Orion (ORN) 10-Q 30 Apr 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	Apr. 29, 2021
Document and Entity Information [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2021
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 Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		30,451,346
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001402829
Amendment Flag	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 4,642	$ 1,589
Accounts receivable:
Trade, net of allowance for credit losses of $323 and $411 respectively	92,553	96,369
Retainage	38,043	36,485
Income taxes receivable	419	419
Other current	57,153	59,492
Inventory	1,680	1,548
Contract assets	21,797	32,271
Prepaid expenses and other	7,254	7,229
Total current assets	223,541	235,402
Property and equipment, net of depreciation	120,879	125,497
Operating lease right-of-use assets, net of amortization	17,480	18,874
Financing lease right-of-use assets, net of amortization	12,097	12,858
Inventory, non-current	6,249	6,455
Intangible assets, net of amortization	9,697	10,077
Deferred income tax asset	41	70
Other non-current	4,871	4,956
Total assets	394,855	414,189
Current liabilities:
Current debt, net of debt issuance costs	4,348	4,344
Accounts payable:
Trade	38,242	48,252
Retainage	990	716
Accrued liabilities	77,701	84,637
Income taxes payable	776	639
Contract liabilities	33,150	33,135
Current portion of operating lease liabilities	4,777	4,989
Current portion of financing lease liabilities	2,878	3,901
Total current liabilities	162,862	180,613
Long-term debt, net of debt issuance costs	23,603	29,523
Operating lease liabilities	13,512	14,537
Financing lease liabilities	8,680	8,376
Other long-term liabilities	23,513	19,837
Deferred income tax liability	228	207
Interest rate swap liability	1,372	1,602
Total liabilities	233,770	254,695
Stockholders' equity:
Preferred stock -- $0.01 par value, 10,000,000 authorized, none issued
Common stock -- $0.01 par value, 50,000,000 authorized, 31,188,886 and 31,171,804 issued; 30,477,655 and 30,460,573 outstanding at March 31, 2021 and December 31, 2020, respectively	312	312
Treasury stock, 711,231 shares, at cost, as of March 31, 2021 and December 31, 2020, respectively	(6,540)	(6,540)
Accumulated other comprehensive loss	(1,372)	(1,602)
Additional paid-in capital	184,757	184,324
Retained loss	(16,072)	(17,000)
Total stockholders' equity	161,085	159,494
Total liabilities and stockholders' equity	$ 394,855	$ 414,189

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Allowance for credit losses	$ 323	$ 411
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	31,188,886	31,171,804
Common stock, shares outstanding	30,477,655	30,460,573
Treasury stock, shares (in shares)	711,231	711,231

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement
Contract revenues	$ 153,309	$ 166,620
Costs of contract revenues	137,854	146,862
Gross profit	15,455	19,758
Selling, general and administrative expenses	14,630	15,869
Amortization of intangible assets	380	516
Gain on disposal of assets, net	(1,610)	(992)
Operating income	2,055	4,365
Other (expense) income:
Other income	37	97
Interest income	26	40
Interest expense	(1,040)	(1,402)
Other expense, net	(977)	(1,265)
Income before income taxes	1,078	3,100
Income tax expense	150	377
Net income	$ 928	$ 2,723
Basic earnings per share (in dollars per share)	$ 0.03	$ 0.09
Diluted earnings per share (in dollars per share)	$ 0.03	$ 0.09
Shares used to compute income per share:
Basic (in shares)	30,465,475	29,653,409
Diluted (in shares)	30,499,978	29,655,557

Consolidated Statements of Comp

Consolidated Statements of Comprehensive (Loss) Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 928	$ 2,723
Change in fair value of cash flow hedge, net of tax expense of $53 and net of tax benefit of $226 for the three months ended March 31, 2021 and March 31, 2020, respectively	177	(758)
Total comprehensive income	$ 1,105	$ 1,965

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Change in fair value of cash flow hedge, tax expense (benefit)	$ 53	$ (226)

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 Earnings	Total
Beginning balance, shares at Dec. 31, 2019	30,303,395
Beginning treasury stock, shares at Dec. 31, 2019		(711,231)
Beginning 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				462		462
Issue restricted stock, shares	185,356
Issuance of restricted stock	$ 2			(2)
Forfeiture of restricted stock (in shares)	(3,351)
Cash flow hedge			(984)			(984)
Net income					2,723	2,723
Ending balance, shares at Mar. 31, 2020	30,485,400
Ending treasury stock, shares at Mar. 31, 2020		(711,231)
Ending balance at Mar. 31, 2020	$ 305	$ (6,540)	(2,029)	182,983	(34,497)	$ 140,222
Beginning balance, shares at Dec. 31, 2020	31,171,804					31,171,804
Beginning treasury stock, shares at Dec. 31, 2020		(711,231)				(711,231)
Beginning balance at Dec. 31, 2020	$ 312	$ (6,540)	(1,602)	184,324	(17,000)	$ 159,494
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation				383		383
Exercise of stock options, shares	23,755
Exercise of stock options				86		86
Payments related to tax withholding for stock-based compensation, shares	(6,673)
Payments related to tax withholding for stock-based compensation				(36)		(36)
Cash flow hedge			230			230
Net income					928	$ 928
Ending balance, shares at Mar. 31, 2021	31,188,886					31,188,886
Ending treasury stock, shares at Mar. 31, 2021		(711,231)				(711,231)
Ending balance at Mar. 31, 2021	$ 312	$ (6,540)	$ (1,372)	$ 184,757	$ (16,072)	$ 161,085

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities
Net income	$ 928	$ 2,723
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation and amortization	5,704	6,192
Amortization of ROU operating leases	1,348	1,673
Amortization of ROU finance leases	781	700
Amortization of deferred debt issuance costs	239	123
Deferred income taxes	50	13
Stock-based compensation	383	462
Gain on disposal of assets, net	(1,610)	(992)
Allowance for credit losses		411
Change in operating assets and liabilities:
Accounts receivable	3,837	13,511
Income tax receivable		(192)
Inventory	74	(218)
Prepaid expenses and other	60	1,540
Contract assets	10,474	9,956
Accounts payable	(9,735)	(22,911)
Accrued liabilities	(2,371)	(543)
Operating lease liabilities	(1,196)	(1,348)
Income tax payable	137	(278)
Contract liabilities	15	4,631
Net cash provided by operating activities	9,118	15,453
Cash flows from investing activities:
Proceeds from sale of property and equipment	1,950	1,302
Purchase of property and equipment	(1,618)	(2,753)
Contributions to CSV life insurance	0	(38)
Insurance claim proceeds related to property and equipment	440	1,164
Net cash provided by (used in) investing activities	772	(325)
Cash flows from financing activities:
Borrowings from Credit Facility	5,000	5,000
Payments made on borrowings from Credit Facility	(11,155)	(6,750)
Payments of finance lease liabilities	(732)	(942)
Payments related to tax withholding for stock-based compensation	(36)
Exercise of stock options	86
Net cash used in by financing activities	(6,837)	(2,692)
Net change in cash and cash equivalents	3,053	12,436
Cash and cash equivalents at beginning of period	1,589	1,086
Cash and cash equivalents at end of period	4,642	13,522
Cash and cash equivalents	4,642	12,591
Restricted cash		931
Supplemental disclosures of cash flow information, cash paid during the period for:
Interest	443	942
Taxes, net of refunds	$ (37)	$ 648

Description of Business and Bas

Description of Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Basis of Presentation	Orion Group Holdings, Inc. and Subsidiaries Notes to Condensed Consolidated Financial Statements (Tabular Amounts in thousands, Except Share and per Share Amounts) (Unaudited) ​ 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 The accompanying condensed consolidated financial statements and financial information included herein have been prepared pursuant to the interim period reporting requirements of Form 10-Q. Consequently, certain information and note disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) have been condensed or omitted. Readers of this report should also read the Company’s consolidated financial statements and the notes thereto included in its Annual Report on Form 10-K for the fiscal year ended December 31, 2020 (“2020 Form 10-K”) as well as Item 7 – Management’s Discussion and Analysis of Financial Condition and Results of Operations In the opinion of management, the accompanying unaudited condensed consolidated financial statements contain all adjustments considered necessary for a fair presentation of the Company’s financial position, results of operations, and cash flows for the periods presented. Such adjustments are of a normal recurring nature. Interim results of operations for the three months ended March 31, 2021 are not necessarily indicative of the results that may be expected for the year ending December 31, 2021.

