Investments Schedule of Gains and Losses on Equity and Other Investments (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Equity Securities [Member]
Gain (Loss) on Securities [Line Items]
Equity Securities, FV-NI, Realized Gain (Loss)	$ (29)	$ 58
Less: Net gains (losses) recognized from sales of securities	(24)	1
Unrealized gains (losses) recognized for securities still held at reporting date	(5)	57
Other Investments [Member]
Gain (Loss) on Securities [Line Items]
Net gains (losses) recognized during the period	5	(44)
Less: Net gains (losses) recognized from sales of securities	0	(2)
Unrealized gains (losses) recognized for securities still held at reporting date	5	(42)
Equity securities and other investments [Member]
Gain (Loss) on Securities [Line Items]
Net gains (losses) recognized during the period	(24)	14
Less: Net gains (losses) recognized from sales of securities	(24)	(1)
Unrealized gains (losses) recognized for securities still held at reporting date	$ 0	$ 15

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=116654751&loc=SL75117546-209714

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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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.3(a))
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