Annual report pursuant to Section 13 and 15(d)

CONSOLIDATED BALANCE SHEETS (Parenthetical)

v3.10.0.1
CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Statement Of Financial Position [Abstract]        
Common stock, par value $ 0.001 $ 0.001    
Common stock, shares authorized 300,000,000 300,000,000    
Common stock, shares issued 121,456,721 121,000,903    
Common stock, shares outstanding 116,830,530 116,475,033    
Treasury stock, shares 4,626,191 4,525,870 4,447,002 4,183,504