Quarterly Results (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Unaudited quarterly consolidated statement of operations
Revenue from operations	$ 78,513	$ 85,188	$ 86,878	$ 65,875	$ 79,293	$ 89,746	$ 102,943	$ 125,143	$ 316,454	$ 397,125	$ 495,661
(Loss) income before provision for income taxes	(24,291)	(141)	(1,117)	(7,351)	(63,024)	(6)	3,811	(84,996)	(32,901)	(144,386)	50,047
Net (loss) income from operations	$ (53,755)	$ (124)	$ (850)	$ (5,197)	$ (43,695)	$ 1,615	$ 1,381	$ (64,116)	$ (59,926)	$ (104,815)	$ 30,390
Unaudited quarterly consolidated statement of operations
Basic (loss) earnings per common share	$ (1.75)	$ 0.00	$ (0.03)	$ (0.17)	$ (1.46)	$ 0.05	$ 0.05	$ (2.14)	$ (1.96)	$ (3.50)	$ 0.97
Diluted (loss) earnings per common share	$ (1.75)	$ 0.00	$ (0.03)	$ (0.17)	$ (1.46)	$ 0.05	$ 0.05	$ (2.14)	$ (1.96)	$ (3.50)	$ 0.97
Basic weighted average shares outstanding (in shares)	30,740,977	30,726,554	30,594,940	30,490,670	30,026,223	30,011,121	29,988,324	29,926,273	30,638,163	29,987,985	31,243,932
Diluted weighted average shares outstanding (in shares)	30,740,977	30,726,554	30,594,940	30,490,670	30,026,223	30,011,121	29,988,324	29,926,273	30,638,163	29,987,985	31,395,301