Retirement and Postretirement Employee Benefit Plans (Tables)

12 Months Ended

Sep. 30, 2022

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:

	Employee Pension Plan		Supplemental Executive Retirement Plans		Postretirement Plan		Total
	(In thousands)
September 30, 2022
Unrecognized prior service credit	$	(121)	$	—	$	(51,079)	$	(51,200)
Unrecognized actuarial (gain) loss	(32,159)		14,029		(87,527)		(105,657)
	$	(32,280)	$	14,029	$	(138,606)	$	(156,857)
September 30, 2021
Unrecognized prior service credit	$	(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)

Schedule of Allocation of Plan Assets

The following table presents asset allocation information for the Master Trust as of September 30, 2022 and 2021.

	Targeted Allocation  Range	Actual Allocation September 30
Security Class		2022	2021
Domestic equities	35%-55%	39.7%	44.5%
International equities	10%-20%	14.6%	16.9%
Fixed income	5%-30%	16.0%	16.0%
Company stock	0%-15%	15.3%	10.6%
Other assets	0%-20%	14.4%	12.0%

The following table presents asset allocation information for the Retiree Medical Plan assets as of September 30, 2022 and 2021.

	Actual Allocation September 30
Security Class	2022	2021
Diversified investment funds	97.7%	97.9%
Cash and cash equivalents	2.3%	2.1%

Schedule of Assumptions Used

The actuarial assumptions used to determine the pension liability for the Pension Plan was determined as of September 30, 2022 and 2021 and the actuarial assumptions used to determine the net periodic pension cost for the Pension Plan was determined as of September 30, 2021, 2020 and 2019.

Additional assumptions are presented in the following table:

	Pension Liability				Pension Cost
	2022		2021		2022		2021		2020
Discount rate	5.66	%	2.97	%	2.97	%	2.80	%	3.29	%
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	%	6.25	%	6.50	%
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, 2022 and 2021 and the actuarial assumptions used to determine the net periodic pension cost for the Supplemental Plans were determined as of September 30, 2021, 2020 and 2019. These assumptions are presented in the following table:

	Pension Liability				Pension Cost
	2022		2021		2022		2021		2020
Discount rate (1)	5.71	%	2.57	%	2.57	%	2.90	%	3.19	%
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 Retiree Medical Plan were determined as of September 30, 2022 and 2021 and the actuarial assumptions used to determine the net periodic pension cost for the Retiree Medical Plan were determined as of September 30, 2021, 2020 and 2019.

The assumptions are presented in the following table:

	Postretirement Liability				Postretirement Cost
	2022		2021		2022		2021		2020
Discount rate	5.61	%	3.01	%	3.01	%	2.80	%	3.29	%
Expected return on plan assets	4.94	%	4.94	%	4.94	%	4.94	%	5.14	%
Initial trend rate	6.25	%	6.25	%	6.25	%	6.25	%	6.25	%
Ultimate trend rate	4.75	%	5.00	%	5.00	%	5.00	%	5.00	%
Ultimate trend reached in	2029		2027		2027		2026		2025

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

The following table presents the Pension Plan’s accumulated benefit obligation, projected benefit obligation and funded status as of September 30, 2022 and 2021:

	2022		2021
	(In thousands)
Accumulated benefit obligation	$	428,629	$	558,639
Change in projected benefit obligation:
Benefit obligation at beginning of year	$	596,029	$	604,221
Service cost	16,165		17,369
Interest cost	17,606		16,883
Actuarial gain	(141,567)		(7,561)
Benefits paid	(38,706)		(34,883)
Benefit obligation at end of year	449,527		596,029
Change in plan assets:
Fair value of plan assets at beginning of year	596,806		528,881
Actual return on plan assets	(87,575)		92,808
Employer contributions	8,500		10,000
Benefits paid	(38,706)		(34,883)
Fair value of plan assets at end of year	479,025		596,806
Reconciliation:
Funded status	29,498		777
Unrecognized prior service cost	—		—
Unrecognized net loss	—		—
Net amount recognized	$	29,498	$	777

The following table presents the Supplemental Plans’ accumulated benefit obligation, projected benefit obligation and funded status as of September 30, 2022 and 2021:

	2022		2021
	(In thousands)
Accumulated benefit obligation	$	79,233	$	100,981
Change in projected benefit obligation:
Benefit obligation at beginning of year	$	104,301	$	129,140
Service cost	1,129		1,067
Interest cost	2,647		3,180
Actuarial (gain) loss	(22,471)		1,332
Benefits paid	(4,831)		(4,720)
Settlements	—		(25,698)
Benefit obligation at end of year	80,775		104,301
Change in plan assets:
Fair value of plan assets at beginning of year	—		—
Employer contribution	4,831		30,418
Benefits paid	(4,831)		(4,720)
Settlements	—		(25,698)
Fair value of plan assets at end of year	—		—
Reconciliation:
Funded status	(80,775)		(104,301)
Unrecognized prior service cost	—		—
Unrecognized net loss	—		—
Accrued pension cost	$	(80,775)	$	(104,301)

