Defined Benefit and Other Postretirement Benefits (Tables)

12 Months Ended

Dec. 31, 2024

Trustmark Capital Accumulation Plan [Member]

Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]

Plan Benefit Obligation, Plan Assets and Funded Status of the Plan

The following tables present information regarding the benefit obligation, plan assets, funded status, amounts recognized in accumulated other comprehensive loss, net periodic benefit cost and other statistical disclosures for the Continuing Plan for the periods presented ($ in thousands):

	December 31,
	2024			2023
Change in benefit obligation:
Benefit obligation, beginning of year	$	5,923		$	6,907
Service cost		40			52
Interest cost		246			292
Actuarial (gain) loss		(214	)		164
Benefits paid		(464	)		(1,492	)
Benefit obligation, end of year	$	5,531		$	5,923
Change in plan assets:
Fair value of plan assets, beginning of year	$	2,403		$	2,907
Actual return on plan assets		233			237
Employer contributions		513			751
Benefit payments		(464	)		(1,492	)
Fair value of plan assets, end of year	$	2,685		$	2,403
Funded status at end of year - net liability	$	(2,846	)	$	(3,520	)
Amounts recognized in accumulated other comprehensive loss:
Net (gain) loss - amount recognized	$	(601	)	$	(262	)
Actuarial (gain) loss included in benefit obligation:
Change in discount rate	$	(344	)	$	124
Change in mortality table		—			(38	)
Other		130			78
Actuarial (gain) loss	$	(214	)	$	164

Net Periodic Benefit Cost

	Years Ended December 31,
	2024			2023			2022
Net periodic benefit cost:
Service cost	$	40		$	52		$	115
Interest cost		246			292			192
Expected return on plan assets		(96	)		(107	)		(121	)
Recognized net (gain) loss due to lump sum settlements		(13	)		25			—
Recognized net actuarial loss		—			—			224
Net periodic benefit cost	$	177		$	262		$	410
Other changes in plan assets and benefit obligation recognized in other    comprehensive income (loss), before taxes:
Net loss - Total recognized in other comprehensive income (loss)	$	(339	)	$	9		$	(1,699	)
Total recognized in net periodic benefit cost and other comprehensive    income (loss)	$	(162	)	$	271		$	(1,289	)
Weighted-average assumptions as of end of year:
Discount rate for benefit obligation		5.30	%		4.67	%		4.88	%
Discount rate for net periodic benefit cost		4.67	%		4.88	%		2.41	%
Expected long-term return on plan assets		5.00	%		5.00	%		5.00	%

Weighted-Average Asset Allocation

The weighted-average asset allocations by asset category are presented below for the Continuing Plan at December 31, 2024 and 2023.

	December 31,
	2024			2023
Money market fund		2.0	%		27.0	%
Exchange traded funds:
Equity securities		33.0	%		36.0	%
Fixed income		59.0	%		28.0	%
International		6.0	%		9.0	%
Total		100.0	%		100.0	%

Plan Assets Measured at Fair Value

The following tables set forth by level, within the fair value hierarchy, the Continuing Plan’s assets measured at fair value at December 31, 2024 and 2023 ($ in thousands):

	December 31, 2024
	Total		Level 1		Level 2		Level 3
Money market fund	$	55	$	55	$	—	$	—
Exchange traded funds:
Equity securities		874		874		—		—
Fixed income		1,600		1,600		—		—
International		156		156		—		—
Total assets at fair value	$	2,685	$	2,685	$	—	$	—

	December 31, 2023
	Total		Level 1		Level 2		Level 3
Money market fund	$	643	$	643	$	—	$	—
Exchange traded funds:
Equity securities		861		861		—		—
Fixed income		690		690		—		—
International		209		209		—		—
Total assets at fair value	$	2,403	$	2,403	$	—	$	—

Estimated Future Benefit Payments and Other Disclosures

The following table presents the expected benefit payments, which reflect expected future service, for the Continuing Plan ($ in thousands):

Year	Amount
2025	$	693
2026		762
2027		961
2028		535
2029		414
2030 - 2034		1,575

Supplemental Retirement Plan [Member]

Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]

Plan Benefit Obligation, Plan Assets and Funded Status of the Plan

The following tables present information regarding the benefit obligation, plan assets, funded status, amounts recognized in accumulated other comprehensive loss, net periodic benefit cost and other statistical disclosures for Trustmark’s nonqualified supplemental retirement plans for the periods presented ($ in thousands):

	December 31,
	2024			2023
Change in benefit obligation:
Benefit obligation, beginning of year	$	41,619		$	43,201
Service cost		45			69
Interest cost		1,851			2,013
Actuarial (gain) loss		(1,009	)		763
Benefits paid		(4,344	)		(4,427	)
Benefit obligation, end of year	$	38,162		$	41,619
Change in plan assets:
Fair value of plan assets, beginning of year	$	—		$	—
Employer contributions		4,344			4,427
Benefit payments		(4,344	)		(4,427	)
Fair value of plan assets, end of year	$	—		$	—
Funded status at end of year - net liability	$	(38,162	)	$	(41,619	)
Amounts recognized in accumulated other comprehensive loss:
Net loss	$	6,880		$	8,235
Prior service cost		15			126
Amounts recognized	$	6,895		$	8,361
Actuarial (gain) loss included in benefit obligation:
Change in discount rate	$	(1,794	)	$	649
Change in mortality table		—			(308	)
Other		785			422
Actuarial (gain) loss	$	(1,009	)	$	763

Net Periodic Benefit Cost

	Years Ended December 31,
	2024			2023			2022
Net periodic benefit cost:
Service cost	$	45		$	69		$	71
Interest cost		1,851			2,013			1,278
Amortization of prior service cost		111			111			111
Recognized net actuarial loss		346			284			986
Net periodic benefit cost	$	2,353		$	2,477		$	2,446
Other changes in plan assets and benefit obligation recognized in other    comprehensive income (loss), before taxes:
Net (gain) loss	$	(1,355	)	$	479		$	(10,181	)
Amortization of prior service cost		(111	)		(111	)		(111	)
Total recognized in other comprehensive income (loss)	$	(1,466	)	$	368		$	(10,292	)
Total recognized in net periodic benefit cost and other comprehensive    income (loss)	$	887		$	2,845		$	(7,846	)
Weighted-average assumptions as of end of year:
Discount rate for benefit obligation		5.30	%		4.67	%		4.88	%
Discount rate for net periodic benefit cost		4.67	%		4.88	%		2.41	%

Estimated Future Benefit Payments and Other Disclosures

The following table presents the expected benefits payments for Trustmark’s supplemental retirement plans ($ in thousands):

Year	Amount
2025	$	3,885
2026		3,850
2027		3,673
2028		3,550
2029		3,545
2030 - 2034		15,563