Financial Instruments (Cash And Cash Equivalents And Investments From Continuing Operations) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010	Dec. 31, 2009
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Cash, Cost	$ 203,260	$ 176,250
Money market funds, Cost	85,390	112,936
Total cash and cash equivalents, Cost	288,650	289,186
Total cash and cash equivalents and short-term investments, Cost	448,573	448,858
Cash, Gross Unrealized Gain
Money market funds, Gross Unrealized Gain	451	296
Total cash and cash equivalents, Gross Unrealized Gain	451	296
Total cash and cash equivalents and short-term investments, Gross Unrealized Gain	513	303
Total cash and cash equivalents and short-term investments, Gross Unrealized (Loss)	(14)	(8)
Cash, Fair Value	203,260	176,250
Money market funds, Fair Value	85,841	113,232
Total cash and cash equivalents, Fair Value	289,101	289,482	283,424	284,334
Total cash and cash equivalents and short-term investments, Fair Value	449,072	449,153
Total investments at fair value	171,048	170,982
Municipal Bonds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Long-term investments, Cost	11,750	11,750
Long-term investments, Gross Unrealized Gain
Long-term investments, Gross Unrealized (Loss)	(673)	(439)
Total investments at fair value	11,077	11,311
U.S. Treasury Bills [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Short-term investments (available-for-sale), Cost	159,923	159,672
Short-term investments (available-for-sale), Gross Unrealized Gain	62	7
Short-term investments (available-for-sale), Gross Unrealized (Loss)	(14)	(8)
Short-term investments (available-for-sale), Fair Value	159,971	159,671
Total investments at fair value	$ 159,971	$ 159,671