Loans and Allowance for Credit Losses - Impaired Loans Average Recorded Investment and Interest Income Recognized (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 4,797	$ 5,316	$ 5,710
Interest Income Recognized	164	204	237
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	497	683	799
Interest Income Recognized	8	7	9
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	273	273	324
Interest Income Recognized	13	11	15
Residential Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,817	2,135	2,422
Interest Income Recognized	76	103	124
Other Retail [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	309	287	293
Interest Income Recognized	16	14	13
Credit Card [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	236	229	214
Interest Income Recognized	3	3	4
Covered Loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	25	37	38
Interest Income Recognized	1	1	1
Total Loans, Excluding Loans Purchased from GNMA Mortgage Pools [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	3,157	3,644	4,090
Interest Income Recognized	117	139	166
Government National Mortgage Association [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,640	1,672	1,620
Interest Income Recognized	$ 47	$ 65	$ 71

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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