Investments (details) - Impairment Charges (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Impairment charges
Impairment charges	$ 3	$ 3	$ 10	$ 11
Fixed maturities [Member]
Impairment charges
Impairment charges		1	2	7
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Impairment charges
Impairment charges			2	3
All other corporate bonds [Member]
Impairment charges
Impairment charges		1		4
Equity securities [Member]
Impairment charges
Impairment charges	2	2	3	2
Equity securities, common stock [Member]
Impairment charges
Impairment charges	2	1	3	1
Equity securities, non-redeemable preferred stock [Member]
Impairment charges
Impairment charges		1		1
Other investments [Member]
Impairment charges
Impairment charges	$ 1		$ 5	$ 2