ALLOWANCE FOR CREDIT LOSSES - Individual and Collective Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Valuation Allowance [Line Items]
Total allowance on acquired loans	$ 170,016	$ 165,699	$ 158,059	$ 156,894	$ 154,369	$ 142,012
Originated Loans and Leases Outstanding, Loans and Leases	20,817,436		14,896,943
Commercial Real Estate [Member]
Valuation Allowance [Line Items]
Originated Loans and Leases Outstanding, Loans and Leases	8,822,023		5,435,162
Commercial and Industrial [Member]
Valuation Allowance [Line Items]
Originated Loans and Leases Outstanding, Loans and Leases	3,980,584		3,042,781
Commercial Leases [Member]
Valuation Allowance [Line Items]
Originated Loans and Leases Outstanding, Loans and Leases	238,724		196,636
Total Commercial Loans and Leases [Member]
Valuation Allowance [Line Items]
Originated Loans and Leases Outstanding, Loans and Leases	13,041,331		8,674,579
Direct Installment [Member]
Valuation Allowance [Line Items]
Originated Loans and Leases Outstanding, Loans and Leases	1,925,995		1,844,399
Residential Mortgages [Member]
Valuation Allowance [Line Items]
Originated Loans and Leases Outstanding, Loans and Leases	2,609,663		1,844,574
Indirect Installment [Member]
Valuation Allowance [Line Items]
Originated Loans and Leases Outstanding, Loans and Leases	1,431,273		1,196,313
Consumer Lines of Credit [Member]
Valuation Allowance [Line Items]
Originated Loans and Leases Outstanding, Loans and Leases	1,769,376		1,301,200
Other [Member]
Valuation Allowance [Line Items]
Originated Loans and Leases Outstanding, Loans and Leases	39,798		35,878
Originated Loans and Leases [Member]
Valuation Allowance [Line Items]
Total allowance on acquired loans	163,234	159,092	150,791	150,513	148,719	135,285
Originated Allowance, Individually Evaluated for Impairment	8,659		3,203
Originated Allowance, Collectively Evaluated for Impairment	154,575		147,588
Originated Loans and Leases Outstanding, Loans and Leases	14,569,696		12,547,987
Originated Loans and Leases Outstanding, Individually Evaluated for Impairment	41,937		34,719
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	14,527,759		12,513,268
Originated Loans and Leases [Member] | Commercial Real Estate [Member]
Valuation Allowance [Line Items]
Total allowance on acquired loans	48,123	46,958	46,635	42,367	44,428	41,741
Originated Allowance, Individually Evaluated for Impairment	416		13
Originated Allowance, Collectively Evaluated for Impairment	47,707		46,622
Originated Loans and Leases Outstanding, Loans and Leases	4,903,796		4,095,817
Originated Loans and Leases Outstanding, Individually Evaluated for Impairment	14,002		12,973
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	4,889,794		4,082,844
Originated Loans and Leases [Member] | Commercial and Industrial [Member]
Valuation Allowance [Line Items]
Total allowance on acquired loans	53,703	54,108	47,991	53,708	51,475	41,023
Originated Allowance, Individually Evaluated for Impairment	8,243		3,190
Originated Allowance, Collectively Evaluated for Impairment	45,460		44,801
Originated Loans and Leases Outstanding, Loans and Leases	3,159,197		2,711,886
Originated Loans and Leases Outstanding, Individually Evaluated for Impairment	27,935		21,746
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	3,131,262		2,690,140
Originated Loans and Leases [Member] | Commercial Leases [Member]
Valuation Allowance [Line Items]
Total allowance on acquired loans	4,829	4,122	3,280	3,207	3,047	2,541
Originated Allowance, Individually Evaluated for Impairment	0		0
Originated Allowance, Collectively Evaluated for Impairment	4,829		3,280
Originated Loans and Leases Outstanding, Loans and Leases	238,724		196,636
Originated Loans and Leases Outstanding, Individually Evaluated for Impairment	0		0
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	238,724		196,636
Originated Loans and Leases [Member] | Total Commercial Loans and Leases [Member]
Valuation Allowance [Line Items]
Total allowance on acquired loans	106,655	105,188	97,906	99,282	98,950	85,305
Originated Allowance, Individually Evaluated for Impairment	8,659		3,203
Originated Allowance, Collectively Evaluated for Impairment	97,996		94,703
Originated Loans and Leases Outstanding, Loans and Leases	8,301,717		7,004,339
Originated Loans and Leases Outstanding, Individually Evaluated for Impairment	41,937		34,719
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	8,259,780		6,969,620
Originated Loans and Leases [Member] | Direct Installment [Member]
Valuation Allowance [Line Items]
Total allowance on acquired loans	20,677	20,736	21,391	21,087	21,543	21,587
Originated Allowance, Individually Evaluated for Impairment	0		0
Originated Allowance, Collectively Evaluated for Impairment	20,677		21,391
Originated Loans and Leases Outstanding, Loans and Leases	1,757,830		1,765,257
Originated Loans and Leases Outstanding, Individually Evaluated for Impairment	0		0
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	1,757,830		1,765,257
Originated Loans and Leases [Member] | Residential Mortgages [Member]
Valuation Allowance [Line Items]
Total allowance on acquired loans	12,735	11,252	10,082	9,246	8,410	7,909
Originated Allowance, Individually Evaluated for Impairment	0		0
Originated Allowance, Collectively Evaluated for Impairment	12,735		10,082
Originated Loans and Leases Outstanding, Loans and Leases	1,904,620		1,446,776
Originated Loans and Leases Outstanding, Individually Evaluated for Impairment	0		0
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	1,904,620		1,446,776
Originated Loans and Leases [Member] | Indirect Installment [Member]
Valuation Allowance [Line Items]
Total allowance on acquired loans	11,347	10,574	10,564	10,362	9,543	9,889
Originated Allowance, Individually Evaluated for Impairment	0		0
Originated Allowance, Collectively Evaluated for Impairment	11,347		10,564
Originated Loans and Leases Outstanding, Loans and Leases	1,431,111		1,196,110
Originated Loans and Leases Outstanding, Individually Evaluated for Impairment	0		0
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	1,431,111		1,196,110
Originated Loans and Leases [Member] | Consumer Lines of Credit [Member]
Valuation Allowance [Line Items]
Total allowance on acquired loans	10,052	9,504	9,456	9,271	9,149	9,582
Originated Allowance, Individually Evaluated for Impairment	0		0
Originated Allowance, Collectively Evaluated for Impairment	10,052		9,456
Originated Loans and Leases Outstanding, Loans and Leases	1,134,620		1,099,627
Originated Loans and Leases Outstanding, Individually Evaluated for Impairment	0		0
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	1,134,620		1,099,627
Originated Loans and Leases [Member] | Other [Member]
Valuation Allowance [Line Items]
Total allowance on acquired loans	1,768	$ 1,838	1,392	$ 1,265	$ 1,124	$ 1,013
Originated Allowance, Individually Evaluated for Impairment	0		0
Originated Allowance, Collectively Evaluated for Impairment	1,768		1,392
Originated Loans and Leases Outstanding, Loans and Leases	39,798		35,878
Originated Loans and Leases Outstanding, Individually Evaluated for Impairment	0		0
Originated Loans and Leases Outstanding, Collectively Evaluated for Impairment	$ 39,798		$ 35,878