LOANS AND LEASES - Outstanding Principal Balance and Carrying Amount of Loans Acquired in a Business Combination (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount	$ 22,620	$ 22,153
Loans Acquired In A Business Combination Accounted For Under ASC 310-30 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding balance	3,515	3,768
Carrying amount	3,252	3,570
Loans Acquired In A Business Combination Accounted For Under ASC 310-20 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding balance	566	602
Carrying amount	547	513
Loans Acquired In Business Combination Including Purchased Credit Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding balance	4,081	4,370
Carrying amount	$ 3,799	$ 4,083