GOODWILL AND OTHER INTANGIBLES - Gross Amount and Accumulated Amortization of Other Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015	Jun. 30, 2012
Finite Lived Intangible Assets [Line Items]
Gross amount			$ 24,500
Goodwill And Intangible Assets Disclosure [Abstract]
Finite Lived Intangible Assets Amortization Expense Year Two	$ 4,495
Finite Lived Intangible Assets Amortization Expense Year Three	3,519
Finite Lived Intangible Assets Amortization Expense Year Four	3,067
Finite Lived Intangible Assets Amortization Expense After Year Five	4,725
Finite Lived Intangible Assets Amortization Expense Remainder Of Fiscal Year	1,226
Finite Lived Intangible Assets Amortization Expense Year Five	2,851
Core Deposits [Member]
Finite Lived Intangible Assets [Line Items]
Gross amount	51,664	$ 45,844
Finite lived Intangible Assets Acquired 1		5,820
Accumulated amortization	(43,974)	(42,498)
Net carrying amount	$ 7,690	$ 9,166
Remaining amortization period	8 years 3 months 18 days	9 years
Purchased Credit Card Relationship Intangible [Member]
Finite Lived Intangible Assets [Line Items]
Gross amount	$ 24,465	$ 24,465
Accumulated amortization	(13,237)	(11,146)
Net carrying amount	$ 11,228	$ 13,319
Remaining amortization period	5 years 2 months 12 days	5 years 9 months 18 days
Customer Related Intangible Assets [Member]
Finite Lived Intangible Assets [Line Items]
Gross amount	$ 1,067	$ 0
Accumulated amortization	(102)	0
Net carrying amount	$ 965	$ 0
Remaining amortization period	6 years 3 months 18 days