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Equity (Schedule of Stock by Class - Preferred) (Details) - USD ($)
$ / shares in Units, $ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Class of Stock [Line Items]      
Preferred Stock, Shares Outstanding 440,000 440,000  
Preferred Stock, Dividends Per Share, Declared     $ 28.88
Preferred Stock, Value, Outstanding $ 880.0 $ 880.0  
Series A Preferred Stock      
Class of Stock [Line Items]      
Preferred Stock, Liquidation Preference Per Share $ 1,000.00    
Preferred Stock, Shares Outstanding 400,000    
Preferred Stock, Dividends Per Share, Declared $ 56.50 $ 56.50 28.88
Preferred Stock, Value, Outstanding $ 393.9 $ 393.9  
Series B Preferred Stock      
Class of Stock [Line Items]      
Preferred Stock, Liquidation Preference Per Share $ 25,000.00    
Preferred Stock, Shares Outstanding 20,000    
Preferred Stock, Dividends Per Share, Declared $ 1,625.00 $ 1,674.65 $ 0
Preferred Stock, Value, Outstanding $ 486.1 $ 486.1