Long-term and Short-term Debt (Long-term and Short-term Outstanding) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Capital lease obligations	$ 28	$ 33
Long-term debt	17,198	16,535
Short-term debt	175	100
Total	17,373	16,635
Senior Notes [Member]
Debt Instrument [Line Items]
Interest Rate Range Minimum	1.52%
Interest Rate Range Maximum	7.72%
Weighted Average Interest Rate	4.96%
Debt Instrument, Maturity Date Range, Start	Feb. 06, 2014
Debt Instrument, Maturity Date Range, End	Jun. 15, 2045
Long-term Debt	15,938	15,669
Surplus Notes [Member]
Debt Instrument [Line Items]
Interest Rate Range Minimum	7.63%
Interest Rate Range Maximum	7.88%
Weighted Average Interest Rate	7.84%
Debt Instrument, Maturity Date Range, Start	Nov. 01, 2015
Debt Instrument, Maturity Date Range, End	Nov. 01, 2025
Long-term Debt	701	700
Other Notes [Member]
Debt Instrument [Line Items]
Interest Rate Range Minimum	1.39%
Interest Rate Range Maximum	8.00%
Weighted Average Interest Rate	4.04%
Debt Instrument, Maturity Date Range, Start	Feb. 01, 2014
Debt Instrument, Maturity Date Range, End	Nov. 30, 2030
Long-term Debt	$ 531	$ 133