Sterling Infrastructure (STRL) 10-Q 6 Nov 18 2018 Q3 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 31, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	STERLING CONSTRUCTION CO INC
Entity Central Index Key	874,238
Trading Symbol	strl
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		27,068,353
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 89,336	$ 83,953
Receivables, including retainage	160,247	133,931
Costs and estimated earnings in excess of billings on uncompleted contracts	40,275	37,112
Inventories	3,140	4,621
Receivables from and equity in construction joint ventures	11,521	11,380
Other current assets	8,857	7,529
Total current assets	313,376	278,526
Property and equipment, net	52,196	54,406
Goodwill	85,231	85,231
Intangibles, net	43,018	44,818
Other assets, net	343	317
Total assets	494,164	463,298
Current liabilities:
Accounts payable	106,271	97,457
Billings in excess of costs and estimated earnings on uncompleted contracts	63,964	62,374
Current maturities of long-term debt	3,014	3,978
Income taxes payable	279	81
Accrued compensation	14,866	9,054
Other current liabilities	6,275	9,348
Total current liabilities	194,669	182,292
Long-term liabilities:
Long-term debt, net of current maturities	78,424	86,160
Members' interest subject to mandatory redemption and undistributed earnings	48,844	47,386
Deferred taxes	1,299	0
Other long-term liabilities	1,230	1,271
Total long-term liabilities	129,797	134,817
Commitments and contingencies (Note 10)
Sterling stockholders’ equity:
Preferred stock, par value $0.01 per share; 1,000,000 shares authorized, none issued	0	0
Common stock, par value $0.01 per share; 38,000,000 shares authorized, 27,068,353 and 27,051,468 shares issued	271	271
Additional paid in capital	233,056	231,183
Retained deficit	(70,544)	(90,121)
Total Sterling common stockholders’ equity	162,783	141,333
Noncontrolling interests	6,915	4,856
Total equity	169,698	146,189
Total liabilities and equity	$ 494,164	$ 463,298

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	1,000,000	1,000,000
Preferred stock, shares issued (in shares)	0	0
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)	27,068,353	27,051,468

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Revenues	$ 291,266	$ 304,219	$ 782,492	$ 704,047
Cost of revenues	(259,735)	(273,588)	(698,975)	(638,924)
Gross profit	31,531	30,631	83,517	65,123
General and administrative expenses	(11,707)	(13,129)	(38,356)	(36,545)
Other operating expense, net	(5,452)	(4,863)	(11,960)	(9,371)
Operating income	14,372	12,639	33,201	19,207
Interest income	274	107	604	192
Interest expense	(3,067)	(3,576)	(9,265)	(6,672)
Loss on extinguishment of debt	0	0	0	(755)
Income before income taxes and noncontrolling interests in earnings	11,579	9,170	24,540	11,972
Current income tax expense	(1,413)	(344)	(1,551)	(469)
Net income	10,166	8,826	22,989	11,503
Noncontrolling interests in earnings	(1,251)	(1,694)	(3,409)	(2,966)
Net income attributable to Sterling common stockholders	$ 8,915	$ 7,132	$ 19,580	$ 8,537
Net income per share attributable to Sterling common stockholders:
Basic (USD per share)	$ 0.33	$ 0.27	$ 0.73	$ 0.33
Diluted (USD per share)	$ 0.33	$ 0.26	$ 0.72	$ 0.33
Weighted average number of common shares outstanding used in computing per share amounts:
Basic (in shares)	26,908	26,486	26,893	25,787
Diluted (in shares)	27,295	26,920	27,174	26,260

Condensed Consolidated Statem_2

Condensed Consolidated Statement of Changes in Equity - 9 months ended Sep. 30, 2018 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid in Capital	Retained Deficit	Noncontrolling Interests
Beginning balance (in shares) at Dec. 31, 2017		27,051
Beginning balance at Dec. 31, 2017	$ 146,189	$ 271	$ 231,183	$ (90,121)	$ 4,856
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	22,989			19,580	3,409
Stock-based compensation (in shares)		40
Share-based compensation	2,181		2,181
Distributions to owners	(1,350)				(1,350)
Other (in shares)		(23)
Other	(311)	$ 0	(308)	(3)
Ending balance (in shares) at Sep. 30, 2018		27,068
Ending balance at Sep. 30, 2018	$ 169,698	$ 271	$ 233,056	$ (70,544)	$ 6,915

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income attributable to Sterling common stockholders	$ 19,580	$ 8,537
Plus: Noncontrolling interests in earnings	3,409	2,966
Net income	22,989	11,503
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	12,511	13,140
(Gain) loss on disposal of property and equipment	(466)	204
Stock-based compensation expense	2,181	2,534
Deferred tax expense	1,299	0
Changes in operating assets and liabilities:
Contracts receivable	(26,316)	(45,044)
Costs and estimated earnings in excess of billings on uncompleted contracts	(3,163)	(7,735)
Inventories	1,481	2,833
Receivables from and equity in construction joint ventures	(141)	(1,939)
Other assets	(1,354)	(4,487)
Accounts payable	8,814	16,687
Billings in excess of costs and estimated earnings on uncompleted contracts	1,590	(1,035)
Accrued compensation and other liabilities	2,936	18,028
Members' interest subject to mandatory redemption and undistributed earnings	1,458	1,099
Net cash provided by operating activities	23,819	5,788
Cash flows from investing activities:
Tealstone acquisition, net of cash acquired	0	(54,861)
Additions to property and equipment	(9,533)	(8,305)
Proceeds from sale of property and equipment	1,499	5,830
Net cash used in investing activities	(8,034)	(57,336)
Cash flows from financing activities:
Cash received – Oaktree Facility	0	85,000
Repayments – equipment-based term loan and other	(869)	(4,449)
Repayments – Oaktree Facility	(10,429)	0
Debt issuance costs	0	(6,889)
Loss on debt extinguishment	0	755
Distributions to noncontrolling interest owners	(1,350)	0
Other	2,246	887
Net cash (used in) provided by financing activities	(10,402)	75,304
Net increase in cash and cash equivalents	5,383	23,756
Cash and cash equivalents at beginning of period	83,953	42,785
Cash and cash equivalents at end of period	89,336	66,541
Supplemental disclosures of cash flow information:
Cash paid during the period for interest	8,262	6,139
Cash paid during the period for income taxes	279	145
Non-cash items:
Share consideration given for Tealstone acquisition (1,882,058 shares)	0	17,061
Notes and deferred payments to sellers	0	11,588
Warrants issued to lenders (1,000,000 Warrants)	0	3,500
Transportation and construction equipment acquired through financing arrangements	$ 0	$ 70
Statement of Cash Flows Parenthetical [Abstract]
Business acquisition, equity interest issued or issuable, number of shares		1,882,058
Class of warrant or right, issued during the period		1,000,000

