Parent Company Only Financial Information - Parent Only Financial Statements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Assets
Other assets	$ 764,902	$ 770,838
Total Assets	18,722,189	18,015,478	$ 17,595,636
Liabilities and Shareholders' Equity:
Subordinated notes	123,482	123,262
Junior subordinated debt securities	61,856	61,856
Shareholders' equity	1,661,847	1,492,268	1,741,311	$ 1,741,117
Total Liabilities and Shareholders' Equity	18,722,189	18,015,478
Expense:
Net Income	165,489	71,887	147,365
Operating Activities
Net income	165,489	71,887	147,365
Adjustments to reconcile net income to net cash provided by operating activities:
Other	1,192	(57,359)	(9,601)
Net cash from operating activities	196,887	296,516	348,771
Financing Activities
Common stock dividends	(56,653)	(56,679)	(58,085)
Repurchase and retirement of common stock	0	(24,604)	(61,799)
Net cash from financing activities	455,043	451,844	970,568
Net change in cash and cash equivalents	240,756	(1,532,042)	314,325
Trustmark Corp (Parent Company Only) [Member]
Assets
Investment in banks	1,770,392	1,602,169
Other assets	77,901	76,325
Total Assets	1,848,293	1,678,494
Liabilities and Shareholders' Equity:
Accrued expense	1,108	1,108
Subordinated notes	123,482	123,262
Junior subordinated debt securities	61,856	61,856
Shareholders' equity	1,661,847	1,492,268
Total Liabilities and Shareholders' Equity	1,848,293	1,678,494
Revenue:
Dividends received from banks	67,189	89,733	45,284
Earnings of subsidiaries over distributions	106,388	(11,269)	108,141
Other income	163	94	95
Total Revenue	173,740	78,558	153,520
Expense:
Other expense	8,251	6,671	6,155
Total Expense	8,251	6,671	6,155
Net Income	165,489	71,887	147,365
Operating Activities
Net income	165,489	71,887	147,365
Adjustments to reconcile net income to net cash provided by operating activities:
Net change in investment in subsidiaries	(106,388)	11,269	(108,141)
Other	(797)	(1,550)	(2,078)
Net cash from operating activities	58,304	81,606	37,146
Financing Activities
Common stock dividends	(56,653)	(56,679)	58,085
Repurchase and retirement of common stock	0	(24,604)	(61,799)
Net cash from financing activities	(56,653)	(81,283)	(119,884)
Net change in cash and cash equivalents	1,651	323	(82,738)
Cash and cash equivalents at beginning of year	75,860	75,537	158,275
Cash and cash equivalents at end of year	$ 77,511	$ 75,860	$ 75,537