Pension Plan and Retirement Benefits (Tables)

12 Months Ended

Sep. 30, 2022

Pension and Post-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,
	2021		2022		2021		2022
Change in Benefit Obligation:
Projected benefit obligation at beginning of year	$	345,390	$	315,466	$	93,339	$	82,964
Service cost		5,795		4,728		1,095		1,825
Interest cost		7,481		7,936		2,292		2,234
Actuarial (gains) losses		(27,225)		(81,225)		(10,943)		(20,343)
Benefits paid		(14,965)		(15,223)		(2,819)		(2,643)
Administrative expenses		(1,010)		(407)		—		—
Projected benefit obligation at end of year	$	315,466	$	231,275	$	82,964	$	64,037
Change in Plan Assets:
Fair value of plan assets at beginning of year	$	245,546	$	297,703	$	—	$	—
Actual return on assets		47,132		(69,752)		—		—
Employer contributions		21,000		6,000		2,819		2,643
Benefits paid		(14,965)		(15,223)		(2,819)		(2,643)
Administrative expenses		(1,010)		(407)		—		—
Fair value of plan assets at end of year	$	297,703	$	218,321	$	—	$	—
Funded Status of Plan:
Unfunded status	$	(17,763)	$	(12,954)	$	(82,964)	$	(64,037)

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,
	2021		2022		2021		2022		2021		2022		2021		2022
Accrued pension and postretirement benefits:
Current	$	—	$	—	$	(3,459)	$	(3,276)	$	(95)	$	(95)	$	(3,554)	$	(3,371)
Non-current		(17,763)		(12,954)		(79,505)		(60,761)		(528)		(435)		(97,796)		(74,150)
Accrued pension and postretirement benefits	$	(17,763)	$	(12,954)	$	(82,964)	$	(64,037)	$	(623)	$	(530)	$	(101,350)	$	(77,521)
Accumulated other comprehensive income (loss):
Net income (loss)		19,150		22,496		(10,704)		(30,807)		—		—		8,446		(8,311)
Prior service cost		1,599		1,365		—		—		—		—		1,599		1,365
Total accumulated other comprehensive income (loss)	$	20,749	$	23,861	$	(10,704)	$	(30,807)	$	—	$	—	$	10,045	$	(6,946)

Schedule of components of net periodic pension and postretirement benefit cost

	Defined Benefit Pension Plans
	Year Ended September 30,
	2020		2021		2022
Service cost	$	5,546	$	5,628	$	4,728
Interest cost		8,866		7,481		7,936
Expected return on assets		(15,061)		(16,356)		(14,818)
Amortization of prior service cost		228		239		233
Recognized actuarial loss		7,288		7,721		—
Net periodic cost	$	6,867	$	4,713	$	(1,921)

	Postretirement
	Health Care Benefits
	Year Ended September 30,
	2020		2021		2022
Service cost	$	1,416	$	1,095	$	1,825
Interest cost		3,493		2,292		2,234
Recognized actuarial loss		1,848		—		(240)
Net periodic cost	$	6,757	$	3,387	$	3,819

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,
	2021		2022
Discount rate (postretirement health care)(1)	2.75	%	5.13	%
Discount rate (U.S. pension plan)(1)	2.63	%	5.13	%
Discount rate (U.K. pension plan)	2.00	%	5.90	%
Rate of compensation increase (U.S. pension plan only)	2.50	%	2.50	%

(1) The discount rate for the Postretirement health care plan and the U.S. pension plan are derived using the FTSE Pension Discount Curve and projected benefit payments.

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,
	2020		2021		2022
Discount rate (postretirement health care plan)	3.13	%	2.50	%	2.75	%
Discount rate (U.S. pension plan)	2.88	%	2.25	%	2.63	%
Discount rate (U.K. pension plan)	1.70	%	1.50	%	2.00	%
Expected return on plan assets (U.S. pension plan)	7.25	%	7.25	%	5.25	%
Expected return on plan assets (U.K. pension plan)	2.20	%	2.00	%	3.00	%
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, 2021
	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	$	23,654	$	169,953	$	—	$	193,607
U.S. common stock mutual funds		—	$	—	$	44,743		44,743
Common /collective funds
U.S. common stock		—		—		19,672		19,672
International equity		—		—		16,245		16,245
Total U.S.	$	23,654	$	169,953	$	80,660	$	274,267
U.K. Plan Assets:
Equities	$	—	$	—	$	8,202	$	8,202
Bonds		—		—		12,890		12,890
Other		—		—		2,344		2,344
Total U.K.	$	—	$	—	$	23,436	$	23,436
Total pension plan assets	$	23,654	$	169,953	$	104,096	$	297,703

	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

Schedule of asset classes as a percent of total assets

Asset Class	Target(1)
Equity	14	%
Fixed Income	86	%
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
2023	$	15,738	$	4,828
2024		16,081		4,841
2025		16,366		4,890
2026		16,573		5,068
2027		16,802		5,007
2028 - 2032 (in total)		83,895		25,956