Allowance for Credit Losses - Summary of Changes in Allowance for Credit Losses and Related Loan Balance by Product (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Residential mortgage loan carried at lower of amortized cost or fair value less cost to sell	$ 718	$ 706
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Financing Receivable, Allowance for Credit Losses [Line Items]
Residential mortgage loan carried at lower of amortized cost or fair value less cost to sell	$ 718	$ 632