Pension Plan and Retirement Benefits (Tables)

12 Months Ended

Sep. 30, 2023

Pension Plan and Retirement Benefits

Schedule of status of employee pension benefit plans and other postretirement benefit plans

	Defined Benefit				Postretirement
	Pension Plans				Health Care Benefits
	Year Ended				Year Ended
	September 30,				September 30,
	2022		2023		2022		2023
Change in Benefit Obligation:
Projected benefit obligation at beginning of year	$	315,466	$	231,275	$	82,964	$	64,037
Service cost		4,728		2,689		1,825		1,389
Interest cost		7,936		11,548		2,234		3,199
Actuarial (gains) losses		(81,225)		(5,236)		(20,343)		(14,171)
Benefits paid		(15,223)		(14,615)		(2,643)		(2,128)
Administrative expenses		(407)		(871)		—		—
Projected benefit obligation at end of year	$	231,275	$	224,790	$	64,037	$	52,326
Change in Plan Assets:
Fair value of plan assets at beginning of year	$	297,703	$	218,321	$	—	$	—
Actual return on assets		(69,752)		11,136		—		—
Employer contributions		6,000		6,000		2,643		2,128
Benefits paid		(15,223)		(14,615)		(2,643)		(2,128)
Administrative expenses		(407)		(871)		—		—
Fair value of plan assets at end of year	$	218,321	$	219,971	$	—	$	—
Funded Status of Plan:
Unfunded status	$	(12,954)	$	(4,819)	$	(64,037)	$	(52,326)

Schedule of amounts recognized in the consolidated balance sheets and amounts expected to be recognized from AOCI into the statement of operations in the following year

	Defined Benefit				Postretirement				Non-Qualified				All Plans
	Pension Plans				Health Care Benefits				Pension Plans				Combined
	September 30,				September 30,				September 30,				September 30,
	2022		2023		2022		2023		2022		2023		2022		2023
Accrued pension and postretirement benefits:
Current	$	—	$	—	$	(3,276)	$	(2,845)	$	(95)	$	(95)	$	(3,371)	$	(2,940)
Non-current		(12,954)		(4,819)		(60,761)		(49,481)		(435)		(397)		(74,150)		(54,697)
Accrued pension and postretirement benefits	$	(12,954)	$	(4,819)	$	(64,037)	$	(52,326)	$	(530)	$	(492)	$	(77,521)	$	(57,637)
Accumulated other comprehensive (income) loss:
Net (income) loss		22,496		20,663		(30,807)		(42,699)		—		—		(8,311)		(22,036)
Prior service cost		1,365		1,130		—		—		—		—		1,365		1,130
Total accumulated other comprehensive (income) loss	$	23,861	$	21,793	$	(30,807)	$	(42,699)	$	—	$	—	$	(6,946)	$	(20,906)

Schedule of components of net periodic pension and postretirement benefit cost

	Defined Benefit Pension Plans
	Year Ended September 30,
	2021		2022		2023
Service cost	$	5,628	$	4,728	$	2,689
Interest cost		7,481		7,936		11,548
Expected return on assets		(16,356)		(14,818)		(14,570)
Amortization of prior service cost		239		233		236
Recognized actuarial loss		7,721		—		31
Net periodic cost	$	4,713	$	(1,921)	$	(66)

	Postretirement
	Health Care Benefits
	Year Ended September 30,
	2021		2022		2023
Service cost	$	1,095	$	1,825	$	1,389
Interest cost		2,292		2,234		3,199
Recognized actuarial loss		—		(240)		(2,279)
Net periodic cost	$	3,387	$	3,819	$	2,309

Schedule of assumptions used to determine actuarial present value of the projected pension benefit obligation and postretirement health care benefit obligation for the plans

	September 30,		September 30,
	2022		2023
Discount rate (postretirement health care)(1)	5.13	%	5.63	%
Discount rate (U.S. pension plan)(1)	5.13	%	5.63	%
Discount rate (U.K. pension plan)	5.90	%	5.70	%
Rate of compensation increase (U.S. pension plan only)	2.50	%	3.50	%

Schedule of assumptions used to determine net periodic pension and postretirement health care benefit costs for the plans

	Defined Benefit
	Pension and
	Postretirement Health
	Care Plans
	Year Ended
	September 30,
	2021		2022		2023
Discount rate (postretirement health care plan)	2.50	%	2.75	%	5.13	%
Discount rate (U.S. pension plan)	2.25	%	2.63	%	5.13	%
Discount rate (U.K. pension plan)	1.50	%	2.00	%	5.90	%
Expected return on plan assets (U.S. pension plan)	7.25	%	5.25	%	6.88	%
Expected return on plan assets (U.K. pension plan)	2.00	%	3.00	%	5.50	%
Rate of compensation increase (U.S. pension plan only)	2.50	%	2.50	%	2.50	%

Schedule of plan assets by level within the fair value hierarchy

	September 30, 2022
	Level 1
	Active		Level 2
	Markets for		Other
	Identical		Observable
	Assets		Inputs		NAV		Total
U.S. Pension Plan Assets:
U.S. corporate and government bonds	$	15,926	$	158,582	$	—	$	174,508
U.S. common stock mutual funds		—	$	—	$	16,471		16,471
Common /collective funds
Bonds		—		—		—		—
Short-term money market		—		—		—		—
U.S. common stock		—		—		6,847		6,847
International equity		—		—		5,390		5,390
Total U.S.	$	15,926	$	158,582	$	28,708	$	203,216
U.K. Plan Assets:
Equities	$	—	$	—	$	5,135	$	5,135
Bonds		—		—		8,006		8,006
Other		—		—		1,964		1,964
Total U.K.	$	—	$	—	$	15,105	$	15,105
Total pension plan assets	$	15,926	$	158,582	$	43,813	$	218,321

	September 30, 2023
	Level 1
	Active		Level 2
	Markets for		Other
	Identical		Observable
	Assets		Inputs		NAV		Total
U.S. Pension Plan Assets:
U.S. corporate and government bonds	$	26,647	$	154,686	$	—	$	181,333
U.S. common stock mutual funds		—		—		17,900		17,900
International equity		—		—		4,538		4,538
Total U.S.	$	26,647	$	154,686	$	22,438	$	203,771
U.K. Plan Assets:
Bonds		—		—		10,692		10,692
Short-term money market		5,508		—		—		5,508
Total U.K.	$	5,508	$	—	$	10,692	$	16,200
Total pension plan assets	$	32,155	$	154,686	$	33,130	$	219,971

Schedule of asset classes as a percent of total assets

Asset Class	Target(1)
Equity	11	%
Fixed Income	89	%
Real Estate and Other	—	%

(1) The Company adjusts the target allocation based on the fair value of pension assets as a percentage of the projected pension obligation.  

Schedule of expected benefit payments

			Postretirement
Fiscal Year Ending September 30	Pension		Health Care
2024	$	16,001	$	3,988
2025		16,308		4,021
2026		16,623		4,124
2027		16,953		4,063
2028		17,002		4,101
2029 - 2033 (in total)		86,225		21,333