GAIN Capital 10-K/A 2 May 16 2015 FY Annual report (amended) Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Apr. 29, 2016	Jun. 30, 2015
Document and Entity Information [Abstract]
Entity Registrant Name	GAIN Capital Holdings, Inc.
Trading Symbol	GCAP
Entity Central Index Key	1,444,363
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Document Type	10-K/A
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Amendment Flag	true
Amendment Description	Amend the Annual Report on Form 10-K for the year ended December 31, 2015, as originally filed with the SEC on March 17, 2016, to restate Note 23 to the consolidated financial statements for the year ended December 31, 2015.
Entity Public Float			$ 211
Entity Common Stock, Shares Outstanding		48,483,199

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	[1]
ASSETS:
Cash and cash equivalents	$ 171,888	$ 139,351
Cash and securities held for customers	920,621	759,559
Receivables from brokers, of which ($12,568) and $717, respectively, are open contracts at fair value	121,153	134,908
Prepaid assets	7,835	2,537
Property and equipment, net of accumulated depreciation of ($44,750) and ($31,544), respectively	30,367	18,796
Intangible assets, net of accumulated amortization of ($47,906) and ($12,670), respectively	91,512	60,806
Goodwill	34,017	33,579
Other assets, net of allowance for doubtful accounts of ($6,832) and ($4,555), respectively	47,422	33,765
Total assets	1,424,815	1,183,301
Liabilities
Payables to customers, of which ($143,918) and ($102,722), respectively, are open contracts at fair value	920,621	759,559
Accrued compensation and benefits	12,362	16,912
Accrued expenses and other liabilities	51,638	76,195
Income tax payable	1,068	1,010
Convertible senior notes	121,996	68,367
Total liabilities	$ 1,107,685	$ 922,043
Commitments and contingent liabilities
Redeemable non-controlling interests	$ 11,046	$ 11,338
Shareholders’ equity
Common stock ($0.00001 par value; 120 million shares authorized, 52,072,884 shares issued and 48,771,015 shares outstanding as of December 31, 2015; 60 million shares authorized, 45,582,066 shares issued and 42,934,559 shares outstanding as of December 31, 2014)	0	0
Accumulated other comprehensive loss	(5,865)	(1,513)
Additional paid-in capital	212,981	148,378
Treasury stock, at cost (3,301,869 shares at December 31, 2015 and 2,647,507 at December 31, 2014, respectively)	(21,808)	(16,720)
Retained earnings	120,776	119,775
Total shareholders’ equity	306,084	249,920
Total liabilities and shareholders’ equity	$ 1,424,815	$ 1,183,301
[1]	As Restated

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Receivables from brokers, open contracts at fair value	$ (12,568)	$ 717	[1]
Property and equipment, accumulated depreciation	(44,750)	(31,544)	[1]
Intangible assets, accumulated amortization	(47,906)	(12,670)	[1]
Other assets, allowance for doubtful accounts	(6,832)	(4,555)	[1]
Payables to customers, open contracts at fair value	$ (143,918)	$ (102,722)	[1]
Common Stock, par value	$ 0.00001	$ 0.00001
Common Stock, shares authorized	120,000,000	60,000,000
Common Stock, shares issued	52,072,884	45,582,066
Common stock, shares outstanding	48,771,015	42,934,559
Treasury stock, shares	3,301,869	2,647,507
[1]	As Restated

Consolidated Statements of Inco

Consolidated Statements of Income and Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	[1]	Dec. 31, 2013	[1]
REVENUE:
Retail revenue	$ 347,489	$ 292,778		$ 215,734
Institutional revenue	33,773	34,518		28,005
Futures revenue	45,427	36,160		22,188
Other revenue	8,487	4,904		1,099
Total non-interest revenue	435,176	368,360		267,026
Interest revenue	1,220	1,428		821
Interest expense	1,049	599		156
Total net interest revenue	171	829		665
Net revenue	435,347	369,189		267,691
EXPENSES:
Employee compensation and benefits	106,581	99,233		74,607
Selling and marketing	27,168	20,213		22,337
Referral fees	103,523	90,972		52,623
Trading expenses	31,914	26,168		18,164
General and administrative	55,067	38,651		26,558
Depreciation and amortization	11,111	6,610		8,283
Purchased intangible amortization	16,550	8,080		2,906
Communications and technology	18,929	15,567		11,315
Bad debt provision	7,462	3,699		1,501
Acquisition expenses	2,819	3,526		1,824
Restructuring expenses	3,482	2,334		450
Integration expenses	33,092	2,489		1,950
Impairment of investment	0	50		450
Total operating expense	417,698	317,592		222,968
OPERATING PROFIT	17,649	51,597		44,723
Interest expense on long term borrowings	9,222	6,147		1,233
Gain on extinguishment of debt	0	0		2,000
INCOME BEFORE INCOME TAX EXPENSE	8,427	45,450		45,490
Income tax (benefit)/expense	(3,512)	19,140		17,383
NET INCOME	11,939	26,310		28,107
Net income attributable to non-controlling interest	1,660	1,433		0
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.	10,279	24,877		28,107
Other comprehensive (loss)/income:
Foreign currency translation adjustment	(4,352)	(4,089)		1,327
NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.	$ 5,927	$ 20,788		$ 29,434
Earnings per common share:
Basic (usd per share)	$ 0.22	$ 0.56		$ 0.76
Diluted (usd per share)	$ 0.22	$ 0.53		$ 0.71
Weighted average common shares outstanding used in computing earnings per common share:
Basic (shares)	47,601,979	40,561,644		36,551,246
Diluted (shares)	48,379,051	43,214,895		39,632,878
[1]	As Restated

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands		Total		Common Stock		Treasury Stock	Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive Income/(Loss)
BEGINNING BALANCE (in shares) at Dec. 31, 2012	[1],[2]			34,924,095
BEGINNING BALANCE at Dec. 31, 2012	[1]	$ 162,568				$ (8,280)	$ 85,009	$ 84,590	$ 1,249
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of options (in shares)	[2]			1,394,975
Exercise of options		2,539					2,539
Issuance of common stock (in shares)	[2]			3,625,721
Issuance of common stock		34,771					34,771
Conversion of restricted stock into common stock (in shares)	[2]			339,686
Shares issued under employee stock purchase plan (in shares)	[2]			75,191
Shares issued under employee stock purchase plan		302					302
Repurchase of shares (in shares)	[2]			(934,234)
Repurchase of shares		(7,189)				(7,189)
Stock compensation expense		2,975					2,975
Tax benefit of stock options exercises		1,026					1,026
Other		(216)					(62)	(154)
Convertible senior note issuance		12,147					12,147
Tax effect of convertible senior note		(4,308)					(4,308)
Adjustment to the redemption value of noncontrolling interests	[1]	0
Dividend declared		(7,326)						(7,326)
Foreign currency translation adjustment		1,327							1,327
Net income		28,107	[1]					28,107
ENDING BALANCE (in shares) at Dec. 31, 2013	[1],[2]			39,425,434
ENDING BALANCE at Dec. 31, 2013	[1]	226,723				(15,469)	134,399	105,217	2,576
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of options (in shares)	[2]			719,719
Exercise of options		2,087					2,087
Issuance of common stock (in shares)	[2]			978,736
Issuance of common stock		$ 6,493					6,493
Conversion of restricted stock into common stock (in shares)	[2]			1,863,396
Shares issued under employee stock purchase plan (in shares)		98,606		98,606	[2]
Shares issued under employee stock purchase plan		$ 740					740
Repurchase of shares (in shares)	[2]			(151,332)
Repurchase of shares		(1,251)				(1,251)
Stock compensation expense		3,452					3,452
Tax benefit of stock options exercises		1,221					1,221
Other		(87)					(14)	(73)
Adjustment to the redemption value of noncontrolling interests		(2,107)	[1]					(2,107)
Dividend declared		(8,139)						(8,139)
Foreign currency translation adjustment		(4,089)							(4,089)
Net income		24,877	[1]					24,877
ENDING BALANCE (in shares) at Dec. 31, 2014	[1],[2]			42,934,559
ENDING BALANCE at Dec. 31, 2014	[1]	$ 249,920				(16,720)	148,378	119,775	(1,513)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of options (in shares)		638,000		638,241	[2]
Exercise of options		$ 2,386					2,386
Issuance of common stock (in shares)	[2]			5,319,149
Issuance of common stock		$ 45,100					45,100
Conversion of restricted stock into common stock (in shares)	[2]			440,651
Shares issued under employee stock purchase plan (in shares)		92,777		92,777	[2]
Shares issued under employee stock purchase plan		$ 789					789
Repurchase of shares (in shares)	[2]			(654,362)
Repurchase of shares		(5,088)				(5,088)
Stock compensation expense		3,680					3,680
Tax benefit of stock options exercises		1,140					1,140
Other		(56)						(56)
Convertible senior note issuance		15,348					15,348
Tax effect of convertible senior note		(3,840)					(3,840)
Adjustment to the redemption value of noncontrolling interests		308						308
Dividend declared		(9,530)						(9,530)
Foreign currency translation adjustment		(4,352)							(4,352)
Net income		10,279						10,279
ENDING BALANCE (in shares) at Dec. 31, 2015	[2]			48,771,015
ENDING BALANCE at Dec. 31, 2015		$ 306,084				$ (21,808)	$ 212,981	$ 120,776	$ (5,865)
[1]	As Restated
[2]	The Company has 15,000,000 shares of authorized preferred stock, of which none are issued or outstanding.

Consolidated Statements of Cha6

Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Stockholders' Equity [Abstract]
Dividend declared (usd per share)	$ 0.20	$ 0.20	$ 0.20
Preferred stock, authorized (in shares)	15,000,000	15,000,000	15,000,000
Preferred stock, issued (in shares)	0	0	0
Preferred stock, outstanding (in shares)	0	0	0

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income		$ 11,939	$ 26,310	[1]	$ 28,107	[1]
Adjustments to reconcile net income to cash provided by / (used for) operating activities
Loss / (gain) on foreign currency exchange rates		2,432	(1,618)	[1]	3,641	[1]
Depreciation and amortization		27,661	14,690	[1]	11,189	[1]
Non-cash integration costs		26,827	1,162	[1]	1,163	[1]
Deferred tax (benefit)/expense		(12,355)	5,108	[1]	(5,431)	[1]
Amortization of deferred financing costs		354	354	[1]	0	[1]
Bad debt provision		7,462	3,699	[1]	1,501	[1]
Impairment of investment		0	50	[1]	450	[1]
Convertible senior note discount amortization		3,624	2,150	[1]	175	[1]
Gain on extinguishment of debt		0	0	[1]	2,000	[1]
Stock compensation expense		3,680	3,452	[1]	2,975	[1]
Adjustment to fair value of contingent consideration		(6,722)	0	[1]	0	[1]
Changes in operating assets and liabilities:
Cash and securities held for customers		101,325	(9,260)	[1]	(74,769)	[1]
Receivables from brokers		45,576	94,933	[1]	(78,556)	[1]
Prepaid assets		(1,445)	2,730	[1]	318	[1]
Other assets		(6,229)	(8,495)	[1]	(1,075)	[1]
Payables to customers		(101,325)	9,260	[1]	74,769	[1]
Accrued compensation and benefits		(7,454)	4,497	[1]	6,375	[1]
Accrued expenses and other liabilities		(18,748)	(2,422)	[1]	7,867	[1]
Income tax payable		611	(9,812)	[1]	4,414	[1]
Cash provided by / (used for) operating activities		77,213	136,788	[1]	(18,887)	[1]
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment		(19,676)	(8,759)	[1]	(6,187)	[1]
Sale of treasury bills		0	614	[1]	599	[1]
Intangible asset purchases		0	(12,400)	[1]	0	[1]
Funding of acquisitions, net of cash acquired		(3,258)	(14,918)	[1]	(4,219)	[1]
Cash received relating to acquisitions		7,612	0	[1]	0	[1]
Purchase of investment		(759)	0	[1]	0	[1]
Cash used for investing activities		(16,081)	(35,463)	[1]	(9,807)	[1]
CASH FLOWS FROM FINANCING ACTIVITIES:
Contractual payments for acquisitions		(13,893)	0	[1]	(2,419)	[1]
Proceeds from issuance of convertible senior note, net		0	0	[1]	77,900	[1]
Principal payment on notes payable		0	0	[1]	(31,200)	[1]
Proceeds from exercise of stock options		2,386	2,087	[1]	2,539	[1]
Proceeds from employee stock purchase plan		789	740	[1]	302	[1]
Purchase of treasury stock		(5,088)	(1,251)	[1]	(7,189)	[1]
Tax benefit from employee stock option exercises		1,140	1,221	[1]	1,026	[1]
Dividend payment		(9,530)	(8,139)	[1]	(7,326)	[1]
Distributions to non-controlling interest holders		(1,644)	(596)	[1]	0	[1]
Cash (used for) / provided by financing activities		(25,840)	(5,938)	[1]	33,633	[1]
Effect of exchange rate changes on cash and cash equivalents		(2,755)	4,093	[1]	(1,888)	[1]
INCREASE / (DECREASE) IN CASH AND CASH EQUIVALENTS		32,537	99,480	[1]	3,051	[1]
CASH AND CASH EQUIVALENTS—Beginning of year	[1]	139,351	39,871		36,820
CASH AND CASH EQUIVALENTS—End of year		171,888	139,351	[1]	39,871	[1]
SUPPLEMENTARY DISCLOSURES OF CASH FLOW INFORMATION:
Interest		(5,065)	(3,373)	[1]	(655)	[1]
Taxes		(9,861)	(13,151)	[1]	(8,376)	[1]
Purchase of fixed assets included in accrued expense and other liabilities		0	701	[1]	0	[1]
Convertible senior notes issued as consideration for business acquisitions		65,000	0	[1]	0	[1]
Deferred taxes related to convertible senior notes		(3,840)	0	[1]	(4,308)	[1]
Senior loan issued by seller		0	0	[1]	33,200	[1]
Common stock issued as consideration for asset and business acquisitions		45,100	6,493	[1]	34,771	[1]
Adjustment to the redemption value of noncontrolling interests		$ 308	$ (2,107)	[1]	$ 0	[1]
[1]	As Restated

Description of Business and Bas

Description of Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2015
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 Delaware corporation formed and incorporated on March 24, 2006. GAIN Holdings, LLC is a wholly-owned subsidiary of GAIN Capital Holdings, Inc., and it owns all outstanding membership units of GAIN Capital Group, LLC (“Group, LLC”), the Company's primary regulated entity in the United States. City Index (Holdings) Ltd ("City Index") is the Company's primary regulated entity outside of the United States. Group, LLC is a retail foreign exchange dealer (“RFED”) and a Futures Commission Merchant (“FCM”) registered with the Commodity Futures Trading Commission (the “CFTC”). As such, it is subject to the regulations of the CFTC, an agency of the U.S. government, and the rules of the National Futures Association (“NFA”), an industry self-regulatory organization. GAIN Capital-Forex.com U.K. Ltd. (“GCUK1”) and GAIN Capital UK Limited ("GCUK2") are each registered in the United Kingdom ("U.K.") and regulated by the Financial Conduct Authority (“FCA”) as full scope €730k IFPRU Investment Firms. The following list includes each of the Company’s significant U.S. and international regulated subsidiaries as of December 31, 2015: GAIN Capital Group, LLC GAIN Capital Forex.com U.K., Ltd. GAIN Capital Japan Co., Ltd. GAIN Capital Forex.com Australia Pty. Ltd. GAIN GTX, LLC Global Assets Advisors, LLC Top Third Ag Marketing LLC Galvan Research and Trading, Ltd. GAIN Capital UK Limited GAIN Capital Australia Pty. Ltd. GAIN Capital Singapore Pte. Ltd. In April 2015, the Company acquired all of the outstanding share capital of City Index from City Index Group Limited. GCUK2, GAIN Capital Australia Pty. Ltd. (“GCAU2”) , and GAIN Capital Singapore Pte. Ltd. ("GCS") are each subsidiaries that were acquired as part of the City Index acquisition. Each of these entities is regulated locally by the relevant regulators, including the FCA. In July 2014, the Company acquired all of the outstanding share capital of Galvan Research and Trading, Ltd. ("Galvan"), a U.K. based corporation, and its subsidiaries, Faraday Research LLP and Galvan LLP. Galvan is regulated by the FCA. In March 2014, the Company acquired controlling interests in Global Asset Advisors, LLC ("GAA") and Top Third Ag Marketing LLC ("Top Third"). In September 2013, the Company purchased all of the outstanding share capital of Global Futures & Forex, Ltd., a Michigan corporation ("GFT"). See Note 11 for further details related to the Company's acquisitions. Basis of Presentation and Principles of Consolidation The consolidated financial statements are presented in accordance with accounting principles generally accepted in the United States of America ("GAAP") and have been prepared in accordance with the regulations of the Securities and Exchange Commission ("SEC"). During the fourth quarter of 2015, the Company changed its segment reporting structure from a single operating segment to three operating segments, Retail, Institutional and Futures. The Company also provides general corporate services to its segments through a corporate function, which only earns revenues that are incidental to the public entity and is therefore not an operating segment. Such costs are reported as "Corporate and Other." The segment reporting structure is consistent with how the Chief Operating Decision Maker reviews the businesses, makes investing and resource decisions and assesses operating performance. Previously disclosed segment information has been retrospectively adjusted to conform with changes made to the current segment presentation. In connection with the change in segments, management determined that it would be more useful to the users of the consolidated financial statements to have revenue presentation on the Consolidated Statements of Income and Comprehensive Income to have operating revenue presented in a manner consistent with segment revenue, and accordingly, reclassified amounts from Trading revenue and Commission revenue to Retail revenue, Institutional revenue and Futures revenue for the years ended December 31 2014 and 2013. This change in presentation had no impact on Total non-interest revenue. Consolidation The consolidated financial statements include the accounts of the Company, its wholly owned subsidiaries and other subsidiaries in which the Company holds a controlling financial interest. All intercompany transactions and balances are eliminated in consolidation. The Company applies relevant accounting standards governing consolidation in determining its principles of consolidation. The Company's consolidated financial statements include non-controlling interests related to certain less than wholly owned subsidiaries. See Note 12 for details regarding non-controlling interests related to certain less than wholly owned subsidiaries. Use of Estimates The preparation of consolidated financial statements in conformity with 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 consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. In presenting the consolidated financial statements, management makes estimates regarding: • Valuation of assets and liabilities requiring fair value estimates; • Certain accruals; • The allowance for doubtful accounts; • The realization of deferred taxes; • The carrying amount of goodwill and other intangible assets; • The useful lives of intangible assets and other long-lived assets with finite lives; • Incentive based compensation accruals and valuation of share-based payment arrangements; • Transfer pricing; • The recognition and measurement of uncertain tax positions; and • Other matters that affect the reported amounts and disclosure of contingencies in the consolidated financial statements. 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. Revenue Recognition Revenue is recognized in accordance with revenue recognition guidance. The Company primarily generates revenue through market making and by providing trading execution services for its clients. The Company categorizes revenue as Retail revenue , Institutional revenue, Futures revenue, Other revenue and Net interest revenue . Retail revenue is the Company's largest source of revenue. Retail revenue comprises trading revenue from the retail OTC business, sales trader, and advisory businesses. OTC trading includes forex trading ("forex"), metals trading, contracts-for-difference (“CFDs”) and spread-betting (in markets which do not prohibit such transactions), as well as other financial products. Gains or losses are realized when customer transactions are liquidated. Unrealized gains or losses on trading positions are revalued at prevailing foreign currency exchange rates (the difference between contract price and market price) at the date of the balance sheet and are included in Receivables from brokers as well as Payables to customers on the Consolidated Balance Sheets. Changes in net unrealized gains or losses are recorded in Retail revenue on the Consolidated Statements of Income and Comprehensive Income. Retail revenue is recorded on a trade date basis. Institutional revenue consists of revenue from the Company's GTX business, which provides a proprietary trading platform and sales and trading services to institutions. Revenue for the GTX business is generated primarily through commissions or spreads on trades executed on the GTX platform or by voice-brokers. The Company acts as an agent for the trades executed on the GTX platform. The Company, therefore, does not assume any market or credit risk in connection with those transactions. Revenues are booked on a trade date basis. Futures revenue consists of revenue from the Company's futures business, which offers exchange-based trading execution services, focusing on the indices, agricultural hedging, and commodities sectors. Revenues in this business are generated through commissions, which are earned for executing the Company's customers' trades. These revenues are booked on a trade date basis. The Company acts in an agency capacity with respect to the clearing of trades, but is a principal with respect to fees paid to introducing brokers in its futures business. The Company does not assume any market risk with respect to customer trades in this business. Other revenue primarily comprises account management and transaction fees, inactivity, training fees charged to customer accounts, and adjustments to contingent consideration, as well as foreign currency transaction gains and losses. Net interest revenue consists primarily of the revenue generated by our cash and customer cash held by us at banks, as well as funds on deposit as collateral with our liquidity providers, less interest paid to our customers. Interest revenue and interest expense are recorded when earned and incurred, respectively. Selling and marketing Selling and marketing costs are relate to producing and communicating advertising, as well as other marketing activities, and are expensed as incurred. Restructuring expenses In 2015, 2014 and 2013, the Company incurred restructuring expenses, which reflected costs arising from headcount reductions and other exit costs, measured and disclosed in accordance with relevant accounting guidance. Acquisition expenses I n 2015, 2014 and 2013, the Company incurred acquisition related expenses, which included costs such as legal, accounting, valuation and other costs specified in accounting guidance. These costs are expensed as incurred. Integration expenses In 2015, 2014 and 2013, the Company incurred integration expenses, which are acquisition related costs that are subsequently incurred while integrating the acquired company into the consolidated group. Investments For equity investments in which the Company exerts significant influence over operating and financial policies but does not have a controlling financial interest, the equity method of accounting is used. The were no distributed or undistributed earnings from equity method investees during 2015, 2014 or 2013. Impairment of investment In 2013, the Company’s investment in Kapitall, Inc. became impaired. During 2013 and 2014, the remaining carrying value was written off and recognized as an impairment loss. Gain on extinguishment of debt In 2013, the Company settled its GFT acquisition financing for less than the principal amount, in exchange for early payment. The difference between the principal and payment constituted Gain on extinguishment of debt . Cash and cash equivalents The Company considers all highly liquid investments with an original maturity of 90 days or less at the time of acquisition to be cash equivalents. At December 31, 2015 and 2014, the Company’s cash equivalents consisted of money market accounts with an initial maturity of 90 days or less. Cash equivalents are recorded at fair value. Cash and securities held for customers Cash and securities held for customers represents cash and other highly liquid assets held to fund customer liabilities in connection with trading positions. 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 . 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. Fair Value Certain financial assets and liabilities are recorded at fair value in accordance with applicable accounting guidance, as discussed in Note 4 Fair Value Information. Other financial assets and liabilities are not measured at fair value on a recurring basis but nevertheless approximate fair value due to their short term maturities. Such financial assets and liabilities include: Receivables from brokers; certain other assets; Payables to customers; and Accrued expenses and other liabilities. The above referenced receivables and payables include open trading positions which are held at fair value, hedging and customer positions, both of which change in value as the price of the underlying product changes. The prices approximate the amounts at which the Company can settle the positions at the balance sheet date. Concentrations of Credit Risk The Company owns financial instruments that subject the Company to credit risk. These financial instruments are held primarily in Cash and cash equivalents as well as Cash and securities held for customers . The Company’s credit risk is managed by investing cash and cash equivalents primarily in high-quality money market and from time to time U.S. and Canadian Government instruments. The majority of the Company’s cash and cash equivalents are held at ten financial institutions. The Company also has credit risk related to receivables from brokers included in Receivables from brokers . As of December 31, 2015 and 2014, 28% and 29% , respectively, of the Company’s Receivables from brokers balance, included in the Consolidated Balance Sheets, was from one large, global financial institution. Receivables from Brokers Receivables from brokers include funds that the Company has posted with brokers as collateral required by agreements for holding hedging positions. Also, Receivables from brokers contains funds required to collateralize customer futures trading, as well as the related excess and the Company's own collateral. These amounts are reflected as Receivables from brokers on the Consolidated Balance Sheets and include gains or losses realized on settled contracts, as well as unrealized gains or losses on open positions. Property and Equipment and Other Long-Lived Assets Property and equipment are recorded at cost, net of accumulated depreciation. Identifiable significant improvements are capitalized and expenditures for maintenance and repairs are charged to expense as incurred. Property and equipment are depreciated on a straight-line basis over a three year useful life, except for leasehold improvements, which are depreciated on a straight-line basis over the shorter of the lease term or estimated useful life. The Company accounts for costs incurred to develop its trading platforms and related software in accordance with Accounting Standards Codification ("ASC") 350-40, Internal-Use Software . ASC 350-40 requires that such technology be capitalized in the application and infrastructure development stages. Costs related to training, administration and non-value-added maintenance are charged to expense as incurred. Capitalized software development costs are being amortized over the useful life of the software, which the Company has estimated at three years . In accordance with ASC 360-10, Property, Plant and Equipment , the Company periodically evaluates the carrying value of long-lived assets when events and circumstances warrant such review. The carrying value of a long-lived asset is considered impaired when the anticipated undiscounted cash flows from such an asset are separately identifiable and are less than the carrying value. In that event, a loss is recognized in the amount by which the carrying value exceeds the fair market value of the long-lived asset. This guidance applies to assets held for use and not to assets held for sale. The Company has no assets held for sale. The Company has identified no such impairment indicators as of December 31, 2015 or December 31, 2014. Foreign Currencies Items included in the financial statements of each of the Company's subsidiaries are measured using the currency of the primary environment in which the subsidiaries operate ("the functional currency"). The Company has determined that its functional currency is U.S. dollars (“USD”). The Company’s Accumulated other comprehensive income/(loss), consists of foreign currency translation adjustments from subsidiaries not using the USD as their functional currency. Foreign currency transactions are remeasured into functional currency using the exchange rates prevailing at the dates of the transactions. Foreign exchange gains and losses resulting from the settlement of such transactions and from the remeasurement at period end exchange rates of monetary assets and liabilities denominated in foreign currencies are recognized in Other revenue on the Consolidated Statements of Income and Comprehensive Income. The Company recorded foreign exchange losses of $2.4 million , gains of $1.6 million and losses of $3.6 million for the years ended December 31, 2015, 2014 and 2013, respectively. Intangible Assets Accounting guidance addressing intangible assets requires purchased intangible assets other than goodwill to be amortized over their estimated useful lives unless their lives are determined to be indefinite. If indefinite-lived assets are determined to have a finite life in the future, the Company will amortize the carrying value over the remaining estimated useful life at that time. The Company analyzes its business, legal, and regulatory environment at least annually and on an interim basis when conditions indicate impairment may have occurred to determine whether its indefinite-lived intangible assets are likely to be impaired. This qualitative assessment indicated that it is more likely than not that the Company's indefinite lived intangible assets are not impaired. See Note 8 for additional information. Goodwill In accordance with relevant accounting guidance, the Company tests goodwill for impairment on an annual basis during the fourth quarter and on an interim basis when conditions indicate impairment may have occurred (see Note 8 ). In performing these assessments, management relies on and considers a number of factors, including operating results, business plans, economic projections, anticipated future cash flows, comparable market transactions (to the extent available), other market data and the Company's overall market capitalization. There are inherent uncertainties related to these factors which require judgment in applying them to the analysis of goodwill and indefinite-lived intangible assets for impairment. Goodwill impairment is determined by comparing the estimated fair value of the reporting units with their respective carrying value. At the date of the latest test as of December 31, 2015, using both the income approach and market approach, the fair value of each of the Company's reporting units was significantly in excess of its book value, as such no impairment was identified. Other Assets The Company records short term investments, receivables from vendors, security deposits, current and deferred tax assets, an indemnification asset, customer debit positions, net of related allowance, and miscellaneous receivables in Other assets on the Consolidated Balance Sheets. The Company considers all investments with an original maturity of greater than 90 days, but less than one year to be short term investments. Short term investments consist of short-term certificates of deposit. All income from the certificates of deposit is recorded as interest income when earned. See Note 9 for additional information. Derivatives Forex, metals, and CFDs allow for exchanging the difference in value of a particular asset such as stock index, energy product, or gold contracts, between the time at which a contract is opened and the time at which it is closed. The Company's retail customer open positions and positions with liquidity providers are considered derivatives under derivatives accounting guidance. Therefore, they are accounted for at fair value, and included in Receivables from brokers and Payables to customers in the Consolidated Balance Sheets. The Company did not designate any of its derivatives as hedging instruments. Net gains and losses with respect to derivative instruments are reflected in Retail Revenue in the accompanying Consolidated Statements of Income and Comprehensive Income. Allowance for Doubtful Accounts The Company records an increase in the allowance for doubtful accounts when the prospect of collecting a specific customer account balance becomes doubtful. Management specifically analyzes accounts receivable and historical bad debt experience when evaluating the adequacy of the allowance for doubtful accounts. Should any of these factors change, the estimates made by management will also change, which could affect the level of the Company’s future provision for doubtful accounts. The customer receivables, net of allowance for doubtful accounts, is included in Other assets on the Consolidated Balance Sheets. Receivables from customers are reserved for and the related reserves are recorded in Bad debt provision on the Consolidated Statements of Income and Comprehensive Income. The allowance for doubtful accounts consisted of the following (amounts in thousands): Balance as of January 1, 2013 $ (148 ) Addition to provision (1,501 ) Amounts written off 491 Balance as of December 31, 2013 (1,158 ) Addition to provision (3,699 ) Amounts written off 302 Balance as of December 31, 2014 (4,555 ) Addition to provision (7,462 ) Amounts written off 5,185 Balance as of December 31, 2015 $ (6,832 ) Payables to Customers Payables to customers , included on the Consolidated Balance Sheets, include amounts due on cash and margin transactions. These transactions include deposits, commissions and gains or losses arising from settled trades. The payables balance also reflects unrealized gains or losses arising from open positions in customer accounts. The Company engages in white label, or omnibus relationships, with other regulated financial institutions. The payables balance includes amounts deposited by these financial institutions in order for the Company to act as clearing broker. Referral fees Introducing brokers direct customers to the Company in return for a commission on each referred customer’s trading volume or a share of net revenue generated by each referred customer’s trading activity. Such fees are referred to as introducing broker fees and are recorded on a trade date basis, in Referral Fees, in the Consolidated Statements of Income and Comprehensive Income. Trading Expenses Trading expenses consist of exchange fees paid to stock exchanges and other third-parties for exchange market data that the Company provides to its customers or uses to create its own derived data products, as well as fees for news services and fees paid to prime brokers in connection with its institutional GTX business and futures business. Income Taxes Income tax expense is provided for using the asset and liability method, under which deferred tax assets and liabilities are determined based upon the temporary differences between the financial statement and income tax bases of assets and liabilities using currently enacted tax rates. The Company operates under a permanent reinvestment strategy, under which earnings derived from foreign businesses remain invested in the Company’s foreign subsidiaries. In accordance with accounting guidance, the Company does not recognize domestic tax expense related to the permanently reinvested earnings. The Company has no plans to repatriate accumulated unremitted earnings as of December 31, 2015. Employee compensation and benefits In accordance with stock compensation guidance, the Company recognizes expense for all share-based payments to employees, including grants of employee stock options as well as restricted stock units on the basis of grant date fair values. The Company estimates fair value using the Black Scholes model for stock options and fair value on grant date for restricted stock units. Shares typically vest incrementally and equally on an annual basis over a four year period, without performance triggers or other requirements beyond continued service. For each type of award, the Company reduces expense by an estimated forfeiture rate. See Note 15 for additional share based payment disclosure. The Company make estimates in determining its quarterly and annual accrued non-share-based compensation. A significant portion of the Company's employee incentive compensation programs is discretionary. Each quarter and year-end the Company determines the amount of its expected discretionary cash bonus pools. Treasury Shares In accordance with ASC 505-30, Equity - Treasury Stock , the Company treats the cost of acquired shares purchased as a deduction from shareholders’ equity and as a reduction of the total shares outstanding when calculating earnings per share. Earnings Per Common Share Basic earnings per common share is calculated using the weighted average common shares outstanding during the year. Common equivalent shares from stock options and restricted stock awards, using the treasury stock method, are also included in the diluted per share calculations unless their effect of inclusion would be anti-dilutive. See Note 16 for discussion of the impact of the Company's convertible note and non-controlling interests on EPS. Risk Management The Company offers its customers access to a diverse range of over 12,500 financial products, including spot foreign exchange, or forex, and precious metals trading, as well as “contracts for difference”, or CFDs, which are investment products with returns linked to the performance of underlying asset. We offer CFDs on currencies, commodities, indices, individual equities, bonds and interest rate products. We also support trading of exchange-traded futures and options on futures on more than 30 global exchanges. In the United Kingdom, we offer spread bets, which are investment products similar to CFDs, but that offer more favorable tax treatment for residents of that country. The Company actively trades currencies in the spot market, earning a dealer spread. The Company seeks to manage its market risk by generally entering into offsetting contracts in the interbank market, also on a margin basis. The Company deposits margin collateral with large money center banks and other major financial institutions. The Company is subject to credit risk or loss from counterparty nonperformance. The Company seeks to control the risks associated with its customers’ activities by requiring its customers to maintain margin collateral. The Company's trading platforms do not allow customers to enter into trades if sufficient margin collateral is not on deposit with the Company. The Company developed risk-management systems and procedures that allow it to manage the market and credit risk associated with managed flow activities in real-time. The Company does not actively initiate directional market positions in anticipation of future movements in the relative prices of currencies and evaluates market risk exposure on a continuous basis. As a result of the Company’s hedging activities, the Company is likely to have open positions in various currencies at any given time. An additional component of the risk-management approach is that levels of capital are maintained in excess of those required under applicable regulations. The Company also maintains liquidity relationships with three established, global prime brokers and at least six other liquidity providers, providing the Company with access to a liquidity pool.

Restatement

Restatement	12 Months Ended
	Dec. 31, 2015
Accounting Changes and Error Corrections [Abstract]
RESTATEMENT	RESTATEMENT The Company has determined that there were errors in the manner in which the Company accounted for income taxes as of and for the years ended December 31, 2014 and 2013 and for certain quarters of 2015 under ASC 740 (ASC 740), Income Taxes . These errors related primarily to the manner in which certain intercompany payables and receivables among domestic and overseas subsidiaries of the Company were treated for accounting and tax purposes during the impacted periods. The consolidated financial statements of the Company as of and for the years ended December 31, 2014 and 2013 included in this report have been restated to reflect the correction of these errors. In addition, certain other adjustments, previously determined to be immaterial individually and in the aggregate, have also been corrected in the restated financial statements. Other immaterial adjustments mentioned above include an error related to the calculation of the redemption value of the non-controlling interests previously recorded as an out of period adjustment in the six month period ended June 30, 2015. This previous out of period adjustment of $1.3 million reduced retained earnings and increased non-controlling interests. This has now been reflected in the appropriate periods. All relevant footnotes to the consolidated financial statements, including the quarterly financial data presented in Note 23 have also been restated to reflect the items discussed above. The following tables reflect the financial statement line items impacted by the restatement. The column headed "Tax Adjustment" reflects the impact of the tax matters discussed above, while the "All Other Adjustments" column reflects the impact of the other previously identified immaterial adjustments in the Consolidated Balance Sheet and Statements of Income and Comprehensive Income. The column headed "Adjustments" reflects the impact of the tax matters discussed above as well as the impact of the other previously identified immaterial adjustments in the Consolidated Statement of Cash Flows. For the avoidance of doubt, the following tables include only those line items impacted by the restatement. Consolidated Balance Sheet As of December 31, 2014 As Reported Tax Adjustment Other Adjustments As Restated ASSETS: Cash and cash equivalents $ 139,403 $ — $ (52 ) $ 139,351 Goodwill 34,567 (988 ) — 33,579 Other assets, net of allowance for doubtful accounts (1) 35,311 917 (2,463 ) 33,765 Total assets $ 1,185,887 $ (71 ) $ (2,515 ) $ 1,183,301 LIABILITIES AND SHAREHOLDERS’ EQUITY: Liabilities Accrued expenses and other liabilities 64,476 12,170 (451 ) 76,195 Income tax payable 1,470 1,603 (2,063 ) 1,010 Total liabilities $ 910,784 $ 13,773 $ (2,514 ) $ 922,043 Redeemable non-controlling interests 10,209 — 1,129 11,338 Shareholders’ equity Accumulated other comprehensive loss (2,054 ) 541 — (1,513 ) Additional paid-in capital 152,684 (4,306 ) — 148,378 Retained earnings 130,984 (10,079 ) (1,130 ) 119,775 Total shareholders’ equity 264,894 (13,844 ) (1,130 ) 249,920 Total liabilities and shareholders’ equity $ 1,185,887 $ (71 ) $ (2,515 ) $ 1,183,301 (1) The Company previously reported $174,000 as Short term investments, at fair value ; this amount has been reclassified to Other assets, net of allowance for doubtful accounts to conform to current year presentation Consolidated Statements of Income and Comprehensive Income For the Fiscal Year Ended December 31, 2014 As Reported Tax Adjustment Other Adjustments Restated REVENUE: Retail revenue (1) $ 293,122 $ — $ (344 ) $ 292,778 Institutional revenue (1) 34,518 — — 34,518 Futures revenue (1) 36,160 — — 36,160 Total non-interest revenue 368,704 — (344 ) 368,360 Net revenue $ 369,533 $ — $ (344 ) $ 369,189 EXPENSES: Employee compensation and benefits $ 99,485 $ — $ (252 ) $ 99,233 Referral fees 91,092 — (120 ) 90,972 Trading expenses 26,285 — (117 ) 26,168 General and administrative 38,509 — 142 38,651 Depreciation and amortization 7,125 — (515 ) 6,610 Restructuring expenses 1,214 — 1,120 2,334 Total operating expense 317,334 — 258 317,592 OPERATING PROFIT 52,199 — (602 ) 51,597 INCOME BEFORE INCOME TAX EXPENSE 46,052 — (602 ) 45,450 Income tax (benefit)/expense 12,993 6,200 (53 ) 19,140 NET INCOME 33,059 (6,200 ) (549 ) 26,310 NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. 31,626 (6,200 ) (549 ) 24,877 Other comprehensive (loss)/income: Foreign currency translation adjustment (4,630 ) 541 (4,089 ) NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. $ 26,996 $ (5,659 ) $ (549 ) $ 20,788 Earnings per common share: Basic $ 0.76 $ (0.16 ) $ (0.04 ) $ 0.56 Diluted $ 0.71 $ (0.14 ) $ (0.04 ) $ 0.53 (1) - The Company has changed its revenue presentation, see Note 1 for detail For the Fiscal Year Ended December 31, 2013 As Reported Tax Adjustment Other Adjustments As Restated REVENUE: Retail revenue (1) $ 215,667 $ — $ 67 $ 215,734 Institutional revenue (1) 28,005 — — 28,005 Futures revenue (1) 22,188 — — 22,188 Total non-interest revenue 266,959 — 67 267,026 Net revenue $ 267,624 $ — $ 67 $ 267,691 EXPENSES: Employee compensation and benefits $ 74,185 $ — $ 422 $ 74,607 Referral fees 52,503 — 120 52,623 General and administrative 26,813 — (255 ) 26,558 Depreciation and amortization 7,768 — 515 8,283 Restructuring expenses 1,570 — (1,120 ) 450 Total operating expense 223,286 — (318 ) 222,968 OPERATING PROFIT 44,338 — 385 44,723 INCOME BEFORE INCOME TAX EXPENSE 45,105 — 385 45,490 Income tax (benefit)/expense 13,794 3,589 — 17,383 NET INCOME 31,311 (3,589 ) 385 28,107 NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. 31,311 (3,589 ) 385 28,107 NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. $ 32,638 $ (3,589 ) $ 385 $ 29,434 Earnings per common share: Basic $ 0.85 $ (0.10 ) $ 0.01 $ 0.76 Diluted $ 0.79 $ (0.09 ) $ 0.01 $ 0.71 (1) - The Company has changed its revenue presentation, see Note 1 for detail Consolidated Statement of Changes in Shareholders' Equity Additional Paid in Capital Retained Earnings Accumulated Other Comprehensive Income/(Loss) Total As Reported As Restated As Reported As Restated As Reported As Restated As Reported As Restated BALANCE—January 1, 2013 $ 85,089 $ 85,009 $ 84,772 $ 84,590 $ 1,249 $ 1,249 $ 162,830 $ 162,568 BALANCE—January 1, 2014 $ 138,691 $ 134,399 $ 108,603 $ 105,217 $ 2,576 $ 2,576 $ 234,401 $ 226,723 BALANCE—December 31, 2014 $ 152,684 $ 148,378 $ 130,984 $ 119,775 $ (2,054 ) $ (1,513 ) $ 264,894 $ 249,920 Consolidated Statement of Cash Flows For the Fiscal Year Ended December 31, 2014 As Reported Adjustments As Restated CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 33,059 $ (6,749 ) $ 26,310 Adjustments to reconcile net income to cash provided by / (used for) operating activities Depreciation and amortization 16,367 (1,677 ) 14,690 Non-cash integration costs — 1,162 1,162 Deferred tax (benefit)/expense 2,536 2,572 5,108 Changes in operating assets and liabilities: Cash and securities held for customers (9,679 ) 419 (9,260 ) Receivables from brokers 94,657 276 94,933 Prepaid assets 2,729 1 2,730 Other assets (11,536 ) 3,041 (8,495 ) Payables to customers 9,679 (419 ) 9,260 Accrued compensation and benefits 3,671 826 4,497 Accrued expenses and other liabilities (8,565 ) 6,143 (2,422 ) Income tax payable (2,832 ) (6,980 ) (9,812 ) Cash provided by / (used for) operating activities 138,173 (1,385 ) 136,788 Effect of exchange rate changes on cash and cash equivalents 2,760 1,333 4,093 INCREASE/ (DECREASE) IN CASH AND CASH EQUIVALENTS 99,532 (52 ) 99,480 CASH AND CASH EQUIVALENTS—End of year $ 139,403 $ (52 ) $ 139,351 SUPPLEMENTARY DISCLOSURES OF CASH FLOW INFORMATION: Adjustment to redemption value of non-controlling interests $ (978 ) $ (1,129 ) $ (2,107 ) For the Fiscal Year Ended December 31, 2013 As Reported Adjustments Restated CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 31,311 $ (3,204 ) $ 28,107 Adjustments to reconcile net income to cash provided by / (used for) operating activities Depreciation and amortization 11,837 (648 ) 11,189 Non-cash integration costs — 1,163 1,163 Deferred tax (benefit)/expense 39 (5,470 ) (5,431 ) Stock compensation expense 2,896 79 2,975 Changes in operating assets and liabilities: Cash and securities held for customers (74,608 ) (161 ) (74,769 ) Receivables from brokers (78,336 ) (220 ) (78,556 ) Prepaid assets 318 — 318 Other assets (383 ) (692 ) (1,075 ) Payables to customers 74,608 161 74,769 Accrued compensation and benefits 7,118 (743 ) 6,375 Accrued expenses and other liabilities 973 6,894 7,867 Income tax payable 2,131 2,283 4,414 Effect of exchange rate changes on cash and cash equivalents (2,446 ) 558 (1,888 ) SUPPLEMENTARY DISCLOSURES OF CASH FLOW INFORMATION: Deferred taxes related to convertible senior notes $ — $ (4,308 ) $ (4,308 )

Recent Accounting Pronouncement

Recent Accounting Pronouncements	12 Months Ended
	Dec. 31, 2015
Accounting Changes and Error Corrections [Abstract]
RECENT ACCOUNTING PRONOUNCEMENTS	RECENT ACCOUNTING PRONOUNCEMENTS In February 2016, the FASB issued new guidance regarding the accounting for leases. The FASB issued this update to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. The guidance is effective for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. The Company is currently assessing the impact on its consolidated financial statements of adopting this guidance. In September 2015, the FASB issued new guidance regarding the accounting for provisional adjustments of business combinations. The guidance states that if changes are required to be made to provisional amounts included in previously issued financial statements, such changes should be included in the period in which they are identified. These changes include adjustments to goodwill, as well as the cumulative impact of adjustments for depreciation, amortization or other income. The guidance is effective for annual periods beginning after December 15, 2015, including interim periods within that reporting period. This guidance will impact how the Company deals with provisional adjustments for business combinations following adoption. In April 2015, the FASB issued new guidance regarding the accounting for debt issuance costs. The guidance requires presenting any deferred financing costs from debt issuances as a reduction in the amount of debt included on the balance sheet, which is a change from currently applicable rules requiring such costs to be classified as assets. In August 2015, the FASB issued updated guidance, which incorporated an SEC staff announcement highlighting that costs incurred for line-of-credit arrangements could be recorded as assets and amortized ratably over the term of the line-of-credit arrangement (regardless of whether there are any outstanding borrowings). The guidance is effective for interim and annual periods beginning after December 15, 2015. Early adoption is permitted for financial statements that have not been previously issued. The Company does not expect this guidance to have a material impact on its consolidated financial statements. In May 2014, the FASB issued new revenue recognition guidance that superseded the previously existing revenue recognition guidance and most industry-specific guidance applicable to revenue recognition. The guidance requires recognizing revenue when transferring promised goods or services to customers. Recognition should reflect the consideration which the company expects to receive in exchange for those goods or services. The guidance requires enhanced disclosures to help financial statement users better understand the nature, amount, timing and uncertainty of the revenues that are recognized. The guidance is effective for interim reporting periods within annual reporting periods beginning after December 15, 2017, which is a one year deferral from the original guidance, approved by the FASB in July 2015. Early application is permitted for annual periods beginning after December 15, 2016, including interim periods within that reporting period. The Company is currently assessing the impact on its consolidated financial statements of adopting this guidance.

