Investments (details) - Impairment Charges - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Impairment charges
Impairment charges	$ 52	$ 26	$ 15
Fixed maturities [Member]
Impairment charges
Impairment charges	13	16	5
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Impairment charges
Impairment charges		1	2
All other corporate bonds [Member]
Impairment charges
Impairment charges	13	15	3
Equity securities [Member]
Impairment charges
Impairment charges	37	9	5
Public common stock [Member]
Impairment charges
Impairment charges	37	9	5
Other investments [Member]
Impairment charges
Impairment charges	$ 2	$ 1	$ 5