Subsequent Event (Details) (USD $)				1 Months Ended		1 Months Ended		1 Months Ended		1 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Oct. 31, 2012 Subsequent Event [Member]	Oct. 31, 2012 Subsequent Event [Member] Common Stock [Member]	Oct. 10, 2012 Subsequent Event [Member] Common Stock [Member]	Oct. 31, 2012 Subsequent Event [Member] Senior Notes [Member] Debt Remarketing Series C Tranche 1 [Member]	Oct. 04, 2012 Subsequent Event [Member] Senior Notes [Member] Debt Remarketing Series C Tranche 1 [Member]	Oct. 31, 2012 Subsequent Event [Member] Senior Notes [Member] Debt Remarketing Series C Tranche 2 [Member]	Oct. 04, 2012 Subsequent Event [Member] Senior Notes [Member] Debt Remarketing Series C Tranche 2 [Member]	Oct. 31, 2012 Subsequent Event [Member] Senior Notes [Member] Debt Remarketing Series C [Member]
Subsequent Event [Line Items]
Approved annual dividend, amount per share			$ 0.74
Estimated aggregate dividend payment			$ 812,000,000
Debt Instrument, Interest Rate, Stated Percentage							1.756%		3.048%
Debt Instrument, Maturity Date						Dec. 15, 2017		Dec. 15, 2022
Proceeds from remarketing										0
Proceeds from common stock issuance				$ 1,000,000,000
Common stock, shares issued	1,065,840,714	1,061,150,915			28,231,956