Related Party Transactions (Details) - Private Placement		12 Months Ended
Nov. 14, 2017 item $ / shares shares	Dec. 31, 2017 shares
Related Party Transactions
Number of warrants issued per common stock \| shares	1
HCV IX and Eli Lilly
Related Party Transactions
Number of affiliated directors and executive officers \| item	3
HCV IX and Eli Lilly \| Minimum
Related Party Transactions
Direct holding percentage	5.00%
Common Stock
Related Party Transactions
Issuance of stock (in shares) \| shares	2,958,094	2,958,094
Price per common stock (in dollars per share) \| $ / shares	$ 6.085
Warrant Liability
Related Party Transactions
Exercise price of warrant \| $ / shares	$ 6.085

Number of new stock issued during the period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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