Other Assets and Accrued Expenses and Other Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2015
Homebuilding other assets
Homebuilding other assets	$ 525.9		$ 499.6
Homebuilding [Member]
Homebuilding other assets
Insurance receivables	82.6		88.7	$ 97.5
Earnest money and refundable deposits	270.8		219.7
Accounts and notes receivable	39.4		35.9
Prepaid assets	12.0		29.5
Rental properties	46.5		56.9
Other assets	19.0		25.5
Homebuilding other assets	470.3		456.2
Homebuilding accrued expenses and other liabilities
Reserves for legal claims	453.5		423.5	426.4		$ 451.0
Employee compensation and related liabilities	171.2		183.3
Warranty liability	120.3	$ 112.8	104.4	$ 93.7	$ 87.9	$ 82.0
Accrued interest	38.4		17.9
Federal and state income tax liabilities	35.8		28.1
Inventory related accruals	22.9		31.9
Homebuyer deposits	55.8		54.2
Accrued property taxes	24.2		35.2
Other liabilities	35.5		38.6
Homebuilding accrued expenses and other liabilities	$ 957.6		$ 917.1