SUPPLEMENTAL FINANCIAL STATEMENT DATA - Accounts Receivable (Details) $ in Millions	9 Months Ended
Sep. 30, 2022 USD ($)
SUPPLEMENTAL FINANCIAL STATEMENT DATA
Cash proceeds from sale of trade receivables	$ 8.0
Discount on trade accounts receivable sold	$ 0.8

The amount of cash inflow from sale of trade accounts receivables.

No definition available.

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