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Basis of Presentation and Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Total revenue	$ 533,112	$ 482,738	$ 1,440,329	$ 1,306,038
Customer deposits	16,293		16,293		$ 11,539
Contract with customer, liability, revenue recognized	600		10,600
Homebuilding revenue
Disaggregation of Revenue [Line Items]
Total revenue	532,465	482,316	1,437,850	1,304,243
Land sales and other revenue
Disaggregation of Revenue [Line Items]
Total revenue	$ 647	$ 422	$ 2,479	$ 1,795