CME (CME) 10-K 26 Feb 15 2014 FY Annual report Financial data

DEI_Statement

DEI Statement (USD $)	12 Months Ended
In Billions, except Share data, unless otherwise specified	Dec. 31, 2014	Jun. 30, 2014	Feb. 11, 2015
Entity Information [Line Items]
Entity Registrant Name	CME GROUP INC.
Entity Central Index Key	1156375
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Amendment Flag	FALSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float		$23.60
Class B Common Stock, Class B1 [Member]
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding			625
Class B Common Stock, Class B2 [Member]
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding			813
Class B Common Stock, Class B3 [Member]
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding			1,287
Class B Common Stock, Class B4 [Member]
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding			413
Class A Common Stock (Shares) [Member]
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding			337,340,642

CONSOLIDATED_BALANCE_SHEETS

CONSOLIDATED BALANCE SHEETS (USD $)	Dec. 31, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Assets
Cash and cash equivalents	$1,366.10		$2,469.70
Marketable securities	74.7		68.4
Accounts receivable, net of allowance of $1.2 and $1.2	341.2		302.7
Other current assets (includes $37.0 and $40.0 in restricted cash)	196.5		209.7
Cash performance bonds and guaranty fund contributions	40,566.80		21,355.10
Total current assets	42,545.30		24,405.60
Property, net of accumulated depreciation and amortization	508.9		513.4
Intangible assets-trading products	17,175.30	[1]	17,175.30	[1]
Intangible assets-other, net	2,637.40		2,741.20
Goodwill	7,569		7,569
Other assets (includes $72.4 and $74.0 in restricted cash)	1,805.60		1,873.30
Total Assets	72,241.50		54,277.80
Liabilities and Shareholders' Equity
Accounts payable	36.9		36.2
Short-term debt	0		749.9
Other current liabilities	927.5		1,169.80
Cash performance bonds and guaranty fund contributions	40,566.80		21,355.10
Total current liabilities	41,531.20		23,311
Long-term debt	2,107.90		2,107.20
Deferred tax liabilities, net	7,302.70		7,249.70
Other liabilities	376.2		449.4
Total Liabilities	51,318		33,117.30
Redeemable non-controlling interest			0
Shareholders' Equity:
Preferred stock, $0.01 par value, 10,000 shares authorized, none issued or outstanding	0		0
Additional paid-in capital	17,596.60		17,504.90
Retained earnings	3,317.30		3,494.60
Accumulated other comprehensive income (loss)	6.2		152
Total Shareholders' Equity	20,923.50		21,154.80
Non-controlling interest	0		5.7
Total Equity	20,923.50		21,160.50
Total Liabilities and Shareholders' Equity	72,241.50		54,277.80
Class A Common Stock (Shares) [Member]
Shareholders' Equity:
Common stock	3.4		3.3
Class B Common Stock (Shares) [Member]
Shareholders' Equity:
Common stock	$0		$0
[1]	(1)Trading products represent futures and options products acquired in our business combinations with CBOT Holdings, Inc., NYMEX Holdings, Inc. and The Board of Trade of Kansas City, Missouri, Inc. Clearing and transaction fees are generated through the trading of these products. These trading products, most of which have traded for decades, require authorization from the CFTC. Product authorizations from the CFTC have no term limits.

CONSOLIDATED_BALANCE_SHEETS_Ba

CONSOLIDATED BALANCE SHEETS Balance Sheet Parenthicals (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, except Share data, unless otherwise specified
Allowance for Doubtful Accounts Receivable	$1.20	$1.20
Restricted Cash and Cash Equivalents, Current	37	40
Restricted Cash and Cash Equivalents, Noncurrent	$72.40	$74
Series A junior participating preferred stock [Member]
Preferred Stock, Par or Stated Value Per Share	$0.01	$0.01
Preferred Stock, Shares Authorized	10,000,000	10,000,000
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0
Series B Preferred Stock [Member]
Preferred Stock, Par or Stated Value Per Share	$0	$0
Preferred Stock, Shares Authorized	0	0
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0
Class A Common Stock (Shares) [Member]
Common Stock, Par or Stated Value Per Share	$0.01	$0.01
Common Stock, Shares Authorized	1,000,000,000	1,000,000,000
Common Stock, Shares, Outstanding	335,452,000	333,852,000
Common Stock, Shares, Issued	335,452,000	333,852,000
Class B Common Stock (Shares) [Member]
Common Stock, Par or Stated Value Per Share	$0.01	$0.01
Common Stock, Shares Authorized	3,000	3,000
Common Stock, Shares, Outstanding	3,000	3,000
Common Stock, Shares, Issued	3,000	3,000

CONSOLIDATED_STATEMENTS_OF_INC

CONSOLIDATED STATEMENTS OF INCOME (USD $)	12 Months Ended
In Millions, except Share data in Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues
Clearing and transaction fees	$2,616.30	$2,460.40	$2,371.50
Market data and information services	356.3	315.4	387.1
Access and communication fees	82.7	83.2	88.8
Other	57.2	77.3	67.2
Total Revenues	3,112.50	2,936.30	2,914.60
Expenses
Compensation and benefits	552.1	518.9	496.7
Communications	32	35.3	40.1
Technology support services	58.2	53.6	50.7
Professional fees and outside services	129	130.3	126.8
Amortization of purchased intangibles	100.6	103	116.2
Depreciation and amortization	132.6	135.1	136.9
Occupancy and building operations	96.8	78.3	77
Licensing and other fee agreements	114.2	97.9	82.6
Other	128.6	146.9	95.6
Total Expenses	1,344.10	1,299.30	1,222.60
Operating Income	1,768.40	1,637	1,692
Non-Operating Income (Expense)
Investment income	35.8	44.9	38.7
Gains (losses) on derivative investments	0	0	-0.1
Interest and other borrowing costs	-119.4	-151.4	-132.2
Equity in net (gains) losses of unconsolidated subsidiaries	84.8	70.5	30.7
Other income (expense)	1.8	0	64.3
Total Non-Operating	3	-36	1.4
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	1,771.40	1,601	1,693.40
Income tax provision	644.5	622.9	786.7
Net Income	1,126.90	978.1	906.7
Less: net income attributable to redeemable non-controlling interest	-0.2	1.3	10.4
Net Income Attributable to CME Group	$1,127.10	$976.80	$896.30
Earnings per Common Share Attributable to CME Group:
Basic	$3.37	$2.94	$2.71
Diluted	$3.35	$2.92	$2.70
Weighted Average Number of Common Shares:
Basic	334,409	332,678	331,252
Diluted	336,063	334,398	332,319

CONSOLIDATED_STATEMENTS_OF_COM

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net income	$1,126.90	$978.10	$906.70
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax	-116.6	-221	174.7
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, before Tax	0	-0.7	-1.8
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	-5.2	63.9	-64.6
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	-121.8	-157.8	108.3
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax	-30	28.4	-13
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax	0.3	3.2	2.5
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax	11.2	-12	4.2
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	-18.5	19.6	-6.3
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	-2.3	128.8	-25.3
Derivative, Net Hedge Ineffectiveness Gain (Loss)	0	0	-0.1
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, before Tax	-1.5	1.6	1.1
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax	1.4	-49	9
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	-2.4	81.4	-15.1
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax	-5.2	-0.8	-1.3
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment Realized upon Sale or Liquidation, before Tax	0	0	18.4
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	2.1	0.3	-6.2
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	-3.1	-0.5	10.9
Other Comprehensive Income (Loss), Net of Tax	-145.8	-57.3	97.8
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	981.1	920.8	1,004.50
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	-0.2	1.3	10.5
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$981.30	$919.50	$994

CONSOLIDATED_STATEMENTS_OF_SHA

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (USD $)	Total	Common Stock and Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Parent [Member]	Noncontrolling Interest [Member]	Class A Common Stock (Shares) [Member]	Class B Common Stock (Shares) [Member]
In Millions, except Share data, unless otherwise specified	USD ($)	USD ($)	USD ($)	USD ($)	USD ($)	USD ($)
Total Equity Beginning Balance at Dec. 31, 2011	$21,552	$17,115.80	$4,324.60	$111.60	$21,552	$0
Beginning Balance (in shares) at Dec. 31, 2011							330,653,000	3,000
Comprehensive income:
Net income attributable to CME Group	896.3		896.3		896.3
Net income including portion attributable to nonredeemable non-controlling interest	896.3
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	97.7			97.7	97.7
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	-6.3
Total comprehensive income attributable to CME Group	994
Cash dividend on common stock	-1,227.50		-1,227.50		-1,227.50
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	5.8					5.8
Repurchase of Class A common stock (in shares)
Stock Repurchased During Period, Value	-18.6	-18.6			-18.6
Exercise of stock options (in shares)							745,000
Excess tax benefits from option exercises and restricted stock vesting	4.6	4.6			4.6
Exercise of stock options	22.1	22.1			22.1
Vesting of issued restricted Class A common stock (in shares)							366,000
Vesting of issued restricted Class A common stock	-9.8	-9.8			-9.8
Shares issued to Board of Directors (in shares)							40,000
Shares issued to Board of Directors	2.1	2.1			2.1
Shares issued under Employee Stock Purchase Plan (in shares)							28,000
Shares issued under Employee Stock Purchase Plan	1.6	1.6			1.6
Stock-based compensation	61.4	61.4			61.4
Total Equity Ending Balance at Dec. 31, 2012	21,424.90	17,216.40	3,993.40	209.3	21,419.10	5.8
Ending Balance (in shares) at Dec. 31, 2012							331,832,000	3,000
Comprehensive income:
Net income attributable to CME Group	976.8				976.8
Net income including portion attributable to nonredeemable non-controlling interest	-0.1
Net income including portion attributable to nonredeemable non-controlling interest	976.7
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	-57.3			-57.3	-57.3
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	19.6
Total comprehensive income attributable to CME Group	919.5
Cash dividend on common stock	-1,475.60		-1,475.60		-1,475.60
Adjustments to Additional Paid in Capital, Other	167.9	167.9			167.9
Exercise of stock options (in shares)							1,532,000
Excess tax benefits from option exercises and restricted stock vesting	6.8	6.8			6.8
Exercise of stock options	73.7	73.7			73.7
Vesting of issued restricted Class A common stock (in shares)							442,000
Vesting of issued restricted Class A common stock	-14.4	-14.4			-14.4
Shares issued to Board of Directors (in shares)							27,000
Shares issued to Board of Directors	2.1	2.1			2.1
Shares issued under Employee Stock Purchase Plan (in shares)							19,000
Shares issued under Employee Stock Purchase Plan	1.3	1.3			1.3
Stock-based compensation	54.4	54.4			54.4
Total Equity Ending Balance at Dec. 31, 2013	21,160.50	17,508.20	3,494.60	152	21,154.80	5.7
Ending Balance (in shares) at Dec. 31, 2013							333,852,000	3,000
Comprehensive income:
Net income attributable to CME Group	1,127.10				1,127.10
Net Income (Loss) Attributable to Noncontrolling Interest						-0.2
Net income including portion attributable to nonredeemable non-controlling interest	1,126.90
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	-145.8			-145.8	-145.8
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	-18.5
Total comprehensive income attributable to CME Group	981.3
Cash dividend on common stock	-1,304.40		-1,304.40		-1,304.40
Adjustments to Additional Paid in Capital, Other	-13.3	-7.8			-7.8
Noncontrolling Interest, Decrease from Deconsolidation						-5.5
Exercise of stock options (in shares)	1,030,952						1,031,000
Excess tax benefits from option exercises and restricted stock vesting	4	4			4
Exercise of stock options	53.3	53.3			53.3
Vesting of issued restricted Class A common stock (in shares)							511,000
Vesting of issued restricted Class A common stock	-16.7	-16.7			-16.7
Shares issued to Board of Directors (in shares)							34,000
Shares issued to Board of Directors	2.4	2.4			2.4
Shares issued under Employee Stock Purchase Plan (in shares)							24,000
Shares issued under Employee Stock Purchase Plan	1.8	1.8			1.8
Stock-based compensation	54.8	54.8			54.8
Total Equity Ending Balance at Dec. 31, 2014	$20,923.50	$17,600	$3,317.30	$6.20	$20,923.50	$0
Ending Balance (in shares) at Dec. 31, 2014							335,452,000	3,000

CONSOLIDATED_STATEMENTS_OF_SHA1

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY Equity Statement Parentheticals (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Stockholders' Equity Parentheticals [Abstract]
Common Stock, Dividends, Per Share, Declared	$3.88	$4.40	$3.70

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash Flows from Operating Activities
Net income	$1,126.90	$978.10	$906.70
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation	54.8	54.4	61.4
Amortization of purchased intangibles	100.6	103	116.2
Depreciation and amortization	132.6	135.1	136.9
Gain on contribution of Dow Jones Index asset group	0	0	-78.8
Loss on sale of Credit Market Analysis Ltd.	0	0	19.9
Gain (Loss) on Sale of Property Plant Equipment	0	27.1	0
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions	-8.6	-2	-15.8
Deferred income taxes	78.9	-6	82.2
Change in assets and liabilities:
Accounts receivable	-38.5	-35.5	-0.3
Other current assets	3.7	-2.6	-18.2
Other assets	-11.5	0.6	-65.6
Accounts payable	0.7	-5.5	11.2
Income tax payable	-105.6	-9.3	71.9
Other current liabilities	-46.1	42.5	-5.6
Other liabilities	-2.8	-5.5	-7.3
Other	6.3	6.1	4.9
Net Cash Provided by Operating Activities	1,291.40	1,280.50	1,219.70
Cash Flows from Investing Activities
Proceeds from maturities of available-for-sale marketable securities	37.5	36.5	29.5
Purchases of available-for-sale marketable securities	-38.3	-36.6	-32.5
Purchases of property, net	-140.7	-125.6	-141.8
Proceeds from sale of building property	7.9	192.4	148.6
Consideration paid in business combinations, net of cash acquired	0	0	-162.9
Investments in business ventures	-59.3	-4	-67.8
Loans and Leases Receivable, Related Parties, Additions	-6.2	0	0
Proceeds from sale of Credit Market Analysis Ltd., net of cash sold with business	0	0	42.4
Settlement of derivative related to debt issuance	0	127.8	-24.4
Net Cash Provided by (Used in) Investing Activities	-199.1	190.5	-208.9
Cash Flows from Financing Activities
Proceeds from other borrowings, net of issuance costs	0	748.7	747.7
Repayment of other borrowings	-750	-750	0
Cash dividends	-1,496.80	-599.1	-1,224.30
Proceeds from exercise of stock options	53.3	73.7	22.1
Distribution paid to non-controlling interest	-4.7	-80	0
Excess tax benefits related to employee option exercises and restricted stock vesting	4	6.8	4.6
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	-3.6	-7.3	0
Other	1.9	1.2	1.5
Net Cash Provided by (Used in) Financing Activities	-2,195.90	-606	-448.4
Net change in cash and cash equivalents	-1,103.60	865	562.4
Cash and cash equivalents, beginning of period	2,469.70	1,604.70	1,042.30
Cash and Cash Equivalents, End of Period	1,366.10	2,469.70	1,604.70
Supplemental Disclosure of Cash Flow Information
Income taxes paid	641.5	612.2	624.4
Interest paid (excluding securities lending program)	111.4	133.4	110.6
Non-cash investing activities:
Investment in S&P/Dow Jones Indices LLC	0	0	878.4
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	-2.3	128.8	-25.3
Non-cash financing activities:
dividends declared	$670.90	$868	$0

