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Stockholders' Equity - Approved Share Repurchase Programs and Open Market Repurchases of Common Stock (Details) - USD ($)
shares in Thousands, $ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Class of Stock [Line Items]      
Aggregate purchase price, including commissions $ 541.7 $ 458.6  
Class A Common Stock      
Class of Stock [Line Items]      
Number of shares repurchased (in shares) 9,986 7,125 0
Aggregate purchase price, including commissions $ 541.7 $ 458.6 $ 0.0
2020 Share Repurchase Program - Approved on May 1, 2020      
Class of Stock [Line Items]      
Total authorized amount 500.0    
Authorized amount remaining 500.0    
2019 Share Repurchase Program - Approved on October 1, 2019      
Class of Stock [Line Items]      
Total authorized amount 500.0    
Authorized amount remaining 0.0    
2018 Share Repurchase Program - Approved on November 1, 2018      
Class of Stock [Line Items]      
Total authorized amount 500.0    
Authorized amount remaining $ 0.0