Notes Payable - Additional Information and Homebuilding Textuals (Details) - USD ($)		3 Months Ended		12 Months Ended
	Aug. 01, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2016	Sep. 30, 2015
Maturities of Long-term Debt [Abstract]
Maturities of notes payable in fiscal 2017				$ 831,600,000
Maturities of notes payable in fiscal 2018				402,100,000
Maturities of notes payable in fiscal 2019				500,800,000
Maturities of notes payable in fiscal 2020				500,000,000
Maturities of notes payable in fiscal 2021				0
Maturities of notes payable thereafter				1,100,000,000
Letters of credit, amount outstanding				96,400,000
Homebuilding [Member]
Maturities of Long-term Debt [Abstract]
Authorized repurchase of debt securities	$ 500,000,000
Debt repurchase program, remaining authorized repurchase amount				500,000,000
Homebuilding [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense				13,300,000	$ 17,300,000
Homebuilding [Member] | Revolving credit facility, maturing 2018 [Member]
Maturities of Long-term Debt [Abstract]
Line of credit, current borrowing capacity				975,000,000
Line of credit, maximum borrowing capacity				$ 1,250,000,000
Letter of Credit, Maximum Borrowing Capacity				50.00%
Line of credit, amount outstanding				$ 0	$ 0
Letters of credit, amount outstanding				$ 93,500,000
Senior Note Eight [Member] | Homebuilding [Member] | Unsecured Debt [Member]
Maturities of Long-term Debt [Abstract]
Maturities of Senior Debt			$ 170,200,000
Senior notes, stated interest rate				5.625%
Senior Note Nine [Member] | Homebuilding [Member] | Unsecured Debt [Member]
Maturities of Long-term Debt [Abstract]
Maturities of Senior Debt		$ 372,700,000
Senior notes, stated interest rate				6.50%
Senior Notes Subject to Repurchase Upon Change of Control and Ratings Downgrade [Member] | Homebuilding [Member] | Unsecured Debt [Member]
Maturities of Long-term Debt [Abstract]
Debt Instrument, Redemption Price, Percentage				101.00%