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Documentation and Entity Information - USD ($)
 12 Months Ended
Dec. 31, 2019
Feb. 25, 2020
Jun. 28, 2019
Document Annual Report true    
Document Transition Report false    
Entity Registrant Name INTERACTIVE BROKERS GROUP, INC.    
Entity Central Index Key 0001381197    
Document Type 10-K    
Document Period End Date Dec. 31, 2019    
Entity Incorporation, State or Country Code DE    
Amendment Flag false    
Fiscal Year Focus 2019    
Fiscal Period Focus FY    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Title of 12(b) Security Common Stock, par value $.01 per share    
Trading Symbol IBKR    
Security Exchange Name NASDAQ    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Public Float     $ 4,032,724,571
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 CT    
Entity File Number 001-33440    
Entity Tax Identification Number 30-0390693    
City Area Code 203    
Local Phone Number 618-5800    
Common Class A      
Common Stock Shares Outstanding   76,750,794  
Common Class B      
Common Stock Shares Outstanding   100