Loans and Leases - Summary of Impaired Loans and Lease, by Class (Detail) - Originated Loans and Leases - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	$ 114	$ 113
Recorded Investment With No Specific Reserve	86	73
Recorded Investment With Specific Reserve	2	14
Total Recorded Investment	88	87
Specific Reserve	4	4
Average Recorded Investment	87	90
Total commercial loans and leases
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	66	68
Recorded Investment With No Specific Reserve	47	38
Recorded Investment With Specific Reserve	2	14
Total Recorded Investment	49	52
Specific Reserve	4	4
Average Recorded Investment	49	54
Commercial real estate
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	30	20
Recorded Investment With No Specific Reserve	25	16
Recorded Investment With Specific Reserve	2	1
Total Recorded Investment	27	17
Specific Reserve	2	0
Average Recorded Investment	26	18
Commercial and industrial
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	35	46
Recorded Investment With No Specific Reserve	21	20
Recorded Investment With Specific Reserve	0	13
Total Recorded Investment	21	33
Specific Reserve	2	4
Average Recorded Investment	22	32
Commercial leases
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	1	2
Recorded Investment With No Specific Reserve	1	2
Recorded Investment With Specific Reserve	0	0
Total Recorded Investment	1	2
Specific Reserve	0	0
Average Recorded Investment	1	4
Total consumer loans
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	48	45
Recorded Investment With No Specific Reserve	39	35
Recorded Investment With Specific Reserve	0	0
Total Recorded Investment	39	35
Specific Reserve	0	0
Average Recorded Investment	38	36
Direct installment
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	16	17
Recorded Investment With No Specific Reserve	13	14
Recorded Investment With Specific Reserve	0	0
Total Recorded Investment	13	14
Specific Reserve	0	0
Average Recorded Investment	13	14
Residential mortgages
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	20	16
Recorded Investment With No Specific Reserve	18	14
Recorded Investment With Specific Reserve	0	0
Total Recorded Investment	18	14
Specific Reserve	0	0
Average Recorded Investment	17	15
Indirect installment
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	5	5
Recorded Investment With No Specific Reserve	3	2
Recorded Investment With Specific Reserve	0	0
Total Recorded Investment	3	2
Specific Reserve	0	0
Average Recorded Investment	3	2
Consumer lines of credit
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	7	7
Recorded Investment With No Specific Reserve	5	5
Recorded Investment With Specific Reserve	0	0
Total Recorded Investment	5	5
Specific Reserve	0	0
Average Recorded Investment	$ 5	$ 5

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Average amount of investment of impaired financing receivables with related allowance for credit losses and without 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

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-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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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953550-111524

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