| Document and Entity Information | Jul. 20, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Jul. 20, 2021 |
| Entity Registrant Name | Interactive Brokers Group, Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-33440 |
| Entity Tax Identification Number | 30-0390693 |
| Entity Address, Address Line One | One Pickwick Plaza |
| Entity Address, City or Town | Greenwich |
| Entity Address, State or Province | CT |
| Entity Address, Postal Zip Code | 06830 |
| City Area Code | 203 |
| Local Phone Number | 618-5800 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001381197 |
| Title of 12(b) Security | Class A common stock |
| Trading Symbol | IBKR |
| Security Exchange Name | NASDAQ |
