Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended
Mar. 31, 2018 USD ($)
Accounting Policies [Abstract]
Expenses incurred to obtain collaboration agreements and costs to fulfill contracts	$ 0
Costs to obtain or fulfill contract capitalized	$ 0

Amount, before accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054

Name:	us-gaap_CapitalizedContractCostGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant