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Regulatory Requirements (Summary Of Capital, Capital Requirements And Excess Capital) (Details) $ in Millions	Dec. 31, 2019 USD ($)
Net Capital / Eligible Equity	$ 7,192
Required net capital	829
Excess regulatory capital	6,363
IB LLC [Member]
Net Capital / Eligible Equity	5,381
Required net capital	549
Excess regulatory capital	4,832
IBKRFS [Member]
Net Capital / Eligible Equity	584
Required net capital	91
Excess regulatory capital	493
IBHK [Member]
Net Capital / Eligible Equity	360
Required net capital	145
Excess regulatory capital	215
Other Regulated Operating Companies [Member]
Net Capital / Eligible Equity	867
Required net capital	44
Excess regulatory capital	$ 823

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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