XML 61 R51.htm IDEA: XBRL DOCUMENT v3.19.1
Convertible Senior Notes - Narrative (Details)
$ / shares in Units, shares in Millions
1 Months Ended
Sep. 30, 2018
USD ($)
trading_day
$ / shares
shares
Apr. 30, 2019
USD ($)
Convertible Senior Notes Due 2023 | Convertible Debt    
Debt Conversion [Line Items]    
Aggregate principal amount of debt issued $ 575,000,000.0 $ 575,000,000.0
Debt interest rate percentage   0.50%
Additional principal amount purchased 75,000,000.0  
Proceeds from issuance of debt $ 560,800,000  
Conversion rate 0.013986  
Conversion price (in usd per share) | $ / shares $ 71.50  
Percentage of principal amount redeemed 100.00%  
Trading days | trading_day 20  
Consecutive trading days | trading_day 30  
Percentage of conversion price 130.00%  
Equity component of conversion option   $ 134,667,000
Transaction costs attributable to liability component   10,900,000
Transaction costs attributable to equity components   $ 3,336,000
Capped Calls    
Debt Conversion [Line Items]    
Conversion price (in usd per share) | $ / shares $ 71.50  
Initial cap price (in usd per share) | $ / shares $ 110.00  
Shares covered by capped calls (in shares) | shares 8.0  
Costs incurred for capped calls $ 67,600,000  
Conversion Covenant One | Convertible Senior Notes Due 2023 | Convertible Debt    
Debt Conversion [Line Items]    
Trading days | trading_day 20  
Consecutive trading days | trading_day 30  
Percentage of conversion price 130.00%  
Conversion Covenant Two | Convertible Senior Notes Due 2023 | Convertible Debt    
Debt Conversion [Line Items]    
Trading days | trading_day 5  
Consecutive trading days | trading_day 10  
Percentage of conversion price 98.00%  
Measurement Input, Discount Rate | Convertible Senior Notes Due 2023 | Convertible Debt    
Debt Conversion [Line Items]    
Discount rate   0.06