Investments - Realized Investment Gains and Losses (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Realized Gains (Losses) on Investments [Line Items]
Realized investment gains (losses) before income taxes	$ 23		$ 27		$ 130		$ 192
Less income taxes (benefits)	8		10		45		65
Net realized investment gains (losses)	15		17		85		127
Impairments Table Details [Abstract]
Credit-related	(1)	[1]	0	[1]	(16)	[1]	(8)	[1]
Other	(9)		(3)		(10)		(11)
Total	(10)		(3)		(26)		(19)
Fixed Maturities [Member]
Realized Gains (Losses) on Investments [Line Items]
Realized investment gains (losses) before income taxes	2		16		14		105
Equity securities [Member]
Realized Gains (Losses) on Investments [Line Items]
Realized investment gains (losses) before income taxes	(3)		0		14		4
Commercial Mortgage Loans [Member]
Realized Gains (Losses) on Investments [Line Items]
Realized investment gains (losses) before income taxes	(2)		0		(6)		(4)
Real Estate [Member]
Realized Gains (Losses) on Investments [Line Items]
Realized investment gains (losses) before income taxes	0		0		13		0
Other Investments Including Derivatives [Member]
Realized Gains (Losses) on Investments [Line Items]
Realized investment gains (losses) before income taxes	$ 26		$ 11		$ 95		$ 87

[1] Credit-related losses include other-than-temporary declines in fair value of equity securities and increases in valuation reserves on commercial mortgage loans and asset write-downs related to investments in real estate entities.