Quarterly report pursuant to Section 13 or 15(d)

Convertible Senior Notes - Narrative (Details)

v3.19.1
Convertible Senior Notes - Narrative (Details)
1 Months Ended 3 Months Ended
Nov. 30, 2018
shares
May 31, 2018
USD ($)
d
$ / shares
shares
Aug. 31, 2014
USD ($)
d
$ / shares
shares
Mar. 31, 2019
USD ($)
$ / shares
shares
Dec. 31, 2018
USD ($)
shares
Sep. 30, 2018
USD ($)
Debt Instrument [Line Items]            
Derivative asset       $ 18,718,000 $ 22,576,000  
Gain (loss) on derivative       $ 3,900,000    
Warrants repurchased (shares) | shares 525,000          
Warrants outstanding (shares) | shares       2,739,643 2,739,643  
Convertible Notes | 2019 Convertible Senior Notes            
Debt Instrument [Line Items]            
Aggregate principal amount outstanding     $ 245,000,000.0 $ 27,323,000 $ 27,326,000  
Effective interest rate (as a percent)     5.83%      
Initial conversion rate (shares per $1,000)     0.0133251      
Initial conversion price (USD per share) | $ / shares     $ 75.05      
Interest rate (as a percent)     0.75%      
Increase (decrease) in if-converted value in excess of principal       $ (4,700,000)    
Warrants issued in public offering (shares) | shares     3,264,643      
Exercise price of convertible bond hedge (USD per share) | $ / shares     $ 75.05 $ 75.05    
Payments for convertible bond hedges     $ 48,100,000      
Derivative asset           $ 18,700,000
Warrant exercise price (USD per share) | $ / shares     $ 125.08      
Value of warrants issued     $ 11,600,000      
Convertible Notes | 2019 Convertible Senior Notes | Debt Instrument, Redemption, Period One            
Debt Instrument [Line Items]            
Threshold trading days | d     20      
Consecutive trading days | d     30      
Stock price trigger to classify convertible debt as current (as a percent)     130.00%      
Convertible Notes | 2019 Convertible Senior Notes | Debt Instrument, Redemption, Period Two            
Debt Instrument [Line Items]            
Threshold trading days | d     5      
Consecutive trading days | d     10      
Maximum threshold of debt trading price trigger (as a percent)     98.00%      
Convertible Notes | 2023 Convertible Senior Notes            
Debt Instrument [Line Items]            
Aggregate principal amount outstanding   $ 750,000,000.0   $ 750,000,000 $ 750,000,000  
Initial conversion rate (shares per $1,000)   0.0040244        
Initial conversion price (USD per share) | $ / shares   $ 248.48        
Interest rate (as a percent)   0.75%        
Warrants issued in public offering (shares) | shares   3,018,327        
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        
Proceeds from debt, net of issuance costs   733,100,000        
Debt issuance costs   16,900,000        
Debt issuance costs related to the liability component of convertible debt   $ 13,700,000        
Convertible Notes | 2023 Convertible Senior Notes | Debt Instrument, Redemption, Period One            
Debt Instrument [Line Items]            
Threshold trading days | d   20        
Consecutive trading days | d   30        
Stock price trigger to classify convertible debt as current (as a percent)   130.00%        
Convertible Notes | 2023 Convertible Senior Notes | Debt Instrument, Redemption, Period Two            
Debt Instrument [Line Items]            
Threshold trading days | d   5        
Consecutive trading days | d   10        
Maximum threshold of debt trading price trigger (as a percent)   98.00%