Investments Schedule of Gains and Losses on Equity and Other Investments (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Gain (Loss) on Securities [Line Items]
Net gains (losses) recognized during the period	$ (141)	$ (155)	$ (1,069)	$ (475)
Equity Securities [Member]
Gain (Loss) on Securities [Line Items]
Equity Securities, FV-NI, Realized Gain (Loss)	0	3	119	66
Less: Net gains (losses) recognized from sales of securities	34	24	197	57
Unrealized gains (losses) recognized for securities still held at reporting date	(34)	(21)	(78)	9
Other Investments [Member]
Gain (Loss) on Securities [Line Items]
Net gains (losses) recognized during the period	31	(4)	(71)	(18)
Less: Net gains (losses) recognized from sales of securities	0	(2)	0	(4)
Unrealized gains (losses) recognized for securities still held at reporting date	31	(2)	(71)	(14)
Equity securities and other investments [Member]
Gain (Loss) on Securities [Line Items]
Net gains (losses) recognized during the period	31	(1)	48	48
Less: Net gains (losses) recognized from sales of securities	34	22	197	53
Unrealized gains (losses) recognized for securities still held at reporting date	$ (3)	$ (23)	$ (149)	$ (5)

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).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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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.

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