Great Lakes Dredge & Dock (GLDD) 10-K 6 Mar 15 2014 FY Annual report Financial data

Document_And_Entity_Informatio

Document And Entity Information (USD $)	12 Months Ended
	Dec. 31, 2014	Jun. 30, 2014	Feb. 20, 2014
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	FALSE
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Trading Symbol	GLDD
Entity Registrant Name	Great Lakes Dredge & Dock CORP
Entity Central Index Key	1372020
Current Fiscal Year End Date	-19
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding			60,236,620
Entity Public Float		$425,660,035
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
CURRENT ASSETS:
Cash and cash equivalents	$42,389	$75,338
Accounts receivable-net	113,188	96,515
Contract revenues in excess of billings	82,557	67,432
Inventories	34,735	32,500
Prepaid expenses	4,708	4,211
Other current assets	64,667	39,953
Assets held for sale		45,104
Total current assets	342,244	361,053
PROPERTY AND EQUIPMENT-Net	399,445	345,620
GOODWILL	86,326	79,326
OTHER INTANGIBLE ASSETS-Net	8,963	1,976
INVENTORIES-Noncurrent	36,262	38,496
INVESTMENTS IN JOINT VENTURES	7,889	8,256
ASSETS HELD FOR SALE-Noncurrent		8,856
OTHER	12,105	9,062
TOTAL	893,234	852,645
CURRENT LIABILITIES:
Accounts payable	119,971	116,121
Accrued expenses	70,041	38,531
Billings in excess of contract revenues	4,639	6,754
Current portion of long term debt	5,859
Liabilities held for sale		32,493
Total current liabilities	200,510	193,899
7 3/8% SENIOR NOTES	274,880	250,000
REVOLVING CREDIT FACILITY		35,000
NOTES PAYABLE	49,497
DEFERRED INCOME TAXES	92,007	108,511
LIABILITIES HELD FOR SALE-Noncurrent		1,212
OTHER	20,377	21,922
Total liabilities	637,271	610,544
COMMITMENTS AND CONTINGENCIES (Note 13)
EQUITY:
Common stock-$.0001 par value; 90,000 authorized, 60,170 and 59,670 shares issued and outstanding at December 31, 2014 and December 31, 2013, respectively.	6	6
Additional paid-in capital	278,166	275,183
Accumulated deficit	-21,475	-31,770
Accumulated other comprehensive loss	-734	-473
Total Great Lakes Dredge & Dock Corporation equity	255,963	242,946
NONCONTROLLING INTERESTS		-845
Total equity	255,963	242,101
TOTAL	$893,234	$852,645

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Consolidated Balance Sheets [Abstract]
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	90,000	90,000
Common stock, shares issued	60,170,000	59,670,000
Common stock, shares outstanding	60,170,000	59,670,000

Consolidated_Statements_Of_Ope

Consolidated Statements Of Operations (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated Statements Of Operations [Abstract]
Contract revenues	$806,831	$731,418	$588,430
Costs of contract revenues	714,335	631,123	510,272
Gross profit	92,496	100,295	78,158
OPERATING EXPENSES:
General and administrative expenses	67,911	68,039	45,723
Proceeds from loss of use claim		-13,372
(GAIN) LOSS ON SALE OF ASSETS-Net	732	-5,773	-198
Total operating income	23,853	51,401	32,633
OTHER EXPENSE:
Interest expense-net	-19,967	-21,941	-20,925
Equity in earnings of joint ventures	2,895	1,208	124
Gain on bargain purchase acquisition	2,197
Other income (expense)	-210	351	118
Loss on foreign currency transactions-net	210	-351	-118
Total other expense	-14,665	-21,084	-20,919
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	9,188	30,317	11,714
Income tax (provision) benefit	11,530	-10,460	-5,419
Income from continuing operations	20,718	19,857	6,295
Loss from discontinued operations, net of income taxes	-10,423	-54,850	-9,635
Net Income (Loss) Attributable to Parent	10,295	-34,993	-3,340
Net loss attributable to noncontrolling interest		632	645
NET INCOME (LOSS)	$10,295	($34,361)	($2,695)
Basic earnings per share attributable to income from continuing operations	$0.35	$0.33	$0.11
Basic loss per share attributable to loss on discontinued operations, net of income taxes	($0.17)	($0.91)	($0.15)
Basic earnings (loss) per share attributable to common stockholders of Great Lakes Dredge & Dock Corporation	$0.18	($0.58)	($0.04)
Basic weighted average shares	59,938	59,495	59,195
Diluted earnings per share attributable to income from continuing operations	$0.34	$0.33	$0.11
Diluted loss per share attributable to loss on discontinued operations, net of income taxes	($0.17)	($0.90)	($0.15)
Diluted earnings (loss) per share attributable to common stockholders of Great Lakes Dredge & Dock Corporation	$0.17	($0.57)	($0.04)
Diluted weighted average shares	60,522	60,101	59,673

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (Loss) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Consolidated Statements of Comprehensive Income (Loss) [Abstract]
Net Income (Loss) Attributable to Parent	$10,295		($34,993)		($3,340)
Currency translation adjustment-net of tax	-62	[1]	-397	[1]	-6	[1]
Net unrealized (gain) loss on derivatives-net of tax	-199	[2]	304	[2]	-377	[2]
Other comprehensive loss-net of tax	-261		-93		-383
Comprehensive income (loss)	10,034		-35,086		-3,723
Comprehensive loss attributable to noncontrolling interests			632		645
Comprehensive income (loss) attributable to Great Lakes Dredge & Dock Corporation	$10,034		($34,454)		($3,078)
[1]	Net of income tax (provision) benefit of $41, $261 and $(7) for the years ended December 31, 2014, 2013 and 2012, respectively
[2]	Net of income tax (provision) benefit of $(132), $204 and $(250) for the years ended December 31, 2014, 2013 and 2012, respectively.

Recovered_Sheet1

Consolidated Statements Of Comprehensive Income (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated Statements of Comprehensive Income (Loss) [Abstract]
Currency translation adjustment, tax	$41	$261	($7)
Net unrealized gain on derivatives-net of tax	($132)	$204	($250)

Consolidated_Statements_Of_Equ

Consolidated Statements Of Equity (USD $)	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Accumulated Other Comprehensive Loss [Member]	Noncontrolling Interests [Member]	Total
In Thousands
BALANCE - value at Dec. 31, 2011	$6	$267,918	$24,042	$3	$568	$292,537
BALANCE - shares at Dec. 31, 2011	58,999
Share-based compensation, Value		3,081				3,081
Share-based compensation, Shares	165
Vesting of restricted stock units, including impact of shares withheld for taxes, value		-231				-231
Vesting of restricted stock units, including impact of shares withheld for taxes, shares	92
Exercise of stock options, Value		461				461
Exercise of stock options, Shares	103
Excess income tax benefit from share based compensation		189				189
Dividends declared and paid			-18,560			-18,560
Dividend equivalents paid on restricted stock units			-196			-196
Purchase of noncontrolling interests					-133	-133
Net Income (Loss) Attributable to Parent			-2,695		-645	-3,340
Other comprehensive loss-net of tax				-383		-383
BALANCE - value at Dec. 31, 2012	6	271,418	2,591	-380	-210	273,425
BALANCE - shares at Dec. 31, 2012	59,359
Share-based compensation, Value		3,251				3,251
Share-based compensation, Shares	96
Vesting of restricted stock units, including impact of shares withheld for taxes, value		-308				-308
Vesting of restricted stock units, including impact of shares withheld for taxes, shares	75
Exercise of stock options, Value		668				668
Exercise of stock options, Shares	140
Excess income tax benefit from share based compensation		154				154
Purchase of noncontrolling interests					-3	-3
Net Income (Loss) Attributable to Parent			-34,361		-632	-34,993
Other comprehensive loss-net of tax				-93		-93
BALANCE - value at Dec. 31, 2013	6	275,183	-31,770	-473	-845	242,101
BALANCE - shares at Dec. 31, 2013	59,670
Share-based compensation, Value		2,694				2,694
Share-based compensation, Shares	118
Vesting of restricted stock units, including impact of shares withheld for taxes, value		-497				-497
Vesting of restricted stock units, including impact of shares withheld for taxes, shares	111
Exercise of stock options, Value		1,568				1,568
Exercise of stock options, Shares	271					142
Excess income tax benefit from share based compensation		206				206
Purchase of noncontrolling interests		-988			845	-143
Net Income (Loss) Attributable to Parent			10,295			10,295
Other comprehensive loss-net of tax				-261		-261
BALANCE - value at Dec. 31, 2014	$6	$278,166	($21,475)	($734)		$255,963
BALANCE - shares at Dec. 31, 2014	60,170

Consolidated_Statements_Of_Equ1

Consolidated Statements Of Equity (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2012
Consolidated Statements Of Equity [Abstract]
Dividends declared per share	$0.31

Consolidated_Statements_Of_Cas

Consolidated Statements Of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
OPERATING ACTIVITIES:
Net Income (Loss) Attributable to Parent	$10,295	($34,993)	($3,340)
Income (Loss) From Discontinued Operations, Net Of Tax	-10,423	-54,850	-9,635
Income from continuing operations	20,718	19,857	6,295
Adjustments to reconcile net income to net cash flows used in operating activities:
Depreciation and amortization	50,129	46,622	37,430
Equity in (earnings) loss of joint ventures, net of cash distributions	-2,895	-1,208	-124
Cash distributions from joint ventures	19,955
Deferred income taxes	-14,504	-304	4,471
(Gain) loss on dispositions of property and equipment	732	-5,773	-198
Gain on adjustment of contingent earnout	-1,086		-240
Amortization of deferred financing fees	1,453	1,153	1,245
Gain on bargain purchase acquisition	2,197
Unrealized foreign currency (gain) loss	593	-179	208
Unrealized net (gain) loss from mark-to-market valuations of derivatives	3,029
Share-based compensation expense	2,694	3,251	3,081
Excess income tax benefit from share based compensation	-206	-154	-189
Changes in assets and liabilities:
Accounts receivable	11,012	36,260	-17,795
Contract revenues in excess of billings	-5,677	-17,142	-29,661
Inventories	120	-5,144	-2,603
Prepaid expenses and other current assets	1,780	-10,124	-1,444
Accounts payable and accrued expenses	-14,113	22,622	20,253
Billings in excess of contract revenues	-2,624	-2,900	-1,177
Other noncurrent assets and liabilities	-1,759	-490	184
Net cash flows provided by operating activities of continuing operations	67,154	86,347	19,736
Net cash flows used in by operating activities of discontinued operations	-18,352	-11,524	-21,596
Cash provided by (used in) operating activities	48,802	74,823	-1,860
INVESTING ACTIVITIES:
Purchases of property and equipment	-91,910	-66,654	-60,516
Proceeds from dispositions of property and equipment	68	6,953	597
Proceeds from (payments on) vendor performance obligations (Note 13)	-3,100	13,600
Payments for acquisitions of businesses, net of cash acquired	-27,048		-2,000
Net cash flows used in investing activities of continuing operations	-121,990	-46,101	-61,919
Net cash flows provided by (used in) investing activities of discontinued operations	5,275	-153	-1,524
Cash used in investing activities	-116,715	-46,254	-63,443
FINANCING ACTIVITIES:
Proceeds from term loan facility	47,360
Proceeds from issuance of 7 3/8% senior notes	24,880
Repayments of term loan facility	-417
Deferred financing fees	-2,532		-2,039
Repayment of long term note payable		-13,047	-2,500
Distributions paid to minority interests	205	-3	-133
Dividends paid			-18,560
Dividend equivalents paid on restricted stock units			-196
Taxes paid on settlement of vested share awards	-497	-308	-231
Purchase of noncontrolling interest	-205
Repayments of equipment debt	-235
Exercise of stock options and purchases from employee stock plans	1,568	668	461
Excess income tax benefit from share-based compensation	206	154	189
Borrowings under revolving loans	236,500	227,000
Repayments of revolving loans	-271,500	-192,000
Cash provided by (used in) financing activities of continuing operations	35,128	22,464	-23,009
Cash used in financing activities of discontinued operations			-543
Cash provided by (used in) financing activities	35,128	22,464	-23,552
Effect of foreign currency exchange rates on cash and cash equivalents	-164	-135	7
Net increase (decrease) in cash and cash equivalents	-32,949	50,898	-88,848
Cash and cash equivalents at beginning of period	75,338	24,440	113,288
Cash and cash equivalents at end of period	42,389	75,338	24,440
Supplemental Cash Flow Information
Cash paid for interest	18,901	20,083	19,462
Cash paid (refunded) for income taxes	-10,544	1,793	-4,859
Non-cash Investing and Financing Activities
Property and equipment purchased but not yet paid	10,316	3,552	7,747
Property and equipment purchased on capital leases and equipment notes	3,665
Terra [Member]
Non-cash Investing and Financing Activities
Purchase price of assets comprised of promissory notes and other liabilities			23,798
Magnus [Member]
Non-cash Investing and Financing Activities
Purchase price of assets comprised of promissory notes and other liabilities	$16,210

Nature_Of_Business_And_Summary

Nature Of Business And Summary Of Signicant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Nature Of Business And Summary Of Significant Accounting Policies [Abstract]
Nature Of Business And Summary Of Signicant Accounting Policies
		1	NATURE OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
	Organization —Great Lakes Dredge & Dock Corporation and its subsidiaries (the “Company” or “Great Lakes”) are in the business of marine construction, primarily dredging, and specialty contracting which primarily offer soil, water and sediment environmental remediation services. The Company’s primary dredging customers are domestic and foreign government agencies, as well as private entities, and its primary environmental & remediation customers are general contractors, corporations, environmental engineering and construction firms that commission projects and local government and municipal agencies.
	Principles of Consolidation and Basis of Presentation —The consolidated financial statements include the accounts of Great Lakes Dredge & Dock Corporation and its majority-owned subsidiaries. All intercompany accounts and transactions are eliminated in consolidation. The equity method of accounting is used for investments in unconsolidated investees in which the Company has significant influence, but not control. Other investments, if any, are carried at cost.
	Use of Estimates —The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (“GAAP”) requires management to make estimates and assumptions that affect certain reported amounts and disclosures. Accordingly, actual results could differ from those estimates.
	Revenue and Cost Recognition on Contracts —Substantially all of the Company’s contracts for dredging services are fixed-price contracts, which provide for remeasurement based on actual quantities dredged. The majority of the Company’s environmental & remediation contracts are also fixed-price contracts, with others performed on a time-and-materials basis. Contract revenues are recognized under the percentage-of-completion method based on the Company’s engineering estimates of the physical percentage completed for dredging projects and based on costs incurred to date compared to total estimated costs for fixed-price environmental & remediation projects. For dredging projects, costs of contract revenues are adjusted to reflect the gross profit percentage expected to be achieved upon ultimate completion. For environmental & remediation contracts, contract revenues are adjusted to reflect the estimated gross profit percentage. 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 reporting periods. Provisions for estimated losses on contracts in progress are made in the period in which such losses are determined. Change orders are not recognized in revenue until the recovery is probable and collectability is reasonably assured. Claims for additional compensation due to the Company are not recognized in contract revenues until such claims are settled. Billings on contracts are generally submitted after verification with the customers of physical progress and may 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. Modifications may be negotiated when a change from the original contract specification is encountered, and a change in project scope, performance methodology and/or material disposal is necessary. Thus, the resulting modification is considered a change in the scope of the original project to which it relates. Significant expenditures incurred incidental to major contracts are deferred and recognized as contract costs based on contract performance over the duration of the related project. These expenditures are reported as prepaid expenses.
	The components of costs of contract revenues include labor, equipment (including depreciation, maintenance, insurance and long-term rentals), subcontracts, fuel 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. Generally, capital dredging projects have the highest margins due to the complexity of the projects, while coastal protection projects have the most volatile margins because they are most often exposed to variability in weather conditions.
	The Company’s cost structure includes significant annual equipment-related costs, including depreciation, maintenance, insurance and long-term rentals. These costs have averaged approximately 22% to 23% of total costs of contract revenues over the prior three years. During the year, both equipment utilization and the timing of fixed cost expenditures fluctuate significantly. Accordingly, the Company allocates these fixed equipment costs to interim periods in proportion to revenues recognized over the year, to better match revenues and expenses. Specifically, at each interim reporting date the Company compares actual revenues earned to date on its dredging contracts to expected annual revenues and recognizes 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.
	For some environmental & remediation contracts, the Company is a 50% partner in multiple construction joint venture. The joint venture agreements provide that the Company’s interests in any profits and assets and respective share in any losses and liabilities that may result from the performance of such contracts are limited to the Company’s stated percentage partnership interest in the project. The joint venture provides that each partner will assume and pay its full proportionate share of any losses resulting from the project.
	Classification of Current Assets and Liabilities —The Company includes in current assets and liabilities amounts realizable and payable in the normal course of contract completion, unless completion of such contracts extends significantly beyond one year.
	Cash Equivalents —The Company considers all highly liquid investments with a maturity at purchase of three months or less to be cash equivalents.
	Accounts Receivable —Accounts receivable represent amounts due or billable under the terms of contracts with customers, including amounts related to retainage. The Company anticipates collection of retainage generally within one year, and accordingly presents retainage as a current asset. The Company provides an allowance for estimated uncollectible accounts receivable when events or conditions indicate that amounts outstanding are not recoverable.
	Inventories —Inventories consist of pipe and spare parts used in the Company’s dredging operations. Pipe and spare parts are purchased in large quantities; therefore, a certain amount of pipe and spare part inventories is not anticipated to be used within the current year and is classified as long-term. Inventories are stated at the lower of net realizable value or weighted average historical cost.
	Property and Equipment —Capital additions, improvements, and major renewals are classified as property and equipment and are carried at depreciated cost. Maintenance and repairs that do not significantly extend the useful lives of the assets or enhance the capabilities of such assets are charged to expenses as incurred. Depreciation is recorded over the estimated useful lives of property and equipment using the straight-line method and the mid-year depreciation convention. The estimated useful lives by class of assets are:
	Class		Useful Life (years)
	Buildings and improvements		10
	Furniture and fixtures		10-May
	Vehicles, dozers, and other light operating equipment and systems		5-Mar
	Heavy operating equipment (dredges and barges)		30-Oct
	Leasehold improvements are amortized over the shorter of their remaining useful lives or the remaining terms of the leases.
	Goodwill and Other Intangible Assets —Goodwill represents the excess of acquisition cost over fair value of the net assets acquired. Other identifiable intangible assets mainly represent developed technology and databases, customer relationships, and customer contracts acquired in business combinations and are being amortized over a one to five-year period. Goodwill is tested annually for impairment in the third quarter of each year, or more frequently should circumstances dictate. GAAP requires that goodwill of a reporting unit be tested for impairment between annual tests if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount.
	The Company assesses the fair values of its reporting units using both a market-based approach and an income-based approach. Under the income approach, the fair value of the reporting unit is based on the present value of estimated future cash flows. The income approach is dependent on a number of factors, including estimates of future market growth trends, forecasted revenues and expenses, appropriate discount rates and other variables. The estimates are based on assumptions that the Company believes to be reasonable, but such assumptions are subject to unpredictability and uncertainty. Changes in these estimates and assumptions could materially affect the determination of fair value, and may result in the impairment of goodwill in the event that actual results differ from those estimates.
	The market approach measures the value of a reporting unit through comparison to comparable companies. Under the market approach, the Company uses the guideline public company method by applying estimated market-based enterprise value multiples to the reporting unit’s estimated revenue and Adjusted EBITDA. The Company analyzed companies that performed similar services or are considered peers. Due to the fact that there are no public companies that are direct competitors, the Company weighed the results of this approach less than the income approach.
	The Company has four operating segments that, through aggregation, comprise two reportable segments: dredging and environmental & remediation, previously referred to as the demolition segment. The historical demolition business has been retrospectively presented as discontinued operations and is no longer reflected in continuing operations. Four operating segments were aggregated into two reportable segments as the segments have similarity in economic margins, services, production processes, customer types, distribution methods and regulatory environment. The Company has determined that the operating segments are the Company’s four reporting units.
	Long-Lived Assets —Long-lived assets are comprised of property and equipment and intangible assets subject to amortization. Long-lived assets to be held and used are reviewed for possible impairment whenever events indicate that the carrying amount of such assets may not be recoverable by comparing the undiscounted cash flows associated with the assets to their carrying amounts. If such a review indicates an impairment, the carrying amount would be reduced to fair value. No triggering events were identified in 2014 or 2013. If long-lived assets are to be disposed, depreciation is discontinued, if applicable, and the assets are reclassified as held for sale at the lower of their carrying amounts or fair values less estimated costs to sell.
	The Company capitalizes construction in progress and records a corresponding long-term liability for build-to-suit lease agreements where we are considered the owner during the construction period for accounting purposes. There was no build-to-suit equipment capitalized at December 31, 2014.
	Self-insurance Reserves —The Company self-insures costs associated with its seagoing employees covered by the provisions of Jones Act, workers’ compensation claims, hull and equipment liability, and general business liabilities up to certain limits. Insurance reserves are established for estimates of the loss that the Company may ultimately incur on reported claims, as well as estimates of claims that have been incurred but not yet reported. In determining its estimates, the Company considers historical loss experience and judgments about the present and expected levels of cost per claim. Trends in actual experience are a significant factor in the determination of such reserves.
	Income Taxes —The provision for income taxes includes federal, foreign, and state income taxes currently payable and those deferred because of temporary differences between the financial statement and tax basis of assets and liabilities. Recorded deferred income tax assets and liabilities are based on the estimated future tax effects of differences between the financial and tax basis of assets and liabilities, given the effect of currently enacted tax laws. The Company’s current policy is to repatriate all earnings from foreign subsidiaries’ operations as generated and at this time no amounts are considered to be permanently reinvested in those operations.
	Hedging Instruments  —At times, the Company designates certain derivative contracts as a cash flow hedge as defined by GAAP. Accordingly, the Company formally documents, at the inception of each hedge, all relationships between hedging instruments and hedged items, as well as our risk-management objective and strategy for undertaking hedge transactions. This process includes linking all derivatives to highly-probable forecasted transactions.
	The Company formally assesses, at inception and on an ongoing basis, the effectiveness of hedges in offsetting changes in the cash flows of hedged items. Hedge accounting treatment may be discontinued when (1) it is determined that the derivative is no longer highly effective in offsetting changes in the cash flows of a hedged item (including hedged items for forecasted future transactions), (2) the derivative expires or is sold, terminated or exercised, (3) it is no longer probable that the forecasted transaction will occur or (4) management determines that designating the derivative as a hedging instrument is no longer appropriate. If management elects to stop hedge accounting, it would be on a prospective basis and any hedges in place would be recognized in accumulated other comprehensive income (loss) until all the related forecasted transactions are completed or are probable of not occurring.
	Foreign Currency Translation —The financial statements of the Company’s foreign subsidiaries where the operations are primarily denominated in the foreign currency are translated into U.S. dollars for reporting. Balance sheet accounts are translated at the current foreign exchange rate at the end of each period and income statement accounts are translated at the average foreign exchange rate for each period. Gains and losses on foreign currency translations are reflected as a currency translation adjustment, net of tax, in accumulated other comprehensive income (loss). Foreign currency transaction gains and losses are included in loss on foreign currency transactions—net.
	Noncontrolling Interest —On January 1, 2009 the Company acquired a 65% interest in Yankee Environmental Services, LLC (“Yankee”). On April 23, 2014, the Company entered into and completed the sale of NASDI, LLC and Yankee, its two former subsidiaries that comprised the historical demolition business. As a result of the sale, the Company purchased the noncontrolling interest related to the membership interest the Company did not own in Yankee. Noncontrolling interest at December 31, 2013 is related to the membership interest the Company did not own in Yankee.
	Recent Accounting Pronouncements —In May 2014, the Financial Accounting Standards Board issued Accounting Standard Update No. 2014-09 (“ASU 2014-09”), Revenue from Contracts with Customers (Topic 606), which supersedes the existing revenue recognition requirements. ASU 2014-09 is based on the principle that revenue is recognized to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASU 2014-09 is effective for fiscal years beginning after December 15, 2016, including interim periods within that reporting period, which will be our first quarter of fiscal 2017. Early adoption is not permitted. We are currently evaluating the impact of ASU 2014-09 on our consolidated financial statements.

