Revenue - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Capitalized Contract Cost [Line Items]
Costs in excess of billings	$ 24,627		$ 20,607
Amounts included in billings in excess of cost at the beginning of the period	42,115	$ 11,357
Amounts included in unearned revenue at the beginning of the period	12,553	$ 6,153
Billings in excess of cost
Capitalized Contract Cost [Line Items]
Contract with customer liability	(29,281)		(47,598)
Unearned revenue
Capitalized Contract Cost [Line Items]
Contract with customer liability	$ (16,503)		$ (17,311)