Owned Inventory - Inventory Impairments and Lot Option Abandonment Charges, by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Real Estate, Write-down or Reserve [Line Items]
Land held for sale	$ 38,600	$ 0	$ 1,300	$ 38,600
Abandonments		853	1,646	0
Total impairment and abandonment charges		853	2,903	148,618
West | Operating Segments
Real Estate, Write-down or Reserve [Line Items]
Abandonments		0	923	0
East | Operating Segments
Real Estate, Write-down or Reserve [Line Items]
Abandonments		465	82	0
Southeast | Operating Segments
Real Estate, Write-down or Reserve [Line Items]
Abandonments		388	641	0
Continuing Operations
Real Estate, Write-down or Reserve [Line Items]
Projects in progress		0	0	110,030
Land held for sale		0	1,257	38,588
Continuing Operations | Corporate and unallocated
Real Estate, Write-down or Reserve [Line Items]
Projects in progress		0	0	16,260
Land held for sale		0	1,160	625
Continuing Operations | West
Real Estate, Write-down or Reserve [Line Items]
Projects in progress		0	0	92,912
Land held for sale		0	89	37,963
Continuing Operations | Southeast
Real Estate, Write-down or Reserve [Line Items]
Projects in progress		0	0	858
Land held for sale		$ 0	$ 8	$ 0