Stockholders' Equity Share Repurchases in the Open Market (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2010
Shares repurchased in the open market	22.8
Total cost	$ 710		$ 2,024		$ 1,000
Open Market
Shares repurchased in the open market	6.2	[1]	26.6	[1]
Weighted-average repurchase price per share	$ 0		$ 76,080,000.00
Total cost	$ 1,700		$ 2,024

[1] All shares repurchased in the open market have been retired and constitute authorized but unissued shares.