LOANS AND LEASES - Consumer Loans by Payment Status (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Credit Quality [Line Items]
Carrying amount	$ 20,817,436	$ 14,896,943
Direct Installment [Member]
Credit Quality [Line Items]
Carrying amount	1,925,995	1,844,399
Residential Mortgages [Member]
Credit Quality [Line Items]
Carrying amount	2,609,663	1,844,574
Indirect Installment [Member]
Credit Quality [Line Items]
Carrying amount	1,431,273	1,196,313
Originated Loans and Leases [Member]
Credit Quality [Line Items]
Carrying amount	14,569,696	12,547,987
Originated Loans and Leases [Member] | Direct Installment [Member]
Credit Quality [Line Items]
Carrying amount	1,757,830	1,765,257
Originated Loans and Leases [Member] | Residential Mortgages [Member]
Credit Quality [Line Items]
Carrying amount	1,904,620	1,446,776
Originated Loans and Leases [Member] | Indirect Installment [Member]
Credit Quality [Line Items]
Carrying amount	1,431,111	1,196,110
Acquired Loans [Member]
Credit Quality [Line Items]
Carrying amount	6,247,740	2,348,956
Acquired Loans [Member] | Direct Installment [Member]
Credit Quality [Line Items]
Carrying amount	168,165	79,142
Acquired Loans [Member] | Residential Mortgages [Member]
Credit Quality [Line Items]
Carrying amount	705,043	397,798
Acquired Loans [Member] | Indirect Installment [Member]
Credit Quality [Line Items]
Carrying amount	162	203
Consumer Loan [Member] | Originated Loans and Leases [Member]
Credit Quality [Line Items]
Carrying amount	6,228,181	5,507,770
Consumer Loan [Member] | Originated Loans and Leases [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	6,189,627	5,474,286
Consumer Loan [Member] | Originated Loans and Leases [Member] | Non-Performing [Member]
Credit Quality [Line Items]
Carrying amount	38,554	33,484
Consumer Loan [Member] | Originated Loans and Leases [Member] | Direct Installment [Member]
Credit Quality [Line Items]
Carrying amount	1,757,830	1,765,257
Consumer Loan [Member] | Originated Loans and Leases [Member] | Direct Installment [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	1,740,699	1,750,305
Consumer Loan [Member] | Originated Loans and Leases [Member] | Direct Installment [Member] | Non-Performing [Member]
Credit Quality [Line Items]
Carrying amount	17,131	14,952
Consumer Loan [Member] | Originated Loans and Leases [Member] | Residential Mortgages [Member]
Credit Quality [Line Items]
Carrying amount	1,904,620	1,446,776
Consumer Loan [Member] | Originated Loans and Leases [Member] | Residential Mortgages [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	1,889,056	1,433,409
Consumer Loan [Member] | Originated Loans and Leases [Member] | Residential Mortgages [Member] | Non-Performing [Member]
Credit Quality [Line Items]
Carrying amount	15,564	13,367
Consumer Loan [Member] | Originated Loans and Leases [Member] | Indirect Installment [Member]
Credit Quality [Line Items]
Carrying amount	1,431,111	1,196,110
Consumer Loan [Member] | Originated Loans and Leases [Member] | Indirect Installment [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	1,428,988	1,193,930
Consumer Loan [Member] | Originated Loans and Leases [Member] | Indirect Installment [Member] | Non-Performing [Member]
Credit Quality [Line Items]
Carrying amount	2,123	2,180
Consumer Loan [Member] | Originated Loans and Leases [Member] | Consumer Lines of Credit [Member]
Credit Quality [Line Items]
Carrying amount	1,134,620	1,099,627
Consumer Loan [Member] | Originated Loans and Leases [Member] | Consumer Lines of Credit [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	1,130,884	1,096,642
Consumer Loan [Member] | Originated Loans and Leases [Member] | Consumer Lines of Credit [Member] | Non-Performing [Member]
Credit Quality [Line Items]
Carrying amount	3,736	2,985
Consumer Loan [Member] | Acquired Loans [Member]
Credit Quality [Line Items]
Carrying amount	1,508,126	678,716
Consumer Loan [Member] | Acquired Loans [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	1,506,288	678,204
Consumer Loan [Member] | Acquired Loans [Member] | Non-Performing [Member]
Credit Quality [Line Items]
Carrying amount	1,838	512
Consumer Loan [Member] | Acquired Loans [Member] | Direct Installment [Member]
Credit Quality [Line Items]
Carrying amount	168,165	79,142
Consumer Loan [Member] | Acquired Loans [Member] | Direct Installment [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	168,093	79,142
Consumer Loan [Member] | Acquired Loans [Member] | Direct Installment [Member] | Non-Performing [Member]
Credit Quality [Line Items]
Carrying amount	72	0
Consumer Loan [Member] | Acquired Loans [Member] | Residential Mortgages [Member]
Credit Quality [Line Items]
Carrying amount	705,043	397,798
Consumer Loan [Member] | Acquired Loans [Member] | Residential Mortgages [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	705,043	397,798
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	203
Consumer Loan [Member] | Acquired Loans [Member] | Indirect Installment [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	162	203
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	634,756	201,573
Consumer Loan [Member] | Acquired Loans [Member] | Consumer Lines of Credit [Member] | Performing [Member]
Credit Quality [Line Items]
Carrying amount	632,990	201,061
Consumer Loan [Member] | Acquired Loans [Member] | Consumer Lines of Credit [Member] | Non-Performing [Member]
Credit Quality [Line Items]
Carrying amount	$ 1,766	$ 512