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Investments Schedule of Gains and Losses on Equity and Other Investments (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
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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)

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- 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 -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 + Details
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- Definition 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=121586364&loc=d3e3602-108585 + Details
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- Definition Amount of realized gain (loss) on investment. + 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)) -URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 + Details
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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. + Details
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- Definition Amount of unrealized gain (loss) on investment. + 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=121586364&loc=d3e3602-108585 + Details
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