Organization and Description of the Business	6 Months Ended
Jun. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of the Business	Organization and Description of the Business Knight Capital Group, Inc. (collectively with its subsidiaries, “Knight” or the “Company”) is a global financial services firm that provides access to the capital markets across multiple asset classes to a broad network of clients, including broker dealers, institutions and corporations. The Company seeks to continually apply its expertise and innovation to the market making and trading process to build lasting client relationships through consistent performance and superior client service. In the first quarter of 2013, the Company changed from four operating segments: (i) Market Making, (ii) Institutional Sales and Trading, (iii) Electronic Execution Services and (iv) Corporate and Other to three operating segments: (i) Market Making; (ii) Global Execution Services; and (iii) Corporate and Other. This change was made to reflect the Company's client offerings, changes in senior management, the combination of the institutional equities sales teams and how the businesses are managed. As of June 30, 2013, the Company's operating segments comprised the following: Market Making The Market Making segment principally consists of market making in global equities and listed domestic options. As a market maker, the Company commits capital for trade executions by offering to buy securities from, or sell securities to, institutions and broker-dealers. The Market Making segment primarily includes client, and to a lesser extent, non-client electronic market making activities in which the Company operates as a market maker in equity securities quoted and traded on the Nasdaq Stock Market; the over-the-counter (“OTC”) market for New York Stock Exchange (“NYSE”), NYSE Amex Equities (“NYSE Amex”), NYSE Arca listed securities and several European exchanges. As a complement to electronic market making, the Company’s cash trading business handles specialized orders and also transacts on the OTC Bulletin Board, marketplaces operated by the OTC Markets Group Inc. and the Alternative Investment Market (“AIM”) of the London Stock Exchange. The segment also provides trade executions as an equities Designated Market Maker (“DMM”) on the NYSE and NYSE Amex. Market Making also includes the Company’s option market making business which trades on substantially all domestic electronic exchanges. Global Execution Services The Global Execution Services segment offers access via its electronic agency-based platforms to markets and self-directed trading in equities, options, fixed income, foreign exchange and futures. In contrast to Market Making, the Global Execution Services segment generally does not act as a principal to transactions that are executed within this segment, however, it will commit capital on behalf of clients as needed, and generally earns commissions for acting as agent between the principals to the trade. Global Execution Services also includes equity sales and trading (including exchange traded funds ("ETFs")) and reverse mortgage origination and securitization. This segment also facilitates client orders through program, block, and riskless principal trades and provides capital markets services, including equity offerings as well as private placements. Additionally, the Global Execution Services segment includes the futures commission merchant ("FCM") business, which comprises certain assets and liabilities that the Company acquired or assumed from the futures division of Penson Financial Services, Inc. on June 1, 2012. This business provides futures execution and clearing services on major U.S. and European futures and options exchanges for clients. Management of the Company from time to time conducts a strategic review of its businesses and evaluates their potential value in the marketplace relative to their current and expected returns. To the extent management and the Company's Board of Directors determine a business may return a higher value to shareholders through a divestiture, or is no longer core to the Company's strategy, management may pursue a sale process. On July 29, 2013, the Company entered into an agreement to sell its reverse mortgage origination and securitization business. While the close process is ongoing, there is no assurance that any transaction will ultimately be consummated. The consummation of the transaction is subject to customary closing conditions, including receipt of required regulatory approvals and applicable consents. See Footnote 22 "Subsequent Events" for further discussion. Corporate and Other The Corporate and Other segment invests in strategic financial services-oriented opportunities, allocates, deploys and monitors all capital, and maintains corporate overhead expenses and all other income and expenses that are not attributable to the other segments. The Corporate and Other segment houses functions that support the Company’s other segments such as self-clearing services, including stock lending activities. Discontinued Operations During the first quarter of 2013, the Company agreed to sell its institutional fixed income sales and trading business, which operated in the U.S. and the U.K., to Stifel, Nicolaus & Company, Inc ("Stifel"). The transaction was completed on June 28, 2013. As the Company has completed the sale and no longer operates the business, the results for this business have been reported as discontinued operations. Discontinued operations also includes the results of the Company's correspondent clearing and asset management businesses, which the Company decided to exit in the first and second quarter of 2013, respectively. See Footnote 5 "Business Held for Sale and Discontinued Operations" for further discussion.

Organization and Description of the Business

Knight Capital Group, Inc. (collectively with its subsidiaries, “Knight” or the “Company”) is a global financial services firm that provides access to the capital markets across multiple asset classes to a broad network of clients, including broker dealers, institutions and corporations. The Company seeks to continually apply its expertise and innovation to the market making and trading process to build lasting client relationships through consistent performance and superior client service. In the first quarter of 2013, the Company changed from four operating segments: (i) Market Making, (ii) Institutional Sales and Trading, (iii) Electronic Execution Services and (iv) Corporate and Other to three operating segments: (i) Market Making; (ii) Global Execution Services; and (iii) Corporate and Other. This change was made to reflect the Company's client offerings, changes in senior management, the combination of the institutional equities sales teams and how the businesses are managed. As of June 30, 2013, the Company's operating segments comprised the following:

Market Making

The Market Making segment principally consists of market making in global equities and listed domestic options. As a market maker, the Company commits capital for trade executions by offering to buy securities from, or sell securities to, institutions and broker-dealers. The Market Making segment primarily includes client, and to a lesser extent, non-client electronic market making activities in which the Company operates as a market maker in equity securities quoted and traded on the Nasdaq Stock Market; the over-the-counter (“OTC”) market for New York Stock Exchange (“NYSE”), NYSE Amex Equities (“NYSE Amex”), NYSE Arca listed securities and several European exchanges. As a complement to electronic market making, the Company’s cash trading business handles specialized orders and also transacts on the OTC Bulletin Board, marketplaces operated by the OTC Markets Group Inc. and the Alternative Investment Market (“AIM”) of the London Stock Exchange. The segment also provides trade executions as an equities Designated Market Maker (“DMM”) on the NYSE and NYSE Amex. Market Making also includes the Company’s option market making business which trades on substantially all domestic electronic exchanges.

Global Execution Services

The Global Execution Services segment offers access via its electronic agency-based platforms to markets and self-directed trading in equities, options, fixed income, foreign exchange and futures. In contrast to Market Making, the Global Execution Services segment generally does not act as a principal to transactions that are executed within this segment, however, it will commit capital on behalf of clients as needed, and generally earns commissions for acting as agent between the principals to the trade. Global Execution Services also includes equity sales and trading (including exchange traded funds ("ETFs")) and reverse mortgage origination and securitization. This segment also facilitates client orders through program, block, and riskless principal trades and provides capital markets services, including equity offerings as well as private placements. Additionally, the Global Execution Services segment includes the futures commission merchant ("FCM") business, which comprises certain assets and liabilities that the Company acquired or assumed from the futures division of Penson Financial Services, Inc. on June 1, 2012. This business provides futures execution and clearing services on major U.S. and European futures and options exchanges for clients.

Management of the Company from time to time conducts a strategic review of its businesses and evaluates their potential value in the marketplace relative to their current and expected returns. To the extent management and the Company's Board of Directors determine a business may return a higher value to shareholders through a divestiture, or is no longer core to the Company's strategy, management may pursue a sale process. On July 29, 2013, the Company entered into an agreement to sell its reverse mortgage origination and securitization business. While the close process is ongoing, there is no assurance that any transaction will ultimately be consummated. The consummation of the transaction is subject to customary closing conditions, including receipt of required regulatory approvals and applicable consents. See Footnote 22 "Subsequent Events" for further discussion.

Corporate and Other

The Corporate and Other segment invests in strategic financial services-oriented opportunities, allocates, deploys and monitors all capital, and maintains corporate overhead expenses and all other income and expenses that are not attributable to the other segments. The Corporate and Other segment houses functions that support the Company’s other segments such as self-clearing services, including stock lending activities.

Discontinued Operations

During the first quarter of 2013, the Company agreed to sell its institutional fixed income sales and trading business, which operated in the U.S. and the U.K., to Stifel, Nicolaus & Company, Inc ("Stifel"). The transaction was completed on June 28, 2013. As the Company has completed the sale and no longer operates the business, the results for this business have been reported as discontinued operations. Discontinued operations also includes the results of the Company's correspondent clearing and asset management businesses, which the Company decided to exit in the first and second quarter of 2013, respectively. See Footnote 5 "Business Held for Sale and Discontinued Operations" for further discussion.