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Debt (Details) - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Jun. 05, 2017
Line of Credit Facility [Line Items]      
Line of credit facility, maximum borrowing capacity     $ 375,000,000
Optional increase (or an accordion feature) $ 200,000,000   200,000,000
Borrowed line of credit amount 100,000,000    
Repaid line of credit 125,000,000    
Amounts outstanding under the revolving credit facility $ 75,000,000 $ 100,000,000  
Interest rate 1.277% 2.816%  
Commitment fee percentage 0.125%    
Available for borrowings $ 300,000,000    
Swing Line      
Line of Credit Facility [Line Items]      
Line of credit facility, maximum borrowing capacity     $ 25,000,000