Investments (Net realized investment gains (losses)) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Net realized investment gains (losses)	$ 46	$ 23
Fixed maturity securities [Member]
Gross realized gains	53	39
Gross realized losses	(15)	(12)
Net realized investment gains (losses)	38	27
Equity securities [Member]
Gross realized gains	5	2
Gross realized losses		(15)
Net realized investment gains (losses)	5	(13)
Derivative [Member]
Net realized investment gains (losses)		2
Short term investments and other [Member]
Net realized investment gains (losses)	$ 3	$ 7