Investments Schedule of Gains and Losses on Equity and Other Investments (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Gain (Loss) on Securities [Line Items]
Realized Investment Gains (Losses)	$ 887	$ (958)
Equity Securities [Member]
Gain (Loss) on Securities [Line Items]
Equity Securities, FV-NI, Realized Gain (Loss)	367	(29)
Less: Net gains (losses) recognized from sales of securities	45	(24)
Unrealized gains (losses) recognized for securities still held at reporting date	322	(5)
Other Investments [Member]
Gain (Loss) on Securities [Line Items]
Realized Investment Gains (Losses)	38	5
Less: Net gains (losses) recognized from sales of securities	0	0
Unrealized gains (losses) recognized for securities still held at reporting date	38	5
Equity securities and other investments [Member]
Gain (Loss) on Securities [Line Items]
Realized Investment Gains (Losses)	405	(24)
Less: Net gains (losses) recognized from sales of securities	45	(24)
Unrealized gains (losses) recognized for securities still held at reporting date	$ 360	$ 0

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
-URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117546-209714

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(3)(d))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

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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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-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-Section S99
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Amount of unrealized gain (loss) on investment.

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