GOODWILL AND OTHER INTANGIBLES - Gross Amount and Accumulated Amortization of Other Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Finite-Lived Intangible Assets, Gross [Abstract]
Beginning balance	$ 77,196	$ 77,196	$ 77,196	$ 77,196
Ending balance	116,428	77,196	116,428	77,196
Finite-Lived Intangible Assets, Net [Abstract]
Beginning balance	(71,048)	(68,089)	(69,623)	(66,537)
Amortization	(1,487)	(767)	(2,912)	(2,319)
Ending balance	(72,535)	(68,856)	(72,535)	(68,856)
Net Intangible assets	43,893	8,340	43,893	8,340	$ 7,573
Santander [Member]
Finite-Lived Intangible Assets, Gross [Abstract]
Additions due to acquisitions	39,232	0	39,232	0
Core Deposits [Member]
Finite-Lived Intangible Assets, Gross [Abstract]
Beginning balance	51,664	51,664	51,664	51,664
Ending balance	87,096	51,664	87,096	51,664
Finite-Lived Intangible Assets, Net [Abstract]
Beginning balance	(48,578)	(47,762)	(48,176)	(47,329)
Amortization	(769)	(207)	(1,171)	(640)
Ending balance	(49,347)	(47,969)	(49,347)	(47,969)
Net Intangible assets	37,749	3,695	37,749	3,695
Core Deposits [Member] | Santander [Member]
Finite-Lived Intangible Assets, Gross [Abstract]
Additions due to acquisitions	35,432	0	35,432	0
Customer Relationships [Member] | Credit Card [Member]
Finite-Lived Intangible Assets, Gross [Abstract]
Beginning balance	24,465	24,465	24,465	24,465
Ending balance	28,265	24,465	28,265	24,465
Finite-Lived Intangible Assets, Net [Abstract]
Beginning balance	(21,797)	(19,806)	(20,850)	(18,763)
Amortization	(679)	(522)	(1,626)	(1,565)
Ending balance	(22,476)	(20,328)	(22,476)	(20,328)
Net Intangible assets	5,789	4,137	5,789	4,137
Customer Relationships [Member] | Credit Card [Member] | Santander [Member]
Finite-Lived Intangible Assets, Gross [Abstract]
Additions due to acquisitions	3,800	0	3,800	0
Customer Relationships [Member] | Insurance Customer Intangible [Member]
Finite-Lived Intangible Assets, Gross [Abstract]
Beginning balance	1,067	1,067	1,067	1,067
Ending balance	1,067	1,067	1,067	1,067
Finite-Lived Intangible Assets, Net [Abstract]
Beginning balance	(673)	(521)	(597)	(445)
Amortization	(39)	(38)	(115)	(114)
Ending balance	(712)	(559)	(712)	(559)
Net Intangible assets	355	508	355	508
Customer Relationships [Member] | Insurance Customer Intangible [Member] | Santander [Member]
Finite-Lived Intangible Assets, Gross [Abstract]
Additions due to acquisitions	$ 0	$ 0	$ 0	$ 0