FAIR VALUE MEASUREMENTS - Financial Instruments (Detail) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 499	$ 488
Debt securities available for sale	3,279	3,341
Securities held to maturity	3,079	3,254
Securities held to maturity, fair value	3,093	3,155
Derivative assets	149	43
Deposits	23,731	23,455
Short-term borrowings	3,711	4,129
Long-term borrowings	1,338	627
Derivative liabilities	27	39
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	499	488
Debt securities available for sale	3,279	3,341
Securities held to maturity	3,079	3,254
Net loans and leases	22,687	21,995
Loan servicing rights	42	41
Derivative assets	149	43
Accrued interest receivable	113	101
Deposits	23,731	23,455
Short-term borrowings	3,711	4,129
Long-term borrowings	1,338	627
Derivative liabilities	27	39
Accrued interest payable	26	20
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, fair value	499	488
Debt securities available for sale	3,279	3,341
Securities held to maturity, fair value	3,093	3,155
Net loans and leases, fair value	22,576	21,742
Loan servicing rights, fair value	44	45
Derivative assets	149	43
Accrued interest receivable	113	101
Deposits, fair value	23,735	23,411
Short-term borrowings, fair value	3,714	4,130
Long-term borrowings, fair value	1,341	618
Derivative liabilities	27	39
Accrued interest payable	26	20
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, fair value	499	488
Debt securities available for sale	0	0
Securities held to maturity, fair value	0	0
Net loans and leases, fair value	0	0
Loan servicing rights, fair value	0	0
Derivative assets	0	0
Accrued interest receivable	113	101
Deposits, fair value	18,247	18,142
Short-term borrowings, fair value	3,714	4,130
Long-term borrowings, fair value	0	0
Derivative liabilities	0	0
Accrued interest payable	26	20
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, fair value	0	0
Debt securities available for sale	3,279	3,341
Securities held to maturity, fair value	3,093	3,155
Net loans and leases, fair value	39	14
Loan servicing rights, fair value	0	0
Derivative assets	146	42
Accrued interest receivable	0	0
Deposits, fair value	5,488	5,269
Short-term borrowings, fair value	0	0
Long-term borrowings, fair value	0	0
Derivative liabilities	27	39
Accrued interest payable	0	0
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, fair value	0	0
Debt securities available for sale	0	0
Securities held to maturity, fair value	0	0
Net loans and leases, fair value	22,537	21,728
Loan servicing rights, fair value	44	45
Derivative assets	3	1
Accrued interest receivable	0	0
Deposits, fair value	0	0
Short-term borrowings, fair value	0	0
Long-term borrowings, fair value	1,341	618
Derivative liabilities	0	0
Accrued interest payable	$ 0	$ 0