Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measures (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details)

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Fair Value Measures (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $)
In Thousands, unless otherwise specified
 6 Months Ended
Jun. 30, 2012
Dec. 31, 2011
Jun. 30, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value $ 173,513 $ 79,294 $ 252,039
Total liabilities measured at fair value 1,900 3,877 7,681
Investments, remaining maturity, minimum 3 months    
Investments, remaining maturity, maximum 2 years    
Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 98,951 70,941 189,699
Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 74,562 8,353 62,340
Total liabilities measured at fair value 1,900 3,877 7,681
Money Market Funds [Member] | Cash Equivalents [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 85,373 55,542 136,840
Money Market Funds [Member] | Cash Equivalents [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 85,373 55,542 136,840
Time Deposits [Member] | Cash Equivalents [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 10,012 10,000 21,659
Time Deposits [Member] | Cash Equivalents [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 10,012 10,000 21,659
Time Deposits [Member] | Cash Equivalents [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0    
Time Deposits [Member] | Available-For-Sale Short-Term Investments [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 2,109 [1] 2,878 [1] 2,856 [1]
Time Deposits [Member] | Available-For-Sale Short-Term Investments [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   2,878 [1] 2,856 [1]
Time Deposits [Member] | Available-For-Sale Short-Term Investments [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 2,109 [1]   0 [1]
Time Deposits [Member] | Available-For-Sale Short-Term Investments [Member] | Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value     0 [1]
Variable Rate Demand Obligation [Member] | Available-For-Sale Short-Term Investments [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 9,870 [1]    
Variable Rate Demand Obligation [Member] | Available-For-Sale Short-Term Investments [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 9,870 [1]    
Certificates of Deposit [Member] | Cash Equivalents [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 3,294    
Certificates of Deposit [Member] | Cash Equivalents [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0    
Certificates of Deposit [Member] | Cash Equivalents [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 3,294    
Certificates of Deposit [Member] | Cash Equivalents [Member] | Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0    
Certificates of Deposit [Member] | Available-For-Sale Short-Term Investments [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 4,598 [1]    
Certificates of Deposit [Member] | Available-For-Sale Short-Term Investments [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 4,598 [1]    
U.S. Government-Backed Municipal Bonds [Member] | Cash Equivalents [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 28,456    
U.S. Government-Backed Municipal Bonds [Member] | Cash Equivalents [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0    
U.S. Government-Backed Municipal Bonds [Member] | Cash Equivalents [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 28,456    
U.S. Government-Backed Municipal Bonds [Member] | Cash Equivalents [Member] | Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0    
U.S. Government-Backed Municipal Bonds [Member] | Available-For-Sale Short-Term Investments [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 18,689 [1]   62,122 [1]
U.S. Government-Backed Municipal Bonds [Member] | Available-For-Sale Short-Term Investments [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 18,689 [1]   62,122 [1]
Mutual Fund Shares [Member] | Non Current Assets [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 3,566 2,521 2,480
Mutual Fund Shares [Member] | Non Current Assets [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 3,566 2,521 2,480
Derivative Financial Instruments, Assets [Member] | Other Current Assets [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 7,546 7,236 218
Derivative Financial Instruments, Assets [Member] | Other Current Assets [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 7,546 7,236 218
Derivative Financial Instruments, Assets [Member] | Non Current Assets [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   1,117  
Derivative Financial Instruments, Assets [Member] | Non Current Assets [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   1,117  
Short Term Municipal Bond Fund [Member] | Available-For-Sale Short-Term Investments [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value     25,864 [1]
Short Term Municipal Bond Fund [Member] | Available-For-Sale Short-Term Investments [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value     25,864 [1]
Accrued Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value 1,900 3,786 7,681
Accrued Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value 1,900 3,786 7,681
Other Long-Term Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value   91  
Other Long-Term Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value   $ 91  
[1] Investments have remaining maturities greater than three months but less than two years and are available for use in current operations.