Revenue Contract Balances (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jan. 01, 2018
Contract with Customer, Asset and Liability [Abstract]
Contract with Customer, Asset, Gross		$ 11,932
Contract with Customer, Asset, Net	$ 13,803	11,932
Contract with Customer, Liability	55,297	58,184
Contract with Customer, Liability, Current	44,992	48,268
Contract with Customer, Liability, Noncurrent	10,305	$ 9,916
Change in Contract with Customer, Asset and Liability [Abstract]
Contract with Customer, Asset, Cumulative Catch-up Adjustment to Revenue, Change in Measure of Progress	356
Contract with Customer, Asset, Estimate of the Stage of Completion	7,211
Contract with Customer, Asset, Reclassified to Receivable	(5,618)
Contract with Customer, Asset, Increase (Decrease) for Contract Acquired in Business Combination	(78)
Contract with Customer, Liability, Cumulative Catch-up Adjustment to Revenue, Change in Measure of Progress	0
Contract with Customer, Liability, Revenue Recognized	(39,484)
Contract with Customer, Liability, Increase (Decrease) for Contract	36,271
Contract with Customer, Liability, Other	$ 326