Revenue Recognition - Summary of Disaggregated Net Sales (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 30, 2019	Mar. 31, 2018
Disaggregation Of Revenue [Line Items]
Net Sales	$ 243,791	$ 227,262
U.S. Customers [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	227,151	210,426
Non-U.S. Customers [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	16,640	16,836
Powertrain [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	95,163	95,152
Chassis [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	77,406	66,999
Automotive Body [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	60,746	55,244
Hardware [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	$ 10,476	$ 9,867

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

Name:	us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration