INTEREST AND DIVIDEND ON INVESTMENTS- Interest on investments and FHLB dividend income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Income And Expenses [Line Items]
Mortgage-backed securities	$ 36,429	$ 34,231	$ 32,167
PR Government obligations, U.S. Treasury securities and U.S. Government agencies	21,052	14,781	17,276
Total Intesrest income investment securities	60,224	51,125	50,905
Interest on money market investments and interest-bearing cash accounts	11,096	4,614	3,365
Total interest and dividends on investments	71,320	55,739	54,270
Taxable [Member]
Other Income And Expenses [Line Items]
Mortgage-backed securities	8,688	9,656	11,246
PR Government obligations, U.S. Treasury securities and U.S. Government agencies	470	2,091	4,131
Other investment securities (including FHLB dividends)	2,743	2,113	1,462
Interest on money market investments and interest-bearing cash accounts	10,863	4,609	2,669
Exempt [Member]
Other Income And Expenses [Line Items]
Mortgage-backed securities	27,741	24,575	20,921
PR Government obligations, U.S. Treasury securities and U.S. Government agencies	20,582	12,690	13,145
Interest on money market investments and interest-bearing cash accounts	$ 233	$ 5	$ 696