Income taxes - Differences between income tax expense (benefit) in Puerto Rico (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Amount
Income tax expense	$ 83,542	$ 41,168	$ 233,466	$ 68,893
PR
Amount
Computed income tax at statutory rates	124,370	78,594	360,859	149,715
Benefit of net tax exempt interest income	(34,294)	(31,177)	(105,297)	(93,497)
Deferred tax asset valuation allowance	3,529	2,185	19,682	10,333
Difference in tax rates due to multiple jurisdictions	(9,600)	(2,584)	(25,429)	2,081
Effect of income subject to preferential tax rate	(5,441)	(3,095)	(10,175)	(7,722)
Unrecognized tax benefits	(5,484)	(2,163)	(5,484)	(2,163)
Adjustments in net deferred tax due to change in tax law	4,001	(4,030)	(6,732)	2,821
State and local taxes	6,352	3,748	8,943	5,807
Other	109	(310)	(2,901)	1,518
Income tax expense	$ 83,542	$ 41,168	$ 233,466	$ 68,893
% of pre-tax income
Computed income tax at statutory rates	38.00%	38.00%	38.00%	38.00%
Benefit of net tax exempt interest income	(10.00%)	(15.00%)	(11.00%)	(24.00%)
Deferred tax asset valuation allowance	1.00%	1.00%	2.00%	3.00%
Difference in tax rates due to multiple jurisdictions	(3.00%)	(1.00%)	(3.00%)	1.00%
Effect of income subject to preferential tax rate	(2.00%)	(2.00%)	(1.00%)	(2.00%)
Unrecognized tax benefits	(2.00%)	(1.00%)	(1.00%)	(1.00%)
Adjustments in net deferred tax due to change in tax law	1.00%	(2.00%)	(1.00%)	1.00%
State and local taxes	2.00%	2.00%	1.00%	1.00%
Others	0.00%	0.00%	0.00%	0.00%
Income tax expense	25.00%	20.00%	24.00%	17.00%

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