Other Assets, Accrued Expenses and Other Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Oct. 01, 2019	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018
Other assets
Earnest money and refundable deposits	$ 580.9			$ 540.0
Insurance receivables	76.6			75.1	$ 56.9
Other receivables	112.4			103.6
Prepaid assets	48.4			49.6
Margin deposits	83.7			19.6
Contract Asset Insurance Renewals	42.2			39.3
Operating Lease, Right-of-Use Asset	37.8		$ 39.0	0.0
Other	104.1			56.7
Other assets	1,086.1			912.8
Accrued expenses and other liabilities
Reserves for legal claims	442.2			434.7	419.1		$ 408.1
Employee compensation and related liabilities	269.2			282.1
Warranty liability	262.7	$ 251.6		247.3	$ 213.9	$ 205.6	$ 202.0
Mortgage hedging instruments and loan commitments	81.5			0.0
Accrued interest	30.7			26.3
Federal and state income tax liabilities	20.0			33.4
Inventory related accruals	48.9			61.5
Customer deposits	68.3			57.7
Accrued property taxes	23.8			40.1
Operating Lease, Liability	40.5		$ 40.3	0.0
Other	93.8			95.0
Accrued expenses and other liabilities	1,381.6			1,278.1
Multifamily [Member]
Other assets
Real Estate Held-for-sale	0.0			28.9
Other Segments [Member]
Other assets
Other assets	47.9			71.5
Accrued expenses and other liabilities
Accrued expenses and other liabilities	$ 10.5			$ 9.3