Amount of unrealized gain (loss) on 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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- Definition

Sum of the carrying amounts as of the balance sheet date of all investments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(h))
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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Investments - Other Segments and Holding Company (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Schedule of Investments [Line Items]
Investments	$ 8,197		$ 9,945
Other Segments and Holding Company
Schedule of Investments [Line Items]
Unrealized gains (losses) that relate to equity securities still held	312	$ 154
Investments	678		738
Other Segments and Holding Company \| Equity method investments
Schedule of Investments [Line Items]
Investments	199		201
Other Segments and Holding Company \| Other investments (measured at fair value)
Schedule of Investments [Line Items]
Investments	$ 479		$ 537