Fair Value Measurements - Additional Information (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair value assets transfers between Level 2 and Level 3	$ 0	$ 0
Cash equivalents and marketable securities	$ 19,283,000	$ 28,960,000

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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