Notes Payable (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Sep. 30, 2013
Unsecured:
Notes payable	$ 3,862.1	$ 3,509.0
Homebuilding [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	0	0
Unsecured:
Notes payable	3,638.3	3,270.4
Homebuilding [Member] | 6.125% senior notes due 2014, net [Member]
Unsecured:
Notes payable	0	145.8
Stated interest rate	6.125%
Homebuilding [Member] | 2% convertible senior notes [Member]
Unsecured:
Notes payable	495.6	478.7
Stated interest rate	2.00%
Homebuilding [Member] | 5.625% senior notes due 2014, net [Member]
Unsecured:
Notes payable	137.9	137.8
Stated interest rate	5.625%
Homebuilding [Member] | 5.25% senior notes due 2015 [Member]
Unsecured:
Notes payable	157.6	157.5
Stated interest rate	5.25%
Homebuilding [Member] | 5.625% senior notes due 2016 [Member]
Unsecured:
Notes payable	169.8	169.7
Stated interest rate	5.625%
Homebuilding [Member] | 6.50% senior notes due 2016 [Member]
Unsecured:
Notes payable	372.5	372.5
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	400.0
Stated interest rate	3.625%
Homebuilding [Member] | 3.75% senior notes due 2019 [Member]
Unsecured:
Notes payable	500.0	0
Stated interest rate	3.75%
Homebuilding [Member] | 4.375% senior notes due 2022 [Member]
Unsecured:
Notes payable	350.0	350.0
Stated interest rate	4.375%
Homebuilding [Member] | 4.75% senior notes due 2023 [Member]
Unsecured:
Notes payable	300.0	300.0
Stated interest rate	4.75%
Homebuilding [Member] | 5.75% senior notes due 2023 [Member]
Unsecured:
Notes payable	400.0	400.0
Stated interest rate	5.75%
Homebuilding [Member] | Other secured [Member]
Unsecured:
Notes payable	4.9	8.4
Financial Services [Member]
Unsecured:
Assets Sold under Agreements to Repurchase, Repurchase Liability	$ 223.8	$ 238.6