Earnings per Share Reconciliation of Weighted Average Common Shares Outstanding for Purposes of Calculating Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Earnings Per Share [Abstract]
Net (loss) income	$ (83,939)	$ 2,711	$ (88,587)	$ (23)
Weighted average common shares outstanding used in computing basic earnings per share	68,556	67,387	68,342	67,255
Weighted average common shares outstanding used in computing basic earnings per share	0	1,027	0	0
Weighted average common shares outstanding used in computing diluted earnings per share	68,556	68,414	68,342	67,255
Basic net income (loss) per share (USD per share)	$ (1.22)	$ 0.04	$ (1.30)	$ 0.00
Diluted net income (loss) per share (USD per share)	$ (1.22)	$ 0.04	$ (1.30)	$ 0.00