Fair Value Measurements - Level 3 Rollforward (Details) - USD ($) $ in Millions		3 Months Ended
		Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014	Dec. 31, 2012	Sep. 30, 2015	Sep. 30, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments to Acquire Other Investments					$ 18.6
Payments to Acquire Land			$ 19.9
Homebuilding [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities collateralized by residential real estate		$ 35.5				$ 33.9
Homebuilding [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt securities collateralized by residential real estate	[1]	35.5		$ 20.8		33.9	$ 20.8
Financial Services [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage loans held for sale		524.4				631.0
Financial Services [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortgage loans held for sale	[2]	17.4		12.6		$ 13.9	$ 12.0
Land [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments to Acquire Land			5.1
Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments to Acquire Land			$ 14.8
Debt Securities [Member] | Homebuilding [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	[1]	1.9		0.0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[1]	0.0		0.0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0.0		0.0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		(0.3)		0.0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	[2]	0.0		0.0
Loans Receivable [Member] | Financial Services [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	[2]	(0.1)		0.2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[2]	0.0		0.0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	[2]	(0.3)		(0.3)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0.0		0.0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	[2]	$ 3.9		$ 0.7

[1] In October 2012, the Company purchased defaulted debt securities, which were secured by residential real estate, for $18.6 million in cash. In fiscal 2015, the Company purchased the residential real estate parcel and all additional defaulted debt securities associated with the parcel for $19.9 million in cash, of which $5.1 million was allocated to the land and $14.8 million was allocated to the debt securities. The Company is developing the property to build and sell homes and sold the debt securities to a third party in January 2016. These securities, which are included in other assets in the consolidated balance sheets, are classified as available for sale and are reflected at fair value. The fair value of the securities was determined based on the proceeds received from their sale in January 2016. Unrealized gains or losses on these securities, net of tax, are recorded in accumulated other comprehensive income (loss) in the consolidated balance sheets.

[2] Mortgage loans held for sale are reflected at fair value. Interest income earned on mortgage loans held for sale is based on contractual interest rates and included in financial services interest and other income. Mortgage loans held for sale at December 31, 2015 includes $17.4 million of originated loans for which the Company elected the fair value option upon origination and which the Company has not sold into the secondary market, but plans to sell as market conditions permit. The fair value of these mortgage loans held for sale is generally calculated considering the secondary market and adjusted for the value of the underlying collateral, including interest rate risk, liquidity risk and prepayment risk.