Assets and Liabilities Measured at Fair Value |
The following is a list of those assets and liabilities that are measured at fair value by hierarchy level as of December 31, 2016 and December 31, 2015: | | | | | | | | | | | | | | | | | | Fair Value Measurements Using | | Quoted Prices in Active Markets for Identical Assets (Level 1) | | Significant Other Observable Inputs (Level 2) | | Significant Unobservable Inputs (Level 3) | | Fair Value | As of December 31, 2016 | (In Thousands) | U.S. Treasury securities and obligations of U.S. government agencies | $ | 50,719 |
| | $ | 12,460 |
| | $ | — |
| | $ | 63,179 |
| Municipal debt securities | — |
| | 40,269 |
| | — |
| | 40,269 |
| Corporate debt securities | — |
| | 349,078 |
| | — |
| | 349,078 |
| Asset-backed securities | — |
| | 114,661 |
| | — |
| | 114,661 |
| Cash, cash equivalents and short-term investments | 109,528 |
| | — |
| | — |
| | 109,528 |
| Total assets | $ | 160,247 |
| | $ | 516,468 |
| | $ | — |
| | $ | 676,715 |
| Warrant liability | $ | — |
| | $ | — |
| | $ | 3,367 |
| | $ | 3,367 |
| Total liabilities | $ | — |
| | $ | — |
| | $ | 3,367 |
| | $ | 3,367 |
|
| | | | | | | | | | | | | | | | | | Fair Value Measurements Using | | Quoted Prices in Active Markets for Identical Assets (Level 1) | | Significant Other Observable Inputs (Level 2) | | Significant Unobservable Inputs (Level 3) | | Fair Value | As of December 31, 2015 | (In Thousands) | U.S. Treasury securities and obligations of U.S. government agencies | $ | 65,185 |
| | $ | 19,297 |
| | $ | — |
| | $ | 84,482 |
| Municipal debt securities | — |
| | 20,079 |
| | — |
| | 20,079 |
| Corporate debt securities | — |
| | 333,327 |
| | — |
| | 333,327 |
| Asset-backed securities | — |
| | 100,793 |
| | — |
| | 100,793 |
| Cash, cash equivalents and short-term investments | 77,872 |
| | — |
| | — |
| | 77,872 |
| Total assets | $ | 143,057 |
| | $ | 473,496 |
| | $ | — |
| | $ | 616,553 |
| Warrant liability | $ | — |
| | $ | — |
| | $ | 1,467 |
| | $ | 1,467 |
| Total liabilities | $ | — |
| | $ | — |
| | $ | 1,467 |
| | $ | 1,467 |
|
|
Roll-Forward of Level 3 Liabilities Measured at Fair Value |
The following is a roll-forward of Level 3 liabilities measured at fair value: | | | | | | | | | | | | | | For the year ended December 31, | | 2016 | | 2015 | | 2014 | | (In Thousands) | Balance, January 1, | $ | 1,467 |
| | $ | 3,372 |
| | $ | 6,371 |
| Change in fair value of warrant liability included in earnings | 1,900 |
| | (1,905 | ) | | (2,949 | ) | Gain on settlement of warrants | — |
| | — |
| | (37 | ) | Issuance of common stock on warrant exercise | — |
| | — |
| | (13 | ) | Balance, December 31 | $ | 3,367 |
| | $ | 1,467 |
| | $ | 3,372 |
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