Investments - Realized Investment Gains and Losses (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Realized Gains (Losses) on Investments [Line Items]
Realized investment gains (losses) before income taxes	$ 65		$ 26		$ 107		$ 165
Less income taxes (benefits)	22		9		37		55
Net realized investment gains (losses)	43		17		70		110
Impairments Table Details [Abstract]
Credit-related	(9)	[1]	(8)	[1]	(15)	[1]	(8)	[1]
Other	(1)		(8)		(1)		(8)
Total	(10)		(16)		(16)		(16)
Fixed Maturities [Member]
Realized Gains (Losses) on Investments [Line Items]
Realized investment gains (losses) before income taxes	4		22		12		89
Equity securities [Member]
Realized Gains (Losses) on Investments [Line Items]
Realized investment gains (losses) before income taxes	0		1		17		4
Commercial Mortgage Loans [Member]
Realized Gains (Losses) on Investments [Line Items]
Realized investment gains (losses) before income taxes	(4)		(4)		(4)		(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	$ 65		$ 7		$ 69		$ 76

[1] Credit related losses include increases in valuation reserves on commercial mortgage loans and asset write-downs related to investments in real estate entities.