Common Stock and Warrants - Activities of Warrants that Company Accounted for as Liabilities and Recorded as Derivative Financial Instruments (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair value of warrants at beginning of period	$ 13,769	$ 6,941
Exercise of warrants	(25)	(2,509)
Foreign exchange loss	288
Change in fair value of warrants during the period	(8,289)	(1,954)
Fair value of warrants at end of period	$ 5,743	$ 2,478

Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 45
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-URI http://asc.fasb.org/extlink&oid=109240200&loc=d3e30690-110894

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration