Great Lakes Dredge & Dock (GLDD) 10-K 24 Feb 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 19, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Trading Symbol	GLDD
Entity Registrant Name	Great Lakes Dredge & Dock Corporation
Entity Central Index Key	0001372020
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Address, Address Line One	9811 Katy Freeway, Suite 1200
Entity Address, City or Town	Houston
Entity Address, State or Province	TX
Entity File Number	001-33225
Entity Tax Identification Number	20-5336063
City Area Code	346
Local Phone Number	359-1010
Entity Address, Postal Zip Code	77024
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, (Par Value $0.0001)
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Annual Report	true
Document Transition Report	false
Entity Common Stock, Shares Outstanding		65,120,437
Entity Public Float			$ 586,573,144
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Part of 10-K Documents Incorporated by Reference Part III Portions of the Proxy Statement to be filed with the Securities and Exchange Commission in connection with the 2021 Annual Meeting of Stockholders.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
CURRENT ASSETS:
Cash and cash equivalents	$ 216,510	$ 186,995
Accounts receivable—net	38,990	19,785
Contract revenues in excess of billings	32,106	22,560
Inventories	34,689	30,189
Prepaid expenses	3,091	1,525
Other current assets	37,307	39,658
Total current assets	362,693	300,712
PROPERTY AND EQUIPMENT—Net	383,042	374,596
OPERATING LEASE ASSETS	65,188	72,612
GOODWILL	76,576	76,576
INVENTORIES—Noncurrent	58,413	61,126
ASSETS HELD FOR SALE— Noncurrent	2,900	3,970
OTHER	9,212	7,960
TOTAL	958,024	897,552
LIABILITIES AND EQUITY
Accounts payable	71,308	76,091
Accrued expenses	52,899	51,225
Operating lease liabilities	19,472	21,351
Billings in excess of contract revenues	32,608	55,266
Total current liabilities	176,287	203,933
LONG-TERM DEBT	323,735	322,843
OPERATING LEASE LIABILITIES—Noncurrent	45,879	51,131
DEFERRED INCOME TAXES	56,466	35,740
OTHER	8,989	4,506
Total liabilities	611,356	618,153
COMMITMENTS AND CONTINGENCIES (Note 13)
EQUITY:
Common stock—$.0001 par value; 90,000 authorized, 65,023 and 64,283 shares issued and outstanding at December 31, 2020 and December 31, 2019, respectively.	6	6
Additional paid-in capital	304,757	302,189
Accumulated retained earnings (accumulated deficit)	40,937	(23,091)
Accumulated other comprehensive income	968	295
Total equity	346,668	279,399
TOTAL	$ 958,024	$ 897,552

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	90,000,000	90,000,000
Common stock, shares issued	65,023,000	64,283,000
Common stock, shares outstanding	65,023,000	64,283,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
CONTRACT REVENUES	$ 733,601	$ 711,518	$ 620,795
Type of Revenue [Extensible List]	gldd:ContractMember	gldd:ContractMember	gldd:ContractMember
COSTS OF CONTRACT REVENUES	$ 562,373	$ 557,761	$ 509,335
Type of Cost, Good or Service [Extensible List]	gldd:ContractMember	gldd:ContractMember	gldd:ContractMember
GROSS PROFIT	$ 171,228	$ 153,757	$ 111,460
OPERATING EXPENSES:
GENERAL AND ADMINISTRATIVE EXPENSES	62,757	59,110	55,108
PROCEEDS FROM LOSS OF USE CLAIM	(1,723)	(4,619)
(GAIN) LOSS ON SALE OF ASSETS—Net	(1,571)	1,138	3,731
Total operating income	111,765	98,128	52,621
OTHER EXPENSE:
Interest expense—net	(26,585)	(27,524)	(33,578)
Other income (expense)	1,110	317	(2,590)
Total other expense	(25,475)	(27,207)	(36,168)
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	86,290	70,921	16,453
INCOME TAX PROVISION	(20,187)	(15,253)	(5,437)
INCOME FROM CONTINUING OPERATIONS	66,103	55,668	11,016
Loss from discontinued operations, net of income taxes		(6,329)	(17,309)
NET INCOME (LOSS)	$ 66,103	$ 49,339	$ (6,293)
Basic earnings per share attributable to income from continuing operations	$ 1.02	$ 0.88	$ 0.18
Basic loss per share attributable to loss on discontinued operations, net of income taxes		(0.10)	(0.28)
Basic earnings (loss) per share	$ 1.02	$ 0.78	$ (0.10)
Basic weighted average shares	64,743	63,597	62,236
Diluted earnings per share attributable to income from continuing operations	$ 1	$ 0.86	$ 0.17
Diluted loss per share attributable to loss on discontinued operations, net of income taxes		(0.10)	(0.27)
Diluted earnings (loss) per share	$ 1	$ 0.76	$ (0.10)
Diluted weighted average shares	65,872	65,042	63,607

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)		$ 66,103	$ 49,339	$ (6,293)
Currency translation adjustment—net of tax	[1]			1,513
Net unrealized (gain) loss on derivatives—net of tax	[2]	673	4,104	(5,325)
Other comprehensive income (loss)—net of tax		673	4,104	(3,812)
Comprehensive income (loss)		$ 66,776	$ 53,443	$ (10,105)
[1]	Net of income tax provision of $(1,017) for the year ended December 31, 2018.
[2]	Net of income tax (provision) benefit of $217, $(421) and $775 for the years ended December 31, 2020, 2019 and 2018, respectively.

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Currency translation adjustment, tax			$ (1,017)
Net unrealized loss on derivatives, tax	$ 217	$ (421)	$ 775

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect of Recent Accounting Pronouncements [Member]	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Retained Earnings (Deficit) [Member]	Accumulated Retained Earnings (Deficit) [Member]Cumulative Effect of Recent Accounting Pronouncements [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
BALANCE - value at Dec. 31, 2017	$ 221,296		$ 6	$ (1,433)	$ 289,821	$ (67,101)		$ 3
BALANCE - shares at Dec. 31, 2017			61,897	(278)
Share-based compensation, value	5,425				5,425
Share-based compensation, shares			132
Vesting of restricted stock units, including impact of shares withheld for taxes, value	(1,205)				(1,205)
Vesting of restricted stock units, including impact of shares withheld for taxes, shares			520
Exercise of stock options and purchases from employee stock purchase plan, value	1,094				1,094
Exercise of stock options and purchases from employee stock purchase plan, shares			281
Net income (loss)	(6,293)					(6,293)
Other comprehensive income (loss)—net of tax	(3,812)							(3,812)
BALANCE - value at Dec. 31, 2018	214,928	$ (1,577)	$ 6	$ (1,433)	295,135	(74,971)	$ (1,577)	(3,809)
BALANCE - shares at Dec. 31, 2018			62,830	(278)
Share-based compensation, value	8,395				8,395
Share-based compensation, shares			73
Vesting of restricted stock units, including impact of shares withheld for taxes, value	(5,008)				(5,008)
Vesting of restricted stock units, including impact of shares withheld for taxes, shares			873
Exercise of stock options and purchases from employee stock purchase plan, value	4,839				4,839
Exercise of stock options and purchases from employee stock purchase plan, shares			785
Cancellation of treasury stock, value				$ 1,433	(1,172)	(261)
Cancellation of treasury stock, shares			(278)	278
Net income (loss)	49,339					49,339
Other comprehensive income (loss)—net of tax	4,104							4,104
BALANCE - value at Dec. 31, 2019	279,399	$ 2,802	$ 6		302,189	(23,091)	$ 2,802	295
BALANCE - shares at Dec. 31, 2019			64,283
Share-based compensation, value	6,754				6,754
Share-based compensation, shares			94
Vesting of restricted stock units, including impact of shares withheld for taxes, value	(4,748)				(4,748)
Vesting of restricted stock units, including impact of shares withheld for taxes, shares			741
Exercise of stock options and purchases from employee stock purchase plan, value	$ 2,360				2,360
Exercise of stock options and purchases from employee stock purchase plan, shares	226		331
Repurchase of common stock, value	$ (3,873)				(1,798)	(2,075)
Repurchase of common stock, shares			(426)
Net income (loss)	66,103					66,103
Other comprehensive income (loss)—net of tax	673							673
BALANCE - value at Dec. 31, 2020	$ 346,668		$ 6		$ 304,757	$ 40,937		$ 968
BALANCE - shares at Dec. 31, 2020			65,023

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
OPERATING ACTIVITIES:
Net income (loss)	$ 66,103	$ 49,339	$ (6,293)
Loss from discontinued operations, net of income taxes		(6,329)	(17,309)
INCOME FROM CONTINUING OPERATIONS	66,103	55,668	11,016
Adjustments to reconcile net income (loss) to net cash flows provided by operating activities:
Depreciation expense	38,183	37,145	50,389
Deferred income taxes	20,508	15,134	5,760
(Gain) loss on dispositions of property and equipment	(1,571)	1,138	3,731
Other non-cash restructuring items			2,337
Amortization of deferred financing fees	1,611	2,746	3,504
Unrealized foreign currency gain			(231)
Share-based compensation expense	6,754	6,908	4,643
Changes in assets and liabilities:
Accounts receivable	(19,205)	44,994	(8,364)
Contract revenues in excess of billings	(9,546)	(4,607)	54,881
Inventories	(2,383)	(1,939)	(921)
Prepaid expenses and other current assets	1,466	(8,539)	11,976
Accounts payable and accrued expenses	(3,328)	12,546	(1,480)
Billings in excess of contract revenues	(22,658)	37,473	7,524
Other noncurrent assets and liabilities	3,013	3,120	(3,093)
Net cash flows provided by operating activities of continuing operations	78,947	201,787	141,672
Net cash flows used in operating activities of discontinued operations		(9,238)	(4,019)
Cash provided by operating activities	78,947	192,549	137,653
INVESTING ACTIVITIES:
Purchases of property and equipment	(47,621)	(49,412)	(49,422)
Proceeds from dispositions of property and equipment	4,450	5,592	13,880
Net cash flows used in investing activities of continuing operations	(43,171)	(43,820)	(35,542)
Net cash flows provided by investing activities of discontinued operations		18,056	425
Cash used in investing activities	(43,171)	(25,764)	(35,117)
FINANCING ACTIVITIES:
Repayments of debt			(298)
Deferred financing fees		(2,388)
Taxes paid on settlement of vested share awards	(4,748)	(5,008)	(1,205)
Exercise of stock options and purchases from employee stock plans	2,360	4,839	1,094
Repurchase of common stock	(3,873)
Borrowings under revolving loans			29,000
Repayments of revolving loans		(11,500)	(112,500)
Net cash flows used in financing activities of continuing operations	(6,261)	(14,057)	(83,909)
Net cash flows used in financing activities of discontinued operations		(191)	(1,547)
Cash (used in) provided by financing activities	(6,261)	(14,248)	(85,456)
Effect of foreign currency exchange rates on cash and cash equivalents			26
Net increase in cash, cash equivalents and restricted cash	29,515	152,537	17,106
Cash, cash equivalents and restricted cash at beginning of period	186,995	34,458	17,352
Cash, cash equivalents and restricted cash at end of period	216,510	186,995	34,458
Supplemental Cash Flow Information
Cash paid for interest	26,430	24,942	30,855
Cash paid for income taxes	392	366	290
Non-cash Investing and Financing Activities
Property and equipment purchased but not yet paid	$ 6,693	$ 6,473	7,303
Repayments of debt with proceeds from sale-leaseback transactions			$ 13,034

