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Accounts Receivable - Narrative (Details) - USD ($)
$ in Thousands
Dec. 31, 2016
Dec. 31, 2015
Receivables [Abstract]    
Contracts in progress $ 121,666 $ 103,178
Unbilled retentions 35,069 31,195
Trade receivables 113,380 77,084
Other receivables 1,102 190
Allowance for doubtful accounts (3,619) (794)
Total accounts receivable $ 267,598 $ 210,853