Accounts Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Receivables [Abstract]
Trade accounts receivable	$ 99,877	$ 102,277
Contract receivables:
Amounts billed	46,414	53,830
Costs in excess of billings	13,544	13,730
Total contract receivables	59,958	67,560
Total accounts receivable	159,835	169,837
Less allowance for doubtful accounts	(4,401)	(4,868)
Accounts receivable	$ 155,434	$ 164,969