Regulatory Requirements (Summary of Capital, Capital Requirements And Excess Capital) (Details) $ in Millions	Jun. 30, 2026 USD ($)
Net Capital / Eligible Equity	$ 17,790
Requirement	3,597
Excess	14,193
IB LLC [Member]
Net Capital / Eligible Equity	10,533
Requirement	2,108
Excess	8,425
IBHK [Member]
Net Capital / Eligible Equity	2,182
Requirement	752
Excess	1,430
IBIE [Member]
Net Capital / Eligible Equity	1,929
Requirement	484
Excess	1,445
Other Regulated Operating Companies [Member]
Net Capital / Eligible Equity	3,146
Requirement	253
Excess	$ 2,893

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.

No definition available.

+ Details

Name:	ibkr_NetCapitalEligibleEquity
Namespace Prefix:	ibkr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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
-Name Rule 15c3-1
-Number 240
-Section 15c3-1
-Publisher SEC

+ Details

Name:	srt_MinimumNetCapitalRequiredForEntity1
Namespace Prefix:	srt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of total risk-based capital exceeding minimum required for capital adequacy as defined by regulatory framework.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1

+ Details

Name:	us-gaap_ExcessCapital
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	dei_LegalEntityAxis=ibkr_IBLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=ibkr_IbhkMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=ibkr_IbieMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=ibkr_OtherRegulatedOperatingCompaniesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: