Revenue - Contract Costs (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Capitalized Contract Cost [Line Items]
Amortization of capitalized costs	$ 14,988
Capitalized costs, net	8,445
Tooling [Member]
Capitalized Contract Cost [Line Items]
Capitalized costs, net	6,155
Design Costs [Member]
Capitalized Contract Cost [Line Items]
Capitalized costs, net	2,285
Other Capitalized Contract Cost [Member]
Capitalized Contract Cost [Line Items]
Capitalized costs, net	$ 5