Business Combinations - Additional Information (Details) - RB Bancorporation [Member] $ / shares in Units, $ in Millions	Dec. 31, 2016 USD ($)	Nov. 14, 2016 USD ($) Office $ / shares
Business Acquisition [Line Items]
Assets	$ 217.7
Number of offices \| Office		7
Business acquisition, share price \| $ / shares		$ 22.00
Business acquisition, total transaction expenses		$ 25.6

The number of branches owned by the business to be acquired by the entity.

No definition available.

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Namespace Prefix:	trmk_
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- Definition

Amount of direct costs of the business combination including legal, accounting, and other costs incurred to consummate the business acquisition.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	debit
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- 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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Period Type:	duration

- Definition

Price of a single share of a number of saleable stocks paid or offered to be paid in a business combination.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of assets acquired at the acquisition date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4845-128472

+ Details

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Balance Type:	debit
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- Details

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