Variable Interest Entities (Summary Of Consolidated Variable Interest Entities) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) joint_venture	Dec. 31, 2016 USD ($)
Variable Interest Entity [Line Items]
Variable interest entity, consolidated, assets no longer considered a variable interest entity		$ 249,500
Number of VIE's guaranteed by company | joint_venture	1
Consolidated Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Assets Held by VIEs	$ 235,713	504,293
Assets Held as Collateral for Debt	42,979	46,136
Maximum Risk of Loss	$ 29,784	$ 29,784