Stockholders' Equity - Summary of Reserved Shares of Common Stock for Future Issuance (Parenthetical) (Details) - shares	Jan. 01, 2019	Dec. 12, 2018	Jan. 01, 2018	Jan. 01, 2017	Feb. 28, 2016	Mar. 31, 2019	Jan. 30, 2019	Dec. 31, 2018	Dec. 19, 2017	Feb. 28, 2014
Class of Stock [Line Items]
Common stock, shares reserved for future issuance						21,420,889		14,948,900
Employee Stock Purchase Plan
Class of Stock [Line Items]
Increase in common stock, shares reserved for future issuance					0
Common stock, shares reserved for future issuance						563,545		603,522
Maximum aggregate number of shares available for purchase					739,611
2014 Plans
Class of Stock [Line Items]
Increase in common stock, shares reserved for future issuance	3,801,198	2,323,213	1,575,329	1,265,863
Common stock, shares reserved for future issuance										1,785,000
Inducement Award Program
Class of Stock [Line Items]
Common stock, shares reserved for future issuance							3,150,000		750,000