Nature of Business and Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Property, Plant and Equipment [Line Items]
Depreciation and amortization, property and equipment	$ 20.7	$ 19.7	$ 14.6
Foreign currency exchange gains (losses)	(1.0)	(0.8)	(1.5)
Advertising and promotion costs	$ 3.8	$ 2.5	$ 1.8
Minimum
Property, Plant and Equipment [Line Items]
Stock option awards vesting period	3 years
Maximum
Property, Plant and Equipment [Line Items]
Stock option awards vesting period	4 years
Internal-use Software | Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	2 years
Internal-use Software | Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	3 years