Pension Plans - Change in Benefit Obligation And Plan Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value, beginning of year	$ 78,385
Actual return on plan assets	2,300	$ 7,400	$ (3,000)
Employer contributions	3,000	3,000	2,600
Plan assets at fair value—end of year	67,581	78,385
Unrecognized actuarial loss	5,400	(30,200)
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation, beginning of year	96,512	97,832
Service cost	1,016	1,127	1,426
Interest cost	550	692	527
Actuarial loss (gain)	(22,616)	1,100
Foreign exchange impact	(12,949)	(1,562)
Participant contributions	96	109
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Benefits paid	(2,343)	(2,786)
Divestiture of business	1,184	0
Settlements	(953)	0
Projected benefit obligation, end of year	58,129	96,512	97,832
Plan assets at fair value, beginning of year	78,385	72,063
Actual return on plan assets	2,348	7,383
Employer contributions	3,007	3,049
Participant contributions	96	109
Foreign exchange impact	(12,959)	(1,433)
Settlements	(953)	0
Benefits paid	(2,343)	(2,786)
Plan assets at fair value—end of year	67,581	78,385	$ 72,063
Accumulated benefit obligation, end of year	57,310	95,090
Non-current asset	19,234	855
Non-current liability	(9,434)	(18,615)
Current liability	(348)	(367)
Unrecognized actuarial loss	5,408	30,213
Pension Plan | Underfunded Plan
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Underfunded or Overfunded Status	(9,782)	(18,982)
Pension Plan | Overfunded Plan
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Underfunded or Overfunded Status	$ 19,234	$ 855