Defined Benefit and Other Postretirement Benefits - Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net periodic benefit cost [Abstract]
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax	Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax	Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax	Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax	Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Immediate Recognition of Actuarial Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax	Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax	Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax
Trustmark Capital Accumulation Plan [Member] | Trustmark Corporation Pension Plan for Certain Employees of Acquired Financial Institutions [Member]
Net periodic benefit cost [Abstract]
Service cost	$ 52	$ 115	$ 252
Interest cost	292	192	173
Expected return on plan assets	(107)	(121)	(130)
Recognized net loss due to lump sum settlements	25	0	183
Recognized net actuarial loss	0	224	594
Net periodic benefit cost	262	410	1,072
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)	9	(1,699)	(1,136)
Total recognized in net periodic benefit cost and other comprehensive income (loss)	$ 271	$ (1,289)	$ (64)
Weighted-average assumptions as of end of year [Abstract]
Discount rate for benefit obligation	4.67%	4.88%	2.41%
Discount rate for net periodic benefit cost	4.88%	2.41%	1.95%
Expected long-term return on plan assets	5.00%	5.00%	5.00%
Supplemental Retirement Plan [Member]
Net periodic benefit cost [Abstract]
Service cost	$ 69	$ 71	$ 75
Interest cost	2,013	1,278	1,125
Amortization of prior service cost	111	111	111
Recognized net actuarial loss	284	986	1,192
Net periodic benefit cost	2,477	2,446	2,503
Other changes in plan assets and benefit obligation recognized in other comprehensive income (loss), before taxes:
Net (gain) loss	479	(10,181)	(3,549)
Amortization of prior service cost	(111)	(111)	(111)
Net loss - Total recognized in other comprehensive income (loss)	368	(10,292)	(3,660)
Total recognized in net periodic benefit cost and other comprehensive income (loss)	$ 2,845	$ (7,846)	$ (1,157)
Weighted-average assumptions as of end of year [Abstract]
Discount rate for benefit obligation	4.67%	4.88%	2.41%
Discount rate for net periodic benefit cost	4.88%	2.41%	1.95%