MirImmune Inc. Acquisition - Additional Information (Detail)	Jan. 06, 2017 USD ($) shares
Research and Development Assets Acquired Other than Through Business Combination [Line Items]
Number of shares acquired	2,750,371
Holdback of aggregate closing consideration, percentage	3.00%
In Process Research and Development [Member]
Research and Development Assets Acquired Other than Through Business Combination [Line Items]
In-process research and development expense \| $	$ 2,990,000
MirImmune Stock Purchase Agreement [Member]
Research and Development Assets Acquired Other than Through Business Combination [Line Items]
Shares of common stock to be issued upon milestone	2,519,091
Additional number of common stock to be issued upon milestone percentage	13.00%
Series C Convertible Preferred Stock [Member]
Research and Development Assets Acquired Other than Through Business Combination [Line Items]
Number of shares acquired	1,118,224

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The amount of purchased research and development assets that are acquired in a business combination have no alternative future use and are therefore written off in the period of acquisition.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 730
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
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