Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Proceeds from issuance of common stock ($40,000 and $20,000 from a related party in 2017 and 2016, respectively), net of issuance costs	$ 48,792	$ 23,964
Proceeds from issuance of Series AB ($5,819 received from related party CRG in 2016)	0	5,819
Related party
Proceeds from issuance of common stock ($40,000 and $20,000 from a related party in 2017 and 2016, respectively), net of issuance costs	$ 40,000	$ 20,000

Proceeds from issuance of capital stock which provides for a specific dividend that is paid to the shareholders before any dividends to common stockholders and which takes precedence over common stockholders in the event of liquidation.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585

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