Annual report pursuant to Section 13 and 15(d)

Debt - Convertible Debt Narrative (Details)

v3.19.3
Debt - Convertible Debt Narrative (Details)
$ in Thousands, shares in Millions
12 Months Ended
Dec. 31, 2018
USD ($)
$ / shares
May 23, 2017
USD ($)
$ / shares
shares
Dec. 31, 2018
USD ($)
$ / shares
day
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
May 31, 2017
USD ($)
Debt Instrument [Line Items]            
Proceeds from borrowings on convertible notes     $ 0 $ 345,000 $ 0  
Convertible notes, net $ 292,843   292,843 281,199    
Number of securities called by warrants (in shares) | shares   8.2        
Purchases of convertible note hedges   $ 62,500   62,549    
Proceeds from issuance of warrants   $ 31,500 0 31,499 $ 0  
Exercise price of warrants (in dollars per share) | $ / shares   $ 57.58        
Maximum            
Debt Instrument [Line Items]            
Number of securities called by warrants (in shares) | shares   8.2        
Convertible Notes            
Debt Instrument [Line Items]            
Proceeds from borrowings on convertible notes   $ 304,200        
Convertible Notes | Convertible Senior Notes Due November 2022            
Debt Instrument [Line Items]            
Principal amount 345,000   $ 345,000 345,000   $ 345,000
Interest rate stated percentage   1.50%        
Conversion ratio (in shares)     0.02384      
Conversion price (in dollars per share) | $ / shares   $ 41.95        
If-converted, value in excess of principal 51,300          
Threshold trading days | day     20      
Threshold consecutive trading days | day     30      
Measurement period threshold trading days | day     5      
Measurement period threshold consecutive trading days | day     5      
Redemption price     100.00%      
Convertible notes, net 292,843   $ 292,843 281,199   282,500
Equity component, net of issuance costs and deferred tax: $ 61,390   $ 61,390 61,390   62,500
Gross debt issuance costs           9,800
Convertible Notes | Convertible Senior Notes Due November 2022 | Minimum            
Debt Instrument [Line Items]            
Threshold percentage of stock price trigger     130.00%      
Ratio of trading price per $1000 principle amount     98.00%      
Percentage of debt held by individual owner     25.00%      
Convertible Notes | Over-Allotment Option            
Debt Instrument [Line Items]            
Principal amount           $ 45,000
Measurement Input, Share Price | Convertible Notes | Convertible Senior Notes Due November 2022            
Debt Instrument [Line Items]            
Closing stock price (in dollars per share) | $ / shares 48.19   48.19      
Level 2 | Convertible Notes            
Debt Instrument [Line Items]            
Convertible debt fair value $ 441,400   $ 441,400 $ 430,300