Deposits - Interest Expense on Deposits by Type (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Interest expense on deposits by type [Abstract]
Interest-bearing demand	$ 18,479	$ 6,820	$ 3,297
Savings	17,980	6,047	2,657
Time	17,477	9,850	6,794
Total	$ 53,936	$ 22,717	$ 12,748

Interest expense on deposits by type [Abstract]

No definition available.

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Namespace Prefix:	trmk_
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Period Type:	duration

- Definition

Interest expense incurred on demand deposit accounts that represent borrowings rather than outstanding drafts.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.6)
-URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260

+ Details

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Balance Type:	debit
Period Type:	duration

- Definition

Aggregate amount of interest expense on all deposits.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Interest expense incurred on all savings account deposits.

+ References

+ Details

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Balance Type:	debit
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- Definition

The aggregate interest expense incurred on time deposits, including certificates of deposits, in domestic offices.

+ References

+ Details

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