v3.4.0.3

Financial Assets And Financial Liabilities (Netting of Financial Assets) (Details) - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets		$ 7,508	$ 5,921
Amounts Assets Offset in the Condensed Consolidated Statement of Financial Condition
Net Amounts of Assets Presented in the Condensed Consolidated Statement of Financial Condition		$ 7,508	$ 5,921
Amounts of Assets Not Offset in the Condensed Consolidated Statement of Financial Condition		(7,209)	(5,606)
Net Amount of Assets		299	315
Securities Segregated For Regulatory Purposes - Purchased Under Agreements To Resell [Member]
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	[1]	$ 1,447	$ 562
Amounts Assets Offset in the Condensed Consolidated Statement of Financial Condition
Net Amounts of Assets Presented in the Condensed Consolidated Statement of Financial Condition		$ 1,447	$ 562
Amounts of Assets Not Offset in the Condensed Consolidated Statement of Financial Condition		(1,447)	(562)
Securities Borrowed [Member]
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets		$ 4,011	$ 3,924
Amounts Assets Offset in the Condensed Consolidated Statement of Financial Condition
Net Amounts of Assets Presented in the Condensed Consolidated Statement of Financial Condition		$ 4,011	$ 3,924
Amounts of Assets Not Offset in the Condensed Consolidated Statement of Financial Condition		(3,863)	(3,816)
Net Amount of Assets		148	108
Securities Purchased Under Agreement to Resell [Member]
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets		$ 805	$ 195
Amounts Assets Offset in the Condensed Consolidated Statement of Financial Condition
Net Amounts of Assets Presented in the Condensed Consolidated Statement of Financial Condition		$ 805	$ 195
Amounts of Assets Not Offset in the Condensed Consolidated Statement of Financial Condition		(805)	(195)
Options owned [Member]
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets		$ 1,131	$ 1,156
Amounts Assets Offset in the Condensed Consolidated Statement of Financial Condition
Net Amounts of Assets Presented in the Condensed Consolidated Statement of Financial Condition		$ 1,131	$ 1,156
Amounts of Assets Not Offset in the Condensed Consolidated Statement of Financial Condition		(1,093)	(1,032)
Net Amount of Assets		38	124
Warrants and discount certificates owned [Member]
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets		$ 93	$ 81
Amounts Assets Offset in the Condensed Consolidated Statement of Financial Condition
Net Amounts of Assets Presented in the Condensed Consolidated Statement of Financial Condition		$ 93	$ 81
Amounts of Assets Not Offset in the Condensed Consolidated Statement of Financial Condition		(1)	(1)
Net Amount of Assets		92	80
Currency forward contracts owned [Member]
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets		$ 21	$ 3
Amounts Assets Offset in the Condensed Consolidated Statement of Financial Condition
Net Amounts of Assets Presented in the Condensed Consolidated Statement of Financial Condition		$ 21	$ 3
Net Amount of Assets		$ 21	$ 3
[1] As of March 31, 2016 and December 31, 2015, the Company had $1.4 billion and $0.6 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

Amounts of Assets Not Offset in the Consolidated Statement of Financial Condition, Cash or Financial Instruments

+ References

No definition available.

+ Details

Name:	ibkr_AmountsOfAssetsNotOffsetInConsolidatedStatementOfFinancialConditionCashOrFinancialInstruments
Namespace Prefix:	ibkr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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

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

- 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_OffsettingAssetsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=ibkr_SecuritiesSegregatedForRegulatoryPurposesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=ibkr_SecuritiesBorrowedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=ibkr_SecuritiesPurchasedUnderAgreementToResellMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_StockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=ibkr_WarrantsAndDiscountCertificatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_ForeignExchangeForwardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: