REVENUE FROM CONTRACT WITH CUSTOMERS (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Line Items]
Net interest income	$ 600,322	$ 567,081	$ 525,383
Noninterest Income	111,226	90,572	82,310
Total Revenues	711,548	657,653	607,693
Service charges and fees on deposit accounts [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	24,612	23,916	21,668
Insurance commissions [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	9,364	10,186	8,431
Total Revenues	3,300	3,000	2,400
Merchant-related income [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	5,844	5,635	5,243
Credit and debit card fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	19,765	20,905	21,442
Other service charges and fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	8,994	8,789	7,870
Not inscope of Topic 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	42,647	21,141	17,656
Mortgage Banking Segment [Member]
Disaggregation Of Revenue [Line Items]
Net interest income	76,025	68,803	79,389
Noninterest Income	22,069	16,825	17,073
Total Revenues	98,094	85,628	96,462
Mortgage Banking Segment [Member] | Service charges and fees on deposit accounts [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	0	0	0
Mortgage Banking Segment [Member] | Insurance commissions [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	0	0	0
Mortgage Banking Segment [Member] | Merchant-related income [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	0	0	0
Mortgage Banking Segment [Member] | Credit and debit card fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	0	0	0
Mortgage Banking Segment [Member] | Other service charges and fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	342	216	252
Mortgage Banking Segment [Member] | Not inscope of Topic 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	21,727	16,609	16,821
Consumer Retail Banking Segment [Member]
Disaggregation Of Revenue [Line Items]
Net interest income	220,678	244,535	217,933
Noninterest Income	50,962	51,729	47,706
Total Revenues	271,640	296,264	265,639
Consumer Retail Banking Segment [Member] | Service charges and fees on deposit accounts [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	13,286	14,534	13,332
Consumer Retail Banking Segment [Member] | Insurance commissions [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	8,754	9,621	7,889
Consumer Retail Banking Segment [Member] | Merchant-related income [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	4,516	4,120	3,561
Consumer Retail Banking Segment [Member] | Credit and debit card fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	18,218	19,014	17,538
Consumer Retail Banking Segment [Member] | Other service charges and fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	2,900	3,012	4,391
Consumer Retail Banking Segment [Member] | Not inscope of Topic 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	3,288	1,428	995
Commercial And Corporate Segment [Member]
Disaggregation Of Revenue [Line Items]
Net interest income	135,591	91,266	78,675
Noninterest Income	12,606	11,714	5,158
Total Revenues	148,197	102,980	83,833
Commercial And Corporate Segment [Member] | Service charges and fees on deposit accounts [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	8,026	5,811	4,965
Commercial And Corporate Segment [Member] | Insurance commissions [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	0	0	0
Commercial And Corporate Segment [Member] | Merchant-related income [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	478	466	748
Commercial And Corporate Segment [Member] | Credit and debit card fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	62	104	1,225
Commercial And Corporate Segment [Member] | Other service charges and fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	2,260	2,690	1,280
Commercial And Corporate Segment [Member] | Not inscope of Topic 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	1,780	2,643	(3,060)
Treasury And Investments Segment [Member]
Disaggregation Of Revenue [Line Items]
Net interest income	87,879	73,626	61,628
Noninterest Income	13,708	(225)	2,505
Total Revenues	101,587	73,401	64,133
Treasury And Investments Segment [Member] | Service charges and fees on deposit accounts [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	0	0	0
Treasury And Investments Segment [Member] | Insurance commissions [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	0	0	0
Treasury And Investments Segment [Member] | Merchant-related income [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	0	0	0
Treasury And Investments Segment [Member] | Credit and debit card fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	0	0	0
Treasury And Investments Segment [Member] | Other service charges and fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	184	0	71
Treasury And Investments Segment [Member] | Not inscope of Topic 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	13,524	(225)	2,434
United States Operations Segment [Member]
Disaggregation Of Revenue [Line Items]
Net interest income	54,025	62,539	59,056
Noninterest Income	4,630	2,807	3,020
Total Revenues	58,655	65,346	62,076
United States Operations Segment [Member] | Service charges and fees on deposit accounts [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	553	631	559
United States Operations Segment [Member] | Insurance commissions [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	52	67	87
United States Operations Segment [Member] | Merchant-related income [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	41	0	0
United States Operations Segment [Member] | Credit and debit card fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	16	43	618
United States Operations Segment [Member] | Other service charges and fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	1,800	1,558	1,351
United States Operations Segment [Member] | Not inscope of Topic 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	2,168	508	405
Virgin Islands Operations Segment [Member]
Disaggregation Of Revenue [Line Items]
Net interest income	26,124	26,312	28,702
Noninterest Income	7,251	7,722	6,848
Total Revenues	33,375	34,034	35,550
Virgin Islands Operations Segment [Member] | Service charges and fees on deposit accounts [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	2,747	2,940	2,812
Virgin Islands Operations Segment [Member] | Insurance commissions [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	558	498	455
Virgin Islands Operations Segment [Member] | Merchant-related income [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	809	1,049	934
Virgin Islands Operations Segment [Member] | Credit and debit card fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	1,469	1,744	2,061
Virgin Islands Operations Segment [Member] | Other service charges and fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	1,508	1,313	525
Virgin Islands Operations Segment [Member] | Not inscope of Topic 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest Income	$ 160	$ 178	$ 61