Investments - Realized Investment Gains and Losses (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Schedule Of Gain Loss On Investments Including Marketable Securities And Investments Held At Cost Income Statement Reported Amounts Summary [Line Items]
Total realized investment gains (losses)	$ 26	$ (4)	$ 165	$ 9
Less income taxes (benefits)	9	(1)	55	0
Realized investment gains (losses) from continuing operations, net of taxes and noncontrolling interest	17	(3)	110	9
Fixed Maturities [Member]
Schedule Of Gain Loss On Investments Including Marketable Securities And Investments Held At Cost Income Statement Reported Amounts Summary [Line Items]
Total realized investment gains (losses)	22	3	89	15
Equity securities [Member]
Schedule Of Gain Loss On Investments Including Marketable Securities And Investments Held At Cost Income Statement Reported Amounts Summary [Line Items]
Total realized investment gains (losses)	1	0	4	4
Commercial Mortgage Loans [Member]
Schedule Of Gain Loss On Investments Including Marketable Securities And Investments Held At Cost Income Statement Reported Amounts Summary [Line Items]
Total realized investment gains (losses)	(4)	(7)	(4)	(10)
Real estate [Member]
Schedule Of Gain Loss On Investments Including Marketable Securities And Investments Held At Cost Income Statement Reported Amounts Summary [Line Items]
Total realized investment gains (losses)	0	0	0	(1)
Other Investments Including Derivatives [Member]
Schedule Of Gain Loss On Investments Including Marketable Securities And Investments Held At Cost Income Statement Reported Amounts Summary [Line Items]
Total realized investment gains (losses)	$ 7	$ 0	$ 76	$ 1