Stockholders' Equity (Narrative) (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended	6 Months Ended		1 Months Ended		3 Months Ended	5 Months Ended
	Apr. 30, 2012	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2011	Jul. 31, 2012 ASR March 2012 [Member]	Mar. 31, 2012 ASR March 2012 [Member]	Jun. 30, 2012 ASR March 2012 [Member]	Jul. 31, 2012 ASR March 2012 [Member]
Stockholders' Equity [Line Items]
Payments for Repurchase of Common Stock			$ 53,000,000	$ 672,000,000		$ 1,200,000,000
Shares Received Under ASR Program					0.6	12.0	0.9	13.5
Authorized Amount of Common Stock Repurchase Plan	700,000,000
Accelerated Share Repurchases, Average Price Paid Per Share								$ 89.10
Share Repurchase Authorization Outstanding		$ 1,000,000,000