Earnings per Share - Tabular Disclosure (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net (loss) income	$ 17,350	$ 8,564	$ 45,226	$ (80,022)
Weighted average common shares outstanding used in computing basic earnings (losses) per share	69,711	68,628	69,496	68,437
Dilutive common stock options and restricted stock units	694	538	702
Weighted average common shares outstanding used in computing diluted earnings (losses) per share	70,405	69,166	70,198	68,437
Basic net income (loss) per share (in dollars per share)	$ 0.25	$ 0.12	$ 0.65	$ (1.17)
Diluted net income (loss) per share (in dollars per share)	$ 0.25	$ 0.12	$ 0.64	$ (1.17)