Fair Value - Changes in Fair Value of Level 3 Instruments (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Preferred shares, derivative liability, Beginning Balance			$ 29,470	$ 69,810
Preferred shares, derivative liability, Conversions			(28,258)	0
Preferred shares, derivative liability, Remeasurement included in earnings	$ 0	$ (8,391)	(1,212)	(1,341)
Preferred shares, derivative liability, Ending Balance	$ 0	$ 68,469	$ 0	$ 68,469

Fair value as of the balance sheet date of the embedded derivative or group of embedded derivatives classified as a liability.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959

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- Definition

Net Increase or Decrease in the fair value of the embedded derivative or group of embedded derivatives included in earnings in the period.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 15
-URI http://asc.fasb.org/subtopic&trid=2229187

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

The excess of (1) the fair value of all securities and other consideration transferred in transactions by the registrant to the holders of the convertible preferred stock over (2) the fair value of securities issuable pursuant to the original conversion terms, during the accounting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section S99
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=27010884&loc=d3e42851-122695

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