Other Assets, Accrued Expenses and Other Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2021	Sep. 30, 2020
Other Assets, Accrued Expenses and Other Liabilities [Abstract]
Receivables, net	$ 3.2	$ 0.4
Earnest money notes receivable on sales contracts	2.6	4.8
Lease right of use assets	4.9	3.6
Prepaid expenses	5.3	4.9
Land purchase contract deposits	9.9	5.5
Other assets	4.3	5.7
Total Other assets	30.2	24.9
Accrued employee compensation and benefits	5.9	6.2
Accrued property taxes	1.8	3.8
Lease liabilities	5.3	3.8
Accrued interest	14.3	14.0
Contract liabilities	0.2	0.2
Deferred income	9.3	9.3
Income taxes payable	2.8	0.5
Accrued development costs	68.2	44.4
Other accrued expenses	3.4	10.2
Other liabilities	1.2	1.4
Total Accrued expenses and other liabilities	$ 112.4	$ 93.8