Stock-Based Compensation - Additional Information (Details)			1 Months Ended	12 Months Ended
	Oct. 07, 2016 shares	Sep. 20, 2016 item shares	Dec. 31, 2016 USD ($) employee $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Nov. 30, 2016 $ / shares
Share-based Compensation
Shares available for future issuance (in shares)			342,500	83,929	342,500	55,330
Number of stock options granted				757,900	563,523
Options remained outstanding			1,414,730	1,593,195	1,414,730	927,175
Weighted-average grant date fair value of options granted | $ / shares				$ 6.48	$ 4.52	$ 4.42
Total grant date fair value of options vested | $				$ 1,500,000	$ 622,000	$ 353,000
Unrecognized compensation expense related to unvested options | $				$ 5,100,000
Unrecognized compensation expense, weighted-average period expected to be recognized				3 years 3 months 18 days
Weighted-average exercise price (per share) | $ / shares			$ 5.28	$ 8.88	$ 5.28	$ 4.43
Stock-based compensation expense | $				$ 2,048,000	$ 1,141,000	$ 416,000
Former Chief Executive Officer | Accelerated Vesting Due To Separation Agreement
Share-based Compensation
Stock-based compensation expense | $				310,000
Employees
Share-based Compensation
Number of vested and unvested stock option award modified			396,028
Number of employees affected | employee			77
Weighted-average exercise price (per share) | $ / shares			$ 6.63		$ 6.63		$ 15.86
Stock-based compensation expense | $				$ 2,000,000	$ 1,100,000	$ 407,000
Incremental modification value | $			$ 629,000
Employees | Immediate vesting
Share-based Compensation
Incremental modification value | $			140,000
Employees | Remaining vesting
Share-based Compensation
Incremental modification value | $			$ 489,000
Non-Employee
Share-based Compensation
Number of stock options granted				16,800	8,073
Options remained outstanding			31,990	37,872	31,990	15,498
Weighted-average grant date fair value of options granted | $ / shares				$ 13.74	$ 7.51
Weighted-average exercise price (per share) | $ / shares			$ 5.26	$ 9.16	$ 5.26	$ 4.42
Stock-based compensation expense | $				$ 69,000	$ 23,000	$ 9,000
2016 Employee Incentive Plan
Share-based Compensation
Maximum number of common stock shares may be issued under the plan	500,000
Annual increases in the number of shares available for issuance, percentage of outstanding capital stock	3.00%
2008 Equity Incentive Plan
Share-based Compensation
Vesting period				4 years
Exercise period				10 years
Options remained outstanding				826,258
2008 Equity Incentive Plan | Incentive Stock Options | Minimum
Share-based Compensation
Percentage of exercise price of fair market value of stock at the date of grant				100.00%
2008 Equity Incentive Plan | Incentive Stock Options | Maximum
Share-based Compensation
Percentage of exercise price of fair market value of stock at the date of grant				110.00%
2016 Employee Stock Purchase Plan
Share-based Compensation
Maximum number of common stock shares may be issued under the plan		96,153
Annual increases in the number of shares available for issuance, percentage of outstanding capital stock		1.00%
Increase in number of shares available for grant				124,981
Number of purchase periods | item		2
Period difference for each offering		6 months
Length of time of purchase period (in months)		6 months
Shares available for future issuance (in shares)				183,544
Number of shares issued (in shares)				37,590
Value of share issued | $				$ 256,000