SEGMENT INFORMATIO - Information about reportable segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Segment Reporting Information [Line Items]
Interest income	$ 152,485	$ 160,571
Net (charge) credit for transfer of funds	0fbp_NetChargeCreditForTransferOfFunds	0fbp_NetChargeCreditForTransferOfFunds
Interest expense	(26,838)us-gaap_InterestExpense	(29,251)us-gaap_InterestExpense
Net interest income (loss)	125,647us-gaap_InterestIncomeExpenseNet	131,320us-gaap_InterestIncomeExpenseNet
(Provision) release for loan and lease losses	(32,970)us-gaap_ProvisionForLoanAndLeaseLosses	(31,915)us-gaap_ProvisionForLoanAndLeaseLosses
Non-interest income (loss)	19,286	17,960
Direct non-interest expenses	(64,705)fbp_DirectNonInterestExpenses	(71,795)fbp_DirectNonInterestExpenses
Segment (loss) income	47,258	45,570
Average earnings assets	11,940,989	12,096,474
Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Interest income	33,876	25,748
Net (charge) credit for transfer of funds	11,236	8,546
Interest expense	0	0
Net interest income (loss)	22,640	17,202
(Provision) release for loan and lease losses	(6,963)	(3,384)
Non-interest income (loss)	3,399	3,102
Direct non-interest expenses	(8,065)	(9,832)
Segment (loss) income	11,011	7,088
Average earnings assets	2,492,247	1,955,990
Consumer Retail Banking [Member]
Segment Reporting Information [Line Items]
Interest income	49,836	55,812
Net (charge) credit for transfer of funds	(3,684)	(3,635)
Interest expense	(5,657)	(6,796)
Net interest income (loss)	47,863	52,651
(Provision) release for loan and lease losses	(16,685)	(20,495)
Non-interest income (loss)	12,417	10,630
Direct non-interest expenses	(31,559)	(32,015)
Segment (loss) income	12,036	10,771
Average earnings assets	2,045,277	2,006,395
Commercial And Corporate [Member]
Segment Reporting Information [Line Items]
Interest income	34,803	42,299
Net (charge) credit for transfer of funds	3,795	2,999
Interest expense	0	0
Net interest income (loss)	31,008	39,300
(Provision) release for loan and lease losses	(9,093)	(13,345)
Non-interest income (loss)	524	1,767
Direct non-interest expenses	(7,979)	(12,578)
Segment (loss) income	14,460	15,144
Average earnings assets	3,028,358	3,921,439
Treasury And Investments [Member]
Segment Reporting Information [Line Items]
Interest income	13,067	15,583
Net (charge) credit for transfer of funds	(7,754)	(5,800)
Interest expense	(16,007)	(16,761)
Net interest income (loss)	4,814	4,622
(Provision) release for loan and lease losses	0	0
Non-interest income (loss)	(100)	53
Direct non-interest expenses	(1,339)	(1,126)
Segment (loss) income	3,375	3,549
Average earnings assets	2,764,058	2,710,930
United States Operations [Member]
Segment Reporting Information [Line Items]
Interest income	11,231	10,896
Net (charge) credit for transfer of funds	(3,593)	(2,110)
Interest expense	(4,339)	(4,797)
Net interest income (loss)	10,485	8,209
(Provision) release for loan and lease losses	2,133	5,959
Non-interest income (loss)	524	441
Direct non-interest expenses	(7,183)	(7,220)
Segment (loss) income	5,959	7,389
Average earnings assets	971,887	846,152
Virgin Islands Operations [Member]
Segment Reporting Information [Line Items]
Interest income	9,672	10,233
Net (charge) credit for transfer of funds	0	0
Interest expense	(835)	(897)
Net interest income (loss)	8,837	9,336
(Provision) release for loan and lease losses	(2,362)	(650)
Non-interest income (loss)	2,522	1,967
Direct non-interest expenses	(8,580)	(9,024)
Segment (loss) income	417	1,629
Average earnings assets	$ 639,162	$ 655,568

Direct non-interest expenses.

No definition available.

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- Definition

Amount charged or credited by reportable segments based on market interest rates.

+ References

No definition available.

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- Definition

Non-interest income for reportable segments

+ References

No definition available.

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- Definition

Amount of average earning assets attributed to the reportable segment.

+ References

No definition available.

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- Definition

This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 940

-SubTopic 20

-Section 25

-Paragraph 1

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-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 10

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- Definition

Represents the total of interest and dividend income, including any amortization and accretion (as applicable) of discounts and premiums, earned from (1) loans and leases whether held-for-sale or held-in-portfolio; (2) investment securities; (3) federal funds sold; (4) securities purchased under agreements to resell; (5) investments in banker's acceptances, commercial paper, or certificates of deposit; (6) dividend income; or (7) other investments not otherwise specified herein.

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-Name Accounting Standards Codification

-Topic 942

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-Section S99

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-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 1, 2 , 3, 4, 5

-Article 9

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- Definition

Amount of the cost of borrowed funds accounted for as interest expense.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 20

-Section 50

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- Definition

The net amount of operating interest income (expense).

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- Definition

Amount of expense related to estimated loss from loan and lease transactions.

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-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

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