Cash Equivalents And Restricted Cash And Securities (Summary Of Cash Equivalents And Restricted Cash And Securities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash and Cash Equivalents [Line Items]
Cost Basis	$ 56,642	$ 37,588	$ 33,375	$ 37,643
Cost Basis		5,000
Cost Basis	699	830
Cash [Member]
Cash and Cash Equivalents [Line Items]
Cost Basis		5,000
Unrealized Holding Gains
Estimated Market Value		5,000
Money Market Funds [Member]
Cash and Cash Equivalents [Line Items]
Cost Basis	3,466	549
Cost Basis	699	830
Unrealized Holding Gains
Estimated Market Value	3,466	549
Estimated Market Value	$ 699	$ 830