LOANS AND LEASES - Consumer Loans by Payment Status (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Credit Quality [Line Items]
Carrying amount	$ 21,839,403	$ 20,998,766
Direct Installment [Member]
Credit Quality [Line Items]
Carrying amount	1,778,123	1,905,535
Residential Mortgages [Member]
Credit Quality [Line Items]
Carrying amount	2,984,662	2,702,691
Indirect Installment [Member]
Credit Quality [Line Items]
Carrying amount	1,880,649	1,448,433
Originated Loans and Leases [Member]
Credit Quality [Line Items]
Carrying amount	17,377,969	15,345,490
Originated Loans and Leases [Member] | Direct Installment [Member]
Credit Quality [Line Items]
Carrying amount	1,670,964	1,755,713
Originated Loans and Leases [Member] | Residential Mortgages [Member]
Credit Quality [Line Items]
Carrying amount	2,457,380	2,036,226
Originated Loans and Leases [Member] | Indirect Installment [Member]
Credit Quality [Line Items]
Carrying amount	1,880,487	1,448,268
Acquired Loans [Member]
Credit Quality [Line Items]
Carrying amount	4,461,434	5,653,276
Acquired Loans [Member] | Direct Installment [Member]
Credit Quality [Line Items]
Carrying amount	107,159	149,822
Acquired Loans [Member] | Residential Mortgages [Member]
Credit Quality [Line Items]
Carrying amount	527,282	666,465
Acquired Loans [Member] | Indirect Installment [Member]
Credit Quality [Line Items]
Carrying amount	162	165
Consumer Loan [Member] | Originated Loans and Leases [Member]
Credit Quality [Line Items]
Carrying amount	7,125,207	6,391,677
Consumer Loan [Member] | Originated Loans and Leases [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	7,086,977	6,352,285
Consumer Loan [Member] | Originated Loans and Leases [Member] | Non-Performing [Member]
Credit Quality [Line Items]
Carrying amount	38,230	39,392
Consumer Loan [Member] | Originated Loans and Leases [Member] | Direct Installment [Member]
Credit Quality [Line Items]
Carrying amount	1,670,964	1,755,713
Consumer Loan [Member] | Originated Loans and Leases [Member] | Direct Installment [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	1,656,375	1,739,060
Consumer Loan [Member] | Originated Loans and Leases [Member] | Direct Installment [Member] | Non-Performing [Member]
Credit Quality [Line Items]
Carrying amount	14,589	16,653
Consumer Loan [Member] | Originated Loans and Leases [Member] | Residential Mortgages [Member]
Credit Quality [Line Items]
Carrying amount	2,457,380	2,036,226
Consumer Loan [Member] | Originated Loans and Leases [Member] | Residential Mortgages [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	2,441,374	2,019,816
Consumer Loan [Member] | Originated Loans and Leases [Member] | Residential Mortgages [Member] | Non-Performing [Member]
Credit Quality [Line Items]
Carrying amount	16,006	16,410
Consumer Loan [Member] | Originated Loans and Leases [Member] | Indirect Installment [Member]
Credit Quality [Line Items]
Carrying amount	1,880,487	1,448,268
Consumer Loan [Member] | Originated Loans and Leases [Member] | Indirect Installment [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	1,878,224	1,445,833
Consumer Loan [Member] | Originated Loans and Leases [Member] | Indirect Installment [Member] | Non-Performing [Member]
Credit Quality [Line Items]
Carrying amount	2,263	2,435
Consumer Loan [Member] | Originated Loans and Leases [Member] | Consumer Lines of Credit [Member]
Credit Quality [Line Items]
Carrying amount	1,116,376	1,151,470
Consumer Loan [Member] | Originated Loans and Leases [Member] | Consumer Lines of Credit [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	1,111,004	1,147,576
Consumer Loan [Member] | Originated Loans and Leases [Member] | Consumer Lines of Credit [Member] | Non-Performing [Member]
Credit Quality [Line Items]
Carrying amount	5,372	3,894
Consumer Loan [Member] | Acquired Loans [Member]
Credit Quality [Line Items]
Carrying amount	1,123,688	1,410,775
Consumer Loan [Member] | Acquired Loans [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	1,122,358	1,408,765
Consumer Loan [Member] | Acquired Loans [Member] | Non-Performing [Member]
Credit Quality [Line Items]
Carrying amount	1,330	2,010
Consumer Loan [Member] | Acquired Loans [Member] | Direct Installment [Member]
Credit Quality [Line Items]
Carrying amount	107,159	149,822
Consumer Loan [Member] | Acquired Loans [Member] | Direct Installment [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	107,091	149,751
Consumer Loan [Member] | Acquired Loans [Member] | Direct Installment [Member] | Non-Performing [Member]
Credit Quality [Line Items]
Carrying amount	68	71
Consumer Loan [Member] | Acquired Loans [Member] | Residential Mortgages [Member]
Credit Quality [Line Items]
Carrying amount	527,282	666,465
Consumer Loan [Member] | Acquired Loans [Member] | Residential Mortgages [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	527,282	666,465
Consumer Loan [Member] | Acquired Loans [Member] | Residential Mortgages [Member] | Non-Performing [Member]
Credit Quality [Line Items]
Carrying amount	0	0
Consumer Loan [Member] | Acquired Loans [Member] | Indirect Installment [Member]
Credit Quality [Line Items]
Carrying amount	162	165
Consumer Loan [Member] | Acquired Loans [Member] | Indirect Installment [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	162	165
Consumer Loan [Member] | Acquired Loans [Member] | Indirect Installment [Member] | Non-Performing [Member]
Credit Quality [Line Items]
Carrying amount	0	0
Consumer Loan [Member] | Acquired Loans [Member] | Consumer Lines of Credit [Member]
Credit Quality [Line Items]
Carrying amount	489,085	594,323
Consumer Loan [Member] | Acquired Loans [Member] | Consumer Lines of Credit [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	487,823	592,384
Consumer Loan [Member] | Acquired Loans [Member] | Consumer Lines of Credit [Member] | Non-Performing [Member]
Credit Quality [Line Items]
Carrying amount	$ 1,262	$ 1,939