GAIN Capital 10-Q/A 3 May 16 2015 Q3 Quarterly report (amended) Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2015	Apr. 29, 2016
Document Documentand 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 Filer Category	Accelerated Filer
Document Type	10-Q/A
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q3
Amendment Flag	true
Amendment Description	Amend the previously issued unaudited condensed consolidated financial statements for the quarters ended September 30, 2015 and September 30, 2014 to correct errors in accounting for income taxes during those periods.
Entity Common Stock, Shares Outstanding		48,483,199

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
ASSETS:
Cash and cash equivalents	$ 186,688	$ 139,351
Cash and securities held for customers	986,376	759,559
Receivables from brokers, of which ($29,077) and $717, respectively, are open contracts at fair value	119,227	134,908
Prepaid assets	9,565	2,537
Property and equipment, net of accumulated depreciation of ($42,401) and ($31,544), respectively	29,215	18,796
Intangible assets, net of accumulated amortization of ($35,756) and ($12,670), respectively	101,461	60,806
Goodwill	41,631	33,579
Other assets, net of allowance for doubtful accounts of ($5,898) and ($4,555), respectively	38,716	33,765
Total assets	1,512,879	1,183,301
Liabilities
Payables to customers, of which ($147,645) and ($102,722), respectively, are open contracts at fair value	986,376	759,559
Accrued compensation and benefits	9,102	16,912
Accrued expenses and other liabilities	72,422	76,195
Income tax payable	6,789	1,010
Convertible senior notes	120,866	68,367
Total liabilities	$ 1,195,555	$ 922,043
Commitments and contingent liabilities
Redeemable noncontrolling interests	$ 11,660	$ 11,338
GAIN Capital Holdings, Inc. Shareholders' equity
Common stock ($0.00001 par value; 120 million shares and 60 million shares authorized as of September 30, 2015 and December 31, 2014, respectively; 51,860,180 shares issued and 48,997,738 shares outstanding as of September 30, 2015; 45,582,066 shares issued and 42,934,559 shares outstanding as of December 31, 2014)	0	0
Accumulated other comprehensive loss	(1,747)	(1,513)
Additional paid-in capital	214,334	148,378
Treasury stock, at cost (2,862,442 shares at September 30, 2015 and 2,647,507 shares at December 31, 2014)	(18,864)	(16,720)
Retained earnings	111,941	119,775
Total shareholders’ equity	305,664	249,920
Total liabilities and shareholders’ equity	$ 1,512,879	$ 1,183,301

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Receivables from brokers, Fair Value	$ (29,077)	$ 717
Property and equipment, accumulated depreciation	(42,401)	(31,544)
Intangible assets, accumulated amortization	(35,756)	(12,670)
Other assets, allowance for doubtful accounts	(5,898)	(4,555)
Payables to customers, at fair value	$ (147,645)	$ (102,722)
Common Stock, par value	$ 0.00001	$ 0.00001
Common Stock, shares authorized	120,000,000	60,000,000
Common Stock, Shares, Issued	51,860,180	45,582,066
Common Stock, shares outstanding	48,997,738	42,934,559
Treasury stock, shares	2,862,442	2,647,507

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
REVENUE:
Retail revenue	$ 118,981	$ 89,771	$ 300,483	$ 222,362
Institutional revenue	8,292	8,537	26,734	25,641
Other revenue	772	4,478	5,248	5,199
Total non-interest revenue	128,045	102,786	332,465	253,202
Interest revenue	285	359	936	1,123
Interest expense	219	189	846	411
Total net interest revenue	66	170	90	712
Net revenue	128,111	102,956	332,555	253,914
EXPENSES:
Employee compensation and benefits	28,885	25,505	81,700	71,188
Selling and marketing	7,422	4,803	20,395	16,118
Referral fees	28,607	24,640	84,724	65,745
Trading expenses	8,959	6,032	24,053	20,089
General and administrative	16,754	8,945	40,270	28,310
Depreciation and amortization	2,925	1,717	7,638	5,210
Purchased intangible amortization	4,280	2,228	10,688	4,841
Communications and technology	5,565	3,822	14,158	11,645
Bad debt provision	1,794	1,528	6,354	2,690
Acquisition expenses	232	917	2,711	1,545
Restructuring expenses	0	436	1,935	2,126
Integration expenses	10,700	0	23,073	1,719
Total operating expense	116,123	80,573	317,699	231,226
OPERATING PROFIT	11,988	22,383	14,856	22,688
Interest expense on long term borrowings	2,570	1,496	6,626	4,390
INCOME BEFORE INCOME TAX EXPENSE	9,418	20,887	8,230	18,298
Income tax expense	7,862	9,206	7,568	10,067
NET INCOME	1,556	11,681	662	8,231
Net income attributable to non-controlling interests	583	785	1,343	987
NET INCOME/(LOSS) APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.	973	10,896	(681)	7,244
Other comprehensive loss
Foreign currency translation adjustment	(7,526)	(2,988)	(234)	(269)
NET COMPREHENSIVE INCOME/(LOSS) APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.	$ (6,553)	$ 7,908	$ (915)	$ 6,975
Earnings/(loss) per common share:
Basic (usd per share)	$ 0.05	$ 0.22	$ (0.01)	$ 0.13
Diluted (usd per share)	$ 0.05	$ 0.21	$ (0.01)	$ 0.12
Weighted average common shares outstanding used in computing earnings per common share:
Basic (shares)	49,149,102	41,038,782	47,163,814	40,243,330
Diluted (shares)	49,918,707	43,523,862	47,163,814	43,054,959

Condensed Consolidated Stateme5

Condensed Consolidated Statement of Changes in Shareholders' Equity - USD ($)		Total	Common Stock		Treasury Stock	Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Par value of common stock		$ 429
Preferred stock, authorized (in shares)		15,000,000
BEGINNING BALANCE at Dec. 31, 2014		$ 249,920,000	$ 0	[1]	$ (16,720,000)	$ 148,378,000	$ 119,775,000	$ (1,513,000)
BEGINNING BALANCE (in shares) at Dec. 31, 2014	[2]		42,934,559
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of options		2,096,000				2,096,000
Exercise of options (in shares)	[2]		543,341
Conversion of restricted stock into common stock		0
Conversion of restricted stock into common stock (in shares)	[2]		422,850
Issuance of common stock		48,280,000				48,280,000
Employee stock purchase plan		394,000				394,000
Employee stock purchase plan, shares	[2]		44,106
Issuance of common stock, shares	[2]		5,319,149
Repurchase of shares		(2,144,000)			(2,144,000)
Repurchase of shares, shares	[2]		(266,267)
Convertible note issuance		15,348,000				15,348,000
Tax effect of convertible senior note		(3,827,000)				(3,827,000)
Other		(55,000)					(55,000)
Stock compensation expense		2,727,000				2,727,000
Foreign currency translation adjustment		(234,000)						(234,000)
Tax benefit of stock option exercises		938,000				938,000
Dividends declared ($0.05 quarterly dividend per share)		(7,084,000)					(7,084,000)
Net income applicable to Gain Capital Holdings, Inc.		(681,000)					(681,000)
Adjustment to the redemption value of put options related to non-controlling interests		(14,000)					(14,000)
ENDING BALANCE at Sep. 30, 2015		305,664,000	$ 0	[1]	$ (18,864,000)	$ 214,334,000	$ 111,941,000	$ (1,747,000)
ENDING BALANCE (in shares) at Sep. 30, 2015	[2]		48,997,738
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Par value of common stock		$ 490
Preferred stock, authorized (in shares)		15,000,000
[1]	The par value of the Company's Common Stock was $490 and $429 (amounts in whole dollars) as of September 30, 2015 and December 31, 2014, respectively.
[2]	The Company has 15,000,000 shares of authorized preferred stock, of which none are issued or outstanding.

Condensed Consolidated Stateme6

Condensed Consolidated Statement of Changes in Shareholders' Equity (Parenthetical) - $ / shares	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Statement of Stockholders' Equity [Abstract]
Dividend payment, per share	$ 0.05
Preferred stock, authorized (in shares)	15,000,000	15,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 662	$ 8,231
Adjustments to reconcile net income to cash provided by operating activities
Loss on foreign currency exchange rates	2,226	3,153
Depreciation and amortization	18,326	10,051
Non-cash integration costs	18,617	0
Deferred taxes	(5,328)	(2,488)
Amortization of deferred financing costs	266	265
Convertible senior notes discount amortization	2,583	1,599
Bad debt provision	(6,354)	(2,690)
Stock compensation expense	2,727	2,666
Adjustment to fair value of contingent consideration	(4,466)	0
Changes in operating assets and liabilities:
Cash and securities held for customers	29,287	(123,377)
Receivables from brokers	50,942	61,371
Prepaid assets	(3,106)	365
Other assets	(3,722)	(7,923)
Payables to customers	(29,287)	123,277
Accrued compensation and benefits	(10,853)	(1,902)
Accrued expenses and other liabilities	586	9,416
Income tax payable	(400)	(3,679)
Cash provided by operating activities	75,414	83,715
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(13,900)	(8,061)
Purchase of certificates of deposit	0	(100)
Cash received relating to acquisitions	7,611	0
Funding of acquisitions, net of cash acquired	(3,258)	(27,013)
Cash used for investing activities	(9,547)	(35,174)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	2,096	1,204
Tax benefit from employee stock option exercises	938	1,263
Proceeds from employee stock purchase plan	394	461
Purchase of treasury stock	(2,144)	(794)
Contractual payments for acquisitions	(13,271)	0
Distributions to non-controlling interest holders	(1,035)	0
Dividend payment	(7,084)	(6,054)
Cash used for financing activities	(20,106)	(3,920)
Effect of exchange rate changes on cash and cash equivalents	1,576	(2,976)
INCREASE IN CASH AND CASH EQUIVALENTS	47,337	41,645
CASH AND CASH EQUIVALENTS-Beginning of period	139,351	39,871
CASH AND CASH EQUIVALENTS-End of period	186,688	81,516
Cash paid during the year for:
Interest	(2,004)	(1,784)
Taxes	(4,641)	(7,121)
Non-cash investing activities:
Common stock issued as consideration for asset and business acquisitions	(48,280)	(6,493)
Convertible senior notes issued as consideration for business acquisitions	(65,000)	0
Deferred taxes related to convertible senior notes	(3,827)
Adjustment to redemption value of non-controlling interests	$ (14)	$ (1,944)

DESCRIPTION OF BUSINESS AND BAS

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION	9 Months Ended
	Sep. 30, 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. 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. (“GCUK”) and GAIN Capital UK Ltd. are each registered in the United Kingdom ("U.K.") and regulated by the Financial Conduct Authority (“FCA”) as full scope €730k BIPRU Investment Firms. The following list includes each of the Company’s significant U.S. and international regulated subsidiaries as of September 30, 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 Ltd. 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 (Holdings) Limited ("City Index") from City Index Group Limited. GAIN Capital UK Ltd., GAIN Capital Australia Pty. Ltd., and GAIN Capital Singapore Pte. Ltd. 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"). See Note 10 for further details related to the Company's acquisitions. Basis of Presentation and Principles of Consolidation The accompanying unaudited condensed consolidated financial statements reflect all adjustments that, in the opinion of management, are necessary for a fair presentation of the condensed consolidated financial statements for the applicable interim periods. The financial statements are presented in accordance with accounting principles generally accepted in the United States. The unaudited condensed consolidated financial statements have been prepared in accordance with the Securities and Exchange Commission's ("SEC") regulations for interim financial statements, and, in accordance with SEC rules, omit or condense certain information and footnote disclosures. Results for the interim periods are not necessarily indicative of results to be expected for any other interim period or for a full year. These financial statements should be read in conjunction with the audited consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K as of and for the year ended December 31, 2014 filed with the SEC on March 16, 2015 and amended on April 30, 2015 (the “2014 Form 10-K”). There have been no changes in the significant accounting policies from those included in the 2014 Form 10-K. The unaudited condensed consolidated financial statements include the accounts of GAIN Capital Holdings, Inc. and its majority owned subsidiaries after the elimination of intercompany transactions and balances. For the nine months ended September 30, 2015, the Company revised its revenue captions to "Retail revenue" , "Institutional revenue" , and "Other revenue" . Previously, certain business lines now presented in "Retail revenue" were presented in "Commission revenue" . Following the City Index acquisition, the Company believes that presenting its revenues in this manner provides for a clearer presentation of the Company's major customer types and the related revenue streams. Revenues for the three and nine months ended September 30, 2014 have been reclassified to reflect this revised presentation. There were no changes to net revenue or net income in any period due to this reclassification. For the period ended September 30, 2015, the Company revised certain captions shown in its condensed consolidated balance sheets. "Receivables from banks and brokers" has been renamed "Receivables from brokers" , and "Payables to customers, brokers, dealers, FCMs and other regulated entities" has been renamed "Payables to customers" . The Company believes that these captions more succinctly represent the nature of the transactions and balances contained within each line item. The composition and the amounts reported in the line items have not changed.

