Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012		Sep. 30, 2011
Fair value balance sheet items measured on a recurring basis
Marketable securities, available-for-sale	$ 283.7		$ 297.6
Homebuilding [Member]
Fair value balance sheet items measured on a recurring basis
Marketable securities, available-for-sale	283.7		297.6
Homebuilding [Member] | Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair value balance sheet items measured on a recurring basis
Marketable securities, available-for-sale	60.7		16.3
Homebuilding [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair value balance sheet items measured on a recurring basis
Marketable securities, available-for-sale	223.0		281.3
Homebuilding [Member] | Estimated Fair Value [Member] | Fair Value, Measurements, Recurring [Member]
Fair value balance sheet items measured on a recurring basis
Marketable securities, available-for-sale	283.7		297.6
Financial Services [Member]
Fair value balance sheet items measured on a recurring basis
Mortgage loans held for sale	295.1		294.1
Financial Services [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair value balance sheet items measured on a recurring basis
Mortgage loans held for sale	295.1	[1]	294.1	[1]
Financial Services [Member] | 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	3.8	[2]	3.9	[2]
Financial Services [Member] | 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	(2.6)	[2]	(4.0)	[2]
Financial Services [Member] | 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	(0.3)	[2]	(0.9)	[2]
Financial Services [Member] | Estimated Fair Value [Member] | Fair Value, Measurements, Recurring [Member]
Fair value balance sheet items measured on a recurring basis
Mortgage loans held for sale	295.1	[1]	294.1	[1]
Financial Services [Member] | Estimated Fair Value [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	3.8	[2]	3.9	[2]
Financial Services [Member] | Estimated Fair Value [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	(2.6)	[2]	(4.0)	[2]
Financial Services [Member] | Estimated Fair Value [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	$ (0.3)	[2]	$ (0.9)	[2]

[1] 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.

[2] Fair value measurements of these derivatives represent changes in fair value since inception. These changes are reflected in the balance sheet and included in financial services revenues on the consolidated statement of operations.