Organization Of Business	3 Months Ended
Mar. 31, 2019
Organization Of Business [Abstract]
Organization Of Business	1. Organization of Business Interactive Brokers Group, Inc. (“IBG, Inc.”) is a Delaware holding company whose primary asset is its ownership of approximately 18.1% 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 specializing in executing and clearing trades in securities, futures, foreign exchange instruments, bonds and mutual funds on more than 120 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, the United Kingdom, Switzerland, India, China (Hong Kong and Shanghai), Japan, and Australia. As of March 31, 2019, the Company had 1,458 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”); IBKR Europe S.a.r.l. (“IBEU”); Interactive Brokers (India) Private Limited (“IBI”); Timber Hill LLC (“TH LLC”); Timber Hill Canada Company (“THC”); Interactive Brokers Software Services (India) Private Limited (“IBSSI”); IB Global Investments LLC (“IBGIL”); IB Exchange Corp. (“IBEC”) and its subsidiaries, 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 Australia Pty Limited and its subsidiary, Interactive Brokers Australia Nominees Pty Limited (collectively, “IBA”), IB Business Services (Shanghai) Company Limited (“IBBSS”), IBKR Financial Services AG (formerly Timber Hill Europe AG) and its subsidiary, THLI AG (formerly Timber Hill (Liechtenstein) AG) (collectively, “IBKRFS”), Interactive Brokers Hungary Informatikai Kft (“IBH”), Interactive Brokers Software Services Estonia OU (“IBEST”), Interactive Brokers Software Services Russia (“IBRUS”), Interactive Brokers Corp. (“IB Corp”), Covestor, Inc. and its subsidiary, Covestor Limited (collectively, “Covestor”), and Greenwich Advisor Compliance Services Corp. (“Greenwich Compliance”). 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 and it currently consists of customer facilitation in products such as CFDs, ETFs and single stock futures, as well as exchange traded market making activities in a few select markets outside the U.S. (See Note 2 – Discontinued Operations and Costs Associated with Exit or Disposal Activities). Corporate enables the Company to operate cohesively and effectively by providing support via development services and 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 15). IB LLC, IBC, IBUK, IBSJ, IBHK, IBI and IBA 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 18.1% 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 specializing in executing and clearing trades in securities, futures, foreign exchange instruments, bonds and mutual funds on more than 120 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, the United Kingdom, Switzerland, India, China (Hong Kong and Shanghai), Japan, and Australia. As of March 31, 2019, the Company had 1,458 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”); IBKR Europe S.a.r.l. (“IBEU”); Interactive Brokers (India) Private Limited (“IBI”); Timber Hill LLC (“TH LLC”); Timber Hill Canada Company (“THC”); Interactive Brokers Software Services (India) Private Limited (“IBSSI”); IB Global Investments LLC (“IBGIL”); IB Exchange Corp. (“IBEC”) and its subsidiaries, 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 Australia Pty Limited and its subsidiary, Interactive Brokers Australia Nominees Pty Limited (collectively, “IBA”), IB Business Services (Shanghai) Company Limited (“IBBSS”), IBKR Financial Services AG (formerly Timber Hill Europe AG) and its subsidiary, THLI AG (formerly Timber Hill (Liechtenstein) AG) (collectively, “IBKRFS”), Interactive Brokers Hungary Informatikai Kft (“IBH”), Interactive Brokers Software Services Estonia OU (“IBEST”), Interactive Brokers Software Services Russia (“IBRUS”), Interactive Brokers Corp. (“IB Corp”), Covestor, Inc. and its subsidiary, Covestor Limited (collectively, “Covestor”), and Greenwich Advisor Compliance Services Corp. (“Greenwich Compliance”).

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 and it currently consists of customer facilitation in products such as CFDs, ETFs and single stock futures, as well as exchange traded market making activities in a few select markets outside the U.S. (See Note 2 – Discontinued Operations and Costs Associated with Exit or Disposal Activities). Corporate enables the Company to operate cohesively and effectively by providing support via development services and 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 15). IB LLC, IBC, IBUK, IBSJ, IBHK, IBI and IBA carry securities accounts for customers or perform custodial functions relating to customer securities.