Segment Information (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017 USD ($) state region	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2017 USD ($) state region segment	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)
Segment Reporting [Abstract]
Number of states with active operations | state	13								13
Number of regions in which entity operates | region	3								3
Number of homebuilding segments | segment									3
Segment Reporting Information [Line Items]
Revenue	$ 672,981	$ 478,588	$ 425,468	$ 339,241	$ 632,121	$ 459,937	$ 385,607	$ 344,449	$ 1,916,278	$ 1,822,114	$ 1,627,413
Operating income	37,783	$ 15,569	$ 7,511	$ 1,275	30,838	$ 16,309	$ 3,030	$ 9,148	62,138	59,325	51,587
Depreciation and amortization									14,009	13,794	13,338
Write-off of a deposit on a legacy land investment									2,700	0	0
Excess insurance recovery										3,600
Unexpected warranty costs											13,600
Reduction in home construction expenses									4,800	59,300
Capital Expenditures									12,440	12,219	15,964
Total Capital Expenditure, cash and noncash									12,440	12,219	16,638
Assets	2,220,995				2,213,158				2,220,995	2,213,158
Operating Segments
Segment Reporting Information [Line Items]
Operating income									222,696	191,290	156,866
Depreciation and amortization									12,698	11,710	11,411
Corporate and unallocated
Segment Reporting Information [Line Items]
Operating income									(160,558)	(131,965)	(105,279)
Depreciation and amortization									1,311	2,084	1,927
Capital Expenditures									341	461	2,219
Assets	810,881				756,238				810,881	756,238
West
Segment Reporting Information [Line Items]
Revenue									853,230	827,907	607,515
West | Operating Segments
Segment Reporting Information [Line Items]
Operating income									110,600	99,835	67,236
Depreciation and amortization									7,207	6,086	5,544
Capital Expenditures									7,086	6,570	7,348
Assets	779,964				778,521				779,964	778,521
East
Segment Reporting Information [Line Items]
Revenue									551,422	526,949	576,560
East | Operating Segments
Segment Reporting Information [Line Items]
Operating income									58,191	42,205	52,516
Depreciation and amortization									2,927	3,173	3,091
Capital Expenditures									2,474	2,441	3,692
Assets	298,532				344,898				298,532	344,898
Southeast
Segment Reporting Information [Line Items]
Revenue									511,626	467,258	443,338
Southeast | Operating Segments
Segment Reporting Information [Line Items]
Operating income									53,905	49,250	37,114
Depreciation and amortization									2,564	2,451	2,776
Capital Expenditures									2,539	2,747	$ 3,379
Assets	$ 331,618				$ 333,501				$ 331,618	$ 333,501