Interactive Brokers (IBKR) 10-K 29 Feb 16 2015 FY Annual report Financial data

Documentation and Entity Inform

Documentation and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Feb. 24, 2016	Jun. 30, 2015
Entity Registrant Name	Interactive Brokers Group, Inc.
Entity Central Index Key	1,381,197
Document Type	10-K
Document Period End Date	Dec. 31, 2015
Amendment Flag	false
Fiscal Year Focus	2,015
Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 2,741,603,954
Common Class A
Common Stock Shares Outstanding		63,985,335
Common Class B
Common Stock Shares Outstanding		100

Consolidated Statements of Fina

Consolidated Statements of Financial Condition - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Assets
Cash and cash equivalents	$ 1,601	$ 1,269
Cash and securities segregated for regulatory purposes	21,309	15,404
Securities borrowed	3,924	3,660
Securities purchased under agreements to resell	195	386
Financial instruments owned, at fair value:
Financial instruments owned	1,987	2,042
Financial instruments owned and pledged as collateral	1,433	1,936
Total financial instruments owned, at fair value	3,420	3,978
Receivables:
Customers receivables	17,050	17,051
Receivables from brokers, dealers and clearing organizations	692	1,131
Interest receivable	63	37
Total receivables	17,805	18,219
Other assets	480	469
Total assets	48,734	43,385
Liabilities and equity
Short-term borrowings		34
Securities Loaned	2,894	3,199
Financial instruments sold, not yet purchased, at fair value	2,617	2,569
Payables:
Payables to customer	37,084	31,796
Payables to brokers, dealers and clearing organizations	423	234
Payable to affiliate	291	277
Accounts payable, accrued expenses and other liabilities	78	87
Interest payable	3	4
Total payables	37,879	32,398
Total liabilities	43,390	38,200
Stockholders' equity:
Additional paid-in capital	718	635
Retained earnings	145	121
Accumulated other comprehensive income, net of income taxes of $0 and $1 as of December 31, 2015 and December 31, 2014	2	12
Treasury stock, at cost, 135,815 and 139,059 shares as of December 31, 2015 and December 31, 2014	(3)	(3)
Total stockholders' equity	863	766
Noncontrolling interests	4,481	4,419
Total equity	5,344	5,185
Total liabilities and stockholders' equity	48,734	43,385
Common Class A
Stockholders' equity:
Common stock	$ 1	$ 1
Common Class B
Stockholders' equity:
Common stock

Consolidated Statements of Fin3

Consolidated Statements of Financial Condition (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Allowance for doubtful accounts	$ 130	$ 7
Common stock, par value	$ 0.01
Common stock, shares outstanding	63,985,335
Accumulated Other Comprehensive Income, Tax	$ 0	$ 1
Treasury stock shares	135,815	139,059
Common Class A
Common stock, par value	$ 0.01	$ 0.01
Shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	64,121,150	58,612,245
Common stock, shares outstanding	63,985,335	58,473,186
Common Class B
Shares authorized	100	100
Common stock, shares issued	100	100
Common stock, shares outstanding	100	100

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Trading gains	$ 269	$ 261	$ 331
Commissions and execution fees	617	549	502
Interest income	492	416	304
Other income (loss)	(122)	(111)	(9)
Total revenues	1,256	1,115	1,128
Interest expense	67	72	52
Total net revenues	1,189	1,043	1,076
Non-interest expenses:
Execution and clearing	231	212	243
Employee compensation and benefits	227	205	205
Occupancy, depreciation and amortization	44	39	39
Communications	25	24	23
General and administrative	58	54	48
Customer bad debt	146	3	67
Total non-interest expenses	731	537	625
Income before income taxes	458	506	451
Income tax expense	43	47	33
Net income	415	459	418
Less net income attributable to noncontrolling interests	366	414	381
Net income available for common stockholders	$ 49	$ 45	$ 37
Earnings per share:
Basic	$ 0.80	$ 0.79	$ 0.74
Diluted	$ 0.78	$ 0.77	$ 0.73
Weighted average common shares outstanding:
Weighted Average Number of Shares Outstanding, Basic	61,043,071	56,492,381	49,742,428
Weighted Average Number of Shares Outstanding, Diluted	62,509,796	57,709,668	50,924,736
Comprehensive income:
Net income available for common stockholders	$ 49	$ 45	$ 37
Other comprehensive income:
Cumulative translation adjustment, before income taxes	(10)	(15)	(3)
Other comprehensive income (loss), net of tax	(10)	(15)	(3)
Comprehensive income available for common stockholders	39	30	34
Comprehensive income attributable to noncontrolling interests:
Net income attributable to noncontrolling interests	366	414	381
Other comprehensive income (loss) - cumulative translation adjustment	(53)	(92)	(25)
Comprehensive income attributable to noncontrolling interests	$ 313	$ 322	$ 356

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income	$ 415	$ 459	$ 418
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Deferred income taxes	15	18	11
Depreciation and amortization	22	20	19
Employee stock compensation	50	41	41
Unrealized losses on other investments, net	7	10	6
Bad debt expense	146	3	67
Change in operating assets and liabilities:
Cash and securities - segregated for regulatory purposes	(5,905)	(1,409)	(1,275)
Securities borrowed	(264)	(908)	82
Securities purchased under agreements to resell	191		43
Financial instruments owned, at fair value	568	468	96
Receivables from customers	(144)	(3,458)	(3,746)
Other receivables	413	(283)	(17)
Other assets	13	36	(75)
increase (decrease) in securities loaned	(305)	635	724
Financial instruments sold but not yet purchased, at fair value	38	(585)	(1,133)
Payable to customers	5,288	5,476	4,897
Other payables	177	(106)	(18)
Net cash provided by operating activities	725	417	140
Cash flows from investing activities:
Purchases of other investments	(16)	(443)	(264)
Distributions received and proceeds from sales of other investments	11	516	248
Purchase of property, equipment and intangible assets	(30)	(19)	(17)
Net cash (used in) provided by investing activities	(35)	54	(33)
Cash flows from financing activities:
Short-term borrowings, net	(34)	10	(86)
Dividends paid to stockholders	(25)	(23)	(20)
Distributions to noncontrolling interests	(227)	(279)	(142)
Repurchases of common stock for employee tax withholding under stock incentive plans	(25)
Proceeds from sales of treasury stock	29
Payments made under the Tax Receivable Agreement	(13)	(16)
Net cash used in financing activities	(295)	(308)	(248)
Effect of exchange rate changes on cash and cash equivalents	(63)	(107)	(27)
Net increase (decrease) in cash and cash equivalents	332	56	(168)
Cash and cash equivalents at beginning of period	1,269	1,213	1,381
Cash and cash equivalents at end of period	1,601	1,269	1,213
Supplemental disclosures of cash flow information:
Cash paid for interest	68	73	53
Cash paid for taxes	31	37	52
Non-cash financing activities:
Issuance of Common Stock in exchange of member interests in IBG LLC	132	35	110
Redemption of member interests from IBG Holdings LLC	(132)	(35)	(110)
Adjustments to additional paid-in capital for changes in proportionate ownership in IBG LLC	26	10	(30)
Adjustments to noncontrolling interests for changes in proportionate ownership in IBG LLC	$ (26)	$ (10)	$ 30

Consolidated Statements of Chan

Consolidated Statements of Changes in Equity - USD ($) $ in Millions	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Total Stockholders' Equity [Member]	Non-controlling Interests [Member]	Total
Balance at Dec. 31, 2012	$ 1	$ 493	$ (8)	$ 82	$ 30	$ 598	$ 4,215	$ 4,813
Common stock, shares issued at Dec. 31, 2012	47,797,844
Issuance of common stock in follow-on offering		110				110	(110)
Number of new stock issued during the period (in shares)	4,683,415
Common stock distributed pursuant to stock incentive plans			5			5		5
Common Stock distributed pursuant to stock incentive plans (in shares)	2,306,790
Compensation for stock grants vesting in the future		5				5	36	41
Deferred tax benefit retained - follow-on offering		5				5		5
Dividends paid to stockholders				(20)		(20)		(20)
Distributions from IBG LLC to noncontrolling interests							(142)	(142)
Adjustments for changes in proportionate ownership in IBG LLC		(30)				(30)	30
Comprehensive Income				37	(3)	34	356	390
Balance at Dec. 31, 2013	$ 1	583	(3)	99	27	707	4,385	5,092
Common stock, shares issued at Dec. 31, 2013	54,788,049
Issuance of common stock in follow-on offering		35				35	(35)
Number of new stock issued during the period (in shares)	1,358,478
Common Stock distributed pursuant to stock incentive plans (in shares)	2,445,200
Compensation for stock grants vesting in the future		6				6	35	41
Stock Incentive Plan Adjustment							1	1
Stock incentive plan adjustment (in shares)	20,518
Deferred tax benefit retained - follow-on offering		1				1		1
Dividends paid to stockholders				(23)		(23)		(23)
Distributions from IBG LLC to noncontrolling interests							(279)	(279)
Adjustments for changes in proportionate ownership in IBG LLC		10				10	(10)
Comprehensive Income				45	(15)	30	322	352
Balance at Dec. 31, 2014	$ 1	635	(3)	121	12	766	4,419	$ 5,185
Common stock, shares issued at Dec. 31, 2014	58,612,245
Issuance of common stock in follow-on offering		39				39	(39)
Number of new stock issued during the period (in shares)	3,021,778							3,021,778
Common Stock distributed pursuant to stock incentive plans (in shares)	2,487,127
Compensation for stock grants vesting in the future		9				9	41	$ 50
Deferred tax benefit retained - follow-on offering		5				5		5
Repurchase of common stock for employee tax withholding under stock incentive plans			(25)			(25)		(25)
Sales of treasury stock		4	25			29		29
Dividends paid to stockholders				(25)		(25)		(25)
Distributions from IBG LLC to noncontrolling interests							(227)	(227)
Adjustments for changes in proportionate ownership in IBG LLC		26				26	(26)
Comprehensive Income				49	(10)	39	313	352
Balance at Dec. 31, 2015	$ 1	$ 718	$ (3)	$ 145	$ 2	$ 863	$ 4,481	$ 5,344
Common stock, shares issued at Dec. 31, 2015	64,121,150

Organization And Nature Of Busi

Organization And Nature Of Business	12 Months Ended
	Dec. 31, 2015
Organization And Nature Of Business [Abstract]
Organization And Nature Of Business	1. Organization and Nature of Business Interactive Brokers Group, Inc. (“IBG, Inc.”) is a Delaware holding company whose primary asset is its ownership of approximately 15.7% of the membership interests of IBG LLC, which, in turn, owns operating subsidiaries (collectively, “IBG LLC”). IBG, Inc. together with IBG LLC and its consolidated subsidiaries (collectively, “the Company”), is an automated global electronic broker and market maker specializing in executing and clearing trades in securities, futures, foreign exchange instruments, bonds and mutual funds on more than 100 electronic exchanges and market centers around the world and offering custody, prime brokerage, securities and margin lending services to customers. In the United States of America (“U.S.”), the Company conducts its business primarily from its headquarters in Greenwich, Connecticut and from Chicago, Illinois. Abroad, the Company conducts its business through offices located in Canada, England, Switzerland, Liechtenstein, India, China (Hong Kong and Shanghai), Japan, and Australia. As of December 31, 201 5 , the Company had 1,087 employees worldwide. IBG LLC is a Connecticut limited liability company that conducts its business through its operating subsidiaries (collectively, the “Operating Companies”): Interactive Brokers LLC (“IB LLC”); Interactive Brokers Canada Inc. (“IBC”); Interactive Brokers (U.K.) Limited and its subsidiary, Interactive Brokers (U.K.) Nominee Limited (collectively, “IBUK”); Interactive Brokers Securities Japan, Inc. (“IBSJ”); Interactive Brokers Hong Kong Limited (“IBHK”); Interactive Brokers (India) Private Limited (“IBI”); Interactive Brokers Australia Pty Limited and its subsidiary, Interactive Brokers Australia Nominees Pty Limited (collectively, “IBA”); Timber Hill LLC (“TH LLC”); Timber Hill Europe AG and its subsidiary, Timber Hill (Liechtenstein) AG (collectively, “THE”); Timber Hill Australia Pty Limited (“THA”); Timber Hill Canada Company (“THC”); Interactive Brokers Financial Products S.A. (“IBFP”); Interactive Brokers Hungary KFT (“IBH”); Interactive Brokers Software Services Estonia OU (“IBEST”); Interactive Brokers Software Services Russia (“IBRUS”); and IB Exchange Corp. (“IBEC”) and its subsidiaries, Interactive Brokers Corp. (“IB Corp”), and Covestor, Inc. and its subsidiary, Covestor Limited (collectively, “Covestor”). The Company operates in two business segments: electronic brokerage and market making, both supported by corporate. The Company conducts its electronic brokerage business through certain Interactive Brokers subsidiaries, which provide electronic execution and clearing services to customers worldwide. The Company conducts its market making business principally through its Timber Hill subsidiaries on the world’s leading exchanges and market centers, primarily in exchange ‑traded equities, equity options and equity ‑index options and futures. Corporate enables the Company to operate cohesively and effectively by providing support via control functions to the business segments and also by executing the Company’s currency diversification strategy. Certain of the Operating Companies are members of various securities and commodities exchanges in North America, Europe and the Asia/Pacific region and are subject to regulatory capital and other requirements (see Note 16). IB LLC, IBUK, IBC, IBI, IBHK and IBSJ carry securities accounts for customers or perform custodial functions relating to customer securities.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Significant Accounting Policies [Abstract]
Significant Accounting Policies	2. Significant Accounting Policies Basis of Presentation These consolidated financial statements are presented in U.S. dollars and have been prepared in accordance with accounting principles generally accepted in the U.S. (“U.S. GAAP”) and pursuant to the rules and regulations of the U.S. Securities and Exchange Commission ( “ SEC ” ) regarding financial reporting with respect to Form 10 ‑K. These consolidated financial statements include the accounts of the Company and its consolidated subsidiaries and reflect all adjustments of a normal and recurring nature that are, in the opinion of management, necessary for the fair presentation of the results for the periods presented. In the third quarter of 2015, the Company changed the presentation of its non-market making financial instruments carried at fair value from other assets and accounts payable, accrued expenses and other liabilities to financial instruments owned, at fair value and financial instruments sold, but not yet purchased, at fair value, respectively, in the consolidated statements of financial condition, in order to consistently present all of the financial instruments held for trading under the same caption. For comparison purposes, as of December 31, 2014, $44 million was reclassified from other assets to financial instruments owned, at fair value, and $8 million was reclassified from accounts payable, accrued expenses and other liabilities to financial instruments sold, but not yet purchased, at fair value. Principles of Consolidation, including Noncontrolling Interests The consolidated financial statements include the accounts of IBG, Inc. and its majority and wholly owned subsidiaries. As sole managing member of IBG LLC, IBG, Inc. exerts control over IBG LLC’ s operations. In accordance with Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 810, “ Consolidation , ” the Company consolidates IBG LLC’ s financial statements and records the interests in IBG LLC that it does not own as noncontrolling interests. The Company ’ s policy is to consolidate all other entities in which it owns more than 50% unless it does not have control. All inter ‑company balances and transactions have been eliminated. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts and disclosures in these consolidated financial statements and accompanying notes. These estimates and assumptions are based on judgment and the best available information at the time. Therefore, actual results could differ materially from those estimates. Such estimates include the allowance for doubtful accounts, valuation of certain investments, compensation accruals, current and deferred income taxes, and contingency reserves. Fair Value Substantially all of the Company’s assets and liabilities, including financial instruments are carried at fair value based on published market prices and are marked to market, or are assets and liabilities which are short ‑term in nature and are carried at amounts that approximate fair value. The Company applies the fair value hierarchy in accordance with FASB ASC Topic 820, “ Fair Value Measurement” (“ASC Topic 820”) , to prioritize the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets and liabilities and the lowest priority to unobservable inputs. The three levels of the fair value hierarchy are: Level 1 Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. Level 2 Quoted prices in markets that are not considered to be active or financial instruments for which all significant inputs are observable, either directly or indirectly. Level 3 Prices or valuations that require inputs that are both significant to fair value measurement and unobservable. Financial instruments owned, at fair value and financial instruments sold, but not yet purchased, at fair value are generally classified as Level 1 of the fair value hierarchy. The Company’s Level 1 financial instruments, which are valued using quoted market prices as published by exchanges and clearing houses or otherwise broadly distributed in active markets, include active listed stocks, options, warrants and discount certificates, and U.S. and foreign government securities. The Company does not adjust quoted prices for financial instruments classified as Level 1 of the fair value hierarchy, even in the event that the Company may hold a large position whereby a purchase or sale could reasonably impact quoted prices. Currency forward contracts are valued using broadly distributed bank and broker prices, and are classified as Level 2 of the fair value hierarchy as such instruments are not exchange ‑traded. Other securities that are not traded in active markets are also classified in Level 2 of the fair value hierarchy. Level 3 financial instruments are comprised of securities that have been delisted or otherwise are no longer tradable and have been valued by the Company based on internal estimates. Earnings Per Share Earnings per share (“EPS”) is computed in accordance with FASB ASC Topic 260, “ Earnings per Share .” Basic EPS is computed by dividing the net income available for common stockholders by the weighted average number of shares outstanding for that period. Diluted EPS is calculated by dividing the net income available for common stockholders by the diluted weighted average shares outstanding for that period. Diluted EPS includes the determinants of the basic EPS and, in addition, reflects the dilutive effect of shares of common stock estimated to be distributed in the future under the Company’s stock-based compensation plans, with no adjustments to net income available for common stockholders for dilutive potential common shares. Stock ‑Based Compensation The Company follows FASB ASC Topic 718, “ Compensation - Stock Compensation” (“ASC Topic 718”) , to account for its stock ‑based compensation plans. ASC Topic 718 requires all share ‑based payments to employees to be recognized in the consolidated financial statements using a fair value ‑based method. Grants, which are denominated in U.S. dollars, are communicated to employees in the year of grant, thereby establishing the fair value of each grant. The fair value of awards granted to employees are generally expensed as follows: 50% in the year of grant in recognition of plan forfeiture provisions (as described below) and the remaining 50% over the related vesting period utilizing the “graded vesting” method permitted under ASC Topic 718. In the case of “retirement eligible” employees (those employees older than 59), 100% of awards are expensed when granted. Awards granted under stock ‑based compensation plans are subject to forfeiture in the event an employee ceases employment with the Company. The plans provide that employees who discontinue employment with the Company without cause and continue to meet the terms of the plans’ post ‑employment provisions will forfeit 50% of unvested previously granted awards unless the employee is over the age of 59, in which case the employee would be eligible to receive 100% of unvested awards p reviously granted. Cash and Cash Equivalents Cash and cash equivalents consist of deposits with banks and all highly liquid investments, with maturities of three months or less, that are not segregated and deposited for regulatory purposes or to meet margin requirements at clearing houses . Cash and Securities - Segregated for Regulatory Purposes As a result of customer activities, certain Operating Companies are obligated by rules mandated by their primary regulators to segregate or set aside cash or qualified securities to satisfy such regulations, which have been promulgated to protect customer assets. Securities segregated for regulatory purposes consisted of U.S. government securities of $15.2 billion and $6.7 billion as of December 31, 201 5 and December 31, 201 4 , respectively, and securities purchased under agreements to resell in the amount of $0.6 billion and $3.9 billion as of December 31, 201 5 and December 31, 201 4 , respectively, which amounts approximate fair value. Securities Borrowed and Securities Loaned Securities borrowed and securities loaned are recorded at the amount of the cash collateral advanced or received. Securities borrowed transactions require the Company to provide counterparties with collateral, which may be in the form of cash, letters of credit or other securities. With respect to securities loaned, the Company receives collateral, which may be in the form of cash or other securities in an amount generally in excess of the fair value of the securities loaned. The Company monitors the market value of securities borrowed and loaned on a daily basis, with additional collateral obtained or refunded as permitted contractually. The Company does not net, in the consolidated statements of financial condition, securities borrowed and securities loaned entered into with the same counterparty that do not meet the offsetting requirements prescribed in FASB ASC Topic 210-20, “Balance Sheet – Offsetting” (“ASC Topic 210-20”). Securities lending fees received and paid by the Company are included in interest income and interest expense, respectively, in the consolidated statements of comprehensive income. Securities Purchased Under Agreements to Resell and Securities Sold Under Agreements to Repurchase Securities purchased under agreements to resell, which are reported as collateralized financing transactions, are recorded at contract value, which approximates fair value. To ensure that the fair value of the underlying collateral remains sufficient, the collateral is valued daily with additional collateral obtained or excess collateral returned, as permitted under contractual provisions. The Company does not net, in the consolidated statements of financial condition, securities purchased under agreements to resell transactions and securities sold under agreements to repurchase transactions entered into with the same counterparty that do not meet the offsetting requirements prescribed in ASC Topic 210-20. Financial Instruments Owned and Financial Instruments Sold , But Not Yet Purchased , at Fair Value Financial instrument transactions are accounted for on a trade date basis. Financial instruments owned and financial instruments sold, but not yet purchased are stated at fair value based upon quoted market prices. The Company’s financial instruments pledged to counterparties where the counterparty has the right, by contract or custom, to sell or repledge the financial instruments are reported as financial instruments owned and pledged as collateral in the consolidated statements of financial condition. The Company also enters into currency forward contracts. These transactions, which are also accounted for on a trade date basis, are agreements to exchange a fixed amount of one currency for a specified amount of a second currency at completion of the currency forward contract term. Unrealized mark ‑to ‑market gains and losses on currency forward contracts are included in financial instruments owned, at fair value or financial instruments sold, but not yet purchased, at fair value in the consolidated statements of financial condition. Customer Receivables and Payables Customer securities transactions are recorded on a settlement date basis and customer commodities transactions are recorded on a trade date basis. Receivables from and payables to customers include amounts due on cash and margin transactions, including futures contracts transacted on behalf of customers. Securities owned by customers, including those that collateralize margin loans or other similar transactions, are not reported in the consolidated statements of financial condition. Amounts receivable from customers that are determined by management to be uncollectible are recorded as customer bad debt expense in the consolidated statements of comprehensive income. Receivables from and Payables to Brokers, Dealers and Clearing Organizations Receivables from and payables to brokers, dealers and clearing organizations include net receivables and payables from unsettled trades, including amounts related to futures and options on futures contracts executed on behalf of customers, amounts receivable for securities not delivered by the Company to the purchaser by the settlement date (“fails to deliver”) and cash deposits. Payables to brokers, dealers and clearing organizations also include amounts payable for securities not received by the Company from a seller by the settlement date (“fails to receive”). Investments The Company makes certain strategic investments related to its business and accounts for these investments under the cost method of accounting or under the equity method of accounting as required under FASB ASC Topic 323, “ Investments - Equity Method and Joint Ventures .” Investments accounted for under the equity method, including where the investee is a limited partnership or limited liability company, are recorded at the fair value amount of the Company’s initial investment and are adjusted each period for the Company’s share of the investee’s income or loss. The Company’s share of the income or losses from equity method investments is included in other income in the consolidated statements of comprehensive income. The recorded amounts of the Company’s equity method investments, $32 million as of December 31, 201 5 ( $37 million as of December 31, 201 4 ), which are included in other assets in the consolidated statements of financial condition, increase or decrease accordingly. Contributions paid to and distributions received from equity method investees are recorded as additions or reductions, respectively, to the respective investment balance. The Company also holds exchange memberships and investments in equity securities of certain exchanges , as required to qualify as a clearing member, and strategic investments in corporate stock that do not qualify for equity method accounting. Such investments, $34 million as of December 31, 201 5 ( $31 million as of December 31, 201 4 ), 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, and are also included in other assets in the consolidated statements of financial condition. Dividends received from cost basis investments are included in other income in the consolidated statements of comprehensive income when such dividends are received. A judgmental aspect of accounting for investments is evaluating whether an other ‑than ‑temporary decline in the value of an investment has occurred. The evaluation of an other ‑than ‑temporary impairment is dependent on specific quantitative and qualitative factors and circumstances surrounding an investment, including recurring operating losses, credit defaults and subsequent rounds of financing. The Company’s equity investments do not have readily determinable market values. All investments are reviewed for changes in circumstances or occurrence of events that suggest the Company’s investment may not be recoverable. If an unrealized loss on any investment is considered to be other ‑than ‑temporary, the loss is recognized in the period the determination is made . Property , Equipment and Intangible Assets Property, equipment and intangible assets, which are included in other assets in the consolidated statements of financial condition, consist of leasehold improvements, computer equipment, software developed for the Company’s internal use, office furniture, equipment and acquired technology . Property and equipment are recorded at historical cost, less accumulated depreciation and amortization. Additions and improvements that extend the lives of assets are capitalized, while expenditures for repairs and maintenance are expensed as incurred. Depreciation and amortization are computed using the straight ‑line method. Equipment is depreciated over the estimated useful lives of the assets, while leasehold improvements are amortized over the lesser of the estimated economic useful life of the asset or the term of the lease. Computer equipment is depreciated over three to five years and office furniture and equipment are depreciated over five to seven years. Qualifying costs for internally developed software are capitalized and amortized over the expected useful life of the developed software, not to exceed three years. Intangible assets with a finite life are amortized on a straight line basis over their estimated useful lives of three years, and tested for recoverability whenever events indicate that the carrying amounts may not be recoverable. Comprehensive Income and Foreign Currency Translation The Company’s operating results are reported in the consolidated statements of comprehensive income pursuant to FASB ASC Topic 220, “ Comprehensive Income. ” Comprehensive income consists of two components: net income and other comprehensive income (“OCI”). The Company’s OCI is comprised of gains and losses resulting from translating foreign currency financial statements of non-U.S. subsidiaries , net of related income taxes, where applicable. In general, the practice and intention of the Company is to reinvest the earnings of its non ‑U.S. subsidiaries in those operations, therefore tax is usually not accrued. The Company’s non ‑U.S. domiciled subsidiaries have a functional currency that is other than the U.S. dollar. Such subsidiaries’ assets and liabilities are translated into U.S. dollars at period ‑end exchange rates, and revenues and expenses are translated at average exchange rates prevailing during the period. Adjustments that result from translating amounts from a subsidiary’s functional currency to the U.S. dollar (as described above) are reported net of tax, where applicable, in accumulated OCI in the consolidated statements of financial condition. During 2013, the Company derecognized accumulated OCI of a $ 5 million loss attributable to its Brazilian subsidiary, IB Brasil Participações Ltda, which was liquidated during the year , and recognized a foreign currency translation loss, before taxes, which is included in other income in the consolidated statements of comprehensive income . Revenue Recognition Trading Gains Trading gains and losses are recorded on trade date and are reported on a net basis. Trading gains and losses are comprised of changes in the fair value of financial instruments owned, at fair value and financial instruments sold, but not yet purchased, at fair value (i.e., unrealized gains and losses) and realized gains and losses related to the Company’s market making business segment. Included in trading gains are net gains and losses on stocks, U.S. and foreign government securities, corporate and municipal bonds, options, futures, foreign exchange and other derivative instruments. Dividends are integral to the valuation of stocks and interest is integral to the valuation of fixed income instruments. Accordingly, both dividends and interest income and expense attributable to financial instruments owned, at fair value and financial instruments sold, but not yet purchased, at fair value are reported on a net basis in trading gains in the consolidated statements of comprehensive income. Commissions and Execution Fees Commissions earned for executing and clearing transactions are accrued on a trade date basis and are reported as commissions and execution fees in the consolidated statements of comprehensive income. Interest Income and Expense The Company earns interest income and incurs interest expense primarily in connection with its electronic brokerage customer business and its securities lending activities, which are recorded on the accrual basis and are included in interest income and interest expense, respectively, in the consolidated statements of comprehensive income. Foreign Currency Gains and Losses Currency translation refers to the gains and losses resulting from foreign currency transactions. Foreign currency translation gains and losses related to the Company’s currency diversification strategy are included in other income in the consolidated statements of comprehensive income. Foreign currency translation gains and losses related to the market making core-business activities are included in trading gains in the consolidated statements of comprehensive income. Electronic brokerage foreign currency translation gains and losses, arising from currency swap transactions, are included in interest income in the consolidated statements of comprehensive income. Income Taxes The Company accounts for income taxes in accordance with FASB ASC Topic 740, “ Income Taxes” (“ASC Topic 740”) . The Company’s income tax expense, deferred tax assets and liabilities, and reserves for unrecognized tax benefits are based on enacted tax laws (see Note 12) and reflect management’s best assessment of estimated future taxes to be paid. The Company is subject to income taxes in both the U.S. and numerous foreign jurisdictions. Determining income tax expense requires significant judgments and estimates. The Company recognizes interest related to income tax matters as interest income or interest expense and penalties related to income tax matters as income tax expense in the consolidated statements of comprehensive income. Deferred income tax assets and liabilities arise from temporary differences between the tax and financial statements recognition of the underlying assets and liabilities. In evaluating the ability to recover deferred tax assets within the jurisdictions from which they arise, the Company considers all available positive and negative evidence, including scheduled reversals of deferred tax liabilities, projected future taxable income, tax ‑planning strategies, and results of recent operations. In projecting future taxable income, historical results are adjusted for changes in accounting policies and incorporate assumptions including the amount of future state, federal and foreign pre-tax operating income, the reversal of temporary differences, and the implementation of feasible and prudent tax ‑planning strategies. These assumptions require significant judgment about the forecasts of future taxable income and are consistent with the plans and estimates the Company is using to manage the underlying businesses. In evaluating the objective evidence that historical results provide, three years of cumulative operating income (loss) are considered. Deferred income taxes have not been provided for U.S. tax liabilities or for additional foreign taxes on the unremitted earnings of foreign subsidiaries that have been indefinitely reinvested. The calculation of the Company’s tax liabilities involves dealing with uncertainties in the application of complex tax laws and regulations in a multitude of jurisdictions across the Company’s global operations. Changes in tax laws and rates could also affect recorded deferred tax assets and liabilities in the future. The Company is not aware of any such changes that would have a material effect on the Company’s results of operations, cash flows, or financial position. The Company recognizes that a tax benefit from an uncertain tax position only when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, on the basis of the technical merits. A tax position that meets this standard is measured at the largest amount of benefit that will more likely than not be realized on settlement. The Company records tax liabilities in accordance with ASC Topic 740 and adjusts these liabilities when management’s judgment changes as a result of the evaluation of new information not previously available. Because of the complexity of some of these uncertainties, the ultimate resolution may result in payments that are different from the current estimates of these tax liabilities. These differences will be reflected as increases or decreases to income tax expense in the period in which new information becomes available. Recently Issued Accounting Pronouncements Following is a summary of recently issued FASB Accounting Standards Updates (“ASUs”) that have affected or may affect the Company’s consolidated financial statements : Affects Status ASU 2015-02 Consolidation (Topic 810): Amendments to the Consolidation Analysis. Effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2015. ASU 2015-08 Business Combinations (Topic 805): Pushdown Accounting. Amendments to SEC Paragraphs Pursuant to Staff Accounting Bulletin No. 115. Measurement of Certain Transfers Between Entities Under Common Control in the Separate Financial Statements of Each Entity. The amendments are effective immediately. ASU 2015-14 Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date. Effective for annual reporting periods beginning after December 15, 2017. ASU 2015-16 Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments. Effective for fiscal years beginning after December 15, 2015. ASU 2016-01 Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. Effective for fiscal years beginning after December 15, 2017. Adoption of those ASUs that became effective during 2015 and 2016 , prior to the issuance of the Company’s consolidated financial statements, did not have a material effect on th e se financial statements.

Trading Activities And Related

Trading Activities And Related Risks	12 Months Ended
	Dec. 31, 2015
Trading Activities And Related Risks [Abstract]
Trading Activities And Related Risks	3. Trading Activities and Related Risks The Company’s trading activities include providing securities market making and brokerage services. Trading activities expose the Company to market and credit risks. These risks are managed in accordance with established risk management policies and procedures. To accomplish this, management has established a risk management process that includes: • a regular review of the risk management process by executive management as part of its oversight role; • defined risk management policies and procedures supported by a rigorous analytic framework; and • articulated risk tolerance levels as defined by executive management that are regularly reviewed to ensure that the Company’s risk ‑taking is consistent with its business strategy, capital structure, and current and anticipated market conditions. Market Risk The Company is exposed to various market risks. Exposures to market risks arise from equity price risk, foreign currency exchange rate fluctuations and changes in interest rates. The Company seeks to mitigate market risk associated with trading inventories by employing hedging strategies that correlate rate, price and spread movements of trading inventories and related financing and hedging activities. The Company uses a combination of cash instruments and exchange traded derivatives to hedge its market exposures. The Company does not apply hedge accounting. The following discussion describes the types of market risk faced: Equity Price Risk Equity price risk arises from the possibility that equity security prices will fluctuate, affecting the value of equity securities and other instruments that derive their value from a particular stock, a defined basket of stocks, or a stock index. The Company is subject to equity price risk primarily in financial instruments held. The Company attempts to limit such risks by continuously reevaluating prices and by diversifying its portfolio across many different options, futures and underlying securities and avoiding concentrations of positions based on the same underlying security. Currency Risk Currency risk arises from the possibility that fluctuations in foreign exchange rates will impact the value of financial instruments. The Company manages this risk using spot (i.e., cash) currency transactions, currency futures contracts and currency forward contracts. As a global market maker trading on exchanges around the world in multiple currencies, the Company is exposed to foreign currency risk. The Company actively manages its currency exposure using hedging strategies that are based on a defined basket of 16 currencies internally referred to as the “GLOBAL.” These strategies minimize the fluctuation of the Company’s net worth as expressed in GLOBALs, thereby diversifying its risk in alignment with these global currencies, weighted by the Company’s view of their importance. As the Company’s financial results are reported in U.S. dollars, the change in the value of the GLOBAL as expressed in U.S. dollars affects the Company’s earnings. The impact of this currency diversification strategy in the Company’s earnings is included in other income in the consolidated statements of comprehensive income. Interest Rate Risk Interest rate risk arises from the possibility that changes in interest rates will affect the value of financial instruments. The Company is exposed to interest rate risk on cash and margin balances, positions carried in equity and fixed income securities, options, and futures and on its borrowings. These risks are managed through investment policies and by entering into interest rate futures contracts. Credit Risk The Company is exposed to risk of loss if an individual, counterparty or issuer fails to perform its obligations under contractual terms (“default risk”). Both cash instruments and derivatives expose the Company to default risk. The Company has established policies and procedures for mitigating credit risk on principal transactions, including reviewing and establishing limits for credit exposure, maintaining collateral, and continually assessing the creditworthiness of counterparties. The Company’s credit risk is limited in that substantially all of the contracts entered into are settled directly at securities and commodities clearing houses and a small portion is settled through member firms and banks with substantial financial and operational resources. The Company seeks to control the risks associated with its customer margin activities by requiring customers to maintain collateral in compliance with regulatory and internal guidelines. In the normal course of business, the Company executes, settles, and finances various customer securities transactions. Execution of these transactions includes the purchase and sale of securities which exposes the Company to default risk arising from the potential that customers or counterparties may fail to satisfy their obligations. In these situations, the Company may be required to purchase or sell financial instruments at unfavorable market prices to satisfy obligations to customers or counterparties. Liabilities to other brokers and dealers related to unsettled transactions (i.e., securities fails to receive) are recorded at the amount for which the securities were purchased, and are paid upon receipt of the securities from other brokers or dealers. In the case of aged securities fails to receive, the Company may purchase the underlying security in the market and seek reimbursement for any losses from the counterparty. For cash management purposes, the Company enters into short ‑term securities purchased under agreements to resell and securities sold under agreements to repurchase transactions (“repos”) in addition to securities borrowing and lending arrangements, all of which may result in credit exposure in the event the counterparty to a transaction is unable to fulfill its contractual obligations. Repos are collateralized by securities with a market value in excess of the obligation under the contract. Similarly, securities lending agreements are collateralized by deposits of cash or securities. The Company attempts to minimize credit risk associated with these activities by monitoring collateral values on a daily basis and requiring additional collateral to be deposited with or returned to the Company as permitted under contractual provisions. Concentrations of Credit Risk The Company’s exposure to credit risk associated with its trading and other activities is measured on an individual counterparty basis, as well as by groups of counterparties that share similar attributes. Concentrations of credit risk can be affected by changes in political, industry, or economic factors. To reduce the potential for risk concentration, credit limits are established and exposure is monitored in light of changing counterparty and market conditions. As of December 31, 2015, the Company did not have any material concentrations of credit risk outside the ordinary course of business. Off ‑Balance Sheet Risks The Company may be exposed to a risk of loss not reflected in the consolidated financial statements to settle futures and certain over ‑the ‑counter contracts at contracted prices, which may require repurchase or sale of the underlying products in the market at prevailing prices. Accordingly, these transactions result in off ‑balance sheet risk as the Company’s cost to liquidate such contracts may exceed the amounts reported in the Company’s consolidated statements of financial condition.

Equity And Earnings Per Share

Equity And Earnings Per Share	12 Months Ended
	Dec. 31, 2015
Equity And Earnings Per Share [Abstract]
Equity And Earnings Per Share	4. Equity and Earnings Per Share In connection with IBG, Inc.’s initial public offering of Class A common stock (“IPO”) in May 2007, it purchased 10.0% of the membership interests in IBG LLC from IBG Holdings LLC (“Holdings”), became the sole managing member of IBG LLC and began to consolidate IBG LLC’s financial results into its financial statements. Holdings owns all of IBG, Inc.’s Class B common stock, which has voting rights in proportion to its ownership interests in IBG LLC, approximately 84.3% as of December 31, 2015 . The consolidated financial statements reflect the results of operations and financial position of IBG, Inc., including consolidation of its investment in IBG LLC and its subsidiaries. The noncontrolling interests in IBG LLC attributable to Holdings are reported as a component of total equity in the consolidated statements of financial condition, as described below. Recapitalization and Post ‑IPO Capital Structure Immediately prior to and immediately following the consummation of the IPO, IBG, Inc., Holdings, IBG LLC and the members of IBG LLC consummated a series of transactions collectively referred to herein as the “Recapitalization.” In connection with the Recapitalization, IBG, Inc., Holdings and the historical members of IBG LLC entered into an exchange agreement, dated as of May 3, 2007 (the “Exchange Agreement”), pursuant to which the historical members of IBG LLC received membership interests in Holdings in exchange for their membership interests in IBG LLC. Additionally, IBG, Inc. became the sole managing member of IBG LLC. In connection with the consummation of the IPO, Holdings used the net proceeds to redeem 10.0% of members’ interests in Holdings in proportion to their interests. Immediately following the Recapitalization and IPO, Holdings owned approximately 90% of IBG LLC and 100% of IBG, Inc.’s Class B common stock, which has voting power in IBG, Inc. in proportion to Holdings’ ownership of IBG LLC. Since consummation of the IPO and Recapitalization, IBG, Inc.’s equity capital structure has been comprised of Class A and Class B common stock. All shares of common stock have a par value of $0.01 per share and have identical rights to earnings and dividends and in liquidation. As described previously in this Note 4, Class B common stock has voting power in IBG, Inc. proportionate to the extent of Holdings’ and IBG, Inc.’s respective ownership of IBG LLC. As of December 31, 2015 and December 31, 2014 , 1,000,000,000 shares of Class A common stock were authorized, of which 64,121,150 and 58,612,245 shares have been issued; and 63,985,335 and 58,473,186 shares were outstanding, respectively. Class B common stock is comprised of 100 authorized shares, of which 100 shares were issued and outstanding as of December 31, 2015 and December 31, 2014 , respectively. In addition, 10,000 shares of preferred stock have been authorized, of which no shares are issued or outstanding as of December 31, 2015 and December 31, 2014 , respectively. As a result of a federal income tax election made by IBG LLC applicable to the acquisition of IBG LLC member interests by IBG, Inc., the income tax basis of the assets of IBG LLC acquired by IBG, Inc. have been adjusted based on the amount paid for such interests. Deferred tax assets were recorded as of the IPO date and in connection with subsequent redemptions of Holdings member interests in exchange for common stock. These deferred tax assets are included in other assets in the Company’s consolidated statements of financial condition and are being amortized as additional deferred income tax expense over 15 years from the IPO date and from the additional redemption dates, respectively, as allowable under current tax law. As of December 31, 2015 and December 31, 2014 , the unamortized balance of these deferred tax assets was $288 million and $279 million, respectively. IBG, Inc. also entered into an agreement (the “Tax Receivable Agreement”) with Holdings to pay Holdings (for the benefit of the former members of IBG LLC) 85% of the tax savings that IBG, Inc. actually realizes as the result of tax basis increases. These payables to Holdings are reported as payable to affiliate in the Company’s consolidated statements of financial condition. The remaining 15% is accounted for as a permanent increase to additional paid ‑in capital in the Company’s consolidated statements of financial condition. The cumulative amounts of deferred tax assets, payables to Holdings and additional paid ‑in capital arising from stock offerings from the date of the IPO through December 31, 2015 were $460 million, $391 million and $69 million, respectively. Amounts payable under the Tax Receivable Agreement are payable to Holdings annually following the filing of IBG, Inc.’s federal income tax return. The Company has paid Holdings a cumulative total of $99 million through December 31, 2015 pursuant to the terms of the Tax Receivable Agreement. The Exchange Agreement, as amended June 6, 2012, provides for future redemptions of member interests and for the purchase of member interests in IBG LLC by IBG, Inc. from Holdings, which could result in IBG, Inc. acquiring the remaining member interests in IBG LLC that it does not own. On an annual basis, members of Holdings are able to request redemption of their interests. At the time of IBG, Inc.’s IPO in 2007, three hundred sixty (360) million shares of authorized common stock were reserved for future sales and redemptions. From 2008 through 2010, Holdings redeemed 5,013,259 IBG LLC interests with a total value of $114 million, which redemptions were funded using cash on hand at IBG LLC. Upon cash redemption these IBG LLC interests were retired. From 2011 through 2014, IBG, Inc. issued 8,025,517 shares of common stock directly to Holdings in exchange for an equivalent number of member interests in IBG LLC. In 2015 , the Company issued 3,021,778 shares of Class A common stock (with a fair value of $132 million) to Holdings in exchange for an equivalent number of member interests in IBG LLC. As a consequence of these redemption transactions, and distribution of shares to employees (see Note 1 1 ), IBG, Inc. ’ s interest in IBG LLC has increased to approximately 15.7% , with Holdings owning the remaining 84.3% as of December 31, 2015 . The redemptions also resulted in an increase in the Holdings interest held by Mr. Thomas Peterffy and his affiliates from approximately 84.6% at the IPO to approximately 88.7% as of December 31, 2015 . Earnings per Share Basic earnings per share is calculated utilizing net income available for common stockholders divided by the weighted average number of shares of Class A and Class B common stock outstanding for that period. Year-Ended December 31, 2015 2014 2013 (in millions, except for shares or per share amounts) Basic earnings per share Net income available for common stockholders $ 49 $ 45 $ 37 Weighted average shares of common stock outstanding Class A 61,042,971 56,492,281 49,742,328 Class B 100 100 100 61,043,071 56,492,381 49,742,428 Basic earnings per share $ 0.80 $ 0.79 $ 0.74 Diluted earnings per share are calculated utilizing the Company’s basic net income available for common stockholders divided by diluted weighted average shares outstanding with no adjustments to net income available to common stockholders for potentially dilutive common shares. Year-Ended December 31, 2015 2014 2013 (in millions, except for shares or per share amounts) Diluted earnings per share Net income available for common stockholders $ 49 $ 45 $ 37 Weighted average shares of common stock outstanding Class A Issued and outstanding 61,042,971 56,492,281 49,742,328 Potentially dilutive common shares Issuable pursuant to employee stock incentive plans 1,466,725 1,217,287 1,182,308 Class B 100 100 100 62,509,796 57,709,668 50,924,736 Diluted earnings per share $ 0.78 $ 0.77 $ 0.73 Member Distributions and Stockholder Dividends During the three years ended December 31, 2015 , 2014 and 2013 , IBG LLC made distributions totaling $267 million, $324 million and $163 million, respectively, to its members, of which IBG, Inc. ’ s proportionate share was $40 million, $45 million and $ 21 million, respectively. The Company paid quarterly cash dividends of $0.10 per share of c ommon s tock, totaling $25 million, $ 23 million and $20 million during 2015 , 2014 and 2013 , respectively. On January 19, 2016 , the Company declared a cash dividend of $0.10 per common share, payable on March 14, 2016 to stockholders of record as of March 1, 2016 .

Comprehensive Income

Comprehensive Income	12 Months Ended
	Dec. 31, 2015
Comprehensive Income Detail [Abstract]
Comprehensive Income	5. Comprehensive Income The following table presents comprehensive income and earnings per share on comprehensive income . Year-Ended December 31, 2015 2014 2013 (in millions, except for shares or per share amounts) Comprehensive income available for common stockholders $ 39 $ 30 $ 34 Earnings per share on comprehensive income Basic $ 0.64 $ 0.52 $ 0.69 Diluted $ 0.62 $ 0.51 $ 0.67 Weighted average common shares outstanding Basic 61,043,071 56,492,381 49,742,428 Diluted 62,509,796 57,709,668 50,924,736

Financial Assets And Financial

Financial Assets And Financial Liabilities	12 Months Ended
	Dec. 31, 2015
Financial Assets And Financial Liabilities [Abstract]
Financial Assets And Financial Liabilities	6. Financial Assets and Financial Liabilities Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis The following tables set forth, by level within the fair value hierarchy (see Note 2), financial assets and liabilities, measured at fair value on a recurring basis as of December 31, 2015 and December 31, 2014 . As required by ASC Topic 820, financial assets and financial liabilities are classified in their entirety based on the lowest level of input that is significant to the respective fair value measurement. As described in Note 2, the Company reclassified its other fair value investments of $44 million from other assets and $8 million from accounts payable, accrued expenses and other liabilities to financial instruments owned, at fair value and financial instruments sold, but not yet purchased, at fair value, respectively, as of December 31, 2014. Financial Assets At Fair Value as of December 31, 2015 Level 1 Level 2 Level 3 Total (in millions) Securities segregated for regulatory purposes $ 15,214 $ — $ — $ 15,214 Financial instruments owned Stocks 1,650 — — 1,650 Options 1,156 — — 1,156 Warrants and discount certificates 81 — — 81 U.S. and foreign government securities 527 — — 527 Corporate and municipal bonds — 3 — 3 Currency forward contracts — 3 — 3 Total financial instruments owned, at fair value 3,414 6 — 3,420 Total financial assets at fair value $ 18,628 $ 6 $ — $ 18,634 Financial Liabilities At Fair Value as of December 31, 2015 Level 1 Level 2 Level 3 Total (in millions) Financial instruments sold, but not yet purchased, at fair value Stocks $ 1,565 $ — $ — $ 1,565 Options 1,042 — — 1,042 Warrants and discount certificates 1 — — 1 Currency forward contracts — 9 — 9 Total financial instruments sold, but not yet purchased, at fair value 2,608 9 — 2,617 Total financial liabilities at fair value $ 2,608 $ 9 $ — $ 2,617 Financial Assets At Fair Value as of December 31, 2014 Level 1 Level 2 Level 3 Total (in millions) Securities segregated for regulatory purposes $ 6,681 $ — $ — $ 6,681 Financial instruments owned, at fair value Stocks 2,592 — — 2,592 Options 1,209 — — 1,209 Warrants and discount certificates 72 — — 72 U.S. and foreign government securities 98 — — 98 Corporate and municipal bonds — 3 3 Currency forward contracts — 4 — 4 Total financial instruments owned, at fair value 3,971 7 — 3,978 Total financial assets at fair value $ 10,652 $ 7 $ — $ 10,659 Financial Liabilities At Fair Value as of December 31, 2014 Level 1 Level 2 Level 3 Total (in millions) Financial instruments sold, but not yet purchased, at fair value Stocks $ 1,360 $ — $ 1 $ 1,361 Options 1,197 — — 1,197 Warrants and discount certificates 1 — — 1 Currency forward contracts — 10 — 10 Total financial instruments sold, but not yet purchased, at fair value 2,558 10 1 2,569 Total financial liabilities at fair value $ 2,558 $ 10 $ 1 $ 2,569 Transfers between Level 1 and Level 2 Transfers of financial assets and financial liabilities at fair value to or from Levels 1 and 2 arise where the market for a specific financial instrument has become active or inactive during the period. The fair values transferred are ascribed as if the financial assets or financial liabilities had been transferred as of the end of the period. During the year ended December 31, 2014, t he Company reclassified approximately $1 million of financial assets, at fair value from Level 1 to Level 2 of the fair value hierarchy. There were no transfers during the year between Level 1 and Level 2 for financial liabilities, at fair value. During the year ended December 31, 2015, there were no transfers between levels for financial assets and liabilities, at fair value. Level 3 Financial Assets and Financial Liabilities The Company’s Level 3 financial assets and financial liabilities were comprised of delisted securities reported within financial instruments sold, but not yet purchased, at fair value in the consolidated statements of financial condition. As of December 31, 2014 financial liabilities included $1 million of Level 3 securities which were transferred to Level 1 during 2015 as a result of the completion of a corporate action. Trading Gains from Market Making Transactions Trading gains and losses from market making transactions reported in the statements of comprehensive income, by major product type, are comprised of : Year-Ended December 31, 2015 2014 2013 (in millions) Equities $ 254 $ 247 $ 285 Fixed income 1 21 25 Foreign exchange 14 (7) 21 Total trading gains, net $ 269 $ 261 $ 331 These transactions are related to the Company’s financial instruments owned and financial instruments sold, but not yet purchased, at fair value and include both derivative and non ‑derivative financial instruments, including exchange traded options and futures. These gains and losses also include market making related dividend and fixed income trading related interest income and expense. The gains (losses) in the above table are not representative of the integrated trading strategies applied by the Company, which utilizes financial instruments across various product types. Gains and losses in one product type frequently offset gains and losses in other product types. Financial Assets and Liabilities Not Measured at Fair Value The following table represents the carrying value, fair value, and fair value hierarchy category of certain financial assets and liabilities that are not recorded at fair value in the Company's consolidated statements of financial condition. The following table excludes certain financial instruments such as equity investments and all non-financial assets and liabilities. December 31, 2015 Carrying Value Fair Value Level 1 Level 2 Level 3 (in millions) Financial assets, not measured at fair value Cash and cash equivalents $ 1,601 $ 1,601 $ 1,601 $ - $ - Cash and securities segregated for regulatory purposes 6,095 6,095 5,533 562 - Securities borrowed 3,924 3,924 - 3,924 - Securities purchased under agreements to resell 195 195 - 195 - Receivables from customer 17,050 17,050 - 17,050 Receivables from broker, dealers, and clearing organizations 692 692 - 692 - Interest receivable 63 63 - 63 - Other assets 28 31 - 31 - Total financial assets, not measured at fair value $ 29,648 $ 29,651 $ 7,134 $ 22,517 $ — Financial liabilities, not measured at fair value Securities loaned 2,894 2,894 - 2,894 - Payables to customer 37,084 37,084 - 37,084 - Payables to brokers, dealers and clearing organizations 423 423 - 423 - Interest payable 3 3 - 3 - Total financial liabilities, not measured at fair value $ 40,404 $ 40,404 $ — $ 40,404 $ — December 31, 2014 Carrying Value Fair Value Level 1 Level 2 Level 3 (in millions) Financial assets, not measured at fair value Cash and cash equivalents $ 1,269 $ 1,269 $ 1,269 $ - $ - Cash and securities segregated for regulatory purposes 8,723 8,723 4,849 3,874 - Securities borrowed 3,660 3,660 - 3,660 - Securities purchased under agreements to resell 386 386 - 386 - Receivables from customer 17,051 17,051 - 17,051 - Receivables from broker, dealers, and clearing organizations 1,131 1,131 - 1,131 - Interest receivable 37 37 - 37 - Other assets 30 55 - 55 - Total financial assets, not measured at fair value $ 32,287 $ 32,312 $ 6,118 $ 26,194 $ — Financial liabilities, not measured at fair value Short-term borrowings $ 34 $ 34 $ - $ 34 $ - Securities loaned 3,199 3,199 - 3,199 - Payables to customer 31,796 31,796 - 31,796 - Payables to brokers, dealers and clearing organizations 234 234 - 234 - Interest payable 4 4 - 4 - Total financial liabilities, not measured at fair value $ 35,267 $ 35,267 $ — $ 35,267 $ — Netting of Financial Assets and Financial Liabilities The Company does not net securities borrowed and securities loaned, and securities purchased under agreements to resell and securities sold under agreements to repurchase that do not meet the offsetting requirements prescribed in ASC Topic 210-20, which are presented on a gross basis in the consolidated statements of financial condition. In the tables below, the amounts of financial instruments that are not offset in the consolidated statements of financial condition, but could be netted against cash or financial instruments with specific counterparties under master netting agreements, according to the terms of the agreements, including clearing houses (exchange traded options, warrants and discount certificates) or over the counter currency forward contract counterparties, are presented to provide financial statement readers with the Company’s net payable or receivable with counterparties for these financial instruments. The following tables sets forth the netting of financial assets and of financial liabilities as of December 31, 2015 and December 31, 2014. December 31, 2015 Gross Amounts Net Amounts Amounts Not Offset Amounts Offset in the Presented in in the Consolidated of Financial Consolidated the Consolidated Statement of Assets and Statement of Statement of Financial Condition Liabilities Financial Financial Cash or Financial Recognized Condition Condition Instruments Net Amount (in millions) Offsetting of Financial Assets Securities segregated for regulatory purposes - purchased under agreements to resell $ 562 1 $ — $ 562 $ (562) $ — Securities borrowed 3,924 — 3,924 (3,816) 108 Securities purchased under agreements to resell 195 — 195 (195) — Financial Instruments owned, at fair value Options 1,156 — 1,156 (1,032) 124 Warrants and discount certificates 81 — 81 (1) 80 Currency forward contracts 3 — 3 — 3 Total $ 5,921 $ — $ 5,921 $ (5,606) $ 315 (in millions) Offsetting of Financial Liabilities Securities loaned $ 2,894 $ — $ 2,894 $ (2,773) $ 121 Financial instruments sold, but not yet purchased, at fair value Options 1,042 — 1,042 (1,032) 10 Warrants and discount certificates 1 — 1 (1) — Currency forward contracts 9 — 9 — 9 Total $ 3,946 $ — $ 3,946 $ (3,806) $ 140 December 31, 2014 Gross Amounts Net Amounts Amounts Not Offset Amounts Offset in the Presented in in the Consolidated of Financial Consolidated the Consolidated Statement of Assets and Statement of Statement of Financial Condition Liabilities Financial Financial Cash or Financial Recognized Condition Condition Instruments Net Amount (in millions) Offsetting of Financial Assets Securities segregated for regulatory purposes - purchased under agreements to resell $ 3,874 1 $ — $ 3,874 $ (3,874) $ — Securities borrowed 3,660 — 3,660 (3,564) 96 Securities purchased under agreements to resell 386 — 386 (386) — Financial Instruments owned, at fair value Options 1,209 — 1,209 (1,150) 59 Warrants and discount certificates 72 — 72 (1) 71 Currency forward contracts 4 — 4 — 4 Total $ 9,205 $ — $ 9,205 $ (8,975) $ 230 (in millions) Offsetting of Financial Liabilities Securities loaned $ 3,199 $ — $ 3,199 $ (3,183) $ 16 Financial instruments sold, but not yet purchased, at fair value Options 1,197 — 1,197 (1,150) 47 Warrants and discount certificates 1 — 1 (1) — Currency forward contracts 10 — 10 — 10 Total $ 4,407 $ — $ 4,407 $ (4,334) $ 73 (1) As of December 31, 2015 and December 31, 2014, the Company had $0.6 billion and $3.9 billion, respectively, of securities purchased under agreements to resell that were segregated to satisfy regulatory requirements. These securities are included in “Cash and securities - segregated for regulatory purposes” in the consolidated statements of financial condition. Secured Financing Transactions – Maturities and Collateral Pledged The following table presents gross obligations for securities loaned transactions by remaining contractual maturity and class of collateral pledged. December 31, 2015 Remaining Contractual Maturity Overnight Less than 30 – 90 Over 90 and Open 30 days days days Total (in millions) Securities Loaned Stocks $ 2,873 $ - $ - $ - $ 2,873 Corporate bonds 21 - - - 21 Total $ 2,894 $ - $ - $ - $ 2,894

Collateralized Transactions

Collateralized Transactions	12 Months Ended
	Dec. 31, 2015
Disclosure Collateralized Transactions [Abstract]
Collateralized Transactions	7. Collateralized Transactions The Company enters into securities borrowing and lending transactions and agreements to repurchase and resell securities to finance trading inventory, to obtain securities for settlement and to earn residual interest rate spreads. In addition, the Company’s customers pledge their securities owned to collateralize margin loans. Under these transactions, the Company either receives or provides collateral, including equity, corporate debt and U.S. government securities. Under many agreements, the Company is permitted to sell or repledge securities received as collateral and use these securities to secure securities purchased under agreements to resell, enter into securities lending transactions or deliver these securities to counterparties to cover short positions. The Company also engages in securities financing transactions with and for customers through margin lending. Customer receivables generated from margin lending activity are collateralized by customer ‑owned securities held by the Company. Customers’ required margin levels and established credit limits are monitored continuously by risk management staff using automated systems. Pursuant to the Company’s policy and as enforced by such systems, customers are required to deposit additional collateral or reduce positions, when necessary to avoid automatic liquidation of their positions. Margin loans are extended to customers on a demand basis and are not committed facilities. Factors considered in the acceptance or rejection of margin loans are the amount of the loan, the degree of leverage being employed in the customer account and an overall evaluation of the customer’s portfolio to ensure proper diversification or, in the case of concentrated positions, appropriate liquidity of the underlying collateral. Additionally, transactions relating to concentrated or restricted positions are limited or prohibited by raising the level of required margin collateral (to 100% in the extreme case). Underlying collateral for margin loans is evaluated with respect to the liquidity of the collateral positions, valuation of securities, volatility analysis and an evaluation of industry concentrations. Adherence to the Company’s collateral policies significantly limits the Company’s credit exposure to margin loans in the event of a customer’s default. Under margin lending agreements, the Company may request additional margin collateral from customers and may sell securities that have not been paid for or purchase securities sold but not delivered from customers, if necessary. As of December 31, 201 5 and December 31, 201 4 , approximately $17.0 billion and $17.1 billion, respectively, of customer margin loans were outstanding. The following table summarizes the amounts related to collateralized transactions as of December 31, 2015 and December 31, 2014 : December 31, 2015 December 31, 2014 Permitted Sold or Permitted Sold or to Repledge Repledged to Repledge Repledged (in millions) Securities lending transactions $ 12,131 $ 2,229 $ 10,907 $ 2,366 Securities purchased under agreements to resell transactions (1) 757 743 4,260 4,260 Customer margin assets 14,905 6,279 14,933 5,740 $ 27,793 $ 9,251 $ 30,100 $ 12,366 (1) As of December 31, 2015 , $0.6 billion or 76% ( as of December 31, 2014 , $3.9 billion or 91% ) of securities acquired through agreements to resell that are shown as repledged have been deposited in a separate bank account for the exclusive benefit of customer s in accordance with SEC Rule 15c3-3. In the normal course of business, the Company pledges qualified securities with clearing organizations to satisfy daily margin and clearing fund requirements. As of December 31, 2015 and December 31, 2014, the majority of the Company’s U.S. and foreign government securities owned were pledged to clearing organizations. Financial instruments owned and pledged as collateral, including amounts pledged to affiliates, where the counterparty has the right to repledge, as of December 31, 2015 and December 31, 2014 are presented in the following table : December 31, December 31, 2015 2014 (in millions) Stocks $ 915 $ 1,860 U.S. and foreign government securities 518 76 $ 1,433 $ 1,936

Short-Term Borrowings

Short-Term Borrowings	12 Months Ended
	Dec. 31, 2015
Short-Term Borrowings [Abstract]
Short-Term Borrowings	8. Short ‑Term Borrowings Short-term borrowings consist primarily of collateralized borrowing facilities with clearing banks in multiple currencies that bear interest at variable overnight rates based on interbank funds rates prevailing in the respective currencies. In addition, the Company has available secured and unsecured overnight bank loan facilities. All short-term borrowings outstanding as of December 31, 2015 and 2014 were either repaid on the next business day or rolled forward and, accordingly, their carrying values approximated fair values . As of December 31, 2015 and 2014 , short ‑term borrowings consisted of: December 31, 2015 December 31, 2014 Weighted Weighted Average Average Principal Rates Principal Rates (in millions) (in millions) Overnight borrowing facilities $ - 0.51% $ 34 0.50% $ - $ 34 Interest expense on short term borrowings for each of the three years ended December 31, 201 5 , 201 4 and 201 3 was $0 million , $1 million and $1 million , respectively.

Senior Secured Revolving Credit

Senior Secured Revolving Credit Facility	12 Months Ended
	Dec. 31, 2015
Senior Secured Revolving Credit Facility [Abstract]
Senior Secured Revolving Credit Facility	9. Senior Secured Revolving Credit Facility On May 17, 2012, IBG LLC entered into a $100 million three ‑year senior secured revolving credit facility with Bank of America, N.A. as administrative agent and Citibank, N.A., as syndication agent. This credit facility replaced a similar two ‑year facility that expired on May 18, 2012. On August 8, 2014 IBG LLC elected to terminate this credit facility.

Other Income

Other Income	12 Months Ended
	Dec. 31, 2015
Other Income [Abstract]
Other Income	1 0 . Other Income The components of other income for the three years ended December 31, 2015 , 2014 and 2013 were: Year-Ended December 31, 2015 2014 2013 (in millions) Payments for order flow $ 17 $ 25 $ 26 Market data fees 30 24 35 Account activity fees 16 14 15 Risk exposure fees 21 6 — Gains (losses) on financial instruments, at fair value and other investments, net (18) (5) (2) Gains (losses) from currency diversification strategy, net (206) (185) (91) Other, net 18 10 8 $ (122) $ (111) $ (9) Payments for order flow are earned from various options exchanges based upon options trading volume originated by the Operating Companies. Market data fees are charged to customers based upon market data services provided and are largely offset by the related cost to obtain the underlying market data from third party vendors. Risk exposure fees are earned from a small minority of customers’ accounts with positions on which market risk exceeds certain thresholds . Gains and losses on financial instruments, at fair value and other investments include realized and unrealized gains and losses on financial instruments that are not held for the Company’s market making operations or from securities that are subject to restrictions, and the Company’s interests in the earnings of equity method investees and dividends received on cost ‑basis investments.

