TRADE ACCOUNTS RECEIVABLE (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Jan. 01, 2017
Subclassifications of assets, liabilities and equities [abstract]
Trade accounts receivables being serviced under a receivables purchase agreement	$ 92.8	$ 80.5
Receivables purchase agreement, maximum of sale of accounts receivables	175.0
Receivables purchase agreement, difference between carrying amount of receivable sold and cash received	$ 1.7	$ 0.7

Receivables Purchase Agreement, Difference Between Carrying Amount Of Receivables Sold And Cash Received

No definition available.

Name:	gil_ReceivablesPurchaseAgreementDifferenceBetweenCarryingAmountOfReceivablesSoldAndCashReceived
Namespace Prefix:	gil_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration