Investment Income and Other (Schedule Of Investment Income and Other) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Dividend income									$ 4,094	$ 4,541	$ 4,668
Interest income									155	84	1,241
Net realized gains and recoveries on sales of marketable securities									9,899		2,403
Other revenue									596	566	269
Investment income and other	1,346	2,196	9,790	1,412	1,232	1,241	1,285	1,433	14,744	5,191	8,581
Recovery of Other Than Temporary Impairment [member]
Net realized gains and recoveries on sales of marketable securities									2,735		1,255
Exluding recovery of previous write-downs [Member]
Net realized gains and recoveries on sales of marketable securities									$ 7,164		$ 1,148