Fair Value Measurements (Details) - USD ($) $ in Millions		Jun. 30, 2016	Sep. 30, 2015	Jun. 30, 2015	Sep. 30, 2014
Homebuilding [Member]
Fair value balance sheet items measured on a recurring basis
Debt securities collateralized by residential real estate		$ 0.0	$ 33.9
Homebuilding [Member] | Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member]
Fair value balance sheet items measured on a recurring basis
Debt securities collateralized by residential real estate	[1]		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
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
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]	0.0	33.9	$ 35.6	$ 20.8
Financial Services [Member]
Fair value balance sheet items measured on a recurring basis
Mortgage loans held for sale		634.5	631.0
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member]
Fair value balance sheet items measured on a recurring basis
Mortgage loans held for sale	[2]	634.5	631.0
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Interest rate lock commitments [Member] | Estimate of Fair Value Measurement [Member]
Fair value balance sheet items measured on a recurring basis
Fair value of interest rate derivatives	[3]	14.1	3.6
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Forward sales of MBS [Member] | Estimate of Fair Value Measurement [Member]
Fair value balance sheet items measured on a recurring basis
Fair value of interest rate derivatives	[3]	(9.4)	(6.0)
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Best-efforts and mandatory commitments [Member] | Estimate of Fair Value Measurement [Member]
Fair value balance sheet items measured on a recurring basis
Fair value of interest rate derivatives	[3]	(1.1)	(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]	620.1	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]	14.1	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]	(9.4)	(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]	(1.1)	(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]	14.4	13.9	$ 13.5	$ 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 sold all of the debt securities to a third party for $35.8 million in January 2016. The resulting gain of $4.5 million on the sale is included in homebuilding other income in the consolidated statement of operations for the nine-month period ended June 30, 2016.

[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 June 30, 2016 and September 30, 2015 include $14.4 million and $13.9 million, respectively, of loans for which the Company elected the fair value option upon origination and which the Company did not sell into the secondary market. Mortgage loans held for sale totaling $14.9 million and $2.9 million were transferred to Level 3 during the nine months ended June 30, 2016 and 2015, respectively, due to significant unobservable inputs used in determining the fair value of the loans. 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.