| Fair Value of Financial Assets and Liabilities |
As of March 31, 2015 and December 31, 2014, the fair value of our financial assets was as follows: | | | | | | | | | | | | | | | | | | Level 1 | | Level 2 | | Level 3 | | Total | March 31, 2015 | | | | | | | | Assets: | | | | | | | | Money market funds (1) | $ | 5,775 |
| | $ | — |
| | $ | — |
| | $ | 5,775 |
| Corporate bonds (2) | — |
| | 112,106 |
| | — |
| | 112,106 |
| Municipal bonds (3) | — |
| | 15,246 |
| | — |
| | 15,246 |
| Commercial paper (4) | — |
| | 51,019 |
| | — |
| | 51,019 |
| Certificates of deposit (2) | — |
| | 498 |
| | — |
| | 498 |
| Total assets measured at fair value | $ | 5,775 |
| | $ | 178,869 |
| | $ | — |
| | $ | 184,644 |
| December 31, 2014 | | | | | | | | Assets: | | | | | | | | Money market funds (1) | $ | 11,903 |
| | $ | — |
| | $ | — |
| | $ | 11,903 |
| Corporate bonds (2) | — |
| | 99,474 |
| | — |
| | 99,474 |
| Municipal bonds (2) | — |
| | 18,137 |
| | — |
| | 18,137 |
| Commercial paper (5) | — |
| | 54,399 |
| | — |
| | 54,399 |
| Certificates of deposit (2) | — |
| | 498 |
| | — |
| | 498 |
| Total assets measured at fair value | $ | 11,903 |
| | $ | 172,508 |
| | $ | — |
| | $ | 184,411 |
|
| | (1) | Classified in cash and cash equivalents |
| | (2) | Classified in marketable securities |
| | (3) | Includes a municipal bond with an original maturity date of three months or less at time purchase of $176 classified in cash and cash equivalents. |
| | (4) | Includes commercial paper with maturities of three months or less at time of purchase of $45,225 classified in cash and cash equivalents and commercial paper with maturities of greater than three months of $5,794 classified in marketable securities. |
| | (5) | Includes commercial paper with maturities of three months or less at time of purchase of $45,203 classified in cash and cash equivalents and commercial paper with maturities of greater than three months of $9,196 classified in marketable securities. |
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