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, 2020	Sep. 30, 2019	Sep. 30, 2018
Real Estate, Write-down or Reserve [Line Items]
Land Held for Sale	$ 38,600	$ 1,300	$ 38,600	$ 5,900
Abandonments		1,646	0	0
Total impairments and abandonments		2,903	148,618	6,949
West | Operating Segments
Real Estate, Write-down or Reserve [Line Items]
Abandonments		923	0	0
East | Operating Segments
Real Estate, Write-down or Reserve [Line Items]
Abandonments		82	0	0
Southeast | Operating Segments
Real Estate, Write-down or Reserve [Line Items]
Abandonments		641	0	0
Continuing Operations
Real Estate, Write-down or Reserve [Line Items]
Projects in progress		0	110,030	1,005
Land Held for Sale		1,257	38,588	5,494
Abandonments		2,903	148,618	6,499
Continuing Operations | Corporate and unallocated
Real Estate, Write-down or Reserve [Line Items]
Projects in progress		0	16,260	212
Land Held for Sale		1,160	625	2,108
Continuing Operations | West
Real Estate, Write-down or Reserve [Line Items]
Projects in progress		0	92,912	0
Land Held for Sale		89	37,963	0
Continuing Operations | East
Real Estate, Write-down or Reserve [Line Items]
Land Held for Sale		0	0	168
Continuing Operations | Southeast
Real Estate, Write-down or Reserve [Line Items]
Projects in progress		0	858	793
Land Held for Sale		8	0	3,218
Discontinued Operations
Real Estate, Write-down or Reserve [Line Items]
Land Held for Sale		0	0	450
Total impairments and abandonments		$ 0	$ 0	$ 450