XML 47 R44.htm IDEA: XBRL DOCUMENT v2.4.0.6
Rollforward of Credit Losses Recognized in Earnings Related to Securities (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2012
Mar. 31, 2011
Schedule of Available-for-sale Securities [Line Items]    
Beginning balance $ 25 $ 20
Additions/reductions 2 1
Ending balance $ 27 $ 21