Note Allowance for loan losses (Average recorded investment and interest income recognized on impaired loans) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 996,030	$ 963,494	$ 979,826	$ 961,013
Interest Income Recognized	7,926	8,214	18,291	15,292
Commercial multi-family | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	414	78	344	79
Interest Income Recognized	0	1	0	3
CRE non-owner occupied | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	132,842	117,744	126,208	118,514
Interest Income Recognized	1,681	1,341	3,104	2,697
CRE owner occupied | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	153,007	160,001	152,761	161,199
Interest Income Recognized	1,596	1,534	3,195	3,198
Commercial and industrial | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	69,493	63,558	65,676	60,602
Interest Income Recognized	702	502	1,397	1,144
Construction | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	12,377		8,251
Interest Income Recognized	0		25
Mortgages | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	518,616	512,355	518,502	510,358
Interest Income Recognized	3,832	4,836	10,316	8,250
Leasing | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,246	1,736	1,316	1,763
Interest Income Recognized	0	0	0	0
Consumer | Credit cards | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	33,293	36,812	33,421	37,029
Interest Income Recognized	0	0	0	0
Consumer | Home equity lines of credit | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	5,436	2,570	5,054	2,620
Interest Income Recognized	0	0	0	0
Consumer | Personal | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	66,569	65,829	65,463	65,939
Interest Income Recognized	115	0	254	0
Consumer | Auto | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,399	2,075	1,602	2,089
Interest Income Recognized	0	0	0	0
Consumer | Other | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,338	736	1,228	821
Interest Income Recognized	0	0	0	0
PUERTO RICO
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	971,469	951,580	958,687	949,166
Interest Income Recognized	7,883	8,192	18,204	15,226
PUERTO RICO | Commercial multi-family | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	414	78	344	79
Interest Income Recognized	0	1	0	3
PUERTO RICO | CRE non-owner occupied | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	132,842	117,744	126,208	118,514
Interest Income Recognized	1,681	1,341	3,104	2,697
PUERTO RICO | CRE owner occupied | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	153,007	160,001	152,761	161,199
Interest Income Recognized	1,596	1,534	3,195	3,198
PUERTO RICO | Commercial and industrial | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	69,493	63,558	65,676	60,602
Interest Income Recognized	702	502	1,397	1,144
PUERTO RICO | Construction | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	3,426		2,284
Interest Income Recognized	0		25
PUERTO RICO | Mortgages | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	509,215	503,446	509,154	501,460
Interest Income Recognized	3,789	4,814	10,229	8,184
PUERTO RICO | Leasing | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,246	1,736	1,316	1,763
Interest Income Recognized	0	0	0	0
PUERTO RICO | Consumer | Credit cards | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	33,293	36,812	33,421	37,029
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	65,796	65,394	64,693	65,610
Interest Income Recognized	115	0	254	0
PUERTO RICO | Consumer | Auto | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,399	2,075	1,602	2,089
Interest Income Recognized	0	0	0	0
PUERTO RICO | Consumer | Other | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,338	736	1,228	821
Interest Income Recognized	0	0	0	0
UNITED STATES
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	24,561	11,914	21,139	11,847
Interest Income Recognized	43	22	87	66
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	8,951		5,967
Interest Income Recognized	0		0
UNITED STATES | Mortgages | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	9,401	8,909	9,348	8,898
Interest Income Recognized	43	22	87	66
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	5,436	2,570	5,054	2,620
Interest Income Recognized	0	0	0	0
UNITED STATES | Consumer | Personal | Non Covered Loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	773	435	770	329
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