Debt (Grouping Of Debt Between Fixed And Variable As Well As Secured And Unsecured) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Long-term Debt, By Type [Line Items]
Total	$ 1,732,338	$ 1,794,684
As To Interest Rate [Member]
Schedule of Long-term Debt, By Type [Line Items]
Fixed-rate debt	1,714,890	1,771,999
Variable-rate debt	17,448	22,685
As To Collateralization [Member]
Schedule of Long-term Debt, By Type [Line Items]
Unsecured debt	1,450,762	1,457,432
Secured debt	$ 281,576	$ 337,252