Summary of Business and Signifi

Summary of Business and Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Summary of Business and Significant Accounting Policies	1. Summary of Business and Significant Accounting Policies Business Summary Sterling Construction Company, Inc. (“Sterling” or “the Company”), a Delaware corporation, is a construction company that specializes in heavy civil infrastructure construction and infrastructure rehabilitation as well as residential construction projects, primarily in Arizona, California, Colorado, Hawaii, Nevada, Texas, Utah and other states in which there are feasible construction opportunities. Heavy civil construction projects include highways, roads, bridges, airfields, ports, light rail, water, wastewater and storm drainage systems, foundations for multi-family homes, commercial concrete projects and parking structures. Residential construction projects include concrete foundations for single-family homes. Presentation The condensed consolidated financial statements included herein have been prepared by Sterling, without audit, in accordance with the rules and regulations of the Securities and Exchange Commission (“SEC”) and should be read in conjunction with the Annual Report on Form 10-K for the year ended December 31, 2017 (“ 2017 Form 10-K”). Certain information and note disclosures prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) have been either condensed or omitted pursuant to SEC rules and regulations. The condensed consolidated financial statements reflect, in the opinion of management, all normal recurring adjustments necessary to present fairly the Company’s financial position at September 30, 2018 and the results of operations and cash flows for the periods presented. The December 31, 2017 condensed consolidated balance sheet data herein was derived from audited financial statements, but as discussed above, does not include all disclosures required by GAAP. Interim results may be subject to significant seasonal variations and the results of operations for the three and nine months ended September 30, 2018 are not necessarily indicative of the results expected for the full year or subsequent quarters. Use of Estimates The preparation of the accompanying condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions 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 of the Company’s accounting policies require higher degrees of judgment than others in their application. These include among other things the recognition of revenue and earnings from construction contracts over time, the valuation of long-term assets, income taxes, purchase accounting, intangibles and goodwill. Management continually evaluates all of its estimates and judgments based on available information and experience; however, actual results could differ from these estimates. Reclassification Reclassifications have been made to historical financial data on our condensed consolidated financial statements to conform to our current year presentation. Significant Accounting Policies The Company’s significant accounting policies are more fully described in Note 1 of the Notes to Consolidated Financial Statements in the 2017 Form 10-K. There have been no material changes to significant accounting policies since December 31, 2017 . Principles of Consolidation The accompanying condensed consolidated financial statements include the accounts of subsidiaries and construction joint ventures in which the Company has 50% or greater ownership interest or otherwise exercises control over such entities. For investments in construction joint ventures that are not wholly-owned, but where the Company exercises control, the equity held by the remaining owners and their portions of net income are reflected in the balance sheet line item “ Noncontrolling interests ” in “Equity” and the statement of operations line item “ Noncontrolling interests in earnings ,” respectively. For investments in subsidiaries that are not wholly-owned, but where the Company exercises control and where the Company has a mandatorily redeemable interest, the equity held by the remaining owners and their portion of net income (loss) is reflected in the balance sheet line item “ Members' interest subject to mandatory redemption and undistributed earnings ” and the statement of operations line item “ Other operating expense, net ” respectively. All significant intercompany accounts and transactions have been eliminated in consolidation. Where the Company is a noncontrolling joint venture partner, and is otherwise not required to consolidate the joint venture entity, its share of the earnings of such construction joint venture is accounted for on a pro rata basis in the condensed consolidated statements of operations and as a single line item (“ Receivables from and equity in construction joint ventures ”) in the condensed consolidated balance sheets. This method is a permissible modification of the equity method of accounting which is a common practice in the construction industry. Revenue Recognition Heavy Civil Construction The Company engages in various types of heavy civil construction projects principally for public (government) owners. Revenues are recognized as performance obligations are satisfied over time (also known as percentage-of-completion method), measured by the ratio of costs incurred up to a given date to estimated total costs for each contract. 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. Administrative and general expenses are charged to expense as incurred. Provisions for estimated losses on uncompleted contracts are made in the period in which such losses are determined. Changes in job performance, job conditions, estimated profitability and associated change orders and claims, 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. Residential Construction Residential construction revenue and related profit are recognized when construction on the concrete foundation unit is completed (i.e., at a point in time). The time from starting construction to finishing is typically less than one month. Recently Adopted Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-9, “Revenue from Contracts with Customers”, which provides a single comprehensive accounting standard for revenue recognition for contracts with customers and supersedes current industry-specific guidance, including ASC 605-35. The new standard requires companies to recognize revenue when control of promised goods or services is transferred to customers at an amount that reflects the consideration to which the company expects to be entitled in exchange for the goods or services. The new model requires companies to identify contractual performance obligations and determine whether revenue should be recognized at a point in time or over time for each of these obligations. The new standard also significantly expands disclosure requirements regarding the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Sterling adopted the new standard on January 1, 2018, for all contracts using the modified retrospective method that is described in the following paragraph. The adoption of the new revenue standard had no material impact on its condensed consolidated financial statements as it did not require a change in revenue recognition for either of its segments. As such, comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. Sterling implemented the new standard's transitional rules as follows: ASC 606-10-65-1 permits the omission of prior-period information about its performance obligations that were not complete at the time of its new adoption of the new standard. Further, rather than applying the new recognition policy on a contract by contract basis, ASC 606-10-32-18 allows the new standard to be applied against a portfolio of contracts (or performance obligations) with similar characteristics. As the majority of its significant contracts are with government entities and major homebuilders that utilize contracts of a similar structure and nature, this new accounting policy did not yield a material difference for the Company than applying the guidance on a contract by contract basis. In addition to the foregoing, ASC 606-10-32-18 allows entities to waive the requirement to adjust the consideration amount for the effects of a significant financing component if the entity expects, at contract inception, that the period between its fulfillment of the performance obligation and receipt of the customer's payment is less than one year. Further ASC 606-10-32-2A allows entities to make an accounting policy election to exclude taxes assessed by and collected on behalf of government authorities from the transaction price allocated to the performance obligation. Sterling has historically excluded such amounts from its revenues and will continue to do so under the new revenue standard. See Note 3 for additional discussion of Sterling's revenue recognition accounting policies and expanded disclosures required by the new standard. Recently Issued Accounting Pronouncements In February 2016, the FASB issued its new lease accounting guidance in ASU No. 2016-2, “Leases” (Topic 842). Under the new guidance, lessees will be required to recognize for all leases (with the exception of short-term leases) a lease liability, which is a lessee’s obligation to make lease payments arising from a lease, measured on a discounted basis, and a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. The standard is effective for the interim and annual reporting periods beginning after December 15, 2018. ASU 2016-02 allows companies to adopt the new standard by either applying a modified retrospective method to the beginning of the earliest period presented in the financial statements or an optional transition method to initially apply the standard on January 1, 2019 and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. The Company expects to adopt the standard using the optional transition method and apply the new guidance prospectively to leases that exist and those entered into on or after January 1, 2019 without adjusting comparative periods in the financial statements. The Company intends to make an accounting policy election to forgo applying Topic 842 to leases with a term of 12 or fewer months. The Company is currently evaluating the impact of adopting this ASU on its consolidated financial statements, including available practical expedients, but expects the adoption to result in a material increase to its assets and liabilities. The Company does not expect this ASU to have a material impact on its consolidated statements of income or cash flows.

Tealstone Acquisition

Tealstone Acquisition	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Tealstone Acquisition	2. Tealstone Acquisition General On April 3, 2017, the Company consummated the acquisition (the “Tealstone Acquisition”) of 100% of the outstanding stock of Tealstone Residential Concrete, Inc. and Tealstone Commercial, Inc. (collectively, “Tealstone”) from the stockholders thereof (the “Sellers”) for consideration consisting of $55,000,000 in cash, 1,882,058 shares of the Company’s common stock, and $5,000,000 of promissory notes issued to the Sellers. In addition, the Company will make $2,426,000 and $7,500,000 of deferred cash payments on the second and third anniversaries of the closing date, respectively, and up to an aggregate of $15,000,000 in earn out payments if specified financial performance levels are achieved (subject to annual maximums) on each of the first, second, third and fourth anniversaries of the closing date to continuing Tealstone management or their affiliates. Tealstone focuses on concrete construction of residential foundations, parking structures, elevated foundations and other concrete work for leading homebuilders, multi-family developers and general contractors in both residential and commercial markets. This acquisition enables expansion into adjacent markets and diversification of revenue streams and customer base with higher margin work. Supplemental Pro Forma Information (Unaudited) The following unaudited pro forma condensed combined financial information (“the pro forma financial information”) gives effect to the acquisition of Tealstone by Sterling, accounted for as a business combination using the purchase method of accounting. The pro forma financial information reflects the Tealstone Acquisition and related events as if they occurred at the beginning of the period covered by the pro formas, 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 Tealstone following the acquisition. The pro forma financial information includes adjustments to: (1) exclude transaction costs that were included in Sterling’s and Tealstone’s historical results and are expected to be non-recurring; and (2) include additional intangibles amortization and net interest expense associated with the Tealstone Acquisition. 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 Tealstone Acquisition. The pro forma for the nine months ended September 30, 2017 (amounts in thousands): Nine Months Ended September 30, 2017 Pro forma revenue $ 749,176 Pro forma net income attributable to Sterling $ 8,848

