XML 92 R77.htm IDEA: XBRL DOCUMENT v3.20.4
Debt (Narrative - Corporate Activities) (Details) - Corporate Activities [Member] - Convertible Notes [Member] - USD ($)
1 Months Ended 12 Months Ended
Aug. 31, 2016
Dec. 31, 2020
Dec. 31, 2019
4.00% Convertible Notes Due 2024 [Member]      
Debt Instrument [Line Items]      
Debt instrument, face amount   $ 115,000,000.0 $ 115,000,000.0
Interest rate, stated percentage   4.00% 4.00%
Debt Instrument, Maturity Date   Jul. 01, 2024  
Common stock for conversion, shares   64.1540  
Debt Instrument Convertible Conversion Price Benchmark1   $ 1,000  
Debt conversion price   $ 15.59  
Debt Conversion, Sale Price Of Common Stock Percent, Minimum   140.00%  
Debt Instrument, Redemption Price, Percentage   100.00%  
4.125% Convertible Notes Due 2022 [Member]      
Debt Instrument [Line Items]      
Debt instrument, face amount $ 170,000,000.0 $ 170,000,000.0 $ 170,000,000.0
Interest rate, stated percentage 4.125%    
Debt conversion, principal amounts for integral multiples $ 1,000    
Common stock for conversion, shares 35.7143    
Debt conversion price $ 28.00    
Conversion price percentage 140.00%    
Principal amount of notes, percentage 100.00%