Revenue Recognition - Summary of Disaggregated Net Sales (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Disaggregation Of Revenue [Line Items]
Net Sales	$ 247,954	$ 224,615	$ 713,363	$ 675,502
U.S. Customers [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	229,761	210,347	663,212	634,422
Non-U.S. Customers [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	18,193	14,268	50,151	41,080
Powertrain [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	100,994	94,177	295,363	284,393
Chassis [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	69,214	57,281	206,483	173,498
Automotive Body [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	67,000	62,791	179,539	185,804
Hardware [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	$ 10,746	$ 10,366	$ 31,978	$ 31,807