Orion (ORN) 10-K 2 Mar 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Feb. 19, 2021	Jun. 30, 2020
Document and Entity Information [Abstract]
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2020
Entity File Number	1-33891
Entity Registrant Name	ORION GROUP HOLDINGS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-0097459
Entity Address, Address Line One	12000 Aerospace Avenue, Suite 300
Entity Address, City or Town	Houston
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77034
City Area Code	713
Local Phone Number	852-6500
Title of 12(b) Security	Common stock, $0.01 par value per share
Trading Symbol	ORN
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 95.3
Entity Common Stock, Shares Outstanding		30,460,573
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Central Index Key	0001402829
Amendment Flag	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 1,589	$ 128	$ 8,684
Restricted cash	0	958
Accounts receivable:
Trade, net of allowance for credit losses of $411 and $2,600, respectively	96,369	116,540
Retainage	36,485	42,547
Income taxes receivable	419	962
Other current	59,492	2,680
Inventory	1,548	1,114
Costs and estimated earnings in excess of billings on uncompleted contracts	32,271	41,389
Prepaid expenses and other	7,229	5,647
Total current assets	235,402	211,965
Property and equipment, net of depreciation	125,497	132,348
Operating lease right-of-use assets, net of amortization	18,874	17,997
Financing lease right-of-use assets, net of amortization	12,858	7,896
Inventory, non-current	6,455	7,037
Intangible assets, net of amortization	10,077	12,147
Deferred income tax asset	70	85
Other non-current	4,956	5,369
Total assets	414,189	394,844
Current liabilities:
Current debt, net of debt issuance costs	4,344	3,668
Accounts payable:
Trade	48,252	70,421
Retainage	716	562
Accrued liabilities	84,637	16,966
Income taxes payable	639	1,523
Billings in excess of costs and estimated earnings on uncompleted contracts	33,135	48,781
Current portion of operating lease liabilities	4,989	5,043
Current portion of financing lease liabilities	3,901	2,788
Total current liabilities	180,613	149,752
Long-term debt, net of debt issuance costs	29,523	68,029
Operating lease liabilities	14,537	13,596
Financing lease liabilities	8,376	3,760
Other long-term liabilities	19,837	20,436
Deferred income tax liability	207	205
Interest rate swap liability	1,602	1,045
Total liabilities	254,695	256,823
Stockholders? equity:
Preferred stock -- $0.01 par value, 10,000,000 authorized, none issued	0	0
Common stock -- $0.01 par value, 50,000,000 authorized, 31,171,804 and 30,303,395 issued; 30,460,573 and 29,592,164 outstanding at December 31, 2020 and December 31, 2019, respectively	312	303
Treasury stock, 711,231 shares, at cost, as of December 31, 2020 and December 31, 2019, respectively	(6,540)	(6,540)
Accumulated other comprehensive loss	(1,602)	(1,045)
Additional paid-in capital	184,324	182,523
Retained loss	(17,000)	(37,220)
Total stockholders' equity	159,494	138,021	$ 141,585
Total liabilities and stockholders' equity	$ 414,189	$ 394,844

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Allowance for credit losses	$ 411	$ 2,600
Stockholders' Equity:
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	31,171,804	30,303,395
Common stock, shares outstanding	30,460,573	29,592,164
Treasury stock, shares (in shares)	711,231	711,231

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement
Contract revenues	$ 709,942	$ 708,390	$ 520,894
Costs of contract revenues	625,239	644,349	504,118
Gross profit	84,703	64,041	16,776
Selling, general and administrative expenses	65,091	61,012	53,197
Amortization of intangible assets	2,070	2,640	3,390
Gain on disposal of assets, net	(9,044)	(1,804)	(3,306)
Goodwill impairment charges		0	69,483
Other gain from continuing operations		0	(5,448)
Operating income (loss)	26,586	2,193	(100,540)
Other (expense) income:
Other income	347	771	1,692
Interest income	183	353	136
Interest expense	(4,920)	(6,808)	(7,943)
Other expense, net	(4,390)	(5,684)	(6,115)
Income (loss) before income taxes	22,196	(3,491)	(106,655)
Income tax expense	1,976	1,868	(12,233)
Net income (loss)	$ 20,220	$ (5,359)	$ (94,422)
Basic earnings (loss) per share (in dollars per share)	$ 0.67	$ (0.18)	$ (3.31)
Diluted earnings (loss) per share (in dollars per share)	$ 0.67	$ (0.18)	$ (3.31)
Shares used to compute income (loss) per share:
Basic (in shares)	30,122,362	29,322,054	28,518,353
Diluted (in shares)	30,122,362	29,322,054	28,518,353

Consolidated Statements of Comp

Consolidated Statements of Comprehensive (Loss) Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 20,220	$ (5,359)	$ (94,422)
Change in fair value of cash flow hedge, net of tax benefit of $128 and $228 for the years ended December 31, 2020 and 2019, respectively	(429)	(765)
Change in fair value of cash flow hedge, net of tax benefit of $15 for the year ended December 31, 2018			(26)
Total comprehensive income (loss)	$ 19,791	$ (6,124)	$ (94,448)

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Change in fair value of cash flow hedge, tax expense (benefit)	$ (128)	$ (228)
Change in fair value of cash flow hedge, net of tax expense (benefit)			$ (15)

Consolidated Statement of Stock

Consolidated Statement of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Additional Paid-In Capital	Retained EarningsCumulative Effect Period of Adoption Adjustment	Retained Earnings	Cumulative Effect Period of Adoption Adjustment	Total
Beginning balance, shares at Dec. 31, 2017	28,860,961
Beginning balance (Accounting Standards Update 2014-09) at Dec. 31, 2017					$ (286)		$ (286)
Beginning balance at Dec. 31, 2017	$ 288	$ (6,540)	$ (26)	$ 174,697		$ 62,847		$ 231,266
Beginning treasury stock, shares at Dec. 31, 2017		(711,231)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation				2,238				$ 2,238
Exercise of stock options, shares	488,303							488,303
Exercise of stock options	$ 5			2,810				$ 2,815
Issue restricted stock, shares	333,864
Issuance of restricted stock	$ 3			(3)
Forfeiture of restricted stock (in shares)	(71,139)
Cash flow hedge			(26)					(26)
Net income (loss)						(94,422)		(94,422)
Ending balance, shares at Dec. 31, 2018	29,611,989
Ending treasury stock, shares at Dec. 31, 2018		(711,231)
Ending balance at Dec. 31, 2018	$ 296	$ (6,540)	(52)	179,742		(31,861)		141,585
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation				2,753				$ 2,753
Exercise of stock options, shares	7,021							7,021
Exercise of stock options				35				$ 35
Issue restricted stock, shares	757,012
Issuance of restricted stock	$ 8			(8)
Forfeiture of restricted stock (in shares)	(72,627)
Forfeiture of restricted stock	$ (1)			1
Cash flow hedge			(993)					(993)
Net income (loss)						(5,359)		$ (5,359)
Ending balance, shares at Dec. 31, 2019	30,303,395							30,303,395
Ending treasury stock, shares at Dec. 31, 2019		(711,231)						(711,231)
Ending balance at Dec. 31, 2019	$ 303	$ (6,540)	(1,045)	182,523		(37,220)		$ 138,021
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation				1,998				$ 1,998
Exercise of stock options, shares								0
Issue restricted stock, shares	1,038,044
Issuance of restricted stock	$ 10			(10)
Forfeiture of restricted stock (in shares)	(107,383)
Purchase of vested stock-based awards, shares	(62,252)
Purchase of vested stock-based awards	$ (1)			(187)				$ (188)
Cash flow hedge			(557)					(557)
Net income (loss)						20,220		$ 20,220
Ending balance, shares at Dec. 31, 2020	31,171,804							31,171,804
Ending treasury stock, shares at Dec. 31, 2020		(711,231)						(711,231)
Ending balance at Dec. 31, 2020	$ 312	$ (6,540)	$ (1,602)	$ 184,324		$ (17,000)		$ 159,494

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities
Net income (loss)	$ 20,220	$ (5,359)	$ (94,422)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Depreciation and amortization	23,893	26,096	31,799
Amortization of ROU operating leases	5,874	5,177
Amortization of ROU finance leases	3,324	2,312
Write-off of debt issuance costs upon debt modification	0	399	2,164
Amortization of deferred debt issuance costs	763	453	725
Deferred income taxes	17	71	(13,194)
Stock-based compensation	1,998	2,753	2,238
Gain on disposal of assets	(6,185)	(1,804)	(3,306)
Gain on involuntary disposition of assets, net	(2,859)
Goodwill impairment charges		0	69,483
Allowance for credit losses	(487)	0	4,280
Other gain from continuing operations	0	0	(5,448)
Change in operating assets and liabilities:
Accounts receivable	23,587	(51,709)	10,936
Income tax receivable	543	(495)	(128)
Inventory	148	503	647
Prepaid expenses and other	(1,070)	131	1,671
Costs and estimated earnings in excess of billings on uncompleted contracts	9,118	(32,172)	36,789
Accounts payable	(22,015)	28,894	(4,584)
Accrued liabilities	11,092	1,334	(5,301)
Operating lease liabilities	(5,399)	(5,843)
Income tax payable	(884)	1,523	(256)
Billings in excess of costs and estimated earnings on uncompleted contracts	(15,646)	27,020	(12,162)
Net cash provided by (used in) operating activities	46,032	(716)	21,931
Cash flows from investing activities:
Proceeds from sale of property and equipment	5,944	2,015	3,234
Purchase of property and equipment	(14,694)	(17,199)	(17,714)
Contributions to CSV life insurance	(99)	(721)	(260)
Proceeds from return of investment			94
Insurance claim proceeds related to property and equipment	5,720	2,574	1,346
Net cash used in investing activities	(3,129)	(13,331)	(13,300)
Cash flows from financing activities:
Borrowings from Credit Facility	10,000	63,000	39,861
Payments made on borrowings from Credit Facility	(48,204)	(70,210)	(48,111)
Proceeds from sale-leaseback arrangement		18,210
Loan costs from Credit Facility	(389)	(1,680)	(861)
Capital lease liability			(2,737)
Payments of finance lease liabilities	(3,619)	(2,906)
Purchase of vested stock-based awards	(188)
Exercise of stock options		35	2,815
Net cash (used in) provided by financing activities	(42,400)	6,449	(9,033)
Net change in cash and cash equivalents	503	(7,598)	(402)
Cash and cash equivalents at beginning of period	1,086	8,684	9,086
Cash and cash equivalents at end of period	1,589	1,086	8,684
Supplemental disclosures of cash flow information, cash paid during the period for:
Interest	3,187	6,311	4,819
Taxes, net of refunds	$ 2,174	$ 578	903
Non-cash investing activity
Capital lease expenditures included in accrued expenses			$ 13,103

Description of Business and Bas

Description of Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Basis of Presentation	Orion Group Holdings, Inc. and Subsidiaries Notes to Consolidated Financial Statements Years Ended December 31, 2020, 2019 and 2018 (Tabular Amounts in thousands, Except Share and per Share Amounts) 1. Description of Business Orion Group Holdings, Inc., its subsidiaries and affiliates (hereafter collectively referred to as the "Company"), provide a broad range of specialty construction services in the infrastructure, industrial, and building sectors of the continental United States, Alaska, Canada and the Caribbean Basin. The Company’s marine segment services the infrastructure sector through marine transportation facility construction, marine pipeline construction, marine environmental structures, dredging of waterways, channels and ports, environmental dredging, design, and specialty services. Its concrete segment services the building sector by providing turnkey concrete construction services including pour and finish, dirt work, layout, forming, rebar, and mesh across the light commercial, structural and other associated business areas. The Company is headquartered in Houston, Texas with offices throughout its operating areas. The tools used by the chief operating decision maker ("CODM") to allocate resources and assess performance are based on two reportable and operating segments: marine, which operates under the Orion brand and logo, and concrete, which operates under the TAS Commercial Concrete brand and logo. Although we describe the business in this report in terms of the services the Company provides, its base of customers and the areas in which it operates, the Company has determined that its operations currently comprise two reportable segments pursuant to Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 280, Segment Reporting In making this determination, the Company considered the similar economic characteristics of its operations that comprise its marine segment. For the marine segment, the methods used, and the internal processes employed, to deliver marine construction services are similar throughout the segment, including standardized estimating, project controls and project management. This segment has the same customers with similar funding drivers, and it complies with regulatory environments driven through Federal agencies such as the U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, U.S. Environmental Protection Agency and U.S. Occupational Safety and Health Administration ("OSHA"), among others. Additionally, the segment is driven by macro-economic considerations including the level of import/export seaborne transportation, development of energy-related infrastructure, cruise line expansion and operations, marine bridge infrastructure development, waterway pipeline crossings and the maintenance of waterways. These considerations, and others, are key catalysts for future prospects and are similar across the segment. For the concrete segment, the Company also considered the similar economic characteristics of these operations. The methods used, and the internal processes employed, to deliver concrete construction services are similar throughout the segment, including standardized estimating, project controls and project management. This segment complies with regulatory environments such as OSHA. Additionally, this segment is driven by macro-economic considerations, including movements in population, commercial real estate development, institutional funding and expansion, and recreational development, specifically in metropolitan areas of Texas. These considerations, and others, are key catalysts for future prospects and are similar across the segment. Basis of Presentation These consolidated financial statements include the accounts of the parent company, Orion Group Holdings, Inc. and its wholly-owned subsidiaries and have been prepared in accordance with U.S. GAAP. All intercompany balances and transactions have been eliminated in consolidation.

Summary of Significant Accounti

Summary of Significant Accounting Principles	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Principles	2. The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and 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. Management’s estimates, judgments and assumptions are continually evaluated based on available information and experience; however, actual amounts could differ from those estimates. On an ongoing basis, the Company evaluates the significant accounting policies used to prepare its consolidated financial statements, including, but not limited to, those related to: ● Revenue recognition from construction contracts; ● Accounts receivable and allowance for credit losses; ● Property, plant and equipment; ● Leases; ● Finite and infinite-lived intangible assets, testing for indicators of impairment; ● Stock-based compensation; ● Income taxes; and ● Self-insurance Revenue Recognition The Company adopted ASU 2014-09, Revenue from Contracts with Customers The Company’s revenue is derived from contracts to provide marine construction, dredging, turnkey concrete services, and other specialty services. The Company’s projects are typically short in duration and usually span a period of less than one year. The Company determines the appropriate accounting treatment for each contract before work begins and generally records revenue on contracts over time. Performance obligations are promises in a contract to transfer distinct goods or services to the customer and are the unit of account under Topic 606. The Company’s contracts and related change orders typically represent a single performance obligation because the Company provides a significant integrated service and individual goods and services are not separately identifiable. Revenue is recognized over time because control is continuously transferred to the customer. For contracts with multiple performance obligations, the Company allocates the contract’s transaction price to each performance obligation using its best estimate of the stand-alone selling price of each distinct good or service. Progress is measured by the percentage of actual contract costs incurred to date to total estimated costs for each contract. This method is used because management considers contract costs incurred to be the best available measure of progress on these contracts. Contract costs include all direct costs, such as material and labor, and those indirect costs incurred that are related to contract performance such as payroll taxes and insurance. General and administrative costs are charged to expense as incurred. Upfront costs, such as costs to mobilize personnel and equipment prior to satisfying a performance obligation are capitalized and amortized over the contract performance period. Changes in job performance, job conditions and estimated profitability, including those arising from final contract settlements, may result in revisions to costs and reported revenue and are recognized in the period in which the revisions are determined. The effect of changes in estimates of contract revenue or contract costs is recognized as an adjustment to recognized revenue on a cumulative catch-up basis. When losses on uncompleted contracts are anticipated, the entire loss is recognized in the period in which such losses are determined. Revenue is recorded net of any sales taxes collected and paid on behalf of the customer, if applicable. Contract revenue is derived from the original contract price as modified by agreed-upon change orders and estimates of variable consideration related to incentive fees and change orders or claims for which price has not yet been agreed by the customer. The Company estimates variable consideration based on its assessment of the most likely amount to which it expects to be entitled. Variable consideration is included in the estimated recognition of revenue to the extent it is probable that a significant reversal of cumulative recognized revenue will not occur. A determination that the collection of a claim is probable is based upon compliance with the terms of the contract and the extent to which the Company performed in accordance therewith but does not guarantee collection in full. Contract assets and liabilities include the following: ● Accounts Receivable: Trade, net of allowance - Represent amounts billed and currently due from customers and are stated at their estimated net realizable value. ● Accounts Receivable: Retainage - Represent amounts which have not been billed to or paid by customers due to retainage provisions in construction contracts, which amounts generally become payable upon contract completion and acceptance by the customer. ● Costs and Estimated Earnings in Excess of Billings on Uncompleted Contracts - Represent revenues recognized in excess of amounts billed, which management believes will be billed and collected within one year of the completion of the contract (i.e. Contract Assets) and are recorded as a current asset, until such amounts are either received or written off. ● Billings in Excess of Costs and Estimated Earnings on Uncompleted Contracts - Represent billings in excess of revenues recognized (i.e. Contract Liabilities) and are recorded as a current liability, until the underlying obligation has been performed or discharged. ​ Classification of Current Assets and Liabilities The Company includes in current assets and liabilities amounts realizable and payable in the normal course of contract completion. Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. At times, cash held by financial institutions may exceed federally insured limits. The Company has not historically sustained losses on its cash balances in excess of federally insured limits. Cash equivalents at December 31, 2020 and December 31, 2019 consisted primarily of overnight bank deposits. Restricted cash of $1.0 million at December 31, 2019 consisted of collateral related to a marine project that was completed during the quarter ended June 30, 2020. The Company had no restricted cash as of December 31, 2020. Risk Concentrations Financial instruments that potentially subject the Company to concentrations of credit risk principally consist of accounts receivable. The Company depends on its ability to continue to obtain federal, state and local governmental contracts, and indirectly, on the amount of funding available to these agencies for new and current governmental projects. Therefore, a portion of the Company’s operations is dependent upon the level and timing of government funding. Statutory mechanics liens provide the Company high priority in the event of lien foreclosures following financial difficulties of private owners, thus minimizing credit risk with private customers. Accounts Receivable Accounts receivable are stated at the historical carrying value, net of allowances for credit losses. The Company has significant investments in billed and unbilled receivables as of December 31, 2020 and December 31, 2019. Billed receivables represent amounts billed upon the completion of small contracts and progress billings on large contracts in accordance with contract terms and milestone achievements. Unbilled receivables on contracts, which are included in costs in excess of billings, arise as revenues are recognized over time. Unbilled amounts on contracts represent recoverable costs and accrued profits not yet billed. Revenue associated with these billings is recorded net of any sales tax, if applicable. Past due balances over 90 days and other higher risk amounts are reviewed individually for collectability. In establishing an allowance for credit losses, the Company evaluates its contract receivables and costs in excess of billings and thoroughly reviews historical collection experience, the financial condition of its customers, billing disputes and other factors. The Company writes off potentially uncollectible accounts receivable against the allowance for credit losses if it is determined that the amounts will not be collected or if a settlement is reached for an amount that is less than the carrying value. As of December 31, 2020, and December 31, 2019, the Company has recorded an allowance for credit losses of $0.4 million and $2.6 million, respectively. Balances billed to customers but not paid pursuant to retainage provisions in construction contracts generally become payable upon contract completion and acceptance by the owner. Retainage at December 31, 2020 totaled $36.5 million, of which $3.6 million is expected to be collected beyond December 31, 2021. Retainage at December 31, 2019 totaled $42.5 million. The Company negotiates change orders and claims with its customers. Unsuccessful negotiations of claims could result in a change to contract revenue that is less than amounts previously recorded, which could result in the recording of a loss in the amount of the shortfall. Successful claims negotiations could result in the recovery of previously recorded losses. Significant losses on receivables could adversely affect the Company’s financial position, results of operations and overall liquidity. Advertising Costs The Company primarily obtains contracts through the open bid process, and therefore advertising costs are not a significant component of expense. Advertising costs are expensed as incurred. Environmental Costs Costs related to environmental remediation are charged to expense. Other environmental costs are also charged to expense unless they increase the value of the property and/or provide future economic benefits, in which event the costs are capitalized. Environmental liabilities, if any, are recognized when the expenditure is considered probable and the amount can be reasonably estimated. The Company did not recognize any environmental liabilities as of December 31, 2020 or 2019. Fair Value Measurements The Company evaluates and presents certain amounts included in the accompanying consolidated financial statements at “fair value” in accordance with U.S. GAAP, which requires the Company to base its estimates on assumptions that market participants, in an orderly transaction, would use to price an asset or liability, and to establish a hierarchy that prioritizes the information used to determine fair value. Refer to Note 8 The Company generally applies fair value valuation techniques on a non-recurring basis associated with (1) valuing assets and liabilities acquired in connection with business combinations and other transactions; (2) valuing potential impairment loss related to long-lived assets; and (3) valuing potential impairment loss related to goodwill and indefinite-lived intangible assets. Inventory Current inventory consists of parts and small equipment held for use in the ordinary course of business and is valued at the lower of cost (using historical average cost) or net realizable value. Where shipping and handling costs are incurred by the Company, these charges are included in inventory and charged to cost of contract revenue upon use. Non-current inventory consists of spare parts (including engines, cutters and gears) that require special order or long-lead times for manufacture or fabrication, but must be kept on hand to reduce downtime and is valued at the lower of cost (using historical average cost) or net realizable value. Property and Equipment Property and equipment are recorded at cost. Ordinary maintenance and repairs that do not improve or extend the useful life of the asset are expensed as incurred. Major renewals and betterments of equipment are capitalized and depreciated generally over three When property and equipment are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the accounts and any resulting gain or loss is included in results of operations for the respective period. Depreciation is computed using the straight-line method over the estimated useful lives of the related assets for financial statement purposes, as follows: ​ ​ ​ ​ Automobiles and trucks 3 to 5 years Buildings and improvements 5 to 30 years Construction equipment 3 to 15 years Vessels and other equipment 1 to 15 years Office equipment 1 to 5 years ​ The Company generally uses accelerated depreciation methods for tax purposes where appropriate. Dry-docking costs are capitalized and amortized using the straight-line method over a period ranging from three Property and equipment are reviewed for impairment whenever events or changes in circumstances indicate the carrying amount of an asset or asset group may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated future cash flows, an impairment charge is recognized in the amount by which the carrying amount of the asset exceeds the fair value of the asset. Assets to be disposed of are separately presented in the balance sheet and reported at the lower of the carrying amount or the fair value, less the costs to sell, and are no longer depreciated. There were no assets classified as held for sale as of December 31, 2020 or December 31, 2019. Leases The Company adopted ASU 2016-02, Leases Note 19 Intangible Assets Intangible assets that have finite lives are amortized. In addition, the Company evaluates the remaining useful life of intangible assets in each reporting period to determine whether events and circumstances warrant a revision of the remaining period of amortization. If the estimate of an intangible asset’s remaining life is changed, the remaining carrying value of such asset is amortized prospectively over that revised remaining useful life. Intangible assets that have infinite lives are not amortized, but are subject to impairment testing at least annually or more frequently if events or circumstances indicate that the asset may be impaired. The Company has one infinite-lived intangible asset, a trade name, which it tests for impairment annually on October 31, or whenever events or circumstances indicate that the carrying amount of the trade name may not be recoverable. Impairment is calculated as the excess of the trade name’s carrying value over its fair value. The fair value of the trade name is determined using the relief from royalty method, a variation of the income approach. This method assumes that if a company owns intellectual property, it does not have to “rent” the asset and is, therefore, “relieved” from paying a royalty. Once a supportable royalty rate is determined, the rate is then applied to the projected revenues over the expected remaining life of the intangible assets to estimate the royalty savings. This approach is dependent on a number of factors, including estimates of future growth and trends, royalty rates, discount rates and other variables. See Note 9 Stock-Based Compensation The Company recognizes compensation expense for equity awards over the vesting period based on the fair value of these awards at the date of grant. The computed fair value of these awards is recognized as a non-cash cost over the period the employee provides services, which is typically the vesting period of the award. The fair value of options granted is estimated on the date of grant using the Black-Scholes option-pricing model. The Black-Scholes option-pricing model requires the use of subjective assumptions in the computation. Changes in these assumptions can cause significant fluctuations in the fair value of the option award. The fair value of restricted stock grants is equivalent to the fair value of the stock issued on the date of grant and is measured as the closing price of the stock on the date of grant. Compensation expense is recognized only for share-based payments expected to vest. The Company estimates forfeitures at the date of grant based on historical experience and future expectations. This assessment is updated on a periodic basis. See Note 15 Income Taxes The Company determines its consolidated income tax provision using the asset and liability method prescribed by U.S. GAAP, which requires the recognition of income tax expense for the amount of taxes payable or refundable for the current period and for deferred tax liabilities and assets for the future tax consequences of events that have been recognized in an entity’s financial statements or tax returns. The Company must make significant assumptions, judgments and estimates to determine its current provision for income taxes, its deferred tax assets and liabilities, and any valuation allowance to be recorded against any deferred tax asset. The current provision for income tax is based upon the current tax laws and the Company’s interpretation of these laws, as well as the probable outcomes of any tax audits. The value of any net deferred tax asset depends upon estimates of the amount and category of future taxable income reduced by the amount of any tax benefits that the Company does not expect to realize. Actual operating results and the underlying amount and category of income in future years could render current assumptions, judgments and estimates of recoverable net deferred taxes inaccurate, thus impacting the Company’s financial position and results of operations. The Company computes deferred income taxes using the liability method. Under the liability method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. Under the liability method, the effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740, Income Taxes See Note 13 Insurance Coverage The Company maintains insurance coverage The marine segment maintains five levels of excess loss insurance coverage, totaling $200 million in excess of primary coverage. The marine segment’s excess loss coverage responds to most of its policies when a primary limit of $1 million has been exhausted; provided that the primary limit for Contingent Maritime Employer’s Liability is $10 million and the Watercraft Pollution Policy primary limit is $5 million. The concrete segment maintains five levels of excess loss insurance coverage, totaling $200 million in excess of primary coverage. The concrete segment’s excess loss coverage responds to most of its policies when a primary limit of $1 million has been exhausted. If a claim arises and a potential insurance recovery is probable, the impending gain is recognized separately from the related loss. The recovery will only be recognized up to the amount of the loss once the recovery of the claim is deemed probable and any excess gain will fall under contingency accounting and will only be recognized once it is realized. The Company does not net insurance recoveries against the related claim liability as the amount of the claim liability is determined without consideration of the anticipated insurance recoveries from third parties. Separately, the Company’s marine segment employee health care is paid for by general assets of the Company and currently administered by a third party. The administrator has purchased appropriate stop-loss coverage. Losses on these policies up to the deductible amounts are accrued based upon known claims incurred and an estimate of claims incurred but not reported. The accruals are derived from known facts, historical trends and industry averages to determine the best estimate of the ultimate expected loss. Actual claims may vary from estimates. Any adjustments to such reserves are included in the Consolidated Results of Operations in the period in which they become known. The Company’s concrete segment employee health care is provided through two policies. A fully funded policy is offered primarily to salaried employees and their dependents while a partially self-funded plan with an appropriate stop-loss is offered primarily to hourly employees and their dependents. The self-funded plan is funded to the maximum exposure and, as a result, is expected to receive a partial refund after the policy expiration. The total accrual for insurance claims liabilities was $60.4 million and $3.7 million at December 31, 2020 and December 31, 2019, respectively, reflected as a component of accrued liabilities in the consolidated balance sheet. The total accrual for insurance claims receivable was $57.0 million and $1.1 million at December 31, 2020 and December 31, 2019, respectively, reflected as a component of other accounts receivable in the consolidated balance sheet. Recent Accounting Pronouncements The Financial Accounting Standards Board (“FASB”) issues accounting standards and updates (each, an "ASU") from time to time to its Accounting Standards Codification (‘ASC’), which is the primary source of U.S. GAAP. The Company regularly monitors ASUs as they are issued and considers applicability to its business. All ASUs are adopted by their respective due dates and in the manner prescribed by the FASB. In June 2016, 2016 13, Measurement of Credit Losses on Financial Instruments ​ During the periods presented in these financial statements, the Company implemented other new accounting pronouncements other than those noted above that are discussed in the notes where applicable.

Revenue

Revenue	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue	3. Contract revenues are recognized when control of the promised goods or services is transferred to the customer in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods or services. The following table represents a disaggregation of the Company’s contract revenues by service line for the marine and concrete segments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2020 2019 2018 Marine Segment ​ ​ ​ Construction ​ $ 272,870 ​ $ 242,527 ​ $ 156,925 Dredging ​ 106,647 ​ 112,303 ​ 73,237 Specialty Services ​ 8,656 ​ 14,308 ​ 13,721 Marine segment contract revenues ​ $ 388,173 ​ $ 369,138 ​ $ 243,883 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Concrete Segment ​ ​ ​ Structural ​ $ 85,904 ​ $ 54,497 ​ $ 60,926 Light Commercial ​ 235,835 ​ 284,624 ​ 215,628 Other ​ 30 ​ 131 ​ 457 Concrete segment contract revenues ​ $ 321,769 ​ $ 339,252 ​ $ 277,011 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total contract revenues ​ $ 709,942 ​ $ 708,390 ​ $ 520,894 ​ The Company has determined that it has two reportable segments pursuant to FASB ASC Topic 280, Segment Reporting Marine Segment Construction services include construction, restoration, maintenance, dredging and repair of marine transportation facilities, marine pipelines, bridges and causeways and marine environmental structures. Dredging services generally enhance or preserve the navigability of waterways or the protection of shorelines through the removal or replenishment of soil, sand or rock. Specialty services include design, salvage, demolition, surveying, towing, diving and underwater inspection, excavation and repair. Concrete Segment Structural services include elevated concrete pouring for products such as columns, elevated beams and structural walls. Light commercial services include horizontally poured concrete for products such as sidewalks, ramps, tilt walls and trenches. Other services comprise labor related to concrete pouring such as rebar installation and pumping services and typically support the Company’s structural and light commercial services.

Concentration of Risk and Enter

Concentration of Risk and Enterprise Wide Disclosures	12 Months Ended
	Dec. 31, 2020
Risks and Uncertainties [Abstract]
Concentration of Risk and Enterprise Wide Disclosures	4. In both reportable segments accounts receivable include amounts billed to governmental agencies and private customers and do not bear interest. Balances billed to customers but not paid pursuant to retainage provisions generally become payable upon contract completion and acceptance by the owner. ​ The table below presents the concentrations of current receivables (trade and retainage) at December 31, 2020 and December 31, 2019, respectively: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ December 31, 2019 Federal Government $ 4,826 4 % $ 4,765 3 % State Governments ​ — - % 5,864 4 % Local Governments ​ 17,823 13 % 41,944 26 % Private Companies ​ 110,616 83 % 109,114 67 % Gross receivables ​ ​ 133,265 ​ 100 % ​ 161,687 ​ 100 % Allowance for credit losses ​ ​ (411) ​ ​ ​ ​ (2,600) ​ ​ ​ Net receivables ​ $ 132,854 ​ ​ $ 159,087 ​ ​ ​ At December 31, 2020 and 2019, no single customer accounted for more than 10.0% of total current receivables. Additionally, the table below represents concentrations of contract revenue by type of customer for the years ended December 31, 2020, 2019 and 2018. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 % 2019 % 2018 % Federal Government $ 51,793 7 % $ 46,425 6 % $ 42,143 8 % State Governments 27,574 4 % 47,831 7 % 30,470 6 % Local Government 202,839 29 % 212,958 30 % 107,478 21 % Private Companies 427,736 60 % 401,176 57 % 340,803 65 % Total contract revenues $ 709,942 100 % $ 708,390 100 % $ 520,894 100 % ​ In the year ended December 31, 2020 one customer in the Local Governments category accounted for 11.4% of total contract revenues. In the years ended December 31, 2019 and 2018, no single customer exceeded 10.0% of total contract revenues. The Company does not believe that the loss of any one of its customers would have a material adverse effect on the Company or its subsidiaries and affiliates since no single specific customer sustains such a large portion of receivables or contract revenue over time. The concrete segment primarily purchases concrete from select suppliers. The loss of any one of these suppliers could adversely impact short-term operations. Contract revenues generated outside the United States totaled 1.8%, 1.6% and 2.3% of total revenues for the years ended December 31, 2020, 2019 and 2018, respectively, and were primarily located in the Caribbean Basin and Mexico.

Contracts in Progress

Contracts in Progress	12 Months Ended
	Dec. 31, 2020
Contractors [Abstract]
Contracts in Progress	​ ​ 5. Contracts in progress are as follows at December 31, 2020 and December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2020 ​ 2019 Costs incurred on uncompleted contracts ​ $ 1,151,987 ​ $ 884,244 Estimated earnings ​ 202,369 ​ 144,160 ​ ​ 1,354,356 ​ 1,028,404 Less: Billings to date ​ (1,355,220) ​ (1,035,796) ​ ​ $ (864) ​ $ (7,392) Included in the accompanying Consolidated Balance Sheets under the following captions: ​ ​ Costs and estimated earnings in excess of billings on uncompleted contracts ​ $ 32,271 ​ $ 41,389 Billings in excess of costs and estimated earnings on uncompleted contracts ​ (33,135) ​ (48,781) ​ ​ $ (864) ​ $ (7,392) ​ Included in cost and estimated earnings in excess of billings on uncompleted projects is approximately $3.1 million and $0.1 million at December 31, 2020 and 2019, respectively, related to claims and unapproved change orders. See Note 2 - Summary of Significant Accounting Policies Remaining performance obligations represent the transaction price of firm orders or other written contractual commitments from customers for which work has not been performed or is partially completed and excludes unexercised contract options and potential orders. As of December 31, 2020, the aggregate amount of the remaining performance obligations was approximately $439.5 million. Of this amount, the current expectation of the Company is that it will recognize $401.9 million, or 91%, in the next 12 months and the remaining balance thereafter.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Property and Equipment	6. The following is a summary of property and equipment at December 31, 2020 and December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2020 ​ 2019 Automobiles and trucks ​ $ 2,379 ​ $ 2,161 Building and improvements ​ 44,324 ​ 44,278 Construction equipment ​ 142,661 ​ 153,147 Vessels and other equipment ​ 79,499 ​ 84,022 Office equipment ​ 5,577 ​ 8,652 ​ ​ 274,440 ​ 292,260 Less: Accumulated depreciation ​ (186,615) ​ (196,973) Net book value of depreciable assets ​ 87,825 ​ 95,287 Construction in progress ​ 1,809 ​ 1,198 Land ​ 35,863 ​ 35,863 ​ ​ $ 125,497 ​ $ 132,348 ​ For the years ended December 31, 2020, 2019 and 2018, depreciation expense was $21.8 million, $23.5 million and $28.4 million, respectively. Substantially all depreciation expense is included in the cost of contract revenue in the Company’s Consolidated Statements of Operations. Substantially all of the assets of the Company are pledged as collateral under the Company’s Credit Agreement (as defined in Note 11 Substantially all of the Company’s long-lived assets are located in the United States.

Other Current Accounts Receivab

Other Current Accounts Receivable	12 Months Ended
	Dec. 31, 2020
Other Current Accounts Receivable
Other Current Accounts Receivable	7. Other current accounts receivable at December 31, 2020 and 2019 consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 December 31, 2019 Insurance claims receivable ​ $ 57,021 ​ $ 1,100 Accident loss receivables ​ 1,448 ​ 624 Other current receivables ​ ​ 1,023 ​ 956 Total other current accounts receivable ​ $ 59,492 ​ $ 2,680 ​

Fair Value

Fair Value	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value	8. Recurring Fair Value Measurements The fair value of financial instruments is the amount at which the instrument could be exchanged in a current transaction between willing parties. Due to their short-term nature, the Company believes that the carrying value of its accounts receivable, other current assets, accounts payable and other current liabilities approximate their fair values. The Company classifies financial assets and liabilities into the following three levels based on the inputs used to measure fair value in the order of priority indicated: ● Level 1- fair values are based on observable inputs such as quoted prices in active markets for identical assets or liabilities; ● Level 2 - fair values are based on pricing inputs other than quoted prices in active markets for identical assets and liabilities and are either directly or indirectly observable as of the measurement date; and ● Level 3- fair values are based on unobservable inputs in which little or no market data exists. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value requires judgment and may affect the placement of assets and liabilities within the fair value hierarchy levels. The following table sets forth by level within the fair value hierarchy the Company’s recurring financial assets and liabilities that were accounted for at fair value on a recurring basis as of December 31, 2020 and December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements ​ Carrying Value Level 1 Level 2 Level 3 December 31, 2020 ​ ​ ​ ​ ​ Assets: ​ Cash surrender value of life insurance policy ​ $ 3,169 — 3,169 — Liabilities: ​ Derivatives ​ $ 1,602 — 1,602 — December 31, 2019 ​ ​ ​ ​ ​ Assets: ​ Cash surrender value of life insurance policy ​ $ 2,714 — 2,714 — Liabilities: ​ Derivatives ​ $ 1,045 — 1,045 — ​ The Company’s derivatives, which are comprised of interest rate swaps, are valued using a discounted cash flow analysis that incorporates observable market parameters, such as interest rate yield curves and credit risk adjustments, that are necessary to reflect the probability of default by us or the counterparty. These derivatives are classified as a Level 2 measurement within the fair value hierarchy. See Note 11 Our concrete segment has life insurance policies with a combined face value of $11.1 million as of December 31, 2020. The policies are invested in mutual funds and the fair value measurement of the cash surrender balance associated with these policies is determined using Level 2 inputs within the fair value hierarchy and will vary with investment performance. These assets are included in the "Other noncurrent" asset section in the Company’s Consolidated Balance Sheets. Non-Recurring Fair Value Measurements The Company generally applies fair value valuation techniques on a non-recurring basis associated with (1) valuing assets and liabilities acquired in connection with business combinations and other transactions; (2) valuing potential impairment loss related to long-lived assets; and (3) valuing potential impairment loss related to the infinite-lived intangible asset. Other Fair Value Measurements The fair value of the Company’s debt at December 31, 2020 and 2019 approximated its carrying value of $35.1 million and $73.3 million, respectively, as interest is based on current market interest rates for debt with similar risk and maturity. If the Company’s debt was measured at fair value, it would have been classified as Level 2 in the fair value hierarchy.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	9. Goodwill In the fourth quarter of 2018, the Company’s annual goodwill impairment test indicated that its goodwill was fully impaired, primarily due to a decline in the Company’s market capitalization and as a result it incurred a goodwill impairment charge of $69.5 million with $33.8 million related to the Marine segment and $35.7 million related to the Concrete segment. Intangible assets The tables below present the activity and amortizations of finite-lived intangible assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2020 ​ 2019 Finite-lived intangible assets, beginning of period ​ $ 35,240 ​ $ 35,240 Additions ​ — ​ — Total finite-lived intangible assets, end of period ​ $ 35,240 ​ $ 35,240 ​ ​ ​ ​ ​ ​ ​ Accumulated amortization, beginning of period ​ $ (29,985) ​ $ (27,345) Current year amortization ​ (2,070) ​ (2,640) Total accumulated amortization ​ (32,055) ​ (29,985) ​ ​ ​ ​ ​ ​ ​ Net finite-lived intangible assets, end of period ​ $ 3,185 ​ ​ 5,255 Infinite-lived intangible assets ​ ​ 6,892 ​ ​ 6,892 Total net intangible assets ​ $ 10,077 ​ $ 12,147 ​ Remaining net finite-lived intangible assets were acquired as part of the purchase of TAS during 2015 and TBC during 2017 and included customer relationships. Customer relationships were valued at approximately $18.8 million and are being amortized over eight years using an accelerated method based on the pattern in which the economic benefits of the assets are consumed. For the year ended December 31, 2020, $2.1 million of amortization expense was recognized for these assets. In 2020 and 2019, the Company evaluated the useful lives of these finite-lived intangible assets and no change was needed. Future expense remaining of approximately $3.2 million will be amortized as follows: ​ ​ ​ ​ ​ 2021 ​ 1,520 2022 ​ 1,239 2023 ​ 389 2024 ​ 37 ​ ​ $ 3,185 ​ The annual impairment test concluded that the fair value of the Company’s infinite-lived trade name was in excess of the carrying value, therefore no impairment was recorded.

Accrued Liabilities

Accrued Liabilities	12 Months Ended
	Dec. 31, 2020
Payables and Accruals [Abstract]
Accrued Liabilities	10. Accrued liabilities at December 31, 2020 and 2019 consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 December 31, 2019 Accrued salaries, wages and benefits ​ $ 15,071 ​ $ 7,323 Accrual for insurance claims liabilities ​ 60,365 ​ 3,714 Sales taxes ​ 5,909 ​ 3,021 Property taxes ​ 908 ​ 389 Sale-leaseback arrangement ​ ​ 676 ​ ​ 482 Accounting and audit fees ​ ​ 344 ​ ​ 267 Interest ​ 22 ​ 76 Equipment purchase ​ ​ 461 ​ ​ — Other accrued expenses ​ 881 ​ 1,694 Total accrued liabilities ​ $ 84,637 ​ $ 16,966 ​

Long-term Debt And Line of Cred

Long-term Debt And Line of Credit	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Long-term Debt and Line of Credit	11. The Company entered into an amended syndicated credit agreement (the “Credit Agreement” also known as the “Fourth Amendment”) on July 31, 2018 with Regions Bank, as administrative agent and collateral agent, and the following co-syndication agents: Bank of America, N.A., BOKF, NA dba Bank of Texas, KeyBank National Association, NBH Bank, IBERIABANK, Trustmark National Bank, First Tennessee Bank NA, and Branch Banking and Trust Company. The Credit Facility matures on July 31, 2023. The Credit Agreement, which may be amended from time to time, provides for borrowings under a revolving line of credit and a term loan (together, the “Credit Facility”). The Credit Facility is guaranteed by the subsidiaries of the Company, secured by the assets of the Company, including stock held in its subsidiaries, and may be used to finance general corporate and working capital purposes, to finance capital expenditures, to refinance existing indebtedness, to finance permitted acquisitions and associated fees, and to pay for all related expenses to the Credit Facility. Interest is due and is computed based on the designation of the loan, with the option of a Base Rate Loan (the base rate plus the Applicable Margin), or an Adjusted LIBOR Rate Loan (the adjusted LIBOR rate plus the Applicable Margin). Interest is due on the last day of each quarter end for Base Rate Loans and at the end of the LIBOR rate period for Adjusted LIBOR Rate Loans. Principal balances drawn under the Credit Facility may be prepaid at any time, in whole or in part, without premium or penalty. Amounts repaid under the revolving line of credit may be re-borrowed. Total debt issuance costs for the Fourth Amendment, which included underwriter fees, legal fees and syndication fees were approximately $0.9 million and were capitalized as non-current deferred charges and amortized using the effective interest rate method over the duration of the loan. Additionally, the Company executed the Fifth Amendment during March 2019, which was made effective as of December 31, 2018, and executed the Sixth Amendment during May 2019. The Company incurred additional debt issuance costs of approximately $0.6 million and $0.9 million respectively for the Fifth and Sixth Amendments. With the execution of the aforementioned Sixth Amendment, $50.0 million of the existing revolving line of credit was modified and accounted for under guidelines of ASC 470-50, Debt, Modifications and Extinguishments, and a pro-rated portion of unamortized debt issuance costs of approximately $0.4 million was recognized as interest expense as of May 2019. The remaining debt issuance costs of approximately $0.9 million related to the Fourth, Fifth, and Sixth Amendments will be amortized over the duration of the loan. The Company entered into a new syndicated credit agreement (the “364-Day Revolving Credit Facility”) on June 8, 2020 with Regions Bank, as administrative agent and collateral agent, and the following co-syndication agents: Bank of America, N.A. and BOKF, NA dba Bank of Texas. Concurrent with this the Company executed an amendment to the Credit Agreement with its existing lenders (“also known as the “Seventh Amendment”) for the sole intent and outcome of executing the 364-Day Revolving Credit Facility. The 364-Day Revolving Credit Facility, which may be amended from time to time, provides for borrowings under a new revolving line of credit. The 364-Day Revolving Credit Facility is guaranteed by the subsidiaries of the Company, secured by the assets of the Company, including stock held in its subsidiaries, and may be used to finance general corporate and working capital purposes, to finance Permitted Acquisitions, and to pay transaction fees, costs and expenses related to the consummation of the Seventh Amendment. Interest is due and is computed based on the designation of the loan, with the option of a Base Rate Loan (the base rate plus the Applicable Margin), or an Adjusted LIBOR Rate Loan (the adjusted LIBOR rate plus the Applicable Margin). Interest is due on the last day of each quarter end for Base Rate Loans and at the end of the LIBOR rate period for Adjusted LIBOR Rate Loans. Principal balances drawn under the 364- Day Revolving Credit Facility may be prepaid at any time, in whole or in part, without premium or penalty. Amounts repaid under the 364-Day Revolving Credit Facility may be re-borrowed. The 364-Day Revolving Credit Facility matures on June 7, 2021. Total debt issuance costs for the 364-Day Revolving Credit Facility, which included underwriter fees, legal fees and syndication fees were approximately $0.4 million and were capitalized as current deferred charges and will be amortized over the duration of the loan. To date the Company has had no borrowings under the 364-Day Revolving Credit Facility. Effective, October 9, 2020, the Company entered into an amendment (the "Eighth Amendment") to its syndicated credit agreement (the "Credit Agreement" , with Regions Bank, as Administrative Agent and Collateral Agent and Bank of America, N.A., BOKF, NA dba Bank of Texas, Iberiabank, NBH Bank, Truist Bank, and Trustmark National Bank, as Lenders. The Eighth Amendment provides for administrative revisions to the Credit Agreement, including changes to repayment requirements for involuntary asset dispositions and changes to the timing of repayment for voluntary asset dispositions. The yearly weighted average interest rate for the Credit Facility as of December 31, 2020 was 3.11%. The Company’s obligations under debt arrangements consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ December 31, 2019 ​ ​ Debt Issuance ​ ​ Debt Issuance ​ ​ ​ Principal ​ Costs (1) ​ Total ​ Principal ​ Costs (1) ​ Total Term loan - current ​ $ 4,500 ​ $ (156) ​ $ 4,344 ​ $ 3,750 ​ $ (82) ​ $ 3,668 Total current debt ​ 4,500 ​ (156) ​ 4,344 ​ 3,750 ​ (82) ​ 3,668 Revolving line of credit ​ 5,000 ​ (174) ​ 4,826 ​ 36,000 ​ (782) ​ 35,218 Term loan - long-term ​ 25,586 ​ (889) ​ 24,697 ​ 33,540 ​ (729) ​ 32,811 Total long-term debt ​ ​ 30,586 ​ ​ (1,063) ​ ​ 29,523 ​ ​ 69,540 ​ ​ (1,511) ​ ​ 68,029 Total debt ​ $ 35,086 ​ $ (1,219) ​ $ 33,867 ​ $ 73,290 ​ $ (1,593) ​ $ 71,697 (1) Total debt issuance costs, include underwriter fees, legal fees and syndication fees and fees related to the execution of the Fourth, Fifth, Sixth, Seventh and Eighth Amendments to the Credit Agreement. Provisions of the revolving line of credit The Company has a maximum borrowing availability under the revolving line of credit and swingline loans (as defined in the Credit Agreement) of $50.0 million. There is a letter of credit sublimit that is equal to the lesser of $20.0 million and the aggregate unused amount of the revolving commitments then in effect. There is also a swingline sublimit equal to the lesser of $5.0 million and the aggregate unused amount of the revolving commitments then in effect. Revolving loans may be designated as Base Rate Loan or Adjusted LIBOR Rate Loans, at the Company’s request, and must be drawn in an aggregate minimum amount of $1.0 million and integral multiples of $250,000 in excess of that amount. Swingline loans must be drawn in an aggregate minimum amount of $250,000 and integral multiples of $50,000 in excess of that amount. The Company may convert, change, or modify such designations from time to time. The Company is subject to a commitment fee for the unused portion of the maximum borrowing availability under the revolving line of credit. The commitment fee, which is due quarterly in arrears, is equal to the Applicable Margin of the actual daily amount by which the Aggregate Revolving Commitments exceeds the Total Revolving Outstanding. The revolving line of credit termination date is the earlier of the Credit Facility termination date, July 31, 2023, or the date the outstanding balance is permanently reduced to zero, in accordance with the terms of the amended Credit Facility. The maturity date for amounts drawn under the revolving line of credit is the earlier of the Facility termination date of July 31, 2023, or the date the outstanding balance is permanently reduced to zero. As of December 31, 2020, the Company determined that it still does not have the intent to repay amounts drawn within the next twelve months. Therefore, the Company has classified the entire outstanding balance of the revolving line of credit as non-current. As of December 31, 2020, the outstanding balance for all borrowings under the revolving line of credit was $5.0 million, designated as a Base Rate Loan at a rate of 4.5%. There were also $1.7 million in outstanding letters of credit as of December 31, 2020, which reduced the maximum borrowing availability on the revolving line of credit to $43.3 million as of December 31, 2020. During the year ended December 31, 2020, the Company drew down $10.0 million for general corporate purposes and made payments of $41.0 million on the revolving line of credit which resulted in a net decrease of $31.0 million. Provisions of the 364-day revolving credit facility The Company has a maximum borrowing availability under the 364-Day Revolving Credit Facility of $20.0 million. Borrowings may be designated as Base Rate Loan or Adjusted LIBOR Rate Loans, at the Company’s request, and must be drawn in an aggregate minimum amount of $1.0 million and integral multiples of $250,000 in excess of that amount. The Company may convert, change, or modify rate designations from time to time. The Company is subject to a commitment fee for the unused portion of the maximum borrowing availability under the 364-Day Revolving Credit Facility. The commitment fee, which is due quarterly in arrears, is equal to the Applicable Margin of the actual daily amount by which the Aggregate Revolving Commitments exceeds the Total Revolving Outstanding. As of December 31, 2020, there were no outstanding borrowings under the 364-Day Revolving Credit Facility. Provisions of the term loan The original principal amount of $60.0 million for the term loan commitment is paid off in quarterly installment payments (as stated in the Credit Agreement). At December 31, 2020, the outstanding term loan component of the Credit Facility totaled $30.1 million and was secured by specific assets of the Company. The table below outlines the total remaining payment amounts annually for the term loan through maturity of the Credit Facility: ​ ​ ​ ​ ​ 2021 ​ 4,500 2022 ​ ​ 5,250 2023 ​ ​ 20,336 ​ ​ $ 30,086 ​ During 2020 the Company made the scheduled quarterly principal payments of $3.8 million, and an additional principal paydown of $3.4 million with proceeds from the sale of equipment which reduced the outstanding principal balance to $30.1 million as of December 31, 2020. The current portion of debt is $4.5 million, and the non-current portion is $25.6 million. As of December 31, 2020, the term loan was designated as an Adjusted LIBOR Rate Loan with an interest rate of 2.44%. Financial covenants Restrictive financial covenants under the Credit Facility include: ● A consolidated Fixed Charge Coverage Ratio to not be less than the following during each noted period: - Fiscal Quarter Ending December 31, 2019 and each Fiscal Quarter thereafter, to not be less than 1.25 to 1.00. ● A consolidated Leverage Ratio to not exceed the following during each noted period: - Fiscal Quarter Ending March 31, 2020 and each Fiscal Quarter thereafter, to not exceed 3.00 to 1.00. ​ In addition, the Credit Facility contains events of default that are usual and customary for similar arrangements, including non-payment of principal, interest or fees; breaches of representations and warranties that are not timely cured; violation of covenants; bankruptcy and insolvency events; and events constituting a change of control. The Company expects to meet its future internal liquidity and working capital needs and maintain or replace its equipment fleet through capital expenditure purchases and major repairs, from funds generated by its operating activities for at least the next 12 months. The Company believes that its cash position and available borrowings together with cash flow from its operations is adequate for general business requirements and to service its debt. The Company was in compliance with all financial covenants as of December 31, 2020. Derivative Financial Instruments On September 16, 2015, the Company entered into a series of receive-variable, pay-fixed interest rate swaps to hedge the variability in the interest payments on 50% of the aggregate principal amount of the Regions Term Loan outstanding, beginning with a notional amount of $67.5 million. There was a total of five sequential interest rate swaps to achieve the hedged position and each year on August 31, with the exception of the final swap, the existing interest rate swap was scheduled to expire and be immediately replaced with a new interest rate swap until the expiration of the final swap on July 31, 2020. On December 6, 2018, the Company entered into a sixth receive-variable, pay-fixed interest rate swap to hedge the variability of interest payments. The sixth swap began with a notional amount of $27.0 million on July 31, 2020 and hedges the variability in the interest payments on the aggregate scheduled principal amount of the Regions Term Loan outstanding. The sixth swap is scheduled to expire on July 31, 2023. At inception, these interest rate swaps were designated as cash flow hedges for hedge accounting, and as such, the effective portion of unrealized changes in market value are recorded in other comprehensive income (loss) and reclassified into earnings during the period in which the hedged forecasted transaction affects earnings. Gains and losses from hedge ineffectiveness are recognized in current earnings. The change in fair market value of the swaps for the comparative periods ended December 31, 2020, December 31, 2019, and December 31, 2018, as reflected in accumulated other comprehensive loss in the Consolidated Statements of Stockholders’ Equity, is approximately $0.6 million, $1.0 million and less than $0.1 million. The fair market value of the swaps as of December 31, 2020 is reflected as a liability of $1.6 million on the Consolidated Balance Sheets. See Note 8

Other Long-Term Liabilities

Other Long-Term Liabilities	12 Months Ended
	Dec. 31, 2020
Liabilities, Other than Long-term Debt, Noncurrent [Abstract]
Other Long-Term Liabilities	​ 12. ​ Other long-term liabilities at December 31, 2020 and 2019 consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 December 31, 2019 Sale-leaseback arrangement ​ $ 16,712 ​ $ 17,447 Deferred compensation ​ 2,818 ​ 2,528 Accrual for insurance claims liabilities ​ ​ 307 ​ 461 Total other long-term liabilities ​ $ 19,837 ​ $ 20,436 ​ Sale-Leaseback Arrangement On September 27, 2019, the Company entered into a purchase and sale agreement (the “Purchase and Sale Agreement”). Pursuant to the terms of the Purchase and Sale Agreement, the Company sold its 17300 & 17140 Market Street location in Channelview, Texas (the “Property”) for a purchase price of $19.1 million. Concurrent with the sale of the Property, the Company entered into a fifteen-year lease agreement (the “Lease Agreement”), whereby the Company will lease back the Property at an annual rental rate of approximately $1.5 million, subject to annual rent increases of 2.0% . Under the Lease Agreement, the Company has two consecutive options to extend the term of the Lease by ten years for each such option. This transaction was recorded as a failed sale-leaseback. The Company recorded a liability for the amounts received, will continue to depreciate the non-land portion of the asset, and has imputed an interest rate so that the net carrying amount of the financial liability and remaining assets will be zero at the end of the initial lease term. Concurrently with the sale, the Company paid $18.2 million towards the Term loan portion of the Company’s Credit Facility, consistent with terms of the Sixth Amendment.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	​ ​ 13. The following table presents the components of our consolidated income tax (benefit) expense for the years ended December 31, 2020, 2019 and 2018: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current Deferred Total Year ended December 31, 2020 ​ ​ ​ U.S. Federal ​ $ — ​ $ — ​ $ — State and local ​ 589 ​ $ 13 ​ $ 602 Foreign ​ 1,370 ​ 4 ​ 1,374 ​ ​ $ 1,959 ​ $ 17 ​ $ 1,976 Year ended December 31, 2019 ​ ​ ​ U.S. Federal ​ $ — ​ $ — ​ $ — State and local ​ 716 ​ $ 104 ​ $ 820 Foreign ​ 1,081 ​ (33) ​ 1,048 ​ ​ $ 1,797 ​ $ 71 ​ $ 1,868 Year ended December 31, 2018 ​ ​ ​ U.S. Federal ​ $ (12) ​ $ (12,664) ​ $ (12,676) State and local ​ 183 ​ $ (471) ​ $ (288) Foreign ​ 731 ​ — ​ 731 ​ ​ $ 902 ​ $ (13,135) ​ $ (12,233) ​ The Company’s income tax provision reconciles to the provision at the statutory U.S. federal income tax rate for each year ended December 31, as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 2019 2018 Statutory amount ​ $ 4,662 ​ $ (733) ​ $ (22,398) ​ Valuation allowance on foreign tax credits ​ 1,344 ​ 1,081 ​ 593 ​ State income tax, net of federal benefit ​ 792 ​ 991 ​ (1,922) ​ Permanent differences, other ​ 558 ​ 461 ​ 1,550 ​ Permanent differences, stock compensation ​ 328 ​ 311 ​ (24) ​ Valuation allowance, other ​ (5,795) ​ (166) ​ 10,384 ​ Other ​ 87 ​ (77) ​ (416) ​ Consolidated income tax provision ​ $ 1,976 ​ $ 1,868 ​ $ (12,233) ​ Consolidated effective tax rate ​ 8.9 % (53.5) % 11.5 % ​ In the year ended 2020, the Company’s effective tax rate differed from the statutory rate of 21% primarily due to the movement in the valuation allowance for current year activity, state income taxes and the non-deductibility of other permanent items. In the year ended 2019, the Company’s effective tax rate differed from the statutory rate of 21% primarily due to the recording of an additional valuation allowance to offset net operating loss carryforwards and foreign tax credits generated during the period, foreign taxes, state income taxes and the non-deductibility of certain permanent items. In the year ended 2018, the Company’s effective tax rate differed from the statutory rate of 21% primarily due to recording an $11.0 million, or $0.39 per share, valuation allowance against the Company’s net deferred tax assets, including net operating losses and foreign tax credits. The Company also recorded tax expense of $1.2 million related to the $69.5 million goodwill impairment. Additionally, the Company recorded tax expense related to permanent differences from meals and entertainment. ​ Deferred Taxes The Company’s deferred tax assets and liabilities are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Long Term ​ ​ As of December 31, ​ 2020 2019 Assets related to: ​ ​ Accrued liabilities ​ $ 1,058 ​ $ 1,030 Intangible assets ​ 2,818 ​ 3,020 Net operating loss carryforward ​ 10,259 ​ 15,246 Stock-based compensation ​ 377 ​ 586 Foreign tax credits ​ 3,782 ​ 2,570 Goodwill ​ 6,199 ​ 7,232 Leases ​ ​ 10,235 ​ ​ 9,038 Other ​ 1,518 ​ 1,347 Total gross deferred tax assets ​ 36,246 ​ 40,069 Less valuation allowance ​ ​ (12,493) ​ ​ (16,960) Total net deferred tax assets ​ ​ 23,753 ​ ​ 23,109 Liabilities related to: ​ ​ Depreciation and amortization ​ (23,308) ​ (22,634) Other ​ (582) ​ (595) Total deferred tax liabilities ​ (23,890) ​ (23,229) Net deferred tax liabilities ​ $ (137) ​ $ (120) ​ The Company has net operating loss carryforwards for federal income tax purposes of $23.1 million as of December 31, 2020, which are available to reduce future taxable income. The Company’s federal net operating losses arose after the 2017 tax year and can be carried forward for an indefinite period of time but are limited to offset 80% of taxable income in any given year. The Company has state net operating losses of $132.6 million that expire beginning in 2027. A portion of the state losses that arose after the 2017 tax year may be carried forward indefinitely. Additionally, the Company has foreign tax credits of $3.8 million that can be carried forward for up to ten years. The Company has foreign tax credits that will expire next year. The Company assesses the available positive and negative evidence to estimate if sufficient future taxable income will be generated to realize the existing deferred tax assets. The Company considers the scheduled reversal of deferred tax liabilities, available carryback periods, and tax-planning strategies in making this assessment. According to ASC subtopic 740-10, the Company’s three-year cumulative loss is a significant piece of objective evidence. This objective evidence is weighed more heavily than the Company’s subjective positive evidence such as our estimated future taxable income and growth. Therefore, as of December 31, 2020, the Company continues to maintain a valuation allowance of $12.5 million. This valuation allowance decreased by $4.5 million during the year ended December 31, 2020 primarily related to the utilization of net operating losses to offset income during the current period. Uncertain Tax Benefits The Company and its subsidiaries file consolidated federal income tax returns in the United States and also file in various states and foreign jurisdictions. With few exceptions, the Company remains subject to federal and state income tax examinations for the years of 2013-2020. As of December 31, 2020, the Company has recorded unrecognized tax benefits of $1.6 million for any uncertain tax positions. The Company does not expect that unrecognized tax benefits as of December 31, 2020 for certain federal income tax matters will significantly change over the next 12 months. The final outcome of these uncertain tax positions is not yet determinable. ​ The change in the total gross unrecognized tax benefits and prior year audit resolutions of the Company during the years ended December 31, 2020 and 2019 are reconciled in the table below: ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 2019 Balances at beginning of the year ​ $ 1,614 ​ $ 1,614 Additions based on tax position related to current year ​ — ​ — Additions based on tax positions related to prior years ​ — ​ — Reductions based on tax positions related to current year ​ — ​ — Reductions based on tax positions related to prior years ​ — ​ — Settlements with tax authorities ​ — ​ — Lapse of statute of limitations ​ — ​ — Balance at the end of year ​ $ 1,614 ​ $ 1,614 ​ The Company’s policy is to recognize interest and penalties related to any unrecognized tax liabilities as additional tax expense. No interest or penalties have been accrued at December 31, 2020, 2019 and 2018. The Company believes it has appropriate and adequate support for the income tax positions taken and to be taken on its tax returns and that its accruals for tax liabilities are adequate for all open years based on an assessment of many factors including past experience and interpretations of tax law applied to the facts of each matter. Although the Company believes its recorded assets and liabilities are reasonable, tax regulations are subject to interpretation and tax litigation is inherently uncertain; therefore the Company’s assessments can involve both a series of complex judgments about future events and rely heavily on estimates and assumptions. Although the Company believes that the estimates and assumptions supporting its assessments are reasonable, the final determination of tax audit settlements and any related litigation could be materially different from that which is reflected in historical income tax provisions and recorded assets and liabilities. If the Company were to settle an audit or a matter under litigation, it could have a material effect on the income tax provision, net income, or cash flows in the period or periods for which that determination is made. Any accruals for tax contingencies are provided for in accordance with U.S. GAAP . The Company does not believe that its tax positions will significantly change due to any settlement and/or expiration of statutes of limitations prior to December 31, 2021.

Earnings (Loss) Per Share

Earnings (Loss) Per Share	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Earnings (Loss) Per Share	14. Basic earnings (loss) per share is based on the weighted average number of common shares outstanding during each period. Diluted earnings (loss) per share is based on the weighted average number of common shares outstanding as well as the effect of all dilutive common stock equivalents during each period net income is generated. For the years ended December 31, 2020, 2019 and 2018, the Company had 1,159,440, 1,636,656, and 1,938,967, securities, respectively, that were potentially dilutive in earnings per share calculations. Such dilution is dependent on the excess of the market price of our stock over the exercise price and other components of the treasury stock method. The exercise price for certain stock options awarded by the Company exceeded the average market price of the Company’s common stock for the years ended December 31, 2020, 2019 and 2018. Such stock options are antidilutive and are not included in the computation of earnings (loss) per share for those periods. The following table reconciles the denominators used in the computations of both basic and diluted earnings (loss) per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2020 2019 2018 Basic: Weighted average shares outstanding 30,122,362 29,322,054 28,518,353 Diluted: Total basic weighted average shares outstanding 30,122,362 29,322,054 28,518,353 Effect of potentially dilutive securities: Common stock options — — — Total weighted average shares outstanding assuming dilution 30,122,362 29,322,054 28,518,353 ​

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2020
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	15. The Compensation Committee of the Company’s Board of Directors is responsible for the administration of the Company’s stock incentive plans, which include the balance of shares remaining under the 2011 Long Term Incentive Plan (the "2011 LTIP") and 2017 Long Term Incentive Plan (the "2017 LTIP"), which was approved by shareholders in May 2017 and authorized the maximum aggregate number of shares to be issued of 2,400,000. In general, the Company’s 2017 LTIP provides for grants of restricted stock and stock options to be issued with a per-share price equal to the fair market value of a share of common stock on the date of grant. Option terms are specified at each grant date, but are generally are 10 years from the date of issuance. Options generally vest over a three Restricted Stock The following table summarizes the restricted stock activity under the Company’s equity incentive plans : ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ Number ​ Average ​ ​ of ​ Fair Value ​ ​ Shares ​ Per Share Nonvested at January 1, 2018 372,460 ​ $ 6.01 Granted 333,864 ​ $ 7.47 Vested (217,244) ​ $ 6.61 Forfeited/repurchased shares (71,139) ​ $ 6.85 Nonvested at December 31, 2018 417,941 ​ $ 7.04 Granted 757,012 ​ $ 2.52 Vested (585,754) ​ $ 3.74 Forfeited/repurchased shares (72,627) ​ $ 6.05 Nonvested at December 31, 2019 516,572 ​ $ 4.29 Granted 1,038,044 ​ $ 2.76 Vested (496,797) ​ $ 2.87 Forfeited/repurchased shares (107,383) ​ $ 7.13 Nonvested at December 31, 2020 950,436 ​ $ 3.04 ​ Independent directors receive equity compensation in the form of grants. In May 2020, the Company’s six independent directors each received equity compensation grants of 39,823 shares, with a fair value of $2.26 per share. In January 2019, two new independent directors each received equity compensation grants of 8,427 shares, with a fair value of $4.45 per share. In May 2019, five of the Company’s independent directors each received equity compensation grants of 45,918 shares, with a fair value of $1.96 per share. In October 2019, a In May 2018, the five of the Company’s independent directors each received equity compensation grants of 12,064 shares, with a fair value of $7.46 per share. In February 2020, the Company granted an executive of the Company 15,121 shares of restricted common stock, which vested immediately on the date of grant. The fair value of all shares awarded on the date of grant was $4.96 per share. In March 2020, certain officers and executives of the Company were awarded 170,235 shares of restricted common stock with a vesting period of three years and a fair value of $3.73 per share. In May 2020, certain officers and executives of the Company were awarded 100,000 shares of restricted common stock with a vesting period of three years and a fair value of $2.26 per share. In September 2020, the Company granted an executive of the Company 25,000 shares of restricted common stock with a vesting period of three years and a fair value of $2.58 per share. In December 2020, certain officers and executives of the Company were awarded 95,000 shares with a vesting period of three years and a fair value of $4.92 per share. In March 2019, the Company granted an executive of the Company 168,350 shares of restricted common stock, which vested one-third at March 31, June 30, and September 30, 2019, respectively. The fair value of all shares awarded on the date of the grant was $2.97 per share. In May 2019, certain officers and executives of the Company were awarded 62,500 shares with a vesting period of three years and a fair value of $1.96 per share. In July 2019, certain officers and executives of the Company were awarded 46,500 shares with a vesting period of three years and a fair value of $3.66. In December 2019, certain officers and executives of the Company were awarded 31,500 shares with a vesting period of three years and a fair value of $5.08 per share. In May 2018, certain officers and executives of the Company were awarded 203,752 shares with a vesting period of three years and a fair value of $7.46 per share. In July 2018 an executive was awarded 2,769 shares of restricted common stock with a fair value of $9.03 per share. Performance Stock In May 2020, the Company awarded certain executives 300,000 shares of performance stock. The performance-based stock will potentially vest 50% if the target is met, with 25% each vesting on the second and third anniversary of the determination that the target was met, with 100% of the shares to be earned based on the achievement of an objective, tiered return on invested capital, measured over a one-year performance period ending June 30,2021. The Company evaluates the probability of achieving this each reporting period. The fair value of all shares awarded on the date of the grant was $2.26 per share. In May 2019, the Company awarded certain executives 187,500 shares of performance stock. The performance-based stock will potentially vest 50% if the target is met, with 25% each vesting on the second and third anniversary of the grant, with 100% of the shares to be earned based on the achievement of an objective, tiered return on invested capital, measured over a one-year performance period. The fair value of all shares awarded on the date of the grant was $1.96 per share. In August 2020, the Company determined the performance-based stock awarded in May 2019 vested at the outperformance level established above the target set based on the achievement of an objective, tiered return on invested capital, measured over a one-year performance period ending June 30, 2020. As a result, the executives earned an additional 93,750 shares of performance-based stock awards with a fair value of $1.96, of which 50% vested immediately on the date of determination and 25% each will vest on the first and second anniversary of the date of determination. In May 2018, the Company awarded certain executives 67,023 shares of performance based stock, which will potentially vest at the end of fiscal 2020, with 100% of the shares to be earned based on the achievement of an objective, tiered return on invested capital measured over a three-year performance period. The fair value of all shares awarded on the date of the grant was $7.46 per share. In January 2021, the Company assessed the performance metric was not met and therefore these shares of performance based stock were forfeited. Stock Options The following table summarizes the stock option activity under the Company’s equity incentive plans: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted Weighted ​ ​ ​ ​ ​ ​ Average ​ Average ​ ​ ​ ​ ​ Number ​ Exercise ​ Contractual ​ Aggregate ​ ​ of ​ Price ​ Life ​ Intrinsic ​ ​ Shares ​ Per Share ​ (Years) ​ Value Outstanding at January 1, 2018 1,911,121 ​ $ 7.79 ​ Granted 374,215 ​ $ 7.49 ​ Exercised (488,303) ​ $ 5.76 ​ Forfeited (132,252) ​ $ 7.89 ​ Outstanding at December 31, 2018 1,664,781 ​ $ 8.31 ​ Granted — ​ $ — ​ Exercised (7,021) ​ $ 4.94 ​ Forfeited (192,994) ​ $ 15.26 ​ Outstanding at December 31, 2019 1,464,766 ​ $ 7.41 ​ Granted — ​ $ — ​ Exercised — ​ $ — ​ Forfeited (542,151) ​ $ 7.94 ​ Outstanding at December 31, 2020 922,615 ​ $ 7.10 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Vested and expected to vest at December 31, 2020 922,246 ​ $ 7.10 5.29 ​ $ 35 Exercisable at December 31, 2020 888,350 ​ $ 7.08 5.21 ​ $ 35 ​ The Company calculates the fair value of each option on the date of grant using the Black-Scholes pricing model and the following weighted-average assumptions in each year: ​ ​ ​ ​ ​ ​ ​ 2018 Weighted average grant-date fair value of options granted ​ $ 2.78 ​ Risk-free interest rate ​ 2.65 % Expected volatility ​ 52 % Expected term of options (in years) ​ 3.0 ​ Dividend yield ​ — % ​ The risk-free interest rate is based on interest rates on U.S. Treasury zero-coupon issues that match the contractual terms of the stock option grants. The expected term represents the period in which the Company’s equity awards are expected to be outstanding, which for the years presented is based on the exercise history. For years ended December 31, 2020, 2019 and 2018, compensation expense related to stock based awards outstanding for the periods was $2.0 million, $2.8 million and $2.2 million, respectively. The Company applies a 3.2% and 5.5% forfeiture rate, which gets compounded over the vesting terms of the individual award, to its restricted stock and option grants, respectively, based on historical analysis. For the year ended December 31, 2020, expense related to the purchase of vested stock-based awards for certain officers of the Company was approximately $0.2 million. During the year ended December 31, 2018, certain officers and executives of the Company were awarded 374,215 options with a vesting period of three years and a weighted average exercise price of $7.49 per share. In the year ended December 31, 2020, no stock options were exercised. In the year ended December 31, 2019, the Company received proceeds of less than $0.1 million upon the exercise of 7,021 options. In the year ended December 31, 2018, the Company received proceeds of approximately $2.8 million upon the exercise of 488,303 options. As of December 31, 2020, total unrecognized compensation expense related to unvested stock and options was approximately $2.4 million, which is expected to be recognized over a period of approximately 2.2 years. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 2019 2018 Total intrinsic value of options exercised ​ $ — ​ $ — ​ $ 1,286 Total fair value of shares vested ​ $ 329 ​ $ 769 ​ $ 705 ​

Employee Benefits

Employee Benefits	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Employee Benefits	16. All of the Company’s marine segment employees except the Associate Divers, the Associate Tugmasters, and union employees in the Pacific Northwest, are eligible to participate in the Company’s 401(k) Retirement Plan after completing six months of service. Each participant may contribute between 1% and 80% of eligible compensation on a pre-tax basis, up to the annual IRS limit. The Company matches 100% on the first 2% of eligible compensation contributed to the Plan and 50% on the next 2% of eligible compensation contributed to the Plan. Participants’ contributions are fully vested at all times. Employer matching contributions vest over a four-year period. At its discretion, the Company may make additional matching and profit-sharing contributions. During the years ended December 31, 2020, 2019 and 2018 the Company contributed $1.2 million, $1.3 million and $1.4 million, respectively to the Plan. All of the Company’s concrete segment employees except Leads, Helpers, Laborers, Finishers, Formsetters, Carpenters, Rodbusters, Patchmen, Equipment Operators, Field Engineering Trainees and certain Highly Compensated Employees are eligible to participate in the AGC Southwest Chapters 401(k) Retirement Plan, a multiple employer plan, after completing three months of service. Each participant may contribute up to the annual IRS limit. The Company matches 50% on the first 6% of eligible compensation contributed to the Plan. Participants’ contributions are fully vested at all times. Employer matching contributions vest over a five-year period. At its discretion, the Company may make additional matching and profit-sharing contributions. During the year ended December 31, 2020, 2019 and 2018, the Company contributed less than $0.1 million, $0.1 million and $0.2 million, respectively. The Company contributes to several multi-employer defined pension plans under the terms of collective-bargaining agreements that cover its union-represented employees. Risks of participating in these multi-employer plans are different from single-employer plans in the following aspects: ● Assets contributed to the multi-employer plan by one employer may be used to provide benefits to employees of other participating employers; ● If a participating employer stops contributing to the plan, the unfunded obligations of the plan may be borne by the remaining participating employers; and ● If the Company chooses to stop participating in its multi-employer plans, it may be required to pay a withdrawal liability based on the underfunded status of the plan. The following table presents the Company’s participation in these plans: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pension Protection ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Expiration ​ ​ ​ ​ Act ("PPA") ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ of ​ ​ Employer ​ Certified Zone Status ​ FIP/RP ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Collective ​ ​ Identification ​ (1) ​ Status ​ Contributions ​ Surcharge ​ Bargaining Pension Trust Fund ​ Number ​ 2020 ​ 2019 ​ P/I (2) ​ 2020 ​ 2019 ​ 2018 ​ Imposed ​ Agreement International Union of Operating Engineers - Employers Construction Industry Retirement Plan - Local 302 and 612 Trust Funds 91-6028571 Green Green N/A $ 2,480 $ 3,021 $ 2,482 — 2022 Washington Laborers ​ 91-6022315 ​ Green ​ Green ​ N/A ​ $ 236 ​ $ 30 ​ $ — ​ — ​ 2023 Carpenters Retirement Plan of Western Washington 91-6029051 Green Green N/A ​ $ 1,898 ​ $ 695 ​ $ 932 — 2022 Cement Masons & Plasterers Trust Funds ​ 91-6066773 ​ Green ​ Green ​ N/A ​ $ 39 ​ $ 2 ​ $ — ​ — ​ 2023 Washington-Idaho-Montana Carpenters-Employers Retirement Trust Fund ​ 91-6123987 ​ Yellow ​ Yellow ​ I ​ $ — ​ $ 36 ​ $ — ​ — ​ 2021 Engineers - AGC Retirement Trust of the Inland Empire ​ 91-6070237 ​ Yellow ​ Yellow ​ I ​ $ — ​ $ 20 ​ $ — ​ — ​ 2021 Western Conference of Teamsters Pension Trust Fund ​ 91-6145047 ​ Green ​ Green ​ N/A ​ $ 15 ​ $ — ​ $ — ​ — ​ 2023 Alaska Carpenters Trust Fund 92-0120866 Yellow Yellow I ​ $ 271 ​ $ 377 ​ $ 328 — 2021 Alaska Laborers Trust Fund 91-6028298 Yellow Yellow I ​ $ 226 ​ $ 552 ​ $ 321 — 2023 (1) The most recent PPA zone status available in 2020 and 2019 is for the plan’s year end during 2019 and 2018, respectively. Zone status is based on information received from the plan and is indicative of the plans funding status. Among other factors, plans in the red zone are generally less than 65 percent funded, plans in the orange zone are less than 80 percent funded and have an Accumulated Funding Deficiency in the current year or projected into the next six years, plans in the yellow zone are less than 80 percent funded, and plans in the green zone are at least 80 percent funded. (2) The FIP/RP Status P/I column indicates plans for which a financial improvement plan ("FIP") or a rehabilitation plan ("RP") is either pending ("P"), or implemented ("I"). There are currently no plans to withdraw from any of the multi-employer plans in which the Company participates.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	17. The Company and one former and two current officers were named defendants in a class action lawsuit filed on April 11, 2019 in the United States District Court for the Southern District of Texas, Houston Division, seeking unstated compensatory damages under the federal securities laws allegedly arising from materially false and misleading statements during the period of March 13, 2018 to March 18, 2019. The complaint asserted, among other things, that the current and former officers caused the Company to overstate goodwill in certain periods; overstate accounts receivable; that the company lacked effective internal controls over financial reporting related to goodwill impairment testing and accounts receivable; and that as a result certain adjustments to goodwill and accounts receivable materially impacted the company’s financial statements, which in turn caused the company’s stock price to be artificially inflated during the class period. The District Court granted the Company’s Motion to Dismiss the Complaint on June 29, 2020 and the ruling became final on July 20, 2020 after no appeal was filed. On August 21, 2020, a Company dredge, the Waymon L. Boyd, was consumed by a fire while working on a project in the Port of Corpus Christi. Five Company as a party of interest in their investigation. Thus far, eight separate lawsuits have been filed against the Company by certain crewmembers or their heirs under the general maritime law and the Jones Act. In response thereto, the Company has filed an action in the U.S. District Court for the Southern District of Texas seeking consolidation of the lawsuits for procedural purposes since they all arise out of the same occurrence and seeking exoneration from or limitation of liability relating to the foregoing incident as provided for in the federal rules of procedure for maritime claims. The Limitation Court set a deadline of February 17, 2021 by which all claims must be filed In addition, the Company is involved in various other legal and other proceedings which are incidental to the conduct of its business, none of which in the opinion of management will have a material effect on the Company’s financial condition, results of operations or cash flows. Management believes that it has recorded adequate accrued liabilities and believes that it has adequate insurance coverage or has meritorious defenses for these other claims and contingencies. A legal matter was settled in the Company’s favor for $5.5 million during the first quarter of 2018. Settlement amounts were recorded in Other gain from continuing operations in the Consolidated Statement of Operations, Prepaid expenses and other (current portion of the notes receivable) and Other non-current assets (non-current portion of the notes receivable) in the Consolidated Balance Sheets. As of December 31, 2020, the current portion of the notes receivable was $0.8 million and the non-current portion was $1.8 million, net of $0.2 million of unamortized discount. Legal fees related to this matter were expensed as incurred during the respective reporting period. During the quarter ended September 30, 2020, the Company settled a long-standing dispute with a customer that resulted in recovery of $0.9 million of previously reserved accounts receivable.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Segment Information	18. The Company currently operates in two reportable segments: marine and concrete. The Company’s financial reporting systems present various data for management to run the business, including profit and loss statements prepared according to the segments presented. Management uses operating income to evaluate performance between the two segments. Segment information for the periods presented is provided as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended Year Ended ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ December 31, 2019 Marine ​ ​ ​ ​ ​ ​ Contract revenues ​ $ 388,173 ​ $ 369,138 Operating income ​ 16,935 ​ 1,057 Depreciation and amortization expense ​ (18,369) ​ (19,889) ​ ​ ​ ​ ​ ​ ​ Total assets ​ $ 290,372 ​ $ 264,681 Property and equipment, net ​ 109,298 ​ 114,873 ​ ​ ​ ​ ​ ​ ​ Concrete ​ ​ Contract revenues ​ $ 321,769 ​ $ 339,252 Operating income ​ 9,651 ​ 1,136 Depreciation and amortization expense ​ (8,848) ​ (8,519) ​ ​ ​ ​ ​ ​ ​ Total assets ​ $ 123,817 ​ $ 130,163 Property and equipment, net ​ 16,199 ​ 17,475 ​ There were $2.8 million in intersegment revenues between the Company’s two reportable segments for the year ended December 31, 2020. There were $1.2 million in intersegment revenues between the Company’s two reportable segments for the year ended December 31, 2019. The marine segment had foreign revenues of $12.5 million and $11.4. million, respectively, for the years ended December 31, 2020 and 2019. These revenues are derived from projects in the Caribbean Basin and Mexico and are paid primarily in U.S. dollars. There was no foreign revenue for the concrete segment.

Leases

Leases	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Leases	19. The Company has operating and finance leases for office space, equipment and vehicles. Management determines if a contract is or contains a lease at inception of the contract or modification of the contract. A contract is or contains a lease if the contract conveys the right to control the use of an identified asset for a period in exchange for consideration. Control over the use of the identified asset means the lessee has both (a) the right to obtain substantially all of the economic benefits from the use of the asset and (b) the right to direct the use of the asset. Finance and operating lease ROU assets and liabilities are recognized based on the present value of future minimum lease payments over the expected lease term at commencement date. As the implicit rate is not determinable in most of the Company’s leases, management uses the Company’s incremental borrowing rate based on the information available at commencement date in determining the present value of future payments. The expected lease term includes options to extend or terminate the lease when it is reasonably certain the Company will exercise such option. Lease expense for minimum lease payments is recognized on a straight-line basis over the expected lease term. The Company’s lease arrangements have lease and non-lease components. Leases with an expected term of 12 months or less are not accounted for on the balance sheet and the related lease expense is recognized on a straight-line basis over the expected lease term. The Company’s lease agreements do not contain any material residual value guarantees or material restrictive covenants. Leases recorded on the balance sheet consists of the following: ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, Leases ​ 2020 2019 Assets ​ ​ ​ ​ ​ Operating lease right-of-use assets, net (1) ​ $ 18,874 $ 17,997 Financing lease right-of-use assets, net (2) ​ 12,858 7,896 Total assets ​ $ 31,732 $ 25,893 Liabilities ​ Current ​ Operating ​ $ 4,989 $ 5,043 Financing ​ 3,901 2,788 Total current ​ 8,890 7,831 Noncurrent ​ Operating ​ 14,537 13,596 Financing ​ 8,376 3,760 Total noncurrent ​ 22,913 17,356 Total liabilities ​ $ 31,803 $ 25,187 (1) Operating lease right-of-use assets are recorded net of accumulated amortization of $9.0 million and $5.2 million as of December 31, 2020 and 2019, respectively. (2) Financing lease right-of-use assets are recorded net of accumulated amortization of $6.4 million and $6.2 million as of December 31, 2020 and 2019, respectively. Other information related to lease term and discount rate is as follows: ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ 2020 2019 Weighted Average Remaining Lease Term (in years) ​ ​ Operating leases 5.25 ​ 5.30 ​ Financing leases 4.96 ​ 1.18 ​ Weighted Average Discount Rate ​ ​ ​ Operating leases (1) 4.73 % 4.80 % Financing leases 4.46 % 5.10 % (1) Upon adoption of the new lease standard, discount rates used for existing operating leases were established on January 1, 2019. The components of lease expense are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 2019 Operating lease costs: ​ ​ Operating lease cost ​ $ 6,430 ​ $ 6,930 Short-term lease cost (1) ​ 3,871 ​ 2,001 Financing lease costs: ​ ​ Interest on lease liabilities ​ 548 ​ 362 Amortization of right-of-use assets ​ 3,324 ​ 2,312 Total lease cost ​ $ 14,173 ​ $ 11,605 (1) Includes expenses related to leases with a lease term of more than one month but less than one year. Supplemental cash flow information related to leases is as follows: ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 ​ 2019 Cash paid for amounts included in the measurement of lease liabilities: ​ ​ ​ ​ ​ Operating cash flows for operating leases $ 6,262 ​ $ 6,887 Operating cash flows for finance leases $ 548 ​ $ 362 Financing cash flows for finance leases $ 3,619 ​ $ 2,906 Non-cash activity: ​ ROU assets obtained in exchange for new operating lease liabilities $ 7,829 ​ $ 25,743 ROU assets obtained in exchange for new financing lease liabilities $ 11,270 ​ $ 1,021 ​ Maturities of lease liabilities are summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating Leases Finance Leases Year ending December 31, ​ ​ ​ ​ ​ ​ 2021 ​ $ 5,696 ​ $ 5,023 2022 ​ 4,275 ​ 1,395 2023 ​ 3,186 ​ 1,989 2024 ​ 2,528 ​ 1,429 2025 ​ 2,354 ​ 1,039 Thereafter ​ 4,130 ​ 3,000 Total future minimum lease payments ​ 22,169 ​ 13,875 Less - amount representing interest ​ 2,643 ​ 1,598 Present value of future minimum lease payments ​ 19,526 ​ 12,277 Less - current lease obligations ​ 4,989 ​ 3,901 Long-term lease obligations ​ $ 14,537 ​ $ 8,376 ​

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data	20. The following tables set forth selected unaudited financial information for the eight quarters in the two-year period ended December 31, 2020. This information has been prepared on the same basis as the audited financial statements and, in the opinion of management, contains all adjustments necessary for a fair presentation. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ First Second Third Fourth Total ​ ​ Quarter ​ Quarter ​ Quarter ​ Quarter ​ Year ​ (in thousands, except per share data) 2020 ​ ​ ​ ​ ​ Revenues ​ $ 166,620 ​ $ 183,713 ​ $ 189,433 ​ $ 170,176 ​ $ 709,942 Gross profit ​ 19,758 ​ 20,744 ​ 22,501 ​ 21,700 ​ 84,703 Operating income ​ 4,365 ​ 4,084 ​ 13,085 ​ 5,052 ​ 26,586 Income before income taxes ​ 3,100 ​ 3,008 ​ 12,106 ​ 3,982 ​ 22,196 Net income ​ 2,723 ​ 2,028 ​ 11,803 ​ 3,666 ​ 20,220 Earnings per share: ​ ​ ​ ​ ​ ​ Basic ​ $ 0.09 ​ $ 0.07 ​ $ 0.39 ​ $ 0.12 ​ $ 0.67 Diluted ​ $ 0.09 ​ $ 0.07 ​ $ 0.39 ​ $ 0.12 ​ $ 0.67 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ First Second Third Fourth Total ​ ​ Quarter ​ Quarter ​ Quarter ​ Quarter ​ Year ​ (in thousands, except per share data) 2019 ​ ​ ​ ​ ​ Revenues ​ $ 143,105 ​ $ 165,985 ​ $ 199,507 ​ $ 199,793 ​ $ 708,390 Gross profit ​ 9,082 ​ 14,977 ​ 20,893 ​ 19,089 ​ 64,041 Operating (loss) income ​ (6,177) ​ (423) ​ 6,092 ​ 2,701 ​ 2,193 (Loss) income before income taxes ​ (7,331) ​ (1,773) ​ 4,506 ​ 1,107 ​ (3,491) Net (loss) income ​ (7,924) ​ (1,633) ​ 4,039 ​ 159 ​ (5,359) (Loss) earnings per share: ​ ​ ​ ​ ​ ​ Basic ​ $ (0.27) ​ $ (0.06) ​ $ 0.14 ​ $ 0.01 ​ $ (0.18) Diluted ​ $ (0.27) ​ $ (0.06) ​ $ 0.14 ​ $ 0.01 ​ $ (0.18) ​

Schedule II - Valuation And Qua

Schedule II - Valuation And Qualifying Accounts	12 Months Ended
	Dec. 31, 2020
Valuation and Qualifying Accounts [Abstract]
Schedule II - Valuation And Qualifying Accounts	ORION GROUP HOLDINGS, INC. SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Dollars in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at the Charged to ​ ​ Balance at the ​ ​ Beginning of ​ Revenue, Cost ​ ​ ​ End of Description ​ the Period ​ or Expense ​ Deduction ​ the Period Year ended December 31, 2018 ​ ​ ​ ​ ​ ​ ​ ​ Allowance for credit losses ​ $ — ​ $ 4,280 ​ $ — ​ $ 4,280 Reserve for losses on uncompleted contracts ​ $ — ​ $ 22,770 ​ $ — ​ $ 22,770 Year ended December 31, 2019 ​ ​ ​ ​ Allowance for credit losses ​ $ 4,280 ​ $ — ​ $ 1,680 ​ $ 2,600 Reserve for losses on uncompleted contracts ​ $ 22,770 ​ $ 2,455 ​ $ 14,300 ​ $ 10,925 Year ended December 31, 2020 ​ ​ ​ ​ Allowance for credit losses ​ $ 2,600 ​ $ (487) ​ $ 1,702 ​ $ 411 Reserve for losses on uncompleted contracts ​ $ 10,925 ​ $ 543 ​ $ 9,995 ​ $ 1,473 ​

Summary of Significant Accoun_2

Summary of Significant Accounting Principles (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation These consolidated financial statements include the accounts of the parent company, Orion Group Holdings, Inc. and its wholly-owned subsidiaries and have been prepared in accordance with U.S. GAAP. All intercompany balances and transactions have been eliminated in consolidation.
Revenue Recognition	Revenue Recognition The Company adopted ASU 2014-09, Revenue from Contracts with Customers The Company’s revenue is derived from contracts to provide marine construction, dredging, turnkey concrete services, and other specialty services. The Company’s projects are typically short in duration and usually span a period of less than one year. The Company determines the appropriate accounting treatment for each contract before work begins and generally records revenue on contracts over time. Performance obligations are promises in a contract to transfer distinct goods or services to the customer and are the unit of account under Topic 606. The Company’s contracts and related change orders typically represent a single performance obligation because the Company provides a significant integrated service and individual goods and services are not separately identifiable. Revenue is recognized over time because control is continuously transferred to the customer. For contracts with multiple performance obligations, the Company allocates the contract’s transaction price to each performance obligation using its best estimate of the stand-alone selling price of each distinct good or service. Progress is measured by the percentage of actual contract costs incurred to date to total estimated costs for each contract. This method is used because management considers contract costs incurred to be the best available measure of progress on these contracts. Contract costs include all direct costs, such as material and labor, and those indirect costs incurred that are related to contract performance such as payroll taxes and insurance. General and administrative costs are charged to expense as incurred. Upfront costs, such as costs to mobilize personnel and equipment prior to satisfying a performance obligation are capitalized and amortized over the contract performance period. Changes in job performance, job conditions and estimated profitability, including those arising from final contract settlements, may result in revisions to costs and reported revenue and are recognized in the period in which the revisions are determined. The effect of changes in estimates of contract revenue or contract costs is recognized as an adjustment to recognized revenue on a cumulative catch-up basis. When losses on uncompleted contracts are anticipated, the entire loss is recognized in the period in which such losses are determined. Revenue is recorded net of any sales taxes collected and paid on behalf of the customer, if applicable. Contract revenue is derived from the original contract price as modified by agreed-upon change orders and estimates of variable consideration related to incentive fees and change orders or claims for which price has not yet been agreed by the customer. The Company estimates variable consideration based on its assessment of the most likely amount to which it expects to be entitled. Variable consideration is included in the estimated recognition of revenue to the extent it is probable that a significant reversal of cumulative recognized revenue will not occur. A determination that the collection of a claim is probable is based upon compliance with the terms of the contract and the extent to which the Company performed in accordance therewith but does not guarantee collection in full. Contract assets and liabilities include the following: ● Accounts Receivable: Trade, net of allowance - Represent amounts billed and currently due from customers and are stated at their estimated net realizable value. ● Accounts Receivable: Retainage - Represent amounts which have not been billed to or paid by customers due to retainage provisions in construction contracts, which amounts generally become payable upon contract completion and acceptance by the customer. ● Costs and Estimated Earnings in Excess of Billings on Uncompleted Contracts - Represent revenues recognized in excess of amounts billed, which management believes will be billed and collected within one year of the completion of the contract (i.e. Contract Assets) and are recorded as a current asset, until such amounts are either received or written off. ● Billings in Excess of Costs and Estimated Earnings on Uncompleted Contracts - Represent billings in excess of revenues recognized (i.e. Contract Liabilities) and are recorded as a current liability, until the underlying obligation has been performed or discharged.
Classification of Current Assets and Liabilities	Classification of Current Assets and Liabilities The Company includes in current assets and liabilities amounts realizable and payable in the normal course of contract completion.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. At times, cash held by financial institutions may exceed federally insured limits. The Company has not historically sustained losses on its cash balances in excess of federally insured limits. Cash equivalents at December 31, 2020 and December 31, 2019 consisted primarily of overnight bank deposits. Restricted cash of $1.0 million at December 31, 2019 consisted of collateral related to a marine project that was completed during the quarter ended June 30, 2020. The Company had no restricted cash as of December 31, 2020.
Risk Concentrations	Risk Concentrations Financial instruments that potentially subject the Company to concentrations of credit risk principally consist of accounts receivable. The Company depends on its ability to continue to obtain federal, state and local governmental contracts, and indirectly, on the amount of funding available to these agencies for new and current governmental projects. Therefore, a portion of the Company’s operations is dependent upon the level and timing of government funding. Statutory mechanics liens provide the Company high priority in the event of lien foreclosures following financial difficulties of private owners, thus minimizing credit risk with private customers.
Accounts Receivable	Accounts Receivable Accounts receivable are stated at the historical carrying value, net of allowances for credit losses. The Company has significant investments in billed and unbilled receivables as of December 31, 2020 and December 31, 2019. Billed receivables represent amounts billed upon the completion of small contracts and progress billings on large contracts in accordance with contract terms and milestone achievements. Unbilled receivables on contracts, which are included in costs in excess of billings, arise as revenues are recognized over time. Unbilled amounts on contracts represent recoverable costs and accrued profits not yet billed. Revenue associated with these billings is recorded net of any sales tax, if applicable. Past due balances over 90 days and other higher risk amounts are reviewed individually for collectability. In establishing an allowance for credit losses, the Company evaluates its contract receivables and costs in excess of billings and thoroughly reviews historical collection experience, the financial condition of its customers, billing disputes and other factors. The Company writes off potentially uncollectible accounts receivable against the allowance for credit losses if it is determined that the amounts will not be collected or if a settlement is reached for an amount that is less than the carrying value. As of December 31, 2020, and December 31, 2019, the Company has recorded an allowance for credit losses of $0.4 million and $2.6 million, respectively. Balances billed to customers but not paid pursuant to retainage provisions in construction contracts generally become payable upon contract completion and acceptance by the owner. Retainage at December 31, 2020 totaled $36.5 million, of which $3.6 million is expected to be collected beyond December 31, 2021. Retainage at December 31, 2019 totaled $42.5 million. The Company negotiates change orders and claims with its customers. Unsuccessful negotiations of claims could result in a change to contract revenue that is less than amounts previously recorded, which could result in the recording of a loss in the amount of the shortfall. Successful claims negotiations could result in the recovery of previously recorded losses. Significant losses on receivables could adversely affect the Company’s financial position, results of operations and overall liquidity.
Advertising Costs	Advertising Costs The Company primarily obtains contracts through the open bid process, and therefore advertising costs are not a significant component of expense. Advertising costs are expensed as incurred.
Environmental Costs	Environmental Costs Costs related to environmental remediation are charged to expense. Other environmental costs are also charged to expense unless they increase the value of the property and/or provide future economic benefits, in which event the costs are capitalized. Environmental liabilities, if any, are recognized when the expenditure is considered probable and the amount can be reasonably estimated. The Company did not recognize any environmental liabilities as of December 31, 2020 or 2019.
Fair Value Measurements	Fair Value Measurements The Company evaluates and presents certain amounts included in the accompanying consolidated financial statements at “fair value” in accordance with U.S. GAAP, which requires the Company to base its estimates on assumptions that market participants, in an orderly transaction, would use to price an asset or liability, and to establish a hierarchy that prioritizes the information used to determine fair value. Refer to Note 8 The Company generally applies fair value valuation techniques on a non-recurring basis associated with (1) valuing assets and liabilities acquired in connection with business combinations and other transactions; (2) valuing potential impairment loss related to long-lived assets; and (3) valuing potential impairment loss related to goodwill and indefinite-lived intangible assets.
Inventory	Inventory Current inventory consists of parts and small equipment held for use in the ordinary course of business and is valued at the lower of cost (using historical average cost) or net realizable value. Where shipping and handling costs are incurred by the Company, these charges are included in inventory and charged to cost of contract revenue upon use. Non-current inventory consists of spare parts (including engines, cutters and gears) that require special order or long-lead times for manufacture or fabrication, but must be kept on hand to reduce downtime and is valued at the lower of cost (using historical average cost) or net realizable value.
Property and Equipment	Property and Equipment Property and equipment are recorded at cost. Ordinary maintenance and repairs that do not improve or extend the useful life of the asset are expensed as incurred. Major renewals and betterments of equipment are capitalized and depreciated generally over three When property and equipment are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the accounts and any resulting gain or loss is included in results of operations for the respective period. Depreciation is computed using the straight-line method over the estimated useful lives of the related assets for financial statement purposes, as follows: ​ ​ ​ ​ Automobiles and trucks 3 to 5 years Buildings and improvements 5 to 30 years Construction equipment 3 to 15 years Vessels and other equipment 1 to 15 years Office equipment 1 to 5 years ​ The Company generally uses accelerated depreciation methods for tax purposes where appropriate. Dry-docking costs are capitalized and amortized using the straight-line method over a period ranging from three Property and equipment are reviewed for impairment whenever events or changes in circumstances indicate the carrying amount of an asset or asset group may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated future cash flows, an impairment charge is recognized in the amount by which the carrying amount of the asset exceeds the fair value of the asset. Assets to be disposed of are separately presented in the balance sheet and reported at the lower of the carrying amount or the fair value, less the costs to sell, and are no longer depreciated. There were no assets classified as held for sale as of December 31, 2020 or December 31, 2019.
Leases	Leases The Company adopted ASU 2016-02, Leases Note 19
Intangible Assets	Intangible Assets Intangible assets that have finite lives are amortized. In addition, the Company evaluates the remaining useful life of intangible assets in each reporting period to determine whether events and circumstances warrant a revision of the remaining period of amortization. If the estimate of an intangible asset’s remaining life is changed, the remaining carrying value of such asset is amortized prospectively over that revised remaining useful life. Intangible assets that have infinite lives are not amortized, but are subject to impairment testing at least annually or more frequently if events or circumstances indicate that the asset may be impaired. The Company has one infinite-lived intangible asset, a trade name, which it tests for impairment annually on October 31, or whenever events or circumstances indicate that the carrying amount of the trade name may not be recoverable. Impairment is calculated as the excess of the trade name’s carrying value over its fair value. The fair value of the trade name is determined using the relief from royalty method, a variation of the income approach. This method assumes that if a company owns intellectual property, it does not have to “rent” the asset and is, therefore, “relieved” from paying a royalty. Once a supportable royalty rate is determined, the rate is then applied to the projected revenues over the expected remaining life of the intangible assets to estimate the royalty savings. This approach is dependent on a number of factors, including estimates of future growth and trends, royalty rates, discount rates and other variables.
Stock-Based Compensation	Stock-Based Compensation The Company recognizes compensation expense for equity awards over the vesting period based on the fair value of these awards at the date of grant. The computed fair value of these awards is recognized as a non-cash cost over the period the employee provides services, which is typically the vesting period of the award. The fair value of options granted is estimated on the date of grant using the Black-Scholes option-pricing model. The Black-Scholes option-pricing model requires the use of subjective assumptions in the computation. Changes in these assumptions can cause significant fluctuations in the fair value of the option award. The fair value of restricted stock grants is equivalent to the fair value of the stock issued on the date of grant and is measured as the closing price of the stock on the date of grant. Compensation expense is recognized only for share-based payments expected to vest. The Company estimates forfeitures at the date of grant based on historical experience and future expectations. This assessment is updated on a periodic basis. See Note 15
Income Taxes	Income Taxes The Company determines its consolidated income tax provision using the asset and liability method prescribed by U.S. GAAP, which requires the recognition of income tax expense for the amount of taxes payable or refundable for the current period and for deferred tax liabilities and assets for the future tax consequences of events that have been recognized in an entity’s financial statements or tax returns. The Company must make significant assumptions, judgments and estimates to determine its current provision for income taxes, its deferred tax assets and liabilities, and any valuation allowance to be recorded against any deferred tax asset. The current provision for income tax is based upon the current tax laws and the Company’s interpretation of these laws, as well as the probable outcomes of any tax audits. The value of any net deferred tax asset depends upon estimates of the amount and category of future taxable income reduced by the amount of any tax benefits that the Company does not expect to realize. Actual operating results and the underlying amount and category of income in future years could render current assumptions, judgments and estimates of recoverable net deferred taxes inaccurate, thus impacting the Company’s financial position and results of operations. The Company computes deferred income taxes using the liability method. Under the liability method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. Under the liability method, the effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740, Income Taxes
Insurance Coverage	Insurance Coverage The Company maintains insurance coverage The marine segment maintains five levels of excess loss insurance coverage, totaling $200 million in excess of primary coverage. The marine segment’s excess loss coverage responds to most of its policies when a primary limit of $1 million has been exhausted; provided that the primary limit for Contingent Maritime Employer’s Liability is $10 million and the Watercraft Pollution Policy primary limit is $5 million. The concrete segment maintains five levels of excess loss insurance coverage, totaling $200 million in excess of primary coverage. The concrete segment’s excess loss coverage responds to most of its policies when a primary limit of $1 million has been exhausted. If a claim arises and a potential insurance recovery is probable, the impending gain is recognized separately from the related loss. The recovery will only be recognized up to the amount of the loss once the recovery of the claim is deemed probable and any excess gain will fall under contingency accounting and will only be recognized once it is realized. The Company does not net insurance recoveries against the related claim liability as the amount of the claim liability is determined without consideration of the anticipated insurance recoveries from third parties. Separately, the Company’s marine segment employee health care is paid for by general assets of the Company and currently administered by a third party. The administrator has purchased appropriate stop-loss coverage. Losses on these policies up to the deductible amounts are accrued based upon known claims incurred and an estimate of claims incurred but not reported. The accruals are derived from known facts, historical trends and industry averages to determine the best estimate of the ultimate expected loss. Actual claims may vary from estimates. Any adjustments to such reserves are included in the Consolidated Results of Operations in the period in which they become known. The Company’s concrete segment employee health care is provided through two policies. A fully funded policy is offered primarily to salaried employees and their dependents while a partially self-funded plan with an appropriate stop-loss is offered primarily to hourly employees and their dependents. The self-funded plan is funded to the maximum exposure and, as a result, is expected to receive a partial refund after the policy expiration. The total accrual for insurance claims liabilities was $60.4 million and $3.7 million at December 31, 2020 and December 31, 2019, respectively, reflected as a component of accrued liabilities in the consolidated balance sheet. The total accrual for insurance claims receivable was $57.0 million and $1.1 million at December 31, 2020 and December 31, 2019, respectively, reflected as a component of other accounts receivable in the consolidated balance sheet.
Recent Accounting Pronouncements	Recent Accounting Pronouncements The Financial Accounting Standards Board (“FASB”) issues accounting standards and updates (each, an "ASU") from time to time to its Accounting Standards Codification (‘ASC’), which is the primary source of U.S. GAAP. The Company regularly monitors ASUs as they are issued and considers applicability to its business. All ASUs are adopted by their respective due dates and in the manner prescribed by the FASB. In June 2016, 2016 13, Measurement of Credit Losses on Financial Instruments ​ During the periods presented in these financial statements, the Company implemented other new accounting pronouncements other than those noted above that are discussed in the notes where applicable.

Summary of Significant Accoun_3

Summary of Significant Accounting Principles (Tables)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Schedule of depreciable lives of property, plant and equipment	​ ​ ​ ​ Automobiles and trucks 3 to 5 years Buildings and improvements 5 to 30 years Construction equipment 3 to 15 years Vessels and other equipment 1 to 15 years Office equipment 1 to 5 years

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Schedule of disaggregation of revenue	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2020 2019 2018 Marine Segment ​ ​ ​ Construction ​ $ 272,870 ​ $ 242,527 ​ $ 156,925 Dredging ​ 106,647 ​ 112,303 ​ 73,237 Specialty Services ​ 8,656 ​ 14,308 ​ 13,721 Marine segment contract revenues ​ $ 388,173 ​ $ 369,138 ​ $ 243,883 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Concrete Segment ​ ​ ​ Structural ​ $ 85,904 ​ $ 54,497 ​ $ 60,926 Light Commercial ​ 235,835 ​ 284,624 ​ 215,628 Other ​ 30 ​ 131 ​ 457 Concrete segment contract revenues ​ $ 321,769 ​ $ 339,252 ​ $ 277,011 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total contract revenues ​ $ 709,942 ​ $ 708,390 ​ $ 520,894

Concentration of Risk and Ent_2

Concentration of Risk and Enterprise Wide Disclosures (Tables)	12 Months Ended
	Dec. 31, 2020
Trade and contract retainage receivables
Concentration Risk [Line Items]
Schedules of concentration of risk, by risk factor	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ December 31, 2019 Federal Government $ 4,826 4 % $ 4,765 3 % State Governments ​ — - % 5,864 4 % Local Governments ​ 17,823 13 % 41,944 26 % Private Companies ​ 110,616 83 % 109,114 67 % Gross receivables ​ ​ 133,265 ​ 100 % ​ 161,687 ​ 100 % Allowance for credit losses ​ ​ (411) ​ ​ ​ ​ (2,600) ​ ​ ​ Net receivables ​ $ 132,854 ​ ​ $ 159,087 ​ ​
Contract revenues
Concentration Risk [Line Items]
Schedules of concentration of risk, by risk factor	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 % 2019 % 2018 % Federal Government $ 51,793 7 % $ 46,425 6 % $ 42,143 8 % State Governments 27,574 4 % 47,831 7 % 30,470 6 % Local Government 202,839 29 % 212,958 30 % 107,478 21 % Private Companies 427,736 60 % 401,176 57 % 340,803 65 % Total contract revenues $ 709,942 100 % $ 708,390 100 % $ 520,894 100 %

Contracts in Progress (Tables)

Contracts in Progress (Tables)	12 Months Ended
	Dec. 31, 2020
Contractors [Abstract]
Schedule of contracts in progress	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2020 ​ 2019 Costs incurred on uncompleted contracts ​ $ 1,151,987 ​ $ 884,244 Estimated earnings ​ 202,369 ​ 144,160 ​ ​ 1,354,356 ​ 1,028,404 Less: Billings to date ​ (1,355,220) ​ (1,035,796) ​ ​ $ (864) ​ $ (7,392) Included in the accompanying Consolidated Balance Sheets under the following captions: ​ ​ Costs and estimated earnings in excess of billings on uncompleted contracts ​ $ 32,271 ​ $ 41,389 Billings in excess of costs and estimated earnings on uncompleted contracts ​ (33,135) ​ (48,781) ​ ​ $ (864) ​ $ (7,392)

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Summary of property and equipment	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2020 ​ 2019 Automobiles and trucks ​ $ 2,379 ​ $ 2,161 Building and improvements ​ 44,324 ​ 44,278 Construction equipment ​ 142,661 ​ 153,147 Vessels and other equipment ​ 79,499 ​ 84,022 Office equipment ​ 5,577 ​ 8,652 ​ ​ 274,440 ​ 292,260 Less: Accumulated depreciation ​ (186,615) ​ (196,973) Net book value of depreciable assets ​ 87,825 ​ 95,287 Construction in progress ​ 1,809 ​ 1,198 Land ​ 35,863 ​ 35,863 ​ ​ $ 125,497 ​ $ 132,348

Other Current Accounts Receiv_2

Other Current Accounts Receivable (Tables)	12 Months Ended
	Dec. 31, 2020
Other Current Accounts Receivable
Schedule of other current accounts receivable	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 December 31, 2019 Insurance claims receivable ​ $ 57,021 ​ $ 1,100 Accident loss receivables ​ 1,448 ​ 624 Other current receivables ​ ​ 1,023 ​ 956 Total other current accounts receivable ​ $ 59,492 ​ $ 2,680

Fair Value (Tables)

Fair Value (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of fair value, assets and liabilities measured on recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements ​ Carrying Value Level 1 Level 2 Level 3 December 31, 2020 ​ ​ ​ ​ ​ Assets: ​ Cash surrender value of life insurance policy ​ $ 3,169 — 3,169 — Liabilities: ​ Derivatives ​ $ 1,602 — 1,602 — December 31, 2019 ​ ​ ​ ​ ​ Assets: ​ Cash surrender value of life insurance policy ​ $ 2,714 — 2,714 — Liabilities: ​ Derivatives ​ $ 1,045 — 1,045 —

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of changes and amortization of finite-lived intangible assets	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2020 ​ 2019 Finite-lived intangible assets, beginning of period ​ $ 35,240 ​ $ 35,240 Additions ​ — ​ — Total finite-lived intangible assets, end of period ​ $ 35,240 ​ $ 35,240 ​ ​ ​ ​ ​ ​ ​ Accumulated amortization, beginning of period ​ $ (29,985) ​ $ (27,345) Current year amortization ​ (2,070) ​ (2,640) Total accumulated amortization ​ (32,055) ​ (29,985) ​ ​ ​ ​ ​ ​ ​ Net finite-lived intangible assets, end of period ​ $ 3,185 ​ ​ 5,255 Infinite-lived intangible assets ​ ​ 6,892 ​ ​ 6,892 Total net intangible assets ​ $ 10,077 ​ $ 12,147
Summary of finite-lived intangible assets amortization expense	​ ​ ​ ​ ​ 2021 ​ 1,520 2022 ​ 1,239 2023 ​ 389 2024 ​ 37 ​ ​ $ 3,185

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Payables and Accruals [Abstract]
Schedule of accrued liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 December 31, 2019 Accrued salaries, wages and benefits ​ $ 15,071 ​ $ 7,323 Accrual for insurance claims liabilities ​ 60,365 ​ 3,714 Sales taxes ​ 5,909 ​ 3,021 Property taxes ​ 908 ​ 389 Sale-leaseback arrangement ​ ​ 676 ​ ​ 482 Accounting and audit fees ​ ​ 344 ​ ​ 267 Interest ​ 22 ​ 76 Equipment purchase ​ ​ 461 ​ ​ — Other accrued expenses ​ 881 ​ 1,694 Total accrued liabilities ​ $ 84,637 ​ $ 16,966 ​

Long-term Debt and Line of Cr_2

Long-term Debt and Line of Credit (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Schedule of debt	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ December 31, 2019 ​ ​ Debt Issuance ​ ​ Debt Issuance ​ ​ ​ Principal ​ Costs (1) ​ Total ​ Principal ​ Costs (1) ​ Total Term loan - current ​ $ 4,500 ​ $ (156) ​ $ 4,344 ​ $ 3,750 ​ $ (82) ​ $ 3,668 Total current debt ​ 4,500 ​ (156) ​ 4,344 ​ 3,750 ​ (82) ​ 3,668 Revolving line of credit ​ 5,000 ​ (174) ​ 4,826 ​ 36,000 ​ (782) ​ 35,218 Term loan - long-term ​ 25,586 ​ (889) ​ 24,697 ​ 33,540 ​ (729) ​ 32,811 Total long-term debt ​ ​ 30,586 ​ ​ (1,063) ​ ​ 29,523 ​ ​ 69,540 ​ ​ (1,511) ​ ​ 68,029 Total debt ​ $ 35,086 ​ $ (1,219) ​ $ 33,867 ​ $ 73,290 ​ $ (1,593) ​ $ 71,697 (1) Total debt issuance costs, include underwriter fees, legal fees and syndication fees and fees related to the execution of the Fourth, Fifth, Sixth, Seventh and Eighth Amendments to the Credit Agreement.
Schedule of debt maturity	​ ​ ​ ​ ​ 2021 ​ 4,500 2022 ​ ​ 5,250 2023 ​ ​ 20,336 ​ ​ $ 30,086

Other Long-Term Liabilities (Ta

Other Long-Term Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Liabilities, Other than Long-term Debt, Noncurrent [Abstract]
Schedule of other long-term liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 December 31, 2019 Sale-leaseback arrangement ​ $ 16,712 ​ $ 17,447 Deferred compensation ​ 2,818 ​ 2,528 Accrual for insurance claims liabilities ​ ​ 307 ​ 461 Total other long-term liabilities ​ $ 19,837 ​ $ 20,436

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Schedule of components of income tax (benefit) expense	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current Deferred Total Year ended December 31, 2020 ​ ​ ​ U.S. Federal ​ $ — ​ $ — ​ $ — State and local ​ 589 ​ $ 13 ​ $ 602 Foreign ​ 1,370 ​ 4 ​ 1,374 ​ ​ $ 1,959 ​ $ 17 ​ $ 1,976 Year ended December 31, 2019 ​ ​ ​ U.S. Federal ​ $ — ​ $ — ​ $ — State and local ​ 716 ​ $ 104 ​ $ 820 Foreign ​ 1,081 ​ (33) ​ 1,048 ​ ​ $ 1,797 ​ $ 71 ​ $ 1,868 Year ended December 31, 2018 ​ ​ ​ U.S. Federal ​ $ (12) ​ $ (12,664) ​ $ (12,676) State and local ​ 183 ​ $ (471) ​ $ (288) Foreign ​ 731 ​ — ​ 731 ​ ​ $ 902 ​ $ (13,135) ​ $ (12,233)
Schedule of effective income tax reconciliation	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 2019 2018 Statutory amount ​ $ 4,662 ​ $ (733) ​ $ (22,398) ​ Valuation allowance on foreign tax credits ​ 1,344 ​ 1,081 ​ 593 ​ State income tax, net of federal benefit ​ 792 ​ 991 ​ (1,922) ​ Permanent differences, other ​ 558 ​ 461 ​ 1,550 ​ Permanent differences, stock compensation ​ 328 ​ 311 ​ (24) ​ Valuation allowance, other ​ (5,795) ​ (166) ​ 10,384 ​ Other ​ 87 ​ (77) ​ (416) ​ Consolidated income tax provision ​ $ 1,976 ​ $ 1,868 ​ $ (12,233) ​ Consolidated effective tax rate ​ 8.9 % (53.5) % 11.5 %
Schedule of deferred tax assets and liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Long Term ​ ​ As of December 31, ​ 2020 2019 Assets related to: ​ ​ Accrued liabilities ​ $ 1,058 ​ $ 1,030 Intangible assets ​ 2,818 ​ 3,020 Net operating loss carryforward ​ 10,259 ​ 15,246 Stock-based compensation ​ 377 ​ 586 Foreign tax credits ​ 3,782 ​ 2,570 Goodwill ​ 6,199 ​ 7,232 Leases ​ ​ 10,235 ​ ​ 9,038 Other ​ 1,518 ​ 1,347 Total gross deferred tax assets ​ 36,246 ​ 40,069 Less valuation allowance ​ ​ (12,493) ​ ​ (16,960) Total net deferred tax assets ​ ​ 23,753 ​ ​ 23,109 Liabilities related to: ​ ​ Depreciation and amortization ​ (23,308) ​ (22,634) Other ​ (582) ​ (595) Total deferred tax liabilities ​ (23,890) ​ (23,229) Net deferred tax liabilities ​ $ (137) ​ $ (120)
Schedule of Unrecognized tax benefits	​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 2019 Balances at beginning of the year ​ $ 1,614 ​ $ 1,614 Additions based on tax position related to current year ​ — ​ — Additions based on tax positions related to prior years ​ — ​ — Reductions based on tax positions related to current year ​ — ​ — Reductions based on tax positions related to prior years ​ — ​ — Settlements with tax authorities ​ — ​ — Lapse of statute of limitations ​ — ​ — Balance at the end of year ​ $ 1,614 ​ $ 1,614

Earnings (Loss) Per Share (Tabl

Earnings (Loss) Per Share (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Schedule of earnings per share, basic and diluted	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2020 2019 2018 Basic: Weighted average shares outstanding 30,122,362 29,322,054 28,518,353 Diluted: Total basic weighted average shares outstanding 30,122,362 29,322,054 28,518,353 Effect of potentially dilutive securities: Common stock options — — — Total weighted average shares outstanding assuming dilution 30,122,362 29,322,054 28,518,353

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of restricted stock activity	​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ Number ​ Average ​ ​ of ​ Fair Value ​ ​ Shares ​ Per Share Nonvested at January 1, 2018 372,460 ​ $ 6.01 Granted 333,864 ​ $ 7.47 Vested (217,244) ​ $ 6.61 Forfeited/repurchased shares (71,139) ​ $ 6.85 Nonvested at December 31, 2018 417,941 ​ $ 7.04 Granted 757,012 ​ $ 2.52 Vested (585,754) ​ $ 3.74 Forfeited/repurchased shares (72,627) ​ $ 6.05 Nonvested at December 31, 2019 516,572 ​ $ 4.29 Granted 1,038,044 ​ $ 2.76 Vested (496,797) ​ $ 2.87 Forfeited/repurchased shares (107,383) ​ $ 7.13 Nonvested at December 31, 2020 950,436 ​ $ 3.04
Schedule of stock options activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted Weighted ​ ​ ​ ​ ​ ​ Average ​ Average ​ ​ ​ ​ ​ Number ​ Exercise ​ Contractual ​ Aggregate ​ ​ of ​ Price ​ Life ​ Intrinsic ​ ​ Shares ​ Per Share ​ (Years) ​ Value Outstanding at January 1, 2018 1,911,121 ​ $ 7.79 ​ Granted 374,215 ​ $ 7.49 ​ Exercised (488,303) ​ $ 5.76 ​ Forfeited (132,252) ​ $ 7.89 ​ Outstanding at December 31, 2018 1,664,781 ​ $ 8.31 ​ Granted — ​ $ — ​ Exercised (7,021) ​ $ 4.94 ​ Forfeited (192,994) ​ $ 15.26 ​ Outstanding at December 31, 2019 1,464,766 ​ $ 7.41 ​ Granted — ​ $ — ​ Exercised — ​ $ — ​ Forfeited (542,151) ​ $ 7.94 ​ Outstanding at December 31, 2020 922,615 ​ $ 7.10 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Vested and expected to vest at December 31, 2020 922,246 ​ $ 7.10 5.29 ​ $ 35 Exercisable at December 31, 2020 888,350 ​ $ 7.08 5.21 ​ $ 35
Schedule of stock option valuation assumptions using Black-Scholes pricing model	​ ​ ​ ​ ​ ​ ​ 2018 Weighted average grant-date fair value of options granted ​ $ 2.78 ​ Risk-free interest rate ​ 2.65 % Expected volatility ​ 52 % Expected term of options (in years) ​ 3.0 ​ Dividend yield ​ — %
Schedule of intrinsic value of options exercised and fair value of shares vested	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 2019 2018 Total intrinsic value of options exercised ​ $ — ​ $ — ​ $ 1,286 Total fair value of shares vested ​ $ 329 ​ $ 769 ​ $ 705

Employee Benefits (Tables)

Employee Benefits (Tables)	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Schedule of multi-employer plans	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pension Protection ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Expiration ​ ​ ​ ​ Act ("PPA") ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ of ​ ​ Employer ​ Certified Zone Status ​ FIP/RP ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Collective ​ ​ Identification ​ (1) ​ Status ​ Contributions ​ Surcharge ​ Bargaining Pension Trust Fund ​ Number ​ 2020 ​ 2019 ​ P/I (2) ​ 2020 ​ 2019 ​ 2018 ​ Imposed ​ Agreement International Union of Operating Engineers - Employers Construction Industry Retirement Plan - Local 302 and 612 Trust Funds 91-6028571 Green Green N/A $ 2,480 $ 3,021 $ 2,482 — 2022 Washington Laborers ​ 91-6022315 ​ Green ​ Green ​ N/A ​ $ 236 ​ $ 30 ​ $ — ​ — ​ 2023 Carpenters Retirement Plan of Western Washington 91-6029051 Green Green N/A ​ $ 1,898 ​ $ 695 ​ $ 932 — 2022 Cement Masons & Plasterers Trust Funds ​ 91-6066773 ​ Green ​ Green ​ N/A ​ $ 39 ​ $ 2 ​ $ — ​ — ​ 2023 Washington-Idaho-Montana Carpenters-Employers Retirement Trust Fund ​ 91-6123987 ​ Yellow ​ Yellow ​ I ​ $ — ​ $ 36 ​ $ — ​ — ​ 2021 Engineers - AGC Retirement Trust of the Inland Empire ​ 91-6070237 ​ Yellow ​ Yellow ​ I ​ $ — ​ $ 20 ​ $ — ​ — ​ 2021 Western Conference of Teamsters Pension Trust Fund ​ 91-6145047 ​ Green ​ Green ​ N/A ​ $ 15 ​ $ — ​ $ — ​ — ​ 2023 Alaska Carpenters Trust Fund 92-0120866 Yellow Yellow I ​ $ 271 ​ $ 377 ​ $ 328 — 2021 Alaska Laborers Trust Fund 91-6028298 Yellow Yellow I ​ $ 226 ​ $ 552 ​ $ 321 — 2023 (1) The most recent PPA zone status available in 2020 and 2019 is for the plan’s year end during 2019 and 2018, respectively. Zone status is based on information received from the plan and is indicative of the plans funding status. Among other factors, plans in the red zone are generally less than 65 percent funded, plans in the orange zone are less than 80 percent funded and have an Accumulated Funding Deficiency in the current year or projected into the next six years, plans in the yellow zone are less than 80 percent funded, and plans in the green zone are at least 80 percent funded. (2) The FIP/RP Status P/I column indicates plans for which a financial improvement plan ("FIP") or a rehabilitation plan ("RP") is either pending ("P"), or implemented ("I").

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Schedule of segment reporting	​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended Year Ended ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ December 31, 2019 Marine ​ ​ ​ ​ ​ ​ Contract revenues ​ $ 388,173 ​ $ 369,138 Operating income ​ 16,935 ​ 1,057 Depreciation and amortization expense ​ (18,369) ​ (19,889) ​ ​ ​ ​ ​ ​ ​ Total assets ​ $ 290,372 ​ $ 264,681 Property and equipment, net ​ 109,298 ​ 114,873 ​ ​ ​ ​ ​ ​ ​ Concrete ​ ​ Contract revenues ​ $ 321,769 ​ $ 339,252 Operating income ​ 9,651 ​ 1,136 Depreciation and amortization expense ​ (8,848) ​ (8,519) ​ ​ ​ ​ ​ ​ ​ Total assets ​ $ 123,817 ​ $ 130,163 Property and equipment, net ​ 16,199 ​ 17,475

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Schedule of leases recorded on the balance sheet	​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, Leases ​ 2020 2019 Assets ​ ​ ​ ​ ​ Operating lease right-of-use assets, net (1) ​ $ 18,874 $ 17,997 Financing lease right-of-use assets, net (2) ​ 12,858 7,896 Total assets ​ $ 31,732 $ 25,893 Liabilities ​ Current ​ Operating ​ $ 4,989 $ 5,043 Financing ​ 3,901 2,788 Total current ​ 8,890 7,831 Noncurrent ​ Operating ​ 14,537 13,596 Financing ​ 8,376 3,760 Total noncurrent ​ 22,913 17,356 Total liabilities ​ $ 31,803 $ 25,187 (1) Operating lease right-of-use assets are recorded net of accumulated amortization of $9.0 million and $5.2 million as of December 31, 2020 and 2019, respectively. (2) Financing lease right-of-use assets are recorded net of accumulated amortization of $6.4 million and $6.2 million as of December 31, 2020 and 2019, respectively.
Schedule of information related to lease terms and discount rates	​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ 2020 2019 Weighted Average Remaining Lease Term (in years) ​ ​ Operating leases 5.25 ​ 5.30 ​ Financing leases 4.96 ​ 1.18 ​ Weighted Average Discount Rate ​ ​ ​ Operating leases (1) 4.73 % 4.80 % Financing leases 4.46 % 5.10 % (1) Upon adoption of the new lease standard, discount rates used for existing operating leases were established on January 1, 2019.
Schedule of components of lease expense	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 2019 Operating lease costs: ​ ​ Operating lease cost ​ $ 6,430 ​ $ 6,930 Short-term lease cost (1) ​ 3,871 ​ 2,001 Financing lease costs: ​ ​ Interest on lease liabilities ​ 548 ​ 362 Amortization of right-of-use assets ​ 3,324 ​ 2,312 Total lease cost ​ $ 14,173 ​ $ 11,605 (1) Includes expenses related to leases with a lease term of more than one month but less than one year.
Schedule of supplemental cash flow information	​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 ​ 2019 Cash paid for amounts included in the measurement of lease liabilities: ​ ​ ​ ​ ​ Operating cash flows for operating leases $ 6,262 ​ $ 6,887 Operating cash flows for finance leases $ 548 ​ $ 362 Financing cash flows for finance leases $ 3,619 ​ $ 2,906 Non-cash activity: ​ ROU assets obtained in exchange for new operating lease liabilities $ 7,829 ​ $ 25,743 ROU assets obtained in exchange for new financing lease liabilities $ 11,270 ​ $ 1,021
Schedule of operating lease maturities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating Leases Finance Leases Year ending December 31, ​ ​ ​ ​ ​ ​ 2021 ​ $ 5,696 ​ $ 5,023 2022 ​ 4,275 ​ 1,395 2023 ​ 3,186 ​ 1,989 2024 ​ 2,528 ​ 1,429 2025 ​ 2,354 ​ 1,039 Thereafter ​ 4,130 ​ 3,000 Total future minimum lease payments ​ 22,169 ​ 13,875 Less - amount representing interest ​ 2,643 ​ 1,598 Present value of future minimum lease payments ​ 19,526 ​ 12,277 Less - current lease obligations ​ 4,989 ​ 3,901 Long-term lease obligations ​ $ 14,537 ​ $ 8,376
Schedule of finance lease maturities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating Leases Finance Leases Year ending December 31, ​ ​ ​ ​ ​ ​ 2021 ​ $ 5,696 ​ $ 5,023 2022 ​ 4,275 ​ 1,395 2023 ​ 3,186 ​ 1,989 2024 ​ 2,528 ​ 1,429 2025 ​ 2,354 ​ 1,039 Thereafter ​ 4,130 ​ 3,000 Total future minimum lease payments ​ 22,169 ​ 13,875 Less - amount representing interest ​ 2,643 ​ 1,598 Present value of future minimum lease payments ​ 19,526 ​ 12,277 Less - current lease obligations ​ 4,989 ​ 3,901 Long-term lease obligations ​ $ 14,537 ​ $ 8,376

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Schedule of quarterly financial information	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ First Second Third Fourth Total ​ ​ Quarter ​ Quarter ​ Quarter ​ Quarter ​ Year ​ (in thousands, except per share data) 2020 ​ ​ ​ ​ ​ Revenues ​ $ 166,620 ​ $ 183,713 ​ $ 189,433 ​ $ 170,176 ​ $ 709,942 Gross profit ​ 19,758 ​ 20,744 ​ 22,501 ​ 21,700 ​ 84,703 Operating income ​ 4,365 ​ 4,084 ​ 13,085 ​ 5,052 ​ 26,586 Income before income taxes ​ 3,100 ​ 3,008 ​ 12,106 ​ 3,982 ​ 22,196 Net income ​ 2,723 ​ 2,028 ​ 11,803 ​ 3,666 ​ 20,220 Earnings per share: ​ ​ ​ ​ ​ ​ Basic ​ $ 0.09 ​ $ 0.07 ​ $ 0.39 ​ $ 0.12 ​ $ 0.67 Diluted ​ $ 0.09 ​ $ 0.07 ​ $ 0.39 ​ $ 0.12 ​ $ 0.67 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ First Second Third Fourth Total ​ ​ Quarter ​ Quarter ​ Quarter ​ Quarter ​ Year ​ (in thousands, except per share data) 2019 ​ ​ ​ ​ ​ Revenues ​ $ 143,105 ​ $ 165,985 ​ $ 199,507 ​ $ 199,793 ​ $ 708,390 Gross profit ​ 9,082 ​ 14,977 ​ 20,893 ​ 19,089 ​ 64,041 Operating (loss) income ​ (6,177) ​ (423) ​ 6,092 ​ 2,701 ​ 2,193 (Loss) income before income taxes ​ (7,331) ​ (1,773) ​ 4,506 ​ 1,107 ​ (3,491) Net (loss) income ​ (7,924) ​ (1,633) ​ 4,039 ​ 159 ​ (5,359) (Loss) earnings per share: ​ ​ ​ ​ ​ ​ Basic ​ $ (0.27) ​ $ (0.06) ​ $ 0.14 ​ $ 0.01 ​ $ (0.18) Diluted ​ $ (0.27) ​ $ (0.06) ​ $ 0.14 ​ $ 0.01 ​ $ (0.18)

Description of Business and B_2

Description of Business and Basis of Presentation (Details) - segment	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments	2
Number of reportable segments	2	2	2

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Restricted Cash and Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Restricted cash
Restricted cash	$ 0	$ 958
Accounts Receivable [Abstract]
Allowance for credit losses	400	2,600
Retainage	36,485	$ 42,547
Retainage, long-term	$ 3,600

Summary of Significant Accoun_5

Summary of Significant Accounting Principles - Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment
Assets classified as held-for-sale	$ 0	$ 0
Equipment improvement | Minimum
Property, Plant and Equipment
Property and equipment useful life	3 years
Equipment improvement | Maximum
Property, Plant and Equipment
Property and equipment useful life	7 years
Automobiles and trucks | Minimum
Property, Plant and Equipment
Property and equipment useful life	3 years
Automobiles and trucks | Maximum
Property, Plant and Equipment
Property and equipment useful life	5 years
Building and improvements | Minimum
Property, Plant and Equipment
Property and equipment useful life	5 years
Building and improvements | Maximum
Property, Plant and Equipment
Property and equipment useful life	30 years
Construction equipment | Minimum
Property, Plant and Equipment
Property and equipment useful life	3 years
Construction equipment | Maximum
Property, Plant and Equipment
Property and equipment useful life	15 years
Vessels and other equipment | Minimum
Property, Plant and Equipment
Property and equipment useful life	1 year
Vessels and other equipment | Maximum
Property, Plant and Equipment
Property and equipment useful life	15 years
Office equipment | Minimum
Property, Plant and Equipment
Property and equipment useful life	1 year
Office equipment | Maximum
Property, Plant and Equipment
Property and equipment useful life	5 years
Dry-docking capitalized costs | Minimum
Property, Plant and Equipment
Property and equipment useful life	3 years
Dry-docking capitalized costs | Maximum
Property, Plant and Equipment
Property and equipment useful life	15 years

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Leases and Intangible Assets (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)Asset	Dec. 31, 2019USD ($)	Jan. 01, 2019USD ($)
Operating lease assets and liabilities
Operating lease, right-of-use assets	$ 18,874	$ 17,997
Operating lease, liability	$ 19,526
Infinite-lived intangible assets
Number of infinite-lived intangible assets | Asset	1
Accounting Standards Update 2016-02 | Restatement Adjustment
Operating lease assets and liabilities
Operating lease, right-of-use assets			$ 23,300
Operating lease, liability			$ 24,000

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Insurance Coverage (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)itempolicy	Dec. 31, 2019USD ($)
Insurance Coverage
Levels of insurance coverage maintained by the Company | item	5
Number of employee health care insurance policies | policy	2
Accrued insurance claims liability	$ 60,400	$ 3,700
Accrued insurance claims receivables	$ 57,021	$ 1,100
Heavy Civil Marine Construction Segment
Insurance Coverage
Levels of insurance coverage maintained by the Company | item	5
Amount in excess of primary insurance coverage	$ 200,000
Heavy Civil Marine Construction Segment | Other liability policies
Insurance Coverage
Primary limit of insurance coverage	1,000
Heavy Civil Marine Construction Segment | Maritime employer's liability
Insurance Coverage
Primary limit of insurance coverage	10,000
Heavy Civil Marine Construction Segment | Watercraft pollution policy
Insurance Coverage
Primary limit of insurance coverage	$ 5,000
Commercial Concrete Segment
Insurance Coverage
Levels of insurance coverage maintained by the Company | item	5
Amount in excess of primary insurance coverage	$ 200,000
Commercial Concrete Segment | Other liability policies
Insurance Coverage
Primary limit of insurance coverage	$ 1,000

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Accounting Standards Adopted (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for credit losses	$ (487)	$ 0	$ 4,280
COVID-19 Pandemic
Allowance for credit losses	$ 400

Revenue (Details)

Revenue (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020USD ($)	Sep. 30, 2020USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2020USD ($)segment	Dec. 31, 2019USD ($)segment	Dec. 31, 2018USD ($)segment
Disaggregation of Revenue [Line Items]
Contract revenues	$ 170,176	$ 189,433	$ 183,713	$ 166,620	$ 199,793	$ 199,507	$ 165,985	$ 143,105	$ 709,942	$ 708,390	$ 520,894
Number of reportable segments | segment									2	2	2
Heavy Civil Marine Construction Segment
Disaggregation of Revenue [Line Items]
Contract revenues									$ 388,173	$ 369,138	$ 243,883
Heavy Civil Marine Construction Segment | Construction
Disaggregation of Revenue [Line Items]
Contract revenues									272,870	242,527	156,925
Heavy Civil Marine Construction Segment | Dredging
Disaggregation of Revenue [Line Items]
Contract revenues									106,647	112,303	73,237
Heavy Civil Marine Construction Segment | Specialty Services
Disaggregation of Revenue [Line Items]
Contract revenues									8,656	14,308	13,721
Commercial Concrete Segment
Disaggregation of Revenue [Line Items]
Contract revenues									321,769	339,252	277,011
Commercial Concrete Segment | Structural
Disaggregation of Revenue [Line Items]
Contract revenues									85,904	54,497	60,926
Commercial Concrete Segment | Light Commercial
Disaggregation of Revenue [Line Items]
Contract revenues									235,835	284,624	215,628
Commercial Concrete Segment | Other
Disaggregation of Revenue [Line Items]
Contract revenues									$ 30	$ 131	$ 457

Concentration of Risk and Ent_3

Concentration of Risk and Enterprise Wide Disclosures (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020USD ($)	Sep. 30, 2020USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2020USD ($)customer	Dec. 31, 2019USD ($)customer	Dec. 31, 2018USD ($)customer
Concentration Risk [Line Items]
Allowance for credit losses	$ (411)				$ (2,600)				$ (411)	$ (2,600)
Contract revenues	170,176	$ 189,433	$ 183,713	$ 166,620	199,793	$ 199,507	$ 165,985	$ 143,105	$ 709,942	$ 708,390	$ 520,894
Foreign
Concentration Risk [Line Items]
Contract revenues, percent									1.80%	1.60%	2.30%
Customer concentration risk | Trade and contract retainage receivables
Concentration Risk [Line Items]
Gross receivables	133,265				161,687				$ 133,265	$ 161,687
Allowance for credit losses	(411)				(2,600)				(411)	(2,600)
Net receivables	132,854				159,087				$ 132,854	$ 159,087
Number of customers exceeding the 10% benchmark percentage | customer									0	0
Concentration risk, percentage									100.00%	100.00%
Customer concentration risk | Contract revenues
Concentration Risk [Line Items]
Number of customers exceeding the 10% benchmark percentage | customer										0	0
Concentration risk, percentage									100.00%	100.00%	100.00%
Contract revenues									$ 709,942	$ 708,390	$ 520,894
Customer concentration risk | Federal Government | Trade and contract retainage receivables
Concentration Risk [Line Items]
Gross receivables	4,826				4,765				$ 4,826	$ 4,765
Concentration risk, percentage									4.00%	3.00%
Customer concentration risk | Federal Government | Contract revenues
Concentration Risk [Line Items]
Concentration risk, percentage									7.00%	6.00%	8.00%
Contract revenues									$ 51,793	$ 46,425	$ 42,143
Customer concentration risk | State Governments | Trade and contract retainage receivables
Concentration Risk [Line Items]
Gross receivables					5,864					$ 5,864
Concentration risk, percentage										4.00%
Customer concentration risk | State Governments | Contract revenues
Concentration Risk [Line Items]
Concentration risk, percentage									4.00%	7.00%	6.00%
Contract revenues									$ 27,574	$ 47,831	$ 30,470
Customer concentration risk | Local Governments | Trade and contract retainage receivables
Concentration Risk [Line Items]
Gross receivables	17,823				41,944				$ 17,823	$ 41,944
Concentration risk, percentage									13.00%	26.00%
Customer concentration risk | Local Governments | Contract revenues
Concentration Risk [Line Items]
Number of customers exceeding the 10% benchmark percentage | customer									1
Concentration risk, percentage									29.00%	30.00%	21.00%
Contract revenues									$ 202,839	$ 212,958	$ 107,478
Customer concentration risk | Local Governments | Contract revenues | Customer One
Concentration Risk [Line Items]
Concentration risk, percentage									11.40%
Customer concentration risk | Private Companies | Trade and contract retainage receivables
Concentration Risk [Line Items]
Gross receivables	$ 110,616				$ 109,114				$ 110,616	$ 109,114
Concentration risk, percentage									83.00%	67.00%
Customer concentration risk | Private Companies | Contract revenues
Concentration Risk [Line Items]
Concentration risk, percentage									60.00%	57.00%	65.00%
Contract revenues									$ 427,736	$ 401,176	$ 340,803

Contracts in Progress (Details)

Contracts in Progress (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Contractors [Abstract]
Costs incurred on uncompleted contracts	$ 1,151,987	$ 884,244
Estimated earnings	202,369	144,160
Costs incurred and estimated earnings on uncompleted contracts	1,354,356	1,028,404
Less: Billings to date	(1,355,220)	(1,035,796)
Costs and estimated earnings in excess of billings on uncompleted contracts, net	(864)	(7,392)
Costs and estimated earnings in excess of billings on uncompleted contracts	32,271	41,389
Billings in excess of costs and estimated earnings on uncompleted contracts	$ (33,135)	$ (48,781)

Contracts in Progress - Additio

Contracts in Progress - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Contract with Customer, Asset, after Allowance for Credit Loss, Current	$ 32,271	$ 41,389
Costs And Estimated Earnings In Excess Of Billings On Uncompleted Contracts
Unbilled contract claims and change orders
Claims and unapproved change orders	$ 3,100	$ 100

Contracts in Progress - Remaini

Contracts in Progress - Remaining Performance Obligation (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction
Performance obligations expected to be satisfied	$ 439.5
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction
Performance obligations expected to be satisfied	$ 401.9
Performance obligations expected to be satisfied, percentage	91.00%
Performance obligations expected to be satisfied, expected timing	12 months

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment
Property, plant and equipment, gross	$ 274,440	$ 292,260
Less: accumulated depreciation	(186,615)	(196,973)
Property, plant and equipment net book value of depreciable assets	87,825	95,287
Property and equipment, net of depreciation	125,497	132,348
Automobiles and trucks
Property, Plant and Equipment
Property, plant and equipment, gross	2,379	2,161
Building and improvements
Property, Plant and Equipment
Property, plant and equipment, gross	44,324	44,278
Construction equipment
Property, Plant and Equipment
Property, plant and equipment, gross	142,661	153,147
Vessels and other equipment
Property, Plant and Equipment
Property, plant and equipment, gross	79,499	84,022
Office equipment
Property, Plant and Equipment
Property, plant and equipment, gross	5,577	8,652
Construction in progress
Property, Plant and Equipment
Property, plant and equipment, gross	1,809	1,198
Land
Property, Plant and Equipment
Property, plant and equipment, gross	$ 35,863	$ 35,863

Property and Equipment Narrativ

Property and Equipment Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 21.8	$ 23.5	$ 28.4

Other Current Accounts Receiv_3

Other Current Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Other Current Accounts Receivable
Insurance claims receivable	$ 57,021	$ 1,100
Accident loss receivables	1,448	624
Other current receivables	1,023	956
Total other current accounts receivable	$ 59,492	$ 2,680

Fair Value - Schedule of Fair V

Fair Value - Schedule of Fair Value Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	$ 1,600
Fair Value, Measurements, Recurring | Reported Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash surrender value of life insurance	3,169	$ 2,714
Derivatives	1,602	1,045
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash surrender value of life insurance	0	0
Derivatives	0	0
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash surrender value of life insurance	3,169	2,714
Derivatives	1,602	1,045
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash surrender value of life insurance	0	0
Derivatives	$ 0	$ 0

Fair Value - Other Fair Value M

Fair Value - Other Fair Value Measurements (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Life Insurance, face amount	$ 11.1
Reported Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of debt	$ 35.1	$ 73.3

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Goodwill
Goodwill impairment charges	$ 69,500	$ 0	$ 69,483
Heavy Civil Marine Construction Segment
Goodwill
Goodwill impairment charges	33,800
Commercial Concrete Segment
Goodwill
Goodwill impairment charges	$ 35,700

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Finite-lived Intangible Assets Roll Forward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-lived Intangible Assets, Gross [Roll Forward]
Intangible assets, January 1	$ 35,240	$ 35,240
Additions	0
Total intangible assets, end of year	35,240	35,240	$ 35,240
Accumulated Amortization [Roll Forward]
Accumulated amortization, January 1	(29,985)	(27,345)
Current year amortization	(2,070)	(2,640)	(3,390)
Total accumulated amortization	(32,055)	(29,985)	$ (27,345)
Net intangible assets
Net intangible assets, end of year	3,185	5,255
Infinite-lived intangible assets	6,892	6,892
Total net intangible assets	$ 10,077	$ 12,147

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended			36 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Amortization expense	$ 2,070	$ 2,640	$ 3,390
Net intangible assets, end of year	3,185	$ 5,255
Customer Relationships
Business Acquisition [Line Items]
Finite-lived intangibles acquired				$ 18,800
Acquired finite-lived intangible assets, useful life				8 years
Amortization expense	2,100
Trade Names
Business Acquisition [Line Items]
impairment of infinite-lived assets	$ 0

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets - Future Amortization Expense of Finite-lived Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
2021	$ 1,520
2022	1,239
2023	389
2024	37
Net intangible assets, end of year	$ 3,185	$ 5,255

Accrued Liabilities (Details)

Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accrued Liabilities, Current [Abstract]
Accrued salaries, wages and benefits	$ 15,071	$ 7,323
Accrual for insurance claims liabilities	60,365	3,714
Sales taxes	5,909	3,021
Property taxes	908	389
Sale-leaseback arrangement	676	482
Accounting and audit fees	344	267
Interest	22	76
Equipment purchase	461	0
Other accrued expenses	881	1,694
Total accrued liabilities	$ 84,637	$ 16,966

Long-term Debt and Line of Cr_3

Long-term Debt and Line of Credit - Obligations under Debt Arrangements (Details) - USD ($) $ in Thousands	1 Months Ended
	Jun. 30, 2020	May 31, 2019	Mar. 31, 2019	Jul. 31, 2018	Dec. 31, 2020	Jun. 08, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Principal current					$ 4,500		$ 3,750
Principal, long-term					30,586		69,540
Principal					35,086		73,290
Deferred Issuance Costs, current					(156)		(82)
Deferred Issuance Costs, long-term					(1,063)		(1,511)
Debt Issuance Costs, Net, Total					(1,219)		(1,593)
Net Value, current					4,344		3,668
Net Value, long-term					29,523		68,029
Total debt					$ 33,867		71,697
Line of Credit
Debt Instrument [Line Items]
Weighted average interest rate					3.11%
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity					$ 50,000
Debt issuance expense		$ 400
Principal, long-term					5,000		36,000
Deferred Issuance Costs, long-term					(174)		(782)
Net Value, long-term					4,826		35,218
Term Loan | Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity					60,000
Principal current					4,500		3,750
Principal, long-term					25,586		33,540
Principal					30,086
Deferred Issuance Costs, current					(156)		(82)
Deferred Issuance Costs, long-term					(889)		(729)
Net Value, current					4,344		3,668
Net Value, long-term					24,697		$ 32,811
364-Day Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity						$ 20,000
Debt issuance expense	$ 400
Borrowings	$ 0
Fourth, Fifth And Sixth Amendments To Credit Agreement
Debt Instrument [Line Items]
Debt Issuance Costs, Net, Total					$ (900)
Fourth Amendment to Credit Agreement | Line of Credit
Debt Instrument [Line Items]
Debt issuance cost				$ 900
Fifth Amendment To Credit Agreement | Line of Credit
Debt Instrument [Line Items]
Debt issuance cost			$ 600
Sixth Amendment To Credit Agreement | Line of Credit
Debt Instrument [Line Items]
Debt issuance cost		$ 900

Long-term Debt and Line of Cr_4

Long-term Debt and Line of Credit - Provisions of Revolving Line of Credit (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Repayments of Debt	$ 48,204,000	$ 70,210,000	$ 48,111,000
Proceeds from lines of credit	$ 10,000,000	$ 63,000,000	$ 39,861,000
Line of Credit
Debt Instrument [Line Items]
Weighted average interest rate	3.11%
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 50,000,000
Minimum borrowing increment amount	1,000,000
Increment borrowing multiple for amounts borrowed in excess of minimum borrowing amount	250,000
Remaining borrowing capacity	43,300,000
Repayments of Debt	41,000,000
Decrease in debt balance	31,000,000
Proceeds from lines of credit	10,000,000
Revolving Credit Facility | Line of Credit | Base Rate
Debt Instrument [Line Items]
Amount outstanding	$ 5,000,000
Weighted average interest rate	4.50%
Letter of Credit | Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 20,000,000
Letters of credit outstanding	1,700,000
Bridge Loan | Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	5,000,000
Minimum borrowing increment amount	250,000
Increment borrowing multiple for amounts borrowed in excess of minimum borrowing amount	$ 50,000

Long-term Debt and Line of Cr_5

Long-term Debt and Line of Credit - Provisions of 364-Day Revolving Credit Facility (Details) - 364-Day Revolving Credit Facility - Line of Credit - USD ($)	Jun. 08, 2020	Dec. 31, 2020
Debt Instrument [Line Items]
Credit facility term	364 days
Line of credit facility, maximum borrowing capacity	$ 20,000,000
Minimum borrowing increment amount	1,000,000
Increment borrowing multiple for amounts borrowed in excess of minimum borrowing amount	$ 250,000
Amount outstanding		$ 0

Long-term Debt and Line of Cr_6

Long-term Debt and Line of Credit - Provisions of Term Loan (Details) - USD ($) $ in Thousands	Sep. 27, 2019	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Outstanding principal balance		$ 35,086	$ 73,290
Additional principal paydown	$ 18,200
Term Loan | Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		60,000
Outstanding principal balance		30,086
Current portion of debt		4,500
Quarterly principal payments		3,800
Additional principal paydown		3,400
Non-current portion of debt		$ 25,600
Term Loan | Line of Credit | LIBOR
Debt Instrument [Line Items]
Effective interest rate		2.44%

Long-term Debt and Line of Cr_7

Long-term Debt and Line of Credit - Debt Maturity Schedule (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Principal	$ 35,086	$ 73,290
Term Loan | Line of Credit
Debt Instrument [Line Items]
2021	4,500
2022	5,250
2023	20,336
Principal	$ 30,086

Long-term Debt and Line of Cr_8

Long-term Debt and Line of Credit - Financial covenants (Details)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Covenant compliance, Fixed Charge Coverage Ratio, minimum	1.25
Covenant compliance, Leverage Ratio, maximum	3

Long-term Debt and Line of Cr_9

Long-term Debt and Line of Credit - Derivative Financial Instruments (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Jul. 31, 2020USD ($)	Sep. 16, 2015USD ($)contract
Debt Instrument [Line Items]
Percent Of aggregate principal amount hedged					50.00%
Change in fair market value of interest rate swaps	$ 0.6	$ 1
Fair market value of interest rate swap liability	$ 1.6
Maximum
Debt Instrument [Line Items]
Change in fair market value of interest rate swaps			$ 0.1
Series of Swaps
Debt Instrument [Line Items]
Derivative, notional amount					$ 67.5
Derivative, number of instruments held | contract					5
Sixth Swap
Debt Instrument [Line Items]
Derivative, notional amount				$ 27

Other Long-Term Liabilities - C

Other Long-Term Liabilities - Components (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Other long-term liabilities
Sale-leaseback arrangement	$ 16,712	$ 17,447
Accrual for insurance claims liabilities	2,818	2,528
Deferred rent	307	461
Total other long-term liabilities	$ 19,837	$ 20,436

Other Long-Term Liabilities - S

Other Long-Term Liabilities - Sale-Leaseback (Details) $ in Millions	Sep. 27, 2019USD ($)Options
Failed Sale Leaseback
Paydown of Term loan	$ 18.2
Failed Sale Leaseback
Failed Sale Leaseback
Sale price of properties sold	$ 19.1
Lease term	15 years
Annual rent	$ 1.5
Annual percentage rent increase	2.00%
Number of consecutive options to extend term | Options	2
Term of available options	10 years

Income Taxes - Components of In

Income Taxes - Components of Income Tax (Benefit) Expense by Jurisdiction and by Classification (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
U.S. Federal
Current			$ (12)
Deferred			(12,664)
Total			(12,676)
State and local
Current	$ 589	$ 716	183
Deferred	13	104	(471)
Total	602	820	(288)
Foreign
Current	1,370	1,081	731
Deferred	4	(33)
Total	1,374	1,048	731
Total Income Taxes
Current	1,959	1,797	902
Deferred	17	71	(13,135)
Total	$ 1,976	$ 1,868	$ (12,233)

Income Taxes - Effective Income

Income Taxes - Effective Income Tax (Benefit) Expense Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Statutory amount	$ 4,662	$ (733)	$ (22,398)
Valuation allowance on foreign tax credits	1,344	1,081	593
State income tax, net of federal benefit	792	991	(1,922)
Permanent differences, other	558	461	1,550
Permanent differences, stock compensation	328	311	(24)
Valuation allowance, other	(5,795)	(166)	10,384
Other	87	(77)	(416)
Consolidated income tax provision	$ 1,976	$ 1,868	$ (12,233)
Consolidated effective tax rate	8.90%	(53.50%)	11.50%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal statutory tax rate		21.00%	21.00%	21.00%
Valuation allowance per share (in dollars per share)	$ 0.39			$ 0.39
Goodwill impairment charges	$ 69,500		$ 0	$ 69,483
Goodwill impairment, permanent tax difference				1,200
Deferred tax assets, net of valuation allowance				$ 11,000

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets related to:
Accrued liabilities	$ 1,058	$ 1,030
Intangible assets	2,818	3,020
Net operating loss carryforward	10,259	15,246
Stock-based compensation	377	586
Foreign tax credits	3,782	2,570
Goodwill	6,199	7,232
Leases	10,235	9,038
Other	1,518	1,347
Total gross deferred tax assets	36,246	40,069
Less valuation allowance	(12,493)	(16,960)
Total net deferred tax assets	23,753	23,109
Liabilities related to:
Depreciation and amortization	(23,308)	(22,634)
Other	(582)	(595)
Total deferred tax liabilities	(23,890)	(23,229)
Net deferred tax liabilities	$ (137)	$ (120)

Income Taxes - Net Operating Lo

Income Taxes - Net Operating Loss Carryforwards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating loss carryforwards
Valuation allowance	$ 12,493	$ 16,960
Change in valuation allowance	(4,500)
Foreign tax credits	$ 3,782	$ 2,570
Percentage of taxable income	80.00%
Period of foreign tax credit carryforwards	10 years
Federal
Operating loss carryforwards
Net operating loss carryforwards	$ 23,100
State
Operating loss carryforwards
Net operating loss carryforwards	$ 132,600

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balances at beginning of the year	$ 1,614	$ 1,614
Additions based on tax position related to current year
Balance at the end of year	1,614	1,614
Accrued interest and penalties on unrecognized tax benefits	$ 0	$ 0	$ 0

Earnings (Loss) Per Share - Ant

Earnings (Loss) Per Share - Anti-dilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Potential antidilutive securities excluded from computations of earnings per share	1,159,440	1,636,656	1,938,967

Earnings (Loss) Per Share - Bas

Earnings (Loss) Per Share - Basic and Diluted (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Basic:
Weighted average shares outstanding, basic	30,122,362	29,322,054	28,518,353
Effect of dilutive securities:
Common stock options	0	0	0
Total weighted average shares outstanding assuming dilution	30,122,362	29,322,054	28,518,353

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details) $ / shares in Units, $ in Thousands	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020USD ($)$ / sharesshares	Sep. 30, 2020$ / sharesshares	Aug. 31, 2020$ / sharesshares	May 31, 2020director$ / sharesshares	Mar. 31, 2020$ / sharesshares	Feb. 29, 2020$ / sharesshares	Dec. 31, 2019$ / sharesshares	Oct. 31, 2019director$ / sharesshares	Sep. 30, 2019	Jul. 31, 2019$ / sharesshares	May 31, 2019director$ / sharesshares	Mar. 31, 2019$ / sharesshares	Jan. 31, 2019director$ / sharesshares	Jul. 31, 2018$ / sharesshares	May 31, 2018director$ / sharesshares	May 31, 2017shares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares
Share-based Compensation
Approved and authorized maximum number of shares to be issued																		2,400,000
Compensation expense related to stock based awards outstanding | $																			$ 2,000	$ 2,800	$ 2,200
Granted (in shares)																					374,215
Proceeds received upon exercise of stock options | $																				$ 35	$ 2,815
Exercise of stock options, shares																			0	7,021	488,303
Total share-based compensation cost not yet recognized | $			$ 2,400																$ 2,400
Share-based compensation cost not yet recognized, period for recognition																			2 years 2 months 12 days
Total intrinsic value of options exercised | $																					$ 1,286
Total fair value of shares vested | $																			$ 329	$ 769	$ 705
Officers And Executives
Share-based Compensation
Vesting period																					3 years
Weighted average grant-date fair value of options granted (in USD per share) | $ / shares																					$ 7.49
Granted (in shares)																					374,215
Certain Officers
Share-based Compensation
Expense related to purchase of vested stock-based awards | $																			$ 200
Maximum
Share-based Compensation
Proceeds received upon exercise of stock options | $																				$ 100
Stock options
Share-based Compensation
Expiration period																		10 years
Forfeiture rate applied to awards																			5.50%
Stock options | Minimum
Share-based Compensation
Vesting period																		3 years
Stock options | Maximum
Share-based Compensation
Vesting period																		5 years
Restricted stock
Share-based Compensation
Awards granted in period (in shares)																			1,038,044	757,012	333,864
Grant date fair value (in dollars per share) | $ / shares																			$ 2.76	$ 2.52	$ 7.47
Forfeiture rate applied to awards																			3.20%
Restricted stock | Independent Directors
Share-based Compensation
Number of new directors | director						6				1			5		2		5
Awards granted in period (in shares)						39,823				14,218			45,918		8,427		12,064
Grant date fair value (in dollars per share) | $ / shares						$ 2.26				$ 4.22			$ 1.96		$ 4.45		$ 7.46
Restricted stock | Officers And Executives
Share-based Compensation
Vesting period			3 years			3 years	3 years		3 years			3 years	3 years				3 years
Awards granted in period (in shares)			95,000			100,000	170,235		31,500			46,500	62,500				203,752
Grant date fair value (in dollars per share) | $ / shares			$ 4.92			$ 2.26	$ 3.73		$ 5.08			$ 3.66	$ 1.96				$ 7.46
Restricted stock | Certain Executives
Share-based Compensation
Vesting percentage	33.30%	33.30%									33.30%
Vesting period				3 years
Awards granted in period (in shares)				25,000				15,121						168,350		2,769
Grant date fair value (in dollars per share) | $ / shares				$ 2.58				$ 4.96						$ 2.97		$ 9.03
Performance Shares | Certain Executives
Share-based Compensation
Shares earned based on achievement of objective, percent						100.00%							100.00%				100.00%
Awards granted in period (in shares)						300,000							187,500				67,023
Grant date fair value (in dollars per share) | $ / shares					$ 1.96	$ 2.26							$ 1.96				$ 7.46
Performance period					1 year	1 year							1 year				3 years
Granted (in shares)					93,750
Performance Shares | Vesting If Performance Target Is Met or Determination | Certain Executives
Share-based Compensation
Vesting percentage					50.00%	50.00%							50.00%
Performance Shares | Vesting On Second And Third Anniversary Of Grant | Certain Executives
Share-based Compensation
Vesting percentage						25.00%							25.00%
Performance Shares | Vesting on First and Second Anniversary of Determination | Certain Executives
Share-based Compensation
Vesting percentage					25.00%

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock Activity (Details) - Restricted stock - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Beginning nonvested shares (in shares)	516,572	417,941	372,460
Granted (in shares)	1,038,044	757,012	333,864
Vested (in shares)	(496,797)	(585,754)	(217,244)
Forfeited/repurchased shares (in shares)	(107,383)	(72,627)	(71,139)
Ending nonvested shares (in shares)	950,436	516,572	417,941
Weighted Average Fair Value Per Share
Beginning nonvested shares (in dollars per share)	$ 4.29	$ 7.04	$ 6.01
Granted (in dollars per share)	2.76	2.52	7.47
Vested (in dollars per share)	2.87	3.74	6.61
Forfeited/repurchased shares (in dollars per share)	7.13	6.05	6.85
Ending nonvested shares (in dollars per share)	$ 3.04	$ 4.29	$ 7.04

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Beginning stock options outstanding (in shares)	1,464,766	1,664,781	1,911,121
Granted (in shares)			374,215
Exercised (in shares)	0	(7,021)	(488,303)
Forfeited (in shares)	(542,151)	(192,994)	(132,252)
Ending stock options outstanding (in shares)	922,615	1,464,766	1,664,781
Weighted Average Exercise Price Per Share
Beginning stock options outstanding (in dollars per share)	$ 7.41	$ 8.31	$ 7.79
Granted (in dollars per share)			7.49
Exercised (in dollars per share)		4.94	5.76
Forfeited (in dollars per share)	7.94	15.26	7.89
Ending stock options outstanding (in dollars per share)	$ 7.10	$ 7.41	$ 8.31
Vested and expected to vest at December 31, 2020
Number of Shares	922,246
Weighted Average Exercise Price Per Share (in dollars per share)	$ 7.10
Weighted Average Contractual Life	5 years 3 months 14 days
Aggregate Intrinsic Value	$ 35
December 31, 2020
Number of Shares	888,350
Weighted Average Exercise Price Per Share (in dollars per share)	$ 7.08
Weighted Average Contractual Life	5 years 2 months 15 days
Aggregate Intrinsic Value	$ 35

Stock-Based Compensation - St_2

Stock-Based Compensation - Stock Option Valuation Assumptions (Details) - Stock Option	12 Months Ended
	Dec. 31, 2018$ / shares
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Weighted average grant-date fair value of options granted (in USD per share)	$ 2.78
Risk-free interest rate	2.65%
Expected volatility	52.00%
Expected term of options	3 years
Dividend yield	0.00%

Employee Benefits - Narrative (

Employee Benefits - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Contribution Plan Disclosure
Minimum service period for plan eligibility	6 months
Minimum allowable contribution to the plan by each employee, percent	1.00%
Maximum allowable contribution to the plan by each employee, percent	80.00%
Employers matching contribution, vesting period	4 years
Company contributions to the plan	$ 1.2	$ 1.3	$ 1.4
Range 1
Defined Contribution Plan Disclosure
Employer matching contribution, percent	100.00%
Employer matching contribution, percent of employees' gross pay	2.00%
Range 2
Defined Contribution Plan Disclosure
Employer matching contribution, percent	50.00%
Employer matching contribution, percent of employees' gross pay	2.00%
AGC Southwest Chapters 401(k) Retirement Plan
Defined Contribution Plan Disclosure
Employer matching contribution, percent	50.00%
Employers matching contribution, vesting period	5 years
Employer matching contribution, percent of employees' gross pay	6.00%
Employer discretionary contribution amount	$ 0.1	$ 0.1	$ 0.2

Employee Benefits - Multiemploy

Employee Benefits - Multiemployer Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
International Union of Operating Engineers - Employers Construction Industry Retirement Plan - Local 302 and 612 Trust Funds
Multiemployer Plans [Line Items]
Certified Zone Status	Green	Green
Contributions	$ 2,480	$ 3,021	$ 2,482
Washington Laborers
Multiemployer Plans [Line Items]
Certified Zone Status	Green	Green
Contributions	$ 236	$ 30
Carpenters Retirement Plan of Western Washington
Multiemployer Plans [Line Items]
Certified Zone Status	Green	Green
Contributions	$ 1,898	$ 695	932
Cement Masons & Plasterers Trust Funds
Multiemployer Plans [Line Items]
Certified Zone Status	Green	Green
Contributions	$ 39	$ 2
Washington-Idaho-Montana Carpenters-Employers Retirement Trust Fund
Multiemployer Plans [Line Items]
Certified Zone Status	Yellow	Yellow
Contributions		$ 36
Engineers - AGC Retirement Trust of the Inland Empire
Multiemployer Plans [Line Items]
Certified Zone Status	Yellow	Yellow
Contributions		$ 20
Western Conference of Teamsters Pension Trust Fund
Multiemployer Plans [Line Items]
Certified Zone Status	Green	Green
Contributions	$ 15
Alaska Carpenters Trust Fund
Multiemployer Plans [Line Items]
Certified Zone Status	Yellow	Yellow
Contributions	$ 271	$ 377	328
Alaska Laborers Trust Fund
Multiemployer Plans [Line Items]
Certified Zone Status	Yellow	Yellow
Contributions	$ 226	$ 552	$ 321

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Millions	Aug. 21, 2018galitem	Sep. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2020USD ($)claimlawsuit
Settled Litigation
Other Commitments [Line Items]
Legal settlement			$ 5.5
Notes receivable, current				$ 0.8
Notes receivables, noncurrent				1.8
Receivable, unamortized discount				$ 0.2
Recovery of reserved accounts receivable		$ 0.9
Waymon L Boyd Dredge Fire
Other Commitments [Line Items]
Number of crew deaths | item	5
Number of gallons of oil, diesel fuel, and contaminated water discharged | gal	18,000
Waymon L Boyd Dredge Fire | Pending Litigation
Other Commitments [Line Items]
Number of lawsuits filed | lawsuit				8
Number of claimants | claim				13

Segment Information (Details)

Segment Information (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020USD ($)	Sep. 30, 2020USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2020USD ($)segment	Dec. 31, 2019USD ($)segment	Dec. 31, 2018USD ($)segment
Segment Reporting Information [Line Items]
Number of reportable segments | segment									2	2	2
Contract revenues	$ 170,176	$ 189,433	$ 183,713	$ 166,620	$ 199,793	$ 199,507	$ 165,985	$ 143,105	$ 709,942	$ 708,390	$ 520,894
Operating income (loss)	5,052	$ 13,085	$ 4,084	$ 4,365	2,701	$ 6,092	$ (423)	$ (6,177)	26,586	2,193	(100,540)
Depreciation and amortization									(23,893)	(26,096)	(31,799)
Assets	414,189				394,844				414,189	394,844
Property and equipment, net of depreciation	125,497				132,348				125,497	132,348
Heavy Civil Marine Construction Segment
Segment Reporting Information [Line Items]
Contract revenues									388,173	369,138	243,883
Heavy Civil Marine Construction Segment | Mexico and the Caribbean
Segment Reporting Information [Line Items]
Contract revenues									12,500	11,400
Commercial Concrete Segment
Segment Reporting Information [Line Items]
Contract revenues									321,769	339,252	$ 277,011
Commercial Concrete Segment | Foreign
Segment Reporting Information [Line Items]
Contract revenues									0	0
Operating Segments | Heavy Civil Marine Construction Segment
Segment Reporting Information [Line Items]
Contract revenues									388,173	369,138
Operating income (loss)									16,935	1,057
Depreciation and amortization									(18,369)	(19,889)
Assets	290,372				264,681				290,372	264,681
Property and equipment, net of depreciation	109,298				114,873				109,298	114,873
Operating Segments | Commercial Concrete Segment
Segment Reporting Information [Line Items]
Contract revenues									321,769	339,252
Operating income (loss)									9,651	1,136
Depreciation and amortization									(8,848)	(8,519)
Assets	123,817				130,163				123,817	130,163
Property and equipment, net of depreciation	$ 16,199				$ 17,475				16,199	17,475
Intersegment Eliminations
Segment Reporting Information [Line Items]
Contract revenues									$ 2,800	$ 1,200

Leases - Assets and Liabilities

Leases - Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease right-of-use assets, net of amortization	$ 18,874	$ 17,997
Financing lease right-of-use assets, net of amortization	12,858	7,896
Total assets	31,732	25,893
Current portion of operating lease liabilities	4,989	5,043
Current portion of financing lease liabilities	3,901	2,788
Total current	8,890	7,831
Operating lease liabilities	14,537	13,596
Financing lease liabilities	8,376	3,760
Total noncurrent	22,913	17,356
Total liabilities	31,803	25,187
Operating lease, right-of-use asset, accumulated amortization	9,000	5,200
Finance lease, right-of-use asset, accumulated amortization	$ 6,400	$ 6,200

Leases - Term and Discount Rate

Leases - Term and Discount Rate (Details)	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Weighted Average Remaining Lease Term, operating lease	5 years 3 months	5 years 3 months 18 days
Weighted Average Remaining Lease Term, finance lease	4 years 11 months 15 days	1 year 2 months 4 days
Weighted Average Discount Rate, operating lease	4.73%	4.80%
Weighted Average Discount Rate, finance lease	4.46%	5.10%

Leases - Lease Cost (Details)

Leases - Lease Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease cost	$ 6,430	$ 6,930
Short-term lease cost	3,871	2,001
Interest on lease liabilities	548	362
Amortization of right-of-use assets	3,324	2,312
Total lease cost	$ 14,173	$ 11,605

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating cash flows for operating leases	$ 6,262	$ 6,887
Operating cash flows for finance leases	548	362
Financing cash flows for finance leases	3,619	2,906
ROU assets obtained in exchange for new operating lease liabilities	7,829	25,743
ROU assets obtained in exchange for new financing lease liabilities	$ 11,270	$ 1,021

Leases - Maturities (Details)

Leases - Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Operating Leases
2021	$ 5,696
2022	4,275
2023	3,186
2024	2,528
2025	2,354
Thereafter	4,130
Total future minimum lease payments	22,169
Less - amount representing interest	2,643
Operating Lease, Liability, Total	19,526
Less - current lease obligations	4,989	$ 5,043
Long-term lease obligations	14,537	13,596
Finance Leases
2021	5,023
2022	1,395
2023	1,989
2024	1,429
2025	1,039
Thereafter	3,000
Total future minimum lease payments	13,875
Less - amount representing interest	1,598
Present value of future minimum lease payments	12,277
Less - current lease obligations	3,901	2,788
Long-term lease obligations	$ 8,376	$ 3,760

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Selected Quarterly Financial Information [Abstract]
Revenues	$ 170,176	$ 189,433	$ 183,713	$ 166,620	$ 199,793	$ 199,507	$ 165,985	$ 143,105	$ 709,942	$ 708,390	$ 520,894
Gross profit	21,700	22,501	20,744	19,758	19,089	20,893	14,977	9,082	84,703	64,041	16,776
Operating (loss) income	5,052	13,085	4,084	4,365	2,701	6,092	(423)	(6,177)	26,586	2,193	(100,540)
(Loss) income before income taxes	3,982	12,106	3,008	3,100	1,107	4,506	(1,773)	(7,331)	22,196	(3,491)	(106,655)
Net income (loss)	$ 3,666	$ 11,803	$ 2,028	$ 2,723	$ 159	$ 4,039	$ (1,633)	$ (7,924)	$ 20,220	$ (5,359)	$ (94,422)
Earnings Per Share, Basic and Diluted [Abstract]
Basic (USD per share)	$ 0.12	$ 0.39	$ 0.07	$ 0.09	$ 0.01	$ 0.14	$ (0.06)	$ (0.27)	$ 0.67	$ (0.18)	$ (3.31)
Diluted earnings (loss) per share (in dollars per share)	$ 0.12	$ 0.39	$ 0.07	$ 0.09	$ 0.01	$ 0.14	$ (0.06)	$ (0.27)	$ 0.67	$ (0.18)	$ (3.31)

Schedule II - Valuation And Q_2

Schedule II - Valuation And Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Provision for doubtful accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at the Beginning of the Period	$ 2,600	$ 4,280	$ 0
Charged to Revenue, Cost or Expense	(487)	0	4,280
Deduction	1,702	1,680	0
Balance at the End of the Period	411	2,600	4,280
Reserve for losses on uncompleted contracts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at the Beginning of the Period	10,925	22,770	0
Charged to Revenue, Cost or Expense	543	2,455	22,770
Deduction	9,995	14,300	0
Balance at the End of the Period	$ 1,473	$ 10,925	$ 22,770