Subsequent Events (Details) - USD ($) $ in Thousands				2 Months Ended	12 Months Ended
	Jan. 01, 2020	Jan. 01, 2019	Jan. 01, 2015	Feb. 19, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Subsequent Events
Net proceeds from issuance of common stock					$ 37,537	$ 61,571	$ 29,238
Common Stock
Subsequent Events
Number of shares issued					8,655,940	11,596,173	4,359,920
Common Stock | 2014 Stock Incentive Plan
Subsequent Events
Increased number of shares of common stock reserved for issuance			1,659,218
Additional number of shares of common stock , percentage			4.00%
Additional number of shares authorized for issuance		1,659,218
Common Stock | 2014 Employee Stock Purchase Plan
Subsequent Events
Increased number of shares of common stock reserved for issuance		207,402	207,402
Additional number of shares of common stock , percentage			0.50%
Subsequent Event | Common Stock | 2019 Sales Agreement
Subsequent Events
Number of shares issued				2,229,514
Net proceeds from issuance of common stock				$ 10,686
Subsequent Event | Common Stock | 2014 Stock Incentive Plan
Subsequent Events
Additional number of shares authorized for issuance	1,659,218
Subsequent Event | Common Stock | 2014 Employee Stock Purchase Plan
Subsequent Events
Additional number of shares authorized for issuance	207,402