Finite Lived and Indefinite Lived Intangible Assets by Major Class [Table] Disclosure of the carrying value of amortizable finite-lived intangible assets, including disclosure of the carrying value of indefinite-lived intangible assets not subject to amortization, excluding goodwill, in total and by major class. Finite Lived and Indefinite Lived Intangible Assets by Major Class [Line Items] Intangible Assets Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Finite and Indefinite Lived Intangible Assets Gross Total gross Sum of the gross carrying amounts (original costs for current and prior period additions adjusted for impairment, if any) before accumulated amortization and foreign currency translation as of the balance sheet date of all intangible assets, excluding goodwill. G F I Brokers Limited [Member] Represents information pertaining to GFI Brokers Limited. GFI Brokers Limited G F I Securities Limited Japanese Branch [Member] GFI Securities Limited's Japanese branch Represents information pertaining to GFI securities limited's Japanese branch. G F I Group Pte Ltd [Member] Represents information pertaining to GFI Group Pte. Ltd. GFI Group Pte. Ltd Award Type [Axis] GFI (HK) Brokers Ltd Represents information pertaining to GFI (HK) Brokers Ltd. G F I H K Brokers Ltd [Member] G F I H K Securities L L C [Member] Represents information pertaining to GFI (HK) Securities LLC. GFI (HK) Securities LLC G F I Korea Money Brokerage Limited [Member] Represents information pertaining to GFI Korea Money Brokerage Limited. GFI Korea Money Brokerage Limited G F I Securities Limited [Member] Represents information pertaining to GFI Securities Limited. GFI Securities Limited Amendment Description G F I Securities L L C [Member] Represents information pertaining to GFI securities LLC. GFI Securities LLC Amendment Flag Kyte Broking Limited [Member] Represents information pertaining to Kyte Broking Limited. Kyte Broking Limited Kyte Group Limited [Member] Represents information pertaining to Kyte Group Limited. The Kyte Group Limited Disclosure of minimum financial requirements for commodities brokers. Net Capital Excess Shortage under Commodity Exchange Act [Table] Amortization Period of Prepaid Bonuses and Forgivable Loans Represents the period for amortization of prepaid bonuses and forgivable loans. Amortization period of prepaid bonuses and forgivable loans Guarantee Obligations Notice Period Maximum Maximum notice period of termination of guarantees Represents the maximum notice period for termination of guarantees provided by entity. Prepaid Bonuses Prepaid bonuses Represents the carrying value as of the balance sheet date of prepaid incentive compensation awarded to certain employees. Forgivable Employee Loans and Advances to Employees Forgivable employee loans and advances to employees Represents the carrying value as of the balance sheet date of forgivable employee loans and advances to employees. Equity Method Investment Convertible Debt Received in Exchange of Membership Interest Face Amount Represents the stated amount of convertible debt received in exchange of the membership interest by the entity. Face value of debt for which membership interest is exchanged Equity Method Investment Debt Instrument, Convertible into Membership Interest Percent Represents the membership interest expressed as a percentage into which the debt may be convertible at the company's discretion. Note convertible into membership interest (as a percent) Equity Method Investment, Difference Between Book Value and Debt Fair Value Represents the difference between the book value of the membership interests and the fair value of the debt. Loss recognized for difference between the book value of the membership interests and the fair value of Note Business Combination Contingent Consideration Period of Future Collection of Accounts Receivable Period of future collections of accounts receivable Represents the period of future collections of accounts receivables under the contingent consideration arrangement. Payables to Clearing Services Customers [Policy Text Block] Disclosure of accounting policy for payables to clearing services customers which include amounts due on cash and margin transactions, including future contracts transacted on behalf of customers. Payables to Clearing Services Customers Prepaid Bonuses and Forgivable Employee Loans Prepaid Bonuses and Forgivable Employee Loans [Policy Text Block] Disclosure of accounting policy for prepaid bonuses and forgivable employee loans. Revenue Recognition Brokerage Transactions [Policy Text Block] Disclosure of accounting policy for revenue recognition relating to brokerage transactions. Brokerage Transactions Revenue Recognition Clearing Services [Policy Text Block] Disclosure of accounting policy for revenue recognition for clearing services. Clearing Services Revenues Revenue Recognition Software Analytics and Market Data [Policy Text Block] Disclosure of accounting policy for revenue recognition for software, analytics and market data. Software, Analytics and Market Data Revenue Recognition Current Fiscal Year End Date Summary of Significant Accounting Policies [Line Items] Significant accounting policies Summary of Significant Accounting Policies [Table] Information related to various accounting policies of the entity. Treasury Stock [Policy Text Block] Represents the accounting policy for treasury stock. Treasury Stock Business Acquisition, Contingent Consideration Cash Paid Represents the amount of cash payments made as a result of a contingent consideration arrangement. Payment of contingent consideration Ownership Residual Percentage Agreed to be Acquired Represents the residual percentage of equity interest, agreed to be acquired by the entity. Residual percentage of ownership agreed to be acquired Future commitment to purchase the remaining equity interest (as a percent) Kyte Group Limited and Kyte Capital Management Limited [Member] Represents information pertaining to the Kyte Group Limited and Kyte Capital Management Limited acquired by the entity. Kyte Mortgage Backed Security Brokerage Business [Member] Represents information pertaining to the mortgage-backed security brokerage business acquired by the entity. Mortgage-Backed Security Brokerage Business OTHER ASSETS AND OTHER LIABILITIES Market Data [Member] Market data Represents the contractual obligation to purchase market data. Network Implementations [Member] Network implementations Represents the contractual obligation for capital expenditures primarily related to network implementations. Hosting and Software License Agreements [Member] Hosting and software license agreements Represents the contractual obligation for hosting and software license agreements. Document Period End Date Unrecorded Unconditional Purchase Obligation Due in One to Three Years Purchase commitments due between one to three years Represents amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing between the next fiscal year and the third fiscal year following the latest fiscal year. Derivative Asset, Counterparty Netting Counterparty netting The amount of netting of derivative exposures covered by a qualifying master netting agreement related to derivative assets. The netting amount of derivative exposures covered by a qualifying master netting agreement related to derivative liabilities. Derivative Liability, Counterparty Netting Counterparty netting Derivative Liabilities, Fair Value Netting Netting Represents the impact of netting on a net-by-counterparty basis to net fair value amounts recognized for derivative liabilities. Netting Represents the impact of netting on a net-by-counterparty basis to net fair value amounts recognized for derivative assets. Derivative Asset, Fair Value Netting Notional Amount of Derivative Purchase Contracts Long Represents the notional amount of derivatives to purchase a derivative contract. Represents the notional amount of derivatives to sell a derivative contract. Notional Amount of Derivative Sale Contracts Short Other Income (Loss) [Member] Other income (loss) Represents the primary financial statement caption in which reported facts about income (loss) not separately disclosed have been included. Represents the senior notes bearing an interest rate of 8.375 percent, due in 2018. Senior Notes 8.375 Percent Due 2018 [Member] 8.375% senior notes Entity [Domain] Represents the price of long-term debt as a percentage of principal amount. Long Term Debt Price as Percentage of Principal Amount Price of notes as percentage of principal amount Americas Brokerage [Member] Americas Brokerage Represents the brokerage component of the entity located in the Americas. EMEA Brokerage [Member] Represents the brokerage component of the entity located in Europe, Middle East and Africa. EMEA Brokerage Asia Brokerage [Member] Asia Brokerage Represents the brokerage component of the entity located in Asia. Clearing and Backed Trading [Member] Clearing and Backed Trading Represents the clearing and backed trading component of the entity. Other Geographical Segment [Member] Other Geographical segments that do not meet quantitative thresholds and thus are not classified as reportable segments for which there is an accounting requirement to report separate financial information on those components that are in the entity's financial statements. Schedule of Finite and Indefinite Lived Intangible Assets by Major Class [Table Text Block] Schedule of intangible assets Tabular disclosure of the carrying value of finite-lived and indefinite-lived intangible assets, excluding goodwill, in total and by major class. A major class is composed of intangible assets that can be grouped together because they are similar, either by their nature or by their use in the operations of the company. Indefinite Lived Proprietary Knowledge Unamortized intangible assets, Proprietary knowledge Carrying amount of proprietary knowledge that lacks physical substance with a projected indefinite period of benefit. Intangible Assets Gross, Excluding Goodwill Total gross Sum of the gross carrying amounts (original costs for current and prior period additions adjusted for impairment, if any) before accumulated amortization and foreign currency translation as of the balance sheet date of all intangible assets, excluding goodwill. Represents the accumulated amount of amortization of assets and foreign currency translation adjustments to assets, excluding financial assets and goodwill, lacking physical substance with a finite life. Finite Lived Intangible Assets, Accumulated Amortization and Translation Adjustments Accumulated amortization and foreign currency translation Core Technology [Member] Core technology Represents core technology which may be defined as those skills present or creatable upon which the organization bases its operations and services and from which it creates its desired future. VARIABLE INTEREST ENTITIES Equity Incentive Plan 2008 [Member] 2008 Equity Incentive Plan Represents the information pertaining to 2008 Equity Incentive Plan of the entity. Equity Incentive Plan 2008 and Equity Incentive Plan 2004 [Member] 2008 Equity Incentive Plan and 2004 Equity Incentive Plan Represents the information pertaining to 2008 Equity Incentive Plan and the 2004 Equity Incentive Plan of the entity. GFI Group 2002 Plan Represents information pertaining to the GFI Group 2002 Plan of the entity. Stock Option Plan 2002 [Member] GFInet 2000 Plan Represents information pertaining to the GFInet 2000 Plan of the entity. Stock Option Plan 2000 [Member] Number of Broad Product Categories of Brokerage Services in which Entity Operates Represents the number of broad product categories in which brokerage operations provide brokerage services. Number of broad product categories Revenues Net of Interest and Transaction Based Expenses Revenues, net of interest and transaction-based expenses: Revenues, net of interest and transaction-based expenses Revenues from agency commissions, principal transactions, clearing services, equity in earnings of unconsolidated subsidiaries, software, analytics and market data, interest income and other income, net of interest and transaction-based expenses. Revenues, net of interest and transaction-based expenses Document and Entity Information Automobiles [Member] Automobiles Total brokerage revenues Brokerage Revenues Total revenues from brokerage operations includes revenues from the following sources: (1) Brokerage commissions revenue and (2) Principal transactions revenue. Other Income (Loss) This element represents the aggregate amount of other income or loss resulting from operating activities, which includes revaluations of foreign currency derivative contracts, realized and unrealized transaction gains and losses on certain foreign currency transactions and balances, and gains and losses on certain investments. Other income Interest and Transaction Based Expenses [Abstract] Interest and transaction-based expenses Transaction Fees on Clearing Services Transaction fees on clearing services The amount of clearing and exchange fees incurred during the period for providing clearing services to customers. Transaction Fees on Brokerage Services Transaction fees on brokerage services The amount of clearing and exchange fees incurred during the period for providing brokerage services to customers. Interest Expense from Clearing Services Interest expense from clearing services Interest incurred from day to day operating activities of the business. Excludes the cost of interest on borrowed funds that was charged against earnings during the period. Total transaction fees on clearing services, brokerage services and interest expense from clearing services. Interest and Transaction Based Expenses Total interest and transaction-based expenses Expenses Other Total other expenses Generally recurring costs associated with normal operations except for the portion of these expenses which are interest and transaction-based expenses. Includes selling, general and administrative expense. Other expenses(1) Realized and Unrealized (Gain) Loss on Sale of Derivatives (Gains) losses on foreign exchange derivative contracts, net This element includes both the difference between the book value and the sale price of options, swaps, futures, forward contracts, and other derivative instruments that was included in earnings for the period and also the net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period. Increase or decrease in the entity's income taxes that arise when compensation cost from share-based compensation recognized in the financial statements is greater than or less than the compensation cost (from non-qualified share-based compensation) recognized on the entity's tax return. This element represents the cash inflow or outflow reported in the entity's operating activities. Tax expense related to share-based compensation Tax (Expense) Benefit from Share Based Compensation Operating Activities United Kingdom UNITED KINGDOM U.K. Mark-to-market of future purchase commitment Business Combination, Future Purchase Commitment, Change in Fair Value, Liability This element represents the amount of any change, including any differences arising upon settlement, recognized during the reporting period in the value of a liability, arising from future purchase commitment, assumed in a business combination. Increase (Decrease) in Cash and Securities Segregated under Federal and other Regulations The change during the period, either increase or decrease, in the amount of cash subject to withdrawal restrictions, restricted deposits, and cash and securities segregated in compliance with regulations (such as cash deposited in a special reserve account for the exclusive benefit of customers). Cash and securities segregated under federal and other regulations Payments to Acquire Businesses Net of Cash Acquired and Purchases of Intangible and Other Assets The cash outflow associated with the acquisitions of businesses, net of the cash acquired from the purchases, and purchases of intangible and other assets. Business acquisitions, net of cash acquired, and purchases of intangible and other assets Payment of Contingent Consideration Liabilities Represents the cash outflow related to contingent consideration liabilities that were recognized in a business combination. Payment of contingent consideration liabilities Tax (Expense) Benefit from Share Based Compensation Financing Activities Increase or decrease in the entity's income taxes that arise when compensation cost from share-based compensation recognized in the financial statements is greater than or less than the compensation cost (from non-qualified share-based compensation) recognized on the entity's tax return. This element represents the cash inflow or outflow reported in the entity's financing activities. Tax expense related to share-based compensation Issuance (cancellation) of common stock in connection with an equity method investment, value Issuance (cancellation) of common stock in connection with an equity method investment, value The fair value of stock issued or cancelled in noncash investing activities in connection with the exchange of the Company's membership interest in an equity method investment for a convertible senior secured promissory note. Stock Canceled Value Noncash Investing Stock Canceled Shares Noncash Investing The number of shares issued or cancelled in noncash investing activities in connection with the exchange of the Company's membership interest in an equity method investment for a convertible senior secured promissory note. Issuance (cancellation) of common stock in connection with an equity method investment (in shares) Issuance (cancellation) of common stock in connection with an equity method investment (in shares) Other Assets and Other Liabilities Disclosure [Text Block] OTHER ASSETS AND OTHER LIABILITIES Represents the entire disclosure of the significant carrying amounts composing other assets and other liabilities as of the balance sheet date. MARKET AND CREDIT RISKS Market and Credit Risks Disclosure [Text Block] Represents the entire disclosure of all significant concentrations of risk, including credit risk and market risk, arising from all financial instruments (as defined), whether from an individual counterparty or groups of counterparties. MARKET AND CREDIT RISKS Variable Interest Entities [Text Block] VARIABLE INTEREST ENTITIES Represents the entire disclosure of variable interest entities (VIE), including, but not limited to the nature, purpose, size, and activities of the VIE, the carrying amount and classification of consolidated assets that are collateral for the VIE's obligations, lack of recourse if creditors (or beneficial interest holders) of a consolidated VIE have no recourse to the general credit of the primary beneficiary. An enterprise that holds a significant variable interest in a VIE but is not the primary beneficiary may disclose the nature of its involvement with the VIE and when that involvement began, the nature, purpose, size, and activities of the VIE and the enterprise's maximum exposure to loss as a result of its involvement with the VIE. REGULATORY REQUIREMENTS Regulatory Capital Requirements under Broker Dealer Regulations [Text Block] The entire disclosure for Broker Dealers for regulatory capital requirements imposed by the Securities Exchange Commission (SEC), National Futures Association, Commodity Futures Trading Commission and the various foreign agencies in the foreign countries the Entity operates in. Variation Margin on Long and Short Derivative Contracts Related to Exchange Traded Futures and Options on Futures Variation margin on long and short derivative contracts related to exchange traded futures and options on futures Represents the amount of variation margin on long and short derivative contracts related to exchange traded futures and options on futures. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Variation Margin on Long and Short Derivative Contracts Related to Exchange Traded Futures and Options on Futures Included Within Receivables from Brokers Dealers and Clearing Organizations Variation margin on long and short derivative contracts related to exchange traded futures included within receivables from brokers, dealers and clearing organizations Represents the amount of variation margin on long and short derivative contracts related to exchange traded futures and options on futures included within receivables from brokers, dealers and clearing organizations as of date. Variation Margin on Long and Short Derivative Contracts Related to Exchange Traded Futures and Options on Futures Included Within Payables to Brokers Dealers and Clearing Organizations Variation margin on long and short derivative contracts related to exchange traded futures and options on futures included within payables to brokers, dealers and clearing organizations Represents the amount of variation margin on long and short derivative contracts related to exchange traded futures and options on futures included within payables to brokers, dealers and clearing organizations as of date. Entity Well-known Seasoned Issuer Schedule of changes in Level 3 financial assets and liabilities measured at fair value on a recurring basis Tabular disclosure of the fair value measurement of assets and liabilities using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances, separately presenting changes during the period attributable to the following: (1) total gains or losses for the period (realized and unrealized), segregating those gains or losses included in earnings (or changes in net assets) and gains or losses recognized in other comprehensive income, and a description of where those gains or losses included in earnings (or changes in net assets) are reported in the statement of income (or activities); (2) purchases, sales, issuances, and settlements (each type disclosed separately); and (3) transfers in and transfers out of Level 3 (for example, transfers due to changes in the observability of significant inputs), by class of asset and liability. Fair Value Assets and Liabilities Measured on Recurring Basis Unobservable Input Reconciliation [Table Text Block] Entity Voluntary Filers Fair Value Inputs Assets and Liabilities Quantitative Information [Table Text Block] Schedule of significant unobservable inputs utilized by the company in the fair value measurement of Level 3 assets and liabilities measured at fair value on a recurring basis Tabular disclosure of quantitative information about the inputs used in the fair value measurement of assets and liabilities. This disclosure may include, but is not limited to, the fair value of the asset and liability, valuation technique used to measure fair value, the inputs used to measure fair value, the ranges of the inputs, and the weighted averages of the inputs. Entity Current Reporting Status Unrealized gains (losses) for Level 3 Assets outstanding at end of the period Represents amount of unrealized gain (loss) arising from assets measured at fair value on a recurring basis using unobservable inputs (level 3). Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Unrealized Gain (Loss) Entity Filer Category Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liabilities Unrealized Gain (Loss) Unrealized gains (losses) for Level 3 Liabilities outstanding at end of the period Represents amount of unrealized gain (loss) arising from liabilities measured at fair value on a recurring basis using unobservable inputs (level 3). Entity Public Float Number of Variable Interest Entities in which Entity is Primary Beneficiary Number of VIEs consolidated in which Company is the primary beneficiary Represents the number of variable interest entities in which the entity is primary beneficiary. Entity Registrant Name Property, Equipment and Leasehold Improvements [Member] Property, equipment and leasehold improvements Represents property, equipment and additions or improvements to assets held under a lease arrangement. Entity Central Index Key Software Revenue [Member] Software revenue Represents software revenue, primarily subscription fees charged for electronic trading software. Analytics Revenue [Member] Analytics revenue Represents analytics revenue, primarily subscription fees charged for pricing tools. Market Data Subscription Revenue [Member] Market data subscription revenue Represents market data subscription revenue for fees charged for market data. Loss Related to Accounting Impact of Increased Ownership Stake in Equity Method Investment Loss related to the accounting impact of an increased ownership stake in an equity method investment Represents the amount of loss related to the accounting impact of an increased ownership stake in an equity method investment. Entity Common Stock, Shares Outstanding Receivables from and Payables to Brokers Dealers and Clearing Organizations [Policy Text Block] Receivables from and Payables to Brokers, Dealers and Clearing Organizations Disclosure of accounting policy for the receivables from and payables to brokers, dealers and clearing organizations, including deposits, and exchanges to facilitate settlement and clearance of matched principal transactions, and spreads on matched principal transactions that have not yet been remitted from/to clearing organizations and exchanges. Receivables from and Deposits with Clearing Organizations Receivables from and deposits with clearing organizations and financial institutions Represents receivables from and deposits with clearing organizations and financial institutions. Tabular disclosure of the fair value of future purchase commitment and the discount rate used in its estimated fair value. Schedule of Business Acquisitions Future Purchase Commitment and Discount Rate Used for Estimated Fair Value [Table Text Block] Schedule of fair value of the future purchase commitment and the discount rate used in its estimated fair value Schedule of Other Liabilities [Table Text Block] Schedule of other liabilities Tabular disclosure of other liabilities not separately disclosed on the balance sheet. Future Purchase Commitment and Contingent Consideration Liabilities Future purchase commitment and contingent consideration liabilities Represents the carrying amount of future purchase commitment and contingent consideration liabilities as of balance sheet date. Payroll Related Liabilities Payroll related liabilities Represents amounts payable as of the balance sheet date incurred in conjunction with compensation related expenses, such as payroll taxes and benefits. Contingent Consideration [Member] Contingent consideration Represents the details pertaining to contingent consideration classified as other liabilities of the entity. Fair Value Inputs Assets and Liabilities Quantitative Information [Table] Schedule of the inputs used in the fair value measurement of assets and liabilities. This disclosure may include, but is not limited to, the fair value of the asset and liability, valuation technique used to measure fair value, the inputs used to measure fair value, the ranges of the inputs, and the weighted averages of the inputs. Black-Scholes-Merton Model Represents the Black-Scholes-Merton Model used to measure fair value. Black Scholes Merton Model [Member] Discounted Cash Flow [Member] Discounted cash flow Represents the discounted cash flow used to measure fair value. Present value of expected payments Represents the present value of expected forecasted financial information used to measure fair value. Present Value of Expected Forecasted Financial Information [Member] Fair Value Inputs Assets and Liabilities Quantitative Information [Line Items] Fair value, Unobservable Input Share Based Compensation Arrangement by Share Based Payment Award, Number of Plan Number of plans Represents number of share-based compensation plans. Share Based Compensation Arrangements by Share Based Payment Award Options Expiration Term Expiration term of options Represents the period of time, from the grant date until the time at which the share-based [option] award expires. Euro Denominated Balance Sheet Position [Member] Euro-denominated balance sheet positions Represents Derivative instrument whose primary underlying risk is tied to euro-denominated balance sheet positions. Debt Instrument, Exchanged Face Amount Aggregate principal amount of notes exchanged for notes registered under the Securities Act Face (par) amount of the original debt instrument that was exchanged for a debt instrument registered under the Securities Act. Schedule of Fair Value of Liabilities Carried at Historical Values [Table Text Block] Schedule of the fair value of the Company's Long-term obligations, categorized within Level 2 of the fair value hierarchy Tabular disclosure of liabilities for which the fair value differs from historical value but which continue to be carried at historical value. Document Fiscal Year Focus Receivables from Brokers Dealers and Clearing Organizations at Fair Value Receivables from brokers, dealers and clearing organizations The aggregate fair value as of the balance sheet date of amount receivable from securities failed to deliver, certain deposits for securities borrowed, open transactions, good faith and margin deposits, commissions and floor brokerage items. Document Fiscal Period Focus Required Net Capital as Percent of Aggregate Debit Items Minimum regulatory capital required as a percent of aggregate debits Minimum amount of net capital required as a percent of total debit items to engage in securities transactions. Other Income (Loss) Policy [Policy Text Block] Other Income Disclosure of accounting policy for other income (loss). Deferred Revenue Recognition Period Period for recognition of deferred revenue Represents the period for recognition of deferred revenue. Business Acquisition Contingent Consideration Performance Period Future purchase commitment contingency performance period Represents the performance period that the potential future purchase commitment contingency will be based on. Contingently Issuable Shares Included in Computation of Diluted Earnings Per Share Contingently issuable shares included in computation of diluted earnings per share Represents the securities attributable to contingently issuable shares that were included in the computation of diluted EPS or EPU. Commissions Receivables [Policy] Disclosure of accounting policy for commissions receivable. Commissions Receivable Minimum Financial Regulatory Requirements [Text Block] Tabular disclosure of regulatory capital, minimum regulatory capital required and excess regulatory capital. Schedule of minimum regulatory capital Commissions Payable to Clearing Organizations and Financial Institutions Balance reflects all of the payable to clearing organizations and financial institutions outside of fails. Payables to clearing organizations and financial institutions Total Brokerage Revenues [Member] Total brokerage revenues Represents the primary financial statement caption in which reported facts about total brokerage revenues have been included. Legal Entity [Axis] Number of consolidated VIEs Represents the number of consolidated variable interest entities. Number of Consolidated Variable Interest Entities Document Type Debt Instrument, Additional Interest Additional interest per annum Represents the amount of additional interest on the debt instrument due to credit downgrades. Future Purchase Commitment [Table] Disclosure related to future purchase commitment. Future Purchase Commitment [Line Items] Valuation Techniques Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Represents the equipment used for disseminating information. Communications equipment Communications Equipment [Member] Business Acquisition Contingent Consideration [Abstract] Fair value of the future purchase commitment and the discount rate used in its estimated fair value Deferred Tax Assets, Foreign Deferred Items Foreign deferred items Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from foreign deferred items. Deferred Tax Assets, Prepaid Expenses Prepaid expenses Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from prepaid expenses. Stockholders Equity Increase (Decrease) Estimated Amount of increase in stockholders' equity if deferred tax assets are realized Represents the amount of increase (decrease) in stockholders' equity if deferred tax assets are realized. Stock Issued During Period [Abstract] Share Issuance Chief Executive Officer and Jersey Partners Inc [Member] Michael Gooch and JPI Represents details pertaining to chief executive officer of the entity and Jersey Partners, Inc. Schedule of Common Stock Authorized and Outstanding [Table Text Block] Schedule of shares of common stock authorized and outstanding Tabular disclosure of the shares of common stock authorized and outstanding Contingently issuable shares excluded from computation of diluted loss per share as a result of net loss Represents the securities attributable to contingently issuable shares that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU due to the net loss for the respective period. Contingently Issuable Shares Excluded from Computation of Earnings Per Share Due to Net Loss Operating Leases Facility Lease Terminated Area Area of portion of former facility lease terminated (in square feet) Represents the space of facility lease which is terminated. Operating Leases Facility Lease Remaining Area Remaining area of lease (in square feet) Represents the remaining leased space. Operating Leases Sublease Area Area of remaining leased space subleased (in square feet) Represents the portion of remaining leased space subleased by the entity. Schedule of Defined Contribution Benefit Plans Disclosures [Table] Disclosures of defined contribution plans. Schedule of Defined Contribution Benefit Plans Disclosures [Line Items] Retirement plans Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Defined Contribution Plan Number Number of defined contribution plans Represents the number of defined contribution plans of the entity. Defined Contribution Plan Eligible Period of Service for Enrollment Eligibility for enrollment, period of service The period of service required for an employee to be eligible for enrollment in the defined contribution plans of the entity. Valuation Techniques Future Purchase Commitment [Abstract] UK and US Based Brokerage Trading and Investment Firms [Member] UK and U.S. based brokerage, trading and investment firms Represents information pertaining to unconsolidated UK brokerage and trading operations acquired and U.S. based brokerage, trading and investment firms in which the entity has investment in common stock accounted for under the equity method of accounting and for which certain information is required or determined to be disclosed. Equity Method Investment Income (Loss) Related Increase Ownership Loss from increased ownership in equity method investment Represents the amount of income (loss) related to the accounting impact of an increased ownership stake in an equity method investment previously accounted for as a cost method investment. Equity Method Investment Income (Loss) Prior Period Income from prior period earnings of equity investment Represents the entity's proportionate share in prior period pre-tax income of an investee under the equity method of accounting. Accounts payable and accrued expenses Accounts Payable and Accrued Liabilities Net Capital Excess Shortage Regulatory Capital [Line Items] REGULATORY REQUIREMENTS Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Income Loss Before Equity Method Investments and Noncontrolling Interest Loss before equity in earnings of subsidiaries Sum of operating profit and non operating income (expense) net of income taxes but before income (loss) from equity method investments and noncontrolling interest. Proceeds from Investments in Subsidiaries Investments in subsidiaries Represents the amount of proceeds from investments in subsidiaries of the entity. Represents the notice period for termination of guarantees provided by entity. Guarantee Obligations Notice Period Notice period of termination of guarantees Fair Value Option [Policy Text Block] Fair Value Option Disclosure of entity's accounting policy for election to apply the fair value option for measurement and reporting of eligible financial assets and liabilities as well as certain other eligible items included in the statement of financial position, whether such option is elected for a single eligible item or a group of similar eligible items. Number of Votes that each Shareholder Entitled on all Matters Submitted to Vote Number of votes which each holder of company's common stock entitled on all matters submitted to a vote of stockholders Represents the number of votes which each holder of entity's common stock entitled on all matters submitted to a vote of stockholders. Number of Classes of Preferred Stock Number of classes of preferred stock Represents the number of classes of preferred stock. Aggregate Deferred Tax Assets Net of Valuation Allowance and Net of Liabilities Net deferred tax assets Represents aggregate deferred tax assets, net of valuation allowances and net of deferred tax liabilities. Securities Excluded from Computation of Earnings Per Share Due to Net Loss Securities excluded from computation of diluted loss per share as a result of net loss (in shares) Represents the securities that could potentially dilute basic earnings per share (EPS) in the future that were not included in the computation of diluted EPS due to the net loss for the respective period. Repurchase Program 2007 [Member] 2007 Repurchase program Represents the details related to the stock repurchase program as authorized by the entity's Board of Directors in 2007. Jersey Partners Inc [Member] JPI Represents details pertaining to Jersey Partners, Inc. Amount Made Available for Investing Amount agreed up to be made available to acquiree for investments in new trading entities. Amount agreed to be made available for investing Basis of Presentation [Abstract] Basis of Presentation Error Corrections in Accounts Payable and Accrued Expenses and Rent and Occupancy Expense Reduction in accounts payable, accrued expenses and rent and occupancy expense Represents the amount of reduction in accounts payable, accrued expenses, and rent and occupancy expense as a result of a cumulative error correction recorded during the period. Goodwill Additional Disclosures [Abstract] Additional disclosures Percentage of Fair Value in Excess of Carrying Value Fair value in excess of carrying value of reporting unit (as a percent) Represents the percentage by which fair value of reporting unit is in excess of its carrying value. Fair Value Inputs Period over which Long Term Revenue Growth Rate Applied to Future Cash Flows Period over which business growth rate assumptions applied to future cash flows Represents the period over which percentage of assumed long-term growth is applied to future cash flows. United States UNITED STATES Accumulated Other Comprehensive Income (Loss) [Member] Accumulated Other Comp. Income (loss) Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Accumulated depreciation and amortization Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive income (loss) Weighted average amortization period of intangible assets Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Additional Paid in Capital, Common Stock Additional paid in capital Additional Paid In Capital Additional Paid-in Capital [Member] Income tax expense from the exercise of stock options and vesting of RSUs recorded directly to additional paid-in capital Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net Adjustments to Additional Paid in Capital, Income Tax Deficiency from Share-based Compensation Tax expense associated with share-based awards Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net (loss) income to net cash provided by operating activities: Adjustments to reconcile net (loss) income to net cash used in operating activities: Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Share-based compensation Adjustments Related to Tax Withholding for Share-based Compensation Withholding of restricted stock units in satisfaction of tax requirements All Other Segments [Member] All other Compensation expense Allocated Share-based Compensation Expense Allowance for Doubtful Accounts Receivable Allowance for doubtful accounts Allowance for Doubtful Accounts [Member] Allowance for Doubtful Accounts Alternative Excess Net Capital Excess regulatory capital Amortization expense Amortization of Intangible Assets Amortization of Financing Costs Amortization of loan fees Antidilutive securities excluded from computation of (loss) earnings per share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount EARNINGS PER SHARE Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities, Name [Domain] Antidilutive Securities [Axis] Impairment loss included within Other expenses in the Condensed Consolidated Statements of Operations Asset Impairment Charges Assets, Fair Value Disclosure Total Fair Value, Assets Assets [Abstract] Assets Assets TOTAL ASSETS Assets, Fair Value Disclosure [Abstract] Assets Fair value of available-for-sale securities Available-for-sale Securities, Fair Value Disclosure Available-for-sale Securities, Equity Securities Equity security, available-for-sale Available-for-sale Securities, Debt Securities Convertible note receivable, available-for-sale Fair value of Note Available-for-sale Securities [Abstract] Other assets: Other: SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation and Significant Accounting Policies [Text Block] Basis of Accounting, Policy [Policy Text Block] Basis of Presentation Brokerage Commissions Revenue Agency commissions Contingently issuable shares Business Acquisition, Contingent Consideration, Shares Issuable Business combinations, common stock, contingently issuable shares (in shares) Business Acquisition [Axis] Fair Value of Future Purchase Commitment (included within Other liabilities) Business Acquisition, Contingent Consideration, at Fair Value Other liabilities: Contingent consideration Business combinations, common stock, contingently issuable value Business Acquisition, Acquiree [Domain] Common stock issued as a part of purchase consideration (in shares) Business Acquisition, Equity Interest Issued or Issuable, Number of Shares Business combinations, common stock, shares issued (in shares) Business Acquisition, Purchase Price Allocation, Liabilities Assumed Business combinations, Other liabilities Business combinations, Other liabilities ACQUISITIONS Fair value of common shares issued Business Acquisition, Equity Interest Issued or Issuable, Value Assigned Business combinations, common stock, shares issued value ACQUISITIONS Business Acquisition [Line Items] Purchase consideration Business Acquisition, Cost of Acquired Entity, Purchase Price Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain Gain on remeasurement of previously held equity interest Business Combination Disclosure [Text Block] ACQUISITIONS Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Contingent Liability Business combinations, Other liabilities, contingent liability Business Combination, Contingent Consideration Arrangements [Abstract] Contingent Consideration Software inventory, net Capitalized Computer Software, Net Cash and securities segregated under federal and other regulations Cash and Securities Segregated under Federal and Other Regulations Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD CASH AND CASH EQUIVALENTS, END OF PERIOD Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] Cash and Securities Segregated Under Federal and Other Regulations Cash and Cash Equivalents Cash and Cash Equivalents, Unrestricted Cash and Cash Equivalents, Policy [Policy Text Block] Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Non-Cash Investing and Financing Activities: Michael Gooch Chief Executive Officer [Member] Variable Interest Entity, Classification [Domain] Clearing Fees Revenue Clearing services revenues Commitments and Contingencies Disclosure [Text Block] COMMITMENTS AND CONTINGENCIES COMMITMENTS AND CONTINGENCIES Commitments and Contingencies. Commitments and contingencies (Note 13) Commitments, Fair Value Disclosure Other liabilities: Future purchase commitment Commodity derivative contracts Commodity Contract [Member] Common Stock Common Stock [Member] Outstanding (in shares) Number of shares outstanding Common Stock, Shares, Outstanding Common Stock, Value, Issued Common stock, $0.01 par value; 400,000,000 shares authorized and 134,689,148 and 131,669,676 shares issued at December 31, 2012 and 2011, respectively Common Stock, Shares, Issued Common stock, shares issued Common Stock, Dividends, Per Share, Declared Dividends declared per share of common stock (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, par value (in dollars per share) Par value per share (in dollars per share) Common Stock, Shares Authorized Common stock, shares authorized Authorized (in shares) Cash dividend paid (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Shares of Common Stock Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract] Communications and Information Technology Communications and market data RETIREMENT PLANS Compensation Related Costs, Policy [Policy Text Block] Compensation and Employee Benefits Deferred tax assets: Components of Deferred Tax Assets [Abstract] Deferred tax liabilities: Components of Deferred Tax Liabilities [Abstract] GFI's comprehensive (loss) income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Comprehensive income attributable to non-controlling stockholders Comprehensive (loss) income including non-controlling stockholders Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Computer Equipment [Member] Computer equipment PARENT COMPANY INFORMATION Condensed Financial Statements, Captions [Line Items] Condensed Financial Information of Parent Company Only Disclosure [Text Block] PARENT COMPANY INFORMATION PARENT COMPANY INFORMATION Consolidation Policies Consolidation, Subsidiaries or Other Investments, Consolidated Entities, Policy [Policy Text Block] Consolidation, Variable Interest Entity, Policy [Policy Text Block] Variable Interest Entities Carrying amount of cost-method investments Cost-method Investments, Aggregate Carrying Amount Expenses Costs and Expenses [Abstract] State and local Current State and Local Tax Expense (Benefit) Current provision (benefit): Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Total current provision Current Income Tax Expense (Benefit) Foreign Current Foreign Tax Expense (Benefit) Federal Current Federal Tax Expense (Benefit) Customer relationships Customer Relationships [Member] Annualized rate of interest Debt Instrument, Description of Variable Rate Basis SHORT-TERM BORROWINGS AND LONG-TERM OBLIGATIONS Debt Instrument [Line Items] Schedule of Long-term Debt Instruments [Table] Debt Disclosure [Text 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from deferred taxes Total deferred (benefit) Deferred tax assets Total deferred tax assets Deferred Tax Assets, Net of Valuation Allowance Deferred Tax Assets, Net Deferred tax assets Deferred Revenue Arrangement Type [Domain] State and local Deferred State and Local Income Tax Expense (Benefit) Deferred Revenue Arrangement Type [Axis] Net operating loss carryforwards Deferred Tax Assets, Operating Loss Carryforwards U.S. federal net operating loss carryforwards Deferred Tax Assets, Operating Loss Carryforwards, Domestic U.S. state and local net operating loss carryforwards Deferred Tax Assets, Operating Loss Carryforwards, State and Local Other, net Deferred Tax Assets, Other Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Accrued Liabilities Liability reserves Share-based compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost Unrealized loss on currency hedging Deferred Tax Assets, Unrealized Currency Losses General business credit Deferred Tax Assets, Tax Credit Carryforwards, General Business Foreign tax credits Deferred Tax Assets, Tax Credit Carryforwards, Foreign Foreign net operating loss carryforwards Deferred Tax Assets, Operating Loss Carryforwards, Foreign Total deferred tax liabilities Deferred Tax Liabilities, Net Deferred tax liabilities Valuation allowance Deferred Tax Assets, Valuation Allowance Deferred Tax Liabilities, Property, Plant and Equipment Depreciation and amortization Intangible amortization Deferred Tax Liabilities, Goodwill and Intangible Assets Aggregate contributions Defined Contribution Plan, Cost Recognized Deposits with Clearing Organizations and Others, Securities Receivables from brokers, dealers and clearing organizations Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Depreciation Depreciation and amortization expense Depreciation, Amortization and Accretion, Net Depreciation and amortization Total fair value Derivative Asset, Fair Value, Net Derivative Instrument Risk [Axis] Total fair value Derivative Liability, Fair Value, Net Notional amount of derivatives Derivative [Line Items] Derivative Instruments and Hedging Activities Disclosure [Text Block] DERIVATIVE FINANCIAL INSTRUMENTS Derivative [Table] DERIVATIVE FINANCIAL INSTRUMENTS Derivative [Member] Derivative contracts Derivative Liabilities Derivative Liability, Fair Value, Net [Abstract] Derivative Assets Derivative Asset, Fair Value, Net [Abstract] Total fair value of derivative contracts Derivative Asset, Fair Value, Gross Asset Total fair value of derivative contracts Derivative Liability, Fair Value, Gross Liability Amount of Gain (Loss) Recognized in Income on Derivatives Derivative Instruments, Gain (Loss) Recognized in Income, Net Mark-to-market of equity warrants Derivative Contract Type [Domain] Effect of derivative contracts on the Condensed Consolidated Statements Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) by Hedging Relationship, by Income Statement Location, by Derivative Instrument Risk [Table] Derivatives, Policy [Policy Text Block] Derivative Financial Instruments DERIVATIVE FINANCIAL INSTRUMENTS Derivatives, Fair Value [Line Items] Difference between Reported Amount and Reporting Currency Denominated Amount, Value Net (losses) resulting from remeasurement of foreign currency transactions and balances Disclosure of Compensation Related Costs, Share-based Payments [Text Block] SHARE-BASED COMPENSATION SHARE-BASED COMPENSATION Dividend declared Dividend Declared [Member] Dividends, Common Stock, Cash Dividends to stockholders Dividends [Axis] Cash dividend declared (in dollars per share) Dividends Payable, Amount Per Share Dividends [Domain] RECEIVABLES FROM AND PAYABLES TO BROKERS, DEALERS AND CLEARING ORGANIZATIONS RECEIVABLES FROM AND PAYABLES TO BROKERS, DEALERS AND CLEARING ORGANIZATIONS Due to and from Broker-Dealers and Clearing Organizations Disclosure [Text Block] Advances to subsidiaries Due from Related Parties Receivables from subsidiaries Basic (loss) earnings per share Earnings Per Share, Basic [Abstract] Diluted (in dollars per share) Earnings Per Share, Diluted Diluted (loss) earnings per share (in dollars per share) Diluted (loss) earnings per share Earnings Per Share, Diluted [Abstract] Basic (in dollars per share) Earnings Per Share, Basic Basic (loss) earnings per share (in dollars per share) Earnings Per Share [Text Block] (LOSS) EARNINGS PER SHARE (LOSS) EARNINGS PER SHARE (Loss) earnings per share available to common stockholders Effect of Exchange Rate on Cash and Cash Equivalents, Continuing Operations Effects of exchange rate changes on cash and cash equivalents Corporate statutory U.S. federal tax rate (as a percent) Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate Weighted average period over which unrecognized compensation cost is expected to be recognized Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition Income tax benefits Employee Service Share-based Compensation, Tax Benefit from Compensation Expense Total unrecognized compensation cost Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Share-based Awards Other than Options Total compensation expense and related income tax benefits Employee Service Share-based Compensation, Aggregate Disclosures [Abstract] Employee-related Liabilities Accrued compensation Payroll related liabilities Equity Method Investments and Joint Ventures Disclosure [Text Block] EQUITY METHOD INVESTMENTS Carrying amount of equity method investments Equity Method Investments. Aggregate carrying amount of investments accounted for under equity method Investments in subsidiaries, equity basis Impairment of equity method investments Equity Method Investment, Other than Temporary Impairment Total losses for the year Equity ownership interest (as a percent) Equity Method Investment, Ownership Percentage Equity Component [Domain] Equity Method Investee, Name [Domain] EQUITY METHOD INVESTMENTS Equity Securities [Member] Equity securities Equity derivative contracts Equity Contract [Member] Deposit in escrow account Escrow Deposit Estimate of Fair Value, Fair Value Disclosure [Member] Total Measurement Frequency [Axis] Fair Value by Asset Class [Domain] Fair Value Assumptions, Expected Volatility Rate Expected volatility (as a percent) Fair Value, Hierarchy [Axis] Liability Class [Axis] Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales Sales Assumed discount rate (as a percent) Fair Value Inputs, Discount Rate Discount rate (as a percent) Fair Value, Measurements, Recurring [Member] Fair value measured on a recurring basis Recurring basis Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value Beginning Balance Ending Balance Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements Settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements Settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issues Issuances Fair Value Inputs, Entity Credit Risk Estimated credit spread (as a percent) Fair Value, Measurement Frequency [Domain] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales Sales Asset Class [Axis] Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Total realized and unrealized gains (losses) included in Income Fair Value by Liability Class [Domain] Fair Value Inputs [Abstract] Unobservable Input(s) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases Purchases Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Issues Issuances Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Financial Assets and Liabilities measured at fair value Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) Unrealized gains (losses) included in Other comprehensive (income) loss Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases Purchases FAIR VALUE OF FINANCIAL INSTRUMENTS FAIR VALUE OF FINANCIAL INSTRUMENTS Fair Value Disclosures [Text Block] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Changes in Level 3 Financial Assets measured at fair value Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value of Financial Instruments, Policy [Policy Text Block] Fair Value of Financial Instruments Fair Value, Inputs, Level 3 [Member] Significant Unobservable Inputs (Level 3) Fair Value, Inputs, Level 1 [Member] Quoted Prices in Active Markets for Identical Assets (Level 1) Fair Value, Inputs, Level 2 [Member] Significant Other Observable Inputs (Level 2) Level 2 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings Total realized and unrealized gains (losses) included in Income Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss) Unrealized gains (losses) included in Other Comprehensive (income) loss Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Changes in Level 3 Financial Liabilities measured at fair value Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Beginning Balance Ending Balance Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Other liabilities: Financial instruments sold, not yet purchased Financial instruments sold, not yet purchased Financial Instruments Sold, Not yet Purchased, at Fair Value Financial Instruments, Owned, at Fair Value Other assets: Financial instruments owned Financial instruments owned Finite-Lived Intangible Assets, Major Class Name [Domain] 2017 Finite-Lived Intangible Assets, Amortization Expense, Year Five Gross amount Finite-Lived Intangible Assets, Gross 2015 Finite-Lived Intangible Assets, Amortization Expense, Year Three Patents purchased Finite-lived Intangible Assets Acquired Expected amortization expense for the definite lived intangible assets Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] Finite-Lived Intangible Assets by Major Class [Axis] Thereafter Finite-Lived Intangible Assets, Amortization Expense, after Year Five Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months 2013 2016 Finite-Lived Intangible Assets, Amortization Expense, Year Four 2014 Finite-Lived Intangible Assets, Amortization Expense, Year Two 2012 (remaining three months) Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year Net carrying value Net carrying value Finite-Lived Intangible Assets, Net Fixed income derivative contracts Fixed Income Securities [Member] Floor Brokerage, Exchange and Clearance Fees Execution, clearing and settlement fees Foreign Government Debt [Member] Foreign government bonds Foreign exchange derivative contracts Foreign Exchange Contract [Member] Foreign Currency Transactions and Translations Policy [Policy Text Block] Foreign Currency Translation Adjustments and Transactions Furniture and Fixtures [Member] Furniture and fixtures Gain (Loss) on Disposition of Assets Loss on disposal of fixed assets Goodwill Goodwill Goodwill at the beginning of the period Goodwill at the end of the period Goodwill and Intangible Assets, Policy [Policy Text Block] Goodwill and Intangible Assets Goodwill, Translation Adjustments Foreign currency translation Goodwill and Intangible Assets Disclosure [Text Block] GOODWILL AND INTANGIBLE ASSETS Goodwill [Line Items] Goodwill Goodwill, Allocation Adjustment Adjustments Goodwill acquired Goodwill, Acquired During Period GOODWILL AND INTANGIBLE ASSETS Guarantees