Pension Plans - Change in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
AOCI Attributable to Parent, Before Tax [Roll Forward]
Beginning balance	$ 2,038,468	$ 1,438,248
Ending balance	2,296,034	2,038,468
Pension Plan
AOCI Attributable to Parent, Before Tax [Roll Forward]
Beginning balance	30,213	37,175
Recognized during year - net actuarial losses	(1,421)	(4,135)
Occurring during year - settlement gain	82	0
Occurring during year - net actuarial losses	(21,253)	(2,640)
Foreign exchange impact	(2,213)	(187)
Ending balance	$ 5,408	$ 30,213