Summary of Significant Accounti

Summary of Significant Accounting Principles	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Principles	2. The preparation of condensed 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 condensed 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’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 an 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. Assets and liabilities derived from contracts with customers 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. ● Contract Assets - 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 and are recorded as a current asset, until such amounts are either received or written off. ● Contract Liabilities - Represent billings in excess of revenues recognized 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 March 31, 2021 and December 31, 2020 consisted primarily of overnight bank deposits. The Company had no restricted cash as of March 31, 2021 and 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 March 31, 2021 and December 31, 2020. 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 contract assets, 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 contract assets 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 March 31, 2021, and December 31, 2020, the Company has recorded an allowance for credit losses of $0.3 million and $0.4 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 March 31, 2021 totaled $38.0 million, of which $4.3 million is expected to be collected beyond March 31, 2022. Retainage at December 31, 2020 totaled $36.5 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 March 31, 2021 or December 31, 2020. Fair Value Measurements The Company evaluates and presents certain amounts included in the accompanying condensed 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 March 31, 2021 or December 31, 2020. Leases 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. See Note 18 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 stock-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 for its business and operations. Insurance related to property, equipment, automobile, general liability, and a portion of workers’ compensation is provided through traditional policies, subject to a deductible or deductibles. A portion of the Company’s workers’ compensation exposure is covered through a mutual association, which is subject to supplemental calls. 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 Condensed 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 $59.2 million and $60.4 million at March 31, 2021 and December 31, 2020, respectively, reflected as a component of accrued liabilities in the condensed consolidated balance sheet. The total accrual for insurance claims receivable was $54.9 million and $57.0 million at March 31, 2021 and December 31, 2020, respectively, reflected as a component of other current accounts receivable in the condensed consolidated balance sheet. Accounting Standards Adopted in 2021 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 December 2019, the FASB issued ASU 2019-12, Income Taxes: Simplifying the Accounting for Income Taxes

Revenue

Revenue	3 Months Ended
	Mar. 31, 2021
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: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, ​ 2021 2020 Marine Segment ​ ​ Construction ​ $ 43,936 ​ $ 53,140 Dredging ​ 24,682 ​ 30,899 Specialty Services ​ 3,528 ​ 1,910 Marine segment contract revenues ​ $ 72,146 ​ $ 85,949 ​ ​ ​ ​ ​ ​ ​ Concrete Segment ​ ​ Structural ​ $ 16,661 ​ $ 21,236 Light Commercial ​ 64,495 ​ 59,433 Other ​ 7 ​ 2 Concrete segment contract revenues ​ $ 81,163 ​ $ 80,671 ​ ​ ​ ​ ​ ​ ​ Total contract revenues ​ $ 153,309 ​ $ 166,620 ​ 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	3 Months Ended
	Mar. 31, 2021
Risks and Uncertainties [Abstract]
Concentration of Risk and Enterprise Wide Disclosures	4. Accounts receivable in both reportable segments 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 accounts receivable from customers (trade and retainage) at March 31, 2021 and December 31, 2020, respectively: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ December 31, 2020 Federal Government $ 4,341 3 % $ 4,826 4 % State Governments ​ 220 - % — - % Local Governments ​ 22,444 17 % 17,823 13 % Private Companies ​ 103,914 79 % 110,616 83 % Gross receivables ​ ​ 130,919 ​ 99 % ​ 133,265 ​ 100 % Allowance for credit losses ​ ​ (323) ​ ​ ​ ​ (411) ​ ​ ​ Net receivables ​ $ 130,596 ​ ​ $ 132,854 ​ ​ ​ At March 31, 2021 one customer in the Private Companies category accounted for 10.6% of total current receivables. At December 31, 2020, 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 three months ended March 31, 2021 and 2020, respectively: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, ​ 2021 % 2020 % Federal Government $ 12,764 8 % $ 5,319 3 % State Governments 168 - % 12,232 7 % Local Government 33,516 22 % 52,012 31 % Private Companies 106,861 70 % 97,057 59 % Total contract revenues $ 153,309 100 % $ 166,620 100 % ​ In the three months ended March 31, 2021 and 2020, 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 1.6% and 2.4% of total revenues for the three months ended March 31, 2021 and 2020, and were primarily located in the Caribbean Basin and Mexico.

Contracts in Progress

Contracts in Progress	3 Months Ended
	Mar. 31, 2021
Contractors [Abstract]
Contracts in Progress	5. Contracts in progress are as follows at March 31, 2021 and December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, December 31, ​ ​ 2021 ​ 2020 Costs incurred on uncompleted contracts ​ $ 1,255,413 ​ $ 1,151,987 Estimated earnings ​ 228,140 ​ 202,369 ​ ​ 1,483,553 ​ 1,354,356 Less: Billings to date ​ (1,494,906) ​ (1,355,220) ​ ​ $ (11,353) ​ $ (864) Included in the accompanying Condensed Consolidated Balance Sheets under the following captions: ​ ​ Contract assets ​ $ 21,797 ​ $ 32,271 Contract liabilities ​ (33,150) ​ (33,135) ​ ​ $ (11,353) ​ $ (864) ​ Included in contract assets is approximately $3.6 million and $3.1 million at March 31, 2021 and December 31, 2020, 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 March 31, 2021, the aggregate amount of the remaining performance obligations was approximately $364.8 million. Of this amount, the current expectation of the Company is that it will recognize $328.6 million, or 90%, in the next 12 months and the remaining balance thereafter.

Property and Equipment

Property and Equipment	3 Months Ended
	Mar. 31, 2021
Property, Plant and Equipment [Abstract]
Property and Equipment	6. The following is a summary of property and equipment at March 31, 2021 and December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, December 31, ​ ​ 2021 ​ 2020 Automobiles and trucks ​ $ 2,722 ​ $ 2,379 Building and improvements ​ 44,325 ​ 44,324 Construction equipment ​ 135,485 ​ 142,661 Vessels and other equipment ​ 80,686 ​ 79,499 Office equipment ​ 5,947 ​ 5,577 ​ ​ 269,165 ​ 274,440 Less: Accumulated depreciation ​ (185,883) ​ (186,615) Net book value of depreciable assets ​ 83,282 ​ 87,825 Construction in progress ​ 1,734 ​ 1,809 Land ​ 35,863 ​ 35,863 ​ ​ $ 120,879 ​ $ 125,497 ​ For the three months ended March 31, 2021 and 2020, depreciation expense was $5.3 million and $5.7 million, respectively. Substantially all depreciation expense is included in the cost of contract revenue in the Company’s Condensed 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. See Note 2

Other Current Accounts Receivab

Other Current Accounts Receivable	3 Months Ended
	Mar. 31, 2021
Other Current Accounts Receivable
Other Current Accounts Receivable	7. Other current accounts receivable at March 31, 2021 and December 31, 2020 consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 December 31, 2020 Insurance claims receivable ​ $ 54,922 ​ $ 57,021 Accident loss receivables ​ 1,206 ​ 1,448 Other current receivables ​ ​ 1,025 ​ 1,023 Total other current accounts receivable ​ $ 57,153 ​ $ 59,492 ​

Fair Value

Fair Value	3 Months Ended
	Mar. 31, 2021
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 March 31, 2021 and December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements ​ Carrying Value Level 1 Level 2 Level 3 March 31, 2021 ​ ​ ​ ​ ​ Assets: ​ Cash surrender value of life insurance policy ​ $ 3,256 — 3,256 — Liabilities: ​ Derivatives ​ $ 1,372 — 1,372 — December 31, 2020 ​ ​ ​ ​ ​ Assets: ​ Cash surrender value of life insurance policy ​ $ 3,169 — 3,169 — Liabilities: ​ Derivatives ​ $ 1,602 — 1,602 — ​ 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 March 31, 2021. 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 Condensed 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 March 31, 2021 and December 31, 2020 approximated its carrying value of $28.9 million and $35.1 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	3 Months Ended
	Mar. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	9. Intangible assets The tables below present the activity and amortizations of finite-lived intangible assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, December 31, ​ ​ 2021 ​ 2020 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 ​ $ (32,055) ​ $ (29,985) Current year amortization ​ (380) ​ (2,070) Total accumulated amortization ​ (32,435) ​ (32,055) ​ ​ ​ ​ ​ ​ ​ Net finite-lived intangible assets, end of period ​ $ 2,805 ​ ​ 3,185 Infinite-lived intangible assets ​ ​ 6,892 ​ ​ 6,892 Total net intangible assets ​ $ 9,697 ​ $ 10,077 ​ 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 three months ended March 31, 2021, $0.4 million of amortization expense was recognized for these assets. Future expense remaining of approximately $2.8 million will be amortized as follows: ​ ​ ​ ​ ​ 2021 ​ 1,140 2022 ​ 1,239 2023 ​ 389 2024 ​ 37 ​ ​ $ 2,805 ​ Additionally, the Company has one indefinite-lived intangible asset, a trade name, which is tested 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. The most recent annual impairment test concluded that the fair value of the trade name was in excess of the carrying value, therefore no impairment was recorded.

