Inventory - Inventory Impairments and Lot Option Abandonment Charges, by Reportable Segment (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Real Estate Properties [Line Items]
Impairment charges on projects in progress	$ 0	$ 0	$ 0	$ 110,030,000
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
Inventory impairments and abandonments	2,266,000	0	2,266,000	148,618,000
Corporate and unallocated
Real Estate Properties [Line Items]
Impairment charges on projects in progress	0	0	0	16,260,000
Impairment of land held for sale	1,160,000	0	1,160,000	625,000
West Segment | Operating Segments
Real Estate Properties [Line Items]
Impairment charges on projects in progress	0	0	0	92,912,000
Impairment of land held for sale	89,000	0	89,000	37,963,000
Impairment charges, abandonments	452,000	0	452,000	0
East Segment | Operating Segments
Real Estate Properties [Line Items]
Impairment charges, abandonments	32,000	0	32,000	0
Southeast Segment | Operating Segments
Real Estate Properties [Line Items]
Impairment charges on projects in progress	0	0	0	858,000
Impairment of land held for sale	8,000	0	8,000	0
Impairment charges, abandonments	$ 525,000	$ 0	$ 525,000	$ 0