Other Assets, Accrued Expenses and Other Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Oct. 01, 2019	Sep. 30, 2019
Segment Reporting Information [Line Items]
Receivables, net	$ 1.1		$ 1.1
Operating Lease, Right-of-Use Asset	2.7	$ 2.7	0.0
Prepaid expenses	2.4		3.4
Land purchase contract deposits	5.0		5.1
Other assets	6.2		4.1
Total Other assets	17.4		13.7
Accrued employee compensation and benefits	4.9		5.6
Accrued property taxes	1.8		2.1
Accrued interest	7.4		13.5
Contract liabilities	4.0		2.5
Deferred income	9.3		9.3
Accrued Development Costs	38.9		35.4
Other accrued expenses	10.6		8.4
Other liabilities	5.8		2.8
Total Accrued expenses and other liabilities	$ 82.7		$ 79.6