REGULATORY MATTERS, COMMITMENTS AND CONTINGENCIES - Regulatory capital positions (Detail) $ in Thousands	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
First BanCorp [Member]
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Total Capital (to Risk-Weighted Assets) Actual	$ 2,416,682	$ 2,286,337
Total Capital (to Risk-Weighted Assets) Actual Ratio	0.2037	0.2522
Total Capital (to Risk-Weighted Assets) Required For Capital Adequacy	$ 948,890	$ 725,236
Total Capital (to Risk-Weighted Assets) Required For Capital Adequacy Ratio	0.080	0.080
Common Equity Tier 1 Capital (to Risk-Weighted Assets) Actual	$ 2,053,045	$ 1,957,887
Common Equity Tier 1 Capital (to Risk-Weighted Assets) Actual Ratio	17.31%	21.60%
Common Equity Tier 1 Captial (to Risk-Weighted Assets) Required For Captial Adequacy	$ 533,751	$ 407,946
Common Equity Tier 1 Captial (to Risk-Weighted Assets) Required For Captial Adequacy Ratio	4.50%	4.50%
Tier 1 Capital (to Risk-Weighted Assets) Actual	$ 2,089,149	$ 1,993,991
Tier 1 Captial (to Risk-Weighted Assets) Actual Ratio	0.1761	0.2200
Tier 1 Capital (to Risk-Weighted Assets) Required For Capital Adequacy	$ 711,667	$ 543,927
Tier 1 Capital (to Risk-Weighted Assets) Required For Capital Adequacy Ratio	0.060	0.060
Leverage Ratio Actual Amount	$ 2,089,149	$ 1,993,991
Leverage Ratio Actual Ratio	0.1126	0.1615
Leverage Ratio Required For Captial Adequacy	$ 742,352	$ 493,786
Leverage Ratio Required For Capital Adequancy Ratio	0.040	0.040
FirstBank [Member]
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Total Capital (to Risk-Weighted Assets) Actual	$ 2,360,493	$ 2,242,262
Total Capital (to Risk-Weighted Assets) Actual Ratio	0.1991	0.2474
Total Capital (to Risk-Weighted Assets) Required For Capital Adequacy	$ 948,624	$ 725,047
Total Capital (to Risk-Weighted Assets) Required For Capital Adequacy Ratio	0.080	0.080
Total Capital (to Risk-Weighted Assets) Required To Be Well Capitalized	$ 1,185,780	$ 906,309
Total Capital (to Risk-Weighted Assets) Required To Be Well Capitalized Ratio	0.100	0.100
Common Equity Tier 1 Capital (to Risk-Weighted Assets) Actual	$ 1,903,251	$ 1,820,571
Common Equity Tier 1 Capital (to Risk-Weighted Assets) Actual Ratio	16.05%	20.09%
Common Equity Tier 1 Captial (to Risk-Weighted Assets) Required For Captial Adequacy	$ 533,601	$ 407,839
Common Equity Tier 1 Captial (to Risk-Weighted Assets) Required For Captial Adequacy Ratio	4.50%	4.50%
Common Equity Tier 1 Captial (to Risk-Weighted Assets) Required To Be Well Capitalized	$ 770,757	$ 589,101
Common Equity Tier 1 Captial (to Risk-Weighted Assets) Required To Be Well Capitalized Ratio	6.50%	6.50%
Tier 1 Capital (to Risk-Weighted Assets) Actual	$ 2,211,251	$ 2,128,571
Tier 1 Captial (to Risk-Weighted Assets) Actual Ratio	0.1865	0.2349
Tier 1 Capital (to Risk-Weighted Assets) Required For Capital Adequacy	$ 711,468	$ 543,785
Tier 1 Capital (to Risk-Weighted Assets) Required For Capital Adequacy Ratio	0.060	0.060
Tier 1 Capital (to Risk-Weighted Assets) Required To Be Well Capitalized	$ 948,624	$ 725,047
Tier 1 Capital (to Risk-Weighted Assets) Required To Be Well Capitalized Ratio	0.080	0.080
Leverage Ratio Actual Amount	$ 2,211,251	$ 2,128,571
Leverage Ratio Actual Ratio	0.1192	0.1726
Leverage Ratio Required For Captial Adequacy	$ 741,841	$ 493,242
Leverage Ratio Required For Capital Adequancy Ratio	0.040	0.040
Leverage Ratio Required To Be Well Capitalized	$ 927,301	$ 616,552
Leverage Ratio Required To Be Well Capitalized Ratio	0.050	0.050

Common Equity Tier 1 capital divided by risk weighted assets as defined by new Basel III rule.

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Minimun common equity tier 1 capital to risk weight assets ratio for well capitalized purposes plus capital conservation buffer as required by Basel III rule.

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Amount of total capital as defined by regulatory framework.

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Amount of minimum total risk-based capital required for capital adequacy as defined by regulatory framework.

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