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v3.20.2

Organization Of Business (Details) - employee | Sep. 30, 2020 | May 03, 2007
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Number of employees | 1,923 |
IBG LLC [Member] |  |
IBG Inc. ownership % of IBG LLC | 19.00% | 10.00%

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- Definition Number of persons employed by the Entity + References No definition available. + Details
Name: | dei_EntityNumberOfEmployees
Namespace Prefix: | dei_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

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- Definition The parent entity's interest in net assets of the subsidiary, expressed as a percentage. + References No definition available. + Details
Name: | us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Details
Name: | srt_OwnershipAxis=ibkr_IbgLlcMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |