Summary of Significant Accounting Policies - Schedule of Total Share Compensation Expense Related to All of Company's Share-Based Awards (Detail) (USD $)	12 Months Ended
Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Share-based compensation expense from:
Share-based compensation expense, total	$ 5,845,793	$ 4,877,482	$ 3,778,453
Stock options [Member]
Share-based compensation expense from:
Share-based compensation expense, total	4,233,133	3,643,210	2,580,836
Restricted stock units [Member]
Share-based compensation expense from:
Share-based compensation expense, total	$ 1,612,660	$ 1,234,272	$ 1,197,617

The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration