Restructuring Expenses - Additional Information (Detail) $ in Thousands	12 Months Ended
	Sep. 30, 2015 USD ($) position	Sep. 30, 2014 USD ($) position	Sep. 30, 2013 USD ($) position
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net of reversals	$ 17,479	$ 4,100	$ 2,500
Restructuring charges		$ 4,130
Number of positions reduced | position	97	88	52
Facilities charges
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 13,571	$ 167	$ 1,624
Employee separation
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 3,908	$ 3,963	1,095
Reversal of severance cost			$ 200