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Fair Value Measurements - Proceeds from the Sale of Investments (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020
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 | $ 8 | $ 26 | $ 13 | $ 39
Realized gains | 0 | 0 | 0 | 4
Realized Losses | (1) | (2) | (1) | (7)
Interest and dividend income | $ 2 | $ 9 | $ 5 | $ 14

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