Inventory - Inventory Impairments and Lot Option Abandonment Charges, by Reportable Segment (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2019 parcel	Sep. 30, 2019 USD ($) lot Community	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
Real Estate, Write-down or Reserve [Line Items]
Land Held for Sale		$ 38,600	$ 5,900	$ 600
Total impairment and abandonment charges		$ 148,618	6,949	2,445
Land held for sale impairments | Community		6
Number Of Parcels Sold | parcel	2
Continuing Operations
Real Estate, Write-down or Reserve [Line Items]
Projects in progress		$ 110,030	1,005	1,693
Land Held for Sale		38,588	5,494	564
Abandonments		0	0	188
Total impairment and abandonment charges		148,618	6,499	2,445
Total impairment and abandonment charges		148,618	6,949	2,445
Continuing Operations | Corporate and unallocated
Real Estate, Write-down or Reserve [Line Items]
Projects in progress		16,260	212	68
Land Held for Sale		625	2,108	0
Continuing Operations | West
Real Estate, Write-down or Reserve [Line Items]
Projects in progress		92,912	0	1,625
Land Held for Sale		37,963	0	94
Continuing Operations | East
Real Estate, Write-down or Reserve [Line Items]
Land Held for Sale		0	168	470
Abandonments		0	0	188
Continuing Operations | Southeast
Real Estate, Write-down or Reserve [Line Items]
Projects in progress		858	793	0
Land Held for Sale		0	3,218	0
Discontinued Operations
Real Estate, Write-down or Reserve [Line Items]
Land Held for Sale		0	450	0
Total impairment and abandonment charges		$ 0	$ 450	$ 0
California
Real Estate, Write-down or Reserve [Line Items]
Number of lots | lot		732