Notes Payable (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	May 31, 2012	Sep. 30, 2011
Unsecured:
Notes payable	$ 2,095.3		$ 1,704.6
Homebuilding [Member]
Unsecured:
Notes payable	1,948.6		1,588.1
Homebuilding [Member] | 6.875% senior notes due 2013 [Member]
Unsecured:
Notes payable	171.7		171.7
Stated interest rate	6.875%
Homebuilding [Member] | 6.125% senior notes due 2014, net [Member]
Unsecured:
Notes payable	145.4		145.2
Stated interest rate	6.125%
Homebuilding [Member] | 2% convertible senior notes due 2014, net [Member]
Unsecured:
Notes payable	439.5		418.1
Stated interest rate	2.00%
Homebuilding [Member] | 5.625% senior notes due 2014, net [Member]
Unsecured:
Notes payable	137.6		137.5
Stated interest rate	5.625%
Homebuilding [Member] | 5.25% senior notes due 2015, net [Member]
Unsecured:
Notes payable	157.3		157.3
Stated interest rate	5.25%
Homebuilding [Member] | 5.625% senior notes due 2016, net [Member]
Unsecured:
Notes payable	169.6		169.5
Stated interest rate	5.625%
Homebuilding [Member] | 6.5% senior notes due 2016, net [Member]
Unsecured:
Notes payable	372.4		383.1
Stated interest rate	6.50%
Homebuilding [Member] | 4.75% senior notes due 2017 [Member]
Unsecured:
Notes payable	350.0		0
Stated interest rate	4.75%	4.75%
Homebuilding [Member] | Other secured [Member]
Unsecured:
Notes payable	5.1		5.7
Financial Services [Member]
Unsecured:
Mortgage repurchase facility, maturing 2013	$ 146.7		$ 116.5