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
 9 Months Ended
Sep. 30, 2014
Dec. 31, 2013
Sep. 30, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value $ 118,911 $ 367,420 $ 242,230
Total liabilities measured at fair value   1,247 599
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 110,217 220,930 183,293
Total liabilities measured at fair value   0 0
Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 8,694 146,490 58,937
Total liabilities measured at fair value   1,247 599
Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0 0 0
Total liabilities measured at fair value   0 0
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   1,152 599
Accrued Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value   0 0
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   1,152 599
Accrued Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member] | Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value   0 0
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   95  
Other Long Term Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value   0  
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   95  
Other Long Term Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member] | Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value   0  
Cash Equivalents [Member] | Money Market Funds [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 79,266 175,624 153,382
Cash Equivalents [Member] | Money Market Funds [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 79,266 175,624 153,382
Cash Equivalents [Member] | Money Market Funds [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0 0 0
Cash Equivalents [Member] | Money Market Funds [Member] | Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0 0 0
Cash Equivalents [Member] | Time Deposits [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 25,167 34,637 25,092
Cash Equivalents [Member] | Time Deposits [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 25,167 25,111 25,092
Cash Equivalents [Member] | Time Deposits [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0 9,526  
Cash Equivalents [Member] | Time Deposits [Member] | Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0 0 0
Cash Equivalents [Member] | Certificates of Deposit [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   735  
Cash Equivalents [Member] | Certificates of Deposit [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   0  
Cash Equivalents [Member] | Certificates of Deposit [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   735  
Cash Equivalents [Member] | Certificates of Deposit [Member] | Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   0  
Cash Equivalents [Member] | Repurchase Agreements [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   45,000 25,000
Cash Equivalents [Member] | Repurchase Agreements [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   0 0
Cash Equivalents [Member] | Repurchase Agreements [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   45,000 25,000
Cash Equivalents [Member] | Repurchase Agreements [Member] | Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   0 0
Cash Equivalents [Member] | U.S. Government-Backed Municipal Bonds [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   9,898 3,218
Cash Equivalents [Member] | U.S. Government-Backed Municipal Bonds [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   0 0
Cash Equivalents [Member] | U.S. Government-Backed Municipal Bonds [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   9,898 3,218
Cash Equivalents [Member] | U.S. Government-Backed Municipal Bonds [Member] | Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   0 0
Available-For-Sale Short-Term Investments [Member] | Short-term municipal bond funds [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   15,004 [1]  
Available-For-Sale Short-Term Investments [Member] | Short-term municipal bond funds [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   15,004 [1]  
Available-For-Sale Short-Term Investments [Member] | Short-term municipal bond funds [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   0 [1]  
Available-For-Sale Short-Term Investments [Member] | Short-term municipal bond funds [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]  
Available-For-Sale Short-Term Investments [Member] | Certificates of Deposit [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   9,546 [1] 1,470 [1]
Available-For-Sale Short-Term Investments [Member] | Certificates of Deposit [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   0 [1] 0 [1]
Available-For-Sale Short-Term Investments [Member] | Certificates of Deposit [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   9,546 [1] 1,470 [1]
Available-For-Sale Short-Term Investments [Member] | Certificates of Deposit [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] 0 [1]
Available-For-Sale Short-Term Investments [Member] | Variable Rate Demand Obligation [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   52,105 [1] 27,320 [1]
Available-For-Sale Short-Term Investments [Member] | Variable Rate Demand Obligation [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   0 [1] 0 [1]
Available-For-Sale Short-Term Investments [Member] | Variable Rate Demand Obligation [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   52,105 [1] 27,320 [1]
Available-For-Sale Short-Term Investments [Member] | Variable Rate Demand Obligation [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] 0 [1]
Available-For-Sale Short-Term Investments [Member] | U.S. Government-Backed Municipal Bonds [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   14,764 [1]  
Available-For-Sale Short-Term Investments [Member] | U.S. Government-Backed Municipal Bonds [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   0 [1]  
Available-For-Sale Short-Term Investments [Member] | U.S. Government-Backed Municipal Bonds [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   14,764 [1]  
Available-For-Sale Short-Term Investments [Member] | U.S. Government-Backed Municipal Bonds [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]  
Trading Securities [Member] | Mutual Fund Shares [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 537 336 259
Trading Securities [Member] | Mutual Fund Shares [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 537 336 259
Trading Securities [Member] | Mutual Fund Shares [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0 0 0
Trading Securities [Member] | Mutual Fund Shares [Member] | Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0 0 0
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 8,694 4,892 1,929
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 0 0 0
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 8,694 4,892 1,929
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 0 0 0
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   24  
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   0  
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   24  
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   0  
Non Current Assets [Member] | Mutual Fund Shares [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 5,247 4,855 4,560
Non Current Assets [Member] | Mutual Fund Shares [Member] | Level 1 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 5,247 4,855 4,560
Non Current Assets [Member] | Mutual Fund Shares [Member] | Level 2 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0 0 0
Non Current Assets [Member] | Mutual Fund Shares [Member] | Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value $ 0 $ 0 $ 0
[1] (1) Investments have remaining maturities greater than three months but less than two years and are available for use in current opera