Debt Securities Held-to-maturity -Additional Information (Details)	Mar. 31, 2021 USD ($) score	Dec. 31, 2020 USD ($) score	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Debt Securities, Held-to-maturity
Amortized cost	$ 89,725,000	$ 92,621,000
Allowance for credit losses	10,096,000	10,261,000
Securities in non-performing status	0	0
Obligations of Puerto Rico, States and political subdivisions
Debt Securities, Held-to-maturity
Amortized cost	78,133,000	81,029,000
Allowance for credit losses	$ 10,096,000	$ 10,261,000	$ 13,390,000	$ 0
Average Credit Score Fico | score	697	697
Percentage of nominal value	67.00%	66.00%
Obligations of Puerto Rico, States and political subdivisions | Munis Payable From Real and Personal Property Taxes
Debt Securities, Held-to-maturity
Amortized cost	$ 32,590,000	$ 35,315,000
Allowance for credit losses	1,200,000	1,400,000
Obligations of Puerto Rico, States and political subdivisions | Munis Not Guaranteed By Puerto Rico Central Government
Debt Securities, Held-to-maturity
Amortized cost	45,000,000	46,000,000
Allowance for credit losses	$ 8,900,000	$ 8,900,000