Acquisition and Divestiture (2021 Divestiture) (Details) $ in Millions	1 Months Ended
Jun. 30, 2021 USD ($) shares
eSpeed \| Common stock
Business Acquisition [Line Items]
Contingent future issuance of common stock (in shares) \| shares	6,200,000
Discontinued Operations, Disposed of by Sale \| U.S. Fixed Income business
Business Acquisition [Line Items]
Gain on disposition of business, before taxes \| $	$ 84

Amount before tax of gain (loss) not previously recognized resulting from the disposal of a discontinued operation.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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