Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Revenue from External Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 1,544.3	$ 1,459.3	$ 1,275.7
Deferred development lot sales	0.0	8.1	29.0
Tract sales and other	118.1	42.0	132.2
Revenues	$ 1,662.4	$ 1,509.4	$ 1,436.9