Defined Benefit and Other Postretirement Benefits (Tables)

12 Months Ended

Dec. 31, 2016

Trustmark Capital Accumulation Plan [Member]

Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]

Plan Benefit Obligation, Plan Assets and Funded Status of the Plan

The following tables present information regarding the benefit obligation, plan assets, funded status, amounts recognized in accumulated other comprehensive loss, net periodic benefit cost and other statistical disclosures for Trustmark’s tax-qualified defined benefit pension plans (Trustmark Capital Accumulation Plan and BancTrust Pension Plan) for the periods presented ($ in thousands):

	December 31,
	2016			2015
Change in benefit obligation:
Benefit obligation, beginning of year	$	91,403		$	101,904
Service cost		428			513
Interest cost		3,355			3,461
Actuarial gain		(893	)		(2,807	)
Benefits paid for the Plan		(18,393	)		(11,668	)
Benefit obligation, end of year	$	75,900		$	91,403
Change in plan assets:
Fair value of plan assets, beginning of year	$	74,137		$	86,287
Actual return on plan assets		(1,079	)		(547	)
Employer contributions		69			65
Benefit payments for the Plan		(18,393	)		(11,668	)
Fair value of plan assets, end of year	$	54,734		$	74,137
Funded status at end of year - net liability	$	(21,166	)	$	(17,266	)
Amounts recognized in accumulated other comprehensive loss:
Net loss - amount recognized	$	21,355		$	24,927

Net Periodic Benefit Cost

	Years Ended December 31,
	2016			2015			2014
Net periodic benefit cost:
Service cost	$	428		$	513		$	495
Interest cost		3,355			3,461			5,299
Expected return on plan assets		(2,897	)		(5,187	)		(6,245	)
Recognized net loss due to BancTrust termination		—			—			1,355
Recognized net loss due to lump sum settlements		3,906			2,221			905
Recognized net actuarial loss (gain)		2,749			3,878			(283	)
Net periodic benefit cost	$	7,541		$	4,886		$	1,526
Other changes in plan assets and benefit obligation recognized in other    comprehensive income (loss), before taxes:
Net (gain) loss - Total recognized in other comprehensive income (loss)	$	(3,572	)	$	(3,173	)	$	12,664
Total recognized in net periodic benefit cost and other comprehensive    income (loss)	$	3,969		$	1,713		$	14,190
Weighted-average assumptions as of end of year:
Discount rate for benefit obligation		3.71	%		3.86	%		3.57	%
Discount rate for net periodic benefit cost		3.86	%		3.57	%		4.30	%
Expected long-term return on plan assets		4.25	%		7.00	%		7.50	%

Weighted-Average Asset Allocation

The weighted-average asset allocations by asset category for the Plan at December 31, 2016 and 2015 are presented below.

	December 31,
	2016			2015
Money market fund		13.0	%		3.6	%
Fixed income mutual funds		—			29.0	%
Equity mutual funds		—			16.1	%
Equity securities		—			51.3	%
U.S. Treasuries		87.0	%		—
Total		100.0	%		100.0	%

Plan Assets Measured at Fair Value

The following table sets forth by level, within the fair value hierarchy, the Plan’s assets measured at fair value at December 31, 2016 and 2015 ($ in thousands):

	December 31, 2016
	Total		Level 1		Level 2		Level 3
Money market fund	$	6,859	$	6,859	$	—	$	—
U.S. Treasuries		47,875		47,875		—		—
Total assets at fair value	$	54,734	$	54,734	$	—	$	—

	December 31, 2015
	Total		Level 1		Level 2		Level 3
Money market fund	$	2,678	$	2,678	$	—	$	—
Fixed income mutual funds		21,472		21,472		—		—
Equity mutual funds		11,922		11,922		—		—
Equity securities		38,065		38,065		—		—
Total assets at fair value	$	74,137	$	74,137	$	—	$	—

Estimated Future Benefit Payments and Other Disclosures

The following table presents the expected benefit payments, which reflect expected future service, for the Plan ($ in thousands):

Year	Amount
2017	$	67,400
2018		210
2019		285
2020		334
2021		391
2022 - 2026		2,706

Supplemental Retirement Plan [Member]

Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]

Plan Benefit Obligation, Plan Assets and Funded Status of the Plan

The following tables present information regarding the benefit obligation, plan assets, funded status, amounts recognized in accumulated other comprehensive loss, net periodic benefit cost and other statistical disclosures for Trustmark’s nonqualified supplemental retirement plans ($ in thousands):

	December 31,
	2016			2015
Change in benefit obligation:
Benefit obligation, beginning of year	$	57,766		$	59,744
Service cost		295			431
Interest cost		2,223			2,082
Actuarial loss (gain)		1,537			(1,702	)
Benefits paid		(3,326	)		(2,789	)
Benefit obligation, end of year	$	58,495		$	57,766
Change in plan assets:
Fair value of plan assets, beginning of year	$	—		$	—
Employer contributions		3,326			2,789
Benefit payments		(3,326	)		(2,789	)
Fair value of plan assets, end of year	$	—		$	—
Funded status at end of year - net liability	$	(58,495	)	$	(57,766	)
Amounts recognized in accumulated other comprehensive loss:
Net loss	$	17,739		$	18,548
Prior service cost		1,359			1,609
Amounts recognized	$	19,098		$	20,157

Net Periodic Benefit Cost

	Years Ended December 31,
	2016			2015			2014
Net periodic benefit cost:
Service cost	$	295		$	431		$	296
Interest cost		2,223			2,082			2,198
Amortization of prior service cost		250			250			250
Recognized net actuarial loss		864			992			661
Net periodic benefit cost	$	3,632		$	3,755		$	3,405
Other changes in plan assets and benefit obligation recognized in other    comprehensive income (loss), before taxes:
Net (gain) loss	$	(810	)	$	(2,694	)	$	6,733
Amortization of prior service cost		(250	)		(250	)		(250	)
Total recognized in other comprehensive income (loss)	$	(1,060	)	$	(2,944	)	$	6,483
Total recognized in net periodic benefit cost and other comprehensive    income (loss)	$	2,572		$	811		$	9,888
Weighted-average assumptions as of end of year:
Discount rate for benefit obligation		3.71	%		3.86	%		3.57	%
Discount rate for net periodic benefit cost		3.86	%		3.57	%		4.30	%

Estimated Future Benefit Payments and Other Disclosures

The following table presents the expected benefits payments for Trustmark’s supplemental retirement plans ($ in thousands):

Year	Amount
2017	$	3,648
2018		3,766
2019		3,845
2020		4,067
2021		4,113
2022 - 2026		19,982