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Cash and Cash Equivalents and Short-term Investments (Tables) | 12 Months Ended
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Dec. 31, 2014
Cash and Cash Equivalents and Short-term Investments |
Cash and cash equivalents and short-term investments |
|  | As of December 31, |
|  | 2014 |  | 2013 |
|  | (In thousands) |
Cash and cash equivalents |  | $ | 501,149 |  | $ | 389,915 |
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Short-term investments: |  |  |  |  |  |  |
Available-for-sale equity securities |  | $ | 35,002 |  | $ | 96,942 |
Available-for-sale debt securities |  |  | 18 |  |  | 20,276 |
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Total short-term investments |  | $ | 35,020 |  | $ | 117,218 |
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Certain information related to our cash and cash equivalents and short term investments |
|  | As of December 31, |
|  | 2014 |  | 2013 |
|  | Fair Value |  | Gross Unrealized Holding Gains |  | Gross Unrealized Holding Losses |  | Fair Value |  | Gross Unrealized Holding Gains |  | Gross Unrealized Holding Losses |
|  | (In thousands) |
Cash and cash equivalents |  | $ | 501,149 |  | $ | — |  | $ | — |  | $ | 389,915 |  | $ | — |  | $ | — |
Short-term investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Available-for-sale equity securities |  |  | 35,002 |  |  | 14,648 |  |  | — |  |  | 96,942 |  |  | 68,395 |  |  | — |
Available-for-sale debt securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate debt securities |  |  | — |  |  | — |  |  | — |  |  | 19,388 |  |  | 4,122 |  |  | — |
Mortgage-backed debt securities |  |  | — |  |  | — |  |  | — |  |  | 210 |  |  | 11 |  |  | — |
Mortgage-CMO debt securities |  |  | 18 |  |  | — |  |  | (1 | ) |  | 20 |  |  | — |  |  | (2 | )
Asset-backed debt securities |  |  | — |  |  | — |  |  | — |  |  | 658 |  |  | 2 |  |  | (54 | )
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Total available-for-sale debt securities |  |  | 18 |  |  | — |  |  | (1 | ) |  | 20,276 |  |  | 4,135 |  |  | (56 | )
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Total available-for-sale securities |  |  | 35,020 |  |  | 14,648 |  |  | (1 | ) |  | 117,218 |  |  | 72,530 |  |  | (56 | )
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Total short-term investments |  |  | 35,020 |  |  | 14,648 |  |  | (1 | ) |  | 117,218 |  |  | 72,530 |  |  | (56 | )
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Total cash, cash equivalents and |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
short-term investments |  | $ | 536,169 |  | $ | 14,648 |  | $ | (1 | ) | $ | 507,133 |  | $ | 72,530 |  | $ | (56 | )
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Gross unrealized losses of cash and cash equivalents and short-term investments |
|  | As of December 31, 2014 |
|  | Less Than 12 Months |  | More Than 12 Months |
|  | Fair Value |  | Gross Unrealized Losses |  | Fair Value |  | Gross Unrealized Losses |
|  | (In thousands) |
Available-for-sale equity securities |  | $ | — |  | $ | — |  | $ | — |  | $ | — |
Available-for-sale debt securities: |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage-CMO debt securities |  |  | — |  |  | — |  |  | 18 |  |  | 1 |
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Total available-for-sale debt securities |  |  | — |  |  | — |  |  | 18 |  |  | 1 |
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Total |  | $ | — |  | $ | — |  | $ | 18 |  | $ | 1 |
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Estimated fair values of corporate, mortgage-backed, mortgage-CMO and asset-backed debt securities |
|  | Estimated Fair Value As of December 31, 2014 |
|  | (In thousands) |
Debt securities: |  |  |  |
Due in one year or less |  | $ | — |
Due after one year through five years |  |  | — |
Due in more than five years |  |  | 18 |
​ | ​ | ​ | ​ | ​
Total debt securities |  | $ | 18 |
​ | ​ | ​ | ​ | ​
Debt and equity securities |
|  | Year Ended December 31, |
|  | 2014 |  | 2013 |  | 2012 |
|  | (In thousands) |
Available-for-sale |  |  |  |  |  |  |  |  |  |
Proceeds from sales and maturities |  | $ | 22,313 |  | $ | 107,586 |  | $ | 24,010 |
Realized gains (losses), net |  | $ | 4,638 |  | $ | 88,158 |  | $ | 13,405 |

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