v2.4.0.6

Senior Notes Payable (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Senior Notes Payable [Abstract]
Senior Notes at 3%	$ 101,411

X

- Definition

Senior Notes outstanding as of the balance sheet date with a 3% stated rate.

+ References

No definition available.

+ Details

Name:	ibkr_NotesCarryingThreePercentInterestRate
Namespace Prefix:	ibkr_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

X

- Details

Name:	ibkr_SeniorNotesPayableAbstract
Namespace Prefix:	ibkr_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration