Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended
Mar. 31, 2018 USD ($)
Adoption of ASC 606 [Member]
Summary of Significant Accounting Policies [Line Items]
Cumulative adjustment to equity	$ 123,000
Grant Income [Member]
Summary of Significant Accounting Policies [Line Items]
Grant income recognized	$ 4,500

Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

No definition available.

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