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
 3 Months Ended
Mar. 31, 2012
Dec. 31, 2011
Mar. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value $ 96,736 $ 79,294 $ 255,540
Total liabilities measured at fair value 488 3,877 7,849
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 73,405 70,941 175,454
Total liabilities measured at fair value        
Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 23,331 8,353 80,086
Total liabilities measured at fair value 488 3,877 7,849
Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value         
Total liabilities measured at fair value         
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 59,853 55,542 139,925
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 59,853 55,542 139,925
Money Market Funds [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        
Money Market Funds [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         
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 15,295 10,000 7,516
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 10,000 10,000 7,516
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 5,295      
Time Deposits [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         
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 2,438 [1] 2,878 [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]  
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 2,438 [1]    [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    [1]    [1]  
Other Current Assets [Member] | Derivative Financial Instruments, Assets [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 5,443 7,236 4,458
Other Current Assets [Member] | Derivative Financial Instruments, Assets [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value        
Other Current Assets [Member] | Derivative Financial Instruments, Assets [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 5,443 7,236 4,458
Other Current Assets [Member] | Derivative Financial Instruments, Assets [Member] | Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value         
Mutual Fund Shares [Member] | Other Non-Current Assets [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 3,552 2,521 2,302
Mutual Fund Shares [Member] | Other 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 3,552 2,521 2,302
Mutual Fund Shares [Member] | Other 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        
Mutual Fund Shares [Member] | Other Non-Current Assets [Member] | Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value         
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     1,008
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       
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     1,008
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       
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 9,590 [1]   74,620 [1]
U.S. Government-Backed Municipal Bonds [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        [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 9,590 [1]   74,620 [1]
U.S. Government-Backed Municipal Bonds [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    [1]      [1]
Other Non-Current Assets [Member] | Derivative Financial Instruments, Assets [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 565 1,117  
Other Non-Current Assets [Member] | Derivative Financial Instruments, Assets [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value       
Other Non-Current Assets [Member] | Derivative Financial Instruments, Assets [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 565 1,117  
Other Non-Current Assets [Member] | Derivative Financial Instruments, Assets [Member] | Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value        
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     25,711 [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     25,711 [1]
Short Term Municipal Bond Fund [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        [1]
Short Term Municipal Bond Fund [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        [1]
Derivative Financial Instruments, Liabilities [Member] | Accrued Liabilities [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value 488 3,786 7,849
Derivative Financial Instruments, Liabilities [Member] | Accrued Liabilities [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value        
Derivative Financial Instruments, Liabilities [Member] | Accrued Liabilities [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value 488 3,786 7,849
Derivative Financial Instruments, Liabilities [Member] | Accrued Liabilities [Member] | Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value         
Derivative Financial Instruments, Liabilities [Member] | Other Long-Term Liabilities [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value   91  
Derivative Financial Instruments, Liabilities [Member] | Other Long-Term Liabilities [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value       
Derivative Financial Instruments, Liabilities [Member] | Other Long-Term 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  
Derivative Financial Instruments, Liabilities [Member] | Other Long-Term Liabilities [Member] | Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value       
[1] Investments have remaining maturities greater than three months but less than two years and are available for use in current operations.