Note Allowance for loan losses (Average recorded investment and interest income recognized on impaired loans) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Financing Receivable, Impaired
Average Recorded Investment	$ 1,039,569	$ 964,327
Interest Income Recognized	8,062	10,059
Commercial multi-family | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	928	168
Interest Income Recognized	12	2
CRE non-owner occupied | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	178,725	123,359
Interest Income Recognized	1,712	1,366
CRE owner occupied | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	140,692	153,453
Interest Income Recognized	1,458	1,486
Commercial and industrial | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	70,662	60,780
Interest Income Recognized	745	582
Construction | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	13,848	2,147
Interest Income Recognized	0	0
Mortgages | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	521,846	519,099
Interest Income Recognized	4,066	6,623
Leasing | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	1,059	1,409
Interest Income Recognized	0	0
Consumer | Credit cards | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	28,354	33,471
Interest Income Recognized	0	0
Consumer | Home equity lines of credit | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	7,962	4,685
Interest Income Recognized	0	0
Consumer | Personal Loan | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	73,084	62,516
Interest Income Recognized	69	0
Consumer | Auto Loan | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	1,162	1,885
Interest Income Recognized	0	0
Consumer | Other | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	1,247	1,355
Interest Income Recognized	0	0
PUERTO RICO
Financing Receivable, Impaired
Average Recorded Investment	1,008,486	949,713
Interest Income Recognized	8,022	10,016
PUERTO RICO | Commercial multi-family | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	928	168
Interest Income Recognized	12	2
PUERTO RICO | CRE non-owner occupied | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	178,725	123,359
Interest Income Recognized	1,712	1,366
PUERTO RICO | CRE owner occupied | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	139,846	153,453
Interest Income Recognized	1,458	1,486
PUERTO RICO | Commercial and industrial | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	70,662	60,780
Interest Income Recognized	745	582
PUERTO RICO | Construction | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	1,788	2,147
Interest Income Recognized	0	0
PUERTO RICO | Mortgages | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	512,417	509,941
Interest Income Recognized	4,026	6,580
PUERTO RICO | Leasing | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	1,059	1,409
Interest Income Recognized	0	0
PUERTO RICO | Consumer | Credit cards | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	28,354	33,471
Interest Income Recognized	0	0
PUERTO RICO | Consumer | Home equity lines of credit | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	0	0
Interest Income Recognized	0	0
PUERTO RICO | Consumer | Personal Loan | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	72,298	61,745
Interest Income Recognized	69	0
PUERTO RICO | Consumer | Auto Loan | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	1,162	1,885
Interest Income Recognized	0	0
PUERTO RICO | Consumer | Other | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	1,247	1,355
Interest Income Recognized	0	0
UNITED STATES
Financing Receivable, Impaired
Average Recorded Investment	31,083	14,614
Interest Income Recognized	40	43
UNITED STATES | Commercial multi-family | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	0	0
Interest Income Recognized	0	0
UNITED STATES | CRE non-owner occupied | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	0	0
Interest Income Recognized	0	0
UNITED STATES | CRE owner occupied | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	846	0
Interest Income Recognized	0	0
UNITED STATES | Commercial and industrial | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	0	0
Interest Income Recognized	0	0
UNITED STATES | Construction | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	12,060	0
Interest Income Recognized	0	0
UNITED STATES | Mortgages | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	9,429	9,158
Interest Income Recognized	40	43
UNITED STATES | Leasing | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	0	0
Interest Income Recognized	0	0
UNITED STATES | Consumer | Credit cards | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	0	0
Interest Income Recognized	0	0
UNITED STATES | Consumer | Home equity lines of credit | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	7,962	4,685
Interest Income Recognized	0	0
UNITED STATES | Consumer | Personal Loan | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	786	771
Interest Income Recognized	0	0
UNITED STATES | Consumer | Auto Loan | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	0	0
Interest Income Recognized	0	0
UNITED STATES | Consumer | Other | Non Covered Loans
Financing Receivable, Impaired
Average Recorded Investment	0	0
Interest Income Recognized	$ 0	$ 0