Fair Value Measurements (Details) (Fair Value, Measurements, Recurring, USD $) | Mar. 31, 2015 | Dec. 31, 2014 |
In Thousands, unless otherwise specified |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | $13,904 | $24,068 |
Available for Sale Securities | 51,390 | 26,984 |
Assets measured at fair value | 65,294 | 51,052 |
Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 10,630 | 2,591 |
Available for Sale Securities | 0 | 0 |
Assets measured at fair value | 10,630 | 2,591 |
Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 3,274 | 21,477 |
Available for Sale Securities | 51,390 | 26,984 |
Assets measured at fair value | 54,664 | 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 | 10,630 | 2,591 |
Money market funds | Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 10,630 | 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 | 1,000 | 12,497 |
Available for Sale Securities | 4,996 | |
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 | 1,000 | 12,497 |
Available for Sale Securities | 4,996 | |
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 | 0 | 8,000 |
Variable-rate demand notes | Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 0 | 0 |
Variable-rate demand notes | Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 0 | 8,000 |
Variable-rate demand notes | Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 0 | 0 |
Certificates of deposit | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 245 | 980 |
Available for Sale Securities | 21,318 | 14,202 |
Certificates of deposit | Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 0 | 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 | 245 | 980 |
Available for Sale Securities | 21,318 | 14,202 |
Certificates of deposit | 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 |
Corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash Equivalents | 2,029 | |
Available for Sale Securities | 25,076 | 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 | 2,029 | |
Available for Sale Securities | 25,076 | 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 |