Debt (Grouping of Debt Between Fixed and Variable as Well as Secured and Unsecured) (Details) - USD ($) $ in Thousands		Jun. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Secured debt		$ 66,000
Total	[1]	2,087,957	$ 1,938,188
As To Interest Rate [Member]
Debt Instrument [Line Items]
Fixed-rate debt		1,919,052	1,651,959
Variable-rate debt		168,905	286,229
Total		2,087,957	1,938,188
As To Collateralization [Member]
Debt Instrument [Line Items]
Unsecured debt		1,585,091	1,343,217
Secured debt		502,866	594,971
Total		$ 2,087,957	$ 1,938,188

[1] * Consolidated variable interest entities' assets held as collateral and debt included in the above balances (see Note 16):