Common Stock and Stockholders' Equity (Deficit) - Warrants (Details)					1 Months Ended	12 Months Ended
	Dec. 09, 2016 $ / shares shares	Dec. 22, 2015 $ / shares shares	Jul. 24, 2015 item $ / shares shares	May 02, 2014 USD ($) item $ / shares shares	Jul. 31, 2016 USD ($) item $ / shares shares	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Warrants
Fair value of warrants issued, resulting in an increase to additional paid in capital | $						$ 7,717,000		$ 219,000
Non-cash fair value adjustment of warrants | $						7,717,000	$ 798,000
Common stock warrants
Warrants
Number of shares issued upon exercise of warrants		54,830
Cashless exercise of warrants (in shares)		65,619
Exercise price of warrants (in dollars per share) | $ / shares		$ 2.95
Affiliates of SVB | Common stock warrants
Warrants
Number of warrants issued				131,239	798,694
Number of shares that may be exercised from warrants				131,239	798,694
Number of shares issued upon exercise of warrants	107,931		59,281
Cashless exercise of warrants (in shares)	399,347		65,620
Exercise price of warrants (in dollars per share) | $ / shares	$ 13.50		$ 2.95	$ 2.95	$ 13.50
Number of affiliates of lender granted warrants | item			1	2	2
Term of warrants				10 years	10 years
Warrants outstanding | $				$ 200,000		$ 399,347
Fair value of warrants issued, resulting in an increase to additional paid in capital | $					$ 7,700,000