Debt Securities Credit Losses Roll Forward Recorded in Earnings (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Beginning balance	$ 266	$ 183	$ 253	$ 182
Add: Initial OTTI credit losses	38	7	49	9
Subsequent OTTI credit losses	29	1	39	4
Less: Realized losses for securities sold / consolidated		4	8	8
Ending balance	$ 333	$ 187	$ 333	$ 187