v2.4.0.6

Income Taxes Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Income Taxes [Abstract]
Undistributed accumulated earnings of foreign subsidiaries	$ 1,020.0	$ 969.8
Accumulated earnings of foreign pass through subsidiaries	395.8	380.6
Accumulated earnings subject to additional foreign tax	$ 302.8	$ 297.5

X

- Definition

Accumulated earnings attributable to our foreign subsidiaries that are considered pass-through entities for U.S. income tax purposes.

+ References

No definition available.

+ Details

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X

- Definition

Accumulated earnings of certain pass through subsidiaries where repatriation would result in additional foreign taxes in the form of dividend withholding tax imposed on the recipient of the distribution or dividend distribution tax imposed on the payor of the distribution.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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X

- Definition

Amount of undistributed earnings of foreign subsidiaries.

+ References

No definition available.

+ Details

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Namespace Prefix:	ibkr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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X

- Details

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