Regulatory Requirements (Summary of Capital, Capital Requirements And Excess Capital) (Details) $ in Millions	Mar. 31, 2026 USD ($)
Net Capital / Eligible Equity	$ 16,748
Requirement	2,816
Excess	13,932
IB LLC [Member]
Net Capital / Eligible Equity	10,262
Requirement	1,676
Excess	8,586
IBHK [Member]
Net Capital / Eligible Equity	1,816
Requirement	542
Excess	1,274
IBIE [Member]
Net Capital / Eligible Equity	1,671
Requirement	393
Excess	1,278
Other Regulated Operating Companies [Member]
Net Capital / Eligible Equity	2,999
Requirement	205
Excess	$ 2,794

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.

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

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- 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

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