Contract Assets and Liabilities - Contract Assets and Contract Liabilities from Contracts with Customers (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Contract with Customer, Asset and Liability [Abstract]
Contract assets, net	$ 6,503	$ 12,065
Contract assets, net - $ change	$ (5,562)
Contract assets, net - % change	(46.00%)
Contract liabilities, net	$ 21,893	19,217
Contract liabilities, net - $ change	$ 2,676
Contract liabilities, net - % change	14.00%
Contract asset amounts classified as current	$ 6,500	9,300
Contract liability amounts classified as current	3,400	$ 1,700
Increase in contract liability	4,000
Revenue recognized	$ 1,000