Cash And Cash Equivalents And Investments (Cash And Cash Equivalents And Investments From Continuing Operations) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Cash, Cost	$ 157,317	$ 147,412
Money market funds, Cost	122,827	112,936
Total cash and cash equivalents, Cost	280,144	260,348
Total short-term investments (available-for-sale), Cost	160,610	159,672
Total cash and cash equivalents and short-term investments, Cost	440,754	420,020
Cash, Gross Unrealized Gain
Money market funds, Gross Unrealized Gain	448	296
Total cash and cash equivalents, Gross Unrealized Gain	448	296
Total short-term investments (available-for-sale), Gross Unrealized Gain	31	7
Total cash and cash equivalents and short-term investments, Gross Unrealized Gain	479	303
Total short-term investments (available-for-sale),Gross Unrealized (Loss)	(34)	(8)
Total cash and cash equivalents and short-term investments, Gross Unrealized (Loss)	(34)	(8)
Cash, Fair Value	157,317	147,412
Money market funds, Fair Value	123,275	113,232
Total cash and cash equivalents, Fair Value	280,592	260,644	258,248	222,411
Long-term investments (available-for-sale), Fair Value	171,022	170,982
Total short-term investments (available-for-sale),Fair Value	160,607	159,671
Total cash and cash equivalents and short-term investments, Fair Value	441,199	420,315
Municipal Bonds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Long-term investments (available-for-sale), Cost	11,150	11,750
Long-term investments (available-for-sale), Gross Unrealized (Loss)	(735)	(439)
Long-term investments (available-for-sale), Fair Value	10,415	11,311
Total investments at fair value	10,415	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	133,648	159,672
Short-term investments (available-for-sale), Gross Unrealized Gain	31	7
Short-term investments (available-for-sale), Gross Unrealized (Loss)	(5)	(8)
Long-term investments (available-for-sale), Fair Value	133,674	159,671
U.S. Government Agencies [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Short-term investments (available-for-sale), Cost	26,962
Short-term investments (available-for-sale), Gross Unrealized (Loss)	(29)
Long-term investments (available-for-sale), Fair Value	$ 26,933