Revenue from Contracts with Customers - Summary of Noninterest Income Disaggregated by Reportable Operating Segment and Revenue Stream (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018	[1]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		$ 10,265	$ 10,857
Bank card and other fees		7,191	6,626
Mortgage banking, net		3,442	11,265
Insurance commissions		10,871	9,419
Wealth management		7,483	7,567
Other, net		2,239	1,059
Total Noninterest Income		41,491	46,793
Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		10,265	10,857
Bank card and other fees		6,889	6,551
Insurance commissions		10,871	9,419
Wealth management		7,483	7,567
Other, net		2,484	1,439
Total Noninterest Income		37,992	35,833
Not Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Bank card and other fees	[2]	302	75
Mortgage banking, net	[2]	3,442	11,265
Other, net	[2]	(245)	(380)
Total Noninterest Income	[2]	3,499	10,960
General Banking Segment [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		10,240	10,833
Bank card and other fees		7,167	6,599
Mortgage banking, net		3,442	11,265
Wealth management		91	47
Other, net		1,973	1,016
Total Noninterest Income		22,913	29,760
General Banking Segment [Member] | Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		10,240	10,833
Bank card and other fees		6,865	6,524
Wealth management		91	47
Other, net		2,244	1,424
Total Noninterest Income		19,440	18,828
General Banking Segment [Member] | Not Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Bank card and other fees	[2]	302	75
Mortgage banking, net	[2]	3,442	11,265
Other, net	[2]	(271)	(408)
Total Noninterest Income	[2]	3,473	10,932
Wealth Management Segment [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		25	24
Bank card and other fees		24	27
Wealth management		7,392	7,520
Other, net		262	43
Total Noninterest Income		7,703	7,614
Wealth Management Segment [Member] | Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Service charges on deposit accounts		25	24
Bank card and other fees		24	27
Wealth management		7,392	7,520
Other, net		236	15
Total Noninterest Income		7,677	7,586
Wealth Management Segment [Member] | Not Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Other, net	[2]	26	28
Total Noninterest Income	[2]	26	28
Insurance Segment [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Insurance commissions		10,871	9,419
Other, net		4
Total Noninterest Income		10,875	9,419
Insurance Segment [Member] | Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Insurance commissions		10,871	9,419
Other, net		4
Total Noninterest Income		$ 10,875	$ 9,419

[1] During the first quarter of 2019, Trustmark revised the composition of its operating segments by moving the Private Banking Group from the General Banking Segment to the Wealth Management Segment as a result of a change in supervision of this group for segment reporting purposes. The prior period amounts presented include reclassifications to conform to the current period presentation.

[2] Noninterest income not in scope for FASB ASC Topic 606 includes customer derivatives revenue and miscellaneous credit card fee income within bank card and other fees; mortgage banking, net; amortization of tax credits, accretion of the FDIC indemnification asset, cash surrender value on various life insurance policies, earnings on Trustmark’s non-qualified deferred compensation plans, other partnership investments and rental income within other, net; and security gains (losses), net