Fair Value Measurements (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands | Jun. 30, 2015 | Dec. 31, 2014 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | $ 29,618 | $ 24,068 |
Available for Sale Securities | 49,748 | 26,984 |
Assets measured at fair value | 79,366 | 51,052 |
Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 17,083 | 2,591 |
Available for Sale Securities | 0 | 0 |
Assets measured at fair value | 17,083 | 2,591 |
Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 12,535 | 21,477 |
Available for Sale Securities | 49,748 | 26,984 |
Assets measured at fair value | 62,283 | 48,461 |
Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 0 | 0 |
Available for Sale Securities | 0 | 0 |
Assets measured at fair value | 0 | 0 |
Money market funds | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 17,083 | 2,591 |
Money market funds | Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 17,083 | 2,591 |
Money market funds | Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 0 | 0 |
Money market funds | Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 0 | 0 |
Commercial paper | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 6,498 | 12,497 |
Available for Sale Securities | 2,999 | |
Commercial paper | Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 0 | 0 |
Available for Sale Securities | 0 | |
Commercial paper | Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 6,498 | 12,497 |
Available for Sale Securities | 2,999 | |
Commercial paper | Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 0 | 0 |
Available for Sale Securities | 0 | |
Variable-rate demand notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | | 8,000 |
Variable-rate demand notes | Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | | 0 |
Variable-rate demand notes | Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | | 8,000 |
Variable-rate demand notes | Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | | 0 |
Certificates of deposit | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | | 980 |
Available for Sale Securities | 24,523 | 14,202 |
Certificates of deposit | Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | | 0 |
Available for Sale Securities | 0 | 0 |
Certificates of deposit | Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | | 980 |
Available for Sale Securities | 24,523 | 14,202 |
Certificates of deposit | Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | | 0 |
Available for Sale Securities | 0 | 0 |
Corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 6,037 | |
Available for Sale Securities | 22,226 | 12,782 |
Corporate bonds | Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 0 | |
Available for Sale Securities | 0 | 0 |
Corporate bonds | Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 6,037 | |
Available for Sale Securities | 22,226 | 12,782 |
Corporate bonds | Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 0 | |
Available for Sale Securities | $ 0 | $ 0 |