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Regulatory Requirements (Summary Of Capital, Capital Requirements And Excess Capital) (Details) $ in Millions	Mar. 31, 2020 USD ($)
Net Capital / Eligible Equity	$ 6,943
Requirement	515
Excess	6,428
IB LLC [Member]
Net Capital / Eligible Equity	5,137
Requirement	343
Excess	4,794
IBKRFS [Member]
Net Capital / Eligible Equity	579
Requirement	21
Excess	558
IBHK [Member]
Net Capital / Eligible Equity	438
Requirement	109
Excess	329
Other Regulated Operating Companies [Member]
Net Capital / Eligible Equity	789
Requirement	42
Excess	$ 747

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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