Investments (Net Investment Income - Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Investments, Debt and Equity Securities [Abstract]
Income (Loss) from Equity Method Investments	$ 1,700	$ 510	$ 4,000	$ 145

Amount of income (loss) for proportionate share of equity method investee's income (loss).

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