Debt Securities Credit Losses Roll Forward Recorded in Earnings (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Beginning balance as of Jan. 1	$ 253	$ 182
Add: Initial OTTI credit losses	9	2
Subsequent OTTI credit losses	12	3
Less: Realized losses for securities sold / consolidated	8	4
Ending balance as of March 31	$ 266	$ 183