Transactions with Affiliates - Schedule of Amounts Charged to UTSI (Detail) - Affiliates [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Related Party Transaction [Line Items]
Cost incurred for services provided by CenTra and affiliates	$ 14,389	$ 20,548	$ 47,026	$ 55,326
Administrative support services [Member]
Related Party Transaction [Line Items]
Cost incurred for services provided by CenTra and affiliates	1,852	615	3,352	2,346
Truck fuel, tolls and maintenance [Member]
Related Party Transaction [Line Items]
Cost incurred for services provided by CenTra and affiliates	212	29	726	910
Real estate rent and related costs [Member]
Related Party Transaction [Line Items]
Cost incurred for services provided by CenTra and affiliates	3,629	3,418	8,822	10,999
Insurance and employee benefit plans [Member]
Related Party Transaction [Line Items]
Cost incurred for services provided by CenTra and affiliates	8,685	16,394	34,097	39,907
Purchased transportation and equipment rent [Member]
Related Party Transaction [Line Items]
Cost incurred for services provided by CenTra and affiliates	$ 11	$ 92	$ 29	$ 1,164