Debt (Grouping Of Debt Between Fixed And Variable As Well As Secured And Unsecured) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Long-term Debt, By Type [Line Items]
Secured debt	$ 66,000
Total	2,114,145	$ 1,938,188
As To Interest Rate [Member]
Schedule of Long-term Debt, By Type [Line Items]
Fixed-rate debt	1,897,338	1,651,959
Variable-rate debt	216,807	286,229
Total	2,114,145	1,938,188
As To Collateralization [Member]
Schedule of Long-term Debt, By Type [Line Items]
Unsecured debt	1,633,595	1,343,217
Secured debt	480,550	594,971
Total	$ 2,114,145	$ 1,938,188