Debt instrument remaining maturity period.

No definition available.

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Namespace Prefix:	trmk_
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Period Type:	duration

- Definition

Represents the number of outstanding long-term FHLB advances.

+ References

No definition available.

+ Details

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- Definition

Represents the number of outstanding short-term FHLB advances.

+ References

No definition available.

+ Details

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- Definition

Weighted average cost related to FHLB advances.

+ References

No definition available.

+ Details

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Data Type:	dtr-types:percentItemType
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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

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Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Amount of unused borrowing capacity under the long-term financing arrangement that is available to the entity as of the balance sheet date.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Interest expense incurred during the reporting period on long-term borrowings associated with Federal Home Loan Bank and Federal Reserve Bank advances.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Interest expense incurred during the reporting period on short-term borrowings associated with Federal Home Loan Bank and Federal Reserve Bank advances.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of addition (reduction) to the amount at which a liability could be incurred (settled) in a current transaction between willing parties.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount, excluding unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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+ Details

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- Definition

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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+ Details

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Borrowings - FHLB Advances - Additional Information (Details)	12 Months Ended
	Dec. 31, 2022 USD ($) Loan	Dec. 31, 2021 USD ($) Loan	Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
Weighted-average cost related to FHLB advances (in hundredths)	4.58%
Weighted average remaining maturity	10 days
Atlanta \| BancTrust [Member] \| Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Number of outstanding short-term FHLB advances \| Loan	0	0
Interest rate (in hundredths)	0.08%	0.08%
Debt instrument remaining maturity period	3 years 8 months 15 days	4 years 8 months 15 days
Number of outstanding long-term FHLB advances \| Loan	1	1
Long-term FHLB advances	$ 78,000	$ 97,000
Atlanta \| BancTrust [Member] \| Fair Market Value Adjustment [Member] \| Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Fair value adjustment on FHLB advances	0	0
Dallas [Member] \| Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Additional debt instrument borrowing capacity	$ 3,034,000,000.000	3,449,000,000
Dallas [Member] \| Fair Market Value Adjustment [Member] \| Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Interest expense, short-term borrowings		$ 2,000
Dallas [Member] \| BancTrust [Member] \| Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Number of outstanding short-term FHLB advances \| Loan	4	0
Short-term FHLB advances	$ 975,000,000.0
Interest expense, long-term borrowings	0	$ 0	$ 8,000
Number of outstanding long-term FHLB advances \| Loan		0
Long-term FHLB advances	0
Dallas [Member] \| BancTrust [Member] \| Short Term FhlbAdvances1 [Member] \| Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Short-term FHLB advances	$ 125,000,000.0
Interest rate (in hundredths)	4.56%
Dallas [Member] \| BancTrust [Member] \| Short Term FhlbAdvances2 [Member] \| Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Short-term FHLB advances	$ 375,000,000.0
Interest rate (in hundredths)	4.59%
Dallas [Member] \| BancTrust [Member] \| Short Term Fhlbadvances3 [Member] \| Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Short-term FHLB advances	$ 300,000,000.0
Interest rate (in hundredths)	4.57%
Dallas [Member] \| BancTrust [Member] \| Short Term Fhlbadvances4 [Member] \| Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Short-term FHLB advances	$ 175,000,000.0
Interest rate (in hundredths)	4.57%
Dallas [Member] \| BancTrust [Member] \| Fair Market Value Adjustment [Member]
Debt Instrument [Line Items]
Interest expense, short-term borrowings	$ 4,800,000		$ 9,000