Significant Accounting Policies (Tables)	12 Months Ended
Dec. 31, 2021
Significant Accounting Policies [Abstract]
Schedule Of Securities Segregated For Regulatory Purposes	December 31, 2021 2020 (in millions)U.S. government securities $ 4,729 $ 4,750 Securities purchased under agreements to resell 1 10,392 23,071 $ 15,121 $ 27,821 ___________________________ (1)These balances are collateralized by U.S. government securities.
Composition Of Investment	December 31, 2021 2020 (in millions)Equity method investments1 $ 123 $ 11 Investments in equity securities at adjusted cost2 17 10 Investments in equity securities at fair value2 49 80 Investments in exchange memberships and equity securities of certain exchanges2 3 3 $ 192 $ 104 ___________________________ (1)The Company’s share of income or losses is included in other income in the consolidated statements of comprehensive income. (2)These investments do not qualify for the equity method of accounting and the dividends received are included in other income in the consolidated statements of comprehensive income.

Tabular disclosure of equity method investments including, but not limited to, name of each investee or group of investments, percentage ownership, difference between recorded amount of an investment and the value of the underlying equity in the net assets, and summarized financial information.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

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