Fair Value Measurements - Loan and Security Agreement (Details) - Solar Capital and Western Alliance Bank Loan Agreement [Member] - USD ($) $ in Thousands	1 Months Ended	7 Months Ended	12 Months Ended
May 31, 2018	Dec. 31, 2018	Dec. 31, 2018
Fair Value Measurements
Exit Fee	$ 1,500
Level 3 [Member]
Fair Value Measurements
Potential payment to Solar Capital Ltd. and Western Alliance Bank			$ 1,500
Percentage of increase in risk component		10.00%	10.00%
Percentage decrease in risk component		10.00%	10.00%
Fair value fluctuation due to increase in risk component		$ 100	$ 100
Fair value fluctuation due to decrease in risk component		100	100
Derivative Liability Exit Fee [Member]
Fair Value Measurements
Decrease in estimated fair value of Exit Fee		13
Derivative Liability Exit Fee [Member] \| Accrued and other liabilities
Fair Value Measurements
Estimated fair value of Exit Fee	$ 546	$ 533	$ 533

Amount of decrease in estimated fair value of Exit Fee.

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- Definition

Amount of potential milestone payment as a result of FDA approval.

+ References

No definition available.

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- Definition

The increase (decrease) in a financial instrument as a result of an decrease in a designated risk component that was reasonably possible at the end of the reporting period. Excludes defined benefit plan obligations.

+ References

No definition available.

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The increase (decrease) in a financial instrument as a result of an increase in a designated risk component that was reasonably possible at the end of the reporting period. Excludes defined benefit plan obligations.

+ References

No definition available.

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- Definition

The reasonably possible percentage of the decrease in the designated risk component used to determine the value of the financial instrument. Excludes defined benefit plan obligations.

+ References

No definition available.

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The reasonably possible percentage of the increase in the designated risk component used to determine the value of the financial instrument. Excludes defined benefit plan obligations.

+ References

No definition available.

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- Definition

Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Includes, but is not limited to, one-time termination benefits, termination of an operating lease or other contract, consolidating or closing facilities, and relocating employees, and termination benefits associated with an ongoing benefit arrangement. Excludes expenses associated with special or contractual termination benefits, a discontinued operation or an asset retirement obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 5.P.3)
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
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-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
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-Section 50
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Fair value of financial and nonfinancial obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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