Quarterly Operating Results (Unaudited) (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Realized gains (losses) and favorable (adverse) development on unpaid loss and loss adjustment expenses
Realized Gains	$ 63	$ 56	$ 41	$ 57	$ 71	$ 241	$ 15	$ 44	$ 217	$ 371
Prior Year Development Favorable (Adverse)	$ 5	$ (40)	$ 22	$ 28	$ 7	$ (23)	$ 27	$ 19	$ 15	$ 30	$ 69