Marketable Securities - Schedule of Gross Unrealized Gains and Losses on Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Gross unrealized gains	$ 933	$ 89
Gross unrealized losses	(198)	(1,899)
Net unrealized gains (losses)	$ 735	$ (1,810)

Equity securities FvNi accumulated gross unrealized gain loss.

No definition available.

Name:	ulh_EquitySecuritiesFvNiAccumulatedGrossUnrealizedGainLoss
Namespace Prefix:	ulh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant