NATURE OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Goodwill and other intangible assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Sep. 01, 2020	Dec. 31, 2017	Feb. 15, 2016	Jun. 30, 2012
Finite Lived Intangible Assets [Line Items]
Gross amount	$ 116,428	$ 77,196	$ 77,196		$ 77,196
Net intangible assets	40,893	7,573	10,659
Intangible assets recognized as part of a business combination	40,900
Goodwill impairment	0	0	0
Santander [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets recognized as part of a business combination				$ 39,200
Customer Relationships [Member] | Credit Card [Member]
Finite Lived Intangible Assets [Line Items]
Gross amount	28,265	24,465	24,465		24,465
Net intangible assets	4,733	3,615	5,702
Intangible assets recognized as part of a business combination	4,700
Customer Relationships [Member] | Credit Card [Member] | Doral Bank Transaction Member [Member]
Finite Lived Intangible Assets [Line Items]
Net intangible assets	1,700	3,600
Intangible assets recognized as part of a business combination							$ 24,500
Customer Relationships [Member] | Credit Card [Member] | Santander [Member]
Finite Lived Intangible Assets [Line Items]
Net intangible assets	3,000
Intangible assets recognized as part of a business combination				3,800
Customer Relationships [Member] | Insurance Customer Intangible [Member]
Finite Lived Intangible Assets [Line Items]
Gross amount	1,067	1,067	1,067		1,067
Net intangible assets	318	470	622
Intangible assets recognized as part of a business combination	300
Customer Relationships [Member] | Insurance Customer Intangible [Member] | Doral Bank Transaction Member [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets recognized as part of a business combination						$ 1,100
Core Deposits [Member]
Finite Lived Intangible Assets [Line Items]
Gross amount	87,096	51,664	51,664		$ 51,664
Net intangible assets	35,842	$ 3,488	$ 4,335
Intangible assets recognized as part of a business combination	$ 35,800
Core Deposits [Member] | Santander [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets recognized as part of a business combination				$ 35,400