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		9 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share [Abstract]
Net income (loss)	$ 8,564	$ 7,681	$ (80,022)	$ 7,658
Weighted average common shares outstanding used in computing basic earnings (losses) per share	68,628	67,454	68,437	67,321
Dilutive restricted stock units	538	1,117	0	1,199
Weighted average common shares outstanding used in computing diluted earnings (losses) per share	69,166	68,571	68,437	68,520
Basic net income (loss) per share (USD per share)	$ 0.12	$ 0.11	$ (1.17)	$ 0.11
Diluted net income (loss) per share (USD per share)	$ 0.12	$ 0.11	$ (1.17)	$ 0.11