LEASES - Rent Expense (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2022	Oct. 01, 2021	Sep. 30, 2022	Oct. 01, 2021
LEASES
Rent expenses	$ 1.6	$ 4.9	$ 1.6	$ 5.2

Amount of operating lease expense. Excludes sublease income.

No definition available.

Name:	wldn_OperatingLeaseRentExpenses
Namespace Prefix:	wldn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration