Defined Contribution Plan Vesting Period

No definition available.

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- Definition

As of the balance sheet date, the aggregate estimated unrecognized future compensation costs for unvested 2007 Stock Incentive Plan shares.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The maximum number of shares authorized to be granted and issued under the 2007 Stock Incentive Plan

+ References

No definition available.

+ Details

Name:	ibkr_ShareBasedCompensationNumberOfSharesAvailableForGrant
Namespace Prefix:	ibkr_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Shares distributed under post employment provisions.

+ References

No definition available.

+ Details

Name:	ibkr_SharesDistributedPostEmployment
Namespace Prefix:	ibkr_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares granted to external directors under the 2007 Stock Incentive Plan.

+ References

No definition available.

+ Details

Name:	ibkr_SharesGrantedExternalDirectors
Namespace Prefix:	ibkr_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

Name:	us-gaap_AllocatedShareBasedCompensationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of cost for defined contribution plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage employer matches of the employee's percentage contribution matched.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of service or performance condition required to be met for earning right to award under share-based payment arrangement. Includes, but is not limited to, combination of market, performance or service condition.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRights
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Data Type:	xbrli:stringItemType
Balance Type:	na
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of vesting of award under share-based payment arrangement.

+ References

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

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- Details

Name:	srt_TitleOfIndividualAxis=srt_DirectorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VestingAxis=ibkr_CommencingOneYearAfterGrantDateMember
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Employee Incentive Plans (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended		161 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	10.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	50.00%
Defined Contribution Plan Vesting Period	6 years
401(k) plan contribution expense	$ 3	$ 3
Maximum shares of stock distributable under 2007 Stock Incentive Plan	30,000,000		30,000,000
Shares granted to external directors			27,245
2007 Stock Incentive Plan Compensation Expense	$ 46	$ 43
Estimated Future 2007 Stock Incentive Plan Compensation Expense	$ 27		$ 27
Post employment shares distribution			1,066,736
2007 Stock Incentive Plan (Shares)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Percentage, description	•10% on the first vesting date, which is on or about May 9 of each year; and•an additional 15% on each of the following six anniversaries of the first vesting, assuming continued employment with the Company and compliance with non-competition and other applicable covenants.
2007 Stock Incentive Plan (Shares) \| External Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	5 years
2007 Stock Incentive Plan (Shares) \| External Director [Member] \| Commencing One Year After Grant Date [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage per year	20.00%