Share-Based Payments - Additional Information (Details) - USD ($)							1 Months Ended		12 Months Ended
	Sep. 14, 2017	Mar. 14, 2017	Jan. 01, 2017	Sep. 20, 2016	Sep. 14, 2016	Mar. 14, 2016	Oct. 31, 2017	Feb. 28, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 21, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				4 years
Stock incentive plan, reserved shares of common stock (in shares)									13,998,426	4,133,703
Stock options granted in connection with acquisition (in shares)				650,000
Purchase price of shares authorized (in dollars per share)				$ 3.37
Percentage of original number of shares subject to the option vesting				25.00%
Additional percentage of shares subject to the option vesting at the end of each successive three-month period				6.25%
Total intrinsic value of options exercised									$ 258,000	$ 942,000	$ 768,000
Total fair value of employee options vested									$ 1,100,000	$ 3,700,000	1,800,000
Share-based compensation expense				$ 1,700,000
Stock options granted (in shares)									1,303,025
Weighted average period unvested stock to be recognized									2 years 4 months 28 days
Options outstanding (in shares)									2,695,796	2,024,468
Unrecognized compensation expense									$ 1,100,000
Non-Employee Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock, issued (in shares)									0	6,660
Unvested stock outstanding (in shares)									0
Share-based compensation expense									$ 0	$ 3,000	45,000
Performance-Based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period									4 years
Share-based compensation expense									$ 344,000	40,000	0
Stock options granted (in shares)							870,000
Options outstanding (in shares)									420,000
Unrecognized compensation expense									$ 499,000
Expected term									10 years
Option granted, weighted average grant date fair value (in dollars per share)							$ 1.12
Employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price of shares authorized (in dollars per share)									$ 0.28
Share-based compensation expense									$ 800,000	$ 3,300,000	$ 2,000,000
Option granted, weighted average grant date fair value (in dollars per share)									$ 1.18	$ 1.09	$ 5.60
Employee stock purchase plan issued during period (in shares)										5,000
Non-Employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted (in shares)									0	0
Expected term									10 years	10 years	10 years
Expense related to options granted to non-employees											$ 168,000
Non-Employee Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units issued to non-employees (in shares)									0	0	0
2009 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of purchase price of common stock owned by shareholder (as a percent)									10.00%
Percentage of fair value exercise price grant date of incentive stock options granted to 10% shareholder employees (as a percent)									110.00%
Award vesting period									4 years
Expected term									10 years
Stock incentive plan, reserved shares of common stock (in shares)								1,347,821
Stock incentive plan, shares remained available for future issuance (in shares)								1,586
2009 Stock Incentive Plan | Cliff for New Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period									1 year
2014 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan, annual increase in reserved shares of common stock (in shares)								1,102,362
2009 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense										$ 100,000
2014 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan, reserved shares of common stock (in shares)								708,661	1,183,739
Stock incentive plan, annual increase in reserved shares as percentage of outstanding common stock (as a percent)								4.00%
Number of shares reserved for issuance (in shares)			982,164
2014 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price of shares authorized (in dollars per share)	$ 1.19	$ 1.71			$ 0.42	$ 0.31
Share-based compensation expense									$ 12,000	$ 18,000
Employee stock purchase plan issued during period (in shares)	6,249	2,899			68,111	20,760
2014 ESPP authorized initial issuance up to (in shares)												157,480