Annual report pursuant to Section 13 and 15(d)

Senior Unsecured Notes (Summary Of Senior Unsecured Notes) (Details)

v3.20.4
Senior Unsecured Notes (Summary Of Senior Unsecured Notes) (Details) - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Debt Instrument [Line Items]    
Principal balance outstanding $ 2,801,797,000 $ 2,808,518,000
Adjustment for unamortized debt discount (1,504,000)  
Total debt $ 2,801,797,000  
4.500% Senior Unsecured Notes Due April 18, 2022 [Member]    
Debt Instrument [Line Items]    
Interest rate of senior unsecured notes 4.50%  
Maturity date of the senior unsecured notes Apr. 18, 2022  
3.150% Senior Unsecured Notes, Due May 15, 2023 [Member]    
Debt Instrument [Line Items]    
Interest rate of senior unsecured notes 3.15%  
Maturity date of the senior unsecured notes May 15, 2023  
Senior Unsecured Notes [Member]    
Debt Instrument [Line Items]    
Principal balance outstanding $ 575,000,000 575,000,000
Adjustment for unamortized debt discount (1,504,000) (2,170,000)
Unamortized deferred financing costs (843,000) (1,346,000)
Total debt 572,653,000 571,484,000
Senior Unsecured Notes [Member] | 4.500% Senior Unsecured Notes Due April 18, 2022 [Member]    
Debt Instrument [Line Items]    
Principal balance outstanding $ 300,000,000 300,000,000
Effective rate 4.612%  
Senior Unsecured Notes [Member] | 3.150% Senior Unsecured Notes, Due May 15, 2023 [Member]    
Debt Instrument [Line Items]    
Principal balance outstanding $ 275,000,000 $ 275,000,000
Effective rate 3.517%