Stockholders' Equity - Summary of Reserved Shares of Common Stock for Future Issuance (Parenthetical) (Details) - shares	Jan. 01, 2018	Feb. 28, 2017	Jan. 01, 2017	Feb. 28, 2016	Jan. 01, 2016	Dec. 31, 2017	Dec. 31, 2016	Feb. 28, 2014
Class of Stock [Line Items]
Common stock, shares reserved for future issuance						7,341,253	5,523,127
2016 Inducement Award Program
Class of Stock [Line Items]
Common stock, shares reserved for future issuance						0
2014 Plans
Class of Stock [Line Items]
Increase in common stock, shares reserved for future issuance			1,265,863		986,800
Common stock, shares reserved for future issuance						1,790,600	1,140,328	1,785,000
Subsequent Event | 2016 Inducement Award Program
Class of Stock [Line Items]
Common stock, shares reserved for future issuance	750,000
Subsequent Event | 2014 Plans
Class of Stock [Line Items]
Increase in common stock, shares reserved for future issuance	1,575,329
Employee Stock Purchase Plan
Class of Stock [Line Items]
Increase in common stock, shares reserved for future issuance		0		273,404
Common stock, shares reserved for future issuance						652,290	803,105