Retirement and Post-Retirement Employee Benefit Plans (Tables)

12 Months Ended

Sep. 30, 2021

Retirement Benefits [Abstract]

Schedule of Net Periodic Benefit Cost Not yet Recognized

Additionally, the amounts that have not yet been recognized in net periodic pension cost that have been recorded as regulatory assets or liabilities are as follows:

	Defined Benefit Plan		Supplemental Executive Retirement Plans		Postretirement Plans		Total
	(In thousands)
September 30, 2021
Unrecognized prior service (credit) cost	$	(353)	$	—	$	(64,313)	$	(64,666)
Unrecognized actuarial (gain) loss	(3,060)		39,666		(28,141)		8,465
	$	(3,413)	$	39,666	$	(92,454)	$	(56,201)
September 30, 2020
Unrecognized prior service (credit) cost	$	(584)	$	—	$	951	$	367
Unrecognized actuarial loss	78,082		51,045		9,110		138,237
	$	77,498	$	51,045	$	10,061	$	138,604

Schedule of Allocation of Plan Assets

The following table presents asset allocation information for the Master Trust as of September 30, 2021 and 2020.

	Targeted Allocation  Range	Actual Allocation September 30
Security Class		2021	2020
Domestic equities	35%-55%	44.5%	45.3%
International equities	10%-20%	16.9%	15.6%
Fixed income	5%-30%	16.0%	17.0%
Company stock	0%-15%	10.6%	13.0%
Other assets	0%-20%	12.0%	9.1%

The following table presents asset allocation information for the postretirement benefit plan assets as of September 30, 2021 and 2020.

	Actual Allocation September 30
Security Class	2021	2020
Diversified investment funds	97.9%	97.4%
Cash and cash equivalents	2.1%	2.6%

Schedule of Assumptions Used

The actuarial assumptions used to determine the pension liability for the Plan was determined as of September 30, 2021 and 2020 and the actuarial assumptions used to determine the net periodic pension cost for the Plan was determined as of September 30, 2020, 2019 and 2018. In October 2021, the Society of Actuaries released its annually-updated mortality improvement scale for pension plans incorporating new assumptions surrounding life expectancies in the United States.  As of September 30, 2021, we updated our assumed mortality rates to incorporate the updated mortality table.

Additional assumptions are presented in the following table:

	Pension Liability				Pension Cost
	2021		2020		2021		2020		2019
Discount rate	2.97	%	2.80	%	2.80	%	3.29	%	4.38	%
Rate of compensation increase	3.50	%	3.50	%	3.50	%	3.50	%	3.50	%
Expected return on plan assets	6.25	%	6.25	%	6.25	%	6.50	%	6.75	%
Interest crediting rate	4.69	%	4.69	%	4.69	%	4.69	%	4.69	%

The actuarial assumptions used to determine the pension liability for the supplemental plans were determined as of September 30, 2021 and 2020 and the actuarial assumptions used to determine the net periodic pension cost for the supplemental plans were determined as of September 30, 2020, 2019 and 2018. These assumptions are presented in the following table:

	Pension Liability				Pension Cost
	2021		2020		2021		2020		2019
Discount rate (1)	2.57	%	2.80	%	2.90	%	3.19	%	4.38	%
Rate of compensation increase	3.50	%	3.50	%	3.50	%	3.50	%	3.50	%
Interest crediting rate	4.69	%	4.69	%	4.69	%	4.69	%	4.69	%

 (1)     Reflects a weighted average discount rate for pension cost for fiscal 2021 and 2020 due to the settlements during the year.

The actuarial assumptions used to determine the pension liability for our postretirement plan were determined as of September 30, 2021 and 2020 and the actuarial assumptions used to determine the net periodic pension cost for the postretirement plan were determined as of September 30, 2020, 2019 and 2018. Effective January 1, 2022, the Retiree Medical Plan for Retirees and Disabled Employees will be amended. The amendments remove the three percent cost increase limitation and change the post-65 retiree coverage to Via Benefits with an Atmos Energy funded Health Reimbursement Account. Eligible post-65 retirees and post-65 spouses will be eligible to enroll in benefits provided by Via Benefits, including those that previously deferred or declined retiree coverage. The amendments were approved by the Atmos Energy Board of Directors in May 2021 and the changes were communicated to participants beginning on July 31, 2021. These amendments to the Retiree Medical Plan for Retirees and Disabled Employees have been included in the actuarial assumptions used to determine the pension liability and net periodic for the postretirement plan as of September 30, 2020.

The assumptions are presented in the following table:

	Postretirement Liability				Postretirement Cost
	2021		2020		2021		2020		2019
Discount rate	3.01	%	2.80	%	2.80	%	3.29	%	4.38	%
Expected return on plan assets	4.94	%	4.94	%	4.94	%	5.14	%	5.33	%
Initial trend rate	6.25	%	6.25	%	6.25	%	6.25	%	6.50	%
Ultimate trend rate	5.00	%	5.00	%	5.00	%	5.00	%	5.00	%
Ultimate trend reached in	2027		2026		2026		2025		2022

Changes in Projected Benefit Obligations, Fair Value of Plan Assets, and Funded Status of Plan

The following table presents the Plan’s accumulated benefit obligation, projected benefit obligation and funded status as of September 30, 2021 and 2020:

	2021		2020
	(In thousands)
Accumulated benefit obligation	$	558,639	$	565,755
Change in projected benefit obligation:
Benefit obligation at beginning of year	$	604,221	$	577,270
Service cost	17,369		17,551
Interest cost	16,883		19,028
Actuarial (gain) loss	(7,561)		22,898
Benefits paid	(34,883)		(32,526)
Benefit obligation at end of year	596,029		604,221
Change in plan assets:
Fair value of plan assets at beginning of year	528,881		530,109
Actual return on plan assets	92,808		31,298
Employer contributions	10,000		—
Benefits paid	(34,883)		(32,526)
Fair value of plan assets at end of year	596,806		528,881
Reconciliation:
Funded status	777		(75,340)
Unrecognized prior service cost	—		—
Unrecognized net loss	—		—
Net amount recognized	$	777	$	(75,340)

The following table presents the supplemental plans’ accumulated benefit obligation, projected benefit obligation and funded status as of September 30, 2021 and 2020:

	2021		2020
	(In thousands)
Accumulated benefit obligation	$	100,981	$	122,207
Change in projected benefit obligation:
Benefit obligation at beginning of year	$	129,140	$	143,987
Service cost	1,067		1,074
Interest cost	3,180		4,188
Actuarial (gain) loss	1,332		7,386
Benefits paid	(4,720)		(4,766)
Settlements	(25,698)		(22,729)
Benefit obligation at end of year	104,301		129,140
Change in plan assets:
Fair value of plan assets at beginning of year	—		—
Employer contribution	30,418		27,495
Benefits paid	(4,720)		(4,766)
Settlements	(25,698)		(22,729)
Fair value of plan assets at end of year	—		—
Reconciliation:
Funded status	(104,301)		(129,140)
Unrecognized prior service cost	—		—
Unrecognized net loss	—		—
Accrued pension cost	$	(104,301)	$	(129,140)

The following table presents the postretirement plan’s benefit obligation and funded status as of September 30, 2021 and 2020:

	2021		2020
	(In thousands)
Change in benefit obligation:
Benefit obligation at beginning of year	$	370,678	$	316,033
Service cost	11,000		13,466
Interest cost	15,372		10,612
Plan participants’ contributions	5,648		5,849
Actuarial (gain) loss	6,800		43,412
Benefits paid	(19,610)		(18,694)
Plan amendments	(34,732)		—
Benefit obligation at end of year	355,156		370,678
Change in plan assets:
Fair value of plan assets at beginning of year	208,245		201,901
Actual return on plan assets	53,335		2,356
Employer contributions	20,581		16,833
Plan participants’ contributions	5,648		5,849
Benefits paid	(19,610)		(18,694)
Fair value of plan assets at end of year	268,199		208,245
Reconciliation:
Funded status	(86,957)		(162,433)
Unrecognized transition obligation	—		—
Unrecognized prior service cost	—		—
Unrecognized net loss	—		—
Accrued postretirement cost	$	(86,957)	$	(162,433)

Schedule of Net Benefit Costs Supplemental Plan

Net periodic pension cost for the Plan for fiscal 2021, 2020 and 2019 is presented in the following table.

	Fiscal Year Ended September 30
	2021		2020		2019
	(In thousands)
Components of net periodic pension cost:
Service cost	$	17,369	$	17,551	$	15,311
Interest cost (1)	16,883		19,028		22,071
Expected return on assets (1)	(27,913)		(28,316)		(28,451)
Amortization of prior service cost (credit) (1)	8,686		(231)		(232)
Recognized actuarial (gain) loss (1)	(231)		9,025		4,201
Net periodic pension cost	$	14,794	$	17,057	$	12,900

(1)    The components of net periodic cost other than the service cost component are included in the line item other non-operating income (expense) in the consolidated statements of comprehensive income or are capitalized on the consolidated balance sheets as a regulatory asset or liability, as described in Note 2 to the consolidated financial statements.

Net periodic pension cost for the supplemental plans for fiscal 2021, 2020 and 2019 is presented in the following table.

	Fiscal Year Ended September 30
	2021		2020		2019
	(In thousands)
Components of net periodic pension cost:
Service cost	$	1,067	$	1,074	$	869
Interest cost (1)	3,180		4,188		5,127
Recognized actuarial loss (1)	3,560		3,945		2,227
Settlements (1)	9,151		9,180		—
Net periodic pension cost	$	16,958	$	18,387	$	8,223

(1)    The components of net periodic cost other than the service cost component are included in the line item other non-operating income (expense) in the consolidated statements of comprehensive income or are capitalized on the consolidated balance sheets as a regulatory asset or liability, as described in Note 2 to the consolidated financial statements.

