Revenue - Contract Costs (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)
Capitalized Contract Cost [Line Items]
Amortization of capitalized costs	$ 3,606	$ 11,548
Capitalized costs, net	6,125	6,125
Tooling [Member]
Capitalized Contract Cost [Line Items]
Capitalized costs, net	3,164	3,164
Design Costs [Member]
Capitalized Contract Cost [Line Items]
Capitalized costs, net	2,930	2,930
Other Capitalized Contract Cost [Member]
Capitalized Contract Cost [Line Items]
Capitalized costs, net	$ 31	$ 31