Fair Value Measures (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $) | 3 Months Ended | | |
In Thousands, unless otherwise specified | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2013 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | | ' | |
Total assets measured at fair value | $411,761 | | $367,420 | | $288,214 | |
Total liabilities measured at fair value | 1,050 | | 1,247 | | 803 | |
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 | 315,862 | | 220,930 | | 160,361 | |
Total liabilities measured at fair value | 0 | | 0 | | 0 | |
Level 2 [Member] | ' | | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | | ' | |
Total assets measured at fair value | 95,899 | | 146,490 | | 127,853 | |
Total liabilities measured at fair value | 1,050 | | 1,247 | | 803 | |
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 | | 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 | 1,017 | | 1,152 | | 803 | |
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 | | 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 | 1,017 | | 1,152 | | 803 | |
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 | | 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 | 33 | | 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 | | 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 | 33 | | 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 | | 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 | 269,786 | | 175,624 | | 130,794 | |
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 | 269,786 | | 175,624 | | 130,794 | |
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 | 39,217 | | 34,637 | | 26,854 | |
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 | 25,129 | | 25,111 | | 25,054 | |
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 | 14,088 | | 9,526 | | 1,800 | |
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 | 55,000 | | 45,000 | | 50,000 | |
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 | | 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 | 55,000 | | 45,000 | | 50,000 | |
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 | | 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 | | ' | |
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 | | ' | |
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 | | ' | |
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 | | ' | |
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 | 15,028 | [1] | 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 | 15,028 | [1] | 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] | 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] | 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 | 9,795 | [1] | 9,546 | [1] | 7,599 | [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] | 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 | 9,795 | [1] | 9,546 | [1] | 7,599 | [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] | 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] | 31,500 | [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] | 31,500 | [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 | 14,185 | [1] | 14,764 | [1] | 31,889 | [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] | 0 | [1] | 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 | 14,185 | [1] | 14,764 | [1] | 31,889 | [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] | 0 | [1] | 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 | 529 | | 336 | | ' | |
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 | 529 | | 336 | | ' | |
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 | | ' | |
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 | | ' | |
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 | 2,703 | | 4,892 | | 5,065 | |
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 | 2,703 | | 4,892 | | 5,065 | |
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 | 128 | | 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 | | 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 | 128 | | 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 | | 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 | 5,390 | | 4,855 | | 4,513 | |
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 | 5,390 | | 4,855 | | 4,513 | |
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 | |
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[1] | Investments have remaining maturities greater than three months but less than two years and are available for use in current operations. |