Fair Value Measurements (Fair Values of Assets and Liabilities (Significant Unobservable Level 3 Inputs Recurring Basis)) (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Quantitative Information About Level 3 Fair Value Measurements
Residential mortgage loans measured at fair value	$ 137	$ 143
Derivative instruments	823	1,057
Residential mortgage loans
Quantitative Information About Level 3 Fair Value Measurements
Residential mortgage loans measured at fair value	137	143
Mortgage Servicing Rights
Quantitative Information About Level 3 Fair Value Measurements
Mortgage Servicing Rights	858
IRLCs, net
Quantitative Information About Level 3 Fair Value Measurements
Derivative instruments	8	12
Swap associated with the sale of Visa, Inc. Class B shares
Quantitative Information About Level 3 Fair Value Measurements
Derivative instruments	$ (137)	$ (91)
Minimum \| Residential mortgage loans
Quantitative Information About Level 3 Fair Value Measurements
Interest rate risk factor	(10.60%)	(11.50%)
Credit risk factor	0.00%	0.00%
Minimum \| Mortgage Servicing Rights
Quantitative Information About Level 3 Fair Value Measurements
Prepayment speed	0.00%	0.70%
OAS spread (bps)	45000.00%	10000.00%
Minimum \| IRLCs, net
Quantitative Information About Level 3 Fair Value Measurements
Loan closing rates	12.50%	23.80%
Minimum \| Swap associated with the sale of Visa, Inc. Class B shares
Quantitative Information About Level 3 Fair Value Measurements
Timing of the resolution of the covered litigation	Dec. 31, 2020	Dec. 31, 2018
Maximum \| Residential mortgage loans
Quantitative Information About Level 3 Fair Value Measurements
Interest rate risk factor	14.50%	13.80%
Credit risk factor	52.10%	75.60%
Maximum \| Mortgage Servicing Rights
Quantitative Information About Level 3 Fair Value Measurements
Prepayment speed	98.10%	100.00%
OAS spread (bps)	151500.00%	151500.00%
Maximum \| IRLCs, net
Quantitative Information About Level 3 Fair Value Measurements
Loan closing rates	97.70%	99.50%
Maximum \| Swap associated with the sale of Visa, Inc. Class B shares
Quantitative Information About Level 3 Fair Value Measurements
Timing of the resolution of the covered litigation	Dec. 31, 2023	Dec. 31, 2022
Weighted-average \| Residential mortgage loans
Quantitative Information About Level 3 Fair Value Measurements
Interest rate risk factor	3.10%	2.30%
Credit risk factor	1.40%	1.40%
Weighted-average \| Mortgage Servicing Rights \| Fixed
Quantitative Information About Level 3 Fair Value Measurements
Prepayment speed	11.40%	10.20%
OAS spread (bps)	54900.00%	65400.00%
Weighted-average \| Mortgage Servicing Rights \| Adjustable
Quantitative Information About Level 3 Fair Value Measurements
Prepayment speed	24.60%	25.30%
OAS spread (bps)	78500.00%	73800.00%
Weighted-average \| IRLCs, net
Quantitative Information About Level 3 Fair Value Measurements
Loan closing rates	71.80%	76.80%
Weighted-average \| Swap associated with the sale of Visa, Inc. Class B shares
Quantitative Information About Level 3 Fair Value Measurements
Timing of the resolution of the covered litigation	Aug. 15, 2021	Aug. 24, 2020

The risk due to the variability of interest rates

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Rate applied to the loan at the closing date used as an input to determine fair value

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Expected timing of a resolution pertaining to covered litigation

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The OAS represents the spread that is added to the discount rate so that the sum of the discounted cash flows equals the market price; therefore, it is a measure of the extra yield over the reference discount factor that the Corporation expects to earn by holding the asset.

+ References

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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 elected not to be offset. Excludes assets not subject to a master netting arrangement.

+ 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

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (a),(c)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624163-113959

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226000-175313

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4D
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=64830801&loc=SL51823488-111719

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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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Risk associated with risk of default, credit spread risk and downgrade risk, expressed as a percentage, used as an input to measure fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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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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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Glossary Loan
-URI http://asc.fasb.org/extlink&oid=6517073

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Aggregate amount of servicing assets that are subsequently measured at fair value and servicing assets that are subsequently measured using the amortization method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

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