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Available-for-Sale and Held-to-Maturity Securities (Parenthetical) (Detail) - USD ($)
$ in Millions
Dec. 31, 2015
Dec. 31, 2014
Investment Holdings [Line Items]    
FHLB, restricted stock holdings $ 248 $ 248
Federal Reserve Bank, restricted stock holdings 355 352
Available-for-sale and other securities [1] 29,044 22,408
DTCC, restricted stock holdings 1  
Interest-Only Mortgage Backed Securities    
Investment Holdings [Line Items]    
Available-for-sale and other securities $ 50 $ 175
[1] Amortized cost of $28,678 and $21,677 at December 31, 2015 and 2014, respectively.