Fair Value Information

Fair Value Information	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
FAIR VALUE INFORMATION	FAIR VALUE INFORMATION Accounting guidance 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): Customer derivative positions $ — $ 143,918 $ — $ 143,918 Broker derivative contracts — (12,568 ) — (12,568 ) Money market accounts 25,167 — — 25,167 Certificates of deposit 174 — — 174 Investment in gold 107 — — 107 Total $ 25,448 $ 131,350 $ — $ 156,798 Fair Value Measurements on a Recurring Basis as of December 31, 2014 Level 1 Level 2 Level 3 Total Financial Assets (Liabilities): Customer derivative contracts $ — $ 102,722 $ — $ 102,722 Broker derivative contracts — 717 — 717 Money market accounts 20,537 — — 20,537 Certificates of deposit 174 — — 174 Investment in gold 118 — — 118 Contingent consideration — — (9,974 ) (9,974 ) Total $ 20,829 $ 103,439 $ (9,974 ) $ 114,294 The Company has not changed its valuation techniques in measuring the fair value of any financial assets and liabilities during the years ended December 31, 2015 and December 31, 2014, nor has there been any movement between levels during these respective periods. Level 1 Financial Assets The Company has money market accounts, certificates of deposit and an investment in gold that are Level 1 financial instruments that are recorded based upon listed or quoted market rates. The money market accounts are recorded in Cash and cash equivalents and Cash and securities held for customers ; the certificates of deposit are recorded in Other Assets and the investment in gold is 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. The fair values of these Level 2 financial instruments are based upon directly observable values for underlying instruments. Level 3 Financial Liabilities Under the agreements governing the Company's acquisition of Galvan, the Company was obligated to make contingent payments that are Level 3 financial liabilities. These contingent payments were recorded under Accrued expenses and other liabilities on the Company's Consolidated Balance Sheets. The fair value of these payments was determined using current Company-specific and risk free interest rates as of the balance sheet date and probability-weighted forecasts of the acquired company's performance and client accounts, the estimation of which does not have any basis in quoted or observable markets. Significant increases (decreases) in any of the forecast inputs in isolation would result in a significantly higher (lower) fair value measurement, while significant increases (decreases) in interest rates would result in a significantly lower (higher) fair value measurement. In December 2015, the Company entered into an agreement with the former owners of Galvan to satisfy all remaining obligations under the contingent earn-out arrangement for a one-time payment of $ 1.5 million, which was paid in early 2016. The following is a rollforward of the Level 3 liabilities from January 1, 2014 to December 31, 2015 (amounts in thousands): Liabilities Contingent Consideration Balance at January 1, 2014 $ — Issuance of contingent payment obligation 10,540 Gains included in earnings - currency revaluation (984 ) Losses included in earnings - discount amortization 418 Balance at January 1, 2015 9,974 Gains included in earnings - adjustment to fair value of contingent consideration (6,722 ) Contingent consideration payments (2,063 ) Gains included in earnings - currency revaluation (212 ) Losses included in earnings - discount amortization 570 Settlement of contingent payment obligation (1,547 ) Balance at December 31, 2015 $ — Gains included in earnings - adjustment to fair value of contingent consideration and Gains included in earnings - currency revaluation for Level 3 liabilities are reported in Other revenue , while losses included in earnings attributable to discount amortization are reported in Interest expense . 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 consolidated balance sheets (amounts in thousands). Receivables from brokers comprise open trades, which are measured at fair value (disclosed above), and the Company's deposits, 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. Such settlement would 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 (disclosed above), 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. The carrying value of Convertible senior notes represents the notes’ principal amounts net of unamortized discount (see Note 14 ). The Company assessed the notes' fair value as determined by current Company-specific and risk free interest rates as of the balance sheet date. The carrying value of Accrued expenses and other liabilities included $20.0 million as of December 31, 2014 , referred to as the Holdback Amount, which is an amount relating to the Company's acquisition of GFT. These liabilities were settled, and accordingly, there are no liabilities for the Holdback Amount as of December 31, 2015. The carrying values of Accrued expense and other liabilities as of December 31, 2014 not measured at fair value approximate fair value because of the relatively short period of time between their origination and expected settlement date. As of December 31, 2015 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 $ 133,721 $ 133,721 $ — $ 133,721 $ — Financial Liabilities: Payables to customers $ 1,064,539 $ 1,064,539 $ — $ 1,064,539 $ — Convertible senior notes $ 121,996 $ 122,264 $ — $ 122,264 $ — As of December 31, 2014 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 $ 134,191 $ 134,191 $ — $ 134,191 $ — Financial Liabilities: Payables to customers $ 862,281 $ 862,281 $ — $ 862,281 $ — Convertible senior notes $ 68,367 $ 66,440 $ — $ 66,440 $ — Accrued expenses and other liabilities $ 20,000 $ 20,000 $ — $ 20,000 $ —

Derivatives

Derivatives	12 Months Ended
	Dec. 31, 2015
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 and Payables to customers on the accompanying Consolidated Balance Sheet (amounts in thousands): December 31, 2015 Gross amounts of assets for derivative open positions at fair value Gross amount of (liabilities) for derivative open positions at fair value Net amounts of assets/(liabilities) for derivative open positions at fair value Derivative Instruments: Foreign currency exchange contracts $ 138,140 $ (59,468 ) $ 78,672 CFD contracts 111,844 (70,429 ) 41,415 Metals contracts 18,866 (7,603 ) 11,263 Total $ 268,850 $ (137,500 ) $ 131,350 December 31, 2015 Cash Collateral Net amounts of assets/(liabilities) for derivative open positions at fair value Net amounts of assets/(liabilities) presented in the balance sheet Derivative Assets/(Liabilities:) Receivables from brokers $ 133,721 $ (12,568 ) $ 121,153 Payables to customers $ (1,064,539 ) $ 143,918 $ (920,621 ) December 31, 2014 Gross amounts of Gross amount of Net amounts of Derivative Instruments: Foreign currency exchange contracts $ 168,034 $ (93,057 ) $ 74,977 CFD contracts 44,329 (24,420 ) 19,909 Metals contracts 16,146 (7,593 ) 8,553 Total $ 228,509 $ (125,070 ) $ 103,439 December 31, 2014 Cash Collateral Net amounts of Net amounts of Derivative Assets/(Liabilities): Receivables from brokers $ 134,191 $ 717 $ 134,908 Payables to customers $ (862,281 ) $ 102,722 $ (759,559 ) 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 be considerably higher priced. The table below presents the number of contracts reported within Receivables from brokers and Payables to customers on the consolidated balance sheets (amounts in thousands): December 31, 2015 Total contracts in long positions Total contracts in short positions Derivative Instruments: Foreign currency exchange contracts 3,106,885 2,931,109 CFD contracts 139,465 285,640 Metals contracts 1,278 308 Total 3,247,628 3,217,057 December 31, 2014 Total contracts in long positions Total contracts in short positions Derivative Instruments: Foreign currency exchange contracts 3,147,518 2,679,041 CFD contracts 873,070 10,753 Metals contracts 835 335 Total 4,021,423 2,690,129 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 Consolidated Statements of Income and Comprehensive Income for the years ended December 31, 2015 and 2014 were as follows (amounts in thousands): For the Years Ended December 31, 2015 2014 Derivative Instruments: Foreign currency exchange contracts $ 163,315 $ 136,546 CFD contracts 151,553 105,174 Metals contracts 28,918 48,608 Total $ 343,786 $ 290,328

Receivables From Brokers

Receivables From Brokers	12 Months Ended
	Dec. 31, 2015
Receivables [Abstract]
RECEIVABLES FROM BROKERS	RECEIVABLES FROM BROKERS Amounts receivable from brokers consisted of the following as of (amounts in thousands): December 31, 2015 December 31, 2014 Required Collateral $ 129,042 $ 95,599 Excess from futures broker - Restricted 4,679 38,592 Open foreign exchange positions (12,568 ) 717 Total $ 121,153 $ 134,908 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 Consolidated Balance Sheets.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
PROPERTY AND EQUIPMENT	PROPERTY AND EQUIPMENT Property and equipment, including leasehold improvements and capitalized software development costs, consisted of the following as of (amounts in thousands): December 31, 2015 December 31, 2014 Software $ 44,194 $ 30,351 Computer equipment 14,300 8,516 Leasehold improvements 11,200 6,719 Telephone equipment 881 719 Office equipment 2,113 2,345 Furniture and fixtures 1,761 1,044 Web site development costs 668 646 Gross property and equipment 75,117 50,340 Less: Accumulated depreciation and amortization (44,750 ) (31,544 ) Property and equipment, net $ 30,367 $ 18,796 As mentioned in Note 1 above, the Company purchased all of the outstanding share capital of City Index in April 2015, Galvan in July 2014 and controlling interests in GAA and Top Third in March 2014. The final purchase price allocation for City Index, Galvan, GAA and Top Third to property and equipment are detailed below in Note 11 . Depreciation and amortization expense for property and equipment was $ 11.1 million , $6.6 million and $8.3 million for the years ended December 31, 2015, 2014 and 2013, respectively. The Company adjusted the depreciation and amortization period of certain property and equipment that experienced changes in estimated useful lives as a result of the City Index and GFT acquisitions. This change in useful lives resulted in an additional charges of $5.4 million and $1.2 million for the years ended December 31, 2015 and 2014. The additional charge was recorded in Integration expenses . In addition, the Company wrote off certain property and equipment that became obsolete as a result of the City Index acquisition. This resulted in an additional charge of $1.9 million for the year ended December 31, 2015. The additional charge was recorded in Integration expenses .

Intangible Assets and Goodwill

Intangible Assets and Goodwill	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
INTANGIBLE ASSETS AND GOODWILL	INTANGIBLE ASSETS AND GOODWILL Intangible Assets The Company's various finite-lived intangible assets consisted of the following as of (amounts in thousands): December 31, 2015 December 31, 2014 Intangibles Gross Accumulated Net Gross Accumulated Net Customer list $ 56,388 $ (14,111 ) $ 42,277 $ 22,944 $ (7,152 ) $ 15,792 Technology 74,378 (32,117 ) 42,261 48,376 (4,671 ) 43,705 Trademark 8,289 (1,678 ) 6,611 1,793 (847 ) 946 Total finite lived intangibles $ 139,055 $ (47,906 ) $ 91,149 $ 73,113 $ (12,670 ) $ 60,443 Trademarks not subject to amortization (1) 363 — 363 363 — 363 Total intangibles assets (2) $ 139,418 $ (47,906 ) $ 91,512 $ 73,476 $ (12,670 ) $ 60,806 (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. These trademarks are also supported annually in the Company's impairment test for intangible assets. (2) The increase in total intangibles for the year ended December 31, 2015 was primarily due to the customer lists, technology and trademarks acquired as part of the City Index acquisition. See Note 11 for details of the intangibles acquired in the Company's City Index, GAA, Top Third and Galvan acquisitions. The technology acquired pursuant to the asset purchase agreements with Valaquenta Intellectual Property Limited ("Valaquenta") and Forexster Limited ("Forexster"), is described in further detail below. The Company has the following identifiable intangible assets as of December 31, 2015: Intangible Asset Amount (in thousands) Weighted average amortization period Customer list $ 56,388 7.6 years Technology 74,378 8.9 years Trademark (1) 8,652 6.7 years Total intangible assets $ 139,418 (1) Trademarks with indefinite lives, as described above, comprise $0.4 million of the gross $8.7 million of trademarks. The final purchase price allocations to intangible assets for the acquisitions of City Index, Galvan, GAA, and Top Third acquisitions are detailed below in Note 11 . On July 10, 2014, the Company entered into asset purchase agreements with Forexster, pursuant to which one of the Company's subsidiaries, GAIN GTX Bermuda, Ltd. ("GTX Bermuda"), agreed to purchase from Valaquenta and Forexster the software and other intellectual property assets utilized to operate the electronic trading platform offered to customers in the Company's Gain GTX, LLC ("GTX") business. The purchase was made with a combination of $12.4 million in cash and $5.3 million in shares of the Company's unregistered common stock. GTX Bermuda agreed to pay Valaquenta contingent consideration in the event that GTX Bermuda or any of its affiliates in the future provide customers the ability to trade new types of financial instruments using the purchased intellectual property and the trading of such new products generates "Net Revenue" (as defined in the agreement with Valaquenta) in excess of thresholds set out in the agreement. Prior to the closing of the acquisitions, the Company had agreements with Valaquenta and Forexster granting it the exclusive right to use the intellectual property in the field of forex trading and non-exclusive rights to use the intellectual property for the trading of financial products in the fields of precious metals and hydrocarbons. Following the closing of the acquisition, GTX Bermuda has full rights and title over the intellectual property for trading of currencies, commodities and all other financial instruments of any kind whatsoever. This purchase added $21.4 million to the Company's intangible assets, $3.7 million of which were previously held as a prepayment made to Forexster under an exclusive rights agreement. The Company has assigned a 10 year useful life to this asset. Amortization expense for the purchased intangibles was $16.6 million , $8.1 million and $2.9 million for the years ended December 31, 2015, 2014 and 2013, respectively. The Company adjusted the amortization periods of certain intangible assets that experienced a change of estimated useful lives as a result of the City Index acquisition. This change resulted in an additional charge of $19.7 million during the year ended December 31, 2015. The additional charge is recorded in Integration expenses . During 2013, the Company accelerated $1.2 million of a software platform which was recorded in Integration expenses . Future annual estimated amortization expense is as follows (amounts in thousands): Years Ended December 31: 2016 $ 15,988 2017 15,132 2018 13,648 2019 11,974 2020 9,992 Thereafter 24,415 Total $ 91,149 Goodwill Goodwill is calculated as the difference between the cost of acquisition and the fair value of the net identifiable assets of an acquired business. As of December 31, 2015 and December 31, 2014 , the Company had recorded goodwill of approximately $34.0 million and $33.6 million , respectively. The increase of $0.4 million was primarily related to the City Index acquisition. There were no goodwill impairments as a result of performing the Company's 2015 and 2014 annual impairment tests. As previously noted, the Company changed its segment reporting structure effective December 31, 2015, from a single operating segment to three operating segments, Retail, Institutional and Futures. Goodwill has been allocated based on the relative fair value of each newly identified reporting units within such segments. The allocation was performed effective as of the same date as the goodwill impairment test. The following represents the carrying amount of goodwill by segment (amounts in thousands): Retail Institutional Futures Total Carrying amount of goodwill as of December 31, 2015 $ 26,722 $ 4,788 $ 2,507 $ 34,017

Other Assets

Other Assets	12 Months Ended
	Dec. 31, 2015
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
OTHER ASSETS	OTHER ASSETS Other assets consisted of the following as of (amounts in thousands): December 31, 2015 December 31, 2014 Vendor and security deposits $ 11,486 $ 3,373 Income tax receivable 9,482 5,163 Deferred tax assets, net 17,827 6,308 Indemnification asset — 8,792 GTX Trade Receivables 4,881 4,190 Customer Debit Positions 7,340 6,594 Allowance on customer debit positions (6,832 ) (4,555 ) Miscellaneous receivables 2,416 3,900 Equity method investment 822 — $ 47,422 $ 33,765 Under the terms of the GFT acquisition, an initial amount of $20.0 million , referred to as the Holdback Amount, was deferred, to be paid following the settlement of certain liabilities of GFT after the closing date of the acquisition. The selling stockholder of GFT agreed to indemnify the Company for these liabilities. At December 31, 2014, based on the Company's best estimate of the amounts necessary to settle such liabilities, the Company recorded an indemnification asset of $8.8 million at December 31, 2014. This was included within Other assets in the purchase price allocation of GFT. During the twelve months ended December 31, 2015, the previous liabilities of GFT were settled and, therefore, the Company made payments to the selling shareholder of GFT, as required by the stock purchase agreement providing for the acquisition of GFT, which settled the liability associated with the Holdback Amount.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2015
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 consolidated balance sheets. The aggregate amount of these funds was $0.3 million and $3.6 million at December 31, 2015 and December 31, 2014 , 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 consolidated balance sheet. The aggregate amount of these funds was $21.7 million at December 31, 2015.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2015
Business Combinations [Abstract]
ACQUISITIONS	ACQUISITIONS City Index (Holdings) Limited On April 1, 2015, the Company acquired the entire issued and outstanding share capital of City Index. City Index is a global online trading firm specializing in offering CFDs, forex and spread betting for retail customers. This acquisition was made to strengthen and diversify the Company's existing global footprint in the retail business. The purchase price consisted of approximately $6.1 million in cash, inclusive of working capital adjustments and $1.0 million in cash to be held in escrow, 5,319,149 shares of the Company's common stock, inclusive of 4,787,234 shares to be held in escrow, and 4.125% unsecured Convertible Senior Notes with an aggregate principal amount of $60.0 million and fair value of $65.0 million , inclusive of an aggregate principal amount of $54.0 million to be held in escrow. In addition, the Company paid City Index approximately $22.4 million , which was used to settle certain inter-company liabilities between City Index and City Index Group Limited (its former parent company). The difference in the purchase price from June 30, 2015 to December 31, 2015 was due to the finalization of working capital adjustments. The purchase price was derived as follows (amounts in thousands): Cash $ 6,103 Convertible senior notes 65,000 Common stock issued 45,100 Total purchase price $ 116,203 The purchase price of City Index was allocated to the fair value of various assets and liabilities as follows (amounts in thousands): Cash $ 10,546 Cash and securities held for customers 281,576 Receivable from brokers 35,974 Property and equipment 10,466 Prepaid assets 4,038 Other assets 5,119 Total tangible assets 347,719 Total liabilities assumed 299,000 Net assets acquired 48,719 Identifiable intangible assets: Customer list 34,277 Trade name 6,645 Technology 26,157 Intangible assets, net 67,079 Goodwill $ 405 Acquisition expenses were $2.8 million or the year ended December 31, 2015. They were recorded in Acquisition Expense. For the period from acquisition to December 31, 2015, revenues generated by City Index were $136.0 million , of which $30.8 million have been eliminated in consolidation, and expenses were $95.0 million of which $2.3 million have been eliminated in consolidation. City Index generated income before taxes of $41.0 million , of which $28.5 million have been eliminated in consolidation. The weighted average lives of City Index's intangible assets are 7.9 years for customer lists, 7.0 years for trade names, and 6.9 years for technology. Galvan Research and Trading, Ltd. In July 2014, the Company acquired all the share capital of Galvan and its wholly owned subsidiaries, Faraday Research LLP and Galvan LLP. The purchase price was $20.3 million . This acquisition was made to add an advisory capability to complement the Company's retail business. The purchase price was $9.7 million in cash and a contingent payment of $10.5 million payable over a three year period. Over the three year period, the contingent payment is subject to a fair value assessment related to achieving specific financial and customer account targets. The actual contingent payment for 2014 was $2.1 million , which was paid on September 30, 2015. For the twelve months ended December 31, 2015, the Company adjusted the contingent payment's value based on forecasts of performance related to 2015 and 2016 payments, and in December 2015 settled the outstanding contingent payment for $1.5 million payable in early 2016 (See Note 4 ). The purchase price was derived as follows (amounts in thousands): Cash $ 9,732 Contingent payment 10,540 Total purchase price $ 20,272 The purchase price of Galvan was allocated to the fair value of various assets and liabilities as follows (amounts in thousands): Cash and cash equivalents $ 2,193 Receivable from brokers 745 Property and equipment 12 Prepaid assets 94 Other assets 64 Total tangible assets 3,108 Total liabilities assumed 1,931 Net assets acquired 1,177 Identifiable intangible assets: Customer list 4,203 Trade name 784 Intangible assets, net 4,987 Goodwill $ 14,108 Acquisition expenses were $0.4 million for the year ended December 31, 2014. They were recorded in Acquisition Expense. For the period from acquisition to December 31, 2014, revenues generated by Galvan were $5.2 million , of which $2.4 million have been eliminated in consolidation, and expenses were $3.0 million , generating income before taxes of $2.2 million . Global Asset Advisors, LLC In March 2014, the Company acquired a 55% interest in GAA. The purchase price was $5.6 million . This acquisition was made to strengthen the Company's futures business. The purchase price was derived as follows (amounts in thousands): Cash $ 4,365 Common Stock issued 1,241 Total purchase price $ 5,606 The purchase price of GAA was allocated to the fair value of various assets and liabilities as follows (amounts in thousands): Non-controlling interest $ 4,509 Cash and cash equivalents $ 360 Receivable from brokers 438 Property and equipment 148 Prepaid assets 153 Other assets 3 Total tangible assets 1,102 Total liabilities assumed 515 Net assets acquired 587 Identifiable intangible assets: Customer list 3,100 Trade name 270 Intangible assets, net 3,370 Goodwill $ 6,158 Acquisition expenses were $0.1 million for the year ended December 31, 2014 and were recorded in Acquisition Expense. For the period from acquisition to December 31, 2014, revenues generated by GAA were $5.5 million , of which $4.3 million was eliminated in consolidation, and expenses were $4.8 million , generating income before taxes of $0.7 million , of which $0.3 million was recorded to non-controlling interests. Top Third Ag Marketing LLC In March 2014, the Company acquired a 55% interest in Top Third. The purchase price was a $3.5 million cash payment. This acquisition was made as part of the Company's strategy to diversify its revenue base. The purchase price of Top Third was allocated to the fair value of various assets and liabilities as follows (amounts in thousands): Non-controlling interest $ 3,885 Cash and cash equivalents $ 73 Receivable from brokers 663 Total tangible assets 736 Total liabilities assumed 1,103 Net liabilities assumed (367 ) Identifiable intangible assets: Customer list 3,900 Trade name 90 Intangible assets, net 3,990 Goodwill $ 3,806 Acquisition expenses were $0.1 million for the year ended December 31, 2014 and were recorded in Acquisition Expense. For the period from acquisition to December 31, 2014, revenues generated by Top Third were $5.1 million and expenses were $2.6 million , generating income before taxes of $2.5 million , of which $1.1 million was recorded to non-controlling interests. Global Futures & Forex, Ltd On September 24, 2013, the Company entered into an Amended and Restated Stock Purchase Agreement with Gary L. Tilkin, a natural person (the “Seller”), and GFT, pursuant to which the Company purchased all of the issued and outstanding share capital of GFT from the Seller. The acquisition was made as part of the Company's strategy to increase its offering of products and to expand its retail and institutional businesses into new markets and geographies. The purchase price allocation was derived as follows (amounts in thousands): Cash $ 40,000 Payment for excess cash adjustment 2,160 Loan payable 33,200 Common Stock issued 34,771 Total purchase price $ 110,131 The purchase price of GFT was allocated to the fair value of various assets and liabilities as follows (amounts in thousands): Cash and cash equivalents $ 15,781 Cash and cash equivalents held for customers 228,419 Receivable from brokers 61,028 Property and equipment 7,515 Other assets 18,942 Total tangible assets 331,685 Total liabilities assumed 251,691 Net assets acquired 79,994 Identifiable intangible assets: Software 25,300 Customer relationships 3,150 Intangible assets, net 28,450 Goodwill $ 1,687 Acquisition expenses were $1.8 million for the year ended December 31, 2013 and were recorded in Acquisition Expense. For the period from acquisition to December 31, 2013, revenues generated by GFT were $26.9 million and expenses were $32.0 million , generating a loss before taxes of $5.1 million . Pro Forma Information (unaudited): The following unaudited pro forma operating data is presented as if the acquisition of City Index had occurred on January 1, 2014, and includes actual results for GFT for periods after their acquisition in September 2013, GAA and Top Third for periods after their acquisition in March 2014, as well as Galvan results after its acquisition in July 2014. This data does not include any proforma adjustments for the GFT, GAA, Top Third or Galvan acquisitions, as the Company believes it is more useful to present the pro forma effects of the City Index acquisition on their own in light of the transaction's significance. The unaudited pro forma data does not include the impact of forecasted operating expense synergies. The unaudited pro forma data is provided for informational purposes only and may not necessarily be indicative of future results of operations or what the results of operations would have been had the Company and City Index operated as a combined entity for the periods presented. Unaudited pro forma income statement line items for the twelve months ended December 31, 2015 and December 31, 2014 were as follows (amounts in thousands): For the Fiscal Year Ended December 31, 2015 2014 REVENUE: Total non-interest revenue $ 471,959 $ 506,228 Interest revenue 1,303 2,288 Interest expense 1,049 599 Total net interest revenue 254 1,689 Net revenue 472,213 507,917 EXPENSES: Depreciation and amortization 11,753 16,500 Purchased intangible amortization 18,619 17,962 Other expense items 424,229 430,263 Total operating expense 454,601 464,725 OPERATING PROFIT 17,612 43,192 Interest on long term borrowings 10,267 9,283 Gain on extinguishment of debt — — Impairment of investment — — INCOME BEFORE INCOME TAX EXPENSE 7,345 33,909 Income tax expense 126 16,399 NET INCOME 7,219 17,510 Net income attributable to non-controlling interests 1,660 1,433 Net income applicable to Gain Capital Holdings, Inc. $ 5,559 $ 16,077 The following unaudited pro forma operating data is presented as if the acquisition of GAA, Top Third and Galvan had occurred on January 1, 2013. The unaudited pro forma data does not include the impact of forecasted operating expense synergies. The unaudited pro forma data is provided for informational purposes only and may not necessarily be indicative of future results of operations or what the results of operations would have been had the Company and the acquired companies operated as a combined entity for the periods presented. Unaudited pro forma income statement line items for the twelve months ended December 31, 2014 and December 31, 2013 were as follows (amounts in thousands): For the Fiscal Year Ended December 31, 2014 2013 REVENUE: Total non-interest revenue $ 376,362 $ 289,810 Interest revenue 1,435 856 Interest expense 599 156 Total net interest revenue 836 700 Net revenue 377,198 290,510 EXPENSES: Depreciation and amortization 6,626 8,407 Purchased intangible amortization 9,044 4,834 Other expense items 308,607 227,273 Total operating expense 324,277 240,514 OPERATING PROFIT 52,921 49,996 Interest on long term borrowings (6,147 ) (1,232 ) Gain on extinguishment of debt — 2,000 INCOME BEFORE INCOME TAX EXPENSE 46,774 50,764 Income tax expense 19,316 18,750 NET INCOME 27,458 32,014 Net income attributable to non-controlling interests 1,308 691 Net income applicable to Gain Capital Holdings, Inc. $ 26,150 $ 31,323 The following unaudited pro forma operating data are presented as if the acquisition of GFT had occurred on January 1, 2012. The unaudited pro forma data does not include the impact of forecasted operating expense synergies. The unaudited pro forma data is provided for informational purposes only and may not necessarily be indicative of future results of operations or what the results of operations would have been had the Company and GFT operated as a combined entity for the periods presented. Unaudited pro forma income statement line items for the twelve months ended December 31, 2013 and December 31, 2012, were as follows (amounts in thousands): For the Fiscal Year Ended December 31, 2013 2012 REVENUE: Total non-interest revenue $ 353,556 $ 248,592 Interest revenue 927 1,096 Interest expense 634 537 Total net interest revenue 293 559 Net revenue 353,849 249,151 EXPENSES: Other expense items (1) 299,945 261,679 Depreciation and amortization 11,527 7,958 Purchased intangible amortization 5,157 7,250 Acquisition expense 1,824 85 Restructuring 451 634 Integration 1,950 — Total expense 320,854 277,606 OPERATING PROFIT/(LOSSES) 32,995 (28,455 ) Interest expense on long term borrowings 1,232 444 Gain on extinguishment of debt 2,000 — INCOME BEFORE INCOME TAX EXPENSE/(BENEFIT) 33,763 (28,899 ) Income tax expense 16,106 (10,837 ) NET INCOME/(LOSS) $ 17,657 $ (18,062 ) (1) Other expenses items for the year ended December 31, 2013, included a one-time, non-recurring expense of $ 5.1 million relating to a GFT accrual for certain liabilities to third parties. Restructuring In 2013, the Company incurred Restructuring expenses, which reflected the cost of reducing global headcount following the GFT acquisition. Additional headcount reductions in the third quarter of 2014 were designed to meet challenging market conditions in the first half of 2014 and to achieve greater cost efficiency in general. The Company incurred $3.5 million of restructuring expenses for the twelve months ended December 31, 2015, which reflected the cost of reducing global headcount following the City Index acquisition. These expenses are recorded under Restructuring expense in the Consolidated Statements of Income and Comprehensive Income and the restructuring liability is recorded in Accrued compensation and benefits in the Consolidated Balance Sheets. (in thousands) Restructuring liability as of January 1, 2014 $ 584 2014 restructuring expenses 2,334 Payments made in 2014 (2,543 ) Liability as of December 31, 2014 375 2015 restructuring expenses 3,482 Payments made in 2015 (3,358 ) Liability as of December 31, 2015 $ 499

Non-controlling Interests

Non-controlling Interests	12 Months Ended
	Dec. 31, 2015
Noncontrolling Interest [Abstract]
NON-CONTROLLING INTERESTS	NON-CONTROLLING INTERESTS Non-controlling interests In March 2014, the Company acquired controlling interests in GAA and Top Third. The Company purchased 55% of each entity, and the respective sellers maintained a 45% interest in each entity. The 45% interests are redeemable at prices determined by applying a contractually agreed upon formula to the respective acquired company's financial results. The Company owns immediately exercisable call options to purchase the remaining interests in each company. The minority owners hold put options, which become exercisable in 2017 or upon the occurrence of certain events, to compel the Company to purchase the remaining interests. The non-controlling interests are not classified as liabilities, because redemption is not mandatory or at fixed prices. They are not classified as equity because their redemption is not exclusively in the Company's control. Therefore, the non-controlling interests are held in temporary equity in the Consolidated Balance Sheets. The non-controlling interests' carrying value is determined by the Company's purchase prices and the non-controlling interests' share of the Company's subsequent net income. This value is benchmarked against the redemption value of the sellers' put options. The carrying value is adjusted to the latter, provided that it does not fall below the initial carrying values, as determined by the Company's purchase price allocation. The Company has made a policy election to reflect any changes caused by such an adjustment in retained earnings, rather than in current earnings. The table below reflects the non-controlling interests effects on the Company's financial statements: Redeemable non-controlling interests December 31, 2013 $ — Non-controlling interests related to 2014 acquisitions 8,394 Adjustment to the redemption value of non-controlling interests 2,107 Net income attributable to non-controlling interests 1,433 Distributions to non-controlling interest holders (596 ) December 31, 2014 $ 11,338 Adjustment to the redemption value of non-controlling interests (308 ) Net income attributable to non-controlling interests 1,660 Distributions to non-controlling interest holders (1,644 ) December 31, 2015 $ 11,046

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
SHAREHOLDERS' EQUITY	SHAREHOLDERS' EQUITY Common Stock — At December 31, 2015 and 2014, the Company had authorized 120,000,000 and 60,000,000 shares of Common Stock, respectively, of which 52,072,884 and 48,771,015 shares were issued and outstanding, respectively as of December 31, 2015, and 45,582,066 and 42,934,559 shares were issued and outstanding, respectively as of December 31, 2014. Treasury Stock — As of December 31, 2015 and 2014, the Company had repurchased 3.3 million shares and 2.6 million shares, respectively, of outstanding Common Stock for an aggregate cost of $21.8 million and $16.7 million , respectively, reducing the number of shares outstanding. Dividends — In February, May, July and November of 2015, 2014 and 2013, the Company announced the payment of a $0.05 quarterly dividend per share of Common Stock. The dividend payments announced in February, May, July and November were paid in March, June, September and December of each year, for an aggregate amount of $ 9.5 million , $8.1 million and $7.3 million respectively, which was applied against Retained Earnings .

Convertible Senior Notes

Convertible Senior Notes	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
CONVERTIBLE SENIOR NOTES	CONVERTIBLE SENIOR NOTES Convertible Senior Notes due 2020 On April 1, 2015, as part of the City Index acquisition consideration, the Company issued to the sellers $60.0 million aggregate principal amount of 4.125% Convertible Senior Notes maturing on April 1, 2020. These Convertible Senior Notes pay interest semi-annually on April 1 and October 1 at a rate of 4.125% per year, which commenced on October 1, 2015. Prior to the date that is six months immediately preceding the maturity date, the Convertible Notes will be convertible only upon the occurrence of specified events set forth in the Note Indenture. Thereafter, until the close of business on the business day immediately preceding the maturity date, holders may convert their Convertible Notes at any time. The Company will settle conversions of the Convertible Notes by paying or delivering, as the case may be, cash, shares of Common Stock or a combination thereof, at its election. The conversion rate for the Convertible Notes will be equal to $1,000 , divided by the initial conversion price, rounded to the nearest 1/10,000th share of Common Stock. The initial conversion price will be equal to 125% of the arithmetic average of the daily volume-weighted average price for the Common Stock over the 20 consecutive trading day period ending on, and including, the trading day immediately preceding the closing date; provided that the initial conversion price shall not exceed the greater of (i) $9.25 and (ii) the last reported sale price of the Common Stock on the Closing Date; and shall not be less than $7.20 . The conversion rate and the corresponding conversion price will be subject to customary anti-dilution adjustments, as described in the Note Indenture, including, but not limited to, Common Stock splits, Common Stock combinations, issuances of Common Stock as a dividend on the Common Stock, issuances of options rights, warrants or other securities of the Company as a dividend on the Common Stock, payment by the Company of any cash dividend in excess of $0.05 per quarter per share of Common Stock, and above-market tender offers or exchange offers by the Company or its subsidiaries for the Common Stock. In addition, in certain circumstances, the Company may be required to increase the conversion rate for any Convertible Notes converted in connection with a make-whole fundamental change as defined in the Note Indenture. If the Company undergoes a fundamental change, holders may require the Company to repurchase for cash all or part of their Convertible Notes at a purchase price equal to 100% of the principal amount of the Convertible Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the date of repurchase. Prior to the date that is two years immediately preceding the maturity date, the Company will not have the right to redeem the Convertible Notes. During the two year period immediately preceding the maturity date, the Company may redeem for cash all, but not less than all, of the Convertible Notes if the last reported sale price of the Common Stock equals or exceeds 130% of the conversion price for the Convertible Notes for at least 20 trading days, whether or not consecutive, during the 30 consecutive trading day period ending on the trading day immediately preceding the date the Company delivers notice of redemption. If the Company elects to redeem the Convertible Notes, holders may convert their Convertible Notes at any time prior to the close of business on the business day immediately preceding the redemption date. The Indenture will contain events of default customary for convertible debt securities (with customary grace periods, as applicable) and will provide that, upon the occurrence of an event of default arising from certain events of bankruptcy or insolvency with respect to the Company, all outstanding Convertible Notes will become due and payable immediately without further action or notice. If any other type of event of default occurs and is continuing, then the holders of at least 25% in aggregate principal amount of the then outstanding Convertible Notes or the trustee may declare all of the outstanding Convertible Notes to be due and payable immediately. Convertible Senior Notes due 2018 On November 27, 2013, the Company issued $80.0 million principal amount of 4.125% Convertible Senior Notes maturing on December 1, 2018. The Company received net proceeds of $77.9 million , after deducting the initial purchasers' discount. These Convertible Senior Notes pay interest semi-annually on June 1 and December 1 at a rate of 4.125% per year, which commenced on June 1, 2014. The Convertible Senior Notes will be convertible at an initial conversion rate of 83.33 shares of the Company's common stock per $1,000 principal amount, which is equivalent to an initial conversion price of approximately $12.00 . In addition, following certain corporate transactions occurring prior to the maturity date, the Company will, in certain circumstances, increase the conversion rate for a holder electing to convert notes in connection with such corporate transaction. Upon conversion, the Company will deliver cash up to the principal amount. With respect to any conversion value in excess of the principal amount, the Company will deliver shares of its common stock, unless it elects to deliver cash in lieu of all or a portion of such shares. Holders may convert notes in integral multiples of $1,000 principal amount, at any time prior to the close of business on the business day immediately preceding June 1, 2018, but only in the following circumstances: • During any calendar quarter commencing after the calendar quarter ending on March 31, 2014 (and only during such quarter), the last reported sale price of the Company’s common stock for each of at least 20 of the preceding 30 trading days, ending on and including the last trading day of the quarter exceeds 130% of the conversion price. These days need not be consecutive; • During the five consecutive business day period immediately after any five consecutive trading day period (such five consecutive trading day period being referred to as the “measurement period”), in which the trading price (as defined in the offering memorandum) per $1,000 principal amount of the notes, as determined following a request by a holder of the notes in the manner described in the offering memorandum, for each trading day of the measurement period, was less than 98% of the product of the last reported sale price of the Company's common stock and the conversion rate on such trading day; • Upon the occurrence of specified corporate events (as described in the offering memorandum); or • If the Company has called the notes for redemption (as described in the offering memorandum). In addition, regardless of the foregoing circumstances, holders may convert their notes at any time on or after June 1, 2018 until the close of business on the business day immediately preceding the maturity date. In addition, if the Company undergoes a fundamental change (as defined in the Note indenture), holders may, subject to certain conditions, require the Company to repurchase their notes for cash at a price equal to 100% of the principal amount of the notes to be purchased, plus accrued and unpaid interest. Under accounting guidance, an entity must separately account for the liability and equity components of a convertible debt instrument that may be settled entirely or partially in cash upon conversion. The separate accounting must reflect the issuer's economic interest cost. The fair value of the equity component, net of pro-rata initial purchasers’ discounts, is included in the additional paid-in capital section of stockholders' equity in the Company's Consolidated Balance Sheets. The principal amount of the Convertible Senior Notes is reduced by unamortized original issue discount, which reflects the Convertible Senior Notes fair value. At issuance, the equity component of the Convertible Senior Notes was valued at $27.9 million before pro-rata initial purchasers' commissions of $0.3 million and related additional costs of $0.1 million . The Convertible Senior Notes were valued at $117.1 million consisting of $140.0 million of principal, net of $27.9 million allocated to equity, not including pro-rata initial purchasers' commissions of $1.8 million and additional related costs of $0.4 million . The original issue discount will be amortized over the life of the Convertible Senior Notes due 2020 and 2018 using the effective interest rate of 8.6% and 8.1% , respectively. Relevant accounting guidance requires entities to disclose the dilutive effects of convertible instruments. As of December 31, 2015 and 2014, the Company’s common stock had not met the convertibility criteria noted in the offering memorandum. Therefore, the Convertible Senior Notes were not dilutive as of December 31, 2015 and 2014. The balances of the liability and equity components as of December 31, 2015 and 2014, were as follows, with amounts in thousands: December 31, December 31, 2015 2014 Liability component - principal $ 140,000 $ 80,000 Deferred bond discount 18,004 11,633 Liability component - net carrying value $ 121,996 $ 68,367 Additional paid in capital $ 27,920 $ 12,572 Discount attributable to equity (412 ) (425 ) Equity component $ 27,508 $ 12,147 Interest expense related to the Convertible Senior Notes, included in Interest expense on long-term borrowings in the Consolidated Statements of Income and Comprehensive Income, was as follows, with amounts in thousands: For the Fiscal Year Ended December 31, 2015 2014 Interest expense - stated coupon rate $ 5,156 $ 3,300 Interest expense - amortization of deferred bond discount and costs 3,712 2,593 Total interest expense - convertible note $ 8,868 $ 5,893

Share Based Compensation

Share Based Compensation	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
SHARE BASED COMPENSATION	SHARE BASED COMPENSATION Share Based Payment Total share-based compensation cost recognized during 2015, 2014 and 2013 consisted of the following ($ in thousands:) For the Years Ended December 31, 2015 2014 2013 Employee compensation and benefits 3,680 3,452 2,975 On September 30, 2015, the Company's board of directors adopted the GAIN Capital Holdings, Inc. 2015 Omnibus Incentive Compensation Plan, (the "2015 Plan"), which became effective November 30, 2015. The 2015 Plan replaces the GAIN Capital Holdings, Inc. 2010 Omnibus Incentive Compensation Plan, (the “2010 Plan”). The 2015 Plan has available 8.7 million shares ( 5.8 million to be issued pursuant to future awards and grants under the 2015 Plan, 2.7 million shares that are subject to outstanding grants under the 2010 Plan, and 0.2 million shares to be issued pursuant to the 2011 Employee Stock Purchase Plan) for awards to employees, nonemployee directors, consultants, and advisors in the form of incentive stock options ("ISO"), nonqualified stock options ("NQSO"), restricted stock awards ("RSA"), restricted stock units ("RSU"), stock appreciation rights and other stock-based awards. The "evergreen" provision that allowed the Company to authorize additional shares to be issued under the 2010 plan was removed from the 2015 Plan. Accordingly, the maximum number of shares that can be issued will be fixed and cannot be increased in the future without shareholder approval. Under the 2015 Plan, the Compensation Committee of the Board of Directors (the "Compensation Committee") will determine the exercise price of the options granted and may grant options to purchase shares of the Company’s common stock in amounts as determined by the Compensation Committee. The Compensation Committee may grant options that are intended to qualify as ISOs under Section 422 of the Internal Revenue Code, or NQSOs which are not intended to so qualify. ISOs may only be granted to employees. Anyone eligible to participate in the 2015 Plan may receive a grant of NQSQs. The exercise price of a stock option granted under the 2015 Plan cannot be less than the fair market value of a share of the Company’s common stock on the date the option is granted. All options granted under the 2015 Plan expire ten years from the date of grant. Stock Options The following table summarizes the stock option activity under all plans from January 1, 2015 through December 31, 2015 (in thousands, except per share amounts): Options Outstanding Weighted Weighted Average Number of Average Remaining Aggregate Options Exercise Price Life (Years) Intrinsic Value Outstanding January 1, 2015 1,908 $ 4.83 3.30 Granted 137 9.51 6.40 Exercised (638 ) 3.74 1.86 Forfeited/Expired (49 ) 6.62 5.00 Outstanding December 31, 2015 1,358 $ 5.76 4.16 $ 3,544 Vested and expected to vest options 1,340 $ 5.71 4.13 $ 3,525 Exercisable, December 31, 2015 938 $ 5.17 3.83 $ 2,792 Fair market value of common stock at exercise date $ 5,869 Cost to exercise 2,388 Net value of stock options exercised $ 3,481 The following table summarizes information concerning outstanding and exercisable stock options as of December 31, 2015 : Options Outstanding Options Exercisable Weighted Average Weighted Remaining Number of Weighted Number Average Contractual Options Average Exercise Price Outstanding Exercise Price Life (Years) Exercisable Exercise Price $3.83 481 $ 3.83 1.64 481 $ 3.83 $4.40 238 4.40 4.22 90 $ 4.40 $5.30 208 5.30 3.31 136 $ 5.30 $8.02 210 8.02 2.29 210 $ 8.02 $9.51 137 9.51 9.51 — $ 9.51 $9.95 84 9.95 5.18 21 $ 9.95 1,358 $ 5.76 4.16 938 $ 5.17 The weighted-average remaining contractual life for the 1.4 million outstanding options as of December 31, 2015 , is approximately 4.16 years. There were 0.9 million stock options exercisable as of December 31, 2015 . The total intrinsic value of stock options exercised during 2015, 2014, and 2013 respectively were $3.5 million , $4.2 million and $4.7 million . During 2015, the Company had 0.3 million stock options vest. The Company received $2.4 million , $2.1 million , and $2.5 million from stock option exercises in 2015, 2014, and 2013, respectively. In 2015, the Company granted 0.1 million options to employees. In 2014, the Company granted 0.1 million options to employees. In 2013, the Company granted 0.5 million options to employees. The weighted average grant-date fair value of stock options granted in the years ended December 31, 2015, 2014, and 2013 was $ 3.43 , $3.79 , and $1.22 , respectively. The Compensation Committee approved stock option grants with a fair market value estimated under a Black-Scholes option pricing valuation model using the following assumptions: For the Fiscal Year Ended December 31, 2015 2014 2013 Valuation Assumptions Risk-free rate 1.47% 1.40% 0.80% Expected volatility 49.08% 51.80% 48.80% Expected term (years) 4.75 4.80 4.80 Dividend yield 2.1% 2.0% 4.9% The expected volatility was calculated on the basis of the volatility of the Company's common stock. The average risk free rate is based upon the risk free rate of the U.S. Treasury bond rate with a maturity commensurate with the expected term. The options granted during 2015 were granted on May 26, 2015. Restricted Stock Units and Restricted Stock Awards The 2015 Plan provides for the issuance of RSUs that are convertible on a 1 :1 basis into shares of the Company’s common stock. The Company maintains a restricted stock unit account for each grantee. RSU grants typically vest over four years , with 25% vesting on each anniversary date of the grant. After the RSUs vest, the grantee shall receive payment in the form of cash, shares of the Company’s common stock, or a combination of the two, as determined by the Company. Payment of cash and/issuance of shares shall be made upon the vesting date, upon a predetermined delivery date, upon a change in control of the Company, or upon the employee leaving the Company. The Company has historically settled these awards through the issuance of common stock to recipients and intends to continue to do so. The Company may also issue performance grants, which vest immediately, but under which delivery of the common stock is deferred until a later date. RSUs are assigned the value of the Company’s common stock at date of grant issuance, and the grant date fair value is amortized over a four year period. During 2015, 2014 and 2013, 0.6 million , 0.5 million and 0.8 million RSUs, respectively, were granted to employees and members of the Board of Directors. The 2015 Plan also provides for the issuance of restricted stock awards, or RSAs, which represent shares of the Company’s common stock subject to transfer and other restrictions. The Company maintains a restricted stock award account for each grantee. Restrictions typically lapse over four years , with 25% vesting on each anniversary date of the grant. After the restrictions lapse, or upon a change in control of the Company, the grantee shall receive payment in the form of cash, shares of the Company’s common stock, or a combination of the two, as determined by the Company. The Company has historically settled these awards through the issuance of common stock to recipients and intends to continue to do so. The Company may also issue performance grants which have immediate vesting. There were no RSAs granted during 2015, 2014 or 2013. A summary of the status of the Company’s nonvested shares of RSUs and RSAs as of December 31, 2015 and changes during the year ended December 31, 2015 , is presented below (in thousands, except per share amounts): Weighted Average Weighted Average Number Grant Date Number Grant Date Non-Vested Shares of RSUs Fair Value of RSAs Fair Value Non-vested at January 1, 2015 1,073 $ 6.69 54 $ 7.31 Granted 601 9.42 — — Vested (387 ) 6.46 (53 ) 7.32 Forfeited (104 ) 8.08 (1 ) 6.48 Non-vested at December 31, 2015 1,183 $ 8.03 — $ — As of December 31, 2015 , there was $7.5 million of total unrecognized compensation cost related to non-vested share-based compensation arrangements granted under the 2010 Plan. The cost is expected to be recognized over a weighted-average period of approximately three years . The fair market value on the grant date for RSUs and RSAs vested during the years ended December 31, 2015, 2014 and 2013 was $2.9 million , $4.3 million and $1.7 million , respectively. The total intrinsic value of the RSUs and RSAs that became unrestricted during the year ended December 31, 2015 was $4.2 million at the date they became unrestricted. RSUs and RSAs that were vested during the year ended December 31, 2015 , had a value at grant date of $2.9 million . The Company granted RSUs during the year ended December 31, 2015 which had a value of $5.7 million at grant date. The fair market value of RSUs and RSAs at the date of grant during the year ended December 31, 2014 was $4.5 million . Employee Stock Purchase Plan The 2011 Employee Stock Purchase Plan ("ESPP") was adopted by the Company’s Board of Directors on November 22, 2010. The ESPP became effective on January 1, 2011. The ESPP permits eligible employees to purchase shares of the Company’s common stock at a 15% discount from the lesser of the fair market value per share of the Company’s common stock on the first day of the offering period or the fair market value of the Company’s common stock on the interim purchase date through after-tax payroll deductions. The total number of shares reserved for issuance under the ESPP was initially 500,000 . It is intended that the ESPP meet the requirements for an “employee stock purchase plan” under Section 423 of the Internal Revenue Code. For the year ended December 31, 2015 , 92,777 shares were issued under the plan. For the year ended December 31, 2014 , 98,606 shares were issued under the ESPP. The discount on the ESPP of $0.1 million is recorded to Employee compensation and benefits on the Consolidated Statement of Income and Comprehensive Income.

Earnings Per Common Share

Earnings Per Common Share	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
EARNINGS PER COMMON SHARE	EARNINGS PER COMMON SHARE Basic and diluted earnings per common share are computed by dividing net income by the weighted average number of common shares outstanding during the period. Diluted earnings per share includes the determinants of basic net 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, vested restricted stock units and vested restricted stock awards which are to be delivered as soon as administratively practicable on or after December 31, 2015, unvested restricted stock units and unvested restricted stock awards. Approximately 0.4 million and 0.1 million stock options were excluded from the calculation of diluted earnings per share for the years ended December 31, 2015 and 2014, respectively, as they were anti-dilutive. Diluted earnings per share excludes any shares of Company common stock potentially issuable under the Company's convertible notes, which are discussed in Note 14 . Based upon an assumed trading price of $13 for each share of the Company's common stock, and if the relevant conditions under the indentures governing both 2018 and 2020 convertible senior notes were satisfied, there would be an additional 0.5 million and 1.5 million dilutive shares for the 2018 and 2020 notes, respectively. The following table sets forth the computation of earnings per share (amounts in thousands except share and per share data): For the years ended December 31, 2015 2014 2013 Net income applicable to GAIN Capital Holdings, Inc. $ 10,279 $ 24,877 $ 28,107 Adjustment (1)(2) 308 (2,107 ) (154 ) Net income available to GAIN common shareholders $ 10,587 $ 22,770 $ 27,953 Weighted average common shares outstanding: Basic weighted average common shares outstanding 47,601,979 40,561,644 36,551,246 Effect of dilutive securities: Stock options 424,087 763,068 1,214,370 RSUs/RSAs 352,985 1,890,183 1,867,262 Diluted weighted average common shares outstanding 48,379,051 43,214,895 39,632,878 Earnings per common share Basic $ 0.22 $ 0.56 $ 0.76 Diluted $ 0.22 $ 0.53 $ 0.71 (1) During the years ending December 31, 2015 and 2014, the Company concluded that the carrying value of the Company's redeemable non-controlling interests was less than its redemption value. The adjustment to increase carrying value reduces earnings available to the Company's shareholders. (2) During the year ending December 31, 2013, an adjustment to retained earnings was made, reflecting the amounts deemed uncollectible associated with previously issued preferred stock, which was converted to common stock immediately prior to the Company's IPO in 2010.

Legal

Legal	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
LEGAL	LEGAL 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 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 or additional loss can be reasonably estimated for any proceeding. Litigation On February 16, 2012, the Company received a Letter of Claim on behalf of certain individuals who had lost money in an investment scheme operated by a third-party money management firm, incorporated in the United Kingdom, which has since been closed down by the United Kingdom’s Financial Services Authority. The investment firm, Cameron Farley Ltd, had opened a corporate account with the Company and invested the individuals’ money, representing such funds as its own, while operating a fraudulent scheme. Though a complaint has been filed and served on the Company, the claimants requested, and the Company agreed, to follow the United Kingdom’s Pre-Action Protocol, a pre-litigation process intended to resolve matters without the need to engage in formal litigation. The Company submitted a Response to the Letter before Claim on July 4, 2012. On July 5, 2012 the Company received a substantially similar Letter of Claim on behalf of further individuals. Subsequently, the parties agreed to consolidate claims by those other similarly situated individuals with the pending Pre-Action Protocol process. The parties agreed it would be more appropriate for the proceedings to be dealt with in the Commercial Court and the matters were transferred pursuant to Consent Orders dated March 14, 2013. The Company subsequently filed an application for strike out and/or summary judgment in respect of all claims on March 15, 2013. The claimants filed an answer to the Company's motion on June 2, 2013 and subsequently the Company filed a response to this answer on July 15, 2013. A hearing was held on the Company's application for strike out and/or summary judgment on September 18 and 19, 2013. After the hearing, the judge asked the claimants to respond in writing to his additional questions from the hearing. The claimants had until October 11, 2013 to provide answers and the Company was given until November 1, 2013 to respond. On February 26, 2014, the judge denied the Company's motion for strike out and/or summary judgment. Case management conferences were held by the Court on October 17, 2014 and June 18, 2015. On August 3, 2015, the claimants filed an Amended Master Particulars of Claim, and on October 6, 2015, the Company filed an Amended Defense. The parties have completed discovery and provided disclosure on October 30, 2015. The current Court timetable provides for a trial date in the first quarter of 2017. The Company can provide no assurances that this matter will be successfully resolved. As of the date of this report, a potential loss or a potential range of loss cannot be reasonably estimated. Through the Company's acquisition of Open E Cry ("OEC"), the Company became the subject of a patent infringement lawsuit originally filed against OEC on February 9, 2010 in the U.S. District Court for the Northern District of Illinois by Trading Technologies International, Inc. ("Trading Technologies") seeking injunctive relief and unspecified damages. As reflected in a Second Amended Complaint filed on June 15, 2011, plaintiff alleged infringement of 12 patents relating to real-time display of price quotes and market depth on OEC's electronic trading interfaces. The case was consolidated with 11 related cases in February 2011, and the parties have exchanged infringement, non-infringement and invalidity contentions for several of the disputed patents. On May 6, 2015, the Company entered into a settlement and license agreement with Trading Technologies pursuant to which the Company made a one-time royalty payment to Trading Technologies in exchange for a volume-based license for the disputed patents. The Company was fully indemnified for the amount of the royalty payment by the former owner of OEC and therefore the Company incurred no net expense. The lawsuit was dismissed on May 6, 2015.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Leases & Purchase Obligations — The Company leases office space under non-cancelable operating lease agreements that expire on various dates through 2025. Such leases do not require any contingent rental payments or impose any financial restrictions. Certain of the Company's leases include renewal options and escalation clauses. In addition, the Company has certain non-cancelable purchase obligations for its operational needs. Future annual minimum lease payments for the Company's non-cancellable operating leases and purchase obligations are as follows (amounts in thousands): Years Ended December 31: 2016 $ 21,369 2017 6,716 2018 5,077 2019 4,478 2020 and beyond 15,937 Total $ 53,577 Rent expense, which is recorded on a straight-line basis, was $3.7 million , $5.1 million , and $3.7 million for the years ended December 31, 2015, 2014 and 2013, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The following table presents the U.S. and non-U.S. components of income before income tax (benefit) / expense for the years ended December 31, 2015, 2014, and 2013 (amounts in thousands): For the Fiscal Year Ended December 31, 2015 2014 2013 U.S. $ (39,761 ) $ 17,439 $ 18,546 Non-U.S. 48,188 28,011 26,944 Total income before tax (benefit) / expense $ 8,427 $ 45,450 $ 45,490 Income tax (benefit) / expense consisted of (amounts in thousands): For the Fiscal Year Ended December 31, 2015 2014 2013 Current Federal $ 1,136 $ 8,658 $ 15,201 State 172 (199 ) 321 UK 7,239 5,322 7,275 Japan 127 173 14 Other non-U.S. 169 78 3 Total current income tax expense 8,843 14,032 22,814 Deferred Federal (9,889 ) 4,966 (5,883 ) State (1,375 ) (99 ) 205 UK (337 ) (122 ) — Japan (148 ) 159 121 Other non-U.S. (545 ) 20 (316 ) Change in valuation allowance (61 ) 184 442 Total deferred tax (benefit) / expense (12,355 ) 5,108 (5,431 ) Total income tax (benefit) / expense $ (3,512 ) $ 19,140 $ 17,383 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. The Company’s net deferred tax assets are included in Other assets on the Consolidated Balance Sheets. The net change in valuation allowance for the year ended December 31, 2015 was $0.2 million . Significant components of the Company’s deferred tax assets and liabilities were as follows (amounts in thousands): December 31, 2015 2014 Deferred tax assets Foreign net operating losses $ 13,286 $ 1,909 Unrealized trading losses — 1,293 Stock-based compensation expense 1,437 1,474 Intangible assets 3,012 6,698 Basis difference in property and equipment 4,950 — Other 2,962 2,126 Total deferred tax assets 25,647 13,500 Valuation allowance (853 ) (913 ) Total deferred tax assets after valuation allowance $ 24,794 $ 12,587 Deferred tax liabilities Basis difference in property and equipment $ — $ (1,717 ) Discount on convertible note (6,186 ) (3,778 ) Other (781 ) (784 ) Total deferred liabilities (6,967 ) (6,279 ) Net deferred tax assets $ 17,827 $ 6,308 The Company has $62.4 million in foreign net operating loss (“NOL”) carry forwards as of December 31, 2015 . These NOLs begin to expire in 2019. The Company has a deferred tax asset of $13.3 million relating to these NOLs for which it has established a valuation allowance of $ 0.9 million . The following table reconciles the effective tax rate to the U.S. federal statutory income tax rate: 2015 2014 2013 Federal income tax at statutory rate 35.00 % 35.00 % 35.00 % Increase/(decrease) in effective tax rate resulting from: State income tax (9.25 )% (0.57 )% 0.76 % Foreign rate differential (96.96 )% (9.71 )% (5.22 )% Deemed dividends 55.30 % — % — % Non deductible transaction costs 11.71 % 1.42 % — % Impact of non-controlling interests (6.89 )% (1.10 )% — % Contingent liability (27.92 )% — % — % Foreign losses (19.20 )% — % — % 162 (m) 3.44 % — % — % GFT Carryback (6.58 )% — % — % Uncertain tax positions 19.67 % 14.04 % 5.88 % Other permanent differences — % 3.03 % 1.79 % Effective Tax Rate (41.68 )% 42.11 % 38.21 % In 2015 the Company had a number of discrete tax items that impacted its effective tax rate: • The Company had outstanding intercompany balances between U.S. and non-U.S. entities, which resulted in a taxable deemed dividend of $37.2 million . This is represented by the deemed dividend adjustment in the table above. • The Company adjusted the fair value of contingent consideration relating to the Galvan acquisition. This resulted in non-taxable earnings of $6.7 million . This is represented by the contingent liability adjustment in the table above. • The Company received a favorable tax ruling on the utilization of historic foreign operating losses and was able to record a deferred tax asset of $1.6 million . This is represented by the foreign losses adjustment in the table above. At December 31, 2015 , the Company had approximately $100.0 million held in earnings of its foreign subsidiaries. The Company has made provision for U.S. taxes that would arise on distribution if $48.3 million of these earnings were repatriated to the United States. The remaining earnings are indefinitely invested outside the United States and are expected to be reinvested in the working capital and other business needs of the foreign subsidiaries. If the remaining earnings had been repatriated into the United States as of December 31, 2015 , in the form of dividends or otherwise, the Company would have been subject to additional income taxes of approximately $9.8 million . The Company has recorded a liability of $11.8 million related to uncertain tax positions at December 31, 2015 in accordance with ASC 740-10, Income Taxes . This liability is recorded in Accrued expenses and other liabilities on the Consolidated Balance Sheet. The following table summarizes the activity to the gross unrecognized tax benefits from uncertain tax positions (amounts in thousands): As of December 31, 2015 2014 2013 Beginning balance as of January 1 $ 10,517 $ 8,345 $ 78 Increases based on tax positions related to the current period 885 2,197 8,287 Increases based on tax positions related to prior periods 429 — — Decreases related to a lapse of applicable statute of limitations (30 ) (25 ) (20 ) Ending balance as of December 31 $ 11,801 $ 10,517 $ 8,345 Included in the balance of unrecognised tax benefits as of December 31, 2015, December 31, 2014 and December 31, 2013 are $11.8 million , $10.5 million and $8.3 million , respectively, of tax benefits that, if recognized, would affect the effective tax rate. The Company’s open tax years range from 2013 through 2015 for its U.S. federal returns, from 2012 through 2015 for the U.K., from March 2015 through March 2016 for Japan and from 2011 through 2015 for its major state jurisdictions. It is reasonably possible that the amount of liability for unrecognized tax benefits could change during the next 12 months. An estimate of the range of the possible change cannot be made until issues are further developed or examinations closed. In addition to the total unrecognized tax benefits noted above, the Company recorded $1.8 million and $2.3 million of penalties and interest for the years ended December 31, 2015 and December 31, 2014, respectively. These amounts are recorded in Income tax (benefit) / expense in the Consolidated Statements of Income and are part of the uncertain tax positions impact when reconciling the federal income tax rate to the Company's effective tax rate.

Retirement Plans

Retirement Plans	12 Months Ended
	Dec. 31, 2015
Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract]
RETIREMENT PLANS	RETIREMENT PLANS The Company sponsors a “Safe Harbor” 401(k) retirement plan which was put into effect as of January 1, 2011. The plan provides for a 100% match by the Company on the first 3% of the employee’s salary contributed to the plan and 50% on the next 2% with immediate vesting on all employer contributions, subject to IRS limitations. Substantially all of the Company’s employees are eligible to participate in the plan. The expense recorded to employee compensation and benefits on the Consolidated Statements of Income and Comprehensive Income by the Company for its employees’ participation in the respective plans during the years ended December 31, 2015, 2014 and 2013 was $0.9 million , $1.3 million , and $0.9 million , respectively.

Regulatory Requirements

Regulatory Requirements	12 Months Ended
	Dec. 31, 2015
Banking and Thrift [Abstract]
REGULATORY REQUIREMENTS	REGULATORY REQUIREMENTS Group, LLC, the Company’s FCM and RFED subsidiary, is subject to the CFTC Net Capital Rule (Rule 1.17) and NFA Financial Requirements Sections 11 and 12. Under applicable provisions of these regulations, Gain Capital Group, LLC is required to maintain adjusted net capital of the greater of $2.5 million or 8% of Customer and Non-Customer Maintenance Margin or $20.0 million plus 5.0% of all liabilities owed to retail customers exceeding $10.0 million . At December 31, 2015 , Group LLC maintained $10.2 million more than the required minimum regulatory capital for a total of 1.4 times the required capital and at all times maintained compliance with all applicable regulations. GAIN Capital Securities, Inc. ("GCSI") is a broker-dealer registered with the SEC under the Securities Exchange Act of 1934, as amended. GCSI is a member of the Financial Industry Regulatory Authority (“FINRA”), Municipal Securities Rulemaking Board (“MSRB”), and Securities Investor Protection Corporation (“SIPC”). Pursuant to the SEC’s Uniform Net Capital Rule 15c3-1, GCSI is required to maintain a minimum net capital balance (as defined) of $0.05 million . GCSI must also maintain a ratio of aggregate indebtedness (as defined) to net capital of not more than 15 to 1. At December 31, 2015 , GCSI maintained $0.3 million more than the minimum required regulatory capital for a total of 4.0 times the required capital and at all times maintained compliance with all applicable regulations. GCUK1 is registered in the U.K. and regulated by the FCA as a full scope €730k IFPRU Investment Firm. GCUK1 is required to maintain the greater of $1.0 million ( €730,000 ) or the Financial Resources Requirement, which is calculated as the sum of the firm’s operational, credit, counterparty, concentration, market and forex risk. At December 31, 2015 , GCUK1 maintained $33.8 million more than the minimum required regulatory capital for a total of 2.2 times the required capital and at all times maintained compliance with all applicable regulations. GCUK2 is registered in the U.K. and regulated by the FCA as a full scope €730k IFPRU Investment Firm. GCUK2 is required to maintain the greater of $1.0 million ( €730,000 ) or the Financial Resources Requirement, which is calculated as the sum of the firm’s operational, credit, counterparty, concentration, market and forex risk. At December 31, 2015 , GCUK2 maintained $73.4 million more than the minimum required regulatory capital for a total of 2.3 times the required capital and at all times maintained compliance with all applicable regulations. Forex.com Japan Co., Ltd. (“GC Japan”) is a registered Type I financial instruments business firm regulated by the Japan Financial Services Agency ("FSA") in accordance with Financial Instruments and Exchange Law (Law No. 25 of 1948, as amended). GC Japan is a member of the Financial Futures Association of Japan. GC Japan is subject to a minimum capital adequacy ratio of 120% , which is derived by dividing Net Capital (as defined in Law No. 25) by the sum of GC Japan’s market, counterparty credit risk and operational risk. At December 31, 2015 , GC Japan maintained $8.7 million more than the minimum required regulatory capital for a total of 10.7 times the required capital and at all times maintained compliance with all applicable regulations. GCAU1 is regulated under the laws of Australia, including the Corporations Act 2001 (Commonwealth of Australia). The Australian Securities and Investments Commission ("ASIC) is the corporate, markets and financial services regulator in Australia responsible for administering aspects of the Corporations Act 2001. GCAU1 holds an Australian Financial Services License that has been issued by ASIC. GCAU1 is required to maintain a minimum capital requirement of $0.7 million ( 1.0 million AUD). The regulatory capital held is required to be in excess of 110% of its requirements at all times. At December 31, 2015 , GCAU1 maintained $1.7 million more than the minimum required regulatory capital for a total of 3.4 times the required capital and at all times maintained compliance with all applicable regulations. Effective January 31, 2014, ASIC increased the Net Tangible Assets (NTA) requirement, as part of RG166: Licensing: Financial Requirements , for OTC derivative issuers. ASIC requires retail OTC derivative issuers to have at all times the greater of $0.8 million or 10% of average revenue on hand at all times. RG166 outlines that, at the minimum, 50% of the NTA requirement is required to be held in cash or cash equivalents and 50% in liquid assets. OTC derivative issuers must report to ASIC if their NTA falls below 110% of the requirement within 3 business days after becoming aware of the event. GCAU2 is regulated under the laws of Australia, including the Corporations Act 2001 (Commonwealth of Australia). GCAU2 holds an Australian Financial Services License that has been issued by ASIC. GCAU2 is required to maintain a minimum capital requirement of $0.7 million ( 1.0 million AUD). The regulatory capital held is required to be in excess of 110% of its requirements at all times. At December 31, 2015 , GCAU2 maintained $2.1 million more than the minimum required regulatory capital for a total of 4.0 times the required capital and at all times maintained compliance with all applicable regulations. GCHK is licensed by the Securities and Futures Commission (“SFC”) to carry out Type 3 Regulated Activity, Leveraged Foreign Exchange Trading. GCHK is subject to the requirements of section 145 of the Securities and Futures Ordinance (Cap.571). Under this rule, GCHK is required to maintain a minimum liquid capital requirement of the higher of $1.9 million or the sum of 1.5% of its aggregate gross foreign currency position and 5% of its adjusted liabilities and clients’ margin calculated in accordance with applicable rules. At December 31, 2015 , GCHK maintained $2.0 million more than the minimum required regulatory capital for a total of 2.1 times the required capital and at all times maintained compliance with all applicable regulations. GAIN Global Markets, Inc. (“GGMI”), the Company’s Cayman Island subsidiary, is a registered securities arranger with the Cayman Islands Monetary Authority (“CIMA”). GGMI is required to maintain a capital level that is the greater of one quarter of relevant annual expenditure, or the financial resources requirement which is the sum of the Base Requirement, counterparty and position risk requirement, or $0.1 million. At December 31, 2015 , GGMI maintained $0.1 million more than the minimum required regulatory capital for a total of 1.5 times the required capital and at all times maintained compliance with all applicable regulations. GAIN Capital - Forex.com Canada, Ltd. ("GCCA") is a Dealer Member of the Investment Industry Regulatory Organization of Canada ("IIROC) and regulated under the laws of Canada, including the Canadian Investor Protection Fund. In Canada, the securities industry is governed by provincial or territorial legislation, and there is no national regulator. Local legislation differs from province to province and territory to territory, but generally requires that forex dealing representatives register with applicable regulators and self-regulatory organizations in order to offer forex and/or CFD products to retail clients. GCCA’s principal provincial regulator is the Ontario Securities Commission, or OSC. GCCA is required to maintain risk-adjusted capital in excess of the minimum capital requirement. At December 31, 2015 , GCCA maintained $1.2 million more than the minimum required regulatory capital for a total of 7.0 times the required capital and at all times maintained compliance with all applicable regulations. GCS is registered by the Monetary Authority of Singapore (“MAS”) and operates as an approved holder of Capital Market Services License. GCS is subject to the requirements of MAS and pursuant to the Securities and Futures Act (Cap 289). Under these rules GCS is required to maintain a minimum base capital of $0.6 million ( 1.0 million SGD) and Financial Resources in excess of 120% of the total risk requirements, which is calculated as the sum of operational, counterparty, large exposure and forex risk at all times. At December 31, 2015 , GCS maintained $6.8 million more than the required minimum regulatory capital for a total of 12.3 times the required capital and at all times maintained compliance with all applicable regulations. Galvan is registered in the U.K. and regulated by the FCA as a BIPRU Limited Licence Firm. Galvan is required to maintain a base financial resources requirement of $0.1 million ( €0.05 million ) and a capital requirement of the higher of either credit risk plus market risk or fixed overhead requirement. At December 31, 2015 , Galvan maintained $3.6 million more than the minimum required regulatory capital for a total of 6.1 times the required capital and at all times maintained compliance with all applicable regulations. GAA is a registered Introducing Broker and is subject to the CFTC Net Capital Rule (Rule 1.17). Under applicable provisions of these rules, GAA is required to maintain adjusted net capital of $0.1 million . At December 31, 2015 , GAA maintained $1.1 million more than the minimum required regulatory capital for a total of 12.0 times the required capital and at all times maintained compliance with all applicable regulations. The following table illustrates the minimum regulatory capital our subsidiaries were required to maintain as of December 31, 2015 and the actual amounts of capital that were maintained (amounts in millions): Entity Name Minimum Capital Excess Percent of GAIN Capital Group, LLC $ 26.1 $ 36.3 $ 10.2 139 % GAIN Capital Forex.com U.K., Ltd. 27.8 61.6 33.8 222 % Forex.com Japan., Ltd. 0.9 9.6 8.7 1,067 % GAIN Capital-Forex.com Hong Kong, Ltd. 1.9 3.9 2.0 205 % GAIN Capital Forex.com Australia, Pty. Ltd. 0.7 2.4 1.7 343 % Galvan Research and Trading, Ltd. 0.7 4.3 3.6 614 % GAIN Capital-Forex.com Canada Ltd. 0.2 1.4 1.2 700 % GAIN Capital Securities, Inc. 0.1 0.4 0.3 400 % GAIN Global Markets, Inc. 0.2 0.3 0.1 150 % GAIN Capital UK, Ltd. 54.5 127.9 73.4 235 % GAIN Capital Singapore Pte, Ltd. 0.6 7.4 6.8 1,233 % GAIN Capital Australia Pty Ltd. 0.7 2.8 2.1 400 % Global Assets Advisors, LLC 0.1 1.2 1.1 1,200 % Total $ 114.5 $ 259.5 $ 145.0 227 %

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION ASC 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) reported profit or loss in absolute amount 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 fourth quarter of 2015, the Company changed its internal reporting structure and the information provided to its chief operating decision maker. As a result the Company has changed its segment reporting structure to include three operating segments, retail, institutional and futures, rather than a single operating segment as had been previously reported. These operating segments are discussed in more detail below. The Company also reports information relating to general corporate services in a fourth component, corporate and other. Information in these consolidated financial statements reflects the information presented to the chief operating decision maker, and prior periods have been retrospectively adjusted to reflect the current segment structure. The chief operating decision maker does not review total assets by operating segment. 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 a diverse range of 12,500 global financial markets, including spot forex, precious metals and CFDs on commodities, indices, individual equities 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. Institutional Segment The institutional segment provides agency execution services and offers access to markets and self-directed trading in foreign exchange, commodities, equities, options and futures via an electronic communications network, or ECN, through the Company's GTX platform. The Company also offers high touch sales and trading aided by a team of sales employees. 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 subsidiary, GAIN Capital Group, LLC, under the GAIN Capital Futures brand. In addition, in 2014, the Company expanded its futures business by acquiring majority interests in GAA and TT. Corporate and other Corporate and other provides general corporate services to the Company's segments and also includes eliminations between operating segments which were $(1.3) million , $(0.9) million and $(0.9) million for the twelve months ended December 31, 2015, 2014 and 2013. Corporate and other revenue primarily comprises foreign currency transaction gains and losses. During the twelve months ended December 31, 2015, corporate and other revenue also included a $6.7 million adjustment to the contingent consideration related to the Galvan acquisition. Selected financial information by segment is presented in the following tables (amounts in thousands): Retail Year Ended December 31, 2015 2014 2013 Net revenue $ 351,472 $ 296,941 $ 218,848 Employee compensation and benefits 67,515 61,989 44,924 Selling and marketing 26,129 19,574 21,761 Referral fees 87,175 78,553 41,459 Other operating expenses 76,301 51,561 33,148 Segment profit $ 94,352 $ 85,264 $ 77,556 Institutional Year Ended December 31, 2015 2014 2013 Net revenue $ 35,072 $ 35,413 $ 29,213 Employee compensation and benefits 15,305 13,963 13,006 Selling and marketing 138 120 244 Referral fees — — — Other operating expenses 9,573 10,939 8,170 Segment profit $ 10,056 $ 10,391 $ 7,793 Futures Year Ended December 31, 2015 2014 2013 Net revenue $ 45,797 36,016 23,360 Employee compensation and benefits 10,634 8,918 3,399 Selling and marketing 901 519 332 Referral fees 16,348 12,419 11,164 Other operating expenses 13,960 11,585 8,948 Segment profit $ 3,954 $ 2,575 $ (483 ) Corporate and Other Year Ended December 31, 2015 2014 2013 Other revenue $ (3,716 ) $ 819 $ (3,729 ) Employee compensation and benefits 13,127 14,362 13,279 Selling and marketing — — — Referral fees — — — Other operating expenses 11,038 10,001 7,272 Loss $ (27,881 ) $ (23,544 ) $ (24,280 ) Reconciliation of operating segment profit / (loss) to Income before income tax (benefit) / expense For the Fiscal Year Ended December 31, 2015 2014 2013 Retail segment $ 94,352 $ 85,264 $ 77,556 Institutional segment 10,056 10,391 7,793 Futures segment 3,954 2,575 (483 ) Corporate and other (27,881 ) (23,544 ) (24,280 ) SEGMENT PROFIT 80,481 74,686 60,586 Depreciation and amortization 11,111 6,610 8,283 Purchased intangible amortization 16,550 8,080 2,906 Acquisition expenses 2,819 3,526 1,824 Restructuring expenses 3,482 2,334 450 Integration expenses 33,092 2,489 1,950 Impairment of investment — 50 450 Change in fair value to contingent consideration (6,722 ) — — SNB bad debt provision 2,500 — — OPERATING PROFIT 17,649 51,597 44,723 Interest expense on long term borrowings 9,222 6,147 1,233 Gain on extinguishment of debt — — 2,000 INCOME BEFORE INCOME TAX EXPENSE $ 8,427 $ 45,450 $ 45,490 Net revenue (loss) by geographic area for the years ended December 31, 2015, 2014 and 2013 is as follows ($ in thousands): 2015 2014 2013 Net Revenue (1) : North America (2) $ 107,534 $ 133,103 $ 153,449 Europe (3) 307,087 237,391 33,347 Other 20,726 (1,305 ) 80,895 Total Net Revenue $ 435,347 $ 369,189 $ 267,691 (1) - Net revenue is attributed to individual countries based on the jurisdiction of the formation of the reporting entity that records the transaction (2) - Includes U.S. net revenue of $107.5 million , $133.1 million , and $153.5 million for 2015, 2014, and 2013 respectively. (3) - Includes UK net revenue of $307.3 million and $237.7 million , and $33.3 million for 2015, 2014, and 2013 respectively. Long-lived assets by geographic area as of December 31, 2015, 2014 and 2013 are as follows (in thousands): 2015 2014 Long-lived assets (1) : North America (2) 6,370 16,729 Europe (3) 23,147 1,820 Other 850 247 Total long-lived assets 30,367 18,796 (1) - Long-lived assets are comprised of property, plant and equipment, net. They exclude goodwill, other intangible assets and other assets, which are not attributable to any one geographic location. (2) - Includes U.S. long-lived assets of $6.4 million , $16.7 million for 2015 and 2014, respectively. (3) - Includes UK long-lived assets of $23.1 million , $1.7 million for 2015 and 2014, respectively.

