Fair Value Measurements - Fair Value Measurements for Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($)	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative liabilities	$ 1,301,604	$ 4,173,943
Acquisition-related contingent consideration obligations	5,862,464	3,970,931	$ 1,595,273
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	81,214,354	132,510,610
Derivative liabilities	1,301,604	4,173,943
Acquisition-related contingent consideration obligations	5,862,464	3,970,931
Fair Value, Measurements, Recurring | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	81,214,354	132,510,610
Fair Value, Measurements, Recurring | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative liabilities	1,301,604	4,173,943
Acquisition-related contingent consideration obligations	$ 5,862,464	$ 3,970,931