v2.4.0.6
Amortized Cost, Gross Unrealized Gains and Losses, and Fair Value of Securities Available for Sale and Securities Held to Maturity (Detail) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2013
Dec. 31, 2012
Investment [Line Items]    
Securities available for sale Amortized Cost $ 48,329 $ 45,644
Securities available for sale Gross Unrealized Gains 532 552
Securities available for sale Gross Unrealized Losses 52 73
Securities available for sale 48,809 46,123
Securities held to maturity 22,920 18,194
Securities held to maturity Gross Unrealized Gains 470 558
Securities held to maturity Gross Unrealized Losses 74 20
Securities held to maturity, fair value 23,316 18,732
U.S. agency mortgage-backed securities
   
Investment [Line Items]    
Securities available for sale Amortized Cost 19,465 20,080
Securities available for sale Gross Unrealized Gains 354 396
Securities available for sale 19,819 [1] 20,476
Securities held to maturity 22,188 17,750
Securities held to maturity Gross Unrealized Gains 470 558
Securities held to maturity Gross Unrealized Losses 63 19
Securities held to maturity, fair value 22,595 [1] 18,289
Asset-backed securities
   
Investment [Line Items]    
Securities available for sale Amortized Cost 9,706 8,104
Securities available for sale Gross Unrealized Gains 81 62
Securities available for sale Gross Unrealized Losses 1 2
Securities available for sale 9,786 8,164
Corporate debt securities
   
Investment [Line Items]    
Securities available for sale Amortized Cost 7,554 6,197
Securities available for sale Gross Unrealized Gains 65 61
Securities available for sale Gross Unrealized Losses 2 2
Securities available for sale 7,617 6,256
Certificates of deposit
   
Investment [Line Items]    
Securities available for sale Amortized Cost 5,890 6,150
Securities available for sale Gross Unrealized Gains 11 12
Securities available for sale Gross Unrealized Losses 1 1
Securities available for sale 5,900 6,161
U.S. agency notes
   
Investment [Line Items]    
Securities available for sale Amortized Cost 4,040 3,465
Securities available for sale Gross Unrealized Gains 2 2
Securities available for sale Gross Unrealized Losses 6 3
Securities available for sale 4,036 3,464
Non-agency residential mortgage-backed securities
   
Investment [Line Items]    
Securities available for sale Amortized Cost 747 796
Securities available for sale Gross Unrealized Gains 4 2
Securities available for sale Gross Unrealized Losses 42 65
Securities available for sale 709 733
Commercial paper
   
Investment [Line Items]    
Securities available for sale Amortized Cost 649 574
Securities available for sale 649 574
Other securities
   
Investment [Line Items]    
Securities available for sale Amortized Cost 278 278
Securities available for sale Gross Unrealized Gains 15 17
Securities available for sale 293 295
Securities held to maturity 732 444
Securities held to maturity Gross Unrealized Losses 11 1
Securities held to maturity, fair value $ 721 $ 443
[1] Mortgage-backed securities have been allocated to maturity groupings based on final contractual maturities. Actual maturities will differ from final contractual maturities because borrowers on a certain portion of loans underlying these securities have the right to prepay their obligations.