Revenue Recognition - Summary of Disaggregated Net Sales (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 26, 2021	Jun. 27, 2020	Jun. 26, 2021	Jun. 27, 2020
Disaggregation Of Revenue [Line Items]
Net sales	$ 310,635	$ 233,182	$ 598,647	$ 490,912
U.S. Customers [Member]
Disaggregation Of Revenue [Line Items]
Net sales	295,081	222,563	568,231	463,955
Non-U.S. Customers [Member]
Disaggregation Of Revenue [Line Items]
Net sales	15,554	10,619	30,416	26,957
Powertrain [Member]
Disaggregation Of Revenue [Line Items]
Net sales	128,811	94,598	249,933	202,740
Chassis [Member]
Disaggregation Of Revenue [Line Items]
Net sales	98,551	66,025	184,038	139,400
Automotive Body [Member]
Disaggregation Of Revenue [Line Items]
Net sales	66,970	58,825	135,632	123,457
Hardware [Member]
Disaggregation Of Revenue [Line Items]
Net sales	$ 16,303	$ 13,734	$ 29,044	$ 25,315