Debt Securities Held-to-maturity - Weighted average yield and contractual maturities of debt securities HTM (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Amortized cost
Amortized cost	$ 9,352,385	$ 9,356,739
Book Value
Book Value	8,563,052	8,525,366
Allowance for credit losses
Allowance for credit losses	6,792	6,911
Net of Allowance
Net of Allowance	8,556,260	8,518,455
Gross unrecognized gains
Gross Unrealized Gains	79,542	4,918
Gross unrealized losses
Gross Unrealized Losses	37,882	83,177
Fair Value
Fair value	$ 8,597,920	$ 8,440,196
Weighted Average Yield
Weighted Average Yield	1.55%	1.55%
US Treasury Securities
Amortized cost
Amortized cost - Within 1 year	$ 649,391	$ 499,034
Amortized cost - After 1 to 5 year	6,591,199	6,147,568
Amortized cost - After 5 to 10 years	2,043,395	2,638,238
Amortized cost	9,283,985	9,284,840
Book Value
Book Value - within 1 year	649,391	499,034
Book Value - Within 1 to 5 years	6,043,507	5,640,767
Book Balue - After 5 to 10 years	1,801,754	2,313,666
Book Value	8,494,652	8,453,467
Allowance for credit losses
Allowance for credit losses - Within 1 Year	0	0
Allowance for credit losses - After 1 to 5 years	0	0
Allowance for credit losses - After 5 to 10 years	0	0
Allowance for credit losses	0	0
Net of Allowance
Net of Allowance - Within 1 Year	649,391	499,034
Net of Allowance - After 1 to 5 Years	6,043,507	5,640,767
Net of Allowance - After 5 to 10 Years	1,801,754	2,313,666
Net of Allowance	8,494,652	8,453,467
Gross unrecognized gains
Gross unrealized gains - Within 1 year	0	0
Gross unrealized gains - After 1 to 5 years	49,211	0
Gross unrealized gains - After 5 to 10 years	25,736	0
Gross Unrealized Gains	74,947	0
Gross unrealized losses
Gross unrealized losses - Within 1 year	6,923	6,203
Gross unrealized losses - After 1 to 5 years	28,571	59,806
Gross unrealized losses - After 5 to 10 years	0	14,857
Gross Unrealized Losses	35,494	80,866
Fair Value
Fair Value - within 1 year	642,468	492,831
Fair Value - After 1 to 5 years	6,064,147	5,580,961
Fair Value - After 5 to 10 years	1,827,490	2,298,809
Fair value	$ 8,534,105	$ 8,372,601
Weighted Average Yield
Weighted average yield - Within 1 Year	2.75%	2.83%
Weighted average yield - After 1 to 5 years	1.45%	1.49%
Weighted average yield - After 5 to 10 years	1.44%	1.41%
Weighted Average Yield	1.54%	1.54%
Obligations of Puerto Rico, States and political subdivisions
Amortized cost
Amortized cost - Within 1 year	$ 4,730	$ 4,530
Amortized cost - After 1 to 5 year	15,805	19,105
Amortized cost - After 5 to 10 years	1,025	1,025
Amortized cost - After 10 years	40,865	41,261
Amortized cost	62,425	65,921
Book Value
Book Value - within 1 year	4,730	4,530
Book Value - Within 1 to 5 years	15,805	19,105
Book Balue - After 5 to 10 years	1,025	1,025
Book Value - After 10 years	40,865	41,261
Book Value	62,425	65,921
Allowance for credit losses
Allowance for credit losses - Within 1 Year	21	8
Allowance for credit losses - After 1 to 5 years	212	234
Allowance for credit losses - After 5 to 10 years	34	34
Allowance for credit losses - After 10 years	6,525	6,635
Allowance for credit losses	6,792	6,911	$ 7,844	$ 8,096
Net of Allowance
Net of Allowance - Within 1 Year	4,709	4,522
Net of Allowance - After 1 to 5 Years	15,593	18,871
Net of Allowance - After 5 to 10 Years	991	991
Net of Allowance - After 10 Years	34,340	34,626
Net of Allowance	55,633	59,010
Gross unrecognized gains
Gross unrealized gains - Within 1 year	18	5
Gross unrealized gains - After 1 to 5 years	119	150
Gross unrealized gains - After 5 to 10 years	34	34
Gross unrealized gains - After 10 years	4,423	4,729
Gross Unrealized Gains	4,594	4,918
Gross unrealized losses
Gross unrealized losses - Within 1 year	3	0
Gross unrealized losses - After 1 to 5 years	115	82
Gross unrealized losses - After 5 to 10 years	0	0
Gross unrealized losses - After 10 years	2,270	2,229
Gross Unrealized Losses	2,388	2,311
Fair Value
Fair Value - within 1 year	4,724	4,527
Fair Value - After 1 to 5 years	15,597	18,939
Fair Value - After 5 to 10 years	1,025	1,025
Fair Value - After 10 years	36,493	37,126
Fair value	$ 57,839	$ 61,617
Weighted Average Yield
Weighted average yield - Within 1 Year	6.15%	6.08%
Weighted average yield - After 1 to 5 years	3.83%	4.24%
Weighted average yield - After 5 to 10 years	5.80%	5.80%
Weighted average yield - After 10 years	1.40%	1.40%
Weighted Average Yield	2.45%	2.61%
Collateralized Mortgage Obligations - Federal agencies
Amortized cost
Amortized cost - After 1 to 5 year	$ 16	$ 19
Amortized cost	16	19
Book Value
Book Value - Within 1 to 5 years	16	19
Book Value	16	19
Allowance for credit losses
Allowance for credit losses - After 1 to 5 years	0	0
Allowance for credit losses	0	0
Net of Allowance
Net of Allowance - After 1 to 5 Years	16	19
Net of Allowance	16	19
Gross unrecognized gains
Gross unrealized gains - After 1 to 5 years	1	0
Gross Unrealized Gains	1	0
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	17	19
Fair value	$ 17	$ 19
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	$ 5,959	$ 5,959
Amortized cost	5,959	5,959
Book Value
Book Value - After 10 years	5,959	5,959
Book Value	5,959	5,959
Allowance for credit losses
Allowance for credit losses - After 10 years	0	0
Allowance for credit losses	0	0
Net of Allowance
Net of Allowance - After 10 Years	5,959	5,959
Net of Allowance	5,959	5,959
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	5,959	5,959
Fair value	$ 5,959	$ 5,959
Weighted Average Yield
Weighted average yield - After 10 years	6.33%	6.33%
Weighted Average Yield	6.33%	6.33%