Net periodic postretirement cost for fiscal 2021, 2020 and 2019 is presented in the following table.

	Fiscal Year Ended September 30
	2021		2020		2019
	(In thousands)
Components of net periodic postretirement cost:
Service cost	$	11,000	$	13,466	$	10,810
Interest cost (1)	15,372		10,612		11,839
Expected return on assets (1)	(10,455)		(10,499)		(10,659)
Amortization of transition obligation (1)	—		—		—
Amortization of prior service cost (1)	30,533		173		173
Recognized actuarial gain (1)	1,172		(1,337)		(8,178)
Net periodic postretirement cost	$	47,622	$	12,415	$	3,985

(1)    The components of net periodic cost other than the service cost component are included in the line item other non-operating income (expense) in the consolidated statements of comprehensive income or are capitalized on the consolidated balance sheets as a regulatory asset or liability, as described in Note 2 to the consolidated financial statements.

Schedule of Employee Pension Plans Investments at Fair Value

In addition to the assets shown below, the Plan had net accounts receivable of $2.1 million and $0.7 million at September 30, 2021 and 2020, which materially approximates fair value due to the short-term nature of these assets.

	Assets at Fair Value as of September 30, 2021
	Level 1		Level 2		Level 3		Total
	(In thousands)
Investments:
Common stocks	$	239,166	$	—	$	—	$	239,166
Money market funds	—		7,060		—		7,060
Registered investment companies	74,236		—		—		74,236
Government securities:
Mortgage-backed securities	—		14,048		—		14,048
U.S. treasuries	7,483		34		—		7,517
Corporate bonds	—		30,834		—		30,834
Total investments measured at fair value	$	320,885	$	51,976	$	—	372,861
Investments measured at net asset value:
Common/collective trusts (1)							121,570
Limited partnerships (1)							100,299
Total investments							$	594,730

	Assets at Fair Value as of September 30, 2020
	Level 1		Level 2		Level 3		Total
	(In thousands)
Investments:
Common stocks	$	211,244	$	—	$	—	$	211,244
Money market funds	—		6,096		—		6,096
Registered investment companies	29,762		—		—		29,762
Government securities:
Mortgage-backed securities	—		15,230		—		15,230
U.S. treasuries	21,755		36		—		21,791
Corporate bonds	—		52,648		—		52,648
Total investments measured at fair value	$	262,761	$	74,010	$	—	336,771
Investments measured at net asset value:
Common/collective trusts (1)							122,207
Limited partnerships (1)							69,176
Total investments							$	528,154

(1)    The fair value of our common/collective trusts and limited partnerships are measured using the net asset value per share practical expedient. There are no redemption restrictions, redemption notice periods or unfunded commitments for these investments. The redemption frequency is daily.

Schedule of Expected Benefit Payments

The following benefit payments for our defined benefit plans, which reflect expected future service, as appropriate, are expected to be paid in the following fiscal years:

	Pension Plan		Supplemental Plans
	(In thousands)
2022	$	39,020	$	4,925
2023	39,624		11,384
2024	40,314		4,496
2025	41,085		39,769
2026	42,053		5,665
2027-2031	203,461		22,079

The following benefit payments paid by us, retirees and prescription drug subsidy payments for our postretirement benefit plans, which reflect expected future service, as appropriate, are expected to be paid in the following fiscal years. Company payments for fiscal 2021 include contributions to our postretirement plan trusts.

	Company Payments		Retiree Payments		Subsidy Payments		Total Postretirement Benefits
	(In thousands)
2022	$	17,701	$	2,490	$	—	$	20,191
2023	18,031		2,465		—		20,496
2024	18,341		2,404		—		20,745
2025	18,981		2,425		—		21,406
2026	19,414		2,395		—		21,809
2027-2031	100,312		10,641		—		110,953

Schedule of Postretirement Benefit Plans Investments at Fair Value

The following tables set forth by level, within the fair value hierarchy, the Retiree Medical Plan’s assets at fair value as of September 30, 2021 and 2020. The methods used to determine fair value for the assets held by the Retiree Medical Plan are fully described in Note 2 to the consolidated financial statements.

	Assets at Fair Value as of September 30, 2021
	Level 1		Level 2		Level 3		Total
	(In thousands)
Investments:
Money market funds	$	—	$	5,527	$	—	$	5,527
Registered investment companies	262,672		—		—		262,672
Total investments measured at fair value	$	262,672	$	5,527	$	—	$	268,199

	Assets at Fair Value as of September 30, 2020
	Level 1		Level 2		Level 3		Total
	(In thousands)
Investments:
Money market funds	$	—	$	5,525	$	—	$	5,525
Registered investment companies	202,720		—		—		202,720
Total investments measured at fair value	$	202,720	$	5,525	$	—	$	208,245