Note Income taxes (Differences between income tax expense (benefit) applicable to income before income taxes and amount computed by applying the statutory tax rate in Puerto Rico) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Amount
Income tax expense	$ 22,155	$ 33,006
PUERTO RICO
Amount
Computed income tax at statutory rates	44,257	49,121
Net benefit of net tax exempt interest income	(22,993)	(18,004)
Deferred tax asset valuation allowance	7,226	5,056
Difference in tax rates due to multiple jurisdictions	(2,959)	(959)
Adjustments in net deferred tax due to change in tax law	(5,133)	0
State and local taxes	1,363	1,279
Income tax expense	$ 22,155	$ 33,006
% of pre-tax income
Computed income tax at statutory rates	39.00%	39.00%
Net benefit of net tax exempt interest income	(20.00%)	(14.00%)
Deferred tax asset valuation allowance	6.00%	4.00%
Difference in tax rates due to multiple jurisdictions	(2.00%)	(1.00%)
Effective Income Tax Rate Reconciliation Change In Enacted Tax Rate	(4.00%)	0.00%
State and local taxes	1.00%	1.00%
Income tax (benefit) expense	20.00%	26.00%
PUERTO RICO | Effect Of Income Subject To Preferential Tax Rate
Amount
Other	$ (3,048)	$ (3,019)
% of pre-tax income
Others	(3.00%)	(3.00%)
PUERTO RICO | Others
Amount
Other	$ 3,442	$ (468)
% of pre-tax income
Others	3.00%	0.00%