Nature of Business and Summary

Nature of Business and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of Business and Summary of Significant Accounting Policies	1. NATURE OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Organization —Great Lakes Dredge & Dock Corporation and its subsidiaries (the “Company” or “Great Lakes”) are in the business of marine construction, primarily dredging. The Company is the largest provider of dredging services in the United States. In addition, the Company has a long history of performing significant international projects. The mobility of the Company’s fleet enables the Company to move equipment in response to changes in demand for dredging services Principles of Consolidation and Basis of Presentation —The consolidated financial statements include the accounts of Great Lakes Dredge & Dock Corporation and its majority-owned subsidiaries. All intercompany accounts and transactions are eliminated in consolidation. The equity method of accounting is used for investments in unconsolidated investees in which the Company has significant influence, but not control. Other investments, if any, are carried at cost. Use of Estimates —The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (“GAAP”) requires management to make estimates and assumptions that affect certain reported amounts and disclosures. Accordingly, actual results could differ from those estimates. Revenue and Cost Recognition on Contracts —Revenue is recognized using contract fulfillment costs incurred to date compared to total estimated costs at completion, also known as cost-to-cost, to measure progress towards completion. Additionally, the Company capitalizes certain pre-contract and pre-construction costs, and defers recognition over the life of the contract. The Company’s performance obligations are satisfied over time and revenue is recognized using the cost-to-cost method, described above. Contract modifications are changes in the scope or price (or both) of a contract that are approved by the parties to the contract. The Company recognizes a contract modification when the parties to a contract approve a modification that either creates new, or changes existing, enforceable rights and obligations of the parties to the contract. Contract modifications are routine in the performance of the Company’s contracts. In most instances, contract modifications are for services that are not distinct, and, therefore, are accounted for as part of the existing contract. Contract modifications are included in the transaction price only if it is probable that the modification estimate will not result in a significant reversal of revenue. Revisions in estimated gross profit percentages are recorded in the period during which the change in circumstances is experienced or becomes known. As the duration of most of the Company’s contracts is one year or less, the cumulative net impact of these revisions in estimates, individually and in the aggregate across projects, does not significantly affect results across annual reporting periods. Provisions for estimated losses on contracts in progress are made in the period in which such losses are determined. The components of costs of contract revenues include labor, equipment (including depreciation, maintenance, insurance and long-term rentals), subcontracts, fuel, supplies, short-term rentals and project overhead. Hourly labor generally is hired on a project-by-project basis. The Company is a party to numerous collective bargaining agreements in the U.S. that govern its relationships with its unionized hourly workforce. 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, unless completion of such contracts extends significantly beyond one year. Cash Equivalents —The Company considers all highly liquid investments with a maturity at purchase of three months or less to be cash equivalents. Accounts Receivable —Accounts receivable represent amounts due or billable under the terms of contracts with customers, including amounts related to retainage. The Company anticipates collection of retainage generally within one year, and accordingly presents retainage as a current asset. The Company provides an allowance for estimated uncollectible accounts receivable based on historical and expected losses and when events or conditions indicate that amounts outstanding are not recoverable. Inventories —Inventories consist of pipe and spare parts used in the Company’s dredging operations. Pipe and spare parts are purchased in large quantities; therefore, a certain amount of pipe and spare part inventories is not anticipated to be used within the current year and is classified as long-term. Spare part inventories are stated at weighted average historical cost, and are charged to expense when used in operations. Pipe inventory is recorded at cost and amortized to expense over the period of its use. Property and Equipment —Capital additions, improvements, and major renewals are classified as property and equipment and are carried at depreciated cost. Maintenance and repairs that do not significantly extend the useful lives of the assets or enhance the capabilities of such assets are charged to expenses as incurred. Depreciation is recorded over the estimated useful lives of property and equipment using the straight-line method and the mid-year depreciation convention. The estimated useful lives by class of assets are: Class Useful Life (years) Buildings and improvements 10 Furniture and fixtures 5-10 Vehicles, dozers, and other light operating equipment and systems 3-5 Heavy operating equipment (dredges and barges) 10-30 Leasehold improvements are amortized over the shorter of their remaining useful lives or the remaining terms of the leases. Goodwill —Goodwill represents the excess of acquisition cost over fair value of the net assets acquired. Goodwill is tested annually for impairment in the third quarter of each year, or more frequently should circumstances dictate. GAAP requires that goodwill of a reporting unit be tested for impairment between annual tests if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. When conducting the annual impairment test for goodwill, the Company can choose to assess qualitative factors to determine whether it is more likely than not the fair value of the reporting unit is below its carrying value. If a qualitative assessment determines an impairment is more likely than not, the Company is required to perform a quantitative impairment test. Otherwise, no further analysis is required. The Company also may elect to forego this step and just perform the quantitative impairment test. The Company assesses the fair values of its reporting unit using both a market-based approach and an income-based approach. Under the income approach, the fair value of the reporting unit is based on the present value of estimated future cash flows. The income approach is dependent on a number of factors, including estimates of future market growth trends, forecasted revenues and expenses, appropriate discount rates and other variables. The estimates are based on assumptions that the Company believes to be reasonable, but such assumptions are subject to unpredictability and uncertainty. Changes in these estimates and assumptions could materially affect the determination of fair value, and may result in the impairment of goodwill in the event that actual results differ from those estimates. The market approach measures the value of a reporting unit through comparison to comparable companies. Under the market approach, the Company uses the guideline public company method by applying estimated market-based enterprise value multiples to the reporting unit’s estimated revenue and Adjusted EBITDA. The Company analyzes companies that performed similar services or are considered peers. Due to the fact that there are no public companies that are direct competitors, the Company weighs the results of this approach less than the income approach. The Company has one operating segment which is also the Company’s one reportable segment and reporting unit of which the Company tests goodwill for impairment. The historical environmental & infrastructure segment, which the Company sold during the second quarter of 2019, has been retrospectively presented as discontinued operations and assets and liabilities held for sale and is no longer reflected in continuing operations. The Company performed its most recent annual test of impairment as of July 1, 2020 with no indication of impairment as of the test date. As of the test date, the fair value of the reporting unit was substantially in excess of its carrying value. The Company will perform its next scheduled annual test of goodwill in the third quarter of 2021 should no triggering events occur which would require a test prior to the next annual test. Long-Lived Assets —Long-lived assets are comprised of property and equipment subject to amortization. Long-lived assets to be held and used are reviewed for possible impairment whenever events indicate that the carrying amount of such assets may not be recoverable by comparing the undiscounted cash flows associated with the assets to their carrying amounts. If such a review indicates an impairment, the carrying amount would be reduced to fair value. No triggering events were identified in 2020 or 2019. If long-lived assets are to be disposed, depreciation is discontinued, if applicable, and the assets are reclassified as held for sale at the lower of their carrying amounts or fair values less estimated costs to sell. Self-insurance Reserves —The Company self-insures costs associated with its seagoing employees covered by the provisions of Jones Act, workers’ compensation claims, hull and equipment liability, and general business liabilities up to certain limits. Insurance reserves are established for estimates of the loss that the Company may ultimately incur on reported claims, as well as estimates of claims that have been incurred but not yet reported. In determining its estimates, the Company considers historical loss experience and judgments about the present and expected levels of cost per claim. Trends in actual experience are a significant factor in the determination of such reserves. Income Taxes —The provision for income taxes includes federal, foreign, and state income taxes currently payable and those deferred because of temporary differences between the financial statement and tax basis of assets and liabilities. Recorded deferred income tax assets and liabilities are based on the estimated future tax effects of differences between the financial and tax basis of assets and liabilities, given the effect of currently enacted tax laws. Refer to Note 8, Income Taxes. Hedging Instruments —At times, the Company designates certain derivative contracts as a cash flow hedge as defined by GAAP. Accordingly, the Company formally documents, at the inception of each hedge, all relationships between hedging instruments and hedged items, as well as its risk-management objective and strategy for undertaking hedge transactions. This process includes linking all derivatives to highly-probable forecasted transactions. The Company formally assesses, at inception and on an ongoing basis, the effectiveness of hedges in offsetting changes in the cash flows of hedged items. Hedge accounting treatment may be discontinued when (1) it is determined that the derivative is no longer highly effective in offsetting changes in the cash flows of a hedged item (including hedged items for forecasted future transactions), (2) the derivative expires or is sold, terminated or exercised, (3) it is no longer probable that the forecasted transaction will occur or (4) management determines that designating the derivative as a hedging instrument is no longer appropriate. If management elects to stop hedge accounting, it would be on a prospective basis and any hedges in place would be recognized in accumulated other comprehensive income (loss) until all the related forecasted transactions are completed or are probable of not occurring. Recent Accounting Pronouncements — In March 2020, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2020-04 (“ASU 2020-04”), Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting. The amendment provides optional expedients and exceptions to applying the guidance on contract modifications, hedge accounting and other transactions to simplify the accounting for transitioning from the London Interbank Offered Rate (“LIBOR”), and other interbank offered rates expected to be discontinued, to alternative reference rates. The guidance in this update was effective upon its issuance; if elected, it is to be applied prospectively through December 31, 2022. The Company is currently evaluating the effect the potential adoption of this ASU will have on the Company’s consolidated financial statements.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Earnings Per Share	2. EARNINGS PER SHARE Basic earnings per share is computed by dividing net income attributable to common stockholders by the weighted-average number of common shares outstanding during the reporting period. Diluted earnings per share is computed similar to basic earnings per share except that it reflects the potential dilution that could occur if dilutive securities or other obligations to issue common stock were exercised or converted into common stock. The computations for basic and diluted earnings per share for the years ended December 31, 2020, 2019 and 2018 are as follows: (shares in thousands) 2020 2019 2018 Income from continuing operations $ 66,103 $ 55,668 $ 11,016 Loss on discontinued operations, net of income taxes — (6,329 ) (17,309 ) Net income (loss) $ 66,103 $ 49,339 $ (6,293 ) Weighted-average common shares outstanding — basic 64,743 63,597 62,236 Effect of stock options and restricted stock units 1,129 1,445 1,371 Weighted-average common shares outstanding — diluted 65,872 65,042 63,607 Earnings per share from continuing operations — basic $ 1.02 $ 0.88 $ 0.18 Earnings per share from continuing operations — diluted $ 1.00 $ 0.86 $ 0.17 For the years ended December 31, 2020, 2019 and 2018 the following amounts of NQSOs and RSUs were excluded from the calculation of diluted earnings per share based on the application of the treasury stock method, as such NQSOs and RSUs were determined to be anti-dilutive: (shares in thousands) 2020 2019 2018 Effect of stock options and restricted stock units 1 16 1,285

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2020
Property Plant And Equipment [Abstract]
Property and Equipment	3. PROPERTY AND EQUIPMENT Property and equipment at December 31, 2020 and 2019 are as follows: 2020 2019 Land $ 9,992 $ 9,992 Buildings and improvements 1,315 5,071 Furniture and fixtures 17,251 16,299 Operating equipment 762,350 738,375 Total property and equipment 790,908 769,737 Accumulated depreciation (407,866 ) (395,141 ) Property and equipment — net $ 383,042 $ 374,596 Operating equipment of $2,900 and $3,970 was classified as held for sale, excluded from property and equipment, as of December 31, 2020 and 2019, respectively. Depreciation expense was $38,183, $37,145 and $50,389, for the years ended December 31, 2020, 2019 and 2018, respectively. For more information about changes in assets held for sale and depreciation expense related to the Company’s restructuring refer to Note 12, Restructuring Charges.

Leases

Leases	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Leases	4. LEASES The Company leases certain operating equipment and office facilities under long-term operating leases expiring at various dates through 2028. Leases with an initial term greater than twelve months are recorded on the Company’s balance sheet as an operating lease asset and operating lease liability and are measured at the present value of lease payments over the lease term. Substantially all of the Company’s leases are classified as operating leases. Leases with an initial term of twelve months or less with purchase options or extension options that are not reasonably certain to be exercised are not recorded on the balance sheet. The Company recognizes lease expense for these leases on a straight-line basis over the lease term. The equipment leases contain renewal or purchase options that specify prices at the then fair value upon the expiration of the lease terms. The leases also contain default provisions that are triggered by an acceleration of debt maturity under the terms of the Company’s Amended Credit Agreement, or, in certain instances, cross default to other equipment leases and certain lease arrangements require that the Company maintain certain financial ratios comparable to those required by its Amended Credit Agreement. Additionally, the leases typically contain provisions whereby the Company indemnifies the lessors for the tax treatment attributable to such leases based on the tax rules in place at lease inception. The tax indemnifications do not have a contractual dollar limit. To date, no lessors have asserted any claims against the Company under these tax indemnification provisions. The exercise of lease renewal options is at the Company’s sole discretion and is considered in the measurement of operating lease assets and operating lease liabilities when it is reasonably certain the Company will exercise the option. Certain leases also include options to purchase the leased property. The depreciable life of assets and leasehold improvements are limited by the expected lease term, unless there is a transfer of title or purchase option reasonably certain of exercise. Lease cost The Company’s lease costs are recorded in cost of contract revenues and general and administrative expenses. For the years ended December 31, 2020 and 2019, respectively, lease costs are as follows: Year Ended Year Ended December 31, 2020 December 31, 2019 Operating lease cost $ 24,602 $ 27,259 Short-term lease cost 87,534 70,382 Total lease cost $ 112,136 $ 97,641 Total rent expense under long-term operating lease arrangements for the year ended December 31, 2018 was $21,160. This excludes expenses for equipment and facilities rented on a short-term, as-needed basis. For more information about charges to rent expense during 2018 related to the Company’s restructuring refer to Note 12, Restructuring Charges. Lease terms and commitments As recorded on the balance sheet, the Company’s maturity analysis of its operating lease liabilities as of December 31, 2020 is as follows: 2021 $ 22,247 2022 18,467 2023 13,321 2024 9,768 2025 5,053 Thereafter 3,975 Minimum lease payments 72,831 Imputed interest 7,480 Present value of minimum operating lease payments $ 65,351 As most of the Company’s leases do not provide an implicit rate, the Company used its incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. At the date of adoption of ASC 842, the Company used the incremental borrowing rate as of December 31, 2018, for operating leases that commenced prior to that date. Additional information related to the Company’s leases as of December 31, 2020 and 2019, respectively, is as follows: December 31, 2020 December 31, 2019 Weighted average remaining lease term 4.1 years 4.2 years Weighted average discount rate 6.2 % 6.7 % Supplemental information related to leases during the year ended December 31, 2020 and 2019, respectively, is as follows: Year Ended Year ended December 31, 2020 December 31, 2019 Operating cash flows from operating leases $ (25,064 ) $ (27,235 ) Operating lease liabilities arising from obtaining new operating lease assets $ 22,746 $ 13,149

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2020
Payables And Accruals [Abstract]
Accrued Expenses	5. ACCRUED EXPENSES Accrued expenses at December 31, 2020 and 2019 were as follows: 2020 2019 Payroll and employee benefits $ 21,675 $ 16,859 Insurance 14,754 15,702 Interest 3,285 3,284 Contract reserves 2,491 6,248 Income and other taxes 2,164 1,597 Other 8,530 7,535 Total accrued expenses $ 52,899 $ 51,225

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Long-Term Debt	6. LONG-TERM DEBT Long-term debt at December 31, 2020 and 2019 were as follows: 2020 2019 Revolving credit facility $ — $ — 8% Senior Notes 323,735 322,843 Total $ 323,735 $ 322,843 Credit agreement On May 3, 2019, the Company, Great Lakes Dredge & Dock Company, LLC, NASDI Holdings, LLC, Great Lakes Dredge & Dock Environmental, Inc., Great Lakes Environmental & Infrastructure Solutions, LLC, Great Lakes U.S. Fleet Management, LLC, and Drews Services LLC (collectively, the “Credit Parties”) entered into an amended and restated revolving credit and security agreement (as amended, supplemented or otherwise modified from time to time, the “Amended Credit Agreement”) with certain financial institutions from time to time party thereto as lenders, PNC Bank, National Association, as Agent (the “Agent”), PNC Capital Markets, CIBC Bank USA, Suntrust Robinson Humphrey, Inc. and Bank of America, N.A., as Joint Lead Arrangers and Joint Bookrunners, and HSBC USA, N.A., as Documentation Agent. The Amended Credit Agreement amends and restates the prior Revolving Credit and Security Agreement dated as of December 30, 2016 (as amended, the “Prior Credit Agreement”) by and among the financial institutions from time to time party thereto as lenders, the Agent and the Credit Parties party thereto, such that the terms and conditions of the Prior Credit Agreement have been subsumed and replaced in their entirety by the terms and conditions of the Amended Credit Agreement, including the amount available under the revolving credit facility. The terms of the Amended Credit Agreement are summarized below. The Amended Credit Agreement provides for a senior secured revolving credit facility in an aggregate principal amount of up to $200,000 of which the full amount is available for the issuance of standby letters of credit. The maximum borrowing capacity under the Amended Credit Agreement is determined by a formula and may fluctuate depending on the value of the collateral included in such formula at the time of determination. The Amended Credit Agreement also includes an increase option that will allow the Company to increase the senior secured revolving credit facility by an aggregate principal amount of up to $100,000. This increase is subject to lenders providing incremental commitments for such increase, the Credit Parties having adequate borrowing capacity and provided that no default or event of default exists both before and after giving effect to such incremental commitment increase. The Amended Credit Agreement contains customary representations and affirmative and negative covenants, including a springing financial covenant that requires the Credit Parties to maintain a fixed charge coverage ratio (ratio of earnings before income taxes, depreciation and amortization, net interest expenses, non-cash charges and losses and certain other non-recurring charges, minus capital expenditures, income and franchise taxes, to net cash interest expense plus scheduled cash principal payments with respect to debt plus restricted payments paid in cash) of not less than 1.10 to 1.00. The Amended Credit Agreement also contains customary events of default (including non-payment of principal or interest on any material debt and breaches of covenants) as well as events of default relating to certain actions by the Company’s surety bonding providers. The obligations of the Credit Parties under the Amended Credit Agreement will be unconditionally guaranteed, on a joint and several basis, by each existing and subsequently acquired or formed material direct and indirect domestic subsidiary of the Company. Borrowings under the Amended Credit Agreement will be used to pay fees and expenses related to the Amended Credit Agreement, finance acquisitions permitted under the Amended Credit Agreement, finance ongoing working capital and for other general corporate purposes. The Amended Credit Agreement matures on May 3, 2024; provided that the maturity date shall be accelerated to the date that is ninety-one days prior to the scheduled maturity date of the Company’s unsecured senior notes if the Company fails to refinance its unsecured senior notes prior to their scheduled maturity date. The refinanced 8% Senior Notes must have a maturity on or after the date that is 180 days after the maturity date of the Amended Credit Agreement. The obligations under the Amended Credit Agreement are secured by substantially all of the assets of the Credit Parties. The outstanding obligations thereunder shall be secured by a valid first priority perfected lien on substantially all of the U.S. flagged and located vessels of the Credit Parties and a valid perfected lien on all domestic accounts receivable and substantially all other assets of the Credit Parties, subject to the permitted liens and interests of other parties (including the Company’s surety bonding providers). Interest on the senior secured revolving credit facility of the Amended Credit Agreement is equal to either a Domestic Rate option or LIBOR option, at the Company’s election. As of the Closing Date, (a) the Domestic Rate option is the highest of (1) the base commercial lending rate of PNC Bank, National Association, as publicly announced, (2) the sum of the federal funds open rate plus 0.5% and (3) the sum of the daily LIBOR rate plus 1.0%, so long as a daily LIBOR rate is offered, ascertainable and not unlawful plus an interest margin of 0.5%; and (b) the LIBOR Rate option is the rate that applies for the applicable interest period on the Bloomberg page BBAMI (or such other substitute page or alternate source as agreed) plus an interest margin of 1.5%. After the date on which a borrowing base certificate is required to be delivered under Section 9.2 of the Amended Credit Agreement (commencing with the fiscal quarter ended September 30, 2019, the “Adjustment Date”), the Domestic Rate option will be the Domestic Rate plus an interest margin ranging between 0.5 % and 1.0 % and the LIBOR Rate option will be the LIBOR Rate plus an interest margin ranging between 1.5 % and 2.0 %, in each case, depending on the quarterly average undrawn availability on the Amended Credit Agreement. The Company had no borrowings on the revolver, $36,407 and $35,779 of letters of credit outstanding and $163,231 and $163,729 of availability under the Amended Credit Agreement as of December 31, 2020 and 2019, respectively. The availability under the Amended Credit Agreement is suppressed by $362 and $492 as of December 31, 2020 and 2019, respectively, as a result of certain limitations set forth in the Amended Credit Agreement. Senior notes and subsidiary guarantors The Company has outstanding $325,000 of 8.000% senior notes (“8% Senior Notes”) due May 15, 2022. In May 2017, the Company issued the 8% Senior Notes at 100% of face value resulting in net proceeds of $321,653, net of underwriting fees. In connection with the issuance of the 8% Senior Notes, the Company retired all of its $275,000 of 7.375% senior notes due February 2019 The Company’s obligations under these Senior Notes are guaranteed by certain of the Company’s 100% owned domestic subsidiaries. Such guarantees are full, unconditional and joint and several. The parent company issuer has no independent assets or operations and all non-guarantor subsidiaries have been determined to be minor. Other The Company enters into note arrangements to finance certain vessels and ancillary equipment. In February 2018, the Company completed a sale-leaseback of a vessel yielding net proceeds of $4,500. Included in this transaction was the retirement of the asset and related equipment note. The scheduled principal payments through the maturity date of the Company’s long-term debt at December 31, 2020, are as follows: Years Ending December 31, 2021 $ — 2022 325,000 2023 — 2024 — 2025 — Thereafter — Total $ 325,000 The Company incurred amortization of deferred financing fees for its long term debt of $1,611, $2,231 and $3,504 for each of the years ended December 31, 2020, 2019 and 2018. Such amortization is recorded as a component of interest expense.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	7. FAIR VALUE MEASUREMENTS Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. A fair value hierarchy has been established by GAAP that requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The accounting guidance describes three levels of inputs that may be used to measure fair value: Level 1—Quoted prices in active markets for identical assets or liabilities. Level 2—Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The Company utilizes the market approach to measure fair value for its financial assets and liabilities. The market approach uses prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities. At times, the Company holds certain derivative contracts that it uses to manage foreign currency risk or commodity price risk. The Company does not hold or issue derivatives for speculative or trading purposes. The fair values of these financial instruments are summarized as follows: Fair Value Measurements at Reporting Date Using Description At December 31, 2020 Quoted Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable (Level 3) Fuel hedge contracts $ 1,739 $ — $ 1,739 $ — Fair Value Measurements at Reporting Date Using Description At December 31, 2019 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fuel hedge contracts $ 849 $ — $ 849 $ — Fuel hedge contracts The Company is exposed to certain market risks, primarily commodity price risk as it relates to the diesel fuel purchase requirements, which occur in the normal course of business. The Company enters into heating oil commodity swap contracts to hedge the risk that fluctuations in diesel fuel prices will have an adverse impact on cash flows associated with its domestic dredging contracts. The Company’s goal is to hedge approximately 80% of the eligible fuel requirements for work in domestic backlog. As of December 31, 2020, the Company was party to various swap arrangements to hedge the price of a portion of its diesel fuel purchase requirements for work in its backlog to be performed through December 2021. As of December 31, 2020, there were 11.9 million gallons remaining on these contracts which represent approximately 80% of the Company’s forecasted domestic fuel purchases through December 2021. Under these swap agreements, the Company will pay fixed prices ranging from $1.12 to $1.90 per gallon. At December 31, 2020 and 2019, the fair value asset of the fuel hedge contracts were estimated to be $1,739 and $849, respectively, and are recorded in other current assets. For fuel hedge contracts considered to be highly effective, the losses reclassified to earnings from changes in fair value of derivatives, net of cash settlements and taxes, for the year ended December 31, 2020 were $5,825. The remaining gains and losses included in the accumulated other comprehensive income (loss) at December 31, 2020 will be reclassified into earnings over the next twelve months, corresponding to the period during which the hedged fuel is expected to be utilized. Changes in the fair value of fuel hedge contracts not considered highly effective are recorded as cost of contract revenues in the Statement of Operations. The fair value of fuel hedges are corroborated using inputs that are readily observable in public markets; therefore, the Company determines fair values of these fuel hedges using Level 2 inputs. The Company is exposed to counterparty credit risk associated with non-performance of its various derivative instruments. The Company’s risk would be limited to any unrealized gains on current positions. To help mitigate this risk, the Company transacts only with counterparties that are rated as investment grade or higher. In addition, all counterparties are monitored on a continuous basis. The fair value of the fuel hedge contracts outstanding as of December 31, 2020 and 2019 is as follows: Balance Sheet Location Fair Value at December 31, 2020 2019 Asset derivatives: Derivatives designated as hedging instruments Fuel hedge contracts Other current assets $ 1,739 $ 849 Assets and liabilities measured at fair value on a nonrecurring basis All other nonfinancial assets and liabilities measured at fair value in the financial statements on a nonrecurring basis are subject to fair value measurements and disclosures. Nonfinancial assets and liabilities included in the consolidated balance sheets and measured on a nonrecurring basis consist of goodwill and long-lived assets. Assets included within assets held for sale are reclassified from property and equipment at fair value less cost to sell. Goodwill and long-lived assets are measured at fair value to test for and measure impairment, if any, at least annually for goodwill or when necessary for both goodwill and long-lived assets. Accumulated other comprehensive income (loss) Changes in the components of the accumulated balances of other comprehensive income (loss) are as follows: 2020 2019 2018 Cumulative translation adjustments—net of tax $ — $ — $ 1,513 Derivatives: Reclassification of derivative (gains) losses to earnings—net of tax 5,825 1,458 (1,569 ) Change in fair value of derivatives—net of tax (5,152 ) 2,646 (3,756 ) Net unrealized (gain) loss on derivatives—net of tax 673 4,104 (5,325 ) Total other comprehensive income (loss) $ 673 $ 4,104 $ (3,812 ) Adjustments reclassified from accumulated balances of other comprehensive income (loss) to earnings are as follows: Statement of Operations Location 2020 2019 2018 Derivatives: Fuel hedge contracts Costs of contract revenues $ 7,703 $ 1,975 $ (2,125 ) Income tax (provision) benefit 1,878 517 (556 ) $ 5,825 $ 1,458 $ (1,569 ) The Company substantially completed the liquidation of the investment in its Brazil and Australia operations during 2018. This liquidation resulted in the reversal of the Company’s cumulative translation adjustment. Adjustments reclassified from accumulated balances of other comprehensive income (loss) to earnings are as follows: Statement of Operations Location 2018 Cumulative translation adjustment: Other expense $ (2,337 ) Income tax benefit 612 $ (1,725 ) Other financial instruments The carrying value of financial instruments included in current assets and current liabilities approximates fair value due to the short-term maturities of these instruments. Based on timing of the cash flows and comparison to current market interest rates, the carrying value of the senior revolving credit agreement approximates fair value. In May 2017, the Company issued a total of $325,000 of 8.000% senior notes due May 15, 2022, which were outstanding at December 31, 2020 (See Note 6, Long-Term Debt). The 8% Senior Notes are senior unsecured obligations of the Company and its subsidiaries that guarantee the Senior Notes. The fair value of the senior notes was $333,320 at December 31, 2020, which is a Level 1 fair value measurement as the senior notes value was obtained using quoted prices in active markets. It is impracticable to determine the fair value of outstanding letters of credit or performance, bid and payment bonds due to uncertainties as to the amount and timing of future obligations, if any.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	8. The Company’s income tax provision (benefit) from continuing and discontinued operations for the year ended December 31, 2020 is as follows: 2020 2019 2018 Income tax provision from continuing operations $ 20,187 $ 15,253 $ 5,437 Income tax benefit from discontinued operations — (4,556 ) (6,162 ) Income tax provision (benefit) $ 20,187 $ 10,697 $ (725 ) The Company’s income (loss) from continuing operations before income tax from domestic and foreign continuing operations for the years ended December 31, 2020, 2019 and 2018 is as follows: 2020 2019 2018 Domestic operations $ 94,826 89,344 $ 26,878 Foreign operations (8,536 ) (18,423 ) (10,425 ) Total income (loss) from continuing operations before income tax $ 86,290 $ 70,921 $ 16,453 The provision (benefit) for income taxes from continuing operations as of December 31, 2020, 2019 and 2018 is as follows: 2020 2019 2018 Federal: Current $ — $ — $ — Deferred 17,464 14,052 3,702 State: Current 128 212 48 Deferred 3,023 989 1,687 Foreign: Current (428 ) — — Deferred — — — Total $ 20,187 $ 15,253 $ 5,437 The Company’s income tax provision (benefit) from continuing operations reconciles to the provision at the statutory U.S. federal income tax rate of 21% for the years ended December 31, 2020, 2019 and 2018, as follows: 2020 2019 2018 Tax provision (benefit) at statutory U.S. federal income tax rate $ 18,121 $ 14,893 $ 3,455 State income tax — net of federal income tax benefit 3,124 3,049 937 Change in state law regarding NOL carryforwards — — 658 Change in deferred state tax rate — (1,835 ) — Stock based compensation (1,212 ) (1,266 ) (8 ) Nondeductible officer compensation 1,212 1,021 201 Research and development tax credits (674 ) (452 ) (218 ) Changes in unrecognized tax benefits — (56 ) 14 Changes in valuation allowance — (3 ) 116 Other (384 ) (98 ) 282 Income tax provision (benefit) $ 20,187 $ 15,253 $ 5,437 At December 31, 2020 and 2019, the Company had loss carryforwards for federal income tax purposes of $92,328 and $137,100 respectively, which expire between 2034 and 2037. At December 31, 2020 and 2019, the Company had gross net operating loss carryforwards for state income tax purposes totaling $170,738 and $223,634, respectively, which expire between 2023 and 2039. Due to changes in state tax law enacted during 2016 in a certain state, a valuation allowance was established. The Company has established a valuation allowance that was $1,628 as of December 31, 2020 and $1,778 as of December 31, 2019. The Company believes that the remaining net operating losses, net of the valuation allowance, will be fully utilized in future periods. The Company also has foreign gross net operating loss carryforwards of approximately $2,414 and $6,777 as of December 31, 2020 and 2019, of which expire between 2020 and 2030. At December 31, 2020 and 2019, a full valuation allowance has been established for the deferred tax asset of $845 and $1,717 related to foreign net operating loss carryforwards, respectively, as the Company believes it is more likely than not that the net operating loss carryforwards will not be realized. The Company does not expect that total unrecognized tax benefits will significantly increase or decrease within the next 12 months. Below is a tabular reconciliation of the total amounts of unrecognized tax benefits at the beginning and end of each period. 2020 2019 2018 Unrecognized tax benefits — January 1 $ — $ 157 $ 157 Gross increases — tax positions in prior period — — — Gross increases — current period tax positions — — — Gross decreases — expirations — — — Gross decreases — tax positions in prior period — (157 ) — Unrecognized tax benefits — December 31, $ — $ — $ 157 The Company’s policy is to recognize interest and penalties related to income tax matters in income tax expense. As of December 31, 2020 and December 31, 2019 the Company had no interest and penalties recorded and as of December 31, 2018 it had approximately $71 of interest and penalties recorded. The Company files income tax returns at the U.S. federal level and in various state and foreign jurisdictions. U.S. federal income tax years prior to 2017 are closed and no longer subject to examination. With few exceptions, the statute of limitations in state taxing jurisdictions in which the Company operates has expired for all years prior to 2016. In foreign jurisdictions in which the Company operates, years prior to 2015 are closed and are no longer subject to examination. The Company’s deferred tax assets (liabilities) at December 31, 2020 and 2019 are as follows: 2020 2019 Deferred tax assets: Operating lease assets $ 16,501 $ 18,301 Accrued liabilities 8,212 7,426 Federal NOLs 19,389 28,791 Foreign NOLs 845 1,717 State NOLs 7,256 9,505 Tax credit carryforwards 3,250 2,620 Charitable contribution — 66 Valuation allowance (2,473 ) (3,495 ) Total deferred tax assets 52,980 64,931 Deferred tax liabilities: Depreciation and amortization (92,547 ) (82,115 ) Operating lease liabilities (16,460 ) (18,334 ) Other liabilities (439 ) (222 ) Total deferred tax liabilities (109,446 ) (100,671 ) Net noncurrent deferred tax liabilities $ (56,466 ) $ (35,740 ) Deferred tax assets relate primarily to reserves and other liabilities for costs and expenses not currently deductible for tax purposes as well as net operating loss and other carryforwards. Deferred tax liabilities relate primarily to the cumulative difference between book depreciation and amounts deducted for tax purposes. The Company evaluates its ability to realize deferred tax assets by considering all available positive and negative evidence. This evidence includes its cumulative earnings or losses in recent years. The Company further considers the impact on these cumulative earnings or losses of discontinued operations and other divested operations and joint ventures, restructuring charges and other nonrecurring adjustments that are not indicative of its ability to generate taxable income in future periods. The Company also considers sources of taxable income, such as the amount and timing of realization of its deferred tax liabilities relative to the timing of expiration of loss carryforwards. When it is estimated to be more likely than not that all or some portion of deferred tax assets will not be realized, the Company establishes a valuation allowance for the amount of such deferred tax assets considered to be unrealizable. After evaluating the positive and negative evidence for future realization of deferred tax assets, the Company recorded valuation allowances for foreign net operating loss carryforwards and certain state net operating loss carryforwards to reduce the balance of these deferred tax assets at December 31, 2020 and 2019 as it was more likely than not that the balance of these tax items would not be realized. By contrast, after evaluating the positive and negative evidence, the Company concluded that it was more likely than not that the deferred federal income tax asset and remaining state net operating loss carryforwards recorded at December 31, 2020 and 2019 would ultimately be realized and determined that no valuation allowance was required .

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-Based Compensation	9. SHARE-BASED COMPENSATION The Company’s 2017 Long-Term Incentive Plan (“Incentive Plan”) permits the granting of stock options, stock appreciation rights, restricted stock and restricted stock units to its employees and directors for up to 3.3 million shares of common stock, plus an additional 1.7 million shares underlying equity awards issued under the 2007 Long-Term Incentive Plan. The Company may also issue share-based compensation as inducement awards to new employees upon approval of the Board of Directors. Compensation cost charged to expense related to share-based compensation arrangements was $6,754, $6,908 and $4,643, for the years ended December 31, 2020, 2019 and 2018, respectively. Non-qualified stock options The NQSO awards were granted with an exercise price equal to the market price of the Company’s common stock at the date of grant. The option awards generally vest in three equal annual installments commencing on the first anniversary of the grant date, and have ten year exercise periods. The fair value of the NQSOs was determined at the grant date using a Black-Scholes option pricing model, which requires the Company to make several assumptions. The risk-free interest rate is based on the U.S. Treasury yield curve in effect for the expected term of the option at the time of grant. The annual dividend yield on the Company’s common stock is based on estimates of future dividends during the expected term of the NQSOs. The expected life of the NQSOs was determined from historical exercise data providing a reasonable basis upon which to estimate the expected life. The volatility assumptions were based on historical volatility of Great Lakes. There is not an active market for options on the Company’s common stock and, as such, implied volatility for the Company’s stock was not considered. Additionally, the Company’s general policy is to issue new shares of registered common stock to satisfy stock option exercises or grants of restricted stock. No NQSO awards were granted in 2020, 2019 and 2018. The aggregate intrinsic value of stock options represents the difference between market value on the date of exercise and the option price. The aggregate intrinsic value of stock options exercised during 2020, 2019 and 2018 was $779, $2,534 and $116, respectively. A summary of stock option activity under the Incentive Plan as of December 31, 2020, and changes during the year ended December 31, 2020, is presented below: Options Shares Weighted Exercise Price Weighted-Average Remaining Contract Term (yrs) Aggregate Intrinsic Value ($000's) Outstanding as of January 1, 2020 504 $ 6.87 Granted — — Exercised (226 ) 6.68 Forfeited or Expired — — Outstanding as of December 31, 2020 278 $ 6.99 2.0 $ 1,785 Vested at December 31, 2020 278 $ 6.99 2.0 $ 1,785 Restricted stock units RSUs can either vest in equal portions over the three year vesting period or vest in one installment on the third anniversary of the grant date. The fair value of RSUs was based upon the Company’s stock price on the date of grant. A summary of the status of the Company’s non-vested RSUs as of December 31, 2020, and changes during the year ended December 31, 2020, is presented below: Nonvested Restricted Stock Units Shares Weighted-Average Grant-Date Fair Value Outstanding as of January 1, 2020 1,809 $ 6.00 Granted 851 8.90 Vested (1,192 ) 5.71 Forfeited (62 ) 6.66 Outstanding as of December 31, 2020 1,406 $ 8.00 Expected to vest at December 31, 2020 1,132 $ 7.52 As of December 31, 2020, there was $4,374 of total unrecognized compensation cost related to non-vested RSUs granted under the Incentive Plan. That cost for non-vested RSUs is expected to be recognized over a weighted-average period of 1.9 years. The Incentive Plan permits the employee to use vested shares from RSUs to satisfy the grantee’s U.S. federal income tax liability resulting from the issuance of the shares through the Company’s retention of that number of common shares having a market value as of the vesting date equal to such tax obligation up to the minimum statutory withholding requirements. The amount related to shares used for such tax withholding obligations was approximately $4,748 and $5,008 for the years ended December 31, 2020 and 2019, respectively. Director compensation The Company uses a combination of cash and share-based compensation to attract and retain qualified candidates to serve on its Board of Directors. Compensation is paid to non-employee directors. Directors who are employees receive no additional compensation for services as members of the Board or any of its committees. Share-based compensation is paid pursuant to the Incentive Plan. Each non-employee director of the Company receives an annual retainer of $155, payable quarterly in arrears, and is generally paid 50% in cash and 50% in common stock or deferred restricted stock units of the Company. Directors may elect to receive some or all of the cash retainer in common stock or deferred restricted stock units. In 2020, the Chairman of the Board received an additional $100 of annual compensation, paid 100% in common stock. In the years ended December 31, 2020, 2019 and 2018, 79 thousand, 78 thousand and 156 thousand shares, respectively, of the Company’s common stock or restricted stock units were issued to non-employee directors under the Incentive Plan.

Revenue

Revenue	12 Months Ended
	Dec. 31, 2020
Revenue From Contract With Customer [Abstract]
Revenue	10. REVENUE The Company’s revenue is derived from contracts for services with federal, state, local and foreign governmental entities and private customers. Revenues are generally derived from the enhancement or preservation of navigability of waterways or the protection of shorelines through the removal or replenishment of soil, sand or rock. Performance obligations A performance obligation is a promise in a contract to transfer a distinct good or service to the customer, and is the unit of account upon which the Company’s revenue is calculated. A contract’s transaction price is allocated to each distinct performance obligation and recognized as revenue as the performance obligation is satisfied. Fixed-price contracts, which comprise substantially all of the Company’s revenue, will most often represent a single performance obligation as the promise to transfer the individual services is not separately identifiable from other promises in the contracts and, therefore, not distinct. The Company’s performance obligations are satisfied over time and revenue is recognized using contract fulfillment costs incurred to date compared to total estimated costs at completion, also known as cost-to-cost, to measure progress towards completion. As the Company’s performance creates an asset that the customer controls, this method provides a faithful depiction of the transfer of an asset to the customer. Generally, the Company has an enforceable right to payment for performance completed to date. The majority of the Company’s contracts are completed in a year or less. At December 31, 2020, the Company had $559,376 of remaining performance obligations, which the Company refers to as total backlog. Approximately 90% of the Company’s backlog will be completed in 2021 with the remaining balance expected to be completed by 2022. Transaction price The transaction price is calculated using the Company’s estimated costs to complete a project. These costs are based on the types of equipment required to perform the specified service, project site conditions, the estimated project duration, seasonality, location and complexity of a project. The nature of the Company’s contracts gives rise to several types of variable consideration, including pay on quantity dredged for dredging projects and dredging project contract modifications. Estimated pay quantity is the amount of material the Company expects to dredge for which it will receive payment. Estimated quantity to be dredged is calculated using engineering estimates based on current survey data and the Company’s knowledge based on historical project experience. Revenue by category Domestically, the Company’s work generally is performed in coastal waterways and deep water ports. The U.S. dredging market consists of four primary types of work: capital, coastal protection, maintenance and rivers & lakes. The following table sets forth, by type of work, the Company’s contract revenues for the years ended December 31, 2020, 2019 and 2018: Revenues 2020 2019 2018 Capital—U.S. $ 336,163 $ 299,706 $ 333,037 Capital—foreign 25,892 48,619 14,088 Coastal protection 201,361 182,369 175,923 Maintenance 148,767 104,753 53,427 Rivers & lakes 21,418 76,071 44,320 Total revenues $ 733,601 $ 711,518 $ 620,795 The following table sets forth, by type of customer, the Company’s contract revenues for the years ended December 31, 2020, 2019 and 2018: Revenues 2020 2019 2018 Federal government $ 582,949 $ 581,157 $ 468,421 State and local government 85,737 71,398 93,499 Private 39,023 10,344 44,787 Foreign 25,892 48,619 14,088 Total revenues $ 733,601 $ 711,518 $ 620,795 Contract balances Billings on contracts are generally submitted after verification with the customers of physical progress and are recognized as accounts receivable in the balance sheet. For billings that do not match the timing of revenue recognition, the difference between amounts billed and recognized as revenue is reflected in the balance sheet as either contract revenues in excess of billings or billings in excess of contract revenues. Certain pre-contract and pre-construction costs are capitalized and reflected as contract assets in the balance sheet. Customer advances, deposits and commissions are reflected in the balance sheet as contract liabilities. Accounts receivable at December 31, 2020 and December 31, 2019 are as follows: 2020 2019 Completed contracts $ 12,347 $ 3,444 Contracts in progress 21,239 9,490 Retainage 5,968 7,415 39,554 20,349 Allowance for doubtful accounts (564 ) (564 ) Total accounts receivable—net $ 38,990 $ 19,785 The components of contracts in progress at December 31, 2020 and December 31, 2019 are as follows: 2020 2019 Costs and earnings in excess of billings: Costs and earnings for contracts in progress $ 199,964 $ 104,620 Amounts billed (168,569 ) (86,074 ) Costs and earnings in excess of billings for contracts in progress 31,395 18,546 Costs and earnings in excess of billings for completed contracts 2,823 6,126 Total contract revenues in excess of billings $ 34,218 $ 24,672 Current portion of contract revenues in excess of billings $ 32,106 $ 22,560 Long-term contract revenues in excess of billings 2,112 2,112 Total contract revenues in excess of billings $ 34,218 $ 24,672 Billings in excess of costs and earnings: Amounts billed $ (550,468 ) $ (628,491 ) Costs and earnings for contracts in progress 517,860 573,225 Total billings in excess of contract revenues $ (32,608 ) $ (55,266 ) At December 31, 2020 and 2019, costs to fulfill contracts with customers recognized as an asset were $10,501 and $10,300, respectively, and are recorded in other current assets and other noncurrent assets. These costs relate to pre-contract and pre-construction activities. During the years ended December 31, 2020 and 2019 the company amortized pre-contract and pre-construction costs of $15,541 and $11,468, respectively. The Company’s largest domestic customer is the U.S. Army Corps of Engineers (the “Corps”), which has responsibility for federally funded projects related to navigation and flood control of U.S. waterways. In 2020, 2019 and 2018, 79.5%, 81.7% and 75.5%, respectively, of contract revenues were earned from contracts with federal government agencies, including the Corps, as well as other federal entities such as the U.S. Coast Guard and U.S. Navy. During the year ended December 31, 2020 and 2019, respectively, the Company recognized $616 and $2,103 of revenue related to the use of equipment by a customer working on a federal government contract. At December 31, 2020 and 2019, approximately 42.6% and 54.6% respectively, of accounts receivable, including contract revenues in excess of billings and retainage, were due on contracts with federal government agencies. The Company depends on its ability to continue to obtain federal government contracts, and indirectly, on the amount of federal funding for new and current government dredging projects. Therefore, the Company’s operations can be influenced by the level and timing of federal funding. The Company derived revenues and gross profit from foreign project operations for the years ended December 31, 2020, 2019, and 2018, as follows: 2020 2019 2018 Contract revenues $ 25,892 $ 48,619 $ 14,088 Costs of contract revenues (34,529 ) (66,347 ) (19,866 ) Gross profit $ (8,637 ) $ (17,728 ) $ (5,778 ) In 2020, 2019 and 2018, foreign revenues were primarily from work done in the Middle East. The majority of the Company’s long-lived assets are marine vessels and related equipment. At any point in time, the Company may employ certain assets outside of the U.S., as needed, to perform work on the Company’s foreign projects. As of December 31, 2020 and 2019, long-lived assets with a net book value of $5,255 and $31,872, respectively, were located outside of the U.S., currently our assets outside of the U.S. do not include dredges. Revenue from foreign projects has been concentrated in the Middle East which comprised less than 10% in 2020, 2019 and 2018. At December 31, 2020 and 2019, approximately 12% and 29%, respectively, of total accounts receivable, including retainage and contract revenues in excess of billings, were due on contracts in the Middle East.

Retirement Plans

Retirement Plans	12 Months Ended
	Dec. 31, 2020
Compensation And Retirement Disclosure [Abstract]
Retirement Plans	11. RETIREMENT PLANS The Company sponsors two 401(k) savings plans, one covering substantially all non-union salaried employees (“Salaried Plan”), a second covering its hourly employees (“Hourly Plan”). Under the Salaried Plan and the Hourly Plan, individual employees may contribute a percentage of compensation and the Company will match a portion of the employees’ contributions. The Salaried Plan also includes a discretionary profit-sharing component, permitting the Company to make discretionary employer contributions to all eligible employees of these plans. Additionally, the Company sponsors a Supplemental Savings Plan in which the Company makes contributions for certain key executives. The Company’s expense for matching, discretionary and Supplemental Savings Plan contributions for 2020, 2019 and 2018, was $5,557, $5,168 and $5,060, respectively. The Company also contributes to various multiemployer pension plans pursuant to collective bargaining agreements. In 2020, 2019 and 2018, the Company contributed $4,929, $4,517 and $4,207 respectively to all of the multiemployer plans that provide pension benefits in its continuing operations. The information available to the Company about the multiemployer plans in which it participates, whether via request to the plan or publicly available, is generally dated due to the nature of the reporting cycle of multiemployer plans and legal requirements under the Employee Retirement Income Security Act (“ERISA”) as amended by the Multiemployer Pension Plan Amendments Act (“MPPAA”). Based upon these plans’ most recently available annual reports, the Company’s contributions to these plans were less than 5% of each plan’s total contributions. The Company does not expect any future increased contributions to have a material negative impact on its financial position, results of operations or cash flows for future years. The risks of participating in multiemployer plans are different from single employer plans as assets contributed are available to provide benefits to employees of other employers and unfunded obligations from an employer that discontinues contributions are the responsibility of all remaining employers. In addition, in the event of a plan’s termination or the Company’s withdrawal from a plan, the Company may be liable for a portion of the plan’s unfunded vested benefits. However, information from the plans’ administrators is not available to permit the Company to determine its share, if any, of unfunded vested benefits.

Restructuring Charges

Restructuring Charges	12 Months Ended
	Dec. 31, 2020
Restructuring And Related Activities [Abstract]
Restructuring Charges	12. RESTRUCTURING CHARGES In 2017, a strategic review was begun to improve the Company's financial results in both domestic and international operations enabling debt reduction, improvements in return on capital and the continued renewal of its extensive fleet with new and efficient dredges to best serve its domestic and international clients. Management executed a plan to reduce general and administrative and overhead expenses, retire certain underperforming and underutilized assets, write-off pre-contract costs on a project that was never formally awarded and that the Company no longer intends to pursue and closeout the Company’s Brazil operations. The cumulative amounts incurred to date as a result of this plan, including amounts presented in discontinued operations, including severance costs of $3,549, asset retirements of $32,309, pre-contract costs of $6,441 and closeout costs of $4,194. Restructuring activities were completed in 2018. Restructuring charges recognized for the above actions for the year ended December 31, 2018 are summarized as follows: 2018 Costs of contract revenues—depreciation $ 6,759 Costs of contract revenues—other 2,292 General and administrative expenses 185 Loss on sale of assets—net 4,572 Other expense 2,337 Total 16,145

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	13. COMMITMENTS AND CONTINGENCIES Commercial commitments Performance and bid bonds are customarily required for dredging and marine construction projects, as well as some environmental & infrastructure projects. The Company has bonding agreements with Argonaut Insurance Company, Berkley Insurance Company, Chubb Surety and Liberty Mutual Insurance Company In connection with the sale of its historical demolition business, the Company was obligated to keep in place the surety bonds on pending demolition projects for the period required under the respective contract for a project and issued Zurich a letter of credit related to this exposure. In February 2017, the Company was notified by Zurich of an alleged default triggered on a historical demolition surety performance bond in the aggregate of approximately $20,000 for failure of the contractor to perform in accordance with the terms of a project. In May 2017, Zurich drew upon the letter of credit in the amount of $20,881. In order to fund the draw on the letter of credit in May 2017, the Company had to increase the borrowings on its revolving credit facility. As the outstanding letters of credit previously reduced the Company’s availability under the revolving credit facility, this draw down on the Company’s letter of credit did not impact its liquidity or capital availability. Pursuant to the terms of sale of its historical demolition business, the Company received an indemnification from the buyer for losses resulting from the bonding arrangement. The Company intends to aggressively pursue enforcement of the indemnification provisions. The Company has recovered some funds but cannot estimate the total amount of recoveries related to the indemnification or resolution of the Company’s responsibilities under the surety bond. Certain foreign projects performed by the Company have warranty periods, typically spanning no more than one to three years beyond project completion, whereby the Company retains responsibility to maintain the project site to certain specifications during the warranty period. Generally, any potential liability of the Company is mitigated by insurance, shared responsibilities with consortium partners, and/or recourse to owner-provided specifications. Legal proceedings and other contingencies As is customary with negotiated contracts and modifications or claims to competitively bid contracts with the federal government, the government has the right to audit the books and records of the Company to ensure compliance with such contracts, modifications, or claims, and the applicable federal laws. The government has the ability to seek a price adjustment based on the results of such audit. Any such audits have not had, and are not expected to have, a material impact on the financial position, operations, or cash flows of the Company. Various legal actions, claims, assessments and other contingencies arising in the ordinary course of business are pending against the Company and certain of its subsidiaries. The Company will defend itself vigorously on all matters. These matters are subject to many uncertainties, and it is possible that some of these matters could ultimately be decided, resolved, or settled adversely to the Company. Although the Company is subject to various claims and legal actions that arise in the ordinary course of business, except as described below, the Company is not currently a party to any material legal proceedings or environmental claims. The Company records an accrual when it is probable a liability has been incurred and the amount of loss can be reasonably estimated. The Company does not believe any of these proceedings, individually or in the aggregate, would be expected to have a material effect on results of operations, cash flows or financial condition. On April 23, 2014, the Company completed the sale of NASDI, LLC (“NASDI”) and Yankee Environmental Services, LLC (“Yankee”), which together comprised the Company’s historical demolition business, to a privately owned demolition company. On January 14, 2015, the Company and its subsidiary, NASDI Holdings, LLC, brought an action in the Delaware Court of Chancery to enforce the terms of the Company's agreement to sell NASDI and Yankee. Under the terms of the agreement, the Company received cash of $5,309 and retained the right to receive additional proceeds based upon future collections of outstanding accounts receivable and work in process existing at the date of close. The Company seeks specific performance of the buyer’s obligation to collect and to remit the additional proceeds, and other related relief. Defendants have filed counterclaims alleging that the Company misrepresented the quality of its contracts and receivables prior to the sale. The Company denies defendants’ allegations. In June 2019, the U.S. Attorney’s Office for the Eastern District of Louisiana informed the Company that it intends to file criminal charges against the Company in connection with a September 2016 oil spill. The oil spill occurred during the Company’s Cheniere Ronquille project, allegedly resulting in the discharge of around 160 barrels of crude oil in Bay Long, Louisiana. The Company has cooperated with the U.S. Attorney’s Office in its investigation of the oil spill and believes that criminal charges are not warranted. While we contest claims of criminal responsibility in this matter, the government may initiate suspension or debarment proceedings against us, pending the outcome of a trial on the matter, which might prohibit us from bidding for, entering into or completing certain government projects. If the Company is ultimately found guilty, suspension or debarment actions could occur automatically. On September 27, 2019, the EPA Region 4 filed an administrative complaint against the Company relating to a project the Company performed at PortMiami from 2013-2015. The EPA is alleging violations of Section 103 of the Marine Protection, Research, and Sanctuaries Act (“MPRSA”) and failure to report violations of the MPRSA. The EPA has calculated and proposed that the administrative court issue a penalty in the total amount of $973. The Company disagrees with the EPA on whether violations occurred and, if any violation did occur, the appropriate penalty calculation. The Company has not accrued any amounts with respect to the above matters as the Company does not believe, based on information currently known to it, that a loss relating to these matters is probable, and an estimate of a range of potential losses relating to these matters cannot reasonably be made.

Business Dispositions

Business Dispositions	12 Months Ended
	Dec. 31, 2020
Discontinued Operations And Disposal Groups [Abstract]
Business Dispositions	14. BUSINESS DISPOSITIONS Discontinued operations During the second quarter of 2019, the Company completed the sale of the historical environmental & infrastructure business. Under the terms of the agreement, the Company received cash of $17,500 in the second quarter of 2019 and received an additional $857 in the third quarter of 2019. The results of the business have been reported in discontinued operations as follows: 2019 2018 Revenue $ 25,040 $ 76,843 Loss before income taxes from discontinued operations $ (8,253 ) $ (9,361 ) Loss on disposal of assets held for sale (2,632 ) (14,110 ) Income tax benefit 4,556 6,162 Loss from discontinued operations, net of income taxes $ (6,329 ) $ (17,309 )

Schedule II-Valuation and Quali

Schedule II-Valuation and Qualify Accounts	12 Months Ended
	Dec. 31, 2020
Valuation And Qualifying Accounts [Abstract]
Schedule II-Valuation and Qualifying Accounts	Great Lakes Dredge & Dock Corporation Schedule II—Valuation and Qualifying Accounts For the Years Ended December 31, 2020, 2019 and 2018 (In thousands) Beginning Balance Additions Deductions Ending balance Description Year ended December 31, 2018 Allowances deducted from assets to which they apply: Allowances for doubtful accounts $ — $ 200 $ — $ 200 Valuation allowance for deferred tax assets 4,294 492 — 4,786 Total $ 4,294 $ 692 $ — $ 4,986 Year ended December 31, 2019 Allowances deducted from assets to which they apply: Allowances for doubtful accounts $ 200 $ 364 $ — $ 564 Valuation allowance for deferred tax assets 4,786 — (1,291 ) 3,495 Total $ 4,986 $ 364 $ (1,291 ) $ 4,059 Year ended December 31, 2020 Allowances deducted from assets to which they apply: Allowances for doubtful accounts $ 564 $ — $ — $ 564 Valuation allowance for deferred tax assets 3,495 — (1,022 ) 2,473 Total $ 4,059 $ — $ (1,022 ) $ 3,037

Nature of Business and Summar_2

Nature of Business and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Principles of Consolidation and Basis of Presentation	Principles of Consolidation and Basis of Presentation —The consolidated financial statements include the accounts of Great Lakes Dredge & Dock Corporation and its majority-owned subsidiaries. All intercompany accounts and transactions are eliminated in consolidation. The equity method of accounting is used for investments in unconsolidated investees in which the Company has significant influence, but not control. Other investments, if any, are carried at cost.
Use of Estimates	Use of Estimates —The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (“GAAP”) requires management to make estimates and assumptions that affect certain reported amounts and disclosures. Accordingly, actual results could differ from those estimates.
Revenue and Cost Recognition on Contracts	Revenue and Cost Recognition on Contracts —Revenue is recognized using contract fulfillment costs incurred to date compared to total estimated costs at completion, also known as cost-to-cost, to measure progress towards completion. Additionally, the Company capitalizes certain pre-contract and pre-construction costs, and defers recognition over the life of the contract. The Company’s performance obligations are satisfied over time and revenue is recognized using the cost-to-cost method, described above. Contract modifications are changes in the scope or price (or both) of a contract that are approved by the parties to the contract. The Company recognizes a contract modification when the parties to a contract approve a modification that either creates new, or changes existing, enforceable rights and obligations of the parties to the contract. Contract modifications are routine in the performance of the Company’s contracts. In most instances, contract modifications are for services that are not distinct, and, therefore, are accounted for as part of the existing contract. Contract modifications are included in the transaction price only if it is probable that the modification estimate will not result in a significant reversal of revenue. Revisions in estimated gross profit percentages are recorded in the period during which the change in circumstances is experienced or becomes known. As the duration of most of the Company’s contracts is one year or less, the cumulative net impact of these revisions in estimates, individually and in the aggregate across projects, does not significantly affect results across annual reporting periods. Provisions for estimated losses on contracts in progress are made in the period in which such losses are determined. The components of costs of contract revenues include labor, equipment (including depreciation, maintenance, insurance and long-term rentals), subcontracts, fuel, supplies, short-term rentals and project overhead. Hourly labor generally is hired on a project-by-project basis. The Company is a party to numerous collective bargaining agreements in the U.S. that govern its relationships with its unionized hourly workforce.
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, unless completion of such contracts extends significantly beyond one year.
Cash Equivalents	Cash Equivalents —The Company considers all highly liquid investments with a maturity at purchase of three months or less to be cash equivalents.
Accounts Receivable	Accounts Receivable —Accounts receivable represent amounts due or billable under the terms of contracts with customers, including amounts related to retainage. The Company anticipates collection of retainage generally within one year, and accordingly presents retainage as a current asset. The Company provides an allowance for estimated uncollectible accounts receivable based on historical and expected losses and when events or conditions indicate that amounts outstanding are not recoverable.
Inventories	Inventories —Inventories consist of pipe and spare parts used in the Company’s dredging operations. Pipe and spare parts are purchased in large quantities; therefore, a certain amount of pipe and spare part inventories is not anticipated to be used within the current year and is classified as long-term. Spare part inventories are stated at weighted average historical cost, and are charged to expense when used in operations. Pipe inventory is recorded at cost and amortized to expense over the period of its use.
Property, Plant and Equipment	Property and Equipment —Capital additions, improvements, and major renewals are classified as property and equipment and are carried at depreciated cost. Maintenance and repairs that do not significantly extend the useful lives of the assets or enhance the capabilities of such assets are charged to expenses as incurred. Depreciation is recorded over the estimated useful lives of property and equipment using the straight-line method and the mid-year depreciation convention. The estimated useful lives by class of assets are: Class Useful Life (years) Buildings and improvements 10 Furniture and fixtures 5-10 Vehicles, dozers, and other light operating equipment and systems 3-5 Heavy operating equipment (dredges and barges) 10-30 Leasehold improvements are amortized over the shorter of their remaining useful lives or the remaining terms of the leases.
Goodwill	Goodwill —Goodwill represents the excess of acquisition cost over fair value of the net assets acquired. Goodwill is tested annually for impairment in the third quarter of each year, or more frequently should circumstances dictate. GAAP requires that goodwill of a reporting unit be tested for impairment between annual tests if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. When conducting the annual impairment test for goodwill, the Company can choose to assess qualitative factors to determine whether it is more likely than not the fair value of the reporting unit is below its carrying value. If a qualitative assessment determines an impairment is more likely than not, the Company is required to perform a quantitative impairment test. Otherwise, no further analysis is required. The Company also may elect to forego this step and just perform the quantitative impairment test. The Company assesses the fair values of its reporting unit using both a market-based approach and an income-based approach. Under the income approach, the fair value of the reporting unit is based on the present value of estimated future cash flows. The income approach is dependent on a number of factors, including estimates of future market growth trends, forecasted revenues and expenses, appropriate discount rates and other variables. The estimates are based on assumptions that the Company believes to be reasonable, but such assumptions are subject to unpredictability and uncertainty. Changes in these estimates and assumptions could materially affect the determination of fair value, and may result in the impairment of goodwill in the event that actual results differ from those estimates. The market approach measures the value of a reporting unit through comparison to comparable companies. Under the market approach, the Company uses the guideline public company method by applying estimated market-based enterprise value multiples to the reporting unit’s estimated revenue and Adjusted EBITDA. The Company analyzes companies that performed similar services or are considered peers. Due to the fact that there are no public companies that are direct competitors, the Company weighs the results of this approach less than the income approach. The Company has one operating segment which is also the Company’s one reportable segment and reporting unit of which the Company tests goodwill for impairment. The historical environmental & infrastructure segment, which the Company sold during the second quarter of 2019, has been retrospectively presented as discontinued operations and assets and liabilities held for sale and is no longer reflected in continuing operations. The Company performed its most recent annual test of impairment as of July 1, 2020 with no indication of impairment as of the test date. As of the test date, the fair value of the reporting unit was substantially in excess of its carrying value. The Company will perform its next scheduled annual test of goodwill in the third quarter of 2021 should no triggering events occur which would require a test prior to the next annual test.
Long-Lived Assets	Long-Lived Assets —Long-lived assets are comprised of property and equipment subject to amortization. Long-lived assets to be held and used are reviewed for possible impairment whenever events indicate that the carrying amount of such assets may not be recoverable by comparing the undiscounted cash flows associated with the assets to their carrying amounts. If such a review indicates an impairment, the carrying amount would be reduced to fair value. No triggering events were identified in 2020 or 2019. If long-lived assets are to be disposed, depreciation is discontinued, if applicable, and the assets are reclassified as held for sale at the lower of their carrying amounts or fair values less estimated costs to sell.
Self-insurance Reserves	Self-insurance Reserves —The Company self-insures costs associated with its seagoing employees covered by the provisions of Jones Act, workers’ compensation claims, hull and equipment liability, and general business liabilities up to certain limits. Insurance reserves are established for estimates of the loss that the Company may ultimately incur on reported claims, as well as estimates of claims that have been incurred but not yet reported. In determining its estimates, the Company considers historical loss experience and judgments about the present and expected levels of cost per claim. Trends in actual experience are a significant factor in the determination of such reserves.
Income Taxes	Income Taxes —The provision for income taxes includes federal, foreign, and state income taxes currently payable and those deferred because of temporary differences between the financial statement and tax basis of assets and liabilities. Recorded deferred income tax assets and liabilities are based on the estimated future tax effects of differences between the financial and tax basis of assets and liabilities, given the effect of currently enacted tax laws. Refer to Note 8, Income Taxes.
Hedging Instruments	Hedging Instruments —At times, the Company designates certain derivative contracts as a cash flow hedge as defined by GAAP. Accordingly, the Company formally documents, at the inception of each hedge, all relationships between hedging instruments and hedged items, as well as its risk-management objective and strategy for undertaking hedge transactions. This process includes linking all derivatives to highly-probable forecasted transactions. The Company formally assesses, at inception and on an ongoing basis, the effectiveness of hedges in offsetting changes in the cash flows of hedged items. Hedge accounting treatment may be discontinued when (1) it is determined that the derivative is no longer highly effective in offsetting changes in the cash flows of a hedged item (including hedged items for forecasted future transactions), (2) the derivative expires or is sold, terminated or exercised, (3) it is no longer probable that the forecasted transaction will occur or (4) management determines that designating the derivative as a hedging instrument is no longer appropriate. If management elects to stop hedge accounting, it would be on a prospective basis and any hedges in place would be recognized in accumulated other comprehensive income (loss) until all the related forecasted transactions are completed or are probable of not occurring.
Recent Accounting Pronouncements	Recent Accounting Pronouncements — In March 2020, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2020-04 (“ASU 2020-04”), Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting. The amendment provides optional expedients and exceptions to applying the guidance on contract modifications, hedge accounting and other transactions to simplify the accounting for transitioning from the London Interbank Offered Rate (“LIBOR”), and other interbank offered rates expected to be discontinued, to alternative reference rates. The guidance in this update was effective upon its issuance; if elected, it is to be applied prospectively through December 31, 2022. The Company is currently evaluating the effect the potential adoption of this ASU will have on the Company’s consolidated financial statements.

Nature of Business and Summar_3

Nature of Business and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Estimated Useful Lives By Class Of Assets	The estimated useful lives by class of assets are: Class Useful Life (years) Buildings and improvements 10 Furniture and fixtures 5-10 Vehicles, dozers, and other light operating equipment and systems 3-5 Heavy operating equipment (dredges and barges) 10-30

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Computations for Basic and Diluted Earnings Per Share	The computations for basic and diluted earnings per share for the years ended December 31, 2020, 2019 and 2018 are as follows: (shares in thousands) 2020 2019 2018 Income from continuing operations $ 66,103 $ 55,668 $ 11,016 Loss on discontinued operations, net of income taxes — (6,329 ) (17,309 ) Net income (loss) $ 66,103 $ 49,339 $ (6,293 ) Weighted-average common shares outstanding — basic 64,743 63,597 62,236 Effect of stock options and restricted stock units 1,129 1,445 1,371 Weighted-average common shares outstanding — diluted 65,872 65,042 63,607 Earnings per share from continuing operations — basic $ 1.02 $ 0.88 $ 0.18 Earnings per share from continuing operations — diluted $ 1.00 $ 0.86 $ 0.17
Schedule of Stock Options and Restricted Stock Units Excluded from Calculation of Anti-Diluted Earnings Per Share	For the years ended December 31, 2020, 2019 and 2018 the following amounts of NQSOs and RSUs were excluded from the calculation of diluted earnings per share based on the application of the treasury stock method, as such NQSOs and RSUs were determined to be anti-dilutive: (shares in thousands) 2020 2019 2018 Effect of stock options and restricted stock units 1 16 1,285

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2020
Property Plant And Equipment [Abstract]
Schedule of Property Plant and Equipment	Property and equipment at December 31, 2020 and 2019 are as follows: 2020 2019 Land $ 9,992 $ 9,992 Buildings and improvements 1,315 5,071 Furniture and fixtures 17,251 16,299 Operating equipment 762,350 738,375 Total property and equipment 790,908 769,737 Accumulated depreciation (407,866 ) (395,141 ) Property and equipment — net $ 383,042 $ 374,596

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Schedule of Lease Costs	The Company’s lease costs are recorded in cost of contract revenues and general and administrative expenses. For the years ended December 31, 2020 and 2019, respectively, lease costs are as follows: Year Ended Year Ended December 31, 2020 December 31, 2019 Operating lease cost $ 24,602 $ 27,259 Short-term lease cost 87,534 70,382 Total lease cost $ 112,136 $ 97,641
Schedule of Maturity Analysis of Operating Lease Liabilities	As recorded on the balance sheet, the Company’s maturity analysis of its operating lease liabilities as of December 31, 2020 is as follows: 2021 $ 22,247 2022 18,467 2023 13,321 2024 9,768 2025 5,053 Thereafter 3,975 Minimum lease payments 72,831 Imputed interest 7,480 Present value of minimum operating lease payments $ 65,351
Schedule of Additional Information Related to Leases	Additional information related to the Company’s leases as of December 31, 2020 and 2019, respectively, is as follows: December 31, 2020 December 31, 2019 Weighted average remaining lease term 4.1 years 4.2 years Weighted average discount rate 6.2 % 6.7 %
Supplemental Information Related to Leases	Supplemental information related to leases during the year ended December 31, 2020 and 2019, respectively, is as follows: Year Ended Year ended December 31, 2020 December 31, 2019 Operating cash flows from operating leases $ (25,064 ) $ (27,235 ) Operating lease liabilities arising from obtaining new operating lease assets $ 22,746 $ 13,149

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2020
Payables And Accruals [Abstract]
Accrued Expenses	Accrued expenses at December 31, 2020 and 2019 were as follows: 2020 2019 Payroll and employee benefits $ 21,675 $ 16,859 Insurance 14,754 15,702 Interest 3,285 3,284 Contract reserves 2,491 6,248 Income and other taxes 2,164 1,597 Other 8,530 7,535 Total accrued expenses $ 52,899 $ 51,225

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Schedule of Long-Term Debt	Long-term debt at December 31, 2020 and 2019 were as follows: 2020 2019 Revolving credit facility $ — $ — 8% Senior Notes 323,735 322,843 Total $ 323,735 $ 322,843
Maturities of Long-Term Debt	The scheduled principal payments through the maturity date of the Company’s long-term debt at December 31, 2020, are as follows: Years Ending December 31, 2021 $ — 2022 325,000 2023 — 2024 — 2025 — Thereafter — Total $ 325,000

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Fair Values of Financial Instruments and Nonfinancial Assets and Liabilities Measured at the Reporting Date	The fair values of these financial instruments are summarized as follows: Fair Value Measurements at Reporting Date Using Description At December 31, 2020 Quoted Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable (Level 3) Fuel hedge contracts $ 1,739 $ — $ 1,739 $ — Fair Value Measurements at Reporting Date Using Description At December 31, 2019 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fuel hedge contracts $ 849 $ — $ 849 $ —
Schedule of Fair Value of Fuel Hedge Contracts Balance Sheet Location	The fair value of the fuel hedge contracts outstanding as of December 31, 2020 and 2019 is as follows: Balance Sheet Location Fair Value at December 31, 2020 2019 Asset derivatives: Derivatives designated as hedging instruments Fuel hedge contracts Other current assets $ 1,739 $ 849
Changes in Components of Accumulated Other Comprehensive Income (Loss)	Changes in the components of the accumulated balances of other comprehensive income (loss) are as follows: 2020 2019 2018 Cumulative translation adjustments—net of tax $ — $ — $ 1,513 Derivatives: Reclassification of derivative (gains) losses to earnings—net of tax 5,825 1,458 (1,569 ) Change in fair value of derivatives—net of tax (5,152 ) 2,646 (3,756 ) Net unrealized (gain) loss on derivatives—net of tax 673 4,104 (5,325 ) Total other comprehensive income (loss) $ 673 $ 4,104 $ (3,812 )
Adjustments Reclassified from Accumulated Balances Other Comprehensive Income (Loss) to Earnings	Adjustments reclassified from accumulated balances of other comprehensive income (loss) to earnings are as follows: Statement of Operations Location 2020 2019 2018 Derivatives: Fuel hedge contracts Costs of contract revenues $ 7,703 $ 1,975 $ (2,125 ) Income tax (provision) benefit 1,878 517 (556 ) $ 5,825 $ 1,458 $ (1,569 ) Statement of Operations Location 2018 Cumulative translation adjustment: Other expense $ (2,337 ) Income tax benefit 612 $ (1,725 )

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Schedule of Income tax Provision (Benefit) from Continuing and Discontinuing Operations	2020 2019 2018 Income tax provision from continuing operations $ 20,187 $ 15,253 $ 5,437 Income tax benefit from discontinued operations — (4,556 ) (6,162 ) Income tax provision (benefit) $ 20,187 $ 10,697 $ (725 )
Income (Loss) from Continuing Operations before Income Tax from Domestic and Foreign Operations	2020 2019 2018 Domestic operations $ 94,826 89,344 $ 26,878 Foreign operations (8,536 ) (18,423 ) (10,425 ) Total income (loss) from continuing operations before income tax $ 86,290 $ 70,921 $ 16,453
Provision (Benefit) For Income Taxes	2020 2019 2018 Federal: Current $ — $ — $ — Deferred 17,464 14,052 3,702 State: Current 128 212 48 Deferred 3,023 989 1,687 Foreign: Current (428 ) — — Deferred — — — Total $ 20,187 $ 15,253 $ 5,437
Income Tax Provision (Benefit) Reconciliation	2020 2019 2018 Tax provision (benefit) at statutory U.S. federal income tax rate $ 18,121 $ 14,893 $ 3,455 State income tax — net of federal income tax benefit 3,124 3,049 937 Change in state law regarding NOL carryforwards — — 658 Change in deferred state tax rate — (1,835 ) — Stock based compensation (1,212 ) (1,266 ) (8 ) Nondeductible officer compensation 1,212 1,021 201 Research and development tax credits (674 ) (452 ) (218 ) Changes in unrecognized tax benefits — (56 ) 14 Changes in valuation allowance — (3 ) 116 Other (384 ) (98 ) 282 Income tax provision (benefit) $ 20,187 $ 15,253 $ 5,437
Reconciliation of Unrecognized Tax Benefits	2020 2019 2018 Unrecognized tax benefits — January 1 $ — $ 157 $ 157 Gross increases — tax positions in prior period — — — Gross increases — current period tax positions — — — Gross decreases — expirations — — — Gross decreases — tax positions in prior period — (157 ) — Unrecognized tax benefits — December 31, $ — $ — $ 157
Deferred Tax Assets (Liabilities)	2020 2019 Deferred tax assets: Operating lease assets $ 16,501 $ 18,301 Accrued liabilities 8,212 7,426 Federal NOLs 19,389 28,791 Foreign NOLs 845 1,717 State NOLs 7,256 9,505 Tax credit carryforwards 3,250 2,620 Charitable contribution — 66 Valuation allowance (2,473 ) (3,495 ) Total deferred tax assets 52,980 64,931 Deferred tax liabilities: Depreciation and amortization (92,547 ) (82,115 ) Operating lease liabilities (16,460 ) (18,334 ) Other liabilities (439 ) (222 ) Total deferred tax liabilities (109,446 ) (100,671 ) Net noncurrent deferred tax liabilities $ (56,466 ) $ (35,740 )

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity	A summary of stock option activity under the Incentive Plan as of December 31, 2020, and changes during the year ended December 31, 2020, is presented below: Options Shares Weighted Exercise Price Weighted-Average Remaining Contract Term (yrs) Aggregate Intrinsic Value ($000's) Outstanding as of January 1, 2020 504 $ 6.87 Granted — — Exercised (226 ) 6.68 Forfeited or Expired — — Outstanding as of December 31, 2020 278 $ 6.99 2.0 $ 1,785 Vested at December 31, 2020 278 $ 6.99 2.0 $ 1,785
Summary of Non-Vested Restricted Stock Units	A summary of the status of the Company’s non-vested RSUs as of December 31, 2020, and changes during the year ended December 31, 2020, is presented below: Nonvested Restricted Stock Units Shares Weighted-Average Grant-Date Fair Value Outstanding as of January 1, 2020 1,809 $ 6.00 Granted 851 8.90 Vested (1,192 ) 5.71 Forfeited (62 ) 6.66 Outstanding as of December 31, 2020 1,406 $ 8.00 Expected to vest at December 31, 2020 1,132 $ 7.52

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2020
Revenue From Contract With Customer [Abstract]
Summary of Type of Work and Customer, Contract Revenues	The following table sets forth, by type of work, the Company’s contract revenues for the years ended December 31, 2020, 2019 and 2018: Revenues 2020 2019 2018 Capital—U.S. $ 336,163 $ 299,706 $ 333,037 Capital—foreign 25,892 48,619 14,088 Coastal protection 201,361 182,369 175,923 Maintenance 148,767 104,753 53,427 Rivers & lakes 21,418 76,071 44,320 Total revenues $ 733,601 $ 711,518 $ 620,795 The following table sets forth, by type of customer, the Company’s contract revenues for the years ended December 31, 2020, 2019 and 2018: Revenues 2020 2019 2018 Federal government $ 582,949 $ 581,157 $ 468,421 State and local government 85,737 71,398 93,499 Private 39,023 10,344 44,787 Foreign 25,892 48,619 14,088 Total revenues $ 733,601 $ 711,518 $ 620,795
Schedule of Accounts Receivable	Accounts receivable at December 31, 2020 and December 31, 2019 are as follows: 2020 2019 Completed contracts $ 12,347 $ 3,444 Contracts in progress 21,239 9,490 Retainage 5,968 7,415 39,554 20,349 Allowance for doubtful accounts (564 ) (564 ) Total accounts receivable—net $ 38,990 $ 19,785
Components of Contracts in Progress	The components of contracts in progress at December 31, 2020 and December 31, 2019 are as follows: 2020 2019 Costs and earnings in excess of billings: Costs and earnings for contracts in progress $ 199,964 $ 104,620 Amounts billed (168,569 ) (86,074 ) Costs and earnings in excess of billings for contracts in progress 31,395 18,546 Costs and earnings in excess of billings for completed contracts 2,823 6,126 Total contract revenues in excess of billings $ 34,218 $ 24,672 Current portion of contract revenues in excess of billings $ 32,106 $ 22,560 Long-term contract revenues in excess of billings 2,112 2,112 Total contract revenues in excess of billings $ 34,218 $ 24,672 Billings in excess of costs and earnings: Amounts billed $ (550,468 ) $ (628,491 ) Costs and earnings for contracts in progress 517,860 573,225 Total billings in excess of contract revenues $ (32,608 ) $ (55,266 )
Summary of Revenues and Gross Profit from Foreign Project Operations	The Company derived revenues and gross profit from foreign project operations for the years ended December 31, 2020, 2019, and 2018, as follows: 2020 2019 2018 Contract revenues $ 25,892 $ 48,619 $ 14,088 Costs of contract revenues (34,529 ) (66,347 ) (19,866 ) Gross profit $ (8,637 ) $ (17,728 ) $ (5,778 )

Restructuring charges (Tables)

Restructuring charges (Tables)	12 Months Ended
	Dec. 31, 2020
Restructuring And Related Activities [Abstract]
Schedule of Restructuring Charges	Restructuring charges recognized for the above actions for the year ended December 31, 2018 are summarized as follows: 2018 Costs of contract revenues—depreciation $ 6,759 Costs of contract revenues—other 2,292 General and administrative expenses 185 Loss on sale of assets—net 4,572 Other expense 2,337 Total 16,145

Business Dispositions (Tables)

Business Dispositions (Tables)	12 Months Ended
	Dec. 31, 2020
Discontinued Operations And Disposal Groups [Abstract]
Schedule of Discontinued Operations	The results of the business have been reported in discontinued operations as follows: 2019 2018 Revenue $ 25,040 $ 76,843 Loss before income taxes from discontinued operations $ (8,253 ) $ (9,361 ) Loss on disposal of assets held for sale (2,632 ) (14,110 ) Income tax benefit 4,556 6,162 Loss from discontinued operations, net of income taxes $ (6,329 ) $ (17,309 )

Nature of Business and Summar_4

Nature of Business and Summary of Significant Accounting Policies (Estimated Useful Lives By Class of Assets) (Details)	12 Months Ended
	Dec. 31, 2020
Building and Improvements [Member]
Property, Plant and Equipment [Line Items]
Useful life	10 years
Furniture and Fixtures [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful life	5 years
Furniture and Fixtures [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful life	10 years
Vehicles, Dozers, And Other Light Operating Equipment And Systems [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful life	3 years
Vehicles, Dozers, And Other Light Operating Equipment And Systems [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful life	5 years
Heavy Operating Equipment (Dredges And Barges) [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful life	10 years
Heavy Operating Equipment (Dredges And Barges) [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful life	30 years

Nature of Business and Summar_5

Nature of Business and Summary of Significant Accounting Policies (Narrative) (Details)	12 Months Ended
	Dec. 31, 2020segment
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of operating Segments	1
Number of reportable segments	1
Number of reportable segment with goodwill	1

Earnings Per Share - (Computati

Earnings Per Share - (Computations for Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Income from continuing operations	$ 66,103	$ 55,668	$ 11,016
Loss on discontinued operations, net of income taxes		(6,329)	(17,309)
NET INCOME (LOSS)	$ 66,103	$ 49,339	$ (6,293)
Weighted-average common shares outstanding — basic	64,743	63,597	62,236
Effect of stock options and restricted stock units	1,129	1,445	1,371
Weighted-average common shares outstanding — diluted	65,872	65,042	63,607
Earnings per share from continuing operations — basic	$ 1.02	$ 0.88	$ 0.18
Earnings per share from continuing operations — diluted	$ 1	$ 0.86	$ 0.17

Earnings Per Share - (Schedule

Earnings Per Share - (Schedule of Stock Options and Restricted Stock Units Excluded from Calculation of Anti-Diluted Earnings Per Share) (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Effect of stock options and restricted stock units	1	16	1,285

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 790,908	$ 769,737
Accumulated depreciation	(407,866)	(395,141)
Property and equipment — net	383,042	374,596
Land [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	9,992	9,992
Building and Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	1,315	5,071
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	17,251	16,299
Operating Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 762,350	$ 738,375

Property and Equipment (Narrati

Property and Equipment (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 38,183	$ 37,145	$ 50,389
Operating Equipment [Member]
Property, Plant and Equipment [Line Items]
Operating equipment excluded from property and equipment held for sale	$ 2,900	$ 3,970

Leases - (Schedule of Lease Cos

Leases - (Schedule of Lease Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease cost	$ 24,602	$ 27,259
Short-term lease cost	87,534	70,382
Total lease cost	$ 112,136	$ 97,641

Lease (Narrative) (Details)

Lease (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Leases [Abstract]
Rent expense under long term operating lease arrangements	$ 21,160

Leases - (Schedule of Maturity

Leases - (Schedule of Maturity Analysis of Operating Lease Liabilities) (Details) $ in Thousands	Dec. 31, 2020USD ($)
Operating Lease Liabilities Payments Due Rolling Maturity [Abstract]
2021	$ 22,247
2022	18,467
2023	13,321
2024	9,768
2025	5,053
Thereafter	3,975
Minimum lease payments	72,831
Imputed interest	7,480
Present value of minimum operating lease payments	$ 65,351

Leases - (Schedule of Additiona

Leases - (Schedule of Additional Information Related to Leases) (Details)	Dec. 31, 2020	Dec. 31, 2019
Lease Cost [Abstract]
Weighted average remaining lease term	4 years 1 month 6 days	4 years 2 months 12 days
Weighted average discount rate	6.20%	6.70%

Leases - (Supplemental Informat

Leases - (Supplemental Information Related to Leases) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating cash flows from operating leases	$ (25,064)	$ (27,235)
Operating lease liabilities arising from obtaining new operating lease assets	$ 22,746	$ 13,149

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Payroll and employee benefits	$ 21,675	$ 16,859
Insurance	14,754	15,702
Interest	3,285	3,284
Contract reserves	2,491	6,248
Income and other taxes	2,164	1,597
Other	8,530	7,535
Total accrued expenses	$ 52,899	$ 51,225

Long-Term Debt (Schedule of Lon

Long-Term Debt (Schedule of Long-Term Debt) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
8% Senior Notes	$ 323,735	$ 322,843
Long term debt	$ 323,735	$ 322,843

Long-Term Debt (Schedule of L_2

Long-Term Debt (Schedule of Long-Term Debt) (Parenthetical) (Details)	Dec. 31, 2020	May 31, 2017
8.000% Senior Notes Due in 2022 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage	8.00%	8.00%

Long-Term Debt (Narrative) (Det

Long-Term Debt (Narrative) (Details) - USD ($)	May 03, 2019	Feb. 28, 2018	May 31, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Revolving credit facility				$ 0	$ 0
Letters of credit outstanding				36,407,000	35,779,000
Letter of credit remaining borrowing capacity				163,231,000	163,729,000
Availability under credit agreement suppressed				362,000	492,000
Amortization of deferred financing fees				$ 1,611,000	$ 2,231,000	$ 3,504,000
Senior Notes [Member]
Debt Instrument [Line Items]
Face value of senior notes issued, percentage			100.00%
Net proceeds from issuance			$ 321,653,000
Vessels and Ancillary Equipment [Member]
Debt Instrument [Line Items]
Net proceeds from sale-leaseback of a vessel yielding		$ 4,500,000
8.000% Senior Notes Due in 2022 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage			8.00%	8.00%
Debt instrument, face amount			$ 325,000,000	$ 325,000,000
Maturity date			May 15, 2022	May 15, 2022
Owned Domestic Subsidiaries Percent			100.00%
7.375% Senior Notes Due In 2019 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage			7.375%
Debt instrument, face amount			$ 275,000,000
Maturity date			Feb. 28, 2019
Redemption of notes			$ 282,638,000
Minimum [Member]
Debt Instrument [Line Items]
Fixed charge coverage ratio	1.10%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 200,000,000
Line of credit facility optional increase capacity	$ 100,000,000
Revolving credit facility, maturity date				May 3, 2024
Description of refinanced notes maturity after the maturity date				The refinanced 8% Senior Notes must have a maturity on or after the date that is 180 days after the maturity date of the Amended Credit Agreement.
Number of days prior to scheduled maturity date				91 days
Debt instrument, interest rate, stated percentage				8.00%
Revolving Credit Facility [Member] | Domestic Rate [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	0.50%
Interest margin applicable	0.50%
Revolving Credit Facility [Member] | Daily LIBOR Rate [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	1.00%
Revolving Credit Facility [Member] | LIBOR Rate [Member]
Debt Instrument [Line Items]
Interest margin applicable	1.50%
Revolving Credit Facility [Member] | Minimum [Member] | Domestic Rate [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	0.50%
Revolving Credit Facility [Member] | Minimum [Member] | LIBOR Rate [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	1.50%
Revolving Credit Facility [Member] | Maximum [Member] | Domestic Rate [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	1.00%
Revolving Credit Facility [Member] | Maximum [Member] | LIBOR Rate [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	2.00%

Long-Term Debt (Maturities of L

Long-Term Debt (Maturities of Long-Term Debt) (Details) $ in Thousands	Dec. 31, 2020USD ($)
Debt Disclosure [Abstract]
2022	$ 325,000
Total	$ 325,000

Fair Value Measurements (Schedu

Fair Value Measurements (Schedule of Fair Values of Financial Instruments and Nonfinancial Assets and Liabilities Measured at the Reporting Date) (Details) - Fuel Hedge Contracts [Member] - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value, Net Asset (Liability)	$ 1,739	$ 849
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value, Net Asset (Liability)	$ 1,739	$ 849

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) gal in Millions	1 Months Ended	12 Months Ended
	May 31, 2017USD ($)	Dec. 31, 2020USD ($)$ / galgal	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Derivatives Fair Value [Line Items]
Derivative underlying hedge percent		80.00%
Derivative, Nonmonetary Notional Amount, Volume | gal		11.9
Fair value hedge assets		$ 1,739,000	$ 849,000
Reclassification of derivative (gains) losses to earnings—net of tax		5,825,000	$ 1,458,000	$ (1,569,000)
8.000% Senior Notes Due in 2022 [Member]
Derivatives Fair Value [Line Items]
Debt instrument, face amount	$ 325,000,000	$ 325,000,000
Stated interest rate	8.00%	8.00%
Maturity date	May 15, 2022	May 15, 2022
8.000% Senior Notes Due in 2022 [Member] | Fair Value, Inputs, Level 1 [Member]
Derivatives Fair Value [Line Items]
Fair value of debt		$ 333,320,000
Minimum [Member]
Derivatives Fair Value [Line Items]
Fixed price range | $ / gal		1.12
Maximum [Member]
Derivatives Fair Value [Line Items]
Fixed price range | $ / gal		1.90
Fuel Hedge Contracts [Member]
Derivatives Fair Value [Line Items]
Derivative underlying hedge percent		80.00%

Fair Value Measurements (Sche_2

Fair Value Measurements (Schedule of Fair Value of Fuel Hedge Contracts Balance Sheet Location) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Derivatives Fair Value [Line Items]
Asset derivatives	$ 1,739	$ 849
Other Current Assets [Member] | Derivatives Designated as Hedging Instruments [Member] | Fuel Hedge Contracts [Member]
Derivatives Fair Value [Line Items]
Asset derivatives	$ 1,739	$ 849

Fair Value Measurements (Change

Fair Value Measurements (Changes in Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Cumulative translation adjustments—net of tax	[1]			$ 1,513
Reclassification of derivative (gains) losses to earnings—net of tax		$ 5,825	$ 1,458	(1,569)
Change in fair value of derivatives—net of tax		(5,152)	2,646	(3,756)
Net unrealized (gain) loss on derivatives—net of tax	[2]	673	4,104	(5,325)
Other comprehensive income (loss)—net of tax		$ 673	$ 4,104	$ (3,812)
[1]	Net of income tax provision of $(1,017) for the year ended December 31, 2018.
[2]	Net of income tax (provision) benefit of $217, $(421) and $775 for the years ended December 31, 2020, 2019 and 2018, respectively.

Fair Value Measurements (Adjust

Fair Value Measurements (Adjustments Reclassified from Accumulated Balances Other Comprehensive Income (Loss) to Earnings) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments Gain Loss [Line Items]
Other expense	$ 1,110	$ 317	$ (2,590)
Costs of contract revenues	562,373	557,761	509,335
Income tax (provision) benefit	(20,187)	(15,253)	(5,437)
Net income (loss)	(66,103)	(49,339)	6,293
Accumulated Foreign Currency Adjustment Attributable to Parent [Member] | Reclassification Out of Accumulated Other Comprehensive Income [Member]
Derivative Instruments Gain Loss [Line Items]
Other expense			(2,337)
Income tax (provision) benefit			612
Net income (loss)			(1,725)
Fuel Hedge Contracts [Member] | Accumulated Gain Loss Net Cash Flow Hedge Parent [Member] | Reclassification Out of Accumulated Other Comprehensive Income [Member]
Derivative Instruments Gain Loss [Line Items]
Costs of contract revenues	7,703	1,975	(2,125)
Income tax (provision) benefit	1,878	517	(556)
Net income (loss)	$ 5,825	$ 1,458	$ (1,569)

Income Taxes (Income Tax Provis

Income Taxes (Income Tax Provision (Benefit) from Continuing and Discontinuing Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income tax provision from continuing operations	$ 20,187	$ 15,253	$ 5,437
Income tax benefit from discontinued operations		(4,556)	(6,162)
Income tax provision (benefit)	$ 20,187	$ 10,697	$ (725)

Income Taxes (Income (Loss) fro

Income Taxes (Income (Loss) from Continuing Operations before Income Tax from Domestic and Foreign Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Domestic operations	$ 94,826	$ 89,344	$ 26,878
Foreign operations	(8,536)	(18,423)	(10,425)
Total income (loss) from continuing operations before income tax	$ 86,290	$ 70,921	$ 16,453

Income Taxes (Provision (Benefi

Income Taxes (Provision (Benefit) For Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Deferred federal tax expense (benefit)	$ 17,464	$ 14,052	$ 3,702
Current state tax expense (benefit)	128	212	48
Deferred state tax expense (benefit)	3,023	989	1,687
Current foreign tax expense (benefit)	(428)
Income tax provision (benefit)	$ 20,187	$ 15,253	$ 5,437

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
U.S. federal statutory income tax rate	21.00%	21.00%	21.00%
Interest and penalties recorded	$ 0	$ 0	$ 71,000
Deferred tax assets valuation allowance	2,473,000	3,495,000
Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Loss carryforwards for federal income tax purposes	92,328,000	137,100,000
Deferred tax assets valuation allowance	$ 0	0
Domestic Tax Authority [Member] | Minimum [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards expiration year	2034
Domestic Tax Authority [Member] | Maximum [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards expiration year	2037
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Loss carryforwards for federal income tax purposes	$ 170,738,000	223,634,000
Valuation allowance for net operating loss carryforwards	$ 1,628,000	1,778,000
State and Local Jurisdiction [Member] | Minimum [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards expiration year	2023
State and Local Jurisdiction [Member] | Maximum [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards expiration year	2039
Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Loss carryforwards for federal income tax purposes	$ 2,414,000	6,777,000
Valuation allowance for net operating loss carryforwards	$ 845,000	$ 1,717,000
Foreign Tax Authority [Member] | Minimum [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards expiration year	2020
Foreign Tax Authority [Member] | Maximum [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards expiration year	2030