Organization_and_Business

Organization and Business	12 Months Ended
	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Business	ORGANIZATION AND BUSINESS
	Chicago Mercantile Exchange Inc. (CME), the Board of Trade of the City of Chicago, Inc. (CBOT), New York Mercantile Exchange, Inc. (NYMEX) and Commodity Exchange, Inc. (COMEX), wholly-owned subsidiaries of CME Group Inc. (CME Group), are designated contract markets for the trading of futures and options on futures contracts. CME, CBOT, NYMEX, COMEX, CME Clearing Europe Limited (CMECE) and CME Europe Limited (CME Europe) and their subsidiaries are referred to collectively as “the exchange” in the notes to the consolidated financial statements. CME Group and its subsidiaries are referred to collectively as “the company” in the notes to the consolidated financial statements.
	CME Group offers a wide range of products for trading and/or clearing, including those based on interest rates, credit default, equities, foreign exchange, agricultural commodities, energy and metals. Trades are executed through CME Group's electronic trading platforms, open outcry and privately negotiated transactions. Through its clearing houses, CME Group offers clearing, settlement and guarantees for all products cleared through the exchange.
	In June 2012, the company contributed certain Dow Jones Index assets and liabilities (DJI asset group) to S&P/Dow Jones Indices LLC (S&P/DJI), a new business venture with The McGraw-Hill Companies Inc. (McGraw). Dow Jones & Company (Dow Jones) retained a 10% redeemable non-controlling interest in the DJI asset group. The company also sold Credit Market Analysis Ltd. (CMA) to McGraw in conjunction with the creation of the business venture. Assets and liabilities contributed or sold as part of this transaction are excluded from the company's consolidated financial statements and accompanying notes beginning on June 30, 2012, while the financial results of the company's 24.4% interest in the new business venture with McGraw are included in the company's consolidated financial statements and accompanying notes beginning on June 30, 2012. In April 2013, the company purchased the remaining 10% non-controlling interest in the DJI asset group from Dow Jones for $80.0 million. As a result of the purchase of the non-controlling interest, the company's interest in S&P/DJI increased from 24.4% to 27%.
	CBOT acquired The Board of Trade of Kansas City, Missouri, Inc. (KCBT) and its subsidiaries, the Kansas City Board of Trade Clearing Corporation (KCBTCC) and the Board of Trade Investment Company (BOTIC), on November 30, 2012. KCBT maintained a 51% controlling interest in BOTIC, resulting in a nonredeemable non-controlling interest included in the company's consolidated statements of equity. The financial statements and accompanying notes presented in this report include the financial results of KCBT beginning on November 30, 2012. As of December 2013, KCBT was no longer regulated as a designated contract market and its operations were transferred to CBOT. In April 2013, KCBTCC was integrated into our U.S. clearing operations. The company purchased the non-controlling interest in BOTIC in June 2014.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
	Basis of Presentation. The accompanying consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States of America and include the accounts of the company and its majority-owned subsidiaries. All intercompany transactions and balances have been eliminated.
	Use of Estimates. The preparation of consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts and the disclosure of contingent amounts in the consolidated financial statements and accompanying notes. Estimates are based on historical experience, where applicable, and assumptions management believes are reasonable under the circumstances. Due to the inherent uncertainty involved with estimates, actual results may differ.
	Cash and Cash Equivalents. Cash and cash equivalents consist of cash and highly liquid investments with a maturity of three months or less at the time of purchase.
	Financial Investments. The company maintains short-term and long-term investments, classified as available-for-sale or trading securities. Available-for-sale investments are carried at their fair value, with unrealized gains and losses, net of deferred income taxes, reported as a component of accumulated other comprehensive income. Trading securities held in connection with non-qualified deferred compensation plans are recorded at fair value, with net realized and unrealized gains and losses and dividend income reported as investment income. Also, the company maintains long-term investments accounted for under the cost method and equity method, depending upon the degree of influence over the investee as held by the company.
	The company reviews its investments to determine whether a decline in fair value below the cost basis is other-than-temporary. If events and circumstances indicate that a decline in the value of the assets has occurred and is deemed to be other-than-temporary, the carrying value of the investments is reduced to its fair value and a corresponding impairment is charged to earnings.
	Fair Value of Financial Instruments. The company uses a three-level classification hierarchy of fair value measurements that establishes the quality of inputs used to measure fair value. The fair value of a financial instrument is the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The fair value of financial instruments is determined using various techniques that involve some level of estimation and judgment, the degree of which is dependent on the price transparency and the complexity of the instruments.
	Derivative Investments. The company uses derivative instruments, designated as cash flow hedges, to limit exposure to changes in interest rates. Derivatives are recorded at fair value in the consolidated balance sheets. The effective portion of the changes in the fair value of cash flow hedges are deferred in accumulated other comprehensive income. Any realized gains and losses from effective hedges are classified as interest expense in the consolidated statements of income, and any ineffective or excluded portion of a hedge is recognized in earnings immediately.
	Accounts Receivable. Accounts receivable are comprised of trade receivables and unbilled revenue including clearing and transaction fees and market data and information services revenue. All accounts receivable are stated at cost. Exposure to losses on receivables for clearing and transaction fees and other amounts owed by clearing firms is dependent on each clearing firm's financial condition and the memberships that collateralize fees owed to the exchange. The exchange retains the right to liquidate exchange memberships to satisfy a clearing firm's receivable. The allowance for doubtful accounts is calculated based on historical losses and management's assessment of probable future collections.
	Performance Bonds and Guaranty Fund Contributions. Performance bonds and guaranty fund contributions held for clearing firms may be in the form of cash, securities or other non-cash deposits.
	Performance bonds and guaranty fund contributions received in the form of cash held by CME and CMECE may be invested in U.S. Government securities and certain foreign government securities acquired through and held by a broker-dealer subsidiary of a bank, reverse repurchase agreements secured with highly rated government securities, money market funds or through CME's Interest Earning Facility (IEF) program. Any interest earned on CME investments accrues to CME and is included in investment income in the consolidated statements of income. CMECE may distribute any interest earned on CMECE investments to the clearing firms at its discretion. Because CME and CMECE have control of the cash collateral and the benefits and risks of ownership accrue to CME and CMECE, cash performance bonds and guaranty fund contributions are reflected in the consolidated balance sheets. Performance bonds and guaranty fund contributions assets on the consolidated balance sheets also include U.S. Treasury securities with maturity dates of 90 days or less. U.S. Treasury securities are purchased by CME, at its discretion, using cash collateral.
	Securities and other non-cash deposits may include U.S. Treasury securities, U.S. Government agency securities, Eurobonds, corporate bonds, other foreign government securities and gold bullion. Securities and other non-cash deposits are held in safekeeping by a custodian bank. Interest and gains or losses on securities deposited to satisfy performance bond and guaranty fund requirements accrue to the clearing firm. Because the benefits and risks of ownership accrue to the clearing firm, non-cash performance bonds and guaranty fund contributions are not reflected in the consolidated balance sheets.
	Cash contributed by CMECE to its guaranty funds is classified as restricted cash and is included in other current assets and other assets in the consolidated balance sheets.
	Property, Equipment and Leasehold Improvements. Property, equipment and leasehold improvements are stated at cost, less accumulated depreciation and amortization. Depreciation and amortization are calculated using the straight-line method, generally over two to thirty-nine years. Property and equipment are depreciated over their estimated useful lives. Leasehold improvements are amortized over the shorter of the remaining term of the respective lease to which they relate or the remaining useful life of the leasehold improvement. Land is reported at cost. Internal and external costs incurred in developing or obtaining computer software for internal use are capitalized and amortized on a straight-line basis over the estimated useful life of the software, generally two to four years.
	Operating Leases. All leases in which the company is the tenant are accounted for as operating leases. Landlord allowances are recorded as a reduction to rent expense on a straight-line basis over the term of the lease.
	Goodwill and Other Intangible Assets. Goodwill represents the excess of the purchase price over the fair value of the net assets acquired in a business combination. The company reviews goodwill and indefinite-lived intangible assets for impairment annually and whenever events or circumstances indicate that their carrying values may not be recoverable. The company may test goodwill quantitatively for impairment by comparing the carrying value of a reporting unit to its estimated fair value. Estimating the fair value of a reporting unit involves significant judgments inherent in the analysis including estimating the amount of and timing of future cash flows and the selection of appropriate discount rates and long-term growth rate assumptions. Changes in these estimates and assumptions could materially affect the determination of fair value of the reporting unit. If the carrying amount exceeds fair value, impairment is recorded. In certain circumstances, goodwill may be reviewed qualitatively for indications of impairment without utilizing valuation techniques to estimate fair value.
	The company evaluates the recoverability of indefinite-lived intangible assets by comparing the estimated fair value of the intangible asset to its carrying value. If the indefinite-lived intangible asset carrying value exceeds its fair value, an impairment loss is recognized in an amount equal to that excess. Estimating the fair value of indefinite-lived intangible assets involves the use of valuation techniques that rely on significant estimates and assumptions including forecasted revenue growth rates, forecasted allocations of expense and risk-adjusted discount rates. Changes in these estimates and assumptions could materially affect the determination of fair value for indefinite-lived intangible assets. In certain circumstances, indefinite-lived intangible assets may be reviewed qualitatively for indications of impairment without utilizing valuation techniques to estimate fair value.
	Intangible assets subject to amortization are also assessed for impairment when indicated by a change in economic or operational circumstances. The impairment assessment of these assets requires management to first compare the book value of the amortizing asset to undiscounted cash flows. If the book value exceeds the undiscounted cash flows, management is then required to estimate the fair value of the assets and record an impairment loss for the excess of the carrying value over the fair value.
	Business Combinations. The company accounts for business combinations using the acquisition method. The method requires the acquirer to recognize the assets acquired, liabilities assumed, and any non-controlling interest in the acquiree at the acquisition date, measured at their fair values as of that date. The company may use independent valuation services to assist in determining the estimated fair values.
	Employee Benefit Plans. The company recognizes the funded status of defined benefit postretirement plans in its consolidated balance sheets. Changes in that funded status are recognized in the year of change in other comprehensive income (loss). Plan assets and obligations are measured at year end. The company recognizes future changes in actuarial gains and losses and prior service costs in the year in which the changes occur through other comprehensive income (loss).
	Foreign Currency Translation. Foreign currency denominated assets and liabilities are re-measured into the functional currency using period-end exchange rates. Gains and losses from foreign currency transactions are included in other expense in the accompanying consolidated statements of income. When the functional currency differs from the reporting currency, revenues and expenses of foreign subsidiaries are translated from their functional currencies into U.S. dollars using weighted-average exchange rates while their assets and liabilities are translated into U.S. dollars using period-end exchange rates. Gains and losses resulting from foreign currency translations are included in accumulated other comprehensive income (loss) within shareholders' equity.
	Revenue Recognition. Revenue recognition policies for specific sources of revenue are discussed below.
	Clearing and Transaction Fees. Clearing and transaction fees include per-contract charges for trade execution, clearing, trading on the company's electronic trading platform and other fees. Fees are charged at various rates based on the product traded, the method of trade, the exchange trading privileges of the customer making the trade and the type of contract. Clearing and transaction fees are recognized as revenue when a buy and sell order are matched and the trade is cleared. Therefore, unfilled or canceled buy and sell orders have no impact on revenue. On occasion, the customer's exchange trading privileges may not be properly entered by the clearing firm and incorrect fees are charged for the transactions. When this information is corrected within the time period allowed by the exchange, a fee adjustment is provided to the clearing firm. A reserve is established for estimated fee adjustments to reflect corrections to customer exchange trading privileges. The reserve is based on the historical pattern of adjustments processed as well as specific adjustment requests. The company believes the allowances are adequate to cover estimated adjustments.
	Market Data and Information Services. Market data and information services represent revenue earned for the dissemination of market information. Revenues are accrued each month based on the number of devices reported by vendors. The exchange conducts periodic examinations of the number of devices reported and assesses additional fees as necessary. On occasion, customers will pay for services in a lump sum payment; however, revenue is recognized as services are provided.
	Access and Communication Fees. Access fees are the connectivity charges to customers of the company's electronic trading platform that are also used by market data vendors and customers. The fees include co-location fees, access fees for the electronic trading platform, line charges and hardware rental charges and can vary depending on the type of connection provided. An additional installation fee may be charged depending on the type of service requested and a disconnection fee may also be charged if certain conditions are met. Revenue is generally recognized monthly as the service is provided.
	Communication fees consist of equipment rental and usage charges to customers and firms that utilize various telecommunications hubs located internationally as well as networks and services in the Chicago and New York City facilities. Revenue is billed and recognized on a monthly basis.
	Other Revenues. Other revenues include processing services revenue, which is revenue generated from various strategic relationships, as well as management fees earned under the IEF programs. For processing services revenue and IEF revenue, revenue is recognized as services are provided.
	Other revenues also included revenue from the rental of commercial space that were recognized over the lease term using the straight-line method. Under this method, revenue was recorded evenly over the entire term of occupancy for leases with scheduled rent increases or rent abatements. Allowances for construction and other tenant costs were considered lease incentives and were recorded as a reduction to rental income on a straight-line basis over the term of the lease.
	Concentration of Revenue. One firm represented 12% of the company's clearing and transaction fees revenue in 2014. In 2013, one firm represented 11% and one firm represented 10% of the company's clearing and transaction fees revenue. Two firms each represented 12% of the company's clearing and transaction fees revenue in 2012. Should a clearing firm withdraw from the exchange, management believes that the customer portion of that firm's trading activity would likely transfer to another clearing firm. Therefore, management does not believe that the company is exposed to significant risk from the ongoing loss of revenue received from a particular clearing firm.
	The two largest resellers of market data represented approximately 44% of market data and information services revenue in 2014, 52% in 2013, and 43% in 2012. Should one of these vendors no longer subscribe to the company's market data, management believes that the majority of that firm's customers would likely subscribe to the market data through another reseller. Therefore, management does not believe that the company is exposed to significant risk from a loss of revenue received from any particular market data reseller.
	Share-Based Payments. The company accounts for share-based payments at fair value, which is based on the grant date price of the equity awards issued. The company recognizes expense relating to stock-based compensation on an accelerated basis. As a result, the expense associated with each vesting date within a stock grant is recognized over the period of time that each portion of that grant vests. The company estimates expected forfeitures of stock grants.
	Marketing Costs. Marketing costs are incurred for the production and communication of advertising as well as other marketing activities. These costs are expensed when incurred, except for costs related to the production of broadcast advertising, which are expensed when the first broadcast occurs.
	Income Taxes. Deferred income taxes arise from temporary differences between the tax basis and book basis of assets and liabilities. A valuation allowance is recognized if it is anticipated that some or all of a deferred tax asset may not be realized. The company accounts for uncertainty in income taxes recognized in its consolidated financial statements by using a more-likely-than-not recognition threshold based on the technical merits of the tax position taken or expected to be taken. The company classifies interest and penalties related to uncertain tax positions in income tax expense.
	Segment Reporting. The company reports the results of its operations as one operating segment primarily comprised of CME, CBOT, NYMEX and COMEX exchanges. The remaining operations do not meet the thresholds for reporting separate segment information.

Marketable_Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2014
Marketable Securities [Abstract]
Marketable Securities	MARKETABLE SECURITIES
	Available-for-Sale Securities. Certain marketable securities have been classified as available-for-sale. The amortized cost and fair value of these securities at December 31 were as follows:
		2014				2013
	(in millions)	Amortized		Fair		Amortized		Fair
		Cost		Value		Cost		Value
	U.S. Treasury securities	$	19.1	$	19.1	$	18.3	$	18.3
	Asset-backed security	0.7		0.4		0.8		0.4
	Equity securities	0.1		0.1		—		0.1
	Total	$	19.9	$	19.6	$	19.1	$	18.8
	Net unrealized gains (losses) on marketable securities classified as available-for-sale are reported as a component of other comprehensive income (loss) and included in the accompanying consolidated statements of comprehensive income and consolidated statements of equity.
	The fair value and gross unrealized losses of the asset-backed security were $0.4 million and $0.3 million, respectively, at December 31, 2014. The asset-backed security was in an unrealized loss position for more than 12 months at December 31, 2014 and was deemed not to be other-than-temporarily impaired. The company does not intend to sell and is not required to sell this asset-backed security.
	The amortized cost and fair value of the U.S. Treasury securities and asset-backed security at December 31, 2014, by contractual maturity, were as follows:
	(in millions)	Amortized		Fair
		Cost		Value
	Maturity of one year or less	$	19.1	$	19.1
	Maturity between one and five years	—		—
	Maturity between five and ten years	—		—
	Maturity greater than ten years	0.7		0.4
	Total	$	19.8	$	19.5
	Trading Securities. The company maintains additional investments in a diverse portfolio of mutual funds related to its non-qualified deferred compensation plans (note 11). The fair value of these securities was $55.1 million and $49.6 million at December 31, 2014 and 2013, respectively.

