Fair Value Measurements (Details) - USD ($) $ in Millions		Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Homebuilding [Member]
Fair value balance sheet items measured on a recurring basis
Debt securities collateralized by residential real estate		$ 35.5	$ 33.9
Homebuilding [Member] | Fair Value, Measurements, Recurring [Member] | Estimated Fair Value [Member]
Fair value balance sheet items measured on a recurring basis
Debt securities collateralized by residential real estate	[1]	35.5	33.9
Homebuilding [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair value balance sheet items measured on a recurring basis
Debt securities collateralized by residential real estate	[1]	0.0	0.0
Homebuilding [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair value balance sheet items measured on a recurring basis
Debt securities collateralized by residential real estate	[1]	0.0	0.0
Homebuilding [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair value balance sheet items measured on a recurring basis
Debt securities collateralized by residential real estate	[1]	35.5	33.9	$ 20.8	$ 20.8
Financial Services [Member]
Fair value balance sheet items measured on a recurring basis
Mortgage loans held for sale		524.4	631.0
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Estimated Fair Value [Member]
Fair value balance sheet items measured on a recurring basis
Mortgage loans held for sale	[2]	524.4	631.0
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Interest rate lock commitments [Member] | Estimated Fair Value [Member]
Fair value balance sheet items measured on a recurring basis
Fair value of interest rate derivatives	[3]	5.5	3.6
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Forward sales of MBS [Member] | Estimated Fair Value [Member]
Fair value balance sheet items measured on a recurring basis
Fair value of interest rate derivatives	[3]	(0.5)	(6.0)
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Best-efforts and mandatory commitments [Member] | Estimated Fair Value [Member]
Fair value balance sheet items measured on a recurring basis
Fair value of interest rate derivatives	[3]	0.1	(1.1)
Financial Services [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair value balance sheet items measured on a recurring basis
Mortgage loans held for sale	[2]	0.0	0.0
Financial Services [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interest rate lock commitments [Member]
Fair value balance sheet items measured on a recurring basis
Fair value of interest rate derivatives	[3]	0.0	0.0
Financial Services [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Forward sales of MBS [Member]
Fair value balance sheet items measured on a recurring basis
Fair value of interest rate derivatives	[3]	0.0	0.0
Financial Services [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Best-efforts and mandatory commitments [Member]
Fair value balance sheet items measured on a recurring basis
Fair value of interest rate derivatives	[3]	0.0	0.0
Financial Services [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair value balance sheet items measured on a recurring basis
Mortgage loans held for sale	[2]	507.0	617.1
Financial Services [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interest rate lock commitments [Member]
Fair value balance sheet items measured on a recurring basis
Fair value of interest rate derivatives	[3]	5.5	3.6
Financial Services [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Forward sales of MBS [Member]
Fair value balance sheet items measured on a recurring basis
Fair value of interest rate derivatives	[3]	(0.5)	(6.0)
Financial Services [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Best-efforts and mandatory commitments [Member]
Fair value balance sheet items measured on a recurring basis
Fair value of interest rate derivatives	[3]	0.1	(1.1)
Financial Services [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair value balance sheet items measured on a recurring basis
Mortgage loans held for sale	[2]	17.4	13.9	$ 12.6	$ 12.0
Financial Services [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interest rate lock commitments [Member]
Fair value balance sheet items measured on a recurring basis
Fair value of interest rate derivatives	[3]	0.0	0.0
Financial Services [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Forward sales of MBS [Member]
Fair value balance sheet items measured on a recurring basis
Fair value of interest rate derivatives	[3]	0.0	0.0
Financial Services [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Best-efforts and mandatory commitments [Member]
Fair value balance sheet items measured on a recurring basis
Fair value of interest rate derivatives	[3]	$ 0.0	$ 0.0

[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.

[3] Fair value measurements of these derivatives represent changes in fair value, as calculated by reference to quoted prices for similar assets, and are reflected in the balance sheet. Changes in these fair values during the periods presented are included in financial services revenues in the consolidated statements of operations.