Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Revenue from External Customer [Line Items]
Deferred development lot sales	$ 7.5	$ 12.5	$ 14.3	$ 12.5
Tract sales and other	41.1	0.1	44.4	3.6
Revenues	301.5	421.6	518.2	829.2
Real Estate | Residential Real Estate [Member]
Revenue from External Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 252.9	$ 409.0	$ 459.5	$ 813.1