Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021 USD ($) state segment region	Mar. 31, 2020 USD ($)	Mar. 31, 2021 USD ($) state region	Mar. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)
Segment Reporting [Abstract]
Number of states in which home building segments operate | state	13		13
Number of regions in which entity operates | region	3		3
Number of reportable segments | segment	3
Segment Reporting Information [Line Items]
Revenue	$ 549,889	$ 489,413	$ 978,428	$ 907,217
Operating income	33,618	16,424	51,306	20,370
Depreciation and amortization	3,683	3,627	6,805	7,054
Capital expenditures			6,514	5,478
Assets	2,055,571		2,055,571		$ 2,007,480
Operating Segments
Segment Reporting Information [Line Items]
Operating income	80,011	53,550	134,990	92,358
Depreciation and amortization	3,187	3,102	5,790	6,004
Corporate and unallocated
Segment Reporting Information [Line Items]
Operating income	(46,393)	(37,126)	(83,684)	(71,988)
Depreciation and amortization	496	525	1,015	1,050
Capital expenditures			2,069	365
Assets	788,894		788,894		779,694
West Segment
Segment Reporting Information [Line Items]
Revenue	278,720	267,731	515,600	522,129
West Segment | Operating Segments
Segment Reporting Information [Line Items]
Operating income	42,488	33,223	75,791	63,554
Depreciation and amortization	1,936	1,851	3,473	3,659
Capital expenditures			3,066	2,667
Assets	678,720		678,720		658,909
East Segment
Segment Reporting Information [Line Items]
Revenue	153,571	110,941	251,535	188,981
East Segment | Operating Segments
Segment Reporting Information [Line Items]
Operating income	22,449	11,513	33,817	16,834
Depreciation and amortization	575	551	1,046	1,105
Capital expenditures			1,001	1,136
Assets	288,933		288,933		267,050
Southeast Segment
Segment Reporting Information [Line Items]
Revenue	117,598	110,741	211,293	196,107
Southeast Segment | Operating Segments
Segment Reporting Information [Line Items]
Operating income	15,074	8,814	25,382	11,970
Depreciation and amortization	676	$ 700	1,271	1,240
Capital expenditures			378	$ 1,310
Assets	$ 299,024		$ 299,024		$ 301,827