Employee Incentive Plans

Employee Incentive Plans	12 Months Ended
	Dec. 31, 2015
Employee Incentive Plans [Abstract]
Employee Incentive Plans	1 1 . Employee Incentive Plans Defined Contribution Plan The Company offers substantially all employees of U.S.-based Operating Companies who have met minimum service requirements the opportunity to participate in defined contribution retirement plans qualifying under the provisions of Section 401(k) of the Internal Revenue Code. The general purpose of this plan is to provide employees with an incentive to make regular savings in order to provide additional financial security during retirement. This plan provides for the Company to match 50% of the employees’ pre-tax contribution, up to a maximum of 10% of eligible earnings. The employee is vested in the matching contribution incrementally over six years. Included in employee compensation and benefits expenses in the consolidated statements of comprehensive income were $3 million of plan contributions for the three years ended December 31, 2015, 2014 and 2013 , respectively. Return on Investment Dollar Units (“ROI Dollar Units”) From 1998 through January 1, 2006, IBG LLC granted all non ‑member employees ROI Dollar Units, which are redeemable under the amended provisions of the plan, and in accordance with regulations issued by the Internal Revenue Service (Section 409A of the Internal Revenue Code). Upon redemption, the grantee is entitled to accumulated earnings on the face value of the certificate, but not the actual face value. For grants made in 1998 and 1999, grantees may redeem the ROI Dollar Units after vesting on the fifth anniversary of the date of their grant and prior to the tenth anniversary of the date of their grant. For grants made between January 1, 2000 and January 1, 2005, grantees must elect to redeem the ROI Dollar Units upon the fifth, seventh or tenth anniversary date. These ROI Dollar Units have vested at the fifth anniversary of the date of their grant and will continue to accumulate earnings until the elected redemption date. For grants made on or after January 1, 2006, all ROI Dollar Units vested on the fifth anniversary date of their grant and were or will be automatically redeemed. Subsequent to the IPO, no additional ROI Dollar Units have been or will be granted, and non ‑ cash compensation to employees will consist primarily of grants of shares of restricted common stock as described below under “2007 Stock Incentive Plan.” During the second quarter of 2015, this plan was terminated as the Company fully paid its remaining obligation to employees. Therefore a s of December 31, 2015 , the Company had no payables to employees for ROI Dollar Units . As of December 31, 2014 , payable to employees for ROI Dollar Units w as $3 million which is included in accounts payable, accrued expenses and other liabilities in the consolidated statements of financial condition. 2007 ROI Unit Stock Plan In connection with the IPO, the Company adopted the IBG , Inc. 2007 ROI Unit Stock Plan (“ ROI Unit Stock Plan”). Under this plan, certain employees of IBG LLC who held ROI Dollar Units, at the employee’s option, elected to invest their ROI Dollar Unit accumulated earnings as of December 31, 2006 in shares of restricted common stock. An aggregate of 1,271,009 shares of restricted common stock (consisting of 1,250,000 shares issued under the ROI Unit Stock Plan and 21,009 shares under the 2007 Stock Incentive Plan, as described below), with a fair value at the date of grant of $38 million were issued to IBG LLC and held as treasury stock, to be distributed to employees in accordance with the following schedule and subject to the conditions below: • 10% on the date of the IPO (or on the first anniversary of the IPO, in the case of U.S. ROI Unit holders who made the above-referenced elections after December 31, 2006); and • an additional 15% on each of the first six anniversaries of the date of the IPO, assuming continued employment with the Company and compliance with other applicable covenants. Of the fair value at the date of grant, $ 18 million represented the accumulated ROI Dollar Unit value elected to be invested by employees in restricted common stock and such amount was accrued for as of December 31, 2006. The remainder was being ratably accrued as compensation expense by the Company from the date of the IPO over the requisite service period represented by the aforementioned distribution schedule. As of December 31, 201 5 , the Company has 6,370 shares of common stock remaining to be distributed to former employees under the ROI Unit Stock Plan. 2007 Stock Incentive Plan Under the Company’s 2007 Stock Incentive Plan (the “Stock Incentive Plan”), up to 30 million shares of the Company’s common stock may be granted and issued to directors, officers, employees, contractors and consultants of the Company. The purpose of the Stock Incentive Plan is to promote the Company’s long ‑term financial success by attracting, retaining and rewarding eligible participants. As a result of the Company’s organizational structure, a description of which can be found in “Business – Our Organizational Structure” in Part I Item 1 of this annual Report Form 10 - K, there is no dilutive effect upon ownership of common stockholders of issuing shares under the Stock Incentive Plan. The issuances do not dilute the book value of the ownership of common stockholders since the restricted stock units are granted at market value , and upon their vesting and the related issuance of shares of c ommon stock, the ownership of IBG, Inc. in IBG LLC, increases proportionately to the shares issued. As a result of such proportionate increase in share ownership, the dilution upon issuance of common stock is borne by IBG LLC’s majority member (i.e., noncontrolling interest), Holdings, and not by IBG, Inc. or its common stockholders . Additionally, dilution of earnings that may take place after issuance of common stock is reflected in EPS reported in the Company’s financial statements. The EPS dilution can be neither estimated nor projected, but historically it has not been material. The Stock Incentive Plan is administered by the Compensation Committee of the Company’s Board of Directors. The Compensation Committee has discretionary authority to determine the eligibility to participate in the Stock Incentive Plan and establishes the terms and conditions of the stock awards, including the number of awards granted to each participant and all other terms and conditions applicable to such awards in individual grant agreements. Awards are expected to be made primarily through grants of restricted common stock. Stock Incentive Plan awards are subject to issuance over time and may be forfeited upon the participant ’s termination of employment or violation of certain applicable covenants prior to issuance, unless determined otherwise by the Compensation Committee. The Stock Incentive Plan provides that, upon a change in control, the Compensation Committee may, at its discretion, fully vest any granted but not yet earned awards under the Stock Incentive Plan, or provide that any such granted but not yet earned awards will be honored or assumed, or new rights substituted by the new employer on a substantially similar basis and on terms and conditions substantially comparable to those of the Stock Incentive Plan. The Company expect s to continue to grant awards on or about December 31 of each year to eligible participants as part of an overall plan of equity compensation. Shares of common stock vest, and become distributable to participants in accordance with the following schedule: • 10% on the first vesting date, which is on or about May 9 of each year; and • an additional 15% on each of the following six anniversaries of the first vesting, assuming continued employment with the Company and compliance with non-competition and other applicable covenants. Awards granted to external directors vest, and are distributed, over a five ‑year period (20% per year) commencing one year after the date of grant. A total of 22,996 shares have been granted to the external directors cumulatively since the plan inception . Stock Incentive Plan share grants (excluding 21,009 shares issued pursuant to the ROI Unit Stock Plan described above) and the related fair values since the plan inception are presented in the table below: Fair Value at Date of Grant Shares ($ millions) Prior periods (since inception) 17,284,454 $ 302 December 31, 2013 1,894,046 46 December 31, 2014 1,709,968 49 December 31, 2015 1,199,079 52 22,087,547 $ 449 Estimated future grants under the Stock Incentive Plan are accrued for ratably during each year (see Note 2). In accordance with the vesting schedule, outstanding awards vest and are distributed to participants yearly on or about May 9 of each year . At the end of each year, there are no vested awards that remain undistributed. Compensation expense related to the Stock Incentive Plan recognized in the consolidated statements of comprehensive income was $50 million, $41 million and $41 million for the three years ended December 31, 201 5 , 201 4 and 201 3 , respectively. Estimated future compensation costs for unvested awards, net of forfeiture credits, as of December 31, 201 5 are $37 million. The following summarizes the Stock Incentive Plan and ROI Unit Stock Plan activities for the three year period from January 1, 201 3 through December 31, 201 5 : Intrinsic Value of SIP Shares Stock which Vested Incentive Plan and were ROI Unit ("SIP") Distributed Stock Plan Shares ($ millions) (2) (Shares) Balance, December 31, 2012 12,402,482 169,289 Granted 1,894,046 — Forfeited (334,111) (6,423) Distributed (2,315,300) $ 36 (162,866) Balance, December 31, 2013 11,647,117 — Granted 1,709,968 — Forfeited (1) (535,085) 15,518 Distributed (2,445,200) $ 56 (5,904) Balance, December 31, 2014 10,376,800 9,614 Granted 1,199,079 — Forfeited (163,221) — Distributed (2,487,127) $ 86 (3,244) Balance, December 31, 2015 8,925,531 6,370 (1) ROI Unit Stock Plan number of forfeited shares related to prior years was adjusted by 15,518 shares during the period. (2) Intrinsic value of SIP shares distributed represents the compensation value reported to the participants. Awards granted under the stock plans are subject to forfeiture in the event a participant ceases employment with the Company. The stock plans provide that participants who discontinue employment with the Company without cause and continue to meet the terms of the plans’ post ‑employment provisions will forfeit 50% of unvested previously granted awards unless the participant is over the age of 59, in which case the participant would be eligible to receive 100% of unvested awards previously granted. Distributions of remaining awards granted on or before January 1, 2009 to former participants will occur within 90 days of the anniversary of the termination of employment date over a five (5) year vesting schedule, 12.5% in each of the first four years and 50% in the fifth year. Distributions of remaining awards granted on or after January 1, 2010 to former participants will occur over the remaining vesting schedule applicable to each grant. Through December 31, 201 5 , a total of 306,668 shares have been distributed under these post ‑employment provisions. These distributions are included in the table above.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Taxes [Abstract]
Income Taxes	12 . Income Taxes Income tax expense for the three years ended December 31, 2015 , 2014 and 2013 differs from the U.S. federal statutory rate primarily due to the taxation treatment of income attributable to noncontrolling interests in IBG LLC. These noncontrolling interests are subject to U.S. taxation as partnerships. Accordingly, the income attributable to these noncontrolling interests is reported in the consolidated statements of comprehensive income, but the related U.S. income tax expense attributable to these noncontrolling interests is not reported by the Company as it is the obligation of the individual partners. Income tax expense is also affected by the differing effective tax rates in foreign, state and local jurisdictions where certain of the Company’s subsidiaries are subject to corporate taxation. Deferred income taxes arise primarily due to the amortization of the deferred tax assets recognized in connection with the common stock offerings (see Note 4), differences in the valuation of financial assets and liabilities, and for other temporary differences arising from the deductibility of compensation and depreciation expenses in different time periods for book and income tax return purposes. For the three years ended December 31, 201 5 , 201 4 and 201 3 , the provision for income taxes consisted of: Year-Ended December 31, 2015 2014 2013 (in millions) Current Federal $ 4 $ 1 $ (1) State and local — — — Foreign 24 28 23 Total current 28 29 22 Deferred Federal 14 21 17 State and local — — — Foreign 1 (3) (6) Total deferred 15 18 11 $ 43 $ 47 $ 33 A reconciliation of the statutory U.S. Federal income tax rate of 35% to the Company ’ s effective tax rate for the three years ending December 31, 2015 , 2014 and 2013 is set forth below: Year-Ended December 31, 2015 2014 2013 U.S. Statutory Tax Rate 35.0% 35.0% 35.0% Less: rate attributable to noncontrolling interests (28.2%) (28.6%) (29.5%) State, local and foreign taxes, net of federal benefit 2.6% 2.9% 2.0% 9.4% 9.3% 7.5% Significant components of the Company ’ s deferred tax assets and liabilities, which are reported in other assets and in other liabilities and accrued expenses, respectively, in the consolidated statements of financial condition, as of December 31, 2015, 2014 and 2013 were as follows: December 31, 2015 2014 2013 (in millions) Deferred tax assets Arising from the acquisition of interests in IBG LLC $ 288 $ 279 $ 295 Deferred compensation 5 6 8 Other 18 8 3 Total deferred tax assets 311 293 306 Deferred tax liabilities Foreign, primarily THE 3 3 8 Other comprehensive income — — — Other — — — Total deferred tax liabilities 3 3 8 Net deferred tax assets $ 308 $ 290 $ 298 As of and for the years ended December 31, 2015 and 2014 , the Company had no unrecognized tax and no valuation allowances on deferred tax assets were required. The Company is subject to taxation in the U.S. and various states and foreign jurisdictions. As of December 31, 2015, the Company is no longer subject to U.S. Federal and State income tax examinations for tax years prior to 2010, and to non-U.S. income tax examinations for tax years prior to 2006. As of December 31, 2015 , accumulated earnings held by non ‑U.S. subsidiaries totaled $1.0 billion ( as of December 31, 2014 $1.0 billion ). Of this amount, approximately $0.4 billion ( as of December 31, 2014 $0.4 billion ) is attributable to earnings of the Company ’ s foreign subsidiaries that are considered “ pass ‑through ” entities for U.S. income tax purposes. Since the Company accounts for U.S. income taxes on these earnings on a current basis, no additional U.S. tax consequences would result from the repatriation of these earnings other than that which would be due arising from currency fluctuations between the time the earnings are reported for U.S. tax purposes and when they are remitted. With respect to certain of these subsidiaries ’ accumulated earnings (approximately $0.3 billion and $0.3 billion as of December 31, 2015 and December 31, 2014 , respectively), repatriation would result in additional foreign taxes in the form of dividend withholding tax imposed on the recipient of the distribution or dividend distribution tax imposed on the payor of the distribution. The Company has not provided for its proportionate share of these additional foreign taxes as it does not intend to repatriate these earnings in the foreseeable future. For the same reason, the Company has not provided deferred U.S. tax on cumulative translation adjustments associated with these earnings. The remainder of the accumulated earnings are attributable to non ‑U.S. subsidiaries that are not considered “pass ‑through” entities for U.S. tax purposes. The Company’s U.S. tax basis in the stock of most of these entities exceeds its book basis. Establishing a deferred tax asset pursuant to ASC Topic 740 is not permitted as this difference will not reverse in the foreseeable future. In the instances in which the Company’s book basis were to exceed its U.S. tax basis, no deferred tax liability would be established as the Company would consider the earnings of those entities to be indefinitely reinvested.

Property, Equipment and Intangi

Property, Equipment and Intangible Assets	12 Months Ended
	Dec. 31, 2015
Property, Equipment and Intangible Assets [Abstract]
Property, Equipment and Intangible Assets	13 . Property , Equipment and Intangible Assets Property , equipment and intangible assets , which are included in other assets in the consolidated statements of financial condition, consist of leasehold improvements, computer equipment , software developed for the Company ’ s internal use , office furniture , equipment and acquired technology . As of December 31, 2015 and 2014 , property , equipment and intangible assets consisted of: December 31, 2015 2014 (in millions) Leasehold improvements $ 16 $ 17 Computer equipment 9 9 Internally developed software 47 44 Office furniture and equipment 2 3 74 73 Less - accumulated depreciation and amortization (40) (41) Property and equipment, net 34 32 Intangible assets (acquired technology) 8 — Less - accumulated amortization (2) — Intangible assets, net 6 — Total property, equipment and intangible assets, net $ 40 $ 32 Depreciation and amortization of $22 million, $20 million and $19 million for the three years ended December 31, 2015 , 2014 and 2013 , respectively, is included in occupancy, depreciation and amortization expenses in the consolidated statements of comprehensive income. Amortization expense related to intangible assets is expect to be approximately $2 million for years ended December 31, 2016, 2017 and 2018 , respectively.

Commitments, Contingencies And

Commitments, Contingencies And Guarantees	12 Months Ended
	Dec. 31, 2015
Commitments, Contingencies And Guarantees [Abstract]
Commitments, Contingencies And Guarantees	14 . Commitments, Contingencies and Guarantees Claims Against Customers On January 15, 2015, due to the sudden move in the value of the Swiss franc that followed an unprecedented action by the Swiss National Bank, which removed a previously instituted and repeatedly reconfirmed cap of the currency relative to the Euro, several of the Company’s customers who held currency futures and spot positions suffered losses in excess of their deposits with the Company. The Company took immediate action to hedge its exposure to the foreign currency receivables from these customers. The Company estimates the losses related to this event, net of hedging activity and debt collection efforts, to be approximately $119 million. The Company is actively pursuing collection of the debts. The ultimate effect of this incident on the Company’s results will depend upon the outcome of the Company’s debt collection efforts. Litigation The Company is subject to certain pending and threatened legal actions which arise out of the normal course of business. Litigation is inherently unpredictable, particularly in proceedings where claimants seek substantial or indeterminate damages, or which are in their early stages. The Company has not been able to quantify the actual loss or range of loss related to such legal proceedings, the manner in which they will be resolved, the timing of final resolution or the ultimate settlement. Management believes that the resolution of these actions will not have a material effect, if any, on the Company’s business or financial condition, but may have a material impact on the results of operations for a given period. The Company accounts for potential losses related to litigation in accordance with FASB ASC Topic 450, “Contingencies.” As of December 31, 2015 and 2014, reserves provided for potential losses related to litigation matters were not material. Trading Technologies Matter On February 3, 2010, Trading Technologies International, Inc. (“Trading Technologies”) commenced an action in the U.S. District Court for the Northern District of Illinois, Eastern Division, against IBG LLC and IB LLC (“Defendants”) alleging infringement of twelve U.S. patents and seeking, among other things, unspecified damages and injunctive relief. The Defendants filed an answer denying the claims and asserted counterclaims seeking a declaration that the patents have not been infringed and are invalid. The Defendants and/or certain codefendants f iled petitions with the U.S. Patent and Trademark Office (“USPTO”) for Covered Business Method (“CBM”) Review on eight of the asserted patents, and will likely file petitions with respect to the others. Thus far the USPTO issued decisions instituting CBM Review on two of the asserted patents and has made a finding that it is more likely than not that the patents are invalid. While it is too early to predict the outcome of the matter, the Company believes it has meritorious defenses to the allegations made in the complaint and intend to defend itself vigorously against them. Class Action Matter On December 18, 2015, a former individual customer filed a purported class action complaint against IB LLC, IBG, Inc., and Thomas Frank, PhD, the Company’s Executive Vice President and Chief Information Officer, in the U.S. District Court for the District of Connecticut. The complaint alleges that the former customer and members of the purported class of IB LLC’s customers were harmed by alleged “flaws” in the computerized system used by the Company to close out (i.e., liquidate) positions in customer brokerage accounts that have margin deficiencies. The complaint seeks, among other things, undefined compensatory damages and declaratory and injunctive relief. The Company believes that the complaint is without merit and the Company has filed a motion to dismiss it. Among other things, the Company’s customer agreement, federal law and associated industry rules grant broker-dealers broad discretion to close out margin-deficient customer accounts for the broker’s protection. Further, the Company does not believe that a purported class action is appropriate given the great differences in portfolios, markets and many other circumstances surrounding the liquidation of any particular customer’s margin-deficient account. IB LLC and the related defendants intend to defend themselves vigorously against the case and, consistent with past practice in connection with this type of unwarranted action, any potential claims for counsel fees and expenses incurred in defending the case shall be fully pursued against the plaintiff. Leases Operating Companies have non ‑cancelable operating leases covering office space. All but one of the office space leases are subject to escalation clauses based on specified costs incurred by the respective landlords and contain renewal elections. Rent expense calculated on a straight ‑line basis for the Company was $14 million, $13 million and $13 million for the three years ended December 31, 2015 , 2014 and 2013 , respectively, and is included in occupancy, depreciation and amortization expenses in the consolidated statements of comprehensive income. As of December 31, 2015 , the Company ’ s minimum annual lease commitments totaled $59 million, as follows: Year (in millions) 2016 $ 13 2017 12 2018 13 2019 4 Thereafter 17 $ 59 Guarantees Certain of the Operating Companies provide guarantees to securities clearing houses and exchanges which meet the accounting definition of a guarantee under FASB ASC Topic 460, “ Guarantees .” Under standard membership agreements, clearing house and exchange members are required to guarantee collectively the performance of other members. Under the agreements, if a member becomes unable to satisfy its obligations, other members would be required to meet shortfalls. In the opinion of management, the Operating Companies’ liability under these arrangements is not quantifiable and could exceed the cash and securities they have posted as collateral. However, the potential for these Operating Companies to be required to make payments under these arrangements is remote. Accordingly, no contingent liability is carried in the consolidated statements of financial condition for these arrangements. In connection with its retail brokerage business, IB LLC or other electronic brokerage Operating Companies perform securities and commodities execution, clearance and settlement on behalf of their customers for whom they commit to settle trades submitted by such customers with the respective clearing houses. If a customer fails to fulfill its settlement obligations, the respective Operating Company must fulfill those settlement obligations. No contingent liability is carried on the consolidated statements of financial condition for such customer obligations. Other Commitments Certain clearing houses, clearing banks and firms used by certain Operating Companies are given a security interest in certain assets of those Operating Companies held by those clearing organizations. These assets may be applied to satisfy the obligations of those Operating Companies to the respective clearing organizations.

