LOAN PORTFOLIO - Additional Information (Detail) (USD $)	0 Months Ended		1 Months Ended	3 Months Ended					9 Months Ended					3 Months Ended					9 Months Ended		3 Months Ended	9 Months Ended		3 Months Ended					3 Months Ended																													3 Months Ended	9 Months Ended						3 Months Ended		9 Months Ended						3 Months Ended			9 Months Ended						3 Months Ended					3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended	3 Months Ended		3 Months Ended		3 Months Ended
	Oct. 02, 2014	May 30, 2012	May 30, 2014	Sep. 30, 2014		Jun. 30, 2014	Sep. 30, 2013	Mar. 31, 2013	Sep. 30, 2014		Sep. 30, 2013	Dec. 31, 2013		Sep. 30, 2014 Puerto Rico Government and Political Subdivisions [Member]	Sep. 30, 2014 Public Corporations [Member]	Sep. 30, 2014 Government [Member]	Sep. 30, 2014 Puerto Rico Tourism Development Fund [Member]	Sep. 30, 2014 Puerto Rico Electric PowerAuthority [Member]	Sep. 30, 2014 GNMA	Sep. 30, 2014 FNMA and FHLMC	Jun. 30, 2013 Residential Mortgage [Member]	Sep. 30, 2014 Government Guaranteed Loans [Member]	Sep. 30, 2014 Loans in trial [Member]	Mar. 31, 2013 Non Accrual [Member]	Sep. 30, 2014 Non Accrual [Member]		Dec. 31, 2013 Non Accrual [Member]		Sep. 30, 2014 Loans Split [Member]	Sep. 30, 2013 Loans Split [Member]	Sep. 30, 2014 Non Fha Va Residential Mortgage Loans [Member]	Dec. 31, 2013 Non Fha Va Residential Mortgage Loans [Member]	Sep. 30, 2014 Commercial And Industrial Loan [Member]	Dec. 31, 2013 Commercial And Industrial Loan [Member]	Sep. 30, 2014 Commercial Mortgage Loans [Member]	Dec. 31, 2013 Commercial Mortgage Loans [Member]	Dec. 31, 2013 Commercial Construction [Member]	Sep. 30, 2014 Residential Construction [Member]	Dec. 31, 2013 Residential Construction [Member]	Sep. 30, 2014 Land Construction [Member]	Dec. 31, 2013 Land Construction [Member]	Sep. 30, 2014 Residential Mortgage [Member]	Sep. 30, 2013 Residential Mortgage [Member]	Sep. 30, 2014 Non Accrual [Member] Troubled Debt Restructurings [Member]	Dec. 31, 2013 Non Accrual [Member] Commercial Construction [Member]		Sep. 30, 2014 Non Accrual [Member] Residential Construction [Member]		Dec. 31, 2013 Non Accrual [Member] Residential Construction [Member]		Sep. 30, 2014 Non Accrual [Member] Land Construction [Member]		Dec. 31, 2013 Non Accrual [Member] Land Construction [Member]		Sep. 30, 2014 Troubled Debt Restructurings [Member]	Dec. 31, 2013 Troubled Debt Restructurings [Member]	Dec. 31, 2013 Troubled Debt Restructurings [Member] Non Accrual [Member]	Mar. 31, 2013 Non Fha Va Residential Mortgage Loans [Member]	Sep. 30, 2014 Non Fha Va Residential Mortgage Loans [Member]	Dec. 31, 2013 Non Fha Va Residential Mortgage Loans [Member]	Sep. 30, 2014 Non Fha Va Residential Mortgage Loans [Member] Non Accrual [Member]		Dec. 31, 2013 Non Fha Va Residential Mortgage Loans [Member] Non Accrual [Member]		Sep. 30, 2014 Commercial And Industrial Loan [Member]	Mar. 31, 2013 Commercial And Industrial Loan [Member]	Sep. 30, 2014 Commercial And Industrial Loan [Member]	Dec. 31, 2013 Commercial And Industrial Loan [Member]	Sep. 30, 2014 Commercial And Industrial Loan [Member] Non Accrual [Member]		Dec. 31, 2013 Commercial And Industrial Loan [Member] Non Accrual [Member]		Sep. 30, 2014 Commercial Mortgage Loans [Member]	Jun. 30, 2013 Commercial Mortgage Loans [Member]	Mar. 31, 2013 Commercial Mortgage Loans [Member]	Sep. 30, 2014 Commercial Mortgage Loans [Member]	Dec. 31, 2013 Commercial Mortgage Loans [Member]	Sep. 30, 2014 Commercial Mortgage Loans [Member] Non Accrual [Member]		Dec. 31, 2013 Commercial Mortgage Loans [Member] Non Accrual [Member]		Mar. 31, 2013 Construction Loans [Member]	Sep. 30, 2014 Construction Loans [Member]	Sep. 30, 2013 Construction Loans [Member]	Sep. 30, 2014 Consumer Loan [Member]	Sep. 30, 2013 Consumer Loan [Member]	Sep. 30, 2014 Commercial Construction [Member]	Sep. 30, 2014 Commercial Construction [Member]	Sep. 30, 2014 Residential Construction [Member]	Sep. 30, 2014 Residential Construction [Member]	Sep. 30, 2014 Land Construction [Member]	Sep. 30, 2014 Land Construction [Member]	Dec. 31, 2013 Other Real Estate Owned [Member]	Sep. 30, 2014 P R	Dec. 31, 2013 P R	Sep. 30, 2014 V I	Dec. 31, 2013 V I	Sep. 30, 2014 U S
Accounts Notes And Loans Receivable [Line Items]
Interest Income Impaired Loans							$ 8,800,000				$ 23,600,000
Interest Income on Impaired Loans Accrual Basis				7,571,000			7,400,000		19,321,000		19,300,000																																																						1,897,000		3,033,000						676,000			2,238,000											0	0	42,000	125,000	21,000	60,000
Purchased credit impaired loans, fair value		15,700,000
Contractually outstanding principal and interest at acquisition		34,600,000		137,500,000					137,500,000			22,700,000
Financing Receivable Significant Purchases																																																											115,100,000
Financing Receivable Significant Sales																						100,900,000
Securitization of mortgage loans into mortgage backed securities									144,600,000
Total gross loans held for investment portfolio				9,315,402,000			9,508,634,000		9,315,402,000		9,508,634,000	9,636,170,000					200,400,000																									2,819,648,000	2,519,457,000																																								141,689,000	163,610,000	2,026,587,000	2,059,426,000
Credit risk concentration																																																																																														83.00%		7.00%		10.00%
Outstanding of credit facilities granted														201,400,000	90,100,000	24,800,000		75,000,000																																																																												316,300,000	397,800,000	40,800,000	60,600,000
Loans to local financial institutions collateralized by real estate mortgages				0	[1]				0	[1]		240,072,000	[1]
Total TDR loans				701,143,000	[2]	628,233,000			701,143,000	[2]		630,258,000	[3]									72,400,000	11,200,000		216,060,000	[4],[5]	204,875,000	[6],[7]	59,764,000	90,914,000	348,446,000	337,244,000	174,297,000	91,951,000	134,934,000	153,576,000	3,924,000	9,960,000	10,894,000	3,267,000	5,325,000				3,924,000	[6],[7]	6,589,000	[4],[5]	7,562,000	[6],[7]	2,295,000	[4],[5]	4,325,000	[6],[7]					348,446,000	337,243,000	88,697,000	[4],[5]	73,324,000	[6],[7]	174,297,000		174,297,000	91,950,000	47,119,000	[4],[5]	38,441,000	[6],[7]	134,934,000			134,934,000	153,575,000	62,333,000	[4],[5]	69,156,000	[6],[7]		13,200,000		30,200,000
Outstanding unfunded commitments on TDR loans				200,000					200,000
Financing receivable loans restructured recorded investment accruals																													53,500,000
Loans repurchased																			6,400,000	1,600,000
Classified and non-performing loans sold								211,400,000																185,000,000																																		1,200,000								100,100,000								40,800,000	68,800,000							41,300,000
Loans transferred to held for sale																																																																																													39,200,000
Other real estate owned sold								6,300,000													19,200,000
Sale price of bulk sale								120,200,000													128,300,000
Reserves allocated to bulk sale								39,900,000													30,100,000
Total charge-offs bulk sale								98,500,000													98,000,000
Incremental losses								58,900,000													69,800,000
Porfessional fees								3,900,000													3,100,000
Charge-offs of loans transferred to loans held for sale								36,000,000
Additional losses loans transferred to loans held for sale								5,200,000
Subsequent Losses Repurchase Of Loans									700,000
Book value of loans transferred to held for sale								181,600,000																																				45,700,000													45,900,000
Residential mortgage loans sold																					203,800,000
Pre-tax loss								62,800,000													72,900,000
Repayment of construction loans held for sale							6,400,000
Line of credit facility provided to fund unfunded commitments														364,300,000
Loans held for sale				80,014,000					80,014,000			75,969,000																																											45,700,000	45,900,000
Servicing Assets Compesatory Fees									500,000
Doral Purchase Unpaid Principal Balance	192,600,000		241,700,000
Doral Purchase Price	192,700,000		232,900,000
Doral Purchase Fair Value			226,000,000
Loss On Acquired Portfolio			6,900,000
Doral Purchase Loss On Allowance						5,500,000
Provision Charge On Doral Purchase						1,400,000
Professional Service Fee On Doral Purchase				700,000		600,000
Sop Unpaid Principal Balance			119,200,000
Non Sop Unpaid Principal Balance			122,500,000
Non Sop Fair Value			123,200,000
Payment To Acquire Credit Card Portfolio		406,000,000
Fair Value Of Credit Card Portfolio Acquired		368,900,000
Proceeds From Sale Of Loans Held For Investment									$ 31,558,000		$ 309,024,000																																																														$ 15,000,000

[1] On May 30, 2014, FirstBank acquired from Doral Financial Corporation ("Doral") mortgage loans, mainly residential mortgage loans, having an unpaid principal balance of $241.7 million (estimated fair value at acquisition of $226.0 million) in full satisfaction of secured borrowings with a book value of $232.9 million owed by Doral to FirstBank. Refer to Acquired Loans, including Purchased Credit-Impaired ("PCI") loans discussion below for additional information.

[2]  Excludes TDRs held for sale amounting to $45.7 million as of September 30, 2014

[3]  Excludes TDRs held for sale amounting to $45.9 million as of December 31, 2013.

[4] Included in non-accrual loans are $65.8 million in loans that are performing under the terms of the restructuring agreement but are reported in non-accrual status until the restructured loans meet the criteria of sustained payment performance under the revised terms for reinstatement to accrual status and there is no doubt about full collectability.

[5] Excludes non-accrual TDRs held for sale with a carrying value of $45.7 million as of September 30, 2014.

[6] Included in non-accrual loans are $95.7 million in loans that are performing under the terms of the restructuring agreement but are reported in non-accrual status until the restructured loans meet the criteria of sustained payment performance under the revised terms for reinstatement to accrual status and there is no doubt about full collectability.

[7] Excludes non-accrual TDRs held for sale with a carrying value of $45.9 million as of December 31, 2013.