Income Taxes (Income Tax Expense (Benefit) On Income (Loss) And Shareholders' Equity) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Federal - Current taxes	$ 3	$ (1)	$ 91
State - Current taxes	2	1	(17)
Foreign - Current taxes	(6)	15	(1)
Federal - Deferred taxes	350	(919)	(239)
Foreign - Deferred taxes	15	(16)	18
Provision (benefit) for income taxes	364	(920)	(148)
Total adjustments due to the adoption of new accounting standards			(21)
Change in unrealized gains and losses on investments	75	119	112
Change in other-than-temporary impairment losses	42	3	(4)
Change in fair value of derivative instruments	11	3	(7)
Change in foreign currency translation	(2)	(1)	2
Share-based compensation	7	4	3
Total income taxes charged (credited) to shareholders' equity	133	128	85
Total effect of income taxes	$ 497	$ (792)	$ (63)