Basis of Presentation and Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Total revenue	$ 570,932	$ 533,112	$ 1,549,360	$ 1,440,329
Customer deposits	28,725		28,725		$ 18,937
Contract with customer, liability, revenue recognized	2,200		17,400
Homebuilding revenue
Disaggregation of Revenue [Line Items]
Total revenue	566,930	532,465	1,538,576	1,437,850
Land sales and other revenue
Disaggregation of Revenue [Line Items]
Total revenue	$ 4,002	$ 647	$ 10,784	$ 2,479