Pension Plans - Change in Benefit Obligation And Plan Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value, beginning of year	$ 67,581
Actual return (loss) on plan assets	(1,900)	$ 2,300	$ 7,400
Employer contributions	1,300	3,000	3,000
Plan assets at fair value, end of year	68,875	67,581
Unrecognized actuarial loss	9,600	(5,400)
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation, beginning of year	58,129	96,512
Service cost	690	1,016	1,127
Interest cost	2,126	550	692
Actuarial gain	(1,589)	(22,616)
Foreign exchange impact	3,714	(12,949)
Participant contributions	96	96
Benefits paid	(2,968)	(2,343)
Plan amendments	235	0
Divestiture of business	0	1,184
Settlements	0	(953)
Projected benefit obligation, end of year	60,433	58,129	96,512
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value, beginning of year	67,581	78,385
Actual return (loss) on plan assets	(1,919)	2,348
Employer contributions	1,343	3,007
Participant contributions	96	96
Foreign exchange impact	4,593	(12,959)
Settlements	0	(953)
Benefits paid	(2,968)	(2,343)
Plan amendments	149	0
Plan assets at fair value, end of year	68,875	67,581	$ 78,385
Accumulated benefit obligation, end of year	59,602	57,310
Non-current asset	19,135	19,234
Non-current liability	(10,419)	(9,434)
Current liability	(274)	(348)
Unrecognized actuarial loss	9,573	5,408
Pension Plan | Underfunded Plan
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Underfunded or Overfunded Status	(10,693)	(9,782)
Pension Plan | Overfunded Plan
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Underfunded or Overfunded Status	$ 19,135	$ 19,234