Great Lakes Dredge & Dock (GLDD) 10-Q 6 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Nov. 02, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Trading Symbol	GLDD
Entity Registrant Name	Great Lakes Dredge & Dock CORP
Entity Central Index Key	1,372,020
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		62,479,490

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
CURRENT ASSETS:
Cash and cash equivalents	$ 23,127	$ 15,852
Accounts receivable—net	86,665	75,533
Contract revenues in excess of billings	36,151	90,788
Inventories	32,004	34,600
Prepaid expenses and other current assets	39,411	45,411
Total current assets	217,358	262,184
PROPERTY AND EQUIPMENT—Net	365,491	407,294
GOODWILL AND OTHER INTANGIBLE ASSETS—Net	84,038	84,484
INVENTORIES—Noncurrent	56,821	54,023
INVESTMENTS IN JOINT VENTURES	5,164	2,714
ASSETS HELD FOR SALE—Noncurrent	8,846	8,530
OTHER	12,588	13,128
TOTAL	750,306	832,357
LIABILITIES AND EQUITY
Accounts payable	80,302	87,659
Accrued expenses	47,411	56,218
Billings in excess of contract revenues	11,152	3,615
Current portion of long-term debt	909	2,758
Total current liabilities	139,774	150,250
LONG-TERM DEBT	321,727	333,141
REVOLVING CREDIT FACILITY	30,882	95,000
DEFERRED INCOME TAXES	25,605	25,561
OTHER	7,883	7,109
Total liabilities	525,871	611,061
COMMITMENTS AND CONTINGENCIES (Note 9)
EQUITY:
Common stock—$.0001 par value; 90,000 authorized, 62,730 and 61,897 shares issued; 62,452 and 61,619 shares outstanding at September 30, 2018 and December 31, 2017, respectively.	6	6
Treasury stock, at cost	(1,433)	(1,433)
Additional paid-in capital	292,902	289,821
Accumulated deficit	(67,271)	(67,101)
Accumulated other comprehensive income	231	3
Total equity	224,435	221,296
TOTAL	$ 750,306	$ 832,357

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
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	62,730,000	61,897,000
Common stock, shares outstanding	62,452,000	61,619,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Contract revenues	$ 204,322	$ 163,317	$ 501,505	$ 510,762
Type of Revenue [Extensible List]	gldd:ContractMember	gldd:ContractMember	gldd:ContractMember	gldd:ContractMember
Costs of contract revenues	$ 162,188	$ 143,499	$ 422,426	$ 455,850
Type of Cost, Good or Service [Extensible List]	gldd:ContractMember	gldd:ContractMember	gldd:ContractMember	gldd:ContractMember
Gross profit	$ 42,134	$ 19,818	$ 79,079	$ 54,912
General and administrative expenses	17,293	17,522	48,406	51,584
Loss on sale of assets—net	1,452	175	190	355
Operating income	23,389	2,121	30,483	2,973
Interest expense—net	(8,062)	(6,417)	(25,719)	(18,440)
Equity in earnings (loss) of joint ventures		26		(1,441)
Loss on extinguishment of debt				(2,330)
Other income (expense)	165	(266)	(2,808)	(343)
Income (loss) from continuing operations before income taxes	15,492	(4,536)	1,956	(19,581)
Income tax (provision) benefit	(3,790)	1,308	(549)	7,555
Income (loss) from continuing operations	11,702	(3,228)	1,407	(12,026)
Loss from discontinued operations, net of income taxes				(12,697)
Net income (loss)	$ 11,702	$ (3,228)	$ 1,407	$ (24,723)
Basic earnings (loss) per share attributable to continuing operations	$ 0.19	$ (0.05)	$ 0.02	$ (0.19)
Basic loss per share attributable to discontinued operations, net of tax				(0.21)
Basic earnings (loss) per share	$ 0.19	$ (0.05)	$ 0.02	$ (0.40)
Basic weighted average shares	62,358	61,462	62,147	61,290
Diluted earnings (loss) per share attributable to continuing operations	$ 0.18	$ (0.05)	$ 0.02	$ (0.19)
Diluted loss per share attributable to discontinued operations, net of tax				(0.21)
Diluted earnings (loss) per share	$ 0.18	$ (0.05)	$ 0.02	$ (0.40)
Diluted weighted average shares	63,260	61,462	63,340	61,290

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)		$ 11,702	$ (3,228)	$ 1,407	$ (24,723)
Currency translation adjustment—net of tax	[1]	(14)	(2)	1,290	(24)
Net unrealized (gain) loss on derivatives—net of tax	[2]	(201)	1,684	(1,062)	232
Other comprehensive income (loss)—net of tax		(215)	1,682	228	208
Comprehensive income (loss)		$ 11,487	$ (1,546)	$ 1,635	$ (24,515)
[1]	Net of income tax benefit of $21 and $13 for the three months ended September 30, 2018 and 2017, respectively. Net of income tax (provision) benefit of $(551) and $46 for the nine months ended September 30, 2018 and 2017, respectively.
[2]	Net of income tax (provision) benefit of $(242) and $1,098 for the three months ended September 30, 2018 and 2017, respectively. Net of income tax (provision) benefit of $(1,191) and $151 for the nine months ended September 30, 2018 and 2017, respectively.

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Currency translation adjustment, tax	$ 21	$ 13	$ (551)	$ 46
Net unrealized (gain) loss on derivatives, tax	$ (242)	$ 1,098	$ (1,191)	$ 151

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (loss) [Member]
BALANCE - value at Dec. 31, 2016	$ 247,890	$ 6	$ (1,433)	$ 286,303	$ (35,841)	$ (1,145)
BALANCE - shares at Dec. 31, 2016		61,240	(278)
Share-based compensation, value	2,514			2,514
Share-based compensation, shares		208
Vesting of restricted stock units, including impact of shares withheld for taxes, value	(328)			(328)
Vesting of restricted stock units, including impact of shares withheld for taxes, shares		147
Exercise of options and purchases from employee stock plans, value	867			867
Exercise of options and purchases from employee stock plans, shares		258
Net income (loss)	(24,723)				(24,723)
Other comprehensive income (loss)—net of tax	208					208
BALANCE - value at Sep. 30, 2017	226,428	$ 6	$ (1,433)	289,356	(60,564)	(937)
BALANCE - shares at Sep. 30, 2017		61,853	(278)
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)
Cumulative effect of recent accounting pronouncements	(1,577)				(1,577)
Share-based compensation, value	3,294			3,294
Share-based compensation, shares		105
Vesting of restricted stock units, including impact of shares withheld for taxes, value	(1,075)			(1,075)
Vesting of restricted stock units, including impact of shares withheld for taxes, shares		492
Exercise of options and purchases from employee stock plans, value	862			862
Exercise of options and purchases from employee stock plans, shares		236
Net income (loss)	1,407				1,407
Other comprehensive income (loss)—net of tax	228					228
BALANCE - value at Sep. 30, 2018	$ 224,435	$ 6	$ (1,433)	$ 292,902	$ (67,271)	$ 231
BALANCE - shares at Sep. 30, 2018		62,730	(278)

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
OPERATING ACTIVITIES:
Net income (loss)	$ 1,407	$ (24,723)
Loss from discontinued operations, net of income taxes		(12,697)
Income (loss) from continuing operations	1,407	(12,026)
Adjustments to reconcile net income (loss) to net cash flows provided by operating activities:
Depreciation and amortization	41,290	38,707
Equity in earnings of joint ventures	(2,988)	(5,726)
Cash distributions from joint ventures	538	4,486
Loss on extinguishment of 7 3/8% senior notes		2,330
Deferred income taxes	931	(7,347)
Loss on sale of assets	190	355
Other non-cash restructuring items	2,015
Amortization of deferred financing fees	2,637	2,468
Unrealized net loss from mark-to-market valuations of derivatives		1,747
Unrealized foreign currency gain	(215)	(64)
Share-based compensation expense	3,294	2,514
Changes in assets and liabilities:
Accounts receivable	(6,657)	8,794
Contract revenues in excess of billings	49,563	12,409
Inventories	(202)	(3,443)
Prepaid expenses and other current assets	12,581	6,148
Accounts payable and accrued expenses	(11,157)	(27,055)
Billings in excess of contract revenues	(146)	(316)
Other noncurrent assets and liabilities	(4,147)	(482)
Net cash flows provided by operating activities from continuing operations	88,934	23,498
Net cash flows used in operating activities of discontinued operations		(20,900)
Cash provided by operating activities	88,934	2,598
INVESTING ACTIVITIES:
Purchases of property and equipment	(29,671)	(49,377)
Proceeds from dispositions of property and equipment	12,245	9,198
Cash used in investing activities	(17,426)	(40,179)
FINANCING ACTIVITIES:
7 3/8% senior notes tender premium		(744)
Deferred financing fees		(4,522)
Repayments of debt	(1,428)	(277,026)
Proceeds from issuance of debt		326,241
Taxes paid on settlement of vested share awards	(1,075)	(328)
Exercise of options and purchases from employee stock plans	862	867
Borrowings under revolving loans	18,000	89,425
Repayments of revolving loans	(82,118)	(103,536)
Cash provided by (used in) financing activities	(65,759)	30,377
Effect of foreign currency exchange rates on cash and cash equivalents	26	(8)
Net increase (decrease) in cash, cash equivalents and restricted cash	5,775	(7,212)
Cash, cash equivalents and restricted cash at beginning of period	17,352	19,702
Cash, cash equivalents and restricted cash at end of period	23,127	12,490
Supplemental Cash Flow Information
Cash paid for interest	17,402	20,986
Cash paid for income taxes	255	574
Non-cash Investing and Financing Activities
Property and equipment purchased but not yet paid	3,920	$ 2,021
Repayments of debt with proceeds from sale-leaseback transactions	$ 13,034

