Loans and Allowance for Credit Losses - Impaired Loans Average Recorded Investment and Interest Income Recognized (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 4,577	$ 4,792	$ 4,610	$ 4,856
Interest Income Recognized	48	40	95	80
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	512	514	498	530
Interest Income Recognized	2	1	3	2
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	248	242	261	255
Interest Income Recognized	3	2	5	4
Residential Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,652	1,846	1,674	1,880
Interest Income Recognized	23	19	47	39
Other Retail [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	321	303	326	301
Interest Income Recognized	3	4	6	8
Credit Card [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	256	234	253	233
Interest Income Recognized		1		2
Covered Loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		37		37
Interest Income Recognized		1		1
Total Loans, Excluding Loans Purchased from GNMA Mortgage Pools [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,989	3,176	3,012	3,236
Interest Income Recognized	31	28	61	56
Government National Mortgage Association [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,588	1,616	1,598	1,620
Interest Income Recognized	$ 17	$ 12	$ 34	$ 24

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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- Definition

Amount of average investment of impaired financing receivables for which there is a related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5258-111524

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- Definition

Amount of interest income, recognized on accrual basis, on financing receivables, for which there is a related allowance for credit losses and are recognized as impaired.

+ References

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