Fair-Value Measurements (Summary Of Valuation Of Financial Instruments At Fair-Value) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 424,049	$ 398,450
Current marketable securities	5,000	13,255
Marketable securities, noncurrent	5,185	5,354
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	84,076	84,872
Current marketable securities	0	0
Marketable securities, noncurrent	0	0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	339,973	313,578
Current marketable securities	5,000	13,255
Marketable securities, noncurrent	0	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	$ 5,185	$ 5,354