Allowance for loan losses - Allowance Movement (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	$ 543,666	$ 643,018	$ 569,348	$ 623,426
Provision (reversal) for loan losses	36,539	54,387	118,555	185,504
Charge-offs	(92,518)	(83,055)	(240,347)	(224,512)
Recoveries	24,678	19,368	64,809	49,300
Balance at end of period	512,365	633,718	512,365	633,718
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	95,846	130,537	95,846	130,537
General ALLL	416,519	503,181	416,519	503,181
Ending balance: loans individually evaluated for impairment	1,058,613	1,008,288	1,058,613	1,008,288
Ending balance: loans collectively evaluated for impairment	25,949,362	25,503,880	25,949,362	25,503,880
Non-covered Loans held-in-portfolio	27,007,975		27,007,975		$ 26,507,889
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	27,007,975	26,512,168	27,007,975	26,512,168
PUERTO RICO
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	19,932,582		19,932,582		19,883,472
PUERTO RICO | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	476,191	567,145	507,158	518,104
Provision (reversal) for loan losses	34,479	51,877	94,908	153,000
Charge-offs	(79,770)	(75,150)	(206,064)	(183,888)
Recoveries	19,870	16,304	54,768	39,350
Allowance Transferred From Covered Loans				33,610
Balance at end of period	450,770	560,176	450,770	560,176
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	91,750	121,294	91,750	121,294
General ALLL	359,020	438,882	359,020	438,882
Ending balance: loans individually evaluated for impairment	1,027,254	974,209	1,027,254	974,209
Ending balance: loans collectively evaluated for impairment	18,905,328	18,849,144	18,905,328	18,849,144
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	19,932,582	19,823,353	19,932,582	19,823,353
PUERTO RICO | Covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period				33,244
Provision (reversal) for loan losses				1,730
Charge-offs				(1,448)
Recoveries				84
Allowance Transferred To Non Covered Loans				(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	7,075,393		7,075,393		6,624,417
UNITED STATES | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	67,475	75,873	62,190	72,078
Provision (reversal) for loan losses	2,060	2,510	23,647	30,774
Charge-offs	(12,748)	(7,905)	(34,283)	(39,176)
Recoveries	4,808	3,064	10,041	9,866
Balance at end of period	61,595	73,542	61,595	73,542
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	4,096	9,243	4,096	9,243
General ALLL	57,499	64,299	57,499	64,299
Ending balance: loans individually evaluated for impairment	31,359	34,079	31,359	34,079
Ending balance: loans collectively evaluated for impairment	7,044,034	6,654,736	7,044,034	6,654,736
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	7,075,393	6,688,815	7,075,393	6,688,815
Commercial
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	225,529	241,846	239,115	215,665
Provision (reversal) for loan losses	(20,543)	6,804	(8,726)	61,850
Charge-offs	(21,331)	(10,127)	(56,012)	(48,061)
Recoveries	7,066	6,017	16,344	15,086
Balance at end of period	190,721	244,540	190,721	244,540
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	30,130	52,250	30,130	52,250
General ALLL	160,591	192,290	160,591	192,290
Ending balance: loans individually evaluated for impairment	409,221	356,007	409,221	356,007
Ending balance: loans collectively evaluated for impairment	11,799,228	11,637,700	11,799,228	11,637,700
Non-covered Loans held-in-portfolio	12,208,449		12,208,449		12,043,019
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	12,208,449	11,993,707	12,208,449	11,993,707
Commercial | PUERTO RICO
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	7,168,653		7,168,653		7,372,643
Commercial | PUERTO RICO | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	190,227	190,926	207,214	171,531
Provision (reversal) for loan losses	(18,036)	21,548	(18,245)	52,846
Charge-offs	(15,419)	(7,335)	(40,275)	(25,626)
Recoveries	4,787	4,966	12,865	11,354
Allowance Transferred From Covered Loans				0
Balance at end of period	161,559	210,105	161,559	210,105
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	30,130	52,250	30,130	52,250
General ALLL	131,429	157,855	131,429	157,855
Ending balance: loans individually evaluated for impairment	407,124	356,007	407,124	356,007
Ending balance: loans collectively evaluated for impairment	6,761,529	7,051,469	6,761,529	7,051,469
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	7,168,653	7,407,476	7,168,653	7,407,476
Commercial | PUERTO RICO | Covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period				0
Provision (reversal) for loan losses				0
Charge-offs				0
Recoveries				0
Allowance Transferred To Non Covered Loans				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	5,039,796		5,039,796		4,670,376
Commercial | UNITED STATES | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	35,302	50,920	31,901	44,134
Provision (reversal) for loan losses	(2,507)	(14,744)	9,519	9,004
Charge-offs	(5,912)	(2,792)	(15,737)	(22,435)
Recoveries	2,279	1,051	3,479	3,732
Balance at end of period	29,162	34,435	29,162	34,435
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	0	0	0	0
General ALLL	29,162	34,435	29,162	34,435
Ending balance: loans individually evaluated for impairment	2,097	0	2,097	0
Ending balance: loans collectively evaluated for impairment	5,037,699	4,586,231	5,037,699	4,586,231
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	5,039,796	4,586,231	5,039,796	4,586,231
