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Fair Value Measurements - Proceeds from the Sale of Investments (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018
Proceeds from the sale of investments in available-for-sale securities, realized gains and losses on those sales, and interest and dividend income |  |  |  |
Sale proceeds | $ 204 | $ 261 | $ 506 | $ 627
Realized gains | 8 | 3 | 20 | 31
Realized Losses | (7) | (7) | (18) | (34)
Interest and Dividend Income | $ 10 | $ 11 | $ 30 | $ 31

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