Condensed Consolidated Statem_6

Condensed Consolidated Statements of Cash Flows (Parenthetical)	Sep. 30, 2018	Sep. 30, 2017	May 31, 2017
7 3/8% SENIOR NOTES [Member]
Debt instrument, interest rate, stated percentage	7.375%	7.375%	7.375%

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation	1. Basis of presentation The unaudited condensed consolidated financial statements and notes herein should be read in conjunction with the audited consolidated financial statements of Great Lakes Dredge & Dock Corporation and Subsidiaries (the “Company” or “Great Lakes”) and the notes thereto, included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. The condensed consolidated financial statements included herein have been prepared by the Company without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) have been condensed or omitted pursuant to the SEC’s rules and regulations, although management believes that the disclosures are adequate and make the information presented not misleading. In the opinion of management, all adjustments, which are of a normal and recurring nature (except as otherwise noted), that are necessary to present fairly the Company’s financial position as of September 30, 2018, and its results of operations for the three and nine months ended September 30, 2018 and 2017 and cash flows for the nine months ended September 30, 2018 and 2017 have been included. The Company adopted Accounting Standard Update No. 2016-18 (“ASU 2016-18”), Statement of Cashflows (Topic 230): Restricted Cash The following table provides a reconciliation of cash, cash equivalents and restricted cash at September 30, 2018 and December 31, 2017 reported within the Condensed Consolidated Balance Sheets that sum to the total of the same such amounts shown in the Condensed Consolidated Statements of Cash Flows. September 30, 2018 December 31, 2017 Cash and cash equivalents $ 23,127 $ 15,852 Restricted cash included in other long-term assets — 1,500 Cash, cash equivalents and restricted cash at end of period $ 23,127 $ 17,352 Effective beginning the first quarter of 2018, the Company changed the method of accounting for allocated fixed equipment costs for interim periods such that fixed equipment costs are now recognized as incurred. The Company adopted this change as a result of management’s belief that the new method is preferable and results in a more objective measure of quarterly expense that will better support planning and resource allocation decisions by management. The change has been applied retrospectively and all prior interim periods presented have been recast. The Company’s cost structure includes significant annual equipment-related costs, including depreciation, maintenance, insurance and long-term rentals. Previously, the Company allocated fixed equipment costs to interim periods in proportion to revenues recognized over the year. Specifically, at each interim reporting date the Company compared actual revenues earned to date on its dredging contracts to expected annual revenues and recognized equipment costs on the same proportionate basis. In the fourth quarter, any over or under allocated equipment costs are recognized such that the expense for the year equals actual equipment costs incurred during the year. The impact of the change in accounting policy on our Condensed Consolidated Statements of Operations and Condensed Consolidated Balance Sheets is as follows: Three Months Ended Nine Months Ended September 30, 2017 September 30, 2017 Costs of contract revenues $ (3,123 ) $ 3,739 Income tax (provision) benefit (1,406 ) 1,443 Income (loss) from continuing operations 1,717 (2,296 ) Net income (loss) $ 1,717 $ (2,296 ) Comprehensive income (loss) $ 1,717 $ (2,296 ) Basic earnings (loss) per share attributable to continuing operations $ 0.03 $ (0.03 ) Diluted earnings (loss) per share attributable to continuing operations $ 0.03 $ (0.03 ) September 30, 2017 Prepaid expenses and other current assets $ (3,739 ) Deferred income taxes (1,443 ) Accumulated deficit $ (2,296 ) The Company adopted Accounting Standard Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) Accounting Standard Updates related to Accounting Standards Codification Topic 606 (collectively, “ASC 606”) on January 1, 2018 In February 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update No. 2018-02 (“ASU 2018-02”), Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. 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 is generally hired on a project-by-project basis. Costs of contract revenues vary significantly depending on the type and location of work performed and assets utilized. The Company has two operating segments: dredging and environmental & infrastructure, which are also the Company’s reportable segments and reporting units of which the Company tests goodwill for impairment. The Company performed its most recent annual test of impairment as of July 1, 2018 with no indication of impairment as of the test date. The Company will perform its next scheduled annual test of goodwill in the third quarter of 2019 should no triggering events occur which would require a test prior to the next annual test. The condensed consolidated results of operations and comprehensive income for the interim periods presented herein are not necessarily indicative of the results to be expected for the full year. Recent accounting pronouncements In January 2017, the FASB issued Accounting Standard Update No. 2017-04 (“ASU 2017-04”), Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment The Company does not anticipate that the adoption of ASU 2017-04 will have a material effect on the Company’s consolidated financial statements. In February 2016, the FASB issued Accounting Standard Update No. 2016-02 (“ASU 2016-02”), Leases (Topic 842)

Earnings Per Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2018
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 the same as 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 (loss) per share are as follows: Three Months Ended Nine Months Ended (shares in thousands) September 30, September 30, 2018 2017 2018 2017 Income (loss) from continuing operations $ 11,702 $ (3,228 ) $ 1,407 $ (12,026 ) Loss from discontinued operations, net of income taxes — — — (12,697 ) Net income (loss) 11,702 (3,228 ) 1,407 (24,723 ) Weighted-average common shares outstanding — basic 62,358 61,462 62,147 61,290 Effect of stock options and restricted stock units 902 — 1,193 — Weighted-average common shares outstanding — diluted 63,260 61,462 63,340 61,290 Earnings (loss) per share from continuing operations — basic $ 0.19 $ (0.05 ) $ 0.02 $ (0.19 ) Earnings (loss) per share from continuing operations — diluted $ 0.18 $ (0.05 ) $ 0.02 $ (0.19 ) For the quarter and nine months ended September 30, 2017, 611 and 646 options and restricted stock units, respectively, were excluded from the diluted weighted-average common shares outstanding as the Company incurred a loss during these periods. For the quarter and nine months ended September 30, 2018 and 2017, the following stock options and restricted stock units were excluded from the calculation of diluted earnings per share as such stock options and restricted stock units were determined to be anti-dilutive: Three Months Ended Nine Months Ended (shares in thousands) September 30, September 30, 2018 2017 2018 2017 Effect of stock options and restricted stock units 1,224 1,288 1,489 1,399

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2018
Payables And Accruals [Abstract]
Accrued Expenses	3. Accrued expenses Accrued expenses at September 30, 2018 and December 31, 2017 are as follows: September 30, December 31, 2018 2017 Insurance $ 13,185 $ 22,941 Payroll and employee benefits 11,829 8,747 Interest 10,103 4,210 Percentage of completion adjustment 3,234 3,591 Income and other taxes 2,193 2,794 Accrued rent 458 6,519 Other 6,409 7,416 Total accrued expenses $ 47,411 $ 56,218