RESTATEMENT

RESTATEMENT	9 Months Ended
	Sep. 30, 2015
Accounting Changes and Error Corrections [Abstract]
RESTATEMENT	RESTATEMENT Subsequent to the date of the Original Filing, the Company has determined that there were errors in the manner in which the Company accounted for income taxes as of and for the quarters ended September 30, 2015 and 2014 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 condensed consolidated financial statements of the Company as of and for the quarters ended September 30, 2015 and September 30, 2014, 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. These immaterial adjustments include the correction of an out of period adjustment related to the calculation of the redemption value of the noncontrolling interests previously recorded 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. The adjustment has now been reflected in the appropriate periods. 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 Unaudited Interim Condensed Consolidated Balance Sheet and Unaudited Interim Condensed Consolidated 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 Consolidated Statement of Cash Flows. For the avoidance of doubt, the following tables include only those line items impacted by the restatement. Condensed Consolidated Balance Sheet As of September 30, 2015 As Reported Tax Adjustment Other Adjustments As Restated ASSETS: Goodwill 44,817 (3,186 ) — 41,631 Other assets, net of allowance for doubtful accounts 38,854 (138 ) — 38,716 Total assets $ 1,516,203 $ (3,324 ) $ — $ 1,512,879 LIABILITIES AND SHAREHOLDERS’ EQUITY: Liabilities Accrued expenses and other liabilities 51,132 21,290 — 72,422 Income tax payable 5,186 1,603 — 6,789 Total liabilities $ 1,172,662 $ 22,893 $ — $ 1,195,555 Shareholders’ equity Accumulated other comprehensive loss (2,288 ) 541 — (1,747 ) Additional paid-in capital 222,467 (8,133 ) — 214,334 Retained earnings 130,566 (18,625 ) — 111,941 Total shareholders’ equity 331,881 (26,217 ) — 305,664 Total liabilities and shareholders’ equity $ 1,516,203 $ (3,324 ) $ — $ 1,512,879 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 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 Condensed Consolidated Statement of Income For the Three Months Ended Sept 30, 2015 As Reported Tax Adjustment Other Adjustments As Restated REVENUE: Retail revenue $ 118,801 $ — $ 180 $ 118,981 Total non interest revenue 127,865 — 180 128,045 Net revenue $ 127,931 $ — $ 180 $ 128,111 EXPENSES: Employee Compensation and benefits $ 29,088 $ — $ (203 ) $ 28,885 Trading expenses 8,779 — 180 8,959 Total operating expense 116,146 — (23 ) 116,123 OPERATING PROFIT 11,785 — 203 11,988 INCOME BEFORE INCOME TAX EXPENSE 9,215 — 203 9,418 Income tax expense 328 7,534 7,862 NET INCOME 8,887 (7,534 ) 203 1,556 NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. $ 8,304 $ (7,534 ) $ 203 $ 973 Earnings per common share: Basic $ 0.20 $ 0.05 Diluted $ 0.20 $ 0.05 Weighted average common shares outstanding used in computing earnings per common share: Basic 49,147,102 49,149,102 Diluted 49,891,101 49,918,707 For the Nine Months Ended Sept 30, 2015 As Reported Tax Adjustment Other Adjustments As Restated REVENUE: Retail revenue $ 300,376 $ — $ 107 $ 300,483 Total non interest revenue 332,358 — 107 332,465 Net revenue $ 332,448 $ — $ 107 $ 332,555 EXPENSES: General and administrative 40,219 — 51 40,270 Total operating expense 317,648 — 51 317,699 OPERATING PROFIT 14,800 — 56 14,856 INCOME BEFORE INCOME TAX EXPENSE 8,174 — 56 8,230 Income tax expense (978 ) 8,546 7,568 NET INCOME 9,152 (8,546 ) 56 662 NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. $ 7,809 $ (8,546 ) $ 56 $ (681 ) NET COMPREHENSIVE INCOME/(LOSS) $ 7,575 (8,546 ) 56 $ (915 ) Earnings per common share: Basic $ 0.14 $ (0.01 ) Diluted $ 0.14 $ (0.01 ) Weighted average common shares outstanding used in computing earnings per common share: Basic 47,163,132 47,163,814 Diluted 48,028,752 47,163,814 For the Three Months Ended Sept 30, 2014 As Reported Tax Adjustment Other Adjustments As Restated REVENUE: Retail revenue $ 90,373 $ — $ (602 ) $ 89,771 Total non interest revenue 103,388 — (602 ) 102,786 Interest Expense 97 — 92 189 Total net interest revenue/(expense) 262 — (92 ) 170 Net revenue $ 103,650 $ — $ (694 ) $ 102,956 EXPENSES: General and administrative 9,056 — (111 ) 8,945 Total operating expense 80,684 — (111 ) 80,573 OPERATING PROFIT 22,966 — (583 ) 22,383 INCOME BEFORE INCOME TAX EXPENSE 21,470 — (583 ) 20,887 Income tax expense 5,340 3,866 — 9,206 NET INCOME 16,130 (3,866 ) (583 ) 11,681 NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. $ 15,345 $ (3,866 ) $ (583 ) $ 10,896 Earnings per common share: Basic $ 0.35 $ 0.22 Diluted $ 0.33 $ 0.21 For the Nine Months Ended Sept 30, 2014 As Reported Tax Adjustment Other Adjustments As Restated REVENUE: Retail revenue $ 223,138 $ — $ (776 ) $ 222,362 Total non interest revenue 253,978 — (776 ) 253,202 Interest expense 319 — 92 411 Total net interest revenue/(expense) 804 — (92 ) 712 Net revenue $ 254,782 $ — $ (868 ) $ 253,914 EXPENSES: Employee compensation and benefits 71,440 — (252 ) 71,188 Referral fees 65,865 — (120 ) 65,745 General and administrative 28,113 — 197 28,310 Depreciation and amortization 5,725 — (515 ) 5,210 Restructuring expenses 1,007 — 1,119 2,126 Total operating expense 230,797 — 429 231,226 OPERATING PROFIT 23,985 — (1,297 ) 22,688 INCOME BEFORE INCOME TAX EXPENSE 19,595 — (1,297 ) 18,298 Income tax expense 4,595 5,472 — 10,067 NET INCOME 15,000 (5,472 ) (1,297 ) 8,231 NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. $ 14,013 $ (5,472 ) $ (1,297 ) $ 7,244 Earnings per common share: Basic $ 0.32 $ 0.13 Diluted $ 0.30 $ 0.12 Condensed 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—December 31, 2014 $ 152,684 $ 148,378 $ 130,984 $ 119,775 $ (2,054 ) $ (1,513 ) $ 264,894 $ 249,920 BALANCE—September 30, 2015 $ 222,467 $ 214,334 $ 130,566 $ 111,941 $ (2,288 ) $ (1,747 ) $ 331,881 $ 305,664 Condensed Statement of Cash Flows Nine Months Ended September 30, 2015 As Reported Adjustments As Restated CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 9,152 $ (8,490 ) $ 662 Adjustments to reconcile net income to cash provided by / (used for) operating activities Deferred taxes (5,797 ) 469 (5,328 ) Changes in operating assets and liabilities: Cash and securities held for customers 30,064 (777 ) 29,287 Receivables from brokers 51,035 (93 ) 50,942 Other assets (6,114 ) 2,392 (3,722 ) Payables to customers (30,064 ) 777 (29,287 ) Accrued compensation and benefits (10,860 ) 7 (10,853 ) Accrued expenses and other liabilities (9,214 ) 9,800 586 Income tax payable 3,746 (4,146 ) (400 ) Cash provided by operating activities 75,475 (61 ) 75,414 Effect of exchange rate changes on cash and cash equivalents 1,463 113 1,576 INCREASE IN CASH AND CASH EQUIVALENTS 47,285 52 47,337 CASH AND CASH EQUIVALENTS-Beginning of period 139,403 (52 ) 139,351 SUPPLEMENTARY DISCLOSURES OF CASH FLOW INFORMATION: Deferred taxes related to convertible senior notes $ — $ (3,827 ) $ (3,827 ) Adjustment to redemption value of non-controlling interests $ (1,143 ) $ 1,129 $ (14 ) Nine Months Ended September 30, 2014 As Reported Adjustments As Restated CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 15,000 $ (6,769 ) $ 8,231 Adjustments to reconcile net income to cash provided by / (used for) operating activities Depreciation and amortization 10,566 (515 ) 10,051 Deferred taxes (2,430 ) (58 ) (2,488 ) Changes in operating assets and liabilities: Cash and securities held for customers (122,523 ) (854 ) (123,377 ) Receivables from brokers 61,316 55 61,371 Other assets (8,595 ) 672 (7,923 ) Payables to customers 122,523 754 123,277 Accrued compensation and benefits (2,745 ) 843 (1,902 ) Accrued expenses and other liabilities (945 ) 10,361 9,416 Income tax payable 1,393 (5,072 ) (3,679 ) Cash provided by operating activities 84,298 (583 ) 83,715 Effect of exchange rate changes on cash and cash equivalents (2,903 ) (73 ) (2,976 ) INCREASE IN CASH AND CASH EQUIVALENTS 42,301 (656 ) 41,645 CASH AND CASH EQUIVALENTS—End of period $ 82,172 $ (656 ) $ 81,516 SUPPLEMENTARY DISCLOSURES OF CASH FLOW INFORMATION: Adjustment to redemption value of non-controlling interests $ (1,066 ) $ (878 ) $ (1,944 )

RECENT ACCOUNTING PRONOUNCEMENT

RECENT ACCOUNTING PRONOUNCEMENTS	9 Months Ended
	Sep. 30, 2015
Accounting Changes and Error Corrections [Abstract]
RECENT ACCOUNTING PRONOUNCEMENTS	RECENT ACCOUNTING PRONOUNCEMENTS In September 2015, the Financial Accounting Standards Board (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 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 financial statements of adopting this guidance.

FAIR VALUE INFORMATION

FAIR VALUE INFORMATION	9 Months Ended
	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
FAIR VALUE INFORMATION	FAIR VALUE INFORMATION Fair Value Measurements 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 hierarchy that categorizes financial instruments into the following three levels based on valuation technique inputs (highest to lowest): 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 $ — $ 147,645 $ — $ 147,645 Broker derivative contracts — (29,077 ) — (29,077 ) Money market accounts 25,158 — — 25,158 Certificates of deposit 174 — — 174 Investment in gold 113 — 113 Contingent consideration — (3,824 ) (3,824 ) Total $ 25,445 $ 118,568 $ (3,824 ) $ 140,189 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 did not change its valuation techniques for measuring the fair value of any financial assets or liabilities during the nine months ended September 30, 2015 , nor was there any movement between levels during this period. 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 and the investment in gold are recorded in Other Assets. Level 2 Financial Assets and Liabilities The Company has customer derivative contracts that are Level 2 financial instruments recorded in Payables to customers. The Company has broker derivative contracts that are Level 2 financial instruments recorded in Receivables from brokers. 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 is obligated to make contingent payments that are Level 3 financial liabilities. These contingent payments are recorded under Accrued expenses and other liabilities on the Company's condensed consolidated balance sheets. The fair value of these payments is 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. The following is a rollforward of the Level 3 liabilities from January 1, 2015 to September 30, 2015 (amounts in thousands): Liabilities Contingent Consideration Balance at January 1, 2015 $ 9,974 Gains included in earnings - adjustment to fair value of contingent consideration (4,466 ) Contingent consideration payments (2,063 ) Gains included in earnings - currency revaluation (113 ) Losses included in earnings - discount amortization 492 Balance at September 30, 2015 $ 3,824 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 condensed 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 12). The Company assessed the notes' fair value as determined by current Company-specific and risk free interest rates as of the balance sheet date. 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 our acquisition of Global Futures & Forex, Ltd. ("GFT"). These liabilities were settled, and accordingly, there are no liabilities for the Holdback Amount as of September 30, 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 September 30, 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 $ 148,304 $ 148,304 $ — $ 148,304 $ — Financial Liabilities: Payables to customers 1,134,021 1,134,021 — 1,134,021 — Convertible senior notes 120,866 121,103 — 121,103 — 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	9 Months Ended
	Sep. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVES	DERIVATIVES The Company's open 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 condensed consolidated balance sheets (amounts in thousands): September 30, 2015 Derivative open positions at fair value Gross assets Gross liabilities Net assets Derivative Instruments: Foreign currency exchange contracts $ 125,047 $ 54,060 $ 70,987 CFD contracts 66,759 28,759 38,000 Metals contracts 15,509 5,928 9,581 Total $ 207,315 $ 88,747 $ 118,568 September 30, 2015 Net assets/liabilities at fair value Cash Collateral Derivative open positions Presented in the balance sheet Derivative Assets/Liabilities: Receivables from brokers $ 148,304 $ (29,077 ) $ 119,227 Payables to customers $ 1,134,021 $ 147,645 $ 986,376 December 31, 2014 Derivative open positions at fair value Gross Gross Net assets 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 Net assets/liabilities at fair value Cash Collateral Derivative Derivative Assets/Liabilities: Receivables from brokers $ 134,191 $ 717 $ 134,908 Payables to customers $ 862,281 $ 102,722 $ 759,559 The Company’s derivatives have many different underlyings, which vary in price. Foreign exchange contracts typically have prices less than two dollars, while certain metals contracts and contracts-for-difference ("CFD") can have considerably higher prices. The table below presents the number of contracts reported within Receivables from brokers and Payables to customers on the condensed consolidated balance sheets (amounts in thousands): September 30, 2015 Total contracts in long positions Total contracts in short positions Derivative Instruments: Foreign currency exchange contracts 3,379,580 2,770,520 CFD contracts 136,600 285,838 Metals contracts 844 441 Total 3,517,024 3,056,799 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 at September 30, 2015 or December 31, 2014 . Net gains/(losses) with respect to derivative instruments reflected in Retail revenue in the accompanying condensed consolidated statements of operations and comprehensive income for the three and nine months ended September 30, 2015 and 2014 were as follows (amounts in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Derivative Instruments: Foreign currency exchange contracts $ 30,436 $ 35,144 $ 128,096 $ 90,256 CFD contracts 56,071 12,074 93,936 29,567 Metals contracts 9,170 16,121 20,696 30,988 Total $ 95,677 $ 63,339 $ 242,728 $ 150,811

RECEIVABLES FROM BROKERS RECEIV

RECEIVABLES FROM BROKERS RECEIVABLES FROM BROKERS	9 Months Ended
	Sep. 30, 2015
Receivables [Abstract]
RECEIVABLES FROM BROKERS	RECEIVABLES FROM BROKERS Amounts receivable from brokers consisted of the following as of (amounts in thousands): September 30, 2015 December 31, 2014 Required collateral $ 144,556 $ 95,599 Futures brokers - Restricted 3,748 38,592 Open positions (29,077 ) 717 $ 119,227 $ 134,908

PROPERTY AND EQUIPMENT PROPERTY

PROPERTY AND EQUIPMENT PROPERTY AND EQUIPMENT	9 Months Ended
	Sep. 30, 2015
Property, Plant and Equipment [Abstract]
PROPERTY AND EQUIPMENT	PROPERTY AND EQUIPMENT Property and equipment consisted of the following as of (amounts in thousands): September 30, 2015 December 31, 2014 Software $ 41,229 $ 30,351 Computer equipment 13,549 8,516 Leasehold improvements 11,356 6,719 Telephone equipment 794 719 Office equipment 2,113 2,345 Furniture and fixtures 1,907 1,044 Web site development costs 668 646 71,616 50,340 Less: Accumulated depreciation and amortization (42,401 ) (31,544 ) Property and equipment, net $ 29,215 $ 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 preliminary purchase price allocation for City Index and the final purchase price allocations for Galvan, GAA and Top Third to property and equipment are detailed below in Note 10. Depreciation and amortization expense for property and equipment was $2.9 million and $ 1.7 million for the three months ended September 30, 2015 and 2014 , respectively, and $7.6 million and $5.2 million for the nine months ended September 30, 2015 and 2014 , 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 acquisition. This change in useful lives resulted in an additional charge of $1.8 million and $3.7 million during the three months and nine months ended September 30, 2015 , respectively. The additional charge was recorded in Integration expenses.

INTANGIBLE ASSETS AND GOODWILL

INTANGIBLE ASSETS AND GOODWILL INTANGIBLE ASSETS AND GOODWILL	9 Months Ended
	Sep. 30, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
INTANGIBLE ASSETS AND GOODWILL	INTANGIBLE ASSETS AND GOODWILL Intangible Assets The Company's various intangible assets consisted of the following as of (amounts in thousands): September 30, 2015 December 31, 2014 Intangibles Gross Accumulated Net Gross Accumulated Net Customer lists $ 53,303 $ (11,080 ) $ 42,223 $ 22,945 $ (7,152 ) $ 15,793 Technology 75,069 (23,291 ) 51,778 48,376 (4,671 ) 43,705 Trademarks 8,483 (1,385 ) 7,098 1,793 (847 ) 946 Total finite lived intangibles 136,855 (35,756 ) 101,099 73,114 (12,670 ) 60,444 Trademarks not subject to amortization (1) 362 — 362 362 — 362 Total intangibles (2) $ 137,217 $ (35,756 ) $ 101,461 $ 73,476 $ (12,670 ) $ 60,806 (1) These indefinite-life trademarks relate to the Forex.com and foreignexchange.com domain names. Management determined there was no legal, regulatory or technological limitation on the domains' useful lives. The trademarks' values are evaluated annually in the Company's impairment test for intangible assets. (2) The increase in total intangibles for the nine months ended September 30, 2015 was primarily due to the customer lists, technology and trademarks acquired as part of the City Index acquisition. See Note 10 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 gross identifiable intangible assets as of September 30, 2015: Intangible Assets Amount (in thousands) Weighted average amortization period Customer lists $ 53,303 8.1 years Technology 75,069 8.9 years Trademarks (1) 8,845 6.7 years $ 137,217 (1) Trademarks with indefinite lives, as described above, comprise $0.4 million of the gross $8.8 million of trademarks. The preliminary purchase price allocations to intangible assets for the acquisition of City Index are detailed below in Note 10, “Acquisitions”, along with the final purchase price allocations for the Galvan, GAA and Top Third acquisitions. On July 10, 2014, the Company entered into asset purchase agreements with Valaquenta and Forexster, pursuant to which one of the Company's subsidiaries, 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 unregistered shares of the Company's common stock. Prior to the closing of the acquisitions, which took place on July 10, 2014, 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 any 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 the aforementioned exclusive rights agreement. The Company has assigned a 10 year useful life to this asset. Amortization expense for the purchased intangibles was $4.3 million and $2.2 million for the three months ended September 30, 2015 and 2014 , respectively, and $10.7 million and $4.8 million for the nine months ended September 30, 2015 and 2014 , 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 $6.5 million and $13.0 million during the three and nine months ended September 30, 2015 . The additional charge is recorded in integration expenses. Future annual estimated purchased intangible amortization expense is as follows (amounts in thousands): Years Ended December 31: 2015 $ 10,761 2016 14,154 2017 12,861 2018 11,760 2019 11,179 Thereafter 40,384 Total $ 101,099 Of the total future estimated amortization expense above, $6.5 million is expected to be recorded as Integration expense for the acceleration of the amortization of technology platforms that are being discontinued as a result of the City Index acquisition, primarily in the fourth quarter of 2015. Goodwill Goodwill is calculated as the difference between the cost of an acquired business and the fair value of the net identifiable assets of that business. As of September 30, 2015 and December 31, 2014 , the Company had recorded goodwill of approximately $41.6 million and $33.6 million , respectively. The increase of $8.0 million was primarily related to the City Index acquisition.

OTHER ASSETS

OTHER ASSETS	9 Months Ended
	Sep. 30, 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): September 30, 2015 December 31, 2014 Vendor and security deposits $ 9,414 $ 3,373 Current tax receivable 8,339 5,163 Deferred tax assets 14,774 6,308 Indemnification asset — 8,792 GTX trade receivables 3,675 4,190 Customer debit positions 6,951 6,594 Allowance for doubtful accounts (5,898 ) (4,555 ) Miscellaneous receivables and other assets 1,461 3,900 $ 38,716 $ 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 . During the nine months ended September 30, 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	9 Months Ended
	Sep. 30, 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, which are recorded in Payables to customers on the condensed consolidated balance sheets. The aggregate amount of these funds was $7.8 million and $3.6 million at September 30, 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 condensed consolidated balance sheet. The aggregate amount of these funds was $5.4 million at September 30, 2015.

ACQUISITIONS

ACQUISITIONS	9 Months Ended
	Sep. 30, 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. The preliminary 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, and 4.125% unsecured Convertible Senior Notes with an aggregate principal amount of $60.0 million and fair value of $ 65.0 million . In addition the Company paid approximately $22.4 million to settle certain inter-company liabilities between City Index and City Index Group Limited (its former parent company). The difference in the preliminary purchase price from June 30 to September 30 was due to the finalization of working capital adjustments. The preliminary purchase price was derived as follows (amounts in thousands): Cash $ 6,102 Convertible senior notes 65,000 Common stock issued (based on the April 1, 2015 quoted price of $9.77) 48,280 Total purchase price $ 119,382 The preliminary purchase price of City Index was allocated to the fair value of various assets and liabilities as follows (amounts in thousands): Cash and cash equivalents $ 32,991 Cash and securities held for customers 265,012 Receivable from brokers 35,974 Property and equipment 10,411 Prepaid assets 3,972 Other current assets 541 Total tangible assets 348,901 Total liabilities assumed 303,280 Net assets acquired 45,621 Identifiable intangible assets: Customer list 30,273 Trade name 6,645 Technology 26,157 Intangible assets, net 63,075 Goodwill $ 10,686 The foregoing purchase price allocation is preliminary. The final allocation will be based on final analyses of assets and liabilities. It will be finalized after the data necessary to complete the analyses of fair value of assets and liabilities is obtained and analyzed. For the period from acquisition to September 30, 2015, revenues generated by City Index were $79.2 million , of which $15.5 million have been eliminated in consolidation, and expenses were $63.7 million , of which $1.3 million have been eliminated in consolidation. City Index generated income before taxes of $15.5 million , of which $14.2 million have been eliminated in consolidation. The weighted average lives of City Index's intangible assets are 8.8 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 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 nine months ended September 30, 2015, the Company adjusted the contingent payment's value based on forecasts of performance related to 2015 and 2016 payments (See Note 3). 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 current 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 Global Assets 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 current 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 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 assets acquired (367 ) Identifiable intangible assets: Customer list 3,900 Trade name 90 Intangible assets, net 3,990 Goodwill $ 3,806 Pro Forma Information: The following unaudited pro forma operating data is presented as if the acquisition of GAA, Top Third and Galvan had occurred on January 1, 2014. 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 nine months ended September 30, 2014 were as follows (amounts in thousands): For the Nine Months Ended September 30, 2014 REVENUE: Total non-interest revenue $ 260,794 Interest revenue 1,130 Interest expense 859 Total net interest revenue 271 Net revenue 261,065 EXPENSES: Depreciation and amortization 5,227 Purchased intangible amortization 5,421 Other expense items 227,917 Total operating expense 238,565 OPERATING PROFIT 22,500 Interest on long term borrowings 4,390 INCOME BEFORE INCOME TAX EXPENSE 18,110 Income tax expense 12,749 NET INCOME 5,361 Net income attributable to non-controlling interests 981 Net income applicable to Gain Capital Holdings, Inc. $ 4,380 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 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 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 nine months ended September 30, 2015 and three and nine months ended September 30, 2014 were as follows (amounts in thousands): For the Nine Months Ended September 30, For the Three Months Ended September 30, For the Nine Months Ended September 30, 2015 2014 2014 REVENUE: Total non-interest revenue $ 369,249 $ 143,228 $ 347,860 Interest revenue 1,019 571 1,983 Interest expense 846 189 411 Total net interest revenue 173 382 1,572 Net revenue 369,422 143,610 349,432 EXPENSES: Depreciation and amortization 8,280 6,505 12,694 Purchased intangible amortization 12,757 4,533 11,694 Other expense items 333,565 109,085 313,871 Total operating expense 354,602 120,123 338,259 OPERATING PROFIT 14,820 23,487 11,173 Interest on long term borrowings 7,671 2,541 7,526 INCOME BEFORE INCOME TAX BENEFIT 7,149 20,946 3,647 Income tax expense 11,207 11,939 7,326 NET INCOME (4,058 ) 9,007 (3,679 ) Net income attributable to non-controlling interests 1,343 785 987 Net income applicable to Gain Capital Holdings, Inc. $ (5,401 ) $ 8,222 $ (4,666 ) Restructuring During the second quarter of 2015, the Company incurred restructuring expenses, which reflected the cost of reducing global headcount following the City Index acquisition. The Company previously incurred restructuring expenses in connection with headcount reductions in the third quarter of 2014 that were designed to meet challenging market conditions in the first half of 2014 and to achieve greater cost efficiency in general. The Company incurred $1.2 million of restructuring expenses for the twelve months ended December 31, 2014 . These expenses are recorded in Restructuring expenses in the condensed consolidated statements of operations and comprehensive income. The restructuring liabilities are recorded in Accrued compensation and benefits in the condensed consolidated balance sheets. For the Nine Months Ended September 30, 2015 Restructuring liability as of January 1, 2015 $ 374 2015 restructuring expenses 1,935 Payments made in 2015 (1,926 ) Restructuring liability as of September 30, 2015 $ 383

NON-CONTROLLING INTERESTS

NON-CONTROLLING INTERESTS	9 Months Ended
	Sep. 30, 2015
Noncontrolling Interest [Abstract]
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 vested 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 classified as temporary equity in the condensed consolidated balance sheets. The non-controlling interests' carrying value is determined by the initial purchase prices for the acquired interests, the non-controlling interests' share of the acquired companies' subsequent net income, the non-controlling interests' share of the acquired companies' current net assets, and distributions to non-controlling interest holders. This value is benchmarked against the redemption value of the sellers' put options. The carrying values are adjusted to the latter, provided that they do 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 (amounts in thousands): Redeemable non-controlling interests January 1, 2015 $ 11,338 Adjustment to the redemption value of non-controlling interests 14 Net income attributable to non-controlling interests 1,343 Distributions to non-controlling interest holders (1,035 ) September 30, 2015 $ 11,660

CONVERTIBLE SENIOR NOTES Conver

CONVERTIBLE SENIOR NOTES Convertible Senior Notes	9 Months Ended
	Sep. 30, 2015
Debt Disclosure [Abstract]
CONVERTIBLE SENIOR NOTES	CONVERTIBLE SENIOR NOTES 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. On November 27, 2013, the Company issued $80.0 million aggregate 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. Under accounting guidance, an entity must separately account for the liability and equity components of convertible debt instruments that may be settled entirely or partially in cash upon conversion. The separate accounting must reflect the issuer's economic interest cost. The balances of the liability and equity components as of September 30, 2015 and December 31, 2014 were as follows (amounts in thousands): September 30, 2015 December 31, 2014 Liability component - principal $ 140,000 $ 80,000 Deferred bond discount (19,134 ) (11,633 ) Liability component - net carrying value $ 120,866 $ 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 on long term borrowings in the condensed consolidated statements of operations and comprehensive income, was as follows (amounts in thousands): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2015 2014 2015 2014 Interest expense - stated coupon rate $ 1,444 $ 825 $ 3,713 $ 2,475 Interest expense - amortization of deferred bond discount and costs 1,038 671 2,648 1,915 Total interest expense - convertible senior notes $ 2,482 $ 1,496 $ 6,361 $ 4,390

EARNINGS PER COMMON SHARE

EARNINGS PER COMMON SHARE	9 Months Ended
	Sep. 30, 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. Anti-dilutive stock options of 0.5 million were excluded from the calculation for the nine months ended September 30, 2015. Anti-dilutive options of 0.4 million were excluded from the calculation for the nine months ended September 30, 2014. Under present market conditions, diluted earnings per share excludes any shares of Company common stock potentially issuable under the Company's convertible senior notes due in 2018 and 2010, which are discussed in Note 12. 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 Three Months Ended September 30, For the Nine Months Ended September 30, 2015 2014 2015 2014 Net income applicable to GAIN Capital Holdings, Inc. $ 973 $ 10,896 $ (681 ) $ 7,244 Adjustment to the redemption value of non-controlling interests (1) 1,428 (1,747 ) (14 ) (1,944 ) Net income available to common shareholders $ 2,401 $ 9,149 $ (695 ) $ 5,300 Weighted average common shares outstanding: Basic weighted average common shares outstanding 49,149,102 41,038,782 47,163,814 40,243,330 Effect of dilutive securities: Stock options 320,770 562,187 471,613 786,956 RSUs/RSAs 448,835 1,922,893 394,007 2,024,673 Diluted weighted average common shares outstanding 49,918,707 43,523,862 47,163,814 43,054,959 Net earnings per common share: Basic $ 0.05 $ 0.22 $ (0.01 ) $ 0.13 Diluted $ 0.05 $ 0.21 $ (0.01 ) $ 0.12 (1) During the nine months ended September 30, 2015 and 2014, the Company concluded that the value of the put options related to the Company's redeemable non-controlling interests in GAA and Top Third was less than redemption value. The adjustment to increase the carrying value reduces earnings available to the Company's shareholders for purposes of calculating basic and diluted earnings per common share.

LEGAL

LEGAL	9 Months Ended
	Sep. 30, 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 condensed consolidated financial statements and the Company can reasonably estimate the amount of that loss, the Company accrues the estimated loss by a charge to income. In many proceedings, however, it is inherently difficult to determine whether any loss is probable or even 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. 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 are in discovery. 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.

INCOME TAXES

INCOME TAXES	9 Months Ended
	Sep. 30, 2015
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company's expense/(benefit) for income taxes was approximately $7.9 million and $7.6 million for the three and nine months ended September 30, 2015, respectively. The Company’s provision for income taxes was approximately $9.2 million and $10.1 million for the three and nine months ended September 30, 2014, respectively. These amounts reflect effective tax rates of 83.5% and 44.1% , adjusted for certain discrete items, for the three months ended September 30, 2015 and 2014, respectively. The Company's effective tax rates of 92.0% and 55.0% for the nine months ended September 30, 2015 and 2014, respectively, reflect the Company's estimate of the annual effective tax rate adjusted for certain discrete items. The negative effective tax rate for the nine months ended September 30, 2015 was primarily due to the tax benefit resulting from the recognition of net operating losses from the Company's operations in Singapore, partially offset by charges relating to certain non-deductible compensation expenses incurred during 2014. Changes in the Company's effective rate arise primarily from changes in the geographic mix of revenues and expenses. Deferred income taxes reflect the net tax effects of temporary differences between the financial reporting and tax bases 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 deferred tax assets are included in Other assets on the condensed consolidated balance sheets.

REGULATORY REQUIREMENTS

REGULATORY REQUIREMENTS	9 Months Ended
	Sep. 30, 2015
Banking and Thrift [Abstract]
REGULATORY REQUIREMENTS	REGULATORY REQUIREMENTS The following table illustrates the minimum regulatory capital our subsidiaries were required to maintain as of September 30, 2015 and the actual amounts of capital that were maintained (amounts in millions): Entity Name Minimum Capital Excess Percent of GAIN Capital Group, LLC $ 25.3 $ 42.3 $ 17.0 167 % GAIN Capital-Forex.com U.K., Ltd. 32.5 81.7 49.2 251 % GAIN Capital Japan Co., Ltd. 1.4 9.5 8.1 679 % GAIN Capital-Forex.com Hong Kong, Ltd. 1.9 2.7 0.8 142 % GAIN Capital Forex.com Australia, Pty. Ltd. 0.7 2.2 1.5 314 % Galvan Research and Trading, Ltd. 0.7 4.4 3.7 629 % 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. 0.1 0.2 0.1 200 % GAIN Capital UK, Ltd. 1 52.3 111.5 59.2 213 % GAIN Capital Singapore Pte. Ltd. 1 0.7 7.1 6.4 1,014 % GAIN Capital Australia Pty Ltd. 1 0.7 2.0 1.3 286 % Global Assets Advisors, LLC 0.1 1.3 1.2 1,300 % Total $ 116.7 $ 266.7 $ 150.0 229 % (1) Entity acquired as part of the City Index acquisition.

SEGMENT INFORMATION

SEGMENT INFORMATION	9 Months Ended
	Sep. 30, 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 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, (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. Based on the Company’s management strategies, and predominantly common production, marketing, development and client coverage teams, the Company has concluded that it operates in a single operating segment.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	9 Months Ended
	Sep. 30, 2015
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS In November 2015, the Company announced the payment of a $ 0.05 dividend per share of Common Stock payable on December 22, 2015 to stockholders of record on December 11, 2015.

RESTATEMENT (Tables)

RESTATEMENT (Tables)	9 Months Ended
	Sep. 30, 2015
Accounting Changes and Error Corrections [Abstract]
Schedule of Prior Period Adjustments	Condensed Consolidated Balance Sheet As of September 30, 2015 As Reported Tax Adjustment Other Adjustments As Restated ASSETS: Goodwill 44,817 (3,186 ) — 41,631 Other assets, net of allowance for doubtful accounts 38,854 (138 ) — 38,716 Total assets $ 1,516,203 $ (3,324 ) $ — $ 1,512,879 LIABILITIES AND SHAREHOLDERS’ EQUITY: Liabilities Accrued expenses and other liabilities 51,132 21,290 — 72,422 Income tax payable 5,186 1,603 — 6,789 Total liabilities $ 1,172,662 $ 22,893 $ — $ 1,195,555 Shareholders’ equity Accumulated other comprehensive loss (2,288 ) 541 — (1,747 ) Additional paid-in capital 222,467 (8,133 ) — 214,334 Retained earnings 130,566 (18,625 ) — 111,941 Total shareholders’ equity 331,881 (26,217 ) — 305,664 Total liabilities and shareholders’ equity $ 1,516,203 $ (3,324 ) $ — $ 1,512,879 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 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 Condensed Consolidated Statement of Income For the Three Months Ended Sept 30, 2015 As Reported Tax Adjustment Other Adjustments As Restated REVENUE: Retail revenue $ 118,801 $ — $ 180 $ 118,981 Total non interest revenue 127,865 — 180 128,045 Net revenue $ 127,931 $ — $ 180 $ 128,111 EXPENSES: Employee Compensation and benefits $ 29,088 $ — $ (203 ) $ 28,885 Trading expenses 8,779 — 180 8,959 Total operating expense 116,146 — (23 ) 116,123 OPERATING PROFIT 11,785 — 203 11,988 INCOME BEFORE INCOME TAX EXPENSE 9,215 — 203 9,418 Income tax expense 328 7,534 7,862 NET INCOME 8,887 (7,534 ) 203 1,556 NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. $ 8,304 $ (7,534 ) $ 203 $ 973 Earnings per common share: Basic $ 0.20 $ 0.05 Diluted $ 0.20 $ 0.05 Weighted average common shares outstanding used in computing earnings per common share: Basic 49,147,102 49,149,102 Diluted 49,891,101 49,918,707 For the Nine Months Ended Sept 30, 2015 As Reported Tax Adjustment Other Adjustments As Restated REVENUE: Retail revenue $ 300,376 $ — $ 107 $ 300,483 Total non interest revenue 332,358 — 107 332,465 Net revenue $ 332,448 $ — $ 107 $ 332,555 EXPENSES: General and administrative 40,219 — 51 40,270 Total operating expense 317,648 — 51 317,699 OPERATING PROFIT 14,800 — 56 14,856 INCOME BEFORE INCOME TAX EXPENSE 8,174 — 56 8,230 Income tax expense (978 ) 8,546 7,568 NET INCOME 9,152 (8,546 ) 56 662 NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. $ 7,809 $ (8,546 ) $ 56 $ (681 ) NET COMPREHENSIVE INCOME/(LOSS) $ 7,575 (8,546 ) 56 $ (915 ) Earnings per common share: Basic $ 0.14 $ (0.01 ) Diluted $ 0.14 $ (0.01 ) Weighted average common shares outstanding used in computing earnings per common share: Basic 47,163,132 47,163,814 Diluted 48,028,752 47,163,814 For the Three Months Ended Sept 30, 2014 As Reported Tax Adjustment Other Adjustments As Restated REVENUE: Retail revenue $ 90,373 $ — $ (602 ) $ 89,771 Total non interest revenue 103,388 — (602 ) 102,786 Interest Expense 97 — 92 189 Total net interest revenue/(expense) 262 — (92 ) 170 Net revenue $ 103,650 $ — $ (694 ) $ 102,956 EXPENSES: General and administrative 9,056 — (111 ) 8,945 Total operating expense 80,684 — (111 ) 80,573 OPERATING PROFIT 22,966 — (583 ) 22,383 INCOME BEFORE INCOME TAX EXPENSE 21,470 — (583 ) 20,887 Income tax expense 5,340 3,866 — 9,206 NET INCOME 16,130 (3,866 ) (583 ) 11,681 NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. $ 15,345 $ (3,866 ) $ (583 ) $ 10,896 Earnings per common share: Basic $ 0.35 $ 0.22 Diluted $ 0.33 $ 0.21 For the Nine Months Ended Sept 30, 2014 As Reported Tax Adjustment Other Adjustments As Restated REVENUE: Retail revenue $ 223,138 $ — $ (776 ) $ 222,362 Total non interest revenue 253,978 — (776 ) 253,202 Interest expense 319 — 92 411 Total net interest revenue/(expense) 804 — (92 ) 712 Net revenue $ 254,782 $ — $ (868 ) $ 253,914 EXPENSES: Employee compensation and benefits 71,440 — (252 ) 71,188 Referral fees 65,865 — (120 ) 65,745 General and administrative 28,113 — 197 28,310 Depreciation and amortization 5,725 — (515 ) 5,210 Restructuring expenses 1,007 — 1,119 2,126 Total operating expense 230,797 — 429 231,226 OPERATING PROFIT 23,985 — (1,297 ) 22,688 INCOME BEFORE INCOME TAX EXPENSE 19,595 — (1,297 ) 18,298 Income tax expense 4,595 5,472 — 10,067 NET INCOME 15,000 (5,472 ) (1,297 ) 8,231 NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC. $ 14,013 $ (5,472 ) $ (1,297 ) $ 7,244 Earnings per common share: Basic $ 0.32 $ 0.13 Diluted $ 0.30 $ 0.12 Condensed 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—December 31, 2014 $ 152,684 $ 148,378 $ 130,984 $ 119,775 $ (2,054 ) $ (1,513 ) $ 264,894 $ 249,920 BALANCE—September 30, 2015 $ 222,467 $ 214,334 $ 130,566 $ 111,941 $ (2,288 ) $ (1,747 ) $ 331,881 $ 305,664 Condensed Statement of Cash Flows Nine Months Ended September 30, 2015 As Reported Adjustments As Restated CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 9,152 $ (8,490 ) $ 662 Adjustments to reconcile net income to cash provided by / (used for) operating activities Deferred taxes (5,797 ) 469 (5,328 ) Changes in operating assets and liabilities: Cash and securities held for customers 30,064 (777 ) 29,287 Receivables from brokers 51,035 (93 ) 50,942 Other assets (6,114 ) 2,392 (3,722 ) Payables to customers (30,064 ) 777 (29,287 ) Accrued compensation and benefits (10,860 ) 7 (10,853 ) Accrued expenses and other liabilities (9,214 ) 9,800 586 Income tax payable 3,746 (4,146 ) (400 ) Cash provided by operating activities 75,475 (61 ) 75,414 Effect of exchange rate changes on cash and cash equivalents 1,463 113 1,576 INCREASE IN CASH AND CASH EQUIVALENTS 47,285 52 47,337 CASH AND CASH EQUIVALENTS-Beginning of period 139,403 (52 ) 139,351 SUPPLEMENTARY DISCLOSURES OF CASH FLOW INFORMATION: Deferred taxes related to convertible senior notes $ — $ (3,827 ) $ (3,827 ) Adjustment to redemption value of non-controlling interests $ (1,143 ) $ 1,129 $ (14 ) Nine Months Ended September 30, 2014 As Reported Adjustments As Restated CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 15,000 $ (6,769 ) $ 8,231 Adjustments to reconcile net income to cash provided by / (used for) operating activities Depreciation and amortization 10,566 (515 ) 10,051 Deferred taxes (2,430 ) (58 ) (2,488 ) Changes in operating assets and liabilities: Cash and securities held for customers (122,523 ) (854 ) (123,377 ) Receivables from brokers 61,316 55 61,371 Other assets (8,595 ) 672 (7,923 ) Payables to customers 122,523 754 123,277 Accrued compensation and benefits (2,745 ) 843 (1,902 ) Accrued expenses and other liabilities (945 ) 10,361 9,416 Income tax payable 1,393 (5,072 ) (3,679 ) Cash provided by operating activities 84,298 (583 ) 83,715 Effect of exchange rate changes on cash and cash equivalents (2,903 ) (73 ) (2,976 ) INCREASE IN CASH AND CASH EQUIVALENTS 42,301 (656 ) 41,645 CASH AND CASH EQUIVALENTS—End of period $ 82,172 $ (656 ) $ 81,516 SUPPLEMENTARY DISCLOSURES OF CASH FLOW INFORMATION: Adjustment to redemption value of non-controlling interests $ (1,066 ) $ (878 ) $ (1,944 )

FAIR VALUE INFORMATION (Tables)

FAIR VALUE INFORMATION (Tables)	9 Months Ended
	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [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 $ — $ 147,645 $ — $ 147,645 Broker derivative contracts — (29,077 ) — (29,077 ) Money market accounts 25,158 — — 25,158 Certificates of deposit 174 — — 174 Investment in gold 113 — 113 Contingent consideration — (3,824 ) (3,824 ) Total $ 25,445 $ 118,568 $ (3,824 ) $ 140,189 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, 2015 to September 30, 2015 (amounts in thousands): Liabilities Contingent Consideration Balance at January 1, 2015 $ 9,974 Gains included in earnings - adjustment to fair value of contingent consideration (4,466 ) Contingent consideration payments (2,063 ) Gains included in earnings - currency revaluation (113 ) Losses included in earnings - discount amortization 492 Balance at September 30, 2015 $ 3,824
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 September 30, 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 $ 148,304 $ 148,304 $ — $ 148,304 $ — Financial Liabilities: Payables to customers 1,134,021 1,134,021 — 1,134,021 — Convertible senior notes 120,866 121,103 — 121,103 — 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)	9 Months Ended
	Sep. 30, 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 condensed consolidated balance sheets (amounts in thousands): September 30, 2015 Derivative open positions at fair value Gross assets Gross liabilities Net assets Derivative Instruments: Foreign currency exchange contracts $ 125,047 $ 54,060 $ 70,987 CFD contracts 66,759 28,759 38,000 Metals contracts 15,509 5,928 9,581 Total $ 207,315 $ 88,747 $ 118,568 September 30, 2015 Net assets/liabilities at fair value Cash Collateral Derivative open positions Presented in the balance sheet Derivative Assets/Liabilities: Receivables from brokers $ 148,304 $ (29,077 ) $ 119,227 Payables to customers $ 1,134,021 $ 147,645 $ 986,376 December 31, 2014 Derivative open positions at fair value Gross Gross Net assets 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 Net assets/liabilities at fair value Cash Collateral Derivative 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 condensed consolidated balance sheets (amounts in thousands): September 30, 2015 Total contracts in long positions Total contracts in short positions Derivative Instruments: Foreign currency exchange contracts 3,379,580 2,770,520 CFD contracts 136,600 285,838 Metals contracts 844 441 Total 3,517,024 3,056,799 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/(losses) with respect to derivative instruments reflected in Retail revenue in the accompanying condensed consolidated statements of operations and comprehensive income for the three and nine months ended September 30, 2015 and 2014 were as follows (amounts in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Derivative Instruments: Foreign currency exchange contracts $ 30,436 $ 35,144 $ 128,096 $ 90,256 CFD contracts 56,071 12,074 93,936 29,567 Metals contracts 9,170 16,121 20,696 30,988 Total $ 95,677 $ 63,339 $ 242,728 $ 150,811

RECEIVABLES FROM BROKERS (Table

RECEIVABLES FROM BROKERS (Tables)	9 Months Ended
	Sep. 30, 2015
Receivables [Abstract]
Receivable from Brokers	Amounts receivable from brokers consisted of the following as of (amounts in thousands): September 30, 2015 December 31, 2014 Required collateral $ 144,556 $ 95,599 Futures brokers - Restricted 3,748 38,592 Open positions (29,077 ) 717 $ 119,227 $ 134,908

PROPERTY AND EQUIPMENT (Tables)

PROPERTY AND EQUIPMENT (Tables)	9 Months Ended
	Sep. 30, 2015
Property, Plant and Equipment [Abstract]
Property and Equipment Including Leasehold Improvements and Capitalized Software Development Costs	Property and equipment consisted of the following as of (amounts in thousands): September 30, 2015 December 31, 2014 Software $ 41,229 $ 30,351 Computer equipment 13,549 8,516 Leasehold improvements 11,356 6,719 Telephone equipment 794 719 Office equipment 2,113 2,345 Furniture and fixtures 1,907 1,044 Web site development costs 668 646 71,616 50,340 Less: Accumulated depreciation and amortization (42,401 ) (31,544 ) Property and equipment, net $ 29,215 $ 18,796

INTANGIBLE ASSETS AND GOODWIL32

INTANGIBLE ASSETS AND GOODWILL (Tables)	9 Months Ended
	Sep. 30, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	The Company's various intangible assets consisted of the following as of (amounts in thousands): September 30, 2015 December 31, 2014 Intangibles Gross Accumulated Net Gross Accumulated Net Customer lists $ 53,303 $ (11,080 ) $ 42,223 $ 22,945 $ (7,152 ) $ 15,793 Technology 75,069 (23,291 ) 51,778 48,376 (4,671 ) 43,705 Trademarks 8,483 (1,385 ) 7,098 1,793 (847 ) 946 Total finite lived intangibles 136,855 (35,756 ) 101,099 73,114 (12,670 ) 60,444 Trademarks not subject to amortization (1) 362 — 362 362 — 362 Total intangibles (2) $ 137,217 $ (35,756 ) $ 101,461 $ 73,476 $ (12,670 ) $ 60,806 (1) These indefinite-life trademarks relate to the Forex.com and foreignexchange.com domain names. Management determined there was no legal, regulatory or technological limitation on the domains' useful lives. The trademarks' values are evaluated annually in the Company's impairment test for intangible assets. (2) The increase in total intangibles for the nine months ended September 30, 2015 was primarily due to the customer lists, technology and trademarks acquired as part of the City Index acquisition. See Note 10 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 gross identifiable intangible assets as of September 30, 2015: Intangible Assets Amount (in thousands) Weighted average amortization period Customer lists $ 53,303 8.1 years Technology 75,069 8.9 years Trademarks (1) 8,845 6.7 years $ 137,217 (1) Trademarks with indefinite lives, as described above, comprise $0.4 million of the gross $8.8 million of trademarks.

OTHER ASSETS (Tables)

OTHER ASSETS (Tables)	9 Months Ended
	Sep. 30, 2015
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Other Assets	Other assets consisted of the following as of (amounts in thousands): September 30, 2015 December 31, 2014 Vendor and security deposits $ 9,414 $ 3,373 Current tax receivable 8,339 5,163 Deferred tax assets 14,774 6,308 Indemnification asset — 8,792 GTX trade receivables 3,675 4,190 Customer debit positions 6,951 6,594 Allowance for doubtful accounts (5,898 ) (4,555 ) Miscellaneous receivables and other assets 1,461 3,900 $ 38,716 $ 33,765

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	9 Months Ended
	Sep. 30, 2015
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Schedule of Restructuring Costs	For the Nine Months Ended September 30, 2015 Restructuring liability as of January 1, 2015 $ 374 2015 restructuring expenses 1,935 Payments made in 2015 (1,926 ) Restructuring liability as of September 30, 2015 $ 383
City Index
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Preliminary Purchase Price	The preliminary purchase price was derived as follows (amounts in thousands): Cash $ 6,102 Convertible senior notes 65,000 Common stock issued (based on the April 1, 2015 quoted price of $9.77) 48,280 Total purchase price $ 119,382
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The preliminary purchase price of City Index was allocated to the fair value of various assets and liabilities as follows (amounts in thousands): Cash and cash equivalents $ 32,991 Cash and securities held for customers 265,012 Receivable from brokers 35,974 Property and equipment 10,411 Prepaid assets 3,972 Other current assets 541 Total tangible assets 348,901 Total liabilities assumed 303,280 Net assets acquired 45,621 Identifiable intangible assets: Customer list 30,273 Trade name 6,645 Technology 26,157 Intangible assets, net 63,075 Goodwill $ 10,686
Pro Forma Information	Unaudited pro forma income statement line items for the nine months ended September 30, 2015 and three and nine months ended September 30, 2014 were as follows (amounts in thousands): For the Nine Months Ended September 30, For the Three Months Ended September 30, For the Nine Months Ended September 30, 2015 2014 2014 REVENUE: Total non-interest revenue $ 369,249 $ 143,228 $ 347,860 Interest revenue 1,019 571 1,983 Interest expense 846 189 411 Total net interest revenue 173 382 1,572 Net revenue 369,422 143,610 349,432 EXPENSES: Depreciation and amortization 8,280 6,505 12,694 Purchased intangible amortization 12,757 4,533 11,694 Other expense items 333,565 109,085 313,871 Total operating expense 354,602 120,123 338,259 OPERATING PROFIT 14,820 23,487 11,173 Interest on long term borrowings 7,671 2,541 7,526 INCOME BEFORE INCOME TAX BENEFIT 7,149 20,946 3,647 Income tax expense 11,207 11,939 7,326 NET INCOME (4,058 ) 9,007 (3,679 ) Net income attributable to non-controlling interests 1,343 785 987 Net income applicable to Gain Capital Holdings, Inc. $ (5,401 ) $ 8,222 $ (4,666 )
Galvan Research and Trading, Ltd.
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Preliminary Purchase Price	The purchase price was derived as follows (amounts in thousands): Cash $ 9,732 Contingent payment 10,540 Total purchase price $ 20,272
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	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 current 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
Global Assets Advisors, LLC
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Preliminary 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
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	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 current 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 Ag Marketing, LLC
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	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 assets acquired (367 ) Identifiable intangible assets: Customer list 3,900 Trade name 90 Intangible assets, net 3,990 Goodwill $ 3,806
Top Third Ag Marketing, LLC, Global Assets Advisors, LLC, and Galvan Research and Trading, Ltd [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Pro Forma Information	Unaudited pro forma income statement line items for the nine months ended September 30, 2014 were as follows (amounts in thousands): For the Nine Months Ended September 30, 2014 REVENUE: Total non-interest revenue $ 260,794 Interest revenue 1,130 Interest expense 859 Total net interest revenue 271 Net revenue 261,065 EXPENSES: Depreciation and amortization 5,227 Purchased intangible amortization 5,421 Other expense items 227,917 Total operating expense 238,565 OPERATING PROFIT 22,500 Interest on long term borrowings 4,390 INCOME BEFORE INCOME TAX EXPENSE 18,110 Income tax expense 12,749 NET INCOME 5,361 Net income attributable to non-controlling interests 981 Net income applicable to Gain Capital Holdings, Inc. $ 4,380

NON-CONTROLLING INTERESTS (Tabl

NON-CONTROLLING INTERESTS (Tables)	9 Months Ended
	Sep. 30, 2015
Noncontrolling Interest [Abstract]
Summary of redeemable noncontrolling interest treatment	The table below reflects the non-controlling interests' effects on the Company's financial statements (amounts in thousands): Redeemable non-controlling interests January 1, 2015 $ 11,338 Adjustment to the redemption value of non-controlling interests 14 Net income attributable to non-controlling interests 1,343 Distributions to non-controlling interest holders (1,035 ) September 30, 2015 $ 11,660

CONVERTIBLE SENIOR NOTES Conv36

CONVERTIBLE SENIOR NOTES Convertible Senior Notes (Tables)	9 Months Ended
	Sep. 30, 2015
Debt Disclosure [Abstract]
Schedule of Liability and Equity Components of Convertible Debt	The balances of the liability and equity components as of September 30, 2015 and December 31, 2014 were as follows (amounts in thousands): September 30, 2015 December 31, 2014 Liability component - principal $ 140,000 $ 80,000 Deferred bond discount (19,134 ) (11,633 ) Liability component - net carrying value $ 120,866 $ 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 on long term borrowings in the condensed consolidated statements of operations and comprehensive income, was as follows (amounts in thousands): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2015 2014 2015 2014 Interest expense - stated coupon rate $ 1,444 $ 825 $ 3,713 $ 2,475 Interest expense - amortization of deferred bond discount and costs 1,038 671 2,648 1,915 Total interest expense - convertible senior notes $ 2,482 $ 1,496 $ 6,361 $ 4,390

EARNINGS PER COMMON SHARE (Tabl

EARNINGS PER COMMON SHARE (Tables)	9 Months Ended
	Sep. 30, 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 Three Months Ended September 30, For the Nine Months Ended September 30, 2015 2014 2015 2014 Net income applicable to GAIN Capital Holdings, Inc. $ 973 $ 10,896 $ (681 ) $ 7,244 Adjustment to the redemption value of non-controlling interests (1) 1,428 (1,747 ) (14 ) (1,944 ) Net income available to common shareholders $ 2,401 $ 9,149 $ (695 ) $ 5,300 Weighted average common shares outstanding: Basic weighted average common shares outstanding 49,149,102 41,038,782 47,163,814 40,243,330 Effect of dilutive securities: Stock options 320,770 562,187 471,613 786,956 RSUs/RSAs 448,835 1,922,893 394,007 2,024,673 Diluted weighted average common shares outstanding 49,918,707 43,523,862 47,163,814 43,054,959 Net earnings per common share: Basic $ 0.05 $ 0.22 $ (0.01 ) $ 0.13 Diluted $ 0.05 $ 0.21 $ (0.01 ) $ 0.12 (1) During the nine months ended September 30, 2015 and 2014, the Company concluded that the value of the put options related to the Company's redeemable non-controlling interests in GAA and Top Third was less than redemption value. The adjustment to increase the carrying value reduces earnings available to the Company's shareholders for purposes of calculating basic and diluted earnings per common share.

REGULATORY REQUIREMENTS (Tables

REGULATORY REQUIREMENTS (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 2015 and the actual amounts of capital that were maintained (amounts in millions): Entity Name Minimum Capital Excess Percent of GAIN Capital Group, LLC $ 25.3 $ 42.3 $ 17.0 167 % GAIN Capital-Forex.com U.K., Ltd. 32.5 81.7 49.2 251 % GAIN Capital Japan Co., Ltd. 1.4 9.5 8.1 679 % GAIN Capital-Forex.com Hong Kong, Ltd. 1.9 2.7 0.8 142 % GAIN Capital Forex.com Australia, Pty. Ltd. 0.7 2.2 1.5 314 % Galvan Research and Trading, Ltd. 0.7 4.4 3.7 629 % 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. 0.1 0.2 0.1 200 % GAIN Capital UK, Ltd. 1 52.3 111.5 59.2 213 % GAIN Capital Singapore Pte. Ltd. 1 0.7 7.1 6.4 1,014 % GAIN Capital Australia Pty Ltd. 1 0.7 2.0 1.3 286 % Global Assets Advisors, LLC 0.1 1.3 1.2 1,300 % Total $ 116.7 $ 266.7 $ 150.0 229 % (1) Entity acquired as part of the City Index acquisition.

RESTATEMENT - Additional Inform

RESTATEMENT - Additional Information (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retained earnings	$ 111,941		$ 119,775
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retained earnings	$ 130,566		$ 130,984
Out of Period Adjustment | Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Adjustment to the redemption value of noncontrolling interests		$ 1,300
Out of Period Adjustment | As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retained earnings		$ (1,300)

RESTATEMENT - Condensed Consoli

RESTATEMENT - Condensed Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cash and cash equivalents	$ 186,688	$ 139,351	$ 81,516	$ 39,871
Goodwill	41,631	33,579
Other assets, net of allowance for doubtful accounts	38,716	33,765
Total assets	1,512,879	1,183,301
Accrued expenses and other liabilities	72,422	76,195
Income tax payable	6,789	1,010
Total liabilities	1,195,555	922,043
Redeemable noncontrolling interests	11,660	11,338
Accumulated other comprehensive loss	(1,747)	(1,513)
Additional paid-in capital	214,334	148,378
Retained earnings	111,941	119,775
Total shareholders’ equity	305,664	249,920
Total liabilities and shareholders’ equity	1,512,879	1,183,301
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cash and cash equivalents		139,403	82,172
Goodwill	44,817	34,567
Other assets, net of allowance for doubtful accounts	38,854	35,311
Total assets	1,516,203	1,185,887
Accrued expenses and other liabilities	51,132	64,476
Income tax payable	5,186	1,470
Total liabilities	1,172,662	910,784
Redeemable noncontrolling interests		10,209
Accumulated other comprehensive loss	(2,288)	(2,054)
Additional paid-in capital	222,467	152,684
Retained earnings	130,566	130,984
Total shareholders’ equity	331,881	264,894
Total liabilities and shareholders’ equity	1,516,203	1,185,887
Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cash and cash equivalents		(52)	$ (656)
Tax Adjustment | Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cash and cash equivalents		0
Goodwill	(3,186)	(988)
Other assets, net of allowance for doubtful accounts	(138)	917
Total assets	(3,324)	(71)
Accrued expenses and other liabilities	21,290	12,170
Income tax payable	1,603	1,603
Total liabilities	22,893	13,773
Redeemable noncontrolling interests		0
Accumulated other comprehensive loss	541	541
Additional paid-in capital	(8,133)	(4,306)
Retained earnings	(18,625)	(10,079)
Total shareholders’ equity	(26,217)	(13,844)
Total liabilities and shareholders’ equity	(3,324)	(71)
Other Adjustments | Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cash and cash equivalents		(52)
Goodwill	0	0
Other assets, net of allowance for doubtful accounts	0	(2,463)
Total assets	0	(2,515)
Accrued expenses and other liabilities	0	(451)
Income tax payable	0	(2,063)
Total liabilities	0	(2,514)
Redeemable noncontrolling interests		1,129
Accumulated other comprehensive loss	0	0
Additional paid-in capital	0	0
Retained earnings	0	(1,130)
Total shareholders’ equity	0	(1,130)
Total liabilities and shareholders’ equity	$ 0	$ (2,515)

RESTATEMENT - Condensed Conso41

RESTATEMENT - Condensed Consolidated Statement of Income (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retail revenue	$ 118,981	$ 89,771	$ 300,483	$ 222,362
Total non-interest revenue	128,045	102,786	332,465	253,202
Interest expense	219	189	846	411
Total net interest revenue	66	170	90	712
Net revenue	128,111	102,956	332,555	253,914
Employee compensation and benefits	28,885	25,505	81,700	71,188
Referral fees	28,607	24,640	84,724	65,745
Trading expenses	8,959	6,032	24,053	20,089
General and administrative	16,754	8,945	40,270	28,310
Depreciation and amortization	2,925	1,717	7,638	5,210
Restructuring expenses	0	436	1,935	2,126	$ 1,200
Total operating expense	116,123	80,573	317,699	231,226
OPERATING PROFIT	11,988	22,383	14,856	22,688
INCOME BEFORE INCOME TAX EXPENSE	9,418	20,887	8,230	18,298
Income tax expense	7,862	9,206	7,568	10,067
NET INCOME	1,556	11,681	662	8,231
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.	973	10,896	(681)	7,244
Foreign currency translation adjustment	(7,526)	(2,988)	(234)	(269)
NET COMPREHENSIVE INCOME/(LOSS) APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.	$ (6,553)	$ 7,908	$ (915)	$ 6,975
Basic (usd per share)	$ 0.05	$ 0.22	$ (0.01)	$ 0.13
Diluted (usd per share)	$ 0.05	$ 0.21	$ (0.01)	$ 0.12
Basic (shares)	49,149,102	41,038,782	47,163,814	40,243,330
Diluted (shares)	49,918,707	43,523,862	47,163,814	43,054,959
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retail revenue	$ 118,801	$ 90,373	$ 300,376	$ 223,138
Total non-interest revenue	127,865	103,388	332,358	253,978
Interest expense		97		319
Total net interest revenue		262		804
Net revenue	127,931	103,650	332,448	254,782
Employee compensation and benefits	29,088			71,440
Referral fees				65,865
Trading expenses	8,779
General and administrative		9,056	40,219	28,113
Depreciation and amortization				5,725
Restructuring expenses				1,007
Total operating expense	116,146	80,684	317,648	230,797
OPERATING PROFIT	11,785	22,966	14,800	23,985
INCOME BEFORE INCOME TAX EXPENSE	9,215	21,470	8,174	19,595
Income tax expense	328	5,340	(978)	4,595
NET INCOME	8,887	16,130	9,152	15,000
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.	$ 8,304	$ 15,345	7,809	$ 14,013
NET COMPREHENSIVE INCOME/(LOSS) APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.			$ 7,575
Basic (usd per share)	$ 0.20	$ 0.35	$ 0.14	$ 0.32
Diluted (usd per share)	$ 0.20	$ 0.33	$ 0.14	$ 0.30
Basic (shares)	49,147,102		47,163,132
Diluted (shares)	49,891,101		48,028,752
Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
NET INCOME			$ (8,490)	$ (6,769)
Tax Adjustment | Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retail revenue	$ 0	$ 0	0	0
Total non-interest revenue	0	0	0	0
Interest expense		0		0
Total net interest revenue		0		0
Net revenue	0	0	0	0
Employee compensation and benefits	0			0
Referral fees				0
Trading expenses	0
General and administrative		0	0	0
Depreciation and amortization				0
Restructuring expenses				0
Total operating expense	0	0	0	0
OPERATING PROFIT	0	0	0	0
INCOME BEFORE INCOME TAX EXPENSE	0	0	0	0
Income tax expense	7,534	3,866	8,546	5,472
NET INCOME	(7,534)	(3,866)	(8,546)	(5,472)
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.	(7,534)	(3,866)	(8,546)	(5,472)
NET COMPREHENSIVE INCOME/(LOSS) APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.			(8,546)
Other Adjustments | Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retail revenue	180	(602)	107	(776)
Total non-interest revenue	180	(602)	107	(776)
Interest expense		92		92
Total net interest revenue		(92)		(92)
Net revenue	180	(694)	107	(868)
Employee compensation and benefits	(203)			(252)
Referral fees				(120)
Trading expenses	180
General and administrative		(111)	51	197
Depreciation and amortization				(515)
Restructuring expenses				1,119
Total operating expense	(23)	(111)	51	429
OPERATING PROFIT	203	(583)	56	(1,297)
INCOME BEFORE INCOME TAX EXPENSE	$ 203	(583)	$ 56	(1,297)
Income tax expense		0		0
NET INCOME	$ 203	(583)	$ 56	(1,297)
NET INCOME APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.	$ 203	$ (583)	56	$ (1,297)
NET COMPREHENSIVE INCOME/(LOSS) APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.			$ 56

RESTATEMENT - Condensed Stateme

RESTATEMENT - Condensed Statement of Changes in Shareholders' Equity (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Shareholders' equity	$ 305,664	$ 249,920
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Shareholders' equity	331,881	264,894
Additional Paid in Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Shareholders' equity	214,334	148,378
Additional Paid in Capital | As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Shareholders' equity	222,467	152,684
Retained Earnings
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Shareholders' equity	111,941	119,775
Retained Earnings | As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Shareholders' equity	130,566	130,984
Accumulated Other Comprehensive (Loss)
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Shareholders' equity	(1,747)	(1,513)
Accumulated Other Comprehensive (Loss) | As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Shareholders' equity	$ (2,288)	$ (2,054)

RESTATEMENT - Condensed State43

RESTATEMENT - Condensed Statement of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income	$ 1,556	$ 11,681	$ 662	$ 8,231
Depreciation and amortization			18,326	10,051
Deferred taxes			(5,328)	(2,488)
Cash and securities held for customers			29,287	(123,377)
Receivables from brokers			50,942	61,371
Other assets			(3,722)	(7,923)
Payables to customers			(29,287)	123,277
Accrued compensation and benefits			(10,853)	(1,902)
Accrued expenses and other liabilities			586	9,416
Income tax payable			(400)	(3,679)
Cash provided by operating activities			75,414	83,715
Effect of exchange rate changes on cash and cash equivalents			1,576	(2,976)
INCREASE IN CASH AND CASH EQUIVALENTS			47,337	41,645
CASH AND CASH EQUIVALENTS—End of period	186,688	81,516	186,688	81,516	$ 139,351	$ 39,871
Deferred taxes related to convertible senior notes			(3,827)
Adjustment to redemption value of non-controlling interests			(14)	(1,944)
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income	$ 8,887	16,130	9,152	15,000
Depreciation and amortization				10,566
Deferred taxes			(5,797)	(2,430)
Cash and securities held for customers			30,064	(122,523)
Receivables from brokers			51,035	61,316
Other assets			(6,114)	(8,595)
Payables to customers			(30,064)	122,523
Accrued compensation and benefits			(10,860)	(2,745)
Accrued expenses and other liabilities			(9,214)	(945)
Income tax payable			3,746	1,393
Cash provided by operating activities			75,475	84,298
Effect of exchange rate changes on cash and cash equivalents			1,463	(2,903)
INCREASE IN CASH AND CASH EQUIVALENTS			47,285	42,301
CASH AND CASH EQUIVALENTS—End of period		82,172		82,172	139,403
Deferred taxes related to convertible senior notes			0
Adjustment to redemption value of non-controlling interests			(1,143)	(1,066)
Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income			(8,490)	(6,769)
Depreciation and amortization				(515)
Deferred taxes			469	(58)
Cash and securities held for customers			(777)	(854)
Receivables from brokers			(93)	55
Other assets			2,392	672
Payables to customers			777	754
Accrued compensation and benefits			7	843
Accrued expenses and other liabilities			9,800	10,361
Income tax payable			(4,146)	(5,072)
Cash provided by operating activities			(61)	(583)
Effect of exchange rate changes on cash and cash equivalents			113	(73)
INCREASE IN CASH AND CASH EQUIVALENTS			52	(656)
CASH AND CASH EQUIVALENTS—End of period		$ (656)		(656)	$ (52)
Deferred taxes related to convertible senior notes			(3,827)
Adjustment to redemption value of non-controlling interests			$ 1,129	$ (878)

FAIR VALUE INFORMATION - Additi

FAIR VALUE INFORMATION - Additional Information (Detail) $ in Millions	Dec. 31, 2014USD ($)
Global Futures & Forex Ltd
Business Acquisition [Line Items]
Contingent consideration liability	$ 20

FAIR VALUE INFORMATION - Assets

FAIR VALUE INFORMATION - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Recurring [Member] - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets (liabilities)	$ 140,189	$ 114,294
Customer open contracts and other positions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	147,645	102,722
Broker open contracts and other positions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets		717
Liabilities	(29,077)
Money market accounts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	25,158	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	113	118
Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities	(3,824)	(9,974)
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets (liabilities)	25,445	20,829
Level 1 | Customer open contracts and other positions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Level 1 | Broker open contracts and other positions
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	25,158	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	113	118
Level 1 | Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets (liabilities)	118,568	103,439
Level 2 | Customer open contracts and other positions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	147,645	102,722
Level 2 | Broker open contracts and other positions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets		717
Liabilities	(29,077)
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)	$ (3,824)	(9,974)
Level 3 | Customer open contracts and other positions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Level 3 | Broker open contracts and other positions
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
Level 3 | Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities	$ (3,824)	$ (9,974)

FAIR VALUE INFORMATION - Reconc

FAIR VALUE INFORMATION - Reconciliation of Unobservable Level 3 Inputs (Details) - Contingent Payments [Member] $ in Thousands	9 Months Ended
	Sep. 30, 2015USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 9,974
Gains included in earnings - adjustment to fair value of contingent consideration	(4,466)
Contingent consideration payments	(2,063)
Gains included in earnings - currency revaluation	(113)
Losses included in earnings - discount amortization	492
Ending balance	$ 3,824

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	Sep. 30, 2015	Dec. 31, 2014
Financial Assets:
Receivable from banks and brokers	$ 119,227	$ 134,908
Financial Liabilities:
Convertible senior notes	120,866	68,367
Derivative Assets
Financial Assets:
Receivable from banks and brokers		134,908
Derivative Assets | Level 2
Financial Assets:
Receivable from banks and brokers	148,304	134,191
Derivative Assets | Carrying Value
Financial Assets:
Receivable from banks and brokers	148,304	134,191
Derivative Assets | Fair Value
Financial Assets:
Receivable from banks and brokers	148,304	134,191
Derivative Liabilities
Financial Liabilities:
Payables to customers	1,134,021	862,281
Derivative Liabilities | Level 2
Financial Liabilities:
Payables to customers	1,134,021	862,281
Convertible senior notes	121,103	66,440
Accrued Liabilities, Current		20,000
Derivative Liabilities | Carrying Value
Financial Liabilities:
Payables to customers	1,134,021	862,281
Convertible senior notes	120,866	68,367
Accrued Liabilities, Current		20,000
Derivative Liabilities | Fair Value
Financial Liabilities:
Payables to customers	1,134,021	862,281
Convertible senior notes	$ 121,103	66,440
Accrued Liabilities, Current		$ 20,000

DERIVATIVES Fair Values of Deri

DERIVATIVES Fair Values of Derivative Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Gross amounts of assets for derivative open positions at fair value	$ 207,315	$ 228,509
Gross amounts of liability for derivative open positions at fair value	88,747	125,070
Net amounts of assets/liabilities for derivative open positions at fair value	118,568	103,439
Receivable from banks and brokers	119,227	134,908
Net amounts of assets/liabilities presented in the balance sheet		759,559
Payables to customers	986,376	759,559
Derivative Assets
Derivatives, Fair Value [Line Items]
Receivables from brokers	148,304	134,191
Net amounts of assets/liabilities for derivative open positions at fair value	(29,077)	717
Receivable from banks and brokers		134,908
Derivative Liabilities
Derivatives, Fair Value [Line Items]
Payables to customers	1,134,021	862,281
Net amounts of assets/liabilities for derivative open positions at fair value	147,645	102,722
Foreign currency exchange contracts
Derivatives, Fair Value [Line Items]
Gross amounts of assets for derivative open positions at fair value	125,047	168,034
Gross amounts of liability for derivative open positions at fair value	54,060	93,057
Net amounts of assets/liabilities for derivative open positions at fair value	70,987	74,977
CFD contracts
Derivatives, Fair Value [Line Items]
Gross amounts of assets for derivative open positions at fair value	66,759	44,329
Gross amounts of liability for derivative open positions at fair value	28,759	24,420
Net amounts of assets/liabilities for derivative open positions at fair value	38,000	19,909
Metal contracts
Derivatives, Fair Value [Line Items]
Gross amounts of assets for derivative open positions at fair value	15,509	16,146
Gross amounts of liability for derivative open positions at fair value	5,928	7,593
Net amounts of assets/liabilities for derivative open positions at fair value	9,581	8,553
Level 2 | Derivative Assets
Derivatives, Fair Value [Line Items]
Receivable from banks and brokers	148,304	134,191
Level 2 | Derivative Liabilities
Derivatives, Fair Value [Line Items]
Payables to customers	1,134,021	862,281
Carrying Value | Derivative Assets
Derivatives, Fair Value [Line Items]
Receivable from banks and brokers	148,304	134,191
Carrying Value | Derivative Liabilities
Derivatives, Fair Value [Line Items]
Payables to customers	$ 1,134,021	$ 862,281

DERIVATIVES Notional Value of D

DERIVATIVES Notional Value of Derivative Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Notional amounts of derivative open long positions
Derivative [Line Items]
Notional amounts of derivative open long positions	$ 3,517,024	$ 4,021,423
Notional amounts of derivative open long positions | Foreign currency exchange contracts
Derivative [Line Items]
Notional amounts of derivative open long positions	3,379,580	3,147,518
Notional amounts of derivative open long positions | CFD contracts
Derivative [Line Items]
Notional amounts of derivative open long positions	136,600	873,070
Notional amounts of derivative open long positions | Metal contracts
Derivative [Line Items]
Notional amounts of derivative open long positions	844	835
Notional amounts of derivative open short positions
Derivative [Line Items]
Notional amounts of derivative open long positions	3,056,799	2,690,129
Notional amounts of derivative open short positions | Foreign currency exchange contracts
Derivative [Line Items]
Notional amounts of derivative open long positions	2,770,520	2,679,041
Notional amounts of derivative open short positions | CFD contracts
Derivative [Line Items]
Notional amounts of derivative open long positions	285,838	10,753
Notional amounts of derivative open short positions | Metal contracts
Derivative [Line Items]
Notional amounts of derivative open long positions	$ 441	$ 335

DERIVATIVES Net Gains (Losses)

DERIVATIVES Net Gains (Losses) with Respect to Derivative Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative [Line Items]
Net gains (losses) on derivative instruments, total	$ 95,677	$ 63,339	$ 242,728	$ 150,811
Foreign currency exchange contracts
Derivative [Line Items]
Net gains (losses) on derivative instruments		35,144		90,256
CFD contracts
Derivative [Line Items]
Net gains (losses) on derivative instruments		12,074		29,567
Metal contracts
Derivative [Line Items]
Net gains (losses) on derivative instruments		$ 16,121		$ 30,988

RECEIVABLES FROM BROKERS (Detai

RECEIVABLES FROM BROKERS (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Receivables from Brokerage Clients [Line Items]
Receivable from banks and brokers	$ 119,227	$ 134,908
Required collateral
Receivables from Brokerage Clients [Line Items]
Receivable from banks and brokers	144,556	95,599
Excess From Futures Broker - Restricted [Member]
Receivables from Brokerage Clients [Line Items]
Receivable from banks and brokers	3,748	38,592
Open Position
Receivables from Brokerage Clients [Line Items]
Receivable from banks and brokers	$ (29,077)	$ 717

PROPERTY AND EQUIPMENT (Details

PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and equipment	$ 71,616		$ 71,616		$ 50,340
Less: Accumulated depreciation and amortization	(42,401)		(42,401)		(31,544)
Property and equipment, net	29,215		29,215		18,796
Depreciation and amortization expense	2,925	$ 1,717	7,638	$ 5,210
Integration costs related to property and equipment	1,800		3,700
Software
Property, Plant and Equipment [Line Items]
Property and equipment	41,229		41,229		30,351
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment	13,549		13,549		8,516
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	11,356		11,356		6,719
Telephone equipment
Property, Plant and Equipment [Line Items]
Property and equipment	794		794		719
Office equipment
Property, Plant and Equipment [Line Items]
Property and equipment	2,113		2,113		2,345
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment	1,907		1,907		1,044
Website development costs
Property, Plant and Equipment [Line Items]
Property and equipment	$ 668		$ 668		$ 646

INTANGIBLE ASSETS AND GOODWIL53

INTANGIBLE ASSETS AND GOODWILL (Details) - USD ($) $ in Thousands	Jul. 10, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Business Acquisition [Line Items]
Common stock issued as consideration for asset and business acquisitions				$ 48,280	$ 6,493
Purchased intangible amortization		$ 4,280	$ 2,228	10,688	$ 4,841
Integration costs related to intangible assets		6,500		13,000
Future amortization expense expected to be recorded as integration expense		6,500		6,500
Goodwill		$ 41,631		41,631		$ 33,579
Increase in goodwill				$ 8,000
Forexster Limited Asset Acquisition [Member]
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

INTANGIBLE ASSETS AND GOODWIL54

INTANGIBLE ASSETS AND GOODWILL Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Intangible Assets by Major Class [Line Items]
Finite-lived intangible assets, gross	$ 136,855	$ 73,114
Accumulated Amortization	(35,756)	(12,670)
Finite-lived intangible assets, net	101,099	60,444
Total intangibles, gross	137,217	73,476
Intangible assets, net	101,461	60,806
Future Annual Estimated Purchased Intangible Amortization Expense
2,015	10,761
2,016	14,154
2,017	12,861
2,018	11,760
2,019	11,179
Thereafter	40,384
Trademark
Intangible Assets by Major Class [Line Items]
Indefinite-lived intangible assets	362	362
Customer list
Intangible Assets by Major Class [Line Items]
Finite-lived intangible assets, gross	53,303	22,945
Accumulated Amortization	(11,080)	(7,152)
Finite-lived intangible assets, net	42,223	15,793
Total intangibles, gross	$ 53,303
Weighted average amortization period	8 years 1 month
Technology
Intangible Assets by Major Class [Line Items]
Finite-lived intangible assets, gross	$ 75,069	48,376
Accumulated Amortization	(23,291)	(4,671)
Finite-lived intangible assets, net	51,778	43,705
Total intangibles, gross	$ 75,069
Weighted average amortization period	8 years 11 months
Trademark
Intangible Assets by Major Class [Line Items]
Finite-lived intangible assets, gross	$ 8,483	1,793
Accumulated Amortization	(1,385)	(847)
Finite-lived intangible assets, net	7,098	$ 946
Total intangibles, gross	$ 8,845
Weighted average amortization period	6 years 8 months

OTHER ASSETS (Details)

OTHER ASSETS (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Vendor and security deposits	$ 9,414	$ 3,373
Current tax receivable	8,339	5,163
Deferred tax assets	14,774	6,308
Indemnification asset	0	8,792
GTX Trade Receivables	3,675	4,190
Customer debit positions	6,951	6,594
Allowance for uncollectible customer debit positions	(5,898)	(4,555)
Miscellaneous receivables	1,461	3,900
Other assets, net	38,716	33,765
Global Futures & Forex Ltd
Business Acquisition [Line Items]
Holdback amount	$ 20,000
Indemnification Asset		$ 8,800

RELATED PARTY TRANSACTIONS - Ad

RELATED PARTY TRANSACTIONS - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Related Party Transaction [Line Items]
Payables to customers	$ 986,376	$ 759,559
Management
Related Party Transaction [Line Items]
Payables to customers	7,800	$ 3,600
IPGL Limited
Related Party Transaction [Line Items]
Payables to customers	$ 5,400

ACQUISITIONS - Additional Infor

ACQUISITIONS - Additional Information (Details) - USD ($)	Apr. 01, 2015	Jul. 31, 2014	Mar. 31, 2014	Sep. 30, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Decrease in goodwill				$ (8,000,000)
Customer list
Business Acquisition [Line Items]
Weighted average amortization period				8 years 1 month
Convertible Debt [Member] | Convertible Notes Due 2020 [Member]
Business Acquisition [Line Items]
Stated interest rate	4.125%
Principal amount	$ 60,000,000
City Index
Business Acquisition [Line Items]
Cash payment	6,102,000
Cash to be held in escrow	$ 1,000,000
Number of shares issued due to acquisitions	5,319,149
Liabilities incurred	$ 65,000,000
Revenues since acquisition date				$ 79,200,000
Expenses since acquisition date				63,700,000
Income before taxes since acquisition date				$ 15,500,000
Payments to settle inter-company liabilities	22,400,000
Total purchase price	$ 119,382,000
City Index | Customer list
Business Acquisition [Line Items]
Weighted average amortization period				8 years 10 months
City Index | Trade name
Business Acquisition [Line Items]
Weighted average amortization period				7 years
City Index | Technology
Business Acquisition [Line Items]
Weighted average amortization period				6 years 11 months
City Index | Consolidation, Eliminations
Business Acquisition [Line Items]
Revenues since acquisition date				$ 15,500,000
Expenses since acquisition date				1,300,000
Income before taxes since acquisition date				$ 14,200,000
Galvan Research and Trading, Ltd.
Business Acquisition [Line Items]
Cash payment		$ 9,732,000
Liabilities incurred		$ 10,540,000
Contingent payment, payable period		3 years
Total purchase price		$ 20,272,000
Payment for earn-out					$ 2,100,000
Global Assets Advisors, LLC
Business Acquisition [Line Items]
Cash payment			$ 4,365,000
Percentage of company acquired			55.00%
Total purchase price			$ 5,606,000
Top Third Ag Marketing, LLC
Business Acquisition [Line Items]
Cash payment			$ 3,500,000
Percentage of company acquired			55.00%

ACQUISITIONS - Schedule of Purc

ACQUISITIONS - Schedule of Purchase Price (Detail) - USD ($) $ / shares in Units, $ in Thousands	Apr. 01, 2015	Jul. 31, 2014	Mar. 31, 2014	Sep. 30, 2015	Sep. 30, 2014
Business Acquisition [Line Items]
Common stock issued as consideration for asset and business acquisitions				$ 48,280	$ 6,493
City Index
Business Acquisition [Line Items]
Cash	$ 6,102
Liabilities incurred	65,000
Common stock issued as consideration for asset and business acquisitions	48,280
Total purchase price	$ 119,382
Share price (in dollars per share)	$ 9.77
Galvan Research and Trading, Ltd.
Business Acquisition [Line Items]
Cash		$ 9,732
Liabilities incurred		10,540
Total purchase price		$ 20,272
Global Assets Advisors, LLC
Business Acquisition [Line Items]
Cash			$ 4,365
Common stock issued as consideration for asset and business acquisitions			1,241
Total purchase price			5,606
Top Third Ag Marketing, LLC
Business Acquisition [Line Items]
Cash			$ 3,500

ACQUISITIONS - Allocation of Pu

ACQUISITIONS - Allocation of Purchase Price to Fair Value of Assets and Liabilities (Detail) - USD ($) $ in Thousands	1 Months Ended
	Mar. 31, 2014	Sep. 30, 2015	Apr. 01, 2015	Dec. 31, 2014	Sep. 30, 2014	Jul. 31, 2014
Business Acquisition [Line Items]
Goodwill		$ 41,631		$ 33,579
City Index
Business Acquisition [Line Items]
Cash and cash equivalents acquired			$ 32,991
Cash and securities held for customers			265,012
Receivable from brokers			35,974
Property and equipment			10,411
Prepaid assets			3,972
Other current assets			541
Total tangible assets			348,901
Total liabilities assumed			303,280
Net assets			45,621
Identifiable intangible assets			63,075
Goodwill			10,686
City Index | Customer list
Business Acquisition [Line Items]
Identifiable intangible assets			30,273
City Index | Trade name
Business Acquisition [Line Items]
Identifiable intangible assets			6,645
City Index | Technology
Business Acquisition [Line Items]
Identifiable intangible assets			$ 26,157
Galvan Research and Trading, Ltd.
Business Acquisition [Line Items]
Cash and cash equivalents acquired						$ 2,193
Receivable from brokers						745
Property and equipment						12
Prepaid assets						94
Other current assets						64
Total tangible assets						3,108
Total liabilities assumed						1,931
Net assets						1,177
Identifiable intangible assets						4,987
Goodwill						14,108
Galvan Research and Trading, Ltd. | Customer list
Business Acquisition [Line Items]
Identifiable intangible assets						4,203
Galvan Research and Trading, Ltd. | Trade name
Business Acquisition [Line Items]
Identifiable intangible assets						$ 784
Global Assets Advisors, LLC
Business Acquisition [Line Items]
Non-controlling interest	$ 4,509
Cash and cash equivalents acquired					$ 360
Receivable from brokers					438
Property and equipment					148
Prepaid assets					153
Other current assets					3
Total tangible assets					1,102
Total liabilities assumed					515
Net assets					587
Identifiable intangible assets					3,370
Goodwill					6,158
Global Assets Advisors, LLC | Customer list
Business Acquisition [Line Items]
Identifiable intangible assets					3,100
Global Assets Advisors, LLC | Trade name
Business Acquisition [Line Items]
Identifiable intangible assets					$ 270
Top Third Ag Marketing, LLC
Business Acquisition [Line Items]
Non-controlling interest	3,885
Cash and cash equivalents acquired	73
Receivable from brokers	663
Total tangible assets	736
Total liabilities assumed	1,103
Net assets	(367)
Identifiable intangible assets	3,990
Goodwill	3,806
Top Third Ag Marketing, LLC | Customer list
Business Acquisition [Line Items]
Identifiable intangible assets	3,900
Top Third Ag Marketing, LLC | Trade name
Business Acquisition [Line Items]
Identifiable intangible assets	$ 90

ACQUISITIONS - Pro Forma Revenu

ACQUISITIONS - Pro Forma Revenue and Net Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Total non-interest revenue	$ 128,045	$ 102,786	$ 332,465	$ 253,202
Interest revenue	285	359	936	1,123
Interest expense	219	189	846	411
Total net interest revenue	66	170	90	712
Depreciation and amortization	2,925	1,717	7,638	5,210
Purchased intangible amortization	4,280	2,228	10,688	4,841
Total operating expense	116,123	80,573	317,699	231,226
OPERATING PROFIT	11,988	22,383	14,856	22,688
Interest expense on long term borrowings	2,570	1,496	6,626	4,390
INCOME BEFORE INCOME TAX EXPENSE	9,418	20,887	8,230	18,298
Income tax expense	7,862	9,206	7,568	10,067
Net income attributable to non-controlling interests	583	785	1,343	987
NET INCOME/(LOSS) APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.	$ 973	10,896	(681)	7,244
Top Third Ag Marketing, LLC, Global Assets Advisors, LLC, and Galvan Research and Trading, Ltd [Member]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Total non-interest revenue				260,794
Interest revenue				1,130
Interest expense				859
Total net interest revenue				271
Net revenue				261,065
Depreciation and amortization				5,227
Purchased intangible amortization				5,421
Other expense items				227,917
Total operating expense				238,565
OPERATING PROFIT				22,500
Interest expense on long term borrowings				4,390
INCOME BEFORE INCOME TAX EXPENSE				18,110
Income tax expense				12,749
NET INCOME				5,361
Net income attributable to non-controlling interests				981
NET INCOME/(LOSS) APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.				4,380
City Index
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Total non-interest revenue		143,228	369,249	347,860
Interest revenue		571	1,019	1,983
Interest expense		189	846	411
Total net interest revenue		382	173	1,572
Net revenue		143,610	369,422	349,432
Depreciation and amortization		6,505	8,280	12,694
Purchased intangible amortization		4,533	12,757	11,694
Other expense items		109,085	333,565	313,871
Total operating expense		120,123	354,602	338,259
OPERATING PROFIT		23,487	14,820	11,173
Interest expense on long term borrowings		2,541	7,671	7,526
INCOME BEFORE INCOME TAX EXPENSE		20,946	7,149	3,647
Income tax expense		11,939	11,207	7,326
NET INCOME		9,007	(4,058)	(3,679)
Net income attributable to non-controlling interests		785	1,343	987
NET INCOME/(LOSS) APPLICABLE TO GAIN CAPITAL HOLDINGS, INC.		$ 8,222	$ (5,401)	$ (4,666)

ACQUISITIONS - Restructuring (D

ACQUISITIONS - Restructuring (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Restructuring Reserve [Roll Forward]
Restructuring liability as of January 1, 2015			$ 374
Restructuring expenses	$ 0	$ 436	1,935	$ 2,126	$ 1,200
Payments made in 2015			(1,926)
Restructuring liability as of September 30, 2015	$ 383		$ 383		$ 374

NON-CONTROLLING INTERESTS (Deta

NON-CONTROLLING INTERESTS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Mar. 31, 2014
Increase (Decrease) in Temporary Equity [Roll Forward]
Redeemable noncontrolling interest, beginning balance			$ 11,338
Adjustment to the redemption value of non-controlling interests			14	$ 1,944
Net income attributable to non-controlling interests	$ 583	$ 785	1,343	$ 987
Distributions to non-controlling interest holders			(1,035)
Redeemable noncontrolling interest, ending balance	$ 11,660		$ 11,660
Top Third Ag Marketing, LLC
Redeemable Noncontrolling Interest [Line Items]
Percentage of company acquired					55.00%
Redeemable noncontrolling interest retained by noncontrolling owners					45.00%
Global Assets Advisors, LLC
Redeemable Noncontrolling Interest [Line Items]
Percentage of company acquired					55.00%
Redeemable noncontrolling interest retained by noncontrolling owners					45.00%

CONVERTIBLE SENIOR NOTES - Addi

CONVERTIBLE SENIOR NOTES - Additional Information (Details) - Convertible Debt [Member] - USD ($)	Nov. 27, 2013	Apr. 01, 2015
Convertible Notes Due 2018 [Member]
Debt Instrument [Line Items]
Principal amount	$ 80,000,000
Stated interest rate	4.125%
Proceeds from Convertible Debt	$ 77,900,000
Convertible Notes Due 2020 [Member]
Debt Instrument [Line Items]
Principal amount		$ 60,000,000
Stated interest rate		4.125%

CONVERTIBLE SENIOR NOTES - Sche

CONVERTIBLE SENIOR NOTES - Schedule of Liability and Equity Components (Details) - Convertible Debt [Member] - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Liability component - principal	$ 140,000	$ 80,000
Deferred bond discount	(19,134)	(11,633)
Liability component - net carrying value	120,866	68,367
Additional paid in capital	27,920	12,572
Discount attributable to equity	(412)	(425)
Equity component	$ 27,508	$ 12,147

CONVERTIBLE SENIOR NOTES - Sc65

CONVERTIBLE SENIOR NOTES - Schedule of Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Debt Instrument [Line Items]
Interest expense - amortization of deferred bond discount and costs			$ 2,583	$ 1,599
Total interest expense - convertible senior notes	$ 2,570	$ 1,496	6,626	4,390
Convertible Debt [Member]
Debt Instrument [Line Items]
Interest expense - stated coupon rate	1,444	825	3,713	2,475
Interest expense - amortization of deferred bond discount and costs	1,038	671	2,648	1,915
Total interest expense - convertible senior notes	$ 2,482	$ 1,496	$ 6,361	$ 4,390

EARNINGS PER COMMON SHARE - Add

EARNINGS PER COMMON SHARE - Additional Information (Detail) - $ / shares shares in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from calculation of diluted earnings per share	0.5	0.4
Common stock threshold for additional dilutive shares (in dollars per share)	$ 13
Convertible Notes Due 2018 [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Additional dilutive shares if indenture conditions were met	0.5
Convertible Notes Due 2020 [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Additional dilutive shares if indenture conditions were met	1.5

EARNINGS PER COMMON SHARE - Com

EARNINGS PER COMMON SHARE - Computation of Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Earnings Per Share [Abstract]
Net income applicable to Gain Capital Holdings, Inc.	$ 973	$ 10,896	$ (681)	$ 7,244
Adjustment	1,428	(1,747)	(14)	(1,944)
Net income applicable to GAIN common shareholders	$ 2,401	$ 9,149	$ (695)	$ 5,300
Weighted average common shares outstanding:
Basic weighted average common shares outstanding	49,149,102	41,038,782	47,163,814	40,243,330
Effect of dilutive securities:
Stock options (in shares)	320,770	562,187	471,613	786,956
RSUs/RSAs (in shares)	448,835	1,922,893	394,007	2,024,673
Diluted weighted average common shares outstanding	49,918,707	43,523,862	47,163,814	43,054,959
Earnings per common share
Basic (usd per share)	$ 0.05	$ 0.22	$ (0.01)	$ 0.13
Diluted (usd per share)	$ 0.05	$ 0.21	$ (0.01)	$ 0.12
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Redeemable noncontrolling interests	$ 11,660		$ 11,660		$ 11,338
Out of period adjustment, effect on diluted earnings per share (in dollars per share)			$ 0.03

INCOME TAXES - Additional Infor

INCOME TAXES - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Tax Disclosure [Abstract]
Provision for income taxes expense (benefit)	$ 7,862	$ 9,206	$ 7,568	$ 10,067
Effective income tax rates	83.50%	44.10%	92.00%	55.00%

REGULATORY REQUIREMENTS - Minim

REGULATORY REQUIREMENTS - Minimum Regulatory Capital Subsidiaries Required to Maintain (Detail) $ in Millions	Sep. 30, 2015USD ($)
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 116.7
Capital Levels Maintained	266.7
Excess Net Capital	$ 150
Percent of Requirement Maintained	229.00%
GAIN Capital Group, LLC
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 25.3
Capital Levels Maintained	42.3
Excess Net Capital	$ 17
Percent of Requirement Maintained	167.00%
GAIN Capital-Forex.com U.K., Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 32.5
Capital Levels Maintained	81.7
Excess Net Capital	$ 49.2
Percent of Requirement Maintained	251.00%
GAIN Capital Japan Co., Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 1.4
Capital Levels Maintained	9.5
Excess Net Capital	$ 8.1
Percent of Requirement Maintained	679.00%
GAIN Capital-Forex.com Hong Kong, Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 1.9
Capital Levels Maintained	2.7
Excess Net Capital	$ 0.8
Percent of Requirement Maintained	142.00%
GAIN Capital Forex.com Australia, Pty. Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 0.7
Capital Levels Maintained	2.2
Excess Net Capital	$ 1.5
Percent of Requirement Maintained	314.00%
Galvan Research and Trading, Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 0.7
Capital Levels Maintained	4.4
Excess Net Capital	$ 3.7
Percent of Requirement Maintained	629.00%
GAIN Capital-Forex.com Canada Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 0.2
Capital Levels Maintained	1.4
Excess Net Capital	$ 1.2
Percent of Requirement Maintained	700.00%
GAIN Capital Securities, Inc.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 0.1
Capital Levels Maintained	0.4
Excess Net Capital	$ 0.3
Percent of Requirement Maintained	400.00%
GAIN Global Markets, Inc.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 0.1
Capital Levels Maintained	0.2
Excess Net Capital	$ 0.1
Percent of Requirement Maintained	200.00%
Gain Capital UK, Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 52.3
Capital Levels Maintained	111.5
Excess Net Capital	$ 59.2
Percent of Requirement Maintained	213.00%
Gain Capital Singapore Pte. Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 0.7
Capital Levels Maintained	7.1
Excess Net Capital	$ 6.4
Percent of Requirement Maintained	1014.00%
Gain Capital Australia Pty Ltd.
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 0.7
Capital Levels Maintained	2
Excess Net Capital	$ 1.3
Percent of Requirement Maintained	286.00%
Global Assets Advisors, LLC
Schedule Of Compliance With Regulatory Capital Requirements For Broker Dealer [Line Items]
Minimum Regulatory Capital Requirements	$ 0.1
Capital Levels Maintained	1.3
Excess Net Capital	$ 1.2
Percent of Requirement Maintained	1300.00%

SEGMENT INFORMATION - Additiona

SEGMENT INFORMATION - Additional Information (Details)	9 Months Ended
	Sep. 30, 2015Segment
Segment Reporting [Abstract]
Number of operating segments	1

SUBSEQUENT EVENTS - Additional

SUBSEQUENT EVENTS - Additional Information (Detail)	Nov. 09, 2015$ / shares
Subsequent event
Subsequent Event [Line Items]
Common stock dividend declared per share (in dollars per share)	$ 0.05