Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 767,945	$ 511,521	$ 455,178	$ 372,489	$ 672,981	$ 478,588	$ 425,468	$ 339,241	$ 2,107,133	$ 1,916,278	$ 1,822,114
Gross profit	125,865	83,244	75,077	60,829	113,360	78,443	67,398	53,663	345,015	312,864	297,207
Operating income	43,462	17,580	13,825	6,681	37,783	15,569	7,511	1,275	81,548	62,138	59,325
Net (loss) income from continuing operations	$ 60,484	$ 13,429	$ 11,616	$ (130,575)	$ 33,693	$ 7,114	$ (7,495)	$ (1,359)	$ (45,046)	$ 31,953	$ 5,205
Basic EPS from continuing operations (in dollars per share)	$ 1.88	$ 0.42	$ 0.36	$ (4.07)	$ 1.05	$ 0.22	$ (0.23)	$ (0.04)	$ (1.40)	$ 1.00	$ 0.16
Diluted EPS from continuing operations (in dollars per share)	$ 1.83	$ 0.41	$ 0.36	$ (4.07)	$ 1.03	$ 0.22	$ (0.23)	$ (0.04)	$ (1.40)	$ 0.99	$ 0.16
Production Related Impairments or Charges [Abstract]
Inventory impairments and abandonments	$ 6,331	$ 168	$ 0	$ 0	$ 1,693	$ 470	$ 282	$ 0	$ 6,499	$ 2,445	$ 15,282
Gain (Loss) on Extinguishment of Debt [Abstract]
Loss on extinguishment of debt	$ (1,935)	$ 0	$ 0	$ (25,904)	$ 2,933	$ 0	$ (15,563)	$ 0	$ (27,839)	$ (12,630)	$ (13,423)