Investment Securities (Tables)

3 Months Ended

Mar. 31, 2024

Summary of Amortized Cost and Estimated Fair Values of Available for Sale Securities

The amortized cost, estimated fair values, and allowance for credit losses of securities available for sale are summarized as follows.

	March 31, 2024
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Allowance For Credit Losses		Estimated Fair Value
U.S. Treasury securities and obligations of U.S. Government corporations and agencies	$	439,648	$	45	$	5,582	$	0	$	434,111
State and political subdivisions		611,240		14		82,953		0		528,301
Residential mortgage-backed securities
Agency		1,183,484		4		176,629		0		1,006,859
Non-agency		83,698		0		8,394		0		75,304
Commercial mortgage-backed securities
Agency		507,889		13		54,189		0		453,713
Asset-backed securities		837,064		75		6,209		0		830,930
Single issue trust preferred securities		16,390		0		1,057		0		15,333
Other corporate securities		301,199		0		31,775		0		269,424
Total	$	3,980,612	$	151	$	366,788	$	0	$	3,613,975

	December 31, 2023
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Allowance For Credit Losses		Estimated Fair Value
U.S. Treasury securities and obligations of U.S. Government corporations and agencies	$	492,638	$	4	$	7,692	$	0	$	484,950
State and political subdivisions		613,588		11		79,768		0		533,831
Residential mortgage-backed securities
Agency		1,217,744		7		167,810		0		1,049,941
Non-agency		100,364		0		9,753		0		90,611
Commercial mortgage-backed securities
Agency		511,560		13		52,275		0		459,298
Asset-backed securities		872,048		44		11,454		0		860,638
Single issue trust preferred securities		16,380		0		1,239		0		15,141
Other corporate securities		325,573		0		33,606		0		291,967
Total	$	4,149,895	$	79	$	363,597	$	0	$	3,786,377

Summary of Securities Available for Sale in an Unrealized Loss Position

The following is a summary of securities available for sale which were in an unrealized loss position at March 31, 2024 and December 31, 2023.

	Less than 12 months				12 months or longer				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
March 31, 2024
U.S. Treasury securities and obligations of U.S. Government corporations and agencies	$	3,561	$	12	$	178,459	$	5,570	$	182,020	$	5,582
State and political subdivisions		4,089		196		512,438		82,757		516,527		82,953
Residential mortgage-backed securities
Agency		6,791		95		999,081		176,534		1,005,872		176,629
Non-agency		0		0		72,662		8,394		72,662		8,394
Commercial mortgage-backed securities
Agency		0		0		451,366		54,189		451,366		54,189
Asset-backed securities		79,624		175		656,712		6,034		736,336		6,209
Single issue trust preferred securities		0		0		15,333		1,057		15,333		1,057
Other corporate securities		2,422		78		261,891		31,697		264,313		31,775
Total	$	96,487	$	556	$	3,147,942	$	366,232	$	3,244,429	$	366,788

	Less than 12 months				12 months or longer				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
December 31, 2023
U.S. Treasury securities and obligations of U.S. Government corporations and agencies	$	4,625	$	11	$	477,615	$	7,681	$	482,240	$	7,692
State and political subdivisions		2,050		193		517,186		79,575		519,236		79,768
Residential mortgage-backed securities
Agency		9,755		51		1,038,632		167,759		1,048,387		167,810
Non-agency		8,964		101		81,647		9,652		90,611		9,753
Commercial mortgage-backed securities
Agency		0		0		456,866		52,275		456,866		52,275
Asset-backed securities		15,866		216		829,778		11,238		845,644		11,454
Single issue trust preferred securities		2,922		182		12,219		1,057		15,141		1,239
Other corporate securities		0		0		274,308		33,606		274,308		33,606
Total	$	44,182	$	754	$	3,688,251	$	362,843	$	3,732,433	$	363,597

Summary of Gains or Losses on Proceeds from Maturities, Sales and Calls of Available for Sale Securities by Specific Identification Method

	Three Months Ended March 31
	2024		2023
Proceeds from maturities, sales and calls	$	416,410	$	185,748
Gross realized gains		0		0
Gross realized losses		0		420

Summary of Maturities of Debt Securities Held to Maturity by Amortized Cost and Estimated Fair Value

	March 31, 2024				December 31, 2023
	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Due in one year or less	$	431,832	$	429,801	$	497,555	$	493,651
Due after one year through five years		483,693		447,504		448,020		416,436
Due after five years through ten years		853,498		754,469		852,698		751,780
Due after ten years		2,211,589		1,982,201		2,351,622		2,124,510
Total	$	3,980,612	$	3,613,975	$	4,149,895	$	3,786,377

Summary of Equity Securities

	Three Months Ended March 31
	2024			2023
Unrealized gains recognized during the period on equity securities still held at period end	$	0			82
Unrealized losses recognized during the period on equity securities still held at period end		(99	)		(67	)
Net (losses) gains recognized during the period	$	(99)		$	15