Long-term Debt

Long-term Debt	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Long-Term Debt	4. Long-term debt Credit agreement On December 30, 2016, the Company, Great Lakes Dredge & Dock Company, LLC, NASDI Holdings, LLC, Great Lakes Dredge & Dock Environmental, Inc., Great Lakes Environmental & Infrastructure Solutions, LLC and Great Lakes Environmental & Infrastructure, LLC (collectively, the “Credit Parties”) entered into a revolving credit and security agreement, as subsequently amended, (the “Credit Agreement”) with certain financial institutions from time to time party thereto as lenders, PNC Bank, National Association, as Agent, PNC Capital Markets, CIBC Bank USA, Suntrust Robinson Humphrey, Inc., Capital One, National Association and Bank of America, N.A., as Joint Lead Arrangers and Joint Bookrunners, Texas Capital Bank, National Association, as Syndication Agent and Woodforest National Bank, as Documentation Agent. The Credit Agreement, which replaced the Company’s former revolving credit agreement, provides for a senior secured revolving credit facility in an aggregate principal amount of up to $250,000, subfacilities for the issuance of standby letters of credit up to a $250,000 sublimit and swingline loans up to a $25,000 sublimit. The maximum borrowing capacity under the 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 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 that no default or event of default exists both before and after giving effect to such incremental commitment increase. The Credit Agreement also provides for certain actions contemplated in the plan of restructuring with respect to the Company’s 2017 and 2018 fiscal years including allowing up to an aggregate of $20,000 of expenses related to the buy-out of operating leases and allowing capital expenditures planned but not incurred by all Credit Parties in fiscal year 2017 to be carried forward to fiscal year 2018; provided that, the aggregate amount of all capital expenditures incurred by all Credit Parties in fiscal years 2017 and 2018 does not exceed $135,000. Additionally, the Credit Agreement contains acknowledgments and agreements from the Agent and the required lenders with respect to certain EBITDA add-backs for fiscal years 2017 and 2018 described therein. See Note 8, Restructuring charges. The 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 more than 1.10 to 1.00. The Company is required to maintain this ratio if its availability under the Credit Agreement falls below $31,250 for five consecutive days or $25,000 for one day. The Credit Parties are also restricted in the amount of capital expenditures they may make in each fiscal year. The 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 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 Credit Agreement were or will be used to refinance existing indebtedness under the Company’s former revolving credit agreement, refinance existing indebtedness under the Company’s former term loan agreement, pay fees and expenses related to the Credit Agreement, finance acquisitions permitted under the Credit Agreement and finance ongoing working capital, and for other general corporate purposes. The Credit Agreement matures on December 30, 2019. The obligations under the 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 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 provider). Interest on the senior secured revolving credit facility of the Credit Agreement is equal to either a base rate option or LIBOR option, at the Company’s election. The base rate option is (1) the base commercial lending rate of PNC Bank, National Association, as publicly announced plus (2)(a) an interest margin of 2.0% or (b) after the date on which a borrowing base certificate is required to be delivered under Section 9.2 of the Credit Agreement (commencing with the fiscal quarter ending December 31, 2017, the “Adjustment Date”), an interest margin ranging between 1.5% and 2.0% depending on the quarterly average undrawn availability on the senior secured revolving credit facility. The LIBOR option is the sum of (1) LIBOR and (2)(a) an interest margin of 3.0% or (b) after the Adjustment Date, an interest rate margin ranging between 2.5% to 3.0% per annum depending on the quarterly average undrawn availability on the senior secured revolving credit facility. The Credit Agreement is subject to an unused fee ranging from 0.25% to 0.375% per annum depending on the amount of average daily outstandings under the senior secured revolving credit facility. As of September 30, 2018, the Company had $30,882 of borrowings on the revolver, $31,587 of letters of credit outstanding and $161,333 of availability under the Credit Agreement. The availability under the Credit Agreement is suppressed by $26,198 as of September 30, 2018 as a result of certain additional limitations set forth in the Credit Agreement. Senior Notes and subsidiary guarantors In May 2017, the Company issued $325,000 of 8.000% senior notes (“8% Senior Notes”) due May 15, 2022. The 8% Senior Notes were issued 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 for $282,638, which included a tender premium and accrued and unpaid interest. The Company used the remaining net proceeds from the debt offering to reduce the Company’s indebtedness under its Credit Agreement. 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. The current portion of all equipment notes is $909. The long-term portion is $278 and is included in notes payable or other long-term liabilities. 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, and the transaction resulted in a deferred gain that will be amortized over the life of the lease.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	5. 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 September 30, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fuel hedge contracts $ 1,064 $ — 1,064 $ — Fair Value Measurements at Reporting Date Using Description At December 31, 2017 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fuel hedge contracts $ 2,501 $ — $ 2,501 $ — Fuel hedge contracts The Company is exposed to certain market risks, primarily commodity price risk as it relates to 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 could have an adverse impact on cash flows associated with its domestic dredging contracts. The Company’s goal is to hedge approximately 80% of the fuel requirements for work in domestic backlog. As of September 30, 2018, 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 September 2019. As of September 30, 2018, there were 5.8 million gallons remaining on these contracts which represent approximately 80% of the Company’s forecasted domestic fuel purchases through September 2019. Under these swap agreements, the Company will pay fixed prices ranging from $1.94 to $2.23 per gallon. At September 30, 2018 and December 31, 2017, the fair value assets of the fuel hedge contracts were estimated to be $1,064 and $2,501, respectively, and are recorded in prepaid expenses and other current assets. For fuel hedge contracts considered to be highly effective, the gains reclassified to earnings from changes in fair value of derivatives, net of cash settlements and taxes, for the nine months ended September 30, 2018 were $2,211. The remaining gains and losses included in accumulated other comprehensive income at September 30, 2018 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 values of fuel hedges are corroborated using inputs that are readily observable in public markets; therefore, the Company determines fair value 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 September 30, 2018 and December 31, 2017 is as follows: Fair Value at September 30, December 31, Balance Sheet Location 2018 2017 Asset derivatives: Derivatives designated as hedging instruments Fuel hedge contracts Prepaid expenses and other current assets $ 1,064 $ 2,501 Accumulated other comprehensive income Changes in the components of the accumulated balances of other comprehensive income (loss) are as follows: Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Cumulative translation adjustments—net of tax $ (14 ) $ (2 ) $ 1,290 $ (24 ) Derivatives: Reclassification of derivative (gains) losses to earnings—net of tax (442 ) (35 ) (2,211 ) 160 Change in fair value of derivatives—net of tax 241 1,719 1,149 72 Net unrealized gain on derivatives—net of tax (201 ) 1,684 (1,062 ) 232 Total other comprehensive income (loss) $ (215 ) $ 1,682 $ 228 $ 208 Adjustments reclassified from accumulated balances of other comprehensive income (loss) to earnings are as follows: Three Months Ended Nine Months Ended September 30, September 30, Statement of Operations Location 2018 2017 2018 2017 Derivatives: Fuel Costs of contract revenues $ (599 ) $ (59 ) $ (2,995 ) $ 264 Income tax (provision) benefit (157 ) (24 ) (784 ) 104 $ (442 ) $ (35 ) $ (2,211 ) $ 160 The Company substantially completed the closeout of its Brazil operations, during the first quarter of 2018. This liquidation resulted in the reversal of the Company’s cumulative translation adjustment of $2,015, recorded during the first quarter of 2018, related to Brazil which is included in other expense in the Condensed Consolidated Statements of Operations. 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 our revolving credit agreement approximates fair value. In May 2017, the Company issued a total of $325,000 of 8% senior notes due May 15, 2022, which were outstanding at September 30, 2018, refer to Note 4, Long-term debt. The 8% Senior Notes are senior unsecured obligations of the Company and its subsidiaries that guarantee the 8% Senior Notes. The fair value of the senior notes was $333,938 at September 30, 2018, 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.

Share-Based Compensation

Share-Based Compensation	9 Months Ended
	Sep. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-Based Compensation	6 . Share-based compensation On May 11, 2017, the Company’s stockholders approved the Great Lakes Dredge & Dock Corporation 2017 Long-Term Incentive Plan (the “Incentive Plan”), which previously had been approved by the Company’s board of directors subject to stockholder approval. The Incentive Plan permits the granting of stock options, stock appreciation rights, restricted stock and restricted stock units to the Company’s 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. During the nine months ended September 30, 2018, the Company granted 2,020 thousand restricted stock units to certain employees. In addition, all non-employee directors on the Company’s board of directors are paid a portion of their board-related compensation in stock grants or restricted stock units. Compensation cost charged to expense related to share-based compensation arrangements was $1,030 and $756 for the three months ended September 30, 2018 and 2017, respectively, and $3,294 and $2,514 for the nine months ended September 30, 2018 and 2017, respectively.

Revenue

Revenue	9 Months Ended
	Sep. 30, 2018
Revenue From Contract With Customer [Abstract]
Revenue	7. Revenue The Company’s revenue is derived from contracts for services with federal, state, local and foreign governmental entities and private customers. Dredging 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. Revenues within the environmental & infrastructure segment are generally generated from environmental and geotechnical construction as well as soil, water and sediment environmental remediation. Prior to January 1, 2018, the Company measured completion based on engineering estimates of the physical percentage completed for dredging contracts and based upon cost incurred to date compared to total estimated costs, also known as cost-to-cost, for environmental & infrastructure contracts. Under the new accounting principle, the Company measures progress toward completion on all contracts utilizing the cost-to-cost method. Additionally, the Company capitalizes certain pre-contract and pre-construction costs, and defers recognition over the life of the contract. At September 30, 2018, the impact of this change in accounting principle on the Condensed Consolidated Balance Sheets is as follows: September 30, 2018 ASSETS Contract revenues in excess of billings $ (18,363 ) Other current assets 8,807 Other 5,012 LIABILITIES AND EQUITY Accrued expenses (1,255 ) Billings in excess of contract revenues 1,918 Deferred taxes (1,354 ) Accumulated deficit $ (3,853 ) For the three and nine months ended September 30, 2018, the impact of this change in accounting principle on the Condensed Consolidated Statements of Operations is as follows: Three Months Ended Nine Months Ended September 30, September 30, 2018 2018 Contract revenues $ 1,331 $ (20,281 ) Cost of contract revenues 795 (15,074 ) Income tax (provision) benefit (139 ) 1,354 Income (loss) from continuing operations 397 (3,853 ) Net income (loss) $ 397 $ (3,853 ) Comprehensive income (loss) $ 397 $ (3,853 ) 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 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 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 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 dredging and environmental & infrastructure segments typically satisfy their performance obligations upon completion of service. The majority of the Company’s contracts are completed in a year or less. At September 30, 2018, the Company had $689,158 of remaining performance obligations, which the Company refers to as total backlog. Approximately 39% of the Company’s backlog will be completed in 2018 with the remaining balance expected to be completed by 2020. 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 contract modifications for both dredging and environmental & infrastructure projects. For dredging projects, 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. 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 included in the transaction price only if it is probable that the modification estimate will not result in a significant reversal of revenue. 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. 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 our projects, does not significantly affect our results across annual reporting periods. Provisions for estimated losses on contracts in progress are made in the period in which such losses are determined. Revenue by category The following series of tables presents our revenue disaggregated by several categories. Domestically, our 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 segment and type of work, the Company’s contract revenues for the periods ended: Three Months Ended Nine Months Ended September 30, September 30, Revenues (in thousands) 2018 2017 2018 2017 Dredging: Capital—U.S. $ 105,934 $ 30,561 $ 252,537 $ 128,634 Capital—foreign 5,045 5,849 13,847 37,423 Coastal protection 42,691 40,726 122,673 141,365 Maintenance 11,581 42,282 38,461 98,532 Rivers & lakes 13,420 14,444 20,046 33,469 Total dredging revenues 178,671 133,862 447,564 439,423 Environmental & infrastructure 25,651 29,667 53,941 73,602 Intersegment revenue — (212 ) — (2,263 ) Total revenues $ 204,322 $ 163,317 $ 501,505 $ 510,762 The following table sets forth, by segment and type of customer, the Company’s contract revenues for the periods ended: Three Months Ended Nine Months Ended September 30, September 30, Revenues (in thousands) 2018 2017 2018 2017 Dredging: Federal government $ 144,050 $ 73,674 $ 313,657 $ 271,162 State and local government 7,107 52,070 77,078 110,380 Private 22,469 2,269 42,982 20,458 Foreign 5,045 5,849 13,847 37,423 Total dredging revenues 178,671 133,862 447,564 439,423 Environmental & infrastructure: Private 11,739 12,786 29,140 34,282 Other 13,912 16,881 24,801 39,320 Intersegment revenue — (212 ) — (2,263 ) Total revenues $ 204,322 $ 163,317 $ 501,505 $ 510,762 Foreign dredging revenue was $5,045 and $5,849 for the three months ended September 30, 2018 and 2017, respectively, and $13,847 and $37,423 for the nine months ended September 30, 2018 and 2017, respectively, and was mostly attributable to work done in the Middle East. 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 September 30, 2018 and December 31, 2017 are as follows: September 30, December 31, 2018 2017 Completed contracts $ 29,501 $ 15,974 Contracts in progress 43,541 42,759 Retainage 14,252 21,866 87,294 80,599 Allowance for doubtful accounts (629 ) (591 ) Total accounts receivable—net $ 86,665 $ 80,008 Current portion of accounts receivable—net $ 86,665 $ 75,533 Long-term accounts receivable and retainage — 4,475 Total accounts receivable—net $ 86,665 $ 80,008 The components of contracts in progress at September 30, 2018 and December 31, 2017 are as follows: September 30, December 31, 2018 2017 Costs and earnings in excess of billings: Costs and earnings for contracts in progress $ 343,847 $ 558,557 Amounts billed (311,955 ) (490,732 ) Costs and earnings in excess of billings for contracts in progress 31,892 67,825 Costs and earnings in excess of billings for completed contracts 6,370 22,963 Total contract revenues in excess of billings $ 38,262 $ 90,788 Current portion of contract revenues in excess of billings $ 36,151 $ 90,788 Long-term contract revenues in excess of billings 2,111 — Total contract revenues in excess of billings $ 38,262 $ 90,788 Billings in excess of costs and earnings: Amounts billed $ (359,914 ) $ (325,350 ) Costs and earnings for contracts in progress 348,762 321,735 Total billings in excess of contract revenues $ (11,152 ) $ (3,615 ) For amounts included in billings in excess of contract revenues balance at the beginning of the year, the Company recognized nearly all of the related revenue during the nine months ended September 30, 2018. At September 30, 2018 and January 1, 2018, costs to fulfill contracts with customers recognized as an asset were $14,797 and $7,732, respectively, and are recorded in other current assets and other noncurrent assets. These costs relate to pre-contract and pre-construction activities. During the three and nine months ended September 30, 2018, the company amortized $6,249 and $13,045 of pre-construction costs, respectively.

Restructuring Charges

Restructuring Charges	9 Months Ended
	Sep. 30, 2018
Restructuring And Related Activities [Abstract]
Restructuring Charges	8 . 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 our extensive fleet with new and efficient dredges to best serve our domestic and international clients. As a result of this review, management began execution of 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. These changes will result in total restructuring charges of approximately $42,000-$47,000, including severance of approximately $3,000, asset retirements of approximately $30,000-$34,000, pre-contract costs of approximately $6,500 and closeout costs of approximately $2,500-$3,500. Approximately $38,000-$43,000 of this charge consists of non-cash items including depreciation, loss on sale of assets and other items, approximating totals of $12,500-$14,500, $3,000-$5,000 and $21,500-$23,500, respectively. Restructuring charges currently recognized for the above actions are summarized as follows: Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Costs of contract revenues—depreciation $ 1,341 $ — $ 6,009 $ — Costs of contract revenues—other 765 316 1,758 316 General and administrative expenses 153 1,306 132 1,306 Loss on sale of assets—net 1,737 — 890 — Other expense — — 2,015 — Total Dredging 3,996 1,622 10,804 1,622 General and administrative expenses 535 415 694 415 Total Environmental & Infrastructure 535 415 694 415 Costs of contract revenues—depreciation 1,341 — 6,009 — Costs of contract revenues—other 765 316 1,758 316 General and administrative expenses 688 1,721 826 1,721 Loss on sale of assets—net 1,737 — 890 — Other expense — — 2,015 — Total Consolidated $ 4,531 $ 2,037 $ 11,498 $ 2,037 The Company accrued rent expense related to restructuring costs of $0 at September 30, 2018, compared to $5,930 at December 31, 2017. The reduction in accrued rent expense relating to restructuring costs is the result of the buyout of two vessel leases during the 2018 third quarter. The Company accrued severance expense of $929 and $1,567 at September 30, 2018 and December 31, 2017, respectively, which are expected to be settled in 2018. Both of these items are included in accrued expenses.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. 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, under which the Company can obtain performance, bid and payment bonds. The Company also has outstanding bonds with Travelers Casualty, Surety Company of America and Zurich American Insurance Company (“Zurich”). Bid bonds are generally obtained for a percentage of bid value and amounts outstanding typically range from $1,000 to $10,000. At September 30, 2018, the Company had outstanding performance bonds with a notional amount of approximately $1,294,631 of which $41,085 relates to projects from the Company’s historical environmental & infrastructure businesses. The revenue value remaining in backlog related to these projects totaled approximately $661,050. In connection with the sale of our 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, the Company had to increase the borrowings on its revolving credit facility. As the outstanding letters of credit previously reduced our availability under the revolving credit facility, this draw down on our letter of credit does not impact our liquidity or capital availability. Pursuant to the terms of sale of our 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 if the buyer of the historical demolition business is found to be in default of its obligations. The Company cannot estimate the amount or range of recoveries related to the indemnification or resolution of the Company’s responsibilities under the surety bond. The surety bond claim impact has been included in discontinued operations and is discussed in Note 11, Business dispositions. 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 U.S. federal government, the U.S. federal 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 U.S. federal 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. 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. In September 2018, Environmental Protection Agency (“EPA”) Region 4 informed the Company of the EPA’s intent to file 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 Company disagrees with EPA on whether a violation occurred and, if a violation did occur, the appropriate penalty calculation, and will defend ourselves vigorously. 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. Legal actions brought by the Company to enforce the buyer’s obligations under the sale agreement are described below. On January 14, 2015, the Company and our 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 and intends to vigorously defend against the counterclaims. Also pursuant to the terms of the agreement to sell NASDI and Yankee and as described above, the Company agreed to keep in place surety bonds for certain pending demolition projects, and the buyer agreed to indemnify the Company for all losses relating to those bonds. As described above, in May 2017, Zurich drew upon the Company’s letter of credit in the amount of $20,881. On May 26, 2017, the Company and NASDI Holdings, LLC brought a second action in the Delaware Court of Chancery seeking indemnification for all losses relating to the bonds for that project. Except as noted above, 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.

Investments

Investments	9 Months Ended
	Sep. 30, 2018
Equity Method Investments And Joint Ventures [Abstract]
Investments	10. Investments The Company owned 50% of TerraSea Environmental Solutions (“TerraSea”) as a joint venture. TerraSea was engaged in the environmental services business through its ability to remediate contaminated soil and dredged sediment treatment. During the second quarter of 2017, the Company and the joint venture partner agreed to a final resolution of the net advances through additional funding of the joint venture. The Company recorded additional losses of $1,458 related to this agreement during the quarter ended June 30, 2017. TerraSea was dissolved in the third quarter of 2017.

Business Combinations and Dispo

Business Combinations and Dispositions	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Business Combinations and Dispositions	11. Business combinations and dispositions Discontinued operations On April 23, 2014, the Company entered into an agreement and completed the sale of NASDI and Yankee, its two former subsidiaries that comprised our historical demolition business. 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, including recovery of outstanding claims for additional compensation from customers, net of future payments of accounts payable existing at the date of close, including any future payments of obligations associated with outstanding claims. The amount and timing of any realization of additional net proceeds has been impacted by the litigation with the buyer of the historical demolition business. However, management believes that the ultimate resolution of these matters will not be material to the Company’s consolidated financial position or results of operations. As discussed in Note 9, Commitments and contingencies, 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. Zurich could be obligated to reimburse the loss, damage and expense that may arise from the alleged default. The Company estimated its exposure to a surety bond claim, including associated expenses, to be $20,900 and has recorded this amount in discontinued operations during the nine months ended September 30, 2017 as follows: Nine Months Ended September 30, 2017 Revenue $ — Loss before income taxes from discontinued operations $ (20,900 ) Income tax benefit 8,203 Loss from discontinued operations, net of income taxes $ (12,697 ) Magnus Pacific acquisition On November 4, 2014, the Company acquired Magnus Pacific Corporation (“Magnus”), a California corporation, for an aggregate purchase price of approximately $40 million. Under the terms of the acquisition, the aggregate purchase price is satisfied by payment of $25 million paid at closing, the issuance of a promissory note and an earnout payment. Magnus did not reach the minimum EBITDA threshold for 2015 designated in the secured promissory note; therefore, during 2015, the Company reduced the remaining fair value to zero. Under the terms of the acquisition, as amended, the maximum potential aggregate earnout (the “Earnout Payment”) is $11,400

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment Information	12. Segment information The Company and its subsidiaries currently operate in two reportable segments: dredging and environmental & infrastructure. The Company’s financial reporting systems present various data for management to run the business, including profit and loss statements prepared according to the segments presented. Management uses operating income to evaluate performance between the two segments. Segment information for the periods presented is provided as follows: Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Dredging Contract revenues $ 178,671 $ 133,862 $ 447,564 $ 439,423 Operating income 25,081 5,848 38,826 9,573 Environmental & infrastructure Contract revenues $ 25,651 $ 29,667 $ 53,941 $ 73,602 Operating loss (1,692 ) (3,727 ) (8,343 ) (6,600 ) Intersegment revenues $ — $ (212 ) $ — $ (2,263 ) Total Contract revenues $ 204,322 $ 163,317 $ 501,505 $ 510,762 Operating income 23,389 2,121 30,483 2,973

Basis of Presentation (Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Recent Accounting Pronouncements	Recent accounting pronouncements In January 2017, the FASB issued Accounting Standard Update No. 2017-04 (“ASU 2017-04”), Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment The Company does not anticipate that the adoption of ASU 2017-04 will have a material effect on the Company’s consolidated financial statements. In February 2016, the FASB issued Accounting Standard Update No. 2016-02 (“ASU 2016-02”), Leases (Topic 842)

Basis of Presentation (Tables)

Basis of Presentation (Tables)	9 Months Ended
	Sep. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash at September 30, 2018 and December 31, 2017 reported within the Condensed Consolidated Balance Sheets that sum to the total of the same such amounts shown in the Condensed Consolidated Statements of Cash Flows. September 30, 2018 December 31, 2017 Cash and cash equivalents $ 23,127 $ 15,852 Restricted cash included in other long-term assets — 1,500 Cash, cash equivalents and restricted cash at end of period $ 23,127 $ 17,352
Schedule of Quarterly Impact of Change in Accounting Policy on Condensed Consolidated Statements of Operations and Condensed Consolidated Balance Sheets	The impact of the change in accounting policy on our Condensed Consolidated Statements of Operations and Condensed Consolidated Balance Sheets is as follows: Three Months Ended Nine Months Ended September 30, 2017 September 30, 2017 Costs of contract revenues $ (3,123 ) $ 3,739 Income tax (provision) benefit (1,406 ) 1,443 Income (loss) from continuing operations 1,717 (2,296 ) Net income (loss) $ 1,717 $ (2,296 ) Comprehensive income (loss) $ 1,717 $ (2,296 ) Basic earnings (loss) per share attributable to continuing operations $ 0.03 $ (0.03 ) Diluted earnings (loss) per share attributable to continuing operations $ 0.03 $ (0.03 ) September 30, 2017 Prepaid expenses and other current assets $ (3,739 ) Deferred income taxes (1,443 ) Accumulated deficit $ (2,296 )

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Computations for Basic and Diluted Earnings (Loss) Per Share	The computations for basic and diluted earnings (loss) per share are as follows: Three Months Ended Nine Months Ended (shares in thousands) September 30, September 30, 2018 2017 2018 2017 Income (loss) from continuing operations $ 11,702 $ (3,228 ) $ 1,407 $ (12,026 ) Loss from discontinued operations, net of income taxes — — — (12,697 ) Net income (loss) 11,702 (3,228 ) 1,407 (24,723 ) Weighted-average common shares outstanding — basic 62,358 61,462 62,147 61,290 Effect of stock options and restricted stock units 902 — 1,193 — Weighted-average common shares outstanding — diluted 63,260 61,462 63,340 61,290 Earnings (loss) per share from continuing operations — basic $ 0.19 $ (0.05 ) $ 0.02 $ (0.19 ) Earnings (loss) per share from continuing operations — diluted $ 0.18 $ (0.05 ) $ 0.02 $ (0.19 )
Schedule of Stock Options and Restricted Stock Units Excluded from Calculation of Anti-Diluted Earnings Per Share	For the quarter and nine months ended September 30, 2018 and 2017, the following stock options and restricted stock units were excluded from the calculation of diluted earnings per share as such stock options and restricted stock units were determined to be anti-dilutive: Three Months Ended Nine Months Ended (shares in thousands) September 30, September 30, 2018 2017 2018 2017 Effect of stock options and restricted stock units 1,224 1,288 1,489 1,399

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2018
Payables And Accruals [Abstract]
Accrued Expenses	Accrued expenses at September 30, 2018 and December 31, 2017 are as follows: September 30, December 31, 2018 2017 Insurance $ 13,185 $ 22,941 Payroll and employee benefits 11,829 8,747 Interest 10,103 4,210 Percentage of completion adjustment 3,234 3,591 Income and other taxes 2,193 2,794 Accrued rent 458 6,519 Other 6,409 7,416 Total accrued expenses $ 47,411 $ 56,218

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2018
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 September 30, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fuel hedge contracts $ 1,064 $ — 1,064 $ — Fair Value Measurements at Reporting Date Using Description At December 31, 2017 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fuel hedge contracts $ 2,501 $ — $ 2,501 $ —
Schedule of Fair Value of Fuel Hedge Contracts Balance Sheet Location	The fair value of the fuel hedge contracts outstanding as of September 30, 2018 and December 31, 2017 is as follows: Fair Value at September 30, December 31, Balance Sheet Location 2018 2017 Asset derivatives: Derivatives designated as hedging instruments Fuel hedge contracts Prepaid expenses and other current assets $ 1,064 $ 2,501
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: Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Cumulative translation adjustments—net of tax $ (14 ) $ (2 ) $ 1,290 $ (24 ) Derivatives: Reclassification of derivative (gains) losses to earnings—net of tax (442 ) (35 ) (2,211 ) 160 Change in fair value of derivatives—net of tax 241 1,719 1,149 72 Net unrealized gain on derivatives—net of tax (201 ) 1,684 (1,062 ) 232 Total other comprehensive income (loss) $ (215 ) $ 1,682 $ 228 $ 208
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: Three Months Ended Nine Months Ended September 30, September 30, Statement of Operations Location 2018 2017 2018 2017 Derivatives: Fuel Costs of contract revenues $ (599 ) $ (59 ) $ (2,995 ) $ 264 Income tax (provision) benefit (157 ) (24 ) (784 ) 104 $ (442 ) $ (35 ) $ (2,211 ) $ 160

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 30, 2018
Revenue Recognition [Line Items]
Summary of Segment and Type of Work and Customer, Contract Revenues	The following table sets forth, by segment and type of work, the Company’s contract revenues for the periods ended: Three Months Ended Nine Months Ended September 30, September 30, Revenues (in thousands) 2018 2017 2018 2017 Dredging: Capital—U.S. $ 105,934 $ 30,561 $ 252,537 $ 128,634 Capital—foreign 5,045 5,849 13,847 37,423 Coastal protection 42,691 40,726 122,673 141,365 Maintenance 11,581 42,282 38,461 98,532 Rivers & lakes 13,420 14,444 20,046 33,469 Total dredging revenues 178,671 133,862 447,564 439,423 Environmental & infrastructure 25,651 29,667 53,941 73,602 Intersegment revenue — (212 ) — (2,263 ) Total revenues $ 204,322 $ 163,317 $ 501,505 $ 510,762 The following table sets forth, by segment and type of customer, the Company’s contract revenues for the periods ended: Three Months Ended Nine Months Ended September 30, September 30, Revenues (in thousands) 2018 2017 2018 2017 Dredging: Federal government $ 144,050 $ 73,674 $ 313,657 $ 271,162 State and local government 7,107 52,070 77,078 110,380 Private 22,469 2,269 42,982 20,458 Foreign 5,045 5,849 13,847 37,423 Total dredging revenues 178,671 133,862 447,564 439,423 Environmental & infrastructure: Private 11,739 12,786 29,140 34,282 Other 13,912 16,881 24,801 39,320 Intersegment revenue — (212 ) — (2,263 ) Total revenues $ 204,322 $ 163,317 $ 501,505 $ 510,762
Schedule of Accounts Receivable	Accounts receivable at September 30, 2018 and December 31, 2017 are as follows: September 30, December 31, 2018 2017 Completed contracts $ 29,501 $ 15,974 Contracts in progress 43,541 42,759 Retainage 14,252 21,866 87,294 80,599 Allowance for doubtful accounts (629 ) (591 ) Total accounts receivable—net $ 86,665 $ 80,008 Current portion of accounts receivable—net $ 86,665 $ 75,533 Long-term accounts receivable and retainage — 4,475 Total accounts receivable—net $ 86,665 $ 80,008
Components of Contracts in Progress	The components of contracts in progress at September 30, 2018 and December 31, 2017 are as follows: September 30, December 31, 2018 2017 Costs and earnings in excess of billings: Costs and earnings for contracts in progress $ 343,847 $ 558,557 Amounts billed (311,955 ) (490,732 ) Costs and earnings in excess of billings for contracts in progress 31,892 67,825 Costs and earnings in excess of billings for completed contracts 6,370 22,963 Total contract revenues in excess of billings $ 38,262 $ 90,788 Current portion of contract revenues in excess of billings $ 36,151 $ 90,788 Long-term contract revenues in excess of billings 2,111 — Total contract revenues in excess of billings $ 38,262 $ 90,788 Billings in excess of costs and earnings: Amounts billed $ (359,914 ) $ (325,350 ) Costs and earnings for contracts in progress 348,762 321,735 Total billings in excess of contract revenues $ (11,152 ) $ (3,615 )
ASU 2014-09 [Member]
Revenue Recognition [Line Items]
Summary of Impact of Change in Accounting Principle on Condensed Consolidated Balance Sheets	At September 30, 2018, the impact of this change in accounting principle on the Condensed Consolidated Balance Sheets is as follows: September 30, 2018 ASSETS Contract revenues in excess of billings $ (18,363 ) Other current assets 8,807 Other 5,012 LIABILITIES AND EQUITY Accrued expenses (1,255 ) Billings in excess of contract revenues 1,918 Deferred taxes (1,354 ) Accumulated deficit $ (3,853 )
Summary of Impact of Change in Accounting Principle on Condensed Consolidated Statements of Operations	For the three and nine months ended September 30, 2018, the impact of this change in accounting principle on the Condensed Consolidated Statements of Operations is as follows: Three Months Ended Nine Months Ended September 30, September 30, 2018 2018 Contract revenues $ 1,331 $ (20,281 ) Cost of contract revenues 795 (15,074 ) Income tax (provision) benefit (139 ) 1,354 Income (loss) from continuing operations 397 (3,853 ) Net income (loss) $ 397 $ (3,853 ) Comprehensive income (loss) $ 397 $ (3,853 )

Restructuring charges (Tables)

Restructuring charges (Tables)	9 Months Ended
	Sep. 30, 2018
Restructuring And Related Activities [Abstract]
Schedule of Restructuring Charges	Restructuring charges currently recognized for the above actions are summarized as follows: Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Costs of contract revenues—depreciation $ 1,341 $ — $ 6,009 $ — Costs of contract revenues—other 765 316 1,758 316 General and administrative expenses 153 1,306 132 1,306 Loss on sale of assets—net 1,737 — 890 — Other expense — — 2,015 — Total Dredging 3,996 1,622 10,804 1,622 General and administrative expenses 535 415 694 415 Total Environmental & Infrastructure 535 415 694 415 Costs of contract revenues—depreciation 1,341 — 6,009 — Costs of contract revenues—other 765 316 1,758 316 General and administrative expenses 688 1,721 826 1,721 Loss on sale of assets—net 1,737 — 890 — Other expense — — 2,015 — Total Consolidated $ 4,531 $ 2,037 $ 11,498 $ 2,037

Business Combinations and Dis_2

Business Combinations and Dispositions (Tables)	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Schedule of Discontinued Operations	The Company estimated its exposure to a surety bond claim, including associated expenses, to be $20,900 and has recorded this amount in discontinued operations during the nine months ended September 30, 2017 as follows Nine Months Ended September 30, 2017 Revenue $ — Loss before income taxes from discontinued operations $ (20,900 ) Income tax benefit 8,203 Loss from discontinued operations, net of income taxes $ (12,697 )

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment Reporting by Segment	Segment information for the periods presented is provided as follows: Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Dredging Contract revenues $ 178,671 $ 133,862 $ 447,564 $ 439,423 Operating income 25,081 5,848 38,826 9,573 Environmental & infrastructure Contract revenues $ 25,651 $ 29,667 $ 53,941 $ 73,602 Operating loss (1,692 ) (3,727 ) (8,343 ) (6,600 ) Intersegment revenues $ — $ (212 ) $ — $ (2,263 ) Total Contract revenues $ 204,322 $ 163,317 $ 501,505 $ 510,762 Operating income 23,389 2,121 30,483 2,973

Basis of Presentation - Schedul

Basis of Presentation - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Organization Consolidation and Presentation [Line Items]
Cash and cash equivalents	$ 23,127	$ 15,852
Cash, cash equivalents and restricted cash at end of period	23,127	17,352	$ 12,490	$ 19,702
Accounting Standards Update 2016-18 [Member]
Organization Consolidation and Presentation [Line Items]
Cash and cash equivalents	23,127	15,852
Restricted cash included in other long-term assets		1,500
Cash, cash equivalents and restricted cash at end of period	$ 23,127	$ 17,352

Basis of Presentation - Sched_2

Basis of Presentation - Schedule of Quarterly Impact of Change in Accounting Policy on Condensed Consolidated Statements of Operations and Condensed Consolidated Balance Sheets (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Organization Consolidation and Presentation [Line Items]
Costs of contract revenues	$ 162,188	$ 143,499	$ 422,426	$ 455,850
Income tax (provision) benefit	3,790	(1,308)	549	(7,555)
Income (loss) from continuing operations	11,702	(3,228)	1,407	(12,026)
Net income (loss)	11,702	(3,228)	1,407	(24,723)
Comprehensive income (loss)	$ 11,487	$ (1,546)	$ 1,635	$ (24,515)
Basic earnings (loss) per share attributable to continuing operations	$ 0.19	$ (0.05)	$ 0.02	$ (0.19)
Diluted earnings (loss) per share attributable to continuing operations	$ 0.18	$ (0.05)	$ 0.02	$ (0.19)
Prepaid expenses and other current assets	$ 39,411		$ 39,411		$ 45,411
Deferred income taxes	25,605		25,605		25,561
Accumulated deficit	$ (67,271)		$ (67,271)		$ (67,101)
Accounting Standards Update 2016-18 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Organization Consolidation and Presentation [Line Items]
Costs of contract revenues		$ (3,123)		$ 3,739
Income tax (provision) benefit		(1,406)		1,443
Income (loss) from continuing operations		1,717		(2,296)
Net income (loss)		1,717		(2,296)
Comprehensive income (loss)		$ 1,717		$ (2,296)
Basic earnings (loss) per share attributable to continuing operations		$ 0.03		$ (0.03)
Diluted earnings (loss) per share attributable to continuing operations		$ 0.03		$ (0.03)
Prepaid expenses and other current assets		$ (3,739)		$ (3,739)
Deferred income taxes		(1,443)		(1,443)
Accumulated deficit		$ (2,296)		$ (2,296)

Basis of Presentation (Narrativ

Basis of Presentation (Narrative) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)segment
Organization Consolidation and Presentation [Line Items]
Number of operating Segments	2
Number of reportable segments	2
Number of reportable segments with goodwill	2
Accounting Standards Update 2014-09 [Member]
Organization Consolidation and Presentation [Line Items]
Cumulative net adjustment to the beginning retained earnings balance | $	$ 1,950

Earnings Per Share - (Computati

Earnings Per Share - (Computations for Basic and Diluted Earnings (Loss) Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Income (loss) from continuing operations	$ 11,702	$ (3,228)	$ 1,407	$ (12,026)
Loss from discontinued operations, net of income taxes				(12,697)
Net income (loss)	$ 11,702	$ (3,228)	$ 1,407	$ (24,723)
Weighted-average common shares outstanding — basic	62,358	61,462	62,147	61,290
Effect of stock options and restricted stock units	902		1,193
Weighted-average common shares outstanding — diluted	63,260	61,462	63,340	61,290
Earnings (loss) per share from continuing operations — basic	$ 0.19	$ (0.05)	$ 0.02	$ (0.19)
Earnings (loss) per share from continuing operations — diluted	$ 0.18	$ (0.05)	$ 0.02	$ (0.19)

Earnings Per Share (Narrative)

Earnings Per Share (Narrative) (Details) - shares shares in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Earnings Per Share [Abstract]
Stock options and restricted stock units excluded from diluted weighted-average common shares	611	646

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	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Effect of stock options and restricted stock units	1,224	1,288	1,489	1,399

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Payables And Accruals [Abstract]
Insurance	$ 13,185	$ 22,941
Payroll and employee benefits	11,829	8,747
Interest	10,103	4,210
Percentage of completion adjustment	3,234	3,591
Income and other taxes	2,193	2,794
Accrued rent	458	6,519
Other	6,409	7,416
Total accrued expenses	$ 47,411	$ 56,218

Long-Term Debt (Narrative) (Det

Long-Term Debt (Narrative) (Details) - USD ($)	Dec. 30, 2016	Feb. 28, 2018	May 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Maximum availability of earnings under credit agreement for five consecutive days				$ 31,250,000
Maximum availability of earnings under credit agreement for one day				25,000,000
Revolving credit facility				30,882,000
Letters of credit outstanding				31,587,000
Letter of credit remaining borrowing capacity				161,333,000
Availability under credit agreement suppressed				26,198,000
Net proceeds from issuance					$ 326,241,000
Long-term debt, current maturities				909,000			$ 2,758,000
Long-term debt, excluding current Maturities				321,727,000			$ 333,141,000
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]
Long-term debt, current maturities				909,000
Long-term debt, excluding current Maturities				$ 278,000
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, face amount			$ 325,000,000
Debt instrument, interest rate, stated percentage			8.00%
Maturity date			May 15, 2022
Owned Domestic Subsidiaries Percent			100.00%
7.375% Senior Notes Due In 2019 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount			$ 275,000,000
Debt instrument, interest rate, stated percentage			7.375%	7.375%	7.375%
Maturity date			Feb. 28, 2019
Redemption of notes			$ 282,638,000
Maximum [Member]
Debt Instrument [Line Items]
Expenses related to buy-out operating leases				$ 20,000,000
Fixed charge coverage ratio	1.10%
Maximum [Member] | Scenario Forecast [Member]
Debt Instrument [Line Items]
Capital expenditures by credit parties						$ 135,000,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 250,000,000
Line of credit facility optional increase capacity	$ 100,000,000
Revolving credit facility, maturity date				Dec. 30, 2019
Revolving Credit Facility [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	2.00%
Revolving Credit Facility [Member] | LIBOR Rate [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	3.00%
Revolving Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Unused fee percentage	0.375%
Revolving Credit Facility [Member] | Maximum [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	2.00%
Revolving Credit Facility [Member] | Maximum [Member] | LIBOR Rate [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	3.00%
Revolving Credit Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Unused fee percentage	0.25%
Revolving Credit Facility [Member] | Minimum [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	1.50%
Revolving Credit Facility [Member] | Minimum [Member] | LIBOR Rate [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	2.50%
Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 250,000,000
Swingline Loans [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 25,000,000

