Net Income (Loss) Per Share (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Net loss per share - basic and diluted    
Net loss $ (46,472) $ (54,647)
Weighted average shares outstanding used to compute basic and diluted net loss per share 81,039 77,416
Net loss per share - basic and diluted (in usd per share) $ (0.57) $ (0.71)
Antidilutive shares excluded from computation of diluted net loss 11,193 12,658
Without Adoption (ASC 605)    
Net loss per share - basic and diluted    
Net loss $ (79,026)  
Weighted average shares outstanding used to compute basic and diluted net loss per share 81,039  
Net loss per share - basic and diluted (in usd per share) $ (0.98)