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LOAN PORTFOLIO - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	6 Months Ended
	Feb. 27, 2015	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Loans and Leases Receivable Disclosure [Line Items]
Branches Doral	10
Financing Receivable Recorded Investment Past Due		$ 507,033	$ 507,033			$ 574,654
Gain on sale of loans			3,844	$ 2,921
Loans and Leases Receivable, Gross		9,113,955	$ 9,113,955	8,640,291		8,858,123
Minimum Period To Be Considered For Loan To Have Defaulted			90 days
TDR [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable Modifications Recorded Investment		582,389	$ 582,389	557,196	$ 589,795	582,647	$ 572,376	$ 587,219
Outstanding unfunded commitments on TDR loans		300	$ 300
Loan Restructuring Trial Modifications Period			6 months
PUERTO RICO
Loans and Leases Receivable Disclosure [Line Items]
Credit risk concentration			74.00%
USVI and BVI [Member]
Loans and Leases Receivable Disclosure [Line Items]
Credit risk concentration			5.00%
United States [Member]
Loans and Leases Receivable Disclosure [Line Items]
Credit risk concentration			21.00%
Performing Financing Receivable [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		8,260,421	$ 8,260,421	7,747,915		7,951,214
Performing Financing Receivable [Member] \| Ab Note Restructure Workout Strategy [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable Modifications Recorded Investment		41,300	41,300
PCI loans
Loans and Leases Receivable Disclosure [Line Items]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Allowance For Loan Losses		11,434	11,434	11,354	11,354	11,354	11,251	11,251
Outstanding principal balance of PCI loans		174,800	174,800			181,100
Financing Receivable Recorded Investment Past Due		34,773	34,773			36,423
Loans and Leases Receivable, Gross		141,706	$ 141,706	152,242	$ 144,443	146,640	$ 155,281	$ 158,174
Residential Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans Foreclosure Delinquency Threshold			120 days
Purchase of loans			$ 9,300
Loans and Leases Receivable, Gross		3,070,746	3,070,746	3,238,001		3,163,208
Residential Portfolio Segment [Member] \| TDR [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans in trial			3,000
Residential Portfolio Segment [Member] \| Other Loans Member [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable Recorded Investment Past Due		213,983	213,983			223,928
Loans and Leases Receivable, Gross		2,937,846	2,937,846			3,016,003
Residential Portfolio Segment [Member] \| Other Loans Member [Member] \| TDR [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable Modifications Recorded Investment		326,703	326,703			333,902
Residential Portfolio Segment [Member] \| PRHFA [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		110,000	110,000			112,100
Residential Portfolio Segment [Member] \| Performing Financing Receivable [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		2,541,363	2,541,363	2,680,891		2,616,300
Residential Portfolio Segment [Member] \| Performing Financing Receivable [Member] \| Other Loans Member [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		2,669,978	2,669,978			2,725,540
Residential Portfolio Segment [Member] \| Nonaccrual [Member] \| Other Loans Member [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		129,501	129,501			147,287
Residential Portfolio Segment [Member] \| PCI loans
Loans and Leases Receivable Disclosure [Line Items]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Allowance For Loan Losses		11,063	11,063	10,954		10,954
Financing Receivable Recorded Investment Past Due		32,376	32,376			33,911
Loans and Leases Receivable, Gross		138,367	138,367	148,025		143,176
Residential Portfolio Segment [Member] \| PCI loans \| Other Loans Member [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		138,367	138,367			143,176
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loan sales			115,000
Financing Receivable Recorded Investment Past Due		94,187	94,187			108,934
Loans and Leases Receivable, Gross		132,900	132,900			147,205
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member] \| TDR [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable Modifications Recorded Investment		61,800	61,800			60,500
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member] \| Performing Financing Receivable [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		132,900	132,900			147,205
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member] \| Nonaccrual [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		0	0			0
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member] \| PCI loans
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		0	0			0
Residential Portfolio Segment [Member] \| FNMA and FHLC loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Purchase of loans			64	3
Loan sales			59,900
Residential Portfolio Segment [Member] \| GNMA [Member] \| Repurchase Option Program [Member]
Loans and Leases Receivable Disclosure [Line Items]
Purchase of loans			10,700	2,000
Financing Receivable Recorded Investment Past Due		41,900	41,900			43,600
Residential Portfolio Segment [Member] \| Residential pass-through mortgage-backed securities [Member]
Loans and Leases Receivable Disclosure [Line Items]
Mortgage Loans In Process Of Foreclosure Amount		159,200	159,200
Residential Portfolio Segment [Member] \| Residential pass-through mortgage-backed securities [Member] \| PCI loans
Loans and Leases Receivable Disclosure [Line Items]
Mortgage Loans In Process Of Foreclosure Amount		18,400	18,400
Residential Portfolio Segment [Member] \| Residential pass-through mortgage-backed securities [Member] \| FHA/VA government-guaranteed loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Mortgage Loans In Process Of Foreclosure Amount		41,000	41,000
Commercial Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		3,930,293	3,930,293			3,750,202
Commercial Portfolio Segment [Member] \| Commercial And Industrial Sector [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable Recorded Investment Past Due		24,360	24,360			38,001
Loans and Leases Receivable, Gross		2,279,685	2,279,685	2,009,049		2,148,111
Commercial Portfolio Segment [Member] \| Substandard [Member] \| Commercial And Industrial Sector [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		34,874	34,874			45,274
Commercial Portfolio Segment [Member] \| TDR [Member] \| Commercial And Industrial Sector [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable Modifications Recorded Investment		70,510	70,510			74,921
Commercial Portfolio Segment [Member] \| Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		100,244	100,244	84,683		79,429
Commercial Portfolio Segment [Member] \| Construction Loans [Member] \| TDR [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable Modifications Recorded Investment		5,000	5,000
Commercial Portfolio Segment [Member] \| PUERTO RICO \| Substandard [Member] \| Commercial And Industrial Sector [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loan sales				5,600
Charge-off of loan sold				1,300
Commercial Portfolio Segment [Member] \| PUERTO RICO \| PREPA [Member]
Loans and Leases Receivable Disclosure [Line Items]
Commercial Government Loans		14,200	14,200
Commercial Portfolio Segment [Member] \| PUERTO RICO \| Government [Member]
Loans and Leases Receivable Disclosure [Line Items]
Commercial Government Loans		60,400	60,400			61,600
Commercial Portfolio Segment [Member] \| PUERTO RICO \| Municipalities Borrower [Member] \| Government [Member]
Loans and Leases Receivable Disclosure [Line Items]
Commercial Government Loans		46,300	46,300
Commercial Portfolio Segment [Member] \| USVI [Member] \| Government [Member]
Loans and Leases Receivable Disclosure [Line Items]
Commercial Government Loans		64,000	64,000			55,800
Commercial Portfolio Segment [Member] \| USVI [Member] \| Public Corporations [Member] \| Government [Member]
Loans and Leases Receivable Disclosure [Line Items]
Commercial Government Loans		40,800	40,800
Commercial Portfolio Segment [Member] \| USVI [Member] \| Independent Instrumentality [Member] \| Government [Member]
Loans and Leases Receivable Disclosure [Line Items]
Commercial Government Loans		23,200	23,200
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable Recorded Investment Past Due		82,572	82,572			111,520
Loans and Leases Receivable, Gross		1,550,364	1,550,364	1,533,308		1,522,662
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member] \| Substandard [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		240,624	240,624			276,935
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member] \| TDR [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable Modifications Recorded Investment		153,366	153,366			137,949
Commercial Portfolio Segment [Member] \| Performing Financing Receivable [Member] \| Commercial And Industrial Sector [Member]
Loans and Leases Receivable Disclosure [Line Items]
Purchase of loans				21,400
Loans and Leases Receivable, Gross		2,199,548	2,199,548	1,897,678		2,056,919
Commercial Portfolio Segment [Member] \| Performing Financing Receivable [Member] \| Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		94,215	94,215	73,422		72,836
Commercial Portfolio Segment [Member] \| Performing Financing Receivable [Member] \| PUERTO RICO \| Commercial And Industrial Sector [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loan sales		20,000
Commercial Portfolio Segment [Member] \| Performing Financing Receivable [Member] \| United States [Member] \| Commercial And Industrial Sector [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loan sales				9,200
Commercial Portfolio Segment [Member] \| Performing Financing Receivable [Member] \| Mortgage Receivable [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		1,339,516	1,339,516	1,353,516		1,291,772
Commercial Portfolio Segment [Member] \| Nonaccrual [Member] \| Loans Held For Sale [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loan sales			4,800
Gain on sale of loans			200
Commercial Portfolio Segment [Member] \| Nonaccrual [Member] \| Loans Held For Sale [Member] \| Mortgage Receivable [Member] \| PUERTO RICO
Loans and Leases Receivable Disclosure [Line Items]
Loan sales				10,400
Commercial Portfolio Segment [Member] \| PCI loans \| Commercial And Industrial Sector [Member]
Loans and Leases Receivable Disclosure [Line Items]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Allowance For Loan Losses		0	0	0		0
Loans and Leases Receivable, Gross		0	0	0		0
Commercial Portfolio Segment [Member] \| PCI loans \| Construction Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Allowance For Loan Losses		0	0	0		0
Loans and Leases Receivable, Gross		0	0	0		0
Commercial Portfolio Segment [Member] \| PCI loans \| Mortgage Receivable [Member]
Loans and Leases Receivable Disclosure [Line Items]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Allowance For Loan Losses		371	371	400		400
Financing Receivable Recorded Investment Past Due		2,397	2,397			2,512
Loans and Leases Receivable, Gross		3,339	3,339	4,217		3,464
Consumer Portfolio Segment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		2,112,916	2,112,916	1,775,250		1,944,713
Consumer Portfolio Segment [Member] \| TDR [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable Modifications Recorded Investment		26,800	26,800
Consumer Portfolio Segment [Member] \| Other Loans Member [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable Recorded Investment Past Due		23,512	23,512			26,057
Loans and Leases Receivable, Gross		706,913	706,913			664,701
Consumer Portfolio Segment [Member] \| Other Loans Member [Member] \| TDR [Member]
Loans and Leases Receivable Disclosure [Line Items]
Financing Receivable Modifications Recorded Investment		9,101	9,101			10,382
Consumer Portfolio Segment [Member] \| Performing Financing Receivable [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		2,085,779	2,085,779	1,742,408		1,913,387
Consumer Portfolio Segment [Member] \| Performing Financing Receivable [Member] \| Other Loans Member [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		700,422	700,422			656,836
Consumer Portfolio Segment [Member] \| Nonaccrual [Member] \| Other Loans Member [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		6,491	6,491			7,865
Consumer Portfolio Segment [Member] \| PCI loans
Loans and Leases Receivable Disclosure [Line Items]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Allowance For Loan Losses		0	0	0		0
Loans and Leases Receivable, Gross		0	0	$ 0		0
Consumer Portfolio Segment [Member] \| PCI loans \| Other Loans Member [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans and Leases Receivable, Gross		$ 0	$ 0			$ 0