Equity Incentive Plans - Awards Granted, Terms and Employee and Non-employee Stock-Based Compensation Expense (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Apr. 30, 2008
Amended and restated 1997 Equity Incentive Plan 1997
Equity incentive plans
Shares available for grant				0
2008 Equity Incentive Plan
Equity incentive plans
Shares available for grant		0
2014 Equity Incentive Plan
Equity incentive plans
Shares available for grant	531,540
Stock options
Equity incentive plans
Stock-based compensation expense	$ 2,965	$ 1,381	$ 1,338
Stock options | Minimum
Equity incentive plans
Exercise prices of options granted through the end of the year (in dollars per share)	$ 0.71
Stock options | Maximum
Equity incentive plans
Exercise prices of options granted through the end of the year (in dollars per share)	$ 285.71
Employee stock options
Equity incentive plans
Expiration period	10 years
Vesting period	4 years
Stock-based compensation expense	$ 2,662	1,185	476
Non-employee stock options
Equity incentive plans
Expiration period	10 years
Vesting period	4 years
Stock-based compensation expense	$ 303	$ 196	$ 862