Fair-Value Measurements (Summary Of Valuation Of Financial Instruments At Fair-Value) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Fair Value, Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	$ 398,450	$ 388,053
Current marketable securities	13,255
Other marketable securities	5,354	6,039
Level 1 [Member]
Fair Value, Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	84,872	118,763
Level 2 [Member]
Fair Value, Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	313,578	269,290
Current marketable securities	13,255
Level 3 [Member]
Fair Value, Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other marketable securities	$ 5,354	$ 6,039