Debt (Grouping Of Debt Between Fixed And Variable As Well As Secured And Unsecured) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011
Debt Instrument [Line Items]
Total	$ 2,497,561	[1]	$ 2,531,837	[1]
As To Interest Rate [Member]
Debt Instrument [Line Items]
Fixed-rate debt	1,981,494		2,014,834
Variable-rate debt	516,067		517,003
Total	2,497,561		2,531,837
As To Collateralization [Member]
Debt Instrument [Line Items]
Total	2,497,561		2,531,837
Unsecured debt	1,513,184		1,510,932
Secured debt	$ 984,377		$ 1,020,905

[1] Consolidated Variable Interest Entities' Assets and Liabilities included in the above balances (See Note 17):