Other Assets, Accrued Expenses and Other Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2020	Mar. 31, 2020	Oct. 01, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018
Other assets
Earnest money and refundable deposits	$ 560.1			$ 540.0
Insurance receivables	82.4			75.1	$ 69.8
Other receivables	130.2			103.6
Prepaid assets	35.0			49.6
Margin deposits	29.2			19.6
Contract Asset Insurance Renewals	44.9			39.3
Operating Lease, Right-of-Use Asset	35.5		$ 39.0	0.0
Servicing Asset	10.0			0.0
Other	49.7			37.5
Other assets	1,005.9			912.8
Accrued expenses and other liabilities
Reserves for legal claims	461.3			434.7	440.9		$ 408.1
Employee compensation and related liabilities	309.9			282.1
Warranty liability	281.3	$ 262.7		247.3	$ 229.0	$ 213.9	$ 202.0
Mortgage hedging instruments and loan commitments	36.6			0.0
Accrued interest	36.5			26.3
Federal and state income tax liabilities	168.3			33.4
Inventory related accruals	53.3			61.5
Contract with Customer, Liability	74.0			57.7
Accrued property taxes	30.2			40.1
Operating Lease, Liability	38.1		$ 40.3	0.0
Other	98.8			95.0
Accrued expenses and other liabilities	1,588.3			1,278.1
Interest rate lock commitments [Member]
Other assets
Interest Rate Derivative Instruments Not Designated as Hedging Instruments, Asset at Fair Value	28.9			19.2
Multifamily [Member]
Other assets
Real Estate Held-for-sale	0.0			28.9
Other Segments [Member]
Other assets
Other assets	50.3			71.5
Accrued expenses and other liabilities
Accrued expenses and other liabilities	$ 8.7			$ 9.3