INTEREST AND DIVIDEND ON INVESTMENTS- Interest on investments and FHLB dividend income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other Income And Expenses [Line Items]
Mortgage-backed securities	$ 40,281	$ 37,044	$ 36,429
PR Government obligations, U.S. Treasury securities and U.S. Government agencies	16,267	19,788	21,052
Total Intesrest income investment securities	58,547	59,546	60,224
Interest on money market investments and interest-bearing cash accounts	3,388	13,353	11,096
Total interest and dividends on investments	61,935	72,899	71,320
Taxable [Member]
Other Income And Expenses [Line Items]
Mortgage-backed securities	9,404	7,812	8,688
PR Government obligations, U.S. Treasury securities and U.S. Government agencies	1,032	165	470
Other investment securities (including FHLB dividends)	1,999	2,714	2,743
Interest on money market investments and interest-bearing cash accounts	3,386	13,205	10,863
Exempt [Member]
Other Income And Expenses [Line Items]
Mortgage-backed securities	30,877	29,232	27,741
PR Government obligations, U.S. Treasury securities and U.S. Government agencies	15,235	19,623	20,582
Interest on money market investments and interest-bearing cash accounts	$ 2	$ 148	$ 233