Shareholders' Equity (Tables)

3 Months Ended

9 Months Ended

Mar. 31, 2022

Sep. 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 March 31, 2022 and December 31, 2021 ($ in thousands):

	Actual
	Regulatory Capital					Minimum			To Be Well
	Amount		Ratio			Requirement			Capitalized
At March 31, 2022:
Common Equity Tier 1 Capital (to Risk Weighted Assets)
Trustmark Corporation	$	1,425,283		11.23	%		7.00	%	n/a
Trustmark National Bank		1,516,646		11.95	%		7.00	%		6.50	%
Tier 1 Capital (to Risk Weighted Assets)
Trustmark Corporation	$	1,485,283		11.70	%		8.50	%	n/a
Trustmark National Bank		1,516,646		11.95	%		8.50	%		8.00	%
Total Capital (to Risk Weighted Assets)
Trustmark Corporation	$	1,717,144		13.53	%		10.50	%	n/a
Trustmark National Bank		1,625,410		12.81	%		10.50	%		10.00	%
Tier 1 Leverage (to Average Assets)
Trustmark Corporation	$	1,485,283		8.66	%		4.00	%	n/a
Trustmark National Bank		1,516,646		8.86	%		4.00	%		5.00	%
At December 31, 2021:
Common Equity Tier 1 Capital (to Risk Weighted Assets)
Trustmark Corporation	$	1,425,227		11.29	%		7.00	%	n/a
Trustmark National Bank		1,518,599		12.03	%		7.00	%		6.50	%
Tier 1 Capital (to Risk Weighted Assets)
Trustmark Corporation	$	1,485,227		11.77	%		8.50	%	n/a
Trustmark National Bank		1,518,599		12.03	%		8.50	%		8.00	%
Total Capital (to Risk Weighted Assets)
Trustmark Corporation	$	1,710,700		13.55	%		10.50	%	n/a
Trustmark National Bank		1,621,030		12.84	%		10.50	%		10.00	%
Tier 1 Leverage (to Average Assets)
Trustmark Corporation	$	1,485,227		8.73	%		4.00	%	n/a
Trustmark National Bank		1,518,599		8.94	%		4.00	%		5.00	%

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

The following table presents the net change in the components of accumulated other comprehensive income (loss) and the related tax effects allocated to each component for the periods presented ($ in thousands). The amortization of prior service cost, recognized net loss due to lump sum settlements and change in net actuarial loss are included in the computation of net periodic benefit cost (see Note 10 – Defined Benefit and Other Postretirement Benefits for additional details). Reclassification adjustments related to pension and other postretirement benefit plans are included in salaries and employee benefits and other expense in the accompanying consolidated statements of income.

	Three Months Ended March 31, 2022									Three Months Ended March 31, 2021
	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	$	(155,671	)	$	38,918		$	(116,753	)	$	(21,800	)	$	5,450		$	(16,350	)
Change in net unrealized holding loss on    securities transferred to held to maturity		533			(133	)		400			711			(178	)		533
Total securities available for sale    and transferred securities		(155,138	)		38,785			(116,353	)		(21,089	)		5,272			(15,817	)
Pension and other postretirement benefit plans:
Reclassification adjustments for changes    realized in net income:
Net change in prior service costs		28			(8	)		20			28			(7	)		21
Recognized net loss due to lump sum    settlements		—			—			—			—			—			—
Change in net actuarial loss		315			(78	)		237			455			(114	)		341
Total pension and other postretirement    benefit plans		343			(86	)		257			483			(121	)		362
Total other comprehensive income (loss)	$	(154,795	)	$	38,699		$	(116,096	)	$	(20,606	)	$	5,151		$	(15,455	)

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, 2022	$	(17,774	)	$	(14,786	)	$	(32,560	)
Other comprehensive income (loss) before reclassification		(116,353	)		—			(116,353	)
Amounts reclassified from accumulated other    comprehensive income (loss)		—			257			257
Net other comprehensive income (loss)		(116,353	)		257			(116,096	)
Balance at March 31, 2022	$	(134,127	)	$	(14,529	)	$	(148,656	)
Balance at January 1, 2021	$	17,331		$	(18,382	)	$	(1,051	)
Other comprehensive income (loss) before reclassification		(15,817	)		—			(15,817	)
Amounts reclassified from accumulated other    comprehensive income (loss)		—			362			362
Net other comprehensive income (loss)		(15,817	)		362			(15,455	)
Balance at March 31, 2021	$	1,514		$	(18,020	)	$	(16,506	)