Inventory - Narrative (Details)	3 Months Ended
	Dec. 31, 2020 USD ($) numberOfContract home	Dec. 31, 2019 USD ($)	Sep. 30, 2020 USD ($) home
Real Estate Properties [Line Items]
Number of substantially completed homes unsold | home	109		133
Total value of substantially completed homes	$ 34,100,000		$ 42,200,000
Threshold number of homes below a minimum threshold of profitability | home	10
Impairment of land held for sale	$ 0	$ 0
Impairment charges, abandonments	$ 500,000	$ 0
Number of terminated land contracts under acquisition | numberOfContract	1