Equity Investments (Schedule Of Summarized Aggregated Financial Information Related To The Subsidiaries) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Equity Investments [Abstract]
Revenues	$ 193,521	$ 141,705	$ 141,664
Operating income	97,954	93,324	118,566
Net income	93,215	93,005	118,602
Current assets	39,754	25,352	18,620
Total assets	591,761	594,645	602,413
Current liabilities	11,012	6,434	415
Total liabilities	$ 27,163	$ 19,695	$ 734