Fair Value Measurement and Election - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Transfer of Portfolio Loans and Leases to Held-for-sale	$ 91	$ 153	$ 218	$ 315
Estimated Fair Value of Loan Portfolio's Net Carrying Value, Percentage	101.00%		101.00%		101.00%
Assets	$ 208,252		$ 208,252		$ 204,875
Loans Receivable, Fair Value Disclosure	206		206		222
Unfunded loan commitments and letters of credit	65,300		65,300		67,200
Allowance for unfunded loan commitments and letters of credit	78		78		71
Other Comprehensive Income (Loss), Unrealized Credit Risk Gain (Loss) on Long-term Debt Arising During Period, Net of Tax	1	(3)	1	(5)
Total Return Swap [Member] \| Fair Value, Inputs, Level 2 [Member]
Loans Receivable, Fair Value Disclosure	2,500		2,500		2,100
Interest Rate Lock Commitments [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	51	$ 116	157	$ 232
Trading Account Assets [Member] \| Commercial and Corporate Leveraged Loans [Member] \| Fair Value, Inputs, Level 2 [Member]
Loans Receivable, Fair Value Disclosure	422		422		356
Loans Held For Sale [Member]
Loans Receivable, Fair Value Disclosure	2,252		2,252		3,540
Fair Value, Measurements, Recurring [Member]
Loans Receivable, Fair Value Disclosure	206		206		222
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Loans Receivable, Fair Value Disclosure	0		0		0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Loans Receivable, Fair Value Disclosure	0		0		0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Loans Receivable, Fair Value Disclosure	$ 206		$ 206		$ 222

Allowance for commercial unfunded loan commitments and letters of credit

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- Definition

Percentage of Carrying Value

+ References

No definition available.

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Other Comprehensive Income (Loss), Unrealized Credit Risk Gain (Loss) on Long-term Debt Arising During Period, Net of Tax

+ References

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- Definition

Unfunded Commercial Loan Commitments and Letters of Credit

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- Definition

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
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Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
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- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

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-Publisher FASB
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Value of loans and leases held in the entity's portfolio transferred to loans and leases held-for-sale in noncash transactions.

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