SUPPLEMENTAL CASH FLOW INFORMATION (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
Jan. 26, 2013
Supplemental Cash Flow Information [Abstract]
Noncash financing items, payments made by landlord directly	$ 24.5

Noncash financing items, payments made by landlord directly to contractors

No definition available.

Name:	unfi_NoncashFinancingItemsPaymentsMadeByLandlordDirectly
Namespace Prefix:	unfi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration