Fair Value Measurements - Change in Fair Value of Contingent Consideration Obligations (Detail) - USD ($)	12 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Business Combinations [Abstract]
Contingent consideration obligations, Beginning balance	$ 5,862,464
Change in fair value of contingent consideration	(5,862,464)	$ 1,891,533	$ 2,375,658
Contingent consideration obligations, Ending balance	$ 0	$ 5,862,464

Amount of liability recognized arising from contingent consideration in a business combination, expected to be settled beyond one year or the normal operating cycle, if longer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 35
-Paragraph 1
-Subparagraph b
-URI http://asc.fasb.org/extlink&oid=6911338&loc=d3e6819-128478

Name:	us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant