| Assets Carried at Fair Value on a Recurring Basis |
As of June 30, 2013 and December 31, 2012, our assets carried at fair value on a recurring basis were as follows: | | | | | | | | | | | | | | | | | | Level 1 | | Level 2 | | Level 3 | | Total Fair Value | June 30, 2013 | (In thousands) | Corporate bonds | $ | — |
| | $ | 38,965 |
| | $ | — |
| | $ | 38,965 |
| Commercial paper | — |
| | 58,970 |
| | — |
| | 58,970 |
| Negotiable certificate of deposit | — |
| | 4,409 |
| | — |
| | 4,409 |
| U.S. Treasury notes | — |
| | 2,304 |
| | — |
| | 2,304 |
| Agency securities | — |
| | 26,504 |
| | — |
| | 26,504 |
| Mortgage-backed securities | — |
| | 1,147 |
| | — |
| | 1,147 |
| Municipal bonds | — |
| | 19,590 |
| | — |
| | 19,590 |
| Asset-backed securities | — |
| | 20,578 |
| | — |
| | 20,578 |
| Total | $ | — |
| | $ | 172,467 |
| | $ | — |
| | $ | 172,467 |
| | | | | | | | | December 31, 2012 | | | | | | | | Corporate bonds | $ | — |
| | $ | 37,357 |
| | $ | — |
| | $ | 37,357 |
| Commercial paper | — |
| | 55,748 |
| | — |
| | 55,748 |
| Negotiable certificate of deposit | — |
| | 4,414 |
| | — |
| | 4,414 |
| U.S. treasury notes | — |
| | 22,267 |
| | — |
| | 22,267 |
| Agency securities | — |
| | 25,867 |
| | — |
| | 25,867 |
| Municipal bonds | — |
| | 11,568 |
| | — |
| | 11,568 |
| Asset-backed securities | — |
| | 26,566 |
| | — |
| | 26,566 |
| Total | $ | — |
| | $ | 183,787 |
| | $ | — |
| | $ | 183,787 |
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