Annual report pursuant to Section 13 and 15(d)

Convertible Senior Notes - Narrative (Details)

v3.10.0.1
Convertible Senior Notes - Narrative (Details)
1 Months Ended 2 Months Ended 12 Months Ended
Dec. 31, 2018
USD ($)
$ / shares
shares
May 22, 2018
USD ($)
$ / shares
shares
Nov. 30, 2018
USD ($)
shares
Jun. 19, 2018
USD ($)
$ / shares
May 31, 2018
trading_day
Aug. 31, 2014
USD ($)
day
trading_day
$ / shares
shares
Nov. 30, 2018
USD ($)
Aug. 31, 2018
USD ($)
Apr. 30, 2018
USD ($)
Dec. 31, 2018
USD ($)
$ / shares
shares
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Debt Instrument [Line Items]                        
Carrying value of equity component of convertible notes $ 0                 $ 0 $ 18,859,000  
Warrants issued in public offering (shares) | shares           3,264,643            
Exercise price of convertible bond hedge (USD per share) | $ / shares           $ 75.05            
Derivative asset 22,576,000                 22,576,000 0  
Net change in fair value of derivatives                   1,800,000    
Warrant exercise price (USD per share) | $ / shares           $ 125.08            
Value of warrants issued           $ 11,600,000            
Debt issuance costs related to the equity component of convertible debt                   18,859,000 10,704,000 $ 10,065,000
Convertible debt, noncurrent $ 609,864,000                 609,864,000 0  
Warrants settled (in shares) | shares     525,000                  
Deduction to additional paid-in-capital for warrants settled                   28,300,000    
Payments for repurchase of warrants     $ 30,100,000             30,094,000 0 $ 0
Gain (loss) on derivative liabilities                   $ (1,800,000)    
Warrants outstanding (in shares) | shares 2,739,643                 2,739,643    
2023 Convertible Senior Notes                        
Debt Instrument [Line Items]                        
Value of warrants issued                   $ 97,805,000    
Convertible Notes | 2019 Convertible Senior Notes                        
Debt Instrument [Line Items]                        
Principal amount outstanding $ 27,326,000         245,000,000.0       27,326,000 245,000,000  
Net proceeds from debt issuance           $ 239,300,000            
Effective rate (as a percent)           5.83%            
Convertible debt conversion ratio           0.0133251            
Debt conversion price per share (USD per share) | $ / shares           $ 75.05            
Interest on debt instrument (as a percent)           0.75%            
If-converted value in excess of principal $ 23,400,000 $ 341,600,000                    
Increase (decrease) in if-converted value in excess of principal                   118,700,000    
Notices for conversion               $ 195,900,000 $ 21,800,000      
Conversion value over the principal amount             $ 439,600,000   $ 31,600,000      
Gain (loss) on extinguishment of debt                   $ (3,200,000)    
Exercise price of convertible bond hedge (USD per share) | $ / shares $ 75.05 $ 75.05               $ 75.05    
Payments for convertible bond hedges           $ 48,100,000            
Derivative asset $ 22,600,000 $ 340,000,000.0               $ 22,600,000    
Net change in fair value of derivatives                   (119,400,000)    
Proceeds from derivative instrument                   471,200,000    
Gain (loss) on derivative liabilities                   119,400,000    
Convertible Notes | 2019 Convertible Senior Notes | Redemption Period One                        
Debt Instrument [Line Items]                        
Number of trading days | trading_day           20            
Number of consecutive trading days | trading_day           30            
Stock price trigger to classify convertible debt as current (as a percent)           130.00%            
Convertible Notes | 2019 Convertible Senior Notes | Redemption Period Two                        
Debt Instrument [Line Items]                        
Number of trading days | day           5            
Number of consecutive trading days | trading_day           10            
Maximum threshold of debt trading price trigger (as a percent)           98.00%            
Convertible Notes | 2023 Convertible Senior Notes                        
Debt Instrument [Line Items]                        
Principal amount outstanding 750,000,000 750,000,000               750,000,000 0  
Net proceeds from debt issuance   $ 733,100,000                    
Convertible debt conversion ratio         0.0040244              
Debt conversion price per share (USD per share) | $ / shares   $ 248.48                    
Interest on debt instrument (as a percent)   0.75%                    
Carrying value of equity component of convertible notes $ 127,997,000                 127,997,000 $ 0  
Warrants issued in public offering (shares) | shares   3,018,327                    
Exercise price of convertible bond hedge (USD per share) | $ / shares   $ 248.48   $ 248.48                
Payments for convertible bond hedges   $ 140,300,000                    
Warrant exercise price (USD per share) | $ / shares   $ 315.38                    
Value of warrants issued   $ 90,000,000.0                    
Fair value of the conversion option derivative liability   144,000,000.0                    
Debt issuance costs   16,900,000                    
Debt issuance costs related to the equity component of convertible debt                   3,200,000    
Debt issuance costs related to the liability component of convertible debt   $ 13,700,000                    
Increase (decrease) in derivative assets                   19,200,000    
Increase (decrease) in derivative liabilities       $ 13,500,000           $ 7,500,000    
Convertible Notes | 2023 Convertible Senior Notes | Redemption Period One                        
Debt Instrument [Line Items]                        
Number of trading days | trading_day         20              
Number of consecutive trading days | trading_day         30              
Stock price trigger to classify convertible debt as current (as a percent)         130.00%              
Convertible Notes | 2023 Convertible Senior Notes | Redemption Period Two                        
Debt Instrument [Line Items]                        
Number of trading days | trading_day         5              
Number of consecutive trading days | trading_day         10              
Maximum threshold of debt trading price trigger (as a percent)         98.00%