Debt Securities Held-to-maturity -Additional Information (Details)	Sep. 30, 2024 USD ($) score	Jun. 30, 2024 USD ($)	Dec. 31, 2023 USD ($) score	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity securities	$ 8,390,024,000		$ 8,852,825,000
Allowance for credit losses	5,430,000		5,780,000
Obligations of Puerto Rico, States and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity securities	57,845,000		65,408,000
Allowance for credit losses	$ 5,430,000	$ 6,251,000	$ 5,780,000	$ 6,057,000	$ 6,145,000	$ 6,911,000
Average Credit Score Fico | score	672		708
Percentage of nominal value	70.00%		67.00%
Obligations of Puerto Rico, States and political subdivisions | Munis Payable From Real and Personal Property Taxes
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity securities	$ 12,615,000		$ 18,820,000
Allowance for credit losses	100,000		200,000
Obligations of Puerto Rico, States and political subdivisions | Munis Not Guaranteed By Puerto Rico Central Government
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity securities	38,000,000		40,000,000
Allowance for credit losses	5,300,000		5,600,000
Obligations of Puerto Rico, States and political subdivisions | Munis payable from US treasure securities proceeds
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity securities	7,000,000		7,000,000
Allowance for credit losses	0		0
Past due
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity securities	$ 0		$ 0