Inventory - Results of Discounted Cash Flow Analysis (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($) Community lot	Sep. 30, 2018 USD ($) Community lot
Real Estate, Write-down or Reserve [Line Items]
Impairment Charge	$ 109,000	$ 1,700	$ 131,700	$ 4,200
Continuing Operations
Real Estate, Write-down or Reserve [Line Items]
Number of communities impaired | Community			10	1
Number of Lots Impaired | lot			854	25
Impairment Charge			$ 110,030	$ 1,005
Estimated Fair Value of Impaired Inventory			$ 84,982	$ 1,312
Corporate and unallocated | Continuing Operations
Real Estate, Write-down or Reserve [Line Items]
Number of communities impaired | Community			0	0
Number of Lots Impaired | lot			0	0
Impairment Charge			$ 16,260	$ 212
Estimated Fair Value of Impaired Inventory			$ 14,166	$ 0
West | Operating Segments | Continuing Operations
Real Estate, Write-down or Reserve [Line Items]
Number of communities impaired | Community			9
Number of Lots Impaired | lot			839
Impairment Charge			$ 92,912
Estimated Fair Value of Impaired Inventory			$ 69,449
Southeast | Operating Segments | Continuing Operations
Real Estate, Write-down or Reserve [Line Items]
Number of communities impaired | Community			1	1
Number of Lots Impaired | lot			15	25
Impairment Charge			$ 858	$ 793
Estimated Fair Value of Impaired Inventory			$ 1,367	$ 1,312