Fair Value Measures (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $) | 9 Months Ended | | |
In Thousands, unless otherwise specified | Sep. 30, 2013 | Dec. 31, 2012 | Sep. 30, 2012 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | | ' | |
Total assets measured at fair value | $242,230 | | $184,139 | | $32,475 | |
Total liabilities measured at fair value | 599 | | 1,322 | | 2,220 | |
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 | 183,293 | | 99,972 | | 27,595 | |
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 | 58,937 | | 84,167 | | 4,880 | |
Total liabilities measured at fair value | 599 | | 1,322 | | 2,220 | |
Level 3 [Member] | ' | | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | | ' | |
Total assets measured at fair value | 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 | 599 | | 1,322 | | 2,220 | |
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 | 599 | | 1,322 | | 2,220 | |
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 | |
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 | 153,382 | | 70,857 | | 13,700 | |
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 | 153,382 | | 70,857 | | 13,700 | |
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 | |
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 | |
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 | 25,092 | | 25,035 | | 10,016 | |
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 | 25,092 | | 25,035 | | 10,016 | |
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 | | ' | | ' | |
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 | | ' | | ' | |
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 | ' | | 2,450 | | ' | |
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 | ' | | 2,450 | | ' | |
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 | 25,000 | | 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 | 25,000 | | 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 | | ' | | ' | |
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 | 3,218 | | 5,348 | | ' | |
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 | 3,218 | | 5,348 | | ' | |
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] | Time Deposits [Member] | ' | | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | | ' | |
Total assets measured at fair value | ' | | ' | | 2,128 | [1] |
Available-For-Sale Short-Term Investments [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 | ' | | ' | | 0 | [1] |
Available-For-Sale Short-Term Investments [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 | ' | | ' | | 2,128 | [1] |
Available-For-Sale Short-Term Investments [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 | [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 | 1,470 | [1] | 7,596 | [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 | 1,470 | [1] | 7,596 | [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 | 27,320 | [1] | 22,640 | [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 | 27,320 | [1] | 22,640 | [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 | ' | | 14,425 | [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 | ' | | 14,425 | [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 | 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 | 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 | | ' | | ' | |
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 | | ' | | ' | |
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 | 1,929 | | 6,219 | | 2,752 | |
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 | |
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 | 1,929 | | 6,219 | | 2,752 | |
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 | |
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 | ' | | 489 | | ' | |
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 | ' | | 489 | | ' | |
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 | 4,560 | | 4,080 | | 3,879 | |
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 | 4,560 | | 4,080 | | 3,879 | |
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 | |
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 | |
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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. |