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Debt - $400 Million 5% Senior Notes (Details) - Senior Notes [Member] - $400 Million 5% Senior Notes [Member] - USD ($)
12 Months Ended
Dec. 31, 2020
Apr. 15, 2015
Debt Instrument [Line Items]    
Face amount $ 400,000,000 $ 400,000,000.0
Stated interest rate (as a percent) 5.00% 5.00%
Debt instrument, maturity date Apr. 15, 2023  
Debt instrument, frequency of periodic payment semi-annually  
2024    
Debt Instrument [Line Items]    
Redemption price (as a percent) 101.25%  
Redemption date Apr. 15, 2020  
2025    
Debt Instrument [Line Items]    
Redemption price (as a percent) 100.00%  
Redemption date Apr. 15, 2021