifications from AOCI to Earnings (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	$ 172,260	$ 146,189	$ 108,090
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Net OCI	(209)
Balance	221,211	172,260	146,189
Income Tax Expense (Benefit)	(26,216)	1,738	118
Net income	40,695	29,540	$ 15,817
Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance	0
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
OCI before reclassifications	(186)
Amounts reclassified from AOCI	23
Net OCI	(209)
Balance	(209)	$ 0
Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest | Reclassification out of Accumulated Other Comprehensive Income
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Interest Expense	30
Income Tax Expense (Benefit)	7
Net income	$ (23)

Consolidated 50% Owned Subsid_5

Consolidated 50% Owned Subsidiaries, including Variable Interest Entities ("VIE") - Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Operating income	$ 9,732	$ 12,115	$ 11,184	$ 4,720	$ 9,410	$ 14,373	$ 12,149	$ 6,679	$ 37,751	$ 42,611	$ 26,176
Net income attributable to Sterling common stockholders	$ 22,301	$ 7,957	$ 7,828	$ 1,815	$ 5,607	$ 8,917	$ 8,174	$ 2,489	39,901	25,187	11,617
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Revenues									205,615	193,677	181,589
Operating income									6,372	8,819	9,069
Net income attributable to Sterling common stockholders									$ 3,196	$ 4,415	$ 4,531

Financial Instruments - Schedul

Financial Instruments - Schedule of Total Value Recognized in Other Comprehensive Income (Details) - Interest Rate Swap $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) Recognized in OCI	$ (273)
Interest Expense
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) Reclassified from AOCI into Earnings	30
Net unrealized gains anticipated to be reclassified within twelve months	$ 135

Stock Incentive Plan - Fair Val

Stock Incentive Plan - Fair Value Assumptions (Details) - Level 3 - Fair Value, Recurring - Warrants to the Lenders Under the Loan Agreement	Apr. 03, 2017USD ($)$ / shares
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Expected term of warrants (in years)	5 years
Total fair value | $	$ 3,500,000
Stock price at grant date
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants outstanding, measurement input	8.88
Exercise option price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants outstanding, measurement input	10.25
Expected volatility rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants outstanding, measurement input	0.4829
Risk-free rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants outstanding, measurement input	0.0188
Expected dividend yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants outstanding, measurement input	0

Construction Joint Ventures - C

Construction Joint Ventures - Change in Non-controlling Interest (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Balance, beginning of period	$ 7,859	$ 4,856	$ 656
Net income attributable to noncontrolling interest included in equity	794	4,353	4,200
Distributions to noncontrolling interest owners	(7,360)	(1,350)	0
Balance, end of period	$ 1,293	$ 7,859	$ 4,856

Construction Joint Ventures - S

Construction Joint Ventures - SEMA Financials (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Revenues	$ 346,544	$ 291,699	$ 264,086	$ 223,949	$ 255,175	$ 291,266	$ 268,734	$ 222,492	$ 1,126,278	$ 1,037,667	$ 957,958
Operating income	9,732	12,115	11,184	4,720	9,410	14,373	12,149	6,679	37,751	42,611	26,176
Net income attributable to Sterling common stockholders	$ 22,301	$ 7,957	$ 7,828	$ 1,815	$ 5,607	$ 8,917	$ 8,174	$ 2,489	$ 39,901	$ 25,187	$ 11,617
RLW | Joint Ventures
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	51.00%								51.00%
SEMA Construction Inc | Joint Ventures
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	49.00%								49.00%
Revenues									$ 6,903
Operating income									467
Net income attributable to Sterling common stockholders									$ 471

Construction Joint Ventures -_2

Construction Joint Ventures - Construction Joint Ventures, Partner Share (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Current assets	$ 357,521	$ 302,616
Current liabilities	(293,504)	(179,174)
Sterling’s receivables from and equity in construction joint ventures	9,196	10,720
Joint Ventures
Schedule of Equity Method Investments [Line Items]
Current assets	92,710	64,815
Current liabilities	(86,705)	(74,543)
Sterling’s receivables from and equity in construction joint ventures	$ 9,196	$ 10,720

