Shareholders' Equity (Tables)

6 Months Ended

Jun. 30, 2021

Stockholders Equity Note [Abstract]

Table of Actual Regulatory Capital Amounts and Ratios

The following table provides Trustmark’s and TNB’s actual regulatory capital amounts and ratios under regulatory capital standards in effect at June 30, 2021 and December 31, 2020 ($ in thousands):

	Actual
	Regulatory Capital					Minimum			To Be Well
	Amount		Ratio			Requirement			Capitalized
At June 30, 2021:
Common Equity Tier 1 Capital (to Risk Weighted Assets)
Trustmark Corporation	$	1,441,102		11.76	%		7.00	%	n/a
Trustmark National Bank		1,491,066		12.17	%		7.00	%		6.50	%
Tier 1 Capital (to Risk Weighted Assets)
Trustmark Corporation	$	1,501,102		12.25	%		8.50	%	n/a
Trustmark National Bank		1,491,066		12.17	%		8.50	%		8.00	%
Total Capital (to Risk Weighted Assets)
Trustmark Corporation	$	1,728,478		14.10	%		10.50	%	n/a
Trustmark National Bank		1,595,510		13.02	%		10.50	%		10.00	%
Tier 1 Leverage (to Average Assets)
Trustmark Corporation	$	1,501,102		9.00	%		4.00	%	n/a
Trustmark National Bank		1,491,066		8.96	%		4.00	%		5.00	%
At December 31, 2020:
Common Equity Tier 1 Capital (to Risk Weighted Assets)
Trustmark Corporation	$	1,395,844		11.62	%		7.00	%	n/a
Trustmark National Bank		1,412,015		11.75	%		7.00	%		6.50	%
Tier 1 Capital (to Risk Weighted Assets)
Trustmark Corporation	$	1,455,844		12.11	%		8.50	%	n/a
Trustmark National Bank		1,412,015		11.75	%		8.50	%		8.00	%
Total Capital (to Risk Weighted Assets)
Trustmark Corporation	$	1,696,794		14.12	%		10.50	%	n/a
Trustmark National Bank		1,530,044		12.73	%		10.50	%		10.00	%
Tier 1 Leverage (to Average Assets)
Trustmark Corporation	$	1,455,844		9.33	%		4.00	%	n/a
Trustmark National Bank		1,412,015		9.07	%		4.00	%		5.00	%

Net Change in Components of Accumulated Other Comprehensive Income (Loss) and the Related Tax Effects

	Three Months Ended June 30, 2021							Three Months Ended June 30, 2020
	Before Tax Amount		Tax (Expense) Benefit			Net of Tax Amount		Before Tax Amount		Tax (Expense) Benefit			Net of Tax Amount
Securities available for sale and transferred securities:
Net unrealized holding gains (losses) arising    during the period	$	6,612	$	(1,653	)	$	4,959	$	2,648	$	(662	)	$	1,986
Change in net unrealized holding loss on    securities transferred to held to maturity		736		(184	)		552		778		(195	)		583
Total securities available for sale    and transferred securities		7,348		(1,837	)		5,511		3,426		(857	)		2,569
Pension and other postretirement benefit plans:
Reclassification adjustments for changes realized    in net income:
Net change in prior service costs		28		(7	)		21		38		(10	)		28
Recognized net loss due to lump sum    settlements		—		—			—		40		(10	)		30
Change in net actuarial loss		443		(110	)		333		318		(78	)		240
Total pension and other postretirement benefit    plans		471		(117	)		354		396		(98	)		298
Total other comprehensive income (loss)	$	7,819	$	(1,954	)	$	5,865	$	3,822	$	(955	)	$	2,867

	Six Months Ended June 30, 2021									Six Months Ended June 30, 2020
	Before Tax Amount			Tax (Expense) Benefit			Net of Tax Amount			Before Tax Amount		Tax (Expense) Benefit			Net of Tax Amount
Securities available for sale and transferred securities:
Net unrealized holding gains (losses) arising    during the period	$	(15,188	)	$	3,797		$	(11,391	)	$	43,155	$	(10,789	)	$	32,366
Change in net unrealized holding loss on    securities transferred to held to maturity		1,447			(362	)		1,085			1,639		(410	)		1,229
Total securities available for sale    and transferred securities		(13,741	)		3,435			(10,306	)		44,794		(11,199	)		33,595
Pension and other postretirement benefit plans:
Reclassification adjustments for changes realized    in net income:
Net change in prior service costs		56			(14	)		42			75		(19	)		56
Recognized net loss due to lump sum    settlements		—			—			—			40		(10	)		30
Change in net actuarial loss		898			(224	)		674			645		(161	)		484
Total pension and other postretirement benefit    plans		954			(238	)		716			760		(190	)		570
Total other comprehensive income (loss)	$	(12,787	)	$	3,197		$	(9,590	)	$	45,554	$	(11,389	)	$	34,165

Summary of Changes in Balances of Accumulated Other Comprehensive Income (Loss)

The following table presents the changes in the balances of each component of accumulated other comprehensive income (loss) for the periods presented ($ in thousands).  All amounts are presented net of tax.

	Securities Available for Sale and Transferred Securities			Defined Benefit Pension Items			Total
Balance at January 1, 2021	$	17,331		$	(18,382	)	$	(1,051	)
Other comprehensive income (loss) before reclassification		(10,306	)		—			(10,306	)
Amounts reclassified from accumulated other    comprehensive income (loss)		—			716			716
Net other comprehensive income (loss)		(10,306	)		716			(9,590	)
Balance at June 30, 2021	$	7,025		$	(17,666	)	$	(10,641	)
Balance at January 1, 2020	$	(8,017	)	$	(15,583	)	$	(23,600	)
Other comprehensive income (loss) before reclassification		33,595			—			33,595
Amounts reclassified from accumulated other    comprehensive income (loss)		—			570			570
Net other comprehensive income (loss)		33,595			570			34,165
Balance at June 30, 2020	$	25,578		$	(15,013	)	$	10,565