Amount of unrealized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in net income (trading).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27357-111563

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.4)
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

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Investments (Details) - USD ($) $ in Millions	12 Months Ended
Investments (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments
Fair Value	$ 1,465	$ 1,434
Change in unrealized gains (losses) on trading securities	74	176	$ (110)
Domestic equity securities
Investments
Fair Value	702	706
Domestic debt securities
Investments
Fair Value	496	460
Foreign equity securities
Investments
Fair Value	133	189
Foreign equity securities \| Denominated in foreign currencies
Investments
Fair Value	1	62
Foreign equity securities \| Denominated in Euros
Investments
Fair Value		32
Foreign equity securities \| Denominated in Japanese Yen
Investments
Fair Value		12
Foreign equity securities \| Denominated in British pounds
Investments
Fair Value		8
Foreign equity securities \| Denominated in other foreign currencies
Investments
Fair Value		10
Foreign debt securities
Investments
Fair Value	68	48
Foreign debt securities \| Denominated in Euros
Investments
Fair Value	28	13
Money market funds held in trading accounts
Investments
Fair Value	47	12
Other trading securities
Investments
Fair Value	$ 19	$ 19