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Investments (Tables) | 9 Months Ended
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Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract] |
Schedule of Investments | The following table presents the details of our investments:
| September 30, 2018 |  | December 31, 2017
| (in millions)
Trading securities | $ | 202 |  |  | $ | 221 |
Available-for-sale investment securities | — |  |  | 14 |
Financial investments, at fair value | $ | 202 |  |  | $ | 235 |
Equity method investments | $ | 131 |  |  | $ | 131 |
Equity securities | $ | 76 |  |  | $ | 152 |

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