v2.4.0.6
Securities (Schedule Of Gross Unrealized Losses And Estimated Fair Value Of Securities Available For Sale) (Detail) (USD $)
In Millions, unless otherwise specified
Jun. 30, 2012
Dec. 31, 2011
Unrealized Loss And Fair Value Available For Sale Securities [Line Items]    
Less Than Twelve Months, Estimated Fair Value $ 1,363 $ 2,069
Less Than Twelve Months, Gross Unrealized Losses (13) (16)
Twelve Months or More, Estimated Fair Value 18 5
Twelve Months or More, Gross Unrealized Losses (1) (2)
Total Estimated Fair Value 1,381 2,074
Total Gross Unrealized Losses (14) (18)
Residential Agency [Member]
    
Unrealized Loss And Fair Value Available For Sale Securities [Line Items]    
Less Than Twelve Months, Estimated Fair Value 950 1,778
Less Than Twelve Months, Gross Unrealized Losses (8) (7)
Total Estimated Fair Value 950 1,778
Total Gross Unrealized Losses (8) (7)
Commercial Agency [Member]
    
Unrealized Loss And Fair Value Available For Sale Securities [Line Items]    
Less Than Twelve Months, Estimated Fair Value     
Less Than Twelve Months, Gross Unrealized Losses     
Twelve Months or More, Estimated Fair Value     
Twelve Months or More, Gross Unrealized Losses     
Total Estimated Fair Value     
Total Gross Unrealized Losses     
All Other Securities [Member]
    
Unrealized Loss And Fair Value Available For Sale Securities [Line Items]    
Less Than Twelve Months, Estimated Fair Value 413 291
Less Than Twelve Months, Gross Unrealized Losses (5) (9)
Twelve Months or More, Estimated Fair Value 18 5
Twelve Months or More, Gross Unrealized Losses (1) (2)
Total Estimated Fair Value 431 296
Total Gross Unrealized Losses $ (6) $ (11)