Revenue - Contract Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Capitalized Contract Cost [Line Items]
Amortization of capitalized costs	$ 12,847	$ 14,078	$ 14,988
Capitalized costs, net	7,847	9,117
Tooling [Member]
Capitalized Contract Cost [Line Items]
Capitalized costs, net	4,976	5,908
Design Costs [Member]
Capitalized Contract Cost [Line Items]
Capitalized costs, net	$ 2,871	$ 3,209