LHFI and ACL, LHFI - Summary of Trustmark's Portfolio Segments, Loan Classes, Loan Pools and the ACL Methodology and Loss Drivers (Details)		12 Months Ended
		Dec. 31, 2025	Dec. 31, 2024
Loans Secured by Real Estate [Member] | Construction, Land Development and Other Land [Member] | 1 -4 Family Residential Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers	[1]	BBB 7-10 US CBI (1), National Unemployment	BBB 7-10 US CBI (1), National Unemployment
Loans Secured by Real Estate [Member] | Construction, Land Development and Other Land [Member] | Lots and Development [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		National HPI, National Unemployment	National HPI, National Unemployment
Loans Secured by Real Estate [Member] | Construction, Land Development and Other Land [Member] | Unimproved Land [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		National HPI, National Unemployment	National HPI, National Unemployment
Loans Secured by Real Estate [Member] | Construction, Land Development and Other Land [Member] | All Other Consumer [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		National HPI, National Unemployment	National HPI, National Unemployment
Loans Secured by Real Estate [Member] | Other Secured by 1-4 Family Residential Properties [Member] | All Other Consumer [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		National HPI, National Unemployment	National HPI, National Unemployment
Loans Secured by Real Estate [Member] | Other Secured by 1-4 Family Residential Properties [Member] | Consumer 1-4 Family - 1st Liens [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers	[2]	National HPI, Southern Unemployment (2)	National HPI, Southern Unemployment (2)
Loans Secured by Real Estate [Member] | Other Secured by 1-4 Family Residential Properties [Member] | Nonresidential Owner- Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		Southern Unemployment, National CRE Price Index	Southern Unemployment, National CRE Price Index
Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Nonresidential Owner- Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		Southern Unemployment, National CRE Price Index	Southern Unemployment, National CRE Price Index
Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Nonowner-Occupied - Hotel/Motel [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		National CRE Price Index, Southern Unemployment	National CRE Price Index, Southern Unemployment
Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Nonowner-Occupied - Office [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		National CRE Price Index, Southern Unemployment	National CRE Price Index, Southern Unemployment
Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Nonowner-Occupied- Retail [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		National CRE Price Index, Southern Unemployment	National CRE Price Index, Southern Unemployment
Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Nonowner-Occupied- Senior Living/ Nursing Homes [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		National CRE Price Index, Southern Unemployment	National CRE Price Index, Southern Unemployment
Loans Secured by Real Estate [Member] | Secured by Nonfarm, Nonresidential Properties [Member] | Nonowner-occupied - All Other [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		National CRE Price Index, Southern Unemployment	National CRE Price Index, Southern Unemployment
Loans Secured by Real Estate [Member] | Other Real Estate Secured [Member] | Nonresidential Owner- Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		Southern Unemployment, National CRE Price Index	Southern Unemployment, National CRE Price Index
Loans Secured by Real Estate [Member] | Other Real Estate Secured [Member] | Nonowner-occupied - All Other [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		National CRE Price Index, Southern Unemployment	National CRE Price Index, Southern Unemployment
Loans Secured by Real Estate [Member] | Other Real Estate Secured [Member] | Nonresidential Nonowner- Occupied - Apartments [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		National CRE Price Index, Southern Unemployment	National CRE Price Index, Southern Unemployment
Commercial and Industrial Loans [Member] | Commercial and Industrial Loans [Member] | Commercial and Industrial - Non-Working Capital [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		Trustmark historical data	Trustmark historical data
Commercial and Industrial Loans [Member] | Commercial and Industrial Loans [Member] | Commercial and Industrial - Working Capital [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		Trustmark historical data	Trustmark historical data
Commercial and Industrial Loans [Member] | Commercial and Industrial Loans [Member] | Equipment Finance Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		WARM	WARM
Loss Drivers		Southern Unemployment, National GDP	Southern Unemployment, National GDP
Commercial and Industrial Loans [Member] | Commercial and Industrial Loans [Member] | Credit Cards [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		WARM	WARM
Loss Drivers		Trustmark call report data	Trustmark call report data
Other Loans Secured by Real Estate [Member] | Other Construction [Member] | Other Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		National CRE Price Index, National Unemployment, BBB 7-10 US CBI	National CRE Price Index, National Unemployment, BBB 7-10 US CBI
Other Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member] | Trustmark Mortgage [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		WARM	WARM
Loss Drivers		Southern Unemployment	Southern Unemployment
Consumer Loans [Member] | Consumer Loans [Member] | All Other Consumer [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		National HPI, National Unemployment	National HPI, National Unemployment
Consumer Loans [Member] | Consumer Loans [Member] | Credit Cards [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		WARM	WARM
Loss Drivers		Trustmark call report data	Trustmark call report data
Consumer Loans [Member] | Consumer Loans [Member] | Overdrafts [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		Loss Rate	Loss Rate
Loss Drivers		Trustmark historical data	Trustmark historical data
State and Other Political Subdivision Loans [Member] | State and Other Political Subdivision Loans [Member] | Obligations of State and Political Subdivisions [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		Moody's Bond Default Study	Moody's Bond Default Study
Other Commercial Loans and Leases [Member] | Other Commercial Loans and Leases [Member] | Commercial and Industrial - Non-Working Capital [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		Trustmark historical data	Trustmark historical data
Other Commercial Loans and Leases [Member] | Other Commercial Loans and Leases [Member] | Commercial and Industrial - Working Capital [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		Trustmark historical data	Trustmark historical data
Other Commercial Loans and Leases [Member] | Other Commercial Loans and Leases [Member] | Equipment Finance Leases [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		WARM	WARM
Loss Drivers		Southern Unemployment, National GDP	Southern Unemployment, National GDP
Other Commercial Loans and Leases [Member] | Other Commercial Loans and Leases [Member] | Other Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Methodology		DCF	DCF
Loss Drivers		BBB 7-10 US CBI, Southern Unemployment	BBB 7-10 US CBI, Southern Unemployment

[1] (1) Loss driver was National HPI at December 31, 2024.

[2] (2) Loss driver was National Unemployment at December 31, 2024.