Pension Plans - Components of Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Amortization Of Acquired Intangible Assets Excluding Purchased Software	Amortization Of Acquired Intangible Assets Excluding Purchased Software	Amortization Of Acquired Intangible Assets Excluding Purchased Software
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Restructuring Costs and Asset Impairment Charges	Restructuring Costs and Asset Impairment Charges	Restructuring Costs and Asset Impairment Charges
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost of projected benefit obligation	$ 2,126	$ 550	$ 692
Service cost	690	1,016	1,127
Expected return on plan assets	(3,541)	(3,712)	(3,643)
Amortization of prior service cost	0	(4)	(5)
Recognized actuarial loss	241	1,425	4,139
Settlement gain	0	(82)	0
Net periodic pension (benefit) cost	$ (484)	$ (807)	$ 2,310