Debt Securities (Tables)

3 Months Ended

Mar. 31, 2025

Investments, Debt and Equity Securities [Abstract]

Amortized Cost, Unrealized Gains And Losses, And Fair Value Of Investment Securities

The following tables present the amortized cost, unrealized gains, unrealized losses, and approximate fair values of debt securities as of the dates presented:


	March 31, 2025
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Available for sale:
U.S. Treasury and agencies	$	1,426,351	$	4,536	$	(57,854)	$	1,373,033
Obligations of states and political subdivisions	1,051,171		2,735		(33,064)		1,020,842
Mortgage-backed securities and collateralized mortgage obligations	6,204,692		21,727		(391,489)		5,834,930
Total available for sale securities	$	8,682,214	$	28,998	$	(482,407)	$	8,228,805
Held to maturity:
Mortgage-backed securities and collateralized mortgage obligations	$	2,057	$	588	$	—	$	2,645
Total held to maturity securities	$	2,057	$	588	$	—	$	2,645


	December 31, 2024
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Available for sale:
U.S. Treasury and agencies	$	1,495,542	$	1,092	$	(73,847)	$	1,422,787
Obligations of states and political subdivisions	1,055,535		2,779		(32,261)		1,026,053
Mortgage-backed securities and collateralized mortgage obligations	6,307,252		3,937		(485,414)		5,825,775
Total available for sale securities	$	8,858,329	$	7,808	$	(591,522)	$	8,274,615
Held to maturity:
Mortgage-backed securities and collateralized mortgage obligations	$	2,101	$	602	$	—	$	2,703
Total held to maturity securities	$	2,101	$	602	$	—	$	2,703

Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value

The following tables present debt securities that were in an unrealized loss position as of the dates presented, based on the length of time individual securities have been in an unrealized loss position:


	March 31, 2025
	Less than 12 Months				12 Months or Longer				Total
(in thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Available for sale:
U.S. Treasury and agencies	$	99,739	$	(1,010)	$	762,609	$	(56,844)	$	862,348	$	(57,854)
Obligations of states and political subdivisions	485,272		(9,118)		269,731		(23,946)		755,003		(33,064)
Mortgage-backed securities and collateralized mortgage obligations	1,795,282		(25,616)		1,837,923		(365,873)		3,633,205		(391,489)
Total temporarily impaired securities	$	2,380,293	$	(35,744)	$	2,870,263	$	(446,663)	$	5,250,556	$	(482,407)


	December 31, 2024
	Less than 12 Months				12 Months or Longer				Total
(in thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Available for sale:
U.S. Treasury and agencies	$	185,042	$	(2,770)	$	794,521	$	(71,077)	$	979,563	$	(73,847)
Obligations of states and political subdivisions	539,440		(8,036)		224,973		(24,225)		764,413		(32,261)
Mortgage-backed securities and collateralized mortgage obligations	3,398,609		(78,817)		1,830,720		(406,597)		5,229,329		(485,414)

Total temporarily impaired securities	$	4,123,091	$	(89,623)	$	2,850,214	$	(501,899)	$	6,973,305	$	(591,522)

Schedule Of Maturities Of Investment Securities

The following table presents the contractual maturities of debt securities as of March 31, 2025:


	Available For Sale				Held To Maturity
(in thousands)	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due within one year	$	263,071	$	263,740	$	—	$	—
Due after one year through five years	2,752,447		2,720,313		2		2
Due after five years through ten years	1,522,998		1,467,666		1		554
Due after ten years	4,143,698		3,777,086		2,054		2,089
Total debt securities	$	8,682,214	$	8,228,805	$	2,057	$	2,645