GAIN Capital 10-Q 10 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	May 06, 2019
Document Documentand Entity Information [Abstract]
Entity Registrant Name	GAIN Capital Holdings, Inc.
Trading Symbol	GCAP
Entity Central Index Key	0001444363
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		36,891,933

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
ASSETS:
Cash and cash equivalents	$ 218,019	$ 278,850
Restricted Cash and Investments	869,688
Cash and securities held for customers	774,743	842,478
Receivables from brokers	98,674	84,271
Property and equipment, net	29,926	30,579
Intangible assets, net	29,438	32,195
Goodwill	28,040	27,820
Other assets	50,492	36,355
Total assets	1,324,277	1,332,548
Liabilities
Payables to customers	869,688	842,478
Payables to brokers	0	1,635
Accrued compensation and benefits	3,291	11,227
Accrued expenses and other liabilities	46,930	41,562
Income tax payable	1,193	5,764
Convertible senior notes	133,680	132,109
Total liabilities	1,054,782	1,034,775
Commitments and contingent liabilities
Shareholders’ equity
Common stock ($0.00001 par value; 120 million shares authorized, 54.7 million shares issued and 37.4 million shares outstanding as of March 31, 2019; 54.5 million shares issued and 37.8 million shares outstanding as of December 31, 2018)	0	0
Additional paid-in capital	244,901	243,216
Retained earnings	173,875	204,483
Accumulated other comprehensive loss	(24,564)	(29,410)
Treasury stock, at cost (17.3 million shares at March 31, 2019 and 16.7 million at December 31, 2018)	(124,717)	(120,516)
Total shareholders’ equity	269,495	297,773
Total liabilities and shareholders’ equity	$ 1,324,277	$ 1,332,548

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Common stock, shares authorized (in shares)	120,000,000	120,000,000
Common stock, shares issued (in shares)	54,690,185	54,507,742
Common stock, shares outstanding (in shares)	37,371,333	37,821,686
Treasury stock, shares (in shares)	17,318,582	16,686,056

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
REVENUE:
Total non-interest revenue	$ 34,754	$ 96,660
Interest revenue	4,294	2,074
Interest expense	613	374
Total net interest revenue	3,681	1,700
Net revenue	38,435	98,360
EXPENSES:
Employee compensation and benefits	20,255	24,338
Selling and marketing	10,224	5,971
Referral fees	7,098	11,431
Trading expenses	5,480	5,811
General and administrative	12,756	12,464
Depreciation and amortization	4,250	5,368
Purchased intangible amortization	3,329	3,668
Communications and technology	5,691	5,391
Bad debt provision	427	1,118
Impairment of investment	0	(130)
Total operating expense	69,510	75,430
OPERATING (LOSS)/PROFIT	(31,075)	22,930
Interest expense on long term borrowings	3,332	3,340
(LOSS)/INCOME BEFORE INCOME TAX	(34,407)	19,590
Income tax (benefit)/expense	(6,053)	7,676
Net (loss)/income from continuing operations	(28,354)	11,914
Income from discontinued operations	0	4,347
NET (LOSS)/INCOME	(28,354)	16,261
Less income attributable to non-controlling interest	0	175
NET (LOSS)/INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.	(28,354)	16,086
Other comprehensive income:
Foreign currency translation adjustment	4,846	9,474
COMPREHENSIVE (LOSS)/INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.	(23,508)	25,560
Retail revenue
REVENUE:
Total non-interest revenue	24,279	84,120
Futures revenue
REVENUE:
Total non-interest revenue	7,990	10,645
Other revenue
REVENUE:
Total non-interest revenue	$ 2,485	$ 1,895

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Operations and Comprehensive Income (Parenthetical) $ in Thousands	3 Months Ended
	Jun. 30, 2018USD ($)
Income Statement [Abstract]
Gain on sale	$ 69,439
Income tax	$ 3,222

Condensed Consolidated Statem_3

Condensed Consolidated Statement of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
BEGINNING BALANCE (in shares) at Dec. 31, 2017		45,152,299
BEGINNING BALANCE at Dec. 31, 2017	$ 285,748	$ 0	$ (56,927)	$ 235,659	$ 122,686	$ (15,670)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) applicable to Gain Capital Holdings, Inc.	16,086				16,086
Exercise of options (in shares)		56,500
Exercise of options	443			443
Conversion of restricted stock into common stock (in shares)		275,314
Conversion of restricted stock into common stock	0
Purchase of treasury stock (in shares)		(580,064)
Purchase of treasury stock	(4,187)		(4,187)
Shares withheld for net settlements of share-based awards (in shares)		(2,424)
Shares withheld for net settlements of share-based awards	(18)		(18)
Share-based compensation	1,458			1,458
Adjustment to fair value of redeemable non-controlling interests	(367)				(367)
Dividends ($0.06 per share)	(2,643)				(2,643)
Foreign currency translation adjustment	9,474					9,474
ENDING BALANCE (in shares) at Mar. 31, 2018		44,901,625
ENDING BALANCE at Mar. 31, 2018	305,994	$ 0	(61,132)	237,560	135,762	(6,196)
BEGINNING BALANCE (in shares) at Dec. 31, 2018		37,821,686
BEGINNING BALANCE at Dec. 31, 2018	297,773	$ 0	(120,516)	243,216	204,483	(29,410)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) applicable to Gain Capital Holdings, Inc.	(28,354)				(28,354)
Conversion of restricted stock into common stock (in shares)		182,443
Conversion of restricted stock into common stock	0
Purchase of treasury stock (in shares)		(632,796)
Purchase of treasury stock	(4,201)		(4,201)
Share-based compensation	1,685			1,685
Adjustment to fair value of redeemable non-controlling interests	0
Dividends ($0.06 per share)	(2,254)				(2,254)
Foreign currency translation adjustment	4,846					4,846
ENDING BALANCE (in shares) at Mar. 31, 2019		37,371,333
ENDING BALANCE at Mar. 31, 2019	$ 269,495	$ 0	$ (124,717)	$ 244,901	$ 173,875	$ (24,564)

Condensed Consolidated Statem_4

Condensed Consolidated Statement of Changes in Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Stockholders' Equity [Abstract]
Dividends declared (usd per share)	$ 0.06	$ 0.06

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net (loss)/income	$ (28,354)	$ 16,261
Adjustments to reconcile net (loss)/income to cash used in operating activities
Gain on foreign currency exchange rates	(964)	(1,325)
Depreciation and amortization	7,579	9,872
Deferred tax benefit	(6,695)	(1,607)
Amortization of deferred financing costs	149	163
Bad debt provision	427	1,118
Convertible senior notes discount amortization	1,422	1,350
Share-based compensation	1,685	1,458
Interest earned on investments	(629)	(37)
Amortization of right of use asset	524
Changes in operating assets and liabilities:
Receivables from brokers	(11,932)	7,304
Other assets	4,676	1,441
Payables to customers	17,826	(36,875)
Payables to brokers	(1,635)	(2,789)
Accrued compensation and benefits	(7,990)	(1,538)
Accrued expenses and other liabilities	(4,641)	(523)
Income tax payable	(4,025)	3,125
Long term securities	10,363	(24,751)
Lease liabilities	(705)
Net cash used in operating activities	(22,919)	(27,353)
Cash used in operating activities - continuing operations	(22,919)	(28,994)
Cash provided by operating activities - discontinued operations	0	1,641
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(3,126)	(3,938)
Purchase of minority interest	(2,422)	0
Net cash used in investing activities	(5,548)	(3,938)
Cash used in investing activities - continuing operations	(5,548)	(3,677)
Cash used in investing activities - discontinued operations	0	(261)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	0	443
Purchase of treasury stock	(4,201)	(4,205)
Dividend payments	(2,254)	(2,643)
Distributions to non-controlling interest holders	0	(90)
Net cash used in financing activities	(6,455)	(6,495)
Effect of exchange rate changes on cash and cash equivalents	11,068	27,406
NET DECREASE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	(23,854)	(10,380)
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH — Beginning of period	1,016,616	1,188,516
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH — End of period	992,762	1,178,136
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH — End of period	1,016,616	1,188,516
Cash paid during the year for:
Interest	2,856	2,585
Income taxes	5,507	166
Non-cash financing activities:
Adjustment to redemption value of non-controlling interests	$ 0	$ (367)

DESCRIPTION OF BUSINESS AND BAS

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION	DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION Description of Business GAIN Capital Holdings, Inc. (together with its subsidiaries, the “Company”) is a global provider of trading services and solutions, specializing in over-the-counter ("OTC") and exchange-traded markets. The Company operates its business in two segments. Through its retail segment, the Company provides its retail customers around the world with access to a diverse range of global financial markets, including spot forex, precious metals, spread bets and contracts for difference ("CFDs") on currencies, commodities, indices, individual equities, cryptocurrencies, bonds and interest rate products, as well as OTC options. The Company’s futures segment offers execution and risk management services for exchange-traded products on major U.S. and European exchanges, including Bitcoin. For more information about the Company’s segments, please see Note 17 . Basis of Presentation and Principles of Consolidation The accompanying unaudited Condensed Consolidated Financial Statements reflect all adjustments that, in the opinion of management, are necessary for a fair presentation of the financial statements for the interim periods. The Condensed Consolidated Financial Statements are presented in accordance with accounting principles generally accepted in the United States of America (“US GAAP”) and have been prepared in accordance with the regulations of the Securities and Exchange Commission (“SEC”) for interim financial statements, and, in accordance with SEC rules, omit or condense certain information and footnote disclosures. Results for the interim periods are not necessarily indicative of results to be expected for any other interim period or for the full year. These financial statements should be read in conjunction with the audited Consolidated Financial Statements and related notes included in the Company’s Annual Report on Form 10-K as of and for the year ended December 31, 2018 , filed with the SEC on March 11, 2019. All significant intercompany transactions and balances have been eliminated in consolidation. The preparation of consolidated financial statements in conformity with US GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the Condensed Consolidated Financial Statements and the reported amounts of revenue and expenses during the reporting period. Estimates, by their nature, are based on judgment and available information. Therefore, actual results could differ from those estimates and could have a material impact on the consolidated financial statements, and it is possible that such changes could occur in the near term. Sale of GTX ECN Business On June 29, 2018, the Company completed the sale of its GTX ECN business, which previously comprised the Company's institutional segment, to Deutsche Börse Group, via its FX unit, 360T, for a total purchase price of $100 million less a working capital adjustment which amounted to a $0.2 million reduction in the purchase price. During the quarter ended June 30, 2018, the Company determined that the institutional segment met the discontinued operations criteria set forth in Accounting Standards Codification ("ASC") Subtopic 205-20-45, Presentation of Financial Statements . As such, the institutional segment results have been classified as discontinued operations in the accompanying Condensed Consolidated Statements of Operations and Comprehensive (Loss)/Income for the three months ended March 31, 2018 . For more information relating to the discontinued operations of the Company's GTX ECN business, please see Note 4 . Cash and securities held for customers Cash and securities held for customers represent cash and highly liquid assets held to fund customer liabilities in connection with trading positions and customers' cash balances. Included in this balance are funds deposited by customers and funds accruing to customers as a result of trades or contracts. The Company records a corresponding liability in connection with this amount in Payables to customers on the Condensed Consolidated Balance Sheets. As of March 31, 2019 and December 31, 2018 , $104.9 million and $104.7 million , respectively, of total C ash and securities held for customers were invested in U.S. government and agency securities, of which $94.9 million were long-term and $10.0 million were short-term as of March 31, 2019 , and all of which were long-term as of December 31, 2018 . For more information relating to C ash and securities held for customers , please see Note 6 . Such securities are carried at fair value, with unrealized and realized gains and losses included in interest revenue in the Condensed Consolidated Statement of Operations and Comprehensive (Loss)/Income. In addition, the Company holds certain customer funds in segregated or secured broker accounts. Legally segregated balances are not available for general use, in accordance with certain jurisdictional regulatory requirements. The table below further breaks out the Cash and securities held for customers on the Condensed Consolidated Balance Sheets: March 31, 2019 2018 Cash and cash equivalents held for customers $ 774,743 $ 938,432 Marketable securities held for customers 94,945 24,789 Cash and securities held for customers $ 869,688 $ 963,221 Long term securities held for customers reclassification To conform with current period presentation, Long term securities were reclassified in the Statement of Cash Flows for the three months ended March 31, 2018 . An amount equal to $24.8 million that was previously a component of the ending Cash and cash equivalents reconciliation is now separately shown within the operating activities section in the Statement of Cash Flows. Non-controlling interest In December 2018, the minority owners of Top Third Ag Marketing, LLC ("TT") notified the Company that they were exercising their put option with respect to their combined 21% ownership of TT. The purchase of the minority ownership interest closed on February 1, 2019 for approximately $2.4 million . Significant Accounting Policies - Leases Effective January 1, 2019, the Company accounts for its leases under ASC 842, Leases . The Company determines if an arrangement is, or contains, a lease at the inception date. Operating leases are included in right-of-use assets, with the related liabilities included in operating lease liabilities in the Condensed Consolidated Balance Sheet. Operating lease assets represent the Company's right to use an underlying asset for the lease term and lease liabilities represent the Company's obligation to make lease payments arising from the lease. Operating lease assets and liabilities are recognized at the lease commencement date based on the estimated present value of lease payments over the lease term. The Company uses the estimated incremental borrowing rate in determining the present value of lease payments. Variable components of the lease payments such as fair market value adjustments, utilities, and maintenance costs are expensed as incurred and not included in determining the present value. The lease terms include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. The Company has lease agreements with lease and non-lease components which are accounted for as a single lease component. As an accounting policy election, the Company excludes short-term leases having initial terms of 12 months or less from the new guidance. Lease expense is recognized on a straight-line basis over the lease term. See Note 3 for additional information on leases. The Company continues to account for leases in the prior period financial statements under ASC Topic 840.

ACCOUNTING PRONOUNCEMENTS

ACCOUNTING PRONOUNCEMENTS	3 Months Ended
	Mar. 31, 2019
Accounting Changes and Error Corrections [Abstract]
ACCOUNTING PRONOUNCEMENTS	ACCOUNTING PRONOUNCEMENTS Recently Adopted In February 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2016-02, Leases (Topic 842) , which amended the guidance on accounting for leases. The FASB issued this update to increase transparency and comparability among organizations. This update requires the recognition of lease assets and lease liabilities on the balance sheet and the disclosure of key information about leasing arrangements. The Company adopted the ASU effective January 1, 2019 using the additional (optional) approach, in accordance with ASU 2018-11 Leases (Topic 842): Targeted Improvements . The Company recorded a right of use asset and lease liability of $12.6 million and $14.9 million , in Other assets and Accrued expenses and other liabilities , respectively. There was no effect on opening retained earnings, and the Company continues to account for leases in the prior period financial statements under ASC Topic 840. In adopting the new standard, the Company elected the package of practical expedients permitted under the adoption of the new standard, which allowed the Company to account for existing leases under their current classification, as well as omit any new costs classified as initial direct costs, under the new standard. This election kept the existing agreements as operating leases. The Company also elected the practical expedient allowing an accounting policy election by class of underlying asset, to account for separate lease and nonlease components as a single lease component. See Note 3 for additional information on leases.

LEASES

LEASES	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
LEASES	LEASES The Company leases office space under agreements classified as operating leases that expire on various dates through 2025. Most of the Company’s lease related assets and liabilities result from the lease of its corporate headquarters in New Jersey, which expires in 2025, and its London office space, which expires in 2023. Such leases do not require any contingent rental payments, impose any financial restrictions, or contain any residual value guarantees. Certain of the Company’s leases include renewal options and escalation clauses; renewal options have not been included in the calculation of the lease liabilities and right of use assets as the Company is not reasonably certain to exercise the options. The Company does not act as a lessor or have any leases classified as financing leases. At March 31, 2019 , the Company had operating lease liabilities of $14.4 million and right of use assets of $12.2 million, which were included in Accrued expenses and other liabilities and Other assets , respectively, in the Condensed Consolidated Balance Sheet. The following summarizes quantitative information about the Company’s operating leases (amounts in thousands, except lease term and discount rate): Three months ended March 31, 2019 Lease cost Operating lease cost $ 796 Total lease cost $ 796 Other information Operating cash flows from operating leases $ 866 Weighted-average remaining lease term - operating leases 3.2 years Weighted-average discount rate - operating leases 7.5 % Maturities of the Company's operating leases, excluding short-term leases, are as follows (amounts in thousands): For the nine months ending at December 31, 2019 $ 2,598 For the year ended December 31, 2020 3,370 For the year ended December 31, 2021 3,492 For the year ended December 31, 2022 3,223 For the year ended December 31, 2023 2,271 For the year ended December 31, 2024 1,215 Thereafter 1,114 Total 17,283 Less: imputed interest (2,846 ) Operating lease liabilities at March 31, 2019 $ 14,437 Total rent expense, which is recorded on a straight-line basis, was $1.5 million for the three months ended March 31, 2019 .

REVENUE RECOGNITION

REVENUE RECOGNITION	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
REVENUE RECOGNITION	REVENUE RECOGNITION Futures Revenue Futures revenue consists primarily of commissions earned on futures and futures options trades. The Company executes trades on behalf of its futures customers, for which the Company earns commissions. The Company is not exposed to any market risk in connection with that activity. The Company’s futures revenue performance obligations also consist of trade execution and are satisfied on the trade date; accordingly, commission revenues are recorded on the trade date. Disaggregation of Revenues The following table presents the Company’s revenue from contracts with customers disaggregated by customer and service type for the services described above, as it relates to the futures segment for the three months ended March 31, 2019 and 2018 (amounts in thousands): Three Months Ended March 31, 2019 2018 Futures Direct Customers (1) $ 2,556 $ 2,473 Indirect Customers (2) 5,434 7,029 Other (3) 1,420 1,989 Total Segment Revenue $ 9,410 $ 11,491 (1) Direct customers are all customers not classified as indirect (2) Indirect customers are referred to the Company by introducing brokers (3) Other revenue comprises interest and fees Contract Assets and Contract Liabilities The timing of revenue recognition may differ from the timing of payment. The Company records an accrual when revenue is recognized prior to payment and when the Company has an unconditional right to payment. The Company records a contract liability when payment is received, prior to the time at which the service obligation is satisfied.

DISCONTINUED OPERATIONS

DISCONTINUED OPERATIONS	3 Months Ended
	Mar. 31, 2019
Discontinued Operations and Disposal Groups [Abstract]
DISCONTINUED OPERATIONS	DISCONTINUED OPERATIONS On June 29, 2018 , the Company completed the sale of its GTX ECN business, which previously comprised the Company's institutional segment, to Deutsche Börse via its FX unit, 360T, for a total purchase price of $100 million less a working capital adjustment which amounted to a $0.2 million reduction in purchase price. The Company determined that the sale of the GTX business qualifies as a discontinued operation under the criteria set forth in Accounting Standards Codification 205-20-45, Presentation of Financial Statements and the Company does not have any significant continuing involvement in these operations. There were no operations from the discontinued segment for the three months ended March 31, 2019 and there were no assets held for sale as of March 31, 2019 . The results of operations from the discontinued segment for the three months ended March 31, 2018 are as follows (in thousands): Three Months Ended March 31, 2018 REVENUE: Institutional revenue $ 8,455 Total non-interest revenue 8,455 Interest revenue 48 Total net interest revenue 48 Net revenue $ 8,503 EXPENSES: Employee compensation and benefits $ 3,413 Trading expenses 2,657 Other expenses 2,064 Total operating expense $ 8,134 OPERATING PROFIT 369 INCOME BEFORE INCOME TAX BENEFIT 369 Income tax benefit (3,978 ) NET INCOME FROM DISCONTINUED OPERATIONS $ 4,347

