Note Allowance for loan losses (Disclosures related to loans individually evaluated for impairment) (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Related Allowance	$ 118,072	$ 111,377
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	136,919	129,350
Impaired Financing Receivable, with Related Allowance, Recorded Investment	833,291	826,707
Recorded Investment	970,210	956,057
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	188,062	182,772
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	919,089	908,563
Unpaid Principal Balance	1,107,151	1,091,335
PUERTO RICO
Financing Receivable, Impaired [Line Items]
Related Allowance	115,196	108,523
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	134,072	126,476
Impaired Financing Receivable, with Related Allowance, Recorded Investment	824,437	817,866
Recorded Investment	958,509	944,342
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	184,308	179,009
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	908,546	898,124
Unpaid Principal Balance	1,092,854	1,077,133
UNITED STATES | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	2,876	2,854
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,847	2,874
Impaired Financing Receivable, with Related Allowance, Recorded Investment	8,854	8,841
Recorded Investment	11,701	11,715
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	3,754	3,763
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	10,543	10,439
Unpaid Principal Balance	14,297	14,202
Commercial multi-family | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	29	34
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	79	82
Recorded Investment	79	82
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	79	82
Unpaid Principal Balance	79	82
Commercial multi-family | PUERTO RICO | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	29	34
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	79	82
Recorded Investment	79	82
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	79	82
Unpaid Principal Balance	79	82
CRE non-owner occupied | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	23,847	24,537
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	13,807	15,935
Impaired Financing Receivable, with Related Allowance, Recorded Investment	103,811	104,119
Recorded Investment	117,618	120,054
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	27,503	29,631
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	104,740	105,047
Unpaid Principal Balance	132,243	134,678
CRE non-owner occupied | PUERTO RICO | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	23,847	24,537
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	13,807	15,935
Impaired Financing Receivable, with Related Allowance, Recorded Investment	103,811	104,119
Recorded Investment	117,618	120,054
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	27,503	29,631
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	104,740	105,047
Unpaid Principal Balance	132,243	134,678
CRE owner occupied | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	16,873	13,007
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	30,972	31,962
Impaired Financing Receivable, with Related Allowance, Recorded Investment	134,455	131,634
Recorded Investment	165,427	163,596
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	46,625	50,094
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	173,707	169,013
Unpaid Principal Balance	220,332	219,107
CRE owner occupied | PUERTO RICO | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	16,873	13,007
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	30,972	31,962
Impaired Financing Receivable, with Related Allowance, Recorded Investment	134,455	131,634
Recorded Investment	165,427	163,596
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	46,625	50,094
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	173,707	169,013
Unpaid Principal Balance	220,332	219,107
Commercial and industrial | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	10,527	4,797
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	12,416	7,828
Impaired Financing Receivable, with Related Allowance, Recorded Investment	53,283	46,862
Recorded Investment	65,699	54,690
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	16,067	11,478
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	55,352	49,301
Unpaid Principal Balance	71,419	60,779
Commercial and industrial | PUERTO RICO | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	10,527	4,797
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	12,416	7,828
Impaired Financing Receivable, with Related Allowance, Recorded Investment	53,283	46,862
Recorded Investment	65,699	54,690
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	16,067	11,478
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	55,352	49,301
Unpaid Principal Balance	71,419	60,779
Mortgages | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	43,264	44,610
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	79,349	73,246
Impaired Financing Receivable, with Related Allowance, Recorded Investment	431,219	433,118
Recorded Investment	510,568	506,364
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	97,477	91,175
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	474,759	474,220
Unpaid Principal Balance	572,236	565,395
Mortgages | PUERTO RICO | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	41,067	42,428
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	76,877	70,751
Impaired Financing Receivable, with Related Allowance, Recorded Investment	424,770	426,737
Recorded Investment	501,647	497,488
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	94,113	87,806
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	466,629	466,249
Unpaid Principal Balance	560,742	554,055
Mortgages | UNITED STATES | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	2,197	2,182
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,472	2,495
Impaired Financing Receivable, with Related Allowance, Recorded Investment	6,449	6,381
Recorded Investment	8,921	8,876
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	3,364	3,369
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	8,130	7,971
Unpaid Principal Balance	11,494	11,340
Leasing | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	522	535
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,803	1,817
Recorded Investment	1,803	1,817
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	1,803	1,817
Unpaid Principal Balance	1,803	1,817
Leasing | PUERTO RICO | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	522	535
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,803	1,817
Recorded Investment	1,803	1,817
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	1,803	1,817
Unpaid Principal Balance	1,803	1,817
Consumer | Credit cards | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	5,686	5,588
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	37,952	37,464
Recorded Investment	37,952	37,464
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	37,952	37,464
Unpaid Principal Balance	37,952	37,464
Consumer | Credit cards | PUERTO RICO | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	5,686	5,588
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	37,952	37,464
Recorded Investment	37,952	37,464
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	37,952	37,464
Unpaid Principal Balance	37,952	37,464
Consumer | Home equity lines of credit | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	673	667
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	298	300
Impaired Financing Receivable, with Related Allowance, Recorded Investment	2,367	2,421
Recorded Investment	2,665	2,721
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	313	315
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	2,375	2,429
Unpaid Principal Balance	2,688	2,744
Consumer | Home equity lines of credit | UNITED STATES | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	673	667
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	298	300
Impaired Financing Receivable, with Related Allowance, Recorded Investment	2,367	2,421
Recorded Investment	2,665	2,721
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	313	315
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	2,375	2,429
Unpaid Principal Balance	2,688	2,744
Consumer | Personal | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	16,151	16,960
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	77	79
Impaired Financing Receivable, with Related Allowance, Recorded Investment	65,660	66,082
Recorded Investment	65,737	66,161
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	77	79
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	65,660	66,082
Unpaid Principal Balance	65,737	66,161
Consumer | Personal | PUERTO RICO | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	16,145	16,955
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	65,622	66,043
Recorded Investment	65,622	66,043
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	65,622	66,043
Unpaid Principal Balance	65,622	66,043
Consumer | Personal | UNITED STATES | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	6	5
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	77	79
Impaired Financing Receivable, with Related Allowance, Recorded Investment	38	39
Recorded Investment	115	118
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	77	79
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	38	39
Unpaid Principal Balance	115	118
Consumer | Auto | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	409	474
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	2,070	2,117
Recorded Investment	2,070	2,117
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	2,070	2,117
Unpaid Principal Balance	2,070	2,117
Consumer | Auto | PUERTO RICO | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	409	474
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	2,070	2,117
Recorded Investment	2,070	2,117
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	2,070	2,117
Unpaid Principal Balance	2,070	2,117
Consumer | Other | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	91	168
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	592	991
Recorded Investment	592	991
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	592	991
Unpaid Principal Balance	592	991
Consumer | Other | PUERTO RICO | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Related Allowance	91	168
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	592	991
Recorded Investment	592	991
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	592	991
Unpaid Principal Balance	$ 592	$ 991