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Investments Investments (Schedule of Gains and Losses on Equity and Other Investments) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Gain (Loss) on Securities [Line Items] |  |  |  |
Unrealized Gain (Loss) on Investments | $ 2,130 | $ 3,088 | $ (1,699) |
Realized Investment Gains (Losses) | (498) | (530) | (652) |
Equity Securities [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Equity Securities, FV-NI, Realized Gain (Loss) | 586 | 104 | (59) | [1]
Other Investments [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Realized Investment Gains (Losses) | (32) | (20) | (5) |
Accounting Standards Update 2016-01 [Member] | Equity Securities [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Equity Securities, FV-NI, Realized Gain (Loss) | 586 | 104 | (59) |
Unrealized Gain (Loss) on Investments | 131 | 46 | (129) |
Gain (Loss) on Sale of Investments | 455 | 58 | 70 |
Accounting Standards Update 2016-01 [Member] | Other Investments [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Unrealized Gain (Loss) on Investments | (32) | (15) | (126) |
Gain (Loss) on Sale of Investments | 0 | (5) | 121 |
Realized Investment Gains (Losses) | (32) | (20) | (5) |
Accounting Standards Update 2016-01 [Member] | Equity securities and other investments [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Unrealized Gain (Loss) on Investments | 99 | 31 | (255) |
Gain (Loss) on Sale of Investments | 455 | 53 | 191 |
Realized Investment Gains (Losses) | $ 554 | $ 84 | $ (64) |
[1] | Relates to certain securities we intended to sell and securities written to market entering default.

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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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