Basic and Diluted Net Loss per Share (Tables)

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Summary of Potential Common Shares

Potential common shares not included in calculating diluted net loss per share are as follows:

	December 31,
	2018		2017		2016
Stock options		19,899,631		15,693,675		12,488,551
Stock warrants		4,329,437		13,162,668		1,426,622
Nonvested restricted stock units		4,967,144		4,394,656		895,328
Total		29,196,212		33,250,999		14,810,501