Revenue Recognition - Summary of Disaggregated Net Sales (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Disaggregation Of Revenue [Line Items]
Net Sales	$ 253,796	$ 247,954	$ 751,762	$ 713,363
U.S. Customers [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	238,466	229,761	701,778	663,212
Non-U.S. Customers [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	15,330	18,193	49,984	50,151
Powertrain [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	104,756	100,994	299,730	295,363
Chassis [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	70,787	69,214	228,446	206,483
Automotive Body [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	65,468	67,000	189,174	179,539
Hardware [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	$ 12,785	$ 10,746	$ 34,412	$ 31,978