Accrued Liabilities

Accrued Liabilities	3 Months Ended
	Mar. 31, 2021
Payables and Accruals [Abstract]
Accrued Liabilities	10. Accrued liabilities at March 31, 2021 and December 31, 2020 consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 December 31, 2020 Accrued salaries, wages and benefits ​ $ 11,434 ​ $ 15,071 Accrual for insurance claims liabilities ​ 59,208 ​ 60,365 Sales taxes ​ 4,318 ​ 5,909 Property taxes ​ 482 ​ 908 Sale-leaseback arrangement ​ ​ 821 ​ ​ 676 Accounting and audit fees ​ ​ 258 ​ ​ 344 Interest ​ 22 ​ 22 Equipment purchase ​ ​ 115 ​ ​ 461 Other accrued expenses ​ 1,043 ​ 881 Total accrued liabilities ​ $ 77,701 ​ $ 84,637 ​

Long-term Debt And Line of Cred

Long-term Debt And Line of Credit	3 Months Ended
	Mar. 31, 2021
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 quarterly weighted average interest rate for the Credit Facility as of March 31, 2021 was 2.48%. The Company’s obligations under debt arrangements consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ December 31, 2020 ​ ​ Debt Issuance ​ ​ Debt Issuance ​ ​ ​ Principal ​ Costs (1) ​ Total ​ Principal ​ Costs (1) ​ Total Term loan - current ​ $ 4,500 ​ $ (152) ​ $ 4,348 ​ $ 4,500 ​ $ (156) ​ $ 4,344 Total current debt ​ 4,500 ​ (152) ​ 4,348 ​ 4,500 ​ (156) ​ 4,344 Revolving line of credit ​ — ​ — ​ — ​ 5,000 ​ (174) ​ 4,826 Term loan - long-term ​ 24,431 ​ (828) ​ 23,603 ​ 25,586 ​ (889) ​ 24,697 Total long-term debt ​ ​ 24,431 ​ ​ (828) ​ ​ 23,603 ​ ​ 30,586 ​ ​ (1,063) ​ ​ 29,523 Total debt ​ $ 28,931 ​ $ (980) ​ $ 27,951 ​ $ 35,086 ​ $ (1,219) ​ $ 33,867 ​ (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 March 31, 2021 the Company had no borrowing under the revolving line of credit. There were $1.7 million in outstanding letters of credit as of March 31, 2021, which reduced the maximum borrowing availability on the revolving line of credit to $48.3 million. During the three months ended March 31, 2021, the Company drew down $5.0 million for general corporate purposes and made payments of $10.0 million on the revolving line of credit which resulted in a net decrease of $5.0 million. Provisions of the 364-day revolving credit facility The Company has a maximum borrowing availability under the 364-Day 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 March 31, 2021, 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 March 31, 2021, the outstanding term loan component of the Credit Facility totaled $28.9 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 ​ 3,375 2022 ​ ​ 5,250 2023 ​ ​ 20,306 ​ ​ $ 28,931 ​ During the three months ended March 31, 2021 the Company made the scheduled quarterly principal payment of $1.2 million, which reduced the outstanding principal balance to $28.9 million as of March 31,2021. The current portion of debt is $4.5 million, and the non-current portion is $24.4 million. As of March 31, 2021, the term loan was designated as an Adjusted LIBOR Rate Loan with an interest rate of 2.38%. 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 was in compliance with all financial covenants as of March 31, 2021. 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 March 31, 2021 and March 31, 2020, as reflected in accumulated other comprehensive loss in the Condensed Consolidated Statements of Stockholders’ Equity, is approximately $(0.2) million and $1.0 million. The fair market value of the swaps as of March 31, 2021 is reflected as a liability of $1.4 million on the Condensed Consolidated Balance Sheets. See Note 8

Other Long-Term Liabilities

Other Long-Term Liabilities	3 Months Ended
	Mar. 31, 2021
Liabilities, Other than Long-term Debt, Noncurrent [Abstract]
Other Long-Term Liabilities	12. Other long-term liabilities at March 31, 2021 and December 31, 2020 consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 December 31, 2020 Sale-leaseback arrangement ​ $ 16,532 ​ $ 16,712 CARES Act deferred payroll taxes ​ ​ 3,821 ​ ​ — Deferred compensation ​ 2,853 ​ 2,818 Accrual for insurance claims liabilities ​ ​ 307 ​ 307 Total other long-term liabilities ​ $ 23,513 ​ $ 19,837 ​ 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. CARES Act On March 27, 2020, the U.S. government enacted the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”) which among other things includes an optional payment deferral of the employer's portion of the Social Security taxes that were otherwise due through December 31, 2020. The Company elected to defer payments of approximately $7.6 million with $3.8 million due December 2021 reflected in accrued liabilities included in the Company’s Condensed Consolidated Balance Sheets and the remaining $3.8 million due December 2022 reflected in other long-term liabilities in the Company’s Condensed Consolidated Balance Sheets.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	13. The Company’s effective tax rate is based on expected income, statutory rates and tax planning opportunities available to it. For interim financial reporting, the Company estimates its annual tax rate based on projected taxable income for the full year and records a quarterly tax provision in accordance with the anticipated annual rate. Income tax expense included in the Company’s accompanying Condensed Consolidated Statements of Operations was as follows (in thousands, except percentages): ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ March 31, ​ ​ ​ 2021 ​ ​ 2020 Income tax expense $ 150 ​ $ 377 ​ Effective tax rate 13.9 % 12.2 % ​ The effective rate for the three months ended March 31, 2021 differed from the Company’s statutory federal 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. During the year ended December 31, 2020 the Company assessed the realizability of its deferred tax assets and determined that it was more likely than not that some portion or all the deferred tax assets would not be realized and therefore recorded a valuation allowance on the net deferred tax assets. The Company assesses the available positive and negative evidence to estimate if sufficient future taxable income will be generated to use 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. For the period ended March 31, 2021 the Company evaluated all positive and negative evidence in determining the amount of deferred tax assets more likely than not to be realized. Based on the review of available evidence, Management believes that a valuation allowance on the net deferred tax assets at March 31, 2021 remains appropriate. The Company does not expect that unrecognized tax benefits as of March 31, 2021 for certain federal income tax matters will significantly change due to any settlement and/or expiration of statutes of limitations over the next 12 months. The final outcome of these tax positions is not yet determinable. The Company’s uncertain tax benefits, if recognized, would affect the Company’s effective tax rate.

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Earnings (Loss) Per Share	14. Basic earnings per share is based on the weighted average number of common shares outstanding during each period. Diluted earnings 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 three months ended March 31, 2021 and 2020, the Company had 915,489 and 1,458,225 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 three months ended March 31, 2021 and 2020. Such stock options are antidilutive and are not included in the computation of earnings per share for those periods. The following table reconciles the denominators used in the computations of both basic and diluted earnings per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, ​ ​ 2021 2020 Basic: Weighted average shares outstanding 30,465,475 29,653,409 Diluted: Total basic weighted average shares outstanding 30,465,475 29,653,409 Effect of potentially dilutive securities: Common stock options 34,503 2,148 Total weighted average shares outstanding assuming dilution 30,499,978 29,655,557 ​

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2021
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 generally are 10 years from the date of issuance. Options generally vest over a three The Company applies a 3.2% and a 5.5% forfeiture rate, which is compounded over the vesting terms of the individual award, to its restricted stock and option grants, respectively, based on historical analysis. In the three months ended March 31, 2021 and 2020, compensation expense related to stock-based awards outstanding was $0.4 million and $0.5 million, respectively. In the three months ended March 31, 2021 and 2020, payments related to tax withholding for stock-based compensation for certain officers and directors of the Company was less than $0.1 million and none, respectively. In the three months ended March 31, 2021, there were 23,755 options exercised generating proceeds to the Company of approximately $0.1 million. In the three months ended March 31, 2020, there were no options exercised. At March 31, 2021, total unrecognized compensation expense related to unvested stock and options was approximately $2.0 million, which is expected to be recognized over a period of approximately two years.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	16. 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 crewmembers were killed, several more were injured, some seriously, and the vessel was declared a total loss. This incident also resulted in the discharge of approximately 18,000 gallons of oil, diesel fuel and contaminated water into the Corpus Christi Ship Channel, all of which was promptly cleaned up. The Company is fully cooperating with the U.S. Coast Guard, the Port of Corpus Christi Authority, and the National Transportation Safety Board, among others, while they investigate the cause of this incident. The National Transportation Safety Board has named the 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 and as of the Court’s deadline,  thirteen persons, estates and/or entities filed claims in the Limitation for personal injuries, death, property damages and business interruption, loss of profit, loss of use of natural resources and other economic damages for unspecified economic and compensatory damages. Some of these claimants may not have standing to bring their claims and will be challenged. Further, the Company filed a Default Motion with the Court which was granted on April 8, 2021 and as such bars the filing of any further claims. Applicable accounting guidance under ASC 450 would require the Company to recognize a loss if the loss is determined to be probable and reasonably estimable. As at March 31, 2021, the Company has recognized $72.2 million in total obligations to date, which includes approximately $18.0 million paid to date to claimants (including nine of 18 crewmembers) and accruals totaling approximately $54.2 million. However, this is a multi-party, complex tort proceeding, and it is too early in the proceedings for the Company to establish loss accruals in regard to the balance of the claims. In any event, insurance coverage is available and the carriers of such insurance have taken over the costs of the defense of the claims and have reimbursed the Company $17.1 million to date. In addition, the Company continues to believe that it has adequate insurance coverage for all pollution, marine, economic and other potential liabilities arising from the incident. The Company is also confident that it otherwise has adequate vessels, equipment and personnel to fulfill all ongoing, booked and reasonably foreseeable work. 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 Condensed 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 Condensed Consolidated Balance Sheets. As of March 31, 2021, the current portion of the notes receivable was $0.8 million and the non-current portion was $1.6 million, net of $0.2 million of unamortized discount. Legal fees related to this matter were expensed as incurred during the respective reporting period.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Segment Information	17. 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: ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ ​ March 31, ​ ​ ​ ​ 2021 ​ 2020 Marine ​ ​ ​ ​ ​ ​ Contract revenues ​ $ 72,146 ​ $ 85,949 Operating income ​ (9) ​ 2,855 Depreciation and amortization expense ​ (4,358) ​ (4,776) ​ ​ ​ ​ ​ ​ ​ Total assets ​ $ 268,345 ​ $ 255,311 Property and equipment, net ​ 106,071 ​ 112,384 ​ ​ ​ ​ ​ ​ ​ Concrete ​ ​ Contract revenues ​ $ 81,163 ​ $ 80,671 Operating income ​ 2,064 ​ 1,510 Depreciation and amortization expense ​ (2,127) ​ (2,116) ​ ​ ​ ​ ​ ​ ​ Total assets ​ $ 126,510 ​ $ 129,509 Property and equipment, net ​ 14,808 ​ 16,731 ​ There were less than $0.1 million and $2.3 million in intersegment revenues between the Company’s two reportable segments for the three months ended March 31, 2021 and 2020, respectively. The marine segment had foreign revenues of $2.4 million and $4.0 million for the three months ended March 31, 2021 and 2020, respectively. 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	3 Months Ended
	Mar. 31, 2021
Leases [Abstract]
Leases	18. The Company has operating and finance leases for office space, equipment and vehicles. Leases recorded on the balance sheet consists of the following: ​ ​ ​ ​ ​ ​ ​ ​ March 31, December 31, Leases ​ 2021 2020 Assets ​ ​ ​ ​ ​ Operating lease right-of-use assets, net (1) ​ $ 17,480 $ 18,874 Financing lease right-of-use assets, net (2) ​ 12,097 12,858 Total assets ​ $ 29,577 $ 31,732 Liabilities ​ Current ​ Operating ​ $ 4,777 $ 4,989 Financing ​ 2,878 3,901 Total current ​ 7,655 8,890 Noncurrent ​ Operating ​ 13,512 14,537 Financing ​ 8,680 8,376 Total noncurrent ​ 22,192 22,913 Total liabilities ​ $ 29,847 $ 31,803 (1) Operating lease right-of-use assets are recorded net of accumulated amortization of $10.0 million and $9.0 million as of March 31, 2021 and December 31, 2020, respectively. (2) Financing lease right-of-use assets are recorded net of accumulated amortization of $5.1 million and $6.4 million as of March 31, 2021 and December 31, 2020, respectively. Other information related to lease term and discount rate is as follows: ​ ​ ​ ​ ​ ​ ​ March 31, December 31, ​ 2021 2020 Weighted Average Remaining Lease Term (in years) ​ ​ Operating leases 5.22 ​ 5.25 ​ Financing leases 5.17 ​ 4.96 ​ Weighted Average Discount Rate ​ ​ ​ Operating leases (1) 4.74 % 4.73 % Financing leases 4.39 % 4.46 % (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: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended March 31, ​ 2021 2020 Operating lease costs: ​ ​ Operating lease cost ​ $ 1,654 ​ $ 1,614 Short-term lease cost (1) ​ 690 ​ 1,161 Financing lease costs: ​ ​ Interest on lease liabilities ​ 126 ​ 106 Amortization of right-of-use assets ​ 781 ​ 700 Total lease cost ​ $ 3,251 ​ $ 3,581 (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: ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended March 31, ​ 2021 ​ 2020 Cash paid for amounts included in the measurement of lease liabilities: ​ ​ ​ ​ ​ Operating cash flows for operating leases $ 1,498 ​ $ 1,585 Operating cash flows for finance leases $ 126 ​ $ 106 Financing cash flows for finance leases $ 732 ​ $ 942 Non-cash activity: ​ ROU assets obtained in exchange for new operating lease liabilities $ 165 ​ $ 2,076 ROU assets obtained in exchange for new financing lease liabilities $ 752 ​ $ 8,412 ​ Maturities of lease liabilities are summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating Leases Finance Leases Year ending December 31, ​ ​ ​ ​ ​ ​ 2021 (excluding the three months ended March 31, 2021) ​ $ 4,184 ​ $ 3,553 2022 ​ 4,313 ​ 1,530 2023 ​ 3,239 ​ 2,123 2024 ​ 2,530 ​ 1,563 2025 ​ 2,354 ​ 1,174 Thereafter ​ 4,146 ​ 3,161 Total future minimum lease payments ​ 20,766 ​ 13,104 Less - amount representing interest ​ 2,477 ​ 1,546 Present value of future minimum lease payments ​ 18,289 ​ 11,558 Less - current lease obligations ​ 4,777 ​ 2,878 Long-term lease obligations ​ $ 13,512 ​ $ 8,680 ​

Summary of Significant Accoun_2

Summary of Significant Accounting Principles (Policies)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements and financial information included herein have been prepared pursuant to the interim period reporting requirements of Form 10-Q. Consequently, certain information and note disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) have been condensed or omitted. Readers of this report should also read the Company’s consolidated financial statements and the notes thereto included in its Annual Report on Form 10-K for the fiscal year ended December 31, 2020 (“2020 Form 10-K”) as well as Item 7 – Management’s Discussion and Analysis of Financial Condition and Results of Operations In the opinion of management, the accompanying unaudited condensed consolidated financial statements contain all adjustments considered necessary for a fair presentation of the Company’s financial position, results of operations, and cash flows for the periods presented. Such adjustments are of a normal recurring nature. Interim results of operations for the three months ended March 31, 2021 are not necessarily indicative of the results that may be expected for the year ending December 31, 2021.
Revenue Recognition	Revenue Recognition 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 an 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. Assets and liabilities derived from contracts with customers 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. ● Contract Assets - 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 and are recorded as a current asset, until such amounts are either received or written off. ● Contract Liabilities - Represent billings in excess of revenues recognized 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 March 31, 2021 and December 31, 2020 consisted primarily of overnight bank deposits. The Company had no restricted cash as of March 31, 2021 and 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 March 31, 2021 and December 31, 2020. 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 contract assets, 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 contract assets 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 March 31, 2021, and December 31, 2020, the Company has recorded an allowance for credit losses of $0.3 million and $0.4 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 March 31, 2021 totaled $38.0 million, of which $4.3 million is expected to be collected beyond March 31, 2022. Retainage at December 31, 2020 totaled $36.5 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 March 31, 2021 or December 31, 2020.
Fair Value Measurements	Fair Value Measurements The Company evaluates and presents certain amounts included in the accompanying condensed 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 March 31, 2021 or December 31, 2020.
Leases	Leases 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. See Note 18
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. See Note 9
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 stock-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 See Note 13
Insurance Coverage	Insurance Coverage The Company maintains insurance coverage for its business and operations. Insurance related to property, equipment, automobile, general liability, and a portion of workers’ compensation is provided through traditional policies, subject to a deductible or deductibles. A portion of the Company’s workers’ compensation exposure is covered through a mutual association, which is subject to supplemental calls. 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 Condensed 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 $59.2 million and $60.4 million at March 31, 2021 and December 31, 2020, respectively, reflected as a component of accrued liabilities in the condensed consolidated balance sheet. The total accrual for insurance claims receivable was $54.9 million and $57.0 million at March 31, 2021 and December 31, 2020, respectively, reflected as a component of other current accounts receivable in the condensed consolidated balance sheet.
Recent Accounting Pronouncements	Accounting Standards Adopted in 2021 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 December 2019, the FASB issued ASU 2019-12, Income Taxes: Simplifying the Accounting for Income Taxes

Summary of Significant Accoun_3

Summary of Significant Accounting Principles (Tables)	3 Months Ended
	Mar. 31, 2021
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)	3 Months Ended
	Mar. 31, 2021
Revenue from Contract with Customer [Abstract]
Schedule of disaggregation of revenue	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, ​ 2021 2020 Marine Segment ​ ​ Construction ​ $ 43,936 ​ $ 53,140 Dredging ​ 24,682 ​ 30,899 Specialty Services ​ 3,528 ​ 1,910 Marine segment contract revenues ​ $ 72,146 ​ $ 85,949 ​ ​ ​ ​ ​ ​ ​ Concrete Segment ​ ​ Structural ​ $ 16,661 ​ $ 21,236 Light Commercial ​ 64,495 ​ 59,433 Other ​ 7 ​ 2 Concrete segment contract revenues ​ $ 81,163 ​ $ 80,671 ​ ​ ​ ​ ​ ​ ​ Total contract revenues ​ $ 153,309 ​ $ 166,620

Concentration of Risk and Ent_2

Concentration of Risk and Enterprise Wide Disclosures (Tables)	3 Months Ended
	Mar. 31, 2021
Trade and contract retainage receivables
Concentration Risk [Line Items]
Schedules of concentration of risk, by risk factor	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ December 31, 2020 Federal Government $ 4,341 3 % $ 4,826 4 % State Governments ​ 220 - % — - % Local Governments ​ 22,444 17 % 17,823 13 % Private Companies ​ 103,914 79 % 110,616 83 % Gross receivables ​ ​ 130,919 ​ 99 % ​ 133,265 ​ 100 % Allowance for credit losses ​ ​ (323) ​ ​ ​ ​ (411) ​ ​ ​ Net receivables ​ $ 130,596 ​ ​ $ 132,854 ​ ​
Contract revenues
Concentration Risk [Line Items]
Schedules of concentration of risk, by risk factor	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, ​ 2021 % 2020 % Federal Government $ 12,764 8 % $ 5,319 3 % State Governments 168 - % 12,232 7 % Local Government 33,516 22 % 52,012 31 % Private Companies 106,861 70 % 97,057 59 % Total contract revenues $ 153,309 100 % $ 166,620 100 %

Contracts in Progress (Tables)

Contracts in Progress (Tables)	3 Months Ended
	Mar. 31, 2021
Contractors [Abstract]
Schedule of contracts in progress	​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, December 31, ​ ​ 2021 ​ 2020 Costs incurred on uncompleted contracts ​ $ 1,255,413 ​ $ 1,151,987 Estimated earnings ​ 228,140 ​ 202,369 ​ ​ 1,483,553 ​ 1,354,356 Less: Billings to date ​ (1,494,906) ​ (1,355,220) ​ ​ $ (11,353) ​ $ (864) Included in the accompanying Condensed Consolidated Balance Sheets under the following captions: ​ ​ Contract assets ​ $ 21,797 ​ $ 32,271 Contract liabilities ​ (33,150) ​ (33,135) ​ ​ $ (11,353) ​ $ (864)

Property and Equipment (Tables)

Property and Equipment (Tables)	3 Months Ended
	Mar. 31, 2021
Property, Plant and Equipment [Abstract]
Summary of property and equipment	​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, December 31, ​ ​ 2021 ​ 2020 Automobiles and trucks ​ $ 2,722 ​ $ 2,379 Building and improvements ​ 44,325 ​ 44,324 Construction equipment ​ 135,485 ​ 142,661 Vessels and other equipment ​ 80,686 ​ 79,499 Office equipment ​ 5,947 ​ 5,577 ​ ​ 269,165 ​ 274,440 Less: Accumulated depreciation ​ (185,883) ​ (186,615) Net book value of depreciable assets ​ 83,282 ​ 87,825 Construction in progress ​ 1,734 ​ 1,809 Land ​ 35,863 ​ 35,863 ​ ​ $ 120,879 ​ $ 125,497

Other Current Accounts Receiv_2

Other Current Accounts Receivable (Tables)	3 Months Ended
	Mar. 31, 2021
Other Current Accounts Receivable
Schedule of other current accounts receivable	​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 December 31, 2020 Insurance claims receivable ​ $ 54,922 ​ $ 57,021 Accident loss receivables ​ 1,206 ​ 1,448 Other current receivables ​ ​ 1,025 ​ 1,023 Total other current accounts receivable ​ $ 57,153 ​ $ 59,492

Fair Value (Tables)

Fair Value (Tables)	3 Months Ended
	Mar. 31, 2021
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 March 31, 2021 ​ ​ ​ ​ ​ Assets: ​ Cash surrender value of life insurance policy ​ $ 3,256 — 3,256 — Liabilities: ​ Derivatives ​ $ 1,372 — 1,372 — December 31, 2020 ​ ​ ​ ​ ​ Assets: ​ Cash surrender value of life insurance policy ​ $ 3,169 — 3,169 — Liabilities: ​ Derivatives ​ $ 1,602 — 1,602 —

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of changes and amortization of finite-lived intangible assets	​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, December 31, ​ ​ 2021 ​ 2020 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 ​ $ (32,055) ​ $ (29,985) Current year amortization ​ (380) ​ (2,070) Total accumulated amortization ​ (32,435) ​ (32,055) ​ ​ ​ ​ ​ ​ ​ Net finite-lived intangible assets, end of period ​ $ 2,805 ​ ​ 3,185 Infinite-lived intangible assets ​ ​ 6,892 ​ ​ 6,892 Total net intangible assets ​ $ 9,697 ​ $ 10,077
Summary of finite-lived intangible assets amortization expense	​ ​ ​ ​ ​ 2021 ​ 1,140 2022 ​ 1,239 2023 ​ 389 2024 ​ 37 ​ ​ $ 2,805

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	3 Months Ended
	Mar. 31, 2021
Payables and Accruals [Abstract]
Schedule of accrued liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 December 31, 2020 Accrued salaries, wages and benefits ​ $ 11,434 ​ $ 15,071 Accrual for insurance claims liabilities ​ 59,208 ​ 60,365 Sales taxes ​ 4,318 ​ 5,909 Property taxes ​ 482 ​ 908 Sale-leaseback arrangement ​ ​ 821 ​ ​ 676 Accounting and audit fees ​ ​ 258 ​ ​ 344 Interest ​ 22 ​ 22 Equipment purchase ​ ​ 115 ​ ​ 461 Other accrued expenses ​ 1,043 ​ 881 Total accrued liabilities ​ $ 77,701 ​ $ 84,637

Long-term Debt and Line of Cr_2

Long-term Debt and Line of Credit (Tables)	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Schedule of debt	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ December 31, 2020 ​ ​ Debt Issuance ​ ​ Debt Issuance ​ ​ ​ Principal ​ Costs (1) ​ Total ​ Principal ​ Costs (1) ​ Total Term loan - current ​ $ 4,500 ​ $ (152) ​ $ 4,348 ​ $ 4,500 ​ $ (156) ​ $ 4,344 Total current debt ​ 4,500 ​ (152) ​ 4,348 ​ 4,500 ​ (156) ​ 4,344 Revolving line of credit ​ — ​ — ​ — ​ 5,000 ​ (174) ​ 4,826 Term loan - long-term ​ 24,431 ​ (828) ​ 23,603 ​ 25,586 ​ (889) ​ 24,697 Total long-term debt ​ ​ 24,431 ​ ​ (828) ​ ​ 23,603 ​ ​ 30,586 ​ ​ (1,063) ​ ​ 29,523 Total debt ​ $ 28,931 ​ $ (980) ​ $ 27,951 ​ $ 35,086 ​ $ (1,219) ​ $ 33,867
Schedule of debt maturity	​ ​ ​ ​ ​ 2021 ​ 3,375 2022 ​ ​ 5,250 2023 ​ ​ 20,306 ​ ​ $ 28,931

Other Long-Term Liabilities (Ta

Other Long-Term Liabilities (Tables)	3 Months Ended
	Mar. 31, 2021
Liabilities, Other than Long-term Debt, Noncurrent [Abstract]
Schedule of other long-term liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 December 31, 2020 Sale-leaseback arrangement ​ $ 16,532 ​ $ 16,712 CARES Act deferred payroll taxes ​ ​ 3,821 ​ ​ — Deferred compensation ​ 2,853 ​ 2,818 Accrual for insurance claims liabilities ​ ​ 307 ​ 307 Total other long-term liabilities ​ $ 23,513 ​ $ 19,837

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Schedule of effective income tax reconciliation	​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ March 31, ​ ​ ​ 2021 ​ ​ 2020 Income tax expense $ 150 ​ $ 377 ​ Effective tax rate 13.9 % 12.2 %

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Schedule of earnings per share, basic and diluted	​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, ​ ​ 2021 2020 Basic: Weighted average shares outstanding 30,465,475 29,653,409 Diluted: Total basic weighted average shares outstanding 30,465,475 29,653,409 Effect of potentially dilutive securities: Common stock options 34,503 2,148 Total weighted average shares outstanding assuming dilution 30,499,978 29,655,557

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Schedule of segment reporting	​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ ​ March 31, ​ ​ ​ ​ 2021 ​ 2020 Marine ​ ​ ​ ​ ​ ​ Contract revenues ​ $ 72,146 ​ $ 85,949 Operating income ​ (9) ​ 2,855 Depreciation and amortization expense ​ (4,358) ​ (4,776) ​ ​ ​ ​ ​ ​ ​ Total assets ​ $ 268,345 ​ $ 255,311 Property and equipment, net ​ 106,071 ​ 112,384 ​ ​ ​ ​ ​ ​ ​ Concrete ​ ​ Contract revenues ​ $ 81,163 ​ $ 80,671 Operating income ​ 2,064 ​ 1,510 Depreciation and amortization expense ​ (2,127) ​ (2,116) ​ ​ ​ ​ ​ ​ ​ Total assets ​ $ 126,510 ​ $ 129,509 Property and equipment, net ​ 14,808 ​ 16,731

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2021
Leases [Abstract]
Schedule of leases recorded on the balance sheet	​ ​ ​ ​ ​ ​ ​ ​ March 31, December 31, Leases ​ 2021 2020 Assets ​ ​ ​ ​ ​ Operating lease right-of-use assets, net (1) ​ $ 17,480 $ 18,874 Financing lease right-of-use assets, net (2) ​ 12,097 12,858 Total assets ​ $ 29,577 $ 31,732 Liabilities ​ Current ​ Operating ​ $ 4,777 $ 4,989 Financing ​ 2,878 3,901 Total current ​ 7,655 8,890 Noncurrent ​ Operating ​ 13,512 14,537 Financing ​ 8,680 8,376 Total noncurrent ​ 22,192 22,913 Total liabilities ​ $ 29,847 $ 31,803 (1) Operating lease right-of-use assets are recorded net of accumulated amortization of $10.0 million and $9.0 million as of March 31, 2021 and December 31, 2020, respectively. (2) Financing lease right-of-use assets are recorded net of accumulated amortization of $5.1 million and $6.4 million as of March 31, 2021 and December 31, 2020, respectively.
Schedule of information related to lease terms and discount rates	​ ​ ​ ​ ​ ​ ​ March 31, December 31, ​ 2021 2020 Weighted Average Remaining Lease Term (in years) ​ ​ Operating leases 5.22 ​ 5.25 ​ Financing leases 5.17 ​ 4.96 ​ Weighted Average Discount Rate ​ ​ ​ Operating leases (1) 4.74 % 4.73 % Financing leases 4.39 % 4.46 % (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	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended March 31, ​ 2021 2020 Operating lease costs: ​ ​ Operating lease cost ​ $ 1,654 ​ $ 1,614 Short-term lease cost (1) ​ 690 ​ 1,161 Financing lease costs: ​ ​ Interest on lease liabilities ​ 126 ​ 106 Amortization of right-of-use assets ​ 781 ​ 700 Total lease cost ​ $ 3,251 ​ $ 3,581 (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	​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended March 31, ​ 2021 ​ 2020 Cash paid for amounts included in the measurement of lease liabilities: ​ ​ ​ ​ ​ Operating cash flows for operating leases $ 1,498 ​ $ 1,585 Operating cash flows for finance leases $ 126 ​ $ 106 Financing cash flows for finance leases $ 732 ​ $ 942 Non-cash activity: ​ ROU assets obtained in exchange for new operating lease liabilities $ 165 ​ $ 2,076 ROU assets obtained in exchange for new financing lease liabilities $ 752 ​ $ 8,412
Schedule of operating lease maturities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating Leases Finance Leases Year ending December 31, ​ ​ ​ ​ ​ ​ 2021 (excluding the three months ended March 31, 2021) ​ $ 4,184 ​ $ 3,553 2022 ​ 4,313 ​ 1,530 2023 ​ 3,239 ​ 2,123 2024 ​ 2,530 ​ 1,563 2025 ​ 2,354 ​ 1,174 Thereafter ​ 4,146 ​ 3,161 Total future minimum lease payments ​ 20,766 ​ 13,104 Less - amount representing interest ​ 2,477 ​ 1,546 Present value of future minimum lease payments ​ 18,289 ​ 11,558 Less - current lease obligations ​ 4,777 ​ 2,878 Long-term lease obligations ​ $ 13,512 ​ $ 8,680
Schedule of finance lease maturities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating Leases Finance Leases Year ending December 31, ​ ​ ​ ​ ​ ​ 2021 (excluding the three months ended March 31, 2021) ​ $ 4,184 ​ $ 3,553 2022 ​ 4,313 ​ 1,530 2023 ​ 3,239 ​ 2,123 2024 ​ 2,530 ​ 1,563 2025 ​ 2,354 ​ 1,174 Thereafter ​ 4,146 ​ 3,161 Total future minimum lease payments ​ 20,766 ​ 13,104 Less - amount representing interest ​ 2,477 ​ 1,546 Present value of future minimum lease payments ​ 18,289 ​ 11,558 Less - current lease obligations ​ 4,777 ​ 2,878 Long-term lease obligations ​ $ 13,512 ​ $ 8,680

Description of Business and B_2

Description of Business and Basis of Presentation (Details) - segment	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments	2	2
Number of reportable segments	2	2

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Restricted Cash and Accounts Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Restricted cash
Restricted cash	$ 0	$ 0
Accounts Receivable [Abstract]
Allowance for credit losses	300	400
Retainage	38,043	$ 36,485
Retainage, long-term	$ 4,300

Summary of Significant Accoun_5

Summary of Significant Accounting Principles - Property and Equipment (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021USD ($)Asset	Dec. 31, 2020USD ($)
Property, Plant and Equipment
Assets classified as held-for-sale | $	$ 0	$ 0
Infinite-lived intangible assets
Number of infinite-lived intangible assets | Asset	1
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 - Insurance Coverage (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)itempolicy	Dec. 31, 2020USD ($)
Insurance Coverage
Number of employee health care insurance policies | policy	2
Accrued insurance claims liability	$ 59,200	$ 60,400
Accrued insurance claims receivables	$ 54,922	$ 57,021
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

Revenue (Details)

Revenue (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)segment	Mar. 31, 2020USD ($)segment
Disaggregation of Revenue [Line Items]
Contract revenues	$ 153,309	$ 166,620
Number of reportable segments | segment	2	2
Heavy Civil Marine Construction Segment
Disaggregation of Revenue [Line Items]
Contract revenues	$ 72,146	$ 85,949
Heavy Civil Marine Construction Segment | Construction
Disaggregation of Revenue [Line Items]
Contract revenues	43,936	53,140
Heavy Civil Marine Construction Segment | Dredging
Disaggregation of Revenue [Line Items]
Contract revenues	24,682	30,899
Heavy Civil Marine Construction Segment | Specialty Services
Disaggregation of Revenue [Line Items]
Contract revenues	3,528	1,910
Commercial Concrete Segment
Disaggregation of Revenue [Line Items]
Contract revenues	81,163	80,671
Commercial Concrete Segment | Structural
Disaggregation of Revenue [Line Items]
Contract revenues	16,661	21,236
Commercial Concrete Segment | Light Commercial
Disaggregation of Revenue [Line Items]
Contract revenues	64,495	59,433
Commercial Concrete Segment | Other
Disaggregation of Revenue [Line Items]
Contract revenues	$ 7	$ 2

Concentration of Risk and Ent_3

Concentration of Risk and Enterprise Wide Disclosures (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021USD ($)customer	Mar. 31, 2020USD ($)customer	Dec. 31, 2020USD ($)customer
Concentration Risk [Line Items]
Allowance for credit losses	$ (323)		$ (411)
Contract revenues	$ 153,309	$ 166,620
Foreign
Concentration Risk [Line Items]
Contract revenues, percent	1.60%	2.40%
Customer concentration risk | Trade and contract retainage receivables
Concentration Risk [Line Items]
Gross receivables	$ 130,919		133,265
Allowance for credit losses	(323)		(411)
Net receivables	$ 130,596		$ 132,854
Number of customers exceeding the 10% benchmark percentage | customer			0
Concentration risk, percentage	99.00%		100.00%
Customer concentration risk | Contract revenues
Concentration Risk [Line Items]
Number of customers exceeding the 10% benchmark percentage | customer	0	0
Contract revenues	$ 153,309	$ 166,620
Contract revenues, percent	100.00%	100.00%
Customer concentration risk | Federal Government | Trade and contract retainage receivables
Concentration Risk [Line Items]
Gross receivables	$ 4,341		$ 4,826
Concentration risk, percentage	3.00%		4.00%
Customer concentration risk | Federal Government | Contract revenues
Concentration Risk [Line Items]
Contract revenues	$ 12,764	$ 5,319
Contract revenues, percent	8.00%	3.00%
Customer concentration risk | State Governments | Trade and contract retainage receivables
Concentration Risk [Line Items]
Gross receivables	$ 220
Customer concentration risk | State Governments | Contract revenues
Concentration Risk [Line Items]
Contract revenues	168	$ 12,232
Contract revenues, percent		7.00%
Customer concentration risk | Local Governments | Trade and contract retainage receivables
Concentration Risk [Line Items]
Gross receivables	$ 22,444		$ 17,823
Concentration risk, percentage	17.00%		13.00%
Customer concentration risk | Local Governments | Contract revenues
Concentration Risk [Line Items]
Contract revenues	$ 33,516	$ 52,012
Contract revenues, percent	22.00%	31.00%
Customer concentration risk | Private Companies | Trade and contract retainage receivables
Concentration Risk [Line Items]
Gross receivables	$ 103,914		$ 110,616
Number of customers exceeding the 10% benchmark percentage | customer	1
Concentration risk, percentage	79.00%		83.00%
Customer concentration risk | Private Companies | Trade and contract retainage receivables | Customer One
Concentration Risk [Line Items]
Contract revenues, percent	10.60%
Customer concentration risk | Private Companies | Contract revenues
Concentration Risk [Line Items]
Contract revenues	$ 106,861	$ 97,057
Contract revenues, percent	70.00%	59.00%

Contracts in Progress (Details)

Contracts in Progress (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Contractors [Abstract]
Costs incurred on uncompleted contracts	$ 1,255,413	$ 1,151,987
Estimated earnings	228,140	202,369
Costs incurred and estimated earnings on uncompleted contracts	1,483,553	1,354,356
Less: Billings to date	(1,494,906)	(1,355,220)
Costs and estimated earnings in excess of billings on uncompleted contracts, net	(11,353)	(864)
Contract assets	21,797	32,271
Contract liabilities	$ (33,150)	$ (33,135)

Contracts in Progress - Additio

Contracts in Progress - Additional Information (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Contract assets	$ 21,797	$ 32,271
Costs And Estimated Earnings In Excess Of Billings On Uncompleted Contracts
Disaggregation of Revenue [Line Items]
Contract assets	$ 3,600	$ 3,100

Contracts in Progress - Remaini

Contracts in Progress - Remaining Performance Obligation (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction
Performance obligations expected to be satisfied	$ 364.8
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction
Performance obligations expected to be satisfied	$ 328.6
Performance obligations expected to be satisfied, percentage	90.00%
Performance obligations expected to be satisfied, expected timing	12 months

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment
Property, plant and equipment, gross	$ 269,165	$ 274,440
Less: accumulated depreciation	(185,883)	(186,615)
Property, plant and equipment net book value of depreciable assets	83,282	87,825
Property and equipment, net of depreciation	120,879	125,497
Automobiles and trucks
Property, Plant and Equipment
Property, plant and equipment, gross	2,722	2,379
Building and improvements
Property, Plant and Equipment
Property, plant and equipment, gross	44,325	44,324
Construction equipment
Property, Plant and Equipment
Property, plant and equipment, gross	135,485	142,661
Vessels and other equipment
Property, Plant and Equipment
Property, plant and equipment, gross	80,686	79,499
Office equipment
Property, Plant and Equipment
Property, plant and equipment, gross	5,947	5,577
Construction in progress
Property, Plant and Equipment
Property, plant and equipment, gross	1,734	1,809
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	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 5.3	$ 5.7

Other Current Accounts Receiv_3

Other Current Accounts Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Other Current Accounts Receivable
Insurance claims receivable	$ 54,922	$ 57,021
Accident loss receivables	1,206	1,448
Other current receivables	1,025	1,023
Total other current accounts receivable	$ 57,153	$ 59,492

Fair Value - Schedule of Fair V

Fair Value - Schedule of Fair Value Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	$ 1,400
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	3,256	$ 3,169
Derivatives	1,372	1,602
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	3,256	3,169
Derivatives	$ 1,372	$ 1,602

Fair Value - Other Fair Value M

Fair Value - Other Fair Value Measurements (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Commercial Concrete Segment
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	$ 28.9	$ 35.1

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Finite-lived Intangible Assets Roll Forward (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Finite-lived Intangible Assets, Gross [Roll Forward]
Intangible assets, beginning of period	$ 35,240	$ 35,240	$ 35,240
Additions	0
Total intangible assets, end of period	35,240		35,240
Accumulated Amortization [Roll Forward]
Accumulated amortization, January 1	(32,055)	(29,985)	(29,985)
Current year amortization	(380)	$ (516)	(2,070)
Total accumulated amortization	(32,435)		(32,055)
Net intangible assets
Net intangible assets, end of year	2,805		3,185
Infinite-lived intangible assets	6,892		6,892
Total net intangible assets	$ 9,697		$ 10,077

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Additional Information (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2017
Business Acquisition [Line Items]
Amortization expense	$ 380,000	$ 516,000	$ 2,070,000
Net intangible assets, end of year	$ 2,805,000		$ 3,185,000
Customer Relationships
Business Acquisition [Line Items]
Finite-lived intangibles acquired				$ 18,800,000
Acquired finite-lived intangible assets, useful life	8 years
Trade Names
Business Acquisition [Line Items]
impairment of infinite-lived assets	$ 0

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Future Amortization Expense of Finite-lived Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
2021	$ 1,140
2022	1,239
2023	389
2024	37
Net intangible assets, end of year	$ 2,805	$ 3,185

Accrued Liabilities (Details)

Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Accrued Liabilities, Current [Abstract]
Accrued salaries, wages and benefits	$ 11,434	$ 15,071
Accrual for insurance claims liabilities	59,208	60,365
Sales taxes	4,318	5,909
Property taxes	482	908
Sale-leaseback arrangement	821	676
Accounting and audit fees	258	344
Interest	22	22
Equipment purchase	115	461
Other accrued expenses	1,043	881
Total accrued liabilities	$ 77,701	$ 84,637

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	Mar. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Net Value, current					$ 4,348	$ 4,344
Net Value, long-term					$ 23,603	29,523
Line of Credit
Debt Instrument [Line Items]
Weighted average interest rate					2.48%
Principal current					$ 4,500	4,500
Principal, long-term					24,431	30,586
Principal					28,931	35,086
Deferred Issuance Costs, current					(152)	(156)
Deferred Issuance Costs, long-term					(828)	(1,063)
Debt Issuance Costs, Net, Total					(980)	(1,219)
Net Value, current					4,348	4,344
Net Value, long-term					23,603	29,523
Total debt					27,951	33,867
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
Deferred Issuance Costs, long-term						(174)
Net Value, long-term						4,826
Term Loan | Line of Credit
Debt Instrument [Line Items]
Principal current					4,500	4,500
Principal, long-term					24,431	25,586
Principal					28,931
Deferred Issuance Costs, current					(152)	(156)
Deferred Issuance Costs, long-term					(828)	(889)
Net Value, current					4,348	4,344
Net Value, long-term					23,603	$ 24,697
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 | Line of Credit
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 ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Debt Instrument [Line Items]
Repayments of Debt	$ 11,155,000	$ 6,750,000
Proceeds from lines of credit	5,000,000	$ 5,000,000
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
Amount outstanding	0
Remaining borrowing capacity	48,300,000
Repayments of Debt	10,000,000
Decrease in debt balance	5,000,000
Proceeds from lines of credit	5,000,000
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	3 Months Ended
	Mar. 31, 2021USD ($)
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) - Line of Credit - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Outstanding principal balance	$ 28,931	$ 35,086
Term Loan
Debt Instrument [Line Items]
Original principal amount	60,000
Outstanding principal balance	28,931
Quarterly principal payments	1,200
Current portion of debt	4,500
Non-current portion of debt	$ 24,400
Term Loan | LIBOR
Debt Instrument [Line Items]
Effective interest rate	2.38%

