Fair-Value Measurements (Summary Of Valuation Of Financial Instruments At Fair-Value) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 398,496	$ 398,450
Current marketable securities	3,200	13,255
Marketable securities, noncurrent	0	5,354
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	84,082	84,872
Current marketable securities	0	0
Marketable securities, noncurrent		0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	314,414	313,578
Current marketable securities	3,200	13,255
Marketable securities, noncurrent		0
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Current marketable securities	0	0
Marketable securities, noncurrent		$ 5,354