Notes Payable (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Sep. 30, 2012
Unsecured:
Notes payable	$ 3,273.0	$ 2,493.1
Homebuilding [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	0	0
Unsecured:
Notes payable	3,027.2	2,305.3
Homebuilding [Member] | 2% convertible senior notes [Member]
Unsecured:
Notes payable	462.4	447.0
Stated interest rate	2.00%
Homebuilding [Member] | 6.875% senior notes due 2013, net [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	145.6	145.5
Stated interest rate	6.125%
Homebuilding [Member] | 5.625% senior notes due 2014, net [Member]
Unsecured:
Notes payable	137.7	137.6
Stated interest rate	5.625%
Homebuilding [Member] | 5.25% senior notes due 2015 [Member]
Unsecured:
Notes payable	157.5	157.4
Stated interest rate	5.25%
Homebuilding [Member] | 4.375% senior notes due 2022 [Member]
Unsecured:
Notes payable	350.0	350.0
Stated interest rate	4.375%
Homebuilding [Member] | Other secured [Member]
Unsecured:
Notes payable	10.1	4.1
Homebuilding [Member] | 5.625% senior notes due 2016 [Member]
Unsecured:
Notes payable	169.7	169.6
Stated interest rate	5.625%
Homebuilding [Member] | 6.50% senior notes due 2016 [Member]
Unsecured:
Notes payable	372.5	372.4
Stated interest rate	6.50%
Homebuilding [Member] | 4.75% senior notes due 2017 [Member]
Unsecured:
Notes payable	350.0	350.0
Stated interest rate	4.75%
Homebuilding [Member] | 3.625% senior notes due 2018 [Member]
Unsecured:
Notes payable	400.0	0
Stated interest rate	3.625%
Homebuilding [Member] | 4.75% senior notes due 2023 [Member]
Unsecured:
Notes payable	300.0	0
Stated interest rate	4.75%
Financial Services [Member]
Unsecured:
Mortgage repurchase facility, maturing 2014	$ 245.8	$ 187.8