FAIR VALUE MEASUREMENT

FAIR VALUE MEASUREMENT	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENT	FAIR VALUE INFORMATION US GAAP defines fair value as the price that would be received in exchange for an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The guidance establishes a three level hierarchy that ranks the quality and reliability of information used in developing fair value estimates for financial instruments. The hierarchy gives the highest priority to quoted prices in active markets and the lowest priority to unobservable data. In cases where two or more levels of inputs are used to determine fair value, a financial instrument’s level is determined based on the lowest level input that is considered significant to the fair value measurement in its entirety. The three levels of fair value hierarchy are summarized below: Level 1 - Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities; Level 2 - Quoted prices in markets that are not considered to be active or financial instruments for which all significant inputs are observable, either directly or indirectly; and Level 3 - Valuations that require inputs that are both unobservable to a market participant and significant to the fair value measurement. For assets and liabilities that are transferred between levels during the period, fair values are ascribed as if the assets or liabilities had been transferred as of the beginning of the period. The following table presents the Company’s assets and liabilities that were measured at fair value on a recurring basis during the reporting period and the related hierarchy levels (amounts in thousands): Fair Value Measurements on a Recurring Basis Level 1 Level 2 Level 3 Total Financial Assets/(Liabilities): Cash and securities held for customers: US treasury bills: U.S. government and agency securities - long term $ 94,945 $ — $ — $ 94,945 US treasury bills: U.S. government and agency securities - short term 9,963 — — 9,963 Receivable from brokers: Broker derivative contracts — 1,787 — 1,787 Other assets: Certificates of deposit 177 — — 177 Other 129 — — 129 Payables to customers: Customer derivative contracts — 105,536 — 105,536 Total $ 105,214 $ 107,323 $ — $ 212,537 Fair Value Measurements on a Recurring Basis Level 1 Level 2 Level 3 Total Financial Assets/(Liabilities): Cash and securities held for customers: US treasury bills: U.S. government and agency securities - long term $ 104,712 $ — $ — $ 104,712 Receivable from brokers: Broker derivative contracts — (7,637 ) — (7,637 ) Other assets: Certificates of deposit 176 — — 176 Other 128 — — 128 Payables to customers: Customer derivative contracts — 144,440 — 144,440 Payables to brokers: Broker derivative contracts — 1,457 — 1,457 Total $ 105,016 $ 138,260 $ — $ 243,276 The Company has not changed its valuation techniques in measuring the fair value of any financial assets and liabilities during the three months ended March 31, 2019 , nor has there been any movement between levels during the period. Level 1 Financial Assets The Company has U.S. Treasury bills and certificates of deposit that are Level 1 financial instruments that are recorded based upon listed or quoted market rates. The U.S. Treasury bills are recorded in Cash and cash equivalents and Cash and securities held for customers and the certificates of deposit are recorded in Other assets . Level 2 Financial Assets and Liabilities The Company has customer derivative contracts that are Level 2 financial instruments recorded in Payables to customers. The Company has broker derivative contracts that are Level 2 financial instruments recorded in Receivables from brokers and Payables to brokers. The fair values of these Level 2 financial instruments are based upon directly observable values for underlying instruments. Level 3 Financial Liabilities The Company did not have any Level 3 Financial Assets or Liabilities as of March 31, 2019 or December 31, 2018 . Financial Instruments Not Measured at Fair Value The table below presents the carrying value, fair value and fair value hierarchy category of certain financial instruments that are not measured at fair value in the Condensed Consolidated Balance Sheets (amounts in thousands). Receivables from brokers comprise open trades, which are measured at fair value, and the Company’s posted funds with brokers that are required as collateral for holding trading positions, which are not measured at fair value but approximate fair value. These deposits approximate fair value because they are cash balances that the Company may withdraw at its discretion. Settlement would be expected to occur within a relatively short period of time once a withdrawal is initiated. Payables to customers comprise open trades, which are measured at fair value, and customer deposits that the Company holds for its role as clearing broker. These deposits are not measured at fair value, but approximate fair value, because they are cash balances that the Company or its customers can settle at either party’s discretion. Such settlement would occur within a relatively short period of time once a withdrawal is initiated. Payables to brokers comprise open trades, which are measured at fair value and the cash due to or from brokers. The cash within this balance is not measured at fair value but does approximate fair value, because it is immediately payable to the brokers. Settlement with brokers generally occurs as soon as a broker initiates a margin call. The carrying value of Convertible senior notes represents the notes’ principal amounts net of unamortized discount (please refer to Note 12 ). The Company assessed the notes’ fair value as determined by current Company-specific and risk free interest rates as of the balance sheet date. As of March 31, 2019 Fair Value Measurements using: Carrying Value Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Financial Assets: Receivables from brokers $ 96,887 $ 96,887 $ — $ 96,887 $ — Financial Liabilities: Payables to customers $ 975,224 $ 975,224 $ — $ 975,224 $ — Convertible senior notes $ 133,680 $ 156,665 $ — $ 156,665 $ — As of December 31, 2018 Fair Value Measurements using: Carrying Value Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Financial Assets: Receivables from brokers $ 91,908 $ 91,908 $ — $ 91,908 $ — Financial Liabilities: Payables to customers $ 986,918 $ 986,918 $ — $ 986,918 $ — Payables to brokers $ 3,092 $ 3,092 $ 3,092 Convertible senior notes $ 132,109 $ 158,752 $ — $ 158,752 $ —

DERIVATIVES

DERIVATIVES	3 Months Ended
	Mar. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVES	DERIVATIVES The Company’s contracts with its customers and its liquidity providers are deemed to be derivative instruments. The table below represents the fair values of the Company’s derivative instruments reported within Receivables from brokers, Payables to customers and Payables to brokers on the accompanying Condensed Consolidated Balance Sheets (amounts in thousands): March 31, 2019 Gross amounts of Gross amount of Net amounts of Derivative Instruments: Foreign currency exchange contracts $ 72,642 $ (18,234 ) $ 54,408 CFD contracts 79,415 (30,699 ) 48,716 Metals contracts 5,851 (1,652 ) 4,199 Total $ 157,908 $ (50,585 ) $ 107,323 March 31, 2019 Cash Collateral Net amounts of Net amounts of Derivative Assets/(Liabilities): Receivables from brokers $ 96,887 $ 1,787 $ 98,674 Payables to customers $ (975,224 ) $ 105,536 $ (869,688 ) December 31, 2018 Gross amounts of Gross amount of Net amounts of Derivative Instruments: Foreign currency exchange contracts $ 100,158 $ (20,382 ) $ 79,776 CFD contracts 77,014 (21,220 ) 55,794 Metals contracts 6,438 (3,748 ) 2,690 Total $ 183,610 $ (45,350 ) $ 138,260 December 31, 2018 Cash Collateral Net amounts of Net amounts of Derivative Assets/(Liabilities): Receivables from brokers $ 91,908 $ (7,637 ) $ 84,271 Payables to customers $ (986,918 ) $ 144,440 $ (842,478 ) Payables to brokers $ (3,092 ) $ 1,457 $ (1,635 ) The Company’s derivatives include different underlyings which vary in price. Foreign exchange contracts typically have prices less than two dollars, while certain metals contracts and CFDs can have considerably higher prices. The amounts reported within Receivables from brokers, Payables to customers, and Payables to brokers on the Condensed Consolidated Balance Sheets are derived from the number of contracts below (amounts in thousands): March 31, 2019 Total contracts in long positions Total contracts in short positions Derivative Instruments: Foreign currency exchange contracts 2,863,433 2,265,453 CFD contracts 138,715 138,062 Metals contracts 598 127 Total 3,002,746 2,403,642 December 31, 2018 Total contracts in long positions Total contracts in short positions Derivative Instruments: Foreign currency exchange contracts 3,780,488 3,238,781 CFD contracts 98,840 134,546 Metals contracts 489 188 Total 3,879,817 3,373,515 The Company did not designate any of its derivatives as hedging instruments. Net gains with respect to derivative instruments reflected in Retail revenue in the accompanying Condensed Consolidated Statements of Operations and Comprehensive (Loss)/Income for the three months ended March 31, 2019 and 2018 were as follows (amounts in thousands): Three Months Ended March 31, 2019 2018 Derivative Instruments: Foreign currency exchange contracts $ 16,137 $ 41,251 CFD contracts 5,938 37,147 Metals contracts 2,204 5,722 Total $ 24,279 $ 84,120

RECEIVABLES FROM BROKERS

RECEIVABLES FROM BROKERS	3 Months Ended
	Mar. 31, 2019
Brokers and Dealers [Abstract]
RECEIVABLES FROM BROKERS	RECEIVABLES FROM BROKERS The Company has posted funds with brokers as collateral required by agreements for holding trading positions. These amounts are reflected as Receivables from brokers on the Condensed Consolidated Balance Sheets. Amounts receivable from brokers consisted of the following as of (amounts in thousands): March 31, 2019 December 31, 2018 Required collateral $ 96,887 $ 91,908 Open foreign exchange positions 1,787 (7,637 ) Total $ 98,674 $ 84,271

INTANGIBLE ASSETS

INTANGIBLE ASSETS	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
INTANGIBLE ASSETS	INTANGIBLE ASSETS The Company’s various intangible assets consisted of the following as of (amounts in thousands): March 31, 2019 December 31, 2018 Intangibles Gross Accumulated Net Gross Accumulated Net Customer lists $ 46,051 $ (29,728 ) $ 16,323 $ 58,494 $ (40,208 ) $ 18,286 Technology 24,246 (13,997 ) 10,249 49,430 (38,555 ) 10,875 Trademarks 6,200 (3,697 ) 2,503 7,308 (4,637 ) 2,671 Total finite lived intangibles 76,497 (47,422 ) 29,075 115,232 (83,400 ) 31,832 Trademark not subject to amortization (1) 363 — 363 363 — 363 Total intangibles $ 76,860 $ (47,422 ) $ 29,438 $ 115,595 $ (83,400 ) $ 32,195 (1) These indefinite-life trademarks relate to the forex.com and foreignexchange.com domain names where management determined there was no legal, regulatory or technological limitation on their useful lives. The Company compares the recorded value of the indefinite-life intangible assets to their fair value on an annual basis and whenever circumstances arise that indicate that impairment may have occurred. As of March 31, 2019 , the Company wrote-off $34.4 million of fully amortized intangible assets, which was an equal amount for both gross and accumulated amortization and did not have any impact on the results of operations or cash flows. The Company had the following identifiable intangible assets and weighted average amortization periods as of March 31, 2019 : Intangible Assets Weighted average amortization period Customer lists 8.2 years Technology 7.2 years Trademarks 7.0 years Amortization expense for the purchased intangibles was $3.3 million and $3.7 million for the three months ended March 31, 2019 and 2018 respectively. Goodwill Goodwill is evaluated for impairment on an annual basis on October 31 and in interim periods when events or changes indicate the carrying value may not be recoverable. The Company operates under two reporting units: retail and futures. There were no additions or impairments to the carrying value of the Company’s goodwill during the three months ended March 31, 2019 . The following represents the changes in the carrying amount of goodwill by segment (amounts in thousands): Retail Futures Total Carrying amount of goodwill as of December 31, 2018 $ 25,435 $ 2,385 $ 27,820 Foreign currency translation adjustments 201 19 220 Carrying amount of goodwill as of March 31, 2019 $ 25,636 $ 2,404 $ 28,040

RELATED PARTY TRANSACTIONS

RELATED PARTY TRANSACTIONS	3 Months Ended
	Mar. 31, 2019
Related Party Transactions [Abstract]
RELATED PARTY TRANSACTIONS	RELATED PARTY TRANSACTIONS Certain officers and directors of the Company have personal funds on deposit in separate customer accounts with the Company. These accounts are recorded in Payables to customers on the Condensed Consolidated Balance Sheets. The aggregate amount of these funds was $0.3 million and $0.4 million as of March 31, 2019 and December 31, 2018 , respectively. IPGL Limited, the majority selling shareholder in the acquisition of City Index, has a trading account with the Company which is recorded in Payables to customers on the Condensed Consolidated Balance Sheets. The aggregate amount of these funds was $11.9 million and $11.7 million as of March 31, 2019 and December 31, 2018 , respectively. The net revenue generated by any individual related party was not deemed to be material in any period. At March 31, 2019 , the Company had receivables of $0.1 million in the aggregate due from certain officers of the Company for taxes paid on equity vestings. The Company recorded these receivables in Other assets , and the Company received the funds in April 2019 . There were no receivables due from the Company's officers as of December 31, 2018 .

REVOLVING CREDIT ARRANGEMENT

REVOLVING CREDIT ARRANGEMENT	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
REVOLVING CREDIT ARRANGEMENT	REVOLVING CREDIT ARRANGEMENT On August 3, 2017 , the Company entered into a Credit Agreement, dated as of August 2, 2017 , for a three year $50.0 million senior secured first lien revolving credit facility that matures in August 2020. Upon request of the Company, the credit facility may be increased by up to $25.0 million , with a minimum increase of $5.0 million . The credit facility contains covenants that are customary for an issuer with senior debt. The commitment fees of $0.5 million are amortized over the life of the facility and are recorded to Other Assets . As of March 31, 2019, the Company was not in compliance with a covenant in the Credit Agreement relating to the Company's Consolidated Interest Coverage Ratio (as defined in the Credit Agreement). The lenders under the Credit Agreement have waived any event of default arising from this noncompliance for the quarter ended March 31, 2019. Further, the Company did not fully satisfy a covenant in the Credit Agreement relating to the Company's Consolidated Gross Leverage Ratio (as defined in the Credit Agreement) as of March 31, 2019, but was deemed to be in compliance with such covenant due to an alternative liquidity test provided in the Credit Agreement. The Company will not be able to draw funds under the Credit Agreement until it is in full compliance with all of the financial covenants in the Credit Agreement, including the Consolidated Gross Leverage Ratio and Consolidated Interest Coverage Ratio. As of March 31, 2019 and December 31, 2018 , there were no amounts outstanding under the revolving line of credit.

