| Summary of fair value hierarchy for its financial assets and liabilities measured at fair value on a recurring basis |
The following table represents the Company's fair value hierarchy for its financial assets (cash, cash equivalents and investments) measured at fair value on a recurring basis as of March 31, 2015 (in thousands):
| | | | | | | | | | | | | | | | | | Level 1 | | Level 2 | | Level 3 | | Total | Assets: | | | | | | | | Cash | $ | 336,204 |
| | $ | — |
| | $ | — |
| | $ | 336,204 |
| Money market funds | 155,816 |
| | — |
| | — |
| | 155,816 |
| Commercial paper | 49,751 |
| | — |
| | — |
| | 49,751 |
| Auction rate securities | — |
| | — |
| | 16,669 |
| | 16,669 |
| Total assets measured at fair value | $ | 541,771 |
| | $ | — |
| | $ | 16,669 |
| | $ | 558,440 |
|
| | 5. | FAIR VALUE — (CONTINUED) |
The following table represents the Company's fair value hierarchy for its financial assets (cash, cash equivalents and investments) measured at fair value on a recurring basis as of December 31, 2014 (in thousands): | | | | | | | | | | | | | | | | | | Level 1 | | Level 2 | | Level 3 | | Total | Assets: | | | | | | | | Cash | $ | 160,275 |
| | $ | — |
| | $ | — |
| | $ | 160,275 |
| Money market funds | 310,482 |
| | — |
| | — |
| | 310,482 |
| Commercial paper | 56,255 |
| | — |
| | — |
| | 56,255 |
| Auction rate securities | — |
| | — |
| | 17,151 |
| | 17,151 |
| Total assets measured at fair value | $ | 527,012 |
| | $ | — |
| | $ | 17,151 |
| | $ | 544,163 |
|
|
| Summary of changes in the fair value of the company's level 3 assets |
The following tables summarize changes in fair value of the Company’s Level 3 assets for the three months ended March 31, 2015 and 2014 (in thousands): | | | | | | | | | | Three Months Ended
March 31, | | 2015 | | 2014 | Balance at beginning of period | $ | 17,151 |
| | $ | 21,990 |
| Decrease in unrealized loss included in accumulated other comprehensive loss | 168 |
| | 178 |
| Settlements | (650 | ) | | — |
| Balance at end of period | $ | 16,669 |
| | $ | 22,168 |
|
| | 5. | FAIR VALUE — (CONTINUED) |
The following table summarizes changes in fair value of the Company’s Level 3 assets from December 31, 2007 to March 31, 2015 (in thousands): | | | | | | Auction Rate Securities | Balance at December 31, 2007 | $ | 53,975 |
| Increase in unrealized loss included in accumulated other comprehensive loss | (3,710 | ) | Settlements | (20,925 | ) | Balance at December 31, 2008 | 29,340 |
| Decrease in unrealized loss included in accumulated other comprehensive loss | 684 |
| Settlements | (300 | ) | Balance at December 31, 2009 | 29,724 |
| Decrease in unrealized loss included in accumulated other comprehensive loss | 40 |
| Settlements | (575 | ) | Balance at December 31, 2010 | 29,189 |
| Decrease in unrealized loss included in accumulated other comprehensive loss | 245 |
| Settlements | (4,850 | ) | Balance at December 31, 2011 | 24,584 |
| Auction rate securities upon acquisition | 442 |
| Decrease in unrealized loss included in accumulated other comprehensive loss | 836 |
| Settlements | (4,200 | ) | Balance at December 31, 2012 | 21,662 |
| Decrease in unrealized loss included in accumulated other comprehensive loss | 378 |
| Settlements | (50 | ) | Balance at December 31, 2013 | 21,990 |
| Decrease in unrealized loss included in accumulated other comprehensive loss | 836 |
| Settlements | (5,675 | ) | Balance at December 31, 2014 | 17,151 |
| Decrease in unrealized loss included in accumulated other comprehensive loss | 168 |
| Settlements | (650 | ) | Balance at March 31, 2015 | $ | 16,669 |
|
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