Note Allowance for loan losses (Average recorded investment and interest income recognized on impaired loans) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 955,782	$ 936,967	$ 959,458	$ 933,591
Interest Income Recognized	6,488	6,843	21,873	20,234
Commercial multi-family | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	141	43	111	21
Interest Income Recognized	1	1	4	4
CRE non-owner occupied | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	117,650	140,083	118,243	129,372
Interest Income Recognized	1,272	1,345	3,997	3,971
CRE owner occupied | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	151,580	136,565	158,046	147,305
Interest Income Recognized	1,413	1,408	4,640	4,349
Commercial and industrial | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	61,950	55,685	61,072	58,518
Interest Income Recognized	531	483	1,682	1,466
Construction | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		518		1,384
Interest Income Recognized		0		0
Mortgages | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	516,684	490,797	512,575	483,154
Interest Income Recognized	3,271	3,606	11,550	10,444
Leasing | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,568	2,005	1,689	2,201
Interest Income Recognized	0	0	0	0
Consumer | Credit cards | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	35,727	38,431	36,718	38,344
Interest Income Recognized	0	0	0	0
Consumer | Home equity lines of credit | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,572	1,883	2,632	1,741
Interest Income Recognized	0	0	0	0
Consumer | Personal | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	64,854	67,728	65,402	68,256
Interest Income Recognized	0	0	0	0
Consumer | Auto | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,065	2,501	2,079	2,689
Interest Income Recognized	0	0	0	0
Consumer | Other | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	991	728	891	606
Interest Income Recognized	0	0	0	0
PUERTO RICO
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	943,452	925,703	947,439	923,172
Interest Income Recognized	6,428	6,775	21,717	20,101
PUERTO RICO | Commercial multi-family | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	141	43	111	21
Interest Income Recognized	1	1	4	4
PUERTO RICO | CRE non-owner occupied | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	117,650	140,083	118,243	129,372
Interest Income Recognized	1,272	1,345	3,997	3,971
PUERTO RICO | CRE owner occupied | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	151,580	136,565	158,046	147,305
Interest Income Recognized	1,413	1,408	4,640	4,349
PUERTO RICO | Commercial and industrial | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	61,950	55,685	61,072	58,518
Interest Income Recognized	531	483	1,682	1,466
PUERTO RICO | Construction | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		518		1,384
Interest Income Recognized		0		0
PUERTO RICO | Mortgages | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	507,689	482,067	503,628	475,108
Interest Income Recognized	3,211	3,538	11,394	10,311
PUERTO RICO | Leasing | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,568	2,005	1,689	2,201
Interest Income Recognized	0	0	0	0
PUERTO RICO | Consumer | Credit cards | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	35,727	38,431	36,718	38,344
Interest Income Recognized	0	0	0	0
PUERTO RICO | Consumer | Home equity lines of credit | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0	0	0
Interest Income Recognized	0	0	0	0
PUERTO RICO | Consumer | Personal | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	64,091	67,077	64,962	67,624
Interest Income Recognized	0	0	0	0
PUERTO RICO | Consumer | Auto | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,065	2,501	2,079	2,689
Interest Income Recognized	0	0	0	0
PUERTO RICO | Consumer | Other | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	991	728	891	606
Interest Income Recognized	0	0	0	0
UNITED STATES
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	12,330	11,264	12,019	10,419
Interest Income Recognized	60	68	156	133
UNITED STATES | Commercial multi-family | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0	0	0
Interest Income Recognized	0	0	0	0
UNITED STATES | CRE non-owner occupied | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0	0	0
Interest Income Recognized	0	0	0	0
UNITED STATES | CRE owner occupied | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0	0	0
Interest Income Recognized	0	0	0	0
UNITED STATES | Commercial and industrial | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0	0	0
Interest Income Recognized	0	0	0	0
UNITED STATES | Construction | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment		0		0
Interest Income Recognized		0		0
UNITED STATES | Mortgages | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	8,995	8,730	8,947	8,046
Interest Income Recognized	60	68	156	133
UNITED STATES | Leasing | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0	0	0
Interest Income Recognized	0	0	0	0
UNITED STATES | Consumer | Credit cards | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0	0	0
Interest Income Recognized	0	0	0	0
UNITED STATES | Consumer | Home equity lines of credit | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,572	1,883	2,632	1,741
Interest Income Recognized	0	0	0	0
UNITED STATES | Consumer | Personal | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	763	651	440	632
Interest Income Recognized	0	0	0	0
UNITED STATES | Consumer | Auto | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0	0	0
Interest Income Recognized	0	0	0	0
UNITED STATES | Consumer | Other | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0	0	0
Interest Income Recognized	$ 0	$ 0	$ 0	$ 0