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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(i)(4))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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Net Loss Per Common Share (Anti-Dilutive Common Share Equivalents) (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common share equivalents (in shares)	11,813,427	16,285,737	11,813,427	16,285,737
Warrants to purchase
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common share equivalents (in shares)	1,985,846	2,206,496	1,985,846	2,206,496
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common share equivalents (in shares)	8,227,736	11,997,551	8,227,736	11,997,551
Common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common share equivalents (in shares)			2,007,846
Common stock \| Warrants to purchase
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common share equivalents (in shares)	22,000	22,000	22,000	22,000
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common share equivalents (in shares)	3,528,871	4,225,480	3,528,871	4,225,480
Employee stock purchase program
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common share equivalents (in shares)	34,820	40,706	34,820	40,706
Weighted Average
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Price of shares entitled to purchase (in dollars per share)	$ 10.70		$ 10.70