Fair Value Measurement - Schedule of Assets Measured at Fair Value on Recurring Basis Quantitative Information about Level 3 Fair Value Measurements (Detail) $ in Millions	Jun. 30, 2017 USD ($) $ / SecurityLoan	Dec. 31, 2016 USD ($) $ / SecurityLoan
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Securities available for sale	$ 41,120	$ 40,737
Derivative Assets, Gross Amount	773	1,494
Consumer MSRs	85	80
Fair Value, Measurements, Recurring [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Securities available for sale	41,120	40,737
Derivative Assets, Gross Amount	464	955
Fair Value, Measurements, Recurring [Member] \| RMBS
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Securities available for sale	29,128	29,249
Fair Value, Measurements, Recurring [Member] \| CMBS
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Securities available for sale	4,926	4,988
Fair Value, Measurements, Recurring [Member] \| Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Securities available for sale	455	578
Derivative Assets, Gross Amount	57	47
Consumer MSRs	85	80
Retained interests in securitizations	188	201
Fair Value, Measurements, Recurring [Member] \| Level 3 \| RMBS
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Securities available for sale	$ 429	$ 518
Fair Value, Measurements, Recurring [Member] \| Level 3 \| RMBS \| Discounted cash flows \| Minimum
Fair Value Inputs [Abstract]
Yield (percent)	1.00%	0.00%
Constant prepayment rate (percent)	0.00%	0.00%
Default rate (percent)	0.00%	0.00%
Loss severity (percent)	9.00%	9.00%
Fair Value, Measurements, Recurring [Member] \| Level 3 \| RMBS \| Discounted cash flows \| Maximum
Fair Value Inputs [Abstract]
Yield (percent)	9.00%	15.00%
Constant prepayment rate (percent)	33.00%	30.00%
Default rate (percent)	17.00%	16.00%
Loss severity (percent)	90.00%	87.00%
Fair Value, Measurements, Recurring [Member] \| Level 3 \| RMBS \| Discounted cash flows \| Weighted Average
Fair Value Inputs [Abstract]
Yield (percent)	5.00%	5.00%
Constant prepayment rate (percent)	4.00%	4.00%
Default rate (percent)	4.00%	4.00%
Loss severity (percent)	58.00%	57.00%
Fair Value, Measurements, Recurring [Member] \| Level 3 \| CMBS
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Securities available for sale	$ 17	$ 51
Fair Value, Measurements, Recurring [Member] \| Level 3 \| CMBS \| Discounted cash flows \| Minimum
Fair Value Inputs [Abstract]
Yield (percent)	3.00%	2.00%
Constant prepayment rate (percent)	0.00%	0.00%
Fair Value, Measurements, Recurring [Member] \| Level 3 \| CMBS \| Discounted cash flows \| Maximum
Fair Value Inputs [Abstract]
Yield (percent)	3.00%	2.00%
Constant prepayment rate (percent)	0.00%	0.00%
Fair Value, Measurements, Recurring [Member] \| Level 3 \| CMBS \| Discounted cash flows \| Weighted Average
Fair Value Inputs [Abstract]
Yield (percent)	3.00%	2.00%
Constant prepayment rate (percent)	0.00%	0.00%
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Foreign government bonds
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Securities available for sale	$ 9	$ 9
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Foreign government bonds \| Discounted cash flows \| Minimum
Fair Value Inputs [Abstract]
Yield (percent)	2.00%	1.00%
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Foreign government bonds \| Discounted cash flows \| Maximum
Fair Value Inputs [Abstract]
Yield (percent)	2.00%	2.00%
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Foreign government bonds \| Discounted cash flows \| Weighted Average
Fair Value Inputs [Abstract]
Yield (percent)	2.00%	1.00%
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Derivative assets
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Derivative Assets, Gross Amount	$ 57	$ 47
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Derivative assets \| Discounted cash flows \| Minimum
Fair Value Inputs [Abstract]
Swap rates (percent)	2.00%	2.00%
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Derivative assets \| Discounted cash flows \| Maximum
Fair Value Inputs [Abstract]
Swap rates (percent)	3.00%	2.00%
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Derivative assets \| Discounted cash flows \| Weighted Average
Fair Value Inputs [Abstract]
Swap rates (percent)	2.00%	2.00%
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Consumer MSRs
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Consumer MSRs	$ 85	$ 80
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Consumer MSRs \| Discounted cash flows \| Minimum
Fair Value Inputs [Abstract]
Total prepayment rate (percent)	8.00%	8.00%
Discount rate (percent)	16.00%	15.00%
Option adjusted spread rate (percent)	5.00%	5.80%
Servicing cost ($ per loan) \| $ / SecurityLoan	75	75
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Consumer MSRs \| Discounted cash flows \| Maximum
Fair Value Inputs [Abstract]
Total prepayment rate (percent)	21.00%	20.00%
Discount rate (percent)	16.00%	15.00%
Option adjusted spread rate (percent)	15.00%	15.00%
Servicing cost ($ per loan) \| $ / SecurityLoan	100	100
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Consumer MSRs \| Discounted cash flows \| Weighted Average
Fair Value Inputs [Abstract]
Total prepayment rate (percent)	15.00%	15.00%
Discount rate (percent)	16.00%	15.00%
Option adjusted spread rate (percent)	5.85%	6.36%
Servicing cost ($ per loan) \| $ / SecurityLoan	76	76
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Retained interest in securitizations
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Retained interests in securitizations	$ 188	$ 201
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Retained interest in securitizations \| Discounted cash flows \| Minimum
Fair Value Inputs [Abstract]
Life of receivables (months)	2 months	6 months
Constant prepayment rate (percent)	2.00%	2.00%
Default rate (percent)	1.00%	1.00%
Loss severity (percent)	9.00%	7.00%
Discount rate (percent)	3.00%	4.00%
Fair Value, Measurements, Recurring [Member] \| Level 3 \| Retained interest in securitizations \| Discounted cash flows \| Maximum
Fair Value Inputs [Abstract]
Life of receivables (months)	85 months	87 months
Constant prepayment rate (percent)	11.00%	11.00%
Default rate (percent)	5.00%	6.00%
Loss severity (percent)	111.00%	102.00%
Discount rate (percent)	12.00%	11.00%

Interest rate correlation, used as an input to measure fair value.

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Fair Value Inputs, Life of Receivables

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Fair Value Inputs, Option Adjusted Spread Rate

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Fair value inputs, swap rate.

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Rate at which loans or a loan portfolio are expected to prepay principal balances with consideration of defaults, used as an input to measure fair value

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Fair value Inputs, Servicing Cost Per Loan

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

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-Name Accounting Standards Codification
-Topic 320
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-Section 50
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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and elected not to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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Loss, including interest and principal, incurred on a defaulted security, expressed as a percentage of the original principal balance, used as an input to measure fair value.

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Rate at which loans or a loan portfolio are expected to prepay principal balances, used as an input to measure fair value.

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Percentage of likelihood a loan will not be repaid and instead default, used as an input to measure fair value.

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Fair value portion of interest continued to be held by a transferor after transferring financial assets to a third party.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 10
-Section 15
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68074228&loc=d3e94415-111705

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Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

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