Investments (Details) (USD $) | Jun. 30, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash & cash equivalents, Total | $34,534 | $65,881 |
Short-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | 38,664 | 32,162 |
Long-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | 12,784 | 9,787 |
Fair Value, Inputs, Level 1 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash & cash equivalents, Total | 34,534 | 65,881 |
Fair Value, Inputs, Level 1 [Member] | Short-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | ' | ' |
Fair Value, Inputs, Level 1 [Member] | Long-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | ' | ' |
Fair Value, Inputs, Level 2 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash & cash equivalents, Total | ' | ' |
Fair Value, Inputs, Level 2 [Member] | Short-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | 38,664 | 32,162 |
Fair Value, Inputs, Level 2 [Member] | Long-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | 12,784 | 9,787 |
Fair Value, Inputs, Level 3 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash & cash equivalents, Total | ' | ' |
Fair Value, Inputs, Level 3 [Member] | Short-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | ' | ' |
Fair Value, Inputs, Level 3 [Member] | Long-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | ' | ' |
Cash [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash & cash equivalents, Total | 30,399 | 57,715 |
Cash [Member] | Fair Value, Inputs, Level 1 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash & cash equivalents, Total | 30,399 | 57,715 |
Cash [Member] | Fair Value, Inputs, Level 2 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash & cash equivalents, Total | ' | ' |
Cash [Member] | Fair Value, Inputs, Level 3 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash & cash equivalents, Total | ' | ' |
Money Market Funds [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash & cash equivalents, Total | 4,135 | 8,166 |
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash & cash equivalents, Total | 4,135 | 8,166 |
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash & cash equivalents, Total | ' | ' |
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash & cash equivalents, Total | ' | ' |
Corporate Notes [Member] | Short-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | 33,717 | 28,307 |
Corporate Notes [Member] | Long-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | 11,783 | 9,787 |
Corporate Notes [Member] | Fair Value, Inputs, Level 1 [Member] | Short-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | ' | ' |
Corporate Notes [Member] | Fair Value, Inputs, Level 1 [Member] | Long-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | ' | ' |
Corporate Notes [Member] | Fair Value, Inputs, Level 2 [Member] | Short-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | 33,717 | 28,307 |
Corporate Notes [Member] | Fair Value, Inputs, Level 2 [Member] | Long-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | 11,783 | 9,787 |
Corporate Notes [Member] | Fair Value, Inputs, Level 3 [Member] | Short-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | ' | ' |
Corporate Notes [Member] | Fair Value, Inputs, Level 3 [Member] | Long-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | ' | ' |
Agency Bonds [Member] | Short-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | 1,002 | 1,008 |
Agency Bonds [Member] | Fair Value, Inputs, Level 1 [Member] | Short-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | ' | ' |
Agency Bonds [Member] | Fair Value, Inputs, Level 2 [Member] | Short-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | 1,002 | 1,008 |
Agency Bonds [Member] | Fair Value, Inputs, Level 3 [Member] | Short-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | ' | ' |
Commercial Paper [Member] | Short-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | 3,945 | 2,297 |
Commercial Paper [Member] | Fair Value, Inputs, Level 1 [Member] | Short-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | ' | ' |
Commercial Paper [Member] | Fair Value, Inputs, Level 2 [Member] | Short-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | 3,945 | 2,297 |
Commercial Paper [Member] | Fair Value, Inputs, Level 3 [Member] | Short-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | ' | ' |
Certificates Of Deposit [Member] | Short-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | ' | 550 |
Certificates Of Deposit [Member] | Fair Value, Inputs, Level 2 [Member] | Short-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | ' | 550 |
US Government Securities [Member] | Long-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | 1,001 | ' |
US Government Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Long-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | ' | ' |
US Government Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Long-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | 1,001 | ' |
US Government Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Long-Term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Investments, Total | ' | ' |