Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
FairValueOfCashEquivalentsRevisedFromFairValueLevel1ToLevel2		$ 180,000,000
Cash equivalents	852,979,000	1,302,367,000
Marketable securities	135,634,000	153,380,000
Derivatives	317,000	16,443,000
Total assets measured at fair value	988,930,000	1,472,190,000
Derivatives, Liabilities	7,920,000	5,136,000
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	690,691,000	1,122,375,000
Marketable securities	0	0
Derivatives	0	0
Total assets measured at fair value	690,691,000	1,122,375,000
Derivatives, Liabilities	0	0
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	162,288,000	179,992,000
Marketable securities	135,634,000	153,380,000
Derivatives	317,000	16,443,000
Total assets measured at fair value	298,239,000	349,815,000
Derivatives, Liabilities	7,920,000	5,136,000
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Marketable securities	0	0
Derivatives	0	0
Total assets measured at fair value	0	0
Derivatives, Liabilities	$ 0	$ 0