Quarterly Financial Data (Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
QUARTERLY FINANCIAL DATA (UNAUDITED)	QUARTERLY FINANCIAL DATA (UNAUDITED) As discussed above, the information for the second, third and fourth quarters of 2015 and each quarter of 2014 has been restated to correct certain errors relating to the manner in which the Company originally presented the allocation of the effects of the Company's previously announced restatement of its consolidated financial statements as of and for the years ended December 31, 2014 and 2013. The errors in the quarterly financial data previously presented in this Note 23 had no impact on our full year financial results. The following table sets forth selected restated quarterly financial data for 2015 and 2014 (in thousands, except per share data): First Second Third Fourth Quarter Quarter Quarter Quarter For the Year Ended December 31, 2015 (As Restated) Total non-interest revenue $ 92,967 $ 111,452 $ 128,045 $ 102,712 Net revenue $ 92,986 $ 111,457 $ 128,111 $ 102,793 Income/(loss) before income tax expense $ 11,554 $ (12,741 ) $ 9,418 $ 196 Income tax (benefit)/expense $ 5,745 $ (6,039 ) $ 7,862 $ (11,080 ) Net income/(loss) $ 5,809 $ (6,702 ) $ 1,556 $ 11,276 Net income attributable to non-controlling interest $ 344 $ 416 $ 583 $ 317 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 5,465 $ (7,118 ) $ 973 $ 10,959 Basic net income/(loss) per share $ 0.11 $ (0.16 ) $ 0.05 $ 0.23 Diluted net income/(loss) per share $ 0.11 $ (0.16 ) $ 0.05 $ 0.23 For the Year Ended December 31, 2014 (As Restated) Total non-interest revenue $ 80,412 $ 70,005 $ 102,786 $ 115,157 Net revenue $ 80,722 $ 70,264 $ 102,956 $ 115,247 Income/(loss) before income tax expense $ 3,833 $ (6,421 ) $ 20,887 $ 27,151 Income tax (benefit)/expense $ 2,787 $ (1,926 ) $ 9,206 $ 9,073 Net income/(loss) $ 1,046 $ (4,495 ) $ 11,681 $ 18,078 Net income attributable to non-controlling interest $ 38 $ 164 $ 785 $ 446 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 1,008 $ (4,659 ) $ 10,896 $ 17,632 Basic net income/(loss) per share $ 0.02 $ (0.12 ) $ 0.22 $ 0.42 Diluted net income/(loss) per share $ 0.02 $ (0.12 ) $ 0.21 $ 0.40 As discussed in Note 2 to our audited consolidated financial statements under the heading "Restatement," the Company has restated its consolidated financial statements as of December 31, 2014, and for the years ending December 31, 2014 and 2013. The following table sets forth the impact of the restatement on the quarterly financial data for the interim periods in 2015 and 2014: As Reported Tax Adjustments Other Adjustments As Restated For the three months ended September 30, 2015 Total non-interest revenue $ 127,865 $ — $ 180 $ 128,045 Net revenue $ 127,931 $ — $ 180 $ 128,111 Income/(loss) before income tax expense $ 9,215 $ — $ 203 $ 9,418 Income tax (benefit)/expense $ 328 $ 7,534 $ — $ 7,862 Net income/(loss) $ 8,887 $ (7,534 ) $ 203 $ 1,556 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 8,304 $ (7,534 ) $ 203 $ 973 Basic net income/(loss)per share $ 0.20 $ 0.05 Diluted net income/(loss) per share $ 0.20 $ 0.05 As Reported Tax Adjustments Other Adjustments As Restated For the three months ended June 30, 2015 Total non-interest revenue $ 111,559 $ — $ (107 ) $ 111,452 Net revenue $ 111,564 $ — $ (107 ) $ 111,457 Income/(loss) before income tax expense $ (12,538 ) $ — $ (203 ) $ (12,741 ) Income tax (benefit)/expense $ (4,124 ) $ (1,915 ) $ — $ (6,039 ) Net income/(loss) $ (8,414 ) $ 1,915 $ (203 ) $ (6,702 ) Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ (8,830 ) $ 1,915 $ (203 ) $ (7,118 ) Basic net income/(loss)per share $ (0.23 ) $ (0.16 ) Diluted net income/(loss) per share $ (0.23 ) $ (0.16 ) As Reported Tax Adjustments Other Adjustments As Restated For the three months ended March 31, 2015 Total non-interest revenue $ 92,933 $ — $ 34 $ 92,967 Net revenue $ 92,952 $ — $ 34 $ 92,986 Income/(loss) before income tax expense $ 11,498 $ — $ 56 $ 11,554 Income tax (benefit)/expense $ 2,818 $ 2,927 $ — $ 5,745 Net income/(loss) $ 8,680 $ (2,927 ) $ 56 $ 5,809 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 8,336 $ (2,927 ) $ 56 $ 5,465 Basic net income/(loss)per share $ 0.19 $ 0.11 Diluted net income/(loss) per share $ 0.18 $ 0.11 As Reported Tax Adjustments Other Adjustments As Restated For the three months ended December 31, 2014 Total non-interest revenue $ 114,725 $ — $ 432 $ 115,157 Net revenue $ 114,723 $ — $ 524 $ 115,247 Income/(loss) before income tax expense $ 26,456 $ — $ 695 $ 27,151 Income tax (benefit)/expense $ 8,398 $ 728 $ (53 ) $ 9,073 Net income/(loss) $ 18,058 $ (728 ) $ 748 $ 18,078 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 17,612 $ (728 ) $ 748 $ 17,632 Basic net income/(loss)per share $ 0.44 $ 0.42 Diluted net income/(loss) per share $ 0.42 $ 0.40 As Reported Tax Adjustments Other Adjustments As Restated For the three months ended September 30, 2014 Total non-interest revenue $ 103,388 $ — $ (602 ) $ 102,786 Net revenue $ 103,650 $ — $ (694 ) $ 102,956 Income/(loss) before income tax expense $ 21,470 $ — $ (583 ) $ 20,887 Income tax (benefit)/expense $ 5,340 $ 3,866 $ — $ 9,206 Net income/(loss) $ 16,130 $ (3,866 ) $ (583 ) $ 11,681 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 15,345 $ (3,866 ) $ (583 ) $ 10,896 Basic net income/(loss)per share $ 0.35 $ 0.22 Diluted net income/(loss) per share $ 0.33 $ 0.21 As Reported Tax Adjustments Other Adjustments As Restated For the three months ended June 30, 2014 Total non-interest revenue $ 69,504 $ — $ 501 $ 70,005 Net revenue $ 69,763 $ — $ 501 $ 70,264 Income/(loss) before income tax expense $ (7,013 ) $ — $ 592 $ (6,421 ) Income tax (benefit)/expense $ (2,021 ) $ 95 $ — $ (1,926 ) Net income/(loss) $ (4,992 ) $ (95 ) $ 592 $ (4,495 ) Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ (5,156 ) $ (95 ) $ 592 $ (4,659 ) Basic net income/(loss)per share $ (0.13 ) $ (0.12 ) Diluted net income/(loss) per share $ (0.13 ) $ (0.12 ) As Reported Tax Adjustments Other Adjustments As Restated For the three months ended March 31, 2014 Total non-interest revenue $ 81,087 $ — $ (675 ) $ 80,412 Net revenue $ 81,397 $ — $ (675 ) $ 80,722 Income/(loss) before income tax expense $ 5,139 $ — $ (1,306 ) $ 3,833 Income tax (benefit)/expense $ 1,276 $ 1,511 $ — $ 2,787 Net income/(loss) $ 3,863 $ (1,511 ) $ (1,306 ) $ 1,046 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 3,825 $ (1,511 ) $ (1,306 ) $ 1,008 Basic net income/(loss)per share $ 0.10 $ 0.02 Diluted net income/(loss) per share $ 0.09 $ 0.02

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2015
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS In March 2016, the Company announced the payment of a $ 0.05 dividend per share of Common Stock payable on March 29, 2016 to stockholders of record on March 25, 2016.

Schedule I - Consolidated Finan

Schedule I - Consolidated Financial Information of GAIN Capital Holdings, Inc. (Parent Company Only)	12 Months Ended
	Dec. 31, 2015
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Consolidated Financial Information of GAIN Capital Holdings, Inc. (Parent Company Only)	GAIN CAPITAL HOLDINGS, INC. (Parent Company Only) Condensed Balance Sheets (in thousands, except share data) As of December 31, 2015 2014 ASSETS: Cash and cash equivalents $ 451 $ 1,184 Equity investments in subsidiaries 447,732 380,110 Receivables from affiliates 2,442 17,545 Prepaid assets 4 2 Income tax receivable 9,482 4,994 Deferred tax assets, net 13,563 5,911 Other assets 495 7,736 Total assets $ 474,169 $ 417,482 LIABILITIES AND SHAREHOLDERS EQUITY: Liabilities Accrued compensation and benefits $ 211 $ 51 Accrued expenses and other liabilities 20,438 37,154 Payable to affiliates 25,440 61,990 Convertible senior notes 121,996 68,367 Total liabilities 168,085 167,562 Commitments and contingent liabilities (see Note 3) Shareholders' Equity Common stock ($0.00001 par value; 120 million shares authorized, 52,072,884 shares issued and 48,771,015 shares outstanding as of December 31, 2015; 60 million shares authorized, 45,582,066 shares issued and 42,934,559 shares outstanding as of December 31, 2014) — — Accumulated other comprehensive income (5,865 ) (1,513 ) Additional paid-in capital 212,981 148,378 Treasury stock, at cost (3,301,869 shares at December 31, 2015 and 2,647,507 at December 31, 2014, respectively) (21,808 ) (16,720 ) Retained earnings 120,776 119,775 Total shareholders' equity 306,084 249,920 Total liabilities and shareholders' equity $ 474,169 $ 417,482 GAIN CAPITAL HOLDINGS, INC. (Parent Company Only) Condensed Statements of Income and Comprehensive Income (in thousands) For the Fiscal Year Ended December 31, 2015 2014 2013 REVENUE: Dividends from subsidiaries $ 38,642 $ — $ 37,099 Interest and other 178 90 181 Total revenue $ 38,820 $ 90 $ 37,280 OPERATING EXPENSES: Interest expense 63 64 63 Employee compensation and benefits 10,096 11,578 187 General and administrative 6,775 8,208 6,075 Total operating expenses 16,934 19,850 6,325 Interest expense on long term borrowings 9,222 6,147 1,233 Gain on extinguishment of debt — — 2,000 INCOME/(LOSS) BEFORE INCOME TAX EXPENSE 12,664 (25,907 ) 31,722 Income tax (benefit) / expense (10,875 ) (2,584 ) 10,325 NET INCOME/(LOSS) BEFORE UNDISTRIBUTED EARNINGS OF SUBSIDIARIES 23,539 (23,323 ) 21,397 Undistributed earnings of subsidiaries (13,260 ) 48,200 6,710 NET INCOME 10,279 24,877 $ 28,107 Other comprehensive (loss) / income Foreign currency translation adjustment (4,352 ) (4,089 ) $ 1,327 NET COMPREHENSIVE INCOME $ 5,927 $ 20,788 $ 29,434 GAIN CAPITAL HOLDINGS, INC. (Parent Company Only) Condensed Statements of Cash Flows (in thousands) For the Fiscal Year Ended December 31, 2015 2014 (As Restated) 2013 (As Restated) CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 10,279 $ 24,877 $ 28,107 Adjustments to reconcile net income to cash provided by operating activities Undistributed earnings of subsidiaries 13,260 (48,200 ) (6,710 ) Gain on extinguishment of debt — — (2,000 ) Gain on foreign currency exchange rates (66 ) — (274 ) Deferred tax (benefit)/expense (11,264 ) 4,867 1,448 Amortization of deferred finance costs 354 354 — Stock compensation expense 3,680 3,452 2,975 Convertible note discount amortization 3,624 2,150 175 Changes in operating assets and liabilities: Receivables from affiliates 37,548 (33,827 ) 19,278 Prepaid assets (3 ) 127 (127 ) Other assets 7,240 (10,123 ) 291 Income tax receivable (9,069 ) (771 ) (9,742 ) Accrued compensation and benefits 160 51 — Accrued expenses and other liabilities (4,876 ) 10,426 1,478 Payable to affiliates (36,549 ) 61,990 — Cash provided by operating activities 14,318 15,373 34,899 CASH FLOWS FROM INVESTING ACTIVITIES: Investment and funding of subsidiaries 7,081 (51,107 ) (28,648 ) Purchase of short term investments — (92 ) — Cash provided by / (used for) investing activities 7,081 (51,199 ) (28,648 ) CASH FLOWS FROM FINANCING ACTIVITIES: Proceeds from issuance of convertible senior note issuance, net — — 77,900 Principal payment on notes payable — — (31,200 ) Contractual payments for acquisitions (11,829 ) — — Proceeds from exercise of stock options 2,386 2,087 2,539 Proceeds from employee stock purchase plan 789 740 302 Purchase of treasury stock (5,088 ) (1,251 ) (7,189 ) Tax benefit from employee stock option exercises 1,140 1,221 1,026 Dividend payments (9,530 ) (8,139 ) (7,326 ) Cash (used for)/provided by financing activities (22,132 ) (5,342 ) 36,052 (DECREASE) / INCREASE IN CASH AND CASH EQUIVALENTS (733 ) (41,168 ) 42,303 CASH AND CASH EQUIVALENTS — Beginning of year 1,184 42,352 49 CASH AND CASH EQUIVALENTS — End of year $ 451 $ 1,184 $ 42,352 SUPPLEMENTARY DISCLOSURES OF CASH FLOW INFORMATION: Cash paid during the year for: Interest paid $ (4,538 ) $ (3,373 ) $ (556 ) Taxes refunds received/taxes (paid) $ 733 $ (3,711 ) $ (5,562 ) Non-cash financing activities related to acquisitions: Seller provided financing — — $ 33,200 Common stock issued as consideration for asset and business acquisitions $ 45,100 $ 6,493 $ 34,771 1. Basis of Presentation Basis of Financial Information — The accompanying condensed financial statements of GAIN Capital Holdings, Inc. (“Parent Company”), including the notes thereto, should be read in conjunction with the consolidated financial statements of GAIN Capital Holdings, Inc. and Subsidiaries (the “Company”) and the related notes. The condensed financial statements are prepared in accordance with accounting principles generally accepted in the U.S. which require the Company or Parent Company to make estimates and assumptions regarding valuations of certain financial instruments and other matters that affect the Parent Company Financial Statements and related disclosures. Actual results could differ from these estimates. The Parent Company on a stand-alone basis, has accounted for majority-owned subsidiaries using the equity method of accounting. Restatement The Company has determined that there were errors in the Company's accounting for income taxes as of December 31, 2014 and for the years ended December 31, 2014 and 2013 and for certain quarters of 2015 under ASC 740 (ASC 740), Income Taxes . These errors relate primarily to the manner in which certain intercompany payables and receivables among domestic and overseas subsidiaries of the Company were treated for accounting and tax purposes during the impacted periods. The condensed financial statements of the Parent Company as of December 31, 2014 and for the years ended December 31, 2014 and 2013 included in this report have been restated to reflect the correction of these errors. In addition, certain other adjustments, previously determined to be immaterial individually and in the aggregate, have also been corrected in the restated condensed financial statements. The following tables reflect the condensed financial statement line items impacted by the restatement. The column headed "Tax Adjustments" reflects the impact of the tax matters discussed above, while the "Other Adjustments" column reflects the impact of the other previously identified immaterial adjustments in the Condensed Balance Sheet and Condensed Statements of Income and Comprehensive Income. The column headed "Adjustments" reflects the impact of the tax matters discussed above as well as the impact of the other previously identified immaterial adjustments in the Condensed Statement of Cash Flows. For the avoidance of doubt, the following tables include only those line items impacted by the restatement. Condensed Balance Sheet As of December 31, 2014 As Reported Tax Adjustment Other Adjustments As Restated ASSETS: Cash and cash equivalents $ 1,235 $ — $ (51 ) $ 1,184 Equity investments in subsidiaries 381,240 — (1,130 ) 380,110 Receivables from affiliates 18,533 (988 ) — 17,545 Current tax receivable 5,084 (90 ) — 4,994 Deferred tax assets, net — 5,911 — 5,911 Other assets 15,703 (5,504 ) (2,463 ) 7,736 Total assets $ 421,797 $ (671 ) $ (3,644 ) $ 417,482 LIABILITIES AND SHAREHOLDERS’ EQUITY: Liabilities Accrued expenses and other liabilities 25,435 12,170 (451 ) 37,154 Income tax payable 1,060 1,003 (2,063 ) — Total liabilities 156,903 13,173 (2,514 ) 167,562 Commitments and contingent liabilities Shareholders’ equity Accumulated other comprehensive income (2,054 ) 541 — (1,513 ) Additional paid-in capital 152,684 (4,306 ) — 148,378 Retained earnings 130,984 (10,079 ) (1,130 ) 119,775 Total shareholders' equity 264,894 (13,844 ) (1,130 ) 249,920 Total liabilities and shareholders’ equity $ 421,797 $ (671 ) $ (3,644 ) $ 417,482 Condensed Statements of Income and Comprehensive Income For the Fiscal Year Ended December 31, 2014 As Reported Tax Adjustment Other Adjustments As Restated Interest expense on long term borrowings $ 5,893 $ — $ 254 $ 6,147 INCOME/(LOSS) BEFORE INCOME TAX EXPENSE (25,653 ) — (254 ) (25,907 ) Income tax (benefit) / expense (8,784 ) 6,200 — (2,584 ) NET INCOME/(LOSS) BEFORE UNDISTRIBUTED EARNINGS OF SUBSIDIARIES (16,869 ) (6,200 ) (254 ) (23,323 ) Undistributed earnings of subsidiaries 48,495 (295 ) 48,200 NET INCOME $ 31,626 $ (6,200 ) $ (549 ) $ 24,877 Other comprehensive (loss) / income, net of tax Foreign currency translation adjustment (4,630 ) 541 — (4,089 ) NET COMPREHENSIVE INCOME $ 26,996 $ (5,659 ) $ (549 ) $ 20,788 For the Fiscal Year Ended December 31, 2013 As Reported Tax Adjustment Other Adjustments As Restated OPERATING EXPENSES: Interest expense 1,199 — (1,136 ) 63 Total operating expense 7,461 — (1,136 ) 6,325 Interest expense on long term borrowings — — 1,233 1,233 INCOME/(LOSS) BEFORE INCOME TAX EXPENSE 31,819 — (97 ) 31,722 Income tax (benefit) / expense 6,736 3,589 — 10,325 NET INCOME/(LOSS) BEFORE UNDISTRIBUTED EARNINGS OF SUBSIDIARIES 25,083 (3,589 ) (97 ) 21,397 Undistributed earnings of subsidiaries 6,228 482 6,710 NET INCOME 31,311 (3,589 ) 385 28,107 Other comprehensive (loss) / income, net of tax NET COMPREHENSIVE INCOME $ 32,638 $ (3,589 ) $ 385 $ 29,434 Condensed Statement of Cash Flows For the Fiscal Year Ended December 31, 2014 As Reported Adjustments As Restated CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 31,626 $ (6,749 ) $ 24,877 Adjustments to reconcile net income to cash provided by operating activities Undistributed earnings of subsidiaries (48,495 ) 295 (48,200 ) Deferred taxes 2,508 2,359 4,867 Changes in operating assets and liabilities: Receivables from affiliates (18,533 ) (15,294 ) (33,827 ) Other assets (5,188 ) (4,935 ) (10,123 ) Current tax receivable (1,591 ) 820 (771 ) Accrued compensation and benefits (21 ) 72 51 Accrued expenses and other liabilities 1,762 8,664 10,426 Payable to affiliates 47,522 14,468 61,990 Cash provided by operating activities 15,673 (300 ) 15,373 CASH FLOWS FROM INVESTING ACTIVITIES: Investment and funding of subsidiaries (46,726 ) (4,381 ) (51,107 ) Cash used for investing activities (46,818 ) (4,381 ) (51,199 ) Effect of exchange rate changes on cash and cash equivalents (4,630 ) 4,630 — (DECREASE) / INCREASE IN CASH AND CASH EQUIVALENTS (41,117 ) (51 ) (41,168 ) CASH AND CASH EQUIVALENTS — Beginning of year 42,352 — 42,352 CASH AND CASH EQUIVALENTS — End of year $ 1,235 $ (51 ) $ 1,184 For the Fiscal Year Ended December 31, 2013 As Reported Adjustments As Restated CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 31,311 $ (3,204 ) $ 28,107 Adjustments to reconcile net income to cash provided by operating activities Undistributed earnings of subsidiaries 6,228 (12,938 ) (6,710 ) Deferred taxes (1,448 ) 2,896 1,448 Amortization of deferred finance costs 30 (30 ) — Stock compensation expense 2,896 79 2,975 Changes in operating assets and liabilities: Receivables from affiliates 17,681 1,597 19,278 Prepaid assets (127 ) — (127 ) Other assets (5,354 ) 5,645 291 Current tax receivable 2,055 (11,797 ) (9,742 ) Accrued expenses and other liabilities (3,486 ) 4,964 1,478 Cash provided by operating activities 47,687 (12,788 ) 34,899 CASH FLOWS FROM INVESTING ACTIVITIES: Investment and funding of subsidiaries (42,764 ) 14,116 (28,648 ) Cash used for investing activities (42,764 ) 14,116 (28,648 ) Effect of exchange rate changes on cash and cash equivalents 1,328 (1,328 ) — Transactions with Subsidiaries The Parent Company has transactions with its subsidiaries determined on an agreed upon basis. Cash dividends from subsidiaries were $38.6 million , $0.0 million , and $37.1 million for the years ended December 31, 2015, 2014, and 2013, respectively. Commitments and Contingencies For a discussion of commitments and contingencies, see Note 18 to the Company’s consolidated financial statements.

Description of Business and B33

Description of Business and Basis of Presentation (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation and Principles of Consolidation The consolidated financial statements are presented in accordance with accounting principles generally accepted in the United States of America ("GAAP") and have been prepared in accordance with the regulations of the Securities and Exchange Commission ("SEC").
Consolidation	Consolidation The consolidated financial statements include the accounts of the Company, its wholly owned subsidiaries and other subsidiaries in which the Company holds a controlling financial interest. All intercompany transactions and balances are eliminated in consolidation. The Company applies relevant accounting standards governing consolidation in determining its principles of consolidation. The Company's consolidated financial statements include non-controlling interests related to certain less than wholly owned subsidiaries. See Note 12 for details regarding non-controlling interests related to certain less than wholly owned subsidiaries.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with 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 consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. In presenting the consolidated financial statements, management makes estimates regarding: • Valuation of assets and liabilities requiring fair value estimates; • Certain accruals; • The allowance for doubtful accounts; • The realization of deferred taxes; • The carrying amount of goodwill and other intangible assets; • The useful lives of intangible assets and other long-lived assets with finite lives; • Incentive based compensation accruals and valuation of share-based payment arrangements; • Transfer pricing; • The recognition and measurement of uncertain tax positions; and • Other matters that affect the reported amounts and disclosure of contingencies in the consolidated financial statements. 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.
Revenue Recognition	Revenue Recognition Revenue is recognized in accordance with revenue recognition guidance. The Company primarily generates revenue through market making and by providing trading execution services for its clients. The Company categorizes revenue as Retail revenue , Institutional revenue, Futures revenue, Other revenue and Net interest revenue . Retail revenue is the Company's largest source of revenue. Retail revenue comprises trading revenue from the retail OTC business, sales trader, and advisory businesses. OTC trading includes forex trading ("forex"), metals trading, contracts-for-difference (“CFDs”) and spread-betting (in markets which do not prohibit such transactions), as well as other financial products. Gains or losses are realized when customer transactions are liquidated. Unrealized gains or losses on trading positions are revalued at prevailing foreign currency exchange rates (the difference between contract price and market price) at the date of the balance sheet and are included in Receivables from brokers as well as Payables to customers on the Consolidated Balance Sheets. Changes in net unrealized gains or losses are recorded in Retail revenue on the Consolidated Statements of Income and Comprehensive Income. Retail revenue is recorded on a trade date basis. Institutional revenue consists of revenue from the Company's GTX business, which provides a proprietary trading platform and sales and trading services to institutions. Revenue for the GTX business is generated primarily through commissions or spreads on trades executed on the GTX platform or by voice-brokers. The Company acts as an agent for the trades executed on the GTX platform. The Company, therefore, does not assume any market or credit risk in connection with those transactions. Revenues are booked on a trade date basis. Futures revenue consists of revenue from the Company's futures business, which offers exchange-based trading execution services, focusing on the indices, agricultural hedging, and commodities sectors. Revenues in this business are generated through commissions, which are earned for executing the Company's customers' trades. These revenues are booked on a trade date basis. The Company acts in an agency capacity with respect to the clearing of trades, but is a principal with respect to fees paid to introducing brokers in its futures business. The Company does not assume any market risk with respect to customer trades in this business. Other revenue primarily comprises account management and transaction fees, inactivity, training fees charged to customer accounts, and adjustments to contingent consideration, as well as foreign currency transaction gains and losses. Net interest revenue consists primarily of the revenue generated by our cash and customer cash held by us at banks, as well as funds on deposit as collateral with our liquidity providers, less interest paid to our customers. Interest revenue and interest expense are recorded when earned and incurred, respectively.
Selling and Marketing	Selling and marketing Selling and marketing costs are relate to producing and communicating advertising, as well as other marketing activities, and are expensed as incurred
Restructuring	Restructuring expenses In 2015, 2014 and 2013, the Company incurred restructuring expenses, which reflected costs arising from headcount reductions and other exit costs, measured and disclosed in accordance with relevant accounting guidance.
Acquisition	Acquisition expenses I n 2015, 2014 and 2013, the Company incurred acquisition related expenses, which included costs such as legal, accounting, valuation and other costs specified in accounting guidance. These costs are expensed as incurred. Integration expenses In 2015, 2014 and 2013, the Company incurred integration expenses, which are acquisition related costs that are subsequently incurred while integrating the acquired company into the consolidated group.
Investments	Investments For equity investments in which the Company exerts significant influence over operating and financial policies but does not have a controlling financial interest, the equity method of accounting is used.
Cash and Cash Equivalents	Cash and cash equivalents The Company considers all highly liquid investments with an original maturity of 90 days or less at the time of acquisition to be cash equivalents. At December 31, 2015 and 2014, the Company’s cash equivalents consisted of money market accounts with an initial maturity of 90 days or less. Cash equivalents are recorded at fair value.
Cash and Cash Securities Held for Customers	Cash and securities held for customers Cash and securities held for customers represents cash and other highly liquid assets held to fund customer liabilities in connection with trading positions. 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 . 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.
Fair Value	Fair Value Certain financial assets and liabilities are recorded at fair value in accordance with applicable accounting guidance, as discussed in Note 4 Fair Value Information. Other financial assets and liabilities are not measured at fair value on a recurring basis but nevertheless approximate fair value due to their short term maturities. Such financial assets and liabilities include: Receivables from brokers; certain other assets; Payables to customers; and Accrued expenses and other liabilities. The above referenced receivables and payables include open trading positions which are held at fair value, hedging and customer positions, both of which change in value as the price of the underlying product changes. The prices approximate the amounts at which the Company can settle the positions at the balance sheet date.
Concentrations of Credit Risk	Risk Management The Company offers its customers access to a diverse range of over 12,500 financial products, including spot foreign exchange, or forex, and precious metals trading, as well as “contracts for difference”, or CFDs, which are investment products with returns linked to the performance of underlying asset. We offer CFDs on currencies, commodities, indices, individual equities, bonds and interest rate products. We also support trading of exchange-traded futures and options on futures on more than 30 global exchanges. In the United Kingdom, we offer spread bets, which are investment products similar to CFDs, but that offer more favorable tax treatment for residents of that country. The Company actively trades currencies in the spot market, earning a dealer spread. The Company seeks to manage its market risk by generally entering into offsetting contracts in the interbank market, also on a margin basis. The Company deposits margin collateral with large money center banks and other major financial institutions. The Company is subject to credit risk or loss from counterparty nonperformance. The Company seeks to control the risks associated with its customers’ activities by requiring its customers to maintain margin collateral. The Company's trading platforms do not allow customers to enter into trades if sufficient margin collateral is not on deposit with the Company. The Company developed risk-management systems and procedures that allow it to manage the market and credit risk associated with managed flow activities in real-time. The Company does not actively initiate directional market positions in anticipation of future movements in the relative prices of currencies and evaluates market risk exposure on a continuous basis. As a result of the Company’s hedging activities, the Company is likely to have open positions in various currencies at any given time. An additional component of the risk-management approach is that levels of capital are maintained in excess of those required under applicable regulations. The Company also maintains liquidity relationships with three established, global prime brokers and at least six other liquidity providers, providing the Company with access to a liquidity pool. Concentrations of Credit Risk The Company owns financial instruments that subject the Company to credit risk. These financial instruments are held primarily in Cash and cash equivalents as well as Cash and securities held for customers . The Company’s credit risk is managed by investing cash and cash equivalents primarily in high-quality money market and from time to time U.S. and Canadian Government instruments. The majority of the Company’s cash and cash equivalents are held at ten financial institutions. The Company also has credit risk related to receivables from brokers included in Receivables from brokers .
Receivables from Brokers	Receivables from Brokers Receivables from brokers include funds that the Company has posted with brokers as collateral required by agreements for holding hedging positions. Also, Receivables from brokers contains funds required to collateralize customer futures trading, as well as the related excess and the Company's own collateral. These amounts are reflected as Receivables from brokers on the Consolidated Balance Sheets and include gains or losses realized on settled contracts, as well as unrealized gains or losses on open positions.
Property and Equipment	Property and Equipment and Other Long-Lived Assets Property and equipment are recorded at cost, net of accumulated depreciation. Identifiable significant improvements are capitalized and expenditures for maintenance and repairs are charged to expense as incurred. Property and equipment are depreciated on a straight-line basis over a three year useful life, except for leasehold improvements, which are depreciated on a straight-line basis over the shorter of the lease term or estimated useful life. The Company accounts for costs incurred to develop its trading platforms and related software in accordance with Accounting Standards Codification ("ASC") 350-40, Internal-Use Software . ASC 350-40 requires that such technology be capitalized in the application and infrastructure development stages. Costs related to training, administration and non-value-added maintenance are charged to expense as incurred. Capitalized software development costs are being amortized over the useful life of the software, which the Company has estimated at three years .
Long Lived Assets	In accordance with ASC 360-10, Property, Plant and Equipment , the Company periodically evaluates the carrying value of long-lived assets when events and circumstances warrant such review. The carrying value of a long-lived asset is considered impaired when the anticipated undiscounted cash flows from such an asset are separately identifiable and are less than the carrying value. In that event, a loss is recognized in the amount by which the carrying value exceeds the fair market value of the long-lived asset. This guidance applies to assets held for use and not to assets held for sale. The Company has no assets held for sale. The Company has identified no such impairment indicators as of December 31, 2015 or December 31, 2014.
Foreign Currencies	Foreign Currencies Items included in the financial statements of each of the Company's subsidiaries are measured using the currency of the primary environment in which the subsidiaries operate ("the functional currency"). The Company has determined that its functional currency is U.S. dollars (“USD”). The Company’s Accumulated other comprehensive income/(loss), consists of foreign currency translation adjustments from subsidiaries not using the USD as their functional currency. Foreign currency transactions are remeasured into functional currency using the exchange rates prevailing at the dates of the transactions. Foreign exchange gains and losses resulting from the settlement of such transactions and from the remeasurement at period end exchange rates of monetary assets and liabilities denominated in foreign currencies are recognized in Other revenue on the Consolidated Statements of Income and Comprehensive Income.
Intangible Assets	Intangible Assets Accounting guidance addressing intangible assets requires purchased intangible assets other than goodwill to be amortized over their estimated useful lives unless their lives are determined to be indefinite. If indefinite-lived assets are determined to have a finite life in the future, the Company will amortize the carrying value over the remaining estimated useful life at that time. The Company analyzes its business, legal, and regulatory environment at least annually and on an interim basis when conditions indicate impairment may have occurred to determine whether its indefinite-lived intangible assets are likely to be impaired. This qualitative assessment indicated that it is more likely than not that the Company's indefinite lived intangible assets are not impaired. See Note 8 for additional information.
Goodwill	Goodwill In accordance with relevant accounting guidance, the Company tests goodwill for impairment on an annual basis during the fourth quarter and on an interim basis when conditions indicate impairment may have occurred (see Note 8 ). In performing these assessments, management relies on and considers a number of factors, including operating results, business plans, economic projections, anticipated future cash flows, comparable market transactions (to the extent available), other market data and the Company's overall market capitalization. There are inherent uncertainties related to these factors which require judgment in applying them to the analysis of goodwill and indefinite-lived intangible assets for impairment. Goodwill impairment is determined by comparing the estimated fair value of the reporting units with their respective carrying value. At the date of the latest test as of December 31, 2015, using both the income approach and market approach, the fair value of each of the Company's reporting units was significantly in excess of its book value, as such no impairment was identified.
Other Assets	Other Assets The Company records short term investments, receivables from vendors, security deposits, current and deferred tax assets, an indemnification asset, customer debit positions, net of related allowance, and miscellaneous receivables in Other assets on the Consolidated Balance Sheets. The Company considers all investments with an original maturity of greater than 90 days, but less than one year to be short term investments. Short term investments consist of short-term certificates of deposit. All income from the certificates of deposit is recorded as interest income when earned. See Note 9 for additional information.
Derivatives	Derivatives Forex, metals, and CFDs allow for exchanging the difference in value of a particular asset such as stock index, energy product, or gold contracts, between the time at which a contract is opened and the time at which it is closed. The Company's retail customer open positions and positions with liquidity providers are considered derivatives under derivatives accounting guidance. Therefore, they are accounted for at fair value, and included in Receivables from brokers and Payables to customers in the Consolidated Balance Sheets.
Allowance For Doubtful Accounts	Allowance for Doubtful Accounts The Company records an increase in the allowance for doubtful accounts when the prospect of collecting a specific customer account balance becomes doubtful. Management specifically analyzes accounts receivable and historical bad debt experience when evaluating the adequacy of the allowance for doubtful accounts. Should any of these factors change, the estimates made by management will also change, which could affect the level of the Company’s future provision for doubtful accounts. The customer receivables, net of allowance for doubtful accounts, is included in Other assets on the Consolidated Balance Sheets. Receivables from customers are reserved for and the related reserves are recorded in Bad debt provision on the Consolidated Statements of Income and Comprehensive Income.
Payables to Customers	Payables to Customers Payables to customers , included on the Consolidated Balance Sheets, include amounts due on cash and margin transactions. These transactions include deposits, commissions and gains or losses arising from settled trades. The payables balance also reflects unrealized gains or losses arising from open positions in customer accounts. The Company engages in white label, or omnibus relationships, with other regulated financial institutions. The payables balance includes amounts deposited by these financial institutions in order for the Company to act as clearing broker.
Referral Fees	Referral fees Introducing brokers direct customers to the Company in return for a commission on each referred customer’s trading volume or a share of net revenue generated by each referred customer’s trading activity. Such fees are referred to as introducing broker fees and are recorded on a trade date basis, in Referral Fees, in the Consolidated Statements of Income and Comprehensive Income.
Trading Expenses	Trading Expenses Trading expenses consist of exchange fees paid to stock exchanges and other third-parties for exchange market data that the Company provides to its customers or uses to create its own derived data products, as well as fees for news services and fees paid to prime brokers in connection with its institutional GTX business and futures business.
Income Taxes	Income Taxes Income tax expense is provided for using the asset and liability method, under which deferred tax assets and liabilities are determined based upon the temporary differences between the financial statement and income tax bases of assets and liabilities using currently enacted tax rates. The Company operates under a permanent reinvestment strategy, under which earnings derived from foreign businesses remain invested in the Company’s foreign subsidiaries. In accordance with accounting guidance, the Company does not recognize domestic tax expense related to the permanently reinvested earnings. The Company has no plans to repatriate accumulated unremitted earnings as of December 31, 2015.
Employee Compensation and Benefits	Employee compensation and benefits In accordance with stock compensation guidance, the Company recognizes expense for all share-based payments to employees, including grants of employee stock options as well as restricted stock units on the basis of grant date fair values. The Company estimates fair value using the Black Scholes model for stock options and fair value on grant date for restricted stock units. Shares typically vest incrementally and equally on an annual basis over a four year period, without performance triggers or other requirements beyond continued service. For each type of award, the Company reduces expense by an estimated forfeiture rate. See Note 15 for additional share based payment disclosure. The Company make estimates in determining its quarterly and annual accrued non-share-based compensation. A significant portion of the Company's employee incentive compensation programs is discretionary. Each quarter and year-end the Company determines the amount of its expected discretionary cash bonus pools.
Treasury Shares	Treasury Shares In accordance with ASC 505-30, Equity - Treasury Stock , the Company treats the cost of acquired shares purchased as a deduction from shareholders’ equity and as a reduction of the total shares outstanding when calculating earnings per share.
Earnings Per Common Share	Earnings Per Common Share Basic earnings per common share is calculated using the weighted average common shares outstanding during the year. Common equivalent shares from stock options and restricted stock awards, using the treasury stock method, are also included in the diluted per share calculations unless their effect of inclusion would be anti-dilutive. See Note 16 for discussion of the impact of the Company's convertible note and non-controlling interests on EPS.

