Fair Value Measurements - Fair Value Measurement (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Liabilities
Securities sold, not yet purchased	$ 4,231		$ 2,521
Derivative liabilities, net	754		639
Level 3
Liabilities
Investments increased	1	$ 0
Recurring measurement
Assets
Investments	10,773		8,761
Derivative assets, net	683		785
Assets, Fair Value Disclosure	11,456		9,546
Liabilities
Securities sold, not yet purchased	4,231		2,521
Derivative liabilities, net	754		639
Other liabilities	485		214
Liabilities, Fair Value Disclosure	5,470		3,374
Recurring measurement \| Level 1
Assets
Investments	10,616		8,546
Assets, Fair Value Disclosure	10,616		8,546
Liabilities
Securities sold, not yet purchased	4,231		2,521
Derivative liabilities, net			11
Liabilities, Fair Value Disclosure	4,231		2,532
Recurring measurement \| Level 2
Assets
Investments	115		174
Derivative assets, net	683		785
Assets, Fair Value Disclosure	798		959
Liabilities
Derivative liabilities, net	754		628
Other liabilities	485		214
Liabilities, Fair Value Disclosure	1,239		842
Recurring measurement \| Level 3
Assets
Investments	42		41
Assets, Fair Value Disclosure	$ 42		$ 41

The amount of increase or decrease in investments.

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Investments measured at fair value.

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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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Fair value, after the effects of master netting arrangements, of a financial asset or other 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, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

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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
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
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- Definition

Fair value of obligations incurred from short sales.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 320
-Section 35
-Paragraph 1
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-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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