Performance_Bonds_and_Guaranty

Performance Bonds and Guaranty Fund Contributions	12 Months Ended
	Dec. 31, 2014
Performance Bonds and Guaranty Fund Contributions [Abstract]
Performance Bonds and Guaranty Fund Contributions	PERFORMANCE BONDS AND GUARANTY FUND CONTRIBUTIONS
	The company maintains two clearing houses: CME Clearing (a division of CME) and CMECE. The clearing houses clear and guarantee the settlement of contracts traded in their respective markets. In their guarantor roles, the clearing houses have precisely equal and offsetting claims to and from clearing firms on opposite sides of each contract, standing as an intermediary on every contract cleared. Clearing firm positions in the United States are held according to Commodity and Futures Trading Commission (CFTC) regulatory account segregation standards. To the extent that funds are not otherwise available to satisfy an obligation under the applicable contract, the clearing houses bear counterparty credit risk in the event that future market movements create conditions that could lead to clearing firms failing to meet their obligations to the clearing houses. The clearing houses reduce the exposure through risk management programs that include initial and ongoing financial standards for designation as a clearing firm, performance bond requirements, daily mark-to-market, mandatory guaranty fund contributions and intra-day monitoring. Each CME clearing firm is required to deposit and maintain balances in the form of cash, U.S. Government securities, certain foreign government securities, bank letters of credit or other approved investments to satisfy performance bond and guaranty fund requirements. Clearing firms that clear through CMECE are required to deposit and maintain collateral in the form of cash, certain U.S. and foreign government securities or other approved investments to satisfy performance bond and guaranty fund requirements. All non-cash deposits are marked to market and haircut on a daily basis.
	In addition, the rules and regulations of CBOT require that collateral be provided for delivery of physical commodities, maintenance of capital requirements and deposits on pending arbitration matters. To satisfy these requirements, clearing firms that have accounts that trade certain CBOT products have deposited cash, U.S. Treasury securities and letters of credit.
	The clearing houses mark-to-market open positions at least once a day (twice a day for futures and options contracts), and require payment from clearing firms whose positions have lost value and make payments to clearing firms whose positions have gained value. The clearing houses have the capability to mark-to-market more frequently as market conditions warrant.
	Under the extremely unlikely scenario of simultaneous default by every clearing firm who has open positions with unrealized losses, the maximum exposure related to positions other than credit default and interest rate swap contracts would be one half day of changes in fair value of all open positions, before considering the clearing houses' ability to access defaulting clearing firms' collateral deposits. For CME's cleared credit default swap and interest rate swap contracts, the maximum exposure related to CME's guarantee would be one full day of changes in fair value of all open positions, before considering CME's ability to access defaulting clearing firms' collateral. During 2014, the clearing houses transferred an average of approximately $3.0 billion a day through their clearing systems for settlement from clearing firms whose positions had lost value to clearing firms whose positions had gained value. The clearing houses reduce the guarantee exposure through initial and maintenance performance bond requirements and mandatory guaranty fund contributions. The company believes that the guarantee liability is immaterial and therefore has not recorded any liability at December 31, 2014.
	At December 31, 2014, performance bond and guaranty fund contribution assets on the consolidated balance sheets include cash and U.S. Treasury securities with maturity dates of 90 days or less. U.S. Treasury securities are purchased by CME, at its discretion, using cash collateral. The benefits, including interest earned, and risks of ownership accrue to CME. Interest earned is included in investment income on the consolidated statements of income. At December 31, 2014, the amortized cost and fair value of the U.S. Treasury securities were both $16.7 billion. The U.S. Treasury securities will mature during the first quarter of 2015. Securities deposited by the clearing firms are not reflected in the consolidated financial statements and the clearing houses do not earn any interest on these deposits. These balances may fluctuate significantly over time due to investment choices available to clearing firms and changes in the amount of contributions required.
	CME Clearing
	Clearing firms, at their option, may instruct CME to deposit the cash held by CME into one of the IEF programs. The total principal in the IEF programs was $16.4 billion at December 31, 2014 and $19.4 billion at December 31, 2013. The consolidated statements of income reflect management fees earned under the IEF programs of $14.9 million, $13.9 million and $10.6 million during 2014, 2013 and 2012, respectively. These fees are included in other revenues.
	CME and The Options Clearing Corporation (OCC) have a perpetual cross-margin arrangement, whereby a clearing firm may maintain a cross-margin account in which a CME clearing firm's positions in certain equity index futures and options are combined with certain positions cleared by OCC for purposes of calculating performance bond requirements. The performance bond deposits are held jointly by CME and OCC. Cross-margin cash, securities and letters of credit jointly held with OCC under the cross-margin agreement are reflected at 50% of the total, or CME's proportionate share per that agreement. If a participating firm defaults, the gain or loss on the liquidation of the firm's open position and the proceeds from the liquidation of the cross-margin account would be allocated 50% each to CME and OCC. The company believes that the guarantee liability is immaterial and therefore has not recorded any liability at December 31, 2014.
	In addition, CME has perpetual cross-margin agreements with Fixed Income Clearing Corporation (FICC) whereby the clearing firms' offsetting positions with CME and FICC are subject to reduced performance bond requirements. Clearing firms maintain separate performance bond deposits with each clearing house, but depending on the net offsetting positions between CME and FICC, each clearing house may reduce that firm's performance bond requirements. In the event of a firm default, the total liquidation net gain or loss on the firm's offsetting open positions and the proceeds from the liquidation of the performance bond collateral held by each clearing house's supporting offsetting positions would be divided evenly between CME and FICC. Additionally, if, after liquidation of all the positions and collateral of the defaulting firm at each respective clearing organization, and taking into account any cross-margining loss sharing payments, any of the participating clearing organizations has a remaining liquidating surplus, and any other participating clearing organization has a remaining liquidating deficit, any additional surplus from the liquidation would be shared with the other clearing house to the extent that it has a remaining liquidating deficit. Any remaining surplus funds would be passed to the bankruptcy trustee. The company believes that the guarantee liability is immaterial and therefore has not recorded any liability at December 31, 2014.
	Each CME clearing firm for futures and options is required to deposit and maintain specified guaranty fund contributions in the form of cash or approved securities. In the event that performance bonds, guaranty fund contributions and other assets required to support clearing membership of a defaulting CME clearing firm are inadequate to fulfill that clearing firm's outstanding financial obligation, the base guaranty fund for contracts other than credit default and interest rate swaps is available to cover potential losses after first utilizing $100.0 million of corporate contributions designated by CME to be used in the event of a default of a clearing firm for the base guaranty fund.
	CME maintains separate guaranty funds to support the clearing firms that clear interest rate swap products and credit default swap products. The funds for interest rate swaps and credit default are independent of the base guaranty fund and are isolated to clearing firms for products in the respective asset class. Each clearing firm for cleared interest rate swaps and cleared credit default swaps is required to deposit and maintain specified guaranty fund contributions in the form of cash or approved securities. In the event that performance bonds, guaranty fund contributions and other assets required to support clearing membership of a defaulting clearing firm for cleared interest rate swap contracts are inadequate to fulfill that clearing firm's outstanding financial obligation, the interest rate swaps contracts guaranty fund is available to cover potential losses after first utilizing $150.0 million of corporate contributions designated by CME to be used in the event of a default of a cleared interest rate swap clearing firm. In the event that performance bonds, guaranty fund contributions and other assets required to support clearing membership of a defaulting clearing firm for cleared credit default swap contracts are inadequate to fulfill that clearing firm's outstanding financial obligation, the credit default swaps contracts guaranty fund is available to cover potential losses after first utilizing corporate contributions designated by CME to be used in the event of default of a cleared credit default swap clearing firm, which is equal to the greater of $50.0 million and 5% of the credit default swap guaranty fund, up to a maximum of $100.0 million.
	CME maintains a 364-day multi-currency line of credit with a consortium of domestic and international banks to be used in certain situations by CME Clearing. CME may use the proceeds to provide temporary liquidity in the unlikely event of a clearing firm default, in the event of a liquidity constraint or default by a depositary (custodian of the collateral), or in the event of a temporary disruption with the domestic payments system that would delay payment of settlement variation between CME and its clearing firms. Clearing firm guaranty fund contributions received in the form of cash or U.S. Treasury securities as well as the performance bond assets of a defaulting firm can be used to collateralize the facility. The line of credit provides for borrowings of up to $7.0 billion. At December 31, 2014, guaranty fund contributions available for CME clearing firms were $6.6 billion. CME has the option to request an increase in the line from $7.0 billion to $10.0 billion, subject to the approval of participating banks. In addition to the 364-day fully secured, committed multi-currency line of credit, the company also has the option to use the $1.8 billion multi-currency revolving senior credit facility to provide liquidity for the clearing house in the unlikely event of default.
	CMECE
	The company maintains a guaranty fund for CMECE commodity and foreign exchange clearing firms. In the unlikely event of default by a CMECE clearing firm, the company would first apply assets of the defaulting clearing firm to satisfy its payment obligations. These assets include the defaulting firm's performance bonds and guaranty fund contributions. Thereafter, if the default remains unsatisfied after first applying assets of the defaulting clearing firm to satisfy its payment obligation, the company would use guaranty fund contributions of $57.0 million of CMECE funds. At December 31, 2014, clearing firms contributed $10.0 million to the commodity and foreign exchange guaranty fund. CMECE will still use at least $20.0 million of CMECE funds in addition to the commodity or foreign exchange clearing firms' guaranty fund contributions in the event of a default.
	The company also maintains a guaranty fund for CMECE interest rate swap clearing firms. In the unlikely event of default by a CMECE clearing firm, the company would first apply assets of the defaulting clearing firm to satisfy its payment obligations. These assets include the defaulting firm's performance bonds and guaranty fund contributions. If the default remains unsatisfied, the company would apply guaranty fund contributions of $50.5 million for interest rate swap clearing firms that will be contributed by CMECE. Interest rate swap clearing firm contributions to the interest rate swap guaranty fund totaled $101.1 million at December 31, 2014.
	CME is required under the Commodity Exchange Act in the United States to segregate cash and securities deposited by clearing firms on behalf of its customers. In addition, CME requires segregation of all funds deposited by its clearing firms from operating funds. CMECE holds cash and securities deposited by clearing firms in segregated accounts, and maintains distinct accounts for its own operating funds.
	Cash and non-cash deposits held as performance bonds and guaranty fund contributions at fair value at December 31 for CME and CMECE were as follows:
		2014				2013
	(in millions)	Cash		Non-Cash		Cash		Non-Cash
				Deposits				Deposits
				and				and
				IEF Funds				IEF Funds
	Performance bonds1	$	38,729.00	$	93,972.70	$	20,060.10	$	88,152.30
	Guaranty fund contributions	1,719.90		5,699.00		1,290.10		4,834.80
	Cross-margin arrangements	102.2		91.2		3.1		76.5
	Performance collateral for delivery	15.7		2.1		1.8		2.6
	Total	$	40,566.80	$	99,765.00	$	21,355.10	$	93,066.20
	(1) Cash performance bonds include cash collateral reinvested in U.S. Treasury securities.
	Performance bonds and guaranty fund contributions include collateral for clearing firms for both clearing houses. Cross-margin arrangements include collateral for the cross-margin accounts with OCC and FICC. The performance bond collateral for delivery includes deposits to meet CBOT delivery requirements.
	Cash performance bonds may include intraday settlement, if any, that is owed to the clearing firms and paid the following business day. The balance of intraday settlements was $224.2 million and $115.6 million at December 31, 2014 and 2013, respectively. Intraday settlements may be invested on an overnight basis and are offset by an equal liability owed to clearing firms.
	In addition to cash, securities and other non-cash deposits, irrevocable letters of credit may be used as performance bond deposits for clearing firms. At December 31, these letters of credit, which are not included in the accompanying consolidated balance sheets, were as follows:
	(in millions)	2014		2013
	Performance bonds	$	2,441.90	$	3,453.10
	Guaranty fund contributions	25		25
	Cross-margin arrangements	5.5		—
	Performance collateral for delivery	950.4		1,005.50
	Total Letters of Credit	$	3,422.80	$	4,483.60
	All cash, securities and letters of credit posted as performance bonds are only available to meet the financial obligations of that clearing firm to the clearing houses.

Property

Property	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment, Net [Abstract]
Property	PROPERTY
	A summary of the property accounts at December 31 is presented below:
	(in millions)	2014			2013			Estimated Useful Life
	Land and land improvements	$	17.7		$	20.1		10 - 20 years (1)
	Building and building improvements	273.5			280			3 - 39 years
	Leasehold improvements	219.1			218.6			3 - 24 years
	Furniture, fixtures and equipment	360.1			352.1			2 - 7 years
	Software and software development costs	379.5			321			2 - 4 years
	Total property	1,249.90			1,191.80
	Less accumulated depreciation and amortization	(741.0		)	(678.4		)
	Property, net	$	508.9		$	513.4
	(1) Estimated useful life applies only to land improvements.
	In November 2013, CME Group sold its building in New York for $200.0 million resulting in a net loss of $27.1 million. At the time of the sale, the company leased back a portion of the property. The company recognized the loss as an operating expense in 2013.

Intangible_Assets_and_Goodwill

Intangible Assets and Goodwill	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets and Goodwill	INTANGIBLE ASSETS AND GOODWILL
	Intangible assets consisted of the following at December 31:
			2014							2013
	(in millions)		Assigned Value		Accumulated			Net Book		Assigned Value		Accumulated			Net Book
					Amortization			Value				Amortization			Value
	Amortizable Intangible Assets:
	Clearing firm, market data and other customer relationships		$	2,838.80	$	(658.8	)	$	2,180.00	$	2,838.80	$	(563.2	)	$	2,275.60
	Technology-related intellectual property		29.4		(23.5		)	5.9		33.8		(19.8		)	14
	Other		2.4		(0.9		)	1.5		2.4		(0.8		)	1.6
	Total amortizable intangible assets		$	2,870.60	$	(683.2	)	2,187.40		$	2,875.00	$	(583.8	)	2,291.20
	Indefinite-Lived Intangible Assets:
	Trade names							450							450
	Total intangible assets—other, net							$	2,637.40						$	2,741.20
	Trading products (1)							$	17,175.30						$	17,175.30
	_______________
	-1	Trading products represent futures and options products acquired in our business combinations with CBOT Holdings, Inc., NYMEX Holdings, Inc. and The Board of Trade of Kansas City, Missouri, Inc. Clearing and transaction fees are generated through the trading of these products. These trading products, most of which have traded for decades, require authorization from the CFTC. Product authorizations from the CFTC have no term limits.
	As part of its sale of its building in New York in November 2013, the company sold the rights to lease agreements with tenants occupying space within the building. The lease agreements, which are included in lease-related intangibles, had a net book value of $13.8 million on the date of sale.
	The originally assigned useful lives for the amortizable intangible assets as of December 31, 2014 are as follows:
	Clearing firm, market data and other customer relationships	5 - 30 years
	Technology-related intellectual property	4 - 5 years
	Other	3 - 24.5 years
	Total amortization expense for intangible assets was $100.6 million, $103.0 million and $116.2 million for the years ended December 31, 2014, 2013 and 2012, respectively. As of December 31, 2014, the future estimated amortization expense related to amortizable intangible assets is expected to be as follows:
	(in millions)
	2015	$	99.5
	2016	96.1
	2017	95.5
	2018	94.7
	2019	94.7
	Thereafter	1,706.90
	Goodwill activity consisted of the following for the years ended December 31, 2014 and 2013:
	(in millions)		Balance at December 31, 2013		Business			Divestitures		Other		Balance at December 31, 2014
					Combinations					Activity
	CBOT Holdings		$	5,035.70	$	—		$	—	$	—	$	5,035.70
	NYMEX Holdings		2,462.20		—			—		—		2,462.20
	Other		71.1		—			—		—		71.1
	Total Goodwill		$	7,569.00	$	—		$	—	$	—	$	7,569.00
	(in millions)		Balance at December 31, 2012		Business			Divestitures		Other		Balance at December 31, 2013
					Combinations					Activity
	CBOT Holdings		$	5,035.70	$	—		$	—	$	—	$	5,035.70
	NYMEX Holdings		2,462.20		—			—		—		2,462.20
	Other		69		—			—		2.1		71.1
	Total Goodwill		$	7,566.90	$	—		$	—	$	2.1	$	7,569.00

Longterm_Investments

Long-term Investments	12 Months Ended
	Dec. 31, 2014
Long-term Investments [Abstract]
Long-term Investments	LONG-TERM INVESTMENTS
	The company maintains various long-term investments as described below. The investments are recorded in other assets in the consolidated balance sheets.
	BM&FBOVESPA S.A. The company owns an approximate 5% interest in BM&FBOVESPA S. A. (BM&FBOVESPA). BM&FBOVESPA is a stock and derivatives exchange in Brazil. The company accounts for its investment in BM&FBOVESPA as an available-for-sale security. The fair value of the investment was $410.8 million and $473.1 million at December 31, 2014 and 2013, respectively. The cost basis of the investment was $405.7 million and $356.9 million at December 31, 2014 and 2013, respectively. The company and BM&FBOVESPA have entered into several agreements including co-location, licensing, order routing and technology development arrangements.
	Bolsa Mexicana de Valores, S.A.B de C.V. In March 2010, the company acquired an approximate 2% interest in Bolsa Mexicana de Valores, S.A.B. de C.V. (Bolsa Mexicana), a financial exchange operator in Mexico. The company accounts for its investment in Bolsa Mexicana stock as an available-for-sale security. The fair value of the investment in Bolsa Mexicana at December 31, 2014 and 2013 was $21.2 million and $26.8 million, respectively. The cost basis of the investment was $17.3 million at December 31, 2014 and 2013. The company and Bolsa Mexicana maintain a strategic partnership that includes an order routing agreement for derivative products.
	Bursa Malaysia Derivatives Berhad. The company owns a 25% interest in Bursa Malaysia Derivatives Berhad (Bursa Malaysia), and accounts for its investment in Bursa Malaysia using the equity method of accounting. The company's investment in Bursa Malaysia was $27.6 million at December 31, 2014. The company and Bursa Malaysia have entered into several agreements including agreements to provide licensing, order routing and trade matching services.
	DME Holdings Limited. The company owns an approximate 50% interest in DME Holdings Limited (DME Holdings), and accounts for its investment in DME Holdings using the equity method of accounting. The company's investment in DME Holdings was $7.6 million at December 31, 2014. The company and DME Holdings maintain an agreement for Dubai Mercantile Exchange (DME) futures contracts to be exclusively traded on the CME Globex platform.
	S&P/DJI Indices LLC. The company owns a 27% interest in S&P/DJI and accounts for its investment in S&P/DJI using the equity method of accounting. The company's investment in S&P/DJI was $962.2 million at December 31, 2014. The company has long-term exclusive licensing agreements with S&P/DJI to list products based on the Standard & Poor's Indices and on Dow Jones Indices.

