Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Dec. 31, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Loss Contingencies [Line Items]
Unused commitments to extend credit		$ 5,472,000	$ 5,472,000	$ 5,238,000
Litigation settlement expense	[1]		100,750	0	$ 0
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Potential exposure to credit loss in the event of nonperformance		144,100	$ 144,100	222,500
Letters of credit, maturity term - maximum			3 years
Collateral held, fair value		15,400	$ 15,400	$ 124,600
Settlement Agreement [Member]
Loss Contingencies [Line Items]
One-time cash payment of legal settlement			$ 100,000
Litigation settlement expense		100,000
Legal fees		$ 750

[1] During 2021, Trustmark reclassified its credit loss expense on off-balance sheet credit exposures from noninterest expense to PCL, off-balance sheet credit exposures. Prior periods have been reclassified accordingly.