v2.4.0.8

Regulatory Requirements (Summary Of Capital, Capital Requirements And Excess Capital) (Details) (USD $) In Millions, unless otherwise specified | Jun. 30, 2014
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Net Capital / Eligible Equity | $ 3,870.2
Required net capital | 637.2
Excess regulatory capital | 3,233.0
IB LLC [Member] |
Net Capital / Eligible Equity | 2,262.1
Required net capital | 332.6
Excess regulatory capital | 1,929.5
TH LLC [Member] |
Net Capital / Eligible Equity | 436.0
Required net capital | 60.3
Excess regulatory capital | 375.7
THE [Member] |
Net Capital / Eligible Equity | 706.8
Required net capital | 197.2
Excess regulatory capital | 509.6
Other Regulated Operating Companies [Member] |
Net Capital / Eligible Equity | 465.3
Required net capital | 47.1
Excess regulatory capital | $ 418.2

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

X
- Definition The amount by which the company's Total Capital exceeds the minimum required for capital adequacy purposes. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=7881181&loc=SL5958568-112826 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Minimum amount of net capital required to be maintained by the entity to engage in securities transactions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Rule 15c3 -Number 240 -Section 1 -Paragraph 1 -Subparagraph i -Article 15c3 -Subsection a + Details
Name: | us-gaap_MinimumNetCapitalRequiredForEntity1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant