Securities Available for Sale and Held to Maturity (Tables)

3 Months Ended

Mar. 31, 2021

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 March 31, 2021 and December 31, 2020 ($ in thousands):

	Securities Available for Sale									Securities Held to Maturity
March 31, 2021	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. Government agency obligations	$	17,778	$	48	$	(477	)	$	17,349	$	—	$	—	$	—		$	—
Obligations of states and political    subdivisions		5,182		616		—			5,798		26,554		158		(9	)		26,703
Mortgage-backed securities
Residential mortgage pass-through    securities
Guaranteed by GNMA		51,065		1,344		(3	)		52,406		7,268		349		—			7,617
Issued by FNMA and FHLMC		1,748,044		16,068		(14,968	)		1,749,144		61,855		1,941		—			63,796
Other residential mortgage-backed    securities
Issued or guaranteed by FNMA,    FHLMC or GNMA		337,616		8,283		(30	)		345,869		324,360		17,162		(46	)		341,476
Commercial mortgage-backed securities
Issued or guaranteed by FNMA,    FHLMC or GNMA		167,749		903		(1,542	)		167,110		73,701		2,003		—			75,704
Total	$	2,327,434	$	27,262	$	(17,020	)	$	2,337,676	$	493,738	$	21,613	$	(55	)	$	515,296
December 31, 2020
U.S. Government agency obligations	$	18,378	$	144	$	(481	)	$	18,041	$	—	$	—	$	—		$	—
Obligations of states and political    subdivisions		5,198		637		—			5,835		26,584		258		(3	)		26,839
Mortgage-backed securities
Residential mortgage pass-through    securities
Guaranteed by GNMA		55,193		1,672		(3	)		56,862		7,598		382		—			7,980
Issued by FNMA and FHLMC		1,421,861		20,768		(1,308	)		1,441,321		67,944		2,397		—			70,341
Other residential mortgage-backed    securities
Issued or guaranteed by FNMA,    FHLMC or GNMA		409,883		9,600		(46	)		419,437		360,361		19,678		(55	)		379,984
Commercial mortgage-backed securities
Issued or guaranteed by FNMA,    FHLMC or GNMA		49,260		1,068		(9	)		50,319		75,585		2,386		—			77,971
Total	$	1,959,773	$	33,889	$	(1,847	)	$	1,991,815	$	538,072	$	25,101	$	(58	)	$	563,115

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 March 31, 2021 and December 31, 2020 ($ in thousands):

	March 31, 2021		December 31, 2020
Aaa	$	467,185	$	511,488
Aa1 to Aa3		8,950		22,528
Not Rated (1)		17,603		4,056
Total	$	493,738	$	538,072

(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 and segregated by length of impairment at March 31, 2021 and December 31, 2020 ($ in thousands):

	Less than 12 Months					12 Months or More					Total
March 31, 2021	Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses
U.S. Government agency obligations	$	1,462	$	(10	)	$	10,986	$	(467	)	$	12,448	$	(477	)
Obligations of states and political subdivisions		5,009		(6	)		667		(3	)		5,676		(9	)
Mortgage-backed securities
Residential mortgage pass-through securities
Guaranteed by GNMA		1,120		(3	)		—		—			1,120		(3	)
Issued by FNMA and FHLMC		1,128,087		(14,968	)		—		—			1,128,087		(14,968	)
Other residential mortgage-backed securities
Issued or guaranteed by FNMA, FHLMC or    GNMA		21,995		(76	)		—		—			21,995		(76	)
Commercial mortgage-backed securities
Issued or guaranteed by FNMA, FHLMC or    GNMA		65,692		(1,533	)		654		(9	)		66,346		(1,542	)
Total	$	1,223,365	$	(16,596	)	$	12,307	$	(479	)	$	1,235,672	$	(17,075	)
December 31, 2020
U.S. Government agency obligations	$	—	$	—		$	11,167	$	(481	)	$	11,167	$	(481	)
Obligations of states and political subdivisions		—		—			667		(3	)		667		(3	)
Mortgage-backed securities
Residential mortgage pass-through securities
Guaranteed by GNMA		1,636		(3	)		—		—			1,636		(3	)
Issued by FNMA and FHLMC		324,905		(1,308	)		—		—			324,905		(1,308	)
Other residential mortgage-backed securities
Issued or guaranteed by FNMA, FHLMC or    GNMA		29,398		(101	)		—		—			29,398		(101	)
Commercial mortgage-backed securities
Issued or guaranteed by FNMA, FHLMC or    GNMA		—		—			659		(9	)		659		(9	)
Total	$	355,939	$	(1,412	)	$	12,493	$	(493	)	$	368,432	$	(1,905	)

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 March 31, 2021, 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	$	1,479	$	1,507	$	19,212	$	19,275
Due after one year through five years		1,510		1,554		7,342		7,428
Due after five years through ten years		1,967		1,928		—		—
Due after ten years		18,004		18,158		—		—
		22,960		23,147		26,554		26,703
Mortgage-backed securities		2,304,474		2,314,529		467,184		488,593
Total	$	2,327,434	$	2,337,676	$	493,738	$	515,296