Revenue Recognition - Summary of Disaggregated Net Sales (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2020	Jun. 29, 2019	Jun. 27, 2020	Jun. 29, 2019
Disaggregation Of Revenue [Line Items]
Net Sales	$ 233,182	$ 254,175	$ 490,912	$ 497,966
U.S. Customers [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	222,563	236,161	463,955	463,312
Non-U.S. Customers [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	10,619	18,014	26,957	34,654
Powertrain [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	94,598	99,378	202,740	194,974
Chassis [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	66,025	80,660	139,400	157,659
Automotive Body [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	58,825	62,859	123,457	123,706
Hardware [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	$ 13,734	$ 11,278	$ 25,315	$ 21,627