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Maximum potential aggregate earnout payment.

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Amount of direct costs of the business combination including legal, accounting, and other costs incurred to consummate the business acquisition.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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Amount of gain (loss) on sale or disposal of assets utilized in financial service operations.

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Amount of addition (reduction) to the amount at which a liability could be incurred (settled) in a current transaction between willing parties.

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The value (monetary amount) of the award the plaintiff seeks in the legal matter.

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Cash outflow representing an adjustment to the purchase price of a previous acquisition.

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The cash inflow associated with the amount received from the sale of a portion of the company's business, for example a segment, division, branch or other business, during the period.

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Business Combinations And Dispositions (Narrative) (Details) - USD ($)				3 Months Ended	12 Months Ended
	Feb. 28, 2017	Nov. 04, 2014	Apr. 23, 2014	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Estimated surety bond claim, including associated expenses					$ 20,900,000
(GAIN) LOSS ON SALE OF ASSETS—Net					$ 5,077,000	$ 6,175,000	$ (855,000)
Environmental And Infrastructure Segment [Member]
Business Acquisition [Line Items]
(GAIN) LOSS ON SALE OF ASSETS—Net						$ 2,758,000
Great Lakes Environmental & Infrastructure, LLC [Member]
Business Acquisition [Line Items]
Fair value of debt				$ 0
Adjustment to fair value of debt				$ 8,940,000
Magnus Pacific Acquisition [Member]
Business Acquisition [Line Items]
Base purchase price		$ 40,000,000
Payments for previous acquisition		25,000,000
Fair value of debt							$ 0
Maximum potential aggregate earnout payment		$ 11,400,000
Surety Bond [Member]
Business Acquisition [Line Items]
Aggregate demolition surety performance bond	$ 20,000,000
NASDI, LLC and Yankee Environmental Services, LLC
Business Acquisition [Line Items]
Proceeds from divestiture of businesses			$ 5,309,000