Acquisitions - Additional Information (Detail) - USD ($)		12 Months Ended
Mar. 03, 2015	Sep. 30, 2015
Asset Acquisition [Line Items]
Cash payment for acquisition		$ 10,000,000
Novartis
Asset Acquisition [Line Items]
Cash payment for acquisition	$ 10,000,000	$ 10,000,000
Number of shares issued to Novartis	3,321,383
Obligation to pay royalties		In addition to the consideration paid by the Company at the closing of the Transaction, the Company is obligated to make certain royalty and milestone payments to Novartis upon the occurrence of certain events. For sales of any RNAi Products for which Novartis and the Company do not enter into a licensing arrangement, the Company will be obligated to pay royalty rates ranging in the low to mid-single digits on Net Sales depending upon the type of RNAi Product provided that the royalty rate may be reduced or offset in certain circumstances. The obligation to pay royalties on such candidates will last until the later of (i) the expiration of the last Valid Claim Covering such RNAi Product in such country and (ii) 11 years after the first commercial sale of such RNAi Product (as such italicized terms are defined in the RNAi Purchase Agreement).

$ 10,000,000

In addition to the consideration paid by the Company at the closing of the Transaction, the Company is obligated to make certain royalty and milestone payments to Novartis upon the occurrence of certain events. For sales of any RNAi Products for which Novartis and the Company do not enter into a licensing arrangement, the Company will be obligated to pay royalty rates ranging in the low to mid-single digits on Net Sales depending upon the type of RNAi Product provided that the royalty rate may be reduced or offset in certain circumstances. The obligation to pay royalties on such candidates will last until the later of (i) the expiration of the last Valid Claim Covering such RNAi Product in such country and (ii) 11 years after the first commercial sale of such RNAi Product (as such italicized terms are defined in the RNAi Purchase Agreement).