Commitments, Contingencies And Guarantees	9 Months Ended
Sep. 30, 2016
Commitments, Contingencies And Guarantees [Abstract]
Commitments, Contingencies And Guarantees	11. Commitments, Contingencies and Guarantees Claims Against Customers On January 15, 2015, due to the sudden move in the value of the Swiss franc that followed an unprecedented action by the Swiss National Bank, which removed a previously instituted and repeatedly reconfirmed cap of the currency relative to the Euro, several of the Company’s customers who held currency futures and spot positions suffered losses in excess of their deposits with the Company. The Company took immediate action to hedge its exposure to the foreign currency receivables from these customers. The Company estimates the cumulative losses related to this event, net of hedging activity and debt collection efforts, to be approximately $118 million. The Company is actively pursuing collection of the debts. The ultimate effect of this incident on the Company’s results will depend upon the outcome of the Company’s debt collection efforts. Litigation The Company is subject to certain pending and threatened legal actions which arise out of the normal course of business. Litigation is inherently unpredictable, particularly in proceedings where claimants seek substantial or indeterminate damages, or which are in their early stages. The Company has not been able to quantify the actual loss or range of loss related to such legal proceedings, the manner in which they will be resolved, the timing of final resolution or the ultimate settlement. Management believes that the resolution of these actions will not have a material effect, if any, on the Company’s business or financial condition, but may have a material impact on the results of operations for a given period. The Company accounts for potential losses related to litigation in accordance with FASB ASC Topic 450, “Contingencies.” As of September 30, 2016 and 2015, reserves provided for potential losses related to litigation matters were not material. Trading Technologies Matter On February 3, 2010, Trading Technologies International, Inc. (“Trading Technologies”) commenced an action in the U.S. District Court for the Northern District of Illinois, Eastern Division, against IBG LLC and IB LLC (“Defendants”) alleging infringement of twelve U.S. patents and seeking, among other things, unspecified damages and injunctive relief. The Defendants filed an answer denying the claims and asserted counterclaims seeking a declaration that the patents have not been infringed and are invalid. The Defendants and/or certain codefendants filed petitions with the U.S. Patent and Trademark Office (“USPTO”) for Covered Business Method (“CBM”) Review on the asserted patents. Thus far the USPTO issued decisions instituting CBM Review on nine of the asserted patents and has made a finding that it is more likely than not that the patents are invalid. On February 19, 2016, the Defendants filed a motion requesting to stay the litigation in light of the CBM Review petitions. On May 9, 2016, the District Court granted the Defendants’ motion to stay the case pending the CBM Reviews. On May 17, 2016, Trading Technologies filed a notice of appeal of the stay. While it is too early to predict the outcome of the matter, the Company believes it has meritorious defenses to the allegations made in the complaint and intend to defend itself vigorously against them. Class Action Matter On December 18, 2015, a former individual customer filed a purported class action complaint against IB LLC, IBG, Inc., and Thomas Frank, PhD, the Company’s Executive Vice President and Chief Information Officer, in the U.S. District Court for the District of Connecticut. The complaint alleged that the former customer and members of the purported class of IB LLC’s customers were harmed by alleged “flaws” in the computerized system used by the Company to close out (i.e., liquidate) positions in customer brokerage accounts that have margin deficiencies. The complaint sought, among other things, undefined compensatory damages and declaratory and injunctive relief. The Company filed a motion to dismiss the complaint. On September 28, 2016, the District Court granted the Company’s motion to dismiss and directed the Clerk of the Court to close the file. The Court noted, among other things, that IB LLC’s customer agreement, federal law and associated industry rules grant IB LLC broad discretion to close out margin deficient customer accounts for IB LLC’s protection. Should the plaintiffs appeal the dismissal of the complaint or seek leave to amend and re-file the complaint, the Company intends to continue its vigorous defense of the claims. Guarantees Certain of the Operating Companies provide guarantees to securities clearing houses and exchanges which meet the accounting definition of a guarantee under FASB ASC Topic 460, “Guarantees.” Under standard membership agreements, clearing house and exchange members are required to guarantee collectively the performance of other members. Under the agreements, if a member becomes unable to satisfy its obligations, other members would be required to meet shortfalls. In the opinion of management, the Operating Companies’ liability under these arrangements is not quantifiable and could exceed the cash and securities they have posted as collateral. However, the potential for these Operating Companies to be required to make payments under these arrangements is remote. Accordingly, no contingent liability is carried in the condensed consolidated statements of financial condition for these arrangements. In connection with its retail brokerage business, IB LLC or other electronic brokerage Operating Companies perform securities and commodities execution, clearance and settlement on behalf of their customers for whom they commit to settle trades submitted by such customers with the respective clearing houses. If a customer fails to fulfill its settlement obligations, the respective Operating Company must fulfill those settlement obligations. No contingent liability is carried on the condensed consolidated statements of financial condition for such customer obligations. Other Commitments Certain clearing houses, clearing banks and firms used by certain Operating Companies are given a security interest in certain assets of those Operating Companies held by those clearing organizations. These assets may be applied to satisfy the obligations of those Operating Companies to the respective clearing organizations.

11. Commitments, Contingencies and Guarantees

Claims Against Customers

On January 15, 2015, due to the sudden move in the value of the Swiss franc that followed an unprecedented action by the Swiss National Bank, which removed a previously instituted and repeatedly reconfirmed cap of the currency relative to the Euro, several of the Company’s customers who held currency futures and spot positions suffered losses in excess of their deposits with the Company. The Company took immediate action to hedge its exposure to the foreign currency receivables from these customers. The Company estimates the cumulative losses related to this event, net of hedging activity and debt collection efforts, to be approximately $118 million. The Company is actively pursuing collection of the debts. The ultimate effect of this incident on the Company’s results will depend upon the outcome of the Company’s debt collection efforts.

Litigation

The Company is subject to certain pending and threatened legal actions which arise out of the normal course of business. Litigation is inherently unpredictable, particularly in proceedings where claimants seek substantial or indeterminate damages, or which are in their early stages. The Company has not been able to quantify the actual loss or range of loss related to such legal proceedings, the manner in which they will be resolved, the timing of final resolution or the ultimate settlement. Management believes that the resolution of these actions will not have a material effect, if any, on the Company’s business or financial condition, but may have a material impact on the results of operations for a given period.

The Company accounts for potential losses related to litigation in accordance with FASB ASC Topic 450, “Contingencies.” As of September 30, 2016 and 2015, reserves provided for potential losses related to litigation matters were not material.

Trading Technologies Matter

On February 3, 2010, Trading Technologies International, Inc. (“Trading Technologies”) commenced an action in the U.S. District Court for the Northern District of Illinois, Eastern Division, against IBG LLC and IB LLC (“Defendants”) alleging infringement of twelve U.S. patents and seeking, among other things, unspecified damages and injunctive relief. The Defendants filed an answer denying the claims and asserted counterclaims seeking a declaration that the patents have not been infringed and are invalid. The Defendants and/or certain codefendants filed petitions with the U.S. Patent and Trademark Office (“USPTO”) for Covered Business Method (“CBM”) Review on the asserted patents. Thus far the USPTO issued decisions instituting CBM Review on nine of the asserted patents and has made a finding that it is more likely than not that the patents are invalid. On February 19, 2016, the Defendants filed a motion requesting to stay the litigation in light of the CBM Review petitions. On May 9, 2016, the District Court granted the Defendants’ motion to stay the case pending the CBM Reviews. On May 17, 2016, Trading Technologies filed a notice of appeal of the stay. While it is too early to predict the outcome of the matter, the Company believes it has meritorious defenses to the allegations made in the complaint and intend to defend itself vigorously against them.

Class Action Matter

On December 18, 2015, a former individual customer filed a purported class action complaint against IB LLC, IBG, Inc., and Thomas Frank, PhD, the Company’s Executive Vice President and Chief Information Officer, in the U.S. District Court for the District of Connecticut. The complaint alleged that the former customer and members of the purported class of IB LLC’s customers were harmed by alleged “flaws” in the computerized system used by the Company to close out (i.e., liquidate) positions in customer brokerage accounts that have margin deficiencies. The complaint sought, among other things, undefined compensatory damages and declaratory and injunctive relief. The Company filed a motion to dismiss the complaint. On September 28, 2016, the District Court granted the Company’s motion to dismiss and directed the Clerk of the Court to close the file. The Court noted, among other things, that IB LLC’s customer agreement, federal law and associated industry rules grant IB LLC broad discretion to close out margin deficient customer accounts for IB LLC’s protection. Should the plaintiffs appeal the dismissal of the complaint or seek leave to amend and re-file the complaint, the Company intends to continue its vigorous defense of the claims.

Guarantees

Certain of the Operating Companies provide guarantees to securities clearing houses and exchanges which meet the accounting definition of a guarantee under FASB ASC Topic 460, “Guarantees.” Under standard membership agreements, clearing house and exchange members are required to guarantee collectively the performance of other members. Under the agreements, if a member becomes unable to satisfy its obligations, other members would be required to meet shortfalls. In the opinion of management, the Operating Companies’ liability under these arrangements is not quantifiable and could exceed the cash and securities they have posted as collateral. However, the potential for these Operating Companies to be required to make payments under these arrangements is remote. Accordingly, no contingent liability is carried in the condensed consolidated statements of financial condition for these arrangements.

In connection with its retail brokerage business, IB LLC or other electronic brokerage Operating Companies perform securities and commodities execution, clearance and settlement on behalf of their customers for whom they commit to settle trades submitted by such customers with the respective clearing houses. If a customer fails to fulfill its settlement obligations, the respective Operating Company must fulfill those settlement obligations. No contingent liability is carried on the condensed consolidated statements of financial condition for such customer obligations.

Other Commitments

Certain clearing houses, clearing banks and firms used by certain Operating Companies are given a security interest in certain assets of those Operating Companies held by those clearing organizations. These assets may be applied to satisfy the obligations of those Operating Companies to the respective clearing organizations.