The following table presents the Retiree Medical Plan’s benefit obligation and funded status as of September 30, 2022 and 2021:

	2022		2021
	(In thousands)
Change in benefit obligation:
Benefit obligation at beginning of year	$	355,156	$	370,678
Service cost	10,235		11,000
Interest cost	10,734		15,372
Plan participants’ contributions	3,210		5,648
Actuarial (gain) loss	(112,748)		6,800
Benefits paid	(16,359)		(19,610)
Plan amendments	—		(34,732)
Benefit obligation at end of year	250,228		355,156
Change in plan assets:
Fair value of plan assets at beginning of year	268,199		208,245
Actual return on plan assets	(40,113)		53,335
Employer contributions	14,749		20,581
Plan participants’ contributions	3,210		5,648
Benefits paid	(16,359)		(19,610)
Fair value of plan assets at end of year	229,686		268,199
Reconciliation:
Funded status	(20,542)		(86,957)
Unrecognized transition obligation	—		—
Unrecognized prior service cost	—		—
Unrecognized net loss	—		—
Accrued postretirement cost	$	(20,542)	$	(86,957)

Schedule of Net Benefit Costs

Net periodic pension cost for the Pension Plan for fiscal 2022, 2021 and 2020 is presented in the following table.

	Fiscal Year Ended September 30
	2022		2021		2020
	(In thousands)
Components of net periodic pension cost:
Service cost	$	16,165	$	17,369	$	17,551
Interest cost (1)	17,606		16,883		19,028
Expected return on assets (1)	(29,531)		(27,913)		(28,316)
Amortization of prior service credit (1)	(231)		(231)		(231)
Recognized actuarial loss (1)	4,638		8,686		9,025
Net periodic pension cost	$	8,647	$	14,794	$	17,057

(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 2022, 2021 and 2020 is presented in the following table.

	Fiscal Year Ended September 30
	2022		2021		2020
	(In thousands)
Components of net periodic pension cost:
Service cost	$	1,129	$	1,067	$	1,074
Interest cost (1)	2,647		3,180		4,188
Recognized actuarial loss (1)	3,166		3,560		3,945
Settlements (1)	—		9,151		9,180
Net periodic pension cost	$	6,942	$	16,958	$	18,387

(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 the Retiree Medical Plan for fiscal 2022, 2021 and 2020 is presented in the following table.

	Fiscal Year Ended September 30
	2022		2021		2020
	(In thousands)
Components of net periodic postretirement cost:
Service cost	$	10,235	$	11,000	$	13,466
Interest cost (1)	10,734		15,372		10,612
Expected return on assets (1)	(13,249)		(10,455)		(10,499)
Amortization of prior service (credit) cost (1)	(13,234)		30,533		173
Recognized actuarial (gain) loss (1)	—		1,172		(1,337)
Net periodic postretirement cost	$	(5,514)	$	47,622	$	12,415

(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 Pension Plan had net accounts receivable of $2.4 million and $2.1 million at September 30, 2022 and 2021, which materially approximates fair value due to the short-term nature of these assets.

	Assets at Fair Value as of September 30, 2022
	Level 1		Level 2		Level 3		Total
	(In thousands)
Investments:
Common stocks	$	210,325	$	—	$	—	$	210,325
Money market funds	—		14,490		—		14,490
Registered investment companies	53,401		—		—		53,401
Government securities:
Mortgage-backed securities	—		14,175		—		14,175
U.S. treasuries	3,681		28		—		3,709
Corporate bonds	—		22,320		—		22,320
Total investments measured at fair value	$	267,407	$	51,013	$	—	318,420
Investments measured at net asset value:
Common/collective trusts (1)							86,891
Limited partnerships (1)							71,331
Total investments							$	476,642

	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

(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)
2023	$	40,569	$	9,995
2024	40,126		9,538
2025	40,396		30,135
2026	41,611		6,594
2027	41,358		3,946
2028-2032	198,156		27,420

The following benefit payments paid by the Company, retirees and prescription drug subsidies for our Retiree Medical Plan, which reflect expected future service, as appropriate, are expected to be paid in the following fiscal years.

	Company Payments		Retiree Payments		Subsidy Payments		Total Postretirement Benefits
	(In thousands)
2023	$	17,141	$	2,445	$	—	$	19,586
2024	17,409		2,410		—		19,819
2025	17,582		2,314		—		19,896
2026	18,022		2,282		—		20,304
2027	18,269		2,193		—		20,462
2028-2032	94,528		9,638		—		104,166

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, 2022 and 2021. 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, 2022
	Level 1		Level 2		Level 3		Total
	(In thousands)
Investments:
Money market funds	$	—	$	5,214	$	—	$	5,214
Registered investment companies	224,472		—		—		224,472
Total investments measured at fair value	$	224,472	$	5,214	$	—	$	229,686

	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