Debt

Debt	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Debt	DEBT
	Short-term debt consisted of the following at December 31:
	(in millions)		2014		2013
	$750.0 million fixed rate notes due February 2014, stated rate of 5.75%		$	—	$	749.9
	Total short-term debt		$	—	$	749.9
	Long-term debt consisted of the following at December 31:
	(in millions)		2014		2013
	$612.5 million fixed rate notes due March 2018, stated rate of 4.40%(1)		$	611	$	610.5
	$750.0 million fixed rate notes due September 2022, stated rate of 3.00% (2)		748.2		748
	$750.0 million fixed rate notes due September 2043, stated rate of 5.30% (3)		748.7		748.7
	Total long-term debt		$	2,107.90	$	2,107.20
	_______________
	-1	In February 2010, the company entered into a forward-starting interest rate swap agreement that modified the interest obligation associated with these notes so that the interest payable on the notes effectively became fixed at a rate of 4.46%.
	-2	In August 2012, the company entered into a forward-starting interest rate swap agreement that modified the interest obligation associated with these notes so that the interest payable on the notes effectively became fixed at a rate of 3.32%.
	-3	In August 2012, CME Group entered into a forward-starting interest rate swap agreement that modified the interest obligation associated with these notes so that the interest payable on the notes effectively became fixed at a rate of 4.73%.
	Long-term debt maturities, at par value, were as follows as of December 31, 2014:
	(in millions)	Par Value
	2015	$	—
	2016	—
	2017	—
	2018	612.5
	2019	—
	Thereafter	1,500.00
	The fair value of the fixed-rate notes due 2018, which are classified as level 3 under the fair value hierarchy, was derived using a standard valuation model with market-based observable inputs including U.S. Treasury yields and interest rate spreads. The fair values of the fixed-rate notes due 2022 and 2043, which are classified as level 2 under the fair value hierarchy, were estimated using quoted market prices. For further information on the three-level classification hierarchy of fair value measurements, see note 19. At December 31, 2014, the fair values of the fixed-rate notes by maturity date were as follows:
	(in millions)		Fair Value
	$612.5 million fixed rate notes due March 2018, stated rate of 4.40%		$	650.5
	$750.0 million fixed rate notes due September 2022, stated rate of 3.00%		763
	$750.0 million fixed rates notes due September 2043, stated rate of 5.30%		913.4

Derivative_Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2014
General Discussion of Derivative Instruments and Hedging Activities [Abstract]
Derivative Instruments	DERIVATIVE INVESTMENTS
	The company mitigates certain financial exposures to interest rate risk through the use of derivative financial instruments as part of its risk management program. All derivatives have been designated as cash flow hedges.
	In December 2014, the company entered into a forward-starting interest rate swap contract, with a notional value of $500.0 million, to hedge the risk of changes in underlying benchmark interest rates associated with the expected issuance of fixed rate debt in 2015. In August 2012, the company entered into two forward-starting interest rate swap contracts, with an aggregate notional value of $1.5 billion, to hedge the risk of changes in underlying benchmark interest rates associated with issuances of fixed rate debt. One of these swap contracts was settled in conjunction with the issuance of fixed rate debt in September 2012. The other swap contract was settled in conjunction with the issuance of the fixed rate debt in September 2013. The hedges were considered highly effective. The effective portion is included in other comprehensive income and is being amortized over the term of the debt.
	The fair value and location of outstanding derivative instruments in the consolidated balance sheet were as follows at December 31:
	(in millions)	Balance Sheet Location		2014			2013
	Interest rate contract	Other current liabilities		$	2.3		$	—
	The pre-tax effect of derivative instruments on the consolidated statements of income as well as accumulated other comprehensive income (OCI) within the consolidated statements of comprehensive income and consolidated statements of shareholders' equity for the years ended December 31, 2014 and 2013 were as follows:
		Gains (Losses)						(Gains) Losses Reclassified from						Gains (Losses)
		Recognized in OCI						Accumulated OCI						Recognized in Income
		(Effective Portion)						(Effective Portion)						(Ineffective Portion)
	(in millions)	2014			2013			Location	2014			2013		Location	2014		2013
	Interest rate contracts	$	(2.3	)	$	128.8		Interest and other borrowing costs	$	(1.5	)	$	1.6	Gains (losses) on derivative investments	$	—	$	—
	At December 31, 2014, the company expects to reclassify $1.4 million of net gains on derivative instruments from accumulated other comprehensive income to net income as a net reduction to interest expense during the next twelve months.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES
	Income before income taxes and the income tax provision consisted of the following for the years ended December 31. The company is subject to regulation under a wide variety of U.S., federal, state and foreign tax laws and regulations.
	(in millions)	2014				2013				2012
	Income before income taxes:
	Domestic	$	1,783.70			$	1,599.20			$	1,703.50
	Foreign	(12.3		)		1.8				(10.1		)
	Total	$	1,771.40			$	1,601.00			$	1,693.40
	Income tax provision:
	Current:
	Federal	$	526.4			$	491.9			$	585.2
	State	36.5				128.8				117.6
	Foreign	2.7				8.2				1.7
	Total	565.6				628.9				704.5
	Deferred:
	Federal	47.1				(157.6		)		50.3
	State	32.4				153.4				37
	Foreign	(0.6		)		(1.8		)		(5.1		)
	Total	78.9				(6.0		)		82.2
	Total Income Tax Provision	$	644.5			$	622.9			$	786.7
	Reconciliation of the statutory U.S. federal income tax rate to the effective tax rate is as follows:
		2014			2013			2012
	Statutory U.S. federal tax rate	35	%		35	%		35	%
	State taxes, net of federal benefit	1.6			4.8			4.8
	Domestic production activities deduction	(1.4	)		(7.7	)		—
	Increase (decrease) in domestic valuation allowance	0.1			0.6			—
	Impact of revised state and local apportionment estimates	1.1			6.6			1
	Deferred taxes associated with McGraw venture and CMA sale	—			—			6.3
	Other, net	—			(0.4	)		(0.6	)
	Effective Tax Rate	36.4	%		38.9	%		46.5	%
	In 2014, the effective tax rate was higher than the statutory tax rate largely due to state income taxes and the impact of revised state and local apportionment factors on the company's deferred tax expense. However, the state income tax expense was reduced for benefits achieved in various settlements of state and local income tax audits. The effective tax rate was primarily reduced by the Section 199 Domestic Productions Activities Deduction (Section 199 deduction). This deduction is related to certain activities performed by the company's electronic platform.
	In 2013, the effective tax rate was higher than the statutory tax rate due to changes in estimate of state and local income tax apportionment factors.  The changes in estimate of state and local income tax apportionment factors significantly impacted the company’s deferred tax expense and expense related to uncertain tax positions. The increase in effective tax rate was partially offset by benefits accrued for the Section 199 deduction.  The benefits accrued include the 2013 estimated benefit as well as benefits accrued for prior periods in which tax returns have been filed claiming the deduction or are expected to be filed claiming the deduction.
	In 2012, the effective tax rate was higher than the statutory tax rate because of an increase to the income tax provision due to the establishment of deferred income tax liabilities associated with the McGraw venture.
	At December 31, deferred income tax assets (liabilities) consisted of the following:
	(in millions)	2014				2013
	Net Current Deferred Income Tax Assets:
	Unrealized loss on securities	$	3			$	3
	Stock-based compensation	19.2				19.1
	Accrued expenses and other	2.2				30.2
	Net Current Deferred Income Tax Assets	$	24.4			$	52.3
	Net Non-Current Deferred Income Tax Assets:
	Domestic unrealized loss on investment in BM&FBOVESPA	$	101.7			$	59.7
	Foreign losses	19.7				18.8
	Domestic losses	7.3				8.5
	Stock-based compensation	30.7				49.3
	Deferred compensation and other benefit plans	38.1				23.8
	Property	44.3				35.2
	Unrealized losses on securities	16.5				22.9
	Accrued expenses and other	—				13.8
	Subtotal	258.3				232
	Valuation allowance	(99.2		)		(47.5		)
	Total non-current deferred income tax assets	159.1				184.5
	Non-Current Deferred Income Tax Liabilities:
	Purchased intangible assets	(7,448.2		)		(7,434.2		)
	Other	(13.6		)		—
	Total non-current deferred income tax liabilities	(7,461.8		)		(7,434.2		)
	Net Non-Current Deferred Income Tax Liabilities	$	(7,302.7	)		$	(7,249.7	)
	A valuation allowance is recorded when it is more-likely-than-not that some portion or all of the deferred income tax assets may not be realized. The ultimate realization of the deferred income tax assets depends on the ability to generate sufficient taxable income of the appropriate character in the future and in the appropriate taxing jurisdictions.
	At December 31, 2014 and 2013, the company had domestic and foreign income tax loss carry forwards of $118.9 million and $117.3 million, respectively. These amounts primarily related to losses from the acquisition of Swapstream Limited and its affiliates, the acquisition of Pivot, Inc., and losses incurred in the operation of various foreign entities. At December 31, 2014 and 2013, the company also had net built-in, unrealized capital losses of $317.7 million and $223.4 million, respectively. At December 31, 2014 and 2013, the company determined that it was not more-likely-than-not that deferred income tax assets related to the acquisition of Swapstream Limited and its affiliates, other deferred income tax assets created from the start-up of various foreign operations and certain built-in losses will be fully realized. As a result, valuation allowances of $99.2 million and $47.5 million were recorded at December 31, 2014 and 2013, respectively.
	The following is a summary of the company’s unrecognized tax benefits:
	(in millions)	2014				2013				2012
	Gross unrecognized tax benefits	$	187.6			$	231.6			$	37.7
	Unrecognized tax benefits, net of tax impacts in other jurisdictions	160.8				183.3				24.5
	Unrecognized interest and penalties related to uncertain tax positions	11				42.5				20.1
	Interest and penalties recognized in the consolidated statements of income	(12.5		)		22.4				3
The company does not believes it is reasonably possible that within the next twelve months, unrecognized domestic tax benefits will change by a significant amount.
A reconciliation of the beginning and ending amounts of unrecognized tax benefits is as follows:
(in millions)	2014				2013				2012
Balance at January 1	$	231.6			$	37.7			$	36.8
Additions based on tax positions related to the current year	30.5				26.1				5.3
Additions for tax positions of prior years	24.9				168.4				3.2
Reductions for tax positions of prior years	(51.8		)		(0.4		)		(2.0		)
Reductions resulting from the lapse of statutes of limitations	—				(0.2		)		(2.2		)
Settlements with taxing authorities	(47.6		)		—				(3.4		)
Balance at December 31	$	187.6			$	231.6			$	37.7
The company is subject to U.S. federal income tax as well as income taxes in Illinois and multiple other state, local and foreign jurisdictions.  As of December 31, 2014, substantially all federal and state income tax matters had been concluded through 2007 and 2006, respectively.

Employee_Benefit_Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2014
General Discussion of Pension and Other Postretirement Benefits [Abstract]
Employee Benefit Plans	EMPLOYEE BENEFIT PLANS
	Pension Plans. CME maintains a non-contributory defined benefit cash balance pension plan for eligible employees. CME's plan provides for a contribution to the cash balance account based on age and earnings and includes salary and cash bonuses in the definition of earnings. Employees who have completed a continuous 12-month period of employment and have reached the age of 21 are eligible to participate. Participant cash balance accounts receive an interest credit equal to the greater of the one-year constant maturity yield for U.S. Treasury notes or 4.0%. Participants become vested in their accounts after three years of service. The measurement date used for the plan is December 31.
	The following is a summary of the change in projected benefit obligation:
	(in millions)		2014				2013
	Balance at January 1		$	175.7			$	181.6
	Service cost		17.1				18
	Interest cost		9.6				7.9
	Actuarial (gain) loss		30.1				(23.4		)
	Benefits paid		(8.8		)		(8.4		)
	Balance at December 31		$	223.7			$	175.7
	The aggregate accumulated benefit obligation was $195.6 million and $154.8 million at December 31, 2014 and 2013, respectively.
	The following is a summary of the change in fair value of plan assets:
	(in millions)		2014				2013			2012
	Balance at January 1		$	193.6			$	183.9		$	149.1
	Actual return on plan assets		14.3				18.1			16.4
	Employer contributions		26				—			28
	Benefits paid		(8.8		)		(8.4		)	(9.6		)
	Balance at December 31		$	225.1			$	193.6		$	183.9
	The plan assets are classified into a fair value hierarchy in their entirety based on the lowest level of input that is significant to each asset or liability’s fair value measurement. Valuation techniques for level 2 assets use significant observable inputs such as quoted prices for similar assets, quoted market prices in inactive markets and other inputs that are observable or can be supported by observable market data. The fair value of each major category of plan assets as of December 31 is indicated below.
	(in millions)		2014				2013
	Level 2:
	Money market funds		$	27.2			$	4.4
	Mutual funds:
	Fixed income		67.2				60.7
	U.S. equity		63.4				59.6
	Foreign equity		57.6				59.7
	Commodity		9.7				9.2
	Total		$	225.1			$	193.6
	At December 31, 2014 and 2013, the fair value of pension plan assets exceeded the projected benefit obligation by $1.4 million and $17.9 million, respectively. This excess was recorded as a non-current pension asset in other assets in the consolidated balance sheet.
	CME's funding goal is to have its pension plan 100% funded at each year-end on a projected benefit obligation basis, while also satisfying any minimum required contribution and obtaining the maximum tax deduction. Year-end 2014 assumptions have been used to project the assets and liabilities from December 31, 2014 to December 31, 2015. The result of this projection is that estimated liabilities would exceed the fair value of the plan assets at December 31, 2015 by approximately $21.8 million. Accordingly, it is estimated that a $21.8 million contribution in 2015 will allow the company to meet its funding goal.
	The components of net pension expense and the assumptions used to determine the end-of-year projected benefit obligation and net pension expense in aggregate are indicated below:
	(in millions)		2014				2013			2012
	Components of Net Pension Expense:
	Service cost		$	17.1			$	18		$	16
	Interest cost		9.6				7.9			7.9
	Expected return on plan assets		(14.0		)		(13.3		)	(11.0		)
	Recognized net actuarial loss		0.6				3.1			2.5
	Net Pension Expense		$	13.3			$	15.7		$	15.4
	Assumptions Used to Determine End-of-Year Benefit Obligation:
	Discount rate		4.2		%		5.1		%	4.1		%
	Rate of compensation increase		5				5			5
	Cash balance interest crediting rate		4				4			4
	Assumptions Used to Determine Net Pension Expense:
	Discount rate		5.1		%		4.1		%	5		%
	Rate of compensation increase		5				5			5
	Expected return on plan assets		7.5				7.5			7.75
	Interest crediting rate		4				4			4
	The discount rate for the plan was determined based on the market value of a theoretical settlement bond portfolio. This portfolio consisted of U.S. dollar denominated Aa-rated corporate bonds across the full maturity spectrum. A single equivalent discount rate was determined to align the present value of the required cash flow with that settlement value. The resulting discount rate was reflective of both the current interest rate environment and the plan's distinct liability characteristics.
	The basis for determining the expected rate of return on plan assets for the plan is comprised of three components: historical returns, industry peers and forecasted return. The plan's total return is expected to equal the composite performance of the security markets over the long term. The security markets are represented by the returns on various domestic and international stock, bond and commodity indexes. These returns are weighted according to the allocation of plan assets to each market and measured individually.
	The overall objective of the plan is to achieve required long-term rates of return in order to meet future benefit payments. The component of the investment policy for the plan that has the most significant impact on returns is the asset mix. The asset mix has a minimum and maximum range depending on asset class. The plan assets are diversified to minimize the risk of large losses by any one or more individual assets. Such diversification is accomplished, in part, through the selection of asset mix and investment management. The asset allocation for the plan, by asset category, at December 31 was as follows:
		2014			2013
	Fixed income	29.8	%		31.4	%
	U.S. equity	28.2			30.8
	Foreign equity	25.6			30.8
	Money market funds	12.1			2.3
	Commodity	4.3			4.7
	The range of target allocation percentages for 2015 is as follows:
		Minimum			Maximum
	Fixed income	33	%		45	%
	U.S. equity	23.5			35
	Foreign equity	23.5			35
	Commodity	2			8
	At times, the company may determine that it is necessary to place some assets in cash equivalent investments in order to pay expected plan liabilities. Given this, the actual asset allocation for the plan may not fall within the target allocation ranges from time to time.
	According to the plan's investment policy, the plan is not allowed to invest in securities that compromise independence, short sales of securities directly owned by the plan, securities purchased on margin or other uses of borrowed funds, derivatives not used for hedging purposes, restricted stock or illiquid securities or any other transaction prohibited by employment laws. If the plan directly invests in short-term and long-term debt obligations, the investments are limited to obligations rated at the highest rating category by Standard & Poor's (S&P) or Moody's.
The pre-tax balance and activity of the prior service costs and actuarial losses for the pension plan, which are included in other comprehensive income (loss), for 2014 are as follows:
(in millions)		Prior				Actuarial
		Service				Loss
		Costs
Balance at January 1		$	0.1			$	22.5
Unrecognized net loss		—				29.7
Recognized as a component of net pension expense		—				(0.6		)
Balance at December 31		$	0.1			$	51.6
The company expects to amortize $2.6 million of actuarial loss and prior service costs from accumulated other comprehensive income (loss) into net periodic benefit costs in 2015.
At December 31, 2014, anticipated benefit payments from the plan in future years are as follows:
(in millions)
2015		$	13.8
2016		14.8
2017		15.7
2018		17.3
2019		18.4
2020-2024		108.5
Savings Plans. CME maintains a defined contribution savings plan pursuant to Section 401(k) of the Internal Revenue Code, whereby all U.S. employees are participants and have the option to contribute to this plan. CME matches employee contributions up to 3% of the employee's base salary and may make additional discretionary contributions.
In addition to the plan for U.S. employees, the company maintains defined contribution savings plans for employees in international locations.
Aggregate expense for all of the defined contribution savings plans amounted to $11.2 million, $9.9 million and $8.9 million in 2014, 2013 and 2012, respectively.
CME Non-Qualified Plans. CME maintains non-qualified plans, under which participants may make assumed investment choices with respect to amounts contributed on their behalf. Although not required to do so, CME invests such contributions in assets that mirror the assumed investment choices. The balances in these plans are subject to the claims of general creditors of the exchange and totaled $55.1 million and $49.6 million at December 31, 2014 and 2013 respectively. Although the value of the plans is recorded as an asset in marketable securities in the consolidated balance sheets, there is an equal and offsetting liability. The investment results of these plans have no impact on net income as the investment results are recorded in equal amounts to both investment income and compensation and benefits expense.
Supplemental Savings Plan. CME maintains a supplemental plan to provide benefits for employees who have been impacted by statutory limits under the provisions of the qualified pension and savings plan. Employees in this plan are subject to the vesting requirements of the underlying qualified plans.
Deferred Compensation Plan. A deferred compensation plan is maintained by CME, under which eligible employees and members of the board of directors may contribute a percentage of their compensation and defer income taxes thereon until the time of distribution.
COMEX Members' Retirement Plan and Benefits. COMEX maintains a non-qualified retirement and benefit plan under the COMEX Members' Recognition and Retention Plan (MRRP). This plan provides benefits to certain members of the COMEX division based on long-term membership, and participation is limited to individuals who were COMEX division members prior to NYMEX's acquisition of COMEX in 1994. No new participants were permitted into the plan after the date of this acquisition. Under the terms of the MRRP, the company is required to fund the plan with a minimum annual contribution of $0.8 million until it is fully funded. All benefits to be paid under the MRRP are based on reasonable actuarial assumptions which are based upon the amounts that are available and are expected to be available to pay benefits. Total contributions to the plan were $0.8 million for each the years 2012 through 2014. At December 31, 2014 and 2013, the obligation for the MRRP totaled $21.2 million and $20.3 million, respectively. Assets with a fair value of $20.0 million and $19.2 million have been allocated to this plan at December 31, 2014 and 2013, respectively, and are included in marketable securities and cash and cash equivalents in the consolidated balance sheets. The balances in this plan are subject to the claims of general creditors of COMEX.

Commitments

Commitments	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments	COMMITMENTS
	Operating Leases. CME Group has entered into various non-cancellable operating lease agreements, with the most significant being as follows:
	•	In November 2013, the company sold a building in New York and leased back a portion of the property. The operating lease, which has an initial lease term ending on December 31, 2028, contains two consecutive renewal options for five years.
	•	In April 2012, the company sold two buildings in Chicago at 141 W. Jackson and leased back a portion of the property.  The operating lease, which has an initial lease term ending on April 30, 2027, contains four consecutive renewal options for five years.
	•	In January 2011, the company entered into an operating lease for office space in London. The initial lease term, which became effective on January 20, 2011, terminates on March 24, 2026, with an option to terminate without penalty in January 2021.
	•	In July 2008, the company renegotiated the operating lease for its headquarters at 20 South Wacker Drive in Chicago. The lease, which has an initial term ending on November 30, 2022, contains two consecutive renewal options for seven and ten years and a contraction option which allows the company to reduce its occupied space after November 30, 2018. In addition, the company may exercise a lease expansion option in December 2017.
	•	In August 2006, the company entered into an operating lease for additional office space in Chicago. The initial lease term, which became effective on August 10, 2006, terminates on November 30, 2023. The lease contains two 5-year renewal options beginning in 2023.
	At December 31, 2014, future minimum payments under non-cancellable operating leases were payable as follows (in millions):
	Year
	2015	$	59.1
	2016	47.8
	2017	42.4
	2018	42
	2019	41.6
	Thereafter	221.7
	Total	$	454.6
	Total rental expense, including equipment rental, was $51.0 million in 2014, $28.6 million in 2013 and $25.3 million in 2012.
	Other Commitments. Commitments include material contractual purchase obligations that are non-cancellable. Purchase obligations relate to advertising, licensing, hardware, software and maintenance as well as telecommunication services. At December 31, 2014, future minimum payments due under purchase obligations were payable as follows (in millions):
	Year
	2015	$	14.6
	2016	9.8
	2017	9.2
	2018	8.3
	2019	1.2
	Thereafter	2.3
	Total	$	45.4

Contingencies

Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Contingencies	CONTINGENCIES
	Legal and Regulatory Matters. In 2008, Fifth Market, Inc. (Fifth Market) filed a complaint against CME Group and CME in the Delaware District Court seeking a permanent injunction against CME's Globex system and unquantified enhanced damages for what the plaintiff alleges is willful infringement of two patents, in addition to costs, expenses and attorneys' fees. The case was stayed pending the outcome of CME's request for reexamination by the U.S. Patent and Trademark Office (USPTO). The reexaminations resulted in some claims being rejected and others being confirmed. In June 2013, the court lifted the stay. The validity of the patents, however, remains subject to further review by the USPTO. Based on its investigation to date and advice from legal counsel, the company believes this suit is without merit and intends to defend itself vigorously against these charges.
	In 2009, CME and CBOT filed a complaint against Howard Garber in the Northern District of Illinois seeking a declaratory judgment that neither CME nor CBOT infringed the Garber patent, which relates to electronic market makers, and that the patent is invalid and unenforceable. The Technology Research Group (TRG) was substituted for Mr. Garber in 2009 and TRG filed counterclaims alleging patent infringement and other related claims. In 2011, the case was dismissed with the right to reinstate pending the outcome of a reexamination by the USPTO. In August and October 2013, the USPTO issued actions resulting in the rejection of all TRG’s claims, completing the reexamination process. In January 2014, TRG appealed the decision of the USPTO. In November 2014, Patent Trial and Appeal Board confirmed the rejection of all claims in the patent. In February 2015, the USPTO published an Intent to Issue a Reexamination Certificate canceling all claims in the Garber patent and indicating that the period for appeal has expired. As a result, the matter is resolved.
	The Fifth Market legal matter involves an alleged infringement of intellectual property which, due to its nature, involves a potential liability that is uncertain, difficult to quantify and involves a wide range of potential outcomes. The company believes that the matter is without merit, and the company intends to defend itself vigorously against the claim. We expect the re-examination by the USPTO in the Fifth Market matter, including any appeals thereof, to result in a determination of the validity of the patent at issue which we expect will have an impact on the merits of the matter. Given the uncertainty of factors which may potentially impact the resolution of the matter, at this time the company is unable to estimate the reasonably possible loss or range of reasonably possible loss in the unlikely event it were found to be liable at trial in the matter.
	In February 2013, the CFTC filed suit against NYMEX and two former employees alleging disclosure of confidential customer information in violation of the Commodity Exchange Act. NYMEX’s motion to dismiss was denied on September 30, 2014. Based on its investigation to date and advice from legal counsel, the company believes that it has strong factual and legal defenses to the claim.
	In the normal course of business, the company discusses matters with its regulators raised during regulatory examinations or otherwise subject to their inquiry and oversight. These matters could result in censures, fines, penalties or other sanctions. Management believes the outcome of any resulting actions will not have a material impact on its consolidated financial position or results of operations. However, the company is unable to predict the outcome or the timing of the ultimate resolution of these matters, or the potential fines, penalties or injunctive or other equitable relief, if any, that may result from these matters.
	In addition, the company is a defendant in, and has potential for, various other legal proceedings arising from its regular business activities. While the ultimate results of such proceedings against the company cannot be predicted with certainty, the company believes that the resolution of any of these matters on an individual basis will not have a material impact on its consolidated financial position or results of operations.
	At December 31, 2014 and 2013, the company had accrued $4.3 million and $11.3 million, respectively, for legal and regulatory matters that were probable and estimable.
	Intellectual Property Indemnifications. Certain agreements with customers and other third parties related to accessing the CME platforms, utilizing market data services and licensing CME SPAN software may contain indemnifications from intellectual property claims that may be made against them as a result of their use of the applicable products and/or services. The potential future claims relating to these indemnifications cannot be estimated and therefore no liability has been recorded.

Guarantees

Guarantees	12 Months Ended
	Dec. 31, 2014
Guarantees [Abstract]
Guarantees	GUARANTEES
	Mutual Offset Agreement. CME and Singapore Exchange Limited (SGX) have a mutual offset agreement with a current term through October 2015. This agreement enables market participants to open a futures position on one exchange and liquidate it on the other. The term of the agreement will automatically renew for a one-year period unless either party provides advance notice of its intent to terminate. CME can maintain collateral in the form of U.S. Treasury securities or irrevocable, standby letters of credit. At December 31, 2014, CME was contingently liable to SGX on irrevocable letters of credit totaling $410.0 million. Regardless of the collateral, CME guarantees all cleared transactions submitted through SGX and would initiate procedures designed to satisfy these financial obligations in the event of a default, such as the use of performance bonds and guaranty fund contributions of the defaulting clearing firm. The company believes that its guarantee liability is immaterial and therefore has not recorded any liability at December 31, 2014.
	Family Farmer and Rancher Protection Fund. In 2012, the company established the Family Farmer and Rancher Protection Fund (the Fund). The Fund is designed to provide payments, up to certain maximum levels, to family farmers, ranchers and other agricultural industry participants who use the company's agricultural products and who suffer losses to their segregated account balances due to their CME clearing member becoming insolvent. Under the terms of the Fund, farmers and ranchers are eligible for up to $25,000 per participant. Farming and ranching cooperatives are eligible for up to $100,000 per cooperative. The Fund has an aggregate maximum payment amount of $100.0 million. Since its establishment, the Fund has made payments of approximately $2.0 million, which leaves $98.0 million available for future claims. If payments to participants were to exceed this amount, payments would be pro-rated. Clearing members and customers must register in advance with the company and provide certain documentation in order to substantiate their eligibility. The company believes that its guarantee liability is immaterial and therefore has not recorded any liability at December 31, 2014.

Redeemable_NonControlling_Inte

Redeemable Non-Controlling Interest	12 Months Ended
	Dec. 31, 2014
Temporary Equity [Abstract]
Redeemable Non-controlling Interest	REDEEMABLE NON-CONTROLLING INTEREST
	The following summarizes the changes in redeemable non-controlling interest for the years presented. Non-controlling interests that do not contain redemption features are presented in the statements of equity.
	(in millions)	2013			2012
	Balance at January 1	$	80.8		$	70.3
	Total comprehensive income attributable to redeemable non-controlling interest	1.5			10.5
	Purchase of non-controlling interest	(82.3		)	—
	Balance at December 31	$	—		$	80.8
	In April 2013, the company purchased the remaining 10% non-controlling interest in its business venture with Dow Jones for $80.0 million. Prior to the purchase, the company maintained a 24.4% interest in S&P/DJI. As a result of the purchase of the non-controlling interest, the company's interest in S&P/DJI increased to 27%. The company recognized a $165.6 million tax benefit through additional paid-in capital. The tax benefit was due to a reduction in deferred tax liabilities related to the tax basis in Index Holdings. The company also recognized a $2.3 million gain through additional paid-in capital related to the purchase of the non-controlling interest.

Capital_Stock

Capital Stock	12 Months Ended
	Dec. 31, 2014
Capital Stock [abstract]
Capital Stock	CAPITAL STOCK
	Shares Outstanding. The following table presents information regarding capital stock:
		December 31,
	(in thousands)	2014	2013
	Class A common stock authorized	1,000,000	1,000,000
	Class A common stock issued and outstanding	335,452	333,852
	Class B-1 common stock authorized, issued and outstanding	0.6	0.6
	Class B-2 common stock authorized, issued and outstanding	0.8	0.8
	Class B-3 common stock authorized, issued and outstanding	1.3	1.3
	Class B-4 common stock authorized, issued and outstanding	0.4	0.4
	CME Group has no shares of preferred stock issued and outstanding.
	Associated Trading Rights. Members of CME, CBOT, NYMEX and COMEX own or lease trading rights which entitle them to access the trading floors, discounts on trading fees and the right to vote on certain exchange matters as provided for by the rules of the particular exchange and CME Group's or the subsidiaries' organizational documents. Each class of CME Group Class B common stock is associated with a membership in a specific division for trading at CME. A CME trading right is a separate asset that is not part of or evidenced by the associated share of Class B common stock of CME Group. The Class B common stock of CME Group is intended only to ensure that the Class B shareholders of CME Group retain rights with respect to representation on the board of directors and approval rights with respect to the core rights described below.
	Trading rights at CBOT are evidenced by Class B memberships in CBOT, at NYMEX by Class A memberships in NYMEX and at COMEX by COMEX Division Memberships. Members of CBOT, NYMEX and COMEX do not have any rights to elect members of the board of directors and are not entitled to receive dividends or other distributions on their memberships or trading permits.
	Core Rights. Holders of CME Group Class B common shares have the right to approve changes in specified rights relating to the trading privileges at CME associated with those shares. These core rights relate primarily to trading right protections, certain trading fee protections and certain membership benefit protections. Votes on changes to these core rights are weighted by class. Each class of Class B common stock has the following number of votes on matters relating to core rights: Class B-1, six votes per share; Class B-2, two votes per share; Class B-3, one vote per share; and Class B-4, 1/6th of one vote per share. The approval of a majority of the votes cast by the holders of shares of Class B common stock is required in order to approve any changes to core rights. Holders of shares of Class A common stock do not have the right to vote on changes to core rights.
	Voting Rights. With the exception of the matters reserved to holders of CME Group Class B common stock, holders of CME Group common stock vote together on all matters for which a vote of common shareholders is required. In these votes, each holder of shares of Class A or Class B common stock of CME Group has one vote per share.
	Transfer Restrictions. Each class of CME Group Class B common stock is subject to transfer restrictions contained in the Certificate of Incorporation of CME Group. These transfer restrictions prohibit the sale or transfer of any shares of Class B common stock separate from the sale of the associated trading rights.
	Election of Directors. The CME Group Board of Directors is currently comprised of 24 members. Holders of Class B-1, Class B-2 and Class B-3 common stock have the right to elect six directors, of which three are elected by Class B-1 shareholders, two are elected by Class B-2 shareholders and one is elected by Class B-3 shareholders. The remaining directors are elected by the Class A and Class B shareholders voting as a single class.
	Dividends. Holders of Class A and Class B common stock of CME Group are entitled to receive proportionately such dividends, if any, as may be declared by the CME Group board of directors.
	CME Group Omnibus Stock Plan. CME Group has adopted an Omnibus Stock Plan under which stock-based awards may be made to employees. A total of 40.2 million Class A common stock shares have been reserved for awards under the plan. Awards totaling 23.1 million shares have been granted and are outstanding or have been exercised under this plan at December 31, 2014 (note 17).
	CBOT Holdings Long-Term Equity Incentive Plan. In connection with the merger with CBOT Holdings, CME Group assumed CBOT Holdings' 2005 Long-Term Equity Incentive Plan. Under the plan, stock-based awards may be made to certain directors, officers and other key employees or individuals. A total of 2.3 million shares have been reserved for awards under the plan. In connection with receiving shareholder approval to increase the amount of authorized shares under the CBOT Omnibus Stock Plan in May 2009, the company undertook to freeze future awards under this plan. As a result, 1.6 million shares that remained authorized for future awards under this plan were frozen.
	NYMEX Holdings Omnibus Long-Term Incentive Plan. In connection with the merger with NYMEX Holdings, CME Group assumed NYMEX Holdings' 2006 Omnibus Long-Term Incentive Plan (NYMEX Omnibus Stock Plan). Under the plan, stock-based awards may be made to any director, officer or employee of the company and other key individuals providing services to the company. A total of 5.0 million shares have been reserved for awards under the plan. In connection with receiving shareholder approval to increase the amount of authorized shares under the NYMEX Omnibus Stock Plan in May 2009, the company undertook to freeze future awards under this plan. As a result, 3.5 million shares that remained authorized for future awards under this plan were frozen.
	Director Stock Plan. CME Group has adopted a Director Stock Plan under which awards are made to non-executive directors as part of their annual compensation. A total of 625,000 Class A shares have been reserved under this plan, and approximately 294,000 shares have been awarded through December 31, 2014.
	Employee Stock Purchase Plan. CME Group has adopted an Employee Stock Purchase Plan (ESPP) under which employees may purchase Class A shares at 90% of the market value of the shares using after-tax payroll deductions. A total of 500,000 Class A shares have been reserved under this plan, of which approximately 201,000 shares have been purchased through December 31, 2014 (note 17).

StockBased_Payments

Stock-Based Payments	12 Months Ended
	Dec. 31, 2014
Share-based Compensation [Abstract]
Stock-Based Payments	STOCK-BASED PAYMENTS
	CME Group adopted an Omnibus Stock Plan under which stock-based awards may be made to employees. A total of 40.2 million Class A shares have been reserved for awards under the plan. Awards totaling 23.1 million shares have been granted and are outstanding or have been exercised under the plan as of December 31, 2014. Awards granted before 2009 generally vest over a five-year period, with 20% vesting one year after the grant date and on that same date in each of the following four years. Beginning in 2009, awards granted generally vest over a four-year period, with 25% vesting one year after the grant date and on that same date in each of the following three years.
	Total compensation expense for stock-based payments and total income tax benefit recognized in the consolidated statements of income for stock-based awards were as follows:
	(in millions)		2014				2013			2012
	Compensation expense		$	55			$	54.4		$	61.4
	Income tax benefit recognized		19.5				20			22.5
	Excluding estimates of future forfeitures, at December 31, 2014, there was $114.5 million of total unrecognized compensation expense related to employee stock-based compensation arrangements that had not yet vested. This expense is expected to be recognized over a weighted average period of 2.1 years.
	Stock options have not been granted since 2012. The Black-Scholes fair value of each option grant was calculated using the following assumptions:
		Grant Year
		2012
	Dividend yield	4.2%-4.5%
	Expected volatility	40%-41%
	Risk-free interest rate	0.8%-1.5%
	Expected life	5.0 to 6.2 years
	The dividend yield was calculated by dividing that year's expected dividends by the market price of the stock at the dates of grant. A weighting of implied and historical volatility was used to estimate expected future volatility. The risk-free interest rate was based on the U.S. Treasury yield in effect at the time of each grant. The expected life of options granted has been determined using the simplified method as outlined in guidance from the Securities and Exchange Commission.
	The following table summarizes stock option activity for 2014. Aggregate intrinsic value is in millions.
			Number of Shares			Weighted			Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value
						Average
						Exercise
						Price
	Outstanding at December 31, 2013		4,191,594			$	67		4.9		$	70.4
	Exercised		(1,030,952	)		52
	Cancelled		(149,375	)		76
	Outstanding at December 31, 2014		3,011,267			72			3.7		60.1
	Exercisable at December 31, 2014		2,761,127			74			3.5		51.5
	The weighted average grant date fair value of options granted during 2012 was $13 per share. The total intrinsic value of options exercised during 2014, 2013 and 2012 was $29.5 million, $35.3 million and $19.0 million, respectively.
	In 2014, the company granted 731,159 shares of restricted Class A common stock and 5,796 shares of restricted stock units. Restricted common stock and restricted stock units generally have a vesting period of two to four years. The fair value related to these grants was $58.6 million, which is recognized as compensation expense on an accelerated basis over the vesting period. Beginning with restricted stock grants in September 2010, dividends are accrued on restricted Class A common stock and restricted stock units and are paid once the restricted stock vests. In 2014, the company also granted 211,785 performance shares. The fair value related to these grants was $18.8 million, which is recognized as compensation expense on an accelerated and straight-lined basis over the vesting period. The vesting of these shares is contingent on meeting stated performance or market conditions.
	The following table summarizes restricted stock, restricted stock units, and performance shares activity for 2014:
		Number of Shares			Weighted
					Average
					Grant Date
					Fair Value
	Outstanding at December 31, 2013	2,085,251			$	63
	Granted	948,740			82
	Vested	(511,575	)		60
	Cancelled	(424,108	)		64
	Outstanding at December 31, 2014	2,098,308			72
	The total fair value of restricted stock, restricted stock units, and performance shares that vested during 2014, 2013 and 2012 was $40.5 million, $31.9 million and $20.9 million, respectively.
	Eligible employees may acquire shares of Class A common stock using after-tax payroll deductions made during consecutive offering periods of approximately six months in duration. Shares are purchased at the end of each offering period at a price of 90% of the closing price of the Class A common stock as reported on the NASDAQ Global Select Market. Compensation expense is recognized on the dates of purchase for the discount from the closing price. In 2014, 2013 and 2012, a total of 23,678, 18,632 and 27,768 shares, respectively, of Class A common stock were issued to participating employees. These shares are subject to a six-month holding period. Annual expense of $0.2 million, $0.1 million and $0.1 million for the purchase discount was recognized in 2014, 2013 and 2012, respectively.
	Beginning in 2014, non-executive directors receive an annual award of Class A common stock with a value equal to $100,000. Non-executive directors may also elect to receive some or all of the cash portion of their annual stipend, up to $60,000, in shares of stock based on the closing price at the date of distribution. As a result, 33,735, 27,168 and 40,260 shares of Class A common stock were issued to non-executive directors during 2014, 2013 and 2012, respectively. These shares are not subject to any vesting restrictions. Expense of $2.1 million, $2.1 million and $2.2 million related to these stock-based payments was recognized for the years ended December 31, 2014, 2013 and 2012, respectively.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Comprehensive Income (Loss) Note [Text Block]	ACCUMULATED OTHER COMPREHENSIVE INCOME
	The following tables present changes in the accumulated balances for each component of other comprehensive income attributable to CME Group, including current period other comprehensive income and reclassifications out of accumulated other comprehensive income:
	(in millions)	Investment Securities			Defined Benefit Plans			Derivative Investments			Foreign Currency Translation			Total
	Balance at December 31, 2013	$	98.9		$	(12.8	)	$	65		$	0.9		$	152
	Other comprehensive income before reclassifications and income tax benefit (expense)	(116.6		)	(30.0		)	(2.3		)	(5.2		)	(154.1		)
	Amounts reclassified from accumulated other comprehensive income	—			0.3			(1.5		)	—			(1.2		)
	Income tax benefit (expense)	(5.2		)	11.2			1.4			2.1			9.5
	Net current period other comprehensive income attributable to CME Group	(121.8		)	(18.5		)	(2.4		)	(3.1		)	(145.8		)
	Balance at December 31, 2014	$	(22.9	)	$	(31.3	)	$	62.6		$	(2.2	)	$	6.2
	(in millions)	Investment Securities			Defined Benefit Plans			Derivative Investments			Foreign Currency Translation			Total
	Balance at December 31, 2012	$	256.7		$	(32.4	)	$	(16.4	)	$	1.4		$	209.3
	Other comprehensive income before reclassifications and income tax benefit (expense)	(221.0		)	28.4			128.8			(0.8		)	(64.6		)
	Amounts reclassified from accumulated other comprehensive income	(0.7		)	3.2			1.6			—			4.1
	Income tax benefit (expense)	63.9			(12.0		)	(49.0		)	0.3			3.2
	Net current period other comprehensive income attributable to CME Group	(157.8		)	19.6			81.4			(0.5		)	(57.3		)
	Balance at December 31, 2013	$	98.9		$	(12.8	)	$	65		$	0.9		$	152
	(in millions)	Investment Securities			Defined Benefit Plans			Derivative Investments			Foreign Currency Translation			Total
	Balance at December 31, 2011	$	148.4		$	(26.1	)	$	(1.2	)	$	(9.5	)	$	111.6
	Other comprehensive income before reclassifications and income tax benefit (expense)	174.7			(13.0		)	(25.3		)	(1.3		)	135.1
	Ineffectiveness on cash flow hedges	—			—			0.1			—			0.1
	Amounts reclassified from accumulated other comprehensive income (1)	(1.8		)	2.5			1			18.4			20.1
	Income tax benefit (expense)	(64.6		)	4.2			9			(6.2		)	(57.6		)
	Net current period other comprehensive income attributable to CME Group	108.3			(6.3		)	(15.2		)	10.9			97.7
	Balance at December 31, 2012	$	256.7		$	(32.4	)	$	(16.4	)	$	1.4		$	209.3
	(1) In the second quarter of 2012, the company recognized an $18.4 million foreign currency translation loss related to the sale of Credit Market Analysis Ltd. (CMA) within other non-operating income (expense).

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2014
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS
	The company uses a three-level classification hierarchy of fair value measurements for disclosure purposes.
	•	Level 1 inputs, which are considered the most reliable evidence of fair value, consist of quoted prices (unadjusted) for identical assets or liabilities in active markets.
	•	Level 2 inputs consist of observable market data, other than level 1 inputs, such as quoted prices for similar assets and liabilities in active markets or inputs other than quoted prices that are directly observable.
	•	Level 3 inputs consist of unobservable inputs which are derived and cannot be corroborated by market data or other entity-specific inputs.
	Level 1 assets generally include U.S. Treasury securities and investments in publicly traded mutual funds with quoted market prices. In general, the company uses quoted prices in active markets for identical assets to determine the fair value of marketable securities and equity investments. If quoted prices are not available to determine fair value, the company uses other inputs that are directly observable.
	Assets and liabilities included in level 2 generally consist of asset-backed securities and interest rate swap contracts. Asset-backed securities were measured at fair value based on matrix pricing using prices of similar securities with similar inputs such as maturity dates, interest rates and credit ratings. The company determined the fair value of its interest rate swap contracts using standard valuation models with market-based observable inputs including forward and spot exchange rates and interest rate curves.
	The company determined the fair value of its contingent consideration liabilities, considered level 3 liabilities, using a discounted cash flow model to calculate the present value of future payouts. The liabilities were included in level 3 because management used significant unobservable inputs, including a discount rate of 20% and payout probabilities ranging from 0% to 100%. Significant increases or decreases in any of those inputs in isolation would result in a significantly different fair value.
	Financial assets and liabilities recorded in the consolidated balance sheet as of December 31, 2014 and 2013 were classified in their entirety based on the lowest level of input that was significant to each asset or liability's fair value measurement.
	Financial Instruments Measured at Fair Value on a Recurring Basis:
			December 31, 2014
	(in millions)		Level 1		Level 2		Level 3		Total
	Assets at Fair Value:
	Marketable securities:
	U.S. Treasury securities		$	19.1	$	—	$	—	$	19.1
	Mutual funds		55.1		—		—		55.1
	Equity securities		0.1		—		—		0.1
	Asset-backed security		—		0.4		—		0.4
	Total		74.3		0.4		—		74.7
	Performance bonds and guaranty fund contributions:
	U.S. Treasury securities (1)		16,699.70		—		—		16,699.70
	Equity investments		432.1		—		—		432.1
	Total Assets at Fair Value		$	17,206.10	$	0.4	$	—	$	17,206.50
	Liabilities at Fair Value:
	Interest rate swap contract		$	—	$	2.3	$	—	$	2.3
	Contingent consideration		—		—		17.7		17.7
	Total Liabilities at Fair Value		$	—	$	2.3	$	17.7	$	20
	(1) Performance bonds and guaranty fund contributions on the consolidated balance sheet at December 31, 2014 include cash collateral that has been invested in U.S. Treasury securities.
			December 31, 2013
	(in millions)		Level 1		Level 2		Level 3		Total
	Assets at Fair Value:
	Marketable securities:
	U.S. Treasury securities		$	18.3	$	—	$	—	$	18.3
	Mutual funds		49.6		—		—		49.6
	Equity securities		0.1		—		—		0.1
	Asset-backed securities		—		0.4		—		0.4
	Total		68		0.4		—		68.4
	Equity investments		499.9		—		—		499.9
	Total Assets at Fair Value		$	567.9	$	0.4	$	—	$	568.3
	Liabilities at Fair Value:
	Contingent consideration		$	—	$	—	$	15.7	$	15.7
	Total Liabilities at Fair Value		$	—	$	—	$	15.7	$	15.7
	There were no transfers of assets between level 1, level 2 and level 3 during 2014 and 2013. The following is a reconciliation of level 3 liabilities valued at fair value on a recurring basis during 2014 and 2013. There were no level 3 assets valued at fair value on a recurring basis during 2014 and 2013.
	(in millions)	Contingent Consideration
	Fair value of liability at December 31, 2012	$	12.6
	Contingent obligation arising from acquisition	4.4
	Realized and unrealized gains (losses):
	Included in operating expense	6
	Settlements	(7.3		)
	Fair value of liability at December 31, 2013	15.7
	Realized and unrealized gains (losses):
	Included in operating expense	7.1
	Settlements	(5.1		)
	Fair value of liability at December 31, 2014	$	17.7
	There were no level 3 assets or liabilities valued at fair value on a nonrecurring basis during 2014 and 2013.

Earnings_Per_Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Earnings Per Share	EARNINGS PER SHARE
	Basic earnings per share is computed by dividing net income attributable to CME Group by the weighted average number of shares of all classes of common stock outstanding for each reporting period. Diluted earnings per share reflects the increase in shares using the treasury stock method to reflect the impact of an equivalent number of shares of common stock if stock options were exercised and restricted stock awards were converted into common stock. Anti-dilutive stock options and stock awards were as follows for the years presented:
	(in thousands)	2014		2013			2012
	Stock options	1,330		1,566			4,851
	Stock awards	124		65			—
	Total	1,454		1,631			4,851
	The following table presents the earnings per share calculation for the years presented:
		2014			2013			2012
	Net Income Attributable to CME Group (in millions)	$	1,127.10		$	976.8		$	896.3
	Weighted Average Common Shares Outstanding (in thousands):
	Basic	334,409			332,678			331,252
	Effect of stock options and stock awards	1,654			1,720			1,067
	Diluted	336,063			334,398			332,319
	Earnings per Common Share Attributable to CME Group:
	Basic	$	3.37		$	2.94		$	2.71
	Diluted	3.35			2.92			2.7

Quarterly_Information_Unaudite

Quarterly Information (Unaudited)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Data [Abstract]
Quarterly Information	QUARTERLY INFORMATION (UNAUDITED)
	(in millions, except per share data)	First			Second			Third			Fourth			Year to Date
		Quarter			Quarter			Quarter			Quarter
	Year Ended December 31, 2014
	Total revenues	$	777.4		$	731.6		$	762.4		$	841.1		$	3,112.50
	Operating income	454.5			412			430.4			471.5			1,768.40
	Non-operating income (expense)	(8.1		)	10.1			(1.3		)	2.3			3
	Income before income taxes	446.4			422.1			429.1			473.8			1,771.40
	Net income attributable to CME Group	266.8			263.8			290			306.5			1,127.10
	Earnings per common share attributable to CME Group:
	Basic	$	0.8		$	0.79		$	0.87		$	0.91		$	3.37
	Diluted	0.79			0.79			0.86			0.91			3.35
	Year Ended December 31, 2013
	Total revenues	$	718.6		$	816.1		$	714.6		$	687		$	2,936.30
	Operating income	405.5			507.8			400.5			323.2			1,637.00
	Non-operating income (expense)	(17.9		)	(0.3		)	(1.6		)	(16.2		)	(36.0		)
	Income before income taxes	387.6			507.5			398.9			307			1,601.00
	Net income attributable to CME Group	235.8			311.2			236.7			193.1			976.8
	Earnings per common share attributable to CME Group:
	Basic	$	0.71		$	0.94		$	0.71		$	0.58		$	2.94
	Diluted	0.71			0.93			0.71			0.58			2.92

Subsequent_Events

Subsequent Events	12 Months Ended
	Dec. 31, 2014
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS
	The company has evaluated subsequent events through the date the financial statements were issued. The company has determined that there were no subsequent events that require disclosure.