Revenue From Contracts With Cus

Revenue From Contracts With Customers	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue From Contracts With Customers	3. Revenue from Contracts with Customers 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. The majority of Sterling's 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 of the contracts have multiple performance obligations, most commonly due to the contract covering multiple phases of the product life cycle (design and construction). For contracts with multiple performance obligations, Sterling allocates the contract transaction price to each performance obligation using its best estimate of the standalone selling price of each distinct good or service in the contract. The primary method used to estimate standalone selling price is the expected cost plus a margin approach, under which Sterling forecasts the expected costs of satisfying a performance obligation and then adds an appropriate margin for that distinct good or service. Performance Obligations Satisfied Over Time Revenue for Sterling's heavy civil construction segment contracts that satisfy the criteria for over time recognition (formerly known as percentage-of-completion method) is recognized as the work progresses. The majority of the revenue is derived from long-term, heavy civil construction contracts and projects that typically span between 12 to 36 months . Sterling's heavy civil construction contracts will continue to be recognized over time 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 Sterling for costs incurred plus a reasonable profit and take control of any work in process. Under the new revenue standard, the cost-to-cost measure of progress continues to best depict the transfer of control of assets to the customer, which occurs as the Company incurs costs. Contract costs include labor, material and indirect costs. Revenue from products and services transferred to customers over time accounted for 87% and 85% of revenue for the three and nine months ended September 30, 2018 , respectively. Revenue from products and services transferred to customers over time accounted for 87% and 89% of revenue for the three and nine months ended September 30, 2017 , respectively. Performance Obligations Satisfied at a Point in Time Revenue for the residential construction segment contracts that do not satisfy the criteria for over time recognition is recognized at a point in time. Substantially all of the revenue recognized at a point in time is for work performed by the residential construction segment. Unlike the heavy civil construction segment that uses a cost-to-cost input measure for performance, the residential construction segment utilizes an output measure for performance based on the completion of a unit of work (e.g., residential foundation). The typical time frame for completion of a residential foundation is less than one month. Upon fulfillment of the performance obligation, the customer is provided an invoice (or equivalent) demonstrating transfer of control to the customer. Sterling believes that point in time recognition remains appropriate for this segment and will continue to recognize revenues upon completion of the performance obligation and issuance of an invoice. Revenue from goods and services transferred to customers at a point in time accounted for 13% and 15% of revenue for the three and nine months ended September 30, 2018 , respectively. Revenue from goods and services transferred to customers at a point in time accounted for 13% and 11% of revenue for the three and nine months ended September 30, 2017 , respectively. Contract modifications are routine in the performance of Sterling's contracts. Contracts are often modified to account for changes in the contract specifications or requirements. In most instances, contract modifications are for goods or services that are not distinct, and, therefore, are accounted for as part of the existing contract. Assurance-type warranties are the only warranties provided by the Company and, as such, Sterling does not recognize revenue on warranty-related work. Sterling generally provides a one to two year warranty for workmanship under its contracts when completed. Warranty claims historically have been insignificant. Pre-contract costs are generally charged to expense as incurred, but in certain cases their recognition may be deferred if specific probability criteria are met. Sterling had no significant deferred pre-contract costs at September 30, 2018 . Backlog On September 30, 2018 , Sterling had $833 million of remaining performance obligations in its heavy civil construction segment, which is also referred to as backlog. Sterling expects to recognize approximately 70% of its backlog as revenue during the next twelve months, and the balance thereafter. 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, Sterling estimates the profit on a contract as the difference between the total estimated revenue and expected costs to complete a contract and recognizes that 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. Changes in estimated revenues and gross margin resulted in a net gain of $2.4 million and $4.1 million for the three and nine months ended September 30, 2018 , respectively, and a net gain of $1.3 million and $0.2 million for the three and nine months ended September 30, 2017 , respectively, included in “Operating income” on the condensed consolidated statements of operations. Provisions for estimated losses on uncompleted contracts are made in the period in which such losses are determined. Variable Consideration The transaction price for contracts may include variable consideration, which includes increases to transaction price for approved and unapproved change orders, claims and incentives, and reductions to transaction price for liquidated damages. Change orders, claims and incentives are generally not distinct from the existing contract due to the significant integration service provided in the context of the contract and are accounted for as a modification of the existing contract and performance obligation. Change orders may include changes in specifications or designs, manner of performance, facilities, equipment, materials, sites and period of completion of the work. Either Sterling or its customers may initiate change orders. Change orders that are unapproved as to both price and scope are evaluated as claims. Sterling 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 Sterling 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). Sterling 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. Sterling'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 Sterling. 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 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 Sterling'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. 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 Sterling'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 Sterling'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, Sterling concluded that it was appropriate to include in project price amounts of $9.3 million and $10.0 million , at September 30, 2018 and December 31, 2017 , respectively, in “Costs and estimated earnings in excess of billings on uncompleted contracts” on its condensed consolidated balance sheets. Sterling expects these matters will be resolved without a material adverse effect on its financial statements. However, unapproved change order and claim amounts are subject to negotiations which may cause actual results to differ materially from estimated and recorded amounts. Revenue by Heavy Civil Construction Category Sterling's heavy civil construction segment's portfolio of products and services consists of over 150 active contracts. The following series of tables presents Sterling's heavy civil construction revenue disaggregated by several categories. Revenue by major end market (amounts in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Heavy Highway $ 151,882 $ 179,608 $ 385,843 $ 438,741 Commercial 32,261 15,209 89,890 27,050 Aviation 30,587 22,863 81,671 56,310 Water Containment and Treatment 18,457 20,518 48,973 43,388 Other 21,357 25,080 58,691 60,398 Heavy Civil Construction Revenue $ 254,544 $ 263,278 $ 665,068 $ 625,887 Revenue by contract type (amounts in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Fixed Unit Price $ 208,070 $ 230,002 $ 562,791 $ 564,797 Lump Sum and Other 46,474 33,276 102,277 61,090 Heavy Civil Construction Revenue $ 254,544 $ 263,278 $ 665,068 $ 625,887 Each of these contract types presents advantages and disadvantages. Typically, Sterling assumes more risk with lump-sum contracts. However, these types of contracts offer additional profits when the work is completed for less than originally estimated. Under fixed-unit price contracts, Sterling'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. Contract Balances The timing of revenue recognition, billings and cash collections results in billed accounts receivable and costs and estimated earnings in excess of billings on uncompleted contracts (contract assets) on the condensed consolidated balance sheet. In Sterling's heavy civil construction segment, 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. Generally, billing occurs subsequent to revenue recognition, resulting in contract assets. However, Sterling sometimes receives 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). These assets and liabilities are reported on the condensed consolidated balance sheet on a contract-by-contract basis at the end of each reporting period. Changes in the contract asset and liability balances during the nine month period ended September 30, 2018 , were not materially impacted by any other factors. The table below reconciles the net excess billings to the amounts included in the condensed consolidated balance sheets at those dates (amounts in thousands): September 30, December 31, Costs and estimated earnings in excess of billings on uncompleted contracts $ 40,275 $ 37,112 Billings in excess of costs and estimated earnings on uncompleted contracts (63,964 ) (62,374 ) Net amount of billings in excess of costs and estimated earnings on uncompleted contracts $ (23,689 ) $ (25,262 ) Revenues recognized and billings on uncompleted contracts include cumulative amounts recognized as revenues and billings in prior periods. This revenue primarily represents progress on Sterling's construction jobs.

Cash and Cash Equivalents

Cash and Cash Equivalents	9 Months Ended
	Sep. 30, 2018
Cash and Cash Equivalents [Abstract]
Cash and Cash Equivalents	4. 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 includes cash balances held by consolidated 50% owned subsidiaries and its majority owned construction joint ventures. At September 30, 2018 and December 31, 2017 , cash and cash equivalents included $25.3 million and $31.1 million , respectively, attributable to consolidated 50% owned subsidiaries. At September 30, 2018 and December 31, 2017 , cash and cash equivalents included $12.9 million and $18.9 million , respectively, attributable to its 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 $4.1 million and $3.6 million is included in “ Other current assets ” on the condensed consolidated balance sheets as of September 30, 2018 and December 31, 2017 . This represents $4.1 million and $3.0 million of cash designated as collateral for a standby letter of credit as of September 30, 2018 and December 31, 2017 respectively. The December 31, 2017 balance also includes $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 does not believe that the risk associated with keeping cash deposits in excess of federal deposit insurance limits represents a material risk.

Consolidated 50% Owned Subsidia

Consolidated 50% Owned Subsidiaries, including Variable Interest Entities ("VIE")	9 Months Ended
	Sep. 30, 2018
Noncontrolling Interest [Abstract]
Consolidated 50% Owned Subsidiaries, including Variable Interest Entities (VIE)	5. Consolidated 50% Owned Subsidiaries, including Variable Interest Entities ("VIE") The Company has a 50% interest in two subsidiaries (Myers and RHB); both subsidiaries have individual provisions which obligate the Company to purchase each partner's 50% interests for $20.0 million ( $40.0 million in the aggregate), due to circumstances outlined in the partner agreements that are certain to occur. Therefore, the Company has consolidated these two entities and classified these obligations as mandatorily redeemable and has recorded a liability in “ Members' interest subject to mandatory redemption and undistributed earnings ” on the condensed consolidated balance sheets. In addition, all undistributed earnings at the time of the noncontrolling owners’ death or permanent disability are also mandatorily payable. In the event of either Mr. Buenting’s or Mr. Myers's death, the Company purchased two separate $20.0 million death and permanent total disability insurance policies to mitigate the Company’s cash draw if such events were to occur. The liability consists of the following (amounts in thousands): September 30, December 31, Members’ interest subject to mandatory redemption $ 40,000 $ 40,000 Net accumulated earnings 8,844 7,386 Total liability $ 48,844 $ 47,386 Fifty percent of the earnings of these consolidated 50% owned subsidiaries for the three and nine months ended September 30, 2018 were $5.1 million , and $10.4 million , respectively and for the three and nine months ended September 30, 2017 were $4.5 million and $7.0 million , respectively. These amounts were included in “Other operating expense, net” on the Company’s condensed consolidated statements of operations. The Company must determine whether any of its entities, including these two 50% owned subsidiaries, in which it participates, is a VIE. The Company determined Myers is a VIE, as Sterling is the primary beneficiary, as pursuant to the terms of the Myers Operating Agreement, Sterling is exposed to the majority of potential losses of the partnership. As such, the following table presents the condensed financial information of Myers, which is reflected in the Company’s condensed consolidated balance sheets and statements of operations, as follows (amounts in thousands): September 30, December 31, Assets: Current assets: Cash and cash equivalents $ 4,580 $ 8,590 Contracts receivable, including retainage 31,158 26,844 Other current assets 16,054 15,672 Total current assets 51,792 51,106 Property and equipment, net 7,696 9,001 Goodwill 1,501 1,501 Total assets $ 60,989 $ 61,608 Liabilities: Current liabilities: Accounts payable $ 28,561 $ 28,448 Other current liabilities 13,150 11,798 Total current liabilities 41,711 40,246 Long-term liabilities: Other long-term liabilities 67 3,491 Total liabilities $ 41,778 $ 43,737 Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Revenues $ 56,816 $ 64,266 $ 142,786 $ 126,333 Operating income 2,488 3,666 5,227 6,307 Net income attributable to Sterling common stockholders 1,245 1,834 2,615 3,149

