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Documentation and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	May 07, 2018
Entity Registrant Name	Interactive Brokers Group, Inc.
Entity Central Index Key	0001381197
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Amendment Flag	false
Fiscal Year Focus	2018
Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Common Class A
Common Stock Shares Outstanding		71,481,133
Common Class B
Common Stock Shares Outstanding		100

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