REGULATORY MATTERS, COMMITMENTS AND CONTINGENCIES - Regulatory capital positions (Detail) $ in Thousands	Sep. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)
First BanCorp [Member]
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Total Capital (to Risk-Weighted Assets) Actual	$ 2,399,483	$ 2,403,319
Total Capital (to Risk-Weighted Assets) Actual Ratio	0.1825	0.1857
Total Capital (to Risk-Weighted Assets) Required For Capital Adequacy	$ 1,051,684	$ 1,035,589
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	$ 2,126,527	$ 2,084,432
Common Equity Tier 1 Capital (to Risk-Weighted Assets) Actual Ratio	0.1618	0.1610
Common Equity Tier 1 Capital (to Risk-Weighted Assets) Required For Capital Adequacy	$ 591,572	$ 528,519
Common Equity Tier 1 Capital (to Risk-Weighted Assets) Required For Capital Adequacy Ratio	0.045	0.045
Tier 1 Capital (to Risk-Weighted Assets) Actual	$ 2,126,527	$ 2,084,432
Tier 1 Capital (to Risk-Weighted Assets) Actual Ratio	0.1618	0.1610
Tier 1 Capital (to Risk-Weighted Assets) Required For Capital Adequacy	$ 788,763	$ 776,692
Tier 1 Capital (to Risk-Weighted Assets) Required For Capital Adequacy Ratio	0.060	0.060
Leverage Ratio Actual Amount	$ 2,126,527	$ 2,084,432
Leverage Ratio Actual Ratio	0.1096	0.1078
Leverage Ratio Required For Capital Adequacy	$ 775,896	$ 773,615
Leverage Ratio Required For Capital Adequacy Ratio	0.040	0.040
FirstBank [Member]
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Total Capital (to Risk-Weighted Assets) Actual	$ 2,367,463	$ 2,376,003
Total Capital (to Risk-Weighted Assets) Actual Ratio	0.1801	0.1836
Total Capital (to Risk-Weighted Assets) Required For Capital Adequacy	$ 1,051,456	$ 1,035,406
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	$ 1,314,320	$ 1,294,257
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	$ 2,102,892	$ 2,113,995
Common Equity Tier 1 Capital (to Risk-Weighted Assets) Actual Ratio	0.1600	0.1633
Common Equity Tier 1 Capital (to Risk-Weighted Assets) Required For Capital Adequacy	$ 591,444	$ 582,416
Common Equity Tier 1 Capital (to Risk-Weighted Assets) Required For Capital Adequacy Ratio	0.045	0.045
Common Equity Tier 1 Capital (to Risk-Weighted Assets) Required To Be Well Capitalized	$ 854,308	$ 841,267
Common Equity Tier 1 Capital (to Risk-Weighted Assets) Required To Be Well Capitalized Ratio	0.065	0.065
Tier 1 Capital (to Risk-Weighted Assets) Actual	$ 2,202,892	$ 2,213,995
Tier 1 Capital (to Risk-Weighted Assets) Actual Ratio	0.1676	0.1711
Tier 1 Capital (to Risk-Weighted Assets) Required For Capital Adequacy	$ 788,592	$ 776,554
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	$ 1,051,456	$ 1,035,406
Tier 1 Capital (to Risk-Weighted Assets) Required To Be Well Capitalized Ratio	0.080	0.080
Leverage Ratio Actual Amount	$ 2,202,892	$ 2,213,995
Leverage Ratio Actual Ratio	0.1136	0.1145
Leverage Ratio Required For Capital Adequacy	$ 775,647	$ 773,345
Leverage Ratio Required For Capital Adequacy Ratio	0.040	0.040
Leverage Ratio Required To Be Well Capitalized	$ 969,558	$ 966,682
Leverage Ratio Required To Be Well Capitalized Ratio	0.050	0.050

Common Equity Tier 1 Capital (to Risk-Weighted Assets) Actual Ratio

No definition available.

Name:	fbp_CommonEquityTier1CapitalToRiskWeightAssetsRatio1
Namespace Prefix:	fbp_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Common Equity Tier 1 Capital (to Risk-Weighted Assets) Required For Capital Adequacy Ratio

+ References

No definition available.

+ Details

Name:	fbp_CommonEquityTier1CapitalToRiskWeightAssetsRatioCapitalAdequacy1
Namespace Prefix:	fbp_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Common Equity Tier 1 Capital (to Risk-Weighted Assets) Required To Be Well Capitalized Ratio

+ References

No definition available.

+ Details

Name:	fbp_CommonEquityTier1CapitalToRiskWeightAssetsRatioWellCapitalized1
Namespace Prefix:	fbp_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of total capital as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_Capital
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1B

+ Details

Name:	us-gaap_CapitalRequiredForCapitalAdequacy
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Ratio of minimum total risk-based capital to risk-weighted assets required for capital adequacy as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of minimum total risk-based capital categorized as well capitalized as defined by regulatory framework for prompt corrective action.

+ References

+ Details

Name:	us-gaap_CapitalRequiredToBeWellCapitalized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Ratio of minimum total risk-based capital to risk-weighted assets categorized as well capitalized as defined by regulatory framework for prompt corrective action.

+ References

+ Details

Name:	us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio of total risk-based capital to risk-weighted assets as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_CapitalToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of Common Equity Tier 1 risk-based capital as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_CommonEquityTierOneCapital
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of minimum Common Equity Tier 1 risk-based capital required for capital adequacy as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_CommonEquityTierOneCapitalRequiredForCapitalAdequacy
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of minimum Common Equity Tier 1 risk-based capital categorized as well capitalized as defined by regulatory framework for prompt corrective action.

+ References

+ Details

Name:	us-gaap_CommonEquityTierOneCapitalRequiredToBeWellCapitalized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1B

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1

+ Details

Name:	us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of Tier 1 leverage capital as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_TierOneLeverageCapital
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of minimum Tier 1 leverage capital required for capital adequacy as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Ratio of minimum Tier 1 leverage capital to average assets required for capital adequacy as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of minimum Tier 1 leverage capital categorized as well capitalized as defined by regulatory framework for prompt corrective action.

+ References

+ Details

Name:	us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Ratio of minimum Tier 1 leverage capital to average assets categorized as well capitalized as defined by regulatory framework for prompt corrective action.

+ References

+ Details

Name:	us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio of Tier 1 capital to average assets as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_TierOneLeverageCapitalToAverageAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of Tier 1 risk-based capital as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_TierOneRiskBasedCapital
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of minimum Tier 1 risk-based capital required for capital adequacy as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Ratio of minimum Tier 1 risk-based capital to risk-weighted assets required for capital adequacy as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of minimum Tier 1 risk-based capital categorized as well capitalized as defined by regulatory framework for prompt corrective action.

+ References

+ Details

Name:	us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Ratio of minimum Tier 1 risk-based capital to risk-weighted assets categorized as well capitalized as defined by regulatory framework for prompt corrective action.

+ References

+ Details

Name:	us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio of Tier 1 risk-based capital to risk-weighted assets as defined by regulatory framework.

+ References

+ Details

Name:	us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	srt_ConsolidatedEntitiesAxis=srt_ParentCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidatedEntitiesAxis=fbp_FirstBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: