Securities Available for Sale and Held to Maturity (Tables)

12 Months Ended

Dec. 31, 2024

Investments, Debt and Equity Securities [Abstract]

Amortized Cost and Estimated Fair Value of Available for Sale and Held to Maturity Securities

The following tables are a summary of the amortized cost and estimated fair value of securities available for sale and held to maturity at December 31, 2024 and 2023 ($ in thousands):

	Securities Available for Sale									Securities Held to Maturity
			Gross		Gross			Estimated				Gross		Gross			Estimated
	Amortized		Unrealized		Unrealized			Fair		Amortized		Unrealized		Unrealized			Fair
December 31, 2024	Cost		Gains		Losses			Value		Cost		Gains		Losses			Value
U.S. Treasury securities	$	203,524	$	548	$	(1,403	)	$	202,669	$	29,842	$	1	$	(522	)	$	29,321
U.S. Government agency obligations		41,194		—		(2,387	)		38,807		—		—		—			—
Mortgage-backed securities
Residential mortgage pass-through securities
Guaranteed by GNMA		31,365		3		(2,957	)		28,411		16,218		—		(844	)		15,374
Issued by FNMA and FHLMC		1,091,122		1,610		(22,194	)		1,070,538		423,372		94		(23,853	)		399,613
Other residential mortgage-backed securities
Issued or guaranteed by FNMA,    FHLMC or GNMA		—		—		—			—		123,685		—		(8,004	)		115,681
Commercial mortgage-backed securities
Issued or guaranteed by FNMA,    FHLMC or GNMA		352,332		827		(1,050	)		352,109		742,268		3		(43,153	)		699,118
Total	$	1,719,537	$	2,988	$	(29,991	)	$	1,692,534	$	1,335,385	$	98	$	(76,376	)	$	1,259,107
December 31, 2023
U.S. Treasury securities	$	396,179	$	—	$	(23,811	)	$	372,368	$	29,068	$	—	$	(26	)	$	29,042
U.S. Government agency obligations		6,207		1		(416	)		5,792		—		—		—			—
Obligations of states and political subdivisions		—		—		—			—		340		—		—			340
Mortgage-backed securities
Residential mortgage pass-through securities
Guaranteed by GNMA		25,744		4		(2,613	)		23,135		13,005		—		(497	)		12,508
Issued by FNMA and FHLMC		1,338,256		32		(161,490	)		1,176,798		469,593		—		(18,205	)		451,388
Other residential mortgage-backed securities
Issued or guaranteed by FNMA,    FHLMC or GNMA		92,076		—		(6,002	)		86,074		154,466		—		(10,113	)		144,353
Commercial mortgage-backed securities
Issued or guaranteed by FNMA,    FHLMC or GNMA		100,545		—		(1,834	)		98,711		759,807		51		(41,985	)		717,873
Total	$	1,959,007	$	37	$	(196,166	)	$	1,762,878	$	1,426,279	$	51	$	(70,826	)	$	1,355,504

Securities Held to Maturity by Credit Rating, as Determined by Moody's

The following table presents the amortized cost of Trustmark’s securities held to maturity by credit rating, as determined by Moody’s, at December 31, 2024 and 2023 ($ in thousands):

	December 31,
	2024		2023
Aaa	$	1,335,385	$	1,425,939
Not Rated (1)		—		340
Total	$	1,335,385	$	1,426,279

(1)Not rated securities primarily consist of Mississippi municipal general obligations.

Securities with Gross Unrealized Losses, Segregated by Length of Impairment

The tables below include securities with gross unrealized losses for which an ACL has not been recorded and segregated by length of impairment at December 31, 2024 and 2023 ($ in thousands):

	Less than 12 Months					12 Months or More					Total
			Gross					Gross					Gross
	Estimated		Unrealized			Estimated		Unrealized			Estimated		Unrealized
December 31, 2024	Fair Value		Losses			Fair Value		Losses			Fair Value		Losses
U.S. Treasury securities	$	123,277	$	(1,925	)	$	—	$	—		$	123,277	$	(1,925	)
U.S. Government agency obligations		38,807		(2,387	)		—		—			38,807		(2,387	)
Mortgage-backed securities
Residential mortgage pass-through    securities
Guaranteed by GNMA		15,802		(293	)		27,803		(3,508	)		43,605		(3,801	)
Issued by FNMA and FHLMC		981,747		(13,848	)		237,487		(32,199	)		1,219,234		(46,047	)
Other residential mortgage-backed    securities
Issued or guaranteed by FNMA,    FHLMC or GNMA		—		—			115,681		(8,004	)		115,681		(8,004	)
Commercial mortgage-backed    securities
Issued or guaranteed by FNMA,    FHLMC or GNMA		164,971		(536	)		767,566		(43,667	)		932,537		(44,203	)
Total	$	1,324,604	$	(18,989	)	$	1,148,537	$	(87,378	)	$	2,473,141	$	(106,367	)
December 31, 2023
U.S. Treasury securities	$	29,042	$	(26	)	$	372,368	$	(23,811	)	$	401,410	$	(23,837	)
U.S. Government agency obligations		—		—			5,791		(416	)		5,791		(416	)
Mortgage-backed securities
Residential mortgage pass-through    securities
Guaranteed by GNMA		9,381		(172	)		25,967		(2,938	)		35,348		(3,110	)
Issued by FNMA and FHLMC		309,466		(3,274	)		1,311,865		(176,421	)		1,621,331		(179,695	)
Other residential mortgage-backed    securities
Issued or guaranteed by FNMA,    FHLMC or GNMA		—		—			230,368		(16,115	)		230,368		(16,115	)
Commercial mortgage-backed    securities
Issued or guaranteed by FNMA,    FHLMC or GNMA		1,656		(13	)		812,520		(43,806	)		814,176		(43,819	)
Total	$	349,545	$	(3,485	)	$	2,758,879	$	(263,507	)	$	3,108,424	$	(266,992	)

Gains and Losses as a Result of Calls and Disposition of Securities

For the periods presented, gross realized gains or losses as a result of calls and dispositions of securities, as well as any associated proceeds, were as follows ($ in thousands):

	Years Ended December 31,
Available for Sale	2024			2023			2022
Proceeds from calls and sales of securities	$	1,378,272		$	4,796		$	—
Gross realized gains		—			47			—
Gross realized losses		(182,792	)		(8	)		—

Contractual Maturities of Available for Sale and Held to Maturity Securities

The amortized cost and estimated fair value of securities available for sale and held to maturity at December 31, 2024, by contractual maturity, are shown below ($ in thousands). Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.

	Securities				Securities
	Available for Sale				Held to Maturity
	Amortized		Estimated		Amortized		Estimated
	Cost		Fair Value		Cost		Fair Value
Due in one year or less	$	45,777	$	45,976	$	—	$	—
Due after one year through five years		62,388		62,737		29,842		29,321
Due after five years through ten years		136,553		132,763		—		—
		244,718		241,476		29,842		29,321
Mortgage-backed securities		1,474,819		1,451,058		1,305,543		1,229,786
Total	$	1,719,537	$	1,692,534	$	1,335,385	$	1,259,107