Global Brokerage (GLBR) 10-K 16 Mar 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2014	Mar. 12, 2015	Jun. 30, 2014
Document Information [Line Items]
Document Type	10-K
Amendment Flag	FALSE
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Trading Symbol	FXCM
Entity Registrant Name	FXCM Inc.
Entity Central Index Key	1499912
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		50,701,418
Entity Public Float			$677,214,689

Consolidated_Statements_of_Fin

Consolidated Statements of Financial Condition (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets
Cash and cash equivalents	$338,814	$365,245
Cash and cash equivalents, held for customers	1,331,723	1,190,880
Restricted time deposits	3,336	0
Trading securities	26	0
Due from brokers	37,298	5,450
Accounts receivable, net	10,481	9,953
Deferred tax asset	9,923	11,910
Notes receivable	0	5,992
Tax receivable	2,446	3,861
Total current assets	1,734,047	1,593,291
Restricted time deposits	5,005	0
Deferred tax asset	179,698	166,576
Office, communication and computer equipment, net	48,194	49,165
Goodwill	323,887	307,936
Other intangible assets, net	57,567	76,713
Notes receivable	9,381	5,950
Other assets	29,648	24,316
Total assets	2,387,427	2,223,947
Current liabilities
Customer account liabilities	1,331,723	1,190,880
Accounts payable and accrued expenses	56,039	69,697
Credit agreement	25,000	0
Notes payable	0	9,800
Due to brokers	16,313	8,652
Securities sold, not yet purchased	4,239	0
Due to related parties pursuant to tax receivable agreement	5,352	18,588
Total current liabilities	1,438,666	1,297,617
Deferred tax liability	2,835	3,687
Due to related parties pursuant to tax receivable agreement	145,224	131,670
Senior convertible notes	151,578	146,303
Other liabilities	6,108	9,289
Total liabilities	1,744,411	1,588,566
Commitments and Contingencies (see Note 21)
Stockholders' Equity
Additional paid-in-capital	273,708	245,426
Retained earnings	22,379	16,352
Accumulated other comprehensive loss	-11,879	-5,344
Total stockholders’ equity, FXCM Inc.	284,688	256,882
Non-controlling interests	358,328	378,499
Total stockholders’ equity	643,016	635,381
Total liabilities and stockholders’ equity	2,387,427	2,223,947
Class A common stock
Stockholders' Equity
Common stock	479	447
Class B common stock
Stockholders' Equity
Common stock	$1	$1

Consolidated_Statements_of_Fin1

Consolidated Statements of Financial Condition (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Class A common stock
Common stock, par value (in dollars per share)	$0.01	$0.01
Common stock, shares authorized (in shares)	3,000,000,000	3,000,000,000
Common stock, shares issued (in shares)	47,889,964	44,664,884
Common stock, shares outstanding (in shares)	47,889,964	44,664,884
Class B common stock
Common stock, par value (in dollars per share)	$0.01	$0.01
Common stock, shares authorized (in shares)	1,000,000	1,000,000
Common stock, shares issued (in shares)	34	41
Common stock, shares outstanding (in shares)	34	41

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues
Retail trading revenue	$338,035	$365,285	$339,685
Institutional trading revenue	103,199	103,994	62,033
Trading revenue	441,234	469,279	401,718
Interest income	2,525	2,614	3,571
Brokerage interest expense	-714	-258	-277
Net interest revenue	1,811	2,356	3,294
Other income	20,712	17,953	12,303
Total net revenues	463,757	489,588	417,315
Operating Expenses
Compensation and benefits	111,716	105,470	105,779
Allocation of income to Lucid members for services provided	9,406	21,290	0
Total compensation and benefits	121,122	126,760	105,779
Referring broker fees	80,850	84,231	76,585
Advertising and marketing	22,666	27,091	30,860
Communication and technology	48,396	38,441	37,113
Trading costs, prime brokerage and clearing fees	33,828	30,821	16,935
General and administrative	62,808	68,230	63,043
Depreciation and amortization	54,945	53,729	36,773
Total operating expenses	424,615	429,303	367,088
Operating income	39,142	60,285	50,227
Other Expense
Loss on equity method investments, net	1,308	752	0
Interest on borrowings	12,186	7,673	2,763
Income before income taxes	25,648	51,860	47,464
Income tax provision	6,001	17,024	8,986
Net income	19,647	34,836	38,478
Net income attributable to FXCM Inc.	17,151	14,832	8,958
Weighted average shares of Class A common stock outstanding:
Basic (in shares)	41,637	32,789	24,086
Diluted (in shares)	44,010	33,957	24,086
Net income per share attributable to stockholders of Class A common stock of FXCM Inc.:
Basic (in dollars per share)	$0.41	$0.45	$0.37
Diluted (in dollars per share)	$0.39	$0.44	$0.37
Dividends declared per common share (in dollars per share)	$0.24	$0.24	$0.24
Other non-controlling interests
Other Expense
Net income (loss) attributable to non-controlling interest	-6,464	-4,846	6,389
FXCM Holdings, LLC
Other Expense
Net income (loss) attributable to non-controlling interest	$8,960	$24,850	$23,131

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net income	$19,647	$34,836	$38,478
Other comprehensive loss
Foreign currency translation loss	-11,253	-9,678	-3,414
Income tax expense (benefit)	108	-108	12
Other comprehensive loss, net of tax	-11,361	-9,570	-3,426
Comprehensive income	8,286	25,266	35,052
Comprehensive income attributable to FXCM Inc.	10,616	10,789	7,515
Other non-controlling interests
Other comprehensive loss
Comprehensive income (loss) attributable to non-controlling interest	-6,483	-4,846	6,389
FXCM Holdings, LLC
Other comprehensive loss
Comprehensive income (loss) attributable to non-controlling interest	$4,153	$19,323	$21,148

Consolidated_Statements_of_Sto

Consolidated Statements of Stockholders' Equity/Members' Capital (USD $)	Total	Non-controlling Interest	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Additional Paid-in Capital	Class A common stock	Class A common stock	Class B common stock
In Thousands, except Share data, unless otherwise specified	USD ($)	USD ($)	USD ($)	USD ($)	USD ($)		Common Stock	Common Stock
							USD ($)	USD ($)
Balance as of beginning of period at Dec. 31, 2011	$293,433	$198,012	$8,977	$142	$86,152		$149	$1
Balance as of beginning of period (in shares) at Dec. 31, 2011							14,899,391	100
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	38,478	29,520	8,958
Other comprehensive loss, net of tax	-3,426	-1,983		-1,443
Comprehensive income	35,052	27,537	8,958	-1,443
Repurchase of class A common stock	-7,475	-2,618			-4,849		-8
Repurchase of class A common stock (in shares)							-750,125
Equity-based compensation	24,354	12,918			11,428		8
Equity based compensation (in shares)							782,015
Dividends on class A common stock	-6,813		-6,813
Exchange of Holdings Units to Class A common stock (see Note 16)	0	-17,759			17,651		108
Exchange of Holdings units to Class A common stock (see Note 15) (in shares)							10,752,318	-57
Effects of Tax Receivable Agreement	5,120				5,120
Settlement of receivable balance with related party (see Note 16)	-3,979	-3,205			-774
Stock issuances, Lucid acquisition (see Note 4)	21,491	7,851			13,622		18
Stock issuances, Lucid acquisition (see Note 5) (in shares)							1,800,000
Contingently issuable shares, Lucid acquisition (see Note 4)	67,915	24,803			43,040		72
Contingently issuable shares, Lucid acquisition (see Note 5) (in shares)							7,200,000
Contributions - other non-controlling interests	578	578
Distributions - non-controlling members	-14,926	-14,926
Non-controlling interest	160,165	160,165
Balance as of end of period at Dec. 31, 2012	574,915	393,356	11,122	-1,301	171,390		347	1
Balance as of end of period (in shares) at Dec. 31, 2012							34,683,599	43
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	34,836	20,004	14,832
Other comprehensive loss, net of tax	-9,570	-5,527		-4,043
Comprehensive income	25,266	14,477	14,832	-4,043
Repurchase of class A common stock	-28,080	-9,270			-18,792		-18
Repurchase of class A common stock (in shares)							-1,815,800
Equity-based compensation	15,299	8,668			6,631
Dividends on class A common stock	-9,602		-9,602
Exchange of Holdings Units to Class A common stock (see Note 16)	0	-53,500			53,399		101
Exchange of Holdings units to Class A common stock (see Note 15) (in shares)							10,094,371	-4
Assignment of permitted transferees	0
Assignment of permitted transferees (in shares)								2
Stock options exercised	22,499	7,777			14,705		17
Stock options exercised (in shares)							1,702,714
Effects of Tax Receivable Agreement	9,441				9,441
Equity component of Convertible Note issuance	29,101	15,512			13,589
Sale of warrants	18,571	9,899			8,672
Purchase of Convertible Note hedges	-29,101	-15,512			-13,589
Contributions - other non-controlling interests	5,650	5,650
Non-controlling interest - Other Adjustment	0	20			-20
Distributions - non-controlling members	-14,147	-14,147
Non-controlling interest	15,569	15,569
Balance as of end of period at Dec. 31, 2013	635,381	378,499	16,352	-5,344	245,426		447	1
Balance as of end of period (in shares) at Dec. 31, 2013							44,664,884	41
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	19,647	2,496	17,151
Other comprehensive loss, net of tax	-11,361	-4,826		-6,535
Comprehensive income	8,286	-2,330	17,151	-6,535
Repurchase of class A common stock	-2,260	-633			-1,626		-1
Repurchase of class A common stock (in shares)						-146,000	-145,985
Equity-based compensation	14,088	7,174			6,913		1
Equity based compensation (in shares)							163,832
Dividends on class A common stock	-11,124		-11,124
Exchange of Holdings Units to Class A common stock (see Note 16)	0	-13,090			13,066		24
Exchange of Holdings units to Class A common stock (see Note 15) (in shares)							2,378,147	-6
Assignment of permitted transferees	0
Assignment of permitted transferees (in shares)								-1
Stock options exercised	11,173	3,262			7,903		8
Stock options exercised (in shares)	829,086					829,086	829,086
Effects of Tax Receivable Agreement	2,026				2,026
Contributions - other non-controlling interests	10,421	10,421
Distributions - non-controlling members	-24,975	-24,975
Balance as of end of period at Dec. 31, 2014	$643,016	$358,328	$22,379	($11,879)	$273,708		$479	$1
Balance as of end of period (in shares) at Dec. 31, 2014							47,889,964	34

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash Flows From Operating Activities
Net income	$19,647,000	$34,836,000	$38,478,000
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	54,945,000	53,729,000	36,773,000
Equity-based compensation	13,047,000	13,959,000	22,979,000
Deferred tax expense	911,000	11,442,000	7,170,000
Gain on Follow-on Payment	-3,672,000	-6,959,000	0
Loss on disposal of fixed assets	10,000	126,000	773,000
Amortization of deferred bond discount	5,275,000	2,904,000	0
Amortization of deferred financing cost	1,867,000	1,263,000	304,000
Loss on equity method investments, net	1,308,000	752,000	0
Gain on settlement of receivables from related parties	0	0	-1,436,000
Due to related parties pursuant to tax receivable agreement	-7,464,000	1,209,000	0
Changes in operating assets and liabilities
Cash and cash equivalents, held for customers	-139,351,000	1,390,000	-142,463,000
Restricted time deposits	-8,341,000	0	0
Trading securities	-26,000	0	0
Due from brokers	-31,847,000	2,590,000	-6,427,000
Accounts receivable, net	-722,000	-3,577,000	13,178,000
Tax receivable, net	1,415,000	2,142,000	-3,987,000
Other assets	837,000	1,521,000	5,172,000
Customer account liabilities	140,843,000	118,000	143,779,000
Accounts payable and accrued expenses	-14,563,000	15,997,000	-11,341,000
Other liabilities	491,000	1,410,000	0
Payments for tax receivable agreement	-3,707,000	-4,079,000	0
Due to brokers	7,661,000	-5,842,000	999,000
Securities sold, not yet purchased	4,239,000	0	0
Foreign currency remeasurement loss	-685,000	-1,359,000	-1,817,000
Net cash provided by operating activities	42,118,000	123,572,000	102,134,000
Cash Flows From Investing Activities
Acquisition of business, net of cash acquired	-29,251,000	-32,312,000	-36,555,000
Payment for equity investment	0	-3,000,000	-4,000,000
Purchases of intangible assets	-9,815,000	-50,000	-134,000
Issuance of notes receivable	-1,500,000	-11,942,000	0
Purchase of office, communication and computer equipment, net	-22,202,000	-23,416,000	-27,263,000
Net cash used in investing activities	-62,768,000	-70,720,000	-67,952,000
Cash Flows From Financing Activities
Distributions to non-controlling members	-24,179,000	-14,147,000	-14,926,000
Contributions from other non-controlling members	2,540,000	5,650,000	578,000
Dividends paid	-11,124,000	-9,602,000	-6,813,000
Proceeds from exercise of stock options	11,173,000	22,499,000	0
Common stock repurchases	-2,260,000	-28,080,000	-7,475,000
Proceeds from issuance of senior convertibles notes, net	0	166,453,000	0
Purchase of convertible note hedges	0	-29,101,000	0
Proceeds from sale of warrants	0	18,571,000	0
Borrowings under the credit agreement	65,000,000	10,000,000	130,000,000
Payments on borrowings under the credit agreement	-40,000,000	-95,000,000	-45,000,000
Net cash provided by financing activities	1,150,000	47,243,000	56,364,000
Effect of foreign currency exchange rate changes on cash and cash equivalents	-6,931,000	-7,182,000	-2,935,000
Net (decrease) increase in cash and cash equivalents	-26,431,000	92,913,000	87,611,000
Cash and cash equivalents
Beginning of year	365,245,000	272,332,000	184,721,000
End of year	338,814,000	365,245,000	272,332,000
Supplemental disclosures of cash flow activities
Net cash paid for taxes	2,329,000	6,936,000	12,617,000
Cash paid for interest	5,020,000	3,449,000	2,334,000
Supplemental disclosure of non-cash investing activities
Exchange of Holdings Units for shares of Class A common stock	13,090,000	53,500,000	17,759,000
Settlement of receivable from related party	0	0	-3,979,000
Notes receivable credited towards consideration for acquisition of business	11,942,000	0	0
Note issued for business acquisition	0	15,300,000	22,867,000
Value of equity interest paid for business acquisition	0	0	89,406,000
Follow-on contingent liability for business acquisition	0	10,631	0
Lucid Markets Trading Limited
Supplemental disclosure of non-cash investing activities
Non-controlling interest	0	0	160,165,000
Faros Trading LLC
Supplemental disclosure of non-cash investing activities
Non-controlling interest	0	15,569,000	0
Non-controlling Interest
Supplemental disclosure of non-cash investing activities
Note issued for business acquisition	7,881,000	0	0
Non-controlling interest	$796,000	$0	$0

Nature_of_Business_and_Organiz

Nature of Business and Organization	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Nature of Business and Organization	Nature of Business and Organization
	FXCM Inc. (the “Corporation”), a Delaware holding company incorporated on August 10, 2010, is an online provider of foreign exchange (“FX”) trading and related services to retail and institutional customers worldwide. The Corporation operates through its managing membership interest in FXCM Holdings, LLC (“Holdings”), the Corporation’s sole operating asset. Prior to the completion of the reorganization and the Corporation’s initial public offering (“IPO”), the Corporation was a wholly-owned subsidiary of Holdings. As used in these notes, the term “Company” collectively refers to the Corporation, Holdings and subsidiaries of Holdings.
	As an online provider of FX trading and related services, the Company offers its retail and institutional customers access to global over-the-counter FX markets. In a FX trade, a participant buys one currency and simultaneously sells another, a combination known as a “currency pair.” The Company’s proprietary trading platform presents its FX customers with the price quotations on several currency pairs from a number of global banks, financial institutions and market makers, or FX market makers. The Company’s primary offering to retail customers is what is referred to as agency execution or an agency model. Under the agency model, when a customer executes a trade on the price quotation presented by the FX market maker, the Company acts as a credit intermediary, or a riskless principal, simultaneously entering into a trade with the customer and the FX market maker. This agency model has the effect of automatically hedging our positions and eliminating market risk exposure. The Company earns trading revenue from fees charged as a markup to the price provided by the FX market makers or commissions, not trading profit or losses. Additionally, the Company offers its customers the ability to trade contracts for difference (“CFDs”), spread betting, equities and equity options through its United Kingdom ("U.K.") subsidiaries. CFDs allow for the exchange of the difference in the value of a particular asset such as a stock index or oil or gold contracts, between the time at which a contract is opened and the time at which it is closed. Spread betting allows our customers to bet on the price fluctuations of various financial markets such as FX, indices, oil and metals.
	Institutional trading revenue includes commission income generated by facilitating spot FX trades on behalf of institutional customers. The Company offers FX trading services to banks, hedge funds and other institutional customers, on an agency model basis, through its FXCM Pro division and Faros Trading LLC ("Faros") (see Note 4). These services allow customers to obtain optimal prices offered by external banks. The counterparties to these trades are external financial institutions that hold customer account balances and settle the transactions. The Company receives commissions for providing these services without taking any market or credit risk. The Company, through its 50.1% controlling interest in Lucid Markets Trading Limited (“Lucid”) (see Note 4), is also an electronic market-maker and trader in the institutional FX market. In addition, with the creation of V3 Markets, LLC ("V3") (see Note 4), the Company expanded market making and electronic trading into other asset classes.

Significant_Accounting_Policie

Significant Accounting Policies and Estimates	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Significant Accounting Policies and Estimates	Significant Accounting Policies and Estimates
	Basis of Presentation
	The accompanying consolidated financial statements are presented in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). The Company consolidates those entities in which it is the primary beneficiary of a variable-interest entity ("VIE") as required by ASC 810, Consolidations (“ASC 810”), or entities where it has a controlling interest. Intercompany accounts and transactions are eliminated in consolidation.
	As indicated above, the Corporation operates and controls all of the businesses and affairs of Holdings and its subsidiaries. As such, the Corporation consolidates the financial results of Holdings and records a non-controlling interest for the economic interest in Holdings not owned by the Corporation. The Corporation’s and the non-controlling unit holders’ economic interest in Holdings was 58.1% and 41.9%, respectively, as of December 31, 2014. The Corporation’s and the non-controlling unit holders’ economic interest in Holdings was 54.8% and 45.2%, respectively, as of December 31, 2013.
	Net income attributable to the non-controlling interest in Holdings in the consolidated statements of operations represents the portion of earnings or loss attributable to the economic interest in Holdings held by the non-controlling unit holders. Net income (loss) attributable to other non-controlling interests in the consolidated statements of operations represents the portion of net income or loss attributable to the non-controlling interests of Lucid, Faros, V3 and other consolidated entities. Net income (loss) attributable to the non-controlling interest in Lucid represents the portion of earnings or loss attributable to the 49.9% economic interest held by Lucid non-controlling members whose allocation among the non-controlling members is not contingent upon services being provided. The portion of the 49.9% of Lucid earnings allocated among the non-controlling members of Lucid contingent on services provided is reported as a component of compensation expense under Allocation of income to Lucid members for services provided in the consolidated statements of operations. Net income (loss) attributable to the non-controlling interest in Faros and V3 (see Note 4) represents the portion of earnings or loss attributable to the 49.9% economic interest held by Faros and V3 non-controlling members. Net income (loss) attributable to the non-controlling interests in other consolidated entities represents the portion of earnings or loss attributable to the economic interests held by the non-controlling members.
	Non-controlling interests in the consolidated statements of financial condition represents the portion of equity attributable to the non-controlling interests of Holdings, Lucid, Faros, V3 and other consolidated entities. The allocation of equity to the non-controlling interests is based on the percentage owned by the non-controlling interest in the respective entity.
	The Company's consolidated financial statements include the following significant subsidiaries of Holdings:
	Forex Capital Markets LLC	(“US”)
	FXCM Asia Limited	(“HK”)
	Forex Capital Markets Limited	(“UK LTD”)
	FXCM Australia Limited	(“Australia”)
	ODL Group Limited	(“ODL”)
	FXCM Securities Limited	(“FSL”)
	FXCM Japan Securities Co., Ltd.	(“FXCMJ”)
	FXCM UK Merger Limited	(“Merger”)
	Lucid Markets Trading Limited	(“Lucid”)
	Lucid Markets LLP	("Lucid LLP")
	Faros Trading LLC	("Faros")
	V3 Markets, LLC	("V3")
	Investments where the Company is deemed to exercise significant influence, but no control, are accounted for using the equity method of accounting. The Company records its pro-rata share of earnings or losses each period and records any dividends as a reduction in the investment balance. The carrying value of these investments is included in Other assets in the consolidated statements of financial condition and earnings or losses are included in Income (Loss) on equity method investments, net in the consolidated statements of operations.
	FXCMJ, a Japanese based foreign exchange provider and a wholly owned subsidiary of Holdings, has a fiscal year end of March 31 while the Company has a fiscal year end of December 31. The difference between the Company's reporting year end and FXCMJ does not result in a material impact on the Company's financial position or results of operations.
	Certain reclassifications have been made to previously reported amounts to conform to the current presentation.
	Use of Estimates
	The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements as well as the reported amount of revenue and expenses during the year. Actual results could differ from those estimates and could have a material impact on the consolidated financial statements.
	Cash and Cash Equivalents
	Cash and cash equivalents include cash at banks and highly liquid instruments with original maturities of less than 90 days at the time of purchase and cash on deposit held with FX and CFD market makers related to economic hedging activities. At times, balances held in U.S. bank accounts may exceed federally insured limits. This potentially subjects the Company to concentration risk. The Company has not experienced losses in such accounts.
	Cash and Cash Equivalents, held for customers
	Cash and cash equivalents, held for customers represents cash held to fund customer liabilities. At times, balances held in U.S. bank accounts may exceed federally insured limits. This potentially subjects the Company to concentration risk. The Company has not experienced losses in such accounts.
	The balance arises primarily from cash deposited by customers and net realized gains from customer trading activity. The Company maintains a corresponding liability in connection with this amount that is included in customer account liabilities in the consolidated statements of financial condition (see Note 13). A portion of the balance is not available for general use due to regulatory restrictions in certain jurisdictions. These restricted balances were $0.9 billion and $1.0 billion as of December 31, 2014 and 2013, respectively.
	Restricted Time Deposits
	Restricted time deposits consist of pledged time deposits with original maturities of three months and one year and for which use is contractually restricted. Restricted time deposits are included in Current assets and Non-current assets in the consolidated statements of financial condition, as appropriate, and recorded at cost, which approximates fair value (see Note 5).
	Due from/to Brokers
	Due from/to brokers represents the amount of the unsettled spot currency trades that the Company has with financial institutions. Also included in due from/to brokers is the fair value of derivative financial instruments discussed below. The Company has master netting agreements with its respective counterparties which allows the Company to present due from/to brokers on a net-by-counterparty basis in accordance with ASC 815 Derivatives and Hedging (“ASC 815”) and ASC Topic 210 Balance Sheet (“ASC 210”).
	Derivatives
	Derivative financial instruments are accounted for in accordance with ASC 815 and are included in Due from/to brokers in the consolidated statements of financial condition. The Company recognizes all derivative financial instruments in the consolidated statements of financial condition as either assets or liabilities at fair value. The Company enters into futures contracts to (i) economically hedge the open customer contracts on its CFD business and (ii) hedge trading in its electronic market making and institutional foreign exchange spot and futures markets. Futures contracts are exchange traded contracts to either purchase or sell a specific asset at a specified future date for a specified price. Gains or losses on futures contracts related to the Company’s CFD business are included in Retail trading revenue and gains or losses on hedge trading in its electronic market making and institutional foreign exchange spot and futures markets and other asset classes are included in Institutional trading revenue in the consolidated statements of operations (see Note 24).
	Fair Value Measurements
	Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Fair value measurement establishes a fair value hierarchy that prioritizes the inputs of valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities and the lowest priority to unobservable inputs. These three levels of fair value hierarchy are defined as follows:
	Level I:  Quoted prices in active markets for identical assets or liabilities, accessible by the Company at the measurement date.
	Level II:  Quoted prices for similar assets or liabilities in active markets, or quoted prices for identical or similar assets or liabilities in markets that are not active, or other observable inputs other than quoted prices.
	Level III:  Unobservable inputs for assets or liabilities.
	When Level I inputs are available, those inputs are selected for determination of fair value. To value financial assets and liabilities that are characterized as Level II and III, the Company uses observable inputs for similar assets and liabilities that are available from pricing services or broker quotes. These observable inputs may be supplemented with other methods, including internal models that result in the most representative prices for assets and liabilities with similar characteristics. Multiple inputs may be used to measure fair value, however, the level of fair value for each financial asset or liability is based on the highest priority level of input within this fair value hierarchy (see Note 25).
	Accounts Receivable, net
	As of December 31, 2014 and 2013, Accounts receivable, net, consisted primarily of amounts due from institutional customers relating to the Company's FX business, fees receivable from the Company's white label service to third parties and amounts due from customers related to the Company's FSL brokerage business. As of December 31, 2013, Accounts receivable, net, also includes receivables related to order flow revenue, described in “Retail Trading Revenue” below. Receivables are shown net of reserves for uncollectible accounts. The reserve for bad debts is maintained at a level that management believes to be sufficient to absorb estimated losses in the accounts receivable portfolio. The reserve is increased by the provision for bad debts which is charged against operating results and decreased by the amount of charge-offs, net of recoveries. The amount charged against operating results is based on several factors including, but not limited to, a continuous assessment of the collectability of each account, the length of time a receivable is past due and our historical experience with the particular customer. As of December 31, 2014 and 2013, the reserve netted against receivables in the consolidated statements of financial condition was not material.
	As of December 31, 2014 and 2013, Accounts receivable, net, also includes advances to employees and non-controlling members of Holdings and, additionally, as of December 31, 2014, advances to Lucid non-controlling members and net amounts due from an equity method investee, as described in Note 16.
	Office, Communication and Computer Equipment, net
	Office, communication and computer equipment, net, consists of computer equipment, purchased technology hardware and software, internally-developed software, leasehold improvements, furniture and fixtures and other equipment, licenses and communication equipment. Office, communication and computer equipment are recorded at historical cost, net of accumulated depreciation. Additions and improvements that extend the lives of assets are capitalized, while expenditures for repairs and maintenance are expensed as incurred. Certain costs of software developed or obtained for internal use are capitalized. Depreciation is computed using the straight-line method. The Company depreciates these assets using the following useful lives:
	Computer equipment	3 to 5 years
	Software	2 to 5 years
	Leasehold improvements	Lesser of the estimated economic useful life or the term of the lease
	Furniture and fixtures and other equipment	3 to 5 years
	Licenses	2 to 3 years
	Communication equipment	3 to 5 years
	Valuation of Other Long-Lived Assets
	The Company also assesses potential impairments of its other long-lived assets, including office, communication and computer equipment, when there is evidence that events or changes in circumstances indicate that the carrying amount of an asset may not be recovered. An impairment loss is recognized when the carrying amount of the long-lived asset exceeds its fair value and is not recoverable. The carrying amount of a long-lived asset is not recoverable if it exceeds the sum of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. Any required impairment loss is measured as the amount by which the carrying amount of a long-lived asset exceeds its fair value and is recorded as a reduction in the carrying value of the related asset and a charge to operating results.
	Business Acquisitions
	The Company accounts for business acquisitions in accordance with ASC 805, Business Combinations ("ASC 805") and records assets acquired and liabilities assumed at their fair values as of the acquisition date. The Company records any excess purchase price over the value assigned to net tangible and identifiable intangible assets of a business acquired as goodwill. Acquisition related costs are expensed as incurred (see Note 4).
	Goodwill
	The Company recorded goodwill from various acquisitions. Goodwill represents the excess purchase price over the value assigned to the net tangible and identifiable intangible assets of a business acquired. Goodwill is allocated to the Company’s reporting units based on the assignment of the fair values of each reporting unit of the acquired company. For purposes of the goodwill impairment test, the Company has identified its Retail and Institutional trading segments as its reporting units. The Company performs a two-step goodwill impairment review at the reporting unit level annually, or in interim periods if certain events occur indicating that the carrying value may be impaired. The Company tests for impairment during the fourth quarter of our fiscal year using October 1 carrying values.
	The first step of the two-step process involves a comparison of the estimated fair value of a reporting unit to its carrying amount, including goodwill. In performing the first step, the Company determines the fair value of a reporting unit using a discounted cash flow ("DCF") analysis. Determining fair value requires the exercise of significant judgment, including judgments about appropriate discount rates, perpetual growth rates and the amount and timing of expected future cash flows. The cash flows employed in the DCF analyses are based on the Company’s most recent budgets and business plans and, when applicable, various growth rates are assumed for years beyond the current business plan period. Discount rate assumptions are based on an assessment of the risk inherent in the future cash flows of the respective reporting units. If the estimated fair value of a reporting unit exceeds its carrying amount, the goodwill of the reporting unit is not impaired and the second step of the impairment test is not necessary. If the carrying amount of a reporting unit exceeds its estimated fair value, then the second step of the goodwill impairment test must be performed. The second step of the goodwill impairment test compares the implied fair value of the reporting unit’s goodwill with its carrying amount to measure the amount of impairment loss, if any. The implied fair value of goodwill is determined in the same manner as the amount of goodwill recognized in a business combination (i.e., the estimated fair value of the reporting unit is allocated to all of the assets and liabilities of that reporting unit including any unrecognized intangible assets as if the reporting unit had been acquired in a business combination and the fair value of the reporting unit was the purchase price paid). If the carrying amount of the reporting unit’s goodwill exceeds the implied fair value of the reporting unit’s goodwill, an impairment loss is recognized in an amount equal to that excess.
	There was no impairment of goodwill for the year ended December 31, 2014. Although there is no impairment as of December 31, 2014, events such as economic weakness and unexpected significant declines in operating results of reporting units may result in having to perform a goodwill impairment test for some or all of our reporting units prior to the required annual assessment. These types of events and the resulting analysis could result in goodwill impairment charges in the future (see Note 10).
	Other Intangible Assets, net
	Other intangible assets, net, primarily include customer relationships, proprietary technology, non-compete agreements, an executory contract and trade names recorded from various acquisitions.
	The customer relationships, non-compete agreements, trade names and executory contract are finite-lived intangibles and are amortized on a straight-line basis over their estimated average useful life of 3 to 9 years, 1 to 9 years, 3 years and 3 years, respectively. Proprietary technology assets are also finite-lived intangibles and are amortized on a straight-line basis over their estimated average useful life of 4 to 7 years. The useful life of these intangibles is based on the period they are expected to contribute to future cash flows as determined by the Company's historical experience. For these finite-lived intangible assets subject to amortization, impairment is considered upon certain “triggering events” and is recognized if the carrying amount is not recoverable and the carrying amount exceeds the fair value of the intangible asset. There was no impairment of finite-lived intangible assets for the years ended December 31, 2014, 2013 or 2012 (see Note 11).
	The FX trading license is an indefinite-lived asset that is not amortized but tested for impairment. The Company’s policy is to test for impairment at least annually or in interim periods if certain events occur indicating that the fair value of the asset may be less than its carrying amount. An impairment test on this indefinite-lived asset is performed during the fourth quarter of the Company’s fiscal year using the October 1 carrying value. Impairment exists if the carrying value of the indefinite-lived intangible asset exceeds its fair value. There was no impairment of indefinite-lived intangible assets for the years ended December 31, 2014, 2013 or 2012 (see Note 11).
Equity Method Investments
Investments where the Company is deemed to exercise significant influence, but no control, are accounted for using the equity method of accounting. The Company records its pro-rata share of earnings or losses each period and records any dividends as a reduction in the investment balance. Additionally, the carrying value of investments accounted for using the equity method of accounting is adjusted downward to reflect any impairment in value. For investments accounted for using the equity method of accounting, the Company evaluates information (e.g., budgets, business plans, financial statements, etc.) in addition to quoted market prices, if any, in determining whether an other-than-temporary decline in value exists. Factors indicative of an impairment in value include recurring operating losses, credit defaults and subsequent rounds of financing at an amount below the cost basis of the Company’s investment.
All of the Company’s equity method investments are included in Other assets in the consolidated statements of financial condition and earnings or losses are included in Loss on equity method investments, net in the consolidated statements of operations (see Note 8). Equity method investments are included in institutional and corporate for purposes of segment reporting.
Notes Receivable
Notes receivable represent receivables for notes acquired for cash plus accrued interest. Notes receivable are initially recorded at the amount of cash exchanged plus accrued interest. Interest income on the notes is recorded on an accrual basis and included in Interest income in the consolidated statements of operations. The Company individually assesses its notes receivables for impairment using methods including internally generated cash flow projections to determine if the notes will be repaid under the expected terms of the note agreements. If the Company concludes that the counterparty will not repay a note in accordance with its terms, the Company considers the note impaired and begins recognizing interest income on a cash basis, if any. To measure impairment, the Company calculates the estimated fair value of the collateral. If the estimated fair value of the collateral is less than the carrying value of the note receivable, the Company establishes an impairment reserve for the difference. If it is likely that a note will not be collected based on financial or other business indicators, the Company’s policy is to charge off the note in the period which it deems it uncollectible (see Note 7).
Other Assets
Other assets include prepaid expenses, equity method investments, deposits for rent security, deferred debt costs and exchange memberships (see Note 12).
Accounts Payable and Accrued Expenses
Accounts payable and accrued expenses include operating expenses payable, amounts due to the Lucid non-controlling members for services provided, commissions payable, which represents balances owed to referring brokers for trades transacted by customers that were introduced to the Company by such brokers, bonuses payable, income taxes payable, and interest due on borrowings. Accounts payable and accrued expenses at December 31, 2013 also included amounts due to the Lucid non-controlling members in connection with trade settlements and net amounts due to an equity method investee, as described in Note 16.
Litigation
The Company may from time to time be involved in litigation and claims that arise in the ordinary course of business, including intellectual property claims. In addition, our business is subject to extensive regulation, which may result in regulatory proceedings against us. The Company records a liability when it is both probable that a loss has been incurred and the amount of the loss can be reasonably estimated. When the reasonable estimate of the possible loss is within a range of amounts, the minimum of the range of possible loss is accrued, unless a higher amount within the range is a better estimate than any other amount within the range. Significant judgment is required to determine both probability and the estimated amount. The Company reviews these provisions at least quarterly and adjusts them accordingly to reflect the impact of negotiations, settlements, rulings, advice of legal counsel, and updated information.
Securities Sold, Not Yet Purchased
Securities sold, not yet purchased, represent the Company’s obligations to deliver a specified security at the contracted price at a future point in time, and thereby create a liability to repurchase the securities in the market at the prevailing prices. The liability for such securities sold short, included in the consolidated statements of financial condition, is marked to market based on the current fair value of the underlying security at the reporting date. Changes in fair value of securities sold, not yet purchased are recorded as unrealized gains or losses in Institutional trading revenue in the consolidated statements of operations. Total unrealized losses related to these securities for the year ended December 31, 2014 amounted to $0.5 million.
Due to Related Parties Pursuant to Tax Receivable Agreement
Exchanges of Holdings membership units ("Holdings Units") for the Corporation’s Class A common stock that are executed by the members of Holdings result in transfers of and increases in the tax basis of the tangible and intangible assets of Holdings, primarily attributable to a portion of the goodwill inherent in the business. These transfers and increases in tax basis will increase (for tax purposes) amortization and therefore reduce the amount of tax that the Company would otherwise be required to pay in the future. This increase in tax basis may also decrease gain (or increase loss) on future dispositions of certain capital assets to the extent tax basis is allocated to those capital assets. Holdings has entered into a tax receivable agreement with the members of Holdings whereby the Corporation has agreed to pay to the exchanging members 85% of the amount of cash tax savings, if any, in U.S. federal, state and local income tax that the Corporation realizes as a result of these increases in tax basis. The Corporation expects to benefit from the remaining 15% of cash tax savings, if any, in income tax it realizes. Payments under the tax receivable agreement will be based on the tax reporting positions that the Corporation takes in preparing its tax returns. The Corporation will not be reimbursed for any payments previously made under the tax receivable agreement if a tax basis increase is successfully challenged by the Internal Revenue Service.
Holdings records an increase in deferred tax assets for the estimated income tax effects of the increases in tax basis based on enacted federal and state tax rates at the date of the exchange. To the extent that Holdings estimates that the exchanging members will not realize the full benefit represented by the deferred tax asset, based on an analysis that will consider, among other things, its expectation of future earnings, the Company will reduce the deferred tax asset with a valuation allowance. The Corporation records 85% of the estimated realizable tax benefit (which is the recorded deferred tax asset less any recorded valuation allowance) as an increase to the contingent liability due under the tax receivable agreement. Presently, the liability is a contingent liability based on the earnings of the Corporation and the expected tax benefit realized by the Corporation, but upon certain events such as a change in control or a material breach of the tax receivable agreement, the liability no longer stays contingent but rather becomes absolute. The remaining 15% of the estimated realizable tax benefit is initially recorded as an increase to the Corporation’s capital. All of the effects to the deferred tax asset of changes in any of the estimates after the tax year of the exchange will be reflected in the provision for income taxes. Similarly, the effect of subsequent changes in the enacted tax rates will be reflected in the provision for income taxes.
Convertible Debt Transactions
The Company separately accounts for the liability and equity components of convertible debt instruments that may be settled entirely or partially in cash upon conversion by allocating the proceeds from issuance between the liability component and the embedded conversion option, or equity component, in accordance with ASC 470, Debt ("ASC 470"). The value of the equity component is calculated by first measuring the fair value of the liability component, using the interest rate of a similar liability that does not have a conversion feature, as of the issuance date. The difference between the proceeds from the convertible debt issuance and the amount measured as the liability component is recorded as the equity component. The Company recognizes the accretion of the resulting discount as part of interest expense in our consolidated statements of operations.
Contingent Consideration
The Company records a liability for contingent consideration resulting from a business combination at its fair value on the acquisition date included in Other liabilities in the consolidated statements of financial condition. Each reporting period thereafter, the Company revalues this liability and records increases or decreases in the fair value as an adjustment to Other income within the consolidated statements of operations. Changes in the fair value of the contingent consideration liability can result from adjustments in the probability targets of achieving profitability and adjustments to the discount rate.
Foreign Currency
Foreign denominated assets and liabilities are re-measured into the functional currency at exchange rates in effect at the statements of financial condition dates through the consolidated statements of operations. Gains or losses resulting from foreign currency transactions are re-measured using the rates on the dates on which those elements are recognized during the period, and are included in Retail and Institutional trading revenue in the consolidated statements of operations. The Company recorded gains of $3.6 million, $5.3 million and $0.8 million for the years ended December 31, 2014, 2013 and 2012, respectively.
Translation gains or losses resulting from translating the Company’s subsidiaries’ financial statements from the functional currency to the reporting currency, net of tax, are included in Foreign currency translation gain (loss) in the consolidated statements of comprehensive income. Assets and liabilities are translated at the statement of financial condition date while revenues and expenses are translated at an applicable average rate.
Revenue Recognition
The Company makes foreign currency markets for customers trading in FX spot markets and through its subsidiary FSL, engages in equity and related brokerage activities. FX transactions are recorded on the trade date and positions are marked to market daily with related gains and losses, including gains and losses on open spot transactions, recognized currently in income. Commissions earned on brokerage activities are recorded on a trade date basis and are recognized currently in income.
Retail Trading Revenue
Under the Company’s retail agency FX offering, trading revenue is earned from charging a separate commission or by adding a markup to the price provided by FX market makers generating trading revenue based on the volume of transactions and is recorded on trade date. Under the agency model, when a customer executes a trade on the best price quotation presented by the FX market maker, the Company acts as a credit intermediary, or a riskless principal, simultaneously entering into a trade with the customer and the FX market maker. This agency model has the effect of automatically hedging the Company's positions and eliminating market risk exposure. Retail trading revenues from mark-up principally represent the difference of the Company's realized and unrealized foreign currency trading gains or losses on its positions with customers and the systematic hedge gains and losses from the trades entered into with the FX market makers. Retail trading revenue also includes fees earned from arrangements with other financial institutions to provide platform, back office and other trade execution services. This service is generally referred to as a white label arrangement. The Company earns a percentage of the commission or markup charged by the financial institutions to their customers. Fees from this service are recorded when earned on a trade date basis.
Additionally, the Company earns income from trading in CFDs, rollovers, payments for order flow, and spread betting. Income or loss on CFDs represents the difference between the Company's realized and unrealized trading gains or losses on its positions and the hedge gains or losses with the other financial institutions. Income or loss on CFDs is recorded on a trade date basis. Income or loss on rollovers is the interest differential customers earn or pay on overnight currency pair positions held and the markup that the Company receives on interest paid or received on currency pair positions held overnight. Income or loss on rollovers is recorded on a trade date basis. In 2013 and through August 2014, the Company earned revenue on order flow. Income earned on order flow represents payments received from certain FX market makers in exchange for routing trade orders to these firms for execution. The Company's order routing software ensures that payments for order flow do not affect the routing of orders in a manner that is detrimental to its retail customers. The Company recognizes payments for order flow as earned on a trade date basis. Spread betting is where a customer takes a position against the value of an underlying financial instrument moving either upward or downward in the market. Income on spread betting is recorded as earned on a trade date basis.
Institutional Trading Revenue
Institutional trading revenue includes commission income generated by facilitating spot FX trades on behalf of institutional customers through the services provided by FXCM Pro and Faros. The counterparties to these trades are external financial institutions that also hold customer account balances and settle the transactions. The Company receives commission income on these trades without taking any market or credit risk. Institutional trading revenue is recorded on a trade date basis. The Company also earns income from market making and electronic trading in the institutional foreign exchange spot and futures markets through Lucid and market making and electronic trading into other asset classes through V3. Income on market making and electronic trading represents the spread between the bid and ask price for positions purchased and sold and the change in value of positions purchased and sold. Income on market making is recorded as trading gains, net of trading losses, on a trade date basis.
Interest Income
Interest income consists of interest earned on cash and cash equivalents and cash and cash equivalents, held for customers and is recognized in the period earned. Interest income also includes interest on the Notes receivable.
Other Income
Other income primarily includes amounts earned from the sale of market data, equity and equity option brokerage activities, including spread betting on equities, account maintenance fees, ancillary fee income and recovery of accounts receivable previously written off.
For the year ended December 31, 2014, Other income in the consolidated statements of operations primarily includes $3.7 million of revenue related to the re-measurement of the contingent consideration recorded for the acquisition of Faros (See Note 4), $2.5 million of account dormancy and ancillary fees, $5.8 million related to FSL's brokerage activities and a credit of $7.5 million attributable to the re-measurement of the Due to related parties pursuant to tax receivable agreement liability to reflect a revised effective tax rate.
For the year ended December 31, 2013, Other income in the consolidated statements of operations primarily includes $6.9 million of revenue related to the re-measurement of the contingent consideration recorded for the acquisition of Faros, $7.2 million of FSL's brokerage activities, $3.1 million of account dormancy and ancillary fees, partially offset by a charge of $1.2 million attributable to the re-measurement of the Due to related parties pursuant to tax receivable agreement liability to reflect a revised U.S. federal tax rate. For the year ended December 31, 2012, Other income in the consolidated statements of operations includes a $1.4 million gain related to a settlement with the former owners of ODL.
Communications and Technology
Communications and technology expense consists primarily of costs for network connections to our electronic trading platforms, telecommunications costs, and fees paid for access to external market data. This expense is affected primarily by the growth of electronic trading, our network/ platform capacity requirements and by changes in the number of telecommunication hubs and connections which provide our customers with direct access to our electronic trading platforms.
Trading Costs, Prime Brokerage and Clearing Fees
Trading costs, prime brokerage and clearing fees primarily represent fees paid to third party clearing banks and prime brokers for clearing foreign exchange spot futures currency and contract transactions, transaction fees paid to exchanges, equity options brokerage activity fees, and fees paid to third party providers for use of their platform for the Company’s market making trading business. Clearing fees primarily fluctuate based on changes in volume, rate of clearing fees charged by clearing banks and rate of fees paid to exchanges.
Referring Broker Fees
Referring broker fees represent commissions paid to brokers for introducing trading customers to the Company. Commissions are determined based on the number and size of transactions executed by the customers and are recorded on a trade date basis.
Compensation and Benefits
Compensation and benefits expense represents employee and member salaries and benefit expense, including stock-based compensation expense. Compensation and benefits also includes the Allocation of income to Lucid members for services provided. This expense represents the 49.9% of Lucid's earnings allocated among the non-controlling members of Lucid based on services provided to Lucid.
Stock-Based Compensation
The Company accounts for stock-based compensation in accordance with ASC 718, Compensation-Stock Compensation (“ASC 718”). The Company's stock-based compensation expense is measured at the date of grant, based on the estimated fair value of the award, and recognized on a straight-line basis over the requisite service period of the award, net of estimated forfeitures. The fair value of the Company's non-qualified stock options is estimated using the Black-Scholes option pricing model. The fair value of restricted stock units ("RSUs") is based on the fair market value of the Corporation's Class A common stock on the date of grant, adjusted for the present value of dividends expected to be paid on the Corporation's Class A common stock prior to vesting. Stock-based compensation expense is included in Compensation and benefits in the consolidated statements of operations (see Note 17).
Advertising and Marketing
Advertising and marketing costs are charged to operations when incurred.
General and Administrative Expenses
General and administrative expenses include bank processing and regulatory fees, professional fees, occupancy and equipment expense and other administrative costs. Bank processing fees are costs associated with the processing of credit card transactions. Regulatory fees are volume-based costs and annual fees charged by certain regulatory authorities and include fines and restitution imposed by regulators from time to time. General and administrative expense for the years ended December 31, 2014 and 2013 includes a charge of $2.5 million and $16.6 million, respectively, related to a liability established pertaining to a settlement with the FCA regarding the Company's pre-August 2010 trade execution practices (see Note 29).
Income Taxes
Holdings operates in the United States (“U.S.”) as a limited liability company that is treated as a partnership for U.S. Federal, state and local income tax purposes. As a result, Holdings' income from its U.S. operations is not subject to U.S. federal income tax because the income is attributable to its members. Accordingly, the Company’s U.S. tax provision is solely based on the portion of Holdings’ income attributable to the Corporation and excludes the income attributable to other members of Holdings whose income is included in Net Income attributable to non-controlling interest in FXCM Holdings, LLC in the consolidated statements of operations.
Income taxes are accounted for in accordance with ASC 740, Income Taxes ("ASC 740"), which requires that deferred tax assets and liabilities are recognized, using enacted tax rates, for the effect of temporary differences between the book and tax basis of recorded assets and liabilities. Deferred tax assets, including net operating losses and income tax credits, are reduced by a valuation allowance if it is "more likely than not" that some portion or all of the deferred tax assets will not be realized (see Note 26).
In addition to U.S. federal and state income taxes, Holdings is subject to Unincorporated Business Tax which is attributable to Holdings' operations apportioned to New York City. The Company’s foreign subsidiaries are also subject to local taxes.
In accordance with ASC 740, the Company evaluates a tax position to determine whether it is more likely than not that the tax position will be sustained upon examination, based on the technical merits of the position. If the position does not meet a more likely than not threshold, a tax reserve is established and no income tax benefit is recognized. The Company is audited by U.S. federal and state, as well as foreign, tax authorities. In some cases, many years may elapse before a tax return containing tax positions for which an ASC 740 reserve has been established is examined and an audit is completed. As audit settlements are reached, the Company adjusts the corresponding reserves, if required, in the period in which the final determination is made. While it is difficult to predict the final outcome or timing of a particular tax matter, the Company believes that reserves for uncertain tax positions are recorded pursuant to the provisions of ASC 740.
Recently Adopted Accounting Pronouncements
In February 2013, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU")No. 2013-04, Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation is Fixed at the Reporting Date. This standard requires an entity to measure obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date as the sum of (i) the amount the entity agreed to pay on the basis of its arrangement among its co-obligors and (ii) any additional amount it expect to pay on behalf of its co-obligors. The Company adopted this update on January 1, 2014 on a retrospective basis for all periods presented, which did not have a material impact on its consolidated financial statements.
In March 2013, the FASB issued ASU No. 2013-05, Parent's Accounting for the Cumulative Translation Adjustment upon Derecognition of Certain Subsidiaries or Groups of Assets within a Foreign Entity or of an Investment in a Foreign Entity. This standard addresses whether consolidation guidance or foreign currency guidance applies to the release of the cumulative translation adjustment into net income when a parent sells all or a part of its investment in a foreign entity or no longer holds a controlling financial interest in a subsidiary or net assets that are a business (other than a sale of in-substance real estate) within a foreign entity. The standard also resolves the diversity in practice for the cumulative translation adjustment treatment in business combinations achieved in stages involving foreign entities. Under this standard, the entire amount of the cumulative translation adjustment associated with the foreign entity should be released into earnings when there has been: (i) a sale of a subsidiary or group of net assets within a foreign entity and the sale represents a complete or substantially complete liquidation of the foreign entity in which the subsidiary or the net assets had resided; (ii) a loss of a controlling financial interest in an investment in a foreign entity; or (iii) a change in accounting method from applying the equity method to an investment in a foreign entity to consolidating the foreign entity. The Company adopted this update on January 1, 2014 on a prospective basis, which did not have a material impact on its consolidated financial statements.
In July 2013, the FASB issued ASU No. 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists. This standard requires a liability related to unrecognized tax benefits to be presented as a reduction to the related deferred tax asset for a net operating loss carryforward or a tax credit carryforward. When the carryforwards are not available at the reporting date under the tax law of the applicable jurisdiction or the tax law of the applicable jurisdiction does not require, and the entity does not intend to use, the deferred tax asset for such purpose, the unrecognized tax benefit will be presented in the financial statements as a liability and will not be combined with the related deferred tax asset. The Company adopted this update on January 1, 2014 on a prospective basis, which did not have a material impact on its consolidated financial statements.
Recently Issued Accounting Pronouncements
In April 2014, the FASB issued ASU No. 2014-08, Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360): Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity. Under this standard, a discontinued operation will include a disposal of a major part of an entity’s operations and financial results such as a separate major line of business or a separate major geographical area of operations. The standard also raises the threshold to be considered a major operation but no longer precludes discontinued operations presentation where there is significant continuing involvement or cash flows with a disposed component of an entity. The standard expands disclosures to include cash flows where there is significant continuing involvement with a discontinued operation and the pre-tax profit or loss of disposal transactions not reported as discontinued operations. The standard is effective prospectively for annual periods beginning on or after December 15, 2014, and interim periods within those years. Early adoption is permitted, but only for disposals that have not been reported in financial statements previously issued or available for issuance. The Company expects to adopt this standard prospectively on its required effective date of January 1, 2015 and the impact, if any, on its consolidated statements of financial condition, results of operations or cash flows will be dependent on the nature of future disposals.
In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers. The guidance in this update supersedes nearly all existing revenue recognition guidance under U.S. GAAP and creates a single, principle-based revenue recognition framework that is codified in a new FASB ASC Topic 606. The core principle of this guidance is for the recognition of revenue to depict the transfer of goods or services to customers at an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The standard sets out the following five steps an entity should apply to achieve this core principle:
•Identify the contract(s) with a customer
•Identify the performance obligations in the contract
•Determine the transaction price
•Allocate the transaction price to the performance obligations in the contract
•Recognize revenue when (or as) the entity satisfies a performance obligation
The standard also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. The new revenue standard is effective for annual reporting periods beginning after December 15, 2016, and interim periods within those years. Early adoption is not permitted. The new standard allows for either the full retrospective or cumulative effect transition method of adoption. The standard will be effective for the Company beginning January 1, 2017. The Company is currently evaluating the transition method that will be elected and the potential effects of the adoption of the new standard on its consolidated financial statements and related disclosures.
In August 2014, the FASB issued ASU No. 2014-15, Presentation of Financial Statements - Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern. The new standard requires management to explicitly evaluate for each reporting period whether there are conditions or events that raise substantial doubt about an entity’s ability to continue as a going concern and provide related footnote disclosure in certain circumstances. The new standard is effective for the annual period ending after December 15, 2016, and for annual and interim periods thereafter. Early application is permitted. The Company expects to adopt this standard for its annual period ending December 31, 2016 and is currently evaluating the impact the new standard will have on the disclosures in its consolidated financial statements.
In November 2014, the FASB issued ASU No. 2014-16, Derivatives and Hedging (Topic 815): Determining Whether the Host Contract in a Hybrid Financial Instrument Issued in the Form of a Share Is More Akin to Debt or to Equity. The new standard clarifies how current U.S. GAAP should be interpreted in evaluating the economic characteristics and risks of a host contract in a hybrid financial instrument that is issued in the form of a share. Specifically, the standard requires an entity to consider all of the stated and implied substantive terms and features of the entire hybrid financial instrument, including the embedded derivative feature that is being evaluated for separate accounting from the host contract, when evaluating whether the host contract is more akin to debt or equity. The new standard is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015. The effects of initially adopting the standard should be applied on a modified retrospective basis to existing hybrid financial instruments issued in the form of a share as of the beginning of the fiscal year for which the amendments are effective. Retrospective application to all relevant prior periods is permitted. Early adoption, including adoption in an interim period, is permitted. The Company expects to adopt this standard beginning January 1, 2016 and is currently evaluating the impact, if any, the new standard will have on its consolidated financial statements.

NonControlling_Interest

Non-Controlling Interest	12 Months Ended
	Dec. 31, 2014
Noncontrolling Interest [Abstract]
Non-Controlling Interest	Non-Controlling Interests
	Holdings
	The Corporation consolidates the financial results of Holdings and records a non-controlling interest for the economic interest in Holdings not owned by the Corporation. Pursuant to an agreement between the Corporation and Holdings, whenever the Corporation cancels, issues or repurchases shares of its Class A common stock, Holdings enters into an equivalent Holdings Unit transaction with the Corporation so that at all times the number of shares of Class A common stock is equal to the Corporation's membership units in Holdings. In addition, whenever the owners of Holdings prior to the initial public offering ("Existing Unit Holders") (other than the Corporation) exchange their Holdings Units for shares of the Corporation’s Class A common stock, Holdings is required to transfer an equal amount of Holdings Units to the Corporation.
	Changes in the non-controlling and the Corporation’s interests in Holdings for the year ended December 31, 2014 are presented in the following table:
		Controlling Units		Non-		Total Units		FXCM		Non-		Total
				Controlling Units				Inc.		Controlling
	Balance as of January 1, 2014	44,664,884		36,835,821		81,500,705		54.8	%	45.2	%	100	%
	Holdings Units acquired by FXCM Inc. related to exchanges of Holdings Units for shares of Class A common stock	2,378,147		(2,378,147	)	—		2.8	%	(2.8	)%	—	%
	Holdings Units repurchased related to Class A common stock repurchased	(145,985	)	—		(145,985	)	(0.1	)%	0.1	%	—	%
	Exercise of stock options	829,086		—		829,086		0.5	%	(0.5	)%	—	%
	Issuance under equity-based compensation	163,832		—		163,832		0.1	%	(0.1	)%	—	%
	Balance as of December 31, 2014	47,889,964		34,457,674		82,347,638		58.1	%	41.9	%	100	%
	Lucid, Faros, V3 and Other Non-Controlling Interests
	The Company owns a controlling interest in Lucid, Faros, V3 and other entities and consolidates the financial results of these entities whereby it records a non-controlling interest for the economic interests not owned by the Company.

Business_Acquisitions

Business Acquisitions	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Business Acquisitions	Business Acquisitions
	V3
	On January 21, 2014 (the "V3 Acquisition Date"), the Company, through a new entity, V3, created with the non-controlling members of Lucid, completed the acquisition of certain assets of Infinium Capital Holdings LLC ("Infinium") and certain of its affiliates. The acquisition expands the Lucid business model into a broader array of financial instruments and provides more robust connectivity to various financial exchanges. The consideration for the acquisition was approximately $32.5 million consisting of cash, assumed liabilities and the credit of $12.1 million of Infinium senior secured notes (the "Infinium Notes") plus interest held and exchanged by a subsidiary of the Company. The Company holds a controlling 50.1% interest in V3.
	The acquisition was accounted for in accordance with ASC 805. The assets acquired and the non-controlling interest were recorded at their estimated fair values in accordance with ASC 820, Fair Value Measurement ("ASC 820") at the V3 Acquisition Date. Full goodwill of $20.2 million was calculated as the fair value of estimated consideration over the estimated fair value of the net assets acquired. The estimated fair value of the non-controlling interest was $16.2 million and was determined by the fair value of the consideration. Goodwill was allocated to the Institutional reporting unit based on an analysis of the fair value of assets acquired. The goodwill is deductible for tax purposes. V3 is included in the Institutional segment for purposes of segment reporting (see Note 28).
	Subsequent to the acquisition date, the purchase price was decreased by $0.9 million, due to the final determination of the assumed liabilities. In connection with this purchase price adjustment, the initial goodwill recorded was reduced by $0.8 million to $19.4 million.
	V3 Purchase Price Allocation (¹)
	(Amounts in thousands)
	Purchase price				$	15,825
	Non-Controlling interest				15,762
	Total fair value at Acquisition Date				31,587
	Net assets acquired	$	10,210
	Adjustments to reflect acquired assets and liabilities at fair value
	Trading platform (2)	950
	Processing platform (3)	150
	Non-compete agreement (4)	450
	Executory contract (5)	470
	Fair value of net assets acquired				12,230
	Goodwill resulting from the V3 acquisition				$	19,357
	___________________
		(1)	The amounts included in the V3 Purchase Price Allocation table represent the allocation of the purchase price and include revisions made during the 12-month remeasurement period from the V3 Acquisition Date.
		(2)	Consists of internally-developed software platforms that support trade execution, with an amortization life of 4 years.
		(3)	Consists of an internally-developed software platform that supports trading, with an amortization life of 5 years.
		(4)	Amortization life is 1 year.
		(5)	Consists of a service agreement relating to fiber optics, wireless and other services, with an amortization life of 3 years.
	The amounts included in the V3 Purchase Price Allocation table represent the preliminary allocation of the purchase price and are subject to revision during the measurement period, a period not to exceed 12 months from the V3 Acquisition Date. Adjustments to the provisional values during the measurement period will be pushed back to the date of acquisition. Comparative information for periods after acquisition but before the period in which the adjustments were identified will be adjusted to reflect the effects of the adjustments as if they were taken into account as of the acquisition date. Changes to the amounts recorded as assets and liabilities will result in a corresponding adjustment to goodwill.
	Condensed Statement of Net Assets Acquired
	The following condensed statement of net assets acquired reflects the amounts of V3 net assets recognized as of the V3 Acquisition Date, with amounts in thousands:
		As of January 21, 2014
	Assets
	Office, communication and computer equipment, net	$	973
	Intangible assets	2,020
	Exchange memberships and common equity shares	6,429
	Equity method investments, net	1,523
	Other assets	1,392
	Total assets	$	12,337
	Liabilities	(107		)
	Fair value of net assets acquired	$	12,230
	Contingencies
	There were no contingent liabilities recorded in the fair value of net assets acquired as of the V3 Acquisition Date.
	Condensed Combined Financial Information:
	The following condensed financial information presents the resulting operations of V3 from the V3 Acquisition Date to December 31, 2014, with amounts in thousands:
		For the period
		January 21, 2014 to
		31-Dec-14
	Total revenue	$	20,706
	Net loss	$	(1,815	)
	Faros
	On September 20, 2013 (the “Faros Acquisition Date”), the Company acquired a 50.1% controlling interest in Faros. Faros is a global leader in foreign exchange intelligence, market coverage, and execution services to the institutional foreign exchange market. The acquisition further expands the Company's presence and capabilities in the institutional marketplace. As consideration, the Company provided an initial cash payment of $5.0 million (the “Initial Payment”) and a follow-on payment (the “ Follow-on Payment”) to be made in 2015 in an amount to be determined, based on the purchase agreement (the “Faros Purchase Agreement”) estimated at $10.6 million on the Faros Acquisition Date for a total estimated purchase price of $15.6 million. Pursuant to the terms of the Faros Purchase Agreement, the Follow-on Payment is payable partly in shares of the Corporation’s Class A common stock to one of the Faros sellers if certain criteria are met. Under the terms of the Faros Purchase Agreement, any of the Corporation’s Class A common stock issued to the Faros seller will be restricted for sale until September 2021 if the Faros seller ceases to be employed by Faros as of either December 31, 2015 or December 31, 2016 for reasons other than death, disability or the sale of the majority of the Corporation’s combined voting power. This restriction ("Faros Liquidity Restriction") had an estimated fair value of $0.4 million at the Faros Acquisition Date and is accounted for as deferred compensation and recognized over the term of the restriction.
	The Company has the option to buy out the remaining interest of the Faros sellers subject to the terms of the Faros Purchase Agreement. In the event the buyout is not exercised by the Company by December 31, 2017, the sellers have the right to market Faros for sale of all the membership interests of Faros.
	The fair value of the Follow-on Payment is included in Other liabilities in the consolidated statements of financial condition. Changes in the fair value of the Follow-on Payment subsequent to the Faros Acquisition Date are recognized in earnings in the period in which the change is recorded. The Company estimated the fair value of the Follow-on Payment using both a discounted cash flow model and guideline public company model. This fair value measurement is based on significant inputs not observed in the market. The discount rate considered in the assessment of the $10.6 million Follow-on Payment at the Faros Acquisition Date was 25.0%. In December 2013, the Company recorded a reduction to the Follow-on Payment of $6.9 million. In March 2014, the Company reduced the Follow-on Payment by the remaining $3.7 million. Both the $6.9 million decrease and the $3.7 million decrease in the estimated fair value of the Follow-on Payment are recorded in Other income in the consolidated statements of operations. The decline in the estimated fair value of the Follow-on Payment is due to lowering our Faros earnings before income taxes and depreciation ("EBITDA") estimate. The Company reassessed the Follow-on Payment liability at December 31, 2014 and determined that no Follow-on payment is due under the terms of the Faros Purchase Agreement.
	The Acquisition was accounted for in accordance with ASC 805. The assets acquired, liabilities assumed and non-controlling interest were recorded at their estimated fair values in accordance with ASC 820 at the Faros Acquisition Date as summarized in the table below. Full goodwill of $23.0 million was calculated as the fair value of estimated consideration over the estimated fair value of the net assets acquired. The estimated fair value of the non-controlling interest was $15.6 million, and was determined by valuing Faros using a discounted cash flow model and guideline public company model, less the Initial Payment and the Follow-on Payment. The estimate of the fair value of the non-controlling interest is based on an assumed discount rate of 25.0%, long term annual earnings growth rate of 3.0% and assumed adjustments due to the lack of control that market participants would consider when estimating the fair value of the non-controlling interest in Faros. Goodwill was allocated to the Institutional reporting unit based on an analysis of the fair value of assets acquired and expected future benefits of synergies created from combining the Faros market making business with the Company's foreign exchange trading expertise. The goodwill is deductible for tax purposes. Faros is included in the Institutional segment for purposes of segment reporting (see Note 28).
	Faros Purchase Price Allocation (¹)
	(Amounts in thousands)
	Purchase price				$	15,631
	Non-Controlling interest				15,569
	Total fair value at Acquisition Date				31,200
	Net assets acquired	$	137
	Adjustments to reflect acquired assets and liabilities at fair value
	Customer relationships (2)	6,000
	Non-compete agreement (3)	1,900
	Trade name (4)	130
	Fair value of net assets acquired				8,167
	Goodwill resulting from the Faros acquisition				$	23,033
	____________________
(1)	The amounts included in the Faros Purchase Price Allocation table represent the allocation of the purchase price and include revisions made during the 12-month remeasurement period from the Faros Acquisition Date.
(2)	Consists of institutional and bank customers, with an amortization life of 4 years.
(3)	Amortization life is 9 years.
(4)	Amortization life is 3 years.
The amounts included in the Faros Purchase Price Allocation table represent the preliminary allocation of the purchase price as well as revisions made during the 12-month measurement period from the Faros Acquisition Date. Adjustments to the provisional values during the measurement period, which were not material, were pushed back to the date of acquisition. Comparative information for periods after acquisition but before the period in which the adjustments were identified were adjusted to reflect the effects of the adjustments as if they were taken into account as of the acquisition date. Changes to the amounts recorded as assets and liabilities resulted in a corresponding adjustment to goodwill.
Condensed Statement of Net Assets Acquired
The following condensed statement of net assets acquired reflects the amounts of Faros net assets recognized as of the Faros Acquisition Date, with amounts in thousands:
	As of September 20, 2013
Assets
Cash and cash equivalents	$	1,055
Accounts receivable, net	40
Office, communication and computer equipment, net	31
Intangible assets	8,030
Other assets	76
Total assets	$	9,232
Liabilities
Accounts payable and accrued expenses	1,065
Total liabilities	1,065
Fair value of net assets acquired	$	8,167
Contingencies and Accounts Receivable
There were no contingent liabilities recorded in the fair value of net assets acquired as of the Faros Acquisition Date and the fair value of net assets acquired includes accounts receivables with book value that approximates fair value. There was no reserve netted against receivables as of the Faros Acquisition Date. The Company has collected all material accounts receivable amounts as of December 31, 2014.
Condensed Combined Financial Information:
The following condensed financial information presents the resulting operations of Faros from the Faros Acquisition Date to December 31, 2013, with amounts in thousands:
	For the period September 20, 2013 to December 31, 2013
Total revenue	$	526
Net loss	$	(301	)
Lucid
On June 18, 2012 (the “Lucid Acquisition Date”), the Company acquired a 50.1% controlling interest in Lucid, an electronic market maker and trader in the institutional foreign exchange spot and futures markets headquartered in the U.K., to expand the Company's presence and capabilities in the institutional marketplace. Lucid's sole material asset is a controlling membership interest in Lucid LLP, an electronic market maker and trader in the institutional foreign exchange spot and futures markets headquartered in the U.K. As consideration, the Company issued $71.4 million, 3.5% unsecured promissory notes, and 9.0 million unregistered shares of the Corporation's Class A common stock to Lucid sellers as well as a $15.8 million, 3.5% unsecured promissory note for all liquid assets for a total estimated purchase price of $177.5 million. The Lucid sellers were entitled to 1.8 million shares of the 9.0 million shares at closing, with the remaining 7.2 million shares held in escrow (the “Remaining Shares”), subject to the achievement of certain fixed profit-based targets (the “Profit Targets”). If the Profit Targets are achieved, the Lucid sellers are entitled to receive the Remaining Shares on the first, second and third anniversary following the Lucid Acquisition Date or over a three year term (the “Term”) pursuant to the sale purchase agreement (the “Purchase Agreement”). Pursuant to the terms of the Acquisition, any of the Corporation’s common shares issuable to a Lucid seller on an anniversary from closing will be restricted (the “Lucid Liquidity Restriction”) for sale until the eighth anniversary of the closing of the Acquisition if the recipient ceases to be employed by Lucid or any entity controlled by the Corporation for reasons other than death or incapacity on such anniversary. The Purchase Agreement includes a contingent arrangement which provides for a claw back of the Remaining Shares in the event that the Profit Targets are not achieved. Additionally, the Company has the option to buy-out the remaining interest of the Lucid sellers subject to terms of the Purchase Agreement. In the event the buy-out is not exercised by the Company within four years from the Lucid Acquisition Date, the Lucid sellers have the ability to buy-back the Company’s ownership interests within 30 days of the fourth anniversary date.
The estimated fair value of the 9.0 million shares was $89.4 million and is accounted for as equity. This fair value consisted of 1.8 million shares with a fair value of $21.5 million based on the Corporation’s closing stock price as of the Lucid Acquisition Date and the Remaining Shares with an estimated fair value of $67.9 million, adjusted for the Lucid Liquidity Restriction. The estimated fair value of the Lucid Liquidity Restriction was $9.4 million, and is accounted for as deferred compensation and recognized over the Term.
The Acquisition was accounted for in accordance with ASC 805. The assets acquired, liabilities assumed and non-controlling interest were recorded at their estimated fair values in accordance with ASC 820 at the Lucid Acquisition Date as summarized in the table below. Full goodwill of $236.5 million was calculated as the fair value over the estimated fair value of the net assets acquired. The estimated fair value of the non-controlling interest was $160.2 million, and was determined by valuing Lucid using a discounted cash flow method, less the considerations transferred. The estimate of the fair value of the non-controlling interest is based on an assumed discount rate between 10.0% and 11.0%, annual earnings growth rate of 4.0% and assumed adjustments due to the lack of control that market participants would consider when estimating the fair value of the non-controlling interest in Lucid. Goodwill was allocated to the Institutional reporting unit based on an analysis of the fair value of assets acquired and expected future benefits of synergies created from combining the Lucid market making business with the Company's foreign exchange trading expertise. The goodwill is deductible for U.K. income tax purposes. Lucid is included in the Institutional segment for purposes of segment reporting (see Note 28).
During the year ended December 31, 2013, the purchase price was increased by $15.3 million due to the final determination of tax balances at the Lucid Acquisition Date adjusted during the measurement period. The Company issued six-month 2.25% unsecured promissory notes to the Lucid sellers for the purchase price increase (see Note 23). In connection with this purchase price adjustment, the initial goodwill recorded was reduced by $1.2 million to $235.3 million.
Lucid Purchase Price Allocation (¹)
(Amounts in thousands)
Purchase price				$	192,784
Non-Controlling interest				160,165
Total fair value at Acquisition Date				352,949
Net assets acquired	$	32,732
Adjustments to reflect acquired assets and liabilities at fair value
Proprietary technology (2)	83,900
Non-compete agreements (3)	1,000
Fair value of net assets acquired				117,632
Goodwill resulting from the Lucid acquisition				$	235,317
____________________
(¹) The amounts included in the Lucid Purchase Price Allocation table represent the allocation of the purchase price and include revisions made during the 12-month remeasurement period from the Lucid Acquisition Date.
(²) Consists of internally-developed software platforms through which the Company: (i) executes its specific trading strategies, with an amortization life of 4 years and (ii) clears and efficiently settle trades, with an amortization life of 7 years.
(³) Consists of two non-compete agreements with amortization lives of 3 years.
The amounts included in the Lucid Purchase Price Allocation table represent the preliminary allocation of the purchase price as well as revisions made during the 12-month measurement period from the Lucid Acquisition Date. Adjustments to the provisional values during the measurement period were pushed back to the date of acquisition. Comparative information for periods after acquisition but before the period in which the adjustments were identified were adjusted to reflect the effects of the adjustments as if they were taken into account as of the acquisition date. Changes to the amounts recorded as assets and liabilities resulted in a corresponding adjustment to goodwill.
Condensed Statement of Net Assets Acquired
The following condensed statement of net assets acquired reflects the amounts of Lucid net assets recognized as of the Lucid Acquisition Date, with amounts in thousands:
	As of June 18, 2012
Assets
Cash and cash equivalents	$	28,656
Accounts receivable, net	5,100
Due from brokers	302
Deferred tax asset	11,311
Office, communication and computer equipment, net	499
Intangible assets	84,900
Other assets	226
Total assets	$	130,994
Liabilities
Accounts payable and accrued expenses	13,362
Total liabilities	13,362
Fair value of net assets acquired	$	117,632
Contingencies and Accounts Receivable
There were no contingent liabilities recorded in the fair value of net assets acquired as of the Lucid Acquisition Date. The Company has collected all accounts receivable amounts.
Condensed Combined Financial Information:
The following condensed financial information presents the resulting operations of Lucid from the Lucid Acquisition Date to December 31, 2012:
	For the period June 18, 2012 to December 31, 2012
Total revenue	$	42,198
Net income	$	21,446
Pro Forma Condensed Combined Financial Information
The following pro forma condensed combined financial information represents the Company's revenues and net income before non-controlling interest as they may have appeared in the consolidated statements of operations if the acquisitions of Lucid, Faros and V3 had occurred on January 1, 2011, 2012 and 2013, respectively, with amounts in thousands:
	Years Ended December 31,
	2014			2013		2012
Total revenues	$	463,757		$	535,130	$	463,767
Net income before non-controlling interest	$	17,583		$	36,838	$	49,224
These pro forma results for the years ended December 31, 2014, 2013 and 2012 primarily include the elimination of certain revenues and expenses resulting from transactions conducted with Lucid prior to the acquisition, as well as adjustments for the intangible assets acquired and the related tax impact.
Acquisition-related Costs
For the year ended December 31, 2014, acquisition-related transaction costs for the V3 acquisition were $1.2 million. For the year ended December 31, 2013, acquisition-related transaction costs for the Faros acquisition were not significant. For the year ended December 31, 2012, acquisition-related costs for Lucid were $0.9 million. Acquisition-related transaction costs are included in General and administrative expense in the consolidated statements of operations.

Restricted_Time_Deposits

Restricted Time Deposits	12 Months Ended
	Dec. 31, 2014
Cash and Cash Equivalents [Abstract]
Restricted Time Deposits	Restricted Time Deposits
	On July 3, 2014, FXCMJ established a $3.3 million, 0.025%, three-month time deposit, which was renewed in October 2014, and a $5.0 million, 0.025%, one-year time deposit with Sumitomo Mitsui Banking Corporation (“SMBC”). The time deposits secure a letter of guarantee issued by SMBC on behalf of FXCMJ and may be withdrawn under limited circumstances subject to certain financial covenants in the letter of guarantee. If the circumstances for withdrawal are not met, the time deposits renew for the same terms. There have been no withdrawals on the time deposits as of December 31, 2014. As a result of the restriction on withdrawal, the time deposits are presented separately in the consolidated statements of financial condition.

Trading_Securities

Trading Securities	12 Months Ended
	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Trading Securities	Trading Securities
	Equity securities purchased with the intent to sell in the near-term are classified as trading securities and are carried at their fair value based on the quoted market prices of the securities in active markets. As of December 31, 2014 and 2013, trading securities amounted to $26 thousand and nil, respectively.
	Net realized and unrealized gains and losses on trading securities are included in Institutional trading revenue in the consolidated statements of operations. For the purpose of determining realized gains and losses, the cost of securities sold is based on specific identification.
	For the year ended December 31, 2014, net realized and unrealized gains related to trading securities were $3.8 million. There were no realized or unrealized gains or losses related to trading securities for the year ended December 31, 2013.

Notes_Receivable

Notes Receivable	12 Months Ended
	Dec. 31, 2014
Receivables [Abstract]
Notes Receivable	Notes Receivable
	As described in Note 4, V3 was formed by the Company and the non-controlling members of Lucid on January 21, 2014. The Company contributed capital of approximately $16.3 million and the non-controlling members of Lucid contributed capital of approximately $16.2 million. The non-controlling members of Lucid originally borrowed approximately $8.1 million from the Company to assist with funding their portion of the capital contribution. As a result of an adjustment to the purchase price subsequent to the acquisition date, the principal amount of the loan was revised to $7.9 million, which is included in Notes receivable within noncurrent assets in the consolidated statements of financial condition as of December 31, 2014. The amount borrowed is due in 2017 and bears interest at the rate of 2% per annum. Interest income related to the notes receivable was not material for the year ended December 31, 2014. As of December 31, 2014, there was no reserve against the Notes receivable.
	In May 2014, the Company loaned $1.5 million to a retail FX provider. The amount borrowed was due in 2017 and bore interest at the rate of 15% per annum, due at the end of each calendar quarter. The principal amount of the loan is included in Notes receivable within noncurrent assets in the consolidated statements of financial condition as of December 31, 2014. The loan was collateralized by the assets of the borrower. In February 2015, the principal amount plus accrued interest was repaid to the Company.
	On October 2, 2013, the Company acquired the Infinium Notes receivable aggregating $11.9 million with an interest rate of 4%. The principal of the Infinium Notes was payable in two lump sums with 50% due on August 1, 2014 and the remaining 50% due on August 1, 2015, and was included in Notes receivable within current and noncurrent assets, respectively, in the consolidated statements of financial condition as of December 31, 2013. The Infinium Notes were secured by liens on capital stock, equity interest held and certain other subsidiaries and other assets of Infinium Capital. On the V3 Acquisition Date, the Infinium Notes plus interest were credited towards the consideration for the V3 Acquisition (See Note 4).

Equity_Method_Investment

Equity Method Investment	12 Months Ended
	Dec. 31, 2014
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investment	Equity Method Investments
	On December 4, 2012, the Company completed the acquisition of a non-controlling equity interest in FastMatch, Inc. ("FastMatch"), an electronic communication network for foreign exchange trading. As the Company holds a 35.3% equity interest and exerts significant influence, the investment is accounted for using the equity method and is included in the institutional segment for purposes of segment reporting (see Note 28). The Company also has a 21.8% equity interest in a developer of FX trading software which is accounted for using the equity method and is included in the corporate segment for purposes of segment reporting.
	In conjunction with the V3 acquisition on January 21, 2014, the Company acquired a 66.3% non-controlling interest in a limited liability company ("LLC") that holds a 17.26% interest in a firm that delivers investment information to investment professionals. As of December 31, 2014, the other members of the LLC have not yet consented to the transfer of the 66.3% non-controlling interest to the Company. Until such consent is received, the Company is only entitled to its share of profits, losses and distributions and the Company does not have any right to participate in the management of the business and affairs of the LLC, including participating in major decisions. Accordingly, the Company’s interest is accounted for using the equity method and is included in the institutional segment for purposes of segment reporting (see Note 28).
	As of December 31, 2014 and 2013, the Company’s carrying values of equity method investments were $10.0 million and $9.8 million, respectively, and are included as a component of Other assets in the consolidated statements of financial condition.
	Loss on equity method investments was $1.3 million and $0.8 million for the years ended December 31, 2014 and 2013, respectively, and is included in Loss on equity method investments, net in the consolidated statements of operations. Income or loss recognized from equity method investments was not material for the year ended December 31, 2012.
	The Company did not receive any dividend distributions from its equity method investments during the years ended December 31, 2014 and 2012. Dividend distributions received from the Company's equity method investments during the year ended December 31, 2013 were not significant.

