Annual report pursuant to Section 13 and 15(d)

Consolidated Balance Sheets (Parenthetical)

v3.8.0.1
Consolidated Balance Sheets (Parenthetical) - $ / shares
Dec. 31, 2017
Dec. 31, 2016
Statement Of Financial Position [Abstract]    
Preferred stock, par value $ 0.00001 $ 0.00001
Preferred stock, shares authorized 20,000,000 20,000,000
Preferred stock, issued 0 0
Common stock, par value $ 0.00001 $ 0.00001
Common stock, shares authorized 200,000,000 200,000,000
Common stock, issued 141,960,462 140,543,545
Common stock, outstanding 139,091,289 137,674,372
Treasury stock, shares 2,869,173 2,869,173