Accounts Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Receivables [Abstract]
Trade accounts receivable	$ 125,237	$ 105,421
Contract receivables:
Amounts billed	39,183	0
Costs in excess of billings	17,411	0
Total contract receivables	56,594	0
Total accounts receivable	181,831	105,421
Less allowance for doubtful accounts	(4,714)	(4,280)
Accounts receivable	$ 177,117	$ 101,141