Allowance for loan losses - Allowance Movement (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	$ 550,628	$ 640,578	$ 569,348	$ 623,426
Provision (reversal) for loan losses	40,191	60,054	82,016	131,117
Charge-offs	(67,988)	(73,641)	(147,829)	(141,457)
Recoveries	20,835	16,027	40,131	29,932
Balance at end of period	543,666	643,018	543,666	643,018
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	100,027	119,339	100,027	119,339
General ALLL	443,639	523,679	443,639	523,679
Ending balance: loans individually evaluated for impairment	1,044,485	1,010,830	1,044,485	1,010,830
Ending balance: loans collectively evaluated for impairment	25,961,260	23,597,686	25,961,260	23,597,686
Non-covered Loans held-in-portfolio	27,005,745		27,005,745		$ 26,507,889
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	27,005,745	24,608,516	27,005,745	24,608,516
PUERTO RICO
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	20,041,661		20,041,661		19,883,472
PUERTO RICO | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	484,383	533,595	507,158	518,104
Provision (reversal) for loan losses	28,975	44,405	60,429	101,123
Charge-offs	(55,672)	(57,321)	(126,294)	(108,738)
Recoveries	18,505	12,856	34,898	23,046
Allowance Transferred From Covered Loans		33,610		33,610
Balance at end of period	476,191	567,145	476,191	567,145
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	95,772	115,580	95,772	115,580
General ALLL	380,419	451,565	380,419	451,565
Ending balance: loans individually evaluated for impairment	1,009,121	976,638	1,009,121	976,638
Ending balance: loans collectively evaluated for impairment	19,032,540	17,070,479	19,032,540	17,070,479
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	20,041,661	18,047,117	20,041,661	18,047,117
PUERTO RICO | Covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period		33,610		33,244
Provision (reversal) for loan losses		0		1,730
Charge-offs		0		(1,448)
Recoveries		0		84
Allowance Transferred To Non Covered Loans		(33,610)		(33,610)
Balance at end of period		0		0
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		0		0
General ALLL		0		0
Ending balance: loans individually evaluated for impairment		0		0
Ending balance: loans collectively evaluated for impairment		0		0
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income		0		0
UNITED STATES
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	6,964,084		6,964,084		6,624,417
UNITED STATES | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	66,245	73,373	62,190	72,078
Provision (reversal) for loan losses	11,216	15,649	21,587	28,264
Charge-offs	(12,316)	(16,320)	(21,535)	(31,271)
Recoveries	2,330	3,171	5,233	6,802
Balance at end of period	67,475	75,873	67,475	75,873
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	4,255	3,759	4,255	3,759
General ALLL	63,220	72,114	63,220	72,114
Ending balance: loans individually evaluated for impairment	35,364	34,192	35,364	34,192
Ending balance: loans collectively evaluated for impairment	6,928,720	6,527,207	6,928,720	6,527,207
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	6,964,084	6,561,399	6,964,084	6,561,399
Commercial
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	224,489	236,381	239,115	215,665
Provision (reversal) for loan losses	7,015	23,557	11,817	55,046
Charge-offs	(11,739)	(22,749)	(34,681)	(37,934)
Recoveries	5,764	4,657	9,278	9,069
Balance at end of period	225,529	241,846	225,529	241,846
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	31,698	46,626	31,698	46,626
General ALLL	193,831	195,220	193,831	195,220
Ending balance: loans individually evaluated for impairment	390,271	359,447	390,271	359,447
Ending balance: loans collectively evaluated for impairment	11,826,332	11,230,546	11,826,332	11,230,546
Non-covered Loans held-in-portfolio	12,216,603		12,216,603		12,043,019
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	12,216,603	11,589,993	12,216,603	11,589,993
Commercial | PUERTO RICO
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	7,339,849		7,339,849		7,372,643
Commercial | PUERTO RICO | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	188,931	188,522	207,214	171,531
Provision (reversal) for loan losses	1,480	10,364	(209)	31,298
Charge-offs	(5,395)	(11,502)	(24,856)	(18,291)
Recoveries	5,211	3,542	8,078	6,388
Allowance Transferred From Covered Loans		0		0
Balance at end of period	190,227	190,926	190,227	190,926
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	31,698	46,626	31,698	46,626
General ALLL	158,529	144,300	158,529	144,300
Ending balance: loans individually evaluated for impairment	386,310	359,447	386,310	359,447
Ending balance: loans collectively evaluated for impairment	6,953,539	6,688,151	6,953,539	6,688,151
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	7,339,849	7,047,598	7,339,849	7,047,598
Commercial | PUERTO RICO | Covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period		0		0
Provision (reversal) for loan losses		0		0
Charge-offs		0		0
Recoveries		0		0
Allowance Transferred To Non Covered Loans		0		0
Balance at end of period		0		0
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		0		0
General ALLL		0		0
Ending balance: loans individually evaluated for impairment		0		0
Ending balance: loans collectively evaluated for impairment		0		0
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income		0		0
Commercial | UNITED STATES
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	4,876,754		4,876,754		4,670,376
Commercial | UNITED STATES | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	35,558	47,859	31,901	44,134
Provision (reversal) for loan losses	5,535	13,193	12,026	23,748
Charge-offs	(6,344)	(11,247)	(9,825)	(19,643)
Recoveries	553	1,115	1,200	2,681
Balance at end of period	35,302	50,920	35,302	50,920
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	0	0	0	0
General ALLL	35,302	50,920	35,302	50,920
Ending balance: loans individually evaluated for impairment	3,961	0	3,961	0
Ending balance: loans collectively evaluated for impairment	4,872,793	4,542,395	4,872,793	4,542,395
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	4,876,754	4,542,395	4,876,754	4,542,395
Construction
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	7,496	9,749	7,424	8,362
Provision (reversal) for loan losses	2,333	(2,348)	2,380	(1,169)
Charge-offs	(30)	(18)	(52)	30
Recoveries	84	319	131	479
Balance at end of period	9,883	7,702	9,883	7,702
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	90	0	90	0
General ALLL	9,793	7,702	9,793	7,702
Ending balance: loans individually evaluated for impairment	13,848	20,460	13,848	20,460
Ending balance: loans collectively evaluated for impairment	811,571	878,863	811,571	878,863
Non-covered Loans held-in-portfolio	825,419		825,419		779,449
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	825,419	899,323	825,419	899,323
Construction | PUERTO RICO
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	108,958		108,958		85,955
Construction | PUERTO RICO | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	822	2,657	886	1,286
Provision (reversal) for loan losses	2,120	(2,193)	2,039	(1,030)
Charge-offs	(30)	(18)	(52)	30
Recoveries	84	319	123	479
Allowance Transferred From Covered Loans		0		0
Balance at end of period	2,996	765	2,996	765
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	90	0	90	0
General ALLL	2,906	765	2,906	765
Ending balance: loans individually evaluated for impairment	1,788	2,559	1,788	2,559
Ending balance: loans collectively evaluated for impairment	107,170	94,616	107,170	94,616
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	108,958	97,175	108,958	97,175
Construction | PUERTO RICO | Covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period		0		0
Provision (reversal) for loan losses		0		0
Charge-offs		0		0
Recoveries		0		0
Allowance Transferred To Non Covered Loans		0		0
Balance at end of period		0		0
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		0		0
General ALLL		0		0
Ending balance: loans individually evaluated for impairment		0		0
Ending balance: loans collectively evaluated for impairment		0		0
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income		0		0
Construction | UNITED STATES
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	716,461		716,461		693,494
Construction | UNITED STATES | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	6,674	7,092	6,538	7,076
Provision (reversal) for loan losses	213	(155)	341	(139)
Charge-offs	0	0	0	0
Recoveries	0	0	8	0
Balance at end of period	6,887	6,937	6,887	6,937
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	0	0	0	0
General ALLL	6,887	6,937	6,887	6,937
Ending balance: loans individually evaluated for impairment	12,060	17,901	12,060	17,901
Ending balance: loans collectively evaluated for impairment	704,401	784,247	704,401	784,247
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	716,461	802,148	716,461	802,148
Mortgages
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	142,298	191,450	147,412	196,143
Provision (reversal) for loan losses	(839)	6,609	5,459	16,220
Charge-offs	(10,339)	(12,908)	(23,764)	(28,227)
Recoveries	1,396	1,315	3,409	2,330
Balance at end of period	132,516	186,466	132,516	186,466
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	43,550	47,515	43,550	47,515
General ALLL	88,966	138,951	88,966	138,951
Ending balance: loans individually evaluated for impairment	530,650	517,308	530,650	517,308
Ending balance: loans collectively evaluated for impairment	6,668,309	6,859,403	6,668,309	6,859,403
Non-covered Loans held-in-portfolio	7,198,959		7,198,959		7,235,258
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	7,198,959	7,376,711	7,198,959	7,376,711
Mortgages | PUERTO RICO
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	6,302,958		6,302,958		6,433,323
Mortgages | PUERTO RICO | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	137,856	153,301	142,978	159,081
Provision (reversal) for loan losses	(1,213)	6,955	4,848	14,419
Charge-offs	(9,996)	(12,847)	(23,170)	(26,638)
Recoveries	1,283	1,272	3,274	1,819
Allowance Transferred From Covered Loans		33,422		33,422
Balance at end of period	127,930	182,103	127,930	182,103
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	41,158	45,039	41,158	45,039
General ALLL	86,772	137,064	86,772	137,064
Ending balance: loans individually evaluated for impairment	521,257	507,580	521,257	507,580
Ending balance: loans collectively evaluated for impairment	5,781,701	6,135,546	5,781,701	6,135,546
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	6,302,958	6,643,126	6,302,958	6,643,126
Mortgages | PUERTO RICO | Covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period		33,422		32,521
Provision (reversal) for loan losses		0		2,265
Charge-offs		0		(1,446)
Recoveries		0		82
Allowance Transferred To Non Covered Loans		(33,422)		(33,422)
Balance at end of period		0		0
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		0		0
General ALLL		0		0
Ending balance: loans individually evaluated for impairment		0		0
Ending balance: loans collectively evaluated for impairment		0		0
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income		0		0
Mortgages | UNITED STATES
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	896,001		896,001		801,935
Mortgages | UNITED STATES | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	4,442	4,727	4,434	4,541
Provision (reversal) for loan losses	374	(346)	611	(464)
Charge-offs	(343)	(61)	(594)	(143)
Recoveries	113	43	135	429
Balance at end of period	4,586	4,363	4,586	4,363
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	2,392	2,476	2,392	2,476
General ALLL	2,194	1,887	2,194	1,887
Ending balance: loans individually evaluated for impairment	9,393	9,728	9,393	9,728
Ending balance: loans collectively evaluated for impairment	886,608	723,857	886,608	723,857
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	896,001	733,585	896,001	733,585
Legacy
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	829	652	969	798
Provision (reversal) for loan losses	(332)	(229)	(1,187)	(706)
Charge-offs	(20)	(14)	144	(171)
Recoveries	297	291	848	779
Balance at end of period	774	700	774	700
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	0	0	0	0
General ALLL	774	700	774	700
Ending balance: loans individually evaluated for impairment	0	0	0	0
Ending balance: loans collectively evaluated for impairment	23,893	29,250	23,893	29,250
Non-covered Loans held-in-portfolio	23,893		23,893		25,949
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	23,893	29,250	23,893	29,250
Legacy | UNITED STATES
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	23,893		23,893		25,949
Legacy | UNITED STATES | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	829	652	969	798
Provision (reversal) for loan losses	(332)	(229)	(1,187)	(706)
Charge-offs	(20)	(14)	144	(171)
Recoveries	297	291	848	779
Balance at end of period	774	700	774	700
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	0	0	0	0
General ALLL	774	700	774	700
Ending balance: loans individually evaluated for impairment	0	0	0	0
Ending balance: loans collectively evaluated for impairment	23,893	29,250	23,893	29,250
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	23,893	29,250	23,893	29,250
Leasing
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	9,109	12,912	11,486	11,991
Provision (reversal) for loan losses	(572)	2,530	(1,463)	5,444
Charge-offs	(2,331)	(1,803)	(4,427)	(4,316)
Recoveries	701	646	1,311	1,166
Balance at end of period	6,907	14,285	6,907	14,285
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	234	362	234	362
General ALLL	6,673	13,923	6,673	13,923
Ending balance: loans individually evaluated for impairment	865	1,130	865	1,130
Ending balance: loans collectively evaluated for impairment	990,681	870,968	990,681	870,968
Non-covered Loans held-in-portfolio	991,546		991,546		934,773
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	991,546	872,098	991,546	872,098
Leasing | PUERTO RICO
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	991,546		991,546		934,773
Leasing | PUERTO RICO | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	9,109	12,912	11,486	11,991
Provision (reversal) for loan losses	(572)	2,530	(1,463)	5,444
Charge-offs	(2,331)	(1,803)	(4,427)	(4,316)
Recoveries	701	646	1,311	1,166
Allowance Transferred From Covered Loans		0		0
Balance at end of period	6,907	14,285	6,907	14,285
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	234	362	234	362
General ALLL	6,673	13,923	6,673	13,923
Ending balance: loans individually evaluated for impairment	865	1,130	865	1,130
Ending balance: loans collectively evaluated for impairment	990,681	870,968	990,681	870,968
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	991,546	872,098	991,546	872,098
Leasing | PUERTO RICO | Covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period		0		0
Provision (reversal) for loan losses		0		0
Charge-offs		0		0
Recoveries		0		0
Allowance Transferred To Non Covered Loans		0		0
Balance at end of period		0		0
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		0		0
General ALLL		0		0
Ending balance: loans individually evaluated for impairment		0		0
Ending balance: loans collectively evaluated for impairment		0		0
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income		0		0
Consumer
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	166,407	189,434	162,942	190,467
Provision (reversal) for loan losses	32,586	29,935	65,010	56,282
Charge-offs	(43,529)	(36,149)	(85,049)	(70,839)
Recoveries	12,593	8,799	25,154	16,109
Balance at end of period	168,057	192,019	168,057	192,019
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	24,455	24,836	24,455	24,836
General ALLL	143,602	167,183	143,602	167,183
Ending balance: loans individually evaluated for impairment	108,851	112,485	108,851	112,485
Ending balance: loans collectively evaluated for impairment	5,640,474	3,728,656	5,640,474	3,728,656
Non-covered Loans held-in-portfolio	5,749,325		5,749,325		5,489,441
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	5,749,325	3,841,141	5,749,325	3,841,141
Consumer | PUERTO RICO
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	5,298,350		5,298,350		5,056,778
Consumer | PUERTO RICO | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	147,665	176,203	144,594	174,215
Provision (reversal) for loan losses	27,160	26,749	55,214	50,992
Charge-offs	(37,920)	(31,151)	(73,789)	(59,523)
Recoveries	11,226	7,077	22,112	13,194
Allowance Transferred From Covered Loans		188		188
Balance at end of period	148,131	179,066	148,131	179,066
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	22,592	23,553	22,592	23,553
General ALLL	125,539	155,513	125,539	155,513
Ending balance: loans individually evaluated for impairment	98,901	105,922	98,901	105,922
Ending balance: loans collectively evaluated for impairment	5,199,449	3,281,198	5,199,449	3,281,198
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	5,298,350	3,387,120	5,298,350	3,387,120
Consumer | PUERTO RICO | Covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period		188		723
Provision (reversal) for loan losses		0		(535)
Charge-offs		0		(2)
Recoveries		0		2
Allowance Transferred To Non Covered Loans		(188)		(188)
Balance at end of period		0		0
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		0		0
General ALLL		0		0
Ending balance: loans individually evaluated for impairment		0		0
Ending balance: loans collectively evaluated for impairment		0		0
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income		0		0
Consumer | UNITED STATES
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	450,975		450,975		$ 432,663
Consumer | UNITED STATES | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	18,742	13,043	18,348	15,529
Provision (reversal) for loan losses	5,426	3,186	9,796	5,825
Charge-offs	(5,609)	(4,998)	(11,260)	(11,314)
Recoveries	1,367	1,722	3,042	2,913
Balance at end of period	19,926	12,953	19,926	12,953
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	1,863	1,283	1,863	1,283
General ALLL	18,063	11,670	18,063	11,670
Ending balance: loans individually evaluated for impairment	9,950	6,563	9,950	6,563
Ending balance: loans collectively evaluated for impairment	441,025	447,458	441,025	447,458
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	$ 450,975	$ 454,021	$ 450,975	$ 454,021