Office_Communication_and_Compu

Office, Communication and Computer Equipment, net	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Office, Communication and Computer Equipment, net	Office, Communication and Computer Equipment, net
	Office, communication and computer equipment, net, including capitalized software development costs, leasehold improvements and capital leases, consisted of the following as of December 31, 2014 and 2013, with amounts in thousands:
		As of December 31,
		2014			2013
	Computer equipment	$	30,961		$	28,047
	Software	63,766			47,138
	Leasehold improvements	10,095			9,687
	Furniture and fixtures and other equipment	3,521			3,427
	Licenses	11,499			10,101
	Communication equipment	2,444			1,664
	Total office, communication and computer equipment	122,286			100,064
	Less: Accumulated depreciation	(74,092		)	(50,899		)
	Office, communication and computer equipment, net	$	48,194		$	49,165
	Depreciation is computed on a straight-line basis (see Note 2). Depreciation expense, including impairments, included in the consolidated statements of operations was $25.2 million, $25.8 million and $17.7 million for the years ended December 31, 2014, 2013 and 2012, respectively. Also included in depreciation expense is amortization related to capitalized software development costs of $13.7 million, $10.6 million and $6.5 million for the years ended December 31, 2014, 2013 and 2012, respectively. Unamortized capitalized software development costs were $28.9 million and $26.0 million as of December 31, 2014 and 2013, respectively.
	Assets disposed of during the year ended December 31, 2014 were $4.4 million. The Company disposed of $19.2 million of fully depreciated assets during the year ended December 31, 2013. During the year ended December 31, 2013, the Company recorded an impairment of $3.5 million to write down the value of an electronic FX option trading platform and, in 2014, recorded an additional impairment of $1.1 million to write down the remaining value of this asset. The impairment charges are included in Depreciation and amortization expense in the consolidated statements of operations and are included in retail trading for purposes of segment reporting.

Goodwill

Goodwill	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Goodwill
	The following table presents the changes in goodwill by segment during the year ended December 31, 2014, with amounts in thousands:
		Retail Trading			Institutional Trading			Total
	Balance at January 1, 2014	$	38,079		$	269,857		$	307,936
	Goodwill acquired	—			19,357			19,357
	Goodwill adjustment	—			(9		)	(9		)
	Foreign currency translation adjustment	(2,703		)	(694		)	(3,397		)
	Balance at December 31, 2014	$	35,376		$	288,511		$	323,887
	The events described in Note 30 “Subsequent Events” occurred after December 31, 2014 and therefore do not impact the carrying value of goodwill as of December 31, 2014. The subsequent events are considered a triggering event that will require an interim impairment evaluation of goodwill in the fiscal quarter ending March 31, 2015. As of the report date, an estimate of the financial impact of the interim assessment cannot be made and will not be determined until the impairment testing is completed.

Other_Intangible_Assets_net

Other Intangible Assets, net	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Other Intangible Assets, net	Other Intangible Assets, net
	The Company’s acquired intangible assets consisted of the following as of December 31, 2014 and 2013, with amounts in thousands:
		December 31, 2014									December 31, 2013
		Gross Carrying Amount			Accumulated Amortization			Net Carrying Amount			Gross Carrying Amount			Accumulated Amortization			Net Carrying Amount
	Finite-lived intangible assets
	Customer relationships	$	47,397		$	(21,944	)	$	25,453		$	37,746		$	(14,529	)	$	23,217
	Non-compete agreements	3,350			(1,489		)	1,861			10,507			(8,177		)	2,330
	Proprietary technology	85,000			(52,844		)	32,156			83,900			(31,849		)	52,051
	Executory contract	470			(131		)	339			—			—			—
	Trade name	241			(56		)	185			177			(13		)	164
	Foreign currency translation adjustment	(4,391		)	1,354			(3,037		)	(1,831		)	172			(1,659		)
	Total finite-lived intangible assets	$	132,067		$	(75,110	)	$	56,957		$	130,499		$	(54,396	)	$	76,103
	Indefinite-lived intangible assets
	License	610			—			610			610			—			610
	Total Other intangible assets, net	$	132,677		$	(75,110	)	$	57,567		$	131,109		$	(54,396	)	$	76,713
	Customer relationships, non-compete agreements, proprietary technology, the executory contract and trade name are amortized on a straight-line basis over 3 to 9 years, 1 to 9 years, 4 to 7 years, 3 years and 3 years, respectively, which approximates the weighted-average useful lives. Indefinite-lived assets are not amortized (see Note 2). Amortization expense included in the consolidated statements of operations was $29.8 million, $27.9 million and $19.0 million for the years ended December 31, 2014, 2013 and 2012 respectively. During 2014, there were disposals of fully amortized intangible assets of $8.1 million.
	Estimated future amortization expense for acquired intangible assets outstanding as of December 31, 2014 is as follows, with amounts in thousands:
	Year Ending December 31,
	2015	$	30,765
	2016	18,836
	2017	4,889
	2018	1,059
	2019	723
	Thereafter	685
		$	56,957
	The events described in Note 30 “Subsequent Events” occurred after December 31, 2014 and therefore do not impact the carrying value of intangible assets as of December 31, 2014. The subsequent events are considered a triggering event that will require an impairment evaluation of intangible assets in the fiscal quarter ending March 31, 2015. As of the report date, an estimate of the financial impact of the assessment cannot be made and will not be determined until the impairment testing is completed.

Other_Assets

Other Assets	12 Months Ended
	Dec. 31, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Other Assets	Other Assets
	Other assets were comprised of the following as of December 31, 2014 and 2013, with amounts in thousands:
		As of December 31,
		2014		2013
	Prepaid expenses	$	5,823	$	5,738
	Equity method investments	10,007		9,793
	Deferred debt issuance costs	5,582		7,131
	Exchange memberships	6,429		—
	Deposits	1,514		1,492
	Other	293		162
	Total	$	29,648	$	24,316

Customer_Account_Liabilities

Customer Account Liabilities	12 Months Ended
	Dec. 31, 2014
Other Liabilities Disclosure [Abstract]
Customer Account Liabilities	Customer Account Liabilities
	Customer account liabilities represent amounts due to customers related to cash and margin transactions. This includes cash deposits and gains and losses on settled FX, CFDs and spread betting trades as well as unrealized gains and losses on open FX commitments, CFDs and spread betting. Customer account liabilities were $1.3 billion and $1.2 billion as of December 31, 2014 and 2013, respectively.

Accounts_Payable_and_Accrued_E

Accounts Payable and Accrued Expenses	12 Months Ended
	Dec. 31, 2014
Payables and Accruals [Abstract]
Accounts Payable and Accrued Expenses	Accounts Payable and Accrued Expenses
	Accounts payable and accrued expenses were comprised of the following as of December 31, 2014 and 2013, with amounts in thousands:
		As of December 31,
		2014		2013
	Operating expenses payable	$	23,256	$	41,528
	Due to Lucid non-controlling members	8,876		9,995
	Commissions payable	11,864		9,485
	Bonus payable	9,664		7,455
	Income tax payable	2,158		1,046
	Interest due on borrowings	202		177
	Other	19		11
	Total	$	56,039	$	69,697

Earnings_per_Share

Earnings per Share	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Earnings per Share	Earnings per Share
	Basic earnings per share (“EPS”) measures the performance of an entity over the reporting period. Diluted EPS measures the performance of an entity over the reporting period while giving effect to all potentially dilutive instruments that were outstanding during the period. The Company uses the treasury stock method in accordance with ASC 260, Earnings per Share (“ASC 260”), to determine diluted EPS.
	In accordance with ASC 260, all outstanding unvested share-based payments that contain rights to non-forfeitable dividends participate in the undistributed earnings with the common stockholders and are therefore participating securities. The Company's unvested RSUs do not contain rights to dividends or dividend equivalents. As a result, unvested RSUs are not considered participating securities and are therefore not required to be included in computing basic EPS under the two-class method. The shares of Class B common stock do not share in the earnings of the Company and are not considered participating securities. Accordingly, basic and diluted net earnings per share of Class B common stock have not been presented.
	For the years ended December 31, 2014 and 2013, stock options and other equity awards granted to certain employees, non-employees and independent directors in the aggregate of 1,002,990 and 426,000, respectively, were not included in the computation of diluted EPS because they were antidilutive under the treasury method.
	The Company issued 7.2 million shares of the Corporation’s Class A common stock in connection with the Lucid acquisition subject to the achievement of certain targets related to the financial performance of Lucid (the "Profit Targets"). The Lucid sellers achieved the Profit Targets for the first anniversary shares during the quarter ended June 30, 2013 and received 1.2 million shares which are included in the computation of basic and diluted EPS for the year ended December 31, 2013. The Lucid sellers achieved the Profit Targets for the second anniversary shares during the quarter ended June 30, 2014 and received 3.0 million shares which are included in the computation of basic and diluted EPS for the year ended December 31, 2014. If the third anniversary Profit Targets are achieved, the Lucid sellers are entitled to receive 3.0 million shares on the third anniversary of the Lucid Acquisition Date. In accordance with ASC 260, the third anniversary shares are considered contingently issuable shares. Accordingly, the third anniversary shares are considered outstanding common shares and included in basic EPS as of the date that all necessary conditions to receiving the shares have been satisfied (that is, when issuance of the shares is no longer contingent) and there is no circumstance under which those shares would not be issued. In accordance with ASC 260, the shares are included in diluted EPS if all necessary conditions have been satisfied by the end of the period. As of December 31, 2014, the necessary conditions to receive the third anniversary shares have not been met and these shares are not included in the computation of basic and diluted EPS for the year ended December 31, 2014.
	As described in Note 23, in June 2013 FXCM Inc. issued $172.5 million principal amount of 2.25% senior convertible notes maturing on June 15, 2018 (the “Convertible Notes”). The Convertible Notes will be convertible at an initial conversion rate of 53.2992 shares of the Corporation's Class A common stock per $1,000 principal amount of the Convertible Notes, which is equivalent to an initial conversion price of approximately $18.76. In accordance with ASC 260, the shares of the Corporation's Class A common stock issuable upon conversion of the Convertible Notes are included in the calculation of diluted EPS to the extent that the conversion value of the securities exceeds the principal amount. For diluted EPS purposes, the number of shares of the Corporation's Class A common stock that is necessary to settle such excess is considered issued. For the year ended December 31, 2014, the conversion value did not exceed the principal amount and therefore the conversion effect was not included in the computation of diluted EPS because it was antidilutive under the treasury method.
	As described in Note 23, the Company also entered into a warrant transaction whereby the Company sold to the counterparties warrants to purchase shares of the Corporation's Class A common stock. For the year ended December 31, 2014, the warrants were not included in the computation of diluted EPS because they were antidilutive under the treasury method.
	Additionally, the non-controlling members of Holdings have the right to exchange their Holdings Units for shares of the Corporation’s Class A common stock on a one-for-one basis at fair value, subject to customary conversion rate adjustments for stock splits, stock dividends and reclassifications. These shares were also excluded from the computation of diluted EPS because they were antidilutive under the treasury method. During the years ended December 31, 2014 and 2013, certain members of Holdings exchanged 2.4 million and 10.1 million, respectively, of their Holdings Units, on a one-for-one basis, for shares of Class A common stock of the Corporation.
	The following is a reconciliation of the numerator and denominator used in the basic and diluted EPS calculations, with amounts in thousands, except per share data:
		For the Years Ended December 31,
		2014		2013		2012
	Basic and diluted net income per share:
	Numerator
	Net income available to holders of Class A common stock	$	17,151	$	14,832	$	8,958
	Earnings allocated to participating securities	—		—		—
	Earnings available for common stockholders	$	17,151	$	14,832	$	8,958
	Denominator for basic net income per share of Class A common stock
	Weighted average shares of Class A common stock	41,637		32,789		24,086
	Add dilutive effect of the following:
	Weighted average of Lucid's first anniversary shares issued on June 18, 2013	—		552		—
	Weighted average of Lucid's second anniversary shares issued on June 18, 2014	1,381		—
	Stock options and RSUs	992		616		—
	Convertible note hedges	—		—		—
	Warrants	—		—		—
	Assumed conversion of Holdings Units for Class A common stock	—		—		—
	Dilutive weighted average shares of Class A common stock	44,010		33,957		24,086
	Basic income per share of Class A common stock	$	0.41	$	0.45	$	0.37
	Diluted income per share of Class A common stock	$	0.39	$	0.44	$	0.37

Related_Party_Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2014
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions
	Amounts receivable from, and payable to, related parties are set forth below, with amounts in thousands:
		As of December 31,
		2014		2013
	Receivables
	Advances to Holdings non-controlling members	$	196	$	940
	Accounts receivable - Lucid non-controlling members	799		—
	Accounts receivable - equity method investment	1,468		—
	Advances to employees	563		826
	Notes receivable and interest - Lucid non-controlling members	8,013		—
	Total receivables from related parties	$	11,039	$	1,766
	Payables
	Guarantee agreement ("Monetary Guaranty")	$	7,078	$	8,363
	Employees	2,009		708
	Shareholders with greater than 5% ownership in the Company	—		200
	Due to Lucid non-controlling members in connection with the allocation of income to Lucid non-controlling members for services provided	8,876		9,826
	Due to Lucid non-controlling members in connection with trade settlements	—		169
	Notes payable to Lucid non-controlling members in connection with the Lucid Acquisition	—		9,800
	Accounts payable - equity method investment	—		378
	Faros Follow-on Payment	—		3,672
	Tax receivable agreement	150,576		150,258
	Total payables to related parties	$	168,539	$	183,374
	The Company has advanced funds for withholding taxes to several non-controlling members of Holdings. The outstanding balances as of December 31, 2014 and 2013, included in the table above, are included in Accounts receivable, net in the consolidated statements of financial condition.
	Included in Accounts receivable, net in the consolidated statements of financial condition as of December 31, 2014 is $0.8 million of advances to the Lucid non-controlling members.
	The Company receives commission or mark-up income from institutional customers’ trades executed on FastMatch's electronic trading platform, an entity in which the Company owns a 35.3% equity interest (see Note 8). The Company pays a per trade fee to FastMatch for use of the platform. During the years ended December 31, 2014 and 2013, fees collected from customer for trades executed on the FastMatch platform were $13.8 million and $5.1 million, respectively, included in Institutional trading revenue in the consolidated statements of operations, and fees paid to FastMatch were $7.4 million and $3.1 million, respectively, which are reflected as a component of Communication and technology in the consolidated statements of operations. The Company has also advanced funds for expenses on behalf of FastMatch. At December 31, 2014, Accounts receivable, net in the consolidated statements of financial condition included a receivable from FastMatch of $1.5 million for net amounts due from FastMatch. Accounts payable and accrued expenses at December 31, 2013 included $0.4 million of net amounts due to FastMatch.
	The Company has advanced funds to several employees. The outstanding balances as of December 31, 2014 and 2013, included in the table above, are included in Accounts receivable, net in the consolidated statements of financial condition.
	As described in Note 4, V3 was formed by the Company and the non-controlling members of Lucid. The Company contributed capital of approximately $16.3 million and the non-controlling members of Lucid contributed capital of approximately $16.2 million. After giving effect to an adjustment of the purchase price subsequent to the acquisition date, the non-controlling members of Lucid borrowed approximately $7.9 million from the Company to assist with funding their portion of the capital contribution, which is included in Notes receivable in the consolidated statements of financial condition as of December 31, 2014. The amount borrowed is due in 2017 and bears interest at the rate of 2% per annum. Interest income related to the notes receivable was not material for the year ended December 31, 2014.
	UK LTD is party to an arrangement with Global Finance Company (Cayman) Limited (“Global Finance”) and Master Capital Group, S.A.L. (“Master Capital”). A shareholder of the Company beneficially owns more than 90% of the equity of Global Finance and Master Capital. Pursuant to such arrangement, Global Finance and Master Capital are permitted to use the brand name “FXCM” and our technology platform to act as the Company’s local presence in certain countries in the Middle East and North Africa (“MENA”). UK LTD collects and remits to Global Finance and Master Capital fees and commissions charged by Global Finance and Master Capital to customers in MENA countries. For the years ended December 31, 2014, 2013 and 2012, these fees and commissions were approximately $1.3 million, $1.6 million and $2.5 million, respectively, and are included in the consolidated statements of operations in Referring broker fees. As of December 31, 2014, the shareholder described above beneficially owns less than 5% of the Corporation's Class A common stock.
	In March 2012, the Company entered into a settlement agreement with the former owners of ODL in connection with the acquisition of ODL by the Company in October 2010. The settlement agreement serves to settle outstanding claims arising out of the acquisition of ODL related to certain warranties and indemnities pursuant to the share and purchase agreement. The settlement to the Company included cash of $1.2 million, return of capital, (i.e., equity interest of Holdings) of $4.0 million, and the forgiveness of the payment of a liability by the Company to the former owners in the amount of $1.4 million. The Company recorded a gain of $1.4 million for the year ended December 31, 2012, included in Other income in the consolidated statements of operations, in connection with this settlement. In addition, the settlement required ODL to establish a collateral account for the benefit of the Company to pay certain outstanding third party claims up to an agreed upon amount. For the year ended December 31, 2013, the Company recorded a net loss of $0.2 million, included in Other income in the consolidated statements of operations, related to this settlement.
	In August 2012, the Company entered into a master guaranty agreement (the “Method Guaranty”) with Method Credit Fund (“Method”), a Cayman Island company, owned by certain directors and shareholders of the Company, including several of the Company’s executive officers. Pursuant to the Method Guaranty, Method unconditionally guaranteed the obligations of certain counterparties that maintained a margin account with the Company. The Method Guaranty required Method to maintain a cash collateral account held by the Company equal to the aggregate amount of margin extended to all counterparties covered by the Method Guaranty. In exchange for this unconditional guaranty, the Company remitted a fee to Method determined on a counterparty by counterparty basis which was agreed upon by the Company, Method and the respective counterparty. The agreement was terminated in November 2013 and upon termination, the aggregate amount of margin extended under the Method Guaranty was reduced to zero. During the year ended December 31, 2013, no payments were made by Method to the Company to satisfy a guaranteed counterparty obligation. For the years ended December 31, 2013 and 2012, fees collected from counterparties and subsequently remitted to Method by the Company were not material and are included in Referring broker fees in the consolidated statements of operations.
	In November 2013, the Company entered into a master guaranty agreement (the “Monetary Guaranty”) with Monetary Credit Group LLC (“Monetary”), a newly formed Texas limited liability company, owned by certain directors and shareholders of the Company, including several of the Company’s executive officers. Pursuant to the Monetary Guaranty, Monetary unconditionally guarantees the obligations of certain counterparties that maintain a margin account with the Company. The Monetary Guaranty requires Monetary to maintain a cash collateral account held by the Company equal to the aggregate amount of margin extended to all counterparties covered by the Monetary Guaranty. In exchange for this unconditional guaranty, the Company remits a fee to Monetary determined on a counterparty by counterparty basis which is agreed upon by the Company, Monetary and the respective counterparty. The Monetary Guaranty may be terminated by either the Company or Monetary at any time provided that if Monetary elects to terminate there are no guaranteed obligations outstanding. As of December 31, 2014 and 2013, the aggregate amount of margin extended under the Monetary Guaranty was $13.2 million and $4.5 million, respectively. During the years ended December 31, 2014 and 2013, no payments were made by Monetary to the Company to satisfy a guaranteed counterparty obligation. For the years ended December 31, 2014 and 2013, fees collected from counterparties and subsequently remitted to Monetary by the Company under the Monetary Guaranty were $1.1 million and $0.4 million and are included in Referring broker fees in the consolidated statements of operations.
	As of December 31, 2014 and 2013, the Company held cash collateral related to the Monetary Guaranty in the amount of $7.1 million and $8.4 million, respectively, which is included in Cash and cash equivalents, held for customers and Customer account liabilities in the consolidated statements of financial condition.
	Effective January 30, 2015, the Company terminated the Monetary Guaranty with Monetary.
	Customer account liabilities in the consolidated statements of financial condition include balances for employees and shareholders with greater than 5% ownership in the Company.
	As of December 31, 2014 and 2013, Accounts payable and accrued expenses in the consolidated statements of financial condition include $8.9 million and $9.8 million, respectively, related to the Allocation of income to Lucid members for services provided (see Note 2). Accounts payable and accrued expenses also includes a balance of nil and $0.2 million of advances from certain Lucid non-controlling members as of December 31, 2014 and 2013, respectively.
	Notes payable of nil and $9.8 million included in the consolidated statements of financial condition as of December 31, 2014 and 2013, respectively, represents the amount borrowed from the Lucid non-controlling members in connection with the Lucid acquisition. The Company repaid the unsecured promissory notes in December 2014 (see Note 23).
	Other liabilities in the consolidated statements of financial condition include the Faros Follow-on Payment of nil and $3.7 million as of December 31, 2014 and 2013, respectively (see Note 4). The Company reassessed the Follow-on Payment liability and determined that no payment was required under the Faros Purchase Agreement as of December 31, 2014.
	Exchange Agreement
	The members of Holdings (other than the Corporation) entered into an exchange agreement under which they (or certain permitted transferees thereof) have the right (subject to the terms of the exchange agreement as described therein) to exchange their Holdings Units for shares of the Corporation’s Class A common stock on a one-for-one basis at fair value, subject to customary conversion rate adjustments for stock splits, stock dividends and reclassifications. During the years ended December 31, 2014 and 2013, certain members of Holdings exchanged 2.4 million and 10.1 million, respectively, of their Holdings Units, on a one-for-one basis, for shares of Class A common stock of the Corporation pursuant to the exchange agreement.
	Payments under Tax Receivable Agreement
	The Corporation entered into a tax receivable agreement with the members of Holdings (other than the Corporation) that will provide for payments by the Corporation to Holdings’ members (other than the Corporation) (see Note 2). The aggregate payments due under the tax receivable agreement were $150.6 million and $150.3 million as of December 31, 2014 and 2013, respectively. During the years ended December 31, 2014 and 2013, payments of $3.7 million and $4.1 million, respectively, were made pursuant to the tax receivable agreement.

StockBased_Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation
	The Company’s Amended and Restated 2010 Long-Term Incentive Plan (the “LTIP”) permits the grant of various equity-based awards to employees, directors or other service providers of the Company and its subsidiaries. Under the LTIP, the Company has granted non-qualified stock options and other equity awards, including shares of the Corporation’s Class A common stock (“Shares”) and, beginning in the fourth quarter of 2014, RSUs. The total number of Shares which may be issued under the LTIP is 15,295,000. The Shares issued may consist, in whole or in part, of unissued Shares or treasury Shares. The issuance of Shares shall reduce the total number of Shares available under the LTIP. As of December 31, 2014, 4.4 million shares remained available for future issuance.
	In arriving at stock-based compensation expense, the Company estimates the number of equity-based awards that will forfeit due to employee turnover. The Company's forfeiture assumption is based primarily on its turn-over historical experience. If the actual forfeiture rate is higher than the estimated forfeiture rate, then an adjustment will be made to increase the estimated forfeiture rate, which will result in a decrease to the expense recognized in the Company's financial statements. If the actual forfeiture rate is lower than the estimated forfeiture rate, then an adjustment will be made to lower the estimated forfeiture rate, which will result in an increase to expense recognized in the Company's financial statements. The expense the Company recognizes in future periods will be affected by changes in the estimated forfeiture rate and may differ significantly from amounts recognized in the current period.
	Stock Options
	Stock options to purchase Shares are granted to employees (“Employee Stock Options”) and the independent members of the board of directors (“Independent Directors Options”) (collectively, the “Stock Options”). The Employee Stock Options have a four-year graded vesting schedule and a contractual term of seven years from the date of grant. The Independent Directors Options vest on the first anniversary after the grant date and have a seven-year contractual term. Under the terms of the LTIP, the Company may issue new shares or treasury shares upon share option exercise.
	During the year ended December 31, 2014, the Company granted 565,000 Employee Stock Options and 83,490 Independent Directors Options. During the year ended December 31, 2013, the Company granted 426,000 Employee Stock Options and 105,636 Independent Directors Options. During the year ended December 31, 2012, the Company granted 725,000 Employee Stock Options and 109,488 Independent Directors Options. Stock options are granted to employees and independent directors with exercise prices at least equal to the fair market value of a Share on the date the option is granted.
	The following table summarizes the Company’s stock options activity as of December 31, 2014 and changes for the year then ended:
	Stock Options	Shares			Weighted-Average Exercise Price				Weighted-Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (In thousands)
	Outstanding at January 1, 2014	7,607,800			$	13.48
	Granted	648,490			$	16.28
	Exercised	(829,086	)		$	13.48
	Forfeited or expired	(236,400	)		$	13.23
	Outstanding at December 31, 2014	7,190,804			$	13.74			3.59		$	20,525
	Options vested and expected to vest at December 31, 2014	7,166,783			$	13.74			3.58		$	20,461
	Options exercisable at December 31, 2014	5,776,564			$	13.67			3.15		$	16,780
	The weighted-average fair value per option granted in the years ended December 31, 2014, 2013, and 2012 was $5.66, $5.67 and $3.55, respectively. The total intrinsic value of options exercised in the years ended December 31, 2014, 2013 and 2012 was $2.3 million, $8.4 million and nil, respectively. The total grant-date fair value of options vested in the years ended December 31, 2014, 2013 and 2012 was $11.2 million, $11.0 million and $10.5 million, respectively.
	Valuation Assumptions
	The fair value of each option awarded to employees is estimated on the date of grant using the Black-Scholes option pricing model, consistent with the provisions of ASC 718. Options granted to the Company's independent directors are considered options granted to employees under ASC 718 as defined therein.
	The following assumptions were used in the Black-Scholes valuation model:
		Employee Stock Options												Independent Directors Options
		For the Years Ended December 31,												For the Years Ended December 31,
		2014				2013				2012				2014			2013			2012
	Expected term in years	4.75				4.75				4.75				4			4			4
	Risk-free interest rate	1.58		%		1.06		%		0.71		%		1.19		%	0.63		%	0.6		%
	Expected volatility	45		%		51		%		52		%		44		%	54		%	63		%
	Dividend yield	1.48		%		1.55		%		2.48		%		1.43		%	2.05		%	2.4		%
	Estimated fair value at grant date	$	5.7			$	6.02			$	3.47			$	5.39		$	4.26		$	4.11
	Expected term for the Employee Stock Options and Independent Directors Options is based on the simplified method outlined in ASC 718. In accordance with ASC 718, options are considered to be exercised halfway between the average vesting date and the contractual term of each option grant. The simplified method is applicable for “plain-vanilla” stock options, as defined in ASC 718, only if the Company does not have sufficient historical share option exercise experience upon which to estimate an expected term. Given that the Corporation’s Shares have been publicly traded for approximately four years, the Company believes that the simplified method is an applicable methodology to estimate the expected term of the options as of the grant date.
	The risk-free interest rates for the Employee Stock Options and Independent Directors Options are based on U.S. Treasury instruments whose terms are commensurate with the Stock Options’ expected terms.
	Expected volatility is based on a weighing of the historical and implied volatilities of the Company and for a set of public guideline companies deemed comparable to it. The guideline companies selected operate in a similar industry, pursue similar market opportunities, and are subject to similar risks of the Company. Changes in the subjective assumptions required in the valuation models may significantly affect the estimated value of the Company's Stock Options, the related stock-based compensation expense and, consequently, its results of operations and comprehensive income.
	Dividend yield is determined based on the Company's expected dividend payouts.
	Stock-based compensation expense before income taxes included in Compensation and benefits in the consolidated statements of operations was $9.5 million, $10.4 million and $9.8 million for the years ended December 31, 2014, 2013 and 2012, respectively, for the Employee Stock Options. Stock-based compensation expense before income taxes included in Compensation and benefits in the consolidated statements of operations was $0.5 million for 2014 and $0.4 million for each year ended December 31, 2013 and 2012, for the Independent Directors Options. The total compensation cost capitalized and included in Office, communication and computer equipment, net, in the consolidated statements of financial condition was $1.0 million for the year ended December 31, 2014 and $1.4 million for each year ended December 31, 2013 and 2012. The Company did not recognize any tax benefit related to stock-based compensation expense for the years ended December 31, 2014, 2013 and 2012.
	As of December 31, 2014, there was $5.2 million of total unrecognized compensation cost related to unvested Stock Options that is expected to be recognized over a weighted average period of 2.5 years.
	Cash proceeds received from the exercise of Stock Options and the income tax benefits realized from the exercise of those options were $11.2 million and nil, respectively, for the year ended December 31, 2014. Cash proceeds received from the exercise of Stock Options and the income tax benefits realized from the exercise of those options were $22.5 million and $1.5 million, respectively, for the year ended December 31, 2013. The Company did not have any cash proceeds or income tax benefits realized from the exercise of Stock Options for the year ended December 31, 2012.
	Other Equity Awards
	The LTIP provides for the grant of other stock-based awards (“Other Equity Awards”) which may include Shares and other awards that are valued in whole or in part by reference to, or are otherwise based on the fair market value of, Shares.
	RSUs
	During December 2014, the Company granted service-based RSUs to employees. The RSUs vest in equal annual installments over a four-year period following the date of grant, subject to the employees' continuing employment. RSUs that vest are settled by issuance of one Share for each RSU. If the employee terminates for any reason, any RSUs which have not vested as of the date of termination are forfeited and returned to the Company.
	Holders of RSUs do not have dividend, voting or any other rights of a shareholder with respect to the Shares underlying the RSUs unless and until the RSUs vest and are settled by the issuance of such Shares. The fair value of RSUs is based on the fair market value of Shares on the date of grant, adjusted for the present value of dividends expected to be paid on Shares prior to vesting. Such value is recognized as an expense over the requisite service period, net of estimated forfeitures.
	The following table summarizes the Company’s unvested RSU activity as of December 31, 2014 and changes for the year then ended:
			Units			Weighted-Average Grant-Date Fair Value				Weighted-Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
												(in thousands)
	Unvested at January 1, 2014		—			—
	Granted		208,500			$	16.25
	Vested		—			—
	Forfeited		—			—
	Unvested at December 31, 2014		208,500			$	16.25			3.96		$	3,455
	RSUs expected to vest at December 31, 2014		182,825			$	16.25			3.96		$	3,029
	Stock-based compensation expense before income taxes for RSUs, which is included in Compensation and benefits in the consolidated statements of operations, and total compensation cost capitalized for RSUs, which is included in Office, communication and computer equipment, net, in the consolidated statements of financial condition, was not material for the year ended December 31, 2014.
	As of December 31, 2014, there was $2.9 million of total unrecognized compensation cost related to unvested RSUs that is expected to be recognized over a weighted-average period of 3.96 years.
	Shares
	During the year ended December 31, 2012, the Company granted 945,847 Shares with a per share fair market value of $11.76 as Other Equity Awards. The Shares were fully vested at the date of the grant. The Company did not grant Shares as Other Equity Awards during the years ended December 31, 2014 and 2013. Stock-based compensation expense included in Compensation and benefits in the consolidated statements of operations related to Shares granted as Other Equity Awards was nil for each year ended December 31, 2014 and 2013 and $11.1 million for the year ended December 31, 2012.

Stockholders_Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity
	The Corporation’s authorized capital stock consists of 3,000,000,000 shares of Class A common stock, par value $.01 per share, 1,000,000 shares of Class B common stock, par value $.01 per share, and 300,000,000 shares of preferred stock, par value $.01 per share.
	Class A Common Stock Repurchase Program
	Our Board of Directors has previously approved the repurchase of $80.0 million of FXCM Inc.'s Class A common stock (the “Stock Repurchase Program”). On November 5, 2014, our Board of Directors approved a $50.0 million incremental increase in the Stock Repurchase Program for an aggregate of $130.0 million. Purchases under the Stock Repurchase Program may be made from time to time in the open market and in privately negotiated transactions. Under the Stock Repurchase Program, there is no expiration date or other restrictions limiting the period over which the Company can make its share repurchase. The Stock Repurchase Program will expire only when and if the Company has repurchased $130.0 million of its shares under this program. Under the Stock Repurchase Program, repurchased shares are retired and returned to unissued stock. The size and timing of these purchases are based on a number of factors, including price, business and market conditions.
	During the year ended December 31, 2014, the Company repurchased and retired 145,985 shares of its Class A common stock, at an average price of $15.48 per share, for approximately $2.3 million. The following table presents the changes in the Company’s Class A common stock outstanding during the year ended December 31, 2014, with amounts in thousands:
	Class A Common Stock
	Balance at January 1, 2014	44,665
	Issued	164
	Repurchased	(146	)
	Exchange of Holdings units into Class A common stock	2,378
	Stock options exercised	829
	Balance at December 31, 2014	47,890
	As of December 31, 2014 and 2013, there were 34 and 41 shares, respectively, of Class B common stock issued and held by the members of Holdings.
	Holders of shares of our Class A common stock and Class B common stock vote together as a single class on all matters presented to our stockholders for their vote or approval, except as otherwise required by applicable law.
	Class A Common Stock
	Holders of shares of the Corporation’s Class A common stock are entitled to one vote for each share held of record on all matters submitted to a vote of stockholders. Holders of shares of Class A common stock are entitled to receive dividends when and if declared by the Corporation’s board of directors out of funds legally available therefore, subject to any statutory or contractual restrictions on the payment of dividends and to any restrictions on the payment of dividends imposed by the terms of any outstanding preferred stock. Upon dissolution or liquidation or the sale of all or substantially all of the Corporation’s assets, after payment in full of all amounts required to be paid to creditors and to the holders of preferred stock having liquidation preferences, if any, the holders of shares of Class A common stock will be entitled to receive pro rata the Corporation’s remaining assets available for distribution. Holders of shares of Class A common stock do not have preemptive, subscription, redemption or conversion rights.
	Class B Common Stock
	Each holder of the Corporation’s Class B common stock is entitled, without regard to the number of shares of Class B common stock held by such holder, to one vote for each Holdings Unit in Holdings held by such holder. The unit holders of Holdings collectively have a number of votes in the Corporation that is equal to the aggregate number of Holdings Units that they hold. Holders of our Class B common stock do not have any right to receive dividends or to receive a distribution upon a liquidation or dissolution of the Corporation.

Employee_Benefit_Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Employee Benefit Plan	Employee Benefit Plan
	The Company maintains a defined contribution employee profit-sharing and savings 401(k) plan for all eligible full-time employees. The Company was not required to and made no contributions to the plan for the years ended December 31, 2014, 2013 and 2012.

Net_Capital_Requirements

Net Capital Requirements	12 Months Ended
	Dec. 31, 2014
Banking and Thrift [Abstract]
Net Capital Requirements	Net Capital Requirements
	Our regulated entities are subject to minimum capital requirements in their respective jurisdictions. The minimum capital requirements of the entities below may effectively restrict the payment of cash distributions by the subsidiaries. The tables below present the capital, as defined by the respective regulatory authority, the minimum capital requirement and the excess capital for US, HK, UK LTD, Australia, ODL, FSL, FXCMJ, Lucid LLP and Faros as of December 31, 2014 and 2013, with amounts in millions:
		As of December 31, 2014
		US		UK LTD		HK		Australia		ODL		FSL		FXCMJ		Lucid LLP		Faros
	Capital	$	69.5	$	101.6	$	31.2	$	3	$	25.5	$	40.2	$	36.3	$	22.8	$	0.4
	Minimum capital requirement	30		29.2		14.8		0.8		3		5.2		6.3		3.8		—
	Excess capital	$	39.5	$	72.4	$	16.4	$	2.2	$	22.5	$	35	$	30	$	19	$	0.4
		As of December 31, 2013
		US		UK LTD		HK		Australia		ODL		FSL		FXCMJ		Lucid LLP		Faros
	Capital	$	64.2	$	86	$	33.6	$	4.7	$	18.4	$	34.8	$	36.3	$	41.8	$	0.1
	Minimum capital requirement	27.1		24.7		12.3		0.4		6.9		8.2		5.6		4.2		—
	Excess capital	$	37.1	$	61.3	$	21.3	$	4.3	$	11.5	$	26.6	$	30.7	$	37.6	$	0.1

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies
	Operating Lease Commitments
	The Company leases office space and equipment under operating leases. Some of the lease agreements contain renewal options ranging from 3 to 5 years at prevailing market rates. The leases for the office facilities are subject to escalation factors primarily related to property taxes and building operating expenses. Future minimum lease payments under non-cancelable operating leases with terms in excess of one year are as follows as of December 31, 2014, with amounts in thousands:
	Year Ending December 31,
	2015	$	6,714
	2016	5,304
	2017	3,781
	2018	3,492
	2019	3,292
	Thereafter	19,858
		$	42,441
	The aggregate operating lease expense, included in General and administrative expense in the consolidated statements of operations for the years ended December 31, 2014, 2013 and 2012, was $10.2 million, $8.3 million and $7.9 million, respectively. For the years ended December 31, 2014 and 2013, there were no sublease commitments. The Company leases its corporate office location under an operating lease agreement expiring in May 2026.
	Capital Lease Commitments
	The Company leases office equipment under capital leases. Interest paid as part of our capital lease obligation was not material for the years ended December 31, 2014, 2013, and 2012, respectively. The capital leases expire in 2015. Future minimum lease payments for capital leases are not material for 2015.
	Other
	The Company holds an interest in an inactive entity that formerly provided online FX educational services (“Online Courses”). Online Courses meets the definition of a VIE under ASC 810 and the Company was considered the primary beneficiary. The members who owned the remaining interest in Online Courses had put options to sell their interest to the Company upon a change in control of Holdings. A change in control occurs when the number of Holdings Units held by unit holders as of the date of the Online Courses operating agreement, November 17, 2008, cease to make up at least 50% of the voting or vested economic interest securities of Holdings. The change in control occurred during the quarter ended September
	30, 2013. Under U.S. GAAP, the value of the put options is recognized upon both the change in control and the exercise of the
	put options.
	In 2014, the put options were exercised and Holdings remitted payments in the amount of $3.6 million. Based on the status (inactive and no assets) of Online Courses, the put option payments resulted in a charge to earnings, and General and administrative expense in the consolidated statements of operations for the year ended December 31, 2014 includes a charge of $3.6 million related to the put option payments.

Exchange_Memberships

Exchange Memberships	12 Months Ended
	Dec. 31, 2014
Brokers and Dealers [Abstract]
Exchange Memberships	Exchange Memberships
	The Company’s exchange memberships, which represent ownership interests and shares owned in the Chicago Mercantile and the Intercontinental exchanges and provide the Company with the right to conduct business on the exchanges, are recorded at cost or, if an other-than-temporary impairment in value has occurred, at a value that reflects management's estimate of the impairment. There were no exchange membership impairments as of December 31, 2014. At December 31, 2014, ownership interests and shares owned with a cost of $2.7 million and $3.7 million, respectively, are included in Other assets in the consolidated statement of financial condition. There were no exchange memberships held at December 31, 2013

Debt

Debt	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Debt	Debt
	Credit Agreement
	On December 19, 2011, Holdings entered into a credit agreement (the “Credit Agreement”) with a syndicate of financial institutions. The Credit Agreement was guaranteed by certain subsidiaries of Holdings and was secured by a pledge of all of the equity interests in certain of Holdings’ domestic subsidiaries and 65% of the voting equity interests in certain of its foreign subsidiaries.
	As of December 31, 2014 and 2013, Holdings’ outstanding balance under the Credit Agreement was $25.0 million and nil, respectively. In connection with the events described in Note 30 “Subsequent Events,” the outstanding balance of $25.0 million and accrued interest and fees of $0.1 million were repaid in full and the Credit Agreement was terminated effective January 20, 2015.
	Interest expense related to borrowings under the Credit Agreement, including the amortization of debt financing costs, included in Interest on borrowings in the consolidated statements of operations was $1.6 million, $1.4 million and $1.2 million for the years ended December 31, 2014, 2013 and 2012, respectively.
	During the year ended December 31, 2014, the weighted average dollar amount of borrowings related to the Credit Agreement was $36.1 million and the weighted average interest rate was 2.74%. During the year ended December 31, 2013, the weighted average dollar amount of borrowings related to the Credit Agreement was $34.9 million and the weighted average interest rate was 2.43%. During the year ended December 31, 2012, the weighted average dollar amount of borrowings related to the Credit Agreement was $41.2 million and the weighted average interest rate was 2.10%.
	Senior Convertible Notes due 2018
	In June 2013, the Corporation issued $172.5 million principal amount of 2.25% Convertible Notes maturing on June 15, 2018 and received net proceeds of $166.5 million, after deducting the initial purchasers' discount and offering expenses. The Convertible Notes pay interest semi-annually on June 15 and December 15 at a rate of 2.25% per year, commencing December 15, 2013. The indenture governing the Convertible Notes does not prohibit the Company from incurring additional senior debt or secured debt, nor does it prohibit any of its subsidiaries from incurring additional liabilities.
	The Convertible Notes will be convertible at an initial conversion rate of 53.2992 shares of the Corporation's Class A common stock per $1,000 principal amount of the Convertible Notes, which is equivalent to an initial conversion price of approximately $18.76. In addition, following certain corporate transactions that occur prior to the maturity date, the Corporation will, in certain circumstances, increase the conversion rate for a holder that elects to convert its Convertible Notes in connection with such corporate transaction. Upon conversion, the Corporation will deliver cash up to the principal amount. With respect to any conversion value in excess of the principal amount, the Corporation will deliver shares of its Class A common stock (unless it elects to deliver cash in lieu of all or a portion of such shares).
	Holders may convert their notes at their option prior to the close of business on the business day immediately preceding March 15, 2018, only under the following circumstances:
	•	during any fiscal quarter commencing after the fiscal quarter ending on September 30, 2013 (and only during such fiscal quarter), if the last reported sale price of the Corporation's Class A common stock for at least 20 trading days (whether or not consecutive) during the period of 30 consecutive trading days ending on the last trading day of the immediately preceding fiscal quarter is greater than or equal to 130% of the applicable conversion price on each applicable trading day;
	•	during the five business day period immediately after any five consecutive trading day period (the “measurement period”) in which the “trading price” (as defined in the offering circular) per $1,000 principal amount of notes for each trading day of such measurement period was less than 98% of the product of the last reported sale price of the Corporation's Class A common stock and the applicable conversion rate on such trading day;
	•	upon the occurrence of specified corporate events; or
	•	on or after March 15, 2018 until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert their notes at any time.
	In addition, if the Company undergoes a fundamental change (as defined in the offering circular), holders may, subject to certain conditions, require the Corporation to repurchase their notes for cash at a price equal to 100% of the principal amount of the notes to be purchased, plus accrued and unpaid interest.
	Convertible Note Hedges
	In connection with the offering of the Convertible Notes, the Company entered into privately negotiated convertible note hedge transactions with certain counterparties (the “Convertible Note Hedge Transaction”). The Convertible Note Hedge Transactions will cover, subject to customary anti-dilution adjustments, the number of shares of the Corporation's Class A common stock that will initially underlie the Convertible Notes. Concurrently with entering into the Convertible Note Hedge Transaction, the Company also entered into a separate, privately negotiated warrant transaction (the “Warrant Transaction”) with the same counterparties, whereby the Company sold to the counterparties warrants to purchase, subject to customary anti-dilution adjustments, up to the same number of shares of the Corporation's Class A common stock as in the Convertible Note Hedge Transaction. The strike price of the Warrant Transaction will initially be $21.24 per share of the Corporation's Class A common stock. Subject to certain conditions, the Company may settle the warrants in cash or on a net-share basis.
	The Convertible Note Hedge Transaction and the Warrant Transaction have the effect of increasing the effective conversion price of the Convertible Notes to $21.24 per share. The cost of the Convertible Note Hedge Transaction and the proceeds from the Warrant Transaction was $29.1 million and $18.6 million, respectively. In accordance with ASC 815, the Company recorded the cost of the Convertible Note Hedge Transaction and the proceeds from the Warrant Transaction to additional-paid-in-capital in stockholders' equity in the consolidated statements of financial condition and the recorded values will not be adjusted for subsequent changes in their respective fair values.
	The Convertible Note Hedge Transaction and the Warrant Transaction are separate transactions, in each case, entered into by the Company with certain counterparties, and are not part of the terms of the Convertible Notes and will not affect any holder's right under the Convertible Notes. Holders of the Convertible Notes will not have any rights with respect to the Convertible Hedge Transaction or the Warrant Transaction.
	Under ASC 470, an entity must separately account for the liability and equity components of the convertible debt instruments (such as the Convertible Notes) that may be settled entirely or partially in cash upon conversion in a manner that reflects the issuer's economic interest cost. The effect of ASC 470 on the accounting for the Convertible Notes is that the fair value of the equity component is included in the additional paid-in capital section of stockholders' equity in the Company's consolidated statements of financial condition and the principal amount of the Convertible Notes is reduced by original issue discount to reflect the Convertible Notes fair value at issuance. At issuance, the equity component of the Convertible Notes was valued at $29.1 million and the Convertible Notes were valued at $144.1 million consisting of $172.5 million of principal net of original issuance discount of $29.1 million. The original issue discount will be amortized over the life of the Convertible Notes using the effective interest rate of 6.20%.
	The balances of the liability and equity components as of December 31, 2014 and 2013, were as follows, with amounts in thousands:
		As of December 31,
		2014			2013
	Liability component - principal	$	172,500		$	172,500
	Deferred bond discount	(20,922		)	(26,197		)
	Liability component - net carrying value	$	151,578		$	146,303
	Equity component	$	29,101		$	29,101
	Interest expense related to the Convertible Notes, included in Interest on borrowings in the consolidated statements of operations for the years ended December 31, 2014 and 2013 was as follows, with amounts in thousands:
		For the Years Ended December 31,
		2014			2013
	Interest expense - stated coupon rate	$	3,881		$	2,232
	Interest expense - amortization of deferred bond discount	5,275			2,904
	Interest expense - amortization of debt issuance cost	1,209			699
	Total interest expense - convertible notes	$	10,365		$	5,835
	The Company incurred $6.0 million of Convertible Notes issuance cost. Amortization of Convertible Notes issuance costs included in Interest on borrowings in the consolidated statements of operations for the years ended December 31, 2014 and 2013 was $1.2 million and $0.7 million, respectively. Unamortized Convertible Notes issuance cost at December 31, 2014 and 2013 was $4.1 million and $5.3 million, respectively, and is included in Other assets in the consolidated statements of financial condition.
	Notes Payable
	In connection with its Lucid acquisition, the Company issued to the Lucid sellers 3.5% unsecured promissory notes in the amounts of $71.4 million and $15.8 million maturing on December 21, 2012. On December 21, 2012, the Company repaid $64.0 million of these notes and issued a series of 2.25%, $22.9 million unsecured promissory notes for the balance. The notes were pre-paid on June 6, 2013 with a portion of the proceeds received from the Convertible Notes issued on June 3, 2013. In the second quarter of 2013, the Lucid purchase price was increased by $15.3 million due to the final determination of tax balances at the acquisition date adjusted during the measurement period. The Company issued six-month 2.25% unsecured promissory notes to the Lucid sellers for the purchase price increase which matured on December 21, 2013. In satisfaction of the matured notes, the Company repaid $5.5 million and issued a series of 2.25% unsecured promissory notes to the Lucid sellers for the balance of $9.8 million which matured on June 6, 2014. In satisfaction of the matured notes, the Company repaid $2.3 million and issued a series of 2.25% unsecured promissory notes for the balance of $7.5 million which matured on December 6, 2014. The Company repaid the $7.5 million on December 6, 2014.

Derivative_Financial_Instrumen

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Derivative Financial Instruments
	Derivative financial instruments are accounted for in accordance with ASC 815 and are recognized as either assets or liabilities at fair value in the consolidated statements of financial condition and recorded within Due from brokers and Due to brokers, respectively. The Company has master netting agreements with its respective counterparties under which derivative financial instruments are presented on a net-by-counterparty basis in accordance with ASC 210 and ASC 815. The Company enters into futures contracts to economically hedge the open customer contracts on its CFD business. Futures contracts are exchange traded contracts to either purchase or sell a specific asset at a specified future date for a specified price. Gains or losses on futures contracts related to the Company's CFD business are included in Retail trading revenue in the consolidated statements of operations. The Company also engages in hedge trading in its electronic market making and institutional foreign exchange spot and futures markets. Gains or losses on hedge trading in the Company's electronic market making and institutional foreign exchange spot and futures markets are included in Institutional trading revenue in the consolidated statements of operations.
	Through its subsidiaries Lucid and V3 (see Note 2), the Company enters into options, futures, forward foreign currency contracts and commodity contracts. Options grant the purchaser, for the payment of a premium, the right to either purchase from or sell to the writer a specified instrument under agreed terms. A forward contract is a commitment to purchase or sell an asset at a future date at a negotiated rate. The Company's derivative transactions held for trading purposes are recorded in Due from/to brokers in the consolidated statements of financial condition. Gains or losses on options, futures and forward contracts held for trading purposes, are included in Institutional trading revenue in the consolidated statements of operations.
	The Company is exposed to risks relating to its derivatives trading positions from the potential inability of counterparties to perform under the terms of the contracts (credit risk) and from changes in the value of the underlying financial instruments (market risk). The Company is subject to credit risk to the extent that any counterparty with which it conducts business is unable to fulfill its contractual obligations. The Company manages its trading positions by monitoring its positions with and the credit quality of the financial institutions that are party to its derivative trading transactions. Additionally, the Company's netting agreements provide the Company with the right, in the event of a default of the counterparty (such as bankruptcy or a failure to perform), to net a counterparty’s rights and obligations under the agreement and to liquidate and set off collateral against any net amount owed by the counterparty.
	The following tables present the gross and net fair values of the Company's derivative transactions and the related offsetting amount permitted under ASC 210 and ASC 815, as of December 31, 2014 and 2013. Derivative assets and liabilities are net of counterparty and collateral offsets. Collateral offsets include cash margin amounts posted with brokers. Under ASC 210, gross positive fair values are offset against gross negative fair values by counterparty pursuant to enforceable master netting agreements, with amounts in thousands:
		As of December 31, 2014
		Derivative Assets						Derivative Liabilities
		(Included in Due from/Due to Brokers)
		Fair Value			Notional			Fair Value			Notional
	Exchange traded options	$	10,724		$	95,498		$	11,422		$	81,053
	Futures contracts	332,346			3,617,128			352,703			3,627,562
	OTC options	—			—			1,086			1,086
	Total derivatives, gross	$	343,070		$	3,712,626		$	365,211		$	3,709,701
	Netting agreements and cash collateral netting	(342,467		)				(353,543		)
	Total derivatives, net	$	603					$	11,668
		As of December 31, 2013
		Derivative Assets						Derivative Liabilities
		(Included in Due from/Due to Brokers)
		Fair Value			Notional			Fair Value			Notional
	Futures contracts	$	84		$	19,475		$	2,404		$	140,429
	Netting agreements	(84		)				(84		)
	Total derivatives, net	$	—					$	2,320
	Gains (losses) on derivative instruments are recorded on a trade date basis. The following table presents the gains (losses) on derivative instruments included in Retail and Institutional trading revenue in the consolidated statements of operations for the years ended December 31, 2014 and 2013, with amounts in thousands:
		Gains (Losses)
		Twelve Months ended December 31, 2014									Twelve Months ended December 31, 2013
		Retail			Institutional			Total			Retail			Institutional		Total
	Exchange traded options	$	—		$	33,318		$	33,318		$	—		$	—	$	—
	Futures contracts	(74,297		)	(5,242		)	(79,539		)	(26,671		)	20,244		(6,427		)
	OTC options	—			(23		)	(23		)	—			—		—
	Total	$	(74,297	)	$	28,053		$	(46,244	)	$	(26,671	)	$	20,244	$	(6,427	)

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements
	Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Fair value measurement establishes a fair value hierarchy that prioritizes the inputs of valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities and the lowest priority to unobservable inputs. The three levels of fair value hierarchy are defined as follows:
	Level I:  Quoted prices in active markets for identical assets or liabilities, accessible by the Company at the measurement date.
	Level II:  Quoted prices for similar assets or liabilities in active markets, or quoted prices for identical or similar assets or liabilities in markets that are not active, or other observable inputs other than quoted prices.
	Level III:  Unobservable inputs for assets or liabilities.
	When Level I inputs are available, those inputs are selected for determination of fair value. To value financial assets or liabilities that are characterized as Level II and III, the Company uses observable inputs for similar assets and liabilities that are available from pricing services or broker quotes. These observable inputs may be supplemented with other methods, including internal models that result in the most representative prices for assets and liabilities with similar characteristics. Multiple inputs may be used to measure fair value, however, the level of fair value for each financial asset or liability is based on the highest priority level of input within this fair value hierarchy.
	The following tables present the Company's assets and liabilities that are measured at fair value on a recurring basis and the related hierarchy levels, with amounts in thousands:
		Fair Value Measurements on a Recurring Basis
		As of December 31, 2014
		Quoted Prices in Active Markets for Identical Assets or Liabilities		Significant Observable Inputs		Significant Unobservable Inputs			Counterparty and Cash Collateral Netting			Total
		(Level I)		(Level II)		(Level III)
	Financial Assets:
	Trading securities	$	26	$	—	$	—		$	—		$	26
	Due from brokers:
	Exchange traded options	10,724		—		—			—			10,724
	Futures contracts	332,346		—		—			—			332,346
	Netting	—		—		—			(342,467		)	(342,467		)
	Total due from brokers	343,070		—		—			(342,467		)	603
	Total assets	$	343,096	$	—	$	—		$	(342,467	)	$	629
	Financial Liabilities:
	Customer account liabilities	$	—	$	1,331,723	$	—		$	—		$	1,331,723
	Due to brokers:
	Exchange traded options	11,422		—		—			—			11,422
	Futures contracts	352,703		—		—			—			352,703
	OTC options	—		1,086		—			—			1,086
	Netting	—		—		—			(353,543		)	(353,543		)
	Total due to brokers	364,125		1,086		—			(353,543		)	11,668
	Securities sold, not yet purchased	4,239		—		—			—			4,239
	Total liabilities	$	368,364	$	1,332,809	$	—		$	(353,543	)	$	1,347,630
		Fair Value Measurements on a Recurring Basis
		As of December 31, 2013
		Quoted Prices in Active Markets for Identical Assets or Liabilities		Significant Observable Inputs		Significant Unobservable Inputs			Counterparty and Cash Collateral Netting			Total
		(Level I)		(Level II)		(Level III)
	Financial Assets:
	Due from brokers - futures contracts	$	84	$	—	$	—		$	(84	)	$	—
	Total assets	$	84	$	—	$	—		$	(84	)	$	—
	Financial Liabilities:
	Customer account liabilities	$	—	$	1,190,880	$	—		$	—		$	1,190,880
	Due to brokers - open futures contracts	2,404		—		—			(84		)	2,320
	Follow-on Payment	—		—		3,672			—			3,672
	Total liabilities	$	2,404	$	1,190,880	$	3,672		$	(84	)	$	1,196,872
	Trading Securities
	Equity securities that the Company purchased with the intent to sell in the near-term are classified as trading securities. These trading securities are reported at their fair value based on the quoted market prices of the securities in active markets. Changes in fair value of equity securities from trading activity are recorded in Institutional trading revenue in the consolidated statements of operations.
	Due from/to Brokers
	Exchange traded options and open futures contracts, included in Due from and Due to brokers in the consolidated statements of financial condition, are measured at fair value based on exchange prices. Over the counter ("OTC") options, included in Due from and Due to brokers in the consolidated statements of financial condition, are valued using market price quotations (where observable) obtained from independent brokers.
	Customer Account Liabilities
	Customer account liabilities represent amounts due to customers related to cash and margin transactions, including cash deposits and gains and losses on settled FX, CFDs and spread betting trades as well as unrealized gains and losses on open FX commitments, CFDs and spread betting. Customer account liabilities, included in the consolidated statements of financial condition, are measured at fair value based on the market prices of the underlying products.
	Securities Sold, Not Yet Purchased
	Securities sold, not yet purchased, represent the Company’s obligations to deliver the specified security at the contracted price at a future point in time, and thereby create a liability to repurchase the securities in the market at the prevailing prices. The liability for such securities sold short, included in the consolidated statements of financial condition, is marked to market based on the current fair value of the underlying security at the reporting date which is determined based on exchange prices. Changes in fair value of securities sold, not yet purchased are recorded as unrealized gains or losses in Institutional trading revenue in the consolidated statements of operations. These transactions may involve market risk in excess of the amount currently reflected in the consolidated statements of financial condition.
	The following tables present the carrying value, fair value and fair value hierarchy category of certain financial instruments that are not measured at fair value in the consolidated statements of financial condition, with amounts in thousands:
		As of December 31, 2014				Fair Value Measurements using:
		Carrying Value		Fair Value		Quoted Prices in Active Markets for Identical Assets or Liabilities			Significant Observable Inputs			Significant Unobservable Inputs
						(Level I)			(Level II)			(Level III)
	Financial Assets:
	Restricted time deposits	$	8,341	$	8,341	$	—		$	8,341		$	—
	Due from brokers - unsettled spot FX	14,635		14,635		—			14,635			—
	Due from brokers - unsettled common stock	3,730		3,730		—			3,730			—
	Due from brokers - excess cash collateral	18,330		18,330		—			18,330			—
	Equity method investments	10,007		17,199		—			—			17,199
	Notes receivable	9,381		9,381		—			—			9,381
	Exchange memberships	6,429		7,802		—			7,802			—
	Total assets	$	70,853	$	79,418	$	—		$	52,838		$	26,580
	Financial Liabilities:
	Due to brokers - unsettled spot FX	4,645		4,645		—			4,645			—
Credit agreement	25,000		25,000		—			25,000			—
Senior convertible notes	151,578		147,266		—			147,266			—
Total liabilities	$	181,223	$	176,911	$	—		$	176,911		$	—
	As of December 31, 2013				Fair Value Measurements using:
	Carrying Value		Fair Value		Quoted Prices in Active Markets for Identical Assets or Liabilities			Significant Observable Inputs			Significant Unobservable Inputs
					(Level I)			(Level II)			(Level III)
Financial Assets:
Due from brokers - unsettled spot FX	$	5,450	$	5,450	$	—		$	5,450		$	—
Equity method investments	9,793		13,504		—			—			13,504
Notes receivable	11,942		11,942		—			—			11,942
Total assets	$	27,185	$	30,896	$	—		$	5,450		$	25,446
Financial Liabilities:
Due to brokers - unsettled spot FX	6,332		6,332		—			6,332			—
Note payable	9,800		9,800		—			—			9,800
Senior convertible notes	146,303		149,418		—			149,418			—
Total liabilities	$	162,435	$	165,550	$	—		$	155,750		$	9,800
Restricted Time Deposits
Restricted time deposits consist of pledged time deposits (see Note 5) with original maturities of three months and one year and for which use is contractually restricted. Restricted time deposits are included in Current assets and Non-current assets in the consolidated statements of financial condition, as appropriate. Restricted time deposits are recorded at cost, which approximates fair value.
Due from/to Brokers - Unsettled Spot FX
Unsettled spot FX, included in Due from brokers and Due to brokers in the consolidated statements of financial condition, is carried at contracted amounts which approximate fair value based on market price quotations (where observable) obtained from independent brokers.
Due from Brokers - Unsettled Common Stock
The receivable for exchange membership shares sold short, included in Due from brokers in the consolidated statements of financial condition, is carried at the contracted amount which approximates fair value based on quoted prices.
Due from Brokers - Excess Cash Collateral
Excess cash collateral, included in Due from brokers in the consolidated statements of financial condition, is carried at contractual amounts which approximate fair value.
Equity Method Investments
Equity method investments, included in Other assets in the consolidated statements of financial condition, are carried at cost. The fair value of these investments is based on comparable market multiples and other valuation methods.
Notes Receivable
Notes receivable are carried at contracted amounts which approximate fair value.
Exchange Memberships
Exchange memberships, which include ownership interests and shares owned, are included in Other assets in the consolidated statements of financial condition. Exchange memberships are carried at cost. The fair value is based on quoted prices or recent sales.
Notes Payable
Notes payable, included in the consolidated statements of financial condition, are carried at contracted amounts, which approximate fair value based on the relatively short amount of time until maturity.
Credit Agreement
Balances due under the Credit Agreement are carried at contracted amounts, which approximate fair value based on the short term nature of the borrowing and the variable interest rate.
Senior Convertible Notes
Senior convertible notes are carried at contractual amounts. The fair value of the Senior convertible notes are based on similar recently executed transactions and market price quotations (where observable) obtained from independent brokers.
The following tables reconcile the ending balances of liabilities classified as Level III and identify the total gains the Company recognized during the years ended December 31, 2014 and 2013 on such liabilities that were included in the consolidated statements of financial condition as of December 31, 2014 and 2013, respectively, with amounts in thousands:
	As of December 31, 2014
	Beginning		Additions		Net Unrealized / Realized Gains			Ending
	Balance							Balance
Follow-on Payment	$	3,672	$	—	$	(3,672	)	$	—
Total Level III liabilities	$	3,672	$	—	$	(3,672	)	$	—
	As of December 31, 2013
	Beginning		Additions		Net Unrealized / Realized Gains			Ending
	Balance							Balance
Follow-on Payment	$	—	$	10,631	$	(6,959	)	$	3,672
Total Level III liabilities	$	—	$	10,631	$	(6,959	)	$	3,672
The Follow-on Payment related to the Faros acquisition was valued using significant unobservable inputs including a multiple of Faros' 2014 EBITDA. The net unrealized/realized gains are included in Other income in the consolidated statements of operations.
The Company did not have any transfers in or out of Level I, II and III during the year ended December 31, 2014.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes
	Holdings operates in the U.S. as a limited liability company that is treated as a partnership for U.S. federal, state, and local income tax purposes. As a result, Holdings' income from its U.S. operations is not subject to U.S. federal income tax because the income is attributable to its members. Accordingly, the Company’s U.S. tax provision is solely based on the portion of Holdings’ income attributable to the Corporation and excludes the income attributable to other members of Holdings whose income is included in Net income attributable to non-controlling interest in FXCM Holdings, LLC in the consolidated statements of operations.
	In addition to U.S. federal and state income taxes, the Company is subject to Unincorporated Business Tax which is attributable to Holdings' operations apportioned to New York City. The Company’s foreign subsidiaries are also subject to local taxes.
	Income before income taxes, as shown in the consolidated statements of operations, includes the following income components, with amounts in thousands:
		For the Years Ended December 31,
		2014				2013				2012
	Domestic	$	3,946			$	10,390			$	19,794
	Foreign	21,702				41,470				27,670
		$	25,648			$	51,860			$	47,464
	The provision for income taxes consists of the following, with amounts in thousands:
		For the Years Ended December 31,
		2014				2013				2012
	Current
	Federal income tax (benefit)	$	2			$	(185	)		$	478
	State and local income tax	331				682				574
	Foreign income tax	4,757				5,085				764
	Subtotal	5,090				5,582				1,816
	Deferred
	Federal income tax	1,053				3,996				2,837
	State and local income tax (benefit)	754				235				(171		)
	Foreign income (benefit) tax	(896		)		7,211				4,504
	Subtotal	911				11,442				7,170
	Total provision for taxes	$	6,001			$	17,024			$	8,986
	The following table reconciles the provision for income taxes to the U.S. federal statutory tax rate:
		For the Years Ended December 31,
		2014			2013			2012
	Statutory U.S. federal income tax rate	34	%		34	%		34	%
	Income passed through to non-controlling members	(2.7	)		(5.4	)		(15.5	)
	State and local income tax	2.8			0.9			1
	Foreign income tax	(3.3	)		(1.4	)		(3.1	)
	Tax Receivable Agreement true-up	(11.7	)		—			—
	Non-deductible FCA fine	—			2			—
	Foreign tax credit valuation allowance	3.7			3.5			2.5
	Impact of rate change on deferred tax assets	—			(0.9	)		—
	Other	0.6			0.1			—
	Effective tax rate	23.4	%		32.8	%		18.9	%
	The decrease in the effective tax rate for the year ended December 31, 2014 compared to the year ended December 31, 2013 was primarily due to a reduction in the effective tax rate that is used to calculate the Company’s obligation under the tax receivable agreement. This was offset by an increase in the Corporation’s ownership in Holdings, a valuation allowance established on the Company's foreign tax credits and state net operating loss carryforwards. The increase in the Corporation’s ownership in Holdings is due to Holdings' members exchanging their membership units for the Corporation’s Class A common stock. The Company’s effective tax rate increases as additional exchanges occur because the portion of Holdings’ income attributable to the Corporation, and therefore taxable, increases. The effect of Holdings Unit exchanges is partially offset by the Corporation's Class A common stock repurchases. Anytime the Corporation repurchases shares of its Class A common stock, Holdings enters into an equivalent Holdings Unit transaction with the Corporation. The effect of these repurchases decreases the Corporation’s ownership in Holdings and, accordingly, decreases the portion of Holdings’ income attributable to the Corporation (see Note 2).
	The Company’s 2014 tax provision does not include any consideration of the January 15, 2015 subsequent event. It is highly probable that the tax expense of the Company and the corresponding tax position of the Company would be significantly different if the events were considered. The events described in Note 30 “Subsequent Events” occurred after December 31, 2014 and therefore do not impact the tax expense or tax position of the Company as of and for the year ended December 31, 2014. It is highly probable that the subsequent events could impact the realizability of the Company's deferred tax assets and will require an assessment in the fiscal quarter ending March 31, 2015. As of the report date, an estimate of the financial impact cannot be made and will not be determined until the assessment for realizability is completed.
	Deferred tax assets and liabilities are determined based on the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. A summary of the tax effects of the temporary differences is as follows, with amounts in thousands:
		As of December 31,
		2014				2013
	Deferred tax assets
	Equity-based compensation	$	983			$	1,059
	Investment in partnership	179,297				178,941
	Fixed assets	1,960				2,279
	Tax loss carryforwards	40,346				25,631
	Intangible assets	92				—
	Tax credit carryforward/foreign sub income	5,380				4,265
	Japan software	838				1,516
	Other	417				577
	Gross deferred tax assets	229,313				214,268
	Less: valuation allowance	(19,704		)		(25,288		)
	Net deferred tax asset	209,609				188,980
	Deferred tax liabilities
	Fixed assets	8				4
	Intangible assets	2,498				3,965
	Goodwill	19,296				8,742
	Software development cost	253				238
	Other	768				1,232
	Gross deferred tax liabilities	22,823				14,181
	Net deferred tax asset	$	186,786			$	174,799
	The increase in deferred tax assets was primarily driven by the increase in the Corporation’s ownership in Holdings as a result of members of Holdings exchanging their membership units for the Corporation's Class A common stock. As Existing Unit Holders exchange their membership units, the Company records a deferred tax benefit related to Holdings election under Section 754 of the Internal Revenue Code (see Note 2). The increase in net operating loss carryforwards also contributed to the increase.
	The Company assesses available positive and negative evidence to estimate if it is more-likely-than-not to use certain jurisdiction-based deferred tax assets including certain tax credits and net operating loss carryovers. On the basis of this assessment, a valuation allowance of $19.7 million was recorded as of December 31, 2014.
	As of December 31, 2014, the Company has $18.8 million of domestic net operating loss carryforwards and $169.8 million of foreign net operating loss carryforwards. The U.S. net operating loss carryforwards have various expiration dates through 2034 with the net operating losses generated by certain of our U.K. subsidiaries having indefinite carryforward periods.
The tax credit carryforward includes foreign tax credits of $4.6 million that may be carried forward for a period of 10 years and begin to expire in 2021 and unincorporated business tax credits of $0.5 million that may be carried forward for 7 years.
The Company does not provide for deferred taxes on the excess of the financial reporting over the tax basis in its investments in foreign subsidiaries that are essentially permanent in duration. That excess totaled $28.9 million as of December 31, 2014. The determination of the additional deferred taxes that have not been provided is not practicable.
Income tax payable as of December 31, 2014 and 2013 was $2.2 million and $1.0 million, respectively, and is included in Accounts payable and accrued expenses in the consolidated statements of financial condition (see Note 14). Tax receivable as of December 31, 2014 and 2013 was $2.4 million and $3.9 million, respectively.
The following is a tabular reconciliation of the total amounts of unrecognized tax benefits, with amounts in thousands:
	For the Years Ended December 31,
	2014				2013				2012
Unrecognized tax benefits – January 1	$	183			$	3,691			$	223
Gross increases – tax positions in prior period	98				—				1
Gross decreases – tax positions in prior period	—				(3,445		)		(16		)
Gross increases – tax positions in current period	128				51				3,483
Settlement	—				(114		)		—
Lapse of statute of limitations	—				—				—
Unrecognized tax benefits – December 31	$	409			$	183			$	3,691
The Company recognizes interest and penalties related to unrecognized tax benefits within the income tax expense line in the consolidated statements of operations. Accrued interest and penalties are included within the related tax liability line in the consolidated statements of financial condition. Related to the unrecognized tax benefits noted above, the Company accrued penalties and interest of immaterial amounts during the years ended December 31, 2014, 2013 and 2012.
The Company does not believe that it will have a material increase in its unrecognized tax benefits during the coming year.
The Company is subject to taxation in the U.S. and various states and foreign jurisdictions. As of December 31, 2014, the Company’s tax years for 2011, 2012, and 2013 are subject to examination by the tax authorities. As of December 31, 2014, several of the companies U.K. subsidiaries are under examination for the 2012 tax year.

Foreign_Currencies_and_Concent

Foreign Currencies and Concentrations of Credit Risk	12 Months Ended
	Dec. 31, 2014
Foreign Currency [Abstract]
Foreign Currencies and Concentrations of Credit Risk	Foreign Currencies and Concentrations of Credit Risk
	Under the agency model, the Company accepts and clears FX spot contracts for the accounts of its customers (see Notes 1 and 2). These activities may expose the Company to off-balance sheet risk in the event that the customer or other broker is unable to fulfill its contracted obligations and the Company has to purchase or sell the financial instrument underlying the contract at a loss.
	In connection with these activities, the Company executes and clears customers’ transactions involving the sale of foreign currency not yet purchased, substantially all of which are transacted on a margin basis subject to internal policies. Such transactions may expose the Company to off-balance sheet risk in the event margin deposits are not sufficient to fully cover losses that customers may incur. In the event that a customer fails to satisfy its obligations, the Company may be required to purchase or sell financial instruments at prevailing market prices to fulfill the customer’s obligation.
	The Company controls such risks associated with its customer activities by requiring customers to maintain margin collateral, in the form of cash, in compliance with various internal guidelines. The Company’s trading software technology monitors margin levels on a real time basis and, pursuant to such guidelines, requires customers to deposit additional cash collateral, or to reduce positions, if necessary. The system is designed to ensure that any breach in a customer’s margin requirement as a result of losses on the trading account will automatically trigger a final liquidation, which will execute the closing of all positions. Exposure to credit risk is dependent on market liquidity. Institutional customers are permitted credit pursuant to limits set by the Company’s prime brokers. The prime brokers incur the credit risk relating to the trading activities of these customers in accordance with the respective agreements between such brokers and the Company.
	The Company is engaged in various trading activities with counterparties which include brokers and dealers, futures commission merchants, banks and other financial institutions. In the event counterparties do not fulfill their obligations, the Company may be exposed to risk. The risk of default depends on the creditworthiness of the counterparty or issuer of the financial instrument. It is the Company’s policy to: (i) perform credit reviews and due diligence prior to conducting business with counterparties; (ii) set exposure limits and monitor exposure against such limits; and (iii) periodically review, as necessary, the credit standing of counterparties using multiple sources of information. The Company’s Due from brokers balance included in the consolidated statements of financial condition was $37.3 million and $5.5 million as of December 31, 2014 and 2013, respectively. As of December 31, 2014, 97.1% of the Company’s Due from brokers balance, included in the consolidated statements of financial condition, was from three large financial institutions. As of December 31, 2013, 96.2% of the Company’s Due from brokers balance, included in the consolidated statements of financial condition, was from one large financial institution. Two banks held more than 10.0% each of the Company’s total cash and cash equivalents and cash and cash equivalents, held for customers as of December 31, 2014 and 2013.

Segments

Segments	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Segments	Segments
	ASC 280, Segment Reporting, 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. The Company’s operations relate to FX trading and related services and operate in two segments — retail and institutional, with different target markets and are covered by a separate sales force, customer support and trading platforms. The Company’s segments are organized around three geographic areas. These geographic areas are the U.S., Asia and Europe and are based on the location of its customers’ accounts.
	Retail Trading
	The Company operates its retail business whereby it acts as an agent between retail customers and a collection of large global banks and financial institutions by making foreign currency markets for customers trading in foreign exchange spot markets through its Retail Trading business segment. The Retail Trading business segment includes the Company’s white label relationships, contracts for difference, payments for order flow (through August 1, 2014) and rollovers. In addition, the Retail Trading business segment includes offerings to some of the Company’s smaller retail clients to trade with a dealing desk, or
	principal model.
	Institutional Trading
	Institutional Trading facilitates spot foreign currency trades on behalf of institutional customers, market making and electronic trading in the institutional foreign exchange spot and futures markets. The facilitation of spot foreign currency trades allows customers to obtain the best execution price from external banks and financial institutions.
	Our Institutional Trading segment also includes Lucid, an electronic market marker and trader in the institutional foreign exchange spot and futures markets, and activity from the acquisitions of Faros and V3. The V3 acquisition expanded the Lucid business model into a broader array of financial instruments and provides more robust connectivity to various financial exchanges.
	Information concerning the Company’s operations by reportable segment is as follows, with amounts in thousands:
		As of and For the
		Year Ended December 31, 2014
		Retail Trading			Institutional Trading			Corporate			Total
	Total net revenues	$	349,630		$	106,663		$	7,464		$	463,757
	Total expenses	210,550			109,247			117,004			436,801
	Loss on equity method investments	—			888			420			1,308
	Income (loss) before income taxes	$	139,080		$	(3,472	)	$	(109,960	)	$	25,648
	Assets	$	1,759,485		$	435,088		$	192,854		$	2,387,427
		As of and For the
		Year Ended December 31, 2013
		Retail Trading			Institutional Trading			Corporate			Total
	Total net revenues	$	379,840		$	110,957		$	(1,209	)	$	489,588
	Total expenses	219,016			98,839			119,121			436,976
	Loss on equity method investments	—			697			55			752
	Income (loss) before income taxes	$	160,824		$	11,421		$	(120,385	)	$	51,860
	Assets	$	1,622,829		$	417,492		$	183,626		$	2,223,947
		As of and For the
		Year Ended December 31, 2012
		Retail Trading			Institutional Trading			Corporate			Total
	Total net revenues	$	355,282		$	62,033		$	—		$	417,315
	Total expenses	218,018			45,164			106,669			369,851
	Income (loss) before income taxes	$	137,264		$	16,869		$	(106,669	)	$	47,464
	Assets	$	1,556,680		$	381,368		$	127,122		$	2,065,170
		For the Years Ended December 31,
		2014			2013			2012
	Total Net Revenues
	U.S.	$	304,507		$	301,005		$	284,511
	Asia	60,086			57,557			51,486
	Europe, Middle East and North Africa	289,232			286,771			191,314
	Other	8,467			4,811			4,183
	Eliminations	(198,535		)	(160,556		)	(114,179		)
	Total	$	463,757		$	489,588		$	417,315
		For the Years Ended December 31,
		2014			2013			2012
	Operating and Other Expenses
	U.S.	$	300,560		$	290,549		$	264,706
	Asia	43,566			39,410			41,228
	Europe, Middle East and North Africa	285,271			265,218			173,467
	Other	7,247			3,107			3,214
	Eliminations	(198,535		)	(160,556		)	(112,764		)
	Total	$	438,109		$	437,728		$	369,851
		For the Years Ended December 31,
		2014			2013			2012
	Income Before Income Taxes
	U.S.	$	3,947		$	10,456		$	19,805
	Asia	16,520			18,147			10,258
	Europe, Middle East and North Africa	3,961			21,553			17,847
	Other	1,220			1,704			969
	Eliminations	—			—			(1,415		)
	Total	$	25,648		$	51,860		$	47,464

Litigation

Litigation	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Litigation	Litigation
	In the ordinary course of business, we and certain of our officers, directors and employees may from time to time be involved in litigation and claims incidental to the conduct of our businesses, including intellectual property claims. In addition, our business is also subject to extensive regulation, which may result in administrative claims, investigations and regulatory proceedings against us. We have been named in various arbitration and civil litigation cases brought by customers seeking damages for trading losses. Management has investigated these matters and believes that such cases are without merit and is defending them vigorously. However, the arbitrations and litigations are presently in various stages of the judicial process and no judgment can be made regarding the ultimate outcome of the arbitrators’ and/or court’s decisions.
	In October 2011, the Trustee in bankruptcy, representing three debtors, Certified, Inc., Global Bullion Trading Group, Inc., and WJS Funding, Inc., filed an adversary complaint in the United States Bankruptcy Court for the Southern District of Florida against US, ODL Securities, Inc. and ODL Securities, Ltd. (the “Defendants”). Before the Defendants filed any response, the Trustee amended the Complaint to add ODL, FXCM Securities, LLC, FSL, FXCM Inc., and Holdings as Defendants. The Amended Complaint asserts claims under the Federal Bankruptcy Code to recover allegedly preferential and fraudulent transfers to the Defendants, under the Racketeer Influenced and Corrupt Organizations Act (“RICO”), 18 U.S.C §1961 et seq., as well as the common law. The Amended Complaint seeks an unspecified amount of compensatory and punitive damages, interests, and costs. The Defendants have filed motions to dismiss the Amended Complaint in its entirety. Thereafter, the parties engaged in non-binding mediation. Ultimately a settlement was reached in the amount of $0.7 million which was approved by the Bankruptcy Court on June 20, 2012.
	In 2012, FXCMJ accrued $2.6 million as an estimate to settle certain trading system matters with the JFSA. The Company settled this matter for $2.3 million, which included an administrative penalty, during the first quarter of 2013.
	In January 2014, the equity receiver for a former client of US, Revelation Forex Fund (“Revelation”), its principal, Kevin G. White, and related entities RFF GP, LLC, KGM Capital Management, LLC, filed suit against US, and certain unrelated defendants, in Texas state court.  The suit alleges that US is liable under the Texas Securities Act, and the common law: (i) as a “control person;” (ii) as an aider and abettor of fraud and a breach of fiduciary obligations; and (iii) for its negligence. The receiver seeks joint and several liability for damages in excess of $3.8 million, plus exemplary damages under Texas law, interest, and attorneys’ fees.  On February 7, 2014, US filed the equivalent of a motion to dismiss and to compel arbitration based on the mandatory forum selection clause and arbitration agreement in its Client Agreement with Revelation. It also filed an Answer with multiple affirmative defenses. The trial court heard argument on US’s motions to dismiss and to compel arbitration and denied them without findings of fact or conclusions of law.  On March 18, 2014, US filed a Notice of Appeal of the trial court's denial of its motion to compel arbitration.  On April 16, 2014, US filed a Petition for a Writ of Mandamus seeking review of the trial court’s refusal to enforce the forum selection clause. After both issues were fully briefed and argued, the court of appeals affirmed the trial court’s denial of US’s motions to dismiss and to compel arbitration by order dated December 31, 2014. In February 2015, US filed a Petition for Review and Petition for Writ of Mandamus in the Supreme Court of Texas. Those Petitions are presently pending.
	In February 2014, UK LTD and FSL entered into a settlement with the FCA following an investigation into trade execution practices of UK LTD and FSL in the period from 2006 to 2010, as well as a breach of notification obligations to the FCA. UK LTD and FSL agreed to pay (a) restitution to affected clients up to $9.9 million; and (b) a financial penalty of GBP 4.0 million (USD 6.6 million), together with any unclaimed restitution. In June 2014 and February 2015, UK LTD and FSL paid an additional $1.8 million and $0.7 million, respectively, in restitution to affected clients.
	In April 2014, the Securities and Futures Commission ("SFC") initiated an investigation relating to HK’s past trade execution practices concerning the handling of price improvements in our trading system prior to August 2010. HK continues to comply with information requests from SFC.
	In July 2014, US settled a complaint brought by the NFA relating to charges of doing business with an unregistered entity and for failing to submit certain trade data reports and was fined $0.2 million. The CFTC is also investigating this matter.
	For the outstanding matters referenced above for which a loss is more than remote but less than likely, whether in excess of an accrued liability or where there is no accrued liability, we have estimated a range of possible loss. We believe the estimate of the aggregate range of possible loss in excess of accrued liabilities for such matters is between nil and $4.7 million as of December 31, 2014.
	In view of the inherent difficulty of predicting the outcome of litigation and claims, we cannot predict what the eventual outcome of the pending matters will be, what the timing of the ultimate resolution of these matters will be, or what the eventual loss related to each pending matter may be. Furthermore, the above-referenced matters represented in the estimated aggregate range of possible loss will change from time to time and actual results may vary significantly from the current estimate. An adverse outcome in one or more of these matters could be material to our results of operations or cash flows for any particular reporting period.

Subsequent_Events

Subsequent Events	12 Months Ended
	Dec. 31, 2014
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events
	On January 15, 2015, the Company's customers suffered significant losses and generated negative equity balances ("debit balances") owed to us of approximately $276.0 million. This was due to the unprecedented volatility in the EUR/CHF currency pair after the Swiss National Bank (SNB) discontinued its currency floor of 1.2 EUR per CHF on that date. When a customer entered a EUR/CHF trade with the Company, the Company executed an identical trade with a FX market maker. During the historic move liquidity became extremely scarce and shallow, which affected execution prices.  This liquidity issue resulted in some customers having losses in excess of their account balance. While customers could not cover their margin call with the Company, the Company still had to cover the same margin call with the FX market maker.  When a customer profits in the trade, the Company gives the profits to the customer, however, when the customer is not profitable on that trade the Company is obligated to pay the FX market maker regardless of whether the Company collects the funds from its customers. These debit balances resulted in a temporary breach of certain regulatory capital requirements.  The event was assessed as a Type II non-recognized subsequent event.
	On January 16, 2015, Holdings and FXCM Newco, LLC (“Newco”), a newly-formed wholly-owned subsidiary of Holdings, entered into a credit agreement (the “Leucadia Credit Agreement”) with Leucadia National Corporation ("Leucadia"), as administrative agent and lender, and a related financing fee agreement (the “Fee Letter”).  The financing provided to the Company pursuant to these agreements, which is described below, enabled the Company to maintain compliance with regulatory capital requirements and continue operations. On January 16, 2015, in connection with the Leucadia Credit Agreement and the Fee Letter, the Corporation, Holdings, Newco and Leucadia also entered into an agreement (the “Letter Agreement”) that set the terms and conditions upon which the Corporation, Holdings and Newco will pay in cash to Leucadia and its assignees a percentage of the proceeds received in connection with certain transactions.  In connection with these financing transactions, Holdings formed Newco and contributed all of the equity interests owned by Holdings in its subsidiaries to Newco.
	As the Company announced on January 28, 2015, we have made the business decision to forgive approximately 90% of the clients who incurred debit balances in certain jurisdictions as a result of the SNB announcement on January 15, 2015. The Company notified certain clients (such as institutional, high net worth and experienced traders who generally maintain higher account balances) that sustained debit balances as a result of the market events on January 15, 2015, that they will be required to pay their debit balances, pursuant to the terms of the FXCM master trading agreements. This group represents approximately 10% of clients who incurred debit balances, but comprises over 60% of the total debit balances owed. The Company is considering various legal options to collect these debit balances. In light of the numerous uncertainties associated with these collection options, the Company cannot provide any assurance that it will be successful in recovering any portion of its clients' debit balances.
	Amended and Restated Letter Agreement
	The Amended and Restated Letter Agreement, dated January 24, 2015, provides, among other things, that Holdings and Newco will pay in cash to Leucadia and its assignees a percentage of the net proceeds received in connection with certain transactions, including sales of assets (subject to certain limited exceptions), dividends or distributions, the sale or indirect sale of Newco (whether by merger, stock purchase, sale of all or substantially all of Newco’s assets or otherwise), the issuance of any debt (subject to certain limited exceptions) or equity securities, and other specified non-ordinary course events, such as certain tax refunds and litigation proceeds.
	The Amended and Restated Letter Agreement allocates net proceeds as follows:
	Aggregate amount of proceeds	Leucadia	FXCM Holdings
	Amounts due under Leucadia term loan, including fees	100%	0%
	Next $350 million	50%	50%
	Next amount equal to 2 times the balance outstanding on the term loan and fees as of April 16, 2015, such amount not to be less than $500 million or more than $680 million	90%	10%
	All aggregate amounts thereafter	60%	40%
	In addition to the payments above, Leucadia and its assignees are entitled to tax distributions in the event that they are allocated income by Newco as a result of their rights under the Letter Agreement. If any such tax distributions are made, the amounts of such distributions reduce the payments to be made to Leucadia and its assignees pursuant to the allocation methodology described above (other than with respect to the repayment of the loan).
	In addition, the Amended and Restated Letter Agreement provides that beginning on January 16, 2018, upon the request of Leucadia or its assignees, the Corporation, Holdings and Newco will cause the sale of Holdings, Newco and/or any of their respective subsidiaries’ assets or equity interests for cash at the highest reasonably available price.  Upon the occurrence of such event, Newco will pay Leucadia and its assignees in accordance with the methodology described above.
	In the event of a change of control, at the request of Leucadia or its assignees, Holdings and Newco will be required to pay Leucadia and its assignees in cash a one-time payment equal to the fair market value of their contractual rights pursuant to the Amended and Restated Letter Agreement. For this purpose, change of control is generally defined as an event or series or events by which (i) a person or group acquires 40% or more of the voting interests of the Corporation, (ii) the Corporation and the existing members of Holdings cease to own 90% of the equity interests of Holdings, (iii) the Corporation ceases to be the sole managing member of Holdings, (iv) Holdings ceases to be the sole member of Newco or (v) subject to certain exceptions, a majority of the members of the Company’s board of directors cease to be directors during a 12-month period.
	The Amended and Restated Letter Agreement will terminate upon the earlier of (i) a change of control of Newco so long as Holdings and Newco have complied with their respective obligations described in the immediately preceding paragraph or (ii) the consummation of a sale of Holdings or Newco pursuant to a sale requested by Leucadia or its assignees as described above.
	The Amended and Restated Letter Agreement includes a variety of restrictive covenants binding on Holdings and Newco, including, but not limited to: limitations on their ability to amend their organizational documents; limitations on their ability to dispose of assets; limitations on the incurrence of liens; limitations on the incurrence of debt by subsidiaries; and limitations on transactions with affiliates, without the prior consent of Leucadia and its assignees.  In addition, there are restrictions on the Corporation’s ability to issue equity securities other than the issuance of equity awards to employees in the ordinary course of business.  The Amended and Restated Letter Agreement further provides that Holdings and Newco shall pay Leucadia’s expenses incurred in connection with the negotiation, execution and administration of such agreement.
	Amended and Restated Credit Agreement
	The Amended and Restated Credit Agreement, dated January 24, 2015, provides for a $300.0 million term loan made by Leucadia to Holdings and Newco (the “Borrowers”).  The net proceeds of the loan (approximately $279.0 million) were used to replace capital in the Company’s regulated entities to cover negative client balances and pay down outstanding revolving debt. Holdings’ prior revolving credit agreement with Bank of America, N.A. was repaid in full and terminated effective January 20, 2015 (see Note 23).
	The Amended and Restated Credit Agreement is subject to various conditions and terms such as requiring mandatory prepayments, including from proceeds of dispositions, condemnation and insurance proceeds, debt issuances, equity issuances, and capital contributions. The Amended and Restated Credit Agreement requires monthly payments of the term loan from proceeds received during the immediately preceding calendar month from accounts receivable related to customer debit balances. The loan may be voluntarily prepaid by the Borrowers without penalty.
	The loan matures on January 16, 2017.  The obligations under the Amended and Restated Credit Agreement are guaranteed by certain wholly-owned unregulated domestic subsidiaries of the Company and are secured by substantially all of the assets of Holdings and certain subsidiaries of the Corporation, including a pledge of all of the equity interests in certain of Holdings’ domestic subsidiaries and 65% of the voting equity interests in certain of its foreign subsidiaries.
	The loan has an initial interest rate of 10% per annum, increasing by 1.5% per annum each quarter for so long as it is outstanding, but in no event exceeding 20.5% per annum (before giving effect to any applicable default rate). Under certain circumstances, a default interest rate will apply on all obligations during the event of default at a per annum rate equal to 2% above the applicable interest rate.
	The Amended and Restated Credit Agreement requires the Borrowers to pay, in accordance with the Amended and Restated Fee Letter, a deferred financing fee in an amount equal to $10.0 million, with an additional fee of up to $30.0 million becoming payable in the event the aggregate principal amount of the term loan outstanding on April 16, 2015 is greater than $250.0 million or the deferred financing fee of $10.0 million (plus interest) has not been paid on or before such date. As of the date of this report, the Company has repaid $12.2 million on the Leucadia term loan.  The aggregate principal amount outstanding is $287.8 million.
	The Amended and Restated Credit Agreement includes a variety of restrictive covenants, including, but not limited to: limitations on the ability to merge, dissolve, liquidate, consolidate or sell, lease or otherwise transfer all or substantially all assets; limitations on the incurrence of liens; limitations on the incurrence of debt by subsidiaries; limitations on the ability of Newco to make distributions in respect of its equity interests including distributions to pay interest due on the Company’s convertible notes and limitations on transactions with affiliates, without the prior consent of the lender.  The Amended and Restated Credit Agreement also provides for events of default, including, among others: non-payments of principal and interest; breach of representations and warranties; failure to maintain compliance with the other covenants contained in the Amended and Restated Credit Agreement; default under other material debt; the existence of bankruptcy or insolvency proceedings; insolvency; and a change of control.
	Stockholder Rights Plan
	On January 28, 2015, the Corporation's Board of Directors approved the adoption of a stockholder rights plan (the "Rights Plan") and declared a dividend distribution of one right on each outstanding share of the Corporation's Class A common stock.
	Under the terms of the Rights Plan, rights to purchase one one-thousandth (1/1000) of a share of a new Series A Junior Participating Preferred Stock of the Corporation (the "Rights") at a price of $11.20 per one one-thousandth (1/1000) of a share were issued at the rate of one right for each outstanding share of the Corporation's common stock held of record on February 9, 2015. Under the terms of the Rights Plan, the Rights will initially trade together with the Corporation's Class A common stock and will not be exercisable. In the absence of further action by the Corporation's Board of Directors, the Rights will generally become exercisable and allow the holder to acquire shares of the Corporation's common stock at a discounted price if (a) a person or group acquires beneficial ownership of 10% or more of the Corporation's outstanding common stock or (b) any person or group commences a tender or exchange offer, the consummation of which would result in such person or group acquiring beneficial ownership of 10% or more of the Corporation's outstanding common stock. Rights held by the person or group triggering the rights will become void and will not be exercisable.
	The issuance of Rights is not a taxable event, will not affect the reported financial condition or results of operations, including earnings per share, of the Corporation and will not change the manner in which the Corporation's Class A common stock is currently traded.

Significant_Accounting_Policie1

Significant Accounting Policies and Estimates (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation
	The accompanying consolidated financial statements are presented in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). The Company consolidates those entities in which it is the primary beneficiary of a variable-interest entity ("VIE") as required by ASC 810, Consolidations (“ASC 810”), or entities where it has a controlling interest. Intercompany accounts and transactions are eliminated in consolidation.
	As indicated above, the Corporation operates and controls all of the businesses and affairs of Holdings and its subsidiaries. As such, the Corporation consolidates the financial results of Holdings and records a non-controlling interest for the economic interest in Holdings not owned by the Corporation. The Corporation’s and the non-controlling unit holders’ economic interest in Holdings was 58.1% and 41.9%, respectively, as of December 31, 2014. The Corporation’s and the non-controlling unit holders’ economic interest in Holdings was 54.8% and 45.2%, respectively, as of December 31, 2013.
	Net income attributable to the non-controlling interest in Holdings in the consolidated statements of operations represents the portion of earnings or loss attributable to the economic interest in Holdings held by the non-controlling unit holders. Net income (loss) attributable to other non-controlling interests in the consolidated statements of operations represents the portion of net income or loss attributable to the non-controlling interests of Lucid, Faros, V3 and other consolidated entities. Net income (loss) attributable to the non-controlling interest in Lucid represents the portion of earnings or loss attributable to the 49.9% economic interest held by Lucid non-controlling members whose allocation among the non-controlling members is not contingent upon services being provided. The portion of the 49.9% of Lucid earnings allocated among the non-controlling members of Lucid contingent on services provided is reported as a component of compensation expense under Allocation of income to Lucid members for services provided in the consolidated statements of operations. Net income (loss) attributable to the non-controlling interest in Faros and V3 (see Note 4) represents the portion of earnings or loss attributable to the 49.9% economic interest held by Faros and V3 non-controlling members. Net income (loss) attributable to the non-controlling interests in other consolidated entities represents the portion of earnings or loss attributable to the economic interests held by the non-controlling members.
	Non-controlling interests in the consolidated statements of financial condition represents the portion of equity attributable to the non-controlling interests of Holdings, Lucid, Faros, V3 and other consolidated entities. The allocation of equity to the non-controlling interests is based on the percentage owned by the non-controlling interest in the respective entity.
	The Company's consolidated financial statements include the following significant subsidiaries of Holdings:
	Forex Capital Markets LLC	(“US”)
	FXCM Asia Limited	(“HK”)
	Forex Capital Markets Limited	(“UK LTD”)
	FXCM Australia Limited	(“Australia”)
	ODL Group Limited	(“ODL”)
	FXCM Securities Limited	(“FSL”)
	FXCM Japan Securities Co., Ltd.	(“FXCMJ”)
	FXCM UK Merger Limited	(“Merger”)
	Lucid Markets Trading Limited	(“Lucid”)
	Lucid Markets LLP	("Lucid LLP")
	Faros Trading LLC	("Faros")
	V3 Markets, LLC	("V3")
	Investments where the Company is deemed to exercise significant influence, but no control, are accounted for using the equity method of accounting. The Company records its pro-rata share of earnings or losses each period and records any dividends as a reduction in the investment balance. The carrying value of these investments is included in Other assets in the consolidated statements of financial condition and earnings or losses are included in Income (Loss) on equity method investments, net in the consolidated statements of operations.
	FXCMJ, a Japanese based foreign exchange provider and a wholly owned subsidiary of Holdings, has a fiscal year end of March 31 while the Company has a fiscal year end of December 31. The difference between the Company's reporting year end and FXCMJ does not result in a material impact on the Company's financial position or results of operations.
	Certain reclassifications have been made to previously reported amounts to conform to the current presentation.
Use of Estimates	Use of Estimates
	The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements as well as the reported amount of revenue and expenses during the year. Actual results could differ from those estimates and could have a material impact on the consolidated financial statements.
Cash and Cash Equivalents	Cash and Cash Equivalents
	Cash and cash equivalents include cash at banks and highly liquid instruments with original maturities of less than 90 days at the time of purchase and cash on deposit held with FX and CFD market makers related to economic hedging activities. At times, balances held in U.S. bank accounts may exceed federally insured limits. This potentially subjects the Company to concentration risk. The Company has not experienced losses in such accounts.
Cash and Cash Equivalents, held for customers	Cash and Cash Equivalents, held for customers
	Cash and cash equivalents, held for customers represents cash held to fund customer liabilities. At times, balances held in U.S. bank accounts may exceed federally insured limits. This potentially subjects the Company to concentration risk. The Company has not experienced losses in such accounts.
	The balance arises primarily from cash deposited by customers and net realized gains from customer trading activity. The Company maintains a corresponding liability in connection with this amount that is included in customer account liabilities in the consolidated statements of financial condition (see Note 13). A portion of the balance is not available for general use due to regulatory restrictions in certain jurisdictions. These restricted balances were $0.9 billion and $1.0 billion as of December 31, 2014 and 2013, respectively.
Derivatives	Due from/to Brokers
	Due from/to brokers represents the amount of the unsettled spot currency trades that the Company has with financial institutions. Also included in due from/to brokers is the fair value of derivative financial instruments discussed below. The Company has master netting agreements with its respective counterparties which allows the Company to present due from/to brokers on a net-by-counterparty basis in accordance with ASC 815 Derivatives and Hedging (“ASC 815”) and ASC Topic 210 Balance Sheet (“ASC 210”).
	Derivatives
	Derivative financial instruments are accounted for in accordance with ASC 815 and are included in Due from/to brokers in the consolidated statements of financial condition. The Company recognizes all derivative financial instruments in the consolidated statements of financial condition as either assets or liabilities at fair value. The Company enters into futures contracts to (i) economically hedge the open customer contracts on its CFD business and (ii) hedge trading in its electronic market making and institutional foreign exchange spot and futures markets. Futures contracts are exchange traded contracts to either purchase or sell a specific asset at a specified future date for a specified price. Gains or losses on futures contracts related to the Company’s CFD business are included in Retail trading revenue and gains or losses on hedge trading in its electronic market making and institutional foreign exchange spot and futures markets and other asset classes are included in Institutional trading revenue in the consolidated statements of operations (see Note 24).
Fair Value Measurements	Fair Value Measurements
	Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Fair value measurement establishes a fair value hierarchy that prioritizes the inputs of valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities and the lowest priority to unobservable inputs. These three levels of fair value hierarchy are defined as follows:
	Level I:  Quoted prices in active markets for identical assets or liabilities, accessible by the Company at the measurement date.
	Level II:  Quoted prices for similar assets or liabilities in active markets, or quoted prices for identical or similar assets or liabilities in markets that are not active, or other observable inputs other than quoted prices.
	Level III:  Unobservable inputs for assets or liabilities.
	When Level I inputs are available, those inputs are selected for determination of fair value. To value financial assets and liabilities that are characterized as Level II and III, the Company uses observable inputs for similar assets and liabilities that are available from pricing services or broker quotes. These observable inputs may be supplemented with other methods, including internal models that result in the most representative prices for assets and liabilities with similar characteristics. Multiple inputs may be used to measure fair value, however, the level of fair value for each financial asset or liability is based on the highest priority level of input within this fair value hierarchy (see Note 25)
Accounts Receivable, net	Accounts Receivable, net
	As of December 31, 2014 and 2013, Accounts receivable, net, consisted primarily of amounts due from institutional customers relating to the Company's FX business, fees receivable from the Company's white label service to third parties and amounts due from customers related to the Company's FSL brokerage business. As of December 31, 2013, Accounts receivable, net, also includes receivables related to order flow revenue, described in “Retail Trading Revenue” below. Receivables are shown net of reserves for uncollectible accounts. The reserve for bad debts is maintained at a level that management believes to be sufficient to absorb estimated losses in the accounts receivable portfolio. The reserve is increased by the provision for bad debts which is charged against operating results and decreased by the amount of charge-offs, net of recoveries. The amount charged against operating results is based on several factors including, but not limited to, a continuous assessment of the collectability of each account, the length of time a receivable is past due and our historical experience with the particular customer. As of December 31, 2014 and 2013, the reserve netted against receivables in the consolidated statements of financial condition was not material.
	As of December 31, 2014 and 2013, Accounts receivable, net, also includes advances to employees and non-controlling members of Holdings and, additionally, as of December 31, 2014, advances to Lucid non-controlling members and net amounts due from an equity method investee, as described in Note 16.
Office, Communication and Computer Equipment, net	Office, Communication and Computer Equipment, net
	Office, communication and computer equipment, net, consists of computer equipment, purchased technology hardware and software, internally-developed software, leasehold improvements, furniture and fixtures and other equipment, licenses and communication equipment. Office, communication and computer equipment are recorded at historical cost, net of accumulated depreciation. Additions and improvements that extend the lives of assets are capitalized, while expenditures for repairs and maintenance are expensed as incurred. Certain costs of software developed or obtained for internal use are capitalized. Depreciation is computed using the straight-line method. The Company depreciates these assets using the following useful lives:
	Computer equipment	3 to 5 years
	Software	2 to 5 years
	Leasehold improvements	Lesser of the estimated economic useful life or the term of the lease
	Furniture and fixtures and other equipment	3 to 5 years
	Licenses	2 to 3 years
	Communication equipment	3 to 5 years
Valuation of Other Long-Lived Assets	Valuation of Other Long-Lived Assets
	The Company also assesses potential impairments of its other long-lived assets, including office, communication and computer equipment, when there is evidence that events or changes in circumstances indicate that the carrying amount of an asset may not be recovered. An impairment loss is recognized when the carrying amount of the long-lived asset exceeds its fair value and is not recoverable. The carrying amount of a long-lived asset is not recoverable if it exceeds the sum of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. Any required impairment loss is measured as the amount by which the carrying amount of a long-lived asset exceeds its fair value and is recorded as a reduction in the carrying value of the related asset and a charge to operating results.
Business Acquisitions	Business Acquisitions
	The Company accounts for business acquisitions in accordance with ASC 805, Business Combinations ("ASC 805") and records assets acquired and liabilities assumed at their fair values as of the acquisition date. The Company records any excess purchase price over the value assigned to net tangible and identifiable intangible assets of a business acquired as goodwill. Acquisition related costs are expensed as incurred (see Note 4).
Goodwill	Goodwill
	The Company recorded goodwill from various acquisitions. Goodwill represents the excess purchase price over the value assigned to the net tangible and identifiable intangible assets of a business acquired. Goodwill is allocated to the Company’s reporting units based on the assignment of the fair values of each reporting unit of the acquired company. For purposes of the goodwill impairment test, the Company has identified its Retail and Institutional trading segments as its reporting units. The Company performs a two-step goodwill impairment review at the reporting unit level annually, or in interim periods if certain events occur indicating that the carrying value may be impaired. The Company tests for impairment during the fourth quarter of our fiscal year using October 1 carrying values.
	The first step of the two-step process involves a comparison of the estimated fair value of a reporting unit to its carrying amount, including goodwill. In performing the first step, the Company determines the fair value of a reporting unit using a discounted cash flow ("DCF") analysis. Determining fair value requires the exercise of significant judgment, including judgments about appropriate discount rates, perpetual growth rates and the amount and timing of expected future cash flows. The cash flows employed in the DCF analyses are based on the Company’s most recent budgets and business plans and, when applicable, various growth rates are assumed for years beyond the current business plan period. Discount rate assumptions are based on an assessment of the risk inherent in the future cash flows of the respective reporting units. If the estimated fair value of a reporting unit exceeds its carrying amount, the goodwill of the reporting unit is not impaired and the second step of the impairment test is not necessary. If the carrying amount of a reporting unit exceeds its estimated fair value, then the second step of the goodwill impairment test must be performed. The second step of the goodwill impairment test compares the implied fair value of the reporting unit’s goodwill with its carrying amount to measure the amount of impairment loss, if any. The implied fair value of goodwill is determined in the same manner as the amount of goodwill recognized in a business combination (i.e., the estimated fair value of the reporting unit is allocated to all of the assets and liabilities of that reporting unit including any unrecognized intangible assets as if the reporting unit had been acquired in a business combination and the fair value of the reporting unit was the purchase price paid). If the carrying amount of the reporting unit’s goodwill exceeds the implied fair value of the reporting unit’s goodwill, an impairment loss is recognized in an amount equal to that excess.
	There was no impairment of goodwill for the year ended December 31, 2014. Although there is no impairment as of December 31, 2014, events such as economic weakness and unexpected significant declines in operating results of reporting units may result in having to perform a goodwill impairment test for some or all of our reporting units prior to the required annual assessment. These types of events and the resulting analysis could result in goodwill impairment charges in the future (see Note 10)
Other Intangible Assets, net	Other Intangible Assets, net
	Other intangible assets, net, primarily include customer relationships, proprietary technology, non-compete agreements, an executory contract and trade names recorded from various acquisitions.
	The customer relationships, non-compete agreements, trade names and executory contract are finite-lived intangibles and are amortized on a straight-line basis over their estimated average useful life of 3 to 9 years, 1 to 9 years, 3 years and 3 years, respectively. Proprietary technology assets are also finite-lived intangibles and are amortized on a straight-line basis over their estimated average useful life of 4 to 7 years. The useful life of these intangibles is based on the period they are expected to contribute to future cash flows as determined by the Company's historical experience. For these finite-lived intangible assets subject to amortization, impairment is considered upon certain “triggering events” and is recognized if the carrying amount is not recoverable and the carrying amount exceeds the fair value of the intangible asset. There was no impairment of finite-lived intangible assets for the years ended December 31, 2014, 2013 or 2012 (see Note 11).
	The FX trading license is an indefinite-lived asset that is not amortized but tested for impairment. The Company’s policy is to test for impairment at least annually or in interim periods if certain events occur indicating that the fair value of the asset may be less than its carrying amount. An impairment test on this indefinite-lived asset is performed during the fourth quarter of the Company’s fiscal year using the October 1 carrying value. Impairment exists if the carrying value of the indefinite-lived intangible asset exceeds its fair value. There was no impairment of indefinite-lived intangible assets for the years ended December 31, 2014, 2013 or 2012
Equity Method Investment	Equity Method Investments
	Investments where the Company is deemed to exercise significant influence, but no control, are accounted for using the equity method of accounting. The Company records its pro-rata share of earnings or losses each period and records any dividends as a reduction in the investment balance. Additionally, the carrying value of investments accounted for using the equity method of accounting is adjusted downward to reflect any impairment in value. For investments accounted for using the equity method of accounting, the Company evaluates information (e.g., budgets, business plans, financial statements, etc.) in addition to quoted market prices, if any, in determining whether an other-than-temporary decline in value exists. Factors indicative of an impairment in value include recurring operating losses, credit defaults and subsequent rounds of financing at an amount below the cost basis of the Company’s investment.
	All of the Company’s equity method investments are included in Other assets in the consolidated statements of financial condition and earnings or losses are included in Loss on equity method investments, net in the consolidated statements of operations (see Note 8). Equity method investments are included in institutional and corporate for purposes of segment reporting.
Notes Receivable	Notes Receivable
	Notes receivable represent receivables for notes acquired for cash plus accrued interest. Notes receivable are initially recorded at the amount of cash exchanged plus accrued interest. Interest income on the notes is recorded on an accrual basis and included in Interest income in the consolidated statements of operations. The Company individually assesses its notes receivables for impairment using methods including internally generated cash flow projections to determine if the notes will be repaid under the expected terms of the note agreements. If the Company concludes that the counterparty will not repay a note in accordance with its terms, the Company considers the note impaired and begins recognizing interest income on a cash basis, if any. To measure impairment, the Company calculates the estimated fair value of the collateral. If the estimated fair value of the collateral is less than the carrying value of the note receivable, the Company establishes an impairment reserve for the difference. If it is likely that a note will not be collected based on financial or other business indicators, the Company’s policy is to charge off the note in the period which it deems it uncollectible (see Note 7).
Other Assets	Other Assets
	Other assets include prepaid expenses, equity method investments, deposits for rent security, deferred debt costs and exchange memberships (see Note 12).
Accounts Payable and Accrued Expenses	Accounts Payable and Accrued Expenses
	Accounts payable and accrued expenses include operating expenses payable, amounts due to the Lucid non-controlling members for services provided, commissions payable, which represents balances owed to referring brokers for trades transacted by customers that were introduced to the Company by such brokers, bonuses payable, income taxes payable, and interest due on borrowings. Accounts payable and accrued expenses at December 31, 2013 also included amounts due to the Lucid non-controlling members in connection with trade settlements and net amounts due to an equity method investee, as described in Note 16.
	Litigation
	The Company may from time to time be involved in litigation and claims that arise in the ordinary course of business, including intellectual property claims. In addition, our business is subject to extensive regulation, which may result in regulatory proceedings against us. The Company records a liability when it is both probable that a loss has been incurred and the amount of the loss can be reasonably estimated. When the reasonable estimate of the possible loss is within a range of amounts, the minimum of the range of possible loss is accrued, unless a higher amount within the range is a better estimate than any other amount within the range. Significant judgment is required to determine both probability and the estimated amount. The Company reviews these provisions at least quarterly and adjusts them accordingly to reflect the impact of negotiations, settlements, rulings, advice of legal counsel, and updated information.
	Securities Sold, Not Yet Purchased
	Securities sold, not yet purchased, represent the Company’s obligations to deliver a specified security at the contracted price at a future point in time, and thereby create a liability to repurchase the securities in the market at the prevailing prices. The liability for such securities sold short, included in the consolidated statements of financial condition, is marked to market based on the current fair value of the underlying security at the reporting date. Changes in fair value of securities sold, not yet purchased are recorded as unrealized gains or losses in Institutional trading revenue in the consolidated statements of operations. Total unrealized losses related to these securities for the year ended December 31, 2014 amounted to $0.5 million.
	Due to Related Parties Pursuant to Tax Receivable Agreement
	Exchanges of Holdings membership units ("Holdings Units") for the Corporation’s Class A common stock that are executed by the members of Holdings result in transfers of and increases in the tax basis of the tangible and intangible assets of Holdings, primarily attributable to a portion of the goodwill inherent in the business. These transfers and increases in tax basis will increase (for tax purposes) amortization and therefore reduce the amount of tax that the Company would otherwise be required to pay in the future. This increase in tax basis may also decrease gain (or increase loss) on future dispositions of certain capital assets to the extent tax basis is allocated to those capital assets. Holdings has entered into a tax receivable agreement with the members of Holdings whereby the Corporation has agreed to pay to the exchanging members 85% of the amount of cash tax savings, if any, in U.S. federal, state and local income tax that the Corporation realizes as a result of these increases in tax basis. The Corporation expects to benefit from the remaining 15% of cash tax savings, if any, in income tax it realizes. Payments under the tax receivable agreement will be based on the tax reporting positions that the Corporation takes in preparing its tax returns. The Corporation will not be reimbursed for any payments previously made under the tax receivable agreement if a tax basis increase is successfully challenged by the Internal Revenue Service.
	Holdings records an increase in deferred tax assets for the estimated income tax effects of the increases in tax basis based on enacted federal and state tax rates at the date of the exchange. To the extent that Holdings estimates that the exchanging members will not realize the full benefit represented by the deferred tax asset, based on an analysis that will consider, among other things, its expectation of future earnings, the Company will reduce the deferred tax asset with a valuation allowance. The Corporation records 85% of the estimated realizable tax benefit (which is the recorded deferred tax asset less any recorded valuation allowance) as an increase to the contingent liability due under the tax receivable agreement. Presently, the liability is a contingent liability based on the earnings of the Corporation and the expected tax benefit realized by the Corporation, but upon certain events such as a change in control or a material breach of the tax receivable agreement, the liability no longer stays contingent but rather becomes absolute. The remaining 15% of the estimated realizable tax benefit is initially recorded as an increase to the Corporation’s capital. All of the effects to the deferred tax asset of changes in any of the estimates after the tax year of the exchange will be reflected in the provision for income taxes. Similarly, the effect of subsequent changes in the enacted tax rates will be reflected in the provision for income taxes.
Convertible Debt Transactions	Convertible Debt Transactions
	The Company separately accounts for the liability and equity components of convertible debt instruments that may be settled entirely or partially in cash upon conversion by allocating the proceeds from issuance between the liability component and the embedded conversion option, or equity component, in accordance with ASC 470, Debt ("ASC 470"). The value of the equity component is calculated by first measuring the fair value of the liability component, using the interest rate of a similar liability that does not have a conversion feature, as of the issuance date. The difference between the proceeds from the convertible debt issuance and the amount measured as the liability component is recorded as the equity component. The Company recognizes the accretion of the resulting discount as part of interest expense in our consolidated statements of operations.
Contingent Consideration	Contingent Consideration
	The Company records a liability for contingent consideration resulting from a business combination at its fair value on the acquisition date included in Other liabilities in the consolidated statements of financial condition. Each reporting period thereafter, the Company revalues this liability and records increases or decreases in the fair value as an adjustment to Other income within the consolidated statements of operations. Changes in the fair value of the contingent consideration liability can result from adjustments in the probability targets of achieving profitability and adjustments to the discount rate.
Foreign Currency	Foreign Currency
	Foreign denominated assets and liabilities are re-measured into the functional currency at exchange rates in effect at the statements of financial condition dates through the consolidated statements of operations. Gains or losses resulting from foreign currency transactions are re-measured using the rates on the dates on which those elements are recognized during the period, and are included in Retail and Institutional trading revenue in the consolidated statements of operations. The Company recorded gains of $3.6 million, $5.3 million and $0.8 million for the years ended December 31, 2014, 2013 and 2012, respectively.
	Translation gains or losses resulting from translating the Company’s subsidiaries’ financial statements from the functional currency to the reporting currency, net of tax, are included in Foreign currency translation gain (loss) in the consolidated statements of comprehensive income. Assets and liabilities are translated at the statement of financial condition date while revenues and expenses are translated at an applicable average rate.
Revenue Recognition	Revenue Recognition
	The Company makes foreign currency markets for customers trading in FX spot markets and through its subsidiary FSL, engages in equity and related brokerage activities. FX transactions are recorded on the trade date and positions are marked to market daily with related gains and losses, including gains and losses on open spot transactions, recognized currently in income. Commissions earned on brokerage activities are recorded on a trade date basis and are recognized currently in income.
Retail Trading Revenue	Retail Trading Revenue
	Under the Company’s retail agency FX offering, trading revenue is earned from charging a separate commission or by adding a markup to the price provided by FX market makers generating trading revenue based on the volume of transactions and is recorded on trade date. Under the agency model, when a customer executes a trade on the best price quotation presented by the FX market maker, the Company acts as a credit intermediary, or a riskless principal, simultaneously entering into a trade with the customer and the FX market maker. This agency model has the effect of automatically hedging the Company's positions and eliminating market risk exposure. Retail trading revenues from mark-up principally represent the difference of the Company's realized and unrealized foreign currency trading gains or losses on its positions with customers and the systematic hedge gains and losses from the trades entered into with the FX market makers. Retail trading revenue also includes fees earned from arrangements with other financial institutions to provide platform, back office and other trade execution services. This service is generally referred to as a white label arrangement. The Company earns a percentage of the commission or markup charged by the financial institutions to their customers. Fees from this service are recorded when earned on a trade date basis.
	Additionally, the Company earns income from trading in CFDs, rollovers, payments for order flow, and spread betting. Income or loss on CFDs represents the difference between the Company's realized and unrealized trading gains or losses on its positions and the hedge gains or losses with the other financial institutions. Income or loss on CFDs is recorded on a trade date basis. Income or loss on rollovers is the interest differential customers earn or pay on overnight currency pair positions held and the markup that the Company receives on interest paid or received on currency pair positions held overnight. Income or loss on rollovers is recorded on a trade date basis. In 2013 and through August 2014, the Company earned revenue on order flow. Income earned on order flow represents payments received from certain FX market makers in exchange for routing trade orders to these firms for execution. The Company's order routing software ensures that payments for order flow do not affect the routing of orders in a manner that is detrimental to its retail customers. The Company recognizes payments for order flow as earned on a trade date basis. Spread betting is where a customer takes a position against the value of an underlying financial instrument moving either upward or downward in the market. Income on spread betting is recorded as earned on a trade date basis.
Institutional Trading Revenue	Institutional Trading Revenue
	Institutional trading revenue includes commission income generated by facilitating spot FX trades on behalf of institutional customers through the services provided by FXCM Pro and Faros. The counterparties to these trades are external financial institutions that also hold customer account balances and settle the transactions. The Company receives commission income on these trades without taking any market or credit risk. Institutional trading revenue is recorded on a trade date basis. The Company also earns income from market making and electronic trading in the institutional foreign exchange spot and futures markets through Lucid and market making and electronic trading into other asset classes through V3. Income on market making and electronic trading represents the spread between the bid and ask price for positions purchased and sold and the change in value of positions purchased and sold. Income on market making is recorded as trading gains, net of trading losses, on a trade date basis.
Interest Income	Interest Income
	Interest income consists of interest earned on cash and cash equivalents and cash and cash equivalents, held for customers and is recognized in the period earned.
Other Income	Other Income
	Other income primarily includes amounts earned from the sale of market data, equity and equity option brokerage activities, including spread betting on equities, account maintenance fees, ancillary fee income and recovery of accounts receivable previously written off.
	For the year ended December 31, 2014, Other income in the consolidated statements of operations primarily includes $3.7 million of revenue related to the re-measurement of the contingent consideration recorded for the acquisition of Faros (See Note 4), $2.5 million of account dormancy and ancillary fees, $5.8 million related to FSL's brokerage activities and a credit of $7.5 million attributable to the re-measurement of the Due to related parties pursuant to tax receivable agreement liability to reflect a revised effective tax rate.
	For the year ended December 31, 2013, Other income in the consolidated statements of operations primarily includes $6.9 million of revenue related to the re-measurement of the contingent consideration recorded for the acquisition of Faros, $7.2 million of FSL's brokerage activities, $3.1 million of account dormancy and ancillary fees, partially offset by a charge of $1.2 million attributable to the re-measurement of the Due to related parties pursuant to tax receivable agreement liability to reflect a revised U.S. federal tax rate. For the year ended December 31, 2012, Other income in the consolidated statements of operations includes a $1.4 million gain related to a settlement with the former owners of ODL.
Communications and Technology	Communications and Technology
	Communications and technology expense consists primarily of costs for network connections to our electronic trading platforms, telecommunications costs, and fees paid for access to external market data. This expense is affected primarily by the growth of electronic trading, our network/ platform capacity requirements and by changes in the number of telecommunication hubs and connections which provide our customers with direct access to our electronic trading platforms.
Trading Costs, Prime Brokerage and Clearing Fees	Trading Costs, Prime Brokerage and Clearing Fees
	Trading costs, prime brokerage and clearing fees primarily represent fees paid to third party clearing banks and prime brokers for clearing foreign exchange spot futures currency and contract transactions, transaction fees paid to exchanges, equity options brokerage activity fees, and fees paid to third party providers for use of their platform for the Company’s market making trading business. Clearing fees primarily fluctuate based on changes in volume, rate of clearing fees charged by clearing banks and rate of fees paid to exchanges.
Referring Broker Fees	Referring Broker Fees
	Referring broker fees represent commissions paid to brokers for introducing trading customers to the Company. Commissions are determined based on the number and size of transactions executed by the customers and are recorded on a trade date basis.
Compensation and Benefits	Compensation and Benefits
	Compensation and benefits expense represents employee and member salaries and benefit expense, including stock-based compensation expense. Compensation and benefits also includes the Allocation of income to Lucid members for services provided. This expense represents the 49.9% of Lucid's earnings allocated among the non-controlling members of Lucid based on services provided to Lucid.
	Stock-Based Compensation
	The Company accounts for stock-based compensation in accordance with ASC 718, Compensation-Stock Compensation (“ASC 718”). The Company's stock-based compensation expense is measured at the date of grant, based on the estimated fair value of the award, and recognized on a straight-line basis over the requisite service period of the award, net of estimated forfeitures. The fair value of the Company's non-qualified stock options is estimated using the Black-Scholes option pricing model. The fair value of restricted stock units ("RSUs") is based on the fair market value of the Corporation's Class A common stock on the date of grant, adjusted for the present value of dividends expected to be paid on the Corporation's Class A common stock prior to vesting. Stock-based compensation expense is included in Compensation and benefits in the consolidated statements of operations (see Note 17)
Advertising and Marketing	Advertising and Marketing
	Advertising and marketing costs are charged to operations when incurred.
General and Administrative Expenses	General and Administrative Expenses
	General and administrative expenses include bank processing and regulatory fees, professional fees, occupancy and equipment expense and other administrative costs. Bank processing fees are costs associated with the processing of credit card transactions. Regulatory fees are volume-based costs and annual fees charged by certain regulatory authorities and include fines and restitution imposed by regulators from time to time. General and administrative expense for the years ended December 31, 2014 and 2013 includes a charge of $2.5 million and $16.6 million, respectively, related to a liability established pertaining to a settlement with the FCA regarding the Company's pre-August 2010 trade execution practices (see Note 29).
Income Taxes	Income Taxes
	Holdings operates in the United States (“U.S.”) as a limited liability company that is treated as a partnership for U.S. Federal, state and local income tax purposes. As a result, Holdings' income from its U.S. operations is not subject to U.S. federal income tax because the income is attributable to its members. Accordingly, the Company’s U.S. tax provision is solely based on the portion of Holdings’ income attributable to the Corporation and excludes the income attributable to other members of Holdings whose income is included in Net Income attributable to non-controlling interest in FXCM Holdings, LLC in the consolidated statements of operations.
	Income taxes are accounted for in accordance with ASC 740, Income Taxes ("ASC 740"), which requires that deferred tax assets and liabilities are recognized, using enacted tax rates, for the effect of temporary differences between the book and tax basis of recorded assets and liabilities. Deferred tax assets, including net operating losses and income tax credits, are reduced by a valuation allowance if it is "more likely than not" that some portion or all of the deferred tax assets will not be realized (see Note 26).
	In addition to U.S. federal and state income taxes, Holdings is subject to Unincorporated Business Tax which is attributable to Holdings' operations apportioned to New York City. The Company’s foreign subsidiaries are also subject to local taxes.
	In accordance with ASC 740, the Company evaluates a tax position to determine whether it is more likely than not that the tax position will be sustained upon examination, based on the technical merits of the position. If the position does not meet a more likely than not threshold, a tax reserve is established and no income tax benefit is recognized. The Company is audited by U.S. federal and state, as well as foreign, tax authorities. In some cases, many years may elapse before a tax return containing tax positions for which an ASC 740 reserve has been established is examined and an audit is completed. As audit settlements are reached, the Company adjusts the corresponding reserves, if required, in the period in which the final determination is made. While it is difficult to predict the final outcome or timing of a particular tax matter, the Company believes that reserves for uncertain tax positions are recorded pursuant to the provisions of ASC 740.
Recent Accounting Pronouncements	Recently Adopted Accounting Pronouncements
	In February 2013, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU")No. 2013-04, Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation is Fixed at the Reporting Date. This standard requires an entity to measure obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date as the sum of (i) the amount the entity agreed to pay on the basis of its arrangement among its co-obligors and (ii) any additional amount it expect to pay on behalf of its co-obligors. The Company adopted this update on January 1, 2014 on a retrospective basis for all periods presented, which did not have a material impact on its consolidated financial statements.
	In March 2013, the FASB issued ASU No. 2013-05, Parent's Accounting for the Cumulative Translation Adjustment upon Derecognition of Certain Subsidiaries or Groups of Assets within a Foreign Entity or of an Investment in a Foreign Entity. This standard addresses whether consolidation guidance or foreign currency guidance applies to the release of the cumulative translation adjustment into net income when a parent sells all or a part of its investment in a foreign entity or no longer holds a controlling financial interest in a subsidiary or net assets that are a business (other than a sale of in-substance real estate) within a foreign entity. The standard also resolves the diversity in practice for the cumulative translation adjustment treatment in business combinations achieved in stages involving foreign entities. Under this standard, the entire amount of the cumulative translation adjustment associated with the foreign entity should be released into earnings when there has been: (i) a sale of a subsidiary or group of net assets within a foreign entity and the sale represents a complete or substantially complete liquidation of the foreign entity in which the subsidiary or the net assets had resided; (ii) a loss of a controlling financial interest in an investment in a foreign entity; or (iii) a change in accounting method from applying the equity method to an investment in a foreign entity to consolidating the foreign entity. The Company adopted this update on January 1, 2014 on a prospective basis, which did not have a material impact on its consolidated financial statements.
	In July 2013, the FASB issued ASU No. 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists. This standard requires a liability related to unrecognized tax benefits to be presented as a reduction to the related deferred tax asset for a net operating loss carryforward or a tax credit carryforward. When the carryforwards are not available at the reporting date under the tax law of the applicable jurisdiction or the tax law of the applicable jurisdiction does not require, and the entity does not intend to use, the deferred tax asset for such purpose, the unrecognized tax benefit will be presented in the financial statements as a liability and will not be combined with the related deferred tax asset. The Company adopted this update on January 1, 2014 on a prospective basis, which did not have a material impact on its consolidated financial statements.
	Recently Issued Accounting Pronouncements
	In April 2014, the FASB issued ASU No. 2014-08, Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360): Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity. Under this standard, a discontinued operation will include a disposal of a major part of an entity’s operations and financial results such as a separate major line of business or a separate major geographical area of operations. The standard also raises the threshold to be considered a major operation but no longer precludes discontinued operations presentation where there is significant continuing involvement or cash flows with a disposed component of an entity. The standard expands disclosures to include cash flows where there is significant continuing involvement with a discontinued operation and the pre-tax profit or loss of disposal transactions not reported as discontinued operations. The standard is effective prospectively for annual periods beginning on or after December 15, 2014, and interim periods within those years. Early adoption is permitted, but only for disposals that have not been reported in financial statements previously issued or available for issuance. The Company expects to adopt this standard prospectively on its required effective date of January 1, 2015 and the impact, if any, on its consolidated statements of financial condition, results of operations or cash flows will be dependent on the nature of future disposals.
	In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers. The guidance in this update supersedes nearly all existing revenue recognition guidance under U.S. GAAP and creates a single, principle-based revenue recognition framework that is codified in a new FASB ASC Topic 606. The core principle of this guidance is for the recognition of revenue to depict the transfer of goods or services to customers at an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The standard sets out the following five steps an entity should apply to achieve this core principle:
	•Identify the contract(s) with a customer
	•Identify the performance obligations in the contract
	•Determine the transaction price
	•Allocate the transaction price to the performance obligations in the contract
	•Recognize revenue when (or as) the entity satisfies a performance obligation
	The standard also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. The new revenue standard is effective for annual reporting periods beginning after December 15, 2016, and interim periods within those years. Early adoption is not permitted. The new standard allows for either the full retrospective or cumulative effect transition method of adoption. The standard will be effective for the Company beginning January 1, 2017. The Company is currently evaluating the transition method that will be elected and the potential effects of the adoption of the new standard on its consolidated financial statements and related disclosures.
	In August 2014, the FASB issued ASU No. 2014-15, Presentation of Financial Statements - Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern. The new standard requires management to explicitly evaluate for each reporting period whether there are conditions or events that raise substantial doubt about an entity’s ability to continue as a going concern and provide related footnote disclosure in certain circumstances. The new standard is effective for the annual period ending after December 15, 2016, and for annual and interim periods thereafter. Early application is permitted. The Company expects to adopt this standard for its annual period ending December 31, 2016 and is currently evaluating the impact the new standard will have on the disclosures in its consolidated financial statements.
	In November 2014, the FASB issued ASU No. 2014-16, Derivatives and Hedging (Topic 815): Determining Whether the Host Contract in a Hybrid Financial Instrument Issued in the Form of a Share Is More Akin to Debt or to Equity. The new standard clarifies how current U.S. GAAP should be interpreted in evaluating the economic characteristics and risks of a host contract in a hybrid financial instrument that is issued in the form of a share. Specifically, the standard requires an entity to consider all of the stated and implied substantive terms and features of the entire hybrid financial instrument, including the embedded derivative feature that is being evaluated for separate accounting from the host contract, when evaluating whether the host contract is more akin to debt or equity. The new standard is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015. The effects of initially adopting the standard should be applied on a modified retrospective basis to existing hybrid financial instruments issued in the form of a share as of the beginning of the fiscal year for which the amendments are effective. Retrospective application to all relevant prior periods is permitted. Early adoption, including adoption in an interim period, is permitted. The Company expects to adopt this standard beginning January 1, 2016 and is currently evaluating the impact, if any, the new standard will have on its consolidated financial statements.

Significant_Accounting_Policie2

Significant Accounting Policies and Estimates (Tables)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Schedule of Significant Subsidiaries	The Company's consolidated financial statements include the following significant subsidiaries of Holdings:
	Forex Capital Markets LLC		(“US”)
	FXCM Asia Limited		(“HK”)
	Forex Capital Markets Limited		(“UK LTD”)
	FXCM Australia Limited		(“Australia”)
	ODL Group Limited		(“ODL”)
	FXCM Securities Limited		(“FSL”)
	FXCM Japan Securities Co., Ltd.		(“FXCMJ”)
	FXCM UK Merger Limited		(“Merger”)
	Lucid Markets Trading Limited		(“Lucid”)
	Lucid Markets LLP		("Lucid LLP")
	Faros Trading LLC		("Faros")
	V3 Markets, LLC		("V3")
Property, Plant and Equipment	Depreciation is computed using the straight-line method. The Company depreciates these assets using the following useful lives:
	Computer equipment		3 to 5 years
	Software		2 to 5 years
	Leasehold improvements		Lesser of the estimated economic useful life or the term of the lease
	Furniture and fixtures and other equipment		3 to 5 years
	Licenses		2 to 3 years
	Communication equipment		3 to 5 years
	Office, communication and computer equipment, net, including capitalized software development costs, leasehold improvements and capital leases, consisted of the following as of December 31, 2014 and 2013, with amounts in thousands:
		As of December 31,
		2014			2013
	Computer equipment	$	30,961		$	28,047
	Software	63,766			47,138
	Leasehold improvements	10,095			9,687
	Furniture and fixtures and other equipment	3,521			3,427
	Licenses	11,499			10,101
	Communication equipment	2,444			1,664
	Total office, communication and computer equipment	122,286			100,064
	Less: Accumulated depreciation	(74,092		)	(50,899		)
	Office, communication and computer equipment, net	$	48,194		$	49,165

NonControlling_Interest_Tables

Non-Controlling Interest (Tables)	12 Months Ended
	Dec. 31, 2014
Noncontrolling Interest [Abstract]
Corporation's interests in Holdings	Changes in the non-controlling and the Corporation’s interests in Holdings for the year ended December 31, 2014 are presented in the following table:
		Controlling Units		Non-		Total Units		FXCM		Non-		Total
				Controlling Units				Inc.		Controlling
	Balance as of January 1, 2014	44,664,884		36,835,821		81,500,705		54.8	%	45.2	%	100	%
	Holdings Units acquired by FXCM Inc. related to exchanges of Holdings Units for shares of Class A common stock	2,378,147		(2,378,147	)	—		2.8	%	(2.8	)%	—	%
	Holdings Units repurchased related to Class A common stock repurchased	(145,985	)	—		(145,985	)	(0.1	)%	0.1	%	—	%
	Exercise of stock options	829,086		—		829,086		0.5	%	(0.5	)%	—	%
	Issuance under equity-based compensation	163,832		—		163,832		0.1	%	(0.1	)%	—	%
	Balance as of December 31, 2014	47,889,964		34,457,674		82,347,638		58.1	%	41.9	%	100	%

Business_Acquisitions_Tables

Business Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2014
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Information	The following pro forma condensed combined financial information represents the Company's revenues and net income before non-controlling interest as they may have appeared in the consolidated statements of operations if the acquisitions of Lucid, Faros and V3 had occurred on January 1, 2011, 2012 and 2013, respectively, with amounts in thousands:
		Years Ended December 31,
		2014			2013		2012
	Total revenues	$	463,757		$	535,130	$	463,767
	Net income before non-controlling interest	$	17,583		$	36,838	$	49,224
V3
Business Acquisition [Line Items]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The following condensed statement of net assets acquired reflects the amounts of V3 net assets recognized as of the V3 Acquisition Date, with amounts in thousands:
		As of January 21, 2014
	Assets
	Office, communication and computer equipment, net	$	973
	Intangible assets	2,020
	Exchange memberships and common equity shares	6,429
	Equity method investments, net	1,523
	Other assets	1,392
	Total assets	$	12,337
	Liabilities	(107		)
	Fair value of net assets acquired	$	12,230
	V3 Purchase Price Allocation (¹)
	(Amounts in thousands)
	Purchase price				$	15,825
	Non-Controlling interest				15,762
	Total fair value at Acquisition Date				31,587
	Net assets acquired	$	10,210
	Adjustments to reflect acquired assets and liabilities at fair value
	Trading platform (2)	950
	Processing platform (3)	150
	Non-compete agreement (4)	450
	Executory contract (5)	470
	Fair value of net assets acquired				12,230
	Goodwill resulting from the V3 acquisition				$	19,357
	___________________
		(1)	The amounts included in the V3 Purchase Price Allocation table represent the allocation of the purchase price and include revisions made during the 12-month remeasurement period from the V3 Acquisition Date.
		(2)	Consists of internally-developed software platforms that support trade execution, with an amortization life of 4 years.
		(3)	Consists of an internally-developed software platform that supports trading, with an amortization life of 5 years.
		(4)	Amortization life is 1 year.
		(5)	Consists of a service agreement relating to fiber optics, wireless and other services, with an amortization life of 3 years.
Business Acquisition, Pro Forma Information	The following condensed financial information presents the resulting operations of V3 from the V3 Acquisition Date to December 31, 2014, with amounts in thousands:
		For the period
		January 21, 2014 to
		31-Dec-14
	Total revenue	$	20,706
	Net loss	$	(1,815	)
Faros Trading LLC
Business Acquisition [Line Items]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	Faros Purchase Price Allocation (¹)
	(Amounts in thousands)
	Purchase price				$	15,631
	Non-Controlling interest				15,569
	Total fair value at Acquisition Date				31,200
	Net assets acquired	$	137
	Adjustments to reflect acquired assets and liabilities at fair value
	Customer relationships (2)	6,000
	Non-compete agreement (3)	1,900
	Trade name (4)	130
	Fair value of net assets acquired				8,167
	Goodwill resulting from the Faros acquisition				$	23,033
	____________________
	(1)	The amounts included in the Faros Purchase Price Allocation table represent the allocation of the purchase price and include revisions made during the 12-month remeasurement period from the Faros Acquisition Date.
	(2)	Consists of institutional and bank customers, with an amortization life of 4 years.
	(3)	Amortization life is 9 years.
	(4)	Amortization life is 3 years.
	The following condensed statement of net assets acquired reflects the amounts of Faros net assets recognized as of the Faros Acquisition Date, with amounts in thousands:
		As of September 20, 2013
	Assets
	Cash and cash equivalents	$	1,055
	Accounts receivable, net	40
	Office, communication and computer equipment, net	31
	Intangible assets	8,030
	Other assets	76
	Total assets	$	9,232
	Liabilities
	Accounts payable and accrued expenses	1,065
	Total liabilities	1,065
	Fair value of net assets acquired	$	8,167
Business Acquisition, Pro Forma Information	The following condensed financial information presents the resulting operations of Faros from the Faros Acquisition Date to December 31, 2013, with amounts in thousands:
		For the period September 20, 2013 to December 31, 2013
	Total revenue	$	526
	Net loss	$	(301	)
Lucid Markets Trading Limited
Business Acquisition [Line Items]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The following condensed statement of net assets acquired reflects the amounts of Lucid net assets recognized as of the Lucid Acquisition Date, with amounts in thousands:
		As of June 18, 2012
	Assets
	Cash and cash equivalents	$	28,656
	Accounts receivable, net	5,100
	Due from brokers	302
	Deferred tax asset	11,311
	Office, communication and computer equipment, net	499
	Intangible assets	84,900
	Other assets	226
	Total assets	$	130,994
	Liabilities
	Accounts payable and accrued expenses	13,362
	Total liabilities	13,362
	Fair value of net assets acquired	$	117,632
	(Amounts in thousands)
	Purchase price				$	192,784
	Non-Controlling interest				160,165
	Total fair value at Acquisition Date				352,949
	Net assets acquired	$	32,732
	Adjustments to reflect acquired assets and liabilities at fair value
	Proprietary technology (2)	83,900
	Non-compete agreements (3)	1,000
	Fair value of net assets acquired				117,632
	Goodwill resulting from the Lucid acquisition				$	235,317
	____________________
	(¹) The amounts included in the Lucid Purchase Price Allocation table represent the allocation of the purchase price and include revisions made during the 12-month remeasurement period from the Lucid Acquisition Date.
	(²) Consists of internally-developed software platforms through which the Company: (i) executes its specific trading strategies, with an amortization life of 4 years and (ii) clears and efficiently settle trades, with an amortization life of 7 years.
	(³) Consists of two non-compete agreements with amortization lives of 3 years
Business Acquisition, Pro Forma Information	The following condensed financial information presents the resulting operations of Lucid from the Lucid Acquisition Date to December 31, 2012:
		For the period June 18, 2012 to December 31, 2012
	Total revenue	$	42,198
	Net income	$	21,446

Office_Communication_and_Compu1

Office, Communication and Computer Equipment, net (Tables)	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Depreciation is computed using the straight-line method. The Company depreciates these assets using the following useful lives:
	Computer equipment		3 to 5 years
	Software		2 to 5 years
	Leasehold improvements		Lesser of the estimated economic useful life or the term of the lease
	Furniture and fixtures and other equipment		3 to 5 years
	Licenses		2 to 3 years
	Communication equipment		3 to 5 years
	Office, communication and computer equipment, net, including capitalized software development costs, leasehold improvements and capital leases, consisted of the following as of December 31, 2014 and 2013, with amounts in thousands:
		As of December 31,
		2014			2013
	Computer equipment	$	30,961		$	28,047
	Software	63,766			47,138
	Leasehold improvements	10,095			9,687
	Furniture and fixtures and other equipment	3,521			3,427
	Licenses	11,499			10,101
	Communication equipment	2,444			1,664
	Total office, communication and computer equipment	122,286			100,064
	Less: Accumulated depreciation	(74,092		)	(50,899		)
	Office, communication and computer equipment, net	$	48,194		$	49,165

Goodwill_Tables

Goodwill (Tables)	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in Goodwill by Segment	The following table presents the changes in goodwill by segment during the year ended December 31, 2014, with amounts in thousands:
		Retail Trading			Institutional Trading			Total
	Balance at January 1, 2014	$	38,079		$	269,857		$	307,936
	Goodwill acquired	—			19,357			19,357
	Goodwill adjustment	—			(9		)	(9		)
	Foreign currency translation adjustment	(2,703		)	(694		)	(3,397		)
	Balance at December 31, 2014	$	35,376		$	288,511		$	323,887

Other_Intangible_Assets_net_Ta

Other Intangible Assets, net (Tables)	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Acquired Finite-Lived Intangible Assets by Major Class	The Company’s acquired intangible assets consisted of the following as of December 31, 2014 and 2013, with amounts in thousands:
		December 31, 2014									December 31, 2013
		Gross Carrying Amount			Accumulated Amortization			Net Carrying Amount			Gross Carrying Amount			Accumulated Amortization			Net Carrying Amount
	Finite-lived intangible assets
	Customer relationships	$	47,397		$	(21,944	)	$	25,453		$	37,746		$	(14,529	)	$	23,217
	Non-compete agreements	3,350			(1,489		)	1,861			10,507			(8,177		)	2,330
	Proprietary technology	85,000			(52,844		)	32,156			83,900			(31,849		)	52,051
	Executory contract	470			(131		)	339			—			—			—
	Trade name	241			(56		)	185			177			(13		)	164
	Foreign currency translation adjustment	(4,391		)	1,354			(3,037		)	(1,831		)	172			(1,659		)
	Total finite-lived intangible assets	$	132,067		$	(75,110	)	$	56,957		$	130,499		$	(54,396	)	$	76,103
	Indefinite-lived intangible assets
	License	610			—			610			610			—			610
	Total Other intangible assets, net	$	132,677		$	(75,110	)	$	57,567		$	131,109		$	(54,396	)	$	76,713
Acquired Intangible Assets	The Company’s acquired intangible assets consisted of the following as of December 31, 2014 and 2013, with amounts in thousands:
		December 31, 2014									December 31, 2013
		Gross Carrying Amount			Accumulated Amortization			Net Carrying Amount			Gross Carrying Amount			Accumulated Amortization			Net Carrying Amount
	Finite-lived intangible assets
	Customer relationships	$	47,397		$	(21,944	)	$	25,453		$	37,746		$	(14,529	)	$	23,217
	Non-compete agreements	3,350			(1,489		)	1,861			10,507			(8,177		)	2,330
	Proprietary technology	85,000			(52,844		)	32,156			83,900			(31,849		)	52,051
	Executory contract	470			(131		)	339			—			—			—
	Trade name	241			(56		)	185			177			(13		)	164
	Foreign currency translation adjustment	(4,391		)	1,354			(3,037		)	(1,831		)	172			(1,659		)
	Total finite-lived intangible assets	$	132,067		$	(75,110	)	$	56,957		$	130,499		$	(54,396	)	$	76,103
	Indefinite-lived intangible assets
	License	610			—			610			610			—			610
	Total Other intangible assets, net	$	132,677		$	(75,110	)	$	57,567		$	131,109		$	(54,396	)	$	76,713
Estimated Future Amortization Expense for Acquired Intangible Assets Outstanding
	Year Ending December 31,
	2015	$	30,765
	2016	18,836
	2017	4,889
	2018	1,059
	2019	723
	Thereafter	685
		$	56,957

Other_Assets_Tables

Other Assets (Tables)	12 Months Ended
	Dec. 31, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Components of Other Assets	Other assets were comprised of the following as of December 31, 2014 and 2013, with amounts in thousands:
		As of December 31,
		2014		2013
	Prepaid expenses	$	5,823	$	5,738
	Equity method investments	10,007		9,793
	Deferred debt issuance costs	5,582		7,131
	Exchange memberships	6,429		—
	Deposits	1,514		1,492
	Other	293		162
	Total	$	29,648	$	24,316

Accounts_Payable_and_Accrued_E1

Accounts Payable and Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2014
Payables and Accruals [Abstract]
Accounts Payable and Accrued Expenses	Accounts payable and accrued expenses were comprised of the following as of December 31, 2014 and 2013, with amounts in thousands:
		As of December 31,
		2014		2013
	Operating expenses payable	$	23,256	$	41,528
	Due to Lucid non-controlling members	8,876		9,995
	Commissions payable	11,864		9,485
	Bonus payable	9,664		7,455
	Income tax payable	2,158		1,046
	Interest due on borrowings	202		177
	Other	19		11
	Total	$	56,039	$	69,697

Earnings_per_Share_Tables

Earnings per Share (Tables)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Reconciliation of Numerator and Denominator Used in Basic and Diluted EPS Calculations	The following is a reconciliation of the numerator and denominator used in the basic and diluted EPS calculations, with amounts in thousands, except per share data:
		For the Years Ended December 31,
		2014		2013		2012
	Basic and diluted net income per share:
	Numerator
	Net income available to holders of Class A common stock	$	17,151	$	14,832	$	8,958
	Earnings allocated to participating securities	—		—		—
	Earnings available for common stockholders	$	17,151	$	14,832	$	8,958
	Denominator for basic net income per share of Class A common stock
	Weighted average shares of Class A common stock	41,637		32,789		24,086
	Add dilutive effect of the following:
	Weighted average of Lucid's first anniversary shares issued on June 18, 2013	—		552		—
	Weighted average of Lucid's second anniversary shares issued on June 18, 2014	1,381		—
	Stock options and RSUs	992		616		—
	Convertible note hedges	—		—		—
	Warrants	—		—		—
	Assumed conversion of Holdings Units for Class A common stock	—		—		—
	Dilutive weighted average shares of Class A common stock	44,010		33,957		24,086
	Basic income per share of Class A common stock	$	0.41	$	0.45	$	0.37
	Diluted income per share of Class A common stock	$	0.39	$	0.44	$	0.37

Related_Party_Transactions_Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2014
Related Party Transactions [Abstract]
Amounts receivable from, and payable to, related parties	Amounts receivable from, and payable to, related parties are set forth below, with amounts in thousands:
		As of December 31,
		2014		2013
	Receivables
	Advances to Holdings non-controlling members	$	196	$	940
	Accounts receivable - Lucid non-controlling members	799		—
	Accounts receivable - equity method investment	1,468		—
	Advances to employees	563		826
	Notes receivable and interest - Lucid non-controlling members	8,013		—
	Total receivables from related parties	$	11,039	$	1,766
	Payables
	Guarantee agreement ("Monetary Guaranty")	$	7,078	$	8,363
	Employees	2,009		708
	Shareholders with greater than 5% ownership in the Company	—		200
	Due to Lucid non-controlling members in connection with the allocation of income to Lucid non-controlling members for services provided	8,876		9,826
	Due to Lucid non-controlling members in connection with trade settlements	—		169
	Notes payable to Lucid non-controlling members in connection with the Lucid Acquisition	—		9,800
	Accounts payable - equity method investment	—		378
	Faros Follow-on Payment	—		3,672
	Tax receivable agreement	150,576		150,258
	Total payables to related parties	$	168,539	$	183,374

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-based Compensation, Stock Options, Activity	The following table summarizes the Company’s stock options activity as of December 31, 2014 and changes for the year then ended:
	Stock Options	Shares			Weighted-Average Exercise Price				Weighted-Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (In thousands)
	Outstanding at January 1, 2014	7,607,800			$	13.48
	Granted	648,490			$	16.28
	Exercised	(829,086	)		$	13.48
	Forfeited or expired	(236,400	)		$	13.23
	Outstanding at December 31, 2014	7,190,804			$	13.74			3.59		$	20,525
	Options vested and expected to vest at December 31, 2014	7,166,783			$	13.74			3.58		$	20,461
	Options exercisable at December 31, 2014	5,776,564			$	13.67			3.15		$	16,780
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The following assumptions were used in the Black-Scholes valuation model:
		Employee Stock Options												Independent Directors Options
		For the Years Ended December 31,												For the Years Ended December 31,
		2014				2013				2012				2014			2013			2012
	Expected term in years	4.75				4.75				4.75				4			4			4
	Risk-free interest rate	1.58		%		1.06		%		0.71		%		1.19		%	0.63		%	0.6		%
	Expected volatility	45		%		51		%		52		%		44		%	54		%	63		%
	Dividend yield	1.48		%		1.55		%		2.48		%		1.43		%	2.05		%	2.4		%
	Estimated fair value at grant date	$	5.7			$	6.02			$	3.47			$	5.39		$	4.26		$	4.11
Schedule of Share-based Compensation, Restricted Stock Units Award Activity	The following table summarizes the Company’s unvested RSU activity as of December 31, 2014 and changes for the year then ended:
			Units			Weighted-Average Grant-Date Fair Value				Weighted-Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
												(in thousands)
	Unvested at January 1, 2014		—			—
	Granted		208,500			$	16.25
	Vested		—			—
	Forfeited		—			—
	Unvested at December 31, 2014		208,500			$	16.25			3.96		$	3,455
	RSUs expected to vest at December 31, 2014		182,825			$	16.25			3.96		$	3,029

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Schedule of Stockholders Equity	The following table presents the changes in the Company’s Class A common stock outstanding during the year ended December 31, 2014, with amounts in thousands:
	Class A Common Stock
	Balance at January 1, 2014	44,665
	Issued	164
	Repurchased	(146	)
	Exchange of Holdings units into Class A common stock	2,378
	Stock options exercised	829
	Balance at December 31, 2014	47,890

Net_Capital_Requirements_Table

Net Capital Requirements (Tables)	12 Months Ended
	Dec. 31, 2014
Banking and Thrift [Abstract]
Minimum Capital Requirement And the Excess Capital	The tables below present the capital, as defined by the respective regulatory authority, the minimum capital requirement and the excess capital for US, HK, UK LTD, Australia, ODL, FSL, FXCMJ, Lucid LLP and Faros as of December 31, 2014 and 2013, with amounts in millions:
		As of December 31, 2014
		US		UK LTD		HK		Australia		ODL		FSL		FXCMJ		Lucid LLP		Faros
	Capital	$	69.5	$	101.6	$	31.2	$	3	$	25.5	$	40.2	$	36.3	$	22.8	$	0.4
	Minimum capital requirement	30		29.2		14.8		0.8		3		5.2		6.3		3.8		—
	Excess capital	$	39.5	$	72.4	$	16.4	$	2.2	$	22.5	$	35	$	30	$	19	$	0.4

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	Future minimum lease payments under non-cancelable operating leases with terms in excess of one year are as follows as of December 31, 2014, with amounts in thousands:
	Year Ending December 31,
	2015	$	6,714
	2016	5,304
	2017	3,781
	2018	3,492
	2019	3,292
	Thereafter	19,858
		$	42,441

Debt_Tables

Debt (Tables)	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Convertible Debt	The balances of the liability and equity components as of December 31, 2014 and 2013, were as follows, with amounts in thousands:
		As of December 31,
		2014			2013
	Liability component - principal	$	172,500		$	172,500
	Deferred bond discount	(20,922		)	(26,197		)
	Liability component - net carrying value	$	151,578		$	146,303
	Equity component	$	29,101		$	29,101
	Interest expense related to the Convertible Notes, included in Interest on borrowings in the consolidated statements of operations for the years ended December 31, 2014 and 2013 was as follows, with amounts in thousands:
		For the Years Ended December 31,
		2014			2013
	Interest expense - stated coupon rate	$	3,881		$	2,232
	Interest expense - amortization of deferred bond discount	5,275			2,904
	Interest expense - amortization of debt issuance cost	1,209			699
	Total interest expense - convertible notes	$	10,365		$	5,835

Derivative_Financial_Instrumen1

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Offsetting Assets	Under ASC 210, gross positive fair values are offset against gross negative fair values by counterparty pursuant to enforceable master netting agreements, with amounts in thousands:
		As of December 31, 2014
		Derivative Assets						Derivative Liabilities
		(Included in Due from/Due to Brokers)
		Fair Value			Notional			Fair Value			Notional
	Exchange traded options	$	10,724		$	95,498		$	11,422		$	81,053
	Futures contracts	332,346			3,617,128			352,703			3,627,562
	OTC options	—			—			1,086			1,086
	Total derivatives, gross	$	343,070		$	3,712,626		$	365,211		$	3,709,701
	Netting agreements and cash collateral netting	(342,467		)				(353,543		)
	Total derivatives, net	$	603					$	11,668
		As of December 31, 2013
		Derivative Assets						Derivative Liabilities
		(Included in Due from/Due to Brokers)
		Fair Value			Notional			Fair Value			Notional
	Futures contracts	$	84		$	19,475		$	2,404		$	140,429
	Netting agreements	(84		)				(84		)
	Total derivatives, net	$	—					$	2,320
	Gains (losses) on derivative instruments are recorded on a trade date basis. The following table presents the gains (losses) on derivative instruments included in Retail and Institutional trading revenue in the consolidated statements of operations for the years ended December 31, 2014 and 2013, with amounts in thousands:
		Gains (Losses)
		Twelve Months ended December 31, 2014									Twelve Months ended December 31, 2013
		Retail			Institutional			Total			Retail			Institutional		Total
	Exchange traded options	$	—		$	33,318		$	33,318		$	—		$	—	$	—
	Futures contracts	(74,297		)	(5,242		)	(79,539		)	(26,671		)	20,244		(6,427		)
	OTC options	—			(23		)	(23		)	—			—		—
	Total	$	(74,297	)	$	28,053		$	(46,244	)	$	(26,671	)	$	20,244	$	(6,427	)
Offsetting Liabilities	Under ASC 210, gross positive fair values are offset against gross negative fair values by counterparty pursuant to enforceable master netting agreements, with amounts in thousands:
		As of December 31, 2014
		Derivative Assets						Derivative Liabilities
		(Included in Due from/Due to Brokers)
		Fair Value			Notional			Fair Value			Notional
	Exchange traded options	$	10,724		$	95,498		$	11,422		$	81,053
	Futures contracts	332,346			3,617,128			352,703			3,627,562
	OTC options	—			—			1,086			1,086
	Total derivatives, gross	$	343,070		$	3,712,626		$	365,211		$	3,709,701
	Netting agreements and cash collateral netting	(342,467		)				(353,543		)
	Total derivatives, net	$	603					$	11,668
		As of December 31, 2013
		Derivative Assets						Derivative Liabilities
		(Included in Due from/Due to Brokers)
		Fair Value			Notional			Fair Value			Notional
	Futures contracts	$	84		$	19,475		$	2,404		$	140,429
	Netting agreements	(84		)				(84		)
	Total derivatives, net	$	—					$	2,320
	Gains (losses) on derivative instruments are recorded on a trade date basis. The following table presents the gains (losses) on derivative instruments included in Retail and Institutional trading revenue in the consolidated statements of operations for the years ended December 31, 2014 and 2013, with amounts in thousands:
		Gains (Losses)
		Twelve Months ended December 31, 2014									Twelve Months ended December 31, 2013
		Retail			Institutional			Total			Retail			Institutional		Total
	Exchange traded options	$	—		$	33,318		$	33,318		$	—		$	—	$	—
	Futures contracts	(74,297		)	(5,242		)	(79,539		)	(26,671		)	20,244		(6,427		)
	OTC options	—			(23		)	(23		)	—			—		—
	Total	$	(74,297	)	$	28,053		$	(46,244	)	$	(26,671	)	$	20,244	$	(6,427	)

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following tables present the Company's assets and liabilities that are measured at fair value on a recurring basis and the related hierarchy levels, with amounts in thousands:
		Fair Value Measurements on a Recurring Basis
		As of December 31, 2014
		Quoted Prices in Active Markets for Identical Assets or Liabilities		Significant Observable Inputs		Significant Unobservable Inputs			Counterparty and Cash Collateral Netting			Total
		(Level I)		(Level II)		(Level III)
	Financial Assets:
	Trading securities	$	26	$	—	$	—		$	—		$	26
	Due from brokers:
	Exchange traded options	10,724		—		—			—			10,724
	Futures contracts	332,346		—		—			—			332,346
	Netting	—		—		—			(342,467		)	(342,467		)
	Total due from brokers	343,070		—		—			(342,467		)	603
	Total assets	$	343,096	$	—	$	—		$	(342,467	)	$	629
	Financial Liabilities:
	Customer account liabilities	$	—	$	1,331,723	$	—		$	—		$	1,331,723
	Due to brokers:
	Exchange traded options	11,422		—		—			—			11,422
	Futures contracts	352,703		—		—			—			352,703
	OTC options	—		1,086		—			—			1,086
	Netting	—		—		—			(353,543		)	(353,543		)
	Total due to brokers	364,125		1,086		—			(353,543		)	11,668
	Securities sold, not yet purchased	4,239		—		—			—			4,239
	Total liabilities	$	368,364	$	1,332,809	$	—		$	(353,543	)	$	1,347,630
		Fair Value Measurements on a Recurring Basis
		As of December 31, 2013
		Quoted Prices in Active Markets for Identical Assets or Liabilities		Significant Observable Inputs		Significant Unobservable Inputs			Counterparty and Cash Collateral Netting			Total
		(Level I)		(Level II)		(Level III)
	Financial Assets:
	Due from brokers - futures contracts	$	84	$	—	$	—		$	(84	)	$	—
	Total assets	$	84	$	—	$	—		$	(84	)	$	—
	Financial Liabilities:
	Customer account liabilities	$	—	$	1,190,880	$	—		$	—		$	1,190,880
	Due to brokers - open futures contracts	2,404		—		—			(84		)	2,320
	Follow-on Payment	—		—		3,672			—			3,672
	Total liabilities	$	2,404	$	1,190,880	$	3,672		$	(84	)	$	1,196,872
Fair Value, by Balance Sheet Grouping	The following tables present the carrying value, fair value and fair value hierarchy category of certain financial instruments that are not measured at fair value in the consolidated statements of financial condition, with amounts in thousands:
		As of December 31, 2014				Fair Value Measurements using:
		Carrying Value		Fair Value		Quoted Prices in Active Markets for Identical Assets or Liabilities			Significant Observable Inputs			Significant Unobservable Inputs
						(Level I)			(Level II)			(Level III)
	Financial Assets:
	Restricted time deposits	$	8,341	$	8,341	$	—		$	8,341		$	—
	Due from brokers - unsettled spot FX	14,635		14,635		—			14,635			—
	Due from brokers - unsettled common stock	3,730		3,730		—			3,730			—
	Due from brokers - excess cash collateral	18,330		18,330		—			18,330			—
	Equity method investments	10,007		17,199		—			—			17,199
	Notes receivable	9,381		9,381		—			—			9,381
	Exchange memberships	6,429		7,802		—			7,802			—
	Total assets	$	70,853	$	79,418	$	—		$	52,838		$	26,580
	Financial Liabilities:
	Due to brokers - unsettled spot FX	4,645		4,645		—			4,645			—
	Credit agreement	25,000		25,000		—			25,000			—
	Senior convertible notes	151,578		147,266		—			147,266			—
	Total liabilities	$	181,223	$	176,911	$	—		$	176,911		$	—
		As of December 31, 2013				Fair Value Measurements using:
		Carrying Value		Fair Value		Quoted Prices in Active Markets for Identical Assets or Liabilities			Significant Observable Inputs			Significant Unobservable Inputs
						(Level I)			(Level II)			(Level III)
	Financial Assets:
	Due from brokers - unsettled spot FX	$	5,450	$	5,450	$	—		$	5,450		$	—
	Equity method investments	9,793		13,504		—			—			13,504
	Notes receivable	11,942		11,942		—			—			11,942
	Total assets	$	27,185	$	30,896	$	—		$	5,450		$	25,446
	Financial Liabilities:
	Due to brokers - unsettled spot FX	6,332		6,332		—			6,332			—
	Note payable	9,800		9,800		—			—			9,800
	Senior convertible notes	146,303		149,418		—			149,418			—
	Total liabilities	$	162,435	$	165,550	$	—		$	155,750		$	9,800
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation	The following tables reconcile the ending balances of liabilities classified as Level III and identify the total gains the Company recognized during the years ended December 31, 2014 and 2013 on such liabilities that were included in the consolidated statements of financial condition as of December 31, 2014 and 2013, respectively, with amounts in thousands:
		As of December 31, 2014
		Beginning		Additions		Net Unrealized / Realized Gains			Ending
		Balance							Balance
	Follow-on Payment	$	3,672	$	—	$	(3,672	)	$	—
	Total Level III liabilities	$	3,672	$	—	$	(3,672	)	$	—
		As of December 31, 2013
		Beginning		Additions		Net Unrealized / Realized Gains			Ending
		Balance							Balance
	Follow-on Payment	$	—	$	10,631	$	(6,959	)	$	3,672
	Total Level III liabilities	$	—	$	10,631	$	(6,959	)	$	3,672

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Schedule of Income before Income Tax, Domestic and Foreign	Income before income taxes, as shown in the consolidated statements of operations, includes the following income components, with amounts in thousands:
		For the Years Ended December 31,
		2014				2013				2012
	Domestic	$	3,946			$	10,390			$	19,794
	Foreign	21,702				41,470				27,670
		$	25,648			$	51,860			$	47,464
Schedule of Components of Income Tax Expense (Benefit)	The provision for income taxes consists of the following, with amounts in thousands:
		For the Years Ended December 31,
		2014				2013				2012
	Current
	Federal income tax (benefit)	$	2			$	(185	)		$	478
	State and local income tax	331				682				574
	Foreign income tax	4,757				5,085				764
	Subtotal	5,090				5,582				1,816
	Deferred
	Federal income tax	1,053				3,996				2,837
	State and local income tax (benefit)	754				235				(171		)
	Foreign income (benefit) tax	(896		)		7,211				4,504
	Subtotal	911				11,442				7,170
	Total provision for taxes	$	6,001			$	17,024			$	8,986
Schedule of Effective Income Tax Rate Reconciliation	The following table reconciles the provision for income taxes to the U.S. federal statutory tax rate:
		For the Years Ended December 31,
		2014			2013			2012
	Statutory U.S. federal income tax rate	34	%		34	%		34	%
	Income passed through to non-controlling members	(2.7	)		(5.4	)		(15.5	)
	State and local income tax	2.8			0.9			1
	Foreign income tax	(3.3	)		(1.4	)		(3.1	)
	Tax Receivable Agreement true-up	(11.7	)		—			—
	Non-deductible FCA fine	—			2			—
	Foreign tax credit valuation allowance	3.7			3.5			2.5
	Impact of rate change on deferred tax assets	—			(0.9	)		—
	Other	0.6			0.1			—
	Effective tax rate	23.4	%		32.8	%		18.9	%
Schedule of Deferred Tax Assets and Liabilities	A summary of the tax effects of the temporary differences is as follows, with amounts in thousands:
		As of December 31,
		2014				2013
	Deferred tax assets
	Equity-based compensation	$	983			$	1,059
	Investment in partnership	179,297				178,941
	Fixed assets	1,960				2,279
	Tax loss carryforwards	40,346				25,631
	Intangible assets	92				—
	Tax credit carryforward/foreign sub income	5,380				4,265
	Japan software	838				1,516
	Other	417				577
	Gross deferred tax assets	229,313				214,268
	Less: valuation allowance	(19,704		)		(25,288		)
	Net deferred tax asset	209,609				188,980
	Deferred tax liabilities
	Fixed assets	8				4
	Intangible assets	2,498				3,965
	Goodwill	19,296				8,742
	Software development cost	253				238
	Other	768				1,232
	Gross deferred tax liabilities	22,823				14,181
	Net deferred tax asset	$	186,786			$	174,799
Schedule of Unrecognized Tax Benefits Roll Forward	The following is a tabular reconciliation of the total amounts of unrecognized tax benefits, with amounts in thousands:
		For the Years Ended December 31,
		2014				2013				2012
	Unrecognized tax benefits – January 1	$	183			$	3,691			$	223
	Gross increases – tax positions in prior period	98				—				1
	Gross decreases – tax positions in prior period	—				(3,445		)		(16		)
	Gross increases – tax positions in current period	128				51				3,483
	Settlement	—				(114		)		—
	Lapse of statute of limitations	—				—				—
	Unrecognized tax benefits – December 31	$	409			$	183			$	3,691

Segments_Tables

Segments (Tables)	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Information concerning the Company’s operations by reportable segment is as follows, with amounts in thousands:
		As of and For the
		Year Ended December 31, 2014
		Retail Trading			Institutional Trading			Corporate			Total
	Total net revenues	$	349,630		$	106,663		$	7,464		$	463,757
	Total expenses	210,550			109,247			117,004			436,801
	Loss on equity method investments	—			888			420			1,308
	Income (loss) before income taxes	$	139,080		$	(3,472	)	$	(109,960	)	$	25,648
	Assets	$	1,759,485		$	435,088		$	192,854		$	2,387,427
		As of and For the
		Year Ended December 31, 2013
		Retail Trading			Institutional Trading			Corporate			Total
	Total net revenues	$	379,840		$	110,957		$	(1,209	)	$	489,588
	Total expenses	219,016			98,839			119,121			436,976
	Loss on equity method investments	—			697			55			752
	Income (loss) before income taxes	$	160,824		$	11,421		$	(120,385	)	$	51,860
	Assets	$	1,622,829		$	417,492		$	183,626		$	2,223,947
		As of and For the
		Year Ended December 31, 2012
		Retail Trading			Institutional Trading			Corporate			Total
	Total net revenues	$	355,282		$	62,033		$	—		$	417,315
	Total expenses	218,018			45,164			106,669			369,851
	Income (loss) before income taxes	$	137,264		$	16,869		$	(106,669	)	$	47,464
	Assets	$	1,556,680		$	381,368		$	127,122		$	2,065,170
		For the Years Ended December 31,
		2014			2013			2012
	Total Net Revenues
	U.S.	$	304,507		$	301,005		$	284,511
	Asia	60,086			57,557			51,486
	Europe, Middle East and North Africa	289,232			286,771			191,314
	Other	8,467			4,811			4,183
	Eliminations	(198,535		)	(160,556		)	(114,179		)
	Total	$	463,757		$	489,588		$	417,315
		For the Years Ended December 31,
		2014			2013			2012
	Operating and Other Expenses
	U.S.	$	300,560		$	290,549		$	264,706
	Asia	43,566			39,410			41,228
	Europe, Middle East and North Africa	285,271			265,218			173,467
	Other	7,247			3,107			3,214
	Eliminations	(198,535		)	(160,556		)	(112,764		)
	Total	$	438,109		$	437,728		$	369,851
		For the Years Ended December 31,
		2014			2013			2012
	Income Before Income Taxes
	U.S.	$	3,947		$	10,456		$	19,805
	Asia	16,520			18,147			10,258
	Europe, Middle East and North Africa	3,961			21,553			17,847
	Other	1,220			1,704			969
	Eliminations	—			—			(1,415		)
	Total	$	25,648		$	51,860		$	47,464
Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas	Information concerning the Company’s operations by reportable segment is as follows, with amounts in thousands:
		As of and For the
		Year Ended December 31, 2014
		Retail Trading			Institutional Trading			Corporate			Total
	Total net revenues	$	349,630		$	106,663		$	7,464		$	463,757
	Total expenses	210,550			109,247			117,004			436,801
	Loss on equity method investments	—			888			420			1,308
	Income (loss) before income taxes	$	139,080		$	(3,472	)	$	(109,960	)	$	25,648
	Assets	$	1,759,485		$	435,088		$	192,854		$	2,387,427
		As of and For the
		Year Ended December 31, 2013
		Retail Trading			Institutional Trading			Corporate			Total
	Total net revenues	$	379,840		$	110,957		$	(1,209	)	$	489,588
	Total expenses	219,016			98,839			119,121			436,976
	Loss on equity method investments	—			697			55			752
	Income (loss) before income taxes	$	160,824		$	11,421		$	(120,385	)	$	51,860
	Assets	$	1,622,829		$	417,492		$	183,626		$	2,223,947
		As of and For the
		Year Ended December 31, 2012
		Retail Trading			Institutional Trading			Corporate			Total
	Total net revenues	$	355,282		$	62,033		$	—		$	417,315
	Total expenses	218,018			45,164			106,669			369,851
	Income (loss) before income taxes	$	137,264		$	16,869		$	(106,669	)	$	47,464
	Assets	$	1,556,680		$	381,368		$	127,122		$	2,065,170
		For the Years Ended December 31,
		2014			2013			2012
	Total Net Revenues
	U.S.	$	304,507		$	301,005		$	284,511
	Asia	60,086			57,557			51,486
	Europe, Middle East and North Africa	289,232			286,771			191,314
	Other	8,467			4,811			4,183
	Eliminations	(198,535		)	(160,556		)	(114,179		)
	Total	$	463,757		$	489,588		$	417,315
		For the Years Ended December 31,
		2014			2013			2012
	Operating and Other Expenses
	U.S.	$	300,560		$	290,549		$	264,706
	Asia	43,566			39,410			41,228
	Europe, Middle East and North Africa	285,271			265,218			173,467
	Other	7,247			3,107			3,214
	Eliminations	(198,535		)	(160,556		)	(112,764		)
	Total	$	438,109		$	437,728		$	369,851
		For the Years Ended December 31,
		2014			2013			2012
	Income Before Income Taxes
	U.S.	$	3,947		$	10,456		$	19,805
	Asia	16,520			18,147			10,258
	Europe, Middle East and North Africa	3,961			21,553			17,847
	Other	1,220			1,704			969
	Eliminations	—			—			(1,415		)
	Total	$	25,648		$	51,860		$	47,464

Nature_of_Business_and_Organiz1

Nature of Business and Organization - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2014	Jun. 18, 2012
Basis of Presentation [Line Items]
Entity Incorporation, Date of Incorporation	10-Aug-10
Lucid Markets Trading Limited
Basis of Presentation [Line Items]
Acquisition of controlling interest	50.10%	50.10%

Significant_Accounting_Policie3

Significant Accounting Policies and Estimates - Useful Lives of Assets (Detail)	12 Months Ended
	Dec. 31, 2014
Customer relationships | Minimum
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Intangible asset amortization period	3 years
Customer relationships | Maximum
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Intangible asset amortization period	9 years
Non-compete agreements | Minimum
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Intangible asset amortization period	1 year
Non-compete agreements | Maximum
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Intangible asset amortization period	9 years
Trade name
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Intangible asset amortization period	3 years
Executory contract
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Intangible asset amortization period	3 years
Proprietary technology | Minimum
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Intangible asset amortization period	4 years
Proprietary technology | Maximum
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Intangible asset amortization period	7 years
Computer equipment | Minimum
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Property plant and equipment estimated useful lives	3 years
Computer equipment | Maximum
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Property plant and equipment estimated useful lives	5 years
Software | Minimum
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Property plant and equipment estimated useful lives	2 years
Software | Maximum
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Property plant and equipment estimated useful lives	5 years
Leasehold improvements
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Property plant and equipment estimated useful lives	Lesser of the estimated economic useful life or the term of the lease
Furniture and fixtures and other equipment | Minimum
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Property plant and equipment estimated useful lives	3 years
Furniture and fixtures and other equipment | Maximum
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Property plant and equipment estimated useful lives	5 years
Licenses | Minimum
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Property plant and equipment estimated useful lives	2 years
Licenses | Maximum
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Property plant and equipment estimated useful lives	3 years
Communication equipment | Minimum
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Property plant and equipment estimated useful lives	3 years
Communication equipment | Maximum
Property, Plant and Equipment, Estimated Useful Lives, Lease Terms [Line Items]
Property plant and equipment estimated useful lives	5 years

Significant_Accounting_Policie4

Significant Accounting Policies and Estimates - Additional Information (Detail)

12 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Feb. 28, 2014

Feb. 28, 2014

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2013

USD ($)

USD ($)

USD ($)

Other Income

Other Income

Lucid Markets Trading Limited

Faros Trading LLC

Faros Trading LLC

FXCM Holdings, LLC

FXCM Holdings, LLC

Settlement with FCA

Settlement with FCA

Settlement with FCA

Settlement with FCA

Positive Outcome of Litigation

USD ($)

USD ($)

Other Income

Other Income

USD ($)

GBP (£)

General and Administrative Expense

General and Administrative Expense

Other Income

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

Significant Accounting Policies [Line Items]

Economic interest in subsidiary

58.10%

54.80%

Non-controlling interest in subsidiary

49.90%

41.90%

45.20%

Restricted cash and cash equivalents

$900,000,000

$1,000,000,000

Goodwill impairment loss

0

Impairment of finite-lived intangible assets

0

0

0

Unrealized losses related to securities sold but not yet purchased

500,000

Percent of cash tax savings to be paid to members of subsidiary

85.00%

Percent of cash tax savings remaining with parent

15.00%

Percent of estimated realizable tax benefits recorded as contingent liability

85.00%

Percent of estimated realizable tax benefits recorded as increase in capital.

15.00%

Foreign currency transactions gain

3,600,000

5,300,000

800,000

Remeasurement gain

3,700,000

6,900,000

Account dormancy and ancillary fees

2,500,000

3,100,000

Brokerage activities

5,800,000

7,200,000

Remeasurement due to tax receivable agreement liability

7,500,000

1,200,000

Settlement

-6,600,000

-4,000,000

1,400,000

Liability established pertaining to a settlement with FCA

$2,500,000

$16,600,000

NonControlling_Interest_Change

Non-Controlling Interest - Change in Interest Holdings of Corporation and Non-Controlling Interest (Detail)	12 Months Ended
	Dec. 31, 2014
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Shares [Roll Forward]
Exercise of stock options	829,086
Issuance under equity-based compensation	648,490
Controlling Units
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Shares [Roll Forward]
Beginning Balance	44,664,884
Holdings Units repurchased related to Class A common stock repurchased	-145,985
Exercise of stock options	829,086
Issuance under equity-based compensation	163,832
Ending Balance	47,889,964
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Percent [Roll Forward]
Beginning balance	54.80%
Holdings Units acquired by FXCM Inc. related to exchanges of Holdings Units for shares of Class A common stock	2.80%
Holdings Units repurchased related to Class A common stock repurchased	-0.10%
Exercise of stock options	0.50%
Issuance under equity-based compensation	0.10%
Ending balance	58.10%
Non- Controlling Units
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Shares [Roll Forward]
Beginning Balance	36,835,821
Holdings Units acquired by FXCM Inc. related to exchanges of Holdings Units for shares of Class A common stock	-2,378,147
Holdings Units repurchased related to Class A common stock repurchased	0
Exercise of stock options	0
Issuance under equity-based compensation	0
Ending Balance	34,457,674
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Percent [Roll Forward]
Noncontrolling interest beginning balance	45.20%
Holdings Units acquired by FXCM Inc. related to exchanges of Holdings Units for shares of Class A common stock	-2.80%
Holdings Units repurchased related to Class A common stock repurchased	0.10%
Exercise of stock options	-0.50%
Issuance under equity-based compensation	-0.10%
Noncontrolling interest ending balance	41.90%
Total Units
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Shares [Roll Forward]
Beginning Balance	81,500,705
Holdings Units acquired by FXCM Inc. related to exchanges of Holdings Units for shares of Class A common stock	0
Holdings Units repurchased related to Class A common stock repurchased	-145,985
Exercise of stock options	829,086
Issuance under equity-based compensation	163,832
Ending Balance	82,347,638
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Percent [Roll Forward]
Beginning balance	100.00%
Holdings Units acquired by FXCM Inc. related to exchanges of Holdings Units for shares of Class A common stock	0.00%
Holdings Units repurchased related to Class A common stock repurchased	0.00%
Exercise of stock options	0.00%
Issuance under equity-based compensation	0.00%
Ending balance	100.00%

Business_Acquisitions_Purchase

Business Acquisitions - Purchase Price Allocation (Detail) (USD $)	0 Months Ended	12 Months Ended		0 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Jan. 21, 2014	Dec. 31, 2014		Sep. 20, 2013	Jun. 18, 2012	Dec. 31, 2013
Adjustments to reflect acquired assets and liabilities at fair value
Goodwill		$323,887				$307,936
V3
Business Combination Allocation of Purchase Price [Line Items]
Purchase price	16,300	15,825
Non-Controlling interest	16,200	15,762
Total fair value at Acquisition Date	32,500	31,587
Net assets acquired		10,210
Adjustments to reflect acquired assets and liabilities at fair value
Fair value of net assets acquired	12,230	12,230
Goodwill	20,200	19,357
V3 | Core Trading Platform
Adjustments to reflect acquired assets and liabilities at fair value
Intangible assets		950	[1]
V3 | Post Trade Processing Platform
Adjustments to reflect acquired assets and liabilities at fair value
Intangible assets		150	[2]
V3 | Non-compete agreements
Adjustments to reflect acquired assets and liabilities at fair value
Intangible assets		450	[3]
V3 | Executory Contract
Adjustments to reflect acquired assets and liabilities at fair value
Intangible assets		470	[4]
Faros Trading LLC
Business Combination Allocation of Purchase Price [Line Items]
Purchase price		15,631		15,631
Non-Controlling interest		15,569		15,569
Total fair value at Acquisition Date		31,200
Net assets acquired		137
Adjustments to reflect acquired assets and liabilities at fair value
Fair value of net assets acquired		8,167		8,167
Goodwill		23,033		23,033
Faros Trading LLC | Customer relationships
Adjustments to reflect acquired assets and liabilities at fair value
Intangible assets		6,000	[5]
Faros Trading LLC | Non-compete agreements
Adjustments to reflect acquired assets and liabilities at fair value
Intangible assets		1,900	[6]
Faros Trading LLC | Trade name
Adjustments to reflect acquired assets and liabilities at fair value
Intangible assets		130	[7]
Lucid Markets Trading Limited
Business Combination Allocation of Purchase Price [Line Items]
Purchase price					177,500	192,784
Non-Controlling interest					160,165	160,165
Total fair value at Acquisition Date						352,949
Net assets acquired						32,732
Adjustments to reflect acquired assets and liabilities at fair value
Fair value of net assets acquired					117,632	117,632
Goodwill					236,500	235,317
Lucid Markets Trading Limited | Non-compete agreements
Adjustments to reflect acquired assets and liabilities at fair value
Intangible assets						1,000	[8]
Lucid Markets Trading Limited | Proprietary technology
Adjustments to reflect acquired assets and liabilities at fair value
Intangible assets						$83,900	[9]
[1]	Consists of internally developed software platforms that support trade execution, with an amortization life of 4 years.
[2]	Consists of an internally developed software platform that supports trading, with an amortization life of 5 years.
[3]	Amortization life is 1 year.
[4]	Consists of a service agreements relating to fiber optics, wireless and other services, with an amortization life of 3 years
[5]	Consists of institutional and bank customers, with an amortization life of 4 years.
[6]	Amortization life is 9 years.
[7]	Amortization life is 3 years.
[8]	Consists of two non-compete agreements with amortization lives of 3 years
[9]	Consists of internally-developed software platforms through which the Company: (i) executes its specific trading strategies, with an amortization life of 4 years and (ii) clears and efficiently settle trades, with an amortization life of 7 years

Business_Acquisitions_Condense

Business Acquisitions - Condensed Statement of Net Assets Acquired (Detail) (USD $)	Dec. 31, 2014	Jan. 21, 2014	Sep. 20, 2013	Dec. 31, 2013	Jun. 18, 2012
In Thousands, unless otherwise specified
V3
Assets
Office, communication and computer equipment, net		$973
Intangible assets		2,020
Exchange memberships and common equity shares		6,429
Equity method investments, net		1,523
Other assets		1,392
Total assets		12,337
Liabilities
Total liabilities		-107
Fair value of net assets acquired	12,230	12,230
Faros Trading LLC
Assets
Cash and cash equivalents			1,055
Accounts receivable, net			40
Office, communication and computer equipment, net			31
Intangible assets			8,030
Other assets			76
Total assets			9,232
Liabilities
Accounts payable and accrued expenses			1,065
Total liabilities			-1,065
Fair value of net assets acquired	8,167		8,167
Lucid Markets Trading Limited
Assets
Cash and cash equivalents					28,656
Accounts receivable, net					5,100
Office, communication and computer equipment, net					499
Intangible assets					84,900
Due from brokers					302
Deferred tax asset					11,311
Other assets					226
Total assets					130,994
Liabilities
Accounts payable and accrued expenses					13,362
Total liabilities					-13,362
Fair value of net assets acquired				$117,632	$117,632

Business_Acquisitions_Condense1

Business Acquisitions - Condensed Combined Financial Information (Detail) (USD $)	11 Months Ended	3 Months Ended	6 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
V3
Pro Forma Information, Actual Revenue Since Acquisition
Total revenue	$20,706
Net loss	-1,815
Faros Trading LLC
Pro Forma Information, Actual Revenue Since Acquisition
Total revenue		526
Net loss		-301
Lucid Markets Trading Limited
Pro Forma Information, Actual Revenue Since Acquisition
Total revenue			42,198
Net loss			$21,446

Business_Acquisitions_Pro_Form

Business Acquisitions - Pro Forma Condensed Combined Financial Information of Acquisitions (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pro Forma Information, as if Combination was Completed at Beginning of Period
Total revenues	$463,757	$535,130	$463,767
Net income before non-controlling interest	$17,583	$36,838	$49,224

Business_Acquisitions_Addition

Business Acquisitions - Additional Information (Detail) (USD $)

12 Months Ended

3 Months Ended

0 Months Ended

11 Months Ended

0 Months Ended

12 Months Ended

Dec. 31, 2014

Jun. 30, 2013

Jan. 21, 2014

Dec. 31, 2014

Sep. 20, 2013

Sep. 20, 2013

Jun. 18, 2012

Dec. 31, 2013

Dec. 21, 2012

Jun. 06, 2014

Dec. 21, 2013

Mar. 31, 2014

Dec. 31, 2012

Business Acquisition [Line Items]

Goodwill

$323,887,000

$323,887,000

$307,936,000

Interest rate on promissory notes

2.25%

Goodwill adjustment

-9,000

Unsecured Promissory Note

Business Acquisition [Line Items]

Interest rate on promissory notes

2.25%

2.25%

2.25%

Term

6 months

V3

Business Acquisition [Line Items]

Total fair value at Acquisition Date

31,587,000

32,500,000

31,587,000

Liabilities incurred

12,100,000

Acquisition of controlling interest

50.10%

50.10%

Goodwill

19,357,000

20,200,000

19,357,000

Fair value of non-controlling interest in acquisition

15,762,000

16,200,000

15,762,000

Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Consideration Transferred

-900,000

Reduction to goodwill

-800,000

Remeasurement period

12 months

Purchase price

15,825,000

16,300,000

Acquisition-related transaction costs

1,200,000

1,200,000

Faros Trading LLC

Business Acquisition [Line Items]

Total fair value at Acquisition Date

31,200,000

31,200,000

Acquisition of controlling interest

50.10%

50.10%

Goodwill

23,033,000

23,033,000

23,033,000

23,033,000

Fair value of non-controlling interest in acquisition

15,569,000

15,569,000

15,569,000

15,569,000

Remeasurement period

12 months

Cost of acquired entity, cash paid

5,000,000

Contingent liability

10,600,000

10,600,000

6,900,000

3,700,000

Purchase price

15,631,000

15,631,000

Business acquisition equity interest issued remaining shares fair value

400,000

400,000

Fair value of controlling interest, discount rate

25.00%

Long-term annual earnings growth rate

3.00%

Lucid Markets Trading Limited

Business Acquisition [Line Items]

Total fair value at Acquisition Date

352,949,000

Acquisition of controlling interest

50.10%

50.10%

50.10%

Goodwill

236,500,000

235,317,000

Fair value of non-controlling interest in acquisition

160,165,000

160,165,000

Remeasurement period

12 months

Purchase price

177,500,000

192,784,000

Business acquisition equity interest issued remaining shares fair value

67,900,000

Issuance of shares for acquisition

9,000,000

Period for share issuance

3 years

Time limit for purchase of buy back of shares

30 days

Fair value of the shares issued for acquisition

89,400,000

Deferred compensation liability

9,400,000

Annual earnings growth rate

4.00%

Increase in purchase price

15,300,000

Goodwill adjustment

-1,200,000

Acquisition-related transaction costs

900,000

Lucid Markets Trading Limited | Maximum

Business Acquisition [Line Items]

Assumed discount rates ,in estimate of fair value of non controlling interest

11.00%

Lucid Markets Trading Limited | Minimum

Business Acquisition [Line Items]

Assumed discount rates ,in estimate of fair value of non controlling interest

10.00%

Lucid Markets Trading Limited | Class A common stock

Business Acquisition [Line Items]

Fair value of the shares issued for acquisition

21,500,000

Lucid Markets Trading Limited | Shares at Closing

Business Acquisition [Line Items]

Issuance of shares for acquisition

1,800,000

Lucid Markets Trading Limited | Shares Held in Escrow

Business Acquisition [Line Items]

Issuance of shares for acquisition

7,200,000

Lucid Markets Trading Limited | Unsecured Promissory Note

Business Acquisition [Line Items]

Interest rate on promissory notes

2.25%

3.50%

Term

6 months

Lucid Markets Trading Limited | Unsecured Promissory Note | $71.4 million 3.5% Unsecured Promissory Note

Business Acquisition [Line Items]

Face amount

71,400,000

Interest rate on promissory notes

3.50%

Lucid Markets Trading Limited | Unsecured Promissory Note | $15.8 million 3.5% Unsecured Promissory Note

Business Acquisition [Line Items]

Face amount

$15,800,000

Interest rate on promissory notes

3.50%

Customer relationships | Maximum

Business Acquisition [Line Items]

Intangible asset amortization period

9 years

Customer relationships | Minimum

Business Acquisition [Line Items]

Intangible asset amortization period

3 years

Customer relationships | Faros Trading LLC

Business Acquisition [Line Items]

Intangible asset amortization period

4 years

Non-compete agreements | Maximum

Business Acquisition [Line Items]

Intangible asset amortization period

9 years

Non-compete agreements | Minimum

Business Acquisition [Line Items]

Intangible asset amortization period

1 year

Non-compete agreements | V3

Business Acquisition [Line Items]

Intangible asset amortization period

1 year

Non-compete agreements | Faros Trading LLC

Business Acquisition [Line Items]

Intangible asset amortization period

9 years

Non-compete agreements | Lucid Markets Trading Limited

Business Acquisition [Line Items]

Intangible asset amortization period

3 years

Number of Non-Compete agreements

2

Trade name

Business Acquisition [Line Items]

Intangible asset amortization period

3 years

Trade name | Faros Trading LLC

Business Acquisition [Line Items]

Intangible asset amortization period

3 years

Core Trading Platform | V3

Business Acquisition [Line Items]

Intangible asset amortization period

4 years

Core Trading Platform | Lucid Markets Trading Limited

Business Acquisition [Line Items]

Intangible asset amortization period

4 years

Post Trade Processing Platform | V3

Business Acquisition [Line Items]

Intangible asset amortization period

5 years

Post Trade Processing Platform | Lucid Markets Trading Limited

Business Acquisition [Line Items]

Intangible asset amortization period

7 years

Executory Contract | V3

Business Acquisition [Line Items]

Intangible asset amortization period

3 years

Restricted_Time_Deposits_Addit

Restricted Time Deposits - Additional Information (Details) (USD $)	Dec. 31, 2014	Jul. 03, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Cash and Cash Equivalents [Abstract]
Current restricted time deposits	$3,336		$0
Current restricted time deposits, interest rate		0.03%
Noncurrent restricted time deposits	$5,005		$0
Noncurrent restricted time deposits, interest rate		0.03%

Trading_Securities_Additional_

Trading Securities - Additional Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Trading securities	$26,000	$0
Net realized and unrealized gain on trading securities	$3,800,000	$0

Notes_Receivable_Additional_De

Notes Receivable - Additional Details (Details) (USD $)	0 Months Ended	1 Months Ended	0 Months Ended	12 Months Ended
	Jan. 21, 2014	31-May-14	Oct. 02, 2013	Dec. 31, 2014
Lucid LLP | Notes Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable	$8,100,000			$7,900,000
Related rarty transaction, interest rate	2.00%
AxiCorp | Notes Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable		1,500,000
Related rarty transaction, interest rate		15.00%
Infinium Capital | Notes Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable			11,900,000
Related rarty transaction, interest rate			4.00%
Number of lump sum payments			2
Lump sum due on August 1, 2014			50.00%
Lump sum due on August 1, 2015			50.00%
V3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Consideration transfered for acquisition	16,300,000			15,825,000
Fair value of non-controlling interest in acquisition	$16,200,000			$15,762,000

Equity_Method_Investment_Addit

Equity Method Investment - Additional Information (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 21, 2014
Schedule of Equity Method Investments [Line Items]
Equity method investments	$10,007	$9,793
Loss on equity method investments, net	1,308	752	0
Loss on Equity Method Investments, Net
Schedule of Equity Method Investments [Line Items]
Loss on equity method investments, net	$1,300	$800
V3
Schedule of Equity Method Investments [Line Items]
Percentage of equity interest				66.30%
Electric Communication Network for Foreign Exchange Trading
Schedule of Equity Method Investments [Line Items]
Percentage of equity interest	35.30%
FX Trading Software Developer
Schedule of Equity Method Investments [Line Items]
Percentage of equity interest	21.80%
V3 | Investment Advisory Company
Schedule of Equity Method Investments [Line Items]
Percentage of equity interest				17.26%

Office_Communication_and_Compu2

Office, Communication and Computer Equipment, net - Schedule of Office, Communication and Computer Equipment (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]
Property plant and equipment	$122,286	$100,064
Less: Accumulated depreciation	-74,092	-50,899
Office, communication and computer equipment, net	48,194	49,165
Computer equipment
Property, Plant and Equipment [Line Items]
Property plant and equipment	30,961	28,047
Software
Property, Plant and Equipment [Line Items]
Property plant and equipment	63,766	47,138
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property plant and equipment	10,095	9,687
Furniture and fixtures and other equipment
Property, Plant and Equipment [Line Items]
Property plant and equipment	3,521	3,427
Licenses
Property, Plant and Equipment [Line Items]
Property plant and equipment	11,499	10,101
Communication equipment
Property, Plant and Equipment [Line Items]
Property plant and equipment	$2,444	$1,664

Office_Communication_and_Compu3

Office, Communication and Computer Equipment, net - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Depreciation	$25,200,000	$25,800,000	$17,700,000
Unamortized capitalized software development costs	28,900,000	26,000,000
Assets of Disposal Group, Including Discontinued Operation	4,400,000	19,200,000
Impairment of finite-lived intangible assets	0	0	0
Core Trading Platform
Property, Plant and Equipment [Line Items]
Impairment of finite-lived intangible assets	1,100,000	3,500,000
Capitalized Computer Software
Property, Plant and Equipment [Line Items]
Amortization cost	$13,700,000	$10,600,000	$6,500,000

Goodwill_Changes_in_Goodwill_b

Goodwill - Changes in Goodwill by Segment (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014
Goodwill [Roll Forward]
Beginning balance	$307,936
Goodwill acquired	19,357
Foreign currency translation adjustment	-3,397
Goodwill adjustment	-9
Ending balance	323,887
Retail Trading
Goodwill [Roll Forward]
Beginning balance	38,079
Goodwill acquired	0
Foreign currency translation adjustment	-2,703
Goodwill adjustment	0
Ending balance	35,376
Institutional Trading
Goodwill [Roll Forward]
Beginning balance	269,857
Goodwill acquired	19,357
Foreign currency translation adjustment	-694
Goodwill adjustment	-9
Ending balance	$288,511

Other_Intangible_Assets_net_Ac

Other Intangible Assets, net - Acquired Intangible Assets (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$132,067	$130,499
Accumulated Amortization	-75,110	-54,396
Net Carrying Amount	56,957	76,103
Total intangible assets, gross (excluding goodwill)	132,677	131,109
Total intangible assets, net (excluding goodwill)	57,567	76,713
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	47,397	37,746
Accumulated Amortization	-21,944	-14,529
Net Carrying Amount	25,453	23,217
Non-compete agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	3,350	10,507
Accumulated Amortization	-1,489	-8,177
Net Carrying Amount	1,861	2,330
Proprietary technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	85,000	83,900
Accumulated Amortization	-52,844	-31,849
Net Carrying Amount	32,156	52,051
Executory contract
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	470	0
Accumulated Amortization	-131	0
Net Carrying Amount	339	0
Trade name
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	241	177
Accumulated Amortization	-56	-13
Net Carrying Amount	185	164
Foreign currency translation adjustment
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	-4,391	-1,831
Accumulated Amortization	1,354	172
Net Carrying Amount	-3,037	-1,659
Licenses
Acquired Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	$610	$610

Other_Intangible_Assets_net_Es

Other Intangible Assets, net - Estimated Future Amortization Expense for Acquired Intangible Assets Outstanding (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2015	$30,765
2016	18,836
2017	4,889
2018	1,059
2019	723
Thereafter	685
Net Carrying Amount	$56,957	$76,103

Other_Intangible_Assets_net_Ad

Other Intangible Assets, net - Additional Information (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Acquired Intangible Assets by Major Class [Line Items]
Intangible asset amortization expense	$29.80	$27.90	$19
Disposition of fully amortized intangible assets	$8.10
Customer relationships | Minimum
Acquired Intangible Assets by Major Class [Line Items]
Intangible asset amortization period	3 years
Customer relationships | Maximum
Acquired Intangible Assets by Major Class [Line Items]
Intangible asset amortization period	9 years
Non-compete agreements | Minimum
Acquired Intangible Assets by Major Class [Line Items]
Intangible asset amortization period	1 year
Non-compete agreements | Maximum
Acquired Intangible Assets by Major Class [Line Items]
Intangible asset amortization period	9 years
Proprietary technology | Minimum
Acquired Intangible Assets by Major Class [Line Items]
Intangible asset amortization period	4 years
Proprietary technology | Maximum
Acquired Intangible Assets by Major Class [Line Items]
Intangible asset amortization period	7 years
Trade name
Acquired Intangible Assets by Major Class [Line Items]
Intangible asset amortization period	3 years
Executory contract
Acquired Intangible Assets by Major Class [Line Items]
Intangible asset amortization period	3 years

Other_Assets_Components_of_Oth

Other Assets - Components of Other Assets (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid expenses	$5,823	$5,738
Equity method investments	10,007	9,793
Deferred debt issuance costs	5,582	7,131
Exchange memberships	6,429	0
Deposits	1,514	1,492
Other	293	162
Total other assets	$29,648	$24,316

Customer_Account_Liabilities_A

Customer Account Liabilities - Additional Information (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Other Liabilities Disclosure [Abstract]
Customer account liabilities	$1,331,723	$1,190,880

Accounts_Payable_and_Accrued_E2

Accounts Payable and Accrued Expenses - Schedule of Accounts Payable and Accrued Expenses (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Payables and Accruals [Abstract]
Operating expenses payable	$23,256	$41,528
Due to Lucid non-controlling members	8,876	9,995
Commissions payable	11,864	9,485
Bonus payable	9,664	7,455
Income tax payable	2,158	1,046
Interest due on borrowings	202	177
Other	19	11
Total accounts payable and accrued expenses	$56,039	$69,697

Earnings_Per_Share_Reconciliat

Earnings Per Share - Reconciliation of Numerator and Denominator Used in Basic and Diluted EPS Calculations (Detail) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator
Net income available to holders of Class A common stock	$17,151	$14,832	$8,958
Denominator for basic net income per share of Class A common stock
Weighted average shares of Class A common stock	41,637	32,789	24,086
Add dilutive effect of the following:
Dilutive weighted average shares of Class A common stock	44,010	33,957	24,086
Basic income per share of Class A common stock (in dollars per share)	$0.41	$0.45	$0.37
Diluted income per share of Class A common stock (in dollars per share)	$0.39	$0.44	$0.37
Common Class A
Numerator
Net income available to holders of Class A common stock	17,151	14,832	8,958
Earnings allocated to participating securities	0	0	0
Earnings available for common stockholders	$17,151	$14,832	$8,958
Denominator for basic net income per share of Class A common stock
Weighted average shares of Class A common stock	41,637	32,789	24,086
Add dilutive effect of the following:
Stock options and RSUs	992	616	0
Convertible note hedges	0	0	0
Warrants	0	0	0
Assumed conversion of Holdings Units for Class A common stock	0	0	0
Dilutive weighted average shares of Class A common stock		33,957	24,086
Basic income per share of Class A common stock (in dollars per share)	$0.41	$0.45	$0.37
Diluted income per share of Class A common stock (in dollars per share)	$0.39	$0.44	$0.37
First Anniversary, Shares Issued | Lucid Markets Trading Limited | Common Class A
Add dilutive effect of the following:
Lucid contingently issuable shares	0	552	0
Second Anniversary, Shares Issued | Lucid Markets Trading Limited | Common Class A
Add dilutive effect of the following:
Lucid contingently issuable shares	1,381	0

Earnings_Per_Share_Additional_

Earnings Per Share - Additional Information (Detail) (USD $)	1 Months Ended	0 Months Ended	12 Months Ended		0 Months Ended	3 Months Ended	12 Months Ended
	Jun. 30, 2013	Jun. 18, 2012	Dec. 31, 2014	Dec. 31, 2013	Jun. 08, 2012	Jun. 30, 2013	Dec. 31, 2015	Dec. 21, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Interest rate								2.25%
2.25% Senior Convertible Notes | Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Face amount	$172,500,000					172,500,000
Interest rate	2.25%					2.25%
Conversion ratio	0.0532992
Conversion price (in dollars per share)	$18.76					18.76
Lucid Markets Trading Limited
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Issuance of shares for acquisition		9,000,000
Common Class A
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Conversion ratio			1	1
Common Class A | Controlling Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Holdings Units acquired by FXCM Inc. related to exchanges of Holdings Units for shares of Class A common stock			2,378,147	10,100,000
Common Class A | Common Stock | Lucid Markets Trading Limited
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Issuance of shares for acquisition					7,200,000
Common Class A | Common Stock | First Anniversary, Shares Issued | Lucid Markets Trading Limited
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Issuance of shares for acquisition						1,200,000
Common Class A | Common Stock | Second Anniversary, Shares Issued | Lucid Markets Trading Limited
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Issuance of shares for acquisition			3,000,000
Common Class A | Common Stock | Third Anniversary, Shares Issued | Scenario, Forecast | Lucid Markets Trading Limited
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Issuance of shares for acquisition							3,000,000
Employee Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stock option granted excluded from computation of earnings per share			1,002,990	426,000

Related_Party_Transactions_Amo

Related Party Transactions - Amounts Receivable From, And Payable To, Related Parties (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Receivables
Advances to Holdings non-controlling members	$196	$940
Advances to employees	563	826
Total receivables from related parties	11,039	1,766
Payables
Employees	2,009	708
Shareholders with greater than 5% ownership in the Company	0	200
Tax receivable agreement	150,576	150,258
Faros Follow-on Payment	0	3,672
Total payables to related parties	168,539	183,374
Lucid Markets Trading Limited
Receivables
Accounts receivable, related parties	799	0
Notes receivable and interest	8,013	0
Holdings non-controlling units
Payables
Due to other related parties	8,876	9,826
Lucid non controlling units - trade settlements
Payables
Due to other related parties	0	169
Lucid non controlling units - acquisition
Payables
Due to other related parties	0	9,800
FastMatch
Receivables
Accounts receivable, related parties	1,468	0
Payables
Accounts payable, related parties	0	378
Cash and Cash Equivalents Held for Customers | Monetary Credit Group LLC
Payables
Guarantee agreement (Monetary Guaranty)	$7,078	$8,363

Related_Party_Transactions_Add

Related Party Transactions - Additional Information (Detail) (USD $)	12 Months Ended			0 Months Ended	1 Months Ended
Share data in Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 21, 2014	Mar. 31, 2012	Dec. 04, 2012
Related Party Transaction [Line Items]
Referring broker fees	$80,850,000	$84,231,000	$76,585,000
Equity amount issued related to acquisition			21,491,000
Faros Follow-on Payment	0	3,672,000
Tax receivable agreement	150,576,000	150,258,000
Payments for tax receivable agreement	3,707,000	4,079,000	0
Common Class A
Related Party Transaction [Line Items]
Exchange of Holdings units into Class A common stock	2,378	10,100
Conversion ratio	1	1
Other Income
Related Party Transaction [Line Items]
Brokerage commissions revenue	5,800,000	7,200,000
V3
Related Party Transaction [Line Items]
Purchase price	15,825,000			16,300,000
Fair value of non-controlling interest in acquisition	15,762,000			16,200,000
ODL Group Limited
Related Party Transaction [Line Items]
Settlement agreement, cash paid					1,200,000
Equity amount issued related to acquisition					4,000,000
Forgiveness of liability related to acquisition					1,400,000
ODL Group Limited | Other Income
Related Party Transaction [Line Items]
Gain from settlement related to acquisition			1,400,000
Loss related to settlement		200,000
Global Finance and Master Capital
Related Party Transaction [Line Items]
Referring broker fees	1,300,000	1,600,000	2,500,000
FastMatch
Related Party Transaction [Line Items]
Ownership percentage by parent						35.30%
Lucid Markets Trading Limited
Related Party Transaction [Line Items]
Accounts receivable, related parties	799,000	0
Notes receivable, related parties, noncurrent	7,900,000
FastMatch
Related Party Transaction [Line Items]
Accounts receivable, related parties	1,468,000	0
Accounts payable, related parties	0	378,000
FastMatch | Institutional Trading Revenue
Related Party Transaction [Line Items]
Brokerage commissions revenue	13,800,000	5,100,000
FastMatch | Communication and Technology
Related Party Transaction [Line Items]
Exchange fees	7,400,000	3,100,000
Shareholders With a Greater Than 5% Ownership
Related Party Transaction [Line Items]
Employee and Shareholders Investment, Ownership Percentage	5.00%
Shareholder | Global Finance and Master Capital
Related Party Transaction [Line Items]
Percentage of ownership interests	90.00%
Method Credit Fund
Related Party Transaction [Line Items]
Cash collateral amount		0
Proceeds from related parties		0
Monetary Credit Group LLC
Related Party Transaction [Line Items]
Proceeds from related parties	0
Unconditional guaranty	13,200,000	4,500,000
Guarantor Obligation, Fees Collected	1,100,000	400,000
Monetary Credit Group LLC | Cash and Cash Equivalents Held for Customers
Related Party Transaction [Line Items]
Borrowings under Guaranteed Investment Agreements	7,078,000	8,363,000
Lucid non controlling units - trade settlements
Related Party Transaction [Line Items]
Due to Other Related Parties	0	169,000
Holdings non-controlling units
Related Party Transaction [Line Items]
Due to Other Related Parties	8,876,000	9,826,000
Lucid non controlling units - acquisition
Related Party Transaction [Line Items]
Due to Other Related Parties	$0	$9,800,000
Maximum | Shareholders With a Greater Than 5% Ownership
Related Party Transaction [Line Items]
Percentage of equity interest	5.00%

StockBased_Compensation_Summar

Stock-Based Compensation - Summary of Company's Stock Options Activity Under LTIP (Detail) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014
Number of Stock Options
Beginning balance outstanding (in shares)	7,607,800
Issuance under equity-based compensation	648,490
Exercised (in shares)	-829,086
Forfeited or expired (in shares)	-236,400
Ending balance outstanding (in shares)	7,190,804
Vested or expected to vest at end of period (in shares)	7,166,783
Exercisable as of end period (in shares)	5,776,564
Stock options outstanding weighted-average exercise price
Beginning balance outstanding (in dollars per share)	$13.48
Granted (in dollars per share)	$16.28
Exercised (in dollars per share)	$13.48
Forfeited or expired (in dollars per share)	$13.23
Ending balance outstanding (in dollars per share)	$13.74
Vested or expected to vest at end of period (in dollars per share)	$13.74
Exercisable as of end period (in dollars per share)	$13.67
Stock Options Weighted-Average Remaining Contractual Term (in years)
Outstanding at period end	3 years 7 months 2 days
Vested or expected to vest at end period	3 years 6 months 29 days
Exercisable at end period	3 years 1 month 24 days
Stock Options Aggregate Intrinsic Value (In thousands)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$20,525
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value	20,461
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value	$16,780

StockBased_Compensation_Assump

Stock-Based Compensation - Assumptions used in Black Scholes valuation model (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Assumptions used to Determine Fair Value Options [Line Items]
Estimated fair value at grant date	$5.66	$5.67	$3.55
Employee Stock Option
Assumptions used to Determine Fair Value Options [Line Items]
Expected term in years	4 years 9 months	4 years 9 months	4 years 9 months
Risk-free interest rate	1.58%	1.06%	0.71%
Expected volatility	45.00%	51.00%	52.00%
Dividend yield	1.48%	1.55%	2.48%
Estimated fair value at grant date	$5.70	$6.02	$3.47
Independent Directors
Assumptions used to Determine Fair Value Options [Line Items]
Expected term in years	4 years	4 years	4 years
Risk-free interest rate	1.19%	0.63%	0.60%
Expected volatility	44.00%	54.00%	63.00%
Dividend yield	1.43%	2.05%	2.40%
Estimated fair value at grant date	$5.39	$4.26	$4.11

StockBased_Compensation_Schedu

Stock-Based Compensation - Schedule of Company's Restricted Stock Units Activity (Details) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Weighted-Average Grant-Date Fair Value (in dollars per share)
Expected to vest at end of period	$16.25
Restricted Stock Units (RSUs)
Units
Unvested beginning balance	0
Granted		208,500
Vested		0
Forfeited		0
Unvested ending balance	208,500	0
Expected to vest at end of period	182,825
Weighted-Average Grant-Date Fair Value (in dollars per share)
Unvested beginning balance	$0
Granted		$16.25
Vested		$0
Forfeited		$0
Unvested ending balance	$16.25	$0
Weighted-Average Remaining Contractual Term (in years)
Unvested at end of period	3 years 11 months 16 days
Expected to vest at end of period	3 years 11 months 16 days
Aggregate Intrinsic Value (in thousands)
Unvested at end of period	$3,455
Expected to vest at end of period	$3,029

StockBased_Compensation_Additi

Stock-Based Compensation - Additional Information (Detail) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Stock options granted during the period(in shares)	648,490
Weighted average grant date fair value of stock options granted during the period (in dollars per share)	$5.66	$5.67	$3.55
Total intrinsic value of options exercised during the period	$2,300,000	$8,400,000	$0
Fair value of vested stock options	11,200,000	11,000,000	10,500,000
Unrecognized expense	5,200,000			5,200,000
Cash received from exercise of stock options	11,200,000	22,500,000	0
Tax benefit from stock option exercise	0	1,500,000	0
Office, Communication and Computer Equipment, Net [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Capitalized compensation cost	1,000,000	1,400,000	1,400,000
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options contractual term	7 years
Weighted average grant date fair value of stock options granted during the period (in dollars per share)	$5.70	$6.02	$3.47
Recognition period	2 years 6 months
Employee Stock Option | Compensation and Benefits
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation expense	9,500,000	10,400,000	9,800,000
Employee Stock Option | Common Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted during the period(in shares)	565,000	426,000	725,000
Independent Directors Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options contractual term	7 years
Weighted average grant date fair value of stock options granted during the period (in dollars per share)	$5.39	$4.26	$4.11
Independent Directors Option | Compensation and Benefits
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation expense	500,000	400,000	400,000
Independent Directors Option | Common Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted during the period(in shares)	83,490	105,636	109,488
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Recognition period	3 years 11 months 16 days
Settlement of vested awards, shares issues per award				1
Unrecognized compensation expense	2,900,000			2,900,000
Other equity awards granted during the period (in shares)		208,500
Fair value of other equity awards granted during the period (in dollars per share)		$16.25
Other Equity Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation expense	$0	$0	$11,100,000
Other equity awards granted during the period (in shares)	0	0	945,847
Fair value of other equity awards granted during the period (in dollars per share)			$11.76
Long Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares that may be issued (in shares)	15,295,000			15,295,000
Shares available for future issuance (in shares)	4,400,000			4,400,000

Stockholders_Equity_Changes_in

Stockholders' Equity - Changes in Class A Common Stock Outstanding (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Stockholders' Equity Note [Roll Forward]
Class A Common Stock	829,086
Common Class A
Stockholders' Equity Note [Roll Forward]
Beginning Balance	44,664,884
Issued	164,000
Repurchased	-146,000
Exchange of Holdings units into Class A common stock	2,378,000	10,100,000
Class A Common Stock	829,086
Ending Balance	47,889,964	44,664,884

Stockholders_Equity_Additional

Stockholders' Equity - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Nov. 05, 2014	Dec. 31, 2013
	vote
Stockholders Equity Note [Line Items]
Preferred stock, shares authorized	300,000,000
Preferred stock, par value	$0.01
Common Class A
Stockholders Equity Note [Line Items]
Common stock, shares authorized (in shares)	3,000,000,000		3,000,000,000
Common stock, par value (in dollars per share)	$0.01		$0.01
Stock repurchase under stock repurchase program	$130,000,000	$130,000,000	$80,000,000
Additional stock repurchase under stock repurchase program		50,000,000
Stock repurchased and retired	145,985
Stock repurchase price	$15.48
Stock repurchased and retired, value	$2,300,000
Class B common stock issued	47,889,964		44,664,884
Common stock votes per share	1
Common Class B
Stockholders Equity Note [Line Items]
Common stock, shares authorized (in shares)	1,000,000		1,000,000
Common stock, par value (in dollars per share)	$0.01		$0.01
Class B common stock issued	34		41
Common stock votes per share	1

Net_Capital_Requirements_Minim

Net Capital Requirements - Minimum Capital Requirement And Excess Capital (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
US
Capital Requirements on Foreign Financial Institutions [Line Items]
Capital	$69.50	$64.20
Minimum capital requirement	30	27.1
Excess capital	39.5	37.1
UK LTD
Capital Requirements on Foreign Financial Institutions [Line Items]
Capital	101.6	86
Minimum capital requirement	29.2	24.7
Excess capital	72.4	61.3
HK
Capital Requirements on Foreign Financial Institutions [Line Items]
Capital	31.2	33.6
Minimum capital requirement	14.8	12.3
Excess capital	16.4	21.3
Australia
Capital Requirements on Foreign Financial Institutions [Line Items]
Capital	3	4.7
Minimum capital requirement	0.8	0.4
Excess capital	2.2	4.3
ODL
Capital Requirements on Foreign Financial Institutions [Line Items]
Capital	25.5	18.4
Minimum capital requirement	3	6.9
Excess capital	22.5	11.5
FSL
Capital Requirements on Foreign Financial Institutions [Line Items]
Capital	40.2	34.8
Minimum capital requirement	5.2	8.2
Excess capital	35	26.6
FXCMJ
Capital Requirements on Foreign Financial Institutions [Line Items]
Capital	36.3	36.3
Minimum capital requirement	6.3	5.6
Excess capital	30	30.7
Lucid LLP
Capital Requirements on Foreign Financial Institutions [Line Items]
Capital	22.8	41.8
Minimum capital requirement	3.8	4.2
Excess capital	19	37.6
Faros
Capital Requirements on Foreign Financial Institutions [Line Items]
Capital	0.4	0.1
Minimum capital requirement	0	0
Excess capital	$0.40	$0.10

Commitments_and_Contingencies_1

Commitments and Contingencies - Future Minimum Lease Payments Under Noncancelable Operating Leases (Detail) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2015	$6,714
2016	5,304
2017	3,781
2018	3,492
2019	3,292
Thereafter	19,858
Total	$42,441

Commitments_and_Contingencies_2

Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Commitments and Contingencies Disclosure [Line Items]
Operating lease rental expense	$10.20	$8.30	$7.90
Variable Interest Entity, Primary Beneficiary
Commitments and Contingencies Disclosure [Line Items]
Payment on put options	3.6
General and Administrative Expense | Variable Interest Entity, Primary Beneficiary
Commitments and Contingencies Disclosure [Line Items]
Loss charged to earnings on put options	$3.60
Minimum
Commitments and Contingencies Disclosure [Line Items]
Lease renewal options	3 years
Maximum
Commitments and Contingencies Disclosure [Line Items]
Lease renewal options	5 years

Exchange_Memberships_Additiona

Exchange Memberships - Additional Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Exchange Memberships [Line Items]
Impairment of exchange membership	$0
Exchange memberships	6,429,000	0
Other Noncurrent Assets | Ownership Interests
Exchange Memberships [Line Items]
Exchange memberships	2,700,000	0
Other Noncurrent Assets | Shares Owned
Exchange Memberships [Line Items]
Exchange memberships	$3,700,000	$0

Debt_Convertible_Debt_Details

Debt - Convertible Debt (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jun. 30, 2013
Debt Instrument [Line Items]
Interest expense - stated coupon rate	$12,186	$7,673	$2,763
Interest expense - amortization of deferred bond discount	5,275	2,904	0
Interest expense - amortization of debt issuance cost	1,867	1,263	304
Convertible Debt
Debt Instrument [Line Items]
Liability component - principal	172,500	172,500
Deferred bond discount	-20,922	-26,197
Liability component - net carrying value	151,578	146,303
Equity component	29,101			29,101
Interest expense - stated coupon rate	3,881	2,232
Interest expense - amortization of deferred bond discount	5,275	2,904
Interest expense - amortization of debt issuance cost	1,209	699
Total interest expense - convertible notes	$10,365	$5,835

Debt_Additional_Information_De

Debt - Additional Information (Detail) (USD $)	0 Months Ended				12 Months Ended			0 Months Ended	3 Months Ended	1 Months Ended	0 Months Ended	1 Months Ended
	Dec. 06, 2014	Jun. 06, 2014	Dec. 21, 2013	Dec. 21, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jun. 18, 2012	Jun. 30, 2013	Jun. 30, 2013	Jan. 20, 2015	Jan. 20, 2015	Nov. 08, 2012	Dec. 19, 2011
										D
Debt Instrument [Line Items]
Repayments of lines of credit					$40,000,000	$95,000,000	$45,000,000
Interest and fees paid					5,020,000	3,449,000	2,334,000
Interest expense, borrowings					12,186,000	7,673,000	2,763,000
Interest rate				2.25%
Proceeds from issuance of senior convertibles notes, net					0	166,453,000	0
Warrant strike price					$21.24
Cost of convertible note hedge					29,100,000
Proceeds from sale of warrants					0	18,571,000	0
Amortization of deferred financing cost					1,867,000	1,263,000	304,000
Repayments of Notes Payable	7,500,000	2,300,000	5,500,000	64,000,000
Lucid Markets Trading Limited
Debt Instrument [Line Items]
Purchase price						192,784,000		177,500,000
Notes payable		7,500,000	9,800,000
Lucid Markets Trading Limited | Restatement Adjustment
Debt Instrument [Line Items]
Purchase price									15,300,000
Convertible Debt
Debt Instrument [Line Items]
Interest expense, borrowings					3,881,000	2,232,000
Equity component					29,101,000				29,101,000	29,101,000
Liability component - net carrying value					151,578,000	146,303,000
Amortization of deferred financing cost					1,209,000	699,000
Convertible Debt | 2.25% Senior Convertible Notes
Debt Instrument [Line Items]
Face amount									172,500,000	172,500,000
Interest rate									2.25%	2.25%
Proceeds from issuance of senior convertibles notes, net										166,500,000
Conversion ratio										0.0532992
Conversion price (in dollars per share)									$18.76	$18.76
Threshold trading days										20
Threshold consecutive trading days										30 days
Threshold percentage of stock price trigger										130.00%
Measurement period, business days										5
Measurement period, trading days										5 days
Measurement period threshold percentage										98.00%
Repurchase percentage under certain conditions										100.00%
Liability component - net carrying value									144,100,000	144,100,000
Effective interest rate									6.20%	6.20%
Debt issuance cost										6,000,000
Debt issuance costs, net					4,100,000	5,300,000
Convertible Debt | 2.25% Senior Convertible Notes | Interest on Borrowings
Debt Instrument [Line Items]
Amortization of deferred financing cost					1,200,000	700,000
Unsecured Promissory Note
Debt Instrument [Line Items]
Interest rate		2.25%	2.25%						2.25%	2.25%
Debt instrument maturity date			21-Dec-12
Line of Credit Facility, Current Borrowing Capacity				22,900,000
Term									6 months
Unsecured Promissory Note | Lucid Markets Trading Limited
Debt Instrument [Line Items]
Interest rate				3.50%		2.25%
Term						6 months
Unsecured Promissory Note, One
Debt Instrument [Line Items]
Face amount								71,400,000
Revolving Credit Facility
Debt Instrument [Line Items]
Percentage of equity interests pledged as collateral														65.00%
Amount outstanding					25,000,000	0
Interest expense, borrowings					1,600,000	1,400,000	1,200,000
Weighted average dollar amount of borrowings related to the credit agreement					36,100,000	34,900,000	41,200,000
Debt, weighted average interest rate					2.74%	2.43%	2.10%
Face amount													15,800,000
Revolving Credit Facility | Subsequent Event
Debt Instrument [Line Items]
Repayments of lines of credit											25,000,000
Interest and fees paid												$100,000

Derivative_Financial_Instrumen2

Derivative Financial Instruments - Offsetting Assets and Liabilities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Derivative Assets
Gross fair values	$343,070
Netting agreements	-342,467	-84
Net fair values	603	0
Derivative Asset, Notional Amount	3,712,626
Derivative Liability [Abstract]
Gross fair values	-365,211
Netting agreements	-353,543	-84
Net fair values	-11,668	-2,320
Derivative Liability, Notional Amount	3,709,701
Exchange traded options
Derivative Assets
Gross fair values	10,724
Derivative Asset, Notional Amount	95,498
Derivative Liability [Abstract]
Gross fair values	-11,422
Derivative Liability, Notional Amount	81,053
Futures contracts
Derivative Assets
Gross fair values	332,346	84
Derivative Asset, Notional Amount	3,617,128	19,475
Derivative Liability [Abstract]
Gross fair values	-352,703	-2,404
Derivative Liability, Notional Amount	3,627,562	140,429
Over The Counter (OTC) options
Derivative Assets
Gross fair values	0
Derivative Asset, Notional Amount	0
Derivative Liability [Abstract]
Gross fair values	-1,086
Derivative Liability, Notional Amount	$1,086

Derivative_Financial_Instrumen3

Derivative Financial Instruments - Gains and Losses on Derivative Instruments in Retail and Institutional Trading Revenues (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	($46,244)	($6,427)
Exchange traded options
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	33,318	0
Futures contracts
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	-79,539	-6,427
OTC Foreign Currency Options [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	-23	0
Retail Trading
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	-74,297	-26,671
Retail Trading | Exchange traded options
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0
Retail Trading | Futures contracts
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	-74,297	-26,671
Retail Trading | OTC Foreign Currency Options [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0
Institutional Trading
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	28,053	20,244
Institutional Trading | Exchange traded options
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	33,318	0
Institutional Trading | Futures contracts
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	-5,242	20,244
Institutional Trading | OTC Foreign Currency Options [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	($23)	$0

Fair_Value_Measurements_Fair_V

Fair Value Measurements - Fair Value Measured on a Recurring Basis (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Financial Assets:
Trading securities	$26	$0
Derivative asset, fair value, gross asset	343,070
Derivative asset, fair value, gross liability	-342,467	-84
Derivative asset, fair value, amount not offset against collateral	603	0
Financial Liabilities:
Derivative liability, fair value, gross liability	365,211
Derivative liability, fair value, gross asset	-353,543	-84
Derivative liability, fair value, amount not offset against collateral	11,668	2,320
Exchange traded options
Financial Assets:
Derivative asset, fair value, gross asset	10,724
Financial Liabilities:
Derivative liability, fair value, gross liability	11,422
Over The Counter (OTC) options
Financial Assets:
Derivative asset, fair value, gross asset	0
Financial Liabilities:
Derivative liability, fair value, gross liability	1,086
Quoted Prices in Active Markets for Identical Assets (Level I)
Financial Assets:
Total assets	0	0
Financial Liabilities:
Total liabilities	0	0
Significant Observable Inputs (Level II)
Financial Assets:
Total assets	52,838	5,450
Financial Liabilities:
Total liabilities	176,911	155,750
Significant Unobservable Inputs (Level III)
Financial Assets:
Total assets	26,580	25,446
Financial Liabilities:
Total liabilities	0	9,800
Fair Value, Measurements, Recurring
Financial Assets:
Trading securities	26
Derivative asset, fair value, gross liability	-342,467	-84
Derivative asset, fair value, amount not offset against collateral	603
Total assets	629	0
Financial Liabilities:
Customer account liabilities	1,331,723	1,190,880
Follow-on Payment		3,672
Derivative liability, fair value, gross asset	-353,543	-84
Derivative liability, fair value, amount not offset against collateral	11,668
Securities sold, not yet purchased	4,239
Total liabilities	1,347,630	1,196,872
Fair Value, Measurements, Recurring | Exchange traded options
Financial Assets:
Derivative asset, fair value, gross asset	10,724
Financial Liabilities:
Derivative liability, fair value, gross liability	11,422
Fair Value, Measurements, Recurring | Futures contracts
Financial Assets:
Derivative asset, fair value, gross asset	332,346	0
Derivative asset, fair value, gross liability		-84
Financial Liabilities:
Derivative liability, fair value, gross liability	352,703
Derivative liability, fair value, gross asset		-84
Derivative liability, fair value, amount not offset against collateral		2,320
Fair Value, Measurements, Recurring | Over The Counter (OTC) options
Financial Liabilities:
Derivative liability, fair value, gross liability	1,086
Fair Value, Measurements, Recurring | Counterparty and Cash Collateral Netting
Financial Assets:
Derivative asset, fair value, gross liability	-342,467
Financial Liabilities:
Derivative liability, fair value, gross asset	-353,543
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level I)
Financial Assets:
Trading securities	26
Derivative asset, fair value, gross asset	343,070
Total assets	343,096	84
Financial Liabilities:
Customer account liabilities	0	0
Follow-on Payment		0
Derivative liability, fair value, gross liability	364,125
Securities sold, not yet purchased	4,239
Total liabilities	368,364	2,404
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level I) | Exchange traded options
Financial Assets:
Derivative asset, fair value, gross asset	10,724
Financial Liabilities:
Derivative liability, fair value, gross liability	11,422
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level I) | Futures contracts
Financial Assets:
Derivative asset, fair value, gross asset	332,346	84
Financial Liabilities:
Derivative liability, fair value, gross liability	352,703	2,404
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level I) | Over The Counter (OTC) options
Financial Liabilities:
Derivative liability, fair value, gross liability	0
Fair Value, Measurements, Recurring | Significant Observable Inputs (Level II)
Financial Assets:
Trading securities	0
Derivative asset, fair value, gross asset	0
Total assets	0	0
Financial Liabilities:
Customer account liabilities	1,331,723	1,190,880
Follow-on Payment		0
Derivative liability, fair value, gross liability	1,086
Securities sold, not yet purchased	0
Total liabilities	1,332,809	1,190,880
Fair Value, Measurements, Recurring | Significant Observable Inputs (Level II) | Exchange traded options
Financial Assets:
Derivative asset, fair value, gross asset	0
Financial Liabilities:
Derivative liability, fair value, gross liability	0
Fair Value, Measurements, Recurring | Significant Observable Inputs (Level II) | Futures contracts
Financial Assets:
Derivative asset, fair value, gross asset	0	0
Financial Liabilities:
Derivative liability, fair value, gross liability	0	0
Fair Value, Measurements, Recurring | Significant Observable Inputs (Level II) | Over The Counter (OTC) options
Financial Liabilities:
Derivative liability, fair value, gross liability	1,086
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level III)
Financial Assets:
Trading securities	0
Derivative asset, fair value, gross asset	0
Total assets	0	0
Financial Liabilities:
Customer account liabilities	0	0
Follow-on Payment		3,672
Derivative liability, fair value, gross liability	0
Securities sold, not yet purchased	0
Total liabilities	0	3,672
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level III) | Exchange traded options
Financial Assets:
Derivative asset, fair value, gross asset	0
Financial Liabilities:
Derivative liability, fair value, gross liability	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level III) | Futures contracts
Financial Assets:
Derivative asset, fair value, gross asset	0	0
Financial Liabilities:
Derivative liability, fair value, gross liability	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level III) | Over The Counter (OTC) options
Financial Liabilities:
Derivative liability, fair value, gross liability	$0

Fair_Value_Measurements_Fair_V1

Fair Value Measurements - Fair Value by Balance Sheet Groupings (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Quoted Prices in Active Markets for Identical Assets (Level I)
Financial Assets:
Restricted time deposits	$0
Due from brokers - unsettled spot FX	0	0
Due from brokers - unsettled common stock	0
Due from brokers - excess cash collateral	0
Equity method investments	0	0
Notes receivable	0	0
Exchange memberships	0
Total assets	0	0
Financial Liabilities:
Due to brokers- unsettled spot FX	0	0
Credit agreement	0
Note payable		0
Senior convertible notes	0	0
Total liabilities	0	0
Significant Observable Inputs (Level II)
Financial Assets:
Restricted time deposits	8,341
Due from brokers - unsettled spot FX	14,635	5,450
Due from brokers - unsettled common stock	3,730
Due from brokers - excess cash collateral	18,330
Equity method investments	0	0
Notes receivable	0	0
Exchange memberships	7,802
Total assets	52,838	5,450
Financial Liabilities:
Due to brokers- unsettled spot FX	4,645	6,332
Credit agreement	25,000
Note payable		0
Senior convertible notes	147,266	149,418
Total liabilities	176,911	155,750
Significant Unobservable Inputs (Level III)
Financial Assets:
Restricted time deposits	0
Due from brokers - unsettled spot FX	0	0
Due from brokers - unsettled common stock	0
Due from brokers - excess cash collateral	0
Equity method investments	17,199	13,504
Notes receivable	9,381	11,942
Exchange memberships	0
Total assets	26,580	25,446
Financial Liabilities:
Due to brokers- unsettled spot FX	0	0
Credit agreement	0
Note payable		9,800
Senior convertible notes	0	0
Total liabilities	0	9,800
Carrying Value
Financial Assets:
Restricted time deposits	8,341
Due from brokers - unsettled spot FX	14,635	5,450
Due from brokers - unsettled common stock	3,730
Due from brokers - excess cash collateral	18,330
Equity method investments	10,007	9,793
Notes receivable	9,381	11,942
Exchange memberships	6,429
Total assets	70,853	27,185
Financial Liabilities:
Due to brokers- unsettled spot FX	4,645	6,332
Credit agreement	25,000
Note payable		9,800
Senior convertible notes	151,578	146,303
Total liabilities	181,223	162,435
Fair Value
Financial Assets:
Restricted time deposits	8,341
Due from brokers - unsettled spot FX	14,635	5,450
Due from brokers - unsettled common stock	3,730
Due from brokers - excess cash collateral	18,330
Equity method investments	17,199	13,504
Notes receivable	9,381	11,942
Exchange memberships	7,802
Total assets	79,418	30,896
Financial Liabilities:
Due to brokers- unsettled spot FX	4,645	6,332
Credit agreement	25,000
Note payable		9,800
Senior convertible notes	147,266	149,418
Total liabilities	$176,911	$165,550

Fair_Value_Measurements_Signif

Fair Value Measurements - Significant Unobservable Inputs Reconciliation (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$3,672	$0
Additions	0	10,631
Net Unrealized / Realized Gains	-3,672	-6,959
Ending Balance	0	3,672
Follow-on Payment
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	3,672	0
Additions	0	10,631
Net Unrealized / Realized Gains	-3,672	-6,959
Ending Balance	$0	$3,672

Income_Taxes_Income_from_Conti

Income Taxes - Income from Continuing Operations Before Income Taxes (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Domestic	$3,946	$10,390	$19,794
Foreign	21,702	41,470	27,670
Income before income taxes	$25,648	$51,860	$47,464

Income_Taxes_Provision_for_inc

Income Taxes - Provision for income taxes consists (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current
Federal income tax (benefit)	$2	($185)	$478
State and local income tax	331	682	574
Foreign income tax	4,757	5,085	764
Subtotal	5,090	5,582	1,816
Deferred
Federal income tax	1,053	3,996	2,837
State and local income tax (benefit)	754	235	-171
Foreign income (benefit) tax	-896	7,211	4,504
Subtotal	911	11,442	7,170
Total provision for taxes	$6,001	$17,024	$8,986

Income_Taxes_Reconciles_provis

Income Taxes - Reconciles provision for taxes (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Statutory U.S. federal income tax rate	34.00%	34.00%	34.00%
Income passed through to non-controlling members	-2.70%	-5.40%	-15.50%
State and local income tax	2.80%	0.90%	1.00%
Foreign income tax	-3.30%	-1.40%	-3.10%
Tax Receivable Agreement true-up	-11.70%	0.00%	0.00%
Non-deductible FCA fine	0.00%	2.00%	0.00%
Foreign tax credit valuation allowance	3.70%	3.50%	2.50%
Impact of rate change on deferred tax assets	0.00%	-0.90%	0.00%
Other	0.60%	0.10%	0.00%
Effective tax rate	23.40%	32.80%	18.90%

Income_Taxes_Tax_effects_of_te

Income Taxes - Tax effects of temporary differences (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred tax assets
Equity-based compensation	$983	$1,059
Investment in partnership	179,297	178,941
Fixed assets	1,960	2,279
Tax loss carryforwards	40,346	25,631
Intangible assets	92	0
Tax credit carryforward/foreign sub income	5,380	4,265
Japan software	838	1,516
Other	417	577
Gross deferred tax assets	229,313	214,268
Less: valuation allowance	-19,704	-25,288
Net deferred tax asset	209,609	188,980
Deferred tax liabilities
Fixed assets	8	4
Intangible assets	2,498	3,965
Goodwill	19,296	8,742
Software development cost	253	238
Other	768	1,232
Gross deferred tax liabilities	22,823	14,181
Net deferred tax asset	$186,786	$174,799

Income_Taxes_Reconciliation_of

Income Taxes - Reconciliation of Unrecognized Tax Benefits (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	$183	$3,691	$223
Gross increases – tax positions in prior period	98	0	1
Gross decreases – tax positions in prior period	0	-3,445	-16
Gross increases – tax positions in current period	128	51	3,483
Settlement	0	-114	0
Lapse of statute of limitations	0	0	0
Unrecognized tax benefits – December 31	$409	$183	$3,691

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Income Tax Contingency [Line Items]
Valuation allowance	$19,704,000	$25,288,000
Income tax reconciliation tax credits foreign	4,600,000
Tax credit carryforward period	10 years
Income tax reconciliation tax credits	500,000
Business tax credit carryforward period	7 years
Deferred tax assets not recognized permanent difference	28,900,000
Tax receivable	2,446,000	3,861,000
Accounts Payable and Accrued Expenses
Income Tax Contingency [Line Items]
Taxes Payable	2,200,000	1,000,000
Domestic Tax Authority
Income Tax Contingency [Line Items]
Operating loss carry forwards, foreign	18,800,000
Foreign Tax Authority
Income Tax Contingency [Line Items]
Operating loss carry forwards, foreign	$169,800,000

Foreign_Currencies_and_Concent1

Foreign Currencies and Concentrations of Credit Risk - Additional Information (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	bank	bank
Foreign Currency [Abstract]
Due from brokers	$37,298	$5,450
Percentage of due from correspondent brokers	97.10%	96.20%
Banks held more than 10% each of the company's total cash and cash equivalents	2	2
Percentage of cash and cash equivalent	10.00%

Segments_Companys_Operations_b

Segments - Company's Operations by Reportable Segment (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	Segment
Segment Reporting Information [Line Items]
Number of operating segments	2
Total net revenues	$463,757	$489,588	$417,315
Total expenses	436,801	436,976	369,851
Loss on equity method investments, net	1,308	752	0
Income (loss) before income taxes	25,648	51,860	47,464
Assets	2,387,427	2,223,947	2,065,170
Corporate
Segment Reporting Information [Line Items]
Total net revenues	7,464	-1,209	0
Total expenses	117,004	119,121	106,669
Loss on equity method investments, net	420	55
Income (loss) before income taxes	-109,960	-120,385	-106,669
Assets	192,854	183,626	127,122
Operating Segments | Retail Trading
Segment Reporting Information [Line Items]
Total net revenues	349,630	379,840	355,282
Total expenses	210,550	219,016	218,018
Loss on equity method investments, net	0	0
Income (loss) before income taxes	139,080	160,824	137,264
Assets	1,759,485	1,622,829	1,556,680
Operating Segments | Institutional Trading
Segment Reporting Information [Line Items]
Total net revenues	106,663	110,957	62,033
Total expenses	109,247	98,839	45,164
Loss on equity method investments, net	888	697
Income (loss) before income taxes	-3,472	11,421	16,869
Assets	$435,088	$417,492	$381,368

Segments_Companys_Operations_b1

Segments - Company's Operations by Geographical Reportable Segment (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting, Asset Reconciling Item [Line Items]
Total net revenues	$463,757	$489,588	$417,315
Operating and other expenses	438,109	437,728	369,851
Income before income taxes	25,648	51,860	47,464
Eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Total net revenues	-198,535	-160,556	-114,179
Operating and other expenses	-198,535	-160,556	-112,764
Income before income taxes	0	0	-1,415
U.S.
Segment Reporting, Asset Reconciling Item [Line Items]
Total net revenues	304,507	301,005	284,511
Operating and other expenses	300,560	290,549	264,706
Income before income taxes	3,947	10,456	19,805
Asia
Segment Reporting, Asset Reconciling Item [Line Items]
Total net revenues	60,086	57,557	51,486
Operating and other expenses	43,566	39,410	41,228
Income before income taxes	16,520	18,147	10,258
Europe, Middle East and North Africa
Segment Reporting, Asset Reconciling Item [Line Items]
Total net revenues	289,232	286,771	191,314
Operating and other expenses	285,271	265,218	173,467
Income before income taxes	3,961	21,553	17,847
Other
Segment Reporting, Asset Reconciling Item [Line Items]
Total net revenues	8,467	4,811	4,183
Operating and other expenses	7,247	3,107	3,214
Income before income taxes	$1,220	$1,704	$969

Litigation_Additional_Informat

Litigation - Additional Information (Details)

Dec. 31, 2014

Feb. 28, 2014

Feb. 28, 2014

Jun. 20, 2012

Oct. 31, 2011

Mar. 31, 2013

Dec. 31, 2012

Jan. 31, 2014

Jun. 30, 2014

Feb. 28, 2014

Jul. 31, 2014

Feb. 28, 2015

USD ($)

Settlement with FCA

Settlement with FCA

United States Bankruptcy Court for the Southern District of Florida

United States Bankruptcy Court for the Southern District of Florida

JFSA

JFSA

Texas Securities Act

Restitution to Affected Clients

Restitution to Affected Clients

US vs. National Futures Association [Member]

Subsequent Event

USD ($)

GBP (£)

USD ($)

debtor

USD ($)

USD ($)

Minimum

Settlement with FCA

Maximum

USD ($)

Restitution to Affected Clients

USD ($)

USD ($)

Settlement with FCA

Settlement with FCA

USD ($)

USD ($)

Loss Contingencies [Line Items]

Number of debtors

3

Settlement

$6,600,000

£ 4,000,000

$700,000

$2,300,000

($1,800,000)

$9,900,000

$200,000

($700,000)

Accrual

2,600,000

Damages claimed

3,800,000

Range of loss, minimum

0

Range of loss, maximum

$4,700,000

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Detail) (USD $)	0 Months Ended
	Feb. 09, 2015	Jan. 28, 2015	Jan. 24, 2015	Mar. 16, 2015	Jan. 15, 2015	Dec. 21, 2012
Subsequent Event [Line Items]
Interest rate						2.25%
Subsequent Event
Subsequent Event [Line Items]
Declared dividend per share of common stock		1
Preferred stock per right		0.001
Rights conversion price per thousandth preferred share		$11.20
Dividend per share of common stock	1
Beneficial ownership in outstanding common stock threshold (percentage)		10.00%
Swiss National Bank | Subsequent Event
Subsequent Event [Line Items]
Currency floor of EUR/CHF					1.2
FXCM | Subsequent Event
Subsequent Event [Line Items]
Change in Control, Majority of Directors No Longer on Board for Period			12 months
Holdings and Newco | Leucadia | Loans Payable | Subsequent Event
Subsequent Event [Line Items]
Face amount			300,000,000
Net proceeds from issuance of debt			279,000,000
Interest rate			10.00%
Quarterly increase in interest rate			1.50%
Maximum interest rate			20.50%
Increase in interest rate in the event of default			2.00%
Deferred financing fee			10,000,000
Repayments of long-term debt				12,200,000
Principal outstanding				287,800,000
Increase to deferred financing fee			30,000,000
Threshold maximum amount outstanding to prevent increase in deferred financing fee			250,000,000
FXCM Holdings, LLC | Subsequent Event
Subsequent Event [Line Items]
Percentage of ownership interests			90.00%
FXCM Holdings, LLC | Leucadia | Loans Payable | Subsequent Event
Subsequent Event [Line Items]
Percentage of equity interests pledged as collateral			65.00%
Minimum | FXCM | Subsequent Event
Subsequent Event [Line Items]
Change of control, group obtains certain voting percentage			40.00%
Amounts due under Leucadia term loan, including fees | Leucadia | Subsequent Event
Subsequent Event [Line Items]
Allocation percentage under Letter Agreement of stipulated proceeds			100.00%
Amounts due under Leucadia term loan, including fees | FXCM Holdings, LLC | Subsequent Event
Subsequent Event [Line Items]
Allocation percentage under Letter Agreement of stipulated proceeds			0.00%
Next $350 million | Subsequent Event
Subsequent Event [Line Items]
Stipulated amount of proceeds, by range, per the Letter Agreement			350,000,000
Next $350 million | Leucadia | Subsequent Event
Subsequent Event [Line Items]
Allocation percentage under Letter Agreement of stipulated proceeds			50.00%
Next $350 million | FXCM Holdings, LLC | Subsequent Event
Subsequent Event [Line Items]
Allocation percentage under Letter Agreement of stipulated proceeds			50.00%
Next amount equal to 2 times the balance outstanding on the term loan and fees as of April 16, 2015, such amount not to be less than $500 million or more than $680 million | Leucadia | Subsequent Event
Subsequent Event [Line Items]
Allocation percentage under Letter Agreement of stipulated proceeds			90.00%
Next amount equal to 2 times the balance outstanding on the term loan and fees as of April 16, 2015, such amount not to be less than $500 million or more than $680 million | FXCM Holdings, LLC | Subsequent Event
Subsequent Event [Line Items]
Allocation percentage under Letter Agreement of stipulated proceeds			10.00%
Next amount equal to 2 times the balance outstanding on the term loan and fees as of April 16, 2015, such amount not to be less than $500 million or more than $680 million | Minimum | Subsequent Event
Subsequent Event [Line Items]
Stipulated amount of proceeds, by range, per the Letter Agreement			500,000,000
Next amount equal to 2 times the balance outstanding on the term loan and fees as of April 16, 2015, such amount not to be less than $500 million or more than $680 million | Maximum | Subsequent Event
Subsequent Event [Line Items]
Stipulated amount of proceeds, by range, per the Letter Agreement			680,000,000
All aggregate amounts thereafter | Leucadia | Subsequent Event
Subsequent Event [Line Items]
Allocation percentage under Letter Agreement of stipulated proceeds			60.00%
All aggregate amounts thereafter | FXCM Holdings, LLC | Subsequent Event
Subsequent Event [Line Items]
Allocation percentage under Letter Agreement of stipulated proceeds			40.00%
Foreign Exchange [Member] | Subsequent Event
Subsequent Event [Line Items]
Negative equity in customer balances resulting from currency pair volatility					$276,000,000
Margin Receivable Expected to be Uncollectible Due to Foreign Currency Losses Incurred by Customers, Percentage of Customers Forgiven		90.00%
Margin Receivable Expected to be Uncollectible Due to Foreign Currency Losses Incurred by Customers, Percentage of Customers Required to Repay Debit Balances		10.00%
Margin Receivable Expected to be Uncollectible Due to Foreign Currency Losses Incurred by Customers, Percentage of Debit Balances Owned by Customers Required to Repay		60.00%