Restructuring Expenses - Additional Information (Detail)	12 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($) position	Sep. 30, 2014 USD ($) position
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 0	$ 17,479,000	$ 4,100,000
Number of positions reduced | position		97	88
Facilities charges
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0	$ 13,571,000	$ 200,000
Employee separation
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 0	$ 3,908,000	$ 3,900,000