Loans and Allowance for Credit Losses - Impaired Loans Average Recorded Investment and Interest Income Recognized (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 4,608	$ 4,797	$ 5,316
Interest Income Recognized	194	164	204
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	520	497	683
Interest Income Recognized	9	8	7
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	248	273	273
Interest Income Recognized	11	13	11
Residential Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,622	1,817	2,135
Interest Income Recognized	92	76	103
Other Retail [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	323	309	287
Interest Income Recognized	12	16	14
Credit Card [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	257	236	229
Interest Income Recognized		3	3
Covered Loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		25	37
Interest Income Recognized		1	1
Total Loans, Excluding Loans Purchased from GNMA Mortgage Pools [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,970	3,157	3,644
Interest Income Recognized	124	117	139
Government National Mortgage Association [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,638	1,640	1,672
Interest Income Recognized	$ 70	$ 47	$ 65

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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