Construction Joint Ventures -_3

Construction Joint Ventures - Construction Joint Ventures, Partner Income (Details) - Joint Ventures - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Revenues	$ 158,291	$ 115,441	$ 93,848
Income before tax	20,449	8,097	7,827
Sterling's noncontrolling interest, revenue	76,419	55,134	44,948
Sterling noncontrolling interest, Income before tax	$ 8,170	$ 4,104	$ 3,847

Property and Equipment - Summar

Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 239,244	$ 161,133
Less accumulated depreciation	(123,214)	(109,134)
Property and equipment, net	116,030	51,999
Construction and transportation equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	217,945	144,630
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	14,641	11,072
Land
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,891	2,720
Office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 2,767	$ 2,711

Property and Equipment - Narrat

Property and Equipment - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Depreciation	$ 15.9	$ 14.2	$ 15.1

Goodwill and Other Intangbiles

Goodwill and Other Intangbiles Summary of Goodwill By Segments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Line Items]
Goodwill	$ 191,892	$ 85,231
Heavy Civil Construction
Goodwill [Line Items]
Goodwill	54,806	54,806
Specialty Service
Goodwill [Line Items]
Goodwill	106,661	0
Residential
Goodwill [Line Items]
Goodwill	$ 30,425	$ 30,425

Goodwill and Other Intangbile_2

Goodwill and Other Intangbiles - Summary of Finite Lived Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	24 years
Gross Carrying Amount	$ 265,217	$ 46,617
Accumulated Amortization	$ (8,894)	(4,199)
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	25 years
Gross Carrying Amount	$ 232,623	40,823
Accumulated Amortization	$ (6,911)	(3,159)
Trade name
Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	23 years
Gross Carrying Amount	$ 30,107	5,307
Accumulated Amortization	$ (1,692)	(919)
Noncompetition agreements
Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	5 years
Gross Carrying Amount	$ 2,487	487
Accumulated Amortization	$ (291)	$ (121)

Goodwill and Other Intangbile_3

Goodwill and Other Intangbiles - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 191,892	$ 85,231
Amortization of intangible assets	4,695	$ 2,400	$ 1,799
Amortization, 2020	11,464
Amortization, 2021	11,464
Amortization, 2022	11,272
Amortization, 2023	11,208
Amortization, 2024	$ 10,897

Debt - Long-term Debt (Details)

Debt - Long-term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Gross long-term debt	$ 443,035	$ 88,755
Less - Current maturities of long-term debt	(42,473)	(2,899)
Less - Unamortized debt issuance costs	(9,935)	(6,739)
Total long-term debt	390,627	79,117
Secured Debt | Credit Facility
Debt Instrument [Line Items]
Gross long-term debt	420,000	0
Secured Debt | Oaktree Facility
Debt Instrument [Line Items]
Gross long-term debt	0	74,571
Notes Payable | Plateau
Debt Instrument [Line Items]
Gross long-term debt	10,000	0
Notes Payable | Tealstone
Debt Instrument [Line Items]
Gross long-term debt		13,572
Notes Payable | Notes Payable for Transportation and Construction Equipment
Debt Instrument [Line Items]
Gross long-term debt	$ 805	$ 612

Debt - Narrative (Details)

