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Fair Value of Financial Instruments - Additional Information (Detail) $ in Millions | 3 Months Ended
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Mar. 31, 2016 USD ($)
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Dealer marks of securities | 68.00%
Percentage of carrying value for which dealer quotes have been received | 84.00%
Mortgage servicing rights |
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Fair value option elected aggregate carrying amount, asset | $ 9
Mortgage servicing rights | Maximum |
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Percentage difference of internal valuation than dealer marks | 1.00%
Residential Subordinate Securities |
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Fair value option elected aggregate carrying amount, asset | $ 48
Residential Loans |
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Fair value option elected aggregate carrying amount, asset | 1,190
Commercial Loans |
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Fair value option elected aggregate carrying amount, asset | $ 38

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