Stock-based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Number of Shares
Beginning balance - Outstanding (shares)	1,819,444
Granted (shares)	950,658
Exercised (shares)	0
Canceled (shares)	73
Ending balance - Outstanding (shares)	2,770,029	1,819,444
Exercisable (shares)	1,138,970
Vested or expected to vest (shares)	2,770,029
Weighted- Average Exercise Price
Beginning balance - Outstanding (in dollars per share)	$ 7.52
Granted (in dollars per shares)	3.10
Exercised (in dollars per share)	0.00
Canceled (in dollars per share)	9.64
Ending balance - Outstanding (in dollars per share)	6.00	$ 7.52
Exercisable — March 31, 2017 (in dollars per share)	8.26
Vested or expected to vest — March 31, 2017	$ 6.00
Weighted- Average Remaining Contractual Life (in years)
Balance - Outstanding	7 years 4 months 10 days	6 years 11 months 23 days
Exercisable	5 years 5 months 27 days
Vested or expected to vest	7 years 4 months 10 days
Aggregate Intrinsic Value ($000)
Balance - Outstanding	$ 14	$ 32
Exercisable	9
Vested or expected to vest	$ 14