Note Allowance for loan losses (Average recorded investment and interest income recognized on impaired loans) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 964,327	$ 963,138
Interest Income Recognized	10,059	6,884
Commercial multi-family | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	168	81
Interest Income Recognized	2	1
CRE non-owner occupied | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	123,359	118,836
Interest Income Recognized	1,366	1,375
CRE owner occupied | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	153,453	164,512
Interest Income Recognized	1,486	1,598
Commercial and industrial | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	60,780	60,195
Interest Income Recognized	582	497
Construction | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,147	0
Interest Income Recognized	0	0
Mortgages | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	519,099	508,467
Interest Income Recognized	6,623	3,413
Leasing | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,409	1,810
Interest Income Recognized	0	0
Consumer | Credit cards | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	33,471	37,708
Interest Income Recognized	0	0
Consumer | Home equity lines of credit | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	4,685	2,693
Interest Income Recognized	0	0
Consumer | Personal | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	62,516	65,950
Interest Income Recognized	0	0
Consumer | Auto | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,885	2,094
Interest Income Recognized	0	0
Consumer | Other | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,355	792
Interest Income Recognized	0	0
PUERTO RICO
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	949,713	951,429
Interest Income Recognized	10,016	6,840
PUERTO RICO | Commercial multi-family | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	168	81
Interest Income Recognized	2	1
PUERTO RICO | CRE non-owner occupied | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	123,359	118,836
Interest Income Recognized	1,366	1,375
PUERTO RICO | CRE owner occupied | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	153,453	164,512
Interest Income Recognized	1,486	1,598
PUERTO RICO | Commercial and industrial | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	60,780	60,195
Interest Income Recognized	582	497
PUERTO RICO | Construction | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,147	0
Interest Income Recognized	0	0
PUERTO RICO | Mortgages | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	509,941	499,568
Interest Income Recognized	6,580	3,369
PUERTO RICO | Leasing | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,409	1,810
Interest Income Recognized	0	0
PUERTO RICO | Consumer | Credit cards | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	33,471	37,708
Interest Income Recognized	0	0
PUERTO RICO | Consumer | Home equity lines of credit | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0
Interest Income Recognized	0	0
PUERTO RICO | Consumer | Personal | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	61,745	65,833
Interest Income Recognized	0	0
PUERTO RICO | Consumer | Auto | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,885	2,094
Interest Income Recognized	0	0
PUERTO RICO | Consumer | Other | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,355	792
Interest Income Recognized	0	0
UNITED STATES
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	14,614	11,709
Interest Income Recognized	43	44
UNITED STATES | Commercial multi-family | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0
Interest Income Recognized	0	0
UNITED STATES | CRE non-owner occupied | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0
Interest Income Recognized	0	0
UNITED STATES | CRE owner occupied | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0
Interest Income Recognized	0	0
UNITED STATES | Commercial and industrial | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0
Interest Income Recognized	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	9,158	8,899
Interest Income Recognized	43	44
UNITED STATES | Leasing | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0
Interest Income Recognized	0	0
UNITED STATES | Consumer | Credit cards | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0
Interest Income Recognized	0	0
UNITED STATES | Consumer | Home equity lines of credit | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	4,685	2,693
Interest Income Recognized	0	0
UNITED STATES | Consumer | Personal | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	771	117
Interest Income Recognized	0	0
UNITED STATES | Consumer | Auto | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0
Interest Income Recognized	0	0
UNITED STATES | Consumer | Other | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	0	0
Interest Income Recognized	$ 0	$ 0