Fair Value Accounting - Recurring Basis (Details) (USD $) | Jun. 30, 2014 | Dec. 31, 2013 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Fair value, current | $16,530,000 | ' |
Fair value, non-current | 4,554,000 | ' |
Corporate Debt Securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Fair value, current | 6,848,000 | ' |
US Government Agencies Debt Securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Fair value, current | 6,130,000 | ' |
Mortgage-backed Securities, Issued by Private Enterprises [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Fair value, current | 3,552,000 | 3,728,000 |
Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Assets, Fair Value Disclosure | 60,664,000 | ' |
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Fair value, current | 6,848,000 | ' |
Fair value, non-current | 4,554,000 | ' |
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Fair value, current | 6,130,000 | ' |
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Fair value, current | 3,552,000 | 3,728,000 |
Fair Value, Measurements, Recurring [Member] | Cash [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and Cash Equivalents, Fair Value Disclosure | 7,616,000 | ' |
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and Cash Equivalents, Fair Value Disclosure | 28,143,000 | ' |
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and Cash Equivalents, Fair Value Disclosure | 2,899,000 | ' |
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and Cash Equivalents, Fair Value Disclosure | 922,000 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Assets, Fair Value Disclosure | 35,759,000 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Fair value, current | 0 | ' |
Fair value, non-current | 0 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Agencies Debt Securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Fair value, current | 0 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Fair value, current | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Cash [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and Cash Equivalents, Fair Value Disclosure | 7,616,000 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and Cash Equivalents, Fair Value Disclosure | 28,143,000 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial Paper [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and Cash Equivalents, Fair Value Disclosure | 0 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Agencies Debt Securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and Cash Equivalents, Fair Value Disclosure | 0 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Assets, Fair Value Disclosure | 21,353,000 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Fair value, current | 6,848,000 | ' |
Fair value, non-current | 4,554,000 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Fair value, current | 6,130,000 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Fair value, current | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Cash [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and Cash Equivalents, Fair Value Disclosure | 0 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and Cash Equivalents, Fair Value Disclosure | 0 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial Paper [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and Cash Equivalents, Fair Value Disclosure | 2,899,000 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and Cash Equivalents, Fair Value Disclosure | 922,000 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Assets, Fair Value Disclosure | 3,552,000 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Fair value, current | 0 | ' |
Fair value, non-current | 0 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Agencies Debt Securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Fair value, current | 0 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Fair value, current | 3,552,000 | 3,728,000 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Cash [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and Cash Equivalents, Fair Value Disclosure | 0 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and Cash Equivalents, Fair Value Disclosure | 0 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commercial Paper [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and Cash Equivalents, Fair Value Disclosure | 0 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Agencies Debt Securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and Cash Equivalents, Fair Value Disclosure | $0 | ' |