Summary of Significant Accounting Policies and Other Information - Schedule of Inventory, Current (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Inventories
Raw materials	$ 126,225		$ 89,684
Work in process	2,850		2,482
Finished goods	19,115		19,375
Total inventories	148,190		111,541
Inventory allowance	(3,376)		(3,328)
Inventories, net	144,814		108,213
Inventory Allowance
Balance at beginning of period	3,328	$ 2,964
Charged to expense	607	1,272
Write-offs	(559)	(1,012)
Balance at end of period	3,376	$ 3,224
6.0L Engine Supply Commitment
Inventories
Raw materials	$ 12,000		$ 36,600