Stock-based Awards - Narrative (Details)
1 Months Ended 3 Months Ended 12 Months Ended
Nov. 30, 2015
USD ($)
$ / shares
shares
Dec. 31, 2015
USD ($)
equity_incentive_plan
$ / shares
shares
May. 31, 2014
shares
Dec. 31, 2015
USD ($)
former_executive
equity_incentive_plan
$ / shares
shares
Mar. 31, 2015
shares
Dec. 31, 2015
USD ($)
equity_incentive_plan
$ / shares
shares
Dec. 31, 2014
USD ($)
$ / shares
shares
Dec. 31, 2013
USD ($)
$ / shares
shares
Dec. 31, 2012
$ / shares
shares
Stock-based Awards                  
Number of equity incentive plans | equity_incentive_plan   4   4   4      
Shares canceled and available for future issuance   3,095,368   3,095,368   3,095,368      
Total stock-based compensation expense | $           $ 42,563,000 $ 29,333,000 $ 9,346,000  
Outstanding stock options (in shares)   24,277,901   24,277,901   24,277,901      
Number of non-vested RSUs (in shares)   3,747,340   3,747,340   3,747,340      
Former CEO                  
Stock-based Awards                  
Shares canceled and available for future issuance 1,333,332                
Total stock-based compensation expense | $           $ 7,700,000      
Weighted average exercise price (in dollars per share) | $ / shares $ 45.00                
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares 1,401,553                
Payments for surrender and cancellation of options | $ $ 100,000                
Former Executive                  
Stock-based Awards                  
Total stock-based compensation expense | $           $ 3,000,000      
Number of former executives | former_executive       4          
Former President                  
Stock-based Awards                  
Shares canceled and available for future issuance   309,722   309,722   309,722      
Total stock-based compensation expense | $           $ 2,100,000      
Weighted average exercise price (in dollars per share) | $ / shares   $ 13.17              
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares   252,431   252,431   252,431      
Common Stock                  
Stock-based Awards                  
Closing price of common stock (in dollars per share) | $ / shares   $ 9.54   $ 9.54   $ 9.54      
Options to Purchase Common Stock                  
Stock-based Awards                  
Shares of common stock, grants to purchase           4,983,099      
Total remaining stock-based compensation expense for unvested option awards | $   $ 32,800,000   $ 32,800,000   $ 32,800,000      
Weighted-average period           2 years 10 months 2 days      
Weighted-average grant-date fair value per share of options granted (in dollars per share) | $ / shares           $ 4.76 $ 6.32 $ 4.79  
Total stock-based compensation expense | $           $ 34,000,000 $ 27,200,000 $ 8,900,000  
Total intrinsic value of options exercised | $           19,200,000 57,100,000 600,000  
Excess tax benefits | $           $ 0 $ 0 $ 0  
Weighted average exercise price (in dollars per share) | $ / shares           $ 9.98      
Outstanding stock options (in shares)   24,277,901   24,277,901   24,277,901 25,589,876    
Weighted average exercise price (in dollars per share) | $ / shares   $ 8.12   $ 8.12   $ 8.12 $ 9.79    
Options to Purchase Common Stock | Stock Options Performance 1                  
Stock-based Awards                  
Shares of common stock, grants to purchase               82,327  
Options to Purchase Common Stock | Stock Options Performance 1 | Executives                  
Stock-based Awards                  
Shares of common stock, grants to purchase                 166,665
Weighted average exercise price (in dollars per share) | $ / shares                 $ 11.51
Options to Purchase Common Stock | Stock Options Performance 2                  
Stock-based Awards                  
Shares of common stock, grants to purchase             2,776,114 1,683,548  
Vesting period           48 months      
Weighted average exercise price (in dollars per share) | $ / shares             $ 12.81    
Outstanding stock options (in shares)             2,241,796    
Weighted average exercise price (in dollars per share) | $ / shares             $ 12.81    
Shares forfeited         288,406        
Options to Purchase Common Stock | Stock Options Performance                  
Stock-based Awards                  
Shares of common stock, grants to purchase               1,765,875  
Weighted average exercise price (in dollars per share) | $ / shares               $ 8.85  
Grant date fair values of awards | $             $ 20,100,000 $ 8,800,000  
Restricted Stock Awards                  
Stock-based Awards                  
Total stock-based compensation expense | $             200,000 400,000  
Fair value of shares of restricted stock awards vested | $             800,000 $ 700,000  
Restricted Stock Units (RSUs)                  
Stock-based Awards                  
Total remaining stock-based compensation expense for unvested option awards | $   $ 23,900,000   $ 23,900,000   $ 23,900,000      
Weighted-average period           3 years 6 months 15 days      
Total stock-based compensation expense | $           $ 8,600,000 2,000,000    
Fair value of shares of restricted stock awards vested | $           $ 6,500,000 $ 300,000    
Weighted average grant date fair value (in dollars per share) | $ / shares           $ 8.17 $ 12.35    
Shares granted           3,980,079      
Number of non-vested RSUs (in shares)   3,747,340   3,747,340   3,747,340 827,997    
Weighted average grant date fair value (in dollars per share) | $ / shares   $ 8.18   $ 8.18   $ 8.18 $ 12.36    
Restricted Stock Units (RSUs) | Former CEO                  
Stock-based Awards                  
Number of non-vested RSUs (in shares) 154,088                
Restricted Stock Units (RSUs) | Former Executive                  
Stock-based Awards                  
Shares of common stock, accelerated vesting of stock       48,113          
Restricted Stock Units (RSUs) | Former President                  
Stock-based Awards                  
Number of non-vested RSUs (in shares)   57,679   57,679   57,679      
Stock Option | Former Executive                  
Stock-based Awards                  
Shares of common stock, accelerated vesting of stock       337,111          
Restricted Stock Units Containing Two Step Vesting Condition                  
Stock-based Awards                  
Vesting period             4 years    
Shares forfeited         73,939        
Weighted average grant date fair value (in dollars per share) | $ / shares             $ 10.04    
Shares granted             720,146    
Number of non-vested RSUs (in shares)             583,537    
Weighted average grant date fair value (in dollars per share) | $ / shares             $ 10.07    
2005 Plan                  
Stock-based Awards                  
Shares of common stock reserved for future issuance               604,093  
2008 Plan                  
Stock-based Awards                  
Shares canceled and available for future issuance               0  
2014 Plan                  
Stock-based Awards                  
Annual increase in the number of shares available for future issuance under the terms of the plan agreement     10,000,000            
Annual increase in the number of shares available for future issuance expressed as a percentage of the total outstanding shares of common stock as of the last day of the previous fiscal year     5.00%            
2014 Plan | Options to Purchase Common Stock                  
Stock-based Awards                  
Vesting period     4 years            
Expiration period     10 years            
2014 Plan | Restricted Stock Units (RSUs) | Minimum                  
Stock-based Awards                  
Vesting period     4 years            
2014 Plan | Restricted Stock Units (RSUs) | Maximum                  
Stock-based Awards                  
Vesting period     5 years            
Inducement Plan                  
Stock-based Awards                  
Shares canceled and available for future issuance   0   0   0      
Shares of common reserved for issuance under non-qualified stock options   1,840,000   1,840,000   1,840,000      
Shares of common stock, grants to purchase           1,840,000      
Vesting period           4 years      
Expiration period           10 years