Revenue from Contracts with Customers - Capitalized Commission Cost (Details) - USD ($)	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Other assets	$ 63,200,000	$ 60,500,000
Capitalized commission cost, amortized period	10 years
Amount of amortization	$ 9,900,000	9,200,000	$ 8,200,000
Impairment loss	$ 0	$ 0	$ 0