LOANS AND LEASES - Impaired Loans and Lease (Detail) - Originated Loans and Leases [Member] - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	$ 114	$ 113
Recorded Investment With No Specific Reserve	73	73
Recorded Investment With Specific Reserve	12	14
Total Recorded Investment	85	87
Specific Reserve	6	4
Average Recorded Investment	89	90
Commercial Real Estate [Member]
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	24	20
Recorded Investment With No Specific Reserve	18	16
Recorded Investment With Specific Reserve	3	1
Total Recorded Investment	21	17
Specific Reserve	0	0
Average Recorded Investment	20	18
Commercial and Industrial [Member]
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	44	46
Recorded Investment With No Specific Reserve	17	20
Recorded Investment With Specific Reserve	9	13
Total Recorded Investment	26	33
Specific Reserve	6	4
Average Recorded Investment	31	32
Commercial Leases [Member]
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	2	2
Recorded Investment With No Specific Reserve	2	2
Recorded Investment With Specific Reserve	0	0
Total Recorded Investment	2	2
Specific Reserve	0	0
Average Recorded Investment	2	4
Total Commercial Loans and Leases [Member]
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	70	68
Recorded Investment With No Specific Reserve	37	38
Recorded Investment With Specific Reserve	12	14
Total Recorded Investment	49	52
Specific Reserve	6	4
Average Recorded Investment	53	54
Direct Installment [Member]
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	17	17
Recorded Investment With No Specific Reserve	14	14
Recorded Investment With Specific Reserve	0	0
Total Recorded Investment	14	14
Specific Reserve	0	0
Average Recorded Investment	14	14
Residential Mortgages [Member]
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	16	16
Recorded Investment With No Specific Reserve	15	14
Recorded Investment With Specific Reserve	0	0
Total Recorded Investment	15	14
Specific Reserve	0	0
Average Recorded Investment	15	15
Indirect Installment [Member]
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	4	5
Recorded Investment With No Specific Reserve	2	2
Recorded Investment With Specific Reserve	0	0
Total Recorded Investment	2	2
Specific Reserve	0	0
Average Recorded Investment	2	2
Consumer Lines of Credit [Member]
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
Consumer Loan [Member]
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	44	45
Recorded Investment With No Specific Reserve	36	35
Recorded Investment With Specific Reserve	0	0
Total Recorded Investment	36	35
Specific Reserve	0	0
Average Recorded Investment	$ 36	$ 36

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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=84173941&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=84173941&loc=d3e5258-111524

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953550-111524

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