Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Receivables [Abstract]
Trade accounts receivable	$ 102,277	$ 105,421
Contract receivables:
Amounts billed	53,830	0
Costs in excess of billings	13,730	0
Total contract receivables	67,560	0
Total accounts receivable	169,837	105,421
Less allowance for doubtful accounts	(4,868)	(4,280)	$ (4,774)	$ (4,481)
Accounts receivable	$ 164,969	$ 101,141