Investments - Realized Investment Gains and Losses (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 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)	$ 139	$ 13
Less income taxes (benefits)	46	1
Realized investment gains (losses) from continuing operations, net of taxes and noncontrolling interest	93	12
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)	67	12
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)	3	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)	0	(3)
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	(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)	$ 69	$ 1