Segment Information (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2015 USD ($) state region	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Sep. 30, 2015 USD ($) state region	Sep. 30, 2014 USD ($)	Sep. 30, 2013 USD ($)
Segment Reporting Information [Line Items]
Number of states with active operations | state	13								13
Number of regions in which entity operates | region	3								3
Revenue
Revenue	$ 632,852	$ 429,438	$ 299,359	$ 265,764	$ 545,905	$ 354,671	$ 270,021	$ 293,170	$ 1,627,413	$ 1,463,767	$ 1,287,577
Operating income (loss)
Operating income	36,945	$ 17,696	$ 6,436	$ (9,490)	23,452	$ 15,088	$ 5,617	$ 11,532	51,587	55,689	27,261
Depreciation and amortization
Depreciation and amortization									13,338	13,279	12,784
Capital Expenditures
Capital Expenditures									15,964	14,553	10,761
Total Capital Expenditure, cash and noncash									16,638
Assets
Assets	2,421,203				2,066,220				2,421,203	2,066,220	1,986,789
Operating Segments
Operating income (loss)
Operating income									156,866	145,423	122,784
Depreciation and amortization
Depreciation and amortization									11,411	11,244	10,467
West
Revenue
Revenue									607,515	556,741	547,636
Operating income (loss)
Operating income									67,236	65,442	59,084
Depreciation and amortization
Depreciation and amortization									5,544	5,722	5,305
Capital Expenditures
Capital Expenditures									7,348	6,660	4,835
Assets
Assets	843,564				756,575				843,564	756,575	680,346
East
Revenue
Revenue									576,560	552,082	483,685
Operating income (loss)
Operating income									52,516	48,127	40,670
Depreciation and amortization
Depreciation and amortization									3,091	3,447	3,479
Capital Expenditures
Capital Expenditures									3,692	3,050	1,915
Assets
Assets	436,346				433,032				436,346	433,032	369,937
Southeast
Revenue
Revenue									443,338	354,944	256,256
Operating income (loss)
Operating income									37,114	31,854	23,030
Depreciation and amortization
Depreciation and amortization									2,776	2,075	1,683
Capital Expenditures
Capital Expenditures									3,379	2,979	1,311
Assets
Assets	317,295				299,215				317,295	299,215	228,814
Corporate and unallocated
Operating income (loss)
Operating income									(105,279)	(89,734)	(95,523)
Depreciation and amortization
Depreciation and amortization									1,927	2,035	2,317
Capital Expenditures
Capital Expenditures									2,219	1,864	2,700
Assets
Assets	$ 823,998				$ 577,398				$ 823,998	$ 577,398	$ 707,692