Notes Payable (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013
Unsecured:
Notes payable	$ 3,682.8		$ 3,509.0
Homebuilding [Member]
Unsecured:
Notes payable	3,323.6		3,270.4
Financial Services [Member]
Unsecured:
Assets Sold under Agreements to Repurchase, Repurchase Liability	359.2	[1]	238.6	[1]
Secured Debt [Member] | Homebuilding [Member]
Unsecured:
Notes payable	23.4		8.4
Unsecured Debt [Member] | SeniorNoteTwentyEight [Member] | Homebuilding [Member]
Unsecured:
Senior notes, stated interest rate	5.75%
Notes payable	400.0		400.0
Unsecured Debt [Member] | Senior Note Twenty Seven [Member] | Homebuilding [Member]
Unsecured:
Senior notes, stated interest rate	4.75%
Notes payable	300.0		300.0
Unsecured Debt [Member] | Senior Note Member Twenty Five [Member] | Homebuilding [Member]
Unsecured:
Senior notes, stated interest rate	4.375%
Notes payable	350.0		350.0
Unsecured Debt [Member] | Senior Note Twenty Nine [Member] | Homebuilding [Member]
Unsecured:
Senior notes, stated interest rate	3.75%
Notes payable	500.0		0
Unsecured Debt [Member] | Senior Note Twenty Six [Member] | Homebuilding [Member]
Unsecured:
Senior notes, stated interest rate	3.625%
Notes payable	400.0		400.0
Unsecured Debt [Member] | Senior Note Twenty Four [Member] | Homebuilding [Member]
Unsecured:
Senior notes, stated interest rate	4.75%
Notes payable	350.0		350.0
Unsecured Debt [Member] | Senior Note Nine [Member] | Homebuilding [Member]
Unsecured:
Senior notes, stated interest rate	6.50%
Notes payable	372.6		372.5
Unsecured Debt [Member] | Senior Note Eight [Member] | Homebuilding [Member]
Unsecured:
Senior notes, stated interest rate	5.625%
Notes payable	169.9		169.7
Unsecured Debt [Member] | Senior Note Seven [Member] | Homebuilding [Member]
Unsecured:
Senior notes, stated interest rate	5.25%
Notes payable	157.7		157.5
Unsecured Debt [Member] | Senior Note Six [Member] | Homebuilding [Member]
Unsecured:
Senior notes, stated interest rate	5.625%
Notes payable	0		137.8
Unsecured Debt [Member] | Convertible Senior Note One [Member] | Homebuilding [Member]
Unsecured:
Senior notes, stated interest rate	2.00%
Notes payable	0	[2]	478.7	[2]
Unsecured Debt [Member] | Senior Note Five [Member] | Homebuilding [Member]
Unsecured:
Senior notes, stated interest rate	6.125%
Notes payable	0		145.8
Line of Credit [Member] | Homebuilding [Member]
Summary of notes payable at principal amounts, net of unamortized discounts
Line of credit, amount outstanding	$ 300.0	[1]	$ 0

[1] The fair value approximates carrying value due to its short-term nature, short maturity or floating interest rate terms, as applicable.

[2] The fair value is determined based on quoted market prices of recent transactions of the notes, which is classified as Level 2 within the fair value hierarchy.