Securities Available for Sale and Held to Maturity (Tables)

9 Months Ended

Sep. 30, 2023

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 September 30, 2023 and December 31, 2022 ($ in thousands):

	Securities Available for Sale									Securities Held to Maturity
September 30, 2023	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. Treasury securities	$	396,070	$	—	$	(32,594	)	$	363,476	$	28,872	$	1	$	(987	)	$	27,886
U.S. Government agency    obligations		7,309		—		(529	)		6,780		—		—		—			—
Obligations of states and    political subdivisions		4,771		—		(129	)		4,642		341		—		—			341
Mortgage-backed securities
Residential mortgage pass-    through securities
Guaranteed by GNMA		27,009		—		(4,128	)		22,881		13,090		—		(1,083	)		12,007
Issued by FNMA and    FHLMC		1,386,253		3		(214,735	)		1,171,521		474,003		1		(36,482	)		437,522
Other residential mortgage-    backed securities
Issued or guaranteed by    FNMA, FHLMC or    GNMA		98,610		—		(8,208	)		90,402		162,031		—		(14,474	)		147,557
Commercial mortgage-backed    securities
Issued or guaranteed by    FNMA, FHLMC or    GNMA		108,841		—		(2,369	)		106,472		759,950		1		(72,393	)		687,558
Total	$	2,028,863	$	3	$	(262,692	)	$	1,766,174	$	1,438,287	$	3	$	(125,419	)	$	1,312,871

	Securities Available for Sale									Securities Held to Maturity
December 31, 2022	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. Treasury Securities	$	425,719	$	308	$	(34,514	)	$	391,513	$	28,295	$	—	$	(115	)	$	28,180
U.S. Government agency    obligations		8,297		—		(531	)		7,766		—		—		—			—
Obligations of states and    political subdivisions		4,820		53		(11	)		4,862		4,510		3		(3	)		4,510
Mortgage-backed securities
Residential mortgage pass-    through securities
Guaranteed by GNMA		30,534		7		(3,444	)		27,097		4,442		—		(395	)		4,047
Issued by FNMA and    FHLMC		1,541,570		12		(196,119	)		1,345,463		509,311		—		(19,586	)		489,725
Other residential mortgage-    backed securities
Issued or guaranteed by    FNMA, FHLMC or    GNMA		123,755		—		(8,615	)		115,140		188,201		—		(13,826	)		174,375
Commercial mortgage-backed    securities
Issued or guaranteed by    FNMA, FHLMC or    GNMA		136,014		—		(3,773	)		132,241		759,755		34		(54,037	)		705,752
Total	$	2,270,709	$	380	$	(247,007	)	$	2,024,082	$	1,494,514	$	37	$	(87,962	)	$	1,406,589

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 September 30, 2023 and December 31, 2022 ($ in thousands):

	September 30, 2023		December 31, 2022
Aaa	$	1,437,946	$	1,490,004
Aa1 to Aa3		—		3,001
Not Rated (1)		341		1,509
Total	$	1,438,287	$	1,494,514

(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 allowance for credit losses has not been recorded segregated by length of impairment at September 30, 2023 and December 31, 2022 ($ in thousands):

	Less than 12 Months					12 Months or More					Total
September 30, 2023	Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses
U.S. Treasury securities	$	70,893	$	(2,494	)	$	320,470	$	(31,087	)	$	391,363	$	(33,581	)
U.S. Government agency obligations		—		—			6,742		(529	)		6,742		(529	)
Obligations of states and political subdivisions		4,642		(129	)		—		—			4,642		(129	)
Mortgage-backed securities
Residential mortgage pass-through    securities
Guaranteed by GNMA		9,998		(652	)		24,768		(4,559	)		34,766		(5,211	)
Issued by FNMA and FHLMC		300,761		(15,670	)		1,304,006		(235,547	)		1,604,767		(251,217	)
Other residential mortgage-backed    securities
Issued or guaranteed by FNMA,    FHLMC or GNMA		8,264		(314	)		229,599		(22,368	)		237,863		(22,682	)
Commercial mortgage-backed securities
Issued or guaranteed by FNMA,    FHLMC or GNMA		491,986		(44,734	)		302,044		(30,028	)		794,030		(74,762	)
Total	$	886,544	$	(63,993	)	$	2,187,629	$	(324,118	)	$	3,074,173	$	(388,111	)
December 31, 2022
U.S. Treasury Securities	$	161,298	$	(5,655	)	$	258,087	$	(28,974	)	$	419,385	$	(34,629	)
U.S. Government agency obligations		1,828		(184	)		5,938		(347	)		7,766		(531	)
Obligations of states and political subdivisions		1,017		(11	)		3,664		(3	)		4,681		(14	)
Mortgage-backed securities
Residential mortgage pass-through    securities
Guaranteed by GNMA		27,223		(3,270	)		3,577		(569	)		30,800		(3,839	)
Issued by FNMA and FHLMC		770,865		(41,807	)		1,062,041		(173,898	)		1,832,906		(215,705	)
Other residential mortgage-backed    securities
Issued or guaranteed by FNMA,    FHLMC or GNMA		281,964		(21,452	)		7,235		(989	)		289,199		(22,441	)
Commercial mortgage-backed securities
Issued or guaranteed by FNMA,    FHLMC or GNMA		833,970		(57,742	)		1,644		(68	)		835,614		(57,810	)
Total	$	2,078,165	$	(130,121	)	$	1,342,186	$	(204,848	)	$	3,420,351	$	(334,969	)

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 September 30, 2023, 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 Available for Sale				Securities Held to Maturity
	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Due in one year or less	$	51,084	$	49,189	$	341	$	341
Due after one year through five years		346,269		315,552		28,872		27,886
Due after five years through ten years		6,188		5,794		—		—
Due after ten years		4,609		4,363		—		—
		408,150		374,898		29,213		28,227
Mortgage-backed securities		1,620,713		1,391,276		1,409,074		1,284,644
Total	$	2,028,863	$	1,766,174	$	1,438,287	$	1,312,871