Revenue - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Costs in excess of billings	$ 26,915	$ 20,607		$ 22,634
Contract with customer liability	(21,325)	(15,389)
Amounts included in billings in excess of cost at the beginning of the period	45,536	17,371	$ 10,097
Amounts included in unearned revenue at the beginning of the period	12,229	10,090	$ 2,988
Billings in excess of cost
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract with customer liability	(34,702)	(47,598)		(17,857)
Unearned revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract with customer liability	$ (21,325)	$ (15,389)		$ (10,847)