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Investments Investments (Schedule of Gains and Losses on Equity and Other Investments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Gain (Loss) on Securities [Line Items]
Unrealized Gain (Loss) on Investments	$ 3,088	$ (1,699)	$ 392
Equity Securities [Member]
Gain (Loss) on Securities [Line Items]
Equity Securities, FV-NI, Realized Gain (Loss)	104	(59)
Unrealized Gain (Loss) on Investments	0	0	88
Other Investments [Member]
Gain (Loss) on Securities [Line Items]
Realized Investment Gains (Losses)	(20)	(5)	$ 0
Accounting Standards Update 2016-01 [Member] | Equity Securities [Member]
Gain (Loss) on Securities [Line Items]
Equity Securities, FV-NI, Realized Gain (Loss)	104	(59)
Unrealized Gain (Loss) on Investments	46	(129)
Gain (Loss) on Sale of Investments	58	70
Accounting Standards Update 2016-01 [Member] | Other Investments [Member]
Gain (Loss) on Securities [Line Items]
Unrealized Gain (Loss) on Investments	(15)	(126)
Gain (Loss) on Sale of Investments	(5)	121
Realized Investment Gains (Losses)	(20)	(5)
Accounting Standards Update 2016-01 [Member] | Equity securities and other investments [Member]
Gain (Loss) on Securities [Line Items]
Unrealized Gain (Loss) on Investments	31	(255)
Gain (Loss) on Sale of Investments	53	191
Realized Investment Gains (Losses)	$ 84	$ (64)

X

- Definition

Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
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The net realized gain (loss) on investments sold during the period, not including gains (losses) on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, which, for cash flow reporting, is a component of proceeds from investing activities.

+ References

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The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of investments, not including unrealized gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, held at each balance sheet date and included in earnings for the period.

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