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Significant Accounting Policies (Tables) | 9 Months Ended
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Sep. 30, 2020
Significant Accounting Policies [Abstract] |
Schedule Of Securities Segregated For Regulatory Purposes |
|  | September 30, |  | December 31,
|  | 2020 |  | 2019
|  | (in billions)
U.S. government securities |  | $ | 5.0 |  | $ | 3.8
Securities purchased under agreements to resell 1 |  |  | 24.3 |  |  | 14.0
|  | $ | 29.3 |  | $ | 17.8
___________________________ (1)These balances are collateralized by U.S. government securities.
Composition Of Investment |
|  | September 30, |  | December 31,
|  | 2020 |  | 2019
|  | (in millions)
Equity method investments 1 |  | $ | 9 |  | $ | 22
Investments in equity securities at adjusted cost 2 |  |  | 7 |  |  | 5
Investments in equity securities at fair value 2 |  |  | 48 |  |  | 36
Investments in exchange memberships and equity securities of certain exchanges 2 |  |  | 3 |  |  | 3
|  | $ | 67 |  | $ | 66
___________________________ (1)The Company’s share of income or losses is included in other income in the condensed consolidated statements of comprehensive income. (2)These investments do not qualify for equity method of accounting and the dividends received are included in other income in the condensed consolidated statements of comprehensive income.

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- Definition 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. + References 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 + Details
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