v2.4.0.8

Financial Assets And Financial Liabilities (Netting of Financial Assets) (Details) (USD $) In Millions, unless otherwise specified | Jun. 30, 2014 | Dec. 31, 2013
--- | --- | ---
Offsetting Assets [Line Items] |  |  |  |
Gross Amounts of Recognized Assets | $ 10,803.6 |  | $ 11,815.6 |
Gross Amounts Assets Offset in the Consolidated Statement of Financial Condition | 0 |  | 0 |
Net Amounts of Assets Presented in the Statement of Financial Condition | 10,803.6 |  | 11,815.6 |
Gross Amounts of Assets Not Offset in the Consolidated Statement of Financial Position (Financial Instruments) | (10,640.3) |  | (11,469.1) |
Gross Amounts of Assets Not Offset in the Consolidated Statement of Financial Position (Cash Collateral Received) | 0 |  | 0 |
Net Amount of Assets | 163.3 |  | 346.5 |
Securities Segregated For Regulatory Purposes - Purchased Under Agreements To Resell [Member] |  |  |  |
Offsetting Assets [Line Items] |  |  |  |
Gross Amounts of Recognized Assets | 5,913.9 | [1] | 6,734.2 | [1]
Gross Amounts Assets Offset in the Consolidated Statement of Financial Condition | 0 |  | 0 |
Net Amounts of Assets Presented in the Statement of Financial Condition | 5,913.9 |  | 6,734.2 |
Gross Amounts of Assets Not Offset in the Consolidated Statement of Financial Position (Financial Instruments) | (5,913.9) |  | (6,734.2) |
Gross Amounts of Assets Not Offset in the Consolidated Statement of Financial Position (Cash Collateral Received) | 0 |  | 0 |
Net Amount of Assets | 0 |  | 0 |
Securities Borrowed [Member] |  |  |  |
Offsetting Assets [Line Items] |  |  |  |
Gross Amounts of Recognized Assets | 3,499.2 |  | 2,751.5 |
Gross Amounts Assets Offset in the Consolidated Statement of Financial Condition | 0 |  | 0 |
Net Amounts of Assets Presented in the Statement of Financial Condition | 3,499.2 |  | 2,751.5 |
Gross Amounts of Assets Not Offset in the Consolidated Statement of Financial Position (Financial Instruments) | (3,419.0) |  | (2,694.6) |
Gross Amounts of Assets Not Offset in the Consolidated Statement of Financial Position (Cash Collateral Received) | 0 |  | 0 |
Net Amount of Assets | 80.2 |  | 56.9 |
Securities Purchased Under Agreement to Resell [Member] |  |  |  |
Offsetting Assets [Line Items] |  |  |  |
Gross Amounts of Recognized Assets | 274.3 |  | 386.3 |
Gross Amounts Assets Offset in the Consolidated Statement of Financial Condition | 0 |  | 0 |
Net Amounts of Assets Presented in the Statement of Financial Condition | 274.3 |  | 386.3 |
Gross Amounts of Assets Not Offset in the Consolidated Statement of Financial Position (Financial Instruments) | (274.3) |  | (386.3) |
Gross Amounts of Assets Not Offset in the Consolidated Statement of Financial Position (Cash Collateral Received) | 0 |  | 0 |
Net Amount of Assets | 0 |  | 0 |
Options [Member] |  |  |  |
Offsetting Assets [Line Items] |  |  |  |
Gross Amounts of Recognized Assets | 1,073.0 |  | 1,880.5 |
Gross Amounts Assets Offset in the Consolidated Statement of Financial Condition | 0 |  | 0 |
Net Amounts of Assets Presented in the Statement of Financial Condition | 1,073.0 |  | 1,880.5 |
Gross Amounts of Assets Not Offset in the Consolidated Statement of Financial Position (Financial Instruments) | (1,032.5) |  | (1,652.8) |
Gross Amounts of Assets Not Offset in the Consolidated Statement of Financial Position (Cash Collateral Received) | 0 |  | 0 |
Net Amount of Assets | 40.5 |  | 227.7 |
Warrants And Discount Certificates [Member] |  |  |  |
Offsetting Assets [Line Items] |  |  |  |
Gross Amounts of Recognized Assets | 34.6 |  | 57.4 |
Gross Amounts Assets Offset in the Consolidated Statement of Financial Condition | 0 |  | 0 |
Net Amounts of Assets Presented in the Statement of Financial Condition | 34.6 |  | 57.4 |
Gross Amounts of Assets Not Offset in the Consolidated Statement of Financial Position (Financial Instruments) | (0.6) |  | (1.2) |
Gross Amounts of Assets Not Offset in the Consolidated Statement of Financial Position (Cash Collateral Received) | 0 |  | 0 |
Net Amount of Assets | 34.0 |  | 56.2 |
Currency Forward Contracts [Member] |  |  |  |
Offsetting Assets [Line Items] |  |  |  |
Gross Amounts of Recognized Assets | 8.6 |  | 5.7 |
Gross Amounts Assets Offset in the Consolidated Statement of Financial Condition | 0 |  | 0 |
Net Amounts of Assets Presented in the Statement of Financial Condition | 8.6 |  | 5.7 |
Gross Amounts of Assets Not Offset in the Consolidated Statement of Financial Position (Financial Instruments) | 0 |  | 0 |
Gross Amounts of Assets Not Offset in the Consolidated Statement of Financial Position (Cash Collateral Received) | 0 |  | 0 |
Net Amount of Assets | $ 8.6 |  | $ 5.7 |
[1] | As of June 30, 2014 and December 31, 2013, the Company had $5.91 billion and $6.73 billion, respectively, of securities purchased under agreements to resell that were segregated to satisfy regulatory requirements. These securities are included in “Cash and securities—segregated for regulatory purposes” in the condensed consolidated statements of financial condition

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

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

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

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

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

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