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Regulatory Requirements (Summary Of Capital, Capital Requirements And Excess Capital) (Details) $ in Millions	Sep. 30, 2020 USD ($)
Net Capital / Eligible Equity	$ 6,742
Requirement	822
Excess	5,920
IB LLC [Member]
Net Capital / Eligible Equity	4,621
Requirement	520
Excess	4,101
IBKRFS [Member]
Net Capital / Eligible Equity	593
Requirement	21
Excess	572
IBHK [Member]
Net Capital / Eligible Equity	632
Requirement	225
Excess	407
Other Regulated Operating Companies [Member]
Net Capital / Eligible Equity	896
Requirement	56
Excess	$ 840

X

- Definition

Eligible equity is equal to the sum of audited capital and reserves and the eligible portion of subordinated debt. Net capital is equal to the net worth of the broker dealer, less certain items such as exchange memberships, carrying value of securities not readily marketable, haircuts on marketable securities in proprietary accounts, furniture and equipment and other illiquid assets as defined.

+ References

No definition available.

+ Details

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- Definition

Minimum amount of net capital required to be maintained by broker-dealer parent, calculated under Aggregate Indebtedness Standard.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher SEC
-Name Rule 15c3-1
-Number 240
-Section 15c3-1

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- Definition

The amount by which the company's Total Capital exceeds the minimum required for capital adequacy purposes.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=117337116&loc=SL5958568-112826

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- Details

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- Details

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- Details

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