Long-term Debt and Line of Cr_7

Long-term Debt and Line of Credit - Debt Maturity Schedule (Details) - Line of Credit - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Principal	$ 28,931	$ 35,086
Term Loan
Debt Instrument [Line Items]
2021	3,375
2022	5,250
2023	20,306
Principal	$ 28,931

Long-term Debt and Line of Cr_8

Long-term Debt and Line of Credit - Financial covenants (Details)	3 Months Ended
	Mar. 31, 2021
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	3 Months Ended
	Mar. 31, 2021USD ($)	Mar. 31, 2020USD ($)	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	$ (0.2)	$ 1
Fair market value of interest rate swap liability	$ 1.4
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	Mar. 31, 2021	Dec. 31, 2020
Other long-term liabilities
Sale-leaseback arrangement	$ 16,532	$ 16,712
CARES Act deferred payroll taxes	3,821
Deferred compensation	2,853	2,818
Accrual for insurance claims liabilities	307	307
Total other long-term liabilities	$ 23,513	$ 19,837

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

Other Long-Term Liabilities -_2

Other Long-Term Liabilities - CARES Act (Details) $ in Thousands	Mar. 31, 2021USD ($)
CARES Act deferred payroll taxes	$ 7,600
CARES Act deferred payroll taxes, noncurrent	3,821
Accrued liabilities
CARES Act deferred payroll taxes, current	3,800
Other long-term liabilities
CARES Act deferred payroll taxes, noncurrent	$ 3,800

Income Taxes - Effective Income

Income Taxes - Effective Income Tax (Benefit) Expense Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income tax expense	$ 150	$ 377
Effective income tax rate	13.90%	12.20%
Federal statutory tax rate	21.00%

Earnings (Loss) Per Share - Ant

Earnings (Loss) Per Share - Anti-dilutive Securities (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Potential antidilutive securities excluded from computations of earnings per share	915,489	1,458,225

Earnings (Loss) Per Share - Bas

Earnings (Loss) Per Share - Basic and Diluted (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Basic:
Weighted average shares outstanding, basic	30,465,475	29,653,409
Effect of dilutive securities:
Common stock options	34,503	2,148
Total weighted average shares outstanding assuming dilution	30,499,978	29,655,557

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	May 31, 2017
Share-based Compensation
Compensation expense related to stock based awards outstanding	$ 400	$ 500
Proceeds received upon exercise of stock options	86
Total share-based compensation cost not yet recognized	$ 2,000
Share-based compensation cost not yet recognized, period for recognition	2 years
Independent Directors and Certain Officers and Executives
Share-based Compensation
Payments related to tax withholding for stock-based compensation		$ 0
Maximum
Share-based Compensation
Approved and authorized maximum number of shares to be issued			2,400,000
Maximum | Independent Directors and Certain Officers and Executives
Share-based Compensation
Payments related to tax withholding for stock-based compensation	$ 100
Stock options
Share-based Compensation
Expiration period	10 years
Forfeiture rate applied to awards	5.50%
Proceeds received upon exercise of stock options	$ 100
Exercise of stock options, shares	23,755	0
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
Forfeiture rate applied to awards	3.20%

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Millions	Aug. 21, 2018itemgal	Mar. 31, 2021USD ($)claimlawsuit	Mar. 31, 2018USD ($)
Settled Litigation
Other Commitments [Line Items]
Legal settlement			$ 5.5
Notes receivable, current		$ 0.8
Notes receivables, noncurrent		1.6
Receivable, unamortized discount		$ 0.2
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
Number of crewmembers | item	18
Waymon L Boyd Dredge Fire | Pending Litigation
Other Commitments [Line Items]
Number of lawsuits filed | lawsuit		8
Number of claimants | claim		13
Estimated costs recognized		$ 72.2
Accrued loss contingency		54.2
Payments to claimants		$ 18
Number of crewmember claimants paid | claim		9
Costs reimbursed from insurance		$ 17.1

Segment Information (Details)

Segment Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)segment	Mar. 31, 2020USD ($)segment	Dec. 31, 2020USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	2	2
Contract revenues	$ 153,309	$ 166,620
Operating income	2,055	4,365
Depreciation and amortization	(5,704)	(6,192)
Assets	394,855		$ 414,189
Property and equipment, net of depreciation	120,879		$ 125,497
Heavy Civil Marine Construction Segment
Segment Reporting Information [Line Items]
Contract revenues	72,146	85,949
Heavy Civil Marine Construction Segment | Mexico and the Caribbean
Segment Reporting Information [Line Items]
Contract revenues	2,400	4,000
Commercial Concrete Segment
Segment Reporting Information [Line Items]
Contract revenues	81,163	80,671
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	72,146	85,949
Operating income	(9)	2,855
Depreciation and amortization	(4,358)	(4,776)
Assets	268,345	255,311
Property and equipment, net of depreciation	106,071	112,384
Operating Segments | Commercial Concrete Segment
Segment Reporting Information [Line Items]
Contract revenues	81,163	80,671
Operating income	2,064	1,510
Depreciation and amortization	(2,127)	(2,116)
Assets	126,510	129,509
Property and equipment, net of depreciation	14,808	16,731
Intersegment Eliminations
Segment Reporting Information [Line Items]
Contract revenues		$ 2,300
Intersegment Eliminations | Maximum
Segment Reporting Information [Line Items]
Contract revenues	$ 100

Leases - Assets and Liabilities

Leases - Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating lease right-of-use assets, net of amortization	$ 17,480	$ 18,874
Financing lease right-of-use assets, net of amortization	12,097	12,858
Total assets	29,577	31,732
Current portion of operating lease liabilities	4,777	4,989
Current portion of financing lease liabilities	2,878	3,901
Total current	7,655	8,890
Operating lease liabilities	13,512	14,537
Financing lease liabilities	8,680	8,376
Total noncurrent	22,192	22,913
Total liabilities	29,847	31,803
Operating lease, right-of-use asset, accumulated amortization	10,000	9,000
Finance lease, right-of-use asset, accumulated amortization	$ 5,100	$ 6,400

Leases - Term and Discount Rate

Leases - Term and Discount Rate (Details)	Mar. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Weighted Average Remaining Lease Term, operating lease	5 years 2 months 19 days	5 years 3 months
Weighted Average Remaining Lease Term, finance lease	5 years 2 months 1 day	4 years 11 months 15 days
Weighted Average Discount Rate, operating lease	4.74%	4.73%
Weighted Average Discount Rate, finance lease	4.39%	4.46%

Leases - Lease Cost (Details)

Leases - Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Leases [Abstract]
Operating lease cost	$ 1,654	$ 1,614
Short-term lease cost	690	1,161
Interest on lease liabilities	126	106
Amortization of right-of-use assets	781	700
Total lease cost	$ 3,251	$ 3,581

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Leases [Abstract]
Operating cash flows for operating leases	$ 1,498	$ 1,585
Operating cash flows for finance leases	126	106
Financing cash flows for finance leases	732	942
ROU assets obtained in exchange for new operating lease liabilities	165	2,076
ROU assets obtained in exchange for new financing lease liabilities	$ 752	$ 8,412

Leases - Maturities (Details)

Leases - Maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Operating Leases
2021 (Excluding the three months ended March 31, 2021)	$ 4,184
2022	4,313
2023	3,239
2024	2,530
2025	2,354
Thereafter	4,146
Total future minimum lease payments	20,766
Less - amount representing interest	2,477
Operating Lease, Liability, Total	18,289
Less - current lease obligations	4,777	$ 4,989
Long-term lease obligations	13,512	14,537
Finance Leases
2021 (excluding the three months ended March 31, 2021)	3,553
2022	1,530
2023	2,123
2024	1,563
2025	1,174
Thereafter	3,161
Total future minimum lease payments	13,104
Less - amount representing interest	1,546
Present value of future minimum lease payments	11,558
Less - current lease obligations	2,878	3,901
Long-term lease obligations	$ 8,680	$ 8,376