CONVERTIBLE SENIOR NOTES

CONVERTIBLE SENIOR NOTES	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
CONVERTIBLE SENIOR NOTES	CONVERTIBLE SENIOR NOTES On August 22, 2017, the Company issued $92.0 million aggregate principal amount of its 5.00% Convertible Senior Notes, due August 15, 2022, and on April 1, 2015, the Company issued $60.0 million aggregate principal amount of its 4.125% Convertible Senior Notes, due April 1, 2020 (collectively the "Convertible Senior Notes"). The balances of the liability and equity components of the Convertible Senior Notes as of March 31, 2019 and December 31, 2018 were as follows (amounts in thousands): March 31, 2019 December 31, 2018 Liability component - principal $ 152,000 $ 152,000 Deferred bond discount (17,959 ) (19,503 ) Deferred financing cost (361 ) (388 ) Liability component - net carrying value $ 133,680 $ 132,109 Additional paid in capital $ 39,405 $ 39,405 Discount attributable to equity (826 ) (826 ) Equity component $ 38,579 $ 38,579 Interest expense related to the Convertible Senior Notes, included in Interest expense on long term borrowings in the Condensed Consolidated Statements of Operations and Comprehensive (Loss)/Income , was as follows (amounts in thousands): For the Three Months Ended March 31, 2019 2018 Interest expense - stated coupon rate $ 1,761 $ 1,834 Interest expense - amortization of deferred bond discount and costs 1,571 1,506 Total interest expense - convertible senior notes $ 3,332 $ 3,340

(LOSS)_EARNINGS PER COMMON SHAR

(LOSS)/EARNINGS PER COMMON SHARE	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
(LOSS)/EARNINGS PER COMMON SHARE	(LOSS)/EARNINGS PER COMMON SHARE Basic and diluted (loss)/earnings per common share are computed by dividing net (loss)/income by the weighted average number of common shares outstanding during the period. Diluted (loss)/earnings per share includes the determinants of basic net (loss)/income per share and, in addition, gives effect to the potential dilution that would occur if securities or other contracts to issue common stock were exercised, vested or converted into common stock, unless they are anti-dilutive. Diluted weighted average common shares include vested and unvested stock options, unvested restricted stock units and unvested restricted stock awards. Diluted (loss)/earnings per share excludes any shares of Company common stock potentially issuable under the Company’s Convertible Senior Notes, which are discussed in Note 12 . Based upon an assumed trading price of $10 for each share of the Company’s common stock, and if the relevant conditions under the indenture governing the 2020 and 2022 Convertible Senior Notes were satisfied, there would be 0.2 million and 2.0 million dilutive shares as of March 31, 2019 , for the 2020 and 2022 Convertible Senior Notes, respectively. The following table sets forth the computation of (loss)/earnings per share (amounts in thousands except share and per share data): For the Three Months Ended March 31, 2019 2018 Net (loss)/income from continuing operations $ (28,354 ) $ 11,914 Less income attributable to non-controlling interests — 175 Net (loss)/income from continuing operations (28,354 ) 11,739 Adjustment (1) — (367 ) Net (loss)/income available to GAIN common shareholders from continuing operations $ (28,354 ) $ 11,372 Net income from discontinued operations — 4,347 Weighted average common shares outstanding: Basic weighted average common shares outstanding 37,525,073 45,017,716 Effect of dilutive securities: Stock options — 261,732 RSUs — 244,318 Diluted weighted average common shares outstanding 37,525,073 45,523,766 Basic (loss)/earnings from continuing operations $ (0.76 ) $ 0.25 Basic earnings from discontinued operations $ — $ 0.10 Diluted (loss)/earnings from continuing operations $ (0.76 ) $ 0.25 Diluted earnings from discontinued operations $ — $ 0.10 (1) During the three months ended March 31, 2018 , the Company concluded that the carrying values of the redeemable noncontrolling interests were less than redemption value and adjusted carrying value to equal redemption value. This adjustment was a component of the earnings per common share calculation. For the three months ended March 31, 2019 , all common stock equivalents are excluded from the computation of diluted loss per share from continuing operations, because the result would be anti-dilutive. The table below shows dilution that the Company would have experienced, under the treasury stock method, had the three months ended March 31, 2019 resulted in net income, rather than net loss. For the Three Months Ended March 31, 2019 Stock options (1) 169,981 RSUs 90,520 Total securities excluded from diluted loss per share calculation 260,501 (1) During the three months ended March 31, 2019 and three months ended March 31, 2018 , 0.4 million stock options were out of the money and excluded from the computation of diluted loss or earnings per share from continuing operations.

COMMITMENT AND CONTINGENCIES

COMMITMENT AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
COMMITMENT AND CONTINGENCIES	COMMITMENT AND CONTINGENCIES From time to time the Company becomes involved in legal proceedings and in each case the Company assesses the likely liability and/or the amount of damages as appropriate. Where available information indicates that it is probable a liability had been incurred at the date of the Condensed Consolidated Financial Statements and the Company can reasonably estimate the amount of that loss, the Company accrues the estimated loss by a charge to income. In many proceedings, however, it is inherently difficult to determine whether any loss is probable or even reasonably possible or to estimate the amount of any loss. In addition, even where loss is possible or an exposure to loss exists in excess of the liability already accrued with respect to a previously recognized loss contingency, it is often not possible to reasonably estimate the size of the possible loss or range of loss. For certain legal proceedings, the Company can estimate possible losses, additional losses, ranges of loss or ranges of additional loss in excess of amounts accrued. For certain other legal proceedings, the Company cannot reasonably estimate such losses, if any, since the Company cannot predict if, how or when such proceedings will be resolved or what the eventual settlement, fine, penalty or other relief, if any, may be, particularly for proceedings that are in their early stages of development or where plaintiffs seek substantial or indeterminate damages. Numerous issues must be developed, including the need to discover and determine important factual matters and the need to address novel or unsettled legal questions relevant to the proceedings in question, before a loss or additional loss or range of loss can be reasonably estimated for any proceeding.

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company's benefit for income taxes was approximately $6.1 million for three months ended March 31, 2019 and an expense provision of approximately $7.7 million for the three months ended March 31, 2018 . These amounts reflect the Company's estimate of the annual effective tax rates of 17.6% and 39.2% , adjusted for certain discrete items, for the three months ended March 31, 2019 and 2018 , respectively. Changes in the Company's effective tax rate arise primarily from changes in the geographic mix of revenues and expenses, as well as changes to statutory tax rates. Deferred income taxes reflect the net tax effects of temporary differences between the financial reporting and tax basis of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when such differences are expected to reverse. Certain net deferred tax assets of the Company are included in Other assets on the Condensed Consolidated Balance Sheets.

REGULATORY REQUIREMENTS

REGULATORY REQUIREMENTS	3 Months Ended
	Mar. 31, 2019
Banking and Thrift [Abstract]
REGULATORY REQUIREMENTS	REGULATORY REQUIREMENTS The following table illustrates the minimum regulatory capital the Company's subsidiaries were required to maintain as of March 31, 2019 and the actual amounts of capital that were maintained (amounts in millions): Entity Name Minimum Capital Excess Percent of GAIN Capital Group, LLC $ 34.7 $ 56.3 $ 21.6 162 % GAIN Capital Securities, Inc. 0.1 0.4 0.3 400 % GAIN Capital U.K., Ltd. 59.1 198.4 139.3 336 % GAIN Capital Japan Co., Ltd. 1.2 11.4 10.2 950 % GAIN Capital Australia, Pty. Ltd. 0.8 6.6 5.8 825 % GAIN Global Markets, Inc. 0.2 1.1 0.9 550 % GAIN Capital-Forex.com Canada, Ltd. 0.5 1.6 1.1 320 % GAIN Capital Singapore Pte., Ltd. 3.7 9.7 6.0 262 % Trade Facts, Ltd. 0.6 3.5 2.9 583 % Global Asset Advisors, LLC 0.0 2.8 2.8 100 % Total $ 100.9 $ 291.8 $ 190.9 289 %

SEGMENT INFORMATION

SEGMENT INFORMATION	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION ASC Topic 280, Disclosures about Segments of an Enterprise and Related Information , establishes standards for reporting information about operating segments. Operating segments are defined as components of an enterprise which engage in business activities from which they may earn revenues and incur expenses and about which separate financial information is available that is evaluated regularly by the chief operating decision-maker, or decision making group, in deciding how to allocate resources and in assessing performance. Reportable segments are defined as an operating segment that either (a) exceeds 10% of revenue, or (b) the reported profit or loss in absolute amount of which exceeds 10% of profit of all operating segments that did not report a loss or (c) exceeds 10% of the combined assets of all operating segments. The Company’s operations relate to global trading services and solutions. During the first quarter of 2018, the Company completed its implementation of global support groups in the areas of finance, legal, human resources, and treasury. These groups are now centrally managed and support all business functions. Therefore, all costs related to these groups previously recorded within the retail segment are now classified in the Company's corporate and other segment to better align the cost reporting with the support services. The change in segment reporting had no impact on the net profit or loss of the Company. To enable comparisons with prior period performance, historical segment information for the periods included in the tables below reflect this reporting change. On June 29, 2018, the Company completed the sale of its GTX ECN business, which previously comprised the Company's institutional segment, to Deutsche Börse Group via its FX unit, 360T, for a total purchase price of $100 million less a working capital adjustment which amounted to a $0.2 million reduction in purchase price. The Company determined that the institutional segment met the discontinued operations criteria set forth in ASC Subtopic 205-20-45, Presentation of Financial Statements , in the quarter ended June 30, 2018. As such, the institutional segment results have been classified as discontinued operations in the accompanying Condensed Consolidated Statements of Operations and Comprehensive (Loss)/Income. For more information relating to the discontinued operations of the Company's GTX ECN business, please see Note 4 . Retail Segment Business in the retail segment is conducted primarily through the Company’s FOREX.com and City Index brands. The Company provides its retail customers around the world with access to over 15,000 global financial markets, including spot forex, precious metals, and CFDs on currencies, commodities, indices, individual equities, cryptocurrencies, bonds and interest rate products, as well as OTC options on forex. In the United Kingdom, the Company also offer spread bets, which are investment products similar to CFDs, but that offer more favorable tax treatment to residents of that country. Futures Segment The futures segment offers execution and related services for exchange-traded futures and futures options on major U.S and European exchanges. The Company offers futures services through its subsidiaries, GAIN Capital Group, LLC, Global Asset Advisors, LLC, and Top Third Ag Marketing, LLC. Corporate and other Corporate and other provides general corporate services to the Company’s segments. Corporate and other revenue primarily comprises foreign currency transaction gains and losses. Selected financial information by segment is presented in the following tables (amounts in thousands): Three Months Ended March 31, 2019 2018 Retail reportable segment: Net revenue $ 28,159 $ 85,672 Employee compensation and benefits 12,992 15,425 Selling and marketing 9,953 5,666 Referral fees 4,390 7,685 Other operating expenses 18,228 17,730 Segment (loss)/profit $ (17,404 ) $ 39,166 Futures reportable segment: Net revenue $ 9,410 $ 11,491 Employee compensation and benefits 2,164 2,511 Selling and marketing 260 241 Referral fees 2,708 3,746 Other operating expenses 3,221 3,794 Segment profit $ 1,057 $ 1,199 Corporate and other: Other revenue $ 866 $ 1,197 Employee compensation and benefits 5,099 6,402 Selling and marketing 11 64 Other operating expenses 2,905 3,260 Loss $ (7,149 ) $ (8,529 ) TOTAL SEGMENT (LOSS)/PROFIT $ (23,496 ) $ 31,836 Depreciation and amortization $ 4,250 $ 5,368 Purchased intangible amortization 3,329 3,668 Impairment of investment — (130 ) OPERATING (LOSS)/PROFIT $ (31,075 ) $ 22,930 Interest expense on long term borrowings 3,332 3,340 (LOSS)/INCOME BEFORE INCOME TAX EXPENSE $ (34,407 ) $ 19,590

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	3 Months Ended
	Mar. 31, 2019
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS On April 25, 2019 , the Company declared a $0.06 dividend per share of Common Stock payable on June 28, 2019 to stockholders of record on June 24, 2019 .

