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Long-Term Debt - 1.00% Notes due 2020 (Details) - 1.00% Notes
Jun. 08, 2015
USD ($)
d
$ / shares
Rate
Dec. 31, 2019
$ / shares
Dec. 31, 2018
Debt Instrument [Line Items]      
Debt instrument, interest rate   1.00%  
Convertible Debt      
Debt Instrument [Line Items]      
Principal amount of debt | $ $ 690,000,000.0    
Debt instrument, interest rate 1.00% 1.00% 1.00%
Conversion rate | Rate 5.40643%    
Conversion price per share (in dollars per share) | $ / shares $ 18.50 $ 18.50  
Debt Conversion One | Convertible Debt      
Debt Instrument [Line Items]      
Threshold trading days 20    
Threshold consecutive trading days 30    
Threshold percentage of stock price trigger (greater than or equal to) 130.00%    
Debt Conversion Two | Convertible Debt      
Debt Instrument [Line Items]      
Threshold consecutive trading days 5    
Period immediately following consecutive trading days (in business days) 5 days    
Ratio of trading price per 1000 principal amount (as a percent) (less than) 0.98