Fair Value Of Financial Instruments (Details) (USD $) | Sep. 30, 2014 | Dec. 31, 2013 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | $23,133,000 | ' |
Level 1 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Assets, fair value disclosure | 6,624,000 | 14,671,000 |
Level 2 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Assets, fair value disclosure | 20,492,000 | 28,407,000 |
Level 3 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Assets, fair value disclosure | 0 | 0 |
Liabilities, fair value disclosure | 0 | 0 |
Fair Value [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Assets, fair value disclosure | 27,116,000 | 43,078,000 |
Money Market Funds [Member] | Level 1 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash equivalents, fair value disclosure | 3,983,000 | 12,796,000 |
Money Market Funds [Member] | Level 2 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash equivalents, fair value disclosure | 0 | 0 |
Money Market Funds [Member] | Level 3 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash equivalents, fair value disclosure | 0 | 0 |
Money Market Funds [Member] | Fair Value [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash equivalents, fair value disclosure | 3,983,000 | 12,796,000 |
Short-term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 19,157,000 | 18,840,000 |
Short-term Investments [Member] | U.S. Agency securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 8,686,000 | 6,772,000 |
Short-term Investments [Member] | U.S. Agency securities [Member] | Level 1 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 0 | 0 |
Short-term Investments [Member] | U.S. Agency securities [Member] | Level 2 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 8,686,000 | 6,772,000 |
Short-term Investments [Member] | U.S. Agency securities [Member] | Level 3 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 0 | 0 |
Short-term Investments [Member] | U.S. Agency securities [Member] | Fair Value [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 8,686,000 | 6,772,000 |
Short-term Investments [Member] | U.S. Treasury [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 1,007,000 | 1,001,000 |
Short-term Investments [Member] | U.S. Treasury [Member] | Level 1 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 0 | 0 |
Short-term Investments [Member] | U.S. Treasury [Member] | Level 2 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 1,007,000 | 1,001,000 |
Short-term Investments [Member] | U.S. Treasury [Member] | Level 3 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 0 | 0 |
Short-term Investments [Member] | U.S. Treasury [Member] | Fair Value [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 1,007,000 | 1,001,000 |
Short-term Investments [Member] | Corporate bonds [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 7,544,000 | 8,870,000 |
Short-term Investments [Member] | Corporate bonds [Member] | Level 1 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 0 | 0 |
Short-term Investments [Member] | Corporate bonds [Member] | Level 2 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 7,544,000 | 8,870,000 |
Short-term Investments [Member] | Corporate bonds [Member] | Level 3 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 0 | 0 |
Short-term Investments [Member] | Corporate bonds [Member] | Fair Value [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 7,544,000 | 8,870,000 |
Short-term Investments [Member] | Commercial Paper [Member] | Level 1 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 0 | 0 |
Short-term Investments [Member] | Commercial Paper [Member] | Level 2 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 749,000 | 999,000 |
Short-term Investments [Member] | Commercial Paper [Member] | Level 3 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 0 | 0 |
Short-term Investments [Member] | Commercial Paper [Member] | Fair Value [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 749,000 | 999,000 |
Short-term Investments [Member] | Certificates of Deposit [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 1,171,000 | 1,198,000 |
Short-term Investments [Member] | Certificates of Deposit [Member] | Level 1 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 1,171,000 | 1,198,000 |
Short-term Investments [Member] | Certificates of Deposit [Member] | Level 2 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 0 | 0 |
Short-term Investments [Member] | Certificates of Deposit [Member] | Level 3 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 0 | 0 |
Short-term Investments [Member] | Certificates of Deposit [Member] | Fair Value [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 1,171,000 | 1,198,000 |
Long-term Investments [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 3,976,000 | 11,442,000 |
Long-term Investments [Member] | U.S. Agency securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 500,000 | 6,956,000 |
Long-term Investments [Member] | U.S. Agency securities [Member] | Level 1 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 0 | 0 |
Long-term Investments [Member] | U.S. Agency securities [Member] | Level 2 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 500,000 | 6,956,000 |
Long-term Investments [Member] | U.S. Agency securities [Member] | Level 3 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 0 | 0 |
Long-term Investments [Member] | U.S. Agency securities [Member] | Fair Value [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 500,000 | 6,956,000 |
Long-term Investments [Member] | U.S. Treasury [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 501,000 | 1,014,000 |
Long-term Investments [Member] | U.S. Treasury [Member] | Level 1 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 0 | 0 |
Long-term Investments [Member] | U.S. Treasury [Member] | Level 2 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 501,000 | 1,014,000 |
Long-term Investments [Member] | U.S. Treasury [Member] | Level 3 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 0 | 0 |
Long-term Investments [Member] | U.S. Treasury [Member] | Fair Value [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 501,000 | 1,014,000 |
Long-term Investments [Member] | Corporate bonds [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 1,505,000 | 2,795,000 |
Long-term Investments [Member] | Corporate bonds [Member] | Level 1 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 0 | 0 |
Long-term Investments [Member] | Corporate bonds [Member] | Level 2 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 1,505,000 | 2,795,000 |
Long-term Investments [Member] | Corporate bonds [Member] | Level 3 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 0 | 0 |
Long-term Investments [Member] | Corporate bonds [Member] | Fair Value [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 1,505,000 | 2,795,000 |
Long-term Investments [Member] | Certificates of Deposit [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 1,470,000 | 677,000 |
Long-term Investments [Member] | Certificates of Deposit [Member] | Level 1 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 1,470,000 | 677,000 |
Long-term Investments [Member] | Certificates of Deposit [Member] | Level 2 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 0 | 0 |
Long-term Investments [Member] | Certificates of Deposit [Member] | Level 3 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | 0 | 0 |
Long-term Investments [Member] | Certificates of Deposit [Member] | Fair Value [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available-for-sale securities, fair value disclosure | $1,470,000 | $677,000 |