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Composition of the Company's Loan Portfolio (Additional Information) (Detail) - USD ($)
$ in Millions
Mar. 31, 2017
Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Loans Receivable, Fair Value Disclosure $ 221 $ 222
Loans Held-for-sale, Fair Value Disclosure 1,819 3,540
Residential Portfolio Segment [Member]    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Loans Receivable, Fair Value Disclosure $ 221 $ 222