Commitments and Contingencies (Details)	Oct. 30, 2011 CAD	Jul. 30, 2011 USD ($)
Commitments and Contingencies
Additional future minimum lease payments		$ 2,900,000,000
Present value of additional future minimum capital lease payments		1,000,000,000
Purchase obligations	912,500,000

The amount of the fixed and determinable portion of an unrecorded unconditional purchase obligation as of the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 47
-Paragraph 7
-Subparagraph b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 440
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25336-109308

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant