Common Stock and Stockholders' Equity - Warrants (Details) - Affiliates of SVB - Common stock warrants $ / shares in Units, $ in Millions			1 Months Ended
	Jan. 31, 2017 $ / shares shares	Dec. 09, 2016 $ / shares shares	Jul. 31, 2016 USD ($) item $ / shares shares	Jun. 30, 2017 shares	Dec. 31, 2016 shares
Warrants
Number of warrants issued			798,694
Number of shares that may be exercised from warrants			798,694
Number of shares issued upon exercise of warrants	138,903	107,931
Cashless exercise of warrants (in shares)	399,347	399,347
Exercise price of warrants (in dollars per share) | $ / shares	$ 13.50	$ 13.50	$ 13.50
Number of affiliates of lender granted warrants | item			2
Term of warrants			10 years
Fair value of warrants outstanding | $			$ 7.7
Warrants outstanding (in shares)				0	399,347