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Amount of other assets expected to be realized or consumed before one year or the normal operating cycle, if longer, acquired at the acquisition date.

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Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.

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Amount of liabilities due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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Acquisitions (Details) - USD ($) $ in Thousands		12 Months Ended
Acquisitions (Details) - USD ($) $ in Thousands	Apr. 01, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Acquisitions
Contingent earn out obligation term		4 years
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets
Goodwill		$ 200,584	$ 149,208	$ 143,874
BCH
Acquisitions
Contingent earn-out obligation	$ 11,600
Promissory note payable	14,300
Purchase price paid in cash	95,400
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets
Cash and cash equivalents	9,613
Receivables	28,263
Costs and estimated earnings in excess of billings	1,690
Other current assets	708
Property and equipment	3,927
Goodwill	50,512
Identifiable intangible assets	46,500
Accounts payable and other current liabilities	(11,763)
Billings in excess of costs and estimated earnings	(8,039)
Other non-current liabilities	(104)
Total purchase price	$ 121,307
BCH \| Minimum
Acquisitions
Cash flow discount rate	13.00%
BCH \| Maximum
Acquisitions
Cash flow discount rate	18.00%
BCH \| Customer relationships
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets
Identifiable intangible assets	$ 36,500
Estimated amortization life	10 years
BCH \| Backlog
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets
Identifiable intangible assets	$ 6,300
Estimated amortization life	1 year
BCH \| Trade names
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets
Identifiable intangible assets	$ 3,700
Estimated amortization life	25 years