Summary of Significant Accounting Policies - Short-Term Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Short-term investments	$ 8,502	$ 14,675
Cash and Fixed Income Securities
Schedule of Held-to-maturity Securities [Line Items]
Short-term investments	$ 8,500	$ 14,700

Amount of investment in debt security measured at amortized cost (held-to-maturity), classified as current.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121553693&loc=d3e26626-111562

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