Stockholders' Equity Share Repurchases in the Open Market (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2011
Stockholders' Equity Attributable to Parent [Abstract]
Shares repurchased in the open market	33	[1]	6	[1]
Weighted-average repurchase price per share	$ 0		$ 0
Total cost	$ 5,365		$ 710		$ 2,024

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