Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Quarterly Financial Information Disclosure [Abstract]
Total 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
Gross profit	113,360	78,443	67,398	53,663	102,406	77,653	59,566	57,582	312,864	297,207	272,444
Operating income	37,783	15,569	7,511	1,275	30,838	16,309	3,030	9,148	62,138	59,325	51,587
Net (loss) income from continuing operations	$ 33,693	$ 7,114	$ (7,495)	$ (1,359)	$ (789)	$ 6,107	$ (1,312)	$ 1,199	$ 31,953	$ 5,205	$ 346,599
Basic EPS from continuing operations (in dollars per share)	$ 1.05	$ 0.22	$ (0.23)	$ (0.04)	$ (0.03)	$ 0.19	$ (0.04)	$ 0.04	$ 1.00	$ 0.16	$ 12.54
Diluted EPS from continuing operations (in dollars per share)	$ 1.03	$ 0.22	$ (0.23)	$ (0.04)	$ (0.03)	$ 0.19	$ (0.04)	$ 0.04	$ 0.99	$ 0.16	$ 10.91
Inventory impairments and abandonments	$ 1,693	$ 470	$ 282	$ 0	$ 184	$ 11,917	$ 1,825	$ 1,356	$ 2,445	$ 15,282	$ 3,109
Loss on extinguishment of debt	$ 2,933	$ 0	$ (15,563)	$ 0	$ (11,393)	$ 429	$ (1,631)	$ (828)	$ (12,630)	$ (13,423)	$ (80)