Investments (details) - Impairment Charges (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Impairment charges
Impairment charges	$ 2	$ 4	$ 7	$ 8
Fixed maturities [Member]
Impairment charges
Impairment charges	1	3	2	6
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Impairment charges
Impairment charges	1	2	2	3
All other corporate bonds [Member]
Impairment charges
Impairment charges		1		3
Equity securities [Member]
Impairment charges
Impairment charges	1		1
Equity securities, common stock [Member]
Impairment charges
Impairment charges	1		1
Other investments [Member]
Impairment charges
Impairment charges		$ 1	$ 4	$ 2