Loans and Allowance for Credit Losses - Impaired Loans Average Recorded Investment and Interest Income Recognized (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 4,604	$ 4,762	$ 4,607	$ 4,825
Interest Income Recognized	51	42	146	122
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	552	470	516	510
Interest Income Recognized	4	3	7	5
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	232	279	251	263
Interest Income Recognized	3	4	8	8
Residential Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,597	1,779	1,649	1,846
Interest Income Recognized	23	18	70	57
Other Retail [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	319	309	323	304
Interest Income Recognized	3	4	9	12
Credit Card [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	260	236	255	234
Interest Income Recognized		1		3
Covered Loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		23		33
Interest Income Recognized				1
Total Loans, Excluding Loans Purchased from GNMA Mortgage Pools [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,960	3,096	2,994	3,190
Interest Income Recognized	33	30	94	86
Government National Mortgage Association [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,644	1,666	1,613	1,635
Interest Income Recognized	$ 18	$ 12	$ 52	$ 36

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=118936363&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=118936363&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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