Derivatives (Notional Amounts and Fair Values for All Derivative Instruments Included in the Consolidated Balance Sheets) (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value
Fair value - Derivative Assets	$ 984	$ 823
Fair value - Derivative Liabilities	913	602
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges
Derivatives, Fair Value
Fair value - Derivative Assets	205	297
Fair value - Derivative Liabilities	26	17
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges \| Fair Value Hedging
Derivatives, Fair Value
Fair value - Derivative Assets	203	297
Fair value - Derivative Liabilities	9	5
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges \| Fair Value Hedging \| Interest Rate Swap \| Long-Term Debt
Derivatives, Fair Value
Derivative, Notional Amount	3,455	3,705
Fair value - Derivative Assets	203	297
Fair value - Derivative Liabilities	9	5
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges \| Cash Flow Hedging
Derivatives, Fair Value
Fair value - Derivative Assets	2	0
Fair value - Derivative Liabilities	17	12
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges \| Cash Flow Hedging \| Interest Rate Swap \| Commercial and Industrial Loans
Derivatives, Fair Value
Derivative, Notional Amount	6,150	4,475
Fair value - Derivative Assets	2	0
Fair value - Derivative Liabilities	17	12
Nondesignated
Derivatives, Fair Value
Fair value - Derivative Assets	779	526
Fair value - Derivative Liabilities	887	585
Nondesignated \| Risk Management And Other Business Purposes
Derivatives, Fair Value
Fair value - Derivative Assets	53	75
Fair value - Derivative Liabilities	159	154
Nondesignated \| Risk Management And Other Business Purposes \| Interest Rate Contract \| Servicing Contracts
Derivatives, Fair Value
Derivative, Notional Amount	13,745	11,035
Fair value - Derivative Assets	49	54
Fair value - Derivative Liabilities	15	15
Nondesignated \| Risk Management And Other Business Purposes \| Forward Contracts \| Loans Held For Sale
Derivatives, Fair Value
Derivative, Notional Amount	955	1,284
Fair value - Derivative Assets	4	1
Fair value - Derivative Liabilities	0	1
Nondesignated \| Risk Management And Other Business Purposes \| Warrant
Derivatives, Fair Value
Derivative, Notional Amount		20
Fair value - Derivative Assets		20
Fair value - Derivative Liabilities		0
Nondesignated \| Risk Management And Other Business Purposes \| Swap
Derivatives, Fair Value
Derivative, Notional Amount	2,473	1,900
Fair value - Derivative Assets	0	0
Fair value - Derivative Liabilities	144	137
Nondesignated \| Risk Management And Other Business Purposes \| Foreign Exchange Contract
Derivatives, Fair Value
Derivative, Notional Amount		112
Fair value - Derivative Assets		0
Fair value - Derivative Liabilities		1
Nondesignated \| Customer Accommodation
Derivatives, Fair Value
Fair value - Derivative Assets	726	451
Fair value - Derivative Liabilities	728	431
Nondesignated \| Customer Accommodation \| Interest Rate Contract
Derivatives, Fair Value
Derivative, Notional Amount	53,651	42,216
Fair value - Derivative Assets	280	154
Fair value - Derivative Liabilities	322	145
Nondesignated \| Customer Accommodation \| Interest Rate Lock Commitments
Derivatives, Fair Value
Derivative, Notional Amount	397	446
Fair value - Derivative Assets	7	8
Fair value - Derivative Liabilities	0	0
Nondesignated \| Customer Accommodation \| Commodity Contract
Derivatives, Fair Value
Derivative, Notional Amount	5,818	4,125
Fair value - Derivative Assets	315	165
Fair value - Derivative Liabilities	296	167
Nondesignated \| Customer Accommodation \| TBAs
Derivatives, Fair Value
Derivative, Notional Amount	20	26
Fair value - Derivative Assets	0	0
Fair value - Derivative Liabilities	0	0
Nondesignated \| Customer Accommodation \| Foreign Exchange Contract
Derivatives, Fair Value
Derivative, Notional Amount	12,940	12,654
Fair value - Derivative Assets	124	124
Fair value - Derivative Liabilities	$ 110	$ 119

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

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- Definition

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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226000-175313

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4D
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=109247956&loc=SL51823488-111719

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-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 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (a),(c)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959

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- Definition

Fair value, before effects of master netting arrangements, of a financial liability or 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 liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4D
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=109247956&loc=SL51823488-111719

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (a),(c)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-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 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226000-175313

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- Definition

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.

+ References

No definition available.

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