Quarterly Operating Results (Unaudited) (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Realized gains (losses) and favorable (adverse) development on unpaid loss and loss adjustment expenses
Realized Gains	$ 8	$ 13	$ 12	$ 19	$ 63	$ 56	$ 41	$ 57	$ 52	$ 217
Prior Year Development Favorable (Adverse)	$ (10)	$ (13)	$ (14)	$ 31	$ 5	$ (40)	$ 22	$ 28	$ (6)	$ 15	$ 30