Fair Value Measurements - Fair Value Measurement (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Assets
Derivative contracts, at fair value	$ 855	$ 785
Liabilities
Securities sold, not yet purchased	4,863	2,521
Derivative contracts at fair value	584	639
Recurring measurement
Assets
Investments	11,340	8,761
Derivative contracts, at fair value	855	785
Assets, Fair Value Disclosure	12,195	9,546
Liabilities
Securities sold, not yet purchased	4,863	2,521
Derivative contracts at fair value	584	639
Other liabilities	342	214
Financial and Nonfinancial Liabilities, Fair Value Disclosure	5,789	3,374
Recurring measurement \| Level 1
Assets
Investments	11,128	8,546
Assets, Fair Value Disclosure	11,128	8,546
Liabilities
Securities sold, not yet purchased	4,863	2,521
Derivative contracts at fair value		11
Financial and Nonfinancial Liabilities, Fair Value Disclosure	4,863	2,532
Recurring measurement \| Level 2
Assets
Investments	171	174
Derivative contracts, at fair value	855	785
Assets, Fair Value Disclosure	1,026	959
Liabilities
Derivative contracts at fair value	584	628
Other liabilities	342	214
Financial and Nonfinancial Liabilities, Fair Value Disclosure	926	842
Recurring measurement \| Level 3
Assets
Investments	41	41
Assets, Fair Value Disclosure	$ 41	$ 41

Investments measured at fair value.

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- Definition

Unrealized Gain On Derivative Contracts

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
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-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611

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-Topic 210
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- Definition

Fair value of obligations incurred from short sales.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 320
-Section 35
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35711043&loc=d3e42429-110968

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Fair value of financial and nonfinancial obligations.

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Fair value portion of other liabilities.

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