Fair Value Measurements - Summary of Changes in Fair Value for the Level 3 Liability (Details) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ (4,559)
Purchases, sales, issuances and settlements (net)	(72)
Unrealized gains/(losses)	2,846
Ending balance	(1,785)
Equity Warrant Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	(4,559)
Unrealized gains/(losses)	3,088
Ending balance	(1,471)
Stock Appreciation Rights
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Purchases, sales, issuances and settlements (net)	(72)
Unrealized gains/(losses)	(242)
Ending balance	$ (314)

Amount of unrealized (holding) gain (loss) which is included in the statement of income (or changes in net assets) related to those liabilities still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3).

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 (d)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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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

Amount of purchases, (sales), issuances and (settlements) of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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 (c)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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- Definition

Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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