Income Taxes (Income Tax Prov_2

Income Taxes (Income Tax Provision (Benefit) Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Tax provision (benefit) at statutory U.S. federal income tax rate	$ 18,121	$ 14,893	$ 3,455
State income tax — net of federal income tax benefit	3,124	3,049	937
Change in state law regarding NOL carryforwards			658
Change in deferred state tax rate		(1,835)
Stock based compensation	(1,212)	(1,266)	(8)
Nondeductible officer compensation	1,212	1,021	201
Research and development tax credits	(674)	(452)	(218)
Changes in unrecognized tax benefits		(56)	14
Changes in valuation allowance		(3)	116
Other	(384)	(98)	282
Income tax provision (benefit)	$ 20,187	$ 15,253	$ 5,437

Income Taxes (Reconciliation of

Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Unrecognized tax benefits — January 1		$ 157	$ 157
Gross increases — tax positions in prior period
Gross decreases — tax positions in prior period		$ (157)
Unrecognized tax benefits — December 31,			$ 157

Income Taxes (Deferred Tax Asse

Income Taxes (Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Operating lease assets	$ 16,501	$ 18,301
Accrued liabilities	8,212	7,426
Federal NOLs	19,389	28,791
Foreign NOLs	845	1,717
State NOLs	7,256	9,505
Tax credit carryforwards	3,250	2,620
Charitable contribution		66
Valuation allowance	(2,473)	(3,495)
Total deferred tax assets	52,980	64,931
Depreciation and amortization	(92,547)	(82,115)
Operating lease liabilities	16,460	18,334
Other liabilities	(439)	(222)
Total deferred tax liabilities	(109,446)	(100,671)
Net noncurrent deferred tax liabilities	$ (56,466)	$ (35,740)

Share-Based Compensation (Narra

Share-Based Compensation (Narrative) (Details) - USD ($) $ in Thousands	May 11, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense		$ 6,754	$ 6,908	$ 4,643
Total unrecognized compensation cost related to non-vested RSUs		4,374
Amount related to shares used for tax withholding obligations		$ 4,748	$ 5,008
Annual retainer per non-employee director, percentage paid in cash		50.00%
Annual retainer per non-employee director, percentage paid in common stock		50.00%
Shares of common stock received by employee directors		79,000	78,000	156,000
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights		RSUs can either vest in equal portions over the three year vesting period or vest in one installment on the third anniversary of the grant date.
Vesting period		3 years
Total unrecognized compensation cost, weighted-average period of recognition		1 year 10 months 24 days
Non Qualified Stock Options (NQSO) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights		The option awards generally vest in three equal annual installments commencing on the first anniversary of the grant date
Exercise period		10 years
Awards granted in period		0	0	0
Aggregate intrinsic value of stock options exercised		$ 779	$ 2,534	$ 116
Employees and Directors [Member] | 2017 Long-Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares available for grant	3,300,000
Employees and Directors [Member] | 2007 Long-Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Underlying equity awards issued	1,700,000
Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual retainer per non-employee director		155
Chairman of the Board [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional annual retainer paid to non-employee director		$ 100
Additional percentage of annual retainer paid to non-employee director in common stock		100.00%

Share-Based Compensation (Summa

Share-Based Compensation (Summary of Stock Option Activity) (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding as of January 1, 2020 | shares	504
Exercised | shares	(226)
Outstanding as of December 31, 2020 | shares	278
Vested at December 31, 2020 | shares	278
Weighted average exercise price outstanding as of January 1, 2020 | $ / shares	$ 6.87
Weighted average exercise price, exercised | $ / shares	6.68
Weighted average exercise price outstanding as of December 31, 2020 | $ / shares	6.99
Weighted average exercise price, vested at December 31, 2020 | $ / shares	$ 6.99
Weighted average remaining contractual term, outstanding at December 31, 2020	2 years
Weighted average remaining contractual term, vested as of December 31, 2020	2 years
Aggregate intrinsic value, outstanding as of December 31, 2020 | $	$ 1,785
Aggregate intrinsic value, vested at December 31, 2020 | $	$ 1,785

Share-Based Compensation (Sum_2

Share-Based Compensation (Summary of Non-Vested Restricted Stock Units) (Details) - Restricted Stock Units (RSUs) [Member] shares in Thousands	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding as of January 1, 2020 | shares	1,809
Options granted | shares	851
Options vested | shares	(1,192)
Options forfeited | shares	(62)
Options outstanding as of December 31, 2020 | shares	1,406
Options expected to vest at December 31, 2020 | shares	1,132
Weighted-average grant-date fair value as of January 1, 2020 | $ / shares	$ 6
Weighted-average grant-date fair value, granted | $ / shares	8.90
Weighted-average grant-date fair value, vested | $ / shares	5.71
Weighted-average grant-date fair value, forfeited | $ / shares	6.66
Weighted-average grant-date fair value as of December 31, 2020 | $ / shares	8
Weighted-average grant-date fair value, expected to vest at December 31, 2020 | $ / shares	$ 7.52

Revenue (Narrative) (Details)

Revenue (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue From Contract With Customer [Line Items]
Revenue, remaining performance obligation	$ 559,376
Percentage of performance obligation to be recognized as revenue	90.00%
Performance obligation, expected to be recognized as revenue year	2021
Remaining performance obligation, expected timing of satisfaction, year	2022
Amortization on pre-contract and pre-construction costs	$ 15,541	$ 11,468
Contract revenues	733,601	711,518	$ 620,795
Long-lived assets, net book value	5,255	31,872
Dredging [Member] | Use of Equipment [Member] | Federal Government [Member]
Revenue From Contract With Customer [Line Items]
Contract revenues	$ 616	$ 2,103
Dredging [Member] | Sales [Member] | Geographic Concentration Risk [Member] | Middle East [Member] | Maximum [Member]
Revenue From Contract With Customer [Line Items]
Concentration risk percentage	10.00%	10.00%	10.00%
Dredging [Member] | Sales [Member] | Federal Government Agencies [Member] | Customer Concentration Risk [Member]
Revenue From Contract With Customer [Line Items]
Concentration risk percentage	79.50%	81.70%	75.50%
Dredging [Member] | Accounts Receivable [Member] | Geographic Concentration Risk [Member] | Middle East [Member]
Revenue From Contract With Customer [Line Items]
Concentration risk percentage	12.00%	29.00%
Dredging [Member] | Accounts Receivable [Member] | Federal Government Agencies [Member] | Customer Concentration Risk [Member]
Revenue From Contract With Customer [Line Items]
Concentration risk percentage	42.60%	54.60%
Other Current and Noncurrent Assets [Member]
Revenue From Contract With Customer [Line Items]
Costs to fulfill contracts with customers recognized as an asset	$ 10,501	$ 10,300

Revenue (Summary of Type of Wor

Revenue (Summary of Type of Work, Contract Revenues) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Line Items]
Revenues	$ 733,601	$ 711,518	$ 620,795
Type of Work [Member] | Operating Segment [Member] | Dredging [Member]
Disaggregation Of Revenue [Line Items]
Revenues	733,601	711,518	620,795
Type of Work [Member] | Operating Segment [Member] | Dredging [Member] | Capital-U.S. [Member]
Disaggregation Of Revenue [Line Items]
Revenues	336,163	299,706	333,037
Type of Work [Member] | Operating Segment [Member] | Dredging [Member] | Capital-Foreign [Member]
Disaggregation Of Revenue [Line Items]
Revenues	25,892	48,619	14,088
Type of Work [Member] | Operating Segment [Member] | Dredging [Member] | Coastal Protection [Member]
Disaggregation Of Revenue [Line Items]
Revenues	201,361	182,369	175,923
Type of Work [Member] | Operating Segment [Member] | Dredging [Member] | Maintenance [Member]
Disaggregation Of Revenue [Line Items]
Revenues	148,767	104,753	53,427
Type of Work [Member] | Operating Segment [Member] | Dredging [Member] | Rivers & Lakes [Member]
Disaggregation Of Revenue [Line Items]
Revenues	$ 21,418	$ 76,071	$ 44,320

Revenue (Summary of Type of Cus

Revenue (Summary of Type of Customer, Contract Revenues) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Line Items]
Revenues	$ 733,601	$ 711,518	$ 620,795
Foreign [Member]
Disaggregation Of Revenue [Line Items]
Revenues	25,892	48,619	14,088
Type of Customer [Member] | Operating Segment [Member]
Disaggregation Of Revenue [Line Items]
Revenues	733,601	711,518	620,795
Type of Customer [Member] | Operating Segment [Member] | Federal Government [Member]
Disaggregation Of Revenue [Line Items]
Revenues	582,949	581,157	468,421
Type of Customer [Member] | Operating Segment [Member] | State and Local Government [Member]
Disaggregation Of Revenue [Line Items]
Revenues	85,737	71,398	93,499
Type of Customer [Member] | Operating Segment [Member] | Private [Member]
Disaggregation Of Revenue [Line Items]
Revenues	39,023	10,344	44,787
Type of Customer [Member] | Operating Segment [Member] | Foreign [Member]
Disaggregation Of Revenue [Line Items]
Revenues	$ 25,892	$ 48,619	$ 14,088

Revenue (Schedule of Accounts R

Revenue (Schedule of Accounts Receivable) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Receivables [Abstract]
Completed contracts	$ 12,347	$ 3,444
Contracts in progress	21,239	9,490
Retainage	5,968	7,415
Accounts receivable, gross	39,554	20,349
Allowance for doubtful accounts	(564)	(564)
Total accounts receivable—net	$ 38,990	$ 19,785

Revenue (Components of Contract

Revenue (Components of Contracts in Progress) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accounts Notes And Loans Receivable [Line Items]
Costs and earnings in excess of billings for contracts in progress	$ 31,395	$ 18,546
Costs and earnings in excess of billings for completed contracts	2,823	6,126
Total contract revenues in excess of billings	34,218	24,672
Current portion of contract revenues in excess of billings	32,106	22,560
Long-term contract revenues in excess of billings	2,112	2,112
Total billings in excess of contract revenues	(32,608)	(55,266)
Costs And Earnings In Excess Of Billings [Member]
Accounts Notes And Loans Receivable [Line Items]
Costs and earnings for contracts in progress	199,964	104,620
Amounts billed	(168,569)	(86,074)
Billings In Excess Of Costs And Earnings [Member]
Accounts Notes And Loans Receivable [Line Items]
Costs and earnings for contracts in progress	517,860	573,225
Amounts billed	$ (550,468)	$ (628,491)

Revenue (Summary of Gross Profi

Revenue (Summary of Gross Profit from Foreign Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Line Items]
CONTRACT REVENUES	$ 733,601	$ 711,518	$ 620,795
Costs of contract revenues	(562,373)	(557,761)	(509,335)
GROSS PROFIT	171,228	153,757	111,460
Foreign [Member]
Disaggregation Of Revenue [Line Items]
CONTRACT REVENUES	25,892	48,619	14,088
Costs of contract revenues	(34,529)	(66,347)	(19,866)
GROSS PROFIT	$ (8,637)	$ (17,728)	$ (5,778)

Retirement Plans (Narrative) (D

Retirement Plans (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)item	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Defined Contribution Plan Disclosure [Line Items]
Number of sponsored 401(k) plans | item	2
Expense for matching and discretionary contributions	$ 5,557	$ 5,168	$ 5,060
Contributes to various multiemployer pension plans	$ 4,929	$ 4,517	$ 4,207
Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Multiemployer plans collective-bargaining arrangement percentage of contributions	5.00%

Restructuring Charges (Narrativ

Restructuring Charges (Narrative) (Details) $ in Thousands	Dec. 31, 2017USD ($)
Severance Costs [Member]
Restructuring Cost And Reserve [Line Items]
Estimated restructuring charge	$ 3,549
Asset Retirements [Member]
Restructuring Cost And Reserve [Line Items]
Estimated restructuring charge	32,309
Pre-contract Costs [Member]
Restructuring Cost And Reserve [Line Items]
Estimated restructuring charge	6,441
Closeout Costs [Member]
Restructuring Cost And Reserve [Line Items]
Estimated restructuring charge	$ 4,194

Restructuring Charges (Schedule

Restructuring Charges (Schedule of Restructuring Charges) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Restructuring Cost And Reserve [Line Items]
Restructuring charges	$ 16,145
Loss on Sale of Assets - Net [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	4,572
Other Expense [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	2,337
Dredging [Member] | Costs of Contract Revenues - Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	6,759
Dredging [Member] | Costs of Contract Revenues - Other [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	2,292
Dredging [Member] | General and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	$ 185

Commitments and Contingencies (

Commitments and Contingencies (Narrative) (Details)	Sep. 27, 2019USD ($)	Feb. 28, 2017USD ($)	Jan. 14, 2015USD ($)	Dec. 31, 2020USD ($)bbl	May 31, 2017USD ($)
Commitments And Contingencies [Line Items]
Outstanding performance bonds				$ 1,187,933,000
Revenue value remaining from outstanding performance bonds				$ 524,375,000
Proceeds from Legal Settlements			$ 5,309,000
Total penalty issued by administrative court	$ 973,000
Crude Oil [Member]
Commitments And Contingencies [Line Items]
Quantity of oil spill | bbl				160
Surety Bond [Member]
Commitments And Contingencies [Line Items]
Aggregate demolition surety performance bond		$ 20,000,000
Letter of Credit [Member]
Commitments And Contingencies [Line Items]
Line of credit facility, maximum borrowing capacity					$ 20,881,000
Environmental and Infrastructure Segment [Member]
Commitments And Contingencies [Line Items]
Outstanding performance bonds				$ 17,401,000
Minimum [Member]
Commitments And Contingencies [Line Items]
Bids bond range				$ 1,000,000
Warranty periods				1 year
Maximum [Member]
Commitments And Contingencies [Line Items]
Bids bond range				$ 10,000,000
Warranty periods				3 years

Business Dispositions (Narrativ

Business Dispositions (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2019	Jun. 30, 2019
Discontinued Operations And Disposal Groups [Abstract]
Proceeds from sale of historical environmental and infrastructure business	$ 857	$ 17,500

Business Dispositions - (Schedu

Business Dispositions - (Schedule of Discontinued Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Discontinued Operation Income Loss From Discontinued Operation Disclosures [Abstract]
Revenue	$ 25,040	$ 76,843
Loss before income taxes from discontinued operations	(8,253)	(9,361)
Loss on disposal of assets held for sale	(2,632)	(14,110)
Income tax benefit	4,556	6,162
Loss from discontinued operations, net of income taxes	$ (6,329)	$ (17,309)

Schedule II-Valuation and Qua_2

Schedule II-Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$ 4,059	$ 4,986	$ 4,294
Additions		364	692
Deductions	(1,022)	(1,291)
Ending Balance	3,037	4,059	4,986
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	564	200
Additions		364	200
Ending Balance	564	564	200
Valuation Allowance for Deferred Tax Assets [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	3,495	4,786	4,294
Additions			492
Deductions	(1,022)	(1,291)
Ending Balance	$ 2,473	$ 3,495	$ 4,786