Schedule_IIValuation_and_Quali

Schedule IIbValuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2014
Valuation and Qualifying Accounts [Abstract]
Schedule of Valuation and Qualifying Accounts Disclosure [Text Block]	CME Group Inc. and Subsidiaries
	Schedule II—Valuation and Qualifying Accounts
	For the Years Ended December 31, 2014, 2013 and 2012
	(dollars in millions)
		Balance at		Charged		Charged			Other(1)			Balance
		beginning		against		(credited) to						at end
		of year		goodwill		costs and						of year
						expenses
	Year Ended December 31, 2014
	Allowance for doubtful accounts	$	1.2	$	—	$	0.1		$	(0.1	)	$	1.2
	Allowance for deferred tax assets	47.5		—		—			51.7			99.2
	Year Ended December 31, 2013
	Allowance for doubtful accounts	$	0.8	$	—	$	0.8		$	(0.4	)	$	1.2
	Allowance for deferred tax assets	24.8		—		4.6			18.1			47.5
	Year Ended December 31, 2012
	Allowance for doubtful accounts	$	1.3	$	—	$	1		$	(1.5	)	$	0.8
	Allowance for deferred tax assets	43.2		0.5		(3.0		)	(15.9		)	24.8
	_______________
	-1	Includes write-offs of doubtful accounts and reversals of deferred tax asset valuation allowances against accumulated other comprehensive income.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policy)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Principles of Consolidation	Basis of Presentation. The accompanying consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States of America and include the accounts of the company and its majority-owned subsidiaries. All intercompany transactions and balances have been eliminated.
Use of Estimates	Use of Estimates. The preparation of consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts and the disclosure of contingent amounts in the consolidated financial statements and accompanying notes. Estimates are based on historical experience, where applicable, and assumptions management believes are reasonable under the circumstances. Due to the inherent uncertainty involved with estimates, actual results may differ.
Cash and Cash Equivalents	Cash and Cash Equivalents. Cash and cash equivalents consist of cash and highly liquid investments with a maturity of three months or less at the time of purchase.
Investment, Policy [Policy Text Block]	Financial Investments. The company maintains short-term and long-term investments, classified as available-for-sale or trading securities. Available-for-sale investments are carried at their fair value, with unrealized gains and losses, net of deferred income taxes, reported as a component of accumulated other comprehensive income. Trading securities held in connection with non-qualified deferred compensation plans are recorded at fair value, with net realized and unrealized gains and losses and dividend income reported as investment income. Also, the company maintains long-term investments accounted for under the cost method and equity method, depending upon the degree of influence over the investee as held by the company.
	The company reviews its investments to determine whether a decline in fair value below the cost basis is other-than-temporary. If events and circumstances indicate that a decline in the value of the assets has occurred and is deemed to be other-than-temporary, the carrying value of the investments is reduced to its fair value and a corresponding impairment is charged to earnings.
Fair Value of Financial Instruments	Fair Value of Financial Instruments. The company uses a three-level classification hierarchy of fair value measurements that establishes the quality of inputs used to measure fair value. The fair value of a financial instrument is the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The fair value of financial instruments is determined using various techniques that involve some level of estimation and judgment, the degree of which is dependent on the price transparency and the complexity of the instruments.
Derivative Investments	Derivative Investments. The company uses derivative instruments, designated as cash flow hedges, to limit exposure to changes in interest rates. Derivatives are recorded at fair value in the consolidated balance sheets. The effective portion of the changes in the fair value of cash flow hedges are deferred in accumulated other comprehensive income. Any realized gains and losses from effective hedges are classified as interest expense in the consolidated statements of income, and any ineffective or excluded portion of a hedge is recognized in earnings immediately.
Accounts Receivable	Accounts Receivable. Accounts receivable are comprised of trade receivables and unbilled revenue including clearing and transaction fees and market data and information services revenue. All accounts receivable are stated at cost. Exposure to losses on receivables for clearing and transaction fees and other amounts owed by clearing firms is dependent on each clearing firm's financial condition and the memberships that collateralize fees owed to the exchange. The exchange retains the right to liquidate exchange memberships to satisfy a clearing firm's receivable. The allowance for doubtful accounts is calculated based on historical losses and management's assessment of probable future collections.
Performance Bonds and Guaranty Fund Contributions	Performance Bonds and Guaranty Fund Contributions. Performance bonds and guaranty fund contributions held for clearing firms may be in the form of cash, securities or other non-cash deposits.
	Performance bonds and guaranty fund contributions received in the form of cash held by CME and CMECE may be invested in U.S. Government securities and certain foreign government securities acquired through and held by a broker-dealer subsidiary of a bank, reverse repurchase agreements secured with highly rated government securities, money market funds or through CME's Interest Earning Facility (IEF) program. Any interest earned on CME investments accrues to CME and is included in investment income in the consolidated statements of income. CMECE may distribute any interest earned on CMECE investments to the clearing firms at its discretion. Because CME and CMECE have control of the cash collateral and the benefits and risks of ownership accrue to CME and CMECE, cash performance bonds and guaranty fund contributions are reflected in the consolidated balance sheets. Performance bonds and guaranty fund contributions assets on the consolidated balance sheets also include U.S. Treasury securities with maturity dates of 90 days or less. U.S. Treasury securities are purchased by CME, at its discretion, using cash collateral.
	Securities and other non-cash deposits may include U.S. Treasury securities, U.S. Government agency securities, Eurobonds, corporate bonds, other foreign government securities and gold bullion. Securities and other non-cash deposits are held in safekeeping by a custodian bank. Interest and gains or losses on securities deposited to satisfy performance bond and guaranty fund requirements accrue to the clearing firm. Because the benefits and risks of ownership accrue to the clearing firm, non-cash performance bonds and guaranty fund contributions are not reflected in the consolidated balance sheets.
Property, Equipment and Leasehold Improvements	Property, Equipment and Leasehold Improvements. Property, equipment and leasehold improvements are stated at cost, less accumulated depreciation and amortization. Depreciation and amortization are calculated using the straight-line method, generally over two to thirty-nine years. Property and equipment are depreciated over their estimated useful lives. Leasehold improvements are amortized over the shorter of the remaining term of the respective lease to which they relate or the remaining useful life of the leasehold improvement. Land is reported at cost. Internal and external costs incurred in developing or obtaining computer software for internal use are capitalized and amortized on a straight-line basis over the estimated useful life of the software, generally two to four years.
Operating Leases	Operating Leases. All leases in which the company is the tenant are accounted for as operating leases. Landlord allowances are recorded as a reduction to rent expense on a straight-line basis over the term of the lease.
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets. Goodwill represents the excess of the purchase price over the fair value of the net assets acquired in a business combination. The company reviews goodwill and indefinite-lived intangible assets for impairment annually and whenever events or circumstances indicate that their carrying values may not be recoverable. The company may test goodwill quantitatively for impairment by comparing the carrying value of a reporting unit to its estimated fair value. Estimating the fair value of a reporting unit involves significant judgments inherent in the analysis including estimating the amount of and timing of future cash flows and the selection of appropriate discount rates and long-term growth rate assumptions. Changes in these estimates and assumptions could materially affect the determination of fair value of the reporting unit. If the carrying amount exceeds fair value, impairment is recorded. In certain circumstances, goodwill may be reviewed qualitatively for indications of impairment without utilizing valuation techniques to estimate fair value.
	The company evaluates the recoverability of indefinite-lived intangible assets by comparing the estimated fair value of the intangible asset to its carrying value. If the indefinite-lived intangible asset carrying value exceeds its fair value, an impairment loss is recognized in an amount equal to that excess. Estimating the fair value of indefinite-lived intangible assets involves the use of valuation techniques that rely on significant estimates and assumptions including forecasted revenue growth rates, forecasted allocations of expense and risk-adjusted discount rates. Changes in these estimates and assumptions could materially affect the determination of fair value for indefinite-lived intangible assets. In certain circumstances, indefinite-lived intangible assets may be reviewed qualitatively for indications of impairment without utilizing valuation techniques to estimate fair value.
	Intangible assets subject to amortization are also assessed for impairment when indicated by a change in economic or operational circumstances. The impairment assessment of these assets requires management to first compare the book value of the amortizing asset to undiscounted cash flows. If the book value exceeds the undiscounted cash flows, management is then required to estimate the fair value of the assets and record an impairment loss for the excess of the carrying value over the fair value.
Business Combinations	Business Combinations. The company accounts for business combinations using the acquisition method. The method requires the acquirer to recognize the assets acquired, liabilities assumed, and any non-controlling interest in the acquiree at the acquisition date, measured at their fair values as of that date. The company may use independent valuation services to assist in determining the estimated fair values.
Employee Benefit Plans	Employee Benefit Plans. The company recognizes the funded status of defined benefit postretirement plans in its consolidated balance sheets. Changes in that funded status are recognized in the year of change in other comprehensive income (loss). Plan assets and obligations are measured at year end. The company recognizes future changes in actuarial gains and losses and prior service costs in the year in which the changes occur through other comprehensive income (loss).
Foreign Currency Translation	Foreign Currency Translation. Foreign currency denominated assets and liabilities are re-measured into the functional currency using period-end exchange rates. Gains and losses from foreign currency transactions are included in other expense in the accompanying consolidated statements of income. When the functional currency differs from the reporting currency, revenues and expenses of foreign subsidiaries are translated from their functional currencies into U.S. dollars using weighted-average exchange rates while their assets and liabilities are translated into U.S. dollars using period-end exchange rates. Gains and losses resulting from foreign currency translations are included in accumulated other comprehensive income (loss) within shareholders' equity.
Revenue Recognition	Revenue Recognition. Revenue recognition policies for specific sources of revenue are discussed below.
	Clearing and Transaction Fees. Clearing and transaction fees include per-contract charges for trade execution, clearing, trading on the company's electronic trading platform and other fees. Fees are charged at various rates based on the product traded, the method of trade, the exchange trading privileges of the customer making the trade and the type of contract. Clearing and transaction fees are recognized as revenue when a buy and sell order are matched and the trade is cleared. Therefore, unfilled or canceled buy and sell orders have no impact on revenue. On occasion, the customer's exchange trading privileges may not be properly entered by the clearing firm and incorrect fees are charged for the transactions. When this information is corrected within the time period allowed by the exchange, a fee adjustment is provided to the clearing firm. A reserve is established for estimated fee adjustments to reflect corrections to customer exchange trading privileges. The reserve is based on the historical pattern of adjustments processed as well as specific adjustment requests. The company believes the allowances are adequate to cover estimated adjustments.
	Market Data and Information Services. Market data and information services represent revenue earned for the dissemination of market information. Revenues are accrued each month based on the number of devices reported by vendors. The exchange conducts periodic examinations of the number of devices reported and assesses additional fees as necessary. On occasion, customers will pay for services in a lump sum payment; however, revenue is recognized as services are provided.
	Access and Communication Fees. Access fees are the connectivity charges to customers of the company's electronic trading platform that are also used by market data vendors and customers. The fees include co-location fees, access fees for the electronic trading platform, line charges and hardware rental charges and can vary depending on the type of connection provided. An additional installation fee may be charged depending on the type of service requested and a disconnection fee may also be charged if certain conditions are met. Revenue is generally recognized monthly as the service is provided.
	Communication fees consist of equipment rental and usage charges to customers and firms that utilize various telecommunications hubs located internationally as well as networks and services in the Chicago and New York City facilities. Revenue is billed and recognized on a monthly basis.
	Other Revenues. Other revenues include processing services revenue, which is revenue generated from various strategic relationships, as well as management fees earned under the IEF programs. For processing services revenue and IEF revenue, revenue is recognized as services are provided.
	Other revenues also included revenue from the rental of commercial space that were recognized over the lease term using the straight-line method. Under this method, revenue was recorded evenly over the entire term of occupancy for leases with scheduled rent increases or rent abatements. Allowances for construction and other tenant costs were considered lease incentives and were recorded as a reduction to rental income on a straight-line basis over the term of the lease.
	Concentration of Revenue. One firm represented 12% of the company's clearing and transaction fees revenue in 2014. In 2013, one firm represented 11% and one firm represented 10% of the company's clearing and transaction fees revenue. Two firms each represented 12% of the company's clearing and transaction fees revenue in 2012. Should a clearing firm withdraw from the exchange, management believes that the customer portion of that firm's trading activity would likely transfer to another clearing firm. Therefore, management does not believe that the company is exposed to significant risk from the ongoing loss of revenue received from a particular clearing firm.
	The two largest resellers of market data represented approximately 44% of market data and information services revenue in 2014, 52% in 2013, and 43% in 2012. Should one of these vendors no longer subscribe to the company's market data, management believes that the majority of that firm's customers would likely subscribe to the market data through another reseller. Therefore, management does not believe that the company is exposed to significant risk from a loss of revenue received from any particular market data reseller.
Share-Based Payments	Share-Based Payments. The company accounts for share-based payments at fair value, which is based on the grant date price of the equity awards issued. The company recognizes expense relating to stock-based compensation on an accelerated basis. As a result, the expense associated with each vesting date within a stock grant is recognized over the period of time that each portion of that grant vests. The company estimates expected forfeitures of stock grants.
Marketing Costs	Marketing Costs. Marketing costs are incurred for the production and communication of advertising as well as other marketing activities. These costs are expensed when incurred, except for costs related to the production of broadcast advertising, which are expensed when the first broadcast occurs.
Income Taxes	Income Taxes. Deferred income taxes arise from temporary differences between the tax basis and book basis of assets and liabilities. A valuation allowance is recognized if it is anticipated that some or all of a deferred tax asset may not be realized. The company accounts for uncertainty in income taxes recognized in its consolidated financial statements by using a more-likely-than-not recognition threshold based on the technical merits of the tax position taken or expected to be taken. The company classifies interest and penalties related to uncertain tax positions in income tax expense.
Segment Reporting	Segment Reporting. The company reports the results of its operations as one operating segment primarily comprised of CME, CBOT, NYMEX and COMEX exchanges. The remaining operations do not meet the thresholds for reporting separate segment information.

Marketable_Securities_Tables

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2014
Marketable Securities [Abstract]
Available-for-sale securities	The amortized cost and fair value of these securities at December 31 were as follows:
		2014				2013
	(in millions)	Amortized		Fair		Amortized		Fair
		Cost		Value		Cost		Value
	U.S. Treasury securities	$	19.1	$	19.1	$	18.3	$	18.3
	Asset-backed security	0.7		0.4		0.8		0.4
	Equity securities	0.1		0.1		—		0.1
	Total	$	19.9	$	19.6	$	19.1	$	18.8
Amortized cost and fair value of marketable securities by contractual maturity	The amortized cost and fair value of the U.S. Treasury securities and asset-backed security at December 31, 2014, by contractual maturity, were as follows:
	(in millions)	Amortized		Fair
		Cost		Value
	Maturity of one year or less	$	19.1	$	19.1
	Maturity between one and five years	—		—
	Maturity between five and ten years	—		—
	Maturity greater than ten years	0.7		0.4
	Total	$	19.8	$	19.5

Performance_Bonds_and_Guaranty1

Performance Bonds and Guaranty Fund Contributions (Tables)	12 Months Ended
	Dec. 31, 2014
Performance Bonds and Guaranty Fund Contributions [Abstract]
Cash and securities held as performance bonds and guaranty fund contributions at fair value	Cash and non-cash deposits held as performance bonds and guaranty fund contributions at fair value at December 31 for CME and CMECE were as follows:
		2014				2013
	(in millions)	Cash		Non-Cash		Cash		Non-Cash
				Deposits				Deposits
				and				and
				IEF Funds				IEF Funds
	Performance bonds1	$	38,729.00	$	93,972.70	$	20,060.10	$	88,152.30
	Guaranty fund contributions	1,719.90		5,699.00		1,290.10		4,834.80
	Cross-margin arrangements	102.2		91.2		3.1		76.5
	Performance collateral for delivery	15.7		2.1		1.8		2.6
	Total	$	40,566.80	$	99,765.00	$	21,355.10	$	93,066.20
	(1) Cash performance bonds include cash collateral reinvested in U.S. Treasury securities.
Letters of credit	At December 31, these letters of credit, which are not included in the accompanying consolidated balance sheets, were as follows:
	(in millions)	2014		2013
	Performance bonds	$	2,441.90	$	3,453.10
	Guaranty fund contributions	25		25
	Cross-margin arrangements	5.5		—
	Performance collateral for delivery	950.4		1,005.50
	Total Letters of Credit	$	3,422.80	$	4,483.60

Property_Tables

Property (Tables)	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment, Net [Abstract]
Summary of the Property Accounts	A summary of the property accounts at December 31 is presented below:
	(in millions)	2014			2013			Estimated Useful Life
	Land and land improvements	$	17.7		$	20.1		10 - 20 years (1)
	Building and building improvements	273.5			280			3 - 39 years
	Leasehold improvements	219.1			218.6			3 - 24 years
	Furniture, fixtures and equipment	360.1			352.1			2 - 7 years
	Software and software development costs	379.5			321			2 - 4 years
	Total property	1,249.90			1,191.80
	Less accumulated depreciation and amortization	(741.0		)	(678.4		)
	Property, net	$	508.9		$	513.4
	(1) Estimated useful life applies only to land improvements.

