| Fair value of financial assets and liabilities |
As of September 30, 2016 and December 31, 2015, the fair value of our financial assets was as follows: | | | | | | | | | | | | | | | | | | Level 1 | | Level 2 | | Level 3 | | Total | | (in thousands) | September 30, 2016 | | | | | | | | Assets: | | | | | | | | Money market funds (1) | $ | 14,733 |
| | $ | — |
| | $ | — |
| | $ | 14,733 |
| Corporate bonds (2) | — |
| | 100,852 |
| | — |
| | 100,852 |
| Government securities (2) | — |
| | 9,705 |
| | — |
| | 9,705 |
| Commercial paper (2) | — |
| | 8,187 |
| | — |
| | 8,187 |
| Agency securities (2) | — |
| | 7,258 |
| | — |
| | 7,258 |
| Municipal bonds (2) | — |
| | 4,048 |
| | — |
| | 4,048 |
| Certificates of deposit (2) | — |
| | 1,248 |
| | — |
| | 1,248 |
| Total assets measured at fair value | $ | 14,733 |
| | $ | 131,298 |
| | $ | — |
| | $ | 146,031 |
| December 31, 2015 | | | | | | | | Assets: | | | | | | | | Money market funds (1) | $ | 18,114 |
| | $ | — |
| | $ | — |
| | $ | 18,114 |
| Corporate bonds (2) | — |
| | 124,829 |
| | — |
| | 124,829 |
| Commercial paper (3) | — |
| | 47,294 |
| | — |
| | 47,294 |
| Municipal bonds (2) | — |
| | 16,223 |
| | — |
| | 16,223 |
| Government securities (2) | — |
| | 8,688 |
| | — |
| | 8,688 |
| Agency securities (2) | — |
| | 7,253 |
| | — |
| | 7,253 |
| Certificates of deposit (2) | — |
| | 2,244 |
| | — |
| | 2,244 |
| Total assets measured at fair value | $ | 18,114 |
| | $ | 206,531 |
| | $ | — |
| | $ | 224,645 |
|
| | (1) | Classified in cash and cash equivalents |
| | (2) | Classified in marketable securities. |
| | (3) | Includes commercial paper with maturities of three months or less at time of purchase of $10.1 million classified in cash and cash equivalents and commercial paper with maturities of greater than three months of $37.2 million classified in marketable securities. |
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