Debt - Narrative (Details)	Oct. 02, 2019USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2024USD ($)	Dec. 31, 2023USD ($)	Dec. 31, 2022USD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 05, 2019USD ($)
Debt Instrument [Line Items]
Gross long-term debt		$ 443,035,000						$ 443,035,000	$ 88,755,000
Loss on extinguishment of debt								7,728,000	0	$ 755,000
Plateau
Debt Instrument [Line Items]
Liabilities incurred	$ 10,000,000
Tealstone
Debt Instrument [Line Items]
Deferred payments								2,400,000
Promissory notes issued to the sellers								5,000,000
Deferred cash payments due		$ 7,500,000						7,500,000
Accretion expense								1,100,000	1,200,000
Credit Facility
Debt Instrument [Line Items]
Fess related to establishment of debt								10,688,000
Oaktree Facility
Debt Instrument [Line Items]
Write off of unamortized debt issuance costs								4,334,000
Secured Debt
Debt Instrument [Line Items]
Fixed charge ratio minimum		1.2
Secured Debt | Interest Rate Swap
Debt Instrument [Line Items]
Derivative notional amount		$ 350,000,000						350,000,000			$ 350,000,000
Secured Debt | Credit Facility
Debt Instrument [Line Items]
Gross long-term debt		$ 420,000,000						$ 420,000,000	0
Secured Debt | Credit Agreement
Debt Instrument [Line Items]
Debt instrument, face amount	475,000,000
Secured Debt | Credit Agreement | October 1, 2019 - June 30, 2020
Debt Instrument [Line Items]
Leverage ratio maximum								4
Secured Debt | Credit Agreement | July 1, 2020 - September 30, 2020
Debt Instrument [Line Items]
Leverage ratio maximum								3.75
Secured Debt | Credit Agreement | October 1, 2020 - March 31, 2021
Debt Instrument [Line Items]
Leverage ratio maximum								3.5
Secured Debt | Credit Agreement | April 1, 2021 - June 30, 2021
Debt Instrument [Line Items]
Leverage ratio maximum								3.25
Secured Debt | Credit Agreement | October 1, 2021 - December 31, 2021
Debt Instrument [Line Items]
Leverage ratio maximum								3
Secured Debt | Term Loan Facility
Debt Instrument [Line Items]
Weighted average interest rate		5.70%						5.70%
Total debt		$ 400,000,000						$ 400,000,000
Secured Debt | Term Loan Facility | Forecast
Debt Instrument [Line Items]
Periodic payments			$ 220,000,000	$ 50,000,000	$ 50,000,000	$ 50,000,000	$ 30,000,000
Secured Debt | Term Loan Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, face amount	400,000,000
Secured Debt | Oaktree Facility
Debt Instrument [Line Items]
Gross long-term debt		0						$ 0	74,571,000
Line of Credit | the Revolving Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit, maximum borrowing capacity	75,000,000
Debt instrument, base interest rate								4.75%
Debt instrument, LIBOR interest rate								1.74%
Line of credit, remaining borrowing capacity		$ 55,000,000						$ 55,000,000
Weighted average interest rate		5.73%						5.73%
Total debt		$ 20,000,000						$ 20,000,000
Line of Credit | the Revolving Credit Facility | Revolving Credit Facility | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate								3.50%
Line of Credit | the Revolving Credit Facility | Revolving Credit Facility | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate								4.50%
Line of Credit | the Revolving Credit Facility | Swing Line Loan
Debt Instrument [Line Items]
Line of credit, maximum borrowing capacity	15,000,000
Senior Secured Term Loans | Loan and Security Agreement
Debt Instrument [Line Items]
Debt instrument, face amount	85,000,000
Senior Secured Term Loans | Oaktree Facility
Debt Instrument [Line Items]
Repayments of debt	$ 67,100,000
Loss on extinguishment of debt								$ 7,728,000
Debt extinguishment costs, prepayment premium								$ 3,394,000
Debt extinguishment costs, percentage of principal								5.00%
Senior Secured Term Loans | Oaktree Facility | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate	8.75%
Notes Payable | Plateau
Debt Instrument [Line Items]
Stated interest rate	8.00%
Liabilities incurred	$ 10,000,000
Notes Payable | Tealstone
Debt Instrument [Line Items]
Total debt		12,230,000						$ 12,230,000
Notes Payable | Notes Payable for Transportation and Construction Equipment
Debt Instrument [Line Items]
Gross long-term debt		$ 805,000						$ 805,000	$ 612,000
Notes Payable | Notes Payable for Transportation and Construction Equipment | Minimum
Debt Instrument [Line Items]
Stated interest rate		2.99%						2.99%
Debt instrument, term								3 years
Notes Payable | Notes Payable for Transportation and Construction Equipment | Maximum
Debt Instrument [Line Items]
Stated interest rate		6.92%						6.92%
Debt instrument, term								5 years

Lease Obligations (Details)