Construction Joint Ventures

Construction Joint Ventures	9 Months Ended
	Sep. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Construction Joint Ventures	6. Construction Joint Ventures Sterling 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. Sterling 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. For these joint ventures, the equity held by the remaining owners and their portions of net income (loss) are reflected in the balance sheet line item “ Noncontrolling interests ” in “Equity” and the statement of operations line item “Noncontrolling interests in earnings,” respectively. Refer to Note 6 of the Notes to Consolidated Financial Statements in the 2017 Form 10-K for further information about Sterling's joint ventures. The following table summarizes the changes in noncontrolling interests (amounts in thousands): Nine Months Ended September 30, 2018 2017 Balance, beginning of period $ 4,856 $ 656 Net income attributable to noncontrolling interest included in equity 3,409 2,966 Distributions to noncontrolling interest owners (1,350 ) — Balance, end of period $ 6,915 $ 3,622 Where Sterling is a noncontrolling venture partner, the Company accounts for their share of the operations of such construction joint ventures on a pro-rata basis using proportionate consolidation on its condensed consolidated statements of operations and as a single line item (“ Receivables from and equity in construction joint ventures ”) in the condensed 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 condensed consolidated financial statements are shown below (amounts in thousands): September 30, December 31, Total combined: Current assets $ 64,957 $ 64,574 Less current liabilities (72,617 ) (78,349 ) Net liabilities $ (7,660 ) $ (13,775 ) Sterling’s receivables from and equity in noncontrolling construction joint ventures $ 11,521 $ 11,380 Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Total combined: Revenues $ 29,557 $ 27,703 $ 89,010 $ 61,210 Income before tax 1,728 (6,281 ) 7,324 (3,611 ) Sterling’s noncontrolling interest: Revenues $ 12,820 $ 13,664 $ 41,739 $ 28,826 Income before tax 858 (1,629 ) 3,716 (358 ) 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 complete and the warranty period, if any, has passed.

Property and Equipment

Property and Equipment	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Property and Equipment	7. Property and Equipment Property and equipment are summarized as follows (amounts in thousands): September 30, December 31, Construction equipment $ 123,551 $ 118,868 Transportation equipment 18,285 17,511 Buildings 9,770 9,577 Office equipment 2,715 3,339 Leasehold Improvement 914 914 Construction in progress 327 258 Land 2,720 2,348 Water rights — 200 158,282 153,015 Less accumulated depreciation (106,086 ) (98,609 ) Total property and equipment, net $ 52,196 $ 54,406

Intangibles

Intangibles	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Intangibles	8. Intangibles The following table presents Sterling's acquired finite-lived intangible assets at September 30, 2018 and December 31, 2017 (in thousands): September 30, 2018 December 31, 2017 Weighted Gross Gross Customer relationships 23 years $ 40,823 $ (2,707 ) $ 40,823 $ (1,353 ) Trade name 13 years 5,307 (788 ) 5,307 (394 ) Noncompetition agreements 7 years 487 (104 ) 487 (52 ) Total 22 years $ 46,617 $ (3,599 ) $ 46,617 $ (1,799 ) Sterling's intangible expense was $0.6 million and $1.8 million for the three and nine months ended September 30, 2018 and $1.8 million for the year ended December 31, 2017 .

Secured Credit Facility and Oth

Secured Credit Facility and Other Debt	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Secured Credit Facility and Other Debt	9. Secured Credit Facility and Other Debt Debt consists of the following (in thousands): September 30, December 31, Loan $ 74,571 $ 85,000 Notes and deferred payments to sellers, Tealstone acquisition 13,265 12,393 Notes payable for transportation and construction equipment and other 859 1,557 Total debt 88,695 98,950 Less - Current maturities of long-term debt (3,014 ) (3,978 ) Less - Unamortized deferred loan costs (7,257 ) (8,812 ) Total long-term debt $ 78,424 $ 86,160 On April 3, 2017, the Company, as borrower, and certain of its subsidiaries, as guarantors, entered into a Loan and Security Agreement with Wilmington Trust, National Association, as agent, and the lenders party thereto (the “Oaktree Facility”), providing for a term loan of $85,000,000 (the “Loan”) with a maturity date of April 4, 2022, which replaced the then existing debt facility. The Loan is secured by substantially all of the assets of the Company and its subsidiaries. Interest on the Loan is equal to the one-, two-, three- or six-month London Interbank Offered Rate, or LIBOR, plus 8.75% per annum on the unpaid principal amount of the Loan, subject to adjustment under certain circumstances. Interest on the Loan is generally payable monthly. There are no amortized principal payments; however, the Company is required to prepay the Loan, and in certain cases pay a prepayment premium thereon, with proceeds received from the issuances of debt or equity, transfers, events of loss and extraordinary receipts. The Company is required to make an offer quarterly to the lenders to prepay the Loan in an amount equal to 75% of its excess cash flow, plus accrued and unpaid interest thereon and a prepayment premium. The Oaktree Facility contains various covenants that limit, among other things, the Company’s ability and certain of its subsidiaries’ ability to incur certain indebtedness, grant certain liens, merge or consolidate, sell assets, make certain loans, enter into acquisitions, incur capital expenditures, make investments, and pay dividends. In addition, the Company is required to maintain the following principal financial covenants: • a ratio of secured indebtedness to EBITDA of not more than 2.00 to 1.00 for the trailing four consecutive fiscal quarters ending September 30, 2018, reducing to 1.80 to 1.00 for the four consecutive quarters ending September 30, 2019 through maturity in 2022; • daily cash collateral of not less than $15,000,000 ; • gross margin in contract backlog of not less than $65,000,000 for the average of the trailing four consecutive fiscal quarters ending September 30, 2018, increasing to $70,000,000 on March 31, 2019; • net capital expenditures during the trailing four consecutive fiscal quarters shall not exceed $15,000,000 ; • bonding capacity shall be maintained at all times in an amount not less than $1,000,000,000 ; and • the EBITDA of Tealstone Residential Concrete, Inc. shall not be less than $12,000,000 for each of the trailing four consecutive fiscal quarters. The Company is in compliance with these covenants at September 30, 2018 . The Oaktree Facility also includes customary events of default, including events of default relating to non-payment of principal or interest, inaccuracy of representations and warranties, breaches of covenants, cross-defaults, bankruptcy and insolvency events, certain unsatisfied judgments, loan documents not being valid, calls under the Company’s bonds, failure of specified individuals to remain employed by the Company, and a change of control. If an event of default occurs, the lenders will be able to accelerate the maturity of the Oaktree Facility and exercise other rights and remedies. Deferred loan costs totaled $10.4 million , which included attorney fees, investment bank fees as well as amounts paid to the lenders. Warrants valued at $3.5 million were included as well. The total amount is amortized on a straight-line basis, which approximates the effective interest method, over the five -year life of the Loan. Total amortization of deferred loan costs in interest expense of $0.5 million and $1.6 million , respectively has been recorded for the three and nine months ended September 30, 2018 . Total amortization expense of deferred loan costs in interest expense of $0.5 million and $1.0 million was recorded for the three and nine months ended September 30, 2017 . The fair value of the Oaktree Facility approximates its book value. Notes and Deferred Payments to Sellers As part of the Tealstone Acquisition, the Company issued $5,000,000 of Promissory Notes to the Sellers and agreed to make $2,426,000 and $7,500,000 of deferred cash payments on the second and third anniversaries of the closing date, respectively. Based on a 12% discount rate, the Company recorded $11.6 million as notes and deferred payments to sellers in long-term debt on its condensed consolidated balance sheet at the acquisition closing date. Accreted interest for the period was $0.3 million and $0.9 million for the three and nine months ended September 30, 2018 , respectively, and was recorded as interest expense. Accreted interest of $0.3 million and $0.5 million was recorded for the three and nine months ended September 30, 2017 , respectively. Notes Payable for Transportation and Construction Equipment The Company has purchased and financed various transportation and construction equipment to enhance the Company’s fleet of equipment. The total long-term notes payable related to the purchase of financed equipment was $0.9 million and $1.6 million at September 30, 2018 and December 31, 2017 , respectively. The purchases have payment terms ranging from 3 to 5 years and the associated interest rates range from 3.15% to 6.92% . The fair value of these notes payable approximates their book value.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	10. Commitments and Contingencies The Company is required by its insurance providers to obtain and hold a standby letter of credit. These letters of credit serve as a guarantee by the banking institution to pay Sterling's insurance providers the incurred claim costs attributable to its general liability, workers compensation and automobile liability claims, up to the amount stated in the standby letters of credit, in the event that these claims were not paid by the Company. Sterling has cash collateralized the letters of credit, resulting in the cash being designated as restricted. 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 actions will have a material impact on the condensed consolidated financial statements of the Company.

Income Taxes and Deferred Tax A

Income Taxes and Deferred Tax Asset/Liability	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes and Deferred Tax Asset/Liability	11. Income Taxes and Deferred Tax Asset/Liability The Company and its subsidiaries file U.S. federal and various U.S. state income tax returns. Current income tax expense (benefit) represents federal and state taxes based on tax paid or expected to be payable or receivable for the periods shown in the condensed consolidated statements of operations. Due to net operating loss carryforwards, Sterling does not expect a current federal liability. The Company may incur current state tax liabilities in states in which the Company does not have sufficient net operating loss carry forwards. Current income tax expense of $114 thousand and $252 thousand was recorded for the three and nine months ended September 30, 2018 , respectively. Income tax expense of $344 thousand and $469 thousand was recorded for the three and nine months ended September 30, 2017 , respectively. Sterling’s deferred tax expense reflects the change in deferred tax assets and liabilities. The Company performs an analysis at the end of each reporting period to determine whether it is more likely than not the deferred tax assets are expected to be realized in future years. Based upon this analysis, a full valuation allowance has been applied to Sterling's net deferred tax assets as of September 30, 2018 and December 31, 2017 . Deferred tax liabilities are 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. The Company expects to have a deferred tax liability for the excess of book over tax basis difference in its goodwill. A $1.3 million deferred tax expense for the three and nine months ended September 30, 2018 has been recorded to reflect this liability. The effective income tax rate varied from the statutory rate primarily as a result of the change in the valuation allowance, net income attributable to noncontrolling interest owners which is taxable to those owners rather than to the Company, state income taxes and other permanent differences. For interim periods, the Company estimates an annual effective tax rate and applies that rate to year-to-date operating results. As a result of the Sterling’s analysis, management has determined that the Company does not have any material uncertain tax positions.

Stockholder's Equity

Stockholder's Equity	9 Months Ended
	Sep. 30, 2018
Stockholders' Equity Note [Abstract]
Stockholder's Equity	12. Stockholder's Equity Stock-Based Compensation Sterling has a stock-based incentive plan that is administered by the Compensation Committee of the Board of Directors. Refer to Note 14 of the Notes to Consolidated Financial Statements included in the 2017 Form 10-K for further information. During the three and nine months ended September 30, 2018 , the Company awarded, subject to vesting restrictions, a total of 35,464 and 398,936 common stock awards, respectively. The nine months ended September 30, 2018 common stock awards was reduced by 999 shares forfeited during the period and the acceleration of 7,404 unvested shares related to the departure of a former Board of Director member. The Company recorded stock-based compensation expense of $0.8 million and $2.2 million for the three and nine months ended September 30, 2018 , respectively. During the three and nine months ended September 30, 2017 , the Company awarded, subject to vesting restrictions, a total of 8,000 and 174,410 common stock awards, respectively. The nine months ended September 30, 2017 included costs for the acceleration of unvested shares related to the departure of our former CEO of $0.7 million . The Company recorded stock-based compensation expense of $0.6 million and $2.5 million for the three and nine months ended September 30, 2017 , respectively. At September 30, 2018 and 2017 , total unrecognized compensation cost related to unvested common stock awards was $5.2 million and $1.1 million , respectively. This cost is expected to be recognized over a weighted average period of 3 years.

Net Income Per Share Attributab

Net Income Per Share Attributable to Sterling Common Stockholders	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Net Income Per Share Attributable to Sterling Common Stockholders	13. Net Income Per Share Attributable to Sterling Common Stockholders 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 (amounts in thousands, except per share data): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Numerator: Net income attributable to Sterling common stockholders $ 8,915 $ 7,132 $ 19,580 $ 8,537 Weighted average common shares outstanding — basic 26,908 26,486 26,893 25,787 Shares for dilutive unvested stock and warrants 387 434 281 473 Weighted average common shares outstanding and incremental shares assumed repurchased— diluted 27,295 26,920 27,174 26,260 Basic income per share attributable to Sterling common stockholders $ 0.33 $ 0.27 $ 0.73 $ 0.33 Diluted income per share attributable to Sterling common stockholders $ 0.33 $ 0.26 $ 0.72 $ 0.33

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment Information	14. Segment Information Due to the April 3, 2017 acquisition of Tealstone, the Company reviewed its reportable segments, operating segments and reporting units. Based on Sterling's review, the Company concluded that their operations consist of two reportable segments, two operating segments and two reporting unit components: heavy civil construction and residential construction. Segment reporting is aligned based upon the services offered by two operating groups, which represent the following reportable segments: heavy civil construction and residential construction. Sterling's Chief Operating Decision Maker (“CODM”) evaluates the performance of the aforementioned 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 and income from operations by reportable segment for the three and nine months ended September 30, 2018 and 2017 (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Revenue Heavy Civil Construction $ 254,544 $ 263,278 $ 665,068 $ 625,887 Residential Construction 36,722 40,941 117,424 78,160 Total Revenue $ 291,266 $ 304,219 $ 782,492 $ 704,047 Operating Income Heavy Civil Construction $ 9,191 $ 6,960 $ 17,488 $ 8,627 Residential Construction 5,181 5,679 15,713 10,580 Total Operating Income $ 14,372 $ 12,639 $ 33,201 $ 19,207 The following table presents total assets by reportable segment at September 30, 2018 and December 31, 2017 (in thousands): September 30, December 31, Assets Heavy Civil Construction $ 363,058 $ 354,090 Residential Construction 131,106 109,208 Total Assets $ 494,164 $ 463,298

Summary of Business and Signi_2

Summary of Business and Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Presentation	Presentation The condensed consolidated financial statements included herein have been prepared by Sterling, without audit, in accordance with the rules and regulations of the Securities and Exchange Commission (“SEC”) and should be read in conjunction with the Annual Report on Form 10-K for the year ended December 31, 2017 (“ 2017 Form 10-K”). Certain information and note disclosures prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) have been either condensed or omitted pursuant to SEC rules and regulations. The condensed consolidated financial statements reflect, in the opinion of management, all normal recurring adjustments necessary to present fairly the Company’s financial position at September 30, 2018 and the results of operations and cash flows for the periods presented. The December 31, 2017 condensed consolidated balance sheet data herein was derived from audited financial statements, but as discussed above, does not include all disclosures required by GAAP. Interim results may be subject to significant seasonal variations and the results of operations for the three and nine months ended September 30, 2018 are not necessarily indicative of the results expected for the full year or subsequent quarters.
Use of Estimates	Use of Estimates The preparation of the accompanying condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions 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 of the Company’s accounting policies require higher degrees of judgment than others in their application. These include among other things the recognition of revenue and earnings from construction contracts over time, the valuation of long-term assets, income taxes, purchase accounting, intangibles and goodwill. Management continually evaluates all of its estimates and judgments based on available information and experience; however, actual results could differ from these estimates.
Reclassifications	Reclassification Reclassifications have been made to historical financial data on our condensed consolidated financial statements to conform to our current year presentation.
Principles of Consolidation	Principles of Consolidation The accompanying condensed consolidated financial statements include the accounts of subsidiaries and construction joint ventures in which the Company has 50% or greater ownership interest or otherwise exercises control over such entities. For investments in construction joint ventures that are not wholly-owned, but where the Company exercises control, the equity held by the remaining owners and their portions of net income are reflected in the balance sheet line item “ Noncontrolling interests ” in “Equity” and the statement of operations line item “ Noncontrolling interests in earnings ,” respectively. For investments in subsidiaries that are not wholly-owned, but where the Company exercises control and where the Company has a mandatorily redeemable interest, the equity held by the remaining owners and their portion of net income (loss) is reflected in the balance sheet line item “ Members' interest subject to mandatory redemption and undistributed earnings ” and the statement of operations line item “ Other operating expense, net ” respectively. All significant intercompany accounts and transactions have been eliminated in consolidation. Where the Company is a noncontrolling joint venture partner, and is otherwise not required to consolidate the joint venture entity, its share of the earnings of such construction joint venture is accounted for on a pro rata basis in the condensed consolidated statements of operations and as a single line item (“ Receivables from and equity in construction joint ventures ”) in the condensed consolidated balance sheets. This method is a permissible modification of the equity method of accounting which is a common practice in the construction industry.
Revenue Recognition	Revenue Recognition Heavy Civil Construction The Company engages in various types of heavy civil construction projects principally for public (government) owners. Revenues are recognized as performance obligations are satisfied over time (also known as percentage-of-completion method), measured by the ratio of costs incurred up to a given date to estimated total costs for each contract. 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. Administrative and general expenses are charged to expense as incurred. Provisions for estimated losses on uncompleted contracts are made in the period in which such losses are determined. Changes in job performance, job conditions, estimated profitability and associated change orders and claims, 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. Residential Construction Residential construction revenue and related profit are recognized when construction on the concrete foundation unit is completed (i.e., at a point in time). The time from starting construction to finishing is typically less than one month.
Recently Adopted and Issued Accounting Pronouncements	Recently Adopted Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-9, “Revenue from Contracts with Customers”, which provides a single comprehensive accounting standard for revenue recognition for contracts with customers and supersedes current industry-specific guidance, including ASC 605-35. The new standard requires companies to recognize revenue when control of promised goods or services is transferred to customers at an amount that reflects the consideration to which the company expects to be entitled in exchange for the goods or services. The new model requires companies to identify contractual performance obligations and determine whether revenue should be recognized at a point in time or over time for each of these obligations. The new standard also significantly expands disclosure requirements regarding the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Sterling adopted the new standard on January 1, 2018, for all contracts using the modified retrospective method that is described in the following paragraph. The adoption of the new revenue standard had no material impact on its condensed consolidated financial statements as it did not require a change in revenue recognition for either of its segments. As such, comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. Sterling implemented the new standard's transitional rules as follows: ASC 606-10-65-1 permits the omission of prior-period information about its performance obligations that were not complete at the time of its new adoption of the new standard. Further, rather than applying the new recognition policy on a contract by contract basis, ASC 606-10-32-18 allows the new standard to be applied against a portfolio of contracts (or performance obligations) with similar characteristics. As the majority of its significant contracts are with government entities and major homebuilders that utilize contracts of a similar structure and nature, this new accounting policy did not yield a material difference for the Company than applying the guidance on a contract by contract basis. In addition to the foregoing, ASC 606-10-32-18 allows entities to waive the requirement to adjust the consideration amount for the effects of a significant financing component if the entity expects, at contract inception, that the period between its fulfillment of the performance obligation and receipt of the customer's payment is less than one year. Further ASC 606-10-32-2A allows entities to make an accounting policy election to exclude taxes assessed by and collected on behalf of government authorities from the transaction price allocated to the performance obligation. Sterling has historically excluded such amounts from its revenues and will continue to do so under the new revenue standard. See Note 3 for additional discussion of Sterling's revenue recognition accounting policies and expanded disclosures required by the new standard. Recently Issued Accounting Pronouncements In February 2016, the FASB issued its new lease accounting guidance in ASU No. 2016-2, “Leases” (Topic 842). Under the new guidance, lessees will be required to recognize for all leases (with the exception of short-term leases) a lease liability, which is a lessee’s obligation to make lease payments arising from a lease, measured on a discounted basis, and a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. The standard is effective for the interim and annual reporting periods beginning after December 15, 2018. ASU 2016-02 allows companies to adopt the new standard by either applying a modified retrospective method to the beginning of the earliest period presented in the financial statements or an optional transition method to initially apply the standard on January 1, 2019 and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. The Company expects to adopt the standard using the optional transition method and apply the new guidance prospectively to leases that exist and those entered into on or after January 1, 2019 without adjusting comparative periods in the financial statements. The Company intends to make an accounting policy election to forgo applying Topic 842 to leases with a term of 12 or fewer months. The Company is currently evaluating the impact of adopting this ASU on its consolidated financial statements, including available practical expedients, but expects the adoption to result in a material increase to its assets and liabilities. The Company does not expect this ASU to have a material impact on its consolidated statements of income or cash flows.

Tealstone Acquisition (Tables)

Tealstone Acquisition (Tables)	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Summary of Proforma Information	The pro forma for the nine months ended September 30, 2017 (amounts in thousands): Nine Months Ended September 30, 2017 Pro forma revenue $ 749,176 Pro forma net income attributable to Sterling $ 8,848

Revenue From Contracts With C_2

Revenue From Contracts With Customers (Tables)	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	Revenue by major end market (amounts in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Heavy Highway $ 151,882 $ 179,608 $ 385,843 $ 438,741 Commercial 32,261 15,209 89,890 27,050 Aviation 30,587 22,863 81,671 56,310 Water Containment and Treatment 18,457 20,518 48,973 43,388 Other 21,357 25,080 58,691 60,398 Heavy Civil Construction Revenue $ 254,544 $ 263,278 $ 665,068 $ 625,887 Revenue by contract type (amounts in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Fixed Unit Price $ 208,070 $ 230,002 $ 562,791 $ 564,797 Lump Sum and Other 46,474 33,276 102,277 61,090 Heavy Civil Construction Revenue $ 254,544 $ 263,278 $ 665,068 $ 625,887
Costs in Excess of Billings and Billings in Excess of Costs	The table below reconciles the net excess billings to the amounts included in the condensed consolidated balance sheets at those dates (amounts in thousands): September 30, December 31, Costs and estimated earnings in excess of billings on uncompleted contracts $ 40,275 $ 37,112 Billings in excess of costs and estimated earnings on uncompleted contracts (63,964 ) (62,374 ) Net amount of billings in excess of costs and estimated earnings on uncompleted contracts $ (23,689 ) $ (25,262 )

Consolidated 50% Owned Subsid_2

Consolidated 50% Owned Subsidiaries, including Variable Interest Entities ("VIE") (Tables)	9 Months Ended
	Sep. 30, 2018
Noncontrolling Interest [Abstract]
Schedule of Components of Agreement Obligation	The liability consists of the following (amounts in thousands): September 30, December 31, Members’ interest subject to mandatory redemption $ 40,000 $ 40,000 Net accumulated earnings 8,844 7,386 Total liability $ 48,844 $ 47,386
Summary of Financial Information of Variable Interest Entities	As such, the following table presents the condensed financial information of Myers, which is reflected in the Company’s condensed consolidated balance sheets and statements of operations, as follows (amounts in thousands): September 30, December 31, Assets: Current assets: Cash and cash equivalents $ 4,580 $ 8,590 Contracts receivable, including retainage 31,158 26,844 Other current assets 16,054 15,672 Total current assets 51,792 51,106 Property and equipment, net 7,696 9,001 Goodwill 1,501 1,501 Total assets $ 60,989 $ 61,608 Liabilities: Current liabilities: Accounts payable $ 28,561 $ 28,448 Other current liabilities 13,150 11,798 Total current liabilities 41,711 40,246 Long-term liabilities: Other long-term liabilities 67 3,491 Total liabilities $ 41,778 $ 43,737 Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Revenues $ 56,816 $ 64,266 $ 142,786 $ 126,333 Operating income 2,488 3,666 5,227 6,307 Net income attributable to Sterling common stockholders 1,245 1,834 2,615 3,149

Construction Joint Ventures (Ta

Construction Joint Ventures (Tables)	9 Months Ended
	Sep. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Change in non-controlling interest	The following table summarizes the changes in noncontrolling interests (amounts in thousands): Nine Months Ended September 30, 2018 2017 Balance, beginning of period $ 4,856 $ 656 Net income attributable to noncontrolling interest included in equity 3,409 2,966 Distributions to noncontrolling interest owners (1,350 ) — Balance, end of period $ 6,915 $ 3,622
Condensed Balance Sheet	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 condensed consolidated financial statements are shown below (amounts in thousands): September 30, December 31, Total combined: Current assets $ 64,957 $ 64,574 Less current liabilities (72,617 ) (78,349 ) Net liabilities $ (7,660 ) $ (13,775 ) Sterling’s receivables from and equity in noncontrolling construction joint ventures $ 11,521 $ 11,380
Condensed Income Statement	Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Total combined: Revenues $ 29,557 $ 27,703 $ 89,010 $ 61,210 Income before tax 1,728 (6,281 ) 7,324 (3,611 ) Sterling’s noncontrolling interest: Revenues $ 12,820 $ 13,664 $ 41,739 $ 28,826 Income before tax 858 (1,629 ) 3,716 (358 )

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Summary of Property and Equipment	Property and equipment are summarized as follows (amounts in thousands): September 30, December 31, Construction equipment $ 123,551 $ 118,868 Transportation equipment 18,285 17,511 Buildings 9,770 9,577 Office equipment 2,715 3,339 Leasehold Improvement 914 914 Construction in progress 327 258 Land 2,720 2,348 Water rights — 200 158,282 153,015 Less accumulated depreciation (106,086 ) (98,609 ) Total property and equipment, net $ 52,196 $ 54,406

Intangibles (Tables)

Intangibles (Tables)	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Finite-Lived Intangible Assets	The following table presents Sterling's acquired finite-lived intangible assets at September 30, 2018 and December 31, 2017 (in thousands): September 30, 2018 December 31, 2017 Weighted Gross Gross Customer relationships 23 years $ 40,823 $ (2,707 ) $ 40,823 $ (1,353 ) Trade name 13 years 5,307 (788 ) 5,307 (394 ) Noncompetition agreements 7 years 487 (104 ) 487 (52 ) Total 22 years $ 46,617 $ (3,599 ) $ 46,617 $ (1,799 )

Secured Credit Facility and O_2

Secured Credit Facility and Other Debt (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	Debt consists of the following (in thousands): September 30, December 31, Loan $ 74,571 $ 85,000 Notes and deferred payments to sellers, Tealstone acquisition 13,265 12,393 Notes payable for transportation and construction equipment and other 859 1,557 Total debt 88,695 98,950 Less - Current maturities of long-term debt (3,014 ) (3,978 ) Less - Unamortized deferred loan costs (7,257 ) (8,812 ) Total long-term debt $ 78,424 $ 86,160

Net Income Per Share Attribut_2

Net Income Per Share Attributable to Sterling Common Stockholders (Tables)	9 Months Ended
	Sep. 30, 2018
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 (amounts in thousands, except per share data): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Numerator: Net income attributable to Sterling common stockholders $ 8,915 $ 7,132 $ 19,580 $ 8,537 Weighted average common shares outstanding — basic 26,908 26,486 26,893 25,787 Shares for dilutive unvested stock and warrants 387 434 281 473 Weighted average common shares outstanding and incremental shares assumed repurchased— diluted 27,295 26,920 27,174 26,260 Basic income per share attributable to Sterling common stockholders $ 0.33 $ 0.27 $ 0.73 $ 0.33 Diluted income per share attributable to Sterling common stockholders $ 0.33 $ 0.26 $ 0.72 $ 0.33

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	The following table presents total revenue and income from operations by reportable segment for the three and nine months ended September 30, 2018 and 2017 (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Revenue Heavy Civil Construction $ 254,544 $ 263,278 $ 665,068 $ 625,887 Residential Construction 36,722 40,941 117,424 78,160 Total Revenue $ 291,266 $ 304,219 $ 782,492 $ 704,047 Operating Income Heavy Civil Construction $ 9,191 $ 6,960 $ 17,488 $ 8,627 Residential Construction 5,181 5,679 15,713 10,580 Total Operating Income $ 14,372 $ 12,639 $ 33,201 $ 19,207 The following table presents total assets by reportable segment at September 30, 2018 and December 31, 2017 (in thousands): September 30, December 31, Assets Heavy Civil Construction $ 363,058 $ 354,090 Residential Construction 131,106 109,208 Total Assets $ 494,164 $ 463,298

Tealstone Acquisition - Narrati

Tealstone Acquisition - Narrative (Details) - Notes and deferred payments to sellers, Tealstone acquisition - USD ($)	Apr. 03, 2020	Apr. 03, 2019	Apr. 03, 2017	Sep. 30, 2018
Business Acquisition [Line Items]
Percentage of outstanding stock			100.00%
Cash			$ 55,000,000
Stock issued for Tealstone acquisition (in shares)			1,882,058
Promissory notes issued to the sellers			$ 5,000,000	$ 5,000,000
Business combination, contingent consideration, liability			$ 15,000,000
Scenario, Forecast
Business Acquisition [Line Items]
Cash	$ 7,500,000	$ 2,426,000

Tealstone Acquisition - Supplem

Tealstone Acquisition - Supplemental Pro Forma Information (Unaudited) (Details) - Notes and deferred payments to sellers, Tealstone acquisition $ in Thousands	9 Months Ended
	Sep. 30, 2017USD ($)
Pro forma revenue	$ 749,176
Pro forma net loss attributable to Sterling	$ 8,848

Revenue From Contracts With C_3

Revenue From Contracts With Customers - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)contract	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)contract	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Disaggregation of Revenue [Line Items]
Remaining performance obligation	$ 833		$ 833
Remaining performance obligation expected to be recognize the remainder of 2018	70.00%		70.00%
Minimum
Disaggregation of Revenue [Line Items]
Revenue recognition, contract term			12 months
Warranty, term			1 year
Maximum
Disaggregation of Revenue [Line Items]
Revenue recognition, contract term			36 months
Warranty, term			2 years
Transferred over Time | Product Concentration Risk | Revenue from Contract with Customer
Disaggregation of Revenue [Line Items]
Concentration risk, percentage	87.00%	87.00%	85.00%	89.00%
Transferred at Point in Time | Product Concentration Risk | Revenue from Contract with Customer
Disaggregation of Revenue [Line Items]
Concentration risk, percentage	13.00%	13.00%	15.00%	11.00%
Heavy Civil Construction
Disaggregation of Revenue [Line Items]
Number of contracts (more than) | contract	150		150
Operating income (Loss)
Disaggregation of Revenue [Line Items]
Estimated construction gain (loss) before tax	$ 2.4	$ 1.3	$ 4.1	$ 0.2
Costs and Estimated Earnings in Excess of Billings
Disaggregation of Revenue [Line Items]
Contracts receivable unpaid project contract price	$ 9.3		$ 9.3		$ 10

Revenue From Contracts With C_4

Revenue From Contracts With Customers - Revenue By Major Market End (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Total Revenue	$ 291,266	$ 304,219	$ 782,492	$ 704,047
Heavy Civil Construction
Disaggregation of Revenue [Line Items]
Total Revenue	254,544	263,278	665,068	625,887
Heavy Civil Construction | Heavy Highway
Disaggregation of Revenue [Line Items]
Total Revenue	151,882	179,608	385,843	438,741
Heavy Civil Construction | Commercial
Disaggregation of Revenue [Line Items]
Total Revenue	32,261	15,209	89,890	27,050
Heavy Civil Construction | Aviation
Disaggregation of Revenue [Line Items]
Total Revenue	30,587	22,863	81,671	56,310
Heavy Civil Construction | Water Containment and Treatment
Disaggregation of Revenue [Line Items]
Total Revenue	18,457	20,518	48,973	43,388
Heavy Civil Construction | Other Revenue
Disaggregation of Revenue [Line Items]
Total Revenue	$ 21,357	$ 25,080	$ 58,691	$ 60,398

Revenue From Contracts With C_5

Revenue From Contracts With Customers - Revenue By Contract Type (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Total Revenue	$ 291,266	$ 304,219	$ 782,492	$ 704,047
Heavy Civil Construction
Disaggregation of Revenue [Line Items]
Total Revenue	254,544	263,278	665,068	625,887
Heavy Civil Construction | Fixed Unit Price
Disaggregation of Revenue [Line Items]
Total Revenue	208,070	230,002	562,791	564,797
Heavy Civil Construction | Lump Sum and Other
Disaggregation of Revenue [Line Items]
Total Revenue	$ 46,474	$ 33,276	$ 102,277	$ 61,090

Revenue From Contracts With C_6

Revenue From Contracts With Customers - Net Excess Billings (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Costs and estimated earnings in excess of billings on uncompleted contracts	$ 40,275	$ 37,112
Billings in excess of costs and estimated earnings on uncompleted contracts	(63,964)	(62,374)
Net amount of billings in excess of costs and estimated earnings on uncompleted contracts	$ (23,689)	$ (25,262)

Cash and Cash Equivalents (Deta

Cash and Cash Equivalents (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Line Items]
Restricted cash and cash equivalents	$ 4.1	$ 3.6
Other assets
Cash and Cash Equivalents [Line Items]
Restricted cash and cash equivalents	4.1	3
Other current assets
Cash and Cash Equivalents [Line Items]
Restricted cash and cash equivalents		0.6
Less than wholly-owned subsidiaries
Cash and Cash Equivalents [Line Items]
Restricted cash and cash equivalents	25.3	31.1
Majority-owned Joint Ventures
Cash and Cash Equivalents [Line Items]
Restricted cash and cash equivalents	$ 12.9	$ 18.9

Consolidated 50% Owned Subsid_3

Consolidated 50% Owned Subsidiaries, including Variable Interest Entities ("VIE") - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Noncontrolling Interest [Line Items]
Members’ interest subject to mandatory redemption	$ 40,000		$ 40,000		$ 40,000
Total disability insurance policies, per policy amount	20,000		20,000
Net accumulated earnings	5,100	$ 4,500	10,400	$ 7,000
Variable Interest Entity, Primary Beneficiary
Noncontrolling Interest [Line Items]
Members’ interest subject to mandatory redemption	40,000		40,000
Myers | Variable Interest Entity, Primary Beneficiary
Noncontrolling Interest [Line Items]
Members’ interest subject to mandatory redemption	$ 20,000		$ 20,000

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	Sep. 30, 2018	Dec. 31, 2017
Noncontrolling Interest [Abstract]
Members’ interest subject to mandatory redemption	$ 40,000	$ 40,000
Net accumulated earnings	8,844	7,386
Total liability	$ 48,844	$ 47,386

Consolidated 50% Owned Subsid_5

Consolidated 50% Owned Subsidiaries, including Variable Interest Entities ("VIE") Consolidated 50% Owned Subsidiaries, including Variable Interest Entities ("VIE") - Balance Sheet Information (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Cash and cash equivalents	$ 89,336	$ 83,953	$ 66,541	$ 42,785
Receivables, including retainage	160,247	133,931
Other current assets	8,857	7,529
Total current assets	313,376	278,526
Property and equipment, net	52,196	54,406
Goodwill	85,231	85,231
Total assets	494,164	463,298
Accounts payable	106,271	97,457
Other current liabilities	6,275	9,348
Total current liabilities	194,669	182,292
Other long-term liabilities	1,230	1,271
Variable Interest Entity, Primary Beneficiary
Schedule of Equity Method Investments [Line Items]
Cash and cash equivalents	4,580	8,590
Receivables, including retainage	31,158	26,844
Other current assets	16,054	15,672
Total current assets	51,792	51,106
Property and equipment, net	7,696	9,001
Goodwill	1,501	1,501
Total assets	60,989	61,608
Accounts payable	28,561	28,448
Other current liabilities	13,150	11,798
Total current liabilities	41,711	40,246
Other long-term liabilities	67	3,491
Total liabilities	$ 41,778	$ 43,737

Consolidated 50% Owned Subsid_6

Consolidated 50% Owned Subsidiaries, including Variable Interest Entities ("VIE") Consolidated 50% Owned Subsidiaries, including Variable Interest Entities ("VIE") - Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Schedule of Equity Method Investments [Line Items]
Operating income	$ 14,372	$ 12,639	$ 33,201	$ 19,207
Net income attributable to Sterling common stockholders	8,915	7,132	19,580	8,537
Variable Interest Entity, Primary Beneficiary
Schedule of Equity Method Investments [Line Items]
Revenues	56,816	64,266	142,786	126,333
Operating income	2,488	3,666	5,227	6,307
Net income attributable to Sterling common stockholders	$ 1,245	$ 1,834	$ 2,615	$ 3,149

Construction Joint Ventures - R

Construction Joint Ventures - Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period			$ 4,856	$ 656
Net income attributable to noncontrolling interest included in equity	$ 1,251	$ 1,694	3,409	2,966
Distributions to noncontrolling interest owners			(1,350)	0
Balance, end of period	$ 6,915	$ 3,622	$ 6,915	$ 3,622

Construction Joint Ventures - B

Construction Joint Ventures - Balance Sheet Information (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Current assets	$ 313,376	$ 278,526
Less current liabilities	(194,669)	(182,292)
Sterling’s receivables from and equity in noncontrolling construction joint ventures	11,521	11,380
Joint Ventures
Schedule of Equity Method Investments [Line Items]
Current assets	64,957	64,574
Less current liabilities	(72,617)	(78,349)
Net liabilities	(7,660)	(13,775)
Sterling’s receivables from and equity in noncontrolling construction joint ventures	$ 11,521	$ 11,380

Construction Joint Ventures - I

Construction Joint Ventures - Income Statement Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Sterling’s noncontrolling interest:
Revenues			$ 3,409	$ 2,966
Joint Ventures
Schedule of Equity Method Investments [Line Items]
Revenues	$ 29,557	$ 27,703	89,010	61,210
Income before tax	1,728	(6,281)	7,324	(3,611)
Sterling’s noncontrolling interest:
Revenues	12,820	13,664	41,739	28,826
Income before tax	$ 858	$ (1,629)	$ 3,716	$ (358)

Property and Equipment - Summar

Property and Equipment - Summary (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 158,282	$ 153,015
Less accumulated depreciation	(106,086)	(98,609)
Total property and equipment, net	52,196	54,406
Construction equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	123,551	118,868
Transportation equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	18,285	17,511
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	9,770	9,577
Office equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,715	3,339
Leasehold Improvement
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	914	914
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	327	258
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,720	2,348
Water rights
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 0	$ 200

Intangibles (Details)

Intangibles (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Weighted Average Life		22 years
Gross Carrying Amount	$ 46,617	$ 46,617	$ 46,617
Accumulated Amortization	(3,599)	(3,599)	(1,799)
Amortization of intangible assets	600	$ 1,800	1,800
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Weighted Average Life		23 years
Gross Carrying Amount	40,823	$ 40,823	40,823
Accumulated Amortization	(2,707)	$ (2,707)	(1,353)
Trade Names
Finite-Lived Intangible Assets [Line Items]
Weighted Average Life		13 years
Gross Carrying Amount	5,307	$ 5,307	5,307
Accumulated Amortization	(788)	$ (788)	(394)
Noncompete Agreements
Finite-Lived Intangible Assets [Line Items]
Weighted Average Life		7 years
Gross Carrying Amount	487	$ 487	487
Accumulated Amortization	$ (104)	$ (104)	$ (52)

Secured Credit Facility and O_3

Secured Credit Facility and Other Debt - Long-term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total debt	$ 88,695	$ 98,950
Less - Current maturities of long-term debt	(3,014)	(3,978)
Less - Unamortized deferred loan costs	(7,257)	(8,812)
Total long-term debt	78,424	86,160
Notes and deferred payments to sellers, Tealstone acquisition
Debt Instrument [Line Items]
Notes payable	13,265	12,393
Notes payable for transportation and construction equipment and other
Debt Instrument [Line Items]
Notes payable	859	1,557
Oaktree facility | Senior secured term loans | Equipment-based facility
Debt Instrument [Line Items]
Loan	$ 74,571	$ 85,000

Secured Credit Facility and O_4

Secured Credit Facility and Other Debt - Narrative (Details)	Apr. 03, 2020USD ($)	Apr. 03, 2019USD ($)	Apr. 03, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Amortization of debt issuance costs				$ 500,000	$ 500,000	$ 1,600,000	$ 1,000,000
Notes and deferred payments to sellers						0	11,588,000
Notes payable for transportation and construction equipment and other
Debt Instrument [Line Items]
Notes payable, noncurrent				$ 900,000		$ 900,000		$ 1,600,000
Notes payable for transportation and construction equipment and other | Minimum
Debt Instrument [Line Items]
Debt instrument, term						3 years
Debt instrument, interest rate, stated percentage				3.15%		3.15%
Notes payable for transportation and construction equipment and other | Maximum
Debt Instrument [Line Items]
Debt instrument, term						5 years
Debt instrument, interest rate, stated percentage				6.92%		6.92%
Warrants to the Lenders Under the Loan Agreement
Debt Instrument [Line Items]
Warrants and rights outstanding			$ 3,500,000
Notes and deferred payments to sellers, Tealstone acquisition
Debt Instrument [Line Items]
Promissory notes issued to the sellers			5,000,000			$ 5,000,000
Cash payments to the seller			55,000,000
Notes and deferred payments to sellers			11,600,000
Accretion expense				$ 300,000	$ 300,000	$ 900,000	$ 500,000
Notes and deferred payments to sellers, Tealstone acquisition | Scenario, Forecast
Debt Instrument [Line Items]
Cash payments to the seller	$ 7,500,000	$ 2,426,000
Term loan | Senior secured term loans | Loan and security agreement
Debt Instrument [Line Items]
Debt instrument face amount			$ 85,000,000
Loan prepayment offer required to make quarterly, percentage			75.00%
Debt instrument, financial covenants, maximum ratio of secured indebtedness to EBITDA, period one			2
Debt Instrument, financial covenants, maximum ratio of secured indebtedness to EBITDA, period two			1.8
Debt Instrument, financial covenants, minimum daily cash collateral, period two			$ 15,000,000
Debt instrument, financial covenants, minimum rolling four quarter gross margin in contract backlog, period one			65,000,000
Debt Instrument, financial covenants, minimum rolling four quarter gross margin in contract backlog, period two			70,000,000
Debt instrument, financial covenants, maximum incurrence of net capital expenditures during each of four consecutive fiscal quarters			15,000,000
Debt instrument, financial covenants, minimum bonding capacity			1,000,000,000
Debt instrument, financial covenants, minimum EBITDA during each four consecutive fiscal quarters			12,000,000
Debt issuance costs, net			$ 10,400,000
Debt instrument, term			5 years
Term loan | Senior secured term loans | Loan and security agreement | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate			8.75%
Measurement Input, Discount Rate | Notes and deferred payments to sellers, Tealstone acquisition
Debt Instrument [Line Items]
Fair value inputs, discount rate			0.12

Income Taxes and Deferred Tax_2

Income Taxes and Deferred Tax Asset/Liability (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Current income tax expense (benefit)	$ 114		$ 252
Income tax expense	1,413	$ 344	1,551	$ 469
Deferred tax expense	$ 1,300		$ 1,299	$ 0

Stockholder's Equity - Narrativ

Stockholder's Equity - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Subsidiary, Sale of Stock [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period (in shares)	35,464		398,936
Shares Forfeited			999
Shares accelerated for board of director exit	7,404		7,404
Allocated share-based compensation expense	$ 0.8	$ 0.6	$ 2.2	$ 2.5
Business exit costs				0.7
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized	$ 5.2	$ 1.1	$ 5.2	$ 1.1
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition			3 years
Restricted stock
Subsidiary, Sale of Stock [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period (in shares)		8,000		174,410

Net Income Per Share Attribut_3

Net Income Per Share Attributable to Sterling Common Stockholders - Computation of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Numerator:
Net income attributable to Sterling common stockholders	$ 8,915	$ 7,132	$ 19,580	$ 8,537
Weighted average common shares outstanding, basic (in shares)	26,908	26,486	26,893	25,787
Shares for dilutive unvested stock and warrants (in shares)	387	434	281	473
Weighted average common shares outstanding and incremental shares assumed repurchased, diluted (in shares)	27,295	26,920	27,174	26,260
Basic income per share attributable to Sterling common stockholders (USD per share)	$ 0.33	$ 0.27	$ 0.73	$ 0.33
Diluted income per share attributable to Sterling common stockholders (USD per share)	$ 0.33	$ 0.26	$ 0.72	$ 0.33

Segment Information - Narrative

Segment Information - Narrative (Details)	9 Months Ended
	Sep. 30, 2018reporting_unitsegment
Segment Reporting [Abstract]
Number of reportable segments | segment	2
Number of reporting units | reporting_unit	2

Segment Information - Revenue,

Segment Information - Revenue, Operating Income, and Assets, By Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total Revenue	$ 291,266	$ 304,219	$ 782,492	$ 704,047
Operating income	14,372	12,639	33,201	19,207
Assets	494,164		494,164		$ 463,298
Heavy Civil Construction
Segment Reporting Information [Line Items]
Total Revenue	254,544	263,278	665,068	625,887
Operating income	9,191	6,960	17,488	8,627
Assets	363,058		363,058		354,090
Residential Construction
Segment Reporting Information [Line Items]
Total Revenue	36,722	40,941	117,424	78,160
Operating income	5,181	$ 5,679	15,713	$ 10,580
Assets	$ 131,106		$ 131,106		$ 109,208