Earnings_Per_Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Earnings Per Share
	2. EARNINGS PER SHARE
	Basic earnings per share is computed by dividing net income attributable to common stockholders by the weighted-average number of common shares outstanding during the reporting period. Diluted earnings per share is computed similar to basic earnings per share except that it reflects the potential dilution that could occur if dilutive securities or other obligations to issue common stock were exercised or converted into common stock. For the year ended December 31, 2014, 540 shares of stock options (“NQSO”) and restricted stock units (“RSU”) were excluded from the calculation of diluted earnings per share based on the application of the treasury stock method, as such NQSOs and RSUs were determined to be anti-dilutive. For the years ended December 31, 2013 and 2012,  no shares of NQSOs and RSUs were excluded from the calculation of diluted earnings per share based on the application of the treasury stock method.
	The computations for basic and diluted earnings per share for the years ended December 31, 2014,  2013 and 2012 are as follows:
	(shares in thousands)
		2014		2013		2012
	Income from continuing operations	$	20,718	$	19,857	$	6,295
	Loss on discontinued operations, net of income taxes, attributable to Great Lakes Dredge & Dock Corporation		-10,423		-54,218		-8,990
	Net income (loss) attributable to common stockholders of Great Lakes Dredge & Dock Corporation		10,295		-34,361		-2,695
	Weighted-average common shares outstanding — basic		59,938		59,495		59,195
	Effect of stock options and restricted stock units		584		606		478
	Weighted-average common shares outstanding — diluted		60,522		60,101		59,673
	Earnings per share from continuing operations — basic	$	0.35	$	0.33	$	0.11
	Earnings per share from continuing operations — diluted	$	0.34	$	0.33	$	0.11

Restricted_And_Escrowed_Cash

Restricted And Escrowed Cash	12 Months Ended
	Dec. 31, 2014
Restricted And Escrowed Cash [Abstract]
Restricted And Escrowed Cash
		3.	RESTRICTED AND ESCROWED CASH
	At December 31, 2014 and 2013, other noncurrent assets include $1,500 of cash held in escrow as security for the Company’s lease rental obligation under a long-term equipment operating lease.
	At December 31, 2014, other current assets include $2,314 of cash held in escrow related to an outstanding lawsuit at our historical demolition business. This same balance was classified as assets held for sale at December 31, 2013.
	At December 31, 2013 the Company held cash and cash equivalents of $2,750 in an escrow account related to its sale of a vessel included in other noncurrent assets.

Accounts_Receivable_And_Contra

Accounts Receivable And Contracts In Progress	12 Months Ended
	Dec. 31, 2014
Accounts Receivable And Contracts In Progress [Abstract]
Accounts Receivables And Contracts In Progress
	4.   ACCOUNTS RECEIVABLE AND CONTRACTS IN PROGRESS
	Accounts receivable at December 31, 2014 and 2013 are as follows:
		2014		2013
	Completed contracts	$	15,342	$	17,361
	Contracts in progress		72,459		62,177
	Retainage		27,371		18,506
			115,172		98,044
	Allowance for doubtful accounts		-578		-1,529
	Total accounts receivable—net	$	114,594	$	96,515
	Current portion of accounts receivable—net	$	113,188	$	96,515
	Long-term accounts receivable and retainage		1,406		-
	Total accounts receivable—net	$	114,594	$	96,515
	The components of contracts in progress at December 31, 2014 and 2013 are as follows:
		2014		2013
	Costs and earnings in excess of billings:
	Costs and earnings for contracts in progress	$	833,368	$	435,470
	Amounts billed		-759,877		-370,730
	Costs and earnings in excess of billings for contracts in progress		73,491		64,740
	Costs and earnings in excess of billings for completed contracts		9,066		2,692
	Total contract revenues in excess of billings	$	82,557	$	67,432
	Billings in excess of costs and earnings:
	Amounts billed	$	-181,698	$	-156,794
	Costs and earnings for contracts in progress		177,059		150,040
	Total billings in excess of contract revenues	$	-4,639	$	-6,754

Property_And_Equipment

Property And Equipment	12 Months Ended
	Dec. 31, 2014
Property And Equipment [Abstract]
Property And Equipment
		5	PROPERTY AND EQUIPMENT
	Property and equipment at December 31, 2014 and 2013 are as follows:
			2014		2013
	Land		$	9,220	$	9,220
	Buildings and improvements			5,729		4,124
	Furniture and fixtures			8,863		6,477
	Operating equipment			698,977		602,395
	Total property and equipment			722,789		622,216
	Accumulated depreciation			-323,344		-276,595
	Property and equipment — net		$	399,445	$	345,620
	No assets were classified as held for sale at December 31, 2014. Operating equipment of $1,704 was classified as held for sale at December 31, 2013.
	Depreciation expense was $48,569, $45,531 and $37,249, for the years ended December 31, 2014,  2013 and 2012, respectively.

Goodwill_And_Other_Intangible_

Goodwill And Other Intangible Assets	12 Months Ended
	Dec. 31, 2014
Goodwill And Other Intangible Assets [Abstract]
Goodwill And Other Intangible Assets
		6.	GOODWILL AND OTHER INTANGIBLE ASSETS
	The Company’s annual goodwill impairment test is conducted in the third quarter of each year and interim evaluations are performed when the Company determines that a triggering event has occurred that would more likely than not reduce the fair value of goodwill below its carrying value. The Company performed its most recent annual test of impairment as of July 1, 2014 for the goodwill at the remaining reporting units with no indication of goodwill impairment as of the test date. The Company will perform its next scheduled annual test of goodwill in the third quarter of 2015 should no triggering events occur which would require a test prior to the next annual test.
	The change in the carrying amount of goodwill during the years ended December 31, 2014 and 2013 is as follows:
			Dredging Segment		Environmental & Remediation Segment		Total
	Balance - January 1, 2013		$	76,575	$	2,751	$	79,326
	Balance - December 31, 2013			76,575		2,751		79,326
	Acquisition of Magnus Pacific			-		7,000		7,000
	Balance - December 31, 2014		$	76,575	$	9,751	$	86,326
	At December 31, 2014 and 2013, the net book value of identifiable intangible assets was as follows:
	As of December 31, 2014		Cost		Accumulated Amortization		Net
	Non-compete agreements		$	3,085	$	940	$	2,145
	Customer relationships			51		34		17
	Acquired backlog			6,278		1,395		4,883
	Trade names			1,037		185		852
	Other			1,306		240		1,066
			$	11,757	$	2,794	$	8,963
	As of December 31, 2013
	Non-compete agreements		$	1,646	$	544	$	1,102
	Acquired backlog			627		502		125
	Trade names			411		82		329
	Other			526		106		420
			$	3,210	$	1,234	$	1,976
	On November 4, 2014, the Company acquired the assets of Magnus Pacific Corporation resulting in recognition of additional intangible assets and goodwill. The weighted average amortization period for intangible assets acquired in 2014 is 2.07 years.
	Amortization expense was $1,560, $1,091 and $181, for the years ended December 31, 2014,  2013 and 2012, respectively, and is included as a component of general and administrative expenses. Amortization expense related to intangible assets is estimated to be $6,055 in 2015, $1,045 in 2016,  $1,045 in 2017,  $579 in 2018 and $238 in 2019.

Accrued_Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2014
Accrued Expenses [Abstract]
Accrued Expenses	7.   ACCRUED EXPENSES
	Accrued expenses at December 31, 2014 and 2013 are as follows:
		2014		2013
	Insurance	$	16,778	$	8,649
	Accumulated deficit in joint venture		10,383		-
	Payroll and employee benefits		8,808		13,664
	Interest		8,270		8,066
	Income and other taxes		5,857		3,709
	Fuel hedge contracts		3,029		-
	Percentage of completion adjustment		1,870		2,135
	Other		15,046		2,308
	Total accrued expenses	$	70,041	$	38,531

LongTerm_Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2014
Long-Term Debt [Abstract]
Long-Term Debt
	8.   LONG-TERM DEBT
	Long-term debt at December 31, 2014 and 2013 is as follows:
		2014		2013
	Revolving credit facility	$	-	$	35,000
	Equipment notes payable		2,857		-
	Notes payable		54,620		-
	7.375% senior notes		274,880		250,000
	Subtotal		332,357		285,000
	Current portion of equipment note payable		-736		-
	Current portion of note payable		-5,123		-
	Capital leases (included in other long term liabilities)		-2,121		-
	Total	$	324,377	$	285,000
	Credit agreement
	On June 4, 2012, the Company entered into a senior revolving credit agreement (the “Credit Agreement”) with certain financial institutions from time to time party thereto as lenders, Wells Fargo Bank, National Association, as Administrative Agent, Swingline Lender and an Issuing Lender, Bank of America, N.A., as Syndication Agent and PNC Bank, National Association, BMO Harris Bank N.A. and Fifth Third Bank, as Co-Documentation Agents. The Credit Agreement, as subsequently amended, provides for a senior revolving credit facility in an aggregate principal amount of up to $210,000, multicurrency borrowings up to a $50,000 sublimit and swingline loans up to a $10,000 sublimit. The Credit Agreement also includes an incremental loans feature that will allow the Company to increase the senior revolving credit facility by an aggregate principal amount of up to $15,000. This is subject to lenders providing incremental commitments for such increase, provided that no default or event of default exists, and the Company being in pro forma compliance with the existing financial covenants, both before and after giving effect to the increase, and subject to other standard conditions. The Credit Agreement is secured by a substantial portion of the Company’s operating equipment with a net book value at December 31, 2014 of $162,037.
	On September 15, 2014, the Company entered into the fifth amendment (the “Fifth Amendment”) to the Credit Agreement which exercised a portion of the incremental loans feature of the Credit Agreement that allowed the Company to increase the aggregate revolving commitment. The Fifth Amendment further amended the Credit Agreement so that the Credit Agreement will remain secured and collateralized by perfected liens on certain of the Company’s vessels and its domestic accounts receivable, subject to permitted liens and prior interests of other parties. In addition, Zurich American Insurance Company, the Company’s surety provider, secured permitted second mortgages on the same vessels securing the obligations under the Credit Agreement.
	On November 4, 2014, the Company entered into the sixth amendment (“Sixth Amendment”) to the Credit Agreement permitting the entrance into the Term Loan Facility (as defined below) and incurrence of liens securing the Term Loan Facility, subject to certain restrictions and conditions; permit voluntary prepayments of the Term Loan Facility so long as, after giving effect to any such voluntary prepayment, the Company’s total leverage ratio is less than or equal to 3.00 to 1.00 and its fixed charge coverage ratio is greater than or equal to 1.25 to 1.00; permit the acquisition of Magnus Pacific Corporation (See Note 16) without diminishing the amount currently available under the Credit Agreement for additional “Permitted Acquisitions” (as defined in the Credit Agreement); exclude the potential earnout obligation of the Company in connection with the acquisition of Magnus Pacific Corporation of up to $11.4 million from “Indebtedness” (as defined in the Credit Agreement) and the total leverage ratio under the Credit Agreement; and permit the issuance of up to an additional $50 million in aggregate principal amount of the Company’s currently outstanding 7.375% senior notes due 2019.
	Depending on the Company’s consolidated leverage ratio (as defined in the Credit Agreement), borrowings under the amended revolving credit facility will bear interest at the option of the Company at either a LIBOR rate plus a margin of between 1.50% to 2.50% per annum or a base rate plus a margin of between 0.50% to 1.50% per annum.
	The amended credit facility contains affirmative, negative and financial covenants customary for financings of this type. 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 provider. The Credit Agreement requires the Company to maintain a net leverage ratio less than or equal to 4.50 to 1.00 as of the end of each fiscal quarter and a minimum fixed charge coverage ratio of 1.25 to 1.00. The obligations of Great Lakes under the Credit Agreement are 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. As of December 31, 2014, the Company had no borrowings and $159,913 of letters of credit outstanding, resulting in $50,087 of availability under the Credit Agreement. At December 31, 2014, the Company was in compliance with its various financial covenants under its Credit Agreement.
	On September 15, 2014, the Company terminated its $24,000 international letter of credit facility with Wells Fargo Bank, National Association, as successor by merger to Wells Fargo HSBC Trade Bank, as amended. On the date of termination, there were no letters of credit or other indebtedness outstanding under this facility, and the loan documents providing for the facility, and the liens and security interests securing it, were terminated and released.
	Term loan facility
	On November 4, 2014, the Company entered into a new senior secured term loan facility consisting of a term loan in an aggregate principal amount of $50,000 (the “Term Loan Facility”) pursuant to a Loan and Security Agreement (the “Loan Agreement”) by and among, the lenders party thereto from time to time and Bank of America, N.A., as administrative agent. Pursuant to the term loan, the Company borrowed an aggregate principal amount of $47,360. The proceeds from the Term Loan Facility will be used for the working capital and general corporate purposes of the Company, including to repay borrowings under the Credit Agreement made to finance the construction of the Company’s dual mode articulated tug/barge trailing suction hopper dredge.
	The Term Loan Facility has a term of 5 years. The borrowings under the Term Loan Facility bear interest at a fixed rate of 4.655% per annum. If an event of default occurs under the Loan Agreement, the interest rate will increase by 2.00% per annum during the continuance of such event of default.
	The Term Loan Facility provides for monthly amortization payments, payable in arrears, commencing on December 4, 2014, at an annual amount of (i) approximately 10% of the principal amount of the Term Loan Facility during the first two years of the term, (ii) approximately 20% of the principal amount of the Term Loan Facility during the third and fourth years of the term, and (iii) approximately 25% of the principal amount of the Term Loan Facility during the final year of the term, with the remainder due on the maturity date of the facility. In addition, the Company has usual and customary mandatory prepayment provisions and may optionally prepay the Term Loan Facility in whole or in part at any time, subject to a minimum prepayment amount.
	The Loan Agreement includes customary representations, affirmative and negative covenants and events of default for financings of this type and includes the same financial covenants that are currently set forth in the Credit Agreement. The Term Loan Facility is secured by a portion of the Company’s operating equipment with a net book value at December 31, 2014 of $50,572.
	Senior notes
	The Company has outstanding $275,000 of 7.375% senior notes due February 2019. In January 2011, the Company issued $250,000 of senior notes and in November 2014 added $25,000 of senior notes. The total balance outstanding for all senior notes at December 31, 2014 was $274,879, based on the discounted issuance of the November 2014 notes. As of February 1, 2015, there is an optional redemption on all notes. The redemption prices are 103.7% in 2015, 101.8% in 2016 and 100% in any year following, until the notes mature in 2019. Interest is paid semi-annually and principal is due at maturity.
	Other
	In conjunction with the acquisition of Magnus Pacific Corporation (See Note 16), the Company issued a secured promissory note with a fair market value of $8,100 to the former owners of Magnus which had terms that could reduce the amount owed based on minimum EBITDA expectations for 2014. The Promissory Note fair value decreased by $1,086 based on adjustments made that have impacted the final Magnus full year pro forma EBITDA in 2014. The secured promissory note accrues interest at a rate of 5% per annum and is due in equal installments on January 1, 2017 and 2018.
	The scheduled principal payments through the maturity date of the Company’s long-term debt, excluding equipment notes and capital leases, at December 31, 2014, are as follows:
	Years Ending December 31
	2015	$	5,000
	2016		5,417
	2017		13,772
	2018		13,980
	2019		291,318
	Thereafter		-
	Total	$	329,487
	The Company incurred amortization of deferred financing fees for its long term debt of $1,453, $1,153 and $1,245 for each of the years ended December 31, 2014,  2013 and 2012. Such amortization is recorded as a component of interest expense.

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2014
Fair Value Measurements [Abstract]
Fair Value Measurements	9.   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, commodity price risk or interest rate risk. The Company does not hold or issue derivatives for speculative or trading purposes. The fair values of these financial instruments are summarized as follows:
						Fair Value Measurements at Reporting Date Using
	Description	At  December 31, 2014			Quoted Prices in Active Markets for Identical Assets (Level 1)			Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (Level 3)
	Fuel hedge contracts	$	3,029		$	-		$	3,029		$	-
						Fair Value Measurements at Reporting Date Using
	Description	At  December 31, 2013			Quoted Prices in Active Markets for Identical Assets (Level 1)			Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (Level 3)
	Fuel hedge contracts	$	332		$	-		$	332		$	-
	Interest rate swap contracts
	In May 2009, the Company entered into two interest rate swap arrangements, which were effective through December 15, 2012, to swap a notional amount of $50 million from a fixed rate of 7.75% to a floating LIBOR-based rate in order to manage the interest rate paid with respect to the Company’s 7.75% senior subordinated notes. Although the senior subordinated notes were redeemed in January 2011, the swaps remained in place. The swaps were not accounted for as a hedge; therefore, the changes in fair value were recorded as adjustments to interest expense in each reporting period. The swaps expired and were settled in December 2012.
	Foreign exchange contracts
	The Company has various exposures to foreign currencies that fluctuate in relation to the U.S. dollar. The Company periodically enters into foreign exchange forward contracts to hedge this risk. At December 31, 2014 and 2013 there were no outstanding contracts.
	Fuel hedge contracts
	The Company is exposed to certain market risks, primarily commodity price risk as it relates to the diesel fuel purchase requirements, which occur in the normal course of business. The Company enters into heating oil commodity swap contracts to hedge the risk that fluctuations in diesel fuel prices will have an adverse impact on cash flows associated with its domestic dredging contracts. The Company’s goal is to hedge approximately 80% of the fuel requirements for work in domestic backlog.
	As of December 31, 2014, 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 2015. As of December 31, 2014, there were 4.9 million gallons remaining on these contracts which represent approximately 80% of the Company’s forecasted domestic fuel purchases through September 2015. Under these swap agreements, the Company will pay fixed prices ranging from $2.08 to $3.01 per gallon.
	At December 31, 2014, the fair value liability of the fuel hedge contracts was estimated to be $3,029 and is recorded in accrued expenses. At December 31, 2013, the fair value asset of the fuel hedge contracts was estimated to be $332 and was recorded in other current assets. The gain reclassified to earnings from changes in fair value of derivatives, net of cash settlements and taxes, for the year ended December 31, 2014 was $332. 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 December 31, 2014 and 2013 is as follows:
		Balance Sheet Location		Fair Value at December 31,
				2014			2013
	Asset derivatives:
	Derivatives designated as hedges
	Fuel hedge contracts	Other current assets		$	-		$	332
	Liability derivatives:
	Derivatives not designated as hedges
	Fuel hedge contracts	Accrued expenses		$	3,029		$	-
	Accumulated other comprehensive loss
	Changes in the components of the accumulated balances of other comprehensive income are as follows:
				2014			2013			2012
	Cumulative translation adjustments—net of tax			$	-62		$	-397		$	-6
	Derivatives:
	Reclassification of derivative losses (gains) to earnings—net of tax				-332			270			3
	Change in fair value of derivatives—net of tax				133			34			-380
	Net unrealized (gain) loss on derivatives—net of tax				-199			304			-377
	Total other comprehensive loss			$	-261		$	-93		$	-383
	Adjustments reclassified from accumulated balances of other comprehensive income to earnings are as follows:
		Statement of Operations Location		2014			2013			2012
	Derivatives:
	Fuel hedge contracts	Costs of contract revenues		$	-286		$	450		$	5
		Income tax benefit			46			180			2
				$	-332		$	270		$	3
	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 senior revolving credit agreement approximates fair value. The Company entered into a senior secured term loan facility in November 2014 that approximates fair value based upon stable market interest rates and Company credit ratings from inception to year end.  In January 2011 and again in November 2014, the Company issued a total of $275,000 of 7.375% senior notes due February 1, 2019, which were outstanding at December 31, 2014 (See Note 8). The senior notes are senior unsecured obligations of the Company and its subsidiaries that guarantee the senior notes. The fair value of the senior notes was $280,500 at December 31, 2014, which is a Level 1 fair value measurement as the senior notes value was obtained using quoted prices in active markets.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Taxes [Abstract]
Income Taxes
		10	INCOME TAXES
	The Company’s income tax (provision) benefit from continuing and discontinued operations for the years ended December 31, 2014,  2013 and 2012 is as follows:
			2014		2013		2012
	Income tax (provision) benefit from continuing operations		$	11,530	$	-10,460	$	-5,419
	Income tax benefit from discontinued operations			8,744		19,116		7,490
	Income tax (provision) benefit		$	20,274	$	8,656	$	2,071
	The Company’s pre- tax income (loss) from domestic and foreign continuing operations for the years ended December 31, 2014,  2013 and 2012 is as follows:
			2014		2013		2012
	Domestic operations		$	-20,823	$	23,716	$	15,884
	Foreign operations			30,011		6,601		-4,170
	Total pre-tax income		$	9,188	$	30,317	$	11,714
	The provision (benefit) for income taxes from continuing operations as of December 31, 2014,  2013 and 2012 is as follows:
			2014		2013		2012
	Federal:
	Current		$	-174	$	8,384	$	859
	Deferred			-9,531		2,107		1,948
	State:
	Current			277		439		156
	Deferred			-3,577		-326		481
	Foreign:
	Current			1,475		1,831		-
	Deferred			-		-1,975		1,975
	Total		$	-11,530	$	10,460	$	5,419
	The Company’s income tax provision from continuing operations reconciles to the provision at the statutory U.S. federal income tax rate of 35% for the years ended December 31, 2014,  2013 and 2012  as follows:
			2014		2013		2012
	Tax provision at statutory U.S. federal
	income tax rate		$	3,214	$	10,611	$	4,100
	State income tax — net of federal income tax benefit			-2,726		500		245
	Worthless stock deduction			-9,631		-		-
	Charitable contributions			-1,764		-		-
	Adjustment to deferred tax depreciation			-1,670		-		-
	Change in deferred state tax rate			-811		-		246
	Research and development tax credits			-691		-		-
	Purchase price adjustment			-393		-		-
	Foreign income tax provision			-		238		-
	Changes in unrecognized tax benefits			127		-196		-137
	Changes in valuation allowance			2,246		-500		228
	Other			569		-193		737
	Income tax provision (benefit)		$	-11,530	$	10,460	$	5,419
	During the fourth quarter of 2014, the Company liquidated one of its domestic subsidiaries which allowed it to claim a worthless stock deduction on its federal income tax return. The Company recorded an income tax benefit of $9,631 related to the worthless stock deduction. The Company utilized part of the benefit to offset current year income and will carry forward the remainder as a net operating loss to offset future income. Accordingly, this benefit is characterized as a component of our continuing operations.
	In 2014, an entity 50% owned by the Company sold property to a third party and as part of the transaction donated adjacent property to a municipality. The fair market value of the donated property in excess of cost resulted in a benefit of $1,764 to the Company in 2014.
	At December 31, 2014 and 2013, the Company had loss carryforwards for federal income tax purposes of $55,328 and $10,443 respectively, which expire between 2034 and 2035.
	At December 31, 2014 and 2013, the Company had gross net operating loss carryforwards for state income tax purposes totaling $105,458 and $37,537, respectively, which expire between 2023 and 2034.
	The Company also has foreign gross net operating loss carryforwards of approximately $13,039 and $7,194 as of December 31, 2014 and 2013, which expire between 2015 and 2034. At December 31, 2014 and 2013, a full valuation allowance has been established for the deferred tax asset of $4,334 and $2,505 related to foreign net operating loss carryforwards, respectively, as the Company believes it is more likely than not that the net operating loss carryforwards will not be realized.
	As of December 31, 2014 and 2013, the Company had $442 and $253, respectively, in unrecognized tax benefits, the recognition of which would have an impact of $287 and $164 on the effective tax rate.
	The Company does not expect that total unrecognized tax benefits will significantly increase or decrease within the next 12 months. Below is a tabular reconciliation of the total amounts of unrecognized tax benefits at the beginning and end of each period.
			2014		2013		2012
	Unrecognized tax benefits — January 1		$	253	$	471	$	633
	Gross increases — tax positions in prior period			-		-		79
	Gross increases — current period tax positions			270		42		80
	Gross decreases — expirations			-65		-201		-321
	Gross decreases — tax positions in prior period			-16		-59		-
	Unrecognized tax benefits — December 31,		$	442	$	253	$	471
	The Company’s policy is to recognize interest and penalties related to income tax matters in income tax expense. As of December 31, 2014 and 2013, the Company had approximately $24 and $18, respectively, of interest and penalties recorded.
	The Company files income tax returns at the U.S. federal level and in various state and foreign jurisdictions. U.S. federal income tax years prior to 2011 are closed and no longer subject to examination. The Company’s 2011 and 2012 U.S. federal income tax returns are currently under examination by the Internal Revenue Service. At this time, no material adjustments are expected to result from the examinations. With few exceptions, the statute of limitations in state taxing jurisdictions in which the Company operates has expired for all years prior to 2010. In foreign jurisdictions in which the Company operates, years prior to 2011 are closed and are no longer subject to examination.
	The Company’s deferred tax assets (liabilities) at December 31, 2014 and 2013 are as follows:
			2014		2013
	Deferred tax assets:
	Accrued liabilities		$	13,288	$	9,427
	Federal NOLs			19,365		-
	Foreign NOLs			4,334		2,505
	State NOLs			4,752		1,599
	Tax credit carryforwards			4,651		2,486
Charitable contribution			1,764		-
Valuation allowance			-6,579		-2,505
Total deferred tax assets			41,575		13,512
Deferred tax liabilities:
Depreciation and amortization			-117,286		-115,542
Other liabilities			-1,811		-
Fuel hedges			-		-132
Total deferred tax liabilities			-119,097		-115,674
Net deferred tax liabilities		$	-77,522		-102,162
As reported in the balance sheet:
Net current deferred tax assets (included in other current assets)		$	14,485		6,349
Net noncurrent deferred tax liabilities			-92,007		-108,511
Net deferred tax liabilities		$	-77,522		-102,162
Deferred tax assets relate primarily to reserves and other liabilities for costs and expenses not currently deductible for tax purposes as well as net operating loss and other carryforwards. Deferred tax liabilities relate primarily to the cumulative difference between book depreciation and amounts deducted for tax purposes. With the exception of certain state and foreign net operating loss carryforwards, a valuation allowance has not been recorded to reduce the balance of deferred tax assets at either December 31, 2014, or  December 31, 2013, because the Company believes that it is more likely than not that the deferred income tax assets will ultimately be realized.

ShareBased_Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2014
Share-Based Compensation
Share-Based Compensation	11.   SHARE-BASED COMPENSATION
	The Company’s 2007 Long-Term Incentive Plan (“Incentive Plan”) permits the granting of stock options, stock appreciation rights, restricted stock and restricted stock units to its employees and directors for up to 5,800 shares of common stock. The Company also issues share-based compensation as inducement awards to new employees upon approval of the Board of Directors.
	Compensation cost charged to expense related to share-based compensation arrangements was $2,694,  $3,251 and $3,081, for the years ended December 31, 2014, 2013 and 2012, respectively.
	Non-qualified stock options
	The NQSO awards were granted with an exercise price equal to the market price of the Company’s common stock at the date of grant. The option awards generally vest in three equal annual installments commencing on the first anniversary of the grant date, and have ten year exercise periods.
	The fair value of the NQSOs was determined at the grant date using a Black-Scholes option pricing model, which requires the Company to make several assumptions. The risk-free interest rate is based on the U.S. Treasury yield curve in effect for the expected term of the option at the time of grant. The annual dividend yield on the Company’s common stock is based on estimates of future dividends during the expected term of the NQSOs. The expected life of the NQSOs was determined from historical exercise data providing a reasonable basis upon which to estimate the expected life. For grants issued in 2014,  2013 and 2012, the volatility assumptions were based on historical volatility of Great Lakes. There is not an active market for options on the Company’s common stock and, as such, implied volatility for the Company’s stock was not considered. Additionally, the Company’s general policy is to issue new shares of registered common stock to satisfy stock option exercises or grants of restricted stock.
	The weighted-average grant-date fair value of options granted during the years ended December 31, 2014,  2013 and 2012 was $4.23, $4.06 and $2.93 respectively. The fair value of each option was estimated using the following assumptions:
			2014		2013		2012
	Expected volatility		53.9%		58.2%		55.0%
	Expected dividends		0.0%		0.0%		1.3%
	Expected term (in years)		7.0		6.0		5.5 - 6.5
	Risk free rate		1.9%		1.0%		0.7% - 1.0%
	A summary of stock option activity under the Incentive Plan as of December 31, 2014, and changes during the year ended December 31, 2014, is presented below:
	Options	Shares		Weighted Average Exercise Price		Weighted-Average Remaining Contract Term (yrs)		Aggregate Intrinsic Value ($000's)
	Outstanding as of January 1, 2014		1,912	$	6.00
	Granted		337		7.62
	Exercised		-142		5.47
	Forfeited or Expired		-218		6.15
	Outstanding as of December 31, 2014		1,889	$	6.31		6.8	$	4,255
	Vested at December 31, 2014		1,204	$	5.70		5.8	$	3,446
	Vested or expected to vest at December 31, 2014		1,882	$	6.30		6.8	$	4,246
	Restricted stock units
	RSUs generally vest in one installment on the third anniversary of the grant date. The fair value of RSUs was based upon the Company’s stock price on the date of grant. A summary of the status of the Company’s non-vested RSUs as of December 31, 2014, and changes during the year ended December 31, 2014, is presented below:
	Nonvested Restricted Stock Units	Shares		Weighted-Average Grant-Date Fair Value
	Outstanding as of January 1, 2014		591	$	6.43
	Granted		1,741		6.89
	Vested		-174		5.43
	Forfeited		-95		6.29
	Outstanding as of December 31, 2014		2,063	$	6.91
	Expected to vest at December 31, 2014		925	$	7.07
	As of December 31, 2014, there was $6,480 of total unrecognized compensation cost related to non-vested NQSOs and RSUs granted under the Plan. That cost is expected to be recognized over a weighted-average period of 1.9 years.
	The Incentive Plan permits the employee to use vested shares from RSUs to satisfy the grantee’s U.S. federal income tax liability resulting from the issuance of the shares through the Company’s retention of that number of common shares having a market value as of the vesting date equal to such tax obligation up to the minimum statutory withholding requirements. The amount related to shares used for such tax withholding obligations was approximately $497 and  $308 for the years ended December 31, 2014 and 2013, respectively.
	Director compensation
	The Company uses a combination of cash and share-based compensation to attract and retain qualified candidates to serve on our Board of Directors. Compensation is paid to non-employee directors. Directors who are employees receive no additional compensation for services as members of the Board or any of its committees. All of our directors are non-employee directors with the exception of Mr. Berger. Share-based compensation is paid pursuant to the Incentive Plan. Each non-employee director of the Company received an annual retainer of $155, payable quarterly in arrears, and was paid 50% in cash and 50% in common stock of the Company. The Chairman of the Board received an additional $250 of compensation, paid in stock.
	In the years ended December 31, 2014, 2013 and 2012,  99 thousand, 96 thousand and 93 thousand shares, respectively, of the Company’s common stock were issued to non-employee directors under the Incentive Plan.

Retirement_Plans

Retirement Plans	12 Months Ended
	Dec. 31, 2014
Retirement Plans [Abstract]
Retirement Plans
		12	RETIREMENT PLANS
	The Company sponsors four 401(k) savings plans, one covering substantially all non-union salaried employees (“Salaried Plan”), a second covering its hourly employees (“Hourly Plan”), a third plan specifically for its employees that are members of a tugboat union and a fourth for the salary and non-union employees of certain subsidiaries (“Affiliated Plan”). Under the Salaried Plan, the Hourly Plan and the Affiliated Plan, individual employees may contribute a percentage of compensation and the Company will match a portion of the employees’ contributions. The Salaried Plan and Affiliated Plan also includes a profit-sharing component, permitting the Company to make discretionary employer contributions to all eligible employees of these plans. Additionally, the Company sponsors a Supplemental Executive Retirement Plan (“SERP”) in which the Company makes contributions for certain key executives. The Company’s expense for matching, discretionary and SERP contributions for  2014,  2013 and 2012, was $5,256, $5,123 and $4,017, respectively.
	The Company also contributes to various multiemployer pension plans pursuant to collective bargaining agreements. In 2014, 2013 and 2012, the Company contributed $4,383,  $3,870 and $3,447 respectively to all of the multiemployer plans that provide pension benefits in our continuing operations. The information available to the Company about the multiemployer plans in which it participates, whether via request to the plan or publicly available, is generally dated due to the nature of the reporting cycle of multiemployer plans and legal requirements under the Employee Retirement Income Security Act (“ERISA”) as amended by the Multiemployer Pension Plan Amendments Act (“MPPAA”). Based upon these plans’ most recently available annual reports, the Company’s contribution to these plans were less than 5% of each such plan’s total contributions.
	The Company does not expect any future increased contributions to have a material negative impact on its financial position, results of operations or cash flows for future years. The risks of participating in multiemployer plans are different from single employer plans as assets contributed are available to provide benefits to employees of other employers and unfunded obligations from an employer that discontinues contributions are the responsibility of all remaining employers. In addition, in the event of a plan’s termination or the Company’s withdrawal from a plan, the Company may be liable for a portion of the plan’s unfunded vested benefits. However, information from the plans’ administrators is not available to permit the Company to determine its share, if any, of unfunded vested benefits.

Commitments_And_Contingencies

Commitments And Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments And Contingencies [Abstract]
Commitments And Contingencies	13.   COMMITMENTS AND CONTINGENCIES
	Commercial commitments
	Performance and bid bonds are customarily required for dredging and marine construction projects, as well as some demolition projects. The Company has a bonding agreement with Zurich American Insurance Company (“Zurich”) under which the Company can obtain performance, bid and payment bonds. The Company also has outstanding bonds with Travelers Casualty and Surety Company of America. Bid bonds are generally obtained for a percentage of bid value and amounts outstanding typically range from $1,000 to $10,000. At December 31, 2014, the Company had outstanding performance bonds with a notional amount of approximately $1,049,311, of which $49,048 relates to projects accounted for in discontinued operations. The revenue value remaining in backlog related to the projects of continuing operations totaled approximately $357,409.
	In connection with the sale of our historic 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.
	Certain foreign projects performed by the Company have warranty periods, typically spanning no more than one to three years beyond project completion, whereby the Company retains responsibility to maintain the project site to certain specifications during the warranty period. Generally, any potential liability of the Company is mitigated by insurance, shared responsibilities with consortium partners, and/or recourse to owner-provided specifications.
	Legal proceedings and other contingencies
	As is customary with negotiated contracts and modifications or claims to competitively bid contracts with the federal government, the government has the right to audit the books and records of the Company to ensure compliance with such contracts, modifications, or claims, and the applicable federal laws. The government has the ability to seek a price adjustment based on the results of such audit. Any such audits have not had, and are not expected to have, a material impact on the financial position, operations, or cash flows of the Company.
	Various legal actions, claims, assessments and other contingencies arising in the ordinary course of business are pending against the Company and certain of its subsidiaries. These matters are subject to many uncertainties, and it is possible that some of these matters could ultimately be decided, resolved, or settled adversely to the Company. Although the Company is subject to various claims and legal actions that arise in the ordinary course of business, except as described below, the Company is not currently a party to any material legal proceedings or environmental claims. The Company records an accrual when it is probable a liability has been incurred and the amount of loss can be reasonably estimated. The Company does not believe any of these proceedings, individually or in the aggregate, would be expected to have a material effect on results of operations, cash flows or financial condition.
	On March 19, 2013, the Company and three of its current and former executives were sued in a securities class action in the Northern District of Illinois captioned United Union of Roofers, Waterproofers & Allied Workers Local Union No. 8 v. Great Lakes Dredge & Dock Corporation et al., Case No. 1:13-cv-02115. The lawsuit, which was brought on behalf of all purchasers of the Company’s securities between August 7, 2012 and March 14, 2013, primarily alleges that the defendants made false and misleading statements regarding the recognition of revenue in the demolition segment and with regard to the Company’s internal control over financial reporting. This suit was filed following the Company’s announcement on March 14, 2013 that it would restate its second and third quarter 2012 financial statements. Two additional, similar lawsuits captioned Boozer v. Great Lakes Dredge & Dock Corporation et al., Case No. 1:13-cv-02339, and Connors v. Great Lakes Dredge & Dock Corporation et al., Case No. 1:13-cv-02450, were filed in the Northern District of Illinois on March 28, 2013, and April 2, 2013, respectively. These three actions were consolidated and recaptioned In re Great Lakes Dredge & Dock Corporation Securities Litigation, Case No. 1:13-cv-02115, on June 10, 2013. The plaintiffs filed an amended class action complaint on August 9, 2013, which the defendants moved to dismiss on October 8, 2013. After briefing and oral argument by the parties, the court entered an order on October 21, 2014 denying that motion to dismiss. The parties have reached an agreement in principle to settle this action. Once finalized, the settlement will be presented to the court for preliminary approval. The settlement is expected to be paid by insurance.
	On March 28, 2013, the Company was named as a nominal defendant, and its directors were named as defendants, in a shareholder derivative action in DuPage County Circuit Court in Illinois captioned Hammoud v. Berger et al., Case No. 2013CH001110. The lawsuit primarily alleges breaches of fiduciary duties related to allegedly false and misleading statements regarding the recognition of revenue in the demolition segment and with regard to the Company’s internal control over financial reporting, which exposed the Company to securities litigation. A second, similar lawsuit captioned The City of Haverhill Retirement System v. Leight et al., Case No. 1:13-cv-02470, was filed in the Northern District of Illinois on April 2, 2013 and was voluntarily dismissed on June 10, 2013. A third, similar lawsuit captioned St. Lucie County Fire District Firefighters Pension Trust Fund v. Leight et al., Case No. 13 CH 15483, was filed in Cook County Circuit Court in Illinois on July 8, 2013, and has since been transferred to DuPage County Circuit Court and consolidated with the Hammoud action. The Hammoud/St. Lucie plaintiffs have filed a consolidated amended complaint on December 9, 2013, but the action was otherwise stayed pending a ruling on the motion to dismiss the securities class action. A fourth, similar lawsuit (that additionally named one current and one former executive as defendants) captioned Griffin v. Berger et al., Case No. 1:13-cv-04907, was filed in the Northern District of Illinois on July 9, 2013. The Griffin action was also stayed pending a ruling on the motion to dismiss the securities class action.  The parties have reached an agreement in principle to settle the pending actions.  Once finalized, the settlement will be presented to the DuPage County Circuit Court for preliminary approval.  The settlement is expected to be paid by insurance.
	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. Under the terms of the divestiture, the Company retained certain pre-closing liabilities relating to the disposed business. Certain of these liabilities and a legal action brought by the Company to enforce the buyer’s obligations under the sale agreement are described below.
	In 2009, NASDI received a letter stating that the Attorney General for the Commonwealth of Massachusetts is investigating alleged violations of the Massachusetts Solid Waste Act. The Company believes that the Massachusetts Attorney General is investigating waste disposal activities at an allegedly unpermitted disposal site owned by a third party with whom NASDI contracted for the disposal of waste materials in 2007 and 2008. Per the Massachusetts Attorney General’s request, NASDI executed a tolling agreement regarding the matter in 2009 and engaged in further discussions with the Massachusetts Attorney General’s office. Should a claim be brought, the Company intends to defend this matter vigorously.
	In 2011, NASDI received a subpoena from a federal grand jury in the District of Massachusetts directing NASDI to furnish certain documents relating to certain projects performed by NASDI since January 2005. The Company conducted an internal investigation into this matter and has cooperated with the grand jury’s investigation. Based on the limited information known to the Company, the Company cannot predict the outcome of the investigation, the U.S. Attorney’s views of the issues being investigated, and any action the U.S. Attorney may take.
	On April 24, 2014, NASDI received a subpoena from a federal grand jury in the District of Massachusetts directing NASDI to furnish certain emails for the years 2004 to the present for the email accounts of certain former and present NASDI employees. The Company is cooperating with the grand jury’s investigation. Based on the limited information known to the Company, the Company cannot predict the outcome of the investigation, the U.S. Attorney’s views of the issues being investigated, and any action the U.S. Attorney may take.
	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 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.
	In 2012, the Company contracted with a shipyard to perform the functional design drawings, detailed design drawings and follow on construction of a new Articulated Tug & Barge (“ATB”) Trailing Suction Hopper Dredge. In April 2013, the Company terminated the contract with the shipyard for default and the counterparty sent the Company a notice requesting arbitration under the contract with respect to the Company’s termination for default, including but not limited to the Company’s right to draw on letters of credit that had been issued by the shipyard as financial security required by the contract. In May 2013, the Company drew upon the shipyard’s letters of credit related to the contract and received $13,600. Arbitration proceedings were initiated. In January 2014, the Company and the shipyard executed a settlement agreement pursuant to which the Company retained $10,500 of the proceeds of the financial security and remitted $3,100 of those funds to the shipyard, all other claims were released, and the arbitration was dismissed with prejudice.
	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.
	Lease obligations
	The Company leases certain operating equipment and office facilities under long-term operating leases expiring at various dates through 2023. The equipment leases contain renewal or purchase options that specify prices at the then fair value upon the expiration of the lease terms. The leases also contain default provisions that are triggered by an acceleration of debt maturity under the terms of the Company’s Credit Agreement, or, in certain instances, cross default to other equipment leases and certain lease arrangements require that the Company maintain certain financial ratios comparable to those required by its Credit Agreement. Additionally, the leases typically contain provisions whereby the Company indemnifies the lessors for the tax treatment attributable to such leases based on the tax rules in place at lease inception. The tax indemnifications do not have a contractual dollar limit. To date, no lessors have asserted any claims against the Company under these tax indemnification provisions.
	Future minimum operating lease payments at December 31, 2014, are as follows:
	2015	$	23,616
	2016		22,069
	2017		19,441
	2018		11,225
	2019		8,384
	Thereafter		16,009
	Total minimum operating lease payments	$	100,744
	Total rent expense under long-term operating lease arrangements for the years ended  December 31, 2014,  2013 and 2012 was $25,318, $21,620 and $18,370, respectively. This excludes expenses for equipment and facilities rented on a short-term, as-needed basis.

Investment

Investment	12 Months Ended
	Dec. 31, 2014
Investments [Abstract]
Investment	14. INVESTMENTS
	Amboy Aggregates
	The Company and a New Jersey aggregates company each own 50% of Amboy Aggregates (“Amboy”). Amboy was formed in December 1984 to mine sand from the entrance channel to New York Harbor to provide sand and aggregate for use in road and building construction and for clean land fill. Amboy sold its interest in a stone import business and its holdings in land during 2014 and is winding down operations. The land owned in conjunction with Lower Main Street Development, LLC (“Lower Main”) was sold for a combined gain of $29,729.
	The Company accounts for this investment under the equity method. The following is summarized financial information for this entity:
		2014		2013		2012
	Revenue	$	13,784	$	24,399	$	18,971
	Gross profit		-118		4,142		827
	Income from continuing operations		11,326		2,329		-281
	Net Income		9,527		3,998		227
	Lower Main Street Development
	The Company and a New Jersey aggregates company each own 50% of Lower Main. Lower Main was organized in February 2003 to hold land for development or sale.  This land owned in conjunction with Amboy Aggregates was sold in 2014.
	The Company accounts for this investment under the equity method. The following is summarized financial information for this entity:
		2014		2013		2012
	Revenue	$	180	$	180	$	180
	Gross profit		180		180		180
	Net Income		14,803		175		88
	TerraSea Environmental Solutions
	The Company owns 50% of TerraSea Environmental Solutions (“TerraSea”) as a joint venture. TerraSea is engaged in the environmental services business through its ability to remediate contaminated soil and dredged sediment treatment. At December 31, 2014 and 2013, the Company has net advances to TerraSea of $22,898 and $7,129, respectively, which are recorded in other current assets. The Company has an accumulated deficit in joint ventures, which represents losses recognized to date in excess of our investment in TerraSea, of $10,383 at December 31, 2014 which is presented in accrued expenses and $866 at December 31, 2013 which is presented in investment in joint ventures. The Company has commenced the winddown of TerraSea with its joint venture partner. The Company believes its net advances to TerraSea are ultimately recoverable either through the operations of the joint venture or as an obligation of our joint venture partner. To the extent that advances are not fully recoverable, additional losses may result in future periods. The Company and its joint venture partner remain obligated to fund TerraSea through the completion of its remaining project, which is expected to occur in 2015.
	The Company accounts for this investment under the equity method. The following is summarized financial information for this entity:
		2014		2013		2012
	Revenue	$	11,278	$	7,368	$	325
	Gross profit		-19,153		-956		318
	Net Income (loss)		-19,856		-956		19

RelatedParty_Transactions

Related-Party Transactions	12 Months Ended
	Dec. 31, 2014
Related-Party Transactions [Abstract]
Related-Party Transactions
		15	RELATED-PARTY TRANSACTIONS
	The historical demolition business is operated out of a building owned by a former minority interest owner in Yankee and prior to 2011, a profits interest owner in NASDI. In 2014,  2013 and 2012, NASDI and Yankee paid the minority interest owner $375,  $449 and $449, respectively, for rent and property taxes. In conjunction with the sale of NASDI and Yankee (See Note 15), the lease was terminated as of October 31, 2014, and the Company also paid $490 in lease termination fees.
	In 2013 and 2012, our rivers & lakes group operated out of facilities owned by the former owner of the group. The Company paid $95 and $103 in rent to the building owner during 2013 and 2012, respectively. As the rivers & lakes group relocated to a new facility in late 2013, there were no rents paid in 2014.
	Our Terra Contracting business operates out of two facilities owned by the former owner of Terra Contracting, LLC. In 2014 and 2013, the Company paid $243 and $243 for rent on these two properties. As the purchase of Terra Contracting, LLC occurred on December 31, 2012, the Company paid no rents in 2012.
	Our Magnus Pacific business operates out of two facilities owned by Magnus Real Estate Group, LLC, which is owned by the formers owners of Magnus Pacific. In 2014, the Company paid rent of $46 for these two properties. As the purchase of Magnus Pacific Corporation occurred in 2014, there were no rents paid in 2013 and 2012.

