Inventory - Narrative (Details)	3 Months Ended		9 Months Ended
	Jun. 30, 2020 USD ($) numberOfContracts home Community lot	Jun. 30, 2019 USD ($) Community	Jun. 30, 2020 USD ($) home Community	Jun. 30, 2019 USD ($) Community	Sep. 30, 2019 USD ($) home
Real Estate Properties [Line Items]
Number of substantially completed homes unsold | home	183		183		238
Total value of substantially completed homes | $	$ 61,700,000		$ 61,700,000		$ 82,200,000
Threshold number of homes below a minimum threshold of profitability | home			10
Number of communities on watch list	5	5	5	5
Lots held for sale | lot	88
Impairment of land held for sale | $	$ 1,257,000	$ 0	$ 1,257,000	$ 38,588,000
Impairment charges, abandonments | $	$ 1,009,000	$ 0	$ 1,009,000	$ 0
Number of terminated land contracts under acquisition | numberOfContracts	4
West Segment
Real Estate Properties [Line Items]
Number of communities on watch list	2	3	2	3
Southeast Segment
Real Estate Properties [Line Items]
Number of communities on watch list	3	1	3	1
East Segment
Real Estate Properties [Line Items]
Number of communities on watch list		1		1
West And Southeast Segment [Member]
Real Estate Properties [Line Items]
Number of communities under development	2