DESCRIPTION OF BUSINESS AND B_2

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation and Principles of Consolidation	The accompanying unaudited Condensed Consolidated Financial Statements reflect all adjustments that, in the opinion of management, are necessary for a fair presentation of the financial statements for the interim periods. The Condensed Consolidated Financial Statements are presented in accordance with accounting principles generally accepted in the United States of America (“US GAAP”) and have been prepared in accordance with the regulations of the Securities and Exchange Commission (“SEC”) for interim financial statements, and, in accordance with SEC rules, omit or condense certain information and footnote disclosures. Results for the interim periods are not necessarily indicative of results to be expected for any other interim period or for the full year. These financial statements should be read in conjunction with the audited Consolidated Financial Statements and related notes included in the Company’s Annual Report on Form 10-K as of and for the year ended December 31, 2018 , filed with the SEC on March 11, 2019. All significant intercompany transactions and balances have been eliminated in consolidation. The preparation of consolidated financial statements in conformity with US GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the Condensed Consolidated Financial Statements and the reported amounts of revenue and expenses during the reporting period. Estimates, by their nature, are based on judgment and available information. Therefore, actual results could differ from those estimates and could have a material impact on the consolidated financial statements, and it is possible that such changes could occur in the near term.
Significant Accounting Policies - Leases	Effective January 1, 2019, the Company accounts for its leases under ASC 842, Leases . The Company determines if an arrangement is, or contains, a lease at the inception date. Operating leases are included in right-of-use assets, with the related liabilities included in operating lease liabilities in the Condensed Consolidated Balance Sheet. Operating lease assets represent the Company's right to use an underlying asset for the lease term and lease liabilities represent the Company's obligation to make lease payments arising from the lease. Operating lease assets and liabilities are recognized at the lease commencement date based on the estimated present value of lease payments over the lease term. The Company uses the estimated incremental borrowing rate in determining the present value of lease payments. Variable components of the lease payments such as fair market value adjustments, utilities, and maintenance costs are expensed as incurred and not included in determining the present value. The lease terms include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. The Company has lease agreements with lease and non-lease components which are accounted for as a single lease component. As an accounting policy election, the Company excludes short-term leases having initial terms of 12 months or less from the new guidance. Lease expense is recognized on a straight-line basis over the lease term. See Note 3 for additional information on leases. The Company continues to account for leases in the prior period financial statements under ASC Topic 840.
Recently Adopted	In February 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2016-02, Leases (Topic 842) , which amended the guidance on accounting for leases. The FASB issued this update to increase transparency and comparability among organizations. This update requires the recognition of lease assets and lease liabilities on the balance sheet and the disclosure of key information about leasing arrangements. The Company adopted the ASU effective January 1, 2019 using the additional (optional) approach, in accordance with ASU 2018-11 Leases (Topic 842): Targeted Improvements . The Company recorded a right of use asset and lease liability of $12.6 million and $14.9 million , in Other assets and Accrued expenses and other liabilities , respectively. There was no effect on opening retained earnings, and the Company continues to account for leases in the prior period financial statements under ASC Topic 840. In adopting the new standard, the Company elected the package of practical expedients permitted under the adoption of the new standard, which allowed the Company to account for existing leases under their current classification, as well as omit any new costs classified as initial direct costs, under the new standard. This election kept the existing agreements as operating leases. The Company also elected the practical expedient allowing an accounting policy election by class of underlying asset, to account for separate lease and nonlease components as a single lease component.
Revenue Recognition	Futures Revenue Futures revenue consists primarily of commissions earned on futures and futures options trades. The Company executes trades on behalf of its futures customers, for which the Company earns commissions. The Company is not exposed to any market risk in connection with that activity. The Company’s futures revenue performance obligations also consist of trade execution and are satisfied on the trade date; accordingly, commission revenues are recorded on the trade date.

DESCRIPTION OF BUSINESS AND B_3

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION (Tables)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Cash and Securities Held for Customers	The table below further breaks out the Cash and securities held for customers on the Condensed Consolidated Balance Sheets: March 31, 2019 2018 Cash and cash equivalents held for customers $ 774,743 $ 938,432 Marketable securities held for customers 94,945 24,789 Cash and securities held for customers $ 869,688 $ 963,221

LEASES (Tables)

LEASES (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Quantitative Information About Operating Leases	The following summarizes quantitative information about the Company’s operating leases (amounts in thousands, except lease term and discount rate): Three months ended March 31, 2019 Lease cost Operating lease cost $ 796 Total lease cost $ 796 Other information Operating cash flows from operating leases $ 866 Weighted-average remaining lease term - operating leases 3.2 years Weighted-average discount rate - operating leases 7.5 %
Maturities of Operating Leases	Maturities of the Company's operating leases, excluding short-term leases, are as follows (amounts in thousands): For the nine months ending at December 31, 2019 $ 2,598 For the year ended December 31, 2020 3,370 For the year ended December 31, 2021 3,492 For the year ended December 31, 2022 3,223 For the year ended December 31, 2023 2,271 For the year ended December 31, 2024 1,215 Thereafter 1,114 Total 17,283 Less: imputed interest (2,846 ) Operating lease liabilities at March 31, 2019 $ 14,437

REVENUE RECOGNITION (Tables)

REVENUE RECOGNITION (Tables)	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table presents the Company’s revenue from contracts with customers disaggregated by customer and service type for the services described above, as it relates to the futures segment for the three months ended March 31, 2019 and 2018 (amounts in thousands): Three Months Ended March 31, 2019 2018 Futures Direct Customers (1) $ 2,556 $ 2,473 Indirect Customers (2) 5,434 7,029 Other (3) 1,420 1,989 Total Segment Revenue $ 9,410 $ 11,491 (1) Direct customers are all customers not classified as indirect (2) Indirect customers are referred to the Company by introducing brokers (3) Other revenue comprises interest and fees

DISCONTINUED OPERATIONS (Tables

DISCONTINUED OPERATIONS (Tables)	3 Months Ended
	Mar. 31, 2019
Discontinued Operations and Disposal Groups [Abstract]
Disposal Groups, Including Discontinued Operations	The results of operations from the discontinued segment for the three months ended March 31, 2018 are as follows (in thousands): Three Months Ended March 31, 2018 REVENUE: Institutional revenue $ 8,455 Total non-interest revenue 8,455 Interest revenue 48 Total net interest revenue 48 Net revenue $ 8,503 EXPENSES: Employee compensation and benefits $ 3,413 Trading expenses 2,657 Other expenses 2,064 Total operating expense $ 8,134 OPERATING PROFIT 369 INCOME BEFORE INCOME TAX BENEFIT 369 Income tax benefit (3,978 ) NET INCOME FROM DISCONTINUED OPERATIONS $ 4,347

FAIR VALUE MEASUREMENT (Tables)

FAIR VALUE MEASUREMENT (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Assets and Liabilities Measured at Fair Value on Recurring Basis	The following table presents the Company’s assets and liabilities that were measured at fair value on a recurring basis during the reporting period and the related hierarchy levels (amounts in thousands): Fair Value Measurements on a Recurring Basis Level 1 Level 2 Level 3 Total Financial Assets/(Liabilities): Cash and securities held for customers: US treasury bills: U.S. government and agency securities - long term $ 94,945 $ — $ — $ 94,945 US treasury bills: U.S. government and agency securities - short term 9,963 — — 9,963 Receivable from brokers: Broker derivative contracts — 1,787 — 1,787 Other assets: Certificates of deposit 177 — — 177 Other 129 — — 129 Payables to customers: Customer derivative contracts — 105,536 — 105,536 Total $ 105,214 $ 107,323 $ — $ 212,537 Fair Value Measurements on a Recurring Basis Level 1 Level 2 Level 3 Total Financial Assets/(Liabilities): Cash and securities held for customers: US treasury bills: U.S. government and agency securities - long term $ 104,712 $ — $ — $ 104,712 Receivable from brokers: Broker derivative contracts — (7,637 ) — (7,637 ) Other assets: Certificates of deposit 176 — — 176 Other 128 — — 128 Payables to customers: Customer derivative contracts — 144,440 — 144,440 Payables to brokers: Broker derivative contracts — 1,457 — 1,457 Total $ 105,016 $ 138,260 $ — $ 243,276
Carrying Value and Fair Value and Fair Value Hierarchy Category of Financial Instruments Not Measured at Fair Value in Condensed Consolidated Statements of Financial Condition	The carrying value of Convertible senior notes represents the notes’ principal amounts net of unamortized discount (please refer to Note 12 ). The Company assessed the notes’ fair value as determined by current Company-specific and risk free interest rates as of the balance sheet date. As of March 31, 2019 Fair Value Measurements using: Carrying Value Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Financial Assets: Receivables from brokers $ 96,887 $ 96,887 $ — $ 96,887 $ — Financial Liabilities: Payables to customers $ 975,224 $ 975,224 $ — $ 975,224 $ — Convertible senior notes $ 133,680 $ 156,665 $ — $ 156,665 $ — As of December 31, 2018 Fair Value Measurements using: Carrying Value Fair Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Financial Assets: Receivables from brokers $ 91,908 $ 91,908 $ — $ 91,908 $ — Financial Liabilities: Payables to customers $ 986,918 $ 986,918 $ — $ 986,918 $ — Payables to brokers $ 3,092 $ 3,092 $ 3,092 Convertible senior notes $ 132,109 $ 158,752 $ — $ 158,752 $ —

DERIVATIVES (Tables)

DERIVATIVES (Tables)	3 Months Ended
	Mar. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fair Values of Derivative Instruments	The table below represents the fair values of the Company’s derivative instruments reported within Receivables from brokers, Payables to customers and Payables to brokers on the accompanying Condensed Consolidated Balance Sheets (amounts in thousands): March 31, 2019 Gross amounts of Gross amount of Net amounts of Derivative Instruments: Foreign currency exchange contracts $ 72,642 $ (18,234 ) $ 54,408 CFD contracts 79,415 (30,699 ) 48,716 Metals contracts 5,851 (1,652 ) 4,199 Total $ 157,908 $ (50,585 ) $ 107,323 March 31, 2019 Cash Collateral Net amounts of Net amounts of Derivative Assets/(Liabilities): Receivables from brokers $ 96,887 $ 1,787 $ 98,674 Payables to customers $ (975,224 ) $ 105,536 $ (869,688 ) December 31, 2018 Gross amounts of Gross amount of Net amounts of Derivative Instruments: Foreign currency exchange contracts $ 100,158 $ (20,382 ) $ 79,776 CFD contracts 77,014 (21,220 ) 55,794 Metals contracts 6,438 (3,748 ) 2,690 Total $ 183,610 $ (45,350 ) $ 138,260 December 31, 2018 Cash Collateral Net amounts of Net amounts of Derivative Assets/(Liabilities): Receivables from brokers $ 91,908 $ (7,637 ) $ 84,271 Payables to customers $ (986,918 ) $ 144,440 $ (842,478 ) Payables to brokers $ (3,092 ) $ 1,457 $ (1,635 )
Notional Values of Derivative Instruments	The amounts reported within Receivables from brokers, Payables to customers, and Payables to brokers on the Condensed Consolidated Balance Sheets are derived from the number of contracts below (amounts in thousands): March 31, 2019 Total contracts in long positions Total contracts in short positions Derivative Instruments: Foreign currency exchange contracts 2,863,433 2,265,453 CFD contracts 138,715 138,062 Metals contracts 598 127 Total 3,002,746 2,403,642 December 31, 2018 Total contracts in long positions Total contracts in short positions Derivative Instruments: Foreign currency exchange contracts 3,780,488 3,238,781 CFD contracts 98,840 134,546 Metals contracts 489 188 Total 3,879,817 3,373,515
Net Gains (Losses) With Respect to Derivative Instruments Which are Reflected in Trading Revenue	Net gains with respect to derivative instruments reflected in Retail revenue in the accompanying Condensed Consolidated Statements of Operations and Comprehensive (Loss)/Income for the three months ended March 31, 2019 and 2018 were as follows (amounts in thousands): Three Months Ended March 31, 2019 2018 Derivative Instruments: Foreign currency exchange contracts $ 16,137 $ 41,251 CFD contracts 5,938 37,147 Metals contracts 2,204 5,722 Total $ 24,279 $ 84,120

RECEIVABLES FROM BROKERS (Table

RECEIVABLES FROM BROKERS (Tables)	3 Months Ended
	Mar. 31, 2019
Brokers and Dealers [Abstract]
Schedule of Receivable from Brokers	Amounts receivable from brokers consisted of the following as of (amounts in thousands): March 31, 2019 December 31, 2018 Required collateral $ 96,887 $ 91,908 Open foreign exchange positions 1,787 (7,637 ) Total $ 98,674 $ 84,271

INTANGIBLE ASSETS (Tables)

INTANGIBLE ASSETS (Tables)	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Finite-Lived Intangible Assets	The Company’s various intangible assets consisted of the following as of (amounts in thousands): March 31, 2019 December 31, 2018 Intangibles Gross Accumulated Net Gross Accumulated Net Customer lists $ 46,051 $ (29,728 ) $ 16,323 $ 58,494 $ (40,208 ) $ 18,286 Technology 24,246 (13,997 ) 10,249 49,430 (38,555 ) 10,875 Trademarks 6,200 (3,697 ) 2,503 7,308 (4,637 ) 2,671 Total finite lived intangibles 76,497 (47,422 ) 29,075 115,232 (83,400 ) 31,832 Trademark not subject to amortization (1) 363 — 363 363 — 363 Total intangibles $ 76,860 $ (47,422 ) $ 29,438 $ 115,595 $ (83,400 ) $ 32,195 (1) These indefinite-life trademarks relate to the forex.com and foreignexchange.com domain names where management determined there was no legal, regulatory or technological limitation on their useful lives. The Company compares the recorded value of the indefinite-life intangible assets to their fair value on an annual basis and whenever circumstances arise that indicate that impairment may have occurred. As of March 31, 2019 , the Company wrote-off $34.4 million of fully amortized intangible assets, which was an equal amount for both gross and accumulated amortization and did not have any impact on the results of operations or cash flows. The Company had the following identifiable intangible assets and weighted average amortization periods as of March 31, 2019 : Intangible Assets Weighted average amortization period Customer lists 8.2 years Technology 7.2 years Trademarks 7.0 years
Schedule of Goodwill	The following represents the changes in the carrying amount of goodwill by segment (amounts in thousands): Retail Futures Total Carrying amount of goodwill as of December 31, 2018 $ 25,435 $ 2,385 $ 27,820 Foreign currency translation adjustments 201 19 220 Carrying amount of goodwill as of March 31, 2019 $ 25,636 $ 2,404 $ 28,040

CONVERTIBLE SENIOR NOTES (Table

CONVERTIBLE SENIOR NOTES (Tables)	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Schedule of Liability and Equity Components of Convertible Debt	The balances of the liability and equity components of the Convertible Senior Notes as of March 31, 2019 and December 31, 2018 were as follows (amounts in thousands): March 31, 2019 December 31, 2018 Liability component - principal $ 152,000 $ 152,000 Deferred bond discount (17,959 ) (19,503 ) Deferred financing cost (361 ) (388 ) Liability component - net carrying value $ 133,680 $ 132,109 Additional paid in capital $ 39,405 $ 39,405 Discount attributable to equity (826 ) (826 ) Equity component $ 38,579 $ 38,579
Schedule of Interest Expense	Interest expense related to the Convertible Senior Notes, included in Interest expense on long term borrowings in the Condensed Consolidated Statements of Operations and Comprehensive (Loss)/Income , was as follows (amounts in thousands): For the Three Months Ended March 31, 2019 2018 Interest expense - stated coupon rate $ 1,761 $ 1,834 Interest expense - amortization of deferred bond discount and costs 1,571 1,506 Total interest expense - convertible senior notes $ 3,332 $ 3,340

(LOSS)_EARNINGS PER COMMON SH_2

(LOSS)/EARNINGS PER COMMON SHARE (Tables)	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Computation of Earnings Per Share	For the Three Months Ended March 31, 2019 2018 Net (loss)/income from continuing operations $ (28,354 ) $ 11,914 Less income attributable to non-controlling interests — 175 Net (loss)/income from continuing operations (28,354 ) 11,739 Adjustment (1) — (367 ) Net (loss)/income available to GAIN common shareholders from continuing operations $ (28,354 ) $ 11,372 Net income from discontinued operations — 4,347 Weighted average common shares outstanding: Basic weighted average common shares outstanding 37,525,073 45,017,716 Effect of dilutive securities: Stock options — 261,732 RSUs — 244,318 Diluted weighted average common shares outstanding 37,525,073 45,523,766 Basic (loss)/earnings from continuing operations $ (0.76 ) $ 0.25 Basic earnings from discontinued operations $ — $ 0.10 Diluted (loss)/earnings from continuing operations $ (0.76 ) $ 0.25 Diluted earnings from discontinued operations $ — $ 0.10 (1) During the three months ended March 31, 2018 , the Company concluded that the carrying values of the redeemable noncontrolling interests were less than redemption value and adjusted carrying value to equal redemption value. This adjustment was a component of the earnings per common share calculation. For the three months ended March 31, 2019 , all common stock equivalents are excluded from the computation of diluted loss per share from continuing operations, because the result would be anti-dilutive. The table below shows dilution that the Company would have experienced, under the treasury stock method, had the three months ended March 31, 2019 resulted in net income, rather than net loss. For the Three Months Ended March 31, 2019 Stock options (1) 169,981 RSUs 90,520 Total securities excluded from diluted loss per share calculation 260,501 (1) During the three months ended March 31, 2019 and three months ended March 31, 2018 , 0.4 million stock options were out of the money and excluded from the computation of diluted loss or earnings per share from continuing operations.
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The table below shows dilution that the Company would have experienced, under the treasury stock method, had the three months ended March 31, 2019 resulted in net income, rather than net loss. For the Three Months Ended March 31, 2019 Stock options (1) 169,981 RSUs 90,520 Total securities excluded from diluted loss per share calculation 260,501 (1) During the three months ended March 31, 2019 and three months ended March 31, 2018 , 0.4 million stock options were out of the money and excluded from the computation of diluted loss or earnings per share from continuing operations.

REGULATORY REQUIREMENTS (Tables

REGULATORY REQUIREMENTS (Tables)	3 Months Ended
	Mar. 31, 2019
Banking and Thrift [Abstract]
Regulatory Capital Subsidiaries Required to Maintain	The following table illustrates the minimum regulatory capital the Company's subsidiaries were required to maintain as of March 31, 2019 and the actual amounts of capital that were maintained (amounts in millions): Entity Name Minimum Capital Excess Percent of GAIN Capital Group, LLC $ 34.7 $ 56.3 $ 21.6 162 % GAIN Capital Securities, Inc. 0.1 0.4 0.3 400 % GAIN Capital U.K., Ltd. 59.1 198.4 139.3 336 % GAIN Capital Japan Co., Ltd. 1.2 11.4 10.2 950 % GAIN Capital Australia, Pty. Ltd. 0.8 6.6 5.8 825 % GAIN Global Markets, Inc. 0.2 1.1 0.9 550 % GAIN Capital-Forex.com Canada, Ltd. 0.5 1.6 1.1 320 % GAIN Capital Singapore Pte., Ltd. 3.7 9.7 6.0 262 % Trade Facts, Ltd. 0.6 3.5 2.9 583 % Global Asset Advisors, LLC 0.0 2.8 2.8 100 % Total $ 100.9 $ 291.8 $ 190.9 289 %

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Selected Financial Information by Segment	Three Months Ended March 31, 2019 2018 Retail reportable segment: Net revenue $ 28,159 $ 85,672 Employee compensation and benefits 12,992 15,425 Selling and marketing 9,953 5,666 Referral fees 4,390 7,685 Other operating expenses 18,228 17,730 Segment (loss)/profit $ (17,404 ) $ 39,166 Futures reportable segment: Net revenue $ 9,410 $ 11,491 Employee compensation and benefits 2,164 2,511 Selling and marketing 260 241 Referral fees 2,708 3,746 Other operating expenses 3,221 3,794 Segment profit $ 1,057 $ 1,199 Corporate and other: Other revenue $ 866 $ 1,197 Employee compensation and benefits 5,099 6,402 Selling and marketing 11 64 Other operating expenses 2,905 3,260 Loss $ (7,149 ) $ (8,529 ) TOTAL SEGMENT (LOSS)/PROFIT $ (23,496 ) $ 31,836 Depreciation and amortization $ 4,250 $ 5,368 Purchased intangible amortization 3,329 3,668 Impairment of investment — (130 ) OPERATING (LOSS)/PROFIT $ (31,075 ) $ 22,930 Interest expense on long term borrowings 3,332 3,340 (LOSS)/INCOME BEFORE INCOME TAX EXPENSE $ (34,407 ) $ 19,590

