Investments (Net realized investment gains (losses)) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Gain (Loss) on Investments
Net realized investment gains (losses), net of participating policyholders’ interests	$ 36		$ 13
Fixed maturity securities [Member]
Gain (Loss) on Investments
Gross realized gains	69		88
Gross realized losses	(39)		(68)
Net realized investment gains (losses), net of participating policyholders’ interests	30		20
Equity securities [Member]
Gain (Loss) on Investments
Gross realized gains	3		5
Gross realized losses	(2)		(5)
Net realized investment gains (losses), net of participating policyholders’ interests	1
Derivatives [Member]
Gain (Loss) on Investments
Net realized investment gains (losses), net of participating policyholders’ interests	(1)		(1)
Short term investments and other [Member]
Gain (Loss) on Investments
Net realized investment gains (losses), net of participating policyholders’ interests	$ 6	[1],[2]	$ (6)	[1],[2]

[1] There were no net unrealized gains (losses) included in the three months ended March 31, 2012 and $1 million of net unrealized gains included in the three months ended March 31, 2011 related to changes in fair value of securities for which the fair value option has been elected.

[2] The three months ended March 31, 2011 includes a $9 million loss related to the early extinguishment of $400 million of senior notes originally due August 15, 2011.