Organization And Nature Of Business	9 Months Ended
Sep. 30, 2016
Organization And Nature Of Business [Abstract]
Nature of Operations [Text Block]	1. Organization of Business Interactive Brokers Group, Inc. (“IBG, Inc.”) is a Delaware holding company whose primary asset is its ownership of approximately 16.6% of the membership interests of IBG LLC, which, in turn, owns operating subsidiaries (collectively, “IBG LLC”). IBG, Inc. together with IBG LLC and its consolidated subsidiaries (collectively, “the Company”), is an automated global electronic broker and market maker specializing in executing and clearing trades in securities, futures, foreign exchange instruments, bonds and mutual funds on more than 100 electronic exchanges and market centers around the world and offering custody, prime brokerage, securities and margin lending services to customers. In the United States of America (“U.S.”), the Company conducts its business primarily from its headquarters in Greenwich, Connecticut and from Chicago, Illinois. Abroad, the Company conducts its business through offices located in Canada, England, Switzerland, Liechtenstein, India, China (Hong Kong and Shanghai), Japan, and Australia. As of September 30, 2016, the Company had 1,194 employees worldwide. IBG LLC is a Connecticut limited liability company that conducts its business through its operating subsidiaries (collectively, the “Operating Companies”): Interactive Brokers LLC (“IB LLC”); Interactive Brokers Canada Inc. (“IBC”); Interactive Brokers (U.K.) Limited and its subsidiary, Interactive Brokers (U.K.) Nominee Limited (collectively, “IBUK”); Interactive Brokers Securities Japan, Inc. (“IBSJ”); Interactive Brokers Hong Kong Limited (“IBHK”); Interactive Brokers (India) Private Limited (“IBI”); Interactive Brokers Australia Pty Limited and its subsidiary, Interactive Brokers Australia Nominees Pty Limited (collectively, “IBA”); IB Business Services (Shanghai) Company Limited (“IBBSS”); Timber Hill LLC (“TH LLC”); Timber Hill Europe AG and its subsidiary, Timber Hill (Liechtenstein) AG (collectively, “THE”); Timber Hill Australia Pty Limited (“THA”); Timber Hill Canada Company (“THC”); Interactive Brokers Financial Products S.A. (“IBFP”); Interactive Brokers Hungary KFT (“IBH”); Interactive Brokers Software Services Estonia OU (“IBEST”); Interactive Brokers Software Services Russia (“IBRUS”); Interactive Brokers Software Services (India) Private Limited (“IBSSI”); and IB Exchange Corp. (“IBEC”) and its subsidiaries, Interactive Brokers Corp. (“IB Corp”), Covestor, Inc. and its subsidiary, Covestor Limited (collectively, “Covestor”), and Greenwich Advisor Compliance Services Corp. (“GACS”). The Company operates in two business segments: electronic brokerage and market making, both supported by corporate. The Company conducts its electronic brokerage business through certain Interactive Brokers subsidiaries, which provide electronic execution and clearing services to customers worldwide. The Company conducts its market making business principally through its Timber Hill subsidiaries on the world’s leading exchanges and market centers, primarily in exchange‑traded equities, equity options and equity‑index options and futures. Corporate enables the Company to operate cohesively and effectively by providing support via control functions to the business segments and also by executing the Company’s currency diversification strategy. Certain of the Operating Companies are members of various securities and commodities exchanges in North America, Europe and the Asia/Pacific region and are subject to regulatory capital and other requirements (see Note 13). IB LLC, IBC, IBUK, IBSJ, IBHK, and IBI carry securities accounts for customers or perform custodial functions relating to customer securities.

1. Organization of Business

Interactive Brokers Group, Inc. (“IBG, Inc.”) is a Delaware holding company whose primary asset is its ownership of approximately 16.6% of the membership interests of IBG LLC, which, in turn, owns operating subsidiaries (collectively, “IBG LLC”). IBG, Inc. together with IBG LLC and its consolidated subsidiaries (collectively, “the Company”), is an automated global electronic broker and market maker specializing in executing and clearing trades in securities, futures, foreign exchange instruments, bonds and mutual funds on more than 100 electronic exchanges and market centers around the world and offering custody, prime brokerage, securities and margin lending services to customers. In the United States of America (“U.S.”), the Company conducts its business primarily from its headquarters in Greenwich, Connecticut and from Chicago, Illinois. Abroad, the Company conducts its business through offices located in Canada, England, Switzerland, Liechtenstein, India, China (Hong Kong and Shanghai), Japan, and Australia. As of September 30, 2016, the Company had 1,194 employees worldwide.

IBG LLC is a Connecticut limited liability company that conducts its business through its operating subsidiaries (collectively, the “Operating Companies”): Interactive Brokers LLC (“IB LLC”); Interactive Brokers Canada Inc. (“IBC”); Interactive Brokers (U.K.) Limited and its subsidiary, Interactive Brokers (U.K.) Nominee Limited (collectively, “IBUK”); Interactive Brokers Securities Japan, Inc. (“IBSJ”); Interactive Brokers Hong Kong Limited (“IBHK”); Interactive Brokers (India) Private Limited (“IBI”); Interactive Brokers Australia Pty Limited and its subsidiary, Interactive Brokers Australia Nominees Pty Limited (collectively, “IBA”); IB Business Services (Shanghai) Company Limited (“IBBSS”); Timber Hill LLC (“TH LLC”); Timber Hill Europe AG and its subsidiary, Timber Hill (Liechtenstein) AG (collectively, “THE”); Timber Hill Australia Pty Limited (“THA”); Timber Hill Canada Company (“THC”); Interactive Brokers Financial Products S.A. (“IBFP”); Interactive Brokers Hungary KFT (“IBH”); Interactive Brokers Software Services Estonia OU (“IBEST”); Interactive Brokers Software Services Russia (“IBRUS”); Interactive Brokers Software Services (India) Private Limited (“IBSSI”); and IB Exchange Corp. (“IBEC”) and its subsidiaries, Interactive Brokers Corp. (“IB Corp”), Covestor, Inc. and its subsidiary, Covestor Limited (collectively, “Covestor”), and Greenwich Advisor Compliance Services Corp. (“GACS”).

The Company operates in two business segments: electronic brokerage and market making, both supported by corporate. The Company conducts its electronic brokerage business through certain Interactive Brokers subsidiaries, which provide electronic execution and clearing services to customers worldwide. The Company conducts its market making business principally through its Timber Hill subsidiaries on the world’s leading exchanges and market centers, primarily in exchange‑traded equities, equity options and equity‑index options and futures. Corporate enables the Company to operate cohesively and effectively by providing support via control functions to the business segments and also by executing the Company’s currency diversification strategy.

Certain of the Operating Companies are members of various securities and commodities exchanges in North America, Europe and the Asia/Pacific region and are subject to regulatory capital and other requirements (see Note 13). IB LLC, IBC, IBUK, IBSJ, IBHK, and IBI carry securities accounts for customers or perform custodial functions relating to customer securities.