Defined Benefit and Other Postretirement Benefits - Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
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	$ 115	$ 252	$ 254
Interest cost	192	173	241
Expected return on plan assets	(121)	(130)	(154)
Recognized net loss due to lump sum settlements	0	183	119
Recognized net actuarial loss	224	594	326
Net periodic benefit cost	410	1,072	786
Other changes in plan assets and benefit obligation recognized in other comprehensive income (loss), before taxes:
Net (gain) loss - Total recognized in other comprehensive income (loss)	(1,699)	(1,136)	671
Total recognized in net periodic benefit cost and other comprehensive income (loss)	$ 1,289	$ (64)	$ 1,457
Weighted-average assumptions as of end of year [Abstract]
Discount rate for benefit obligation	4.88%	2.41%	1.95%
Discount rate for net periodic benefit cost	2.41%	1.95%	2.84%
Expected long-term return on plan assets	5.00%	5.00%	5.00%
Supplemental Retirement Plan [Member]
Net periodic benefit cost [Abstract]
Service cost	$ 71	$ 75	$ 77
Interest cost	1,278	1,125	1,576
Amortization of prior service cost	111	111	150
Recognized net actuarial loss	986	1,192	957
Net periodic benefit cost	2,446	2,503	2,760
Other changes in plan assets and benefit obligation recognized in other comprehensive income (loss), before taxes:
Net (gain) loss	(10,181)	(3,549)	3,211
Amortization of prior service cost	(111)	(111)	(150)
Net (gain) loss - Total recognized in other comprehensive income (loss)	10,292	(3,660)	3,061
Total recognized in net periodic benefit cost and other comprehensive income (loss)	$ 7,846	$ (1,157)	$ 5,821
Weighted-average assumptions as of end of year [Abstract]
Discount rate for benefit obligation	4.88%	2.41%	1.95%
Discount rate for net periodic benefit cost	2.41%	1.95%	2.84%