Debt instrument remaining maturity period.

No definition available.

Name:	trmk_DebtInstrumentRemainingMaturityPeriod
Namespace Prefix:	trmk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of outstanding short-term FHLB advances.

+ References

No definition available.

+ Details

Name:	trmk_NumberOfOutstandingShortTermFHLBAdvances
Namespace Prefix:	trmk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The cost of acquiring the advances.

+ References

No definition available.

+ Details

Name:	trmk_WeightedAverageCost
Namespace Prefix:	trmk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average remaining maturity on FHLB advances

+ References

No definition available.

+ Details

Name:	trmk_WeightedAverageRemainingMaturity
Namespace Prefix:	trmk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
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.

+ References

+ Details

Name:	us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

Name:	us-gaap_InterestExpenseFederalHomeLoanBankAndFederalReserveBankAdvancesShortTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(a))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(13))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16)(a)(1))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

Name:	us-gaap_ShortTermBorrowings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_ShortTermBorrowingsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The portion of the carrying amount of short-term borrowings outstanding as of the balance sheet date which accrues interest at a set, unchanging rate.

+ References

No definition available.

+ Details

Name:	us-gaap_ShortTermDebtPercentageBearingFixedInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_ShortTermDebtTypeAxis=us-gaap_FederalHomeLoanBankAdvancesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=trmk_DallasMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=trmk_AdvanceOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=trmk_AdvanceTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=trmk_AdvanceThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=trmk_AtlantaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=trmk_AtlantaAndDallasMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Borrowings - Short-Term Borrowings - Additional information (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) Loan	Dec. 31, 2015 USD ($) Loan	Dec. 31, 2014 USD ($)
Short-term Debt [Abstract]
Total short-term borrowings	$ 769,778,000	$ 412,617,000
Maturity date	Dec. 15, 2016
Federal Home Loan Bank Advances [Member]
Short-term Debt [Abstract]
Total short-term borrowings	$ 700,008,000	350,000,000
Dallas [Member]
Short-term Debt [Abstract]
Additional debt instrument borrowing capacity	$ 1,511,000,000	$ 1,328,000,000
Dallas [Member] \| Federal Home Loan Bank Advances [Member]
Short-term Debt [Abstract]
Number of outstanding short-term FHLB advances \| Loan	3	2
Total short-term borrowings	$ 700,000,000	$ 350,000,000
Interest rate (in hundredths)		0.31%
Weighted average remaining maturity		13 days
Weighted-average cost related to FHLB advances (in hundredths)		0.31%
Dallas [Member] \| Federal Home Loan Bank Advances [Member] \| Advance One [Member]
Short-term Debt [Abstract]
Total short-term borrowings	$ 100,000,000	$ 100,000,000
Interest rate (in hundredths)	0.55%
Weighted average remaining maturity	7 days
Weighted-average cost related to FHLB advances (in hundredths)	0.68%
Dallas [Member] \| Federal Home Loan Bank Advances [Member] \| Advance Two [Member]
Short-term Debt [Abstract]
Total short-term borrowings	$ 100,000,000	250,000,000
Interest rate (in hundredths)	0.80%
Weighted average remaining maturity	7 days
Weighted-average cost related to FHLB advances (in hundredths)	0.68%
Dallas [Member] \| Federal Home Loan Bank Advances [Member] \| Advance Three [Member]
Short-term Debt [Abstract]
Total short-term borrowings	$ 500,000,000
Weighted average remaining maturity	354 days
Weighted-average cost related to FHLB advances (in hundredths)	0.36%
Maturity date	Dec. 20, 2017
Atlanta [Member]
Short-term Debt [Abstract]
Additional debt instrument borrowing capacity	$ 0	$ 0
Atlanta [Member] \| Federal Home Loan Bank Advances [Member]
Short-term Debt [Abstract]
Number of outstanding short-term FHLB advances \| Loan	1	0
Total short-term borrowings	$ 8,000
Interest rate (in hundredths)	6.50%
Remaining maturity	310 days
Atlanta and Dallas [Member]
Short-term Debt [Abstract]
Interest expense, short-term borrowings	$ 1,800,000	$ 727,000	$ 197,000