Fair Value of Financial Measurements - Summary of Fair Value of Financial Assets by Level within Fair Value Hierarchy (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Financial Assets:
Securities Available for Sale, Fair Value		$ 14,106
U.S. Treasury Securities
Financial Assets:
Securities Available for Sale, Fair Value		14,106
Fair Value Measurements Recurring
Financial Assets:
Total Financial Assets	$ 3,108	18,987
Fair Value Measurements Recurring \| Money Market Funds
Financial Assets:
Cash equivalents, Fair value disclosure	3,108	4,881
Fair Value Measurements Recurring \| U.S. Treasury Securities
Financial Assets:
Securities Available for Sale, Fair Value		14,106
Fair Value Measurements Recurring \| Level 1
Financial Assets:
Total Financial Assets	3,108	4,881
Fair Value Measurements Recurring \| Level 1 \| Money Market Funds
Financial Assets:
Cash equivalents, Fair value disclosure	$ 3,108	4,881
Fair Value Measurements Recurring \| Level 2
Financial Assets:
Total Financial Assets		14,106
Fair Value Measurements Recurring \| Level 2 \| U.S. Treasury Securities
Financial Assets:
Securities Available for Sale, Fair Value		$ 14,106

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
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-Subparagraph (a)
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Section 50
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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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