LOANS AND LEASES - Outstanding Principal Balance and Carrying Amount of Acquired Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount	$ 21,839,403	$ 20,998,766
Accounted for under ASC 310-30 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding balance	4,110,019	5,176,015
Carrying amount	3,830,823	4,834,256
Accounted for under ASC 310-20 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding balance	644,077	835,130
Carrying amount	626,041	812,322
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding balance	4,754,096	6,011,145
Carrying amount	$ 4,456,864	$ 5,646,578