Debt Securities Held-to-maturity - Weighted average yield and contractual maturities of debt securities HTM (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
Amortized cost
Amortized cost	$ 9,156,996		$ 9,356,739
Book Value
Book Value	8,410,566		8,525,366
Allowance for credit losses
Allowance for credit losses	6,145		6,911
Net of Allowance
Net of Allowance	8,404,421		8,518,455
Gross unrecognized gains
Gross Unrealized Gains	3,312		4,918
Gross unrealized losses
Gross Unrealized Losses	132,783		83,177
Fair Value
Fair value	$ 8,274,950		$ 8,440,196
Weighted Average Yield
Weighted Average Yield	1.52%		1.55%
US Treasury Securities
Amortized cost
Amortized cost - Within 1 year	$ 598,603		$ 499,034
Amortized cost - After 1 to 5 year	7,056,531		6,147,568
Amortized cost - After 5 to 10 years	1,427,865		2,638,238
Amortized cost	9,082,999		9,284,840
Book Value
Book Value - within 1 year	598,603		499,034
Book Value - Within 1 to 5 years	6,471,438		5,640,767
Book Balue - After 5 to 10 years	1,266,528		2,313,666
Book Value	8,336,569		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	598,603		499,034
Net of Allowance - After 1 to 5 Years	6,471,438		5,640,767
Net of Allowance - After 5 to 10 Years	1,266,528		2,313,666
Net of Allowance	8,336,569		8,453,467
Gross unrecognized gains
Gross unrealized gains - Within 1 year	0		0
Gross unrealized gains - After 1 to 5 years	0		0
Gross unrealized gains - After 5 to 10 years	0		0
Gross Unrealized Gains	0		0
Gross unrealized losses
Gross unrealized losses - Within 1 year	8,926		6,203
Gross unrealized losses - After 1 to 5 years	106,735		59,806
Gross unrealized losses - After 5 to 10 years	14,050		14,857
Gross Unrealized Losses	129,711		80,866
Fair Value
Fair Value - within 1 year	589,677		492,831
Fair Value - After 1 to 5 years	6,364,703		5,580,961
Fair Value - After 5 to 10 years	1,252,478		2,298,809
Fair value	$ 8,206,858		$ 8,372,601
Weighted Average Yield
Weighted average yield - Within 1 Year	2.55%		2.83%
Weighted average yield - After 1 to 5 years	1.42%		1.49%
Weighted average yield - After 5 to 10 years	1.50%		1.41%
Weighted Average Yield	1.51%		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	20,282		19,105
Amortized cost - After 5 to 10 years	1,025		1,025
Amortized cost - After 10 years	40,434		41,261
Amortized cost	66,471		65,921
Book Value
Book Value - within 1 year	4,730		4,530
Book Value - Within 1 to 5 years	20,282		19,105
Book Balue - After 5 to 10 years	1,025		1,025
Book Value - After 10 years	40,434		41,261
Book Value	66,471		65,921
Allowance for credit losses
Allowance for credit losses - Within 1 Year	12		8
Allowance for credit losses - After 1 to 5 years	195		234
Allowance for credit losses - After 5 to 10 years	33		34
Allowance for credit losses - After 10 years	5,905		6,635
Allowance for credit losses	6,145	$ 6,792	6,911	$ 7,495	$ 7,844	$ 8,096
Net of Allowance
Net of Allowance - Within 1 Year	4,718		4,522
Net of Allowance - After 1 to 5 Years	20,087		18,871
Net of Allowance - After 5 to 10 Years	992		991
Net of Allowance - After 10 Years	34,529		34,626
Net of Allowance	60,326		59,010
Gross unrecognized gains
Gross unrealized gains - Within 1 year	12		5
Gross unrealized gains - After 1 to 5 years	95		150
Gross unrealized gains - After 5 to 10 years	33		34
Gross unrealized gains - After 10 years	3,172		4,729
Gross Unrealized Gains	3,312		4,918
Gross unrealized losses
Gross unrealized losses - Within 1 year	5		0
Gross unrealized losses - After 1 to 5 years	156		82
Gross unrealized losses - After 5 to 10 years	0		0
Gross unrealized losses - After 10 years	2,801		2,229
Gross Unrealized Losses	2,962		2,311
Fair Value
Fair Value - within 1 year	4,725		4,527
Fair Value - After 1 to 5 years	20,026		18,939
Fair Value - After 5 to 10 years	1,025		1,025
Fair Value - After 10 years	34,900		37,126
Fair value	$ 60,676		$ 61,617
Weighted Average Yield
Weighted average yield - Within 1 Year	6.14%		6.08%
Weighted average yield - After 1 to 5 years	3.74%		4.24%
Weighted average yield - After 5 to 10 years	5.80%		5.80%
Weighted average yield - After 10 years	1.41%		1.40%
Weighted Average Yield	2.53%		2.61%
Collateralized Mortgage Obligations - Federal agencies
Amortized cost
Amortized cost - Within 1 year	$ 16
Amortized cost - After 1 to 5 year			$ 19
Amortized cost - After 10 years	1,550
Amortized cost	1,566		19
Book Value
Book Value - within 1 year	16
Book Value - Within 1 to 5 years			19
Book Value - After 10 years	1,550
Book Value	1,566		19
Allowance for credit losses
Allowance for credit losses - Within 1 Year	0
Allowance for credit losses - After 1 to 5 years			0
Allowance for credit losses - After 10 years	0
Allowance for credit losses	0		0
Net of Allowance
Net of Allowance - Within 1 Year	16
Net of Allowance - After 1 to 5 Years			19
Net of Allowance - After 10 Years	1,550
Net of Allowance	1,566		19
Gross unrecognized gains
Gross unrealized gains - Within 1 year	0
Gross unrealized gains - After 1 to 5 years			0
Gross unrealized gains - After 10 years	0
Gross Unrealized Gains	0		0
Gross unrealized losses
Gross unrealized losses - Within 1 year	0
Gross unrealized losses - After 1 to 5 years			0
Gross unrealized losses - After 10 years	110
Gross Unrealized Losses	110		0
Fair Value
Fair Value - within 1 year	16
Fair Value - After 1 to 5 years			19
Fair Value - After 10 years	1,440
Fair value	$ 1,456		$ 19
Weighted Average Yield
Weighted average yield - Within 1 Year	6.44%
Weighted average yield - After 1 to 5 years			6.44%
Weighted average yield - After 10 years	2.87%
Weighted Average Yield	2.91%		6.44%
Securities in wholly owned statutory business trusts
Amortized cost
Amortized cost - After 10 years	$ 5,960		$ 5,959
Amortized cost	5,960		5,959
Book Value
Book Value - After 10 years	5,960		5,959
Book Value	5,960		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	5,960		5,959
Net of Allowance	5,960		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	5,960		5,959
Fair value	$ 5,960		$ 5,959
Weighted Average Yield
Weighted average yield - After 10 years	6.33%		6.33%
Weighted Average Yield	6.33%		6.33%