Contingencies - Narrative (Details) $ in Thousands	3 Months Ended	12 Months Ended		63 Months Ended
	Mar. 31, 2019 Community	Sep. 30, 2019 USD ($) home	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) home	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Loss Contingencies [Line Items]
Limited product warranty length		10 years
Accrued warranty expenses		$ 13,388	$ 15,331	$ 13,388	$ 18,091	$ 39,131
Insurance recoveries		(400)	(200)
Accrued amounts for litigation and other contingent liabilities		3,400	3,700	3,400
California
Loss Contingencies [Line Items]
Number of communities | Community	15
Specific Warranty Issue
Loss Contingencies [Line Items]
Product warranty expense				$ 82,400
Specific Warranty Issue | Florida
Loss Contingencies [Line Items]
Product warranty expense		$ 700	600
Numer of homes likely to require more than minor repairs | home		707		707
Number of homes that have been repaired | home		686		686
Accrued product warranty, decrease for payments		$ 500
Accrued warranty expenses		500	$ 1,700	$ 500
Performance Bonds
Loss Contingencies [Line Items]
Letters of credit secured using cash collateral		48,300		48,300
Cash collateral in restricted accounts securing letters of credit		$ 276,500		$ 276,500
Minimum
Loss Contingencies [Line Items]
Standard product warranty period		1 year
Maximum
Loss Contingencies [Line Items]
Standard product warranty period		2 years