Revenue - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) supplyAgreement	Dec. 31, 2019 USD ($)
Disaggregation of Revenue [Line Items]
Revenue recognized at a point in time	$ 370,700	$ 489,000
Revenue recognized over time	46,900	57,100
Revenue recognized upon satisfaction of performance obligations	$ 30,800	6,700
Number of supply agreements | supplyAgreement	2
Revenue recognized	$ 417,639	546,076
Contract liabilities	47,960	26,898
6.0 Liter Engines
Disaggregation of Revenue [Line Items]
Revenue recognized	70,000
Contract liabilities	$ 46,400	$ 38,000