Fair-Value Measurements (Summary Of Valuation Of Financial Instruments At Fair-Value) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Fair Value, Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	$ 351,020	$ 398,450
Current marketable securities	16,215	13,255
Other marketable securities	5,394	5,354
Level 1 [Member]
Fair Value, Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	84,870	84,872
Level 2 [Member]
Fair Value, Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	266,150	313,578
Current marketable securities	16,215	13,255
Level 3 [Member]
Fair Value, Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other marketable securities	$ 5,394	$ 5,354