Defined Benefit and Other Postretirement Benefits - Plan Benefit Obligation, Plan Assets and Funded Status of the Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Trustmark Capital Accumulation Plan [Member] | Trustmark Corporation Pension Plan for Certain Employees of Acquired Financial Institutions [Member]
Change in benefit obligation [Roll Forward]
Benefit obligation, beginning of year	$ 5,923	$ 6,907
Service cost	40	52	$ 115
Interest cost	246	292	192
Actuarial (gain) loss	(214)	164
Benefits paid	(464)	(1,492)
Benefit obligation, end of year	5,531	5,923	6,907
Change in plan assets [ Roll Forward]
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	2,907
Funded status at end of year - net liability	(2,846)	(3,520)
Amounts recognized in accumulated other comprehensive loss [Abstract]
Net (gain) loss - amount recognized	(601)	(262)
Actuarial (gain) loss included in benefit obligation:
Change in discount rate	(344)	124
Change in mortality table	0	(38)
Other	130	78
Actuarial (gain) loss	(214)	164
Supplemental Retirement Plan [Member]
Change in benefit obligation [Roll Forward]
Benefit obligation, beginning of year	41,619	43,201
Service cost	45	69	71
Interest cost	1,851	2,013	1,278
Actuarial (gain) loss	(1,009)	763
Benefits paid	(4,344)	(4,427)
Benefit obligation, end of year	38,162	41,619	$ 43,201
Change in plan assets [ Roll Forward]
Employer contributions	4,344	4,427
Benefit payments	(4,344)	(4,427)
Funded status at end of year - net liability	(38,162)	(41,619)
Amounts recognized in accumulated other comprehensive loss [Abstract]
Net (gain) loss - amount recognized	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	0	(308)
Other	785	422
Actuarial (gain) loss	$ (1,009)	$ 763