Segment And Geographic Informat

Segment And Geographic Information	12 Months Ended
	Dec. 31, 2015
Segment And Geographic Information [Abstract]
Segment And Geographic Information	15. Segment and Geographic Information The Company has two operating business segments: electronic brokerage and market making. These segments are supported by the corporate segment which provides centralized services and executes the Company’s currency diversification strategy. The Company conducts its electronic brokerage business through its Interactive Brokers subsidiaries, which provide electronic execution and clearing services to customers worldwide. The Company conducts its market making business principally through its Timber Hill subsidiaries on the world’s leading exchanges and market centers, primarily in exchange ‑traded equities, equity options and equity ‑index options and futures. Significant transactions and balances between the Operating Companies occur, primarily as a result of certain Operating Companies holding exchange or clearing organization memberships, which are utilized to provide execution and clearing services to affiliates. Charges for transactions between segments are designed to approximate full costs. Intra ‑segment and intra ‑region income and expenses and related balances have been eliminated in this segment and geographic information to reflect the external business conducted in each segment or geographical region. Corporate items include non ‑allocated corporate income and expenses that are not attributed to segments for performance measurement, net gains and losses on positions held as part of our overall currency diversification strategy, corporate assets and eliminations. Management believes that the following information by business segment provides a reasonable representation of each segment’s contribution to total net revenues and income before income taxes for the three years ended December 31, 2015 , 2014 and 2013 , and to total assets as of December 31, 2015 , 2014 and 2013 . Year-Ended December 31, 2015 2014 2013 (in millions) Net revenues Electronic brokerage $ 1,097 $ 952 $ 819 Market making 298 284 361 Corporate (206) (193) (103) Total net revenues $ 1,189 $ 1,043 $ 1,076 Income before income taxes Electronic brokerage $ 536 $ 589 $ 396 Market making 130 114 159 Corporate (208) (197) (103) Total income before income taxes $ 458 $ 506 $ 451 December 31, December 31, December 31, 2015 2014 2013 (in millions) Segment Assets Electronic brokerage $ 44,421 $ 38,280 $ 31,334 Market making 10,825 12,172 12,140 Corporate (6,512) (7,067) (5,602) Total assets $ 48,734 $ 43,385 $ 37,871 The Company operates its automated global business in the U.S. and international markets on more than 100 electronic exchanges and market centers. A significant portion of the Company’s net revenues are generated by subsidiaries operating outside the U.S. International operations are comprised of electronic brokerage and market making activities in 25 countries in Europe, Asia and the Americas (outside the U.S.). In the first quarter of this year, the Company changed the presentation of its geographic segments, moving the companies and eliminations that were in the corporate segment to their respective geographic region. To provide meaningful comparison, prior period amounts have been reclassified for this change in presentation. The following table presents total net revenues and income before income taxes by geographic area for the three years ended December 31, 2015 , 2014 and 2013 . Year-Ended December 31, 2015 2014 2013 (in millions) Net revenues United States $ 832 $ 773 $ 754 International 357 270 322 Total net revenues $ 1,189 $ 1,043 $ 1,076 Income before income taxes United States $ 294 $ 425 $ 324 International 164 81 127 Total income before income taxes $ 458 $ 506 $ 451

Regulatory Requirements

Regulatory Requirements	12 Months Ended
	Dec. 31, 2015
Regulatory Requirements [Abstract]
Regulatory Requirements	16 . Regulatory Requirements As of December 31, 2015 , aggregate excess regulatory capital for all of the Operating Companies was $3.4 billion. IB LLC and TH LLC are subject to the Uniform Net Capital Rule (Rule 15c3 ‑1) under the Exchange Act and the Commodities and Futures Trading Commission’s minimum financial requirements (Regulation 1.17), and THE is subject to the Swiss Financial Market Supervisory Authority eligible equity requirement. Additionally, IBHK is subject to the Hong Kong Securities Futures Commission liquid capital requirement, THA is subject to the Australian Stock Exchange liquid capital requirement, THLI is subject to the Financial Market Authority Liechtenstein eligible capital requirements, THC and IBC are subject to the Investment Industry Regulatory Organization of Canada risk adjusted capital requirement, IBUK is subject to the U.K. Financial Conduct Authority Capital Requirements Directive, IBI is subject to the National Stock Exchange of India net capital requirements and IBSJ is subject to the Japanese Financial Supervisory Agency capital requirements. The following table summarizes capital, capital requirements and excess regulatory capital. Net Capital/ Eligible Equity Requirement Excess (in millions) IB LLC $ 2,367 $ 259 $ 2,108 TH LLC 375 1 374 THE 605 180 425 Other regulated Operating Companies 567 35 532 $ 3,914 $ 475 $ 3,439 Regulatory capital requirements could restrict the Operating Companies from expanding their business and declaring dividends if their net capital does not meet regulatory requirements. Also, certain Operating Companies are subject to other regulatory restrictions and requirements. As of December 31, 2015 , all of the regulated Operating Companies were in compliance with their respective regulatory capital requirements.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2015
Related Party Transactions [Abstract]
Related Party Transactions	17 . Related Party Transactions Receivable from affiliate, reported in other assets in the consolidated statement of financial condition, represents amounts advanced to Holdings and payable to affiliate represents amounts payable to Holdings under the Tax Receivable Agreement (see Note 4). Included in receivables from and payables to customers in the consolidated statements of financial condition as of December 31, 2015 and December 31, 2014 were accounts receivable from directors, officers and their affiliates of $85 million and $ 152 million and payables of $698 million and $ 274 million, respectively. The Company may extend credit to these related parties in connection with margin loans. Such loans are (i) made in the ordinary course of business, (ii) are made on substantially the same terms, including interest rates and collateral, as those prevailing at the time for comparable loans with persons not related to the company, and (iii) do not involve more than the normal risk of collectability or present other unfavorable features.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2015
Subsequent Events [Abstract]
Subsequent Events	18 . Subsequent Events As required by FASB ASC Topic 855, “ Subsequent Events,” the Company has evaluated subsequent events for adjustment to or disclosure in its consolidated financial statements through the date the consolidated financial statements were issued. Except as disclosed in Note 4, no other recordable or disclosable events occurred. *****

Schedule I_Condensed Financial

Schedule I—Condensed Financial Information of Registrant (Parent Company Only)	12 Months Ended
	Dec. 31, 2015
Schedule I—Condensed Financial Information of Registrant (Parent Company Only) [Abstract]
Schedule I—Condensed Financial Information of Registrant (Parent Company Only)	INTERACTIVE BROKERS GROUP, INC. (Parent Company Only) CONDENSED STATEMENTS OF FINANCIAL CONDITION December 31, (in millions, except share amounts) 2015 2014 Assets Cash and cash equivalents $ 1 $ 1 Investments in subsidiaries, equity basis 839 748 Other assets 317 294 Total assets $ 1,157 $ 1,043 Liabilities and Equity Liabilities: Payable to affiliates $ 291 $ 277 Accrued expenses and other liabilities 4 — 295 277 Stockholders' equity: Common stock, $0.01 par value per share: Class A – Authorized - 1,000,000,000, Issued - 64,121,150 and 58,612,245 shares, Outstanding – 63,985,335 and 58,473,186 shares as of December 31, 2015 and 2014 1 1 Class B – Authorized, Issued and Outstanding – 100 shares as of December 31, 2015 and 2014 — — Additional paid-in capital 718 636 Retained earnings 144 120 Accumulated other comprehensive income, net of income taxes of $0 and $1 as of December 31, 2015 and 2014 2 12 Treasury stock, at cost, 135,815 and 139,059 shares as of December 31, 2015 and 2014 (3) (3) Total equity 862 766 Total liabilities and equity $ 1,157 $ 1,043 See accompanying notes to the condensed financial statements. INTERACTIVE BROKERS GROUP, INC. (Parent Company Only) CONDENSED STATEMENTS OF COMPREHENSIVE INCOME Year Ended December 31, (in millions) 2015 2014 2013 Undistributed gains of subsidiaries, net $ 67 $ 63 $ 53 Income tax expense 18 18 16 Net income $ 49 $ 45 $ 37 Net income available for common stockholders $ 49 $ 45 $ 37 Cumulative translation adjustment, net of tax (10) (15) (3) Comprehensive income available for common stockholders $ 39 $ 30 $ 34 See accompanying notes to the condensed financial statements. INTERACTIVE BROKERS GROUP, INC. (Parent Company Only) CONDENSED STATEMENTS OF CASH FLOWS Year Ended December 31, (in millions) 2015 2014 2013 Cash flows from operating activities Net income $ 49 $ 45 $ 37 Adjustments to reconcile net income to net cash provided by operating activities Undistributed gains of subsidiaries, net (67) (63) (53) Deferred income taxes 13 22 18 Changes in operating assets and liabilities 9 5 2 Net cash provided by operating activities 4 9 4 Cash flows provided by investing activities 40 45 20 Cash flows used in financing activities (34) (39) (20) Effect of exchange rate changes on cash and cash equivalents (10) (15) (3) Net increase in cash and cash equivalents — — 1 Cash and cash equivalents at beginning of period 1 1 — Cash and cash equivalents at end of period $ 1 $ 1 $ 1 Supplemental disclosures of cash flow information Cash paid for interest $ — $ — $ — Cash paid for taxes $ — $ 6 $ — See accompanying notes to the condensed financial statements. INTERACTIVE BROKERS GROUP, INC. (Parent Company Only) NOTES TO CONDEN SED FINANCIAL STATEMENTS 1. Basis of Presentation The accompanying condensed financial statements (the “Parent Company Financial Statements”) of Interactive Brokers Group, Inc. (“IBG, Inc.”), a Delaware holding company, including the notes thereto, should be read in conjunction with the consolidated financial statements of IBG, Inc. and its subsidiaries (the “Company”) and the notes thereto. IBG, Inc.’s primary operating asset is its ownership interest in IBG LLC, an automated global electronic broker and market maker specializing in executing and clearing trades in securities, futures, foreign exchange instruments, bonds and mutual funds on more than 100 electronic exchanges and market centers around the world and offering custody, prime brokerage, securities and margin lending services to customers. The preparation of the Parent Company Financial Statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts and disclosures in the condensed financial statements and accompanying notes. Income Taxes Refer to Note 2 to the consolidated financial statements. 2. Related Party Transactions As of December 31, 2015, there were no receivables from affiliates. Dividends received from IBG LLC for the three years ended December 31, 2015, 2014 and 2013 were $40 million, $45 million and $20 million, respectively. As of December 31, 2015 and 2014, respectively, payable to affiliates of $291 million and $277 million consisted primarily of amounts payable to Holdings under the Tax Receivable Agreement. 3. Stockholders’ Equity Refer to Note 4 to the consolidated financial statements. 4. Employee Incentive Plans Refer to Note 11 to the consolidated financial statements. 5. Commitments, Contingencies and Guarantees Refer to Note 14 to the consolidated financial statements. 6. Subsequent Events As required by FASB ASC Topic, “Subsequent Events,” IBG, Inc. has evaluated subsequent events for adjustment to or disclosure in its condensed financial statements through the date the condensed financial statements were issued. No recordable or disclosable events, not otherwise reported in these condensed financial statements or the notes thereto, occurred. ****

Significant Accounting Polici26

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Significant Accounting Policies [Abstract]
Basis Of Presentation	Basis of Presentation These consolidated financial statements are presented in U.S. dollars and have been prepared in accordance with accounting principles generally accepted in the U.S. (“U.S. GAAP”) and pursuant to the rules and regulations of the U.S. Securities and Exchange Commission ( “ SEC ” ) regarding financial reporting with respect to Form 10 ‑K. These consolidated financial statements include the accounts of the Company and its consolidated subsidiaries and reflect all adjustments of a normal and recurring nature that are, in the opinion of management, necessary for the fair presentation of the results for the periods presented. In the third quarter of 2015, the Company changed the presentation of its non-market making financial instruments carried at fair value from other assets and accounts payable, accrued expenses and other liabilities to financial instruments owned, at fair value and financial instruments sold, but not yet purchased, at fair value, respectively, in the consolidated statements of financial condition, in order to consistently present all of the financial instruments held for trading under the same caption. For comparison purposes, as of December 31, 2014, $44 million was reclassified from other assets to financial instruments owned, at fair value, and $8 million was reclassified from accounts payable, accrued expenses and other liabilities to financial instruments sold, but not yet purchased, at fair value.
Principles Of Consolidation, Including Noncontrolling Interests	Principles of Consolidation, including Noncontrolling Interests The consolidated financial statements include the accounts of IBG, Inc. and its majority and wholly owned subsidiaries. As sole managing member of IBG LLC, IBG, Inc. exerts control over IBG LLC’ s operations. In accordance with Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 810, “ Consolidation , ” the Company consolidates IBG LLC’ s financial statements and records the interests in IBG LLC that it does not own as noncontrolling interests. The Company ’ s policy is to consolidate all other entities in which it owns more than 50% unless it does not have control. All inter ‑company balances and transactions have been eliminated.
Use Of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts and disclosures in these consolidated financial statements and accompanying notes. These estimates and assumptions are based on judgment and the best available information at the time. Therefore, actual results could differ materially from those estimates. Such estimates include the allowance for doubtful accounts, valuation of certain investments, compensation accruals, current and deferred income taxes, and contingency reserves.
Fair Value	Fair Value Substantially all of the Company’s assets and liabilities, including financial instruments are carried at fair value based on published market prices and are marked to market, or are assets and liabilities which are short ‑term in nature and are carried at amounts that approximate fair value. The Company applies the fair value hierarchy in accordance with FASB ASC Topic 820, “ Fair Value Measurement” (“ASC Topic 820”) , to prioritize the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets and liabilities and the lowest priority to unobservable inputs. The three levels of the fair value hierarchy are: Level 1 Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. Level 2 Quoted prices in markets that are not considered to be active or financial instruments for which all significant inputs are observable, either directly or indirectly. Level 3 Prices or valuations that require inputs that are both significant to fair value measurement and unobservable. Financial instruments owned, at fair value and financial instruments sold, but not yet purchased, at fair value are generally classified as Level 1 of the fair value hierarchy. The Company’s Level 1 financial instruments, which are valued using quoted market prices as published by exchanges and clearing houses or otherwise broadly distributed in active markets, include active listed stocks, options, warrants and discount certificates, and U.S. and foreign government securities. The Company does not adjust quoted prices for financial instruments classified as Level 1 of the fair value hierarchy, even in the event that the Company may hold a large position whereby a purchase or sale could reasonably impact quoted prices. Currency forward contracts are valued using broadly distributed bank and broker prices, and are classified as Level 2 of the fair value hierarchy as such instruments are not exchange ‑traded. Other securities that are not traded in active markets are also classified in Level 2 of the fair value hierarchy. Level 3 financial instruments are comprised of securities that have been delisted or otherwise are no longer tradable and have been valued by the Company based on internal estimates.
Earnings Per Share	Earnings Per Share Earnings per share (“EPS”) is computed in accordance with FASB ASC Topic 260, “ Earnings per Share .” Basic EPS is computed by dividing the net income available for common stockholders by the weighted average number of shares outstanding for that period. Diluted EPS is calculated by dividing the net income available for common stockholders by the diluted weighted average shares outstanding for that period. Diluted EPS includes the determinants of the basic EPS and, in addition, reflects the dilutive effect of shares of common stock estimated to be distributed in the future under the Company’s stock-based compensation plans, with no adjustments to net income available for common stockholders for dilutive potential common shares.
Stock-Based Compensation	Stock ‑Based Compensation The Company follows FASB ASC Topic 718, “ Compensation - Stock Compensation” (“ASC Topic 718”) , to account for its stock ‑based compensation plans. ASC Topic 718 requires all share ‑based payments to employees to be recognized in the consolidated financial statements using a fair value ‑based method. Grants, which are denominated in U.S. dollars, are communicated to employees in the year of grant, thereby establishing the fair value of each grant. The fair value of awards granted to employees are generally expensed as follows: 50% in the year of grant in recognition of plan forfeiture provisions (as described below) and the remaining 50% over the related vesting period utilizing the “graded vesting” method permitted under ASC Topic 718. In the case of “retirement eligible” employees (those employees older than 59), 100% of awards are expensed when granted. Awards granted under stock ‑based compensation plans are subject to forfeiture in the event an employee ceases employment with the Company. The plans provide that employees who discontinue employment with the Company without cause and continue to meet the terms of the plans’ post ‑employment provisions will forfeit 50% of unvested previously granted awards unless the employee is over the age of 59, in which case the employee would be eligible to receive 100% of unvested awards p reviously granted.
Cash And Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist of deposits with banks and all highly liquid investments, with maturities of three months or less, that are not segregated and deposited for regulatory purposes or to meet margin requirements at clearing houses .
Cash And Securities - Segregated For Regulatory Purposes	Cash and Securities - Segregated for Regulatory Purposes As a result of customer activities, certain Operating Companies are obligated by rules mandated by their primary regulators to segregate or set aside cash or qualified securities to satisfy such regulations, which have been promulgated to protect customer assets. Securities segregated for regulatory purposes consisted of U.S. government securities of $15.2 billion and $6.7 billion as of December 31, 201 5 and December 31, 201 4 , respectively, and securities purchased under agreements to resell in the amount of $0.6 billion and $3.9 billion as of December 31, 201 5 and December 31, 201 4 , respectively, which amounts approximate fair value.
Securities Borrowed And Securities Loaned	Securities Borrowed and Securities Loaned Securities borrowed and securities loaned are recorded at the amount of the cash collateral advanced or received. Securities borrowed transactions require the Company to provide counterparties with collateral, which may be in the form of cash, letters of credit or other securities. With respect to securities loaned, the Company receives collateral, which may be in the form of cash or other securities in an amount generally in excess of the fair value of the securities loaned. The Company monitors the market value of securities borrowed and loaned on a daily basis, with additional collateral obtained or refunded as permitted contractually. The Company does not net, in the consolidated statements of financial condition, securities borrowed and securities loaned entered into with the same counterparty that do not meet the offsetting requirements prescribed in FASB ASC Topic 210-20, “Balance Sheet – Offsetting” (“ASC Topic 210-20”). Securities lending fees received and paid by the Company are included in interest income and interest expense, respectively, in the consolidated statements of comprehensive income.
Securities Purchased Under Agreements To Resell and Secruities Sold Under Agreements to Repurchase	Securities Purchased Under Agreements to Resell and Securities Sold Under Agreements to Repurchase Securities purchased under agreements to resell, which are reported as collateralized financing transactions, are recorded at contract value, which approximates fair value. To ensure that the fair value of the underlying collateral remains sufficient, the collateral is valued daily with additional collateral obtained or excess collateral returned, as permitted under contractual provisions. The Company does not net, in the consolidated statements of financial condition, securities purchased under agreements to resell transactions and securities sold under agreements to repurchase transactions entered into with the same counterparty that do not meet the offsetting requirements prescribed in ASC Topic 210-20.
Financial Instruments Owned And Sold But Not Yet Purchased	Financial Instruments Owned and Financial Instruments Sold , But Not Yet Purchased , at Fair Value Financial instrument transactions are accounted for on a trade date basis. Financial instruments owned and financial instruments sold, but not yet purchased are stated at fair value based upon quoted market prices. The Company’s financial instruments pledged to counterparties where the counterparty has the right, by contract or custom, to sell or repledge the financial instruments are reported as financial instruments owned and pledged as collateral in the consolidated statements of financial condition. The Company also enters into currency forward contracts. These transactions, which are also accounted for on a trade date basis, are agreements to exchange a fixed amount of one currency for a specified amount of a second currency at completion of the currency forward contract term. Unrealized mark ‑to ‑market gains and losses on currency forward contracts are included in financial instruments owned, at fair value or financial instruments sold, but not yet purchased, at fair value in the consolidated statements of financial condition.
Customer Receivables And Payables	Customer Receivables and Payables Customer securities transactions are recorded on a settlement date basis and customer commodities transactions are recorded on a trade date basis. Receivables from and payables to customers include amounts due on cash and margin transactions, including futures contracts transacted on behalf of customers. Securities owned by customers, including those that collateralize margin loans or other similar transactions, are not reported in the consolidated statements of financial condition. Amounts receivable from customers that are determined by management to be uncollectible are recorded as customer bad debt expense in the consolidated statements of comprehensive income.
Receivables From And Payables To Brokers, Dealers And Clearing Organizations	Receivables from and Payables to Brokers, Dealers and Clearing Organizations Receivables from and payables to brokers, dealers and clearing organizations include net receivables and payables from unsettled trades, including amounts related to futures and options on futures contracts executed on behalf of customers, amounts receivable for securities not delivered by the Company to the purchaser by the settlement date (“fails to deliver”) and cash deposits. Payables to brokers, dealers and clearing organizations also include amounts payable for securities not received by the Company from a seller by the settlement date (“fails to receive”).
Investments	Investments The Company makes certain strategic investments related to its business and accounts for these investments under the cost method of accounting or under the equity method of accounting as required under FASB ASC Topic 323, “ Investments - Equity Method and Joint Ventures .” Investments accounted for under the equity method, including where the investee is a limited partnership or limited liability company, are recorded at the fair value amount of the Company’s initial investment and are adjusted each period for the Company’s share of the investee’s income or loss. The Company’s share of the income or losses from equity method investments is included in other income in the consolidated statements of comprehensive income. The recorded amounts of the Company’s equity method investments, $32 million as of December 31, 201 5 ( $37 million as of December 31, 201 4 ), which are included in other assets in the consolidated statements of financial condition, increase or decrease accordingly. Contributions paid to and distributions received from equity method investees are recorded as additions or reductions, respectively, to the respective investment balance. The Company also holds exchange memberships and investments in equity securities of certain exchanges , as required to qualify as a clearing member, and strategic investments in corporate stock that do not qualify for equity method accounting. Such investments, $34 million as of December 31, 201 5 ( $31 million as of December 31, 201 4 ), 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, and are also included in other assets in the consolidated statements of financial condition. Dividends received from cost basis investments are included in other income in the consolidated statements of comprehensive income when such dividends are received. A judgmental aspect of accounting for investments is evaluating whether an other ‑than ‑temporary decline in the value of an investment has occurred. The evaluation of an other ‑than ‑temporary impairment is dependent on specific quantitative and qualitative factors and circumstances surrounding an investment, including recurring operating losses, credit defaults and subsequent rounds of financing. The Company’s equity investments do not have readily determinable market values. All investments are reviewed for changes in circumstances or occurrence of events that suggest the Company’s investment may not be recoverable. If an unrealized loss on any investment is considered to be other ‑than ‑temporary, the loss is recognized in the period the determination is made .
Property And Equipment	Property , Equipment and Intangible Assets Property, equipment and intangible assets, which are included in other assets in the consolidated statements of financial condition, consist of leasehold improvements, computer equipment, software developed for the Company’s internal use, office furniture, equipment and acquired technology . Property and equipment are recorded at historical cost, less accumulated depreciation and amortization. Additions and improvements that extend the lives of assets are capitalized, while expenditures for repairs and maintenance are expensed as incurred. Depreciation and amortization are computed using the straight ‑line method. Equipment is depreciated over the estimated useful lives of the assets, while leasehold improvements are amortized over the lesser of the estimated economic useful life of the asset or the term of the lease. Computer equipment is depreciated over three to five years and office furniture and equipment are depreciated over five to seven years. Qualifying costs for internally developed software are capitalized and amortized over the expected useful life of the developed software, not to exceed three years. Intangible assets with a finite life are amortized on a straight line basis over their estimated useful lives of three years, and tested for recoverability whenever events indicate that the carrying amounts may not be recoverable.
Comprehensive Income And Foreign Currency Translation	Comprehensive Income and Foreign Currency Translation The Company’s operating results are reported in the consolidated statements of comprehensive income pursuant to FASB ASC Topic 220, “ Comprehensive Income. ” Comprehensive income consists of two components: net income and other comprehensive income (“OCI”). The Company’s OCI is comprised of gains and losses resulting from translating foreign currency financial statements of non-U.S. subsidiaries , net of related income taxes, where applicable. In general, the practice and intention of the Company is to reinvest the earnings of its non ‑U.S. subsidiaries in those operations, therefore tax is usually not accrued. The Company’s non ‑U.S. domiciled subsidiaries have a functional currency that is other than the U.S. dollar. Such subsidiaries’ assets and liabilities are translated into U.S. dollars at period ‑end exchange rates, and revenues and expenses are translated at average exchange rates prevailing during the period. Adjustments that result from translating amounts from a subsidiary’s functional currency to the U.S. dollar (as described above) are reported net of tax, where applicable, in accumulated OCI in the consolidated statements of financial condition. During 2013, the Company derecognized accumulated OCI of a $ 5 million loss attributable to its Brazilian subsidiary, IB Brasil Participações Ltda, which was liquidated during the year , and recognized a foreign currency translation loss, before taxes, which is included in other income in the consolidated statements of comprehensive income .
Revenue Recognition	Revenue Recognition Trading Gains Trading gains and losses are recorded on trade date and are reported on a net basis. Trading gains and losses are comprised of changes in the fair value of financial instruments owned, at fair value and financial instruments sold, but not yet purchased, at fair value (i.e., unrealized gains and losses) and realized gains and losses related to the Company’s market making business segment. Included in trading gains are net gains and losses on stocks, U.S. and foreign government securities, corporate and municipal bonds, options, futures, foreign exchange and other derivative instruments. Dividends are integral to the valuation of stocks and interest is integral to the valuation of fixed income instruments. Accordingly, both dividends and interest income and expense attributable to financial instruments owned, at fair value and financial instruments sold, but not yet purchased, at fair value are reported on a net basis in trading gains in the consolidated statements of comprehensive income. Commissions and Execution Fees Commissions earned for executing and clearing transactions are accrued on a trade date basis and are reported as commissions and execution fees in the consolidated statements of comprehensive income. Interest Income and Expense The Company earns interest income and incurs interest expense primarily in connection with its electronic brokerage customer business and its securities lending activities, which are recorded on the accrual basis and are included in interest income and interest expense, respectively, in the consolidated statements of comprehensive income. Foreign Currency Gains and Losses Currency translation refers to the gains and losses resulting from foreign currency transactions. Foreign currency translation gains and losses related to the Company’s currency diversification strategy are included in other income in the consolidated statements of comprehensive income. Foreign currency translation gains and losses related to the market making core-business activities are included in trading gains in the consolidated statements of comprehensive income. Electronic brokerage foreign currency translation gains and losses, arising from currency swap transactions, are included in interest income in the consolidated statements of comprehensive income.
Income Taxes	Income Taxes The Company accounts for income taxes in accordance with FASB ASC Topic 740, “ Income Taxes” (“ASC Topic 740”) . The Company’s income tax expense, deferred tax assets and liabilities, and reserves for unrecognized tax benefits are based on enacted tax laws (see Note 12) and reflect management’s best assessment of estimated future taxes to be paid. The Company is subject to income taxes in both the U.S. and numerous foreign jurisdictions. Determining income tax expense requires significant judgments and estimates. The Company recognizes interest related to income tax matters as interest income or interest expense and penalties related to income tax matters as income tax expense in the consolidated statements of comprehensive income. Deferred income tax assets and liabilities arise from temporary differences between the tax and financial statements recognition of the underlying assets and liabilities. In evaluating the ability to recover deferred tax assets within the jurisdictions from which they arise, the Company considers all available positive and negative evidence, including scheduled reversals of deferred tax liabilities, projected future taxable income, tax ‑planning strategies, and results of recent operations. In projecting future taxable income, historical results are adjusted for changes in accounting policies and incorporate assumptions including the amount of future state, federal and foreign pre-tax operating income, the reversal of temporary differences, and the implementation of feasible and prudent tax ‑planning strategies. These assumptions require significant judgment about the forecasts of future taxable income and are consistent with the plans and estimates the Company is using to manage the underlying businesses. In evaluating the objective evidence that historical results provide, three years of cumulative operating income (loss) are considered. Deferred income taxes have not been provided for U.S. tax liabilities or for additional foreign taxes on the unremitted earnings of foreign subsidiaries that have been indefinitely reinvested. The calculation of the Company’s tax liabilities involves dealing with uncertainties in the application of complex tax laws and regulations in a multitude of jurisdictions across the Company’s global operations. Changes in tax laws and rates could also affect recorded deferred tax assets and liabilities in the future. The Company is not aware of any such changes that would have a material effect on the Company’s results of operations, cash flows, or financial position. The Company recognizes that a tax benefit from an uncertain tax position only when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, on the basis of the technical merits. A tax position that meets this standard is measured at the largest amount of benefit that will more likely than not be realized on settlement. The Company records tax liabilities in accordance with ASC Topic 740 and adjusts these liabilities when management’s judgment changes as a result of the evaluation of new information not previously available. Because of the complexity of some of these uncertainties, the ultimate resolution may result in payments that are different from the current estimates of these tax liabilities. These differences will be reflected as increases or decreases to income tax expense in the period in which new information becomes available.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements Following is a summary of recently issued FASB Accounting Standards Updates (“ASUs”) that have affected or may affect the Company’s consolidated financial statements : Affects Status ASU 2015-02 Consolidation (Topic 810): Amendments to the Consolidation Analysis. Effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2015. ASU 2015-08 Business Combinations (Topic 805): Pushdown Accounting. Amendments to SEC Paragraphs Pursuant to Staff Accounting Bulletin No. 115. Measurement of Certain Transfers Between Entities Under Common Control in the Separate Financial Statements of Each Entity. The amendments are effective immediately. ASU 2015-14 Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date. Effective for annual reporting periods beginning after December 15, 2017. ASU 2015-16 Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments. Effective for fiscal years beginning after December 15, 2015. ASU 2016-01 Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. Effective for fiscal years beginning after December 15, 2017. Adoption of those ASUs that became effective during 2015 and 2016 , prior to the issuance of the Company’s consolidated financial statements, did not have a material effect on th e se financial statements.

Equity And Earnings Per Share (

Equity And Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2015
Equity And Earnings Per Share [Abstract]
Earnings Per Share Basic And Diluted	Basic earnings per share is calculated utilizing net income available for common stockholders divided by the weighted average number of shares of Class A and Class B common stock outstanding for that period. Year-Ended December 31, 2015 2014 2013 (in millions, except for shares or per share amounts) Basic earnings per share Net income available for common stockholders $ 49 $ 45 $ 37 Weighted average shares of common stock outstanding Class A 61,042,971 56,492,281 49,742,328 Class B 100 100 100 61,043,071 56,492,381 49,742,428 Basic earnings per share $ 0.80 $ 0.79 $ 0.74 Diluted earnings per share are calculated utilizing the Company’s basic net income available for common stockholders divided by diluted weighted average shares outstanding with no adjustments to net income available to common stockholders for potentially dilutive common shares. Year-Ended December 31, 2015 2014 2013 (in millions, except for shares or per share amounts) Diluted earnings per share Net income available for common stockholders $ 49 $ 45 $ 37 Weighted average shares of common stock outstanding Class A Issued and outstanding 61,042,971 56,492,281 49,742,328 Potentially dilutive common shares Issuable pursuant to employee stock incentive plans 1,466,725 1,217,287 1,182,308 Class B 100 100 100 62,509,796 57,709,668 50,924,736 Diluted earnings per share $ 0.78 $ 0.77 $ 0.73

Comprehensive Income (Tables)

Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2015
Comprehensive Income Detail [Abstract]
Comprehensive Income Table	Year-Ended December 31, 2015 2014 2013 (in millions, except for shares or per share amounts) Comprehensive income available for common stockholders $ 39 $ 30 $ 34 Earnings per share on comprehensive income Basic $ 0.64 $ 0.52 $ 0.69 Diluted $ 0.62 $ 0.51 $ 0.67 Weighted average common shares outstanding Basic 61,043,071 56,492,381 49,742,428 Diluted 62,509,796 57,709,668 50,924,736

Financial Assets And Financia29

Financial Assets And Financial Liabilities (Tables)	12 Months Ended
	Dec. 31, 2015
Financial Assets And Financial Liabilities [Abstract]
Fair Value Table	Financial Assets At Fair Value as of December 31, 2015 Level 1 Level 2 Level 3 Total (in millions) Securities segregated for regulatory purposes $ 15,214 $ — $ — $ 15,214 Financial instruments owned Stocks 1,650 — — 1,650 Options 1,156 — — 1,156 Warrants and discount certificates 81 — — 81 U.S. and foreign government securities 527 — — 527 Corporate and municipal bonds — 3 — 3 Currency forward contracts — 3 — 3 Total financial instruments owned, at fair value 3,414 6 — 3,420 Total financial assets at fair value $ 18,628 $ 6 $ — $ 18,634 Financial Liabilities At Fair Value as of December 31, 2015 Level 1 Level 2 Level 3 Total (in millions) Financial instruments sold, but not yet purchased, at fair value Stocks $ 1,565 $ — $ — $ 1,565 Options 1,042 — — 1,042 Warrants and discount certificates 1 — — 1 Currency forward contracts — 9 — 9 Total financial instruments sold, but not yet purchased, at fair value 2,608 9 — 2,617 Total financial liabilities at fair value $ 2,608 $ 9 $ — $ 2,617 Financial Assets At Fair Value as of December 31, 2014 Level 1 Level 2 Level 3 Total (in millions) Securities segregated for regulatory purposes $ 6,681 $ — $ — $ 6,681 Financial instruments owned, at fair value Stocks 2,592 — — 2,592 Options 1,209 — — 1,209 Warrants and discount certificates 72 — — 72 U.S. and foreign government securities 98 — — 98 Corporate and municipal bonds — 3 3 Currency forward contracts — 4 — 4 Total financial instruments owned, at fair value 3,971 7 — 3,978 Total financial assets at fair value $ 10,652 $ 7 $ — $ 10,659 Financial Liabilities At Fair Value as of December 31, 2014 Level 1 Level 2 Level 3 Total (in millions) Financial instruments sold, but not yet purchased, at fair value Stocks $ 1,360 $ — $ 1 $ 1,361 Options 1,197 — — 1,197 Warrants and discount certificates 1 — — 1 Currency forward contracts — 10 — 10 Total financial instruments sold, but not yet purchased, at fair value 2,558 10 1 2,569 Total financial liabilities at fair value $ 2,558 $ 10 $ 1 $ 2,569
Trading Gains From Market Making Transactions	Year-Ended December 31, 2015 2014 2013 (in millions) Equities $ 254 $ 247 $ 285 Fixed income 1 21 25 Foreign exchange 14 (7) 21 Total trading gains, net $ 269 $ 261 $ 331
Financial Assets and Liabilities Not Measured at Fair Value	December 31, 2015 Carrying Value Fair Value Level 1 Level 2 Level 3 (in millions) Financial assets, not measured at fair value Cash and cash equivalents $ 1,601 $ 1,601 $ 1,601 $ - $ - Cash and securities segregated for regulatory purposes 6,095 6,095 5,533 562 - Securities borrowed 3,924 3,924 - 3,924 - Securities purchased under agreements to resell 195 195 - 195 - Receivables from customer 17,050 17,050 - 17,050 Receivables from broker, dealers, and clearing organizations 692 692 - 692 - Interest receivable 63 63 - 63 - Other assets 28 31 - 31 - Total financial assets, not measured at fair value $ 29,648 $ 29,651 $ 7,134 $ 22,517 $ — Financial liabilities, not measured at fair value Securities loaned 2,894 2,894 - 2,894 - Payables to customer 37,084 37,084 - 37,084 - Payables to brokers, dealers and clearing organizations 423 423 - 423 - Interest payable 3 3 - 3 - Total financial liabilities, not measured at fair value $ 40,404 $ 40,404 $ — $ 40,404 $ — December 31, 2014 Carrying Value Fair Value Level 1 Level 2 Level 3 (in millions) Financial assets, not measured at fair value Cash and cash equivalents $ 1,269 $ 1,269 $ 1,269 $ - $ - Cash and securities segregated for regulatory purposes 8,723 8,723 4,849 3,874 - Securities borrowed 3,660 3,660 - 3,660 - Securities purchased under agreements to resell 386 386 - 386 - Receivables from customer 17,051 17,051 - 17,051 - Receivables from broker, dealers, and clearing organizations 1,131 1,131 - 1,131 - Interest receivable 37 37 - 37 - Other assets 30 55 - 55 - Total financial assets, not measured at fair value $ 32,287 $ 32,312 $ 6,118 $ 26,194 $ —
Netting Of Financial Assets And Financial Liabilities	December 31, 2015 Gross Amounts Net Amounts Amounts Not Offset Amounts Offset in the Presented in in the Consolidated of Financial Consolidated the Consolidated Statement of Assets and Statement of Statement of Financial Condition Liabilities Financial Financial Cash or Financial Recognized Condition Condition Instruments Net Amount (in millions) Offsetting of Financial Assets Securities segregated for regulatory purposes - purchased under agreements to resell $ 562 1 $ — $ 562 $ (562) $ — Securities borrowed 3,924 — 3,924 (3,816) 108 Securities purchased under agreements to resell 195 — 195 (195) — Financial Instruments owned, at fair value Options 1,156 — 1,156 (1,032) 124 Warrants and discount certificates 81 — 81 (1) 80 Currency forward contracts 3 — 3 — 3 Total $ 5,921 $ — $ 5,921 $ (5,606) $ 315 (in millions) Offsetting of Financial Liabilities Securities loaned $ 2,894 $ — $ 2,894 $ (2,773) $ 121 Financial instruments sold, but not yet purchased, at fair value Options 1,042 — 1,042 (1,032) 10 Warrants and discount certificates 1 — 1 (1) — Currency forward contracts 9 — 9 — 9 Total $ 3,946 $ — $ 3,946 $ (3,806) $ 140 December 31, 2014 Gross Amounts Net Amounts Amounts Not Offset Amounts Offset in the Presented in in the Consolidated of Financial Consolidated the Consolidated Statement of Assets and Statement of Statement of Financial Condition Liabilities Financial Financial Cash or Financial Recognized Condition Condition Instruments Net Amount (in millions) Offsetting of Financial Assets Securities segregated for regulatory purposes - purchased under agreements to resell $ 3,874 1 $ — $ 3,874 $ (3,874) $ — Securities borrowed 3,660 — 3,660 (3,564) 96 Securities purchased under agreements to resell 386 — 386 (386) — Financial Instruments owned, at fair value Options 1,209 — 1,209 (1,150) 59 Warrants and discount certificates 72 — 72 (1) 71 Currency forward contracts 4 — 4 — 4 Total $ 9,205 $ — $ 9,205 $ (8,975) $ 230 (in millions) Offsetting of Financial Liabilities Securities loaned $ 3,199 $ — $ 3,199 $ (3,183) $ 16 Financial instruments sold, but not yet purchased, at fair value Options 1,197 — 1,197 (1,150) 47 Warrants and discount certificates 1 — 1 (1) — Currency forward contracts 10 — 10 — 10 Total $ 4,407 $ — $ 4,407 $ (4,334) $ 73 As of December 31, 2015 and December 31, 2014, the Company had $0.6 billion and $3.9 billion, respectively, of securities purchased under agreements to resell that were segregated to satisfy regulatory requirements. These securities are included in “Cash and securities - segregated for regulatory purposes” in the consolidated statements of financial condition.
Schedule of Securities Financing Transactions [Table Text Block]	December 31, 2015 Remaining Contractual Maturity Overnight Less than 30 – 90 Over 90 and Open 30 days days days Total (in millions) Securities Loaned Stocks $ 2,873 $ - $ - $ - $ 2,873 Corporate bonds 21 - - - 21 Total $ 2,894 $ - $ - $ - $ 2,894

Collateralized Transactions (Ta

Collateralized Transactions (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure Collateralized Transactions [Abstract]
Amounts Related To Collateralized Transactions	December 31, 2015 December 31, 2014 Permitted Sold or Permitted Sold or to Repledge Repledged to Repledge Repledged (in millions) Securities lending transactions $ 12,131 $ 2,229 $ 10,907 $ 2,366 Securities purchased under agreements to resell transactions (1) 757 743 4,260 4,260 Customer margin assets 14,905 6,279 14,933 5,740 $ 27,793 $ 9,251 $ 30,100 $ 12,366 (1) As of December 31, 2015 , $0.6 billion or 76% ( as of December 31, 2014 , $3.9 billion or 91% ) of securities acquired through agreements to resell that are shown as repledged have been deposited in a separate bank account for the exclusive benefit of customer s in accordance with SEC Rule 15c3-3.
Financial Instruments Owned And Pledged Where The Counterparty Has The Right To Repledge	December 31, December 31, 2015 2014 (in millions) Stocks $ 915 $ 1,860 U.S. and foreign government securities 518 76 $ 1,433 $ 1,936

Short-Term Borrowings (Tables)

Short-Term Borrowings (Tables)	12 Months Ended
	Dec. 31, 2015
Short-Term Borrowings [Abstract]
Schedule Of Short-term Borrowings	December 31, 2015 December 31, 2014 Weighted Weighted Average Average Principal Rates Principal Rates (in millions) (in millions) Overnight borrowing facilities $ - 0.51% $ 34 0.50% $ - $ 34

Other Income (Tables)

Other Income (Tables)	12 Months Ended
	Dec. 31, 2015
Other Income [Abstract]
Schedule Of Components Of Other Income	Year-Ended December 31, 2015 2014 2013 (in millions) Payments for order flow $ 17 $ 25 $ 26 Market data fees 30 24 35 Account activity fees 16 14 15 Risk exposure fees 21 6 — Gains (losses) on financial instruments, at fair value and other investments, net (18) (5) (2) Gains (losses) from currency diversification strategy, net (206) (185) (91) Other, net 18 10 8 $ (122) $ (111) $ (9)

Employee Incentive Plans (Table

Employee Incentive Plans (Tables)	12 Months Ended
	Dec. 31, 2015
Employee Incentive Plans [Abstract]
Share Grants And Fair Value	Fair Value at Date of Grant Shares ($ millions) Prior periods (since inception) 17,284,454 $ 302 December 31, 2013 1,894,046 46 December 31, 2014 1,709,968 49 December 31, 2015 1,199,079 52 22,087,547 $ 449
2007 Stock Incentive Plan, ROI Summary	Intrinsic Value of SIP Shares Stock which Vested Incentive Plan and were ROI Unit ("SIP") Distributed Stock Plan Shares ($ millions) (2) (Shares) Balance, December 31, 2012 12,402,482 169,289 Granted 1,894,046 — Forfeited (334,111) (6,423) Distributed (2,315,300) $ 36 (162,866) Balance, December 31, 2013 11,647,117 — Granted 1,709,968 — Forfeited (1) (535,085) 15,518 Distributed (2,445,200) $ 56 (5,904) Balance, December 31, 2014 10,376,800 9,614 Granted 1,199,079 — Forfeited (163,221) — Distributed (2,487,127) $ 86 (3,244) Balance, December 31, 2015 8,925,531 6,370 (1) ROI Unit Stock Plan number of forfeited shares related to prior years was adjusted by 15,518 shares during the period. (2) Intrinsic value of SIP shares distributed represents the compensation value reported to the participants.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Taxes [Abstract]
Schedule Of The Provision For Income Taxes	Year-Ended December 31, 2015 2014 2013 (in millions) Current Federal $ 4 $ 1 $ (1) State and local — — — Foreign 24 28 23 Total current 28 29 22 Deferred Federal 14 21 17 State and local — — — Foreign 1 (3) (6) Total deferred 15 18 11 $ 43 $ 47 $ 33
Reconciliation Of The Statutory U.S. Federal Income Tax Rate Of 35% To The Company’s Effective Tax Rate	Year-Ended December 31, 2015 2014 2013 U.S. Statutory Tax Rate 35.0% 35.0% 35.0% Less: rate attributable to noncontrolling interests (28.2%) (28.6%) (29.5%) State, local and foreign taxes, net of federal benefit 2.6% 2.9% 2.0% 9.4% 9.3% 7.5%
Significant Components Of The Company’s Deferred Tax Assets (Liabilities)	December 31, 2015 2014 2013 (in millions) Deferred tax assets Arising from the acquisition of interests in IBG LLC $ 288 $ 279 $ 295 Deferred compensation 5 6 8 Other 18 8 3 Total deferred tax assets 311 293 306 Deferred tax liabilities Foreign, primarily THE 3 3 8 Other comprehensive income — — — Other — — — Total deferred tax liabilities 3 3 8 Net deferred tax assets $ 308 $ 290 $ 298

Property, Equipment and Intan35

Property, Equipment and Intangible Assets(Tables)	12 Months Ended
	Dec. 31, 2015
Property, Equipment and Intangible Assets [Abstract]
Property, Equipment and Intangible Assets	December 31, 2015 2014 (in millions) Leasehold improvements $ 16 $ 17 Computer equipment 9 9 Internally developed software 47 44 Office furniture and equipment 2 3 74 73 Less - accumulated depreciation and amortization (40) (41) Property and equipment, net 34 32 Intangible assets (acquired technology) 8 — Less - accumulated amortization (2) — Intangible assets, net 6 — Total property, equipment and intangible assets, net $ 40 $ 32

Commitments, Contingencies An36

Commitments, Contingencies And Guarantees (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments, Contingencies And Guarantees [Abstract]
Minimum Annual Lease Commitments	Year (in millions) 2016 $ 13 2017 12 2018 13 2019 4 Thereafter 17 $ 59

Segment And Geographic Inform37

Segment And Geographic Information (Tables)	12 Months Ended
	Dec. 31, 2015
Segment And Geographic Information [Abstract]
Segment And Geographic Information	Year-Ended December 31, 2015 2014 2013 (in millions) Net revenues Electronic brokerage $ 1,097 $ 952 $ 819 Market making 298 284 361 Corporate (206) (193) (103) Total net revenues $ 1,189 $ 1,043 $ 1,076 Income before income taxes Electronic brokerage $ 536 $ 589 $ 396 Market making 130 114 159 Corporate (208) (197) (103) Total income before income taxes $ 458 $ 506 $ 451 December 31, December 31, December 31, 2015 2014 2013 (in millions) Segment Assets Electronic brokerage $ 44,421 $ 38,280 $ 31,334 Market making 10,825 12,172 12,140 Corporate (6,512) (7,067) (5,602) Total assets $ 48,734 $ 43,385 $ 37,871
Schedule Of Total Net Revenues And Income Before Income Taxes By Geographic Area	Year-Ended December 31, 2015 2014 2013 (in millions) Net revenues United States $ 832 $ 773 $ 754 International 357 270 322 Total net revenues $ 1,189 $ 1,043 $ 1,076 Income before income taxes United States $ 294 $ 425 $ 324 International 164 81 127 Total income before income taxes $ 458 $ 506 $ 451

Regulatory Requirements (Tables

Regulatory Requirements (Tables)	12 Months Ended
	Dec. 31, 2015
Regulatory Requirements [Abstract]
Summary Of Capital, Capital Requirements And Excess Capital	Net Capital/ Eligible Equity Requirement Excess (in millions) IB LLC $ 2,367 $ 259 $ 2,108 TH LLC 375 1 374 THE 605 180 425 Other regulated Operating Companies 567 35 532 $ 3,914 $ 475 $ 3,439

Schedule I_Condensed Financia39

Schedule I—Condensed Financial Information of Registrant (Parent Company Only) (Tables)	12 Months Ended
	Dec. 31, 2015
Condensed Statements Of Comprehensive Income (Parent Company Only)	INTERACTIVE BROKERS GROUP, INC. (Parent Company Only) CONDENSED STATEMENTS OF COMPREHENSIVE INCOME Year Ended December 31, (in millions) 2015 2014 2013 Undistributed gains of subsidiaries, net $ 67 $ 63 $ 53 Income tax expense 18 18 16 Net income $ 49 $ 45 $ 37 Net income available for common stockholders $ 49 $ 45 $ 37 Cumulative translation adjustment, net of tax (10) (15) (3) Comprehensive income available for common stockholders $ 39 $ 30 $ 34
Condensed Statements Of Cash Flows (Parent Company Only)	INTERACTIVE BROKERS GROUP, INC. (Parent Company Only) CONDENSED STATEMENTS OF CASH FLOWS Year Ended December 31, (in millions) 2015 2014 2013 Cash flows from operating activities Net income $ 49 $ 45 $ 37 Adjustments to reconcile net income to net cash provided by operating activities Undistributed gains of subsidiaries, net (67) (63) (53) Deferred income taxes 13 22 18 Changes in operating assets and liabilities 9 5 2 Net cash provided by operating activities 4 9 4 Cash flows provided by investing activities 40 45 20 Cash flows used in financing activities (34) (39) (20) Effect of exchange rate changes on cash and cash equivalents (10) (15) (3) Net increase in cash and cash equivalents — — 1 Cash and cash equivalents at beginning of period 1 1 — Cash and cash equivalents at end of period $ 1 $ 1 $ 1 Supplemental disclosures of cash flow information Cash paid for interest $ — $ — $ — Cash paid for taxes $ — $ 6 $ —
Parent Company [Member]
Condensed Statements Of Financial Condition (Parent Company Only)	INTERACTIVE BROKERS GROUP, INC. (Parent Company Only) CONDENSED STATEMENTS OF FINANCIAL CONDITION December 31, (in millions, except share amounts) 2015 2014 Assets Cash and cash equivalents $ 1 $ 1 Investments in subsidiaries, equity basis 839 748 Other assets 317 294 Total assets $ 1,157 $ 1,043 Liabilities and Equity Liabilities: Payable to affiliates $ 291 $ 277 Accrued expenses and other liabilities 4 — 295 277 Stockholders' equity: Common stock, $0.01 par value per share: Class A – Authorized - 1,000,000,000, Issued - 64,121,150 and 58,612,245 shares, Outstanding – 63,985,335 and 58,473,186 shares as of December 31, 2015 and 2014 1 1 Class B – Authorized, Issued and Outstanding – 100 shares as of December 31, 2015 and 2014 — — Additional paid-in capital 718 636 Retained earnings 144 120 Accumulated other comprehensive income, net of income taxes of $0 and $1 as of December 31, 2015 and 2014 2 12 Treasury stock, at cost, 135,815 and 139,059 shares as of December 31, 2015 and 2014 (3) (3) Total equity 862 766 Total liabilities and equity $ 1,157 $ 1,043

Organization and Nature of Bu40

Organization and Nature of Business (Details)	12 Months Ended
	Dec. 31, 2015employeesegment	May. 03, 2007
Organization And Nature Of Business [Abstract]
IBG Inc. ownership % of IBG LLC	15.70%	10.00%
Number of employees | employee	1,087
Number of operating segments | segment	2

Significant Accounting Polici41

Significant Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	May. 03, 2007
Other assets reclass		$ 44
Other liabilities reclass		8
SIP expense - Year of grant			50.00%
SIP expense - Remaining vesting period			50.00%
SIP expense - Employees over 59 in year of grant			100.00%
Percent of shares forfeited post employment			50.00%
Over 59 percent of shares eligible			100.00%
U.S. Treasury Securities	$ 15,200	6,700
Securities Purchased Under Agreement to Resell Segregated for Regulatory Purposes	600	3,900
Equity method investments	32	37
Cost method investments	$ 34	$ 31
Property and equipment useful lives, description	Computer equipment is depreciated over three to five years and office furniture and equipment are depreciated over five to seven years. Qualifying costs for internally developed software are capitalized and amortized over the expected useful life of the developed software, not to exceed three years. Intangible assets with a finite life are amortized on a straight line basis over their estimated useful lives of three years, and tested for recoverability whenever events indicate that the carrying amounts may not be recoverable.
Maximum [Member] | Computer Equipment [Member]
Property and equipment useful lives	5 years
Maximum [Member] | Office Furniture And Equipment [Member]
Property and equipment useful lives	7 years
Maximum [Member] | Internally Developed Software [Member]
Property and equipment useful lives	3 years
Maximum [Member] | Finite-Lived Intangible Assets [Member]
Property and equipment useful lives	3 years
Minimum [Member] | Computer Equipment [Member]
Property and equipment useful lives	3 years
Minimum [Member] | Office Furniture And Equipment [Member]
Property and equipment useful lives	5 years

Equity And Earnings Per Share42

Equity And Earnings Per Share (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended			36 Months Ended	48 Months Ended	104 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2010	Dec. 31, 2014	Dec. 31, 2015	May. 03, 2007
Equity And Earnings Per Share [Line Items]
IBG Inc. ownership % of IBG LLC	15.70%					15.70%	10.00%
IBG Holdings ownership % of IBG LLC	84.30%					84.30%	90.00%
IBG Holdings Redemption of IBG LLC							10.00%
IBG Holdings LLC Ownership Percentage of Class B Common Stock							100.00%
Common stock, par value	$ 0.01					$ 0.01
Common stock, shares outstanding	63,985,335					63,985,335
Preferred stock shares authorized	10,000	10,000			10,000	10,000
Preferred stock shares issued	0	0			0	0
Preferred stock shares outstanding	0	0			0	0
Amortization period DTA (years)	15 years
Unamortized deferred tax asset arising from equity offerings	$ 288	$ 279			$ 279	$ 288
Percent of tax savings owed to IBG Holdings LLC	85.00%
Percentage of tax savings retained by IBG Inc.	15.00%
Deferred tax asset from common stock offerings	$ 460					460
Tax savings owed to IBG Holdings LLC	391					391
Tax savings retained by IBG Inc.	69					69
Tax savings paid to IBG Holdings LLC						99
Shares reserved for future issuance							360,000,000
Shares redeemed by IBG Holdings from IBG LLC				5,013,259
Cash Redemptions IBG Holdings				$ 114
Fair Value Of Issued Shares For Membership Exchange	$ 132					$ 132
Shares Issued	3,021,778				8,025,517
Thomas Peterffy and Affiliates Ownership	88.70%					88.70%	84.60%
Distribution from IBG LLC	$ 267	324	$ 163
Cash distribution to IBG, Inc.	$ 40	45	21
Dividend per share	$ 0.10
Dividends paid to common shareholders	$ 25	$ 23	$ 20
Declaration Date	Jan. 19, 2016
Payment Date	Mar. 14, 2016
Record Date	Mar. 1, 2016
Common Class A
Equity And Earnings Per Share [Line Items]
Common stock, par value	$ 0.01	$ 0.01			$ 0.01	$ 0.01
Shares authorized	1,000,000,000	1,000,000,000			1,000,000,000	1,000,000,000
Common stock, shares issued	64,121,150	58,612,245			58,612,245	64,121,150
Common stock, shares outstanding	63,985,335	58,473,186			58,473,186	63,985,335
Common Class B
Equity And Earnings Per Share [Line Items]
Shares authorized	100	100			100	100
Common stock, shares issued	100	100			100	100
Common stock, shares outstanding	100	100			100	100

Equity And Earnings Per Share43

Equity And Earnings Per Share (Basic Table) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Basic earnings per share:
Net income available for common stockholders	$ 49	$ 45	$ 37
Weighted average shares of common stock outstanding:
Weighted Average Number of Shares Outstanding, Basic	61,043,071	56,492,381	49,742,428
Basic earnings per share	$ 0.80	$ 0.79	$ 0.74
Common Class A
Weighted average shares of common stock outstanding:
Weighted Average Number of Shares Outstanding, Basic	61,042,971	56,492,281	49,742,328
Common Class B
Weighted average shares of common stock outstanding:
Weighted Average Number of Shares Outstanding, Basic	100	100	100

Equity And Earnings Per Share44

Equity And Earnings Per Share (Diluted Table) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Diluted earnings per share:
Net income available for common stockholders	$ 49	$ 45	$ 37
Weighted Average Shares Outstanding [Abstract]
Weighted Average Number of Shares Outstanding, Basic	61,043,071	56,492,381	49,742,428
Potentially dilutive common shares:
Issuable pursuant to employee incentive plans	1,466,725	1,217,287	1,182,308
Weighted Average Number of Shares Outstanding, Diluted	62,509,796	57,709,668	50,924,736
Earnings Per Share, Diluted	$ 0.78	$ 0.77	$ 0.73
Common Class A
Weighted Average Shares Outstanding [Abstract]
Weighted Average Number of Shares Outstanding, Basic	61,042,971	56,492,281	49,742,328
Common Class B
Weighted Average Shares Outstanding [Abstract]
Weighted Average Number of Shares Outstanding, Basic	100	100	100

Comprehensive Income (Details)

Comprehensive Income (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Comprehensive Income Detail [Abstract]
Comprehensive income available for common stockholders	$ 39	$ 30	$ 34
Earnings per share on comprehensive income:
Basic	$ 0.64	$ 0.52	$ 0.69
Diluted	$ 0.62	$ 0.51	$ 0.67
Weighted average common shares outstanding:
Weighted Average Number of Shares Outstanding, Basic	61,043,071	56,492,381	49,742,428
Weighted Average Number of Shares Outstanding, Diluted	62,509,796	57,709,668	50,924,736

Financial Assets And Financia46

Financial Assets And Financial Liabilities (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Financial Assets And Financial Liabilities [Abstract]
Other assets reclass		$ 44
Other liabilities reclass		8
Transfers of financial instruments sold, but not yet purchased from level 3 to level 1	$ 1
Transfers of other financial instruments owned from level 1 to level 2		1
Securities Purchased Under Agreement to Resell Segregated for Regulatory Purposes	$ 600	$ 3,900

Financial Assets And Financia47

Financial Assets And Financial Liabilities (Fair Value Table) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities segregated for regulatory purposes	$ 15,214	$ 6,681
Total financial instruments owned, at fair value	3,420	3,978
Total Financial Assets at Fair Value	18,634	10,659
Financial instruments sold, not yet purchased, at fair value	2,617	2,569
Total Financial Liabilities at Fair Value	2,617	2,569
Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial instruments owned, at fair value	1,650	2,592
Financial instruments sold, not yet purchased, at fair value	1,565	1,361
Options owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial instruments owned, at fair value	1,156	1,209
Financial instruments sold, not yet purchased, at fair value	1,042	1,197
Warrants and discount certificates owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial instruments owned, at fair value	81	72
Financial instruments sold, not yet purchased, at fair value	1	1
U.S. And Foreign Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial instruments owned, at fair value	527	98
Corporate And Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial instruments owned, at fair value	3	3
Currency forward contracts owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial instruments owned, at fair value	3	4
Financial instruments sold, not yet purchased, at fair value	9	10
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities segregated for regulatory purposes	15,214	6,681
Total financial instruments owned, at fair value	3,414	3,971
Total Financial Assets at Fair Value	18,628	10,652
Financial instruments sold, not yet purchased, at fair value	2,608	2,558
Total Financial Liabilities at Fair Value	2,608	2,558
Level 1 | Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial instruments owned, at fair value	1,650	2,592
Financial instruments sold, not yet purchased, at fair value	1,565	1,360
Level 1 | Options owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial instruments owned, at fair value	1,156	1,209
Financial instruments sold, not yet purchased, at fair value	1,042	1,197
Level 1 | Warrants and discount certificates owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial instruments owned, at fair value	81	72
Financial instruments sold, not yet purchased, at fair value	1	1
Level 1 | U.S. And Foreign Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial instruments owned, at fair value	527	98
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial instruments owned, at fair value	6	7
Total Financial Assets at Fair Value	6	7
Financial instruments sold, not yet purchased, at fair value	9	10
Total Financial Liabilities at Fair Value	9	10
Level 2 | Corporate And Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial instruments owned, at fair value	3	3
Level 2 | Currency forward contracts owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial instruments owned, at fair value	3	4
Financial instruments sold, not yet purchased, at fair value	$ 9	10
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, not yet purchased, at fair value		1
Total Financial Liabilities at Fair Value		1
Level 3 | Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, not yet purchased, at fair value		$ 1

Financial Assets And Financia48

Financial Assets And Financial Liabilities (Trading Gains from Market Making Transactions) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financial Assets And Financial Liabilities [Abstract]
Equities	$ 254	$ 247	$ 285
Fixed Income	1	21	25
Foreign Exchange	14	(7)	21
Trading gains	$ 269	$ 261	$ 331

Financial Assets And Financia49

Financial Assets And Financial Liabilities (Financial Assets and Liabilities Not Measured at Fair Value) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash and cash equivalents	$ 1,601	$ 1,269	$ 1,213	$ 1,381
Cash and securities segregated for regulatory purposes	21,309	15,404
Securities borrowed	3,924	3,660
Securities purchased under agreements to resell	195	386
Receivables from customer	17,050	17,051
Receivables from brokers, dealers and clearing organizations	692	1,131
Interest receivable	63	37
Other assets	480	469
Short-term borrowings		34
Securities Loaned	2,894	3,199
Payables to customer	37,084	31,796
Payables to brokers, dealers and clearing organizations	423	234
Interest payable	3	4
at Fair Value
Cash and cash equivalents	1,601	1,269
Cash and securities segregated for regulatory purposes	6,095	8,723
Securities borrowed	3,924	3,660
Securities purchased under agreements to resell	195	386
Receivables from customer	17,050	17,051
Receivables from brokers, dealers and clearing organizations	692	1,131
Interest receivable	63	37
Other assets	31	55
Total financial assets, not measured at fair value	29,651	32,312
Short-term borrowings		34
Securities Loaned	2,894	3,199
Payables to customer	37,084	31,796
Payables to brokers, dealers and clearing organizations	423	234
Interest payable	3	4
Total financial liabilities, not measured at fair value	40,404	35,267
Carrying Value
Cash and cash equivalents	1,601	1,269
Cash and securities segregated for regulatory purposes	6,095	8,723
Securities borrowed	3,924	3,660
Securities purchased under agreements to resell	195	386
Receivables from customer	17,050	17,051
Receivables from brokers, dealers and clearing organizations	692	1,131
Interest receivable	63	37
Other assets	28	30
Total financial assets, not measured at fair value	29,648	32,287
Short-term borrowings		34
Securities Loaned	2,894	3,199
Payables to customer	37,084	31,796
Payables to brokers, dealers and clearing organizations	423	234
Interest payable	3	4
Total financial liabilities, not measured at fair value	40,404	35,267
Level 1
Cash and cash equivalents	1,601	1,269
Cash and securities segregated for regulatory purposes	5,533	4,849
Total financial assets, not measured at fair value	$ 7,134	$ 6,118
Short-term borrowings
Securities Loaned
Payables to customer
Payables to brokers, dealers and clearing organizations
Interest payable
Total financial liabilities, not measured at fair value
Level 2
Cash and securities segregated for regulatory purposes	$ 562	$ 3,874
Securities borrowed	3,924	3,660
Securities purchased under agreements to resell	195	386
Receivables from customer	17,050	17,051
Receivables from brokers, dealers and clearing organizations	692	1,131
Interest receivable	63	37
Other assets	31	55
Total financial assets, not measured at fair value	22,517	26,194
Short-term borrowings		34
Securities Loaned	2,894	3,199
Payables to customer	37,084	31,796
Payables to brokers, dealers and clearing organizations	423	234
Interest payable	3	4
Total financial liabilities, not measured at fair value	$ 40,404	$ 35,267
Level 3
Cash and cash equivalents
Cash and securities segregated for regulatory purposes
Securities borrowed
Securities purchased under agreements to resell
Receivables from customer
Receivables from brokers, dealers and clearing organizations
Interest receivable
Other assets
Total financial assets, not measured at fair value
Short-term borrowings
Securities Loaned
Payables to customer
Payables to brokers, dealers and clearing organizations
Interest payable
Total financial liabilities, not measured at fair value

Financial Assets And Financia50

Financial Assets And Financial Liabilities (Netting of Financial Assets) (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets		$ 5,921	$ 9,205
Amounts Assets Offset in the Consolidated Statement of Financial Condition
Net Amounts of Assets Presented in the Statement of Financial Condition		$ 5,921	$ 9,205
Amounts of Assets Not Offset in the Condensed Consolidated Statement of Financial Condition		(5,606)	(8,975)
Net Exposure of Assets		315	230
Securities Segregated For Regulatory Purposes - Purchased Under Agreements To Resell [Member]
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	[1]	$ 562	$ 3,874
Amounts Assets Offset in the Consolidated Statement of Financial Condition
Net Amounts of Assets Presented in the Statement of Financial Condition		$ 562	$ 3,874
Amounts of Assets Not Offset in the Condensed Consolidated Statement of Financial Condition		(562)	(3,874)
Securities Borrowed [Member]
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets		$ 3,924	$ 3,660
Amounts Assets Offset in the Consolidated Statement of Financial Condition
Net Amounts of Assets Presented in the Statement of Financial Condition		$ 3,924	$ 3,660
Amounts of Assets Not Offset in the Condensed Consolidated Statement of Financial Condition		(3,816)	(3,564)
Net Exposure of Assets		108	96
Securities Purchased Under Agreement to Resell [Member]
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets		$ 195	$ 386
Amounts Assets Offset in the Consolidated Statement of Financial Condition
Net Amounts of Assets Presented in the Statement of Financial Condition		$ 195	$ 386
Amounts of Assets Not Offset in the Condensed Consolidated Statement of Financial Condition		(195)	(386)
Options owned [Member]
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets		$ 1,156	$ 1,209
Amounts Assets Offset in the Consolidated Statement of Financial Condition
Net Amounts of Assets Presented in the Statement of Financial Condition		$ 1,156	$ 1,209
Amounts of Assets Not Offset in the Condensed Consolidated Statement of Financial Condition		(1,032)	(1,150)
Net Exposure of Assets		124	59
Warrants and discount certificates owned [Member]
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets		$ 81	$ 72
Amounts Assets Offset in the Consolidated Statement of Financial Condition
Net Amounts of Assets Presented in the Statement of Financial Condition		$ 81	$ 72
Amounts of Assets Not Offset in the Condensed Consolidated Statement of Financial Condition		(1)	(1)
Net Exposure of Assets		80	71
Currency forward contracts owned [Member]
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets		$ 3	$ 4
Amounts Assets Offset in the Consolidated Statement of Financial Condition
Net Amounts of Assets Presented in the Statement of Financial Condition		$ 3	$ 4
Net Exposure of Assets		$ 3	$ 4
[1]	As of December 31, 2015 and December 31, 2014, the Company had $0.6 billion and $3.9 billion, respectively, of securities purchased under agreements to resell that were segregated to satisfy regulatory requirements. These securities are included in "Cash and securities - segregated for regulatory purposes" in the consolidated statements of financial condition.

Financial Assets And Financia51

Financial Assets And Financial Liabilities (Netting of Financial Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	$ 3,946	$ 4,407
Amounts Liabilities Offset in the Consolidated Statement of Financial Condition
Net Amounts of Liabilities Presented in the Statement of Financial Condition	$ 3,946	$ 4,407
Amounts of Liabilities Not Offset in the Consolidated Statement of Financial Condition (Cash or Financial Instruments)	(3,806)	(4,334)
Net Exposure of Liabilities	140	73
Securities Loaned [Member]
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	$ 2,894	$ 3,199
Amounts Liabilities Offset in the Consolidated Statement of Financial Condition
Net Amounts of Liabilities Presented in the Statement of Financial Condition	$ 2,894	$ 3,199
Amounts of Liabilities Not Offset in the Consolidated Statement of Financial Condition (Cash or Financial Instruments)	(2,773)	(3,183)
Net Exposure of Liabilities	121	16
Options Sold, Not Yet Purchased [Member]
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	$ 1,042	$ 1,197
Amounts Liabilities Offset in the Consolidated Statement of Financial Condition
Net Amounts of Liabilities Presented in the Statement of Financial Condition	$ 1,042	$ 1,197
Amounts of Liabilities Not Offset in the Consolidated Statement of Financial Condition (Cash or Financial Instruments)	(1,032)	(1,150)
Net Exposure of Liabilities	10	47
Warrants And Discount Certificates Sold, Not Yet Purchased [Member]
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	$ 1	$ 1
Amounts Liabilities Offset in the Consolidated Statement of Financial Condition
Net Amounts of Liabilities Presented in the Statement of Financial Condition	$ 1	$ 1
Amounts of Liabilities Not Offset in the Consolidated Statement of Financial Condition (Cash or Financial Instruments)	(1)	(1)
Currency Forward Contracts Sold, Not Yet Purchased [Member]
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	$ 9	$ 10
Amounts Liabilities Offset in the Consolidated Statement of Financial Condition
Net Amounts of Liabilities Presented in the Statement of Financial Condition	$ 9	$ 10
Net Exposure of Liabilities	$ 9	$ 10

Financial Assets And Financia52

Financial Assets And Financial Liabilities (Secured Financing Transactions) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities Loaned	$ 2,894	$ 3,199
Overnight and Open [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities Loaned	2,894
Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities Loaned	2,873
Common Stock [Member] | Overnight and Open [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities Loaned	2,873
Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities Loaned	21
Corporate Bonds [Member] | Overnight and Open [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities Loaned	$ 21

Collateralized Transactions (Na

Collateralized Transactions (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Disclosure Collateralized Transactions [Abstract]
Customers receivables	$ 17,050	$ 17,051
Securities repledged and deposited for customers	$ 600	$ 3,900
Percentage of securities repledged and deposited for customers	76.00%	91.00%

Collateralized Transactions (Am

Collateralized Transactions (Amounts Related to Collateralized Transactions) (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Permitted To Repledge [Member]
Collateralized Transactions [Line Items]
Securities lending transactions		$ 12,131	$ 10,907
Agreements to resell	[1]	757	4,260
Customer margin assets		14,905	14,933
Total collateralized transactions		27,793	30,100
Sold Or Repledged [Member]
Collateralized Transactions [Line Items]
Securities lending transactions		2,229	2,366
Agreements to resell	[1]	743	4,260
Customer margin assets		6,279	5,740
Total collateralized transactions		$ 9,251	$ 12,366
[1]	As of December 31, 2015, $0.6 billion or 76% (as of December 31, 2014, $3.9 billion or 91%) of securities acquired through agreements to resell that are shown as repledged have been deposited in a separate bank account for the exclusive benefit of customers in accordance with SEC Rule 15c3-3.

Collateralized Transactions (Fi

Collateralized Transactions (Financial instruments owned and pledged where the counterparty has the right to repledge) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Disclosure Collateralized Transactions [Abstract]
Stocks	$ 915	$ 1,860
U.S. and foreign government securities	518	76
Financial Instruments Owned and Pledged as Collateral - Eligible to be Repledged by Counterparty	$ 1,433	$ 1,936

Short-Term Borrowings (Narrativ

Short-Term Borrowings (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Short-Term Borrowings [Abstract]
Interest expense on short-term borrowings	$ 0	$ 1	$ 1

Short-Term Borrowings (Schedule

Short-Term Borrowings (Schedule Of Short-term Borrowings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Short-Term Borrowings [Abstract]
Overnight borrowing facilities, Principal		$ 34
Overnight borrowing facilities, Weighted Average Rates	0.51%	0.50%
Short-term borrowings		$ 34

Senior Secured Revolving Cred58

Senior Secured Revolving Credit Facility (Details)	May. 17, 2012USD ($)
Senior Secured Revolving Credit Facility [Abstract]
Senior secured revolving credit facility maximum capacity	$ 100,000,000

Other Income (Schedule Of Compo

Other Income (Schedule Of Components Of Other Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Income [Abstract]
Payments for order flow	$ 17	$ 25	$ 26
Market data fees	30	24	35
Account activity fees	16	14	15
Risk exposure fees	21	6
Gains (losses) on financial instruments, at fair value and other investments, net	(18)	(5)	(2)
Gains (losses) from currency diversification strategy, net	(206)	(185)	(91)
Other, net	18	10	8
Other income	$ (122)	$ (111)	$ (9)

Employee Incentive Plans (Narra

Employee Incentive Plans (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended			104 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	May. 03, 2007	Dec. 31, 2006
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
401(k) plan contribution expense	$ 3	$ 3	$ 3
ROI Dollar Unit Payable	$ 0	$ 3		$ 0
Common Stock Shares issued under ROI Unit Stock Plan					1,271,009
ROI Shares issued to IBG LLC					1,250,000
2007 SIP shares issued under ROI Unit Stock Plan					21,009
Fair value ROI Treasury Stock					$ 38
Vesting Percentage	• 10% on the date of the IPO (or on the first anniversary of the IPO, in the case of U.S. ROI Unit holders who made the above-referenced elections after December 31, 2006); and• an additional 15% on each of the first six anniversaries of the date of the IPO, assuming continued employment with the Company and compliance with other applicable covenants.
Fair Value ROI Accrual						$ 18
Common stock to be distributed to former employees under the ROI Unit Stock Plan	6,370
Maximum shares of stock distributable under 2007 Stock Incentive Plan	30,000,000			30,000,000
Shares granted to external directors				22,996
ROI stock plan forfeited shares adjustment		15,518
2007 Stock Incentive Plan Compensation Expense	$ 50	$ 41	$ 41
Estimated Future 2007 Stock Incentive Plan Compensation Expense	$ 37			$ 37
Percent Shares Forfeited Post Employment					50.00%
Over Fifty Nine Percent Unvested Shares Eligible					100.00%
Former employees vesting schedule (Years)	5 years
Post employment vesting percentage (Years 1 - 4)					12.50%
Post employment vesting percentage (Year 5)					50.00%
Post employment shares distribution				306,668
2007 Stock Incentive Plan (Shares)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Percentage	• 10% on the first vesting date, which is on or about May 9 of each year; and• an additional 15% on each of the following six anniversaries of the first vesting, assuming continued employment with the Company and compliance with non-competition and other applicable covenants.

Employee Incentive Plans (Share

Employee Incentive Plans (Share Grants And Fair Value) (Details) - USD ($) $ in Millions	12 Months Ended			68 Months Ended	104 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2015
Employee Incentive Plans [Abstract]
Shares granted	1,199,079	1,709,968	1,894,046	17,284,454
Fair Value - Date of Grant	$ 52	$ 49	$ 46	$ 302	$ 52
Shares Granted IPO to Date					22,087,547
Fair Value - Date of Grant IPO to Date					$ 449

Employee Incentive Plans (2007

Employee Incentive Plans (2007 Stock Incentive Plan, ROI Summary) (Details) - shares		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
2007 Stock Incentive Plan (Shares)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance		10,376,800	11,647,117		12,402,482
Shares Granted		1,199,079	1,709,968		1,894,046
Shares Forfeited		(163,221)	(535,085)	[1]	(334,111)
Shares Distributed		(2,487,127)	(2,445,200)		(2,315,300)
Ending Balance		8,925,531	10,376,800		11,647,117
Intrinsic Value Of SIP Shares Which Vested And Were Distributed [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Distributed	[2]	86,000,000	56,000,000		36,000,000
2007 ROI Unit Stock Plan (Shares) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance		9,614			169,289
Shares Forfeited			15,518	[1]	(6,423)
Shares Distributed		(3,244)	(5,904)		(162,866)
Ending Balance		6,370	9,614
[1]	ROI Unit Stock Plan number of forfeited shares related to prior years was adjusted by 15,518 shares during the period.
[2]	Intrinsic value of SIP shares distributed represents the compensation value reported to the participants.

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Abstract]
U.S. Statutory Tax Rate	35.00%	35.00%	35.00%
Undistributed accumulated earnings of foreign subsidiaries	$ 1,000	$ 1
Accumulated earnings of foreign pass through subsidiaries	400	400
Accumulated earnings subject to additional foreign tax	$ 300	$ 300

Income Taxes (Schedule Of The P

Income Taxes (Schedule Of The Provision For Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current:
Federal	$ 4	$ 1	$ (1)
Foreign	24	28	23
Total current	28	29	22
Deferred:
Federal	14	21	17
Foreign	1	(3)	(6)
Total deferred	15	18	11
Income tax expense	$ 43	$ 47	$ 33

Income Taxes (Reconciliation Of

Income Taxes (Reconciliation Of The Statutory U.S. Federal Income Tax Rate Of 35% To The Company’s Effective Tax Rate) (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Abstract]
U.S. Statutory Tax Rate	35.00%	35.00%	35.00%
Less: rate attributable to noncontrolling interests	(28.20%)	(28.60%)	(29.50%)
State, local and foreign taxes, net of federal benefit	2.60%	2.90%	2.00%
Effective income tax rate	9.40%	9.30%	7.50%

Income Taxes (Significant Compo

Income Taxes (Significant Components Of The Company’s Deferred Tax Assets (Liabilities)) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deferred tax assets:
Deferred tax asset arising from the acquisition of interests in IBGLLC	$ 288	$ 279	$ 295
Deferred compensation	5	6	8
Other	18	8	3
Total deferred tax assets	311	293	306
Deferred tax liabilities:
Foreign, primarily THE	3	3	8
Total deferred tax liabilities	3	3	8
Net deferred tax assets	$ 308	$ 290	$ 298

Property, Equipment and Intan67

Property, Equipment and Intangible Assets (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Equipment and Intangible Assets [Abstract]
Depreciation and amortization				$ 22	$ 20	$ 19
Amortization of Intangible Assets	$ 2	$ 2	$ 2

Property, Equipment and Intan68

Property, Equipment and Intangible Assets (Property And Equipment) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Property, Equipment and Intangible Assets [Abstract]
Leasehold improvements	$ 16	$ 17
Computer equipment	9	9
Internally developed software	47	44
Office furniture and equipment	2	3
Property and equipment, gross	74	73
Less—accumulated depreciation and amortization	(40)	(41)
Property and equipment, net	34	32
Intangible assets (acquired technology)	8
Less-accumulated amortization	(2)
Intangible assets, net	6
Total property equipment and intangible assets, net	$ 40	$ 32

Commitments, Contingencies an69

Commitments, Contingencies and Guarantees (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Commitments, Contingencies And Guarantees [Abstract]
Net Loss from Unsecured Customer Receivables	$ 119
Rent expense	14	$ 13	$ 13
Total future minimum annual lease commitments	$ 59

Commitments, Contingencies An70

Commitments, Contingencies And Guarantees (Minimum Annual Lease Commitments) (Details) $ in Millions	Dec. 31, 2015USD ($)
Commitments, Contingencies And Guarantees [Abstract]
2,016	$ 13
2,017	12
2,018	13
2,019	4
Thereafter	17
Total future minimum annual lease commitments	$ 59

Segment And Geographic Inform71

Segment And Geographic Information (Segment Table) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Net revenues	$ 1,189	$ 1,043	$ 1,076
Income before income taxes	458	506	451
Assets	48,734	43,385
Electronic Brokerage [Member]
Segment Reporting Information [Line Items]
Net revenues	1,097	952	819
Income before income taxes	536	589	396
Assets	44,421	38,280	31,334
Market Making [Member]
Segment Reporting Information [Line Items]
Net revenues	298	284	361
Income before income taxes	130	114	159
Assets	10,825	12,172	12,140
Corporate And Eliminations [Member]
Segment Reporting Information [Line Items]
Net revenues	(206)	(193)	(103)
Income before income taxes	(208)	(197)	(103)
Assets	$ (6,512)	$ (7,067)	$ (5,602)

Segment And Geographic Inform72

Segment And Geographic Information (Geographic Table) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Net revenues	$ 1,189	$ 1,043	$ 1,076
Income before income taxes	458	506	451
United States [Member]
Segment Reporting Information [Line Items]
Net revenues	832	773	754
Income before income taxes	294	425	324
International [Member]
Segment Reporting Information [Line Items]
Net revenues	357	270	322
Income before income taxes	$ 164	$ 81	$ 127

Regulatory Requirements (Narrat

Regulatory Requirements (Narrative) (Details) $ in Millions	Dec. 31, 2015USD ($)
Regulatory Requirements [Abstract]
Excess regulatory capital	$ 3,439

Regulatory Requirements (Summar

Regulatory Requirements (Summary Of Capital, Capital Requirements And Excess Capital) (Details) $ in Millions	Dec. 31, 2015USD ($)
Net Capital / Eligible Equity	$ 3,914
Required net capital	475
Excess regulatory capital	3,439
IB LLC [Member]
Net Capital / Eligible Equity	2,367
Required net capital	259
Excess regulatory capital	2,108
TH LLC [Member]
Net Capital / Eligible Equity	375
Required net capital	1
Excess regulatory capital	374
THE [Member]
Net Capital / Eligible Equity	605
Required net capital	180
Excess regulatory capital	425
Other Regulated Operating Companies [Member]
Net Capital / Eligible Equity	567
Required net capital	35
Excess regulatory capital	$ 532

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Related Party Transactions [Abstract]
Due from Related Parties - Customers	$ 85	$ 152
Due to Related Parties - Customers	$ 698	$ 274

Schedule I_Condensed Financia76

Schedule I—Condensed Financial Information of Registrant (Parent Company Only) (Condensed Statements Of Financial Conditions) (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Assets
Cash and cash equivalents	$ 1,601	$ 1,269	$ 1,213	$ 1,381
Other assets	480	469
Total assets	48,734	43,385
Liabilities and stockholders' equity
Payable to affiliates	291	277
Accrued expenses and other liabilities	78	87
Total liabilities	43,390	38,200
Stockholders’ equity:
Additional paid-in capital	718	635
Retained earnings	145	121
Accumulated other comprehensive income, net of income taxes of $0 and $1 at December 31, 2015 and 2014	2	12
Treasury stock, at cost, 135,815 and 139,059 shares as of December 31, 2015 and December 31, 2014	(3)	(3)
Total stockholders' equity	863	766
Total liabilities and stockholders' equity	$ 48,734	$ 43,385
Common stock, par value	$ 0.01
Common stock, shares outstanding	63,985,335
Treasury stock shares	135,815	139,059
Parent Company [Member]
Assets
Cash and cash equivalents	$ 1	$ 1	$ 1
Investments in subsidiaries, equity basis	839	748
Other assets	317	294
Total assets	1,157	1,043
Liabilities and stockholders' equity
Payable to affiliates	291	277
Accrued expenses and other liabilities	4
Total liabilities	295	277
Stockholders’ equity:
Additional paid-in capital	718	636
Retained earnings	144	120
Accumulated other comprehensive income, net of income taxes of $0 and $1 at December 31, 2015 and 2014	2	12
Treasury stock, at cost, 135,815 and 139,059 shares as of December 31, 2015 and December 31, 2014	(3)	(3)
Total stockholders' equity	862	766
Total liabilities and stockholders' equity	1,157	1,043
Common Class A
Stockholders’ equity:
Common stock	$ 1	$ 1
Common stock, par value	$ 0.01	$ 0.01
Shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	64,121,150	58,612,245
Common stock, shares outstanding	63,985,335	58,473,186
Common Class A | Parent Company [Member]
Stockholders’ equity:
Common stock	$ 1	$ 1
Common Class B
Stockholders’ equity:
Common stock
Shares authorized	100	100
Common stock, shares issued	100	100
Common stock, shares outstanding	100	100
Common Class B | Parent Company [Member]
Stockholders’ equity:
Common stock

Schedule I_Condensed Financia77

Schedule I—Condensed Financial Information of Registrant (Parent Company Only) (Condensed Statements Of Comprehensive Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income tax expense	$ 43	$ 47	$ 33
Net income	415	459	418
Net income available to common stockholders	49	45	37
Parent Company [Member]
Undistributed Gain Loss of Subsidiaries	67	63	53
Income tax expense	18	18	16
Net income	49	45	37
Net income available to common stockholders	49	45	37
Cumulative translation adjustment, net of tax	(10)	(15)	(3)
Comprehensive income attributable to common stockholders	$ 39	$ 30	$ 34

Schedule I_Condensed Financia78

Schedule I—Condensed Financial Information of Registrant (Parent Company Only) (Condensed Statements Of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net income	$ 415	$ 459	$ 418
Deferred income taxes	15	18	11
Net cash provided by operating activities	725	417	140
Net cash (used in) provided by investing activities	(35)	54	(33)
Net cash used in financing activities	(295)	(308)	(248)
Effect of exchange rate changes on cash and cash equivalents	(63)	(107)	(27)
Net increase (decrease) in cash and cash equivalents	332	56	(168)
Cash and cash equivalents at beginning of period	1,269	1,213	1,381
Cash and cash equivalents at end of period	1,601	1,269	1,213
Cash paid for interest	68	73	53
Cash paid for taxes	31	37	52
Parent Company [Member]
Net income	49	45	37
Undistributed Gain Loss of Subsidiaries	(67)	(63)	(53)
Deferred income taxes	13	22	18
Changes in operating assets and liabilities	9	5	2
Net cash provided by operating activities	4	9	4
Net cash (used in) provided by investing activities	40	45	20
Net cash used in financing activities	(34)	(39)	(20)
Effect of exchange rate changes on cash and cash equivalents	(10)	(15)	(3)
Net increase (decrease) in cash and cash equivalents			1
Cash and cash equivalents at beginning of period	1	1
Cash and cash equivalents at end of period	$ 1	1	$ 1
Cash paid for taxes		$ 6

Schedule I_Condensed Financia79

Schedule I—Condensed Financial Information of Registrant (Parent Company Only) (Transactions With Affiliates) (Details) - Parent Company [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Receivables from affiliates	$ 0
Dividends received	40	$ 45	$ 20
Payable to affiliates	$ 291	$ 277