Construction
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	9,883	7,702	7,424	8,362
Provision (reversal) for loan losses	(2,090)	7,293	290	6,124
Charge-offs	(2,242)	(21)	(2,294)	9
Recoveries	3,013	146	3,144	625
Balance at end of period	8,564	15,120	8,564	15,120
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	57	5,530	57	5,530
General ALLL	8,507	9,590	8,507	9,590
Ending balance: loans individually evaluated for impairment	10,334	19,695	10,334	19,695
Ending balance: loans collectively evaluated for impairment	743,722	923,670	743,722	923,670
Non-covered Loans held-in-portfolio	754,056		754,056		779,449
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	754,056	943,365	754,056	943,365
Construction | PUERTO RICO
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	124,072		124,072		85,955
Construction | PUERTO RICO | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	2,996	765	886	1,286
Provision (reversal) for loan losses	(4,916)	(12)	(2,877)	(1,042)
Charge-offs	(27)	(21)	(79)	9
Recoveries	3,013	146	3,136	625
Allowance Transferred From Covered Loans				0
Balance at end of period	1,066	878	1,066	878
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	57	0	57	0
General ALLL	1,009	878	1,009	878
Ending balance: loans individually evaluated for impairment	274	1,829	274	1,829
Ending balance: loans collectively evaluated for impairment	123,798	75,964	123,798	75,964
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	124,072	77,793	124,072	77,793
Construction | PUERTO RICO | Covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period				0
Provision (reversal) for loan losses				0
Charge-offs				0
Recoveries				0
Allowance Transferred To Non Covered Loans				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	629,984		629,984		693,494
Construction | UNITED STATES | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	6,887	6,937	6,538	7,076
Provision (reversal) for loan losses	2,826	7,305	3,167	7,166
Charge-offs	(2,215)	0	(2,215)	0
Recoveries	0	0	8	0
Balance at end of period	7,498	14,242	7,498	14,242
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	0	5,530	0	5,530
General ALLL	7,498	8,712	7,498	8,712
Ending balance: loans individually evaluated for impairment	10,060	17,866	10,060	17,866
Ending balance: loans collectively evaluated for impairment	619,924	847,706	619,924	847,706
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	629,984	865,572	629,984	865,572
Mortgages
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	132,516	186,466	147,412	196,143
Provision (reversal) for loan losses	6,782	10,080	12,241	26,300
Charge-offs	(13,886)	(23,543)	(37,650)	(51,770)
Recoveries	1,215	1,584	4,624	3,914
Balance at end of period	126,627	174,587	126,627	174,587
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	42,868	46,205	42,868	46,205
General ALLL	83,759	128,382	83,759	128,382
Ending balance: loans individually evaluated for impairment	533,317	517,083	533,317	517,083
Ending balance: loans collectively evaluated for impairment	6,635,302	6,787,087	6,635,302	6,787,087
Non-covered Loans held-in-portfolio	7,168,619		7,168,619		7,235,258
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	7,168,619	7,304,170	7,168,619	7,304,170
Mortgages | PUERTO RICO
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	6,235,576		6,235,576		6,433,323
Mortgages | PUERTO RICO | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	127,930	182,103	142,978	159,081
Provision (reversal) for loan losses	6,494	10,145	11,342	24,564
Charge-offs	(13,886)	(23,526)	(37,056)	(50,164)
Recoveries	1,197	1,564	4,471	3,383
Allowance Transferred From Covered Loans				33,422
Balance at end of period	121,735	170,286	121,735	170,286
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	40,483	43,841	40,483	43,841
General ALLL	81,252	126,445	81,252	126,445
Ending balance: loans individually evaluated for impairment	523,876	508,258	523,876	508,258
Ending balance: loans collectively evaluated for impairment	5,711,700	6,023,018	5,711,700	6,023,018
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	6,235,576	6,531,276	6,235,576	6,531,276
Mortgages | PUERTO RICO | Covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period				32,521
Provision (reversal) for loan losses				2,265
Charge-offs				(1,446)
Recoveries				82
Allowance Transferred To Non Covered Loans				(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	933,043		933,043		801,935
Mortgages | UNITED STATES | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	4,586	4,363	4,434	4,541
Provision (reversal) for loan losses	288	(65)	899	(529)
Charge-offs	0	(17)	(594)	(160)
Recoveries	18	20	153	449
Balance at end of period	4,892	4,301	4,892	4,301
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	2,385	2,364	2,385	2,364
General ALLL	2,507	1,937	2,507	1,937
Ending balance: loans individually evaluated for impairment	9,441	8,825	9,441	8,825
Ending balance: loans collectively evaluated for impairment	923,602	764,069	923,602	764,069
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	933,043	772,894	933,043	772,894
Legacy
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	774	700	969	798
Provision (reversal) for loan losses	(280)	(1,008)	(1,467)	(1,714)
Charge-offs	(2)	(81)	142	(252)
Recoveries	299	766	1,147	1,545
Balance at end of period	791	377	791	377
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	0	0	0	0
General ALLL	791	377	791	377
Ending balance: loans individually evaluated for impairment	0	0	0	0
Ending balance: loans collectively evaluated for impairment	23,192	27,566	23,192	27,566
Non-covered Loans held-in-portfolio	23,192		23,192		25,949
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	23,192	27,566	23,192	27,566
Legacy | UNITED STATES
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	23,192		23,192		25,949
Legacy | UNITED STATES | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	774	700	969	798
Provision (reversal) for loan losses	(280)	(1,008)	(1,467)	(1,714)
Charge-offs	(2)	(81)	142	(252)
Recoveries	299	766	1,147	1,545
Balance at end of period	791	377	791	377
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	0	0	0	0
General ALLL	791	377	791	377
Ending balance: loans individually evaluated for impairment	0	0	0	0
Ending balance: loans collectively evaluated for impairment	23,192	27,566	23,192	27,566
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	23,192	27,566	23,192	27,566
Leasing
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	6,907	14,285	11,486	11,991
Provision (reversal) for loan losses	3,739	(422)	2,276	5,022
Charge-offs	(4,040)	(2,088)	(8,467)	(6,404)
Recoveries	587	531	1,898	1,697
Balance at end of period	7,193	12,306	7,193	12,306
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	71	297	71	297
General ALLL	7,122	12,009	7,122	12,009
Ending balance: loans individually evaluated for impairment	624	931	624	931
Ending balance: loans collectively evaluated for impairment	1,021,860	902,609	1,021,860	902,609
Non-covered Loans held-in-portfolio	1,022,484		1,022,484		934,773
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	1,022,484	903,540	1,022,484	903,540
Leasing | PUERTO RICO
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	1,022,484		1,022,484		934,773
Leasing | PUERTO RICO | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	6,907	14,285	11,486	11,991
Provision (reversal) for loan losses	3,739	(422)	2,276	5,022
Charge-offs	(4,040)	(2,088)	(8,467)	(6,404)
Recoveries	587	531	1,898	1,697
Allowance Transferred From Covered Loans				0
Balance at end of period	7,193	12,306	7,193	12,306
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	71	297	71	297
General ALLL	7,122	12,009	7,122	12,009
Ending balance: loans individually evaluated for impairment	624	931	624	931
Ending balance: loans collectively evaluated for impairment	1,021,860	902,609	1,021,860	902,609
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	1,022,484	903,540	1,022,484	903,540
Leasing | PUERTO RICO | Covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period				0
Provision (reversal) for loan losses				0
Charge-offs				0
Recoveries				0
Allowance Transferred To Non Covered Loans				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	168,057	192,019	162,942	190,467
Provision (reversal) for loan losses	48,931	31,640	113,941	87,922
Charge-offs	(51,017)	(47,195)	(136,066)	(118,034)
Recoveries	12,498	10,324	37,652	26,433
Balance at end of period	178,469	186,788	178,469	186,788
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	22,720	26,255	22,720	26,255
General ALLL	155,749	160,533	155,749	160,533
Ending balance: loans individually evaluated for impairment	105,117	114,572	105,117	114,572
Ending balance: loans collectively evaluated for impairment	5,726,058	5,225,248	5,726,058	5,225,248
Non-covered Loans held-in-portfolio	5,831,175		5,831,175		5,489,441
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	5,831,175	5,339,820	5,831,175	5,339,820
Consumer | PUERTO RICO
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	5,381,797		5,381,797		5,056,778
Consumer | PUERTO RICO | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	148,131	179,066	144,594	174,215
Provision (reversal) for loan losses	47,198	20,618	102,412	71,610
Charge-offs	(46,398)	(42,180)	(120,187)	(101,703)
Recoveries	10,286	9,097	32,398	22,291
Allowance Transferred From Covered Loans				188
Balance at end of period	159,217	166,601	159,217	166,601
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	21,009	24,906	21,009	24,906
General ALLL	138,208	141,695	138,208	141,695
Ending balance: loans individually evaluated for impairment	95,356	107,184	95,356	107,184
Ending balance: loans collectively evaluated for impairment	5,286,441	4,796,084	5,286,441	4,796,084
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	5,381,797	4,903,268	5,381,797	4,903,268
Consumer | PUERTO RICO | Covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period				723
Provision (reversal) for loan losses				(535)
Charge-offs				(2)
Recoveries				2
Allowance Transferred To Non Covered Loans				(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	449,378		449,378		$ 432,663
Consumer | UNITED STATES | Non-covered loans
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	19,926	12,953	18,348	15,529
Provision (reversal) for loan losses	1,733	11,022	11,529	16,847
Charge-offs	(4,619)	(5,015)	(15,879)	(16,329)
Recoveries	2,212	1,227	5,254	4,140
Balance at end of period	19,252	20,187	19,252	20,187
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL	1,711	1,349	1,711	1,349
General ALLL	17,541	18,838	17,541	18,838
Ending balance: loans individually evaluated for impairment	9,761	7,388	9,761	7,388
Ending balance: loans collectively evaluated for impairment	439,617	429,164	439,617	429,164
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income	$ 449,378	$ 436,552	$ 449,378	$ 436,552