Business_Combinations_And_Disp

Business Combinations And Dispositions	12 Months Ended
	Dec. 31, 2014
Business Combinations And Dispositions [Abstract]
Business Combinations And Dispositions
		16	BUSINESS COMBINATIONS AND DISPOSITIONS
	Discontinued operations
	On April 23, 2014, the Company entered into an agreement and completed the sale of NASDI, LLC and Yankee Environmental Services, LLC, its two former subsidiaries that comprised the 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, and net of future payments of accounts payable existing at the date of close, including any future payments of obligations associated with outstanding claims.  In the fourth quarter of 2013, the Company recorded a preliminary loss on disposal of assets held for sale in discontinued operations. The loss on disposal is subject to change based on the value of additional proceeds received on the working capital existing at the date of disposition.  The amount and timing of the working capital settlement and the amount and timing of the realization of additional net proceeds may be impacted by the litigation with the buyer of the historical demolition business (see Note 13). 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.  The results of the businesses have been reported in discontinued operations as follows:
				2014			2013		2012
	Revenue			$	14,803		$	39,550	$	100,602
	Loss before income taxes from discontinued operations			$	-19,167		$	-55,530	$	-17,125
	Loss on disposal of assets held for sale				-			-18,436		-
	Income tax benefit				8,744			19,116		7,490
	Loss from discontinued operations, net of income taxes			$	-10,423		$	-54,850	$	-9,635
	Magnus Pacific acquisition
	On November 4, 2014, the Company acquired Magnus Pacific Corporation, a California corporation, for an aggregate purchase price of approximately $40 million. Magnus Pacific Corporation is engaged in the business of environmental remediation, geotechnical construction, demolition, and sediments and wetlands construction.
	Under the terms of the acquisition, the aggregate purchase price is satisfied by payment of $25,000 paid at closing, the issuance of a promissory note and an earnout payment. The original principal amount of the promissory note will be finally determined within 60 days after the 2014 fiscal year end and is expected to approximate $7,544. Payments on the promissory note will be made in two equal installments on January 1, 2017 and January 1, 2018. The promissory note shall bear interest at 5% per annum, which shall begin to accrue on January 1, 2015, and shall continue to accrue until payment of the second installment. In the event Magnus Pacific (“Magnus”) does not achieve minimum earnings before interest, taxes, depreciation and amortization, as adjusted in the 2015 fiscal year, the principal amount of the promissory note will be reduced. The promissory note also is subject to reduction based on certain indemnification obligations of the shareholders under the acquisition agreement. The maximum potential aggregate earnout payment is $11,400 and will be determined based on the attainment of combined Adjusted EBITDA targets of Magnus and Terra Contracting Services, LLC (“Terra”), a wholly-owned subsidiary of the Company for the year ending December 31, 2019. The Earnout Payment may be paid in cash or shares of the Company’s common stock, at the Company’s option. At December 31, 2014 the fair value of the recorded earnout liability was $8,024, which is recorded in other liabilities.
	The preliminary purchase price has been allocated to the assets acquired and liabilities assumed using estimated fair values as of the acquisition date. Tangible assets acquired of $57,303 primarily were receivables and contract revenues in excess of billings of $41,067 and property and equipment of $11,573. Finite-lived intangible assets acquired of $8,422 were primarily related to acquired backlog and also include a non-compete agreement, patents and trade names. The acquired backlog is being amortized on a straight-line basis over one year while all other finite-lived intangible assets are being amortized on a straight-line basis over five years. Liabilities assumed of $27,586, includes primarily $20,732 of accounts payable. Goodwill of $7,000 represents the excess of cost over the fair value of the net tangible and intangible assets acquired and is included in the environmental & remediation segment.
	Concurrent with the closing of the acquisition of Magnus Pacific Corporation, the Company granted restricted stock unit awards to the shareholders representing the right to receive, in aggregate, up to 1,500 shares of Great Lakes’ common stock. Each award vests on March 31, 2020, subject to the applicable employee’s continuous employment with Great Lakes through such date and satisfaction of certain business milestones.
	As the acquisition took place on November 4, 2014, no income or earnings of Magnus were included in the consolidated statement of operations of the Company for the periods ended December 31, 2013 or 2012.
	The following unaudited pro forma financial information present the consolidated results of operations of the Company as they may have appeared had the acquisition described above occurred as of January 1, 2013 for purposes of the unaudited pro forma consolidated statements of operations
	The unaudited pro forma consolidated financial information are provided for illustrative purposes only and do not purport to present what the actual results of operations would have been had the transaction actually occurred on the date indicated, nor does it purport to represent results of operations for any future period. The information does not reflect any cost savings or benefits that may be obtained through synergies among the operations of the Company.
			2014			2013
			(Unaudited)
	Revenue as reported		$	806,831		$	731,418
	Revenue of purchased businesses for the period prior to the acquisition including proforma accounting adjustments			106,723			87,943
	Pro forma revenue		$	913,554		$	819,361
	Net income (loss) attributable to common stockholders of Great Lakes Dredge & Dock Corporation		$	10,295		$	-34,361
	Net income of Magnus including pro forma acquisition accounting adjustments			6,328			1,069
	Pro forma net income (loss) attributable to common stockholders of Great Lakes Dredge & Dock Corporation		$	16,623		$	-33,292
	The pro forma adjustments to net income represent amortization of intangibles established in purchase accounting, interest on the debt used to purchase Magnus and taxes on net income at the Company’s effective tax rate, all applied to the period prior to acquisition.
	Terra Contracting acquisition
	On December 31, 2012, the Company acquired the assets including certain assumed liabilities of Terra Contracting, LLC, a provider of a wide variety of essential services for environmental, maintenance and infrastructure-related applications headquartered in Kalamazoo, MI, for a purchase price of approximately $26 million. The Terra acquisition broadened the Company’s environmental & remediation segment with additional services and expertise as well as expanded its footprint in the Midwest. The seller may receive cash payments for any of the calendar years ended 2013, 2014 and 2015 if certain earnings based criteria are met. Per the purchase agreement, for each calendar year, the earnout payment amount shall be equal to (i) 25% of the amount, up to $500, by which EBITDA exceeds $4,000 plus (ii) 50% of the amount by which EBITDA exceeds $4,500; provided, that in no event shall seller receive an amount more than $2,000.  At December 31, 2014, the fair value of the recorded earnout liability was $1,541 and is recorded in accrued liabilities. At December 31, 2013, the fair value of the recorded earnout liabilities was $1,833 of which $725 is recorded in accrued liabilities and $1,108 is recorded in other liabilities.  After assuming the seller’s indebtedness, the acquisition was funded with a seller note of $10,547 and future contingent consideration.  In addition, $2,000 of cash was placed in escrow pursuant to the indemnification clauses in the purchase agreement.  The balance of the note was paid in January 2013.
	The purchase price has been allocated to the assets acquired and liabilities assumed using estimated fair values as of the acquisition date. Tangible assets acquired of $27 million primarily were receivables of $14.6 million and property, plant, and equipment of $11.3 million. Finite-lived intangible assets acquired of $2.7 million were primarily related to a non-compete agreement and also included acquired backlog, patents and trade names. The acquired backlog was amortized on a straight-line basis over one year while all other finite-lived intangible assets are being amortized on a straight-line basis over five years. Liabilities assumed of $18.3 million, includes primarily $17.5 million of accounts payable. Goodwill of $2.8 million represents the excess of cost over the fair value of the net tangible and intangible assets acquired.
	As the acquisition took place on December 31, 2012, no income or earnings of Terra were included in the consolidated statement of operations of the Company for the period ended December 31, 2012.
	Other
	The Company recorded a $2,197 noncash bargain purchase gain on a small asset acquisition in 2014.

Segment_Information

Segment Information	12 Months Ended
	Dec. 31, 2014
Segment Information [Abstract]
Segment Information
	17.   SEGMENT INFORMATION
	The Company and its subsidiaries currently operate in two reportable segments: dredging and environmental & remediation. 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 2014,  2013 and 2012, is provided as follows:
		2014		2013		2012
	Dredging:
	Contract revenues	$	697,711	$	642,602	$	588,229
	Operating income		41,620		54,683		32,947
	Depreciation and amortization		43,620		44,118		37,279
	Total assets		815,683		821,253		757,666
	Property and equipment—net		366,027		330,689		323,082
	Goodwill		76,576		76,575		76,575
	Investment in joint ventures		2,114		8,256		7,047
	Capital expenditures		79,186		57,902		64,598
	Environmental & remediation:
	Contract revenues		114,412		94,840		201
	Operating loss		-17,767		-3,282		-314
	Depreciation and amortization		6,509		2,504		150
	Total assets		77,551		31,392		68,802
	Property and equipment—net		33,418		14,931		12,427
	Goodwill		9,750		2,751		2,751
	Investment in joint ventures		5,775		-		-
	Capital expenditures		12,892		4,100		-
	Intersegment:
	Contract revenues		-5,292		-6,024		-
	Total:
	Contract revenues		806,831		731,418		588,430
	Operating income		23,853		51,401		32,633
	Depreciation and amortization		50,129		46,622		37,430
	Total assets		893,234		852,645		826,468
	Property and equipment—net		399,445		345,620		335,509
	Goodwill		86,326		79,326		79,326
	Investment in joint ventures		7,889		8,256		7,047
	Capital expenditures		92,078		62,002		64,598
	The Company classifies the revenue related to its dredging projects into the following types of work:
		2014		2013		2012
	Capital dredging — U.S.	$	195,635	$	153,781	$	175,317
	Capital dredging — foreign		155,000		138,436		112,242
	Coastal protection dredging		194,219		228,868		126,873
	Maintenance dredging		123,923		90,833		137,924
	Rivers & lakes		28,934		30,684		35,873
	Total dredging	$	697,711	$	642,602	$	588,229
	The Company derived revenues and gross profit from foreign project operations for the years ended December 31, 2014,  2013, and 2012, as follows:
		2014		2013		2012
	Contract revenues	$	155,000	$	138,436	$	112,242
	Costs of contract revenues		-118,682		-117,029		-104,038
	Gross profit	$	36,318	$	21,407	$	8,204
	In 2014 and 2013, foreign revenues were primarily from projects in the Middle East as well as for the Wheatstone LNG project in Western Australia. In 2012, the majority of the Company’s foreign revenue came from projects in the Middle East. The majority of the Company’s long-lived assets are marine vessels and related equipment. At any point in time, the Company may employ certain assets outside of the U.S., as needed, to perform work on the Company’s foreign projects. As of December 31, 2014 and 2013, long-lived assets with a net book value of $93,839 and $104,099, respectively, were located outside of the U.S.
	The Company’s primary customer is the U.S. Army Corps of Engineers (the “Corps”), which has responsibility for federally funded projects related to waterway navigation and flood control. In 2014,  2013 and 2012, 60.4%, 45.0% and 68.9%, respectively, of contract revenues were earned from contracts with federal government agencies, including the Corps, as well as other federal entities such as the U.S. Coast Guard and U.S. Navy. At December 31, 2014 and 2013, approximately 45.9% and 48.7%, respectively, of accounts receivable, including contract revenues in excess of billings and retainage, were due on contracts with federal government agencies. The Company depends on its ability to continue to obtain federal government contracts, and indirectly, on the amount of federal funding for new and current government dredging projects. Therefore, the Company’s operations can be influenced by the level and timing of federal funding.
	In 2014, the Company earned significant revenue from a large, single customer foreign contract. A revision to the estimated gross profit percentage was recognized in the year resulting in a cumulative net impact on the project margin, which increased gross profit by $22,418 for the year ended December 31, 2014, including an increase in gross profit of $7,645 during the fourth quarter. The project was completed in 2014.
	Prior to 2013, revenue from foreign projects was concentrated in Bahrain and primarily with the government of Bahrain which comprised of 14.2% of total revenue in 2012. At December 31, 2014 and 2013, approximately 11.4% and 13.1%, respectively, of accounts receivable, including retainage and contract revenues in excess of billings, were due on contracts with the government of Bahrain. There is a dependence on future projects in the Bahrain region, as vessels are currently located there. However, certain of the vessels located in Bahrain can be moved back to the U.S. or all can be moved to other international markets as opportunities arise.

Subsidiary_Guarantors

Subsidiary Guarantors	12 Months Ended
	Dec. 31, 2014
Subsidiary Guarantors [Abstract]
Subsidiary Guarantors	18.   SUBSIDIARY GUARANTORS
	The Company’s long-term debt at December 31, 2014 includes $274,880 of 7.375% senior notes due February 1, 2019. The Company’s obligations under these senior unsecured notes are guaranteed by the Company’s 100% owned domestic subsidiaries. Such guarantees are full, unconditional and joint and several.
	The following supplemental financial information sets forth for the Company’s subsidiary guarantors (on a combined basis), the Company’s non-guarantor subsidiaries (on a combined basis) and Great Lakes Dredge & Dock Corporation, exclusive of its subsidiaries (“GLDD Corporation”):
		(i)	balance sheets as of December 31, 2014 and 2013;
		(ii)	statements of operations and comprehensive income (loss) for the years ended December 31, 2014, 2013 and 2012; and
		(iii)	statements of cash flows for the years ended December 31, 2014, 2013 and 2012.
	GREAT LAKES DREDGE & DOCK CORPORATION AND SUBSIDIARIES
	CONDENSED CONSOLIDATING BALANCE SHEET
	AS OF DECEMBER 31, 2014
	(In thousands)
	ASSETS	Subsidiary Guarantors			Non-Guarantor Subsidiaries			GLDD Corporation			Eliminations			Consolidated Totals
	CURRENT ASSETS:
	Cash and cash equivalents	$	41,724		$	663		$	2		$	-		$	42,389
	Accounts receivable — net		115,739			355			-			-2,906			113,188
	Receivables from affiliates		152,822			3,673			55,805			-212,300			-
	Contract revenues in excess of billings		78,631			4,236			-			-310			82,557
	Inventories		34,735			-			-			-			34,735
	Prepaid expenses		4,708			-			-			-			4,708
	Other current assets		49,619			431			14,617			-			64,667
	Assets held for sale		-			-			-			-			-
	Total current assets		477,978			9,358			70,424			-215,516			342,244
	PROPERTY AND EQUIPMENT—Net		399,421			24			-			-			399,445
	GOODWILL		86,326			-			-			-			86,326
	OTHER INTANGIBLE ASSETS—Net		8,963			-			-			-			8,963
	INVENTORIES — Noncurrent		36,262			-			-			-			36,262
	INVESTMENTS IN JOINT VENTURES		7,889			-			-			-			7,889
	INVESTMENTS IN SUBSIDIARIES		3,757			-			619,220			-622,977			-
	OTHER		7,135			3			4,967			-			12,105
	TOTAL	$	1,027,731		$	9,385		$	694,611		$	-838,493		$	893,234
	LIABILITIES AND EQUITY
	CURRENT LIABILITIES:
	Accounts payable	$	121,282		$	1,389		$	516		$	-3,216		$	119,971
	Payables to affiliates		196,829			403			15,068			-212,300			-
	Accrued expenses		60,415			659			8,967			-			70,041
	Billings in excess of contract revenues		4,639			-			-			-			4,639
	Current portion of long term debt		859			-			5,000			-			5,859
	Total current liabilities		384,024			2,451			29,551			-215,516			200,510
	7 3/8% SENIOR NOTES		-			-			274,880			-			274,880
	NOTE PAYABLE		7,553			-			41,944			-			49,497
	DEFERRED INCOME TAXES		172			-			91,835			-			92,007
	OTHER		19,939			-			438			-			20,377
	Total liabilities		411,688			2,451			438,648			-215,516			637,271
	Total Great Lakes Dredge & Dock Corporation Equity		616,043			6,934			255,963			-622,977			255,963
	NONCONTROLLING INTERESTS		-			-			-			-			-
	TOTAL EQUITY		616,043			6,934			255,963			-622,977			255,963
	TOTAL	$	1,027,731		$	9,385		$	694,611		$	-838,493		$	893,234
	GREAT LAKES DREDGE & DOCK CORPORATION AND SUBSIDIARIES
	CONDENSED CONSOLIDATING BALANCE SHEET
	AS OF DECEMBER 31, 2013
	(In thousands)
	ASSETS	Subsidiary Guarantors			Non-Guarantor Subsidiaries			GLDD Corporation			Eliminations			Consolidated Totals
	CURRENT ASSETS:
	Cash and cash equivalents	$	71,939		$	3,399		$	-		$	-		$	75,338
	Accounts receivable — net		95,476			1,039			-			-			96,515
	Receivables from affiliates		131,984			7,337			12,205			-151,526			-
	Contract revenues in excess of billings		63,591			3,841			-			-			67,432
	Inventories		32,500			-			-			-			32,500
	Prepaid expenses		3,913			-			298			-			4,211
	Other current assets		19,636			137			20,180			-			39,953
	Assets held for sale		41,763			11,877			-			-8,536			45,104
	Total current assets		460,802			27,630			32,683			-160,062			361,053
	PROPERTY AND EQUIPMENT—Net		345,612			8			-			-			345,620
	GOODWILL		79,326			-			-			-			79,326
	OTHER INTANGIBLE ASSETS—Net		1,976			-			-			-			1,976
INVENTORIES — Noncurrent		38,496			-			-			-			38,496
INVESTMENTS IN JOINT VENTURES		8,256			-			-			-			8,256
INVESTMENTS IN SUBSIDIARIES		1,212			-			638,955			-640,167			-
ASSETS HELD FOR SALE—Noncurrent		8,796			60			-			-			8,856
OTHER		3,886			3			5,193			-20			9,062
TOTAL	$	948,362		$	27,701		$	676,831		$	-800,249		$	852,645
LIABILITIES AND EQUITY
CURRENT LIABILITIES:
Accounts payable	$	115,235		$	754		$	132		$	-		$	116,121
Payables to affiliates		96,270			24,862			30,394			-151,526			-
Accrued expenses		28,086			15			10,430			-			38,531
Billings in excess of contract revenues		6,754			-			-			-			6,754
Liabilities held for sale		38,158			2,871			-			-8,536			32,493
Total current liabilities		284,503			28,502			40,956			-160,062			193,899
7 3/8% SENIOR NOTES		-			-			250,000			-			250,000
REVOLVING CREDIT FACILITY		-			-			35,000			-			35,000
DEFERRED INCOME TAXES		-			-			108,531			-20
LIABILITIES HELD FOR SALE—Noncurrent		1,212			-			-			-			1,212
OTHER		21,679			-			243			-			21,922
Total liabilities		307,394			28,502			434,730			-160,082			610,544
Total Great Lakes Dredge & Dock Corporation Equity		640,968			-801			242,946			-640,167			242,946
NONCONTROLLING INTERESTS		-			-			-845			-			-845
TOTAL EQUITY		640,968			-801			242,101			-640,167			242,101
TOTAL	$	948,362		$	27,701		$	676,831		$	-800,249		$	852,645
GREAT LAKES DREDGE & DOCK CORPORATION AND SUBSIDIARIES
CONDENSED CONSOLIDATING STATEMENT OF OPERATIONS AND COMPREHENSIVE INCOME
FOR THE YEAR ENDED DECEMBER 31, 2014
(In thousands)
	Subsidiary Guarantors			Non-Guarantor Subsidiaries			GLDD Corporation			Eliminations			Consolidated Totals
Contract revenues	$	799,579		$	26,282		$	-		$	-19,030		$	806,831
Costs of contract revenues		-707,474			-25,891			-			19,030			-714,335
Gross profit		92,105			391			-			-			92,496
OPERATING EXPENSES:
General and administrative expenses		67,905			6			-			-			67,911
Loss on sale of assets—net		732			-			-			-			732
Operating income		23,468			385			-			-			23,853
Interest income (expense)—net		61			-261			-19,767			-			-19,967
Equity in earnings of subsidiaries		20			-			10,373			-10,393			-
Equity in earnings of joint ventures		2,895			-			-			-			2,895
Gain on bargain purchase acquisition		2,197			-			-			-			2,197
Other income		203			7			-			-			210
Income (loss) from continuing operations before income taxes		28,844			131			-9,394			-10,393			9,188
Income tax (provision) benefit		-18,173			-409			30,112			-			11,530
Income (loss) from continuing operations		10,671			-278			20,718			-10,393			20,718
Loss from discontinued operations, net of income taxes		-10,423			-1,343			-10,423			11,766			-10,423
Net income (loss)		248			-1,621			10,295			1,373			10,295
Net income (loss) attributable to Great Lakes	$	248		$	-1,621		$	10,295		$	1,373		$	10,295
Dredge & Dock Corporation
Comprehensive income (loss) attributable to	$	49		$	-1,683		$	10,034		$	1,634		$	10,034
Great Lakes Dredge & Dock Corporation
GREAT LAKES DREDGE & DOCK CORPORATION AND SUBSIDIARIES
CONDENSED CONSOLIDATING STATEMENT OF OPERATIONS AND COMPREHENSIVE INCOME
FOR THE YEAR ENDED DECEMBER 31, 2013
(In thousands)
	Subsidiary Guarantors			Non-Guarantor Subsidiaries			GLDD Corporation			Eliminations			Consolidated Totals
Contract revenues	$	718,041		$	24,932		$	-		$	-11,555		$	731,418
Costs of contract revenues		-614,908			-27,770			-			11,555			-631,123
Gross profit		103,133			-2,838			-			-			100,295
OPERATING EXPENSES:
General and administrative expenses		68,029			10			-			-			68,039
Proceeds from loss of use claim		-13,372			-			-			-			-13,372
(Gain) loss on sale of assets—net		-5,775			-			2			-			-5,773
Operating income (loss)		54,251			-2,848			-2			-			51,401
Interest expense—net		-136			-256			-21,549			-			-21,941
Equity in earnings of subsidiaries		212			-			59,477			-59,689			-
Equity in earnings of joint ventures		1,208			-			-			-			1,208
Other expense		-3			-348			-			-			-351
Income (loss) from continuing operations before income taxes		55,532			-3,452			37,926			-59,689			30,317
Income tax (provision) benefit		293			4			-10,757			-			-10,460
Income (loss) from continuing operations		55,825			-3,448			27,169			-59,689			19,857
Loss from discontinued operations, net of income taxes		-55,106			-1,448			-62,162			63,866			-54,850
Net income (loss)		719			-4,896			-34,993			4,177			-34,993
Net loss attributable to noncontrolling interests		-			-			632			-			632
Net income (loss) attributable to Great Lakes	$	719		$	-4,896		$	-34,361		$	4,177		$	-34,361
Dredge & Dock Corporation
Comprehensive income (loss) attributable to	$	1,023		$	-5,293		$	-34,454		$	4,270		$	-34,454
Great Lakes Dredge & Dock Corporation
GREAT LAKES DREDGE & DOCK CORPORATION AND SUBSIDIARIES
CONDENSED CONSOLIDATING STATEMENT OF OPERATIONS AND COMPREHENSIVE INCOME
FOR THE YEAR ENDED DECEMBER 31, 2012
(In thousands)
	Subsidiary Guarantors			Non-Guarantor Subsidiaries			GLDD Corporation			Eliminations			Consolidated Totals
Contract revenues	$	588,430		$	-		$	-		$	-		$	588,430
Costs of contract revenues		-509,620			-652			-			-			-510,272
Gross profit		78,810			-652			-			-			78,158
OPERATING EXPENSES:
General and administrative expenses		42,547			31			3,145			-			45,723
Gain on sale of assets—net		-293			-			95			-			-198
Operating income (loss)		36,556			-683			-3,240			-			32,633
Interest expense—net		-580			-133			-20,212			-			-20,925
Equity in earnings (loss) of subsidiaries		-1			-			36,888			-36,887			-
Equity in earnings of joint ventures		124			-			-			-			124
Other expense		-118			-			-			-			-118
Income (loss) from continuing operations before income taxes		35,981			-816			13,436			-36,887			11,714
Income tax provision		-6			-			-5,413			-			-5,419
Income (loss) from continuing operations		35,975			-816			8,023			-36,887			6,295
Loss from discontinued operations, net of income taxes		-9,798			-1,707			-11,363			13,233			-9,635
Net income (loss)		26,177			-2,523			-3,340			-23,654			-3,340
Net loss attributable to noncontrolling interests		-			-			645			-			645
Net income (loss) attributable to Great Lakes	$	26,177		$	-2,523		$	-2,695		$	-23,654		$	-2,695
Dredge & Dock Corporation
Comprehensive income (loss) attributable to	$	25,800		$	-2,529		$	-3,078		$	-23,271		$	-3,078
Great Lakes Dredge & Dock Corporation
GREAT LAKES DREDGE & DOCK CORPORATION AND SUBSIDIARIES
CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS
FOR THE YEAR ENDED DECEMBER 31, 2014
(In thousands)
		Subsidiary Guarantors			Non-Guarantor Subsidiaries			GLDD Corporation			Eliminations			Consolidated Totals
OPERATING ACTIVITIES:
Net cash flows provided by (used in) operating activities of continuing operations		$	63,276		$	999		$	2,879		$	-		$	67,154
Net cash flows used in operating activities of discontinued operations			-17,328			-1,024			-			-			-18,352
Cash provided by (used in) operating activities			45,948			-25			2,879			-			48,802
INVESTING ACTIVITIES:
Purchases of property and equipment			-91,910			-			-			-			-91,910
Proceeds from dispositions of property and equipment			68			-			-			-			68
Payments for acquisitions of businesses			-2,048			-			-25,000			-			-27,048
Proceeds from vendor performance obligations			-3,100			-			-			-			-3,100
Net change in accounts with affiliates			68,187			-			-			-68,187			-
Net cash flows used in investing activities of continuing operations			-28,803			-			-25,000			-68,187			-121,990
Net cash flows provided by investing activities of discontinued operations			5,275			-			-			-			5,275
Cash used in investing activities			-23,528			-			-25,000			-68,187			-116,715
FINANCING ACTIVITIES:
Proceeds from term loan facility			-			-			47,360			-			47,360
Repayments of term loan facility			-			-			-417			-			-417
Proceeds from issuance of 7 3/8% senior notes			-			-			24,880			-			24,880
Deferred financing fees			-			-			-2,532			-			-2,532
Taxes paid on settlement of vested share awards			-			-			-497			-			-497
Purchase of noncontrolling interest			-			-			-205			-			-205
Net change in accounts with affiliates			-			-2,547			-65,640			68,187			-
Intercompany dividends			-52,400			-			52,400			-			-
Repayments of equipment debt			-235			-			-			-			-235
Exercise of stock options and purchases from employee stock plans			-			-			1,568			-			1,568
Excess income tax benefit from share-based compensation			-			-			206			-			206
Borrowings under revolving loans			-			-			236,500			-			236,500
Repayments of revolving loans			-			-			-271,500			-			-271,500
Net cash flows provided by (used in) financing activities of continuing operations			-52,635			-2,547			22,123			68,187			35,128
Net cash flows provided by financing activities of discontinued operations			-			-			-			-			-
Cash provided by financing activities			-52,635			-2,547			22,123			68,187			35,128
Effect of foreign currency exchange rates on cash and cash equivalents			-			-164			-			-			-164
Net increase (decrease) in cash and cash equivalents			-30,215			-2,736			2			-			-32,949
Cash and cash equivalents at beginning of period			71,939			3,399			-			-			75,338
Cash and cash equivalents at end of period		$	41,724		$	663		$	2		$	-		$	42,389
GREAT LAKES DREDGE & DOCK CORPORATION AND SUBSIDIARIES
CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS
FOR THE YEAR ENDED DECEMBER 31, 2013
(In thousands)
		Subsidiary Guarantors			Non-Guarantor Subsidiaries			GLDD Corporation			Eliminations			Consolidated Totals
OPERATING ACTIVITIES:
Net cash flows provided by (used in) operating activities of continuing operations		$	126,736		$	-7,748		$	-32,641		$	-		$	86,347
Net cash flows used in operating activities of discontinued operations			-5,049			-6,475			-			-			-11,524
Cash provided by (used in) operating activities			121,687			-14,223			-32,641			-			74,823
INVESTING ACTIVITIES:
Purchases of property and equipment			-66,654			-			-			-			-66,654
Proceeds from dispositions of property and equipment			6,953			-			-			-			6,953
Proceeds from vendor performance obligations			13,600			-			-			-			13,600
Net change in accounts with affiliates			-37,282			-302			-			37,584			-
Net cash flows used in investing activities of continuing operations			-83,383			-302			-			37,584			-46,101
Net cash flows used in investing activities of discontinued operations			-153			-			-			-			-153
Cash used in investing activities			-83,536			-302			-			37,584			-46,254
FINANCING ACTIVITIES:
Repayment of long term note payable			-2,500			-			-10,547			-			-13,047
Distributions paid to minority interests			-			-			-3			-			-3
Taxes paid on settlement of vested share awards			-			-			-308			-			-308
Net change in accounts with affiliates			-			10,342			8,603			-18,945			-
Capital contributions			-			926			-926			-			-
Exercise of stock options and purchases from employee stock plans			-			-			668			-			668
Excess income tax benefit from share-based compensation			-			-			154			-			154
Borrowings under revolving loans			-			-			227,000			-			227,000
Repayments of revolving loans			-			-			-192,000			-			-192,000
Net cash flows provided by (used in) financing activities of continuing operations			-2,500			11,268			32,641			-18,945			22,464
Net cash flows provided by financing activities of discontinued operations			12,016			6,623			-			-18,639			-
Cash provided by financing activities			9,516			17,891			32,641			-37,584			22,464
Effect of foreign currency exchange rates on cash and cash equivalents			-			-135			-			-			-135
Net increase in cash and cash equivalents			47,667			3,231			-			-			50,898
Cash and cash equivalents at beginning of period			24,272			168			-			-			24,440
Cash and cash equivalents at end of period		$	71,939		$	3,399		$	-		$	-		$	75,338
GREAT LAKES DREDGE & DOCK CORPORATION AND SUBSIDIARIES
CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS
FOR THE YEAR ENDED DECEMBER 31, 2012
(In thousands)
		Subsidiary Guarantors			Non-Guarantor Subsidiaries			GLDD Corporation			Eliminations			Consolidated Totals
OPERATING ACTIVITIES:
Net cash flows provided by (used in) operating activities of continuing operations		$	48,544		$	-831		$	-27,977		$	-		$	19,736
Net cash flows used in operating activities of discontinued operations			-20,636			-960			-			-			-21,596
Cash provided by (used in) operating activities			27,908			-1,791			-27,977			-			-1,860
INVESTING ACTIVITIES:
Purchases of property and equipment			-60,516			-			-			-			-60,516
Proceeds from dispositions of property and equipment			597			-			-			-			597
Acquisition of Terra assets			-2,000			-			-			-			-2,000
Net cash flows used in investing activities of continuing operations			-61,919			-			-			-			-61,919
Net cash flows used in investing activities of discontinued operations			-1,524			-			-			-			-1,524
Cash used in investing activities			-63,443			-			-			-			-63,443
FINANCING ACTIVITIES:
Deferred financing fees			-			-			-2,039			-			-2,039
Repayment of long term note payable			-2,500			-			-			-			-2,500
Distributions paid to minority interests			-			-			-133			-			-133
Dividends paid			-			-			-18,560			-			-18,560
Dividend equivalents paid on restricted stock units			-			-			-196			-			-196
Taxes paid on vested share awards			-			-			-231			-			-231
Net change in accounts with affiliates			-46,135			-2,351			48,486			-			-
Exercise of stock options			-			-			461			-			461
Excess income tax benefit from share-based compensation			-			-			189			-			189
Net cash flows provided by (used in) financing activities of continuing operations			-48,635			-2,351			27,977			-			-23,009
Net cash flows used in financing activities of discontinued operations			-543			-			-			-			-543
Cash provided by (used in) financing activities			-49,178			-2,351			27,977			-			-23,552
Effect of foreign currency exchange rates on cash and cash equivalents			-			7			-			-			7
Net decrease in cash and cash equivalents			-84,713			-4,135			-			-			-88,848
Cash and cash equivalents at beginning of period			108,985			4,303			-			-			113,288
Cash and cash equivalents at end of period		$	24,272		$	168		$	-		$	-		$	24,440

Schedule_IIValuation_And_Quali

Schedule II-Valuation And Qualify Accounts	12 Months Ended
	Dec. 31, 2014
Schedule II-Valuation And Qualifying Accounts [Abstract]
Schedule II-Valuation And Qualifying Accounts
	Great Lakes Dredge & Dock Corporation
	Schedule II—Valuation and Qualifying Accounts
	For the Years Ended December 31, 2014, 2013 and 2012
	(In thousands)
				Additions
		Beginning Balance		Charged to costs and expenses		Charged to other accounts		Deductions		Ending balance
	Description
	Year ended December 31, 2012
	Allowances deducted from assets to which they apply:
	Allowances for doubtful accounts	$	855	$	946	$	-	$	-750	$	1,051
	Valuation reserve for deferred tax assets		3,124		228						3,352
	Total	$	3,979	$	1,174	$	-	$	-750	$	4,403
	Year ended December 31, 2013
	Allowances deducted from assets to which they apply:
	Allowances for doubtful accounts	$	1,051	$	478	$	-	$	-	$	1,529
	Valuation reserve for deferred tax assets		3,352		-847						2,505
	Total	$	4,403	$	-369	$	-	$	-	$	4,034
	Year ended December 31, 2014
	Allowances deducted from assets to which they apply:
	Allowances for doubtful accounts	$	1,529	$	100	$	-	$	-1,051	$	578
	Valuation reserve for deferred tax assets		2,505		4,074						6,579
	Total	$	4,034	$	4,174	$	-	$	-1,051	$	7,157

Nature_Of_Business_And_Summary1

Nature Of Business And Summary Of Signicant Accounting Policies (Policy)	12 Months Ended
	Dec. 31, 2014
Nature Of Business And Summary Of Significant Accounting Policies [Abstract]
Principles Of Consolidation And Basis Of Presentation	Principles of Consolidation and Basis of Presentation —The consolidated financial statements include the accounts of Great Lakes Dredge & Dock Corporation and its majority-owned subsidiaries. All intercompany accounts and transactions are eliminated in consolidation. The equity method of accounting is used for investments in unconsolidated investees in which the Company has significant influence, but not control. Other investments, if any, are carried at cost.
Use Of Estimates	Use of Estimates —The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (“GAAP”) requires management to make estimates and assumptions that affect certain reported amounts and disclosures. Accordingly, actual results could differ from those estimates.
Revenue and Cost Recognition on Contracts	Revenue and Cost Recognition on Contracts —Substantially all of the Company’s contracts for dredging services are fixed-price contracts, which provide for remeasurement based on actual quantities dredged. The majority of the Company’s environmental & remediation contracts are also fixed-price contracts, with others performed on a time-and-materials basis. Contract revenues are recognized under the percentage-of-completion method based on the Company’s engineering estimates of the physical percentage completed for dredging projects and based on costs incurred to date compared to total estimated costs for fixed-price environmental & remediation projects. For dredging projects, costs of contract revenues are adjusted to reflect the gross profit percentage expected to be achieved upon ultimate completion. For environmental & remediation contracts, contract revenues are adjusted to reflect the estimated gross profit percentage. 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 reporting periods. Provisions for estimated losses on contracts in progress are made in the period in which such losses are determined. Change orders are not recognized in revenue until the recovery is probable and collectability is reasonably assured. Claims for additional compensation due to the Company are not recognized in contract revenues until such claims are settled. Billings on contracts are generally submitted after verification with the customers of physical progress and may 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. Modifications may be negotiated when a change from the original contract specification is encountered, and a change in project scope, performance methodology and/or material disposal is necessary. Thus, the resulting modification is considered a change in the scope of the original project to which it relates. Significant expenditures incurred incidental to major contracts are deferred and recognized as contract costs based on contract performance over the duration of the related project. These expenditures are reported as prepaid expenses.
	The components of costs of contract revenues include labor, equipment (including depreciation, maintenance, insurance and long-term rentals), subcontracts, fuel 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. Generally, capital dredging projects have the highest margins due to the complexity of the projects, while coastal protection projects have the most volatile margins because they are most often exposed to variability in weather conditions.
	The Company’s cost structure includes significant annual equipment-related costs, including depreciation, maintenance, insurance and long-term rentals. These costs have averaged approximately 22% to 23% of total costs of contract revenues over the prior three years. During the year, both equipment utilization and the timing of fixed cost expenditures fluctuate significantly. Accordingly, the Company allocates these fixed equipment costs to interim periods in proportion to revenues recognized over the year, to better match revenues and expenses. Specifically, at each interim reporting date the Company compares actual revenues earned to date on its dredging contracts to expected annual revenues and recognizes 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.
	For some environmental & remediation contracts, the Company is a 50% partner in multiple construction joint venture. The joint venture agreements provide that the Company’s interests in any profits and assets and respective share in any losses and liabilities that may result from the performance of such contracts are limited to the Company’s stated percentage partnership interest in the project. The joint venture provides that each partner will assume and pay its full proportionate share of any losses resulting from the project.
Classification of Current Assets and Liabilities	Classification of Current Assets and Liabilities —The Company includes in current assets and liabilities amounts realizable and payable in the normal course of contract completion, unless completion of such contracts extends significantly beyond one year.
Cash Equivalents	Cash Equivalents —The Company considers all highly liquid investments with a maturity at purchase of three months or less to be cash equivalents.
Accounts Receivable , Net	Accounts Receivable —Accounts receivable represent amounts due or billable under the terms of contracts with customers, including amounts related to retainage. The Company anticipates collection of retainage generally within one year, and accordingly presents retainage as a current asset. The Company provides an allowance for estimated uncollectible accounts receivable when events or conditions indicate that amounts outstanding are not recoverable.
Inventories	Inventories —Inventories consist of pipe and spare parts used in the Company’s dredging operations. Pipe and spare parts are purchased in large quantities; therefore, a certain amount of pipe and spare part inventories is not anticipated to be used within the current year and is classified as long-term. Inventories are stated at the lower of net realizable value or weighted average historical cost.
Property, Plant and Equipment	Property and Equipment —Capital additions, improvements, and major renewals are classified as property and equipment and are carried at depreciated cost. Maintenance and repairs that do not significantly extend the useful lives of the assets or enhance the capabilities of such assets are charged to expenses as incurred. Depreciation is recorded over the estimated useful lives of property and equipment using the straight-line method and the mid-year depreciation convention. The estimated useful lives by class of assets are:
	Class	Useful Life (years)
	Buildings and improvements	10
	Furniture and fixtures	10-May
	Vehicles, dozers, and other light operating equipment and systems	5-Mar
	Heavy operating equipment (dredges and barges)	30-Oct
	Leasehold improvements are amortized over the shorter of their remaining useful lives or the remaining terms of the leases.
Goodwill and Intangible Assets	Goodwill and Other Intangible Assets —Goodwill represents the excess of acquisition cost over fair value of the net assets acquired. Other identifiable intangible assets mainly represent developed technology and databases, customer relationships, and customer contracts acquired in business combinations and are being amortized over a one to five-year period. Goodwill is tested annually for impairment in the third quarter of each year, or more frequently should circumstances dictate. GAAP requires that goodwill of a reporting unit be tested for impairment between annual tests if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount.
	The Company assesses the fair values of its reporting units using both a market-based approach and an income-based approach. Under the income approach, the fair value of the reporting unit is based on the present value of estimated future cash flows. The income approach is dependent on a number of factors, including estimates of future market growth trends, forecasted revenues and expenses, appropriate discount rates and other variables. The estimates are based on assumptions that the Company believes to be reasonable, but such assumptions are subject to unpredictability and uncertainty. Changes in these estimates and assumptions could materially affect the determination of fair value, and may result in the impairment of goodwill in the event that actual results differ from those estimates.
	The market approach measures the value of a reporting unit through comparison to comparable companies. Under the market approach, the Company uses the guideline public company method by applying estimated market-based enterprise value multiples to the reporting unit’s estimated revenue and Adjusted EBITDA. The Company analyzed companies that performed similar services or are considered peers. Due to the fact that there are no public companies that are direct competitors, the Company weighed the results of this approach less than the income approach.
	The Company has four operating segments that, through aggregation, comprise two reportable segments: dredging and environmental & remediation, previously referred to as the demolition segment. The historical demolition business has been retrospectively presented as discontinued operations and is no longer reflected in continuing operations. Four operating segments were aggregated into two reportable segments as the segments have similarity in economic margins, services, production processes, customer types, distribution methods and regulatory environment. The Company has determined that the operating segments are the Company’s four reporting units.
Long-Lived Assets
	Long-Lived Assets —Long-lived assets are comprised of property and equipment and intangible assets subject to amortization. Long-lived assets to be held and used are reviewed for possible impairment whenever events indicate that the carrying amount of such assets may not be recoverable by comparing the undiscounted cash flows associated with the assets to their carrying amounts. If such a review indicates an impairment, the carrying amount would be reduced to fair value. No triggering events were identified in 2014 or 2013. If long-lived assets are to be disposed, depreciation is discontinued, if applicable, and the assets are reclassified as held for sale at the lower of their carrying amounts or fair values less estimated costs to sell.
	The Company capitalizes construction in progress and records a corresponding long-term liability for build-to-suit lease agreements where we are considered the owner during the construction period for accounting purposes. There was no build-to-suit equipment capitalized at December 31, 2014.
Self-insurance Reserves	Self-insurance Reserves —The Company self-insures costs associated with its seagoing employees covered by the provisions of Jones Act, workers’ compensation claims, hull and equipment liability, and general business liabilities up to certain limits. Insurance reserves are established for estimates of the loss that the Company may ultimately incur on reported claims, as well as estimates of claims that have been incurred but not yet reported. In determining its estimates, the Company considers historical loss experience and judgments about the present and expected levels of cost per claim. Trends in actual experience are a significant factor in the determination of such reserves.
Income Taxes	Income Taxes —The provision for income taxes includes federal, foreign, and state income taxes currently payable and those deferred because of temporary differences between the financial statement and tax basis of assets and liabilities. Recorded deferred income tax assets and liabilities are based on the estimated future tax effects of differences between the financial and tax basis of assets and liabilities, given the effect of currently enacted tax laws. The Company’s current policy is to repatriate all earnings from foreign subsidiaries’ operations as generated and at this time no amounts are considered to be permanently reinvested in those operations.
Hedging Instruments	Hedging Instruments  —At times, the Company designates certain derivative contracts as a cash flow hedge as defined by GAAP. Accordingly, the Company formally documents, at the inception of each hedge, all relationships between hedging instruments and hedged items, as well as our risk-management objective and strategy for undertaking hedge transactions. This process includes linking all derivatives to highly-probable forecasted transactions.
	The Company formally assesses, at inception and on an ongoing basis, the effectiveness of hedges in offsetting changes in the cash flows of hedged items. Hedge accounting treatment may be discontinued when (1) it is determined that the derivative is no longer highly effective in offsetting changes in the cash flows of a hedged item (including hedged items for forecasted future transactions), (2) the derivative expires or is sold, terminated or exercised, (3) it is no longer probable that the forecasted transaction will occur or (4) management determines that designating the derivative as a hedging instrument is no longer appropriate. If management elects to stop hedge accounting, it would be on a prospective basis and any hedges in place would be recognized in accumulated other comprehensive income (loss) until all the related forecasted transactions are completed or are probable of not occurring.
Foreign Currency Translation	Foreign Currency Translation —The financial statements of the Company’s foreign subsidiaries where the operations are primarily denominated in the foreign currency are translated into U.S. dollars for reporting. Balance sheet accounts are translated at the current foreign exchange rate at the end of each period and income statement accounts are translated at the average foreign exchange rate for each period. Gains and losses on foreign currency translations are reflected as a currency translation adjustment, net of tax, in accumulated other comprehensive income (loss). Foreign currency transaction gains and losses are included in loss on foreign currency transactions—net.
Noncontrolling Interest	Noncontrolling Interest —On January 1, 2009 the Company acquired a 65% interest in Yankee Environmental Services, LLC (“Yankee”). On April 23, 2014, the Company entered into and completed the sale of NASDI, LLC and Yankee, its two former subsidiaries that comprised the historical demolition business. As a result of the sale, the Company purchased the noncontrolling interest related to the membership interest the Company did not own in Yankee. Noncontrolling interest at December 31, 2013 is related to the membership interest the Company did not own in Yankee.
Recent Accounting Pronouncements	Recent Accounting Pronouncements —In May 2014, the Financial Accounting Standards Board issued Accounting Standard Update No. 2014-09 (“ASU 2014-09”), Revenue from Contracts with Customers (Topic 606), which supersedes the existing revenue recognition requirements. ASU 2014-09 is based on the principle that revenue is recognized to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASU 2014-09 is effective for fiscal years beginning after December 15, 2016, including interim periods within that reporting period, which will be our first quarter of fiscal 2017. Early adoption is not permitted. We are currently evaluating the impact of ASU 2014-09 on our consolidated financial statements.

Nature_Of_Business_And_Summary2

Nature Of Business And Summary Of Signicant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Estimated Useful Lives By Class Of Assets
	Class	Useful Life (years)
	Buildings and improvements	10
	Furniture and fixtures	10-May
	Vehicles, dozers, and other light operating equipment and systems	5-Mar
	Heavy operating equipment (dredges and barges)	30-Oct

Earning_Per_Share_Tables

Earning Per Share (Tables)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]
	(shares in thousands)
		2014		2013		2012
	Income from continuing operations	$	20,718	$	19,857	$	6,295
	Loss on discontinued operations, net of income taxes, attributable to Great Lakes Dredge & Dock Corporation		-10,423		-54,218		-8,990
	Net income (loss) attributable to common stockholders of Great Lakes Dredge & Dock Corporation		10,295		-34,361		-2,695
	Weighted-average common shares outstanding — basic		59,938		59,495		59,195
	Effect of stock options and restricted stock units		584		606		478
	Weighted-average common shares outstanding — diluted		60,522		60,101		59,673
	Earnings per share from continuing operations — basic	$	0.35	$	0.33	$	0.11
	Earnings per share from continuing operations — diluted	$	0.34	$	0.33	$	0.11

Accounts_Receivable_And_Contra1

Accounts Receivable And Contracts In Progress (Tables)	12 Months Ended
	Dec. 31, 2014
Accounts Receivable And Contracts In Progress [Abstract]
Schedule Of Accounts Receivable
		2014		2013
	Completed contracts	$	15,342	$	17,361
	Contracts in progress		72,459		62,177
	Retainage		27,371		18,506
			115,172		98,044
	Allowance for doubtful accounts		-578		-1,529
	Total accounts receivable—net	$	114,594	$	96,515
	Current portion of accounts receivable—net	$	113,188	$	96,515
	Long-term accounts receivable and retainage		1,406		-
	Total accounts receivable—net	$	114,594	$	96,515
Components Of Contracts In Progress
		2014		2013
	Costs and earnings in excess of billings:
	Costs and earnings for contracts in progress	$	833,368	$	435,470
	Amounts billed		-759,877		-370,730
	Costs and earnings in excess of billings for contracts in progress		73,491		64,740
	Costs and earnings in excess of billings for completed contracts		9,066		2,692
	Total contract revenues in excess of billings	$	82,557	$	67,432
	Billings in excess of costs and earnings:
	Amounts billed	$	-181,698	$	-156,794
	Costs and earnings for contracts in progress		177,059		150,040
	Total billings in excess of contract revenues	$	-4,639	$	-6,754

Property_And_Equipment_Tables

Property And Equipment (Tables)	12 Months Ended
	Dec. 31, 2014
Property And Equipment [Abstract]
Schedule Of Property Plant And Equipment
		2014		2013
	Land	$	9,220	$	9,220
	Buildings and improvements		5,729		4,124
	Furniture and fixtures		8,863		6,477
	Operating equipment		698,977		602,395
	Total property and equipment		722,789		622,216
	Accumulated depreciation		-323,344		-276,595
	Property and equipment — net	$	399,445	$	345,620

Goodwill_And_Other_Intangible_1

Goodwill And Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2014
Goodwill And Other Intangible Assets [Abstract]
Schedule of Goodwill
		Dredging Segment		Environmental & Remediation Segment		Total
	Balance - January 1, 2013	$	76,575	$	2,751	$	79,326
	Balance - December 31, 2013		76,575		2,751		79,326
	Acquisition of Magnus Pacific		-		7,000		7,000
	Balance - December 31, 2014	$	76,575	$	9,751	$	86,326
Schedule of the Net Book Value Of Indentifiable Intangible Assets
	As of December 31, 2014	Cost		Accumulated Amortization		Net
	Non-compete agreements	$	3,085	$	940	$	2,145
	Customer relationships		51		34		17
	Acquired backlog		6,278		1,395		4,883
	Trade names		1,037		185		852
	Other		1,306		240		1,066
		$	11,757	$	2,794	$	8,963
	As of December 31, 2013
	Non-compete agreements	$	1,646	$	544	$	1,102
	Acquired backlog		627		502		125
	Trade names		411		82		329
	Other		526		106		420
		$	3,210	$	1,234	$	1,976

Accrued_Expenses_Tables

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2014
Accrued Expenses [Abstract]
Accrued Expenses
		2014		2013
	Insurance	$	16,778	$	8,649
	Accumulated deficit in joint venture		10,383		-
	Payroll and employee benefits		8,808		13,664
	Interest		8,270		8,066
	Income and other taxes		5,857		3,709
	Fuel hedge contracts		3,029		-
	Percentage of completion adjustment		1,870		2,135
	Other		15,046		2,308
	Total accrued expenses	$	70,041	$	38,531

LongTerm_Debt_Tables

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2014
Long-Term Debt [Abstract]
Schedule Of Long-Term Debt
		2014		2013
	Revolving credit facility	$	-	$	35,000
	Equipment notes payable		2,857		-
	Notes payable		54,620		-
	7.375% senior notes		274,880		250,000
	Subtotal		332,357		285,000
	Current portion of equipment note payable		-736		-
	Current portion of note payable		-5,123		-
	Capital leases (included in other long term liabilities)		-2,121		-
	Total	$	324,377	$	285,000
Maturities Of Long-Term Debt
	Years Ending December 31
	2015	$	5,000
	2016		5,417
	2017		13,772
	2018		13,980
	2019		291,318
	Thereafter		-
	Total	$	329,487

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Measurements [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]
						Fair Value Measurements at Reporting Date Using
	Description	At  December 31, 2014			Quoted Prices in Active Markets for Identical Assets (Level 1)			Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (Level 3)
	Fuel hedge contracts	$	3,029		$	-		$	3,029		$	-
						Fair Value Measurements at Reporting Date Using
	Description	At  December 31, 2013			Quoted Prices in Active Markets for Identical Assets (Level 1)			Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (Level 3)
	Fuel hedge contracts	$	332		$	-		$	332		$	-
Schedule Of Fair Value Measurements Balance Sheet Location
		Balance Sheet Location		Fair Value at December 31,
				2014			2013
	Asset derivatives:
	Derivatives designated as hedges
	Fuel hedge contracts	Other current assets		$	-		$	332
	Liability derivatives:
	Derivatives not designated as hedges
	Fuel hedge contracts	Accrued expenses		$	3,029		$	-
Changes In Components Of Accumulated Other Comprehensive Income
				2014			2013			2012
	Cumulative translation adjustments—net of tax			$	-62		$	-397		$	-6
	Derivatives:
	Reclassification of derivative losses (gains) to earnings—net of tax				-332			270			3
	Change in fair value of derivatives—net of tax				133			34			-380
	Net unrealized (gain) loss on derivatives—net of tax				-199			304			-377
	Total other comprehensive loss			$	-261		$	-93		$	-383
Adjustments Reclassified From Accumulated Other Comprehensive Income To Earnings
		Statement of Operations Location		2014			2013			2012
	Derivatives:
	Fuel hedge contracts	Costs of contract revenues		$	-286		$	450		$	5
		Income tax benefit			46			180			2
				$	-332		$	270		$	3

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Taxes [Abstract]
Pre-Tax Income From Domestic And Foreign Operations
		2014		2013		2012
	Domestic operations	$	-20,823	$	23,716	$	15,884
	Foreign operations		30,011		6,601		-4,170
	Total pre-tax income	$	9,188	$	30,317	$	11,714
Provision For Income Taxes
		2014		2013		2012
	Federal:
	Current	$	-174	$	8,384	$	859
	Deferred		-9,531		2,107		1,948
	State:
	Current		277		439		156
	Deferred		-3,577		-326		481
	Foreign:
	Current		1,475		1,831		-
	Deferred		-		-1,975		1,975
	Total	$	-11,530	$	10,460	$	5,419
Income Tax Provision Reconciliation
		2014		2013		2012
	Tax provision at statutory U.S. federal
	income tax rate	$	3,214	$	10,611	$	4,100
	State income tax — net of federal income tax benefit		-2,726		500		245
	Worthless stock deduction		-9,631		-		-
	Charitable contributions		-1,764		-		-
	Adjustment to deferred tax depreciation		-1,670		-		-
	Change in deferred state tax rate		-811		-		246
	Research and development tax credits		-691		-		-
	Purchase price adjustment		-393		-		-
	Foreign income tax provision		-		238		-
	Changes in unrecognized tax benefits		127		-196		-137
	Changes in valuation allowance		2,246		-500		228
	Other		569		-193		737
	Income tax provision (benefit)	$	-11,530	$	10,460	$	5,419
Reconciliation Of Unrecognized Tax Benefits
		2014		2013		2012
	Unrecognized tax benefits — January 1	$	253	$	471	$	633
	Gross increases — tax positions in prior period		-		-		79
	Gross increases — current period tax positions		270		42		80
	Gross decreases — expirations		-65		-201		-321
	Gross decreases — tax positions in prior period		-16		-59		-
	Unrecognized tax benefits — December 31,	$	442	$	253	$	471
Deferred Tax Assets (Liabilities)
		2014		2013
	Deferred tax assets:
	Accrued liabilities	$	13,288	$	9,427
	Federal NOLs		19,365		-
	Foreign NOLs		4,334		2,505
	State NOLs		4,752		1,599
	Tax credit carryforwards		4,651		2,486
	Charitable contribution		1,764		-
	Valuation allowance		-6,579		-2,505
	Total deferred tax assets		41,575		13,512
	Deferred tax liabilities:
	Depreciation and amortization		-117,286		-115,542
	Other liabilities		-1,811		-
	Fuel hedges		-		-132
	Total deferred tax liabilities		-119,097		-115,674
	Net deferred tax liabilities	$	-77,522		-102,162
	As reported in the balance sheet:
	Net current deferred tax assets (included in other current assets)	$	14,485		6,349
	Net noncurrent deferred tax liabilities		-92,007		-108,511
	Net deferred tax liabilities	$	-77,522		-102,162

ShareBased_Compensation_Tables

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2014
Share-Based Compensation [Abstract]
Option Pricing Assumptions
			2014		2013		2012
	Expected volatility		53.9%		58.2%		55.0%
	Expected dividends		0.0%		0.0%		1.3%
	Expected term (in years)		7.0		6.0		5.5 - 6.5
	Risk free rate		1.9%		1.0%		0.7% - 1.0%
Summary Of Stock Option Activity
	Options	Shares		Weighted Average Exercise Price		Weighted-Average Remaining Contract Term (yrs)		Aggregate Intrinsic Value ($000's)
	Outstanding as of January 1, 2014		1,912	$	6.00
	Granted		337		7.62
	Exercised		-142		5.47
	Forfeited or Expired		-218		6.15
	Outstanding as of December 31, 2014		1,889	$	6.31		6.8	$	4,255
	Vested at December 31, 2014		1,204	$	5.70		5.8	$	3,446
	Vested or expected to vest at December 31, 2014		1,882	$	6.30		6.8	$	4,246
Summary Of Non-Vested Restricted Stock Units
	Nonvested Restricted Stock Units	Shares		Weighted-Average Grant-Date Fair Value
	Outstanding as of January 1, 2014		591	$	6.43
	Granted		1,741		6.89
	Vested		-174		5.43
	Forfeited		-95		6.29
	Outstanding as of December 31, 2014		2,063	$	6.91
	Expected to vest at December 31, 2014		925	$	7.07

Commitments_And_Contingencies_

Commitments And Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments And Contingencies [Abstract]
Future Minimum Operating Lease Payments
	2015	$	23,616
	2016		22,069
	2017		19,441
	2018		11,225
	2019		8,384
	Thereafter		16,009
	Total minimum operating lease payments	$	100,744

Investment_Tables

Investment (Tables)	12 Months Ended
	Dec. 31, 2014
Investments [Abstract]
Equity Method Investments
		2014		2013		2012
	Revenue	$	13,784	$	24,399	$	18,971
	Gross profit		-118		4,142		827
	Income from continuing operations		11,326		2,329		-281
	Net Income		9,527		3,998		227
	Lower Main Street Development
	The Company and a New Jersey aggregates company each own 50% of Lower Main. Lower Main was organized in February 2003 to hold land for development or sale.  This land owned in conjunction with Amboy Aggregates was sold in 2014.
	The Company accounts for this investment under the equity method. The following is summarized financial information for this entity:
		2014		2013		2012
	Revenue	$	180	$	180	$	180
	Gross profit		180		180		180
	Net Income		14,803		175		88

Business_Combinations_And_Disp1

Business Combinations And Dispositions (Tables)	12 Months Ended
	Dec. 31, 2014
Business Combinations And Dispositions [Abstract]
Unaudited Pro Forma Consolidated Financial Information
		2014			2013
		(Unaudited)
	Revenue as reported	$	806,831		$	731,418
	Revenue of purchased businesses for the period prior to the acquisition including proforma accounting adjustments		106,723			87,943
	Pro forma revenue	$	913,554		$	819,361
	Net income (loss) attributable to common stockholders of Great Lakes Dredge & Dock Corporation	$	10,295		$	-34,361
	Net income of Magnus including pro forma acquisition accounting adjustments		6,328			1,069
	Pro forma net income (loss) attributable to common stockholders of Great Lakes Dredge & Dock Corporation	$	16,623		$	-33,292
Schedule Of Discontinued Operations
			2014			2013		2012
	Revenue		$	14,803		$	39,550	$	100,602
	Loss before income taxes from discontinued operations		$	-19,167		$	-55,530	$	-17,125
	Loss on disposal of assets held for sale			-			-18,436		-
	Income tax benefit			8,744			19,116		7,490
	Loss from discontinued operations, net of income taxes		$	-10,423		$	-54,850	$	-9,635

Segment_Information_Tables

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2014
Segment Information [Abstract]
Segment Reporting By Segment
		2014		2013		2012
	Dredging:
	Contract revenues	$	697,711	$	642,602	$	588,229
	Operating income		41,620		54,683		32,947
	Depreciation and amortization		43,620		44,118		37,279
	Total assets		815,683		821,253		757,666
	Property and equipment—net		366,027		330,689		323,082
	Goodwill		76,576		76,575		76,575
	Investment in joint ventures		2,114		8,256		7,047
	Capital expenditures		79,186		57,902		64,598
	Environmental & remediation:
	Contract revenues		114,412		94,840		201
	Operating loss		-17,767		-3,282		-314
	Depreciation and amortization		6,509		2,504		150
	Total assets		77,551		31,392		68,802
	Property and equipment—net		33,418		14,931		12,427
	Goodwill		9,750		2,751		2,751
	Investment in joint ventures		5,775		-		-
	Capital expenditures		12,892		4,100		-
	Intersegment:
	Contract revenues		-5,292		-6,024		-
	Total:
	Contract revenues		806,831		731,418		588,430
	Operating income		23,853		51,401		32,633
	Depreciation and amortization		50,129		46,622		37,430
	Total assets		893,234		852,645		826,468
	Property and equipment—net		399,445		345,620		335,509
	Goodwill		86,326		79,326		79,326
	Investment in joint ventures		7,889		8,256		7,047
	Capital expenditures		92,078		62,002		64,598
Revenue Related to Dredging Projects By Type Of Work
		2014		2013		2012
	Capital dredging — U.S.	$	195,635	$	153,781	$	175,317
	Capital dredging — foreign		155,000		138,436		112,242
	Coastal protection dredging		194,219		228,868		126,873
	Maintenance dredging		123,923		90,833		137,924
	Rivers & lakes		28,934		30,684		35,873
	Total dredging	$	697,711	$	642,602	$	588,229
Revenues And Gross Profit From Foreign Project Operations
		2014		2013		2012
	Contract revenues	$	155,000	$	138,436	$	112,242
	Costs of contract revenues		-118,682		-117,029		-104,038
	Gross profit	$	36,318	$	21,407	$	8,204

Subsidiary_Guarantors_Tables

Subsidiary Guarantors (Tables)	12 Months Ended
	Dec. 31, 2014
Subsidiary Guarantors [Abstract]
Subsidiary Guarantors (Condensed Consolidated Balance Sheets)
	GREAT LAKES DREDGE & DOCK CORPORATION AND SUBSIDIARIES
	CONDENSED CONSOLIDATING BALANCE SHEET
	AS OF DECEMBER 31, 2014
	(In thousands)
	ASSETS	Subsidiary Guarantors		Non-Guarantor Subsidiaries		GLDD Corporation		Eliminations		Consolidated Totals
	CURRENT ASSETS:
	Cash and cash equivalents	$	41,724	$	663	$	2	$	-	$	42,389
	Accounts receivable — net		115,739		355		-		-2,906		113,188
	Receivables from affiliates		152,822		3,673		55,805		-212,300		-
	Contract revenues in excess of billings		78,631		4,236		-		-310		82,557
	Inventories		34,735		-		-		-		34,735
	Prepaid expenses		4,708		-		-		-		4,708
	Other current assets		49,619		431		14,617		-		64,667
	Assets held for sale		-		-		-		-		-
	Total current assets		477,978		9,358		70,424		-215,516		342,244
	PROPERTY AND EQUIPMENT—Net		399,421		24		-		-		399,445
	GOODWILL		86,326		-		-		-		86,326
	OTHER INTANGIBLE ASSETS—Net		8,963		-		-		-		8,963
	INVENTORIES — Noncurrent		36,262		-		-		-		36,262
	INVESTMENTS IN JOINT VENTURES		7,889		-		-		-		7,889
	INVESTMENTS IN SUBSIDIARIES		3,757		-		619,220		-622,977		-
	OTHER		7,135		3		4,967		-		12,105
	TOTAL	$	1,027,731	$	9,385	$	694,611	$	-838,493	$	893,234
	LIABILITIES AND EQUITY
	CURRENT LIABILITIES:
	Accounts payable	$	121,282	$	1,389	$	516	$	-3,216	$	119,971
	Payables to affiliates		196,829		403		15,068		-212,300		-
	Accrued expenses		60,415		659		8,967		-		70,041
	Billings in excess of contract revenues		4,639		-		-		-		4,639
	Current portion of long term debt		859		-		5,000		-		5,859
	Total current liabilities		384,024		2,451		29,551		-215,516		200,510
	7 3/8% SENIOR NOTES		-		-		274,880		-		274,880
	NOTE PAYABLE		7,553		-		41,944		-		49,497
	DEFERRED INCOME TAXES		172		-		91,835		-		92,007
	OTHER		19,939		-		438		-		20,377
	Total liabilities		411,688		2,451		438,648		-215,516		637,271
	Total Great Lakes Dredge & Dock Corporation Equity		616,043		6,934		255,963		-622,977		255,963
	NONCONTROLLING INTERESTS		-		-		-		-		-
	TOTAL EQUITY		616,043		6,934		255,963		-622,977		255,963
	TOTAL	$	1,027,731	$	9,385	$	694,611	$	-838,493	$	893,234
	GREAT LAKES DREDGE & DOCK CORPORATION AND SUBSIDIARIES
	CONDENSED CONSOLIDATING BALANCE SHEET
	AS OF DECEMBER 31, 2013
	(In thousands)
	ASSETS	Subsidiary Guarantors		Non-Guarantor Subsidiaries		GLDD Corporation		Eliminations		Consolidated Totals
	CURRENT ASSETS:
	Cash and cash equivalents	$	71,939	$	3,399	$	-	$	-	$	75,338
	Accounts receivable — net		95,476		1,039		-		-		96,515
	Receivables from affiliates		131,984		7,337		12,205		-151,526		-
	Contract revenues in excess of billings		63,591		3,841		-		-		67,432
	Inventories		32,500		-		-		-		32,500
	Prepaid expenses		3,913		-		298		-		4,211
	Other current assets		19,636		137		20,180		-		39,953
	Assets held for sale		41,763		11,877		-		-8,536		45,104
	Total current assets		460,802		27,630		32,683		-160,062		361,053
	PROPERTY AND EQUIPMENT—Net		345,612		8		-		-		345,620
	GOODWILL		79,326		-		-		-		79,326
	OTHER INTANGIBLE ASSETS—Net		1,976		-		-		-		1,976
	INVENTORIES — Noncurrent		38,496		-		-		-		38,496
	INVESTMENTS IN JOINT VENTURES		8,256		-		-		-		8,256
	INVESTMENTS IN SUBSIDIARIES		1,212		-		638,955		-640,167		-
	ASSETS HELD FOR SALE—Noncurrent		8,796		60		-		-		8,856
	OTHER		3,886		3		5,193		-20		9,062
TOTAL	$	948,362	$	27,701	$	676,831	$	-800,249	$	852,645
LIABILITIES AND EQUITY
CURRENT LIABILITIES:
Accounts payable	$	115,235	$	754	$	132	$	-	$	116,121
Payables to affiliates		96,270		24,862		30,394		-151,526		-
Accrued expenses		28,086		15		10,430		-		38,531
Billings in excess of contract revenues		6,754		-		-		-		6,754
Liabilities held for sale		38,158		2,871		-		-8,536		32,493
Total current liabilities		284,503		28,502		40,956		-160,062		193,899
7 3/8% SENIOR NOTES		-		-		250,000		-		250,000
REVOLVING CREDIT FACILITY		-		-		35,000		-		35,000
DEFERRED INCOME TAXES		-		-		108,531		-20
LIABILITIES HELD FOR SALE—Noncurrent		1,212		-		-		-		1,212
OTHER		21,679		-		243		-		21,922
Total liabilities		307,394		28,502		434,730		-160,082		610,544
Total Great Lakes Dredge & Dock Corporation Equity		640,968		-801		242,946		-640,167		242,946
NONCONTROLLING INTERESTS		-		-		-845		-		-845
TOTAL EQUITY		640,968		-801		242,101		-640,167		242,101
TOTAL	$	948,362	$	27,701	$	676,831	$	-800,249	$	852,645
Subsidiary Guarantors (Condensed Consolidated Statement Operations And Comprehensive Income)
	GREAT LAKES DREDGE & DOCK CORPORATION AND SUBSIDIARIES
	CONDENSED CONSOLIDATING STATEMENT OF OPERATIONS AND COMPREHENSIVE INCOME
	FOR THE YEAR ENDED DECEMBER 31, 2014
	(In thousands)
		Subsidiary Guarantors		Non-Guarantor Subsidiaries		GLDD Corporation		Eliminations		Consolidated Totals
	Contract revenues	$	799,579	$	26,282	$	-	$	-19,030	$	806,831
	Costs of contract revenues		-707,474		-25,891		-		19,030		-714,335
	Gross profit		92,105		391		-		-		92,496
	OPERATING EXPENSES:
	General and administrative expenses		67,905		6		-		-		67,911
	Loss on sale of assets—net		732		-		-		-		732
	Operating income		23,468		385		-		-		23,853
	Interest income (expense)—net		61		-261		-19,767		-		-19,967
	Equity in earnings of subsidiaries		20		-		10,373		-10,393		-
	Equity in earnings of joint ventures		2,895		-		-		-		2,895
	Gain on bargain purchase acquisition		2,197		-		-		-		2,197
	Other income		203		7		-		-		210
	Income (loss) from continuing operations before income taxes		28,844		131		-9,394		-10,393		9,188
	Income tax (provision) benefit		-18,173		-409		30,112		-		11,530
	Income (loss) from continuing operations		10,671		-278		20,718		-10,393		20,718
	Loss from discontinued operations, net of income taxes		-10,423		-1,343		-10,423		11,766		-10,423
	Net income (loss)		248		-1,621		10,295		1,373		10,295
	Net income (loss) attributable to Great Lakes	$	248	$	-1,621	$	10,295	$	1,373	$	10,295
	Dredge & Dock Corporation
	Comprehensive income (loss) attributable to	$	49	$	-1,683	$	10,034	$	1,634	$	10,034
	Great Lakes Dredge & Dock Corporation
	GREAT LAKES DREDGE & DOCK CORPORATION AND SUBSIDIARIES
	CONDENSED CONSOLIDATING STATEMENT OF OPERATIONS AND COMPREHENSIVE INCOME
	FOR THE YEAR ENDED DECEMBER 31, 2013
	(In thousands)
		Subsidiary Guarantors		Non-Guarantor Subsidiaries		GLDD Corporation		Eliminations		Consolidated Totals
	Contract revenues	$	718,041	$	24,932	$	-	$	-11,555	$	731,418
	Costs of contract revenues		-614,908		-27,770		-		11,555		-631,123
	Gross profit		103,133		-2,838		-		-		100,295
	OPERATING EXPENSES:
	General and administrative expenses		68,029		10		-		-		68,039
	Proceeds from loss of use claim		-13,372		-		-		-		-13,372
	(Gain) loss on sale of assets—net		-5,775		-		2		-		-5,773
	Operating income (loss)		54,251		-2,848		-2		-		51,401
	Interest expense—net		-136		-256		-21,549		-		-21,941
	Equity in earnings of subsidiaries		212		-		59,477		-59,689		-
	Equity in earnings of joint ventures		1,208		-		-		-		1,208
	Other expense		-3		-348		-		-		-351
	Income (loss) from continuing operations before income taxes		55,532		-3,452		37,926		-59,689		30,317
	Income tax (provision) benefit		293		4		-10,757		-		-10,460
	Income (loss) from continuing operations		55,825		-3,448		27,169		-59,689		19,857
	Loss from discontinued operations, net of income taxes		-55,106		-1,448		-62,162		63,866		-54,850
	Net income (loss)		719		-4,896		-34,993		4,177		-34,993
	Net loss attributable to noncontrolling interests		-		-		632		-		632
	Net income (loss) attributable to Great Lakes	$	719	$	-4,896	$	-34,361	$	4,177	$	-34,361
	Dredge & Dock Corporation
	Comprehensive income (loss) attributable to	$	1,023	$	-5,293	$	-34,454	$	4,270	$	-34,454
	Great Lakes Dredge & Dock Corporation
	GREAT LAKES DREDGE & DOCK CORPORATION AND SUBSIDIARIES
	CONDENSED CONSOLIDATING STATEMENT OF OPERATIONS AND COMPREHENSIVE INCOME
	FOR THE YEAR ENDED DECEMBER 31, 2012
	(In thousands)
		Subsidiary Guarantors		Non-Guarantor Subsidiaries		GLDD Corporation		Eliminations		Consolidated Totals
	Contract revenues	$	588,430	$	-	$	-	$	-	$	588,430
	Costs of contract revenues		-509,620		-652		-		-		-510,272
	Gross profit		78,810		-652		-		-		78,158
	OPERATING EXPENSES:
	General and administrative expenses		42,547		31		3,145		-		45,723
Gain on sale of assets—net		-293		-		95		-		-198
Operating income (loss)		36,556		-683		-3,240		-		32,633
Interest expense—net		-580		-133		-20,212		-		-20,925
Equity in earnings (loss) of subsidiaries		-1		-		36,888		-36,887		-
Equity in earnings of joint ventures		124		-		-		-		124
Other expense		-118		-		-		-		-118
Income (loss) from continuing operations before income taxes		35,981		-816		13,436		-36,887		11,714
Income tax provision		-6		-		-5,413		-		-5,419
Income (loss) from continuing operations		35,975		-816		8,023		-36,887		6,295
Loss from discontinued operations, net of income taxes		-9,798		-1,707		-11,363		13,233		-9,635
Net income (loss)		26,177		-2,523		-3,340		-23,654		-3,340
Net loss attributable to noncontrolling interests		-		-		645		-		645
Net income (loss) attributable to Great Lakes	$	26,177	$	-2,523	$	-2,695	$	-23,654	$	-2,695
Dredge & Dock Corporation
Comprehensive income (loss) attributable to	$	25,800	$	-2,529	$	-3,078	$	-23,271	$	-3,078
Great Lakes Dredge & Dock Corporation

Nature_Of_Business_And_Summary3

Nature Of Business And Summary Of Signicant Accounting Policies (Narrative) (Details)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Jan. 02, 2009
	segment
Nature Of Business And Summary Of Significant Accounting Policies [Line Items]
Number of reportable segments	2
Shares excluded from computation of diluted earnings per share	540
Yankee Environmental Services, LLC [Member]
Nature Of Business And Summary Of Significant Accounting Policies [Line Items]
Acquired membership interest		65.00%
Maximum [Member]
Nature Of Business And Summary Of Significant Accounting Policies [Line Items]
Average equipment-related costs of total costs of contract revenue	23.00%
Minimum [Member]
Nature Of Business And Summary Of Significant Accounting Policies [Line Items]
Average equipment-related costs of total costs of contract revenue	22.00%

Nature_Of_Business_And_Summary4

Nature Of Business And Summary Of Significant Accounting Policies (Estimated Useful Lives By Class Of Assets) (Details)	12 Months Ended
	Dec. 31, 2014
Building and Improvements [Member]
Property, Plant and Equipment [Line Items]
Useful life	10 years
Furniture and Fixtures [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful life	10 years
Furniture and Fixtures [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful life	5 years
Vehicles, Dozers, And Other Light Operating Equipment And Systems [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful life	5 years
Vehicles, Dozers, And Other Light Operating Equipment And Systems [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful life	3 years
Heavy Operating Equipment (Dredges And Barges) [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful life	30 years
Heavy Operating Equipment (Dredges And Barges) [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful life	10 years

Nature_Of_Business_And_Summary5

Nature Of Business And Summary Of Significant Accounting Policies (Computations For Basic And Diluted Earnings Per Share) (Details) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income from continuing operations	$20,718	$19,857	$6,295
Loss on discontinued operations, net of income taxes, attributable to Great Lakes Dredge & Dock Corporation	-10,423	-54,218	-8,990
Net income attributable to common stockholders of Great Lakes Dredge & Dock Corporation	10,295	-34,993	-3,340
Weighted-average common shares outstanding - basic	59,938	59,495	59,195
Effect of stock options and restricted stock units	584	606	478
Weighted-average common shares outstanding - diluted	60,522	60,101	59,673
Earnings per share from continuing operations - basic	$0.35	$0.33	$0.11
Earnings per share from continuing operations - diluted	$0.34	$0.33	$0.11
Parent Company [Member]
Income from continuing operations	20,718	27,169	8,023
Net income attributable to common stockholders of Great Lakes Dredge & Dock Corporation	$10,295	($34,993)	($3,340)

Earnings_Per_Share_Details

Earnings Per Share (Details) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	540
Net income	$10,295	($34,361)	($2,695)
Weighted-average common shares outstanding - basic	59,938	59,495	59,195
Effect of stock options and restricted stock units	584	606	478
Weighted-average common shares outstanding - diluted	60,522	60,101	59,673
Earnings per share - basic	$0.18	($0.58)	($0.04)
Earnings per share - diluted	$0.17	($0.57)	($0.04)

Restricted_And_Escrowed_Cash_D

Accounts Receivable And Contracts In Progress (Components Of Contracts In Progress) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accounts, Notes, Loans and Financing Receivable [Line Items]
Costs and earnings in excess of billings on contracts in progress	$73,491	$64,740
Costs and earnings in excess of billings for completed contracts	9,066	2,692
Total contract revenues in excess of billings	82,557	67,432
Current portion of contract revenues in excess of billings	82,557	67,432
Total billings in excess of contract revenues	-4,639	-6,754
Costs And Earnings In Excess Of Billings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Costs and earnings for contracts in progress	833,368	435,470
Amounts billed	-759,877	-370,730
Billings In Excess Of Costs And Earnings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Costs and earnings for contracts in progress	177,059	150,040
Amounts billed	($181,698)	($156,794)

Accounts_Receivable_And_Contra2

Accounts Receivable And Contracts In Progress (Components Of Contracts In Progress) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accounts, Notes, Loans and Financing Receivable [Line Items]
Costs and earnings in excess of billings on contracts in progress	$73,491	$64,740
Costs and earnings in excess of billings for completed contracts	9,066	2,692
Total contract revenues in excess of billings	82,557	67,432
Current portion of contract revenues in excess of billings	82,557	67,432
Total billings in excess of contract revenues	-4,639	-6,754
Costs And Earnings In Excess Of Billings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Costs and earnings for contracts in progress	833,368	435,470
Amounts billed	-759,877	-370,730
Billings In Excess Of Costs And Earnings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Costs and earnings for contracts in progress	177,059	150,040
Amounts billed	($181,698)	($156,794)

Accounts_Receivable_And_Contra3

Accounts Receivable And Contracts In Progress (Components Of Contracts In Progress) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accounts, Notes, Loans and Financing Receivable [Line Items]
Costs and earnings in excess of billings on contracts in progress	$73,491	$64,740
Costs and earnings in excess of billings for completed contracts	9,066	2,692
Total contract revenues in excess of billings	82,557	67,432
Current portion of contract revenues in excess of billings	82,557	67,432
Total billings in excess of contract revenues	-4,639	-6,754
Costs And Earnings In Excess Of Billings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Costs and earnings for contracts in progress	833,368	435,470
Amounts billed	-759,877	-370,730
Billings In Excess Of Costs And Earnings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Costs and earnings for contracts in progress	177,059	150,040
Amounts billed	($181,698)	($156,794)

Property_And_Equipment_Details

Property And Equipment (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Total property and equipment	$722,789	$622,216
Accumulated depreciation	-323,344	-276,595
Property and equipment - net	399,445	345,620	335,509
Depreciation	48,569	45,531	37,249
Operating equipment held for sale		1,704
Land [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	9,220	9,220
Building and Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	5,729	4,124
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	8,863	6,477
Operating Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$698,977	$602,395

Goodwill_And_Other_Intangible_2

Goodwill And Other Intangible Assets (Narrative) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Weighted average amortization period	2 years 26 days
Amortization expense	$1,560	$1,091	$181
2015	6,055
2016	1,045
2017	1,045
2018	579
2019	$238

Goddwill_And_Other_Intangible_

Goddwill And Other Intangible Assets (Schedule Of Goodwill) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2012	Dec. 31, 2013
Goodwill [Line Items]
Goodwill, Beginning Balance	$79,326	$79,326
Acquisition of Magnus Pacific	7,000
Goodwill, Ending Balance	86,326	79,326
Dredging Segment [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance		76,575	76,575
Goodwill, Ending Balance	76,575	76,575	76,575
Demolition Segment [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	2,751	2,751
Acquisition of Magnus Pacific	7,000
Goodwill, Ending Balance	$9,751	$2,751

Goodwill_And_Other_Intangible_3

Goodwill And Other Intangible Assets (Net Book Value Of Identifiable Assetsl) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Finite-Lived Intangible Assets [Line Items]
Cost	$11,757	$3,210
Accumulated amortization	2,794	1,234
Net	8,963	1,976
Non-compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	3,085	1,646
Accumulated amortization	940	544
Net	2,145	1,102
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	51
Accumulated amortization	34
Net	17
Backlog [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	6,278	627
Accumulated amortization	1,395	502
Net	4,883	125
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	1,037	411
Accumulated amortization	185	82
Net	852	329
Other [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	1,306	526
Accumulated amortization	240	106
Net	$1,066	$420

Accrued_Expenses_Details

Accrued Expenses (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accrued Expenses [Abstract]
Insurance	$16,778	$8,649
Interest	8,270	8,066
Payroll and employee benefits	8,808	13,664
Accumulated deficit in joint venture	10,383
Percentage of completion adjustment	1,870	2,135
Income and other taxes	5,857	3,709
Derivative Instruments and Hedges, Liabilities	3,029
Other	15,046	2,308
Total accrued expenses	$70,041	$38,531

Longterm_Debt_Narrative_Detail

Long-term Debt (Narrative) (Details) (USD $)

12 Months Ended

0 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2015

Dec. 31, 2016

Dec. 31, 2019

Nov. 04, 2014

Jan. 31, 2011

Jun. 04, 2012

Feb. 28, 2019

Nov. 30, 2014

Aug. 15, 2014

Mar. 31, 2017

Debt Instrument [Line Items]

Maximum leverage ratio under sixth Term Loan Facility covenant amendment

1.25%

Minimum fixed charge coverage ratio under sixth Term Loan Facility covenant amendment

3.00%

Letters of credit outstanding

$159,913,000

Letter of credit remaining borrowing capacity

50,087,000

Long-term Debt

324,377,000

285,000,000

Senior Notes

274,880,000

250,000,000

275,000,000

Equipment notes payable

2,857,000

Equipment notes payable

736,000

Amortization of deferred financing fees

1,453,000

1,153,000

1,245,000

Noncurrent portion of equipment debt

54,620,000

If Redeemed In 2015 [Member]

Debt Instrument [Line Items]

Debt Instrument, Redemption Price, Percentage

103.70%

If Redeemed In 2016 [Member]

Debt Instrument [Line Items]

Debt Instrument, Redemption Price, Percentage

101.80%

If Redeemed After 2016 [Member]

Debt Instrument [Line Items]

Debt Instrument, Redemption Price, Percentage

100.00%

Credit Agreement [Member]

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

210,000

Line of credit maximum borrowing capacity increase under incremental loans feature

15,000

Business Combination, Contingent Consideration, Liability

11,400,000

Debt Instrument, Collateral Amount

162,037,000

Multicurrency Borrowing Sublimit [Member]

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

50,000

Swingline Loans Sublimit [Member]

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

10,000

Notes 7.375% due 2019 [Member]

Debt Instrument [Line Items]

Potential senior notes to be issued under sixth Term Loan Facility amendment

50,000,000

Debt Instrument, Interest Rate, Stated Percentage

7.38%

Stated interest rate

7.38%

Term Loan Facility [Member]

Debt Instrument [Line Items]

Debt Instrument, Collateral Amount

50,572,000

Terra [Member]

Debt Instrument [Line Items]

Business Combination, Contingent Consideration, Liability

1,541,000

1,833,000

Senior Notes [Member]

Debt Instrument [Line Items]

Debt Instrument, Face Amount

250,000

275,000

25,000

Debt Instrument, Interest Rate, Stated Percentage

7.38%

Senior Notes

274,879,000

Debt instrument, face amount

250,000

275,000

25,000

Stated interest rate

7.38%

Term Loan Facility [Member]

Debt Instrument [Line Items]

Long-term Debt

47,360,000

Debt Instrument, Term

5 years

Debt instrument interest rate stated percentage increase per annum in event of default

2.00%

Percentage of principal to be repaid yearly during first two years of term

10.00%

Percentage of principal to be repaid yearly during third and fourth years of term

20.00%

Percentage of principal to be repaid during fifth year of term

25.00%

Debt Instrument, Face Amount

50,000

Debt Instrument, Interest Rate, Stated Percentage

4.66%

Debt instrument, face amount

50,000

Stated interest rate

4.66%

Internaional Line Of Credit [Member]

Debt Instrument [Line Items]

Line of Credit Facility, Amount Outstanding

24,000,000

Promissory Note [Member]

Debt Instrument [Line Items]

Debt Instrument, Interest Rate, Stated Percentage

5.00%

Secured Debt

8,100,000

Secured debt decrease in fair value under terms

1,086,000

Stated interest rate

5.00%

Parent Company [Member]

Debt Instrument [Line Items]

Senior Notes

$274,880,000

$250,000,000

Maximum [Member] | LIBOR Rate [Member] | Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Revolving credit facility, basis spread on variable rate

2.50%

Maximum [Member] | Base Rate [Member] | Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Revolving credit facility, basis spread on variable rate

1.50%

Minimum [Member] | LIBOR Rate [Member] | Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Revolving credit facility, basis spread on variable rate

1.50%

Minimum [Member] | Base Rate [Member] | Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Revolving credit facility, basis spread on variable rate

0.50%

Longterm_Debt_Schedule_Of_Long

Long-term Debt (Schedule Of Long-Term Debt) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Jan. 31, 2011
In Thousands, unless otherwise specified
Revolving credit facility		$35,000
Equipment notes payable	2,857
Other Notes Payable, Noncurrent	54,620
7.375% senior notes	274,880	250,000	275,000
Line of credit, senior note payable, equipment notes payable and senior note	332,357	285,000
Long term debt	324,377	285,000
Current portion of equipment note payable	-736
Current portion of note payable	-5,123
Capital leases (included in other long term liabilities)	2,121
Parent Company [Member]
Revolving credit facility		35,000
7.375% senior notes	$274,880	$250,000

LongTerm_Debt_Maturities_Of_Lo

Long-Term Debt (Maturities Of Long-Term Debt) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Long-Term Debt [Abstract]
2015	$5,000
2016	5,417
2017	13,772
2018	13,980
2019	291,318
Long term debt	324,377	285,000
Long term debt current and non current excluding equipment notes	$329,487

Fair_Value_Measurements_Narrat

Fair Value Measurements (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Jan. 31, 2011	31-May-09
	gal
Derivative asset, notional amount				$50,000,000
Derivative, average fixed interest rate				7.75%
Derivative underlying hedge percent	80.00%
Derivative nonmonetary notional gallons amount	4,900,000
Senior Notes	274,880,000	250,000,000	275,000,000
Reclassification of derivative losses to earnings-net of tax	332,000
Fair value hedge liabilities	3,029,000
Fair value hedge assets		332,000
Senior notes interest rate	7.38%		7.38%
Maximum [Member]
Fixed price range	3.01
Minimum [Member]
Fixed price range	2.08
Parent Company [Member]
Senior Notes	274,880,000	250,000,000
Senior Notes [Member]
Senior Notes	274,879,000
Senior Notes [Member] | Fair Value, Inputs, Level 1 [Member]
Senior Notes	$280,500,000

Fair_Value_Measurements_Fair_V

Fair Value Measurements (Fair Value Measurements at Reporting Date Using) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Assets, fair value disclosure	$3,029	$332
Fair Value, Inputs, Level 2 [Member]
Assets, fair value disclosure	$3,029	$332

Fair_Value_Measurements_Schedu

Fair Value Measurements (Schedule Of Fair Value Measurements Balance Sheet Location) (Details) (Fuel Hedge Contracts [Member], Designated as Hedging Instrument [Member], USD $)	Dec. 31, 2013	Dec. 31, 2014
In Thousands, unless otherwise specified
Other Current Assets [Member]
Derivative asset, fair value, gross asset	$332
Accrued Expenses [Member]
Derivative asset, fair value, gross liability		$3,029

Fair_Value_Measurements_Change

Fair Value Measurements (Changes In Components Of Accumulated Other Comprehensive Income) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Fair Value Measurements [Abstract]
Cumulative translation adjustments-net of tax	($62)		($397)		($6)
Reclassification of derivative losses (gains) to earnings-net of tax	-332		270		3
Change in fair value of derivatives-net of tax	133		34		-380
Net unrealized gain on derivatives-net of tax	-199	[1]	304	[1]	-377	[1]
Other comprehensive loss-net of tax	($261)		($93)		($383)
[1]	Net of income tax (provision) benefit of $(132), $204 and $(250) for the years ended December 31, 2014, 2013 and 2012, respectively.

Fair_Value_Measurement_Adjustm

Fair Value Measurement (Adjustments Reclassified From Accumulated Other Comprehensive Income To Earnings) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Costs of contract revenues	$714,335	$631,123	$510,272
Income tax provision	-11,530	10,460	5,419
Net income	10,295	-34,361	-2,695
Parent Company [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Income tax provision	-30,112	10,757	5,413
Net income	10,295	-34,361	-2,695
Fuel Hedge Contracts [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Costs of contract revenues	-286	450	5
Income tax provision	46	180	2
Net income	($332)	$270	$3

Income_Taxes_Narrative_Details

Income Taxes (Narrative) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating Loss Carryforwards [Line Items]
U.S. federal statutory income tax rate	35.00%	35.00%	35.00%
Unrecognized tax benefits	$442	$253	$471	$633
Amount of unrecognized tax benefits which would have an impact on the effective tax rate	287	164
loss carryforwards for federal income tax purposes	55,328	10,443
Interest and penalties recorded	24	18
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	105,458	37,537
Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	13,039	7,194
Valuation allowance for net operating loss carryforwards	$4,334	$2,505

Income_Taxes_Income_tax_Provis

Income Taxes (Income tax (Provision Benefit from Continuing and Discontinuing Operations) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income tax (provision) benefit	$11,530	($10,460)	($5,419)
Income tax benefit	8,744	19,116	7,490
Income tax (provision) benefit from continuing and discontinuing operations	20,274	8,656	2,071
Parent Company [Member]
Income tax (provision) benefit	$30,112	($10,757)	($5,413)

Income_Taxes_PreTax_Income_Fro

Income Taxes (Pre-Tax Income From Domestic And Foreign Operations) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Abstract]
Domestic operations	($20,823)	$23,716	$15,884
Foreign operations	30,011	6,601	-4,170
Total pre-tax income	$9,188	$30,317	$11,714

Income_Taxes_Provision_For_Inc

Income Taxes (Provision For Income Taxes) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Abstract]
Current federal tax expense (benefit)	($174)	$8,384	$859
Deferred federal tax expense (benefit)	-9,531	2,107	1,948
Current state tax expense (benefit)	277	439	156
Deferred state tax expense (benefit)	-3,577	-326	481
Current foreign tax expense (benefit)	1,475	1,831
Deferred foreign tax expense (benefit)		-1,975	1,975
Income tax provision	($11,530)	$10,460	$5,419

Recovered_Sheet2

Income Taxes (Income Tax Provision Reconciliation) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Abstract]
Tax provision (benefit) at statutory U.S. federal income tax rate	$3,214	$10,611	$4,100
State income tax - net of federal income tax benefit	-2,726	500	245
Worthless stock deduction	-9,631
Charitable contributions	-1,764
Adjustment to deferred tax depreciation	-1,670
Change in deferred state tax rate	-811		246
Research and development tax credits	-691
Purchase price adjustment	-393
Foreign income tax provision (benefit)		238
Changes in unrecognized tax benefits	127	-196	-137
Changes in valuation allowance	2,246	-500	228
Other	569	-193	737
Income tax provision	($11,530)	$10,460	$5,419

Income_Taxes_Reconciliation_Of

Income Taxes (Reconciliation Of Unrecognized Tax Benefits) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Abstract]
Unrecognized tax benefits - January 1	$253	$471	$633
Gross increases - tax positions in prior period			79
Gross increases - current period tax positions	270	42	80
Gross decreases - expirations in prior period	-65	-201	-321
Gross decreases - tax positions in prior period	-16	-59
Unrecognized tax benefits - December 31,	$442	$253	$471

Income_Taxes_Deferred_Tax_Asse

Income Taxes (Deferred Tax Assets (Liabilities)) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Income Taxes [Abstract]
Accrued liabilities	$13,288	$9,427
Tax credit carryforwards	4,651	2,486
Federal NOLs	19,365
Foreign NOLs	4,334	2,505
State NOLs	4,752	1,599
Charitable contributions	1,764
Valuation allowance	-6,579	-2,505
Total deferred tax assets	41,575	13,512
Depreciation and amortization	-117,286	-115,542
Other liabilities	-1,811
Fuel hedges		-132
Total deferred tax liabilities	-119,097	-115,674
Net current deferred tax assets (included in other current assets)	14,485	6,349
Net noncurrent deferred tax liabilites	-92,007	-108,511
Net deferred tax liabilities	($77,522)	($102,162)

ShareBased_Compensation_Narrat

Share-Based Compensation (Narrative) (Details) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2007
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				5,800
Allocated share-based compensation expense	$2,694	$3,251	$3,081
Weighted-average grant-date fair value of options granted	$4.23	$4.06	$2.93
Total unrecognized compensation cost related to non-vested NQSOs and RSUs	6,480
Total unrecognized compensation cost, weighted-average period of recognition	1 year 10 months 24 days
Amount related to shares used for tax withholding obligations	497	308
Shares of common stock received by employee directors	99	96	93
Annual retainer per non-employee director, percentage paid in cash	50.00%
Annual retainer per non-employee director, percentage paid in common stock	50.00%
Shares of common stock received by nonemployee directors	99
Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual retainer per non-employee director	155
Chairman of the Board [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional compensation to annual retainer, paid in stock	$250
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	1,741

ShareBased_Compensation_Option

Share-Based Compensation (Option Pricing Assumptions) (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	53.90%	58.20%	55.00%
Expected dividends	0.00%	0.00%	1.30%
Risk free rate, minimum	1.90%	1.00%	0.70%
Risk free rate, maximum			1.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	7 years	6 years	5 years 6 months
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term			6 years 6 months

ShareBased_Compensation_Summar

Share-Based Compensation (Summary Of Stock Option Activity) (Details) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014
Share-Based Compensation [Abstract]
Outstanding as of January 1, 2014	1,912
Options granted	337
Options exercised	-142
Options foreited or expired	-218
Options outstanding as of December 31, 2014	1,889
Options vested at December 31, 2014	1,204
Options vested and expected to vest at December 31, 2014	1,882
Weighted average exercise price outstanding as of January 1, 2014	$6
Weighted average exercise price, granted	$7.62
Weighted average exercise price, exercised	$5.47
Weighted average exercise price, forfeited or expired	$6.15
Weighted average exercise price outstanding as of December 31, 2014	$6.31
Weighted avergage exercise price, vested at December 31, 2014	$5.70
Weighted avergage exercise price, vested and expected to vest at December 31, 2014	$6.30
Weighted average remaining contractual term at December 31, 2014	6 years 9 months 18 days
Weighted average remaining contractual term, vested as of December 31, 2014	5 years 9 months 18 days
Weighted average remaining contractual term, vested and expected to vest as of December 31, 2014	6 years 9 months 18 days
Aggregate intrinsic value, outstanding as of December 31, 2014	$4,255
Aggregate intrinsic value, vested at December 31, 2014	3,446
Aggregate intrinsic value, vested and expected to vest at December 31, 2014	$4,246

ShareBased_Compensation_Summar1

Share-Based Compensation (Summary Of Non-Vested Restricted Stock Units) (Details) (Restricted Stock Units (RSUs) [Member], USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding as of January 1, 2014	591
Options granted	1,741
Options vested	-174
Options forfeited	-95
Options outstanding as of December 31, 2014	2,063
Options expected to vest	925
Weighted-average grant-date fair value as of January 1, 2014	$6.43
Weighted-average grant-date fair value, granted	$6.89
Weighted-average grant-date fair value, vested	$5.43
Weighted-average grant-date fair value, forfeited	$6.29
Weighted-average grant-date fair value as of December 31, 2014	$6.91
Weighted-average grant-date fair value, expected to vest at December 31, 2014	$7.07

Retirement_Plans_Narrative_Det

Retirement Plans (Narrative) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	item
Retirement Plans [Abstract]
Number of sponsored 401(k) plans	4
Expense for matching and discretionary contributions	$5,256	$5,123	$4,017
Contributes to various multiemployer pension plans	$4,383	$3,870	$3,447

Commitments_And_Contingencies_1

Commitments And Contingencies (Narrative) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2011
Senior notes interest rate	7.38%			7.38%
Outstanding performance bonds	$1,049,311
Revenue value remaining from outstanding performance bonds	357,409
Proceeds from Divestiture of Businesses	5,309
Letters of credit related to the shipyards contract received amount	13,600
Shipyard a settlement agreement , amount	10,500
Shipyard a settlement remitted , amount	3,100
Senior Notes	274,880	250,000		275,000
Rent expense under long term operating lease arrangements	25,318	21,620	18,370
Maximum [Member]
Bids bond range	10,000
Minimum [Member]
Bids bond range	1,000
Parent Company [Member]
Senior Notes	274,880	250,000
Discontinued Operations [Member]
Outstanding performance bonds	$49,048

Commitments_And_Contingencies_2

Commitments And Contingencies (Future Minimum Operating Lease Payments) (Details) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Commitments And Contingencies [Abstract]
2014	$23,616
2015	22,069
2016	19,441
2017	11,225
2018	8,384
Thereafter	16,009
Total minimum operating lease payments	$100,744

Investment_Narrative_Details

Investment (Narrative) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other current assets	$64,667	$39,953
Land sold	29,729
Parent Company [Member]
Other current assets	14,617	20,180
Amboy [Member]
Equity Method Investment, Ownership Percentage	50.00%
Equity Method Investment, Summarized Financial Information, Revenue	13,784	24,399	18,971
Equity Method Investment, Summarized Financial Information, Gross Profit (Loss)	-118	4,142	827
Equity Method Investment, Summarized Financial Information, Income (Loss) from Continuing Operations before Extraordinary Items	11,326	2,329	-281
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	9,527	3,998	227
TerraSea Environmental Solutions [Member]
Equity Method Investment, Ownership Percentage	50.00%
Equity Method Investment, Summarized Financial Information, Revenue	11,278	7,368	325
Equity Method Investment, Summarized Financial Information, Gross Profit (Loss)	-19,153	-956	318
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	-19,856	-956	19
Other current assets	22,898
Lower Main Street Development [Member]
Equity Method Investment, Summarized Financial Information, Revenue	180	180	180
Equity Method Investment, Summarized Financial Information, Gross Profit (Loss)	180	180	180
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	$14,803	$175	$88

RelatedParty_Transactions_Deta

Related-Party Transactions (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Related Party Transaction [Line Items]
Related party expenses		$95	$103
Beneficial Owner [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	375	449	449
Majority Shareholder [Member]
Related Party Transaction [Line Items]
Related party expenses		0	0
Magnus Real Estate Group, LLC [Member]
Related Party Transaction [Line Items]
Related party expenses	$46

Business_Combinations_And_Disp2

Business Combinations And Dispositions (Narrative) (Details) (USD $)	12 Months Ended			0 Months Ended
Share data in Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Nov. 04, 2014	Jan. 02, 2018	Jan. 17, 2017
Business Acquisition [Line Items]
Costs of contract revenues	$714,335,000	$631,123,000	$510,272,000
Property, Plant and Equipment, Gross	722,789,000	622,216,000
Accounts payable	119,971,000	116,121,000
GOODWILL	86,326,000	79,326,000	79,326,000
Weighted average amortization period	2 years 26 days
Goodwill	86,326,000	79,326,000	79,326,000
Terra [Member]
Business Acquisition [Line Items]
Base purchase price	26,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets	27,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables	14,600,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	11,300,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangibles	2,700,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	18,300,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable	17,500,000
GOODWILL	2,800,000
Purchase agreement, multiplication factor	25.00%
Purchase agreement, base additional amount	500,000
Purchase agreement, multiplication factor for amount exceeded	50.00%
Maximum earnout payment	2,000,000,000
Fair value of the earnout liability	1,541,000	1,833,000
Seller note	10,547,000
Tangible assets acquired	27,000,000
Receivables	14,600,000
Property, plant, and equipment	11,300,000
Finite-lived intangible assets acquired	2,700,000
Accounts payable	17,500,000
Liabilities assumed	18,300,000
Goodwill	2,800,000
Terra [Member] | Accrued Liabilities [Member]
Business Acquisition [Line Items]
Fair value of the earnout liability		725,000
Magnus Pacific Acquisition [Member]
Business Acquisition [Line Items]
Base purchase price				40,000
Payments for Previous Acquisition				25,000,000
Expected amount on the promissory note					7,544,000	7,544,000
Maximum potential aggregate earnout payment	11,400,000
Fair value of the recorded earnout liability	8,024,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables	57,303,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	11,573,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangibles	8,422,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	27,586,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable	20,732,000
GOODWILL	7,000,000
Right to receive, in aggregate maximum, shares	1,500
Receivables	57,303,000
Property, plant, and equipment	11,573,000
Finite-lived intangible assets acquired	8,422,000
Accounts payable	20,732,000
Liabilities assumed	27,586,000
Goodwill	7,000,000
Magnus Pacific Acquisition [Member] | Excess Of Billings [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables	41,067,000
Receivables	41,067,000
Parent Company [Member]
Business Acquisition [Line Items]
Accounts payable	516,000	132,000
Maximum [Member] | Terra [Member]
Business Acquisition [Line Items]
Purchase agreement, earnings before income taxes, depreciation and amortization, amount	4,500,000,000
Weighted average amortization period	5 years
Minimum [Member] | Terra [Member]
Business Acquisition [Line Items]
Purchase agreement, earnings before income taxes, depreciation and amortization, amount	$4,000,000,000
Weighted average amortization period	1 year

Business_Combinations_And_Disp3

Business Combinations And Dispositions (Results Of Discontinued Operations) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue	$14,803	$39,550	$100,602
Income (loss) before income taxes from discontinued operations	-19,167	-55,530	-17,125
Loss on disposition of assets held for sale		-18,436
Income tax benefit	8,744	19,116	7,490
Income (loss) from discontinued operations, net of income taxes	-10,423	-54,850	-9,635
Parent Company [Member]
Income (loss) from discontinued operations, net of income taxes	($10,423)	($62,162)	($11,363)

Business_Combinations_And_Disp4

Business Combinations And Dispositions Unaudited Pro Forma) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues	$806,831	$731,418	$588,430
Revenue of purchased businesses for the period prior to the acquisition including pro forma accounting adjustments	106,723	87,943
Pro forma revenue	913,554	819,361
Net income	10,295	-34,361	-2,695
Net income of L.W. Matteson, Inc., including pro forma purchase accounting adjustments	6,328	1,069
Pro forma net income attributable to common stockholders of Great Lakes Dredge & Dock Corporation	16,623	-33,292
As Reported [Member]
Revenues	806,831	731,418
Parent Company [Member]
Net income	$10,295	($34,361)	($2,695)

Segment_Information_Narrative_

Segment Information (Narrative) (Details) (USD $)	12 Months Ended			3 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014
	segment
Segment Reporting Information [Line Items]
Number of reportable segments	2
Long-lived assets, net book value	$93,839	$104,099		$93,839
Gross Profit	92,496	100,295	78,158
Single Customer Foreign Contract [Member]
Segment Reporting Information [Line Items]
Gross Profit	22,418
Increase gross profit from foreign contract				$7,645
Bahrain [Member] | Sales [Member]
Segment Reporting Information [Line Items]
Concentration risk percentage			14.20%
Dredging [Member] | Sales [Member] | Federal Government Agencies [Member]
Segment Reporting Information [Line Items]
Concentration risk percentage	60.40%	45.00%	68.90%
Dredging [Member] | Accounts Receivable [Member] | Federal Government Agencies [Member]
Segment Reporting Information [Line Items]
Concentration risk percentage	45.90%	48.70%
Dredging [Member] | Bahrain [Member] | Accounts Receivable [Member]
Segment Reporting Information [Line Items]
Concentration risk percentage	11.40%	13.10%

Segment_Information_Segment_Re

Segment Information (Segment Reporting By Segment) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Contract revenues	$806,831	$731,418	$588,430
Operating income (loss)	23,853	51,401	32,633
Depreciation and amortization	50,129	46,622	37,430
Total assets	893,234	852,645	826,468
Property and equipment - net	399,445	345,620	335,509
Goodwill	86,326	79,326	79,326
Investment in joint ventures	7,889	8,256	7,047
Capital expenditures	92,078	62,002	64,598
Parent Company [Member]
Segment Reporting Information [Line Items]
Operating income (loss)		-2	-3,240
Total assets	694,611	676,831
Dredging [Member]
Segment Reporting Information [Line Items]
Contract revenues	697,711	642,602	588,229
Operating income (loss)	41,620	54,683	32,947
Depreciation and amortization	43,620	44,118	37,279
Total assets	815,683	821,253	757,666
Property and equipment - net	366,027	330,689	323,082
Goodwill	76,576	76,575	76,575
Investment in joint ventures	2,114	8,256	7,047
Capital expenditures	79,186	57,902	64,598
Intersegment [Member]
Segment Reporting Information [Line Items]
Contract revenues	-5,292	-6,024
Environmental & remediation [Member]
Segment Reporting Information [Line Items]
Contract revenues	114,412	94,840	201
Operating income (loss)	-17,767	-3,282	-314
Depreciation and amortization	6,509	2,504	150
Total assets	77,551	31,392	68,802
Property and equipment - net	33,418	14,931	12,427
Goodwill	9,750	2,751	2,751
Investment in joint ventures	5,775
Capital expenditures	$12,892	$4,100

Segment_Information_Dredging_R

Segment Information (Dredging Revenue By Type Of Work) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue from External Customer [Line Items]
Revenues	$806,831	$731,418	$588,430
Dredging [Member]
Revenue from External Customer [Line Items]
Revenues	697,711	642,602	588,229
Dredging [Member] | Capital dredging - Foreign [Member]
Revenue from External Customer [Line Items]
Revenues	155,000	138,436	112,242
Dredging [Member] | Capital Dredging - U.S. [Member]
Revenue from External Customer [Line Items]
Revenues	195,635	153,781	175,317
Dredging [Member] | Beach Nourishment Dredging [Member]
Revenue from External Customer [Line Items]
Revenues	194,219	228,868	126,873
Dredging [Member] | Maintenance Dredging [Member]
Revenue from External Customer [Line Items]
Revenues	123,923	90,833	137,924
Dredging [Member] | Rivers & Lakes [Member]
Revenue from External Customer [Line Items]
Revenues	$28,934	$30,684	$35,873

Segment_Information_Revenues_A

Segment Information (Revenues And Gross Profit From Foreign Operations) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue from External Customer [Line Items]
Contract revenues	$806,831	$731,418	$588,430
Costs of contract revenues	714,335	631,123	510,272
Gross profit	92,496	100,295	78,158
Foreign [Member]
Revenue from External Customer [Line Items]
Contract revenues	155,000	138,436	112,242
Costs of contract revenues	-118,682	-117,029	-104,038
Gross profit	$36,318	$21,407	$8,204

Subsidiary_Guarantors_Narrativ

Subsidiary Guarantors (Narrative) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Jan. 31, 2011
In Thousands, unless otherwise specified
Subsidiary Guarantors [Abstract]
Senior Notes	$274,880	$250,000	$275,000
Senior notes interest rate	7.38%		7.38%

Subsidiary_Guarantors_Condense

Subsidiary Guarantors (Condensed Consolidating Balance Sheets) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jan. 31, 2011
In Thousands, unless otherwise specified
ASSETS
Cash and cash equivalents	$42,389	$75,338	$24,440	$113,288
Accounts receivable-net	113,188	96,515
Contract revenues in excess of billings	82,557	67,432
Inventories	34,735	32,500
Prepaid expenses	4,708	4,211
Other current assets	64,667	39,953
Assets held for sale		45,104
Total current assets	342,244	361,053
PROPERTY AND EQUIPMENT-Net	399,445	345,620	335,509
GOODWILL	86,326	79,326	79,326
OTHER INTANGIBLE ASSETS-Net	8,963	1,976
INVENTORIES-Noncurrent	36,262	38,496
INVESTMENTS IN JOINT VENTURES	7,889	8,256	7,047
Assets Held-for-sale, Other, Noncurrent		8,856
OTHER	12,105	9,062
TOTAL	893,234	852,645	826,468
LIABILITIES AND EQUITY
Accounts payable	119,971	116,121
Accrued expenses	70,041	38,531
Billings in excess of contract revenues	4,639	6,754
Current portion of long term debt	5,859
Liabilities held for sale		32,493
Total current liabilities	200,510	193,899
7 3/8% SENIOR NOTES	274,880	250,000			275,000
Notes Payable	49,497
REVOLVING CREDIT FACILITY		35,000
Deferred income taxe	-92,007
LIABILITIES HELD FOR SALE-Noncurrent		1,212
Other	20,377	21,922
Total liabilities	637,271	610,544
EQUITY:
Total Great Lakes Dredge & Dock Corporation equity	255,963	242,946
NONCONTROLLING INTERESTS		-845
Total equity	255,963	242,101	273,425	292,537
TOTAL	893,234	852,645
Parent Company [Member]
ASSETS
Cash and cash equivalents	2
Receivables from affiliates	55,805	12,205
Prepaid expenses		298
Other current assets	14,617	20,180
Total current assets	70,424	32,683
INVESTMENTS IN SUBSIDIARIES	619,220	638,955
OTHER	4,967	5,193
TOTAL	694,611	676,831
LIABILITIES AND EQUITY
Accounts payable	516	132
Payables to affiliates	15,068	30,394
Accrued expenses	8,967	10,430
Current portion of long term debt	5,000
Total current liabilities	29,551	40,956
7 3/8% SENIOR NOTES	274,880	250,000
Notes Payable	41,944
REVOLVING CREDIT FACILITY		35,000
Deferred income taxe	-91,835	-108,531
Other	438	243
Total liabilities	438,648	434,730
EQUITY:
Total Great Lakes Dredge & Dock Corporation equity	255,963	242,946
NONCONTROLLING INTERESTS		-845
Total equity	255,963	242,101
TOTAL	694,611	676,831
Subsidiary Guarantors [Member]
ASSETS
Cash and cash equivalents	41,724	71,939	24,272	108,985
Accounts receivable-net	115,739	95,476
Receivables from affiliates	152,822	131,984
Contract revenues in excess of billings	78,631	63,591
Inventories	34,735	32,500
Prepaid expenses	4,708	3,913
Other current assets	49,619	19,636
Assets held for sale		41,763
Total current assets	477,978	460,802
PROPERTY AND EQUIPMENT-Net	399,421	345,612
GOODWILL	86,326	79,326
OTHER INTANGIBLE ASSETS-Net	8,963	1,976
INVENTORIES-Noncurrent	36,262	38,496
INVESTMENTS IN JOINT VENTURES	7,889	8,256
INVESTMENTS IN SUBSIDIARIES	3,757	1,212
Assets Held-for-sale, Other, Noncurrent		8,796
OTHER	7,135	3,886
TOTAL	1,027,731	948,362
LIABILITIES AND EQUITY
Accounts payable	121,282	115,235
Payables to affiliates	196,829	96,270
Accrued expenses	60,415	28,086
Billings in excess of contract revenues	4,639	6,754
Current portion of long term debt	859
Liabilities held for sale		38,158
Total current liabilities	384,024	284,503
Notes Payable	7,553
Deferred income taxe	-172
LIABILITIES HELD FOR SALE-Noncurrent		1,212
Other	19,939	21,679
Total liabilities	411,688	307,394
EQUITY:
Total Great Lakes Dredge & Dock Corporation equity	616,043	640,968
Total equity	616,043	640,968
TOTAL	1,027,731	948,362
Non-Guarantor Subsidiaries [Member]
ASSETS
Cash and cash equivalents	663	3,399	168	4,303
Accounts receivable-net	355	1,039
Receivables from affiliates	3,673	7,337
Contract revenues in excess of billings	4,236	3,841
Other current assets	431	137
Assets held for sale		11,877
Total current assets	9,358	27,630
PROPERTY AND EQUIPMENT-Net	24	8
Assets Held-for-sale, Other, Noncurrent		60
OTHER	3	3
TOTAL	9,385	27,701
LIABILITIES AND EQUITY
Accounts payable	1,389	754
Payables to affiliates	403	24,862
Accrued expenses	659	15
Liabilities held for sale		2,871
Total current liabilities	2,451	28,502
Total liabilities	2,451	28,502
EQUITY:
Total Great Lakes Dredge & Dock Corporation equity	6,934	-801
Total equity	6,934	-801
TOTAL	9,385	27,701
Eliminations [Member]
ASSETS
Accounts receivable-net	-2,906
Receivables from affiliates	-212,300	-151,526
Contract revenues in excess of billings	-310
Assets held for sale		-8,536
Total current assets	-215,516	-160,062
INVESTMENTS IN SUBSIDIARIES	-622,977	-640,167
OTHER		-20
TOTAL	-838,493	-800,249
LIABILITIES AND EQUITY
Accounts payable	-3,216
Payables to affiliates	-212,300	-151,526
Liabilities held for sale		-8,536
Total current liabilities	-215,516	-160,062
Deferred income taxe		20
Total liabilities	-215,516	-160,082
EQUITY:
Total Great Lakes Dredge & Dock Corporation equity	-622,977	-640,167
Total equity	-622,977	-640,167
TOTAL	($838,493)	($800,249)

Subsidiary_Guarantors_Condense1

Subsidiary Guarantors (Condensed Consolidating Statement Operations And Comprehensive Income) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Contract revenues	$806,831	$731,418	$588,430
Costs of contract revenues	-714,335	-631,123	-510,272
Gross profit	92,496	100,295	78,158
General and administrative expenses	67,911	68,039	45,723
Proceeds from loss of use claim		-13,372
Gain on sale of assets-net	732	-5,773	-198
Total operating income	23,853	51,401	32,633
Interest expense-net	-19,967	-21,941	-20,925
Equity in earnings of joint ventures	2,895	1,208	124
Gain on bargain purchase acquisition	2,197
Loss on foreign currency transactions-net	210	-351	-118
Income from continuing operations	20,718	19,857	6,295
Income (Loss) From Discontinued Operations, Net Of Tax	-10,423	-54,850	-9,635
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	9,188	30,317	11,714
Income tax (provision) benefit	11,530	-10,460	-5,419
Net loss attributable to noncontrolling interest		632	645
Net Income (Loss) Attributable to Parent	10,295	-34,993	-3,340
NET INCOME (LOSS)	10,295	-34,361	-2,695
Comprehensive income (loss) attributable to Great Lakes Dredge & Dock Corporation	10,034	-34,454	-3,078
Parent Company [Member]
General and administrative expenses			3,145
Gain on sale of assets-net		2	95
Total operating income		-2	-3,240
Interest expense-net	-19,767	-21,549	-20,212
Equity in earnings (loss) of subsidiaries	10,373	59,477	36,888
Income from continuing operations	20,718	27,169	8,023
Income (Loss) From Discontinued Operations, Net Of Tax	-10,423	-62,162	-11,363
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	-9,394	37,926	13,436
Income tax (provision) benefit	30,112	-10,757	-5,413
Net loss attributable to noncontrolling interest		632	645
Net Income (Loss) Attributable to Parent	10,295	-34,993	-3,340
NET INCOME (LOSS)	10,295	-34,361	-2,695
Comprehensive income (loss) attributable to Great Lakes Dredge & Dock Corporation	10,034	-34,454	-3,078
Subsidiary Guarantors [Member]
Contract revenues	799,579	718,041	588,430
Costs of contract revenues	-707,474	-614,908	-509,620
Gross profit	92,105	103,133	78,810
General and administrative expenses	67,905	68,029	42,547
Proceeds from loss of use claim		-13,372
Gain on sale of assets-net	732	-5,775	-293
Total operating income	23,468	54,251	36,556
Interest expense-net	61	-136	-580
Equity in earnings (loss) of subsidiaries	20	212	-1
Equity in earnings of joint ventures	2,895	1,208	124
Gain on bargain purchase acquisition	2,197
Loss on foreign currency transactions-net	203	-3	-118
Income from continuing operations	10,671	55,825	35,975
Income (Loss) From Discontinued Operations, Net Of Tax	-10,423	-55,106	-9,798
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	28,844	55,532	35,981
Income tax (provision) benefit	-18,173	293	-6
Net Income (Loss) Attributable to Parent	248	719	26,177
NET INCOME (LOSS)	248	719	26,177
Comprehensive income (loss) attributable to Great Lakes Dredge & Dock Corporation	49	1,023	25,800
Non-Guarantor Subsidiaries [Member]
Contract revenues	26,282	24,932
Costs of contract revenues	-25,891	-27,770	-652
Gross profit	391	-2,838	-652
General and administrative expenses	6	10	31
Total operating income	385	-2,848	-683
Interest expense-net	-261	-256	-133
Loss on foreign currency transactions-net	7	-348
Income from continuing operations	-278	-3,448	-816
Income (Loss) From Discontinued Operations, Net Of Tax	-1,343	-1,448	-1,707
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	131	-3,452	-816
Income tax (provision) benefit	-409	4
Net Income (Loss) Attributable to Parent	-1,621	-4,896	-2,523
NET INCOME (LOSS)	-1,621	-4,896	-2,523
Comprehensive income (loss) attributable to Great Lakes Dredge & Dock Corporation	-1,683	-5,293	-2,529
Eliminations [Member]
Contract revenues	-19,030	-11,555
Costs of contract revenues	19,030	11,555
Equity in earnings (loss) of subsidiaries	-10,393	-59,689	-36,887
Income from continuing operations	-10,393	-59,689	-36,887
Income (Loss) From Discontinued Operations, Net Of Tax	11,766	63,866	13,233
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	-10,393	-59,689	-36,887
Net Income (Loss) Attributable to Parent	1,373	4,177	-23,654
NET INCOME (LOSS)	1,373	4,177	-23,654
Comprehensive income (loss) attributable to Great Lakes Dredge & Dock Corporation	$1,634	$4,270	($23,271)

Subsidiary_Guarantors_Condense2

Subsidiary Guarantors (Condensed Consolidated of Cash Flow) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
OPERATING ACTIVITIES:
Net cash flows provided by (used in) operating activities of continuing operations	$67,154	$86,347	$19,736
Net cash flows used in by operating activities of discontinued operations	-18,352	-11,524	-21,596
Net Cash Provided by (Used in) Operating Activities	48,802	74,823	-1,860
Adjustments to reconcile net income to net cash flows used in operating activities:
Depreciation and amortization	50,129	46,622	37,430
Equity in (earnings) loss of joint ventures, net of cash distributions	-2,895	-1,208	-124
Deferred income taxes	-14,504	-304	4,471
(Gain) loss on dispositions of property and equipment	732	-5,773	-198
Amortization of deferred financing fees	1,453	1,153	1,245
Unrealized foreign currency (gain) loss	-593	179	-208
Share-based compensation expense	2,694	3,251	3,081
Excess income tax benefit from share based compensation	-206	-154	-189
Changes in assets and liabilities:
Accounts receivable	11,012	36,260	-17,795
Inventories	120	-5,144	-2,603
Prepaid expenses and other current assets	1,780	-10,124	-1,444
Accounts payable and accrued expenses	-14,113	22,622	20,253
Cash provided by (used in) operating activities	48,802	74,823	-1,860
INVESTING ACTIVITIES:
Purchases of property and equipment	-91,910	-66,654	-60,516
Proceeds from dispositions of property and equipment	68	6,953	597
Payments for acquisitions of businesses	-27,048
Acquisition of Terra assets			-2,000
Proceeds from vendor performance obligations	-3,100	13,600
Net cash flows used in investing activities of continuing operations	-121,990	-46,101	-61,919
Net cash flows provided by (used in) investing activities of discontinued operations	5,275	-153	-1,524
Cash used in investing activities	-116,715	-46,254	-63,443
FINANCING ACTIVITIES:
Proceeds from term loan facility	47,360
Repayments of term loan facility	-417
Proceeds from issuance of 7 3/8% senior notes	24,880
Deferred financing fees	-2,532		-2,039
Repayment of long term note payable		-13,047	-2,500
Distributions paid to minority interests	205	-3	-133
Dividends paid			-18,560
Dividend equivalents paid on restricted stock units			-196
Taxes paid on settlement of vested share awards	-497	-308	-231
Payments to Noncontrolling Interests	-205	3	133
Exercise of stock options and purchases from employee stock plans		668	461
Excess income tax benefit from share-based compensation		154	189
Repayments of equipment debt	-235
Exercise of stock options	1,568	668	461
Excess income tax benefit from share-based compensation	206	154	189
Borrowings under revolving loans	236,500	227,000
Repayments of revolving loans	-271,500	-192,000
Net cash flows provided by (used in) financing activities of continuing operations	35,128	22,464	-23,009
Net cash flows provided by (used in) financing activities of discontinued operations			-543
Cash provided by financing activities	35,128	22,464	-23,552
Effect of foreign currency exchange rates on cash and cash equivalents	-164	-135	7
Net increase (decrease) in cash and cash equivalents	-32,949	50,898	-88,848
Cash and cash equivalents at beginning of period	75,338	24,440	113,288
Cash and cash equivalents at end of period	42,389	75,338	24,440
Parent Company [Member]
OPERATING ACTIVITIES:
Net cash flows provided by (used in) operating activities of continuing operations	2,879	-32,641	-27,977
Net Cash Provided by (Used in) Operating Activities	2,879	-32,641	-27,977
Changes in assets and liabilities:
Cash provided by (used in) operating activities	2,879	-32,641	-27,977
INVESTING ACTIVITIES:
Payments for acquisitions of businesses	-25,000
Net cash flows used in investing activities of continuing operations	-25,000
Cash used in investing activities	-25,000
FINANCING ACTIVITIES:
Proceeds from term loan facility	47,360
Repayments of term loan facility	-417
Proceeds from issuance of 7 3/8% senior notes	24,880
Deferred financing fees	-2,532		-2,039
Repayment of long term note payable		-10,547
Distributions paid to minority interests	205	-3	-133
Dividends paid			-18,560
Dividend equivalents paid on restricted stock units			-196
Taxes paid on settlement of vested share awards	-497	-308	-231
Payments to Noncontrolling Interests	-205	3	133
Net change in accounts with affiliates	-65,640	-8,603	-48,486
Intercompany dividends	52,400
Capital contributions		-926
Exercise of stock options and purchases from employee stock plans		668	461
Excess income tax benefit from share-based compensation		154	189
Exercise of stock options	1,568
Excess income tax benefit from share-based compensation	206
Borrowings under revolving loans	236,500	227,000
Repayments of revolving loans	-271,500	-192,000
Net cash flows provided by (used in) financing activities of continuing operations	22,123	32,641	27,977
Cash provided by financing activities	22,123	32,641	27,977
Net increase (decrease) in cash and cash equivalents	2
Cash and cash equivalents at end of period	2
Subsidiary Guarantors [Member]
OPERATING ACTIVITIES:
Net cash flows provided by (used in) operating activities of continuing operations	63,276	126,736	48,544
Net cash flows used in by operating activities of discontinued operations	-17,328	-5,049	-20,636
Net Cash Provided by (Used in) Operating Activities	45,948	121,687	27,908
Changes in assets and liabilities:
Cash provided by (used in) operating activities	45,948	121,687	27,908
INVESTING ACTIVITIES:
Purchases of property and equipment	-91,910	-66,654	-60,516
Proceeds from dispositions of property and equipment	68	6,953	597
Payments for acquisitions of businesses	-2,048
Acquisition of Terra assets		-37,282
Acquisition of Terra assets			-2,000
Proceeds from vendor performance obligations	-3,100	13,600
Net change in accounts with affiliates from investing activities	68,187
Net cash flows used in investing activities of continuing operations	-28,803	-83,383	-61,919
Net cash flows provided by (used in) investing activities of discontinued operations	5,275	-153	-1,524
Cash used in investing activities	-23,528	-83,536	-63,443
FINANCING ACTIVITIES:
Repayment of long term note payable		-2,500	-2,500
Net change in accounts with affiliates			46,135
Intercompany dividends	-52,400
Repayments of equipment debt	-235
Net cash flows provided by (used in) financing activities of continuing operations	-52,635	-2,500	-48,635
Net cash flows provided by (used in) financing activities of discontinued operations		12,016	-543
Cash provided by financing activities	-52,635	9,516	-49,178
Net increase (decrease) in cash and cash equivalents	-30,215	47,667	-84,713
Cash and cash equivalents at beginning of period	71,939	24,272	108,985
Cash and cash equivalents at end of period	41,724	71,939	24,272
Non-Guarantor Subsidiaries [Member]
OPERATING ACTIVITIES:
Net cash flows provided by (used in) operating activities of continuing operations	999	-7,748	-831
Net cash flows used in by operating activities of discontinued operations	-1,024	-6,475	-960
Net Cash Provided by (Used in) Operating Activities	-25	-14,223	-1,791
Changes in assets and liabilities:
Cash provided by (used in) operating activities	-25	-14,223	-1,791
INVESTING ACTIVITIES:
Acquisition of Terra assets		-302
Net cash flows used in investing activities of continuing operations		-302
Cash used in investing activities		-302
FINANCING ACTIVITIES:
Net change in accounts with affiliates	-2,547	-10,342	2,351
Capital contributions		926
Net cash flows provided by (used in) financing activities of continuing operations	-2,547	11,268	-2,351
Net cash flows provided by (used in) financing activities of discontinued operations		6,623
Cash provided by financing activities	-2,547	17,891	-2,351
Effect of foreign currency exchange rates on cash and cash equivalents	-164	-135	7
Net increase (decrease) in cash and cash equivalents	-2,736	3,231	-4,135
Cash and cash equivalents at beginning of period	3,399	168	4,303
Cash and cash equivalents at end of period	663	3,399	168
Eliminations [Member]
INVESTING ACTIVITIES:
Acquisition of Terra assets		37,584
Net change in accounts with affiliates from investing activities	-68,187
Net cash flows used in investing activities of continuing operations	-68,187	37,584
Cash used in investing activities	-68,187	37,584
FINANCING ACTIVITIES:
Net change in accounts with affiliates	68,187	18,945
Net cash flows provided by (used in) financing activities of continuing operations	68,187	-18,945
Net cash flows provided by (used in) financing activities of discontinued operations		-18,639
Cash provided by financing activities	$68,187	($37,584)

Schedule_IIValuation_And_Quali1

Schedule II-Valuation And Qualifying Accounts (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$4,034	$4,403	$3,979
Additions charged to costs and expenses	4,174	-369	1,174
Deductions	-1,051		-750
Ending Balance	7,157	4,034	4,403
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	1,529	1,051	855
Additions charged to costs and expenses	100	478	946
Deductions	-1,051		-750
Ending Balance	578	1,529	1,051
Valuation Allowance of Deferred Tax Assets [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	2,505	3,352	3,124
Additions charged to costs and expenses	4,074	-847	228
Ending Balance	$6,579	$2,505	$3,352