Inventory - Narrative (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019 USD ($) Community numberOfContract	Sep. 30, 2020 USD ($) home	Sep. 30, 2020 USD ($) home	Sep. 30, 2020 USD ($) home lot	Sep. 30, 2020 USD ($) home numberOfContract	Sep. 30, 2019 USD ($) Community home	Sep. 30, 2018 USD ($) Community
Segment Reporting Information [Line Items]
Number of substantially completed homes not subject to a sales contract | home		133	133	133	133	238
Total value of substantially completed homes		$ 42,200	$ 42,200	$ 42,200	$ 42,200	$ 82,200
Threshold number of homes below a minimum threshold of profitability		10		10
Impairment of land held for sale	$ 38,600		1,300			38,600	$ 5,900
Abandonments			1,646			0	0
Number of terminated land contracts under acquisition | numberOfContract					6
Impairment Charge	$ 109,000		1,700			131,700	4,200
Number of impaired communities in projects in progress | numberOfContract	9
Number of impaired communities, classified as land held for development | numberOfContract	6
Number of impaired communities in projects in progress | Community	9
California
Segment Reporting Information [Line Items]
Number of communities impaired | Community	15
Impairment Charge	$ 147,600
Continuing Operations
Segment Reporting Information [Line Items]
Impairment of land held for sale			1,257			38,588	5,494
Abandonments			2,903			$ 148,618	$ 6,499
Number of communities impaired | Community						10	1
Impairment Charge						$ 110,030	$ 1,005
Discontinued Operations
Segment Reporting Information [Line Items]
Impairment of land held for sale			0			0	450
West | Operating Segments
Segment Reporting Information [Line Items]
Abandonments			923			0	0
West | Continuing Operations
Segment Reporting Information [Line Items]
Impairment of land held for sale			89			$ 37,963	0
West | Continuing Operations | Operating Segments
Segment Reporting Information [Line Items]
Number of communities impaired | Community						9
Impairment Charge						$ 92,912
East | Operating Segments
Segment Reporting Information [Line Items]
Abandonments			82			0	0
East | Continuing Operations
Segment Reporting Information [Line Items]
Impairment of land held for sale			0			0	168
Southeast | Operating Segments
Segment Reporting Information [Line Items]
Abandonments			641			0	0
Southeast | Continuing Operations
Segment Reporting Information [Line Items]
Impairment of land held for sale			$ 8			$ 0	$ 3,218
Southeast | Continuing Operations | Operating Segments
Segment Reporting Information [Line Items]
Number of communities impaired | Community						1	1
Impairment Charge						$ 858	$ 793
East And Southeast Segment [Member]
Segment Reporting Information [Line Items]
Impairment of land held for sale							$ 5,500