Transactions with Affiliates - Schedule of Amounts Charged to UTSI (Detail) - Affiliates [Member] - USD ($) $ in Thousands	3 Months Ended
Apr. 04, 2026	Mar. 29, 2025
Related Party Transaction [Line Items]
Cost incurred for services provided by CenTra and affiliates	$ 39,691	$ 30,508
Insurance [Member]
Related Party Transaction [Line Items]
Cost incurred for services provided by CenTra and affiliates	27,380	23,067
Real estate rent and related costs [Member]
Related Party Transaction [Line Items]
Cost incurred for services provided by CenTra and affiliates	8,386	3,886
Administrative support services [Member]
Related Party Transaction [Line Items]
Cost incurred for services provided by CenTra and affiliates	2,469	2,001
Truck fuel, maintenance and other operating costs [Member]
Related Party Transaction [Line Items]
Cost incurred for services provided by CenTra and affiliates	1,448	1,553
Contracted transportation services [Member]
Related Party Transaction [Line Items]
Cost incurred for services provided by CenTra and affiliates	$ 8	$ 1

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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+ Details