Accounts Receivable (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Receivables [Abstract]
Trade accounts receivable	$ 105,485	$ 102,277
Contract receivables:
Amounts billed	39,941	53,830
Costs in excess of billings	9,816	13,730
Total contract receivables	49,757	67,560
Total accounts receivable	155,242	169,837
Less allowance for doubtful accounts	(5,072)	(4,868)
Accounts receivable	$ 150,170	$ 164,969