Quarterly Financial Data (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Revenue	$ 272,717	$ 243,294	$ 179,725	$ 199,597	$ 245,921	$ 223,399	$ 156,512	$ 165,615	$ 895,333	$ 791,447	$ 702,576
Gross profit	90,301	76,762	47,141	55,687	78,577	67,672	38,551	40,893	269,891	225,693	192,482
Net income (loss)	$ 126,774	$ 23,008	$ (25,198)	$ 7,084	$ 16,681	$ 10,893	$ (10,082)	$ (1,434)	$ 131,668	$ 16,058	$ 7,137
Basic and diluted earnings (loss) per share					$ 0.22	$ 0.14	$ (0.14)	$ (0.02)		$ 0.20
Basic earnings (loss) per share (in dollars per share)	$ 1.72	$ 0.30	$ (0.34)	$ 0.09					$ 1.78	0.20	$ 0.10
Diluted earnings (loss) per share (in dollars per share)	$ 1.68	$ 0.30	$ (0.34)	$ 0.09					$ 1.73	$ 0.20	$ 0.10
Income Tax Expense (Benefit)	$ 96,800								$ (94,458)	$ 3,574	$ 3,924
Additional valuation allowance	$ 10,146	$ 12,500			$ 119,424				10,146	119,424
Release of deferred tax valuation allowance									$ (109,277)	$ (7,994)	$ (3,955)
Loss on extinguishment of debt			$ 24,800