Stock-based compensation - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Executive Officers
Stock-based compensation
Total unrecognized compensation cost related to non-vested restricted stock awards and performance shares to members of management, period of recognition (in years)			2 years 6 months
Fair value of stocks vested at grant date			$ 13,700,000
Fair Market Value of stock vested at vesting date			18,900,000
Windfall Net Of Shortfall			$ 1,900,000
Restricted Stock Award | Executive Officers
Stock-based compensation
Stock granted	619	8,395	152,773	163,701
Restricted Stock Expense	$ 1,000,000.0	$ 1,100,000	$ 6,800,000	$ 5,900,000
Incentive award, tax benefit	$ 200,000	$ 200,000	$ 1,100,000	900,000
Restricted Stock Award | Directors
Stock-based compensation
Stock granted	0	2,765	1,052		25,159
Restricted Stock Expense		$ 100,000	$ 52,000	1,600,000
Incentive award, tax benefit		$ 16,000,000	6,000	$ 200,000
Fair Market Value of stock vested at vesting date			$ 52,000
Restricted Stock Units (RSUs)
Stock-based compensation
Restricted Stock Expense	$ 100,000
Restricted Stock Units (RSUs) | TARP Interim Final Rule
Stock-based compensation
Stock-Based Compensation, vesting rights			The restricted shares for employees, will become vested based on the employees’ continued service with Popular. Unless otherwise stated in an agreement, the compensation cost associated with the shares of restricted stock is determined based on a two-prong vesting schedule. The first part is vested ratably over five years commencing at the date of grant (the “graduated vesting portion”) and the second part is vested at termination of employment after attainment of 55 years of age and 10 years of service (the “retirement vesting portion”). The graduated vesting portion is accelerated at termination of employment after attaining 55 years of age and 10 years of service. The vesting schedule for restricted shares granted on or after 2014 was modified as follows, the first part is vested ratably over four years commencing at the date of the grant (the “graduated vesting portion”) and the second part is vested at termination of employment after attainment of the earlier of 55 years of age and 10 years of service or 60 years of age and 5 years of service (the “retirement vesting portion”). The graduated vesting portion is accelerated at termination of employment after attaining the earlier of 55 years of age and 10 years of service or 60 years of age and 5 years of service.
Restricted Stock Units (RSUs) | Directors
Stock-based compensation
Stock granted	1,989		27,449	25,159	0
Restricted Stock Expense	$ 0			$ 1,500,000
Incentive award, tax benefit				$ 200,000
Fair Market Value of stock vested at vesting date			$ 1,500,000
Performance Based Shares | Executive Officers
Stock-based compensation
Total unrecognized compensation cost related to non-vested restricted stock awards and performance shares to members of management	$ 9,200,000		$ 9,200,000
Stock granted	0	0	65,396	72,414
Restricted Stock Expense	$ 400,000	$ 600,000	$ 4,300,000	$ 3,800,000
Incentive award, tax benefit	$ 23,000	$ 12,000	$ 300,000	$ 300,000
Stock-Based Compensation, vesting rights			The number of shares that will ultimately vest ranges from 50% to a 150% of target based on both market (TSR) and performance (EPS) conditions. The performance shares vest at the end of the three-year performance cycle. If a participant terminates employment after attaining the earlier of 55 years of age and 10 years of service or 60 years of age and 5 years of service, the performance shares shall continue outstanding and vest at the end of the performance cycle.