Description of Business and B34

Description of Business and Basis of Presentation (Tables)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Allowance For Doubtful Accounts	The allowance for doubtful accounts consisted of the following (amounts in thousands): Balance as of January 1, 2013 $ (148 ) Addition to provision (1,501 ) Amounts written off 491 Balance as of December 31, 2013 (1,158 ) Addition to provision (3,699 ) Amounts written off 302 Balance as of December 31, 2014 (4,555 ) Addition to provision (7,462 ) Amounts written off 5,185 Balance as of December 31, 2015 $ (6,832 )

Restatement (Tables)

Restatement (Tables)	12 Months Ended
	Dec. 31, 2015
Accounting Changes and Error Corrections [Abstract]
Schedule of Prior Period Adjustments	Consolidated Balance Sheet As of December 31, 2014 As Reported Tax Adjustment Other Adjustments As Restated ASSETS: Cash and cash equivalents $ 139,403 $ — $ (52 ) $ 139,351 Goodwill 34,567 (988 ) — 33,579 Other assets, net of allowance for doubtful accounts (1) 35,311 917 (2,463 ) 33,765 Total assets $ 1,185,887 $ (71 ) $ (2,515 ) $ 1,183,301 LIABILITIES AND SHAREHOLDERS’ EQUITY: Liabilities Accrued expenses and other liabilities 64,476 12,170 (451 ) 76,195 Income tax payable 1,470 1,603 (2,063 ) 1,010 Total liabilities $ 910,784 $ 13,773 $ (2,514 ) $ 922,043 Redeemable non-controlling interests 10,209 — 1,129 11,338 Shareholders’ equity Accumulated other comprehensive loss (2,054 ) 541 — (1,513 ) Additional paid-in capital 152,684 (4,306 ) — 148,378 Retained earnings 130,984 (10,079 ) (1,130 ) 119,775 Total shareholders’ equity 264,894 (13,844 ) (1,130 ) 249,920 Total liabilities and shareholders’ equity $ 1,185,887 $ (71 ) $ (2,515 ) $ 1,183,301 (1) The Company previously reported $174,000 as Short term investments, at fair value ; this amount has been reclassified to Other assets, net of allowance for doubtful accounts to conform to current year presentation Consolidated Statements of Income and Comprehensive Income For the Fiscal Year Ended December 31, 2014 As Reported Tax Adjustment Other Adjustments Restated REVENUE: Retail revenue (1) $ 293,122 $ — $ (344 ) $ 292,778 Institutional revenue (1) 34,518 — — 34,518 Futures revenue (1) 36,160 — — 36,160 Total non-interest revenue 368,704 — (344 ) 368,360 Net revenue $ 369,533 $ — $ (344 ) $ 369,189 EXPENSES: Employee compensation and benefits $ 99,485 $ — $ (252 ) $ 99,233 Referral fees 91,092 — (120 ) 90,972 Trading expenses 26,285 — (117 ) 26,168 General and administrative 38,509 — 142 38,651 Depreciation and amortization 7,125 — (515 ) 6,610 Restructuring expenses 1,214 — 1,120 2,334 Total operating expense 317,334 — 258 317,592 OPERATING PROFIT 52,199 — (602 ) 51,597 INCOME BEFORE INCOME TAX EXPENSE 46,052 — (602 ) 45,450 Income tax (benefit)/expense 12,993 6,200 (53 ) 19,140 NET INCOME 33,059 (6,200 ) (549 ) 26,310 NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. 31,626 (6,200 ) (549 ) 24,877 Other comprehensive (loss)/income: Foreign currency translation adjustment (4,630 ) 541 (4,089 ) NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. $ 26,996 $ (5,659 ) $ (549 ) $ 20,788 Earnings per common share: Basic $ 0.76 $ (0.16 ) $ (0.04 ) $ 0.56 Diluted $ 0.71 $ (0.14 ) $ (0.04 ) $ 0.53 (1) - The Company has changed its revenue presentation, see Note 1 for detail For the Fiscal Year Ended December 31, 2013 As Reported Tax Adjustment Other Adjustments As Restated REVENUE: Retail revenue (1) $ 215,667 $ — $ 67 $ 215,734 Institutional revenue (1) 28,005 — — 28,005 Futures revenue (1) 22,188 — — 22,188 Total non-interest revenue 266,959 — 67 267,026 Net revenue $ 267,624 $ — $ 67 $ 267,691 EXPENSES: Employee compensation and benefits $ 74,185 $ — $ 422 $ 74,607 Referral fees 52,503 — 120 52,623 General and administrative 26,813 — (255 ) 26,558 Depreciation and amortization 7,768 — 515 8,283 Restructuring expenses 1,570 — (1,120 ) 450 Total operating expense 223,286 — (318 ) 222,968 OPERATING PROFIT 44,338 — 385 44,723 INCOME BEFORE INCOME TAX EXPENSE 45,105 — 385 45,490 Income tax (benefit)/expense 13,794 3,589 — 17,383 NET INCOME 31,311 (3,589 ) 385 28,107 NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. 31,311 (3,589 ) 385 28,107 NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. $ 32,638 $ (3,589 ) $ 385 $ 29,434 Earnings per common share: Basic $ 0.85 $ (0.10 ) $ 0.01 $ 0.76 Diluted $ 0.79 $ (0.09 ) $ 0.01 $ 0.71 (1) - The Company has changed its revenue presentation, see Note 1 for detail Consolidated Statement of Changes in Shareholders' Equity Additional Paid in Capital Retained Earnings Accumulated Other Comprehensive Income/(Loss) Total As Reported As Restated As Reported As Restated As Reported As Restated As Reported As Restated BALANCE—January 1, 2013 $ 85,089 $ 85,009 $ 84,772 $ 84,590 $ 1,249 $ 1,249 $ 162,830 $ 162,568 BALANCE—January 1, 2014 $ 138,691 $ 134,399 $ 108,603 $ 105,217 $ 2,576 $ 2,576 $ 234,401 $ 226,723 BALANCE—December 31, 2014 $ 152,684 $ 148,378 $ 130,984 $ 119,775 $ (2,054 ) $ (1,513 ) $ 264,894 $ 249,920 Consolidated Statement of Cash Flows For the Fiscal Year Ended December 31, 2014 As Reported Adjustments As Restated CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 33,059 $ (6,749 ) $ 26,310 Adjustments to reconcile net income to cash provided by / (used for) operating activities Depreciation and amortization 16,367 (1,677 ) 14,690 Non-cash integration costs — 1,162 1,162 Deferred tax (benefit)/expense 2,536 2,572 5,108 Changes in operating assets and liabilities: Cash and securities held for customers (9,679 ) 419 (9,260 ) Receivables from brokers 94,657 276 94,933 Prepaid assets 2,729 1 2,730 Other assets (11,536 ) 3,041 (8,495 ) Payables to customers 9,679 (419 ) 9,260 Accrued compensation and benefits 3,671 826 4,497 Accrued expenses and other liabilities (8,565 ) 6,143 (2,422 ) Income tax payable (2,832 ) (6,980 ) (9,812 ) Cash provided by / (used for) operating activities 138,173 (1,385 ) 136,788 Effect of exchange rate changes on cash and cash equivalents 2,760 1,333 4,093 INCREASE/ (DECREASE) IN CASH AND CASH EQUIVALENTS 99,532 (52 ) 99,480 CASH AND CASH EQUIVALENTS—End of year $ 139,403 $ (52 ) $ 139,351 SUPPLEMENTARY DISCLOSURES OF CASH FLOW INFORMATION: Adjustment to redemption value of non-controlling interests $ (978 ) $ (1,129 ) $ (2,107 ) For the Fiscal Year Ended December 31, 2013 As Reported Adjustments Restated CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 31,311 $ (3,204 ) $ 28,107 Adjustments to reconcile net income to cash provided by / (used for) operating activities Depreciation and amortization 11,837 (648 ) 11,189 Non-cash integration costs — 1,163 1,163 Deferred tax (benefit)/expense 39 (5,470 ) (5,431 ) Stock compensation expense 2,896 79 2,975 Changes in operating assets and liabilities: Cash and securities held for customers (74,608 ) (161 ) (74,769 ) Receivables from brokers (78,336 ) (220 ) (78,556 ) Prepaid assets 318 — 318 Other assets (383 ) (692 ) (1,075 ) Payables to customers 74,608 161 74,769 Accrued compensation and benefits 7,118 (743 ) 6,375 Accrued expenses and other liabilities 973 6,894 7,867 Income tax payable 2,131 2,283 4,414 Effect of exchange rate changes on cash and cash equivalents (2,446 ) 558 (1,888 ) SUPPLEMENTARY DISCLOSURES OF CASH FLOW INFORMATION: Deferred taxes related to convertible senior notes $ — $ (4,308 ) $ (4,308 ) The following table sets forth the impact of the restatement on the quarterly financial data for the interim periods in 2015 and 2014: As Reported Tax Adjustments Other Adjustments As Restated For the three months ended September 30, 2015 Total non-interest revenue $ 127,865 $ — $ 180 $ 128,045 Net revenue $ 127,931 $ — $ 180 $ 128,111 Income/(loss) before income tax expense $ 9,215 $ — $ 203 $ 9,418 Income tax (benefit)/expense $ 328 $ 7,534 $ — $ 7,862 Net income/(loss) $ 8,887 $ (7,534 ) $ 203 $ 1,556 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 8,304 $ (7,534 ) $ 203 $ 973 Basic net income/(loss)per share $ 0.20 $ 0.05 Diluted net income/(loss) per share $ 0.20 $ 0.05 As Reported Tax Adjustments Other Adjustments As Restated For the three months ended June 30, 2015 Total non-interest revenue $ 111,559 $ — $ (107 ) $ 111,452 Net revenue $ 111,564 $ — $ (107 ) $ 111,457 Income/(loss) before income tax expense $ (12,538 ) $ — $ (203 ) $ (12,741 ) Income tax (benefit)/expense $ (4,124 ) $ (1,915 ) $ — $ (6,039 ) Net income/(loss) $ (8,414 ) $ 1,915 $ (203 ) $ (6,702 ) Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ (8,830 ) $ 1,915 $ (203 ) $ (7,118 ) Basic net income/(loss)per share $ (0.23 ) $ (0.16 ) Diluted net income/(loss) per share $ (0.23 ) $ (0.16 ) As Reported Tax Adjustments Other Adjustments As Restated For the three months ended March 31, 2015 Total non-interest revenue $ 92,933 $ — $ 34 $ 92,967 Net revenue $ 92,952 $ — $ 34 $ 92,986 Income/(loss) before income tax expense $ 11,498 $ — $ 56 $ 11,554 Income tax (benefit)/expense $ 2,818 $ 2,927 $ — $ 5,745 Net income/(loss) $ 8,680 $ (2,927 ) $ 56 $ 5,809 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 8,336 $ (2,927 ) $ 56 $ 5,465 Basic net income/(loss)per share $ 0.19 $ 0.11 Diluted net income/(loss) per share $ 0.18 $ 0.11 As Reported Tax Adjustments Other Adjustments As Restated For the three months ended December 31, 2014 Total non-interest revenue $ 114,725 $ — $ 432 $ 115,157 Net revenue $ 114,723 $ — $ 524 $ 115,247 Income/(loss) before income tax expense $ 26,456 $ — $ 695 $ 27,151 Income tax (benefit)/expense $ 8,398 $ 728 $ (53 ) $ 9,073 Net income/(loss) $ 18,058 $ (728 ) $ 748 $ 18,078 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 17,612 $ (728 ) $ 748 $ 17,632 Basic net income/(loss)per share $ 0.44 $ 0.42 Diluted net income/(loss) per share $ 0.42 $ 0.40 As Reported Tax Adjustments Other Adjustments As Restated For the three months ended September 30, 2014 Total non-interest revenue $ 103,388 $ — $ (602 ) $ 102,786 Net revenue $ 103,650 $ — $ (694 ) $ 102,956 Income/(loss) before income tax expense $ 21,470 $ — $ (583 ) $ 20,887 Income tax (benefit)/expense $ 5,340 $ 3,866 $ — $ 9,206 Net income/(loss) $ 16,130 $ (3,866 ) $ (583 ) $ 11,681 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 15,345 $ (3,866 ) $ (583 ) $ 10,896 Basic net income/(loss)per share $ 0.35 $ 0.22 Diluted net income/(loss) per share $ 0.33 $ 0.21 As Reported Tax Adjustments Other Adjustments As Restated For the three months ended June 30, 2014 Total non-interest revenue $ 69,504 $ — $ 501 $ 70,005 Net revenue $ 69,763 $ — $ 501 $ 70,264 Income/(loss) before income tax expense $ (7,013 ) $ — $ 592 $ (6,421 ) Income tax (benefit)/expense $ (2,021 ) $ 95 $ — $ (1,926 ) Net income/(loss) $ (4,992 ) $ (95 ) $ 592 $ (4,495 ) Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ (5,156 ) $ (95 ) $ 592 $ (4,659 ) Basic net income/(loss)per share $ (0.13 ) $ (0.12 ) Diluted net income/(loss) per share $ (0.13 ) $ (0.12 ) As Reported Tax Adjustments Other Adjustments As Restated For the three months ended March 31, 2014 Total non-interest revenue $ 81,087 $ — $ (675 ) $ 80,412 Net revenue $ 81,397 $ — $ (675 ) $ 80,722 Income/(loss) before income tax expense $ 5,139 $ — $ (1,306 ) $ 3,833 Income tax (benefit)/expense $ 1,276 $ 1,511 $ — $ 2,787 Net income/(loss) $ 3,863 $ (1,511 ) $ (1,306 ) $ 1,046 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 3,825 $ (1,511 ) $ (1,306 ) $ 1,008 Basic net income/(loss)per share $ 0.10 $ 0.02 Diluted net income/(loss) per share $ 0.09 $ 0.02

Fair Value Information (Tables)

Fair Value Information (Tables)	12 Months Ended
	Dec. 31, 2015
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): Customer derivative positions $ — $ 143,918 $ — $ 143,918 Broker derivative contracts — (12,568 ) — (12,568 ) Money market accounts 25,167 — — 25,167 Certificates of deposit 174 — — 174 Investment in gold 107 — — 107 Total $ 25,448 $ 131,350 $ — $ 156,798 Fair Value Measurements on a Recurring Basis as of December 31, 2014 Level 1 Level 2 Level 3 Total Financial Assets (Liabilities): Customer derivative contracts $ — $ 102,722 $ — $ 102,722 Broker derivative contracts — 717 — 717 Money market accounts 20,537 — — 20,537 Certificates of deposit 174 — — 174 Investment in gold 118 — — 118 Contingent consideration — — (9,974 ) (9,974 ) Total $ 20,829 $ 103,439 $ (9,974 ) $ 114,294
Rollforward of Level 3 Liabilities	The following is a rollforward of the Level 3 liabilities from January 1, 2014 to December 31, 2015 (amounts in thousands): Liabilities Contingent Consideration Balance at January 1, 2014 $ — Issuance of contingent payment obligation 10,540 Gains included in earnings - currency revaluation (984 ) Losses included in earnings - discount amortization 418 Balance at January 1, 2015 9,974 Gains included in earnings - adjustment to fair value of contingent consideration (6,722 ) Contingent consideration payments (2,063 ) Gains included in earnings - currency revaluation (212 ) Losses included in earnings - discount amortization 570 Settlement of contingent payment obligation (1,547 ) Balance at December 31, 2015 $ —
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	As of December 31, 2015 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 $ 133,721 $ 133,721 $ — $ 133,721 $ — Financial Liabilities: Payables to customers $ 1,064,539 $ 1,064,539 $ — $ 1,064,539 $ — Convertible senior notes $ 121,996 $ 122,264 $ — $ 122,264 $ — As of December 31, 2014 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 $ 134,191 $ 134,191 $ — $ 134,191 $ — Financial Liabilities: Payables to customers $ 862,281 $ 862,281 $ — $ 862,281 $ — Convertible senior notes $ 68,367 $ 66,440 $ — $ 66,440 $ — Accrued expenses and other liabilities $ 20,000 $ 20,000 $ — $ 20,000 $ —

Derivatives (Tables)

Derivatives (Tables)	12 Months Ended
	Dec. 31, 2015
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 and Payables to customers on the accompanying Consolidated Balance Sheet (amounts in thousands): December 31, 2015 Gross amounts of assets for derivative open positions at fair value Gross amount of (liabilities) for derivative open positions at fair value Net amounts of assets/(liabilities) for derivative open positions at fair value Derivative Instruments: Foreign currency exchange contracts $ 138,140 $ (59,468 ) $ 78,672 CFD contracts 111,844 (70,429 ) 41,415 Metals contracts 18,866 (7,603 ) 11,263 Total $ 268,850 $ (137,500 ) $ 131,350 December 31, 2015 Cash Collateral Net amounts of assets/(liabilities) for derivative open positions at fair value Net amounts of assets/(liabilities) presented in the balance sheet Derivative Assets/(Liabilities:) Receivables from brokers $ 133,721 $ (12,568 ) $ 121,153 Payables to customers $ (1,064,539 ) $ 143,918 $ (920,621 ) December 31, 2014 Gross amounts of Gross amount of Net amounts of Derivative Instruments: Foreign currency exchange contracts $ 168,034 $ (93,057 ) $ 74,977 CFD contracts 44,329 (24,420 ) 19,909 Metals contracts 16,146 (7,593 ) 8,553 Total $ 228,509 $ (125,070 ) $ 103,439 December 31, 2014 Cash Collateral Net amounts of Net amounts of Derivative Assets/(Liabilities): Receivables from brokers $ 134,191 $ 717 $ 134,908 Payables to customers $ (862,281 ) $ 102,722 $ (759,559 )
Notional Values of Derivative Instruments	The table below presents the number of contracts reported within Receivables from brokers and Payables to customers on the consolidated balance sheets (amounts in thousands): December 31, 2015 Total contracts in long positions Total contracts in short positions Derivative Instruments: Foreign currency exchange contracts 3,106,885 2,931,109 CFD contracts 139,465 285,640 Metals contracts 1,278 308 Total 3,247,628 3,217,057 December 31, 2014 Total contracts in long positions Total contracts in short positions Derivative Instruments: Foreign currency exchange contracts 3,147,518 2,679,041 CFD contracts 873,070 10,753 Metals contracts 835 335 Total 4,021,423 2,690,129
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 Consolidated Statements of Income and Comprehensive Income for the years ended December 31, 2015 and 2014 were as follows (amounts in thousands): For the Years Ended December 31, 2015 2014 Derivative Instruments: Foreign currency exchange contracts $ 163,315 $ 136,546 CFD contracts 151,553 105,174 Metals contracts 28,918 48,608 Total $ 343,786 $ 290,328

Receivables From Brokers (Table

Receivables From Brokers (Tables)	12 Months Ended
	Dec. 31, 2015
Receivables [Abstract]
Receivable from Brokers	Amounts receivable from brokers consisted of the following as of (amounts in thousands): December 31, 2015 December 31, 2014 Required Collateral $ 129,042 $ 95,599 Excess from futures broker - Restricted 4,679 38,592 Open foreign exchange positions (12,568 ) 717 Total $ 121,153 $ 134,908

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment, including leasehold improvements and capitalized software development costs, consisted of the following as of (amounts in thousands): December 31, 2015 December 31, 2014 Software $ 44,194 $ 30,351 Computer equipment 14,300 8,516 Leasehold improvements 11,200 6,719 Telephone equipment 881 719 Office equipment 2,113 2,345 Furniture and fixtures 1,761 1,044 Web site development costs 668 646 Gross property and equipment 75,117 50,340 Less: Accumulated depreciation and amortization (44,750 ) (31,544 ) Property and equipment, net $ 30,367 $ 18,796

Intangible Assets and Goodwill

Intangible Assets and Goodwill (Tables)	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets	The Company has the following identifiable intangible assets as of December 31, 2015: Intangible Asset Amount (in thousands) Weighted average amortization period Customer list $ 56,388 7.6 years Technology 74,378 8.9 years Trademark (1) 8,652 6.7 years Total intangible assets $ 139,418 (1) Trademarks with indefinite lives, as described above, comprise $0.4 million of the gross $8.7 million of trademarks. Future annual estimated amortization expense is as follows (amounts in thousands): Years Ended December 31: 2016 $ 15,988 2017 15,132 2018 13,648 2019 11,974 2020 9,992 Thereafter 24,415 Total $ 91,149 The Company's various finite-lived intangible assets consisted of the following as of (amounts in thousands): December 31, 2015 December 31, 2014 Intangibles Gross Accumulated Net Gross Accumulated Net Customer list $ 56,388 $ (14,111 ) $ 42,277 $ 22,944 $ (7,152 ) $ 15,792 Technology 74,378 (32,117 ) 42,261 48,376 (4,671 ) 43,705 Trademark 8,289 (1,678 ) 6,611 1,793 (847 ) 946 Total finite lived intangibles $ 139,055 $ (47,906 ) $ 91,149 $ 73,113 $ (12,670 ) $ 60,443 Trademarks not subject to amortization (1) 363 — 363 363 — 363 Total intangibles assets (2) $ 139,418 $ (47,906 ) $ 91,512 $ 73,476 $ (12,670 ) $ 60,806 (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. These trademarks are also supported annually in the Company's impairment test for intangible assets. (2) The increase in total intangibles for the year ended December 31, 2015 was primarily due to the customer lists, technology and trademarks acquired as part of the City Index acquisition. See Note 11 for details of the intangibles acquired in the Company's City Index, GAA, Top Third and Galvan acquisitions. The technology acquired pursuant to the asset purchase agreements with Valaquenta Intellectual Property Limited ("Valaquenta") and Forexster Limited ("Forexster"), is described in further detail below.
Schedule of Goodwill	The following represents the carrying amount of goodwill by segment (amounts in thousands): Retail Institutional Futures Total Carrying amount of goodwill as of December 31, 2015 $ 26,722 $ 4,788 $ 2,507 $ 34,017

Other Assets (Tables)

Other Assets (Tables)	12 Months Ended
	Dec. 31, 2015
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Other Assets	Other assets consisted of the following as of (amounts in thousands): December 31, 2015 December 31, 2014 Vendor and security deposits $ 11,486 $ 3,373 Income tax receivable 9,482 5,163 Deferred tax assets, net 17,827 6,308 Indemnification asset — 8,792 GTX Trade Receivables 4,881 4,190 Customer Debit Positions 7,340 6,594 Allowance on customer debit positions (6,832 ) (4,555 ) Miscellaneous receivables 2,416 3,900 Equity method investment 822 — $ 47,422 $ 33,765

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2015
Business Acquisition [Line Items]
Schedule of Restructuring Costs	(in thousands) Restructuring liability as of January 1, 2014 $ 584 2014 restructuring expenses 2,334 Payments made in 2014 (2,543 ) Liability as of December 31, 2014 375 2015 restructuring expenses 3,482 Payments made in 2015 (3,358 ) Liability as of December 31, 2015 $ 499
City Index
Business Acquisition [Line Items]
Summary of Purchase Price	The purchase price was derived as follows (amounts in thousands): Cash $ 6,103 Convertible senior notes 65,000 Common stock issued 45,100 Total purchase price $ 116,203
Preliminary Purchase Price Allocated to the Fair Value of Assets and Liabilities	The purchase price of City Index was allocated to the fair value of various assets and liabilities as follows (amounts in thousands): Cash $ 10,546 Cash and securities held for customers 281,576 Receivable from brokers 35,974 Property and equipment 10,466 Prepaid assets 4,038 Other assets 5,119 Total tangible assets 347,719 Total liabilities assumed 299,000 Net assets acquired 48,719 Identifiable intangible assets: Customer list 34,277 Trade name 6,645 Technology 26,157 Intangible assets, net 67,079 Goodwill $ 405
Galvan, GAA, and Top Third
Business Acquisition [Line Items]
Unaudited Pro Forma Income Statement Line Items	Unaudited pro forma income statement line items for the twelve months ended December 31, 2014 and December 31, 2013 were as follows (amounts in thousands): For the Fiscal Year Ended December 31, 2014 2013 REVENUE: Total non-interest revenue $ 376,362 $ 289,810 Interest revenue 1,435 856 Interest expense 599 156 Total net interest revenue 836 700 Net revenue 377,198 290,510 EXPENSES: Depreciation and amortization 6,626 8,407 Purchased intangible amortization 9,044 4,834 Other expense items 308,607 227,273 Total operating expense 324,277 240,514 OPERATING PROFIT 52,921 49,996 Interest on long term borrowings (6,147 ) (1,232 ) Gain on extinguishment of debt — 2,000 INCOME BEFORE INCOME TAX EXPENSE 46,774 50,764 Income tax expense 19,316 18,750 NET INCOME 27,458 32,014 Net income attributable to non-controlling interests 1,308 691 Net income applicable to Gain Capital Holdings, Inc. $ 26,150 $ 31,323
Galvan
Business Acquisition [Line Items]
Summary of Purchase Price	The purchase price was derived as follows (amounts in thousands): Cash $ 9,732 Contingent payment 10,540 Total purchase price $ 20,272
Preliminary Purchase Price Allocated to the Fair Value of Assets and Liabilities	The purchase price of Galvan was allocated to the fair value of various assets and liabilities as follows (amounts in thousands): Cash and cash equivalents $ 2,193 Receivable from brokers 745 Property and equipment 12 Prepaid assets 94 Other assets 64 Total tangible assets 3,108 Total liabilities assumed 1,931 Net assets acquired 1,177 Identifiable intangible assets: Customer list 4,203 Trade name 784 Intangible assets, net 4,987 Goodwill $ 14,108
GAA
Business Acquisition [Line Items]
Summary of Purchase Price	The purchase price was derived as follows (amounts in thousands): Cash $ 4,365 Common Stock issued 1,241 Total purchase price $ 5,606
Preliminary Purchase Price Allocated to the Fair Value of Assets and Liabilities	The purchase price of GAA was allocated to the fair value of various assets and liabilities as follows (amounts in thousands): Non-controlling interest $ 4,509 Cash and cash equivalents $ 360 Receivable from brokers 438 Property and equipment 148 Prepaid assets 153 Other assets 3 Total tangible assets 1,102 Total liabilities assumed 515 Net assets acquired 587 Identifiable intangible assets: Customer list 3,100 Trade name 270 Intangible assets, net 3,370 Goodwill $ 6,158
Top Third
Business Acquisition [Line Items]
Preliminary Purchase Price Allocated to the Fair Value of Assets and Liabilities	The purchase price of Top Third was allocated to the fair value of various assets and liabilities as follows (amounts in thousands): Non-controlling interest $ 3,885 Cash and cash equivalents $ 73 Receivable from brokers 663 Total tangible assets 736 Total liabilities assumed 1,103 Net liabilities assumed (367 ) Identifiable intangible assets: Customer list 3,900 Trade name 90 Intangible assets, net 3,990 Goodwill $ 3,806
Global Futures & Forex Ltd
Business Acquisition [Line Items]
Summary of Purchase Price	The purchase price allocation was derived as follows (amounts in thousands): Cash $ 40,000 Payment for excess cash adjustment 2,160 Loan payable 33,200 Common Stock issued 34,771 Total purchase price $ 110,131
Preliminary Purchase Price Allocated to the Fair Value of Assets and Liabilities	The purchase price of GFT was allocated to the fair value of various assets and liabilities as follows (amounts in thousands): Cash and cash equivalents $ 15,781 Cash and cash equivalents held for customers 228,419 Receivable from brokers 61,028 Property and equipment 7,515 Other assets 18,942 Total tangible assets 331,685 Total liabilities assumed 251,691 Net assets acquired 79,994 Identifiable intangible assets: Software 25,300 Customer relationships 3,150 Intangible assets, net 28,450 Goodwill $ 1,687
Unaudited Pro Forma Income Statement Line Items	Unaudited pro forma income statement line items for the twelve months ended December 31, 2013 and December 31, 2012, were as follows (amounts in thousands): For the Fiscal Year Ended December 31, 2013 2012 REVENUE: Total non-interest revenue $ 353,556 $ 248,592 Interest revenue 927 1,096 Interest expense 634 537 Total net interest revenue 293 559 Net revenue 353,849 249,151 EXPENSES: Other expense items (1) 299,945 261,679 Depreciation and amortization 11,527 7,958 Purchased intangible amortization 5,157 7,250 Acquisition expense 1,824 85 Restructuring 451 634 Integration 1,950 — Total expense 320,854 277,606 OPERATING PROFIT/(LOSSES) 32,995 (28,455 ) Interest expense on long term borrowings 1,232 444 Gain on extinguishment of debt 2,000 — INCOME BEFORE INCOME TAX EXPENSE/(BENEFIT) 33,763 (28,899 ) Income tax expense 16,106 (10,837 ) NET INCOME/(LOSS) $ 17,657 $ (18,062 ) (1) Other expenses items for the year ended December 31, 2013, included a one-time, non-recurring expense of $ 5.1 million relating to a GFT accrual for certain liabilities to third parties.
City Index, GFT, GAA, Top Third, Galvan
Business Acquisition [Line Items]
Unaudited Pro Forma Income Statement Line Items	Unaudited pro forma income statement line items for the twelve months ended December 31, 2015 and December 31, 2014 were as follows (amounts in thousands): For the Fiscal Year Ended December 31, 2015 2014 REVENUE: Total non-interest revenue $ 471,959 $ 506,228 Interest revenue 1,303 2,288 Interest expense 1,049 599 Total net interest revenue 254 1,689 Net revenue 472,213 507,917 EXPENSES: Depreciation and amortization 11,753 16,500 Purchased intangible amortization 18,619 17,962 Other expense items 424,229 430,263 Total operating expense 454,601 464,725 OPERATING PROFIT 17,612 43,192 Interest on long term borrowings 10,267 9,283 Gain on extinguishment of debt — — Impairment of investment — — INCOME BEFORE INCOME TAX EXPENSE 7,345 33,909 Income tax expense 126 16,399 NET INCOME 7,219 17,510 Net income attributable to non-controlling interests 1,660 1,433 Net income applicable to Gain Capital Holdings, Inc. $ 5,559 $ 16,077

Non-controlling Interests (Tabl

Non-controlling Interests (Tables)	12 Months Ended
	Dec. 31, 2015
Noncontrolling Interest [Abstract]
Schedule of Non-controlling Interests	The table below reflects the non-controlling interests effects on the Company's financial statements: Redeemable non-controlling interests December 31, 2013 $ — Non-controlling interests related to 2014 acquisitions 8,394 Adjustment to the redemption value of non-controlling interests 2,107 Net income attributable to non-controlling interests 1,433 Distributions to non-controlling interest holders (596 ) December 31, 2014 $ 11,338 Adjustment to the redemption value of non-controlling interests (308 ) Net income attributable to non-controlling interests 1,660 Distributions to non-controlling interest holders (1,644 ) December 31, 2015 $ 11,046

Convertible Senior Notes (Table

Convertible Senior Notes (Tables)	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Schedule of Liability and Equity Components of Convertible Debt	The balances of the liability and equity components as of December 31, 2015 and 2014, were as follows, with amounts in thousands: December 31, December 31, 2015 2014 Liability component - principal $ 140,000 $ 80,000 Deferred bond discount 18,004 11,633 Liability component - net carrying value $ 121,996 $ 68,367 Additional paid in capital $ 27,920 $ 12,572 Discount attributable to equity (412 ) (425 ) Equity component $ 27,508 $ 12,147
Schedule of Interest Expense	Interest expense related to the Convertible Senior Notes, included in Interest expense on long-term borrowings in the Consolidated Statements of Income and Comprehensive Income, was as follows, with amounts in thousands: For the Fiscal Year Ended December 31, 2015 2014 Interest expense - stated coupon rate $ 5,156 $ 3,300 Interest expense - amortization of deferred bond discount and costs 3,712 2,593 Total interest expense - convertible note $ 8,868 $ 5,893

Share Based Compensation (Table

Share Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-Based Compensation Cost	Total share-based compensation cost recognized during 2015, 2014 and 2013 consisted of the following ($ in thousands:) For the Years Ended December 31, 2015 2014 2013 Employee compensation and benefits 3,680 3,452 2,975
Summary of Stock Option Activity Under All plans	The following table summarizes the stock option activity under all plans from January 1, 2015 through December 31, 2015 (in thousands, except per share amounts): Options Outstanding Weighted Weighted Average Number of Average Remaining Aggregate Options Exercise Price Life (Years) Intrinsic Value Outstanding January 1, 2015 1,908 $ 4.83 3.30 Granted 137 9.51 6.40 Exercised (638 ) 3.74 1.86 Forfeited/Expired (49 ) 6.62 5.00 Outstanding December 31, 2015 1,358 $ 5.76 4.16 $ 3,544 Vested and expected to vest options 1,340 $ 5.71 4.13 $ 3,525 Exercisable, December 31, 2015 938 $ 5.17 3.83 $ 2,792 Fair market value of common stock at exercise date $ 5,869 Cost to exercise 2,388 Net value of stock options exercised $ 3,481
Summary of Outstanding and Exercisable Stock Options	The following table summarizes information concerning outstanding and exercisable stock options as of December 31, 2015 : Options Outstanding Options Exercisable Weighted Average Weighted Remaining Number of Weighted Number Average Contractual Options Average Exercise Price Outstanding Exercise Price Life (Years) Exercisable Exercise Price $3.83 481 $ 3.83 1.64 481 $ 3.83 $4.40 238 4.40 4.22 90 $ 4.40 $5.30 208 5.30 3.31 136 $ 5.30 $8.02 210 8.02 2.29 210 $ 8.02 $9.51 137 9.51 9.51 — $ 9.51 $9.95 84 9.95 5.18 21 $ 9.95 1,358 $ 5.76 4.16 938 $ 5.17
Assumptions For Stock Options Granted	The Compensation Committee approved stock option grants with a fair market value estimated under a Black-Scholes option pricing valuation model using the following assumptions: For the Fiscal Year Ended December 31, 2015 2014 2013 Valuation Assumptions Risk-free rate 1.47% 1.40% 0.80% Expected volatility 49.08% 51.80% 48.80% Expected term (years) 4.75 4.80 4.80 Dividend yield 2.1% 2.0% 4.9%
Summary of Nonvested Shares of Restricted Stock Units and Restricted Stock Awards	A summary of the status of the Company’s nonvested shares of RSUs and RSAs as of December 31, 2015 and changes during the year ended December 31, 2015 , is presented below (in thousands, except per share amounts): Weighted Average Weighted Average Number Grant Date Number Grant Date Non-Vested Shares of RSUs Fair Value of RSAs Fair Value Non-vested at January 1, 2015 1,073 $ 6.69 54 $ 7.31 Granted 601 9.42 — — Vested (387 ) 6.46 (53 ) 7.32 Forfeited (104 ) 8.08 (1 ) 6.48 Non-vested at December 31, 2015 1,183 $ 8.03 — $ —

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Computation of Earnings Per Share	The following table sets forth the computation of earnings per share (amounts in thousands except share and per share data): For the years ended December 31, 2015 2014 2013 Net income applicable to GAIN Capital Holdings, Inc. $ 10,279 $ 24,877 $ 28,107 Adjustment (1)(2) 308 (2,107 ) (154 ) Net income available to GAIN common shareholders $ 10,587 $ 22,770 $ 27,953 Weighted average common shares outstanding: Basic weighted average common shares outstanding 47,601,979 40,561,644 36,551,246 Effect of dilutive securities: Stock options 424,087 763,068 1,214,370 RSUs/RSAs 352,985 1,890,183 1,867,262 Diluted weighted average common shares outstanding 48,379,051 43,214,895 39,632,878 Earnings per common share Basic $ 0.22 $ 0.56 $ 0.76 Diluted $ 0.22 $ 0.53 $ 0.71 (1) During the years ending December 31, 2015 and 2014, the Company concluded that the carrying value of the Company's redeemable non-controlling interests was less than its redemption value. The adjustment to increase carrying value reduces earnings available to the Company's shareholders. (2) During the year ending December 31, 2013, an adjustment to retained earnings was made, reflecting the amounts deemed uncollectible associated with previously issued preferred stock, which was converted to common stock immediately prior to the Company's IPO in 2010.

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Future Annual Minimum Lease Payments	Future annual minimum lease payments for the Company's non-cancellable operating leases and purchase obligations are as follows (amounts in thousands): Years Ended December 31: 2016 $ 21,369 2017 6,716 2018 5,077 2019 4,478 2020 and beyond 15,937 Total $ 53,577

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Components of Income from Continuing Operations Before Income Tax Expense	The following table presents the U.S. and non-U.S. components of income before income tax (benefit) / expense for the years ended December 31, 2015, 2014, and 2013 (amounts in thousands): For the Fiscal Year Ended December 31, 2015 2014 2013 U.S. $ (39,761 ) $ 17,439 $ 18,546 Non-U.S. 48,188 28,011 26,944 Total income before tax (benefit) / expense $ 8,427 $ 45,450 $ 45,490
Income Tax Expense (Benefit)	ncome tax (benefit) / expense consisted of (amounts in thousands): For the Fiscal Year Ended December 31, 2015 2014 2013 Current Federal $ 1,136 $ 8,658 $ 15,201 State 172 (199 ) 321 UK 7,239 5,322 7,275 Japan 127 173 14 Other non-U.S. 169 78 3 Total current income tax expense 8,843 14,032 22,814 Deferred Federal (9,889 ) 4,966 (5,883 ) State (1,375 ) (99 ) 205 UK (337 ) (122 ) — Japan (148 ) 159 121 Other non-U.S. (545 ) 20 (316 ) Change in valuation allowance (61 ) 184 442 Total deferred tax (benefit) / expense (12,355 ) 5,108 (5,431 ) Total income tax (benefit) / expense $ (3,512 ) $ 19,140 $ 17,383
Components of Company Deferred Tax Assets and Liabilities	Significant components of the Company’s deferred tax assets and liabilities were as follows (amounts in thousands): December 31, 2015 2014 Deferred tax assets Foreign net operating losses $ 13,286 $ 1,909 Unrealized trading losses — 1,293 Stock-based compensation expense 1,437 1,474 Intangible assets 3,012 6,698 Basis difference in property and equipment 4,950 — Other 2,962 2,126 Total deferred tax assets 25,647 13,500 Valuation allowance (853 ) (913 ) Total deferred tax assets after valuation allowance $ 24,794 $ 12,587 Deferred tax liabilities Basis difference in property and equipment $ — $ (1,717 ) Discount on convertible note (6,186 ) (3,778 ) Other (781 ) (784 ) Total deferred liabilities (6,967 ) (6,279 ) Net deferred tax assets $ 17,827 $ 6,308
Reconciles Provision to United States Federal Statutory Income Tax Rate	The following table reconciles the effective tax rate to the U.S. federal statutory income tax rate: 2015 2014 2013 Federal income tax at statutory rate 35.00 % 35.00 % 35.00 % Increase/(decrease) in effective tax rate resulting from: State income tax (9.25 )% (0.57 )% 0.76 % Foreign rate differential (96.96 )% (9.71 )% (5.22 )% Deemed dividends 55.30 % — % — % Non deductible transaction costs 11.71 % 1.42 % — % Impact of non-controlling interests (6.89 )% (1.10 )% — % Contingent liability (27.92 )% — % — % Foreign losses (19.20 )% — % — % 162 (m) 3.44 % — % — % GFT Carryback (6.58 )% — % — % Uncertain tax positions 19.67 % 14.04 % 5.88 % Other permanent differences — % 3.03 % 1.79 % Effective Tax Rate (41.68 )% 42.11 % 38.21 %
Gross Unrecognized Tax Benefits from Uncertain Tax Positions	The following table summarizes the activity to the gross unrecognized tax benefits from uncertain tax positions (amounts in thousands): As of December 31, 2015 2014 2013 Beginning balance as of January 1 $ 10,517 $ 8,345 $ 78 Increases based on tax positions related to the current period 885 2,197 8,287 Increases based on tax positions related to prior periods 429 — — Decreases related to a lapse of applicable statute of limitations (30 ) (25 ) (20 ) Ending balance as of December 31 $ 11,801 $ 10,517 $ 8,345

Regulatory Requirements (Tables

Regulatory Requirements (Tables)	12 Months Ended
	Dec. 31, 2015
Banking and Thrift [Abstract]
Minimum Regulatory Capital Subsidiaries Required to Maintain	The following table illustrates the minimum regulatory capital our subsidiaries were required to maintain as of December 31, 2015 and the actual amounts of capital that were maintained (amounts in millions): Entity Name Minimum Capital Excess Percent of GAIN Capital Group, LLC $ 26.1 $ 36.3 $ 10.2 139 % GAIN Capital Forex.com U.K., Ltd. 27.8 61.6 33.8 222 % Forex.com Japan., Ltd. 0.9 9.6 8.7 1,067 % GAIN Capital-Forex.com Hong Kong, Ltd. 1.9 3.9 2.0 205 % GAIN Capital Forex.com Australia, Pty. Ltd. 0.7 2.4 1.7 343 % Galvan Research and Trading, Ltd. 0.7 4.3 3.6 614 % GAIN Capital-Forex.com Canada Ltd. 0.2 1.4 1.2 700 % GAIN Capital Securities, Inc. 0.1 0.4 0.3 400 % GAIN Global Markets, Inc. 0.2 0.3 0.1 150 % GAIN Capital UK, Ltd. 54.5 127.9 73.4 235 % GAIN Capital Singapore Pte, Ltd. 0.6 7.4 6.8 1,233 % GAIN Capital Australia Pty Ltd. 0.7 2.8 2.1 400 % Global Assets Advisors, LLC 0.1 1.2 1.1 1,200 % Total $ 114.5 $ 259.5 $ 145.0 227 %

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Selected financial information by segment is presented in the following tables (amounts in thousands): Retail Year Ended December 31, 2015 2014 2013 Net revenue $ 351,472 $ 296,941 $ 218,848 Employee compensation and benefits 67,515 61,989 44,924 Selling and marketing 26,129 19,574 21,761 Referral fees 87,175 78,553 41,459 Other operating expenses 76,301 51,561 33,148 Segment profit $ 94,352 $ 85,264 $ 77,556 Institutional Year Ended December 31, 2015 2014 2013 Net revenue $ 35,072 $ 35,413 $ 29,213 Employee compensation and benefits 15,305 13,963 13,006 Selling and marketing 138 120 244 Referral fees — — — Other operating expenses 9,573 10,939 8,170 Segment profit $ 10,056 $ 10,391 $ 7,793 Futures Year Ended December 31, 2015 2014 2013 Net revenue $ 45,797 36,016 23,360 Employee compensation and benefits 10,634 8,918 3,399 Selling and marketing 901 519 332 Referral fees 16,348 12,419 11,164 Other operating expenses 13,960 11,585 8,948 Segment profit $ 3,954 $ 2,575 $ (483 ) Corporate and Other Year Ended December 31, 2015 2014 2013 Other revenue $ (3,716 ) $ 819 $ (3,729 ) Employee compensation and benefits 13,127 14,362 13,279 Selling and marketing — — — Referral fees — — — Other operating expenses 11,038 10,001 7,272 Loss $ (27,881 ) $ (23,544 ) $ (24,280 )
Reconciliation of Operating Segment Profit (Loss) to Total Profit (Loss)	Reconciliation of operating segment profit / (loss) to Income before income tax (benefit) / expense For the Fiscal Year Ended December 31, 2015 2014 2013 Retail segment $ 94,352 $ 85,264 $ 77,556 Institutional segment 10,056 10,391 7,793 Futures segment 3,954 2,575 (483 ) Corporate and other (27,881 ) (23,544 ) (24,280 ) SEGMENT PROFIT 80,481 74,686 60,586 Depreciation and amortization 11,111 6,610 8,283 Purchased intangible amortization 16,550 8,080 2,906 Acquisition expenses 2,819 3,526 1,824 Restructuring expenses 3,482 2,334 450 Integration expenses 33,092 2,489 1,950 Impairment of investment — 50 450 Change in fair value to contingent consideration (6,722 ) — — SNB bad debt provision 2,500 — — OPERATING PROFIT 17,649 51,597 44,723 Interest expense on long term borrowings 9,222 6,147 1,233 Gain on extinguishment of debt — — 2,000 INCOME BEFORE INCOME TAX EXPENSE $ 8,427 $ 45,450 $ 45,490
Net Revenue by Geographic Area	Net revenue (loss) by geographic area for the years ended December 31, 2015, 2014 and 2013 is as follows ($ in thousands): 2015 2014 2013 Net Revenue (1) : North America (2) $ 107,534 $ 133,103 $ 153,449 Europe (3) 307,087 237,391 33,347 Other 20,726 (1,305 ) 80,895 Total Net Revenue $ 435,347 $ 369,189 $ 267,691 (1) - Net revenue is attributed to individual countries based on the jurisdiction of the formation of the reporting entity that records the transaction (2) - Includes U.S. net revenue of $107.5 million , $133.1 million , and $153.5 million for 2015, 2014, and 2013 respectively. (3) - Includes UK net revenue of $307.3 million and $237.7 million , and $33.3 million for 2015, 2014, and 2013 respectively.
Long-lived Assets by Geographic Area	Long-lived assets by geographic area as of December 31, 2015, 2014 and 2013 are as follows (in thousands): 2015 2014 Long-lived assets (1) : North America (2) 6,370 16,729 Europe (3) 23,147 1,820 Other 850 247 Total long-lived assets 30,367 18,796 (1) - Long-lived assets are comprised of property, plant and equipment, net. They exclude goodwill, other intangible assets and other assets, which are not attributable to any one geographic location. (2) - Includes U.S. long-lived assets of $6.4 million , $16.7 million for 2015 and 2014, respectively. (3) - Includes UK long-lived assets of $23.1 million , $1.7 million for 2015 and 2014, respectively.

Quarterly Financial Data (Una51

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data	As discussed above, the information for the second, third and fourth quarters of 2015 and each quarter of 2014 has been restated to correct certain errors relating to the manner in which the Company originally presented the allocation of the effects of the Company's previously announced restatement of its consolidated financial statements as of and for the years ended December 31, 2014 and 2013. The errors in the quarterly financial data previously presented in this Note 23 had no impact on our full year financial results. The following table sets forth selected restated quarterly financial data for 2015 and 2014 (in thousands, except per share data): First Second Third Fourth Quarter Quarter Quarter Quarter For the Year Ended December 31, 2015 (As Restated) Total non-interest revenue $ 92,967 $ 111,452 $ 128,045 $ 102,712 Net revenue $ 92,986 $ 111,457 $ 128,111 $ 102,793 Income/(loss) before income tax expense $ 11,554 $ (12,741 ) $ 9,418 $ 196 Income tax (benefit)/expense $ 5,745 $ (6,039 ) $ 7,862 $ (11,080 ) Net income/(loss) $ 5,809 $ (6,702 ) $ 1,556 $ 11,276 Net income attributable to non-controlling interest $ 344 $ 416 $ 583 $ 317 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 5,465 $ (7,118 ) $ 973 $ 10,959 Basic net income/(loss) per share $ 0.11 $ (0.16 ) $ 0.05 $ 0.23 Diluted net income/(loss) per share $ 0.11 $ (0.16 ) $ 0.05 $ 0.23 For the Year Ended December 31, 2014 (As Restated) Total non-interest revenue $ 80,412 $ 70,005 $ 102,786 $ 115,157 Net revenue $ 80,722 $ 70,264 $ 102,956 $ 115,247 Income/(loss) before income tax expense $ 3,833 $ (6,421 ) $ 20,887 $ 27,151 Income tax (benefit)/expense $ 2,787 $ (1,926 ) $ 9,206 $ 9,073 Net income/(loss) $ 1,046 $ (4,495 ) $ 11,681 $ 18,078 Net income attributable to non-controlling interest $ 38 $ 164 $ 785 $ 446 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 1,008 $ (4,659 ) $ 10,896 $ 17,632 Basic net income/(loss) per share $ 0.02 $ (0.12 ) $ 0.22 $ 0.42 Diluted net income/(loss) per share $ 0.02 $ (0.12 ) $ 0.21 $ 0.40
Schedule of Prior Period Adjustments	Consolidated Balance Sheet As of December 31, 2014 As Reported Tax Adjustment Other Adjustments As Restated ASSETS: Cash and cash equivalents $ 139,403 $ — $ (52 ) $ 139,351 Goodwill 34,567 (988 ) — 33,579 Other assets, net of allowance for doubtful accounts (1) 35,311 917 (2,463 ) 33,765 Total assets $ 1,185,887 $ (71 ) $ (2,515 ) $ 1,183,301 LIABILITIES AND SHAREHOLDERS’ EQUITY: Liabilities Accrued expenses and other liabilities 64,476 12,170 (451 ) 76,195 Income tax payable 1,470 1,603 (2,063 ) 1,010 Total liabilities $ 910,784 $ 13,773 $ (2,514 ) $ 922,043 Redeemable non-controlling interests 10,209 — 1,129 11,338 Shareholders’ equity Accumulated other comprehensive loss (2,054 ) 541 — (1,513 ) Additional paid-in capital 152,684 (4,306 ) — 148,378 Retained earnings 130,984 (10,079 ) (1,130 ) 119,775 Total shareholders’ equity 264,894 (13,844 ) (1,130 ) 249,920 Total liabilities and shareholders’ equity $ 1,185,887 $ (71 ) $ (2,515 ) $ 1,183,301 (1) The Company previously reported $174,000 as Short term investments, at fair value ; this amount has been reclassified to Other assets, net of allowance for doubtful accounts to conform to current year presentation Consolidated Statements of Income and Comprehensive Income For the Fiscal Year Ended December 31, 2014 As Reported Tax Adjustment Other Adjustments Restated REVENUE: Retail revenue (1) $ 293,122 $ — $ (344 ) $ 292,778 Institutional revenue (1) 34,518 — — 34,518 Futures revenue (1) 36,160 — — 36,160 Total non-interest revenue 368,704 — (344 ) 368,360 Net revenue $ 369,533 $ — $ (344 ) $ 369,189 EXPENSES: Employee compensation and benefits $ 99,485 $ — $ (252 ) $ 99,233 Referral fees 91,092 — (120 ) 90,972 Trading expenses 26,285 — (117 ) 26,168 General and administrative 38,509 — 142 38,651 Depreciation and amortization 7,125 — (515 ) 6,610 Restructuring expenses 1,214 — 1,120 2,334 Total operating expense 317,334 — 258 317,592 OPERATING PROFIT 52,199 — (602 ) 51,597 INCOME BEFORE INCOME TAX EXPENSE 46,052 — (602 ) 45,450 Income tax (benefit)/expense 12,993 6,200 (53 ) 19,140 NET INCOME 33,059 (6,200 ) (549 ) 26,310 NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. 31,626 (6,200 ) (549 ) 24,877 Other comprehensive (loss)/income: Foreign currency translation adjustment (4,630 ) 541 (4,089 ) NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. $ 26,996 $ (5,659 ) $ (549 ) $ 20,788 Earnings per common share: Basic $ 0.76 $ (0.16 ) $ (0.04 ) $ 0.56 Diluted $ 0.71 $ (0.14 ) $ (0.04 ) $ 0.53 (1) - The Company has changed its revenue presentation, see Note 1 for detail For the Fiscal Year Ended December 31, 2013 As Reported Tax Adjustment Other Adjustments As Restated REVENUE: Retail revenue (1) $ 215,667 $ — $ 67 $ 215,734 Institutional revenue (1) 28,005 — — 28,005 Futures revenue (1) 22,188 — — 22,188 Total non-interest revenue 266,959 — 67 267,026 Net revenue $ 267,624 $ — $ 67 $ 267,691 EXPENSES: Employee compensation and benefits $ 74,185 $ — $ 422 $ 74,607 Referral fees 52,503 — 120 52,623 General and administrative 26,813 — (255 ) 26,558 Depreciation and amortization 7,768 — 515 8,283 Restructuring expenses 1,570 — (1,120 ) 450 Total operating expense 223,286 — (318 ) 222,968 OPERATING PROFIT 44,338 — 385 44,723 INCOME BEFORE INCOME TAX EXPENSE 45,105 — 385 45,490 Income tax (benefit)/expense 13,794 3,589 — 17,383 NET INCOME 31,311 (3,589 ) 385 28,107 NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. 31,311 (3,589 ) 385 28,107 NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. $ 32,638 $ (3,589 ) $ 385 $ 29,434 Earnings per common share: Basic $ 0.85 $ (0.10 ) $ 0.01 $ 0.76 Diluted $ 0.79 $ (0.09 ) $ 0.01 $ 0.71 (1) - The Company has changed its revenue presentation, see Note 1 for detail Consolidated Statement of Changes in Shareholders' Equity Additional Paid in Capital Retained Earnings Accumulated Other Comprehensive Income/(Loss) Total As Reported As Restated As Reported As Restated As Reported As Restated As Reported As Restated BALANCE—January 1, 2013 $ 85,089 $ 85,009 $ 84,772 $ 84,590 $ 1,249 $ 1,249 $ 162,830 $ 162,568 BALANCE—January 1, 2014 $ 138,691 $ 134,399 $ 108,603 $ 105,217 $ 2,576 $ 2,576 $ 234,401 $ 226,723 BALANCE—December 31, 2014 $ 152,684 $ 148,378 $ 130,984 $ 119,775 $ (2,054 ) $ (1,513 ) $ 264,894 $ 249,920 Consolidated Statement of Cash Flows For the Fiscal Year Ended December 31, 2014 As Reported Adjustments As Restated CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 33,059 $ (6,749 ) $ 26,310 Adjustments to reconcile net income to cash provided by / (used for) operating activities Depreciation and amortization 16,367 (1,677 ) 14,690 Non-cash integration costs — 1,162 1,162 Deferred tax (benefit)/expense 2,536 2,572 5,108 Changes in operating assets and liabilities: Cash and securities held for customers (9,679 ) 419 (9,260 ) Receivables from brokers 94,657 276 94,933 Prepaid assets 2,729 1 2,730 Other assets (11,536 ) 3,041 (8,495 ) Payables to customers 9,679 (419 ) 9,260 Accrued compensation and benefits 3,671 826 4,497 Accrued expenses and other liabilities (8,565 ) 6,143 (2,422 ) Income tax payable (2,832 ) (6,980 ) (9,812 ) Cash provided by / (used for) operating activities 138,173 (1,385 ) 136,788 Effect of exchange rate changes on cash and cash equivalents 2,760 1,333 4,093 INCREASE/ (DECREASE) IN CASH AND CASH EQUIVALENTS 99,532 (52 ) 99,480 CASH AND CASH EQUIVALENTS—End of year $ 139,403 $ (52 ) $ 139,351 SUPPLEMENTARY DISCLOSURES OF CASH FLOW INFORMATION: Adjustment to redemption value of non-controlling interests $ (978 ) $ (1,129 ) $ (2,107 ) For the Fiscal Year Ended December 31, 2013 As Reported Adjustments Restated CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 31,311 $ (3,204 ) $ 28,107 Adjustments to reconcile net income to cash provided by / (used for) operating activities Depreciation and amortization 11,837 (648 ) 11,189 Non-cash integration costs — 1,163 1,163 Deferred tax (benefit)/expense 39 (5,470 ) (5,431 ) Stock compensation expense 2,896 79 2,975 Changes in operating assets and liabilities: Cash and securities held for customers (74,608 ) (161 ) (74,769 ) Receivables from brokers (78,336 ) (220 ) (78,556 ) Prepaid assets 318 — 318 Other assets (383 ) (692 ) (1,075 ) Payables to customers 74,608 161 74,769 Accrued compensation and benefits 7,118 (743 ) 6,375 Accrued expenses and other liabilities 973 6,894 7,867 Income tax payable 2,131 2,283 4,414 Effect of exchange rate changes on cash and cash equivalents (2,446 ) 558 (1,888 ) SUPPLEMENTARY DISCLOSURES OF CASH FLOW INFORMATION: Deferred taxes related to convertible senior notes $ — $ (4,308 ) $ (4,308 ) The following table sets forth the impact of the restatement on the quarterly financial data for the interim periods in 2015 and 2014: As Reported Tax Adjustments Other Adjustments As Restated For the three months ended September 30, 2015 Total non-interest revenue $ 127,865 $ — $ 180 $ 128,045 Net revenue $ 127,931 $ — $ 180 $ 128,111 Income/(loss) before income tax expense $ 9,215 $ — $ 203 $ 9,418 Income tax (benefit)/expense $ 328 $ 7,534 $ — $ 7,862 Net income/(loss) $ 8,887 $ (7,534 ) $ 203 $ 1,556 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 8,304 $ (7,534 ) $ 203 $ 973 Basic net income/(loss)per share $ 0.20 $ 0.05 Diluted net income/(loss) per share $ 0.20 $ 0.05 As Reported Tax Adjustments Other Adjustments As Restated For the three months ended June 30, 2015 Total non-interest revenue $ 111,559 $ — $ (107 ) $ 111,452 Net revenue $ 111,564 $ — $ (107 ) $ 111,457 Income/(loss) before income tax expense $ (12,538 ) $ — $ (203 ) $ (12,741 ) Income tax (benefit)/expense $ (4,124 ) $ (1,915 ) $ — $ (6,039 ) Net income/(loss) $ (8,414 ) $ 1,915 $ (203 ) $ (6,702 ) Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ (8,830 ) $ 1,915 $ (203 ) $ (7,118 ) Basic net income/(loss)per share $ (0.23 ) $ (0.16 ) Diluted net income/(loss) per share $ (0.23 ) $ (0.16 ) As Reported Tax Adjustments Other Adjustments As Restated For the three months ended March 31, 2015 Total non-interest revenue $ 92,933 $ — $ 34 $ 92,967 Net revenue $ 92,952 $ — $ 34 $ 92,986 Income/(loss) before income tax expense $ 11,498 $ — $ 56 $ 11,554 Income tax (benefit)/expense $ 2,818 $ 2,927 $ — $ 5,745 Net income/(loss) $ 8,680 $ (2,927 ) $ 56 $ 5,809 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 8,336 $ (2,927 ) $ 56 $ 5,465 Basic net income/(loss)per share $ 0.19 $ 0.11 Diluted net income/(loss) per share $ 0.18 $ 0.11 As Reported Tax Adjustments Other Adjustments As Restated For the three months ended December 31, 2014 Total non-interest revenue $ 114,725 $ — $ 432 $ 115,157 Net revenue $ 114,723 $ — $ 524 $ 115,247 Income/(loss) before income tax expense $ 26,456 $ — $ 695 $ 27,151 Income tax (benefit)/expense $ 8,398 $ 728 $ (53 ) $ 9,073 Net income/(loss) $ 18,058 $ (728 ) $ 748 $ 18,078 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 17,612 $ (728 ) $ 748 $ 17,632 Basic net income/(loss)per share $ 0.44 $ 0.42 Diluted net income/(loss) per share $ 0.42 $ 0.40 As Reported Tax Adjustments Other Adjustments As Restated For the three months ended September 30, 2014 Total non-interest revenue $ 103,388 $ — $ (602 ) $ 102,786 Net revenue $ 103,650 $ — $ (694 ) $ 102,956 Income/(loss) before income tax expense $ 21,470 $ — $ (583 ) $ 20,887 Income tax (benefit)/expense $ 5,340 $ 3,866 $ — $ 9,206 Net income/(loss) $ 16,130 $ (3,866 ) $ (583 ) $ 11,681 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 15,345 $ (3,866 ) $ (583 ) $ 10,896 Basic net income/(loss)per share $ 0.35 $ 0.22 Diluted net income/(loss) per share $ 0.33 $ 0.21 As Reported Tax Adjustments Other Adjustments As Restated For the three months ended June 30, 2014 Total non-interest revenue $ 69,504 $ — $ 501 $ 70,005 Net revenue $ 69,763 $ — $ 501 $ 70,264 Income/(loss) before income tax expense $ (7,013 ) $ — $ 592 $ (6,421 ) Income tax (benefit)/expense $ (2,021 ) $ 95 $ — $ (1,926 ) Net income/(loss) $ (4,992 ) $ (95 ) $ 592 $ (4,495 ) Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ (5,156 ) $ (95 ) $ 592 $ (4,659 ) Basic net income/(loss)per share $ (0.13 ) $ (0.12 ) Diluted net income/(loss) per share $ (0.13 ) $ (0.12 ) As Reported Tax Adjustments Other Adjustments As Restated For the three months ended March 31, 2014 Total non-interest revenue $ 81,087 $ — $ (675 ) $ 80,412 Net revenue $ 81,397 $ — $ (675 ) $ 80,722 Income/(loss) before income tax expense $ 5,139 $ — $ (1,306 ) $ 3,833 Income tax (benefit)/expense $ 1,276 $ 1,511 $ — $ 2,787 Net income/(loss) $ 3,863 $ (1,511 ) $ (1,306 ) $ 1,046 Net income/(loss) applicable to GAIN Capital Holdings, Inc. $ 3,825 $ (1,511 ) $ (1,306 ) $ 1,008 Basic net income/(loss)per share $ 0.10 $ 0.02 Diluted net income/(loss) per share $ 0.09 $ 0.02

Description of Business and B52

Description of Business and Basis of Presentation - Additional Information (Details)	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2015Segment	Sep. 30, 2015Segment	Dec. 31, 2015USD ($)Segment	Dec. 31, 2014USD ($)Segment		Dec. 31, 2013USD ($)
Basis of Presentation [Line Items]
Number of operating segments | Segment	3	1	3	1
Distributed earnings of equity method investees			$ 0	$ 0		$ 0
Undistributed earnings of equity method investees			0	0		0
Foreign currency gain (loss)			$ (2,432,000)	$ 1,618,000	[1]	$ (3,641,000)	[1]
Award vesting period			4 years
Tranche 1
Basis of Presentation [Line Items]
Award vesting percentage			25.00%
Tranche 2
Basis of Presentation [Line Items]
Award vesting percentage			25.00%
Tranche 3
Basis of Presentation [Line Items]
Award vesting percentage			25.00%
Tranche 4
Basis of Presentation [Line Items]
Award vesting percentage			25.00%
[1]	As Restated

Description of Business and B53

Description of Business and Basis of Presentation - Concentration Risk (Details) - Credit Concentration Risk - financial_institution	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Cash and Cash Equivalents
Concentration Risk [Line Items]
Number of financial institutions	10
Accounts Receivable
Concentration Risk [Line Items]
Concentration risk, percentage	28.00%	29.00%
Number of financial institutions	1	1

Description of Business and B54

Description of Business and Basis of Presentation - Estimated Useful Lives (Details)	12 Months Ended
	Dec. 31, 2015
Property and equipment excluding leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years
Software development
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years

Description of Business and B55

Description of Business and Basis of Presentation - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning balance	$ (4,555)	[1]	$ (1,158)		$ (148)
Addition to provision	(7,462)		(3,699)	[1]	(1,501)	[1]
Amounts written off	5,185		302		491
Ending balance	$ (6,832)		$ (4,555)	[1]	$ (1,158)
[1]	As Restated

Description of Business and B56

Description of Business and Basis of Presentation - Risk Management (Details)	12 Months Ended
	Dec. 31, 2015productexchangecounterparty
Derivative [Line Items]
Number of financial products offered | product	12,500
Number of global exchanges, more than 30 | exchange	30
Global Prime Brokers
Derivative [Line Items]
Liquidity relationships, number of counterparties	3
Forex Trading Partners
Derivative [Line Items]
Liquidity relationships, number of counterparties	6

Restatement - Additional Inform

Restatement - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retained earnings	$ 120,776		$ 119,775	[1]
Other assets	$ 47,422		33,765	[1]
Scenario, Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retained earnings			130,984
Other assets			35,311
Out of Period Adjustment | Scenario, Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retained earnings		$ 1,300
Out of Period Adjustment | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Adjustment to the redemption value of noncontrolling interests		$ 1,300
Short-term Investments | Scenario, Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other assets			174,000
Other assets, net of allowance for doubtful accounts | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other assets			$ 174,000
[1]	As Restated

Restatement - Consolidated Bala

Restatement - Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cash and cash equivalents	$ 171,888	$ 139,351	[1]	$ 39,871	[1]	$ 36,820	[1]
Goodwill	34,017	33,579	[1]
Other assets	47,422	33,765	[1]
Total assets	1,424,815	1,183,301	[1]
Accrued expenses and other liabilities	51,638	76,195	[1]
Income tax payable	1,068	1,010	[1]
Total liabilities	1,107,685	922,043	[1]
Redeemable non-controlling interests	11,046	11,338	[1]	0
Accumulated other comprehensive loss	(5,865)	(1,513)	[1]
Additional paid-in capital	212,981	148,378	[1]
Retained earnings	120,776	119,775	[1]
Total shareholders’ equity	306,084	249,920	[1]	226,723	[1]	162,568	[1]
Total liabilities and shareholders’ equity	$ 1,424,815	1,183,301	[1]
Scenario, Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cash and cash equivalents		139,403
Goodwill		34,567
Other assets		35,311
Total assets		1,185,887
Accrued expenses and other liabilities		64,476
Income tax payable		1,470
Total liabilities		910,784
Redeemable non-controlling interests		10,209
Accumulated other comprehensive loss		(2,054)
Additional paid-in capital		152,684
Retained earnings		130,984
Total shareholders’ equity		264,894		$ 234,401		$ 162,830
Total liabilities and shareholders’ equity		1,185,887
Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cash and cash equivalents		(52)
Tax Adjustment | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cash and cash equivalents		0
Goodwill		(988)
Other assets		917
Total assets		(71)
Accrued expenses and other liabilities		12,170
Income tax payable		1,603
Total liabilities		13,773
Redeemable non-controlling interests		0
Accumulated other comprehensive loss		541
Additional paid-in capital		(4,306)
Retained earnings		(10,079)
Total shareholders’ equity		(13,844)
Total liabilities and shareholders’ equity		(71)
Other Adjustments | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cash and cash equivalents		(52)
Goodwill		0
Other assets		(2,463)
Total assets		(2,515)
Accrued expenses and other liabilities		(451)
Income tax payable		(2,063)
Total liabilities		(2,514)
Redeemable non-controlling interests		1,129
Accumulated other comprehensive loss		0
Additional paid-in capital		0
Retained earnings		(1,130)
Total shareholders’ equity		(1,130)
Total liabilities and shareholders’ equity		$ (2,515)
[1]	As Restated

Restatement - Consolidated Stat

Restatement - Consolidated Statements of Income and Comprehensive Income (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retail revenue									$ 347,489	$ 292,778	[1]	$ 215,734	[1]
Institutional revenue									33,773	34,518	[1]	28,005	[1]
Futures revenue									45,427	36,160	[1]	22,188	[1]
Total non-interest revenue	$ 102,712	$ 128,045	$ 111,452	$ 92,967	$ 115,157	$ 102,786	$ 70,005	$ 80,412	435,176	368,360	[1]	267,026	[1]
Net revenue	102,793	128,111	111,457	92,986	115,247	102,956	70,264	80,722	435,347	369,189	[1]	267,691	[1]
Employee compensation and benefits									106,581	99,233	[1]	74,607	[1]
Referral fees									103,523	90,972	[1]	52,623	[1]
Trading expenses									31,914	26,168	[1]	18,164	[1]
General and administrative									55,067	38,651	[1]	26,558	[1]
Depreciation and amortization									11,111	6,610	[1]	8,283	[1]
Restructuring expenses									3,482	2,334	[1]	450	[1]
Total operating expense									417,698	317,592	[1]	222,968	[1]
OPERATING PROFIT									17,649	51,597	[1]	44,723	[1]
INCOME BEFORE INCOME TAX EXPENSE	196	9,418	(12,741)	11,554	27,151	20,887	(6,421)	3,833	8,427	45,450	[1]	45,490	[1]
Income tax (benefit)/expense	(11,080)	7,862	(6,039)	5,745	9,073	9,206	(1,926)	2,787	(3,512)	19,140	[1]	17,383	[1]
Net income	11,276	1,556	(6,702)	5,809	18,078	11,681	(4,495)	1,046	11,939	26,310	[1]	28,107	[1]
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.	$ 10,959	$ 973	$ (7,118)	$ 5,465	$ 17,632	$ 10,896	$ (4,659)	$ 1,008	10,279	24,877	[1]	28,107	[1]
Foreign currency translation adjustment									(4,352)	(4,089)	[1]	1,327	[1]
NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.									$ 5,927	$ 20,788	[1]	$ 29,434	[1]
Basic (usd per share)	$ 0.23	$ 0.05	$ (0.16)	$ 0.11	$ 0.42	$ 0.22	$ (0.12)	$ 0.02	$ 0.22	$ 0.56	[1]	$ 0.76	[1]
Diluted (usd per share)	$ 0.23	$ 0.05	$ (0.16)	$ 0.11	$ 0.40	$ 0.21	$ (0.12)	$ 0.02	$ 0.22	$ 0.53	[1]	$ 0.71	[1]
Scenario, Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retail revenue										$ 293,122		$ 215,667
Institutional revenue										34,518		28,005
Futures revenue										36,160		22,188
Total non-interest revenue		$ 127,865	$ 111,559	$ 92,933	$ 114,725	$ 103,388	$ 69,504	$ 81,087		368,704		266,959
Net revenue		127,931	111,564	92,952	114,723	103,650	69,763	81,397		369,533		267,624
Employee compensation and benefits										99,485		74,185
Referral fees										91,092		52,503
Trading expenses										26,285
General and administrative										38,509		26,813
Depreciation and amortization										7,125		7,768
Restructuring expenses										1,214		1,570
Total operating expense										317,334		223,286
OPERATING PROFIT										52,199		44,338
INCOME BEFORE INCOME TAX EXPENSE		9,215	(12,538)	11,498	26,456	21,470	(7,013)	5,139		46,052		45,105
Income tax (benefit)/expense		328	(4,124)	2,818	8,398	5,340	(2,021)	1,276		12,993		13,794
Net income		8,887	(8,414)	8,680	18,058	16,130	(4,992)	3,863		33,059		31,311
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.		$ 8,304	$ (8,830)	$ 8,336	$ 17,612	$ 15,345	$ (5,156)	$ 3,825		31,626		31,311
Foreign currency translation adjustment										(4,630)
NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.										$ 26,996		$ 32,638
Basic (usd per share)		$ 0.20	$ (0.23)	$ 0.19	$ 0.44	$ 0.35	$ (0.13)	$ 0.10		$ 0.76		$ 0.85
Diluted (usd per share)		$ 0.20	$ (0.23)	$ 0.18	$ 0.42	$ 0.33	$ (0.13)	$ 0.09		$ 0.71		$ 0.79
Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income										$ (6,749)		$ (3,204)
Tax Adjustment | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retail revenue										0		0
Institutional revenue										0		0
Futures revenue										0		0
Total non-interest revenue		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0		0		0
Net revenue		0	0	0	0	0	0	0		0		0
Employee compensation and benefits										0		0
Referral fees										0		0
Trading expenses										0
General and administrative										0		0
Depreciation and amortization										0		0
Restructuring expenses										0		0
Total operating expense										0		0
OPERATING PROFIT										0		0
INCOME BEFORE INCOME TAX EXPENSE		0	0	0	0	0	0	0		0		0
Income tax (benefit)/expense		7,534	(1,915)	2,927	728	3,866	95	1,511		6,200		3,589
Net income		(7,534)	1,915	(2,927)	(728)	(3,866)	(95)	(1,511)		(6,200)		(3,589)
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.		(7,534)	1,915	(2,927)	(728)	(3,866)	(95)	$ (1,511)		(6,200)		(3,589)
Foreign currency translation adjustment										541
NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.										$ (5,659)		$ (3,589)
Basic (usd per share)										$ (0.16)		$ (0.10)
Diluted (usd per share)										$ (0.14)		$ (0.09)
Other Adjustments | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retail revenue										$ (344)		$ 67
Institutional revenue										0		0
Futures revenue										0		0
Total non-interest revenue		180	(107)	34	432	(602)	501	$ (675)		(344)		67
Net revenue		180	(107)	34	524	(694)	501	(675)		(344)		67
Employee compensation and benefits										(252)		422
Referral fees										(120)		120
Trading expenses										(117)
General and administrative										142		(255)
Depreciation and amortization										(515)		515
Restructuring expenses										1,120		(1,120)
Total operating expense										258		(318)
OPERATING PROFIT										(602)		385
INCOME BEFORE INCOME TAX EXPENSE		203	(203)	56	695	(583)	592	(1,306)		(602)		385
Income tax (benefit)/expense		0	0	0	(53)	0	0	0		(53)		0
Net income		203	(203)	56	748	(583)	592	(1,306)		(549)		385
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.		$ 203	$ (203)	$ 56	$ 748	$ (583)	$ 592	$ (1,306)		$ (549)		385
Foreign currency translation adjustment
NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.										$ (549)		$ 385
Basic (usd per share)										$ (0.04)		$ 0.01
Diluted (usd per share)										$ (0.04)		$ 0.01
[1]	As Restated

Restatement - Consolidated St60

Restatement - Consolidated Statement of Changes in Shareholders' Equity (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Shareholders' equity	$ 306,084	$ 249,920	[1]	$ 226,723	[1]	$ 162,568	[1]
Scenario, Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Shareholders' equity		264,894		234,401		162,830
Additional Paid in Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Shareholders' equity	212,981	148,378	[1]	134,399	[1]	85,009	[1]
Additional Paid in Capital | Scenario, Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Shareholders' equity		152,684		138,691		85,089
Retained Earnings
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Shareholders' equity	120,776	119,775	[1]	105,217	[1]	84,590	[1]
Retained Earnings | Scenario, Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Shareholders' equity		130,984		108,603		84,772
Accumulated Other Comprehensive Income/(Loss)
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Shareholders' equity	$ (5,865)	(1,513)	[1]	2,576	[1]	1,249	[1]
Accumulated Other Comprehensive Income/(Loss) | Scenario, Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Shareholders' equity		$ (2,054)		$ 2,576		$ 1,249
[1]	As Restated

Restatement - Consolidated St61

Restatement - Consolidated Statement of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012	[1]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income	$ 11,276	$ 1,556	$ (6,702)	$ 5,809	$ 18,078		$ 11,681	$ (4,495)	$ 1,046	$ 11,939	$ 26,310	[1]	$ 28,107	[1]
Depreciation and amortization										27,661	14,690	[1]	11,189	[1]
Non-cash integration costs										26,827	1,162	[1]	1,163	[1]
Deferred tax (benefit)/expense										(12,355)	5,108	[1]	(5,431)	[1]
Stock compensation expense													2,975
Cash and securities held for customers										101,325	(9,260)	[1]	(74,769)	[1]
Receivables from brokers										45,576	94,933	[1]	(78,556)	[1]
Prepaid assets										(1,445)	2,730	[1]	318	[1]
Other assets										(6,229)	(8,495)	[1]	(1,075)	[1]
Payables to customers										(101,325)	9,260	[1]	74,769	[1]
Accrued compensation and benefits										(7,454)	4,497	[1]	6,375	[1]
Accrued expenses and other liabilities										(18,748)	(2,422)	[1]	7,867	[1]
Income tax payable										611	(9,812)	[1]	4,414	[1]
Cash provided by / (used for) operating activities										77,213	136,788	[1]	(18,887)	[1]
Effect of exchange rate changes on cash and cash equivalents										(2,755)	4,093	[1]	(1,888)	[1]
INCREASE / (DECREASE) IN CASH AND CASH EQUIVALENTS										32,537	99,480	[1]	3,051	[1]
Cash and cash equivalents	$ 171,888				139,351	[1]				171,888	139,351	[1]	39,871	[1]	$ 36,820
Adjustment to the redemption value of noncontrolling interests										308	(2,107)	[1]	0	[1]
Deferred taxes related to convertible senior notes										$ (3,840)	0	[1]	(4,308)	[1]
Scenario, Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income		$ 8,887	$ (8,414)	$ 8,680	18,058		$ 16,130	$ (4,992)	$ 3,863		33,059		31,311
Depreciation and amortization											16,367		11,837
Non-cash integration costs											0		0
Deferred tax (benefit)/expense											2,536		39
Stock compensation expense													2,896
Cash and securities held for customers											(9,679)		(74,608)
Receivables from brokers											94,657		(78,336)
Prepaid assets											2,729		318
Other assets											(11,536)		(383)
Payables to customers											9,679		74,608
Accrued compensation and benefits											3,671		7,118
Accrued expenses and other liabilities											(8,565)		973
Income tax payable											(2,832)		2,131
Cash provided by / (used for) operating activities											138,173
Effect of exchange rate changes on cash and cash equivalents											2,760		(2,446)
INCREASE / (DECREASE) IN CASH AND CASH EQUIVALENTS											99,532
Cash and cash equivalents					139,403						139,403
Adjustment to the redemption value of noncontrolling interests											(978)
Deferred taxes related to convertible senior notes													0
Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income											(6,749)		(3,204)
Depreciation and amortization											(1,677)		(648)
Non-cash integration costs											1,162		1,163
Deferred tax (benefit)/expense											2,572		(5,470)
Stock compensation expense													79
Cash and securities held for customers											419		(161)
Receivables from brokers											276		(220)
Prepaid assets											1		0
Other assets											3,041		(692)
Payables to customers											(419)		161
Accrued compensation and benefits											826		(743)
Accrued expenses and other liabilities											6,143		6,894
Income tax payable											(6,980)		2,283
Cash provided by / (used for) operating activities											(1,385)
Effect of exchange rate changes on cash and cash equivalents											1,333		558
INCREASE / (DECREASE) IN CASH AND CASH EQUIVALENTS											(52)
Cash and cash equivalents					$ (52)						(52)
Adjustment to the redemption value of noncontrolling interests											$ (1,129)
Deferred taxes related to convertible senior notes													$ (4,308)
[1]	As Restated

Fair Value Information - Additi

Fair Value Information - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013	[1]
Business Acquisition [Line Items]
Settlement amount for contingent consideration		$ 13,893	$ 0	[1]	$ 2,419
Galvan
Business Acquisition [Line Items]
Settlement amount for contingent consideration	$ 1,500
Global Futures & Forex Ltd
Business Acquisition [Line Items]
Contingent consideration liability			$ 20,000
[1]	As Restated

Fair Value Information - Assets

Fair Value Information - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Recurring - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets (liabilities)	$ 156,798	$ 114,294
Customer derivative positions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	143,918	102,722
Broker derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets		717
Liabilities	(12,568)
Money market accounts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	25,167	20,537
Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	174	174
Investment in gold
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	107	118
Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities		(9,974)
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets (liabilities)	25,448	20,829
Level 1 | Customer derivative positions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Level 1 | Broker derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets		0
Liabilities	0
Level 1 | Money market accounts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	25,167	20,537
Level 1 | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	174	174
Level 1 | Investment in gold
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	107	118
Level 1 | Contingent consideration
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]
Financial assets (liabilities)	131,350	103,439
Level 2 | Customer derivative positions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	143,918	102,722
Level 2 | Broker derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets		717
Liabilities	(12,568)
Level 2 | Money market accounts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Level 2 | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Level 2 | Investment in gold
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Level 2 | Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities		0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets (liabilities)	0	(9,974)
Level 3 | Customer derivative positions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Level 3 | Broker derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets		0
Liabilities	0
Level 3 | Money market accounts
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 | Investment in gold
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 0	0
Level 3 | Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities		$ (9,974)

Fair Value Information - Reconc

Fair Value Information - Reconciliation of Unobservable Level 3 Inputs (Details) - Contingent consideration - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 9,974	$ 0
Issuance of contingent payment obligation		10,540
Gains included in earnings - adjustment to fair value of contingent consideration	(6,722)
Contingent consideration payments	(2,063)
Gains included in earnings - currency revaluation	(212)	(984)
Losses included in earnings - discount amortization	570	418
Settlement of contingent consideration	(1,547)
Ending balance	$ 0	$ 9,974

Fair Value Information - Carryi

Fair Value Information - 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 (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financial Assets:
Receivable from brokers	$ 121,153	$ 134,908	[1]
Financial Liabilities:
Convertible senior notes	121,996	68,367	[1]
Derivative Assets | Level 2
Financial Assets:
Receivable from brokers	133,721	134,191
Derivative Assets | Carrying Value
Financial Assets:
Receivable from brokers	133,721	134,191
Derivative Assets | Fair Value
Financial Assets:
Receivable from brokers	133,721	134,191
Derivative Liabilities
Financial Liabilities:
Payables to customers	(1,064,539)	862,281
Derivative Liabilities | Level 2
Financial Liabilities:
Payables to customers	1,064,539	862,281
Convertible senior notes	122,264	66,440
Accrued expenses and other liabilities		20,000
Derivative Liabilities | Carrying Value
Financial Liabilities:
Payables to customers	1,064,539	862,281
Convertible senior notes	121,996	68,367
Accrued expenses and other liabilities		20,000
Derivative Liabilities | Fair Value
Financial Liabilities:
Payables to customers	1,064,539	862,281
Convertible senior notes	$ 122,264	66,440
Accrued expenses and other liabilities		$ 20,000
[1]	As Restated

Derivatives - Fair Values of De

Derivatives - Fair Values of Derivative Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Gross amounts of assets for derivative open positions at fair value	$ 268,850	$ 228,509
Gross amounts of liability for derivative open positions at fair value	137,500	(125,070)
Net amounts of assets/liabilities for derivative open positions at fair value	131,350	103,439
Receivable from brokers	121,153	134,908	[1]
Payables to customers	(920,621)	(759,559)	[1]
Derivative Assets
Derivatives, Fair Value [Line Items]
Receivables from brokers	133,721	134,191
Net amounts of assets/liabilities for derivative open positions at fair value	(12,568)	717
Derivative Liabilities
Derivatives, Fair Value [Line Items]
Payables to customers	1,064,539	(862,281)
Net amounts of assets/liabilities for derivative open positions at fair value	143,918	102,722
Foreign currency exchange contracts
Derivatives, Fair Value [Line Items]
Gross amounts of assets for derivative open positions at fair value	138,140	168,034
Gross amounts of liability for derivative open positions at fair value	(59,468)	(93,057)
Net amounts of assets/liabilities for derivative open positions at fair value	78,672	74,977
CFD contracts
Derivatives, Fair Value [Line Items]
Gross amounts of assets for derivative open positions at fair value	111,844	44,329
Gross amounts of liability for derivative open positions at fair value	70,429	(24,420)
Net amounts of assets/liabilities for derivative open positions at fair value	41,415	19,909
Metal contracts
Derivatives, Fair Value [Line Items]
Gross amounts of assets for derivative open positions at fair value	18,866	16,146
Gross amounts of liability for derivative open positions at fair value	(7,603)	(7,593)
Net amounts of assets/liabilities for derivative open positions at fair value	$ 11,263	$ 8,553
[1]	As Restated

Derivatives - Notional Value of

Derivatives - Notional Value of Derivative Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Notional amounts of derivative open short positions
Derivative [Line Items]
Notional amounts of derivative open long positions	$ 3,217,057	$ 2,690,129
Notional amounts of derivative open short positions | Foreign currency exchange contracts
Derivative [Line Items]
Notional amounts of derivative open long positions	2,931,109	2,679,041
Notional amounts of derivative open short positions | CFD contracts
Derivative [Line Items]
Notional amounts of derivative open long positions	285,640	10,753
Notional amounts of derivative open short positions | Metal contracts
Derivative [Line Items]
Notional amounts of derivative open long positions	308	335
Notional amounts of derivative open long positions
Derivative [Line Items]
Notional amounts of derivative open long positions	3,247,628	4,021,423
Notional amounts of derivative open long positions | Foreign currency exchange contracts
Derivative [Line Items]
Notional amounts of derivative open long positions	3,106,885	3,147,518
Notional amounts of derivative open long positions | CFD contracts
Derivative [Line Items]
Notional amounts of derivative open long positions	139,465	873,070
Notional amounts of derivative open long positions | Metal contracts
Derivative [Line Items]
Notional amounts of derivative open long positions	$ 1,278	$ 835

Derivatives - Net Gains (Losses

Derivatives - Net Gains (Losses) with Respect to Derivative Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Net gains (losses) on derivative instruments, total	$ 343,786	$ 290,328
Foreign currency exchange contracts
Derivative [Line Items]
Net gains (losses) on derivative instruments	163,315	136,546
CFD contracts
Derivative [Line Items]
Net gains (losses) on derivative instruments	151,553	105,174
Metal contracts
Derivative [Line Items]
Net gains (losses) on derivative instruments	$ 28,918	$ 48,608

Receivables From Brokers (Detai

Receivables From Brokers (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Receivables from Brokerage Clients [Line Items]
Receivable from brokers	$ 121,153	$ 134,908	[1]
Required Collateral
Receivables from Brokerage Clients [Line Items]
Receivable from brokers	129,042	95,599
Excess from futures broker - Restricted
Receivables from Brokerage Clients [Line Items]
Receivable from brokers	4,679	38,592
Open foreign exchange positions
Receivables from Brokerage Clients [Line Items]
Receivable from brokers	$ (12,568)	$ 717
[1]	As Restated

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013	[1]
Property, Plant and Equipment [Line Items]
Property and equipment	$ 75,117	$ 50,340
Less: Accumulated depreciation and amortization	(44,750)	(31,544)	[1]
Property and equipment, net	30,367	18,796	[1]
Depreciation and amortization expense	11,111	6,610	[1]	$ 8,283
Integration costs related to property and equipment	5,400	1,200
Software
Property, Plant and Equipment [Line Items]
Property and equipment	44,194	30,351
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment	14,300	8,516
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	11,200	6,719
Telephone equipment
Property, Plant and Equipment [Line Items]
Property and equipment	881	719
Office equipment
Property, Plant and Equipment [Line Items]
Property and equipment	2,113	2,345
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment	1,761	1,044
Website development costs
Property, Plant and Equipment [Line Items]
Property and equipment	668	$ 646
City Index
Property, Plant and Equipment [Line Items]
Integration costs related to property and equipment	$ 1,900
[1]	As Restated

Intangible Assets and Goodwil71

Intangible Assets and Goodwill (Details) - USD ($) $ in Thousands	Jul. 10, 2014	Jul. 31, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	[1]	Dec. 31, 2013
Business Acquisition [Line Items]
Purchased intangible amortization				$ 16,550	$ 8,080		$ 2,906	[1]
Integration costs related to intangible assets				19,700			$ 1,200
Goodwill				34,017	$ 33,579
Increase in goodwill				$ 400
Forexster
Business Acquisition [Line Items]
Cash payment	$ 12,400
Common stock issued as consideration for asset and business acquisitions	5,300
Intangible assets acquired	21,400
Intangible assets previously held as a prepayment	$ 3,700
Useful life of asset	10 years
Galvan
Business Acquisition [Line Items]
Cash payment		$ 9,732
Goodwill		$ 14,108
GAA
Business Acquisition [Line Items]
Cash payment			$ 4,365
Common stock issued as consideration for asset and business acquisitions			1,241
Goodwill			6,158
Top Third
Business Acquisition [Line Items]
Cash payment			3,500
Goodwill			$ 3,806
[1]	As Restated

Intangible Assets and Goodwil72

Intangible Assets and Goodwill - Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Intangible Assets by Major Class [Line Items]
Finite-lived intangible assets, gross	$ 139,055	$ 73,113
Accumulated Amortization	(47,906)	(12,670)	[1]
Finite-lived intangible assets, net	91,149	60,443
Total intangibles, gross	139,418	73,476
Intangible assets, net	91,512	60,806	[1]
Future Annual Estimated Purchased Intangible Amortization Expense
2,016	15,988
2,017	15,132
2,018	13,648
2,019	11,974
2,020	9,992
Thereafter	24,415
Trademark
Intangible Assets by Major Class [Line Items]
Indefinite-lived intangible assets	363	363
Intangible assets, net	400
Customer lists
Intangible Assets by Major Class [Line Items]
Finite-lived intangible assets, gross	56,388	22,944
Accumulated Amortization	(14,111)	(7,152)
Finite-lived intangible assets, net	42,277	15,792
Total intangibles, gross	$ 56,388
Weighted-average useful life	7 years 7 months 6 days
Technology
Intangible Assets by Major Class [Line Items]
Finite-lived intangible assets, gross	$ 74,378	48,376
Accumulated Amortization	(32,117)	(4,671)
Finite-lived intangible assets, net	42,261	43,705
Total intangibles, gross	$ 74,378
Weighted-average useful life	8 years 10 months 24 days
Trademark
Intangible Assets by Major Class [Line Items]
Finite-lived intangible assets, gross	$ 8,289	1,793
Accumulated Amortization	(1,678)	(847)
Finite-lived intangible assets, net	6,611	$ 946
Total intangibles, gross	8,652
Intangible assets, net	$ 8,700
Weighted-average useful life	6 years 8 months 12 days
[1]	As Restated

Intangible Assets and Goodwil73

Intangible Assets and Goodwill - Goodwill (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	[1]
Segment Reporting Information [Line Items]
Goodwill	$ 34,017	$ 33,579
Operating Segments | Retail Segment
Segment Reporting Information [Line Items]
Goodwill	26,722
Operating Segments | Institutional Segment
Segment Reporting Information [Line Items]
Goodwill	4,788
Operating Segments | Futures Segment
Segment Reporting Information [Line Items]
Goodwill	$ 2,507
[1]	As Restated

Other Assets (Details)

Other Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Business Acquisition [Line Items]
Vendor and security deposits	$ 11,486	$ 3,373
Current tax receivable	9,482	5,163
Deferred tax assets	17,827	6,308
Indemnification asset	0	8,792
GTX Trade Receivables	4,881	4,190
Customer debit positions	7,340	6,594
Allowance for uncollectible customer debit positions	(6,832)	(4,555)	[1]	$ (1,158)	$ (148)
Miscellaneous receivables	2,416	3,900
Equity method investment	822	0
Other assets, net	47,422	$ 33,765	[1]
Global Futures & Forex Ltd
Business Acquisition [Line Items]
Holdback amount	$ 20,000
[1]	As Restated

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Related Party Transaction [Line Items]
Payables to customers	$ 920,621	$ 759,559	[1]
Management
Related Party Transaction [Line Items]
Payables to customers	300	$ 3,600
IPGL Limited
Related Party Transaction [Line Items]
Payables to customers	$ 21,700
[1]	As Restated

Acquisitions - Additional Infor

Acquisitions - Additional Information (Details) - USD ($)

Apr. 01, 2015

Sep. 24, 2013

Dec. 31, 2015

Jul. 31, 2014

Mar. 31, 2014

Dec. 31, 2015

Sep. 30, 2015

Jun. 30, 2015

Mar. 31, 2015

Dec. 31, 2014

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2015

Dec. 31, 2014

Dec. 31, 2013

Nov. 27, 2013

Business Acquisition [Line Items]

Settlement amount for contingent consideration

$ 13,893,000

$ 0

[1]

$ 2,419,000

[1]

Acquisition expense

2,819,000

3,526,000

[1]

1,824,000

[1]

Net income attributable to non-controlling interest

$ 317,000

$ 583,000

$ 416,000

$ 344,000

$ 446,000

$ 785,000

$ 164,000

$ 38,000

1,660,000

1,433,000

[1]

0

[1]

Restructuring expenses

$ 3,482,000

2,334,000

[1]

450,000

[1]

Convertible Debt

Business Acquisition [Line Items]

Debt instrument, principal

$ 140,000,000

Convertible Notes Due 2020 | Convertible Debt

Business Acquisition [Line Items]

Stated interest rate

4.125%

Debt instrument, principal

$ 60,000,000

Customer lists

Business Acquisition [Line Items]

Weighted-average useful life

7 years 7 months 6 days

Technology

Business Acquisition [Line Items]

Weighted-average useful life

8 years 10 months 24 days

City Index

Business Acquisition [Line Items]

Cash paid

6,103,000

Cash paid, amount held in escrow

$ 1,000,000

Shares issued to acquire business

5,319,149

Shares issued to acquire business, amount held in escrow

4,787,234

Liabilities incurred

$ 65,000,000

Liabilities incurred, amount held in escrow

54,000,000

Cash used to settle intercompany liabilities

22,400,000

Revenue from acquiree from acquisition date

$ 136,000,000

Expenses from acquiree from acquisition date

95,000,000

Income (loss) before taxes from acquiree from acquisition date

41,000,000

Total purchase price

$ 116,203,000

Acquisition expense

2,800,000

City Index | Convertible Notes Due 2020 | Convertible Debt

Business Acquisition [Line Items]

Stated interest rate

4.125%

Debt instrument, principal

$ 60,000,000

City Index | Consolidation, Eliminations

Business Acquisition [Line Items]

Revenue from acquiree from acquisition date

30,800,000

Expenses from acquiree from acquisition date

2,300,000

Income (loss) before taxes from acquiree from acquisition date

$ 28,500,000

City Index | Customer lists

Business Acquisition [Line Items]

Weighted-average useful life

7 years 10 months 24 days

City Index | Trade name

Business Acquisition [Line Items]

Weighted-average useful life

7 years

City Index | Technology

Business Acquisition [Line Items]

Weighted-average useful life

6 years 10 months 24 days

Galvan

Business Acquisition [Line Items]

Cash paid

$ 9,732,000

Liabilities incurred

10,540,000

Revenue from acquiree from acquisition date

5,200,000

Expenses from acquiree from acquisition date

3,000,000

Income (loss) before taxes from acquiree from acquisition date

$ 2,200,000

Total purchase price

$ 20,272,000

Contingent consideration payable period

3 years

Earnout payment

$ 2,100,000

Settlement amount for contingent consideration

$ 1,500,000

Acquisition expense

400,000

Galvan | Consolidation, Eliminations

Business Acquisition [Line Items]

Revenue from acquiree from acquisition date

2,400,000

GAA

Business Acquisition [Line Items]

Cash paid

$ 4,365,000

Revenue from acquiree from acquisition date

5,500,000

Expenses from acquiree from acquisition date

4,800,000

Income (loss) before taxes from acquiree from acquisition date

700,000

Total purchase price

$ 5,606,000

Percent acquired

55.00%

55.00%

Acquisition expense

100,000

Net income attributable to non-controlling interest

300,000

GAA | Consolidation, Eliminations

Business Acquisition [Line Items]

Revenue from acquiree from acquisition date

4,300,000

Top Third

Business Acquisition [Line Items]

Cash paid

$ 3,500,000

Revenue from acquiree from acquisition date

5,100,000

Expenses from acquiree from acquisition date

2,600,000

Income (loss) before taxes from acquiree from acquisition date

2,500,000

Percent acquired

55.00%

55.00%

Acquisition expense

100,000

Net income attributable to non-controlling interest

1,100,000

Global Futures & Forex Ltd

Business Acquisition [Line Items]

Cash paid

$ 40,000,000

Liabilities incurred

33,200,000

Revenue from acquiree from acquisition date

26,900,000

Expenses from acquiree from acquisition date

32,000,000

Income (loss) before taxes from acquiree from acquisition date

(5,100,000)

Total purchase price

$ 110,131,000

Acquisition expense

1,800,000

Non-recurring expense

$ 5,100,000

Restructuring expenses

$ 3,482,000

$ 2,334,000

[1]

As Restated

Acquisitions - Schedule of Purc

Acquisitions - Schedule of Purchase Price (Details) - USD ($) $ in Thousands	Apr. 01, 2015	Sep. 24, 2013	Jul. 31, 2014	Mar. 31, 2014
City Index
Business Acquisition [Line Items]
Cash paid	$ 6,103
Liabilities incurred	65,000
Common stock issued	45,100
Total purchase price	$ 116,203
Galvan
Business Acquisition [Line Items]
Cash paid			$ 9,732
Liabilities incurred			10,540
Total purchase price			$ 20,272
GAA
Business Acquisition [Line Items]
Cash paid				$ 4,365
Common stock issued				1,241
Total purchase price				$ 5,606
Global Futures & Forex Ltd
Business Acquisition [Line Items]
Cash paid		$ 40,000
Payment for excess cash adjustment		2,160
Liabilities incurred		33,200
Common stock issued		34,771
Total purchase price		$ 110,131

Acquisitions - Allocation of Pu

Acquisitions - Allocation of Purchase Price to Fair Value of Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Apr. 01, 2015	Dec. 31, 2014	[1]	Jul. 31, 2014	Mar. 31, 2014	Sep. 24, 2013
Business Acquisition [Line Items]
Goodwill	$ 34,017		$ 33,579
City Index
Business Acquisition [Line Items]
Cash and cash equivalents acquired		$ 10,546
Cash and securities held for customers acquired		281,576
Receivables from brokers acquired		35,974
Property and equipment		10,466
Prepaid assets		4,038
Other assets acquired		5,119
Total tangible assets acquired		347,719
Total liabilities assumed		299,000
Net assets		48,719
Identified intangible assets		67,079
Goodwill		405
City Index | Customer lists
Business Acquisition [Line Items]
Identified intangible assets		34,277
City Index | Trade name
Business Acquisition [Line Items]
Identified intangible assets		6,645
City Index | Technology
Business Acquisition [Line Items]
Identified intangible assets		$ 26,157
Galvan
Business Acquisition [Line Items]
Cash and cash equivalents acquired					$ 2,193
Receivables from brokers acquired					745
Property and equipment					12
Prepaid assets					94
Other assets acquired					64
Total tangible assets acquired					3,108
Total liabilities assumed					1,931
Net assets					1,177
Identified intangible assets					4,987
Goodwill					14,108
Galvan | Customer lists
Business Acquisition [Line Items]
Identified intangible assets					4,203
Galvan | Trade name
Business Acquisition [Line Items]
Identified intangible assets					$ 784
GAA
Business Acquisition [Line Items]
Non-controlling interest						$ 4,509
Cash and cash equivalents acquired						360
Receivables from brokers acquired						438
Property and equipment						148
Prepaid assets						153
Other assets acquired						3
Total tangible assets acquired						1,102
Total liabilities assumed						515
Net assets						587
Identified intangible assets						3,370
Goodwill						6,158
GAA | Customer lists
Business Acquisition [Line Items]
Identified intangible assets						3,100
GAA | Trade name
Business Acquisition [Line Items]
Identified intangible assets						270
Top Third
Business Acquisition [Line Items]
Non-controlling interest						3,885
Cash and cash equivalents acquired						73
Receivables from brokers acquired						663
Total tangible assets acquired						736
Total liabilities assumed						1,103
Net assets						(367)
Identified intangible assets						3,990
Goodwill						3,806
Top Third | Customer lists
Business Acquisition [Line Items]
Identified intangible assets						3,900
Top Third | Trade name
Business Acquisition [Line Items]
Identified intangible assets						$ 90
Global Futures & Forex Ltd
Business Acquisition [Line Items]
Cash and cash equivalents acquired							$ 15,781
Cash and securities held for customers acquired							228,419
Receivables from brokers acquired							61,028
Property and equipment							7,515
Other assets acquired							18,942
Total tangible assets acquired							331,685
Total liabilities assumed							251,691
Net assets							79,994
Identified intangible assets							28,450
Goodwill							1,687
Global Futures & Forex Ltd | Software
Business Acquisition [Line Items]
Identified intangible assets							25,300
Global Futures & Forex Ltd | Customer relationships
Business Acquisition [Line Items]
Identified intangible assets							$ 3,150
[1]	As Restated

Acquisitions - Pro Forma Revenu

Acquisitions - Pro Forma Revenue and Net Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Revenues:
Total non-interest revenue	$ 102,712	$ 128,045	$ 111,452	$ 92,967	$ 115,157	$ 102,786	$ 70,005	$ 80,412	$ 435,176	$ 368,360	[1]	$ 267,026	[1]
Interest revenue									1,220	1,428	[1]	821	[1]
Interest expense									1,049	599	[1]	156	[1]
Total net interest revenue									171	829	[1]	665	[1]
EXPENSES:
Depreciation and amortization									11,111	6,610	[1]	8,283	[1]
Purchased intangible amortization									16,550	8,080	[1]	2,906	[1]
Acquisition expense									2,819	3,526	[1]	1,824	[1]
Restructuring expenses									3,482	2,334	[1]	450	[1]
Integration expenses									33,092	2,489	[1]	1,950	[1]
Total operating expense									417,698	317,592	[1]	222,968	[1]
OPERATING PROFIT									17,649	51,597	[1]	44,723	[1]
Gain on extinguishment of debt									0	0	[1]	2,000	[1]
Impairment of investment									0	50	[1]	450	[1]
INCOME BEFORE INCOME TAX EXPENSE	196	9,418	(12,741)	11,554	27,151	20,887	(6,421)	3,833	8,427	45,450	[1]	45,490	[1]
Income tax (benefit)/expense	(11,080)	7,862	(6,039)	5,745	9,073	9,206	(1,926)	2,787	(3,512)	19,140	[1]	17,383	[1]
Net income attributable to non-controlling interest	317	583	416	344	446	785	164	38	1,660	1,433	[1]	0	[1]
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.	$ 10,959	$ 973	$ (7,118)	$ 5,465	$ 17,632	$ 10,896	$ (4,659)	$ 1,008	10,279	24,877	[1]	28,107	[1]
City Index, GFT, GAA, Top Third, Galvan | Pro Forma
Revenues:
Total non-interest revenue									471,959	506,228
Interest revenue									1,303	2,288
Interest expense									1,049	599
Total net interest revenue									254	1,689
Net revenue									472,213	507,917
EXPENSES:
Other expense items									424,229	430,263
Depreciation and amortization									11,753	16,500
Purchased intangible amortization									18,619	17,962
Total operating expense									454,601	464,725
OPERATING PROFIT									17,612	43,192
Interest expense on long term borrowings									(10,267)	(9,283)
Gain on extinguishment of debt									0	0
Impairment of investment									0	0
INCOME BEFORE INCOME TAX EXPENSE									7,345	33,909
Income tax (benefit)/expense									126	16,399
NET INCOME									7,219	17,510
Net income attributable to non-controlling interest									1,660	1,433
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.									5,559	16,077
Galvan, GAA, and Top Third | Pro Forma
Revenues:
Total non-interest revenue										376,362		289,810
Interest revenue										1,435		856
Interest expense										599		156
Total net interest revenue										836		700
Net revenue										377,198		290,510
EXPENSES:
Other expense items										308,607		227,273
Depreciation and amortization										6,626		8,407
Purchased intangible amortization										9,044		4,834
Total operating expense										324,277		240,514
OPERATING PROFIT										52,921		49,996
Interest expense on long term borrowings										(6,147)		(1,232)
Gain on extinguishment of debt										0		2,000
INCOME BEFORE INCOME TAX EXPENSE										46,774		50,764
Income tax (benefit)/expense										19,316		18,750
NET INCOME										27,458		32,014
Net income attributable to non-controlling interest										1,308		691
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.										26,150		31,323
Global Futures & Forex Ltd
EXPENSES:
Acquisition expense												1,800
Restructuring expenses									$ 3,482	$ 2,334
Global Futures & Forex Ltd | Pro Forma
Revenues:
Total non-interest revenue												353,556		$ 248,592
Interest revenue												927		1,096
Interest expense												634		537
Total net interest revenue												293		559
Net revenue												353,849		249,151
EXPENSES:
Other expense items												299,945		261,679
Depreciation and amortization												11,527		7,958
Purchased intangible amortization												5,157		7,250
Acquisition expense												1,824		85
Restructuring expenses												451		634
Integration expenses												1,950		0
Total operating expense												320,854		277,606
OPERATING PROFIT												32,995		(28,455)
Interest expense on long term borrowings												(1,232)		(444)
Gain on extinguishment of debt												2,000		0
INCOME BEFORE INCOME TAX EXPENSE												33,763		(28,899)
Income tax (benefit)/expense												16,106		(10,837)
NET INCOME												$ 17,657		$ (18,062)
[1]	As Restated

Acquisitions - Restructuring (D

Acquisitions - Restructuring (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Restructuring Reserve [Roll Forward]
Restructuring expenses	$ 3,482	$ 2,334	[1]	$ 450	[1]
Global Futures & Forex Ltd
Restructuring Reserve [Roll Forward]
Restructuring liability, beginning balance	375	584
Restructuring expenses	3,482	2,334
Restructuring payments	(3,358)	(2,543)
Restructuring liability, ending balance	$ 499	$ 375		$ 584
[1]	As Restated

Non-controlling Interests (Deta

Non-controlling Interests (Details) - USD ($) $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015		Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Increase (decrease) in non-controlling interests
Beginning balance				$ 11,338	[1]					$ 0	$ 11,338	[1]	$ 0
Non-controlling interests related to acquisitions													8,394
Adjustment to the redemption value of noncontrolling interests											(308)		2,107	[1]	$ 0	[1]
Net income attributable to non-controlling interest	$ 317	$ 583	$ 416	$ 344		$ 446		$ 785	$ 164	$ 38	1,660		1,433	[1]	0	[1]
Distributions to non-controlling interest holders											(1,644)		(596)
Ending balance	$ 11,046					$ 11,338	[1]				$ 11,046		11,338	[1]	$ 0
Global Assets Advisors, LLC
Noncontrolling Interest [Line Items]
Ownership percentage held by parent										55.00%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners										45.00%
Increase (decrease) in non-controlling interests
Net income attributable to non-controlling interest													300
Top Third
Noncontrolling Interest [Line Items]
Ownership percentage held by parent										55.00%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners										45.00%
Increase (decrease) in non-controlling interests
Net income attributable to non-controlling interest													$ 1,100
[1]	As Restated

Shareholders' Equity - Addition

Shareholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended								12 Months Ended
	Nov. 30, 2015	Jul. 31, 2015	May. 31, 2015	Feb. 28, 2015	Nov. 30, 2014	Jul. 31, 2014	May. 31, 2014	Feb. 28, 2014	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013	[1]
Equity [Abstract]
Common stock, shares authorized									120,000,000	60,000,000
Common stock, shares issued									52,072,884	45,582,066
Common stock, shares outstanding									48,771,015	42,934,559
Treasury stock, shares									3,301,869	2,647,507
Treasury stock, value									$ 21,808	$ 16,720	[1]
Common stock, dividend declared (usd per share)	$ 0.05	$ 0.05	$ 0.05	$ 0.05	$ 0.05	$ 0.05	$ 0.05	$ 0.05
Payments of dividends									$ 9,530	$ 8,139	[1]	$ 7,326
[1]	As Restated

Convertible Senior Notes - Addi

Convertible Senior Notes - Additional Information (Details)	Apr. 01, 2015USD ($)$ / sharesshares	Nov. 27, 2013USD ($)$ / shares	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)		Dec. 31, 2013USD ($)	[1]
Debt Instrument [Line Items]
Proceeds from issuance of convertible senior note, net			$ 0	$ 0	[1]	$ 77,900,000
Convertible Debt
Debt Instrument [Line Items]
Debt instrument, principal		$ 140,000,000
Debt Instrument, Convertible, Issuance Amount of Equity Component		27,900,000	27,920,000	12,572,000
Debt Issuance Cost, Purchasers Commission, Equity Component		300,000
Debt Issuance Cost, Additional Cost, Equity Component		100,000
Long-term Debt		117,100,000	121,996,000	68,367,000
Debt Instrument, Unamortized Discount		27,900,000	$ 18,004,000	$ 11,633,000
Debt Issuance Cost, Purchasers Commission		1,800,000
Debt Issuance Cost, Additional Cost		400,000
Convertible Notes Due 2020 | Convertible Debt
Debt Instrument [Line Items]
Debt instrument, principal	$ 60,000,000
Stated interest rate	4.125%
Conversion period, term preceding maturity date	6 months
Debt Instrument, Convertible, Conversion Rate Calculation, Amount Divided by Initial Conversion Price	$ 1,000
Debt Instrument, Convertible, Conversion Rate Calculation, Rounding, Shares | shares	0.0001
Debt Instrument, Convertible, Initial Conversion Price Calculation, Percentage of Arithmetic Average of Daily Volume-Weighted Average Price of Common Stock	125.00%
Debt Instrument, Convertible, Conversion Price, Anti-Dilution Adjustments, Dividend Threshold | $ / shares	$ 0.05
Debt Instrument, Redemption Price, Percentage	100.00%
Debt Instrument, Convertible, Term Preceding Maturity Date Before Which Instrument May Not Be Converted	2 years
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger	130.00%
Debt Instrument, Convertible, Threshold Trading Days	20 days
Debt Instrument, Convertible, Threshold Consecutive Trading Days	30 days
Debt Instrument, Convertible, Default, Ownership Threshold	25.00%
Debt Instrument, Unamortized Discount, Effective Interest Rate			8.60%
Convertible Notes Due 2018 | Convertible Debt
Debt Instrument [Line Items]
Debt instrument, principal		$ 80,000,000
Stated interest rate		4.125%
Debt Instrument, Redemption Price, Percentage		100.00%
Proceeds from issuance of convertible senior note, net		$ 77,900,000
Debt Instrument, Convertible, Conversion Ratio		83.33
Debt Instrument, Convertible, Incremental Principal Convertible		$ 1,000
Debt Instrument, Convertible, Conversion Price | $ / shares		$ 12
Debt Instrument, Unamortized Discount, Effective Interest Rate			8.10%
Convertible Notes Due 2018 | Convertible Debt | Debt Instrument, Redemption, Period One
Debt Instrument [Line Items]
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger		130.00%
Debt Instrument, Convertible, Number of Days Stock Price Exceeds Conversion Price Trigger		20 days
Debt Instrument, Convertible, Threshold Consecutive Trading Days		30 days
Convertible Notes Due 2018 | Convertible Debt | Debt Instrument, Redemption, Period Two and Three
Debt Instrument [Line Items]
Debt Instrument Convertible, Conversion Period		5 days
Convertible Notes Due 2018 | Convertible Debt | Debt Instrument, Redemption, Period Two
Debt Instrument [Line Items]
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger		98.00%
Debt Instrument, Convertible, Threshold Consecutive Trading Days		5 days
Minimum | Convertible Notes Due 2020 | Convertible Debt
Debt Instrument [Line Items]
Debt Instrument, Convertible, Conversion Price | $ / shares	$ 7.20
Maximum | Convertible Notes Due 2020 | Convertible Debt
Debt Instrument [Line Items]
Debt Instrument, Convertible, Conversion Price | $ / shares	$ 9.25
[1]	As Restated

Convertible Senior Notes - Sche

Convertible Senior Notes - Schedule of Liability and Equity Components (Details) - Convertible Debt - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Nov. 27, 2013
Debt Instrument [Line Items]
Liability component - principal	$ 140,000	$ 80,000
Deferred bond discount	18,004	11,633	$ 27,900
Liability component - net carrying value	121,996	68,367	117,100
Additional paid in capital	27,920	12,572	$ 27,900
Discount attributable to equity	(412)	(425)
Equity component	$ 27,508	$ 12,147

Convertible Senior Notes - Sc85

Convertible Senior Notes - Schedule of Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013	[1]
Debt Instrument [Line Items]
Interest expense - amortization of deferred bond discount and costs	$ 354	$ 354	[1]	$ 0
Convertible Debt
Debt Instrument [Line Items]
Interest expense - stated coupon rate	5,156	3,300
Interest expense - amortization of deferred bond discount and costs	3,712	2,593
Total interest expense - convertible note	$ 8,868	$ 5,893
[1]	As Restated

Share Based Compensation - Addi

Share Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013		Nov. 22, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, number of shares available for issuance						8,700,000
Share based compensation, grants expiry period	10 years
Stock options, outstanding	1,358,000	1,908,000
Stock option, weighted average remaining contractual life	4 years 1 month 28 days	3 years 3 months 18 days
Stock options, exercisable	938,000
Total intrinsic value of stock options exercised	$ 3,481	$ 4,233		$ 4,700
Stock options vested	300,000
Proceeds from exercise of stock options	$ 2,386	$ 2,087	[1]	$ 2,539	[1]
Stock options granted	137,000	100,000		500,000
Weighted average grant-date fair value of stock options granted (in dollars per share)	$ 3.43	$ 3.79		$ 1.22
Award vesting period	4 years
Total unrecognized compensation cost related to non-vested share-based compensation	$ 7,500
Total unrecognized compensation cost related to non-vested share-based compensation, recognition period	3 years
Fair market value on the grant date for RSUs and RSAs vested	$ 2,900	$ 4,300		$ 1,700
Total intrinsic value of the RSUs and RSAs unrestricted	4,200
Restricted Stock Units and Restricted Stock awards vested and outstanding	$ 2,900
Restricted Stock Units and Restricted Stock awards, granted		$ 4,500
Shares issued under employee stock purchase plan (in shares)	92,777	98,606
Employee Stock Purchase Plan, discount	$ 100
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion ratio to shares of common stock	1
Award vesting period	4 years
Restiricted stock lapsing percentage	25.00%
Restricted stock, shares granted	601,000	500,000		800,000
Number of shares vested	387,000
Restricted Stock Units and Restricted Stock awards, granted	$ 5,700
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Restiricted stock lapsing percentage	25.00%
Restricted stock, shares granted	0	0		0
Number of shares vested	53,000
2015 Omnibus Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, number of shares available for issuance						5,800,000
2010 Omnibus Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, number of shares available for issuance						2,700,000
Employee Stock Purchase Plan 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, number of shares available for issuance						200,000
Employee Stock Purchase Plan, employee discount rate to purchase shares	15.00%
Shares reserved for issuance under employee Stock Purchase Plan	500,000
[1]	As Restated

Share Based Compensation - Sche

Share Based Compensation - Schedule of Share-Based Compensation Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock compensation expense	$ 3,680	$ 3,452	[1]	$ 2,975	[1]
[1]	As Restated

Share Based Compensation - Summ

Share Based Compensation - Summary of Stock Option Activity Under All Plans (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Number of Options
Beginning balance	1,908
Granted	137	100	500
Exercised	(638)
Forfeited	(49)
Ending balance	1,358	1,908
Vested and expected to vest options	1,340
Number of Options Exercisable	938
Fair market value of common stock at exercise date	$ 5,869
Cost to exercise	2,388
Total intrinsic value of stock options exercised	$ 3,481	$ 4,233	$ 4,700
Weighted average exercise price
Beginning balance	$ 4.83
Granted	9.51
Exercised	3.74
Forfeited	6.62
Ending balance	5.76	$ 4.83
Vested and expected to vest options	5.71
Exercisable, end of period	$ 5.17
Weighted average remaining contractual term
SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	4 years 1 month 28 days	3 years 3 months 18 days
Granted	6 years 4 months 24 days
Exercised	1 year 10 months 10 days
Forfeited	5 years
SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	4 years 1 month 28 days	3 years 3 months 18 days
Vested and expected to vest options	4 years 1 month 17 days
Exercisable, end of period	3 years 9 months 29 days
Aggregate intrinsic value
Outstanding, end of period	$ 3,544
Vested and expected to vest options	3,525
Exercisable, end of period	$ 2,792

Share Based Compensation - Su89

Share Based Compensation - Summary of Outstanding and Exercisable Stock Options (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding	1,358	1,908
Weighted Average Exercise Price	$ 5.76	$ 4.83
Weighted Average Remaining Contractual Life (Years)	4 years 1 month 28 days	3 years 3 months 18 days
Number of Options Exercisable	938
Weighted Average Exercise Price	$ 5.17
$ 3.83
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding	481
Weighted Average Exercise Price	$ 3.83
Weighted Average Remaining Contractual Life (Years)	1 year 7 months 21 days
Number of Options Exercisable	481
Weighted Average Exercise Price	$ 3.83
$ 4.4
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding	238
Weighted Average Exercise Price	$ 4.40
Weighted Average Remaining Contractual Life (Years)	4 years 2 months 19 days
Number of Options Exercisable	90
Weighted Average Exercise Price	$ 4.40
$ 5.30
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding	208
Weighted Average Exercise Price	$ 5.30
Weighted Average Remaining Contractual Life (Years)	3 years 3 months 22 days
Number of Options Exercisable	136
Weighted Average Exercise Price	$ 5.30
$ 8.02
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding	210
Weighted Average Exercise Price	$ 8.02
Weighted Average Remaining Contractual Life (Years)	2 years 3 months 15 days
Number of Options Exercisable	210
Weighted Average Exercise Price	$ 8.02
$ 9.51
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding	137
Weighted Average Exercise Price	$ 9.51
Weighted Average Remaining Contractual Life (Years)	9 years 6 months 4 days
Number of Options Exercisable	0
Weighted Average Exercise Price	$ 9.51
$ 9.95
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding	84
Weighted Average Exercise Price	$ 9.95
Weighted Average Remaining Contractual Life (Years)	5 years 2 months 5 days
Number of Options Exercisable	21
Weighted Average Exercise Price	$ 9.95

Share Based Compensation - Assu

Share Based Compensation - Assumptions for Stock Options Granted (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Valuation Assumptions
Risk-free rate	1.47%	1.40%	0.80%
Expected volatility	49.08%	51.80%	48.80%
Expected life	4 years 9 months	4 years 9 months 18 days	4 years 9 months 18 days
Dividend yield	2.10%	2.00%	4.90%

Share Based Compensation - Su91

Share Based Compensation - Summary of Nonvested Shares of Restricted Stock Units and Restricted Stock Awards (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Restricted Stock Units (RSUs)
Number of Shares
Non-vested, beginning balance	1,073,000
Granted	601,000	500,000	800,000
Vested	(387,000)
Forfeited	(104,000)
Non-vested, ending balance	1,183,000	1,073,000
Weighted Average Grant Date Fair Value
Non-vested, beginning balance	$ 6.69
Granted	9.42
Vested	6.46
Forfeited	8.08
Non-vested, ending balance	$ 8.03	$ 6.69
Restricted Stock Awards
Number of Shares
Non-vested, beginning balance	54,000
Granted	0	0	0
Vested	(53,000)
Forfeited	(1,000)
Non-vested, ending balance	0	54,000
Weighted Average Grant Date Fair Value
Non-vested, beginning balance	$ 7.31
Granted	0
Vested	7.32
Forfeited	6.48
Non-vested, ending balance	$ 0	$ 7.31

Earnings Per Common Share - Add

Earnings Per Common Share - Additional Information (Details) - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Anti-dilutive awards excluded from calculation of diluted earnings per share	0.4	0.1
Common stock threshold for additional dilutive shares	$ 13
Convertible Notes Due 2018
Debt Instrument [Line Items]
Additional dilutive shares if common stock threshold is reached	0.5
Convertible Notes Due 2020
Debt Instrument [Line Items]
Additional dilutive shares if common stock threshold is reached	1.5

Earnings Per Common Share - Com

Earnings Per Common Share - Computation of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Earnings Per Share [Abstract]
Net income	$ 10,959	$ 973	$ (7,118)	$ 5,465	$ 17,632	$ 10,896	$ (4,659)	$ 1,008	$ 10,279	$ 24,877	[1]	$ 28,107	[1]
Series E correction									308	(2,107)		(154)
Net income available to GAIN common shareholders									$ 10,587	$ 22,770		$ 27,953
Weighted average common shares outstanding:
Basic weighted average common shares outstanding									47,601,979	40,561,644	[1]	36,551,246	[1]
Effect of dilutive securities:
Stock options (in shares)									424,087	763,068		1,214,370
RSUs/RSAs (in shares)									352,985	1,890,183		1,867,262
Diluted weighted average common shares outstanding									48,379,051	43,214,895	[1]	39,632,878	[1]
Earnings per common share
Basic (usd per share)	$ 0.23	$ 0.05	$ (0.16)	$ 0.11	$ 0.42	$ 0.22	$ (0.12)	$ 0.02	$ 0.22	$ 0.56	[1]	$ 0.76	[1]
Diluted (usd per share)	$ 0.23	$ 0.05	$ (0.16)	$ 0.11	$ 0.40	$ 0.21	$ (0.12)	$ 0.02	$ 0.22	$ 0.53	[1]	$ 0.71	[1]
[1]	As Restated

Legal - Additional Information

Legal - Additional Information (Details)	Jun. 15, 2011patents	Feb. 28, 2011cases
Long-term Purchase Commitment [Line Items]
Number of alleged patent infringement lawsuit against the company | cases		11
Open E Cry Limited Liability Company
Long-term Purchase Commitment [Line Items]
Number of alleged patent infringement lawsuit against the company | patents	12

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]
Rent expense	$ 3.7	$ 5.1	$ 3.7

Commitments and Contingencies96

Commitments and Contingencies - Future Annual Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2015USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,016	$ 21,369
2,017	6,716
2,018	5,077
2,019	4,478
2020 and beyond	15,937
Total future annual lease payments	$ 53,577

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, Deduction, Dividends, Amount	$ 37,200
Effective Income Tax Rate Reconciliation, Contingent Liability, Amount	6,700
Effective Income Tax Rate Reconciliation, Tax Credit, Foreign, Amount	1,600
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Net, Amount	(200)
Foreign operating loss carryforwards	62,400
Foreign net operating loss carryforwards	13,286	$ 1,909
Valuation allowance on Foreign Operating loss carry forwards	853
Undistributed earnings of foreign subsidiaries	100,000
Income tax expense on undistributed earnings of foreign subsidiaries upon repatriation	48,300
Amount of unrecognized deferred tax liability, undistributed earnings of foreign subsidiaries	9,800
Liability for uncertain tax positions	11,801	10,517	$ 8,345	$ 78
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	11,800	10,500	$ 8,300
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	$ 1,800	$ 2,300

Income Taxes - Components of In

Income Taxes - Components of Income from Continuing Operations Before Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Income Tax Disclosure [Abstract]
U.S.									$ (39,761)	$ 17,439		$ 18,546
Non-U.S.									48,188	28,011		26,944
INCOME BEFORE INCOME TAX EXPENSE	$ 196	$ 9,418	$ (12,741)	$ 11,554	$ 27,151	$ 20,887	$ (6,421)	$ 3,833	$ 8,427	$ 45,450	[1]	$ 45,490	[1]
[1]	As Restated

Income Taxes - Provision for In

Income Taxes - Provision for Income Tax Expense Benefit (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Current
Federal									$ 1,136	$ 8,658		$ 15,201
State									172	(199)		321
Current Income Tax Expense (Benefit)									8,843	14,032		22,814
Deferred
Federal									(9,889)	4,966		(5,883)
State									(1,375)	(99)		205
Change in valuation allowance									(61)	184		442
Deferred Tax Expense (Benefit)									(12,355)	5,108		(5,431)
Total income tax (benefit) / expense	$ (11,080)	$ 7,862	$ (6,039)	$ 5,745	$ 9,073	$ 9,206	$ (1,926)	$ 2,787	(3,512)	19,140	[1]	17,383	[1]
UK
Current
Foreign									7,239	5,322		7,275
Deferred
Foreign									(337)	(122)		0
Japan
Current
Foreign									127	173		14
Deferred
Foreign									(148)	159		121
Other non-U.S.
Current
Foreign									169	78		3
Deferred
Foreign									$ (545)	$ 20		$ (316)
[1]	As Restated

Income Taxes - Components of Co

Income Taxes - Components of Company Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets
Foreign net operating loss carryforwards	$ 13,286	$ 1,909
Unrealized trading losses	0	1,293
Stock-based compensation expense	1,437	1,474
Intangible assets	3,012	6,698
Basis difference in property and equipment	4,950	0
Other	2,962	2,126
Total deferred tax assets	25,647	13,500
Valuation allowance	(853)	(913)
Total deferred tax assets after valuation allowance	24,794	12,587
Deferred tax liabilities
Basis difference in property and equipment	0	(1,717)
Discount on convertible note	(6,186)	(3,778)
Other	(781)	(784)
Total deferred tax liabilities	(6,967)	(6,279)
Net deferred tax assets	$ 17,827	$ 6,308

Income Taxes - Reconciles Provi

Income Taxes - Reconciles Provision to United States Federal Statutory Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Federal income tax at statutory rate	35.00%	35.00%	35.00%
Increase/(decrease) in taxes resulting from:
State income tax	(9.25%)	(0.57%)	0.76%
Foreign rate differential	(96.96%)	(9.71%)	(5.22%)
Deemed dividends	55.30%	(0.00%)	(0.00%)
R&D credit	11.71%	1.42%	(0.00%)
Impact of non-controlling interests	(6.89%)	(1.10%)	(0.00%)
Contingent liability	(27.92%)	0.00%	0.00%
Foreign tax credit	(19.20%)	(0.00%)	(0.00%)
162 (m)	3.44%	0.00%	0.00%
GFT Carryback	(6.58%)	(0.00%)	(0.00%)
Uncertain tax positions	19.67%	14.04%	5.88%
Other permanent differences	0.00%	3.03%	1.79%
Effective Tax Rate	(41.68%)	42.11%	38.21%

Income Taxes - Gross Unrecogniz

Income Taxes - Gross Unrecognized Tax Benefits from Uncertain Tax Positions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance as of January 1	$ 10,517	$ 8,345	$ 78
Increases based on tax positions related to the current period	885	2,197	8,287
Increases based on tax positions related to prior periods	429	0	0
Decreases related to a lapse of applicable statute of limitations	(30)	(25)	(20)
Ending balance as of December 31	$ 11,801	$ 10,517	$ 8,345

Retirement Plans - Additional I

Retirement Plans - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Employee compensation, benefits and expense	$ 0.9	$ 1.3	$ 0.9
401(K) retirement plan | First Contributions
Defined Benefit Plan Disclosure [Line Items]
Employer's matching contribution percentage	100.00%
Employer's contribution percentage	3.00%
401(K) retirement plan | Next Contributions
Defined Benefit Plan Disclosure [Line Items]
Employer's matching contribution percentage	50.00%
Employer's contribution percentage	2.00%

Regulatory Requirements - Addit

Regulatory Requirements - Additional Information (Details) € in Thousands, $ in Thousands, SGD in Millions, AUD in Millions	12 Months Ended
	Dec. 31, 2015USD ($)	Dec. 31, 2015SGD	Dec. 31, 2015EUR (€)	Dec. 31, 2015AUD	Dec. 31, 2014USD ($)	[1]
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Payables to customers	$ 920,621				$ 759,559
Requirement Maintained	227.00%	227.00%	227.00%	227.00%
Capital Requirements	$ 114,500
Capital in excess of regulatory capital, value	145,000
GAIN Capital Group, LLC
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum adjusted net capital requirement of Customer and Non-Customer Maintenance Margin	$ 2,500
Minimum adjusted net capital requirement of Customer and Non-Customer Maintenance Margin, Percent	8.00%	8.00%	8.00%	8.00%
Net capital requirement	$ 20,000
Percentage of total payables to customers required to be maintained	5.00%	5.00%	5.00%	5.00%
Requirement Maintained	139.00%	139.00%	139.00%	139.00%
Capital Requirements	$ 26,100
Capital in excess of regulatory capital, value	10,200
GAIN Capital Group, LLC | Minimum
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Payables to customers	10,000
GAIN Capital Securities, Inc.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Net capital requirement	$ 50
Requirement Maintained	400.00%	400.00%	400.00%	400.00%
Capital Requirements	$ 100
Capital in excess of regulatory capital, value	$ 300
GAIN Capital Securities, Inc. | Maximum
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Aggregate indebtedness to net capital ratio	15	15	15	15
GAIN Capital-Forex.com U.K., Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Requirement Maintained	222.00%	222.00%	222.00%	222.00%
Capital Requirements	$ 27,800
Capital in excess of regulatory capital, value	33,800
GAIN Capital-Forex.com U.K., Ltd. | Minimum
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Net capital requirement	$ 1,000		€ 730
Gain Capital UK, Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Requirement Maintained	235.00%	235.00%	235.00%	235.00%
Capital Requirements	$ 54,500
Capital in excess of regulatory capital, value	73,400
Gain Capital UK, Ltd. | Minimum
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Net capital requirement	$ 1,000		€ 730
Forex.com Japan Co., Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Requirement Maintained	1067.00%	1067.00%	1067.00%	1067.00%
Capital Requirements	$ 900
Capital in excess of regulatory capital, value	$ 8,700
Minimum capital adequacy ratio	120.00%	120.00%	120.00%	120.00%
GAIN Capital Forex.com Australia, Pty. Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Net capital requirement	$ 700			AUD 1
Excess regulatory capital required, percentage	110.00%
Requirement Maintained	343.00%	343.00%	343.00%	343.00%
Capital in excess of regulatory capital, value	$ 1,700
Gain Capital Australia Pty Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Requirement Maintained	400.00%	400.00%	400.00%	400.00%
Tangible Capital Held in Cash, Minimum Requirement	50.00%	50.00%	50.00%	50.00%
Tangible Capital Held in Liquid Assets, Minimum Requirement	50.00%	50.00%	50.00%	50.00%
Capital Requirements	$ 700			AUD 1
Tangible Capital Required for Capital Adequacy to Tangible Assets	110.00%	110.00%	110.00%	110.00%
Capital in excess of regulatory capital, value	$ 2,100
Gain Capital Australia Pty Ltd. | Australian Securities & Investments Commission [Member]
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Number of days to report NTA noncompliance	3 days
Gain Capital Australia Pty Ltd. | Maximum
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Tangible capital required (greater of)	$ 800
Average revenue required, percentage (greater of)	10.00%
GAIN Capital-Forex.com Hong Kong, Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Percentage of total payables to customers required to be maintained	5.00%	5.00%	5.00%	5.00%
Requirement Maintained	205.00%	205.00%	205.00%	205.00%
Capital Requirements	$ 1,900
Capital in excess of regulatory capital, value	$ 2,000
Aggregate gross foreign currency position	1.50%	1.50%	1.50%	1.50%
GAIN Capital-Forex.com Hong Kong, Ltd. | Maximum
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Net capital requirement	$ 1,900
Gain Global Markets, Inc.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Requirement Maintained	150.00%	150.00%	150.00%	150.00%
Capital Requirements	$ 200
Capital in excess of regulatory capital, value	100
Net capital requirement	$ 100
GAIN Capital-Forex.com Canada Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Requirement Maintained	700.00%	700.00%	700.00%	700.00%
Capital Requirements	$ 200
Capital in excess of regulatory capital, value	$ 1,200
Gain Capital Singapore Pte. Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Requirement Maintained	1233.00%	1233.00%	1233.00%	1233.00%
Capital Requirements	$ 600	SGD 1
Capital in excess of regulatory capital, value	$ 6,800
Minimum capital adequacy ratio	120.00%	120.00%	120.00%	120.00%
Galvan
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Requirement Maintained	614.00%	614.00%	614.00%	614.00%
Base financial resources requirement	$ 100		€ 50
Capital Requirements	700
Capital in excess of regulatory capital, value	3,600
Global Assets Advisors, LLC
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Net capital requirement	$ 100
Requirement Maintained	1200.00%	1200.00%	1200.00%	1200.00%
Capital Requirements	$ 100
Capital in excess of regulatory capital, value	$ 1,100
[1]	As Restated

Regulatory Requirements - Minim

Regulatory Requirements - Minimum Regulatory Capital Subsidiaries Required to Maintain (Details) $ in Thousands, SGD in Millions, AUD in Millions	Dec. 31, 2015USD ($)	Dec. 31, 2015SGD	Dec. 31, 2015AUD
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Capital Requirements	$ 114,500
Capital Levels Maintained	259,500
Excess Net Capital	$ 145,000
Requirement Maintained	227.00%	227.00%	227.00%
GAIN Capital Group, LLC
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Capital Requirements	$ 26,100
Capital Levels Maintained	36,300
Excess Net Capital	$ 10,200
Requirement Maintained	139.00%	139.00%	139.00%
Net capital requirement	$ 20,000
GAIN Capital Securities, Inc.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Capital Requirements	100
Capital Levels Maintained	400
Excess Net Capital	$ 300
Requirement Maintained	400.00%	400.00%	400.00%
Net capital requirement	$ 50
Gain Global Markets, Inc.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Capital Requirements	200
Capital Levels Maintained	300
Excess Net Capital	$ 100
Requirement Maintained	150.00%	150.00%	150.00%
Gain Capital UK, Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Capital Requirements	$ 54,500
Capital Levels Maintained	127,900
Excess Net Capital	$ 73,400
Requirement Maintained	235.00%	235.00%	235.00%
Gain Capital Singapore Pte. Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Capital Requirements	$ 600	SGD 1
Capital Levels Maintained	7,400
Excess Net Capital	$ 6,800
Requirement Maintained	1233.00%	1233.00%	1233.00%
Gain Capital Australia Pty Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Capital Requirements	$ 700		AUD 1
Capital Levels Maintained	2,800
Excess Net Capital	$ 2,100
Requirement Maintained	400.00%	400.00%	400.00%
GAIN Capital Forex.com Australia, Pty. Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Capital Levels Maintained	$ 2,400
Excess Net Capital	$ 1,700
Requirement Maintained	343.00%	343.00%	343.00%
Net capital requirement	$ 700		AUD 1
GAIN Capital-Forex.com U.K., Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Capital Requirements	27,800
Capital Levels Maintained	61,600
Excess Net Capital	$ 33,800
Requirement Maintained	222.00%	222.00%	222.00%
GAIN Capital-Forex.com Hong Kong, Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Capital Requirements	$ 1,900
Capital Levels Maintained	3,900
Excess Net Capital	$ 2,000
Requirement Maintained	205.00%	205.00%	205.00%
GAIN Capital-Forex.com Canada Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Capital Requirements	$ 200
Capital Levels Maintained	1,400
Excess Net Capital	$ 1,200
Requirement Maintained	700.00%	700.00%	700.00%
Forex.com Japan Co., Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Capital Requirements	$ 900
Capital Levels Maintained	9,600
Excess Net Capital	$ 8,700
Requirement Maintained	1067.00%	1067.00%	1067.00%
Galvan
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Capital Requirements	$ 700
Capital Levels Maintained	4,300
Excess Net Capital	$ 3,600
Requirement Maintained	614.00%	614.00%	614.00%
Global Assets Advisors, LLC
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Capital Requirements	$ 100
Capital Levels Maintained	1,200
Excess Net Capital	$ 1,100
Requirement Maintained	1200.00%	1200.00%	1200.00%
Net capital requirement	$ 100

Segment Information - Additiona

Segment Information - Additional Information (Details) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2015Segment	Sep. 30, 2015Segment	Dec. 31, 2015USD ($)Segmentmarket	Dec. 31, 2014USD ($)Segment		Dec. 31, 2013USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | Segment	3	1	3	1
Number of accessible global financial markets | market			12,500
Adjustment to fair value of contingent consideration			$ 6,722	$ 0	[1]	$ 0	[1]
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue			(1,300)	(900)		(900)
Corporate and other
Segment Reporting Information [Line Items]
Revenue			3,716	$ (819)		$ 3,729
Revenue | Corporate and other
Segment Reporting Information [Line Items]
Adjustment to fair value of contingent consideration			$ 6,700
[1]	As Restated

Segment Information - Selected

Segment Information - Selected Financial Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Segment Reporting Information [Line Items]
Employee compensation and benefits	$ 106,581	$ 99,233	[1]	$ 74,607	[1]
Selling and marketing	27,168	20,213	[1]	22,337	[1]
Referral fees	103,523	90,972	[1]	52,623	[1]
Segment Profit	80,481	74,686		60,586
Operating Segments | Retail Segment
Segment Reporting Information [Line Items]
Revenue	351,472	296,941		218,848
Employee compensation and benefits	67,515	61,989		44,924
Selling and marketing	26,129	19,574		21,761
Referral fees	87,175	78,553		41,459
Other operating expenses	76,301	51,561		33,148
Segment Profit	94,352	85,264		77,556
Operating Segments | Institutional Segment
Segment Reporting Information [Line Items]
Revenue	35,072	35,413		29,213
Employee compensation and benefits	15,305	13,963		13,006
Selling and marketing	138	120		244
Referral fees	0	0		0
Other operating expenses	9,573	10,939		8,170
Segment Profit	10,056	10,391		7,793
Operating Segments | Futures Segment
Segment Reporting Information [Line Items]
Revenue	45,797	36,016		23,360
Employee compensation and benefits	10,634	8,918		3,399
Selling and marketing	901	519		332
Referral fees	16,348	12,419		11,164
Other operating expenses	13,960	11,585		8,948
Segment Profit	3,954	2,575		(483)
Corporate and other
Segment Reporting Information [Line Items]
Revenue	(3,716)	819		(3,729)
Employee compensation and benefits	13,127	14,362		13,279
Selling and marketing	0	0		0
Referral fees	0	0		0
Other operating expenses	11,038	10,001		7,272
Segment Profit	$ (27,881)	$ (23,544)		$ (24,280)
[1]	As Restated

Segment Information - Reconcili

Segment Information - Reconciliation of Segment Profit (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Segment Reporting Information [Line Items]
Segment Profit									$ 80,481	$ 74,686		$ 60,586
Depreciation and amortization									11,111	6,610	[1]	8,283	[1]
Purchased intangible amortization									16,550	8,080	[1]	2,906	[1]
Acquisition expenses									2,819	3,526	[1]	1,824	[1]
Restructuring expenses									3,482	2,334	[1]	450	[1]
Integration expenses									33,092	2,489	[1]	1,950	[1]
Impairment of investment									0	50	[1]	450	[1]
Adjustment to fair value of contingent consideration									(6,722)	0	[1]	0	[1]
SNB bad debt provision									2,500	0		0
OPERATING PROFIT									17,649	51,597	[1]	44,723	[1]
Interest expense on long term borrowings									9,222	6,147	[1]	1,233	[1]
Gain on extinguishment of debt									0	0	[1]	2,000	[1]
INCOME BEFORE INCOME TAX EXPENSE	$ 196	$ 9,418	$ (12,741)	$ 11,554	$ 27,151	$ 20,887	$ (6,421)	$ 3,833	8,427	45,450	[1]	45,490	[1]
Operating Segments | Retail Segment
Segment Reporting Information [Line Items]
Segment Profit									94,352	85,264		77,556
Operating Segments | Institutional Segment
Segment Reporting Information [Line Items]
Segment Profit									10,056	10,391		7,793
Operating Segments | Futures Segment
Segment Reporting Information [Line Items]
Segment Profit									3,954	2,575		(483)
Corporate and other
Segment Reporting Information [Line Items]
Segment Profit									$ (27,881)	$ (23,544)		$ (24,280)
[1]	As Restated

Segment Information - Net Reven

Segment Information - Net Revenue and Long-Lived Assets by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue	$ 102,793	$ 128,111	$ 111,457	$ 92,986	$ 115,247	$ 102,956	$ 70,264	$ 80,722	$ 435,347	$ 369,189	[1]	$ 267,691	[1]
Long-lived assets	30,367				18,796				30,367	18,796
North America
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue									107,534	133,103		153,449
Long-lived assets	6,370				16,729				6,370	16,729
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue									307,087	237,391		33,347
Long-lived assets	23,147				1,820				23,147	1,820
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue									20,726	(1,305)		80,895
Long-lived assets	850				247				850	247
U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue									107,500	133,100		153,500
Long-lived assets	6,400				16,700				6,400	16,700
UK
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenue									307,300	237,700		$ 33,300
Long-lived assets	$ 23,100				$ 1,700				$ 23,100	$ 1,700
[1]	As Restated

Quarterly Financial Data (Detai

Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total non-interest revenue	$ 102,712	$ 128,045	$ 111,452	$ 92,967	$ 115,157	$ 102,786	$ 70,005	$ 80,412	$ 435,176	$ 368,360	[1]	$ 267,026	[1]
Net revenue	102,793	128,111	111,457	92,986	115,247	102,956	70,264	80,722	435,347	369,189	[1]	267,691	[1]
Income/(loss) before income tax expense	196	9,418	(12,741)	11,554	27,151	20,887	(6,421)	3,833	8,427	45,450	[1]	45,490	[1]
Income tax (benefit)/expense	(11,080)	7,862	(6,039)	5,745	9,073	9,206	(1,926)	2,787	(3,512)	19,140	[1]	17,383	[1]
Net income/(loss)	11,276	1,556	(6,702)	5,809	18,078	11,681	(4,495)	1,046	11,939	26,310	[1]	28,107	[1]
Net income attributable to non-controlling interest	317	583	416	344	446	785	164	38	1,660	1,433	[1]	0	[1]
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.	$ 10,959	$ 973	$ (7,118)	$ 5,465	$ 17,632	$ 10,896	$ (4,659)	$ 1,008	$ 10,279	$ 24,877	[1]	$ 28,107	[1]
Basic net income (loss) per share (in dollars per share)	$ 0.23	$ 0.05	$ (0.16)	$ 0.11	$ 0.42	$ 0.22	$ (0.12)	$ 0.02	$ 0.22	$ 0.56	[1]	$ 0.76	[1]
Diluted net income (loss) per share (in dollars per share)	$ 0.23	$ 0.05	$ (0.16)	$ 0.11	$ 0.40	$ 0.21	$ (0.12)	$ 0.02	$ 0.22	$ 0.53	[1]	$ 0.71	[1]
Scenario, Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total non-interest revenue		$ 127,865	$ 111,559	$ 92,933	$ 114,725	$ 103,388	$ 69,504	$ 81,087		$ 368,704		$ 266,959
Net revenue		127,931	111,564	92,952	114,723	103,650	69,763	81,397		369,533		267,624
Income/(loss) before income tax expense		9,215	(12,538)	11,498	26,456	21,470	(7,013)	5,139		46,052		45,105
Income tax (benefit)/expense		328	(4,124)	2,818	8,398	5,340	(2,021)	1,276		12,993		13,794
Net income/(loss)		8,887	(8,414)	8,680	18,058	16,130	(4,992)	3,863		33,059		31,311
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.		$ 8,304	$ (8,830)	$ 8,336	$ 17,612	$ 15,345	$ (5,156)	$ 3,825		$ 31,626		$ 31,311
Basic net income (loss) per share (in dollars per share)		$ 0.20	$ (0.23)	$ 0.19	$ 0.44	$ 0.35	$ (0.13)	$ 0.10		$ 0.76		$ 0.85
Diluted net income (loss) per share (in dollars per share)		$ 0.20	$ (0.23)	$ 0.18	$ 0.42	$ 0.33	$ (0.13)	$ 0.09		$ 0.71		$ 0.79
Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income/(loss)										$ (6,749)		$ (3,204)
Tax Adjustment | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total non-interest revenue		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0		0		0
Net revenue		0	0	0	0	0	0	0		0		0
Income/(loss) before income tax expense		0	0	0	0	0	0	0		0		0
Income tax (benefit)/expense		7,534	(1,915)	2,927	728	3,866	95	1,511		6,200		3,589
Net income/(loss)		(7,534)	1,915	(2,927)	(728)	(3,866)	(95)	(1,511)		(6,200)		(3,589)
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.		(7,534)	1,915	(2,927)	(728)	(3,866)	(95)	$ (1,511)		$ (6,200)		$ (3,589)
Basic net income (loss) per share (in dollars per share)										$ (0.16)		$ (0.10)
Diluted net income (loss) per share (in dollars per share)										$ (0.14)		$ (0.09)
Other Adjustments | Restatement Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total non-interest revenue		180	(107)	34	432	(602)	501	$ (675)		$ (344)		$ 67
Net revenue		180	(107)	34	524	(694)	501	(675)		(344)		67
Income/(loss) before income tax expense		203	(203)	56	695	(583)	592	(1,306)		(602)		385
Income tax (benefit)/expense		0	0	0	(53)	0	0	0		(53)		0
Net income/(loss)		203	(203)	56	748	(583)	592	(1,306)		(549)		385
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.		$ 203	$ (203)	$ 56	$ 748	$ (583)	$ 592	$ (1,306)		$ (549)		$ 385
Basic net income (loss) per share (in dollars per share)										$ (0.04)		$ 0.01
Diluted net income (loss) per share (in dollars per share)										$ (0.04)		$ 0.01
[1]	As Restated

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - $ / shares	1 Months Ended
	Mar. 31, 2016	Nov. 30, 2015	Jul. 31, 2015	May. 31, 2015	Feb. 28, 2015	Nov. 30, 2014	Jul. 31, 2014	May. 31, 2014	Feb. 28, 2014
Subsequent Event [Line Items]
Common stock, dividend declared (usd per share)		$ 0.05	$ 0.05	$ 0.05	$ 0.05	$ 0.05	$ 0.05	$ 0.05	$ 0.05
Subsequent Event
Subsequent Event [Line Items]
Common stock, dividend declared (usd per share)	$ 0.05

Schedule I - Consolidated Fi112

Schedule I - Consolidated Financial Information of GAIN Capital Holdings, Inc. (Parent Company Only) - Condensed Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
ASSETS:
Cash and cash equivalents	$ 171,888	$ 139,351	[1]	$ 39,871	[1]	$ 36,820	[1]
Equity investments in subsidiaries	822	0
Prepaid assets	7,835	2,537	[1]
Deferred tax assets	17,827	6,308
Other assets	47,422	33,765	[1]
Total assets	1,424,815	1,183,301	[1]
Liabilities
Accrued compensation and benefits	12,362	16,912	[1]
Accrued expenses and other liabilities	51,638	76,195	[1]
Convertible senior notes	121,996	68,367	[1]
Total liabilities	$ 1,107,685	$ 922,043	[1]
Commitments and contingent liabilities			[1]
GAIN Capital Holdings, Inc. Shareholders' equity
Common stock ($0.00001 par value; 120 million shares authorized, 52,072,884 shares issued and 48,771,015 shares outstanding as of December 31, 2015; 60 million shares authorized, 45,582,066 shares issued and 42,934,559 shares outstanding as of December 31, 2014)	$ 0	$ 0	[1]
Accumulated other comprehensive income	(5,865)	(1,513)	[1]
Additional paid-in capital	212,981	148,378	[1]
Treasury stock, at cost (3,301,869 shares at December 31, 2015 and 2,647,507 at December 31, 2014, respectively)	(21,808)	(16,720)	[1]
Retained earnings	120,776	119,775	[1]
Total shareholders’ equity	306,084	249,920	[1]	226,723	[1]	162,568	[1]
Total liabilities and shareholders’ equity	1,424,815	1,183,301	[1]
Parent Company
ASSETS:
Cash and cash equivalents	451	1,184		42,352		49
Equity investments in subsidiaries	447,732	380,110
Receivables from affiliates	2,442	17,545
Prepaid assets	4	2
Current tax receivable	9,482	4,994
Deferred tax assets	13,563	5,911
Other assets	495	7,736
Total assets	474,169	417,482
Liabilities
Accrued compensation and benefits	211	51
Accrued expenses and other liabilities	20,438	37,154
Payable to affiliates	25,440	61,990
Convertible senior notes	121,996	68,367
Income tax payable		0
Total liabilities	$ 168,085	$ 167,562
Commitments and contingent liabilities
GAIN Capital Holdings, Inc. Shareholders' equity
Common stock ($0.00001 par value; 120 million shares authorized, 52,072,884 shares issued and 48,771,015 shares outstanding as of December 31, 2015; 60 million shares authorized, 45,582,066 shares issued and 42,934,559 shares outstanding as of December 31, 2014)	$ 0	$ 0
Accumulated other comprehensive income	(5,865)	(1,513)
Additional paid-in capital	212,981	148,378
Treasury stock, at cost (3,301,869 shares at December 31, 2015 and 2,647,507 at December 31, 2014, respectively)	(21,808)	(16,720)
Retained earnings	120,776	119,775
Total shareholders’ equity	306,084	249,920
Total liabilities and shareholders’ equity	$ 474,169	417,482
Scenario, Previously Reported
ASSETS:
Cash and cash equivalents		139,403
Other assets		35,311
Total assets		1,185,887
Liabilities
Accrued expenses and other liabilities		64,476
Total liabilities		910,784
GAIN Capital Holdings, Inc. Shareholders' equity
Accumulated other comprehensive income		(2,054)
Additional paid-in capital		152,684
Retained earnings		130,984
Total shareholders’ equity		264,894		234,401		$ 162,830
Total liabilities and shareholders’ equity		1,185,887
Scenario, Previously Reported | Parent Company
ASSETS:
Cash and cash equivalents		1,235		42,352
Equity investments in subsidiaries		381,240
Receivables from affiliates		18,533
Current tax receivable		5,084
Deferred tax assets		0
Other assets		15,703
Total assets		421,797
Liabilities
Accrued expenses and other liabilities		25,435
Income tax payable		1,060
Total liabilities		156,903
GAIN Capital Holdings, Inc. Shareholders' equity
Accumulated other comprehensive income		(2,054)
Additional paid-in capital		152,684
Retained earnings		130,984
Total shareholders’ equity		264,894
Total liabilities and shareholders’ equity		421,797
Restatement Adjustments
ASSETS:
Cash and cash equivalents		(52)
Restatement Adjustments | Parent Company
ASSETS:
Cash and cash equivalents		(51)		$ 0
Tax Adjustment | Restatement Adjustments
ASSETS:
Cash and cash equivalents		0
Other assets		917
Total assets		(71)
Liabilities
Accrued expenses and other liabilities		12,170
Total liabilities		13,773
GAIN Capital Holdings, Inc. Shareholders' equity
Accumulated other comprehensive income		541
Additional paid-in capital		(4,306)
Retained earnings		(10,079)
Total shareholders’ equity		(13,844)
Total liabilities and shareholders’ equity		(71)
Tax Adjustment | Restatement Adjustments | Parent Company
ASSETS:
Cash and cash equivalents		0
Equity investments in subsidiaries		0
Receivables from affiliates		(988)
Current tax receivable		(90)
Deferred tax assets		5,911
Other assets		(5,504)
Total assets		(671)
Liabilities
Accrued expenses and other liabilities		12,170
Income tax payable		1,003
Total liabilities		13,173
GAIN Capital Holdings, Inc. Shareholders' equity
Accumulated other comprehensive income		541
Additional paid-in capital		(4,306)
Retained earnings		(10,079)
Total shareholders’ equity		(13,844)
Total liabilities and shareholders’ equity		(671)
Other Adjustments | Restatement Adjustments
ASSETS:
Cash and cash equivalents		(52)
Other assets		(2,463)
Total assets		(2,515)
Liabilities
Accrued expenses and other liabilities		(451)
Total liabilities		(2,514)
GAIN Capital Holdings, Inc. Shareholders' equity
Accumulated other comprehensive income		0
Additional paid-in capital		0
Retained earnings		(1,130)
Total shareholders’ equity		(1,130)
Total liabilities and shareholders’ equity		(2,515)
Other Adjustments | Restatement Adjustments | Parent Company
ASSETS:
Cash and cash equivalents		(51)
Equity investments in subsidiaries		(1,130)
Receivables from affiliates		0
Current tax receivable		0
Deferred tax assets		0
Other assets		(2,463)
Total assets		(3,644)
Liabilities
Accrued expenses and other liabilities		(451)
Income tax payable		(2,063)
Total liabilities		(2,514)
GAIN Capital Holdings, Inc. Shareholders' equity
Accumulated other comprehensive income		0
Additional paid-in capital		0
Retained earnings		(1,130)
Total shareholders’ equity		(1,130)
Total liabilities and shareholders’ equity		$ (3,644)
[1]	As Restated

Schedule I - Consolidated Fi113

Schedule I - Consolidated Financial Information of GAIN Capital Holdings, Inc. (Parent Company Only) - Condensed Balance Sheets (Parentheticals) (Details) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Condensed Balance Sheet Statements, Captions [Line Items]
Common Stock, par value	$ 0.00001	$ 0.00001
Common Stock, shares authorized	120,000,000	60,000,000
Common Stock, shares issued	52,072,884	45,582,066
Common stock, shares outstanding	48,771,015	42,934,559
Treasury stock, shares	3,301,869	2,647,507
Parent Company
Condensed Balance Sheet Statements, Captions [Line Items]
Common Stock, par value	$ 0.00001	$ 0.00001
Common Stock, shares authorized	120,000,000	60,000,000
Common Stock, shares issued	52,072,884	45,582,066
Common stock, shares outstanding	48,771,015	42,934,559
Treasury stock, shares	3,301,869	2,647,507

Schedule I - Consolidated Fi114

Schedule I - Consolidated Financial Information of GAIN Capital Holdings, Inc. (Parent Company Only) - Consolidated Statements of Operations and Comprehensive Income (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
REVENUE:
Interest and other									$ 8,487,000	$ 4,904,000	[1]	$ 1,099,000	[1]
EXPENSES:
Interest expense									1,049,000	599,000	[1]	156,000	[1]
Employee compensation and benefits									106,581,000	99,233,000	[1]	74,607,000	[1]
General and administrative									55,067,000	38,651,000	[1]	26,558,000	[1]
Interest expense on long term borrowings									9,222,000	6,147,000	[1]	1,233,000	[1]
Gain on extinguishment of debt									0	0	[1]	2,000,000	[1]
INCOME BEFORE INCOME TAX EXPENSE	$ 196,000	$ 9,418,000	$ (12,741,000)	$ 11,554,000	$ 27,151,000	$ 20,887,000	$ (6,421,000)	$ 3,833,000	8,427,000	45,450,000	[1]	45,490,000	[1]
Income tax (benefit)/expense	(11,080,000)	7,862,000	(6,039,000)	5,745,000	9,073,000	9,206,000	(1,926,000)	2,787,000	(3,512,000)	19,140,000	[1]	17,383,000	[1]
Undistributed earnings of subsidiaries									0	0		0
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.	$ 10,959,000	973,000	(7,118,000)	5,465,000	17,632,000	10,896,000	(4,659,000)	1,008,000	10,279,000	24,877,000	[1]	28,107,000	[1]
Other comprehensive income, net of tax:
Foreign currency translation adjustment									(4,352,000)	(4,089,000)	[1]	1,327,000	[1]
NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.									5,927,000	20,788,000	[1]	29,434,000	[1]
Parent Company
REVENUE:
Dividends from subsidiaries									38,642,000	0		37,099,000
Interest and other									178,000	90,000		181,000
Net revenue									38,820,000	90,000		37,280,000
EXPENSES:
Interest expense									63,000	64,000		63,000
Employee compensation and benefits									10,096,000	11,578,000		187,000
General and administrative									6,775,000	8,208,000		6,075,000
Total operating expense									16,934,000	19,850,000		6,325,000
Interest expense on long term borrowings									9,222,000	6,147,000		1,233,000
Gain on extinguishment of debt									0	0		2,000,000
INCOME BEFORE INCOME TAX EXPENSE									12,664,000	(25,907,000)		31,722,000
Income tax (benefit)/expense									(10,875,000)	(2,584,000)		10,325,000
NET INCOME/(LOSS) BEFORE UNDISTRUBTED EARNINGS OF SUBSIDIARES									23,539,000	(23,323,000)		21,397,000
Undistributed earnings of subsidiaries									(13,260,000)	48,200,000		6,710,000
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.									10,279,000	24,877,000		28,107,000
Other comprehensive income, net of tax:
Foreign currency translation adjustment									(4,352,000)	(4,089,000)		1,327,000
NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.									$ 5,927,000	20,788,000		29,434,000
Scenario, Previously Reported
EXPENSES:
Employee compensation and benefits										99,485,000		74,185,000
General and administrative										38,509,000		26,813,000
INCOME BEFORE INCOME TAX EXPENSE		9,215,000	(12,538,000)	11,498,000	26,456,000	21,470,000	(7,013,000)	5,139,000		46,052,000		45,105,000
Income tax (benefit)/expense		328,000	(4,124,000)	2,818,000	8,398,000	5,340,000	(2,021,000)	1,276,000		12,993,000		13,794,000
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.		8,304,000	(8,830,000)	8,336,000	17,612,000	15,345,000	(5,156,000)	3,825,000		31,626,000		31,311,000
Other comprehensive income, net of tax:
Foreign currency translation adjustment										(4,630,000)
NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.										26,996,000		32,638,000
Scenario, Previously Reported | Parent Company
EXPENSES:
Interest expense												1,199,000
Total operating expense												7,461,000
Interest expense on long term borrowings										5,893,000		0
INCOME BEFORE INCOME TAX EXPENSE										(25,653,000)		31,819,000
Income tax (benefit)/expense										(8,784,000)		6,736,000
NET INCOME/(LOSS) BEFORE UNDISTRUBTED EARNINGS OF SUBSIDIARES										(16,869,000)		25,083,000
Undistributed earnings of subsidiaries										48,495,000		6,228,000
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.										31,626,000		31,311,000
Other comprehensive income, net of tax:
Foreign currency translation adjustment										(4,630,000)
NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.										26,996,000		32,638,000
Tax Adjustment | Restatement Adjustments
EXPENSES:
Employee compensation and benefits										0		0
General and administrative										0		0
INCOME BEFORE INCOME TAX EXPENSE		0	0	0	0	0	0	0		0		0
Income tax (benefit)/expense		7,534,000	(1,915,000)	2,927,000	728,000	3,866,000	95,000	1,511,000		6,200,000		3,589,000
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.		(7,534,000)	1,915,000	(2,927,000)	(728,000)	(3,866,000)	(95,000)	(1,511,000)		(6,200,000)		(3,589,000)
Other comprehensive income, net of tax:
Foreign currency translation adjustment										541,000
NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.										(5,659,000)		(3,589,000)
Tax Adjustment | Restatement Adjustments | Parent Company
EXPENSES:
Total operating expense												0
Interest expense on long term borrowings										0		0
INCOME BEFORE INCOME TAX EXPENSE										0		0
Income tax (benefit)/expense										6,200,000		3,589,000
NET INCOME/(LOSS) BEFORE UNDISTRUBTED EARNINGS OF SUBSIDIARES										(6,200,000)		(3,589,000)
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.										(6,200,000)		(3,589,000)
Other comprehensive income, net of tax:
Foreign currency translation adjustment										541,000
NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.										(5,659,000)		(3,589,000)
Other Adjustments | Restatement Adjustments
EXPENSES:
Employee compensation and benefits										(252,000)		422,000
General and administrative										142,000		(255,000)
INCOME BEFORE INCOME TAX EXPENSE		203,000	(203,000)	56,000	695,000	(583,000)	592,000	(1,306,000)		(602,000)		385,000
Income tax (benefit)/expense		0	0	0	(53,000)	0	0	0		(53,000)		0
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.		$ 203,000	$ (203,000)	$ 56,000	$ 748,000	$ (583,000)	$ 592,000	$ (1,306,000)		$ (549,000)		385,000
Other comprehensive income, net of tax:
Foreign currency translation adjustment
NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.										$ (549,000)		385,000
Other Adjustments | Restatement Adjustments | Parent Company
EXPENSES:
Interest expense												(1,136,000)
Total operating expense												(1,136,000)
Interest expense on long term borrowings										254,000		1,233,000
INCOME BEFORE INCOME TAX EXPENSE										(254,000)		(97,000)
Income tax (benefit)/expense										0		0
NET INCOME/(LOSS) BEFORE UNDISTRUBTED EARNINGS OF SUBSIDIARES										(254,000)		(97,000)
Undistributed earnings of subsidiaries										(295,000)		482,000
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.										(549,000)		385,000
Other comprehensive income, net of tax:
Foreign currency translation adjustment										0
NET COMPREHENSIVE INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.										$ (549,000)		$ 385,000
[1]	As Restated

Schedule I - Consolidated Fi115

Schedule I - Consolidated Financial Information of GAIN Capital Holdings, Inc. (Parent Company Only) - Consolidated Statements of Cash Flows (Details) - USD ($) $ in Thousands		3 Months Ended									12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income		$ 11,276	$ 1,556	$ (6,702)	$ 5,809	$ 18,078		$ 11,681	$ (4,495)	$ 1,046	$ 11,939	$ 26,310	[1]	$ 28,107	[1]
Adjustments to reconcile net income to cash provided by / (used for) operating activities
Gain on extinguishment of debt											0	0	[1]	(2,000)	[1]
Loss / (gain) on foreign currency exchange rates											2,432	(1,618)	[1]	3,641	[1]
Deferred tax (benefit)/expense											(12,355)	5,108	[1]	(5,431)	[1]
Amortization of deferred financing costs											354	354	[1]	0	[1]
Stock compensation expense														2,975
Convertible senior note discount amortization											3,624	2,150	[1]	175	[1]
Changes in operating assets and liabilities:
Prepaid assets											(1,445)	2,730	[1]	318	[1]
Current tax receivable											(6,229)	(8,495)	[1]	(1,075)	[1]
Income tax payable											611	(9,812)	[1]	4,414	[1]
Accrued compensation and benefits											(7,454)	4,497	[1]	6,375	[1]
Accrued expenses and other liabilities											(18,748)	(2,422)	[1]	7,867	[1]
Cash provided by / (used for) operating activities											77,213	136,788	[1]	(18,887)	[1]
CASH FLOWS FROM INVESTING ACTIVITIES:
Cash used for investing activities											(16,081)	(35,463)	[1]	(9,807)	[1]
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of convertible senior note, net											0	0	[1]	77,900	[1]
Contractual payments for acquisitions											(13,893)	0	[1]	(2,419)	[1]
Proceeds from exercise of stock options											2,386	2,087	[1]	2,539	[1]
Proceeds from employee stock purchase plan											789	740	[1]	302	[1]
Purchase of treasury stock											(5,088)	(1,251)	[1]	(7,189)	[1]
Tax benefit from employee stock option exercises											1,140	1,221	[1]	1,026	[1]
Dividend payment											(9,530)	(8,139)	[1]	(7,326)	[1]
Cash (used for) / provided by financing activities											(25,840)	(5,938)	[1]	33,633	[1]
Effect of exchange rate changes on cash and cash equivalents											(2,755)	4,093	[1]	(1,888)	[1]
INCREASE / (DECREASE) IN CASH AND CASH EQUIVALENTS											32,537	99,480	[1]	3,051	[1]
CASH AND CASH EQUIVALENTS—Beginning of year	[1]				139,351					39,871	139,351	39,871		36,820
CASH AND CASH EQUIVALENTS—End of year		171,888				139,351	[1]				171,888	139,351	[1]	39,871	[1]
SUPPLEMENTARY DISCLOSURES OF CASH FLOW INFORMATION:
Interest											(5,065)	(3,373)	[1]	(655)	[1]
Taxes											(9,861)	(13,151)	[1]	(8,376)	[1]
Stock issued											45,100	6,493	[1]	34,771	[1]
Parent Company
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income											10,279	24,877		28,107
Adjustments to reconcile net income to cash provided by / (used for) operating activities
Equity in income of subsidiaries											13,260	(48,200)		(6,710)
Gain on extinguishment of debt											0	0		(2,000)
Loss / (gain) on foreign currency exchange rates											(66)	0		(274)
Deferred tax (benefit)/expense											(11,264)	4,867		1,448
Amortization of deferred financing costs											354	354		0
Stock compensation expense											3,680	3,452		2,975
Convertible senior note discount amortization											3,624	2,150		175
Changes in operating assets and liabilities:
Receivables from affiliates											37,548	(33,827)		19,278
Prepaid assets											(3)	127		(127)
Current tax receivable											7,240	(10,123)		291
Current tax payable											(9,069)	(771)		(9,742)
Accrued compensation and benefits											160	51		0
Accrued expenses and other liabilities											(4,876)	10,426		1,478
Payable to affiliates											(36,549)	61,990		0
Cash provided by / (used for) operating activities											14,318	15,373		34,899
CASH FLOWS FROM INVESTING ACTIVITIES:
Investment and funding of subsidiaries											7,081	(51,107)		(28,648)
Purchase of short term investments											0	(92)		0
Cash used for investing activities											7,081	(51,199)		(28,648)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of convertible senior note, net											0	0		77,900
Principal payment on notes payable											0	0		(31,200)
Contractual payments for acquisitions											(11,829)	0		0
Proceeds from exercise of stock options											2,386	2,087		2,539
Proceeds from employee stock purchase plan											789	740		302
Purchase of treasury stock											(5,088)	(1,251)		(7,189)
Tax benefit from employee stock option exercises											1,140	1,221		1,026
Dividend payment											(9,530)	(8,139)		(7,326)
Cash (used for) / provided by financing activities											(22,132)	(5,342)		36,052
Effect of exchange rate changes on cash and cash equivalents												0		0
INCREASE / (DECREASE) IN CASH AND CASH EQUIVALENTS											(733)	(41,168)		42,303
CASH AND CASH EQUIVALENTS—Beginning of year					1,184					42,352	1,184	42,352		49
CASH AND CASH EQUIVALENTS—End of year		$ 451				1,184					451	1,184		42,352
SUPPLEMENTARY DISCLOSURES OF CASH FLOW INFORMATION:
Interest											(4,538)	(3,373)		(556)
Taxes											733	(3,711)		(5,562)
Seller provided financing											0	0		33,200
Stock issued											45,100	6,493		34,771
Scenario, Previously Reported
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income			$ 8,887	$ (8,414)	8,680	18,058		$ 16,130	$ (4,992)	3,863		33,059		31,311
Adjustments to reconcile net income to cash provided by / (used for) operating activities
Deferred tax (benefit)/expense												2,536		39
Stock compensation expense														2,896
Changes in operating assets and liabilities:
Prepaid assets												2,729		318
Current tax receivable												(11,536)		(383)
Income tax payable												(2,832)		2,131
Accrued compensation and benefits												3,671		7,118
Accrued expenses and other liabilities												(8,565)		973
Cash provided by / (used for) operating activities												138,173
CASH FLOWS FROM FINANCING ACTIVITIES:
Effect of exchange rate changes on cash and cash equivalents												2,760		(2,446)
INCREASE / (DECREASE) IN CASH AND CASH EQUIVALENTS												99,532
CASH AND CASH EQUIVALENTS—Beginning of year					139,403						139,403
CASH AND CASH EQUIVALENTS—End of year						139,403						139,403
Scenario, Previously Reported | Parent Company
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income												31,626		31,311
Adjustments to reconcile net income to cash provided by / (used for) operating activities
Equity in income of subsidiaries												(48,495)		6,228
Deferred tax (benefit)/expense												2,508		(1,448)
Amortization of deferred financing costs														30
Stock compensation expense														2,896
Changes in operating assets and liabilities:
Receivables from affiliates												(18,533)		17,681
Prepaid assets														(127)
Current tax receivable												(5,188)		(5,354)
Current tax payable												(1,591)		2,055
Accrued compensation and benefits												(21)
Accrued expenses and other liabilities												1,762		(3,486)
Payable to affiliates												47,522
Cash provided by / (used for) operating activities												15,673		47,687
CASH FLOWS FROM INVESTING ACTIVITIES:
Investment and funding of subsidiaries												(46,726)		(42,764)
Cash used for investing activities												(46,818)		(42,764)
CASH FLOWS FROM FINANCING ACTIVITIES:
Effect of exchange rate changes on cash and cash equivalents												(4,630)		1,328
INCREASE / (DECREASE) IN CASH AND CASH EQUIVALENTS												(41,117)
CASH AND CASH EQUIVALENTS—Beginning of year					1,235					42,352	1,235	42,352
CASH AND CASH EQUIVALENTS—End of year						1,235						1,235		42,352
Restatement Adjustments
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income												(6,749)		(3,204)
Adjustments to reconcile net income to cash provided by / (used for) operating activities
Deferred tax (benefit)/expense												2,572		(5,470)
Stock compensation expense														79
Changes in operating assets and liabilities:
Prepaid assets												1		0
Current tax receivable												3,041		(692)
Income tax payable												(6,980)		2,283
Accrued compensation and benefits												826		(743)
Accrued expenses and other liabilities												6,143		6,894
Cash provided by / (used for) operating activities												(1,385)
CASH FLOWS FROM FINANCING ACTIVITIES:
Effect of exchange rate changes on cash and cash equivalents												1,333		558
INCREASE / (DECREASE) IN CASH AND CASH EQUIVALENTS												(52)
CASH AND CASH EQUIVALENTS—Beginning of year					(52)						(52)
CASH AND CASH EQUIVALENTS—End of year						(52)						(52)
Restatement Adjustments | Parent Company
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income												(6,749)		(3,204)
Adjustments to reconcile net income to cash provided by / (used for) operating activities
Equity in income of subsidiaries												295		(12,938)
Deferred tax (benefit)/expense												2,359		2,896
Amortization of deferred financing costs														(30)
Stock compensation expense														79
Changes in operating assets and liabilities:
Receivables from affiliates												(15,294)		1,597
Prepaid assets														0
Current tax receivable												(4,935)		5,645
Current tax payable												820		(11,797)
Accrued compensation and benefits												72
Accrued expenses and other liabilities												8,664		4,964
Payable to affiliates												14,468
Cash provided by / (used for) operating activities												(300)		(12,788)
CASH FLOWS FROM INVESTING ACTIVITIES:
Investment and funding of subsidiaries												(4,381)		14,116
Cash used for investing activities												(4,381)		14,116
CASH FLOWS FROM FINANCING ACTIVITIES:
Effect of exchange rate changes on cash and cash equivalents												4,630		(1,328)
INCREASE / (DECREASE) IN CASH AND CASH EQUIVALENTS												(51)
CASH AND CASH EQUIVALENTS—Beginning of year					$ (51)					$ 0	$ (51)	0
CASH AND CASH EQUIVALENTS—End of year						$ (51)						$ (51)		$ 0
[1]	As Restated

Schedule I - Consolidated Fi116

Schedule I - Consolidated Financial Information of GAIN Capital Holdings, Inc. (Parent Company Only) - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Parent Company
Condensed Financial Statements, Captions [Line Items]
Cash dividends from subsidiaries	$ 38.6	$ 0	$ 37.1