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	Sep. 30, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value, Net Asset (Liability)	$ 1,064	$ 2,501
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)	$ 1,064	$ 2,501

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) gal in Millions	1 Months Ended	3 Months Ended			9 Months Ended
	May 31, 2017USD ($)	Sep. 30, 2018USD ($)$ / gal	Mar. 31, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)$ / galgal	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Derivatives Fair Value [Line Items]
Derivative underlying hedge percent					80.00%
Derivative, Nonmonetary Notional Amount, Volume | gal					5.8
Fair value hedge assets		$ 1,064,000			$ 1,064,000		$ 2,501,000
Reclassification of derivative losses to earnings-net of tax		442,000		$ 35,000	2,211,000	$ (160,000)
8.000% Senior Notes Due in 2022 [Member]
Derivatives Fair Value [Line Items]
Debt instrument, face amount	$ 325,000,000
Stated interest rate	8.00%
Maturity date	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		$ 333,938,000			$ 333,938,000
Other Expense [Member]
Derivatives Fair Value [Line Items]
Reversal of cumulative translation adjustment			$ 2,015,000
Minimum [Member]
Derivatives Fair Value [Line Items]
Fixed price range | $ / gal		1.94			1.94
Maximum [Member]
Derivatives Fair Value [Line Items]
Fixed price range | $ / gal		2.23			2.23

Fair Value Measurements (Sche_2

Fair Value Measurements (Schedule of Fair Value of Fuel Hedge Contracts Balance Sheet Location) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivatives Fair Value [Line Items]
Asset derivatives	$ 1,064	$ 2,501
Prepaid Expenses and Other Current Assets [Member] | Derivatives Designated as Hedging Instruments [Member] | Fuel Hedge Contracts [Member]
Derivatives Fair Value [Line Items]
Asset derivatives	$ 1,064	$ 2,501

Fair Value Measurements (Change

Fair Value Measurements (Changes in Components of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Cumulative translation adjustments—net of tax	[1]	$ (14)	$ (2)	$ 1,290	$ (24)
Reclassification of derivative (gains) losses to earnings—net of tax		(442)	(35)	(2,211)	160
Change in fair value of derivatives—net of tax		241	1,719	1,149	72
Net unrealized gain on derivatives—net of tax	[2]	(201)	1,684	(1,062)	232
Other comprehensive income (loss)—net of tax		$ (215)	$ 1,682	$ 228	$ 208
[1]	Net of income tax benefit of $21 and $13 for the three months ended September 30, 2018 and 2017, respectively. Net of income tax (provision) benefit of $(551) and $46 for the nine months ended September 30, 2018 and 2017, respectively.
[2]	Net of income tax (provision) benefit of $(242) and $1,098 for the three months ended September 30, 2018 and 2017, respectively. Net of income tax (provision) benefit of $(1,191) and $151 for the nine months ended September 30, 2018 and 2017, respectively.

Fair Value Measurements (Adjust

Fair Value Measurements (Adjustments Reclassified from Accumulated Balances Other Comprehensive Income (Loss) to Earnings) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments Gain Loss [Line Items]
Costs of contract revenues	$ 162,188	$ 143,499	$ 422,426	$ 455,850
Income tax (provision) benefit	(3,790)	1,308	(549)	7,555
Net income (loss)	(11,702)	3,228	(1,407)	24,723
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	(599)	(59)	(2,995)	264
Income tax (provision) benefit	(157)	(24)	(784)	104
Net income (loss)	$ (442)	$ (35)	$ (2,211)	$ 160

Share-Based Compensation (Narra

Share-Based Compensation (Narrative) (Details) - USD ($) shares in Thousands, $ in Thousands	May 11, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units				2,020
Share-based compensation expense		$ 1,030	$ 756	$ 3,294	$ 2,514
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
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

Revenue - (Summary of Impact of

Revenue - (Summary of Impact of Change in Accounting Principle on Condensed Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
ASSETS
Contract revenues in excess of billings	$ 36,151	$ 90,788
Other	12,588	13,128
LIABILITIES AND EQUITY
Accrued expenses	(47,411)	(56,218)
Billings in excess of contract revenues	(11,152)	(3,615)
Deferred taxes	(25,605)	(25,561)
Accumulated deficit	(67,271)	$ (67,101)
ASU 2014-09 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
ASSETS
Contract revenues in excess of billings	(18,363)
Other current assets	8,807
Other	5,012
LIABILITIES AND EQUITY
Accrued expenses	(1,255)
Billings in excess of contract revenues	1,918
Deferred taxes	(1,354)
Accumulated deficit	$ (3,853)

Revenue (Summary of Impact of C

Revenue (Summary of Impact of Change in Accounting Principle on Condensed Consolidated Statements of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Contract revenues	$ 204,322	$ 163,317	$ 501,505	$ 510,762
Type of Revenue [Extensible List]	gldd:ContractMember	gldd:ContractMember	gldd:ContractMember	gldd:ContractMember
Costs of contract revenues	$ 162,188	$ 143,499	$ 422,426	$ 455,850
Type of Cost, Good or Service [Extensible List]	gldd:ContractMember	gldd:ContractMember	gldd:ContractMember	gldd:ContractMember
Income tax (provision) benefit	$ 3,790	$ (1,308)	$ 549	$ (7,555)
Income (loss) from continuing operations	11,702	(3,228)	1,407	(12,026)
Net income (loss)	11,702	(3,228)	1,407	(24,723)
Comprehensive income (loss)	11,487	$ (1,546)	1,635	$ (24,515)
ASU 2014-09 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Contract revenues	$ 1,331		$ (20,281)
Type of Revenue [Extensible List]	gldd:ContractMember		gldd:ContractMember
Costs of contract revenues	$ 795		$ (15,074)
Type of Cost, Good or Service [Extensible List]	gldd:ContractMember		gldd:ContractMember
Income tax (provision) benefit	$ (139)		$ 1,354
Income (loss) from continuing operations	397		(3,853)
Net income (loss)	397		(3,853)
Comprehensive income (loss)	$ 397		$ (3,853)

Revenue (Narrative) (Details)

Revenue (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018
Revenue Recognition [Line Items]
Revenue, remaining performance obligation	$ 689,158		$ 689,158
Percentage of performance obligation to be recognized as revenue			39.00%
Performance obligation, expected to be recognized as revenue year			2,018
Remaining performance obligation, expected timing of satisfaction, year	2,020		2,020
Revenue, description of timing			one year or less
Revenues	$ 204,322	$ 163,317	$ 501,505	$ 510,762
Amortization on pre-construction costs	6,249		6,249		$ 13,045
Other Current and Noncurrent Assets [Member]
Revenue Recognition [Line Items]
Costs to fulfill contracts with customers recognized as an asset	14,797		14,797		$ 7,732
Dredging [Member] | Foreign [Member]
Revenue Recognition [Line Items]
Revenues	$ 5,045	$ 5,849	$ 13,847	$ 37,423

Revenue (Summary of Segment and

Revenue (Summary of Segment and Type of Work, Contract Revenues) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation Of Revenue [Line Items]
Revenues	$ 204,322	$ 163,317	$ 501,505	$ 510,762
Operating Segment [Member] | Environmental and Infrastructure [Member]
Disaggregation Of Revenue [Line Items]
Revenues	25,651	29,667	53,941	73,602
Intersegment Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenues		(212)		(2,263)
Type of Work [Member]
Disaggregation Of Revenue [Line Items]
Revenues	204,322	163,317	501,505	510,762
Type of Work [Member] | Operating Segment [Member] | Dredging [Member]
Disaggregation Of Revenue [Line Items]
Revenues	178,671	133,862	447,564	439,423
Type of Work [Member] | Operating Segment [Member] | Dredging [Member] | Capital-U.S. [Member]
Disaggregation Of Revenue [Line Items]
Revenues	105,934	30,561	252,537	128,634
Type of Work [Member] | Operating Segment [Member] | Dredging [Member] | Capital-Foreign [Member]
Disaggregation Of Revenue [Line Items]
Revenues	5,045	5,849	13,847	37,423
Type of Work [Member] | Operating Segment [Member] | Dredging [Member] | Coastal Protection [Member]
Disaggregation Of Revenue [Line Items]
Revenues	42,691	40,726	122,673	141,365
Type of Work [Member] | Operating Segment [Member] | Dredging [Member] | Maintenance [Member]
Disaggregation Of Revenue [Line Items]
Revenues	11,581	42,282	38,461	98,532
Type of Work [Member] | Operating Segment [Member] | Dredging [Member] | Rivers & Lakes [Member]
Disaggregation Of Revenue [Line Items]
Revenues	13,420	14,444	20,046	33,469
Type of Work [Member] | Operating Segment [Member] | Environmental and Infrastructure [Member]
Disaggregation Of Revenue [Line Items]
Revenues	$ 25,651	29,667	$ 53,941	73,602
Type of Work [Member] | Intersegment Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenues		$ (212)		$ (2,263)

Revenue (Summary of Segment a_2

Revenue (Summary of Segment and Type of Customer, Contract Revenues) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation Of Revenue [Line Items]
Revenues	$ 204,322	$ 163,317	$ 501,505	$ 510,762
Dredging [Member] | Foreign [Member]
Disaggregation Of Revenue [Line Items]
Revenues	5,045	5,849	13,847	37,423
Operating Segment [Member] | Environmental and Infrastructure [Member]
Disaggregation Of Revenue [Line Items]
Revenues	25,651	29,667	53,941	73,602
Intersegment Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenues		(212)		(2,263)
Type of Customer [Member]
Disaggregation Of Revenue [Line Items]
Revenues	204,322	163,317	501,505	510,762
Type of Customer [Member] | Federal Government [Member]
Disaggregation Of Revenue [Line Items]
Revenues	144,050	73,674	313,657	271,162
Type of Customer [Member] | State and Local Government [Member]
Disaggregation Of Revenue [Line Items]
Revenues	7,107	52,070	77,078	110,380
Type of Customer [Member] | Private [Member]
Disaggregation Of Revenue [Line Items]
Revenues	22,469	2,269	42,982	20,458
Type of Customer [Member] | Foreign [Member]
Disaggregation Of Revenue [Line Items]
Revenues	5,045	5,849	13,847	37,423
Type of Customer [Member] | Operating Segment [Member] | Dredging [Member]
Disaggregation Of Revenue [Line Items]
Revenues	178,671	133,862	447,564	439,423
Type of Customer [Member] | Operating Segment [Member] | Environmental and Infrastructure [Member] | Private [Member]
Disaggregation Of Revenue [Line Items]
Revenues	11,739	12,786	29,140	34,282
Type of Customer [Member] | Operating Segment [Member] | Environmental and Infrastructure [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenues	$ 13,912	16,881	$ 24,801	39,320
Type of Customer [Member] | Intersegment Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenues		$ (212)		$ (2,263)

Revenue (Schedule of Accounts R

Revenue (Schedule of Accounts Receivable) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Receivables [Abstract]
Completed contracts	$ 29,501	$ 15,974
Contracts in progress	43,541	42,759
Retainage	14,252	21,866
Accounts receivable, gross	87,294	80,599
Allowance for doubtful accounts	(629)	(591)
Total accounts receivable—net	86,665	80,008
Accounts receivable—net	$ 86,665	75,533
Long-term accounts receivable and retainage		$ 4,475

Revenue (Components of Contract

Revenue (Components of Contracts in Progress) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounts Notes And Loans Receivable [Line Items]
Costs and earnings in excess of billings for contracts in progress	$ 31,892	$ 67,825
Costs and earnings in excess of billings for completed contracts	6,370	22,963
Total contract revenues in excess of billings	38,262	90,788
Current portion of contract revenues in excess of billings	36,151	90,788
Long-term contract revenues in excess of billings	2,111
Total billings in excess of contract revenues	(11,152)	(3,615)
Costs And Earnings In Excess Of Billings [Member]
Accounts Notes And Loans Receivable [Line Items]
Costs and earnings for contracts in progress	343,847	558,557
Amounts billed	(311,955)	(490,732)
Billings In Excess Of Costs And Earnings [Member]
Accounts Notes And Loans Receivable [Line Items]
Costs and earnings for contracts in progress	(348,762)	(321,735)
Amounts billed	$ (359,914)	$ (325,350)

Restructuring Charges (Narrativ

Restructuring Charges (Narrative) (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018USD ($)Vessel	Dec. 31, 2017USD ($)
Restructuring Cost And Reserve [Line Items]
Accrued rent expense	$ 0	$ 5,930
Accrued severance expense	$ 929	1,567
Number of vessels related to lease buyout | Vessel	2
Minimum [Member]
Restructuring Cost And Reserve [Line Items]
Estimated restructuring charges		42,000
Restructuring charge related to non-cash		38,000
Minimum [Member] | Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charge related to non-cash		12,500
Minimum [Member] | Loss on Sale of Assets [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charge related to non-cash		3,000
Minimum [Member] | Other Items [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charge related to non-cash		21,500
Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Estimated restructuring charges		47,000
Restructuring charge related to non-cash		43,000
Maximum [Member] | Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charge related to non-cash		14,500
Maximum [Member] | Loss on Sale of Assets [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charge related to non-cash		5,000
Maximum [Member] | Other Items [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charge related to non-cash		23,500
Severance [Member]
Restructuring Cost And Reserve [Line Items]
Estimated restructuring charges		3,000
Asset Retirements [Member] | Minimum [Member]
Restructuring Cost And Reserve [Line Items]
Estimated restructuring charges		30,000
Asset Retirements [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Estimated restructuring charges		34,000
Pre-contract Costs [Member]
Restructuring Cost And Reserve [Line Items]
Estimated restructuring charges		6,500
Closeout Costs [Member] | Minimum [Member]
Restructuring Cost And Reserve [Line Items]
Estimated restructuring charges		2,500
Closeout Costs [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Estimated restructuring charges		$ 3,500

Restructuring Charges (Schedule

Restructuring Charges (Schedule of Restructuring Charges) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Restructuring Cost And Reserve [Line Items]
Restructuring charges	$ 4,531	$ 2,037	$ 11,498	$ 2,037
Costs of Contract Revenues - Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	1,341		6,009
Costs of Contract Revenues - Other [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	765	316	1,758	316
General and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	688	1,721	826	1,721
Loss on Sale of Assets—Net [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	1,737		890
Other Expense [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges			2,015
Dredging [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	3,996	1,622	10,804	1,622
Dredging [Member] | Costs of Contract Revenues - Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	1,341		6,009
Dredging [Member] | Costs of Contract Revenues - Other [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	765	316	1,758	316
Dredging [Member] | General and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	153	1,306	132	1,306
Dredging [Member] | Loss on Sale of Assets—Net [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	1,737		890
Dredging [Member] | Other Expense [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges			2,015
Environmental and Infrastructure [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	535	415	694	415
Environmental and Infrastructure [Member] | General and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring charges	$ 535	$ 415	$ 694	$ 415

Commitments and Contingencies (

Commitments and Contingencies (Narrative) (Details) - USD ($)	Feb. 28, 2017	Jan. 14, 2015	Sep. 30, 2018	May 31, 2017
Commitments And Contingencies [Line Items]
Outstanding performance bonds			$ 1,294,631,000
Revenue value remaining from outstanding performance bonds			661,050,000
Proceeds from Legal Settlements		$ 5,309,000
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			41,085,000
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

Investments (Details)

Investments (Details) - TerraSea Environmental Solutions [Member] - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2017	Sep. 30, 2018
Schedule Of Equity Method Investments [Line Items]
Ownership percentage		50.00%
Loss from joint venture	$ 1,458

Business Combinations and Dis_3

Business Combinations and Dispositions (Narrative) (Details) - USD ($)	Feb. 28, 2017	Nov. 04, 2014	Apr. 23, 2014	Sep. 30, 2017	Dec. 31, 2015
Business Acquisition [Line Items]
Estimated surety bond claim, including associated expenses				$ 20,900,000
Great Lakes Environmental & Infrastructure, LLC [Member]
Business Acquisition [Line Items]
Maximum potential aggregate earnout payment		$ 11,400,000
Magnus Pacific Acquisition [Member]
Business Acquisition [Line Items]
Base purchase price		40,000,000
Payments for previous acquisition		$ 25,000,000
Fair value of debt					$ 0
Surety Bond [Member]
Business Acquisition [Line Items]
Aggregate demolition surety performance bond	$ 20,000,000
NASDI, LLC and Yankee Environmental Services, LLC
Business Acquisition [Line Items]
Proceeds from divestiture of businesses			$ 5,309,000

Business Combinations and Dis_4

Business Combinations and Dispositions - (Schedule of Discontinued Operations) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017USD ($)
Business Combinations [Abstract]
Loss before income taxes from discontinued operations	$ (20,900)
Income tax benefit	8,203
Loss from discontinued operations, net of income taxes	$ (12,697)

Segment Information (Narrative)

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

Segment Information (Segment Re

Segment Information (Segment Reporting by Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Contract revenues	$ 204,322	$ 163,317	$ 501,505	$ 510,762
Operating income (loss)	23,389	2,121	30,483	2,973
Dredging Segment [Member]
Segment Reporting Information [Line Items]
Operating income (loss)	25,081	5,848	38,826	9,573
Environmental and Infrastructure Segment [Member]
Segment Reporting Information [Line Items]
Operating income (loss)	(1,692)	(3,727)	(8,343)	(6,600)
Operating Segment [Member] | Dredging Segment [Member]
Segment Reporting Information [Line Items]
Contract revenues	178,671	133,862	447,564	439,423
Operating Segment [Member] | Environmental and Infrastructure Segment [Member]
Segment Reporting Information [Line Items]
Contract revenues	$ 25,651	29,667	$ 53,941	73,602
Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Contract revenues		$ (212)		$ (2,263)