Lease Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Jan. 01, 2019
Lessee, Lease, Description [Line Items]
Lease termination period	10 years
Lease, Cost [Abstract]
Operating lease cost	$ 8,594
Short-term lease cost	18,032
Finance lease cost:
Amortization of right-of-use assets	213
Interest on lease liabilities	20
Total finance lease cost	233
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	8,127
Operating cash flows from finance leases	20
Financing cash flows from finance leases	213
Right-of-use assets obtained in exchange for lease obligations (non-cash):
Operating leases	8,955
Finance leases	816
Assets and Liabilities, Lessee [Abstract]
Operating lease right-of-use assets	13,979	$ 13,600
Current portion of long-term lease obligations ($1,838 and $0 related to VIEs)	7,095	6,200
Long-term lease obligations ($1,979 and $0 related to VIEs)	6,976	$ 7,400
Total operating lease liabilities	14,071
Property and equipment, at cost	1,479
Accumulated depreciation	(482)
Property and equipment, net	997
Current maturities of long-term debt	204
Long-term debt	560
Total finance lease liabilities	$ 764
Operating leases	2 years 6 months 7 days
Finance leases	4 years 11 days
Operating leases	6.00%
Finance leases	4.20%
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2020	$ 6,813
2021	5,180
2022	2,858
2023	784
2024	45
Thereafter	0
Total lease payments	15,680
Less imputed interest	1,609
Total operating lease liabilities	14,071
Finance Lease, Liability, Payment, Due [Abstract]
2020	233
2021	208
2022	161
2023	154
2024	77
Thereafter	0
Total lease payments	833
Less imputed interest	69
Total finance lease liabilities	$ 764
Minimum
Lessee, Lease, Description [Line Items]
Lease renewal term	1 month
Maximum
Lessee, Lease, Description [Line Items]
Lease renewal term	5 years

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Claim amounts that affect ultimate liability	$ 25,000
Payments for general liability per occurrence	275,000
Maximum liability	4,000,000
Commercial insurance coverage	75,000,000
Minimum
Loss Contingencies [Line Items]
Payments for workers compensation per occurrence	2,000
Maximum
Loss Contingencies [Line Items]
Payments for workers compensation per occurrence	250,000
JBC Former Owners
Loss Contingencies [Line Items]
Earn-out expense			$ 1,300,000
Tealstone
Loss Contingencies [Line Items]
Earn-out expense	2,000,000	$ 1,900,000	$ 400,000
Tealstone | Maximum
Loss Contingencies [Line Items]
Earn-out expense	$ 15,000,000

Income Taxes and Deferred Tax_3

Income Taxes and Deferred Tax Asset/Liability - Income Tax Expense (Benefit) Components (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Current tax expense	$ 1,182	$ 288	$ 118
Deferred tax (benefit) expense	(27,398)	1,450	0
Income tax (benefit) expense	$ (26,216)	$ 1,738	$ 118

Income Taxes and Deferred Tax_4

Income Taxes and Deferred Tax Asset/Liability - Summary Reconciliation Reported Amount of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Tax expense (recovery) at the U.S. federal statutory rate		$ 3,041	$ 6,568	$ 5,577
State tax based on income, net of refunds and federal benefits		1,670	364	(264)
Taxes on subsidiaries’ and joint ventures’ earnings allocated to noncontrolling interests owners		(2,241)	(4,097)	(5,504)
Valuation allowance	$ (29,375)	(29,375)	(1,013)	(18,006)
Tax credits		(397)	(286)	(349)
Tax rate change		0	(281)	19,545
Return to provision		48	21	(62)
Earn-out liability		0	0	460
Equity compensation		805	26	(1,371)
Other permanent differences		233	436	92
Income tax (benefit) expense		$ (26,216)	$ 1,738	$ 118
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Tax expense (recovery) at the U.S. federal statutory rate		21.00%	21.00%	35.00%
State tax based on income, net of refunds and federal benefits		11.50%	1.20%	(1.70%)
Taxes on subsidiaries’ and joint ventures’ earnings allocated to noncontrolling interests owners		(15.50%)	(13.10%)	(34.50%)
Valuation allowance		(202.90%)	(3.30%)	(113.00%)
Tax credits		(2.70%)	(0.90%)	(2.20%)
Tax rate change		0.00%	(0.90%)	122.70%
Return to provision		0.30%	0.10%	(0.40%)
Earn-out liability		0.00%	0.00%	2.90%
Equity compensation		5.60%	0.10%	(8.60%)
Other permanent differences		1.60%	1.40%	0.60%
Effective income rate, percent		(181.10%)	5.60%	0.80%

