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Financial Assets And Financial Liabilities (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Financial Assets And Financial Liabilities [Abstract]
Transfers of financial instruments owned from level 2 to level 3	$ 1
Securities Purchased Under Agreement to Resell Segregated for Regulatory Purposes	$ 11,000	$ 600

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- Definition

Transfers of financial instruments owned from level 2 to level 3

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No definition available.

+ Details

Name:	ibkr_FairValueAssetsLevel2ToLevel3Amount
Namespace Prefix:	ibkr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

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- Definition

The carrying value of funds, segregated for regulatory purposes and for the exclusive benefit of customers, outstanding loaned in the form of security resale agreements if the agreement requires the purchaser to resell the identical security purchased or a security that meets the definition of "substantially the same" in the case of a dollar roll. Also includes purchases of participations in pools of securities that are subject to a resale agreement.

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No definition available.

+ Details

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

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- References

No definition available.

+ Details

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