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Documentation and Entity Information - shares
 9 Months Ended
Sep. 30, 2019
Nov. 07, 2019
Entity Registrant Name INTERACTIVE BROKERS GROUP, INC.  
Entity Central Index Key 0001381197  
Document Type 10-Q  
Document Period End Date Sep. 30, 2019  
Amendment Flag false  
Fiscal Year Focus 2019  
Fiscal Period Focus Q3  
Current Fiscal Year End Date --12-31  
Trading Symbol IBKR  
Entity Current Reporting Status Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Address, Address Line One One Pickwick Plaza  
Entity Address, City or Town Greenwich  
Entity Address, Postal Zip Code 06830  
Entity Address, State or Province Connecticut  
Entity File Number 001-33440  
Entity Tax Identification Number 300390693  
City Area Code 203  
Local Phone Number 618-5800  
Common Class A    
Common Stock Shares Outstanding   76,748,874
Common Class B    
Common Stock Shares Outstanding   100