Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Feb. 28, 2013	Feb. 29, 2012	Feb. 28, 2013	Feb. 29, 2012	Aug. 31, 2012
Related Party Transaction [Line Items]
Subsequent Event, Date			Mar. 08, 2013
Corporate Joint Venture [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	$ 6	$ 13	$ 12	$ 23
Payments for Advance to Affiliate (Less Than $1 Million For The Six Months Ended February 29, 2012)	1	1	1	1
Due to Affiliate	1		1		2
Other Affiliates [Member]
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties (MMGL - Immediate Family Member of Management or Principal, Less Than $1 Million as of February 28, 2013 and August 31, 2012)					1
Immediate Family Member of Management or Principal Owner [Member]
Related Party Transaction [Line Items]
Related Party Transaction Percentage Of Shared Legal And Consulting Costs			50.00%
Accounts Receivable, Related Parties (MMGL - Immediate Family Member of Management or Principal, Less Than $1 Million as of February 28, 2013 and August 31, 2012)	1		1		1
Partnership Interest [Member]
Related Party Transaction [Line Items]
Related Party Number Of Stores	5		5
Partnership Interest [Member] | Auto Parts Business Segment President [Member]
Related Party Transaction [Line Items]
Related Party Noncontrolling Ownership Percentage By Noncontrolling Owners	25.00%		25.00%
Related Party Noncontrolling Ownership Percentage By Parent	75.00%		75.00%
Related Party Transaction Related Party Share Of Profit (Less Than $1 Million For The Three Month Periods Ended February 28, 2013 and February 29, 2012)	1	1	1	1
Related Party Transaction Rent Expense (Less Than $1 Million For the Three and Six Month Periods Ended February 28, 2013 and February 29, 2012)	1	1	1	1
Related Party Transaction Lease Term	5 years
Amix Salvage And Sales Ltd [Member] | Minority Shareholder Of Subsidiary [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	2	2	4	5
Accounts Payable, Related Parties (Less Than $1 Million as of February 28, 2013 and August 31, 2012)	$ 1		$ 1		$ 1