Condensed Financial Information (Parent Company) (Details 4) (Parent Company [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Long-term Debt [Abstract]
Senior notes	$ 15,669	$ 15,666
Other Affiliated Debt	3,250	500
Long-term Debt	18,919	16,166
Senior Notes, Unaffiliated [Member]
Long-term Debt [Abstract]
Interest Rate Range Minimum	0.79%
Interest Rate Range Maximum	7.72%
Weighted Average Interest Rate	4.83%
Debt Instrument, Maturity Date Range, Start	Aug. 06, 2013
Debt Instrument, Maturity Date Range, End	Jun. 15, 2045
Senior notes	15,669	15,666
Senior Notes, Affiliated [Member]
Long-term Debt [Abstract]
Interest Rate Range Minimum	3.57%
Interest Rate Range Maximum	7.44%
Weighted Average Interest Rate	5.57%
Debt Instrument, Maturity Date Range, Start	Jun. 30, 2014
Debt Instrument, Maturity Date Range, End	Sep. 30, 2032
Senior notes	2,750	0
Other Affiliated Debt [Member]
Long-term Debt [Abstract]
Interest Rate Range Minimum	1.06%
Interest Rate Range Maximum	1.28%
Weighted Average Interest Rate	1.17%
Debt Instrument, Maturity Date Range, Start	Dec. 30, 2015
Debt Instrument, Maturity Date Range, End	Mar. 31, 2016
Other Affiliated Debt	$ 500	$ 500