Guarantor Obligations [Line Items] Hedging Designation [Axis] Hedging Designation [Domain] Income (loss) before income taxes Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest Income before provision for income taxes (Loss) income before provision for income taxes (Gains) losses from equity method investments, net Income (Loss) from Equity Method Investments, Net of Dividends or Distributions Income from equity method investments Pre-tax income from foreign operations Income (Loss) from Continuing Operations before Income Taxes, Foreign CONSOLIDATED STATEMENTS OF OPERATIONS Income Statement Location [Axis] Income Tax Disclosure [Text Block] INCOME TAXES INCOME TAXES Loss before benefit from income taxes and equity in earnings of subsidiaries Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest Income Statement Location [Domain] Income (Loss) from Equity Method Investments Equity in net earnings of unconsolidated businesses Equity in net earnings of unconsolidated businesses related to investments accounted for under equity method Equity in earnings of subsidiaries, net of tax Pre-tax (loss) from domestic operations Income (Loss) from Continuing Operations before Income Taxes, Domestic Income Tax Expense (Benefit) Provision for income taxes Provision for income taxes Benefit from income taxes Federal income tax provision (benefit) at statutory rate Income Tax Reconciliation, Income Tax Expense (Benefit), at Federal Statutory Income Tax Rate Reconciliation of the Company's provision for income tax and the statutory tax rate Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract] Non-deductible expenses Income Tax Reconciliation, Nondeductible Expense U.S. valuation allowance Income Tax Reconciliation, Change in Deferred Tax Assets Valuation Allowance Foreign operations Income Tax Reconciliation, Foreign Income Tax Rate Differential Income Taxes Paid, Net Cash paid for income taxes Income Tax Reconciliation, Repatriation of Foreign Earnings U.S. tax on foreign profits Tax-Exempt Income Income Tax Reconciliation, Tax Exempt Income U.S. state and local income taxes, net of federal tax benefit Income Tax Reconciliation, State and Local Income Taxes Income Tax, Policy [Policy Text Block] Income Taxes Income Tax Reconciliation, Prior Year Income Taxes Net adjustment related to the reconciliation of income tax provision (benefit) accruals to tax returns Income Tax Reconciliation, Tax Credits General business credit Other Income Tax Reconciliation, Other Adjustments Increase (Decrease) in Payables to Customers Payables to clearing services customers Increase (Decrease) in Receivables from Brokers-Dealers and Clearing Organizations Receivables from brokers, dealers and clearing organizations Increase (Decrease) in Accounts Receivable Commissions receivable Increase (Decrease) in Accounts Payable and Accrued Liabilities Accounts payable and accrued expenses Increase (Decrease) in Deposit Assets Deposits with clearing organizations Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Increase (Decrease) in Employee Related Liabilities Accrued compensation Increase (Decrease) in Other Operating Assets Other assets Increase (Decrease) in Payables to Broker-Dealers and Clearing Organizations Payables to brokers, dealers and clearing organizations Increase (Decrease) in Operating Liabilities [Abstract] Increase (decrease) in operating liabilities: Increase (Decrease) in Other Operating Liabilities Other liabilities Increase (Decrease) in Operating Assets [Abstract] (Increase) decrease in operating assets: Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity Unamortized intangible assets, Proprietary knowledge Indefinite-Lived Intangible Assets (Excluding Goodwill) Total net carrying value Intangible Assets, Net (Excluding Goodwill) Intangible assets, net Interest Expense Interest expense Interest on borrowings Interest Income, Operating Interest income from clearing services Interest income Interest Paid, Net Interest paid Cash paid for interest Investment, Policy [Policy Text Block] Investments Investments Investments accounted for under the cost method and equity method Long-term Debt, Type [Domain] Long-term Debt, Type [Axis] Labor and Related Expense Compensation and employee benefits Rent expense Operating Leases, Rent Expense Favorable lease agreements Lease Agreements [Member] Leasehold Improvements [Member] Leasehold improvements Letters of credit Letter of Credit [Member] Liabilities, Fair Value Disclosure Total Fair Value, Liabilities Liabilities [Abstract] LIABILITIES Liabilities Total Liabilities Liabilities and Equity [Abstract] Liabilities and stockholders' equity Liabilities, Fair Value Disclosure [Abstract] Liabilities Liabilities and Equity TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY Software, analytics and market data License and Services Revenue Licenses Licensing Agreements [Member] Maximum borrowings Line of Credit Facility, Maximum Borrowing Capacity Line of Credit Facility, Decrease, Repayments Repayment of outstanding amounts with net proceeds from the Offering Available borrowing capacity Line of Credit Facility, Remaining Borrowing Capacity Line of Credit Facility, Amount Outstanding Loans Outstanding Credit Agreement Line of Credit [Member] Long-term obligations Long-term Debt Long-term obligations Long-term Debt, Fair Value Long-term obligations, at estimated fair value Marketing and Advertising Expense Travel and promotion Maximum Maximum [Member] Less than Minimum Minimum [Member] Minimum Net Capital Required Minimum regulatory capital required Stockholders' Equity Attributable to Noncontrolling Interest Non-controlling interests Ownership by Jersey Partners, Inc. (as a percent) Noncontrolling Interest, Ownership Percentage by Parent Ownership by Jersey Partners, Inc. (as a percent) Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners Movement in Valuation Allowances and Reserves [Roll Forward] VALUATION AND QUALIFYING ACCOUNTS Long-lived Assets, as defined: Long-Lived Assets ORGANIZATION AND BUSINESS Nature of Operations [Text Block] CASH FLOWS FROM FINANCING ACTIVITIES: Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Cash provided by operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations CASH FLOWS FROM OPERATING ACTIVITIES: Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Net Cash Provided by (Used in) Continuing Operations DECREASE IN CASH AND CASH EQUIVALENTS Cash used in investing activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations Net Income (Loss) Available to Common Stockholders, Basic GFI's net (loss) income GFI'S net (loss) income Net Capital Regulatory capital Cash used in financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations CASH FLOWS FROM INVESTING ACTIVITIES: Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Net Income (Loss) Attributable to Noncontrolling Interest Less: Net income attributable to non-controlling interests New Accounting Pronouncements, Policy [Policy Text Block] Recent Accounting Pronouncements Non-compete agreements Noncompete Agreements [Member] Notes Receivable [Member] Convertible note receivable, available-for-sale Notional Amount of Foreign Currency Derivatives Notional value of derivative Number of operating segments Number of Operating Segments Number of reportable segments Number of Reportable Segments Noncontrolling Interest, Increase from Business Combination Adjustment to non-controlling interests from business acquisitions Noncontrolling Interest [Member] Non-Controlling Interests Derivatives not designated as hedging instruments Not Designated as Hedging Instrument [Member] Occupancy, Net Rent and occupancy Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Operating Leases Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] Operating Leases, Rent Expense, Sublease Rentals Monthly sublease receipts 2015 Operating Leases, Future Minimum Payments, Due in Three Years 2014 Operating Leases, Future Minimum Payments, Due in Two Years 2013 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2016 Operating Leases, Future Minimum Payments, Due in Four Years 2017 Operating Leases, Future Minimum Payments, Due in Five Years Total Operating Leases, Future Minimum Payments Due ORGANIZATION AND BUSINESS Other Assets Other assets Total Other assets Unrealized (loss) gain on available-for-sale securities, net of tax Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax Unrealized gain (loss) on available-for-sale securities, net of tax Other Liabilities [Abstract] Other liabilities Other non-cash charges, net Other Noncash Income (Expense) Other Assets, Miscellaneous Other Other Amortization of Deferred Charges Amortization of prepaid bonuses and forgivable loans Amortization of prepaid bonuses and forgivable employee loans Other Assets [Abstract] Other assets Unrealized gain (loss) on available-for-sale securities, tax expense (benefit) Other Comprehensive Income (Loss), Available-for-sale Securities, Tax Other Asset Impairment Charges Impairment of investments Other than Temporary Impairment Losses, Investments, Available-for-sale Securities Impairment charges (Included within Other expenses). Foreign currency translation adjustment Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Foreign currency translation adjustment Other Sundry Liabilities Other Other Comprehensive Income (Loss), Net of Tax [Abstract] Other comprehensive income (loss): Other comprehensive (loss) income, net of tax: Other Expenses Other expenses Other Liabilities Other liabilities Total Other liabilities Other Payables to Broker-Dealers and Clearing Organizations Net pending trades Net pending trades Other Receivables from Broker-Dealers and Clearing Organizations other Other Assets [Member] Parent Company Parent Company [Member] Total Stockholders' Equity Parent [Member] Patents Patents [Member] Payables to Customers Payables to clearing services customers Total Payables to Broker-Dealers and Clearing Organizations Payables to brokers, dealers and clearing organizations Payables to brokers, dealers and clearing organizations: Payables to Broker-Dealers and Clearing Organizations [Abstract] Payments Related to Tax Withholding for Share-based Compensation Cash paid for taxes on vested restricted stock units Payment of debt issuance costs Payments of Debt Issuance Costs Payment of loan fees Payments for Derivative Instrument, Investing Activities Payments on foreign exchange derivative contracts Payments for Repurchase of Common Stock Purchases of treasury stock Payments to Develop Software Payments for internally developed software Payments to Acquire Property, Plant, and Equipment Purchase of property, equipment and leasehold improvements Payments to Acquire Notes Receivable Issuance of notes receivable Payments of Ordinary Dividends, Noncontrolling Interest Cash dividends paid to non-controlling interests Payments of Ordinary Dividends, Common Stock Cash dividends paid to common stockholders Total cash dividend paid Cash dividends paid Payments to Acquire Other Investments Purchases of other investments Pension and Other Postretirement Benefits Disclosure [Text Block] RETIREMENT PLANS Plan Name [Domain] Plan Name [Axis] Preferred Stock, Value, Issued Preferred stock, $0.01 par value; 5,000,000 shares authorized, none outstanding at December 31, 2012 and 2011 Preferred Stock, Shares Authorized Preferred stock, shares authorized Number of shares of preferred stock authorized Preferred Stock, Par or Stated Value Per Share Preferred stock, par value (in dollars per share) Preferred Stock, Shares Outstanding Preferred stock, shares outstanding Preferred Stock Preferred Stock [Member] Principal Transactions Revenue Principal transactions Principal transactions Principal or Proprietary Transactions [Member] Prior Period Reclassification Adjustment Amount previously presented in the "Other expenses" reclassified to the "Equity in net earnings of unconsolidated businesses" Receipts from subsidiaries Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital Proceeds from Collection of Notes Receivable Proceeds from notes receivable Proceeds from Derivative Instrument, Investing Activities Proceeds on foreign exchange derivative contracts Proceeds from long-term obligations Proceeds from Issuance of Long-term Debt Proceeds from Income Tax Refunds Cash received from income tax refunds Proceeds from Sale and Maturity of Other Investments Proceeds from other investments Proceeds from Short-term Debt Proceeds from short-term borrowings Proceeds from Stock Options Exercised Proceeds from exercises of stock options Cash proceeds received in connection with the exercise of stock options Professional Fees Professional fees Net (loss) income before attribution to non-controlling stockholders Net (loss) income before attribution to non-controlling stockholders Net (loss) income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Property, Plant and Equipment, Useful Life Useful life Property, Plant and Equipment, Type [Domain] PROPERTY, EQUIPMENT AND LEASEHOLD IMPROVEMENTS Property, Plant and Equipment, Policy [Policy Text Block] Property, Equipment and Leasehold Improvements Property, Plant and Equipment, Net Property, equipment and leasehold improvements, net Property, equipment and leasehold improvements less accumulated depreciation and amortization Property, Plant and Equipment [Line Items] Property, equipment and leasehold improvements Property, Plant and Equipment, Gross Total Schedule of property, equipment and leasehold improvements Property, Plant and Equipment [Table Text Block] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment Disclosure [Text Block] PROPERTY, EQUIPMENT AND LEASEHOLD IMPROVEMENTS Provision for Doubtful Accounts Provision for doubtful accounts Purchase Commitment [Member] Future purchase commitment Range [Axis] Range [Domain] Receivables from Customers Commissions receivable, net Receivables from brokers, dealers and clearing organizations: Receivables from Brokers-Dealers and Clearing Organizations [Abstract] Total Receivables from Brokers-Dealers and Clearing Organizations Receivables from brokers, dealers and clearing organizations Reconciliation of the beginning and ending amount of unrecognized tax benefits Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] REGULATORY REQUIREMENTS Related Party [Domain] Related Party [Axis] Repayments of Short-term Debt Repayments of short-term borrowings Repayments of Long-term Debt Repayment of long-term obligations Restatement Adjustment [Member] Restatement Adjustment (Note 2) RSUs Restricted Stock Units (RSUs) [Member] Restructuring Charges Charge to Compensation and Employee Benefits relating to severance costs and restructuring of certain employment agreements Retained Earnings (Accumulated Deficit) Retained earnings Retained Earnings Retained Earnings [Member] Revenues, Excluding Interest and Dividends [Abstract] Brokerage revenues: SEGMENT AND GEOGRAPHIC INFORMATION Revenues from External Customers and Long-Lived Assets [Line Items] Total revenues Revenues Total revenues Revenues: Revenues [Abstract] Revenues Intrinsic value of options outstanding and exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Weighted Average Contractual Term, Exercisable at the end of the period Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Weighted Average Contractual Term, Outstanding at the end of the period Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Schedule of expected amortization expense for the definite lived intangible assets Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Scenario, Previously Reported [Member] as previously reported Scenario, Unspecified [Domain] Schedule of geographic information regarding revenues and long-lived assets Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block] Schedule of Other Assets [Table Text Block] Schedule of other assets Stock options outstanding under both the GFI Group 2002 Plan and the GFInet 2000 Plan Schedule of Stock Options Roll Forward [Table Text Block] Schedule of components of provision for income taxes Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Schedule of financial assets and liabilities measured at fair value on a recurring basis Summary of RSU transactions Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block] Schedule of basic and diluted (loss) earnings per share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of reconciliation of the Company's provision for income tax and the statutory tax rate Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of reconciliation of the beginning and ending amount of unrecognized tax benefits Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block] Schedule of outstanding long and short notional amounts on a gross basis of derivative financial instruments Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] Schedule of Finite-Lived Intangible Assets [Table] Schedule of future minimum rental commitments under such leases Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule of significant components of the Company's gross deferred tax assets and liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Schedule of Condensed Statements of Financial Condition Schedule of Condensed Balance Sheet [Table Text Block] Schedule of Revenues from External Customers and Long-Lived Assets [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Condensed Consolidating Statements of Cash Flows Schedule of Condensed Cash Flow Statement [Table Text Block] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Condensed Statements of Operations and Comprehensive (Loss) Income Schedule of Condensed Income Statement [Table Text Block] Schedule of outstanding Long-term obligations Schedule of Long-term Debt Instruments [Table Text Block] Schedule of amounts receivable from and payable to brokers, dealers and clearing organizations Schedule of Due to (from) Broker-Dealers and Clearing Organizations [Table Text Block] Schedule of Condensed Financial Statements [Table] Schedule of Equity Method Investments [Table] Schedule of total compensation expense and related income tax benefits recognized in relation to RSUs Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block] Equity method investments Schedule of Equity Method Investments [Line Items] Equity Method Investee, Name [Axis] Schedule of Line of Credit Facilities [Table Text Block] Credit agreement borrowings Schedule of Guarantor Obligations [Table] Schedule of Goodwill [Table Text Block] Schedule of changes in the carrying amount of the Company's goodwill Schedule of Goodwill [Table] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of financial information for the company's reportable segments Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of Property, Plant and Equipment [Table] Schedule of Variable Interest Entities [Table Text Block] Schedule of the carrying amount and maximum exposure to loss associated with the Company's variable interests in non-consolidated VIEs Schedule of Valuation and Qualifying Accounts Disclosure [Text Block] SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS Schedule of fair values of derivative contracts on a gross and net basis Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Schedule of Variable Interest Entities [Table] Summary of the effect of derivative contracts on the Consolidated Statements of Operations Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance [Table Text Block] Contract value of fails to receive Securities Failed-to-Receive Contract value of fails to deliver Securities Failed-to-Deliver Segment Reporting Information [Line Items] SEGMENT AND GEOGRAPHIC INFORMATION SEGMENT AND GEOGRAPHIC INFORMATION Segment Reporting Disclosure [Text Block] SEGMENT AND GEOGRAPHIC INFORMATION Segment [Domain] Segment, Geographical [Domain] Total fair value of shares vested Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value RSUs Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Share-based Compensation. Share-based compensation Share Repurchase Program [Axis] Cancelled (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Granted (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Cancelled (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Outstanding at the beginning of the period (in dollars per share) Outstanding at the end of the period (in dollars per share) Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward] Weighted-Average Grant Date Fair Value SHARE-BASED COMPENSATION Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Outstanding at the beginning of the period (in shares) Outstanding at the end of the period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Share Repurchase Program [Domain] Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Cancelled (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Share Price Estimated share price (in dollars per share) Expired (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Exercised (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Exercisable at the end of the period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Expired (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period Vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Intrinsic value of options exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value Additional disclosures Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract] Exercisable at the end of the period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Shares of common stock available for future grants of awards Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Options Cancelled (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Incremental compensation expense due to modifications Share-based Compensation Arrangement by Share-based Payment Award, Plan Modification, Incremental Compensation Cost Outstanding at the beginning of the period (in dollars per share) Outstanding at the end of the period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Outstanding at the beginning of the period (in shares) Outstanding at the end of the period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Award Type [Domain] Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Share-Based Compensation Short-term Debt Short-term borrowings, net Software and Software Development Costs [Member] Computer software Software, including software development costs Statement [Table] Scenario [Axis] Statement [Line Items] Statement Stockholders' equity CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY CONSOLIDATED STATEMENTS OF CASH FLOWS Business Segments [Axis] Equity Components [Axis] CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME Geographical [Axis] Number of shares of common stock issued as part of the purchase price Stock Issued During Period, Shares, Acquisitions Options Stock Options [Member] Stock option Stock Issued During Period, Value, Acquisitions Common stock issued (cancelled) in connection with an investment Issuance of treasury stock Stock Issued During Period, Value, Restricted Stock Award, Gross Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures Issuance of common stock for exercise of stock options and vesting of restricted stock units Exercised (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Number of shares of common stock issued in connection with the exercise of stock options and vesting of RSUs Stock Issued During Period, Shares, Share-based Compensation, Gross Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] STOCKHOLDERS' EQUITY Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Total Equity Balance Balance Stockholders' Equity Attributable to Parent Total Stockholders' Equity STOCKHOLDERS' EQUITY Stockholders' Equity Note Disclosure [Text Block] STOCKHOLDERS' EQUITY Stockholders' equity, other disclosure Stockholders' Equity, Number of Shares, Par Value and Other Disclosures [Abstract] Stockholders' Equity, Period Increase (Decrease) Subsequent Events [Text Block] SUBSEQUENT EVENTS SUBSEQUENT EVENTS Subsequent Event Type [Domain] SUBSEQUENT EVENTS Subsequent Event [Line Items] Subsequent Event Type [Axis] Subsequent Event [Table] Subsequent event Subsequent Event [Member] Supplemental Cash Flow Information [Abstract] SUPPLEMENTAL DISCLOSURE: Tax Adjustments, Settlements, and Unusual Provisions Liability for unrecognized tax benefit relating to years prior to 2009 Trade names Trade Names [Member] Treasury Stock, Value Treasury stock, 17,313,686 and 14,145,038 common shares at cost at December 31, 2012 and 2011, respectively Treasury stock, 17,313,686 and 14,145,038 common shares at cost at December 31, 2011 and 2010, respectively Treasury Stock, Shares, Acquired Shares of common stock repurchased Average price of shares of common stock repurchased (in dollars per share) Treasury Stock Acquired, Average Cost Per Share Treasury Stock, Shares Treasury stock, common shares at cost Treasury Stock Treasury Stock [Member] Treasury Stock, Value, Acquired, Cost Method Purchase of treasury stock Total cost of shares repurchased including sales commissions Unconditional Purchase Obligation, Category of Goods or Services Acquired [Domain] Cumulative undistributed earnings Undistributed Earnings of Foreign Subsidiaries Gross increases-current period tax positions Unrecognized Tax Benefits, Increases Resulting from Current Period Tax Positions Unrecognized Tax Benefits Unrecognized tax benefits Unrecognized tax benefits (net of the federal benefit on state tax positions) Unrecognized tax benefits balance at the beginning of the period, as previously reported Unrecognized tax benefits balance at the end of the period Accrued interest related to uncertain tax positions Unrecognized Tax Benefits, Interest on Income Taxes Accrued Lapse of statute of limitations Unrecognized Tax Benefits, Reductions Resulting from Lapse of Applicable Statute of Limitations (Decreases) increases in unrecognized tax benefits, net Unrecognized Tax Benefits, Period Increase (Decrease) Unrecognized Tax Benefits that Would Impact Effective Tax Rate Unrecognized tax benefits (net of the federal benefit on state tax positions) Purchase commitments due within next twelve months Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months Unrecorded Unconditional Purchase Obligation [Table] Unrecorded Unconditional Purchase Obligation by Category of Item Purchased [Axis] Purchase Obligations Unrecorded Unconditional Purchase Obligation [Line Items] Purchase commitments Unrecorded Unconditional Purchase Obligation US Treasury Securities [Member] U.S. Treasury securities Valuation Allowances and Reserves, Charged to Cost and Expense Charged to Cost/Expense Valuation Technique [Axis] Valuation Allowances and Reserves, Balance Balance at Beginning of Period Balance at End of Period Valuation Allowances and Reserves, Deductions Deductions Valuation Technique [Domain] Valuation Allowances and Reserves, Charged to Other Accounts Charged to Other Accounts SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS Valuation and Qualifying Accounts Disclosure [Line Items] SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS Variable Interest Entity, Consolidated, Carrying Amount, Assets Total assets of consolidated VIE Variable Interest Entity, Primary Beneficiary [Member] Consolidated Variable Interest Entities Maximum exposure to loss Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount VARIABLE INTEREST ENTITIES Variable Interest Entity [Line Items] Non-consolidated Variable Interest Entities Variable Interest Entity, Not Primary Beneficiary [Member] Variable Interest Entity, Consolidated, Carrying Amount, Liabilities Total liabilities of consolidated VIE Variable Interest Entities [Axis] Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets Carrying Amount of Assets Weighted Average Number of Shares Outstanding, Diluted [Abstract] Weighted average shares outstanding Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Weighted average common shares outstanding Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Weighted average shares outstanding and common stock equivalents Valuation and Qualifying Accounts Disclosure [Table] Valuation Allowances and Reserves Type [Axis] Valuation Allowances and Reserves [Domain] Stockholders' Equity, Other Other capital adjustments Other than Temporary Impairment, Credit Losses Recognized in Earnings [Table Text Block] Schedule of impairment charges related to investment in third party brokerage firm Debt Instrument Aggregate Additional Interest Represents the aggregate amount of additional interest on the debt due to credit downgrades. Aggregate additional interest per annum Stock Issued During Period, Shares, Treasury Stock Reissued Number of treasury stock reissued for the settlement of RSUs Stock Issued During Period, Value, Treasury Stock Reissued Value of treasury stock reissued for the settlement of RSUs Other Comprehensive Income (Loss), Net of Tax Total other comprehensive income (loss) Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent Foreign currency translation adjustment Foreign currency translation adjustment, attributable to parent Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent Unrealized gain (loss) on available-for-sale securities, net of tax Error Corrections in Accounts Payable and Accrued Expenses and Rent and Occupancy Expense Attributable to Years Prior to 2010 Reduction in accounts payable, accrued expenses and rent and occupancy expense related to years prior to 2010 Represents the potential impact if error corrections were applied to years prior to 2010 in accounts payable, accrued expenses, and rent and occupancy expense as a result of a cumulative error correction recorded during the period. Maturity Period [Axis] Maturity Period [Domain] Maturity by December 2013 [Member] Maturity by December 2013 Represents the maturity period of lender commitments by December 2013. Maturity by December 2015 [Member] Maturity by December 2015 Represents the maturity period of lender commitments by December 2015. Deferred Tax Assets Tax Deferred Expense Capitalized Research and Development Capitalized R&D expenses Represents the amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from capitalized research and development expenses. Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals Accrued reserve Variation Margin on Net Long Derivative Contracts Related to Exchange Traded Futures Included Within Receivables from Brokers Dealers and Clearing Organizations Variation margin on net long derivative contracts related to exchange traded futures included within receivables from brokers, dealers and clearing organizations Represents the amount of variation margin on net long derivative contracts related to exchange traded futures included within receivables from brokers, dealers and clearing organizations as of date. Variation Margin on Net Short Derivative Contracts Related to Exchange Traded Futures Included within Receivables from Brokers Dealers and Clearing Organizations Variation margin on net short derivative contracts related to exchange traded futures included within receivables from brokers, dealers and clearing organizations Represents the amount of variation margin on net short derivative contracts related to exchange traded futures included within receivables from brokers, dealers and clearing organizations as of date. Fair Value Measurements, Nonrecurring [Table Text Block] Schedule of balance of equity method investments that have been measured at fair value on a non-recurring basis Fair Value, Measurements, Nonrecurring [Member] Fair value measured on a non-recurring basis Equity Method Investments, Fair Value Disclosure Other Assets: Investments accounted for under the cost method and equity method Debt Instrument, Repurchase Amount Aggregate purchase price Debt Instrument, Repurchased Face Amount Principal amount Variable Interest Entity Direct Equity Interests and Convertible Note [Member] VIEs in the form of direct equity interests and a convertible note Variable Interest Entities (VIEs) in the form of direct equity interests and a convertible note. Variable Interest Entity Trading Margin Accounts [Member] VIEs in the form of trading margin accounts Variable Interest Entities (VIEs) in the form of trading margin accounts. UK Based Brokerage Trading and Investment Firm [Member] UK based brokerage, trading and investment firm Represents information pertaining to unconsolidated UK brokerage and trading operations acquired firm in which the entity has investment in common stock accounted for under the equity method of accounting and for which certain information is required or determined to be disclosed. Number of Equity Method Investments Number of equity method investments Represents the number of equity method investments held by the entity that are immaterial for summarized financial information disclosure purposes. Equity Method Investment, Summarized Financial Information, Liabilities Total liabilities Equity Method Investment, Summarized Financial Information, Assets Total assets Equity Method Investment, Summarized Financial Information, Revenue Revenues Equity Method Investment, Summarized Financial Information, Gross Profit (Loss) Gross profit Equity Method Investment, Summarized Financial Information, Net Income (Loss) Net income GFI Brokers LLC and Amerex Brokers LLc [Member] GFI Brokers LLC and Amerex Brokers LLC Represents information pertaining to GFI Brokers LLC and Amerex Brokers LLC. Minimum Net Capital Required for Broker-Dealer Subsidiary Adjusted net capital for brokers Minimum Net Capital Required for Broker Dealer Subsidiary Per Office Adjusted net capital for brokers per office Minimum amount of net capital required to be maintained by the entity's broker-dealer subsidiary to engage in securities transactions per office. Minimum Net Capital Required for Broker Dealer Subsidiary Per Associated Person Adjusted net capital for brokers per associated person Minimum amount of net capital required to be maintained by the entity's broker-dealer subsidiary to engage in securities transactions per associated person. Represents the potential impact if error corrections were applied to prior years in accounts payable, accrued expenses, and rent and occupancy expense as a result of a cumulative error correction recorded during the period. Reduction in accounts payable, accrued expenses and rent and occupancy expense Error Corrections Impact in Accounts Payable and Accrued Expenses and Rent and Occupancy Expense to Prior Years Variable Interest Entities Form [Axis] Information about the form of a Variable Interest Entity (VIE). Variable Interest Entities Form [Domain] The form of a Variable Interest Entity (VIE). Dilutive Options RSUs And Contingently Issuable Shares Effect of dilutive options, RSUs and other contingently issuable shares Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of options, RSUs, and contingently issuable shares.