Basis of Presentation and Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Summary of Significant Accounting Policies [Line Items]
Total revenue	$ 2,087,739	$ 2,107,133	$ 1,916,278
Homebuilding revenue
Summary of Significant Accounting Policies [Line Items]
Total revenue	2,077,245	2,077,360	1,895,855
Land sales and other revenue
Summary of Significant Accounting Policies [Line Items]
Total revenue	$ 10,494	$ 29,773	$ 20,423