LOANS AND LEASES - Additional Allowance for Credit Losses Relating to Acquired Loans (Detail) - USD ($) $ in Millions	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Loss [Line Items]
Total allowance on loans acquired in a business combination	$ 188	$ 186	$ 180	$ 177	$ 179	$ 175
Loans Acquired in a Business Combination [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Total allowance on loans acquired in a business combination	5		7	$ 4		$ 7
Loans Acquired in a Business Combination [Member] | Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Total allowance on loans acquired in a business combination	2		2
Loans Acquired in a Business Combination [Member] | Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Total allowance on loans acquired in a business combination	1		4
Loans Acquired in a Business Combination [Member] | Total Commercial Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Total allowance on loans acquired in a business combination	3		6
Loans Acquired in a Business Combination [Member] | Direct Installment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Total allowance on loans acquired in a business combination	1		1
Loans Acquired in a Business Combination [Member] | Consumer Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Total allowance on loans acquired in a business combination	2		1
Loans Acquired in a Business Combination [Member] | Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Total allowance on loans acquired in a business combination	$ 1		$ 0