Intangible_Assets_and_Goodwill1

Intangible Assets and Goodwill (Tables)	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Components of intangible assets	Intangible assets consisted of the following at December 31:
			2014							2013
	(in millions)		Assigned Value		Accumulated			Net Book		Assigned Value		Accumulated			Net Book
					Amortization			Value				Amortization			Value
	Amortizable Intangible Assets:
	Clearing firm, market data and other customer relationships		$	2,838.80	$	(658.8	)	$	2,180.00	$	2,838.80	$	(563.2	)	$	2,275.60
	Technology-related intellectual property		29.4		(23.5		)	5.9		33.8		(19.8		)	14
	Other		2.4		(0.9		)	1.5		2.4		(0.8		)	1.6
	Total amortizable intangible assets		$	2,870.60	$	(683.2	)	2,187.40		$	2,875.00	$	(583.8	)	2,291.20
	Indefinite-Lived Intangible Assets:
	Trade names							450							450
	Total intangible assets—other, net							$	2,637.40						$	2,741.20
	Trading products (1)							$	17,175.30						$	17,175.30
	_______________
	-1	Trading products represent futures and options products acquired in our business combinations with CBOT Holdings, Inc., NYMEX Holdings, Inc. and The Board of Trade of Kansas City, Missouri, Inc. Clearing and transaction fees are generated through the trading of these products. These trading products, most of which have traded for decades, require authorization from the CFTC. Product authorizations from the CFTC have no term limits.
Weighted average useful life for the amortizable intangible assets	The originally assigned useful lives for the amortizable intangible assets as of December 31, 2014 are as follows:
	Clearing firm, market data and other customer relationships	5 - 30 years
	Technology-related intellectual property	4 - 5 years
	Other	3 - 24.5 years
Future estimated amortization expense	As of December 31, 2014, the future estimated amortization expense related to amortizable intangible assets is expected to be as follows:
	(in millions)
	2015	$	99.5
	2016	96.1
	2017	95.5
	2018	94.7
	2019	94.7
	Thereafter	1,706.90
Goodwill activity	Goodwill activity consisted of the following for the years ended December 31, 2014 and 2013:
	(in millions)		Balance at December 31, 2013		Business			Divestitures		Other		Balance at December 31, 2014
					Combinations					Activity
	CBOT Holdings		$	5,035.70	$	—		$	—	$	—	$	5,035.70
	NYMEX Holdings		2,462.20		—			—		—		2,462.20
	Other		71.1		—			—		—		71.1
	Total Goodwill		$	7,569.00	$	—		$	—	$	—	$	7,569.00
	(in millions)		Balance at December 31, 2012		Business			Divestitures		Other		Balance at December 31, 2013
					Combinations					Activity
	CBOT Holdings		$	5,035.70	$	—		$	—	$	—	$	5,035.70
	NYMEX Holdings		2,462.20		—			—		—		2,462.20
	Other		69		—			—		2.1		71.1
	Total Goodwill		$	7,566.90	$	—		$	—	$	2.1	$	7,569.00

Debt_Tables

Debt (Tables)	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Schedule of Short-term Debt	Short-term debt consisted of the following at December 31:
	(in millions)		2014		2013
	$750.0 million fixed rate notes due February 2014, stated rate of 5.75%		$	—	$	749.9
	Total short-term debt		$	—	$	749.9
Schedule of Long-term Debt	Long-term debt consisted of the following at December 31:
	(in millions)		2014		2013
	$612.5 million fixed rate notes due March 2018, stated rate of 4.40%(1)		$	611	$	610.5
	$750.0 million fixed rate notes due September 2022, stated rate of 3.00% (2)		748.2		748
	$750.0 million fixed rate notes due September 2043, stated rate of 5.30% (3)		748.7		748.7
	Total long-term debt		$	2,107.90	$	2,107.20
	_______________
	-1	In February 2010, the company entered into a forward-starting interest rate swap agreement that modified the interest obligation associated with these notes so that the interest payable on the notes effectively became fixed at a rate of 4.46%.
	-2	In August 2012, the company entered into a forward-starting interest rate swap agreement that modified the interest obligation associated with these notes so that the interest payable on the notes effectively became fixed at a rate of 3.32%.
	-3	In August 2012, CME Group entered into a forward-starting interest rate swap agreement that modified the interest obligation associated with these notes so that the interest payable on the notes effectively became fixed at a rate of 4.73%
Long-term debt maturities at par value	Long-term debt maturities, at par value, were as follows as of December 31, 2014:
	(in millions)	Par Value
	2015	$	—
	2016	—
	2017	—
	2018	612.5
	2019	—
	Thereafter	1,500.00
Fair value of fixed rate notes by maturity date	At December 31, 2014, the fair values of the fixed-rate notes by maturity date were as follows:
	(in millions)		Fair Value
	$612.5 million fixed rate notes due March 2018, stated rate of 4.40%		$	650.5
	$750.0 million fixed rate notes due September 2022, stated rate of 3.00%		763
	$750.0 million fixed rates notes due September 2043, stated rate of 5.30%		913.4

Derivative_Instruments_Tables

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2014
General Discussion of Derivative Instruments and Hedging Activities [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]	The fair value and location of outstanding derivative instruments in the consolidated balance sheet were as follows at December 31:
	(in millions)	Balance Sheet Location		2014			2013
	Interest rate contract	Other current liabilities		$	2.3		$	—
Effect of derivative instruments on the statements of Income and Shareholders' Equity	The pre-tax effect of derivative instruments on the consolidated statements of income as well as accumulated other comprehensive income (OCI) within the consolidated statements of comprehensive income and consolidated statements of shareholders' equity for the years ended December 31, 2014 and 2013 were as follows:
		Gains (Losses)						(Gains) Losses Reclassified from						Gains (Losses)
		Recognized in OCI						Accumulated OCI						Recognized in Income
		(Effective Portion)						(Effective Portion)						(Ineffective Portion)
	(in millions)	2014			2013			Location	2014			2013		Location	2014		2013
	Interest rate contracts	$	(2.3	)	$	128.8		Interest and other borrowing costs	$	(1.5	)	$	1.6	Gains (losses) on derivative investments	$	—	$	—

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Taxes on income	Income before income taxes and the income tax provision consisted of the following for the years ended December 31. The company is subject to regulation under a wide variety of U.S., federal, state and foreign tax laws and regulations.
	(in millions)	2014				2013				2012
	Income before income taxes:
	Domestic	$	1,783.70			$	1,599.20			$	1,703.50
	Foreign	(12.3		)		1.8				(10.1		)
	Total	$	1,771.40			$	1,601.00			$	1,693.40
	Income tax provision:
	Current:
	Federal	$	526.4			$	491.9			$	585.2
	State	36.5				128.8				117.6
	Foreign	2.7				8.2				1.7
	Total	565.6				628.9				704.5
	Deferred:
	Federal	47.1				(157.6		)		50.3
	State	32.4				153.4				37
	Foreign	(0.6		)		(1.8		)		(5.1		)
	Total	78.9				(6.0		)		82.2
	Total Income Tax Provision	$	644.5			$	622.9			$	786.7
Reconciliation of the statutory U.S. federal income tax rate to the effective tax rate	Reconciliation of the statutory U.S. federal income tax rate to the effective tax rate is as follows:
		2014			2013			2012
	Statutory U.S. federal tax rate	35	%		35	%		35	%
	State taxes, net of federal benefit	1.6			4.8			4.8
	Domestic production activities deduction	(1.4	)		(7.7	)		—
	Increase (decrease) in domestic valuation allowance	0.1			0.6			—
	Impact of revised state and local apportionment estimates	1.1			6.6			1
	Deferred taxes associated with McGraw venture and CMA sale	—			—			6.3
	Other, net	—			(0.4	)		(0.6	)
	Effective Tax Rate	36.4	%		38.9	%		46.5	%
Deferred tax assets (liabilities)	At December 31, deferred income tax assets (liabilities) consisted of the following:
	(in millions)	2014				2013
	Net Current Deferred Income Tax Assets:
	Unrealized loss on securities	$	3			$	3
	Stock-based compensation	19.2				19.1
	Accrued expenses and other	2.2				30.2
	Net Current Deferred Income Tax Assets	$	24.4			$	52.3
	Net Non-Current Deferred Income Tax Assets:
	Domestic unrealized loss on investment in BM&FBOVESPA	$	101.7			$	59.7
	Foreign losses	19.7				18.8
	Domestic losses	7.3				8.5
	Stock-based compensation	30.7				49.3
	Deferred compensation and other benefit plans	38.1				23.8
	Property	44.3				35.2
	Unrealized losses on securities	16.5				22.9
	Accrued expenses and other	—				13.8
	Subtotal	258.3				232
	Valuation allowance	(99.2		)		(47.5		)
	Total non-current deferred income tax assets	159.1				184.5
	Non-Current Deferred Income Tax Liabilities:
	Purchased intangible assets	(7,448.2		)		(7,434.2		)
	Other	(13.6		)		—
	Total non-current deferred income tax liabilities	(7,461.8		)		(7,434.2		)
	Net Non-Current Deferred Income Tax Liabilities	$	(7,302.7	)		$	(7,249.7	)
Unrecognized tax benefits	The following is a summary of the company’s unrecognized tax benefits:
	(in millions)	2014				2013				2012
	Gross unrecognized tax benefits	$	187.6			$	231.6			$	37.7
	Unrecognized tax benefits, net of tax impacts in other jurisdictions	160.8				183.3				24.5
	Unrecognized interest and penalties related to uncertain tax positions	11				42.5				20.1
	Interest and penalties recognized in the consolidated statements of income	(12.5		)		22.4				3
Reconciliation of unrecognized tax benefits	A reconciliation of the beginning and ending amounts of unrecognized tax benefits is as follows:
	(in millions)	2014				2013				2012
	Balance at January 1	$	231.6			$	37.7			$	36.8
	Additions based on tax positions related to the current year	30.5				26.1				5.3
	Additions for tax positions of prior years	24.9				168.4				3.2
	Reductions for tax positions of prior years	(51.8		)		(0.4		)		(2.0		)
	Reductions resulting from the lapse of statutes of limitations	—				(0.2		)		(2.2		)
	Settlements with taxing authorities	(47.6		)		—				(3.4		)
	Balance at December 31	$	187.6			$	231.6			$	37.7

Employee_Benefit_Plans_Tables

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2014
General Discussion of Pension and Other Postretirement Benefits [Abstract]
Summary of the change in projected benefit obligation	The following is a summary of the change in projected benefit obligation:
	(in millions)		2014				2013
	Balance at January 1		$	175.7			$	181.6
	Service cost		17.1				18
	Interest cost		9.6				7.9
	Actuarial (gain) loss		30.1				(23.4		)
	Benefits paid		(8.8		)		(8.4		)
	Balance at December 31		$	223.7			$	175.7
Change in plan assets	The following is a summary of the change in fair value of plan assets:
	(in millions)		2014				2013			2012
	Balance at January 1		$	193.6			$	183.9		$	149.1
	Actual return on plan assets		14.3				18.1			16.4
	Employer contributions		26				—			28
	Benefits paid		(8.8		)		(8.4		)	(9.6		)
	Balance at December 31		$	225.1			$	193.6		$	183.9
Fair value of plan assets	The fair value of each major category of plan assets as of December 31 is indicated below.
	(in millions)		2014				2013
	Level 2:
	Money market funds		$	27.2			$	4.4
	Mutual funds:
	Fixed income		67.2				60.7
	U.S. equity		63.4				59.6
	Foreign equity		57.6				59.7
	Commodity		9.7				9.2
	Total		$	225.1			$	193.6
Components of net pension expenses and the assumptions used to determine the end-of-year projected benefit obligation and net pension expense in aggregate	The components of net pension expense and the assumptions used to determine the end-of-year projected benefit obligation and net pension expense in aggregate are indicated below:
	(in millions)		2014				2013			2012
	Components of Net Pension Expense:
	Service cost		$	17.1			$	18		$	16
	Interest cost		9.6				7.9			7.9
	Expected return on plan assets		(14.0		)		(13.3		)	(11.0		)
	Recognized net actuarial loss		0.6				3.1			2.5
	Net Pension Expense		$	13.3			$	15.7		$	15.4
	Assumptions Used to Determine End-of-Year Benefit Obligation:
	Discount rate		4.2		%		5.1		%	4.1		%
	Rate of compensation increase		5				5			5
	Cash balance interest crediting rate		4				4			4
	Assumptions Used to Determine Net Pension Expense:
	Discount rate		5.1		%		4.1		%	5		%
	Rate of compensation increase		5				5			5
	Expected return on plan assets		7.5				7.5			7.75
	Interest crediting rate		4				4			4
Asset allocation for the plan	The asset allocation for the plan, by asset category, at December 31 was as follows:
		2014			2013
	Fixed income	29.8	%		31.4	%
	U.S. equity	28.2			30.8
	Foreign equity	25.6			30.8
	Money market funds	12.1			2.3
	Commodity	4.3			4.7
	The range of target allocation percentages for 2015 is as follows:
		Minimum			Maximum
	Fixed income	33	%		45	%
	U.S. equity	23.5			35
	Foreign equity	23.5			35
	Commodity	2			8
Prior service costs and actuarial losses included in accumulated other comprehensive income (loss)	The pre-tax balance and activity of the prior service costs and actuarial losses for the pension plan, which are included in other comprehensive income (loss), for 2014 are as follows:
	(in millions)		Prior				Actuarial
			Service				Loss
			Costs
	Balance at January 1		$	0.1			$	22.5
	Unrecognized net loss		—				29.7
	Recognized as a component of net pension expense		—				(0.6		)
	Balance at December 31		$	0.1			$	51.6
Anticipated benefit payments from the plan in future years	At December 31, 2014, anticipated benefit payments from the plan in future years are as follows:
	(in millions)
	2015		$	13.8
	2016		14.8
	2017		15.7
	2018		17.3
	2019		18.4
	2020-2024		108.5

Commitments_Tables

Commitments (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Schedule of future minimum payments under non-cancelable operating leases	At December 31, 2014, future minimum payments under non-cancellable operating leases were payable as follows (in millions):
	Year
	2015	$	59.1
	2016	47.8
	2017	42.4
	2018	42
	2019	41.6
	Thereafter	221.7
	Total	$	454.6
Schedule of other commitments	At December 31, 2014, future minimum payments due under purchase obligations were payable as follows (in millions):
	Year
	2015	$	14.6
	2016	9.8
	2017	9.2
	2018	8.3
	2019	1.2
	Thereafter	2.3
	Total	$	45.4

Redeemable_NonControlling_Inte1

Redeemable Non-Controlling Interest (Tables)	12 Months Ended
	Dec. 31, 2014
Temporary Equity [Abstract]
Changes in redeemable non-controlling interest	The following summarizes the changes in redeemable non-controlling interest for the years presented. Non-controlling interests that do not contain redemption features are presented in the statements of equity.
	(in millions)	2013			2012
	Balance at January 1	$	80.8		$	70.3
	Total comprehensive income attributable to redeemable non-controlling interest	1.5			10.5
	Purchase of non-controlling interest	(82.3		)	—
	Balance at December 31	$	—		$	80.8

Capital_Stock_Tables

Capital Stock (Tables)	12 Months Ended
	Dec. 31, 2014
Capital Stock [abstract]
Capital stock	The following table presents information regarding capital stock:
		December 31,
	(in thousands)	2014	2013
	Class A common stock authorized	1,000,000	1,000,000
	Class A common stock issued and outstanding	335,452	333,852
	Class B-1 common stock authorized, issued and outstanding	0.6	0.6
	Class B-2 common stock authorized, issued and outstanding	0.8	0.8
	Class B-3 common stock authorized, issued and outstanding	1.3	1.3
	Class B-4 common stock authorized, issued and outstanding	0.4	0.4

StockBased_Payments_Tables

Stock-Based Payments (Tables)	12 Months Ended
	Dec. 31, 2014
Share-based Compensation [Abstract]
Compensation expense for stock-based payments and total income tax benefit recognized	Total compensation expense for stock-based payments and total income tax benefit recognized in the consolidated statements of income for stock-based awards were as follows:
	(in millions)		2014				2013			2012
	Compensation expense		$	55			$	54.4		$	61.4
	Income tax benefit recognized		19.5				20			22.5
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	The Black-Scholes fair value of each option grant was calculated using the following assumptions:
		Grant Year
		2012
	Dividend yield	4.2%-4.5%
	Expected volatility	40%-41%
	Risk-free interest rate	0.8%-1.5%
	Expected life	5.0 to 6.2 years
Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]	The following table summarizes stock option activity for 2014. Aggregate intrinsic value is in millions.
			Number of Shares			Weighted			Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value
						Average
						Exercise
						Price
	Outstanding at December 31, 2013		4,191,594			$	67		4.9		$	70.4
	Exercised		(1,030,952	)		52
	Cancelled		(149,375	)		76
	Outstanding at December 31, 2014		3,011,267			72			3.7		60.1
	Exercisable at December 31, 2014		2,761,127			74			3.5		51.5
Schedule of Nonvested Share Activity [Table Text Block]	The following table summarizes restricted stock, restricted stock units, and performance shares activity for 2014:
		Number of Shares			Weighted
					Average
					Grant Date
					Fair Value
	Outstanding at December 31, 2013	2,085,251			$	63
	Granted	948,740			82
	Vested	(511,575	)		60
	Cancelled	(424,108	)		64
	Outstanding at December 31, 2014	2,098,308			72

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]
	(in millions)	Investment Securities			Defined Benefit Plans			Derivative Investments			Foreign Currency Translation			Total
	Balance at December 31, 2013	$	98.9		$	(12.8	)	$	65		$	0.9		$	152
	Other comprehensive income before reclassifications and income tax benefit (expense)	(116.6		)	(30.