DESCRIPTION OF BUSINESS AND B_4

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION - Narrative (Details) $ in Thousands	Feb. 01, 2019USD ($)	Mar. 31, 2019USD ($)segment	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)	Jun. 29, 2018USD ($)
Accounting Policies [Abstract]
Number of operating segments | segment		2
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and securities held for customers		$ 774,743	$ 938,432	$ 842,478
Marketable securities held for customers			24,789
Purchase of minority ownership interests		2,422	$ 0
Discontinued Operations, Disposed of by Sale | GTX ECN
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group, including discontinued operation, consideration					$ 100,000
Working capital adjustment					$ 200
US Government Corporations and Agencies Securities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and securities held for customers		104,900		$ 104,712
Short-term restricted cash and securities held for customers		$ 9,963
Top Third Ag Marketing, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Noncontrolling interest by seller (as percent)				21.00%
Purchase of minority ownership interests	$ 2,400

DESCRIPTION OF BUSINESS AND B_5

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION - Cash and Securities Held for Customers (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Accounting Policies [Abstract]
Cash and securities held for customers	$ 774,743	$ 842,478	$ 938,432
Marketable securities held for customers			24,789
Cash and securities held for customers	$ 869,688		$ 963,221

ACCOUNTING PRONOUNCEMENTS (Deta

ACCOUNTING PRONOUNCEMENTS (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right of use asset	$ 12,200
Lease liability	$ 14,437
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right of use asset		$ 12,600
Lease liability		$ 14,900

LEASES - Narrative (Details)

LEASES - Narrative (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Leases [Abstract]
Operating lease liabilities	$ 14,437
Right of use assets	12,200
Rent expense	$ 1,500

REVENUE RECOGNITION (Details)

REVENUE RECOGNITION (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Total non-interest revenue	$ 34,754	$ 96,660
Futures
Disaggregation of Revenue [Line Items]
Total non-interest revenue	9,410	11,491
Direct Customers | Futures
Disaggregation of Revenue [Line Items]
Total non-interest revenue	2,556	2,473
Indirect Customers | Futures
Disaggregation of Revenue [Line Items]
Total non-interest revenue	5,434	7,029
Other | Futures
Disaggregation of Revenue [Line Items]
Total non-interest revenue	$ 1,420	$ 1,989

LEASES - Quantitative Informati

LEASES - Quantitative Information About Operating Leases (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Lease cost
Operating lease cost	$ 796
Total lease cost	796
Other information
Operating cash flows from operating leases	$ 866
Weighted-average remaining lease term - operating leases	3 years 2 months 12 days
Weighted-average discount rate - operating leases	7.50%

LEASES - Maturities of Operatin

LEASES - Maturities of Operating Leases (Details) $ in Thousands	Mar. 31, 2019USD ($)
Leases [Abstract]
For the nine months ending at December 31, 2019	$ 2,598
For the year ended December 31, 2020	3,370
For the year ended December 31, 2021	3,492
For the year ended December 31, 2022	3,223
For the year ended December 31, 2023	2,271
For the year ended December 31, 2024	1,215
Thereafter	1,114
Total	17,283
Less: imputed interest	(2,846)
Operating lease liabilities at March 31, 2019	$ 14,437

DISCONTINUED OPERATIONS (Detail

DISCONTINUED OPERATIONS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 29, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
INCOME BEFORE INCOME TAX BENEFIT		$ 69,439
Income tax benefit		$ 3,222
NET INCOME FROM DISCONTINUED OPERATIONS	$ 0		$ 4,347
GTX ECN | Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group, including discontinued operation, consideration				$ 100,000
Working capital adjustment				$ 200
Total non-interest revenue			8,455
Interest revenue			48
Total net interest revenue			48
Net revenue			8,503
Employee compensation and benefits			3,413
Trading expenses			2,657
Other expenses			2,064
Total operating expense			8,134
OPERATING PROFIT			369
INCOME BEFORE INCOME TAX BENEFIT			369
Income tax benefit			(3,978)
NET INCOME FROM DISCONTINUED OPERATIONS			4,347
GTX ECN | Discontinued Operations, Disposed of by Sale | Institutional revenue
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total non-interest revenue			$ 8,455

FAIR VALUE MEASUREMENT - Assets

FAIR VALUE MEASUREMENT - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Recurring - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	$ 212,537	$ 243,276
US treasury bills: U.S. government and agency securities - long term
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets		104,712
Cash and securities held for customers - long term	94,945
Cash and securities held for customers - short term	9,963
Broker derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	1,787	(7,637)
Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	177	176
Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	129	128
Customer derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities	105,536	144,440
Broker derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities		1,457
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	105,214	105,016
Level 1 | US treasury bills: U.S. government and agency securities - long term
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	94,945
Level 1 | Broker derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Level 1 | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	177	176
Level 1 | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	129	128
Level 1 | Customer derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities	0	0
Level 1 | Broker derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities		0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	107,323	138,260
Level 2 | US treasury bills: U.S. government and agency securities - long term
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets		0
Cash and securities held for customers - long term	0
Cash and securities held for customers - short term	0
Level 2 | Broker derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	1,787	(7,637)
Level 2 | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Level 2 | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Level 2 | Customer derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities	105,536	144,440
Level 2 | Broker derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities		1,457
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	0	0
Level 3 | US treasury bills: U.S. government and agency securities - long term
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets		0
Cash and securities held for customers - long term	0
Cash and securities held for customers - short term	0
Level 3 | Broker derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Level 3 | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Level 3 | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Level 3 | Customer derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities	$ 0	0
Level 3 | Broker derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities		$ 0

FAIR VALUE MEASUREMENT - Carryi

FAIR VALUE MEASUREMENT - Carrying Value and Fair Value of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financial Assets:
Receivables from brokers	$ 98,674	$ 84,271
Financial Liabilities:
Payables to brokers	0	1,635
Convertible senior notes	133,680	132,109
Derivative Assets | Level 1
Financial Assets:
Receivables from brokers	0	0
Derivative Assets | Level 2
Financial Assets:
Receivables from brokers	96,887	91,908
Derivative Assets | Level 3
Financial Assets:
Receivables from brokers	0	0
Derivative Assets | Carrying Value
Financial Assets:
Receivables from brokers	96,887	91,908
Derivative Assets | Fair Value
Financial Assets:
Receivables from brokers	96,887	91,908
Derivative Liabilities | Level 1
Financial Liabilities:
Payables to customers	0	0
Convertible senior notes	0	0
Derivative Liabilities | Level 2
Financial Liabilities:
Payables to customers	975,224	986,918
Payables to brokers		3,092
Convertible senior notes	156,665	158,752
Derivative Liabilities | Level 3
Financial Liabilities:
Payables to customers	0	0
Convertible senior notes	0	0
Derivative Liabilities | Carrying Value
Financial Liabilities:
Payables to customers	975,224	986,918
Payables to brokers		3,092
Convertible senior notes	133,680	132,109
Derivative Liabilities | Fair Value
Financial Liabilities:
Payables to customers	975,224	986,918
Payables to brokers		3,092
Convertible senior notes	$ 156,665	$ 158,752

DERIVATIVES - Fair Value of Der

DERIVATIVES - Fair Value of Derivative Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Gross amounts of assets for derivative open positions at fair value	$ 157,908	$ 183,610
Gross amount of (liabilities) for derivative open positions at fair value	(50,585)	(45,350)
Net amounts of assets/(liabilities) for derivative open positions at fair value	107,323	138,260
Receivables from brokers	98,674	84,271
Payables to customers	(869,688)	(842,478)
Payables to brokers	0	(1,635)
Receivables from brokers
Derivatives, Fair Value [Line Items]
Receivables from brokers	98,674	84,271
Receivables from brokers | Derivative Assets
Derivatives, Fair Value [Line Items]
Cash Collateral	96,887	91,908
Net amounts of assets/(liabilities) for derivative open positions at fair value	1,787	(7,637)
Payables to customers
Derivatives, Fair Value [Line Items]
Payables to customers	(869,688)	(842,478)
Payables to customers | Derivative Liabilities
Derivatives, Fair Value [Line Items]
Cash Collateral	975,224	986,918
Net amounts of assets/(liabilities) for derivative open positions at fair value	105,536	144,440
Foreign currency exchange contracts
Derivatives, Fair Value [Line Items]
Gross amounts of assets for derivative open positions at fair value	72,642	100,158
Gross amount of (liabilities) for derivative open positions at fair value	(18,234)	(20,382)
Net amounts of assets/(liabilities) for derivative open positions at fair value	54,408	79,776
CFD contracts
Derivatives, Fair Value [Line Items]
Gross amounts of assets for derivative open positions at fair value	79,415	77,014
Gross amount of (liabilities) for derivative open positions at fair value	(30,699)	(21,220)
Net amounts of assets/(liabilities) for derivative open positions at fair value	48,716	55,794
Metals contracts
Derivatives, Fair Value [Line Items]
Gross amounts of assets for derivative open positions at fair value	5,851	6,438
Gross amount of (liabilities) for derivative open positions at fair value	(1,652)	(3,748)
Net amounts of assets/(liabilities) for derivative open positions at fair value	$ 4,199	2,690
Broker derivative contracts
Derivatives, Fair Value [Line Items]
Payables to brokers		(1,635)
Broker derivative contracts | Derivative Liabilities
Derivatives, Fair Value [Line Items]
Cash Collateral		(3,092)
Net amounts of assets/(liabilities) for derivative open positions at fair value		$ 1,457

DERIVATIVES - Narrative (Detail

DERIVATIVES - Narrative (Details)	Mar. 31, 2019$ / contract
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Foreign exchange contract price (less than)	2

DERIVATIVES - Notional Values o

DERIVATIVES - Notional Values of Derivative Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Total contracts in long positions
Derivative [Line Items]
Notional amounts of derivative	$ 3,002,746	$ 3,879,817
Total contracts in long positions | Foreign currency exchange contracts
Derivative [Line Items]
Notional amounts of derivative	2,863,433	3,780,488
Total contracts in long positions | CFD contracts
Derivative [Line Items]
Notional amounts of derivative	138,715	98,840
Total contracts in long positions | Metal contracts
Derivative [Line Items]
Notional amounts of derivative	598	489
Total contracts in short positions
Derivative [Line Items]
Notional amounts of derivative	2,403,642	3,373,515
Total contracts in short positions | Foreign currency exchange contracts
Derivative [Line Items]
Notional amounts of derivative	2,265,453	3,238,781
Total contracts in short positions | CFD contracts
Derivative [Line Items]
Notional amounts of derivative	138,062	134,546
Total contracts in short positions | Metal contracts
Derivative [Line Items]
Notional amounts of derivative	$ 127	$ 188

DERIVATIVES - Net Gains (Losses

DERIVATIVES - Net Gains (Losses) on Derivatives (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Derivative [Line Items]
Net gains (losses) on derivative instruments, total	$ 24,279	$ 84,120
Foreign currency exchange contracts
Derivative [Line Items]
Net gains (losses) on derivative instruments	16,137	41,251
CFD contracts
Derivative [Line Items]
Net gains (losses) on derivative instruments	5,938	37,147
Metal contracts
Derivative [Line Items]
Net gains (losses) on derivative instruments	$ 2,204	$ 5,722

RECEIVABLES FROM BROKERS (Detai

RECEIVABLES FROM BROKERS (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Receivables from Brokerage Clients [Line Items]
Receivables from brokers	$ 98,674	$ 84,271
Required collateral
Receivables from Brokerage Clients [Line Items]
Receivables from brokers	96,887	91,908
Open foreign exchange positions
Receivables from Brokerage Clients [Line Items]
Receivables from brokers	$ 1,787	$ (7,637)

INTANGIBLE ASSETS - Intangible

INTANGIBLE ASSETS - Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Intangible Assets by Major Class [Line Items]
Finite-lived intangible assets, gross	$ 76,497		$ 115,232
Accumulated Amortization	(47,422)		(83,400)
Finite-lived intangible assets, net	29,075		31,832
Total intangibles, gross	76,860		115,595
Intangible assets, net	29,438		32,195
Write-off of fully amortized intangible assets	34,400
Purchased intangible amortization	3,329	$ 3,668
Trademarks
Intangible Assets by Major Class [Line Items]
Indefinite-lived intangible assets	363		363
Customer lists
Intangible Assets by Major Class [Line Items]
Finite-lived intangible assets, gross	46,051		58,494
Accumulated Amortization	(29,728)		(40,208)
Finite-lived intangible assets, net	$ 16,323		18,286
Weighted average amortization period	8 years 2 months 12 days
Technology
Intangible Assets by Major Class [Line Items]
Finite-lived intangible assets, gross	$ 24,246		49,430
Accumulated Amortization	(13,997)		(38,555)
Finite-lived intangible assets, net	$ 10,249		10,875
Weighted average amortization period	7 years 2 months
Trademarks
Intangible Assets by Major Class [Line Items]
Finite-lived intangible assets, gross	$ 6,200		7,308
Accumulated Amortization	(3,697)		(4,637)
Finite-lived intangible assets, net	$ 2,503		$ 2,671
Weighted average amortization period	7 years

INTANGIBLE ASSETS - Goodwill (D

INTANGIBLE ASSETS - Goodwill (Details)	3 Months Ended
	Mar. 31, 2019USD ($)reporting_unit
Goodwill [Line Items]
Number of reporting units | reporting_unit	2
Goodwill additions or impairments	$ 0
Goodwill [Roll Forward]
Goodwill. beginning balance	27,820,000
Foreign currency translation adjustments	220,000
Goodwill. ending balance	28,040,000
Operating Segments | Retail
Goodwill [Roll Forward]
Goodwill. beginning balance	25,435,000
Foreign currency translation adjustments	201,000
Goodwill. ending balance	25,636,000
Operating Segments | Futures
Goodwill [Roll Forward]
Goodwill. beginning balance	2,385,000
Foreign currency translation adjustments	19,000
Goodwill. ending balance	$ 2,404,000

RELATED PARTY TRANSACTIONS (Det

RELATED PARTY TRANSACTIONS (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Payables to customers	$ 869,688,000	$ 842,478,000
Receivables due from certain officers	100,000	0
Management
Related Party Transaction [Line Items]
Payables to customers	300,000	400,000
IPGL Limited
Related Party Transaction [Line Items]
Payables to customers	$ 11,900,000	$ 11,700,000

REVOLVING CREDIT ARRANGEMENT (D

REVOLVING CREDIT ARRANGEMENT (Details) - Revolving Credit Facility - USD ($)	Aug. 03, 2017	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Maximum amount under facility	$ 50,000,000
Commitment fee amount	500,000
Line of credit outstanding		$ 0	$ 0
Maximum
Debt Instrument [Line Items]
Increase in borrowing capacity available	25,000,000
Minimum
Debt Instrument [Line Items]
Increase in borrowing capacity available	$ 5,000,000
Line of Credit
Debt Instrument [Line Items]
Term of credit facility	3 years

CONVERTIBLE SENIOR NOTES - Narr

CONVERTIBLE SENIOR NOTES - Narrative (Details) - Convertible Debt - USD ($)	Aug. 22, 2017	Apr. 01, 2015
Convertible Notes Due 2022
Debt Instrument [Line Items]
Aggregate principal amount	$ 92,000,000
Interest rate	5.00%
Convertible Notes Due 2020
Debt Instrument [Line Items]
Aggregate principal amount		$ 60,000,000
Interest rate		4.125%

CONVERTIBLE SENIOR NOTES - Sche

CONVERTIBLE SENIOR NOTES - Schedule of Liability and Equity Components (Details) - Convertible Debt - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Liability component - principal	$ 152,000	$ 152,000
Deferred bond discount	(17,959)	(19,503)
Deferred financing cost	(361)	(388)
Liability component - net carrying value	133,680	132,109
Additional paid in capital	39,405	39,405
Discount attributable to equity	(826)	(826)
Equity component	$ 38,579	$ 38,579

CONVERTIBLE SENIOR NOTES - Sc_2

CONVERTIBLE SENIOR NOTES - Schedule of Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Debt Instrument [Line Items]
Interest expense - amortization of deferred bond discount and costs	$ 149	$ 163
Convertible Debt
Debt Instrument [Line Items]
Interest expense - stated coupon rate	1,761	1,834
Interest expense - amortization of deferred bond discount and costs	1,571	1,506
Total interest expense - convertible senior notes	$ 3,332	$ 3,340

(LOSS)_EARNINGS PER COMMON SH_3

(LOSS)/EARNINGS PER COMMON SHARE - Narrative (Detail) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)$ / sharesshares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total securities excluded from diluted loss per share calculation | shares	260,501
Common stock threshold for additional dilutive shares (in dollars per share) | $ / shares	$ 10
Convertible Notes Due 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities, effect on basic earnings per share, dilutive convertible securities	$ 0.2
Convertible Notes Due 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities, effect on basic earnings per share, dilutive convertible securities	$ 2

(LOSS)_EARNINGS PER COMMON SH_4

(LOSS)/EARNINGS PER COMMON SHARE - Computation of Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Net (loss)/income from continuing operations	$ (28,354)	$ 11,914
Less income attributable to non-controlling interests	0	175
Net (loss)/income from continuing operations	(28,354)	11,739
Adjustment	0	(367)
Net (loss)/income available to GAIN common shareholders from continuing operations	(28,354)	11,372
Net income from discontinued operations	$ 0	$ 4,347
Weighted average common shares outstanding:
Basic weighted average common shares outstanding	37,525,073	45,017,716
Effect of dilutive securities:
Stock options (in shares)	0	261,732
RSUs/RSAs (in shares)	0	244,318
Diluted weighted average common shares outstanding	37,525,073	45,523,766
Earnings/(loss) per common share:
Basic (loss) earnings from continuing operations (usd per share)	$ (0.76)	$ 0.25
Basic earnings from discontinued operations (usd per share)	0	0.10
Diluted (loss) earnings from continuing operations (usd per share)	(0.76)	0.25
Diluted earnings from discontinued operations (usd per share)	$ 0	$ 0.10

(LOSS)_EARNINGS PER COMMON SH_5

(LOSS)/EARNINGS PER COMMON SHARE - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Details)	3 Months Ended
	Mar. 31, 2019shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total securities excluded from diluted loss per share calculation	260,501
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total securities excluded from diluted loss per share calculation	169,981
RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total securities excluded from diluted loss per share calculation	90,520
Stock options, out of the money
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total securities excluded from diluted loss per share calculation	400,000

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Provision (benefit) for income taxes	$ (6,053)	$ 7,676
Effective income tax rates (as percent)	17.60%	39.20%

REGULATORY REQUIREMENTS (Detail

REGULATORY REQUIREMENTS (Details) $ in Millions	Mar. 31, 2019USD ($)
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 100.9
Capital Levels Maintained	291.8
Excess Net Capital	$ 190.9
Percent of Requirement Maintained	289.00%
GAIN Capital Group, LLC
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 34.7
Capital Levels Maintained	56.3
Excess Net Capital	$ 21.6
Percent of Requirement Maintained	162.00%
GAIN Capital Securities, Inc.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 0.1
Capital Levels Maintained	0.4
Excess Net Capital	$ 0.3
Percent of Requirement Maintained	400.00%
GAIN Capital U.K., Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 59.1
Capital Levels Maintained	198.4
Excess Net Capital	$ 139.3
Percent of Requirement Maintained	336.00%
GAIN Capital Japan Co., Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 1.2
Capital Levels Maintained	11.4
Excess Net Capital	$ 10.2
Percent of Requirement Maintained	950.00%
GAIN Capital Australia, Pty. Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 0.8
Capital Levels Maintained	6.6
Excess Net Capital	$ 5.8
Percent of Requirement Maintained	825.00%
GAIN Global Markets, Inc.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 0.2
Capital Levels Maintained	1.1
Excess Net Capital	$ 0.9
Percent of Requirement Maintained	550.00%
GAIN Capital-Forex.com Canada, Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 0.5
Capital Levels Maintained	1.6
Excess Net Capital	$ 1.1
Percent of Requirement Maintained	320.00%
GAIN Capital Singapore Pte., Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 3.7
Capital Levels Maintained	9.7
Excess Net Capital	$ 6
Percent of Requirement Maintained	262.00%
Trade Facts, Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 0.6
Capital Levels Maintained	3.5
Excess Net Capital	$ 2.9
Percent of Requirement Maintained	583.00%
Global Asset Advisors, LLC
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 0
Capital Levels Maintained	2.8
Excess Net Capital	$ 2.8
Percent of Requirement Maintained	100.00%

SEGMENT INFORMATION - Narrative

SEGMENT INFORMATION - Narrative (Details) market in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2019market	Jun. 29, 2018USD ($)
Segment Reporting Information [Line Items]
Number of accessible global financial markets (more than) | market	15
GTX ECN | Discontinued Operations, Disposed of by Sale
Segment Reporting Information [Line Items]
Disposal group, including discontinued operation, consideration		$ 100
Working capital adjustment		$ 0.2

SEGMENT INFORMATION - Selected

SEGMENT INFORMATION - Selected Financial Information by Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Employee compensation and benefits	$ 20,255	$ 24,338
Selling and marketing	10,224	5,971
Referral fees	7,098	11,431
TOTAL SEGMENT (LOSS)/PROFIT	(23,496)	31,836
Depreciation and amortization	4,250	5,368
Purchased intangible amortization	3,329	3,668
Impairment of investment	0	(130)
OPERATING (LOSS)/PROFIT	(31,075)	22,930
Interest expense on long term borrowings	3,332	3,340
(LOSS)/INCOME BEFORE INCOME TAX	(34,407)	19,590
Operating Segments | Retail
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net revenue	28,159	85,672
Employee compensation and benefits	12,992	15,425
Selling and marketing	9,953	5,666
Referral fees	4,390	7,685
Other operating expenses	18,228	17,730
TOTAL SEGMENT (LOSS)/PROFIT	(17,404)	39,166
Operating Segments | Futures
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net revenue	9,410	11,491
Employee compensation and benefits	2,164	2,511
Selling and marketing	260	241
Referral fees	2,708	3,746
Other operating expenses	3,221	3,794
TOTAL SEGMENT (LOSS)/PROFIT	1,057	1,199
Corporate and Other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net revenue	866	1,197
Employee compensation and benefits	5,099	6,402
Selling and marketing	11	64
Other operating expenses	2,905	3,260
TOTAL SEGMENT (LOSS)/PROFIT	$ (7,149)	$ (8,529)

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - $ / shares	Apr. 25, 2019	Mar. 31, 2019	Mar. 31, 2018
Subsequent Event [Line Items]
Common stock dividend declared (usd per share)		$ 0.06	$ 0.06
Subsequent event
Subsequent Event [Line Items]
Common stock dividend declared (usd per share)	$ 0.06