Debt (Grouping Of Debt Between Fixed And Variable As Well As Secured And Unsecured) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule of Long-term Debt, By Type [Line Items]
Total	$ 1,794,684	$ 2,081,152
As To Interest Rate [Member]
Schedule of Long-term Debt, By Type [Line Items]
Fixed-rate debt	1,771,999	2,063,263
Variable-rate debt	22,685	17,889
As To Collateralization [Member]
Schedule of Long-term Debt, By Type [Line Items]
Unsecured debt	1,457,432	1,667,462
Secured debt	$ 337,252	$ 413,690