Debt Securities Held-to-maturity - Weighted average yield and contractual maturities of debt securities HTM (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Amortized cost
Amortized cost	$ 85,655		$ 92,621
Allowance for credit losses
Less - Allowance for credit losses	9,222		10,261
Net of Allowance
Net of Allowance	76,433		82,360
Gross unrecognized gains
Gross Unrealized Gains	13,342		12,554
Gross unrealized losses
Gross Unrealized Losses	0		23
Fair Value
Fair value	$ 89,775		$ 94,891
Weighted Average Yield
Weighted Average Yield	3.30%		3.38%
Obligations of Puerto Rico, States and political subdivisions
Amortized cost
Amortized cost - Within 1 year	$ 4,240		$ 3,990
Amortized cost - After 1 to 5 years	14,395		16,030
Amortized cost - After 5 to 10 years	11,280		14,845
Amortized cost - After 10 years	44,149		46,164
Amortized cost	74,064		81,029
Allowance for credit losses
Allowance for credit losses - Within 1 Year	46		50
Allowance for credit losses - After 1 to 5 years	555		710
Allowance for credit losses - After 5 to 10 years	347		573
Allowance for credit losses - After 10 years	8,274		8,928
Less - Allowance for credit losses	9,222	$ 10,214	10,261	$ 12,421	$ 12,735	$ 0
Net of Allowance
Net of Allowance - Within 1 Year	4,194		3,940
Net of Allowance - After 1 to 5 Years	13,840		15,320
Net of Allowance - After 5 to 10 Years	10,933		14,272
Net of Allowance - After 10 Years	35,875		37,236
Net of Allowance	64,842		70,768
Gross unrecognized gains
Gross unrealized gains - Within 1 year	47		47
Gross unrealized gains - After 1 to 5 years	555		710
Gross unrealized gains - After 5 to 10 years	194		295
Gross unrealized gains - After 10 years	12,545		11,501
Gross Unrealized Gains	13,341		12,553
Gross unrealized losses
Gross unrealized losses - Within 1 year	0		0
Gross unrealized losses - After 1 to 5 years	0		0
Gross unrealized losses - After 5 to 10 years	0		23
Gross unrealized losses - After 10 years	0		0
Gross Unrealized Losses	0		23
Fair Value
Fair Value - within 1 year	4,241		3,987
Fair Value - After 1 to 5 years	14,395		16,030
Fair Value - After 5 to 10 years	11,127		14,544
Fair Value - After 10 years	48,420		48,737
Fair value	$ 78,183		$ 83,298
Weighted Average Yield
Weighted average yield - Within 1 Year	6.09%		6.05%
Weighted average yield - After 1 to 5 years	6.23%		6.16%
Weighted average yield - After 5 to 10 years	2.18%		2.77%
Weighted average yield - After 10 years	1.52%		1.58%
Weighted Average Yield	2.80%		2.93%
Collateralized Mortgage Obligations - Federal agencies
Amortized cost
Amortized cost - After 1 to 5 years	$ 30		$ 31
Amortized cost	30		31
Allowance for credit losses
Allowance for credit losses - After 1 to 5 years	0		0
Less - Allowance for credit losses	0		0
Net of Allowance
Net of Allowance - After 1 to 5 Years	30		31
Net of Allowance	30		31
Gross unrecognized gains
Gross unrealized gains - After 1 to 5 years	1		1
Gross Unrealized Gains	1		1
Gross unrealized losses
Gross unrealized losses - After 1 to 5 years	0		0
Gross Unrealized Losses	0		0
Fair Value
Fair Value - After 1 to 5 years	31		32
Fair value	$ 31		$ 32
Weighted Average Yield
Weighted average yield - After 1 to 5 years	6.44%		6.44%
Weighted Average Yield	6.44%		6.44%
Securities in wholly owned statutory business trusts
Amortized cost
Amortized cost - After 10 years	$ 11,561		$ 11,561
Amortized cost	11,561		11,561
Allowance for credit losses
Allowance for credit losses - After 10 years	0		0
Less - Allowance for credit losses	0		0
Net of Allowance
Net of Allowance - After 10 Years	11,561		11,561
Net of Allowance	11,561		11,561
Gross unrecognized gains
Gross unrealized gains - After 10 years	0		0
Gross Unrealized Gains	0		0
Gross unrealized losses
Gross unrealized losses - After 10 years	0		0
Gross Unrealized Losses	0		0
Fair Value
Fair Value - After 10 years	11,561		11,561
Fair value	$ 11,561		$ 11,561
Weighted Average Yield
Weighted average yield - After 10 years	6.51%		6.51%
Weighted Average Yield	6.51%		6.51%