Income Taxes and Deferred Tax_5

Income Taxes and Deferred Tax Asset/Liability - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets related to:
Accrued compensation and other	$ 3,981	$ 3,707
Goodwill	0	0
Noncontrolling interests	1,812	1,687
Deferred revenue	922	232
Members interest liabilities	11,328	11,570
Right of use liabilities	3,253
Net operating loss carryforwards	19,801	22,818
Total deferred tax assets	41,097	40,014
Valuation allowance for deferred tax assets	0	(31,718)
Net deferred tax assets	41,097	8,296
Liabilities related to:
Depreciation of property and equipment	(7,911)	(7,709)
Right of use assets	(3,232)
Amortization of tax basis goodwill	(3,091)	(1,450)
Other	(851)	(587)
Net deferred tax liabilities	(15,085)	(9,746)
Net total deferred tax asset (liability)	$ 26,012	$ (1,450)

Income Taxes and Deferred Tax_6

Income Taxes and Deferred Tax Asset/Liability - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Effective tax rate		21.00%	21.00%	35.00%
Reduction of deferred tax asset valuation allowance				$ 19,300
Valuation allowance	$ (29,375)	$ (29,375)	$ (1,013)	$ (18,006)
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	83,270	$ 83,270
Operating loss carryforward, expiration period		18 years
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 44,857	$ 44,857
Minimum | State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, expiration period		8 years
Maximum | State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforward, expiration period		18 years

Net Income (Loss) Per Share A_2

Net Income (Loss) Per Share Attributable to Sterling Common Stockholders - Earnings Per Share Summary (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net income attributable to Sterling common stockholders	$ 22,301	$ 7,957	$ 7,828	$ 1,815	$ 5,607	$ 8,917	$ 8,174	$ 2,489	$ 39,901	$ 25,187	$ 11,617
Weighted average common shares outstanding — basic (in shares)									26,671	26,903	26,274
Shares for dilutive unvested stock (in shares)									448	291	438
Weighted average common shares outstanding and assumed conversions— diluted (in shares)									27,119	27,194	26,712
Basic net income (loss) per share attributable to Sterling common stockholders (in usd per share)	$ 0.81	$ 0.30	$ 0.30	$ 0.07	$ 0.22	$ 0.33	$ 0.30	$ 0.09	$ 1.50	$ 0.94	$ 0.44
Diluted net income (loss) per share attributable to Sterling common stockholders (in usd per share)	$ 0.79	$ 0.30	$ 0.29	$ 0.07	$ 0.21	$ 0.33	$ 0.30	$ 0.09	$ 1.47	$ 0.93	$ 0.43

Retirement Benefits - Narrative

Retirement Benefits - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)employee	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Defined Contribution Plan Disclosure [Line Items]
Employer matching contributions | $	$ 2,800	$ 2,700	$ 2,300
Number of employees	2,800
Entity number of employees, field personnel	2,400
Contributions | $	$ 829	$ 1,300	$ 1,500
Red Zone
Defined Contribution Plan Disclosure [Line Items]
Multiemployer plan, collective-bargaining arrangement, percentage of contributions required for multiple collective-bargaining arrangements	65.00%
Orange Zone
Defined Contribution Plan Disclosure [Line Items]
Multiemployer plan, collective-bargaining arrangement, percentage of contributions required for multiple collective-bargaining arrangements	80.00%
Yellow Zone
Defined Contribution Plan Disclosure [Line Items]
Multiemployer plan, collective-bargaining arrangement, percentage of contributions required for multiple collective-bargaining arrangements	80.00%
Green Zone
Defined Contribution Plan Disclosure [Line Items]
Multiemployer plan, collective-bargaining arrangement, percentage of contributions required for multiple collective-bargaining arrangements	80.00%
Union Members
Defined Contribution Plan Disclosure [Line Items]
Number of employees	400
Number of employees, percent	17.00%

Retirement Benefits - Participa

Retirement Benefits - Participation in Multiemployer Defined Benefit Pension Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Contribution Plan Disclosure [Line Items]
Contributions	$ 829	$ 1,300	$ 1,500
Multiemployer Plans, Pension
Defined Contribution Plan Disclosure [Line Items]
Contributions	11,182	11,347	12,586
Multiemployer Plans, Pension | Pension Trust Fund for Operating Engineers Pension Plan
Defined Contribution Plan Disclosure [Line Items]
Contributions	2,314	1,932	2,477
Multiemployer Plans, Pension | Laborers Pension Trust for Northern California
Defined Contribution Plan Disclosure [Line Items]
Contributions	857	880	953
Multiemployer Plans, Pension | Carpenter Funds Administrative Office
Defined Contribution Plan Disclosure [Line Items]
Contributions	547	748	727
Multiemployer Plans, Pension | Cement Mason Pension Trust Fund For Northern California
Defined Contribution Plan Disclosure [Line Items]
Contributions	320	504	423
Multiemployer Plans, Pension | All other funds
Defined Contribution Plan Disclosure [Line Items]
Contributions	$ 7,144	$ 7,283	$ 8,006

Concentration of Risk and Ent_3

Concentration of Risk and Enterprise Wide Disclosures - Contract Revenues by Customer (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue, Major Customer [Line Items]
Contract revenues	$ 1,018,484	$ 927,335	$ 868,866
Utah Department of Transportation (“UDOT”) | Customer Concentration Risk
Revenue, Major Customer [Line Items]
Contract revenues	$ 135,496	$ 153,276	$ 140,529
Utah Department of Transportation (“UDOT”) | Customer Concentration Risk | Revenue from Contract with Customer
Revenue, Major Customer [Line Items]
Concentration risk percentage	12.00%	14.80%	14.70%
Texas Department of Transportation (“TXDOT”) | Customer Concentration Risk
Revenue, Major Customer [Line Items]
Contract revenues			$ 103,236
Texas Department of Transportation (“TXDOT”) | Customer Concentration Risk | Revenue from Contract with Customer
Revenue, Major Customer [Line Items]
Concentration risk percentage			10.80%
The Conlan Company
Revenue, Major Customer [Line Items]
Contract receivable	$ 18,700
The Conlan Company | Customer Concentration Risk | Contract Receivables
Revenue, Major Customer [Line Items]
Concentration risk percentage	11.00%

Related Party Transactions (Det

Related Party Transactions (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Related party transaction, amount of transaction	$ 0.3	$ 0.3	$ 0.2
RLW
Related Party Transaction [Line Items]
Revenue from related parties	6.4	$ 15.3	$ 0.7
RLW | Main Office
Related Party Transaction [Line Items]
Rent expense	$ 0.8

Segment Information - Narrative

Segment Information - Narrative (Details)	12 Months Ended
	Dec. 31, 2019segment
Segment Reporting [Abstract]
Number of reportable segments	3
Number of operating segments	3
Number of reporting units	3

Segment Information - Revenue,

Segment Information - Revenue, Operating Income, and Assets, By Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues	$ 346,544	$ 291,699	$ 264,086	$ 223,949	$ 255,175	$ 291,266	$ 268,734	$ 222,492	$ 1,126,278	$ 1,037,667	$ 957,958
Depreciation and amortization									20,740	16,770	16,994
Operating Income	9,732	12,115	11,184	4,720	9,410	14,373	12,149	6,679	37,751	42,611	26,176
Acquisition related costs	(2,153)	(1,896)	(262)	0					(4,311)	0	0
Assets	961,940				482,573				961,940	482,573
Heavy Civil
Segment Reporting Information [Line Items]
Revenues	190,690	218,894	200,236	150,505	190,443	222,299	194,174	158,722	760,325	765,638	801,652
Depreciation and amortization									12,839	13,492	14,789
Operating Income	(7,704)	7,420	5,747	(2,147)	4,245	7,385	4,322	1,092	3,316	17,044	8,246
Assets	287,779				318,586				287,779	318,586
Specialty Services
Segment Reporting Information [Line Items]
Revenues	121,388	32,863	27,894	30,679	30,460	32,245	29,109	28,519	212,824	120,333	48,314
Depreciation and amortization									6,059	1,439	815
Operating Income	14,923	1,371	865	1,048	983	1,647	1,480	519	18,207	4,629	2,284
Assets	587,642				76,170				587,642	76,170
Residential
Segment Reporting Information [Line Items]
Revenues	34,466	39,942	35,956	42,765	34,272	36,722	45,451	35,251	153,129	151,696	107,992
Depreciation and amortization									1,842	1,839	1,390
Operating Income	4,666	5,220	4,834	5,819	4,182	$ 5,341	$ 6,347	$ 5,068	20,539	20,938	15,646
Assets	86,519				$ 87,817				86,519	87,817
Operating Segments
Segment Reporting Information [Line Items]
Operating Income	$ 11,885	$ 14,011	$ 11,446	$ 4,720					$ 42,062	$ 42,611	$ 26,176

Quarterly Financial Informati_3

Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 346,544	$ 291,699	$ 264,086	$ 223,949	$ 255,175	$ 291,266	$ 268,734	$ 222,492	$ 1,126,278	$ 1,037,667	$ 957,958
Gross profit	33,579	29,216	25,496	19,503	28,173	31,279	31,046	19,834	107,794	110,332	89,092
Income (loss) before income taxes	(5,538)	9,422	8,571	2,024	6,738	11,581	9,238	3,721	14,479	31,278	15,935
Net income attributable to Sterling common stockholders	$ 22,301	$ 7,957	$ 7,828	$ 1,815	$ 5,607	$ 8,917	$ 8,174	$ 2,489	$ 39,901	$ 25,187	$ 11,617
Net income (loss) per share attributable to Sterling common stockholders:
Net income (loss) attributable to Sterling common stockholders, basic (in USD per share)	$ 0.81	$ 0.30	$ 0.30	$ 0.07	$ 0.22	$ 0.33	$ 0.30	$ 0.09	$ 1.50	$ 0.94	$ 0.44
Net income (loss) attributable to Sterling common stockholders, diluted (in dollars per share)	$ 0.79	$ 0.30	$ 0.29	$ 0.07	$ 0.21	$ 0.33	$ 0.30	$ 0.09	$ 1.47	$ 0.93	$ 0.43

Quarterly Financial Informati_4

Quarterly Financial Information Quarterly Financial Information By Segment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues	$ 346,544	$ 291,699	$ 264,086	$ 223,949	$ 255,175	$ 291,266	$ 268,734	$ 222,492	$ 1,126,278	$ 1,037,667	$ 957,958
Acquisition related costs	(2,153)	(1,896)	(262)	0					(4,311)	0	0
Operating income	9,732	12,115	11,184	4,720	9,410	14,373	12,149	6,679	37,751	42,611	26,176
Heavy Civil Construction
Segment Reporting Information [Line Items]
Revenues	190,690	218,894	200,236	150,505	190,443	222,299	194,174	158,722	760,325	765,638	801,652
Operating income	(7,704)	7,420	5,747	(2,147)	4,245	7,385	4,322	1,092	3,316	17,044	8,246
Specialty Service
Segment Reporting Information [Line Items]
Revenues	121,388	32,863	27,894	30,679	30,460	32,245	29,109	28,519	212,824	120,333	48,314
Operating income	14,923	1,371	865	1,048	983	1,647	1,480	519	18,207	4,629	2,284
Residential
Segment Reporting Information [Line Items]
Revenues	34,466	39,942	35,956	42,765	34,272	36,722	45,451	35,251	153,129	151,696	107,992
Operating income	4,666	5,220	4,834	5,819	$ 4,182	$ 5,341	$ 6,347	$ 5,068	20,539	20,938	15,646
Operating Segments
Segment Reporting Information [Line Items]
Operating income	$ 11,885	$ 14,011	$ 11,446	$ 4,720					$ 42,062	$ 42,611	$ 26,176