XML 34 R42.htm IDEA: XBRL DOCUMENT v3.19.3
Debt - Schedule of senior convertible notes (Details) - USD ($)
9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2018
Nov. 30, 2018
Jun. 30, 2017
Senior Notes [Abstract]          
Net carrying amount of Senior Convertible Notes due 2022 $ 1,047,100,000   $ 1,010,300,000    
Senior Notes          
Senior Notes [Abstract]          
Fair value of outstanding senior convertible notes: 1,632,100,000   1,399,800,000    
Amount by which the notes' if-converted value exceeds their principal amount: 315,500,000 $ 125,400,000      
Senior Notes | Senior convertible notes due 2022          
Senior Notes [Abstract]          
Principal amount 400,000,000.0   400,000,000.0   $ 400,000,000.0
Unamortized debt discount (40,700,000)   (51,100,000)    
Unamortized debt issuance costs (5,000,000.0)   (6,300,000)    
Net carrying amount of Senior Convertible Notes due 2022 354,300,000   342,600,000    
Fair value of outstanding senior convertible notes: 635,600,000   540,200,000    
Amount by which the notes' if-converted value exceeds their principal amount: 221,600,000 125,400,000      
Senior Notes | Senior convertible notes due 2023          
Senior Notes [Abstract]          
Principal amount 850,000,000.0   850,000,000.0 $ 850,000,000.0  
Unamortized debt discount (148,100,000)   (171,800,000)    
Unamortized debt issuance costs (9,100,000)   (10,500,000)    
Net carrying amount of Senior Convertible Notes due 2022 692,800,000   667,700,000    
Fair value of outstanding senior convertible notes: 996,500,000   859,600,000    
Amount by which the notes' if-converted value exceeds their principal amount: 93,900,000 $ 0      
Senior Notes | Zero Point Seven Five Percent Senior Convertible Notes          
Senior Notes [Abstract]          
Total net carrying amount of senior convertible notes $ 1,047,100,000   $ 1,010,300,000