v2.4.0.8

Financial Assets And Financial Liabilities (Netting of Financial Liabilities) (Details) (USD $) In Millions, unless otherwise specified | Jun. 30, 2014 | Dec. 31, 2013
--- | --- | ---
Offsetting Liabilities [Line Items] |  |
Gross Amounts of Recognized Liabilities | $ 4,101.8 | $ 4,358.9
Gross Amounts Liabilities Offset in the Consolidated Statement of Financial Condition | 0 | 0
Net Amounts of Liabilities Presented in the Statement of Financial Condition | 4,101.8 | 4,358.9
Gross Amounts of Liabilities Not Offset in the Consolidated Satement of Financial Position (Financial Instruments) | (3,965.1) | (4,198.6)
Gross Amounts Not Offset in the Consolidated Statement of Financial Position (Cash Collateral Pledged) | 0 | 0
Net Amount of Liabilities | 136.7 | 160.3
Securities Loaned [Member] |  |
Offsetting Liabilities [Line Items] |  |
Gross Amounts of Recognized Liabilities | 2,932.4 | 2,563.7
Gross Amounts Liabilities Offset in the Consolidated Statement of Financial Condition | 0 | 0
Net Amounts of Liabilities Presented in the Statement of Financial Condition | 2,932.4 | 2,563.7
Gross Amounts of Liabilities Not Offset in the Consolidated Satement of Financial Position (Financial Instruments) | (2,932.0) | (2,544.6)
Gross Amounts Not Offset in the Consolidated Statement of Financial Position (Cash Collateral Pledged) | 0 | 0
Net Amount of Liabilities | 0.4 | 19.1
Options Sold, Not Yet Purchased [Member] |  |
Offsetting Liabilities [Line Items] |  |
Gross Amounts of Recognized Liabilities | 1,168.8 | 1,793.2
Gross Amounts Liabilities Offset in the Consolidated Statement of Financial Condition | 0 | 0
Net Amounts of Liabilities Presented in the Statement of Financial Condition | 1,168.8 | 1,793.2
Gross Amounts of Liabilities Not Offset in the Consolidated Satement of Financial Position (Financial Instruments) | (1,032.5) | (1,652.8)
Gross Amounts Not Offset in the Consolidated Statement of Financial Position (Cash Collateral Pledged) | 0 | 0
Net Amount of Liabilities | 136.3 | 140.4
Warrants And Discount Certificates Sold, Not Yet Purchased [Member] |  |
Offsetting Liabilities [Line Items] |  |
Gross Amounts of Recognized Liabilities | 0.6 | 1.2
Gross Amounts Liabilities Offset in the Consolidated Statement of Financial Condition | 0 | 0
Net Amounts of Liabilities Presented in the Statement of Financial Condition | 0.6 | 1.2
Gross Amounts of Liabilities Not Offset in the Consolidated Satement of Financial Position (Financial Instruments) | (0.6) | (1.2)
Gross Amounts Not Offset in the Consolidated Statement of Financial Position (Cash Collateral Pledged) | 0 | 0
Net Amount of Liabilities | 0 | 0
Currency Forward Contracts Sold, Not Yet Purchased [Member] |  |
Offsetting Liabilities [Line Items] |  |
Gross Amounts of Recognized Liabilities | 0 | 0.8
Gross Amounts Liabilities Offset in the Consolidated Statement of Financial Condition | 0 | 0
Net Amounts of Liabilities Presented in the Statement of Financial Condition | 0 | 0.8
Gross Amounts of Liabilities Not Offset in the Consolidated Satement of Financial Position (Financial Instruments) | 0 | 0
Gross Amounts Not Offset in the Consolidated Statement of Financial Position (Cash Collateral Pledged) | 0 | 0
Net Amount of Liabilities | $ 0 | $ 0.8

X
- Definition Fair Value of Liability Amount after the effects of master netting arrangements, if applied. + References No definition available. + Details
Name: | ibkr_FairValueOfLiability
Namespace Prefix: | ibkr_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fair Value of Liability Amount before the effects of master netting arrangements + References No definition available. + Details
Name: | ibkr_FairValueOfLiabilityAmountNotOffsetAgainstCollateral
Namespace Prefix: | ibkr_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fair Value of Liability Amount netted in Statement of Financial Condition per master netting arrangements + References No definition available. + Details
Name: | ibkr_FairValueOfLiabilityAmountOffsetAgainstCollateral
Namespace Prefix: | ibkr_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Cash collateral amount subject to netting that Management elects not to offset + References No definition available. + Details
Name: | ibkr_GrossAmountsLiabilitiesNotOffsetCashCollateralReceived
Namespace Prefix: | ibkr_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Financial collateral amount subject to master netting agreements that Management elects not to offset. + References No definition available. + Details
Name: | ibkr_GrossAmountsLiabilitiesNotOffsetFinancialInstruments
Namespace Prefix: | ibkr_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Liabilities net amount after the effects of netting financial/cash collateral. + References No definition available. + Details
Name: | ibkr_NetAmountLiabilities
Namespace Prefix: | ibkr_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_OffsettingLiabilitiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration