Net Income (Loss) Per Share (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]        
Net loss $ (18,979) $ (4,574) $ (29,006) $ (10,203)
Weighted Average Number of Shares Outstanding, Basic and Diluted 71,426 68,292 70,961 65,882
Net loss per share - basic and diluted (in USD per share) $ (0.27) $ (0.07) $ (0.41) $ (0.15)
Employee Stock Option [Member]        
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]        
Antidilutive shares excluded from computation of diluted net loss 11,326 11,430 11,326 11,430