Basic and Diluted Net Loss per Share (Tables)

12 Months Ended

Dec. 31, 2017

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,
	2017		2016		2015
Stock options		15,693,675		12,488,551		8,300,819
Stock warrants		13,162,668		1,426,622		1,426,622
Nonvested restricted stock units		4,394,656		895,328		422,500
Total		33,250,999		14,810,501		10,149,941