Revenue Recognition - Summary of Disaggregated Net Sales (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 25, 2021	Sep. 26, 2020	Sep. 25, 2021	Sep. 26, 2020
Disaggregation Of Revenue [Line Items]
Net sales	$ 348,426	$ 300,620	$ 947,073	$ 791,532
U.S. Customers [Member]
Disaggregation Of Revenue [Line Items]
Net sales	328,315	280,330	896,545	744,285
Non-U.S. Customers [Member]
Disaggregation Of Revenue [Line Items]
Net sales	20,111	20,290	50,528	47,247
Powertrain [Member]
Disaggregation Of Revenue [Line Items]
Net sales	136,770	120,565	386,732	323,396
Chassis [Member]
Disaggregation Of Revenue [Line Items]
Net sales	118,273	87,977	302,219	227,273
Automotive Body [Member]
Disaggregation Of Revenue [Line Items]
Net sales	78,477	74,445	214,180	197,624
Hardware [Member]
Disaggregation Of Revenue [Line Items]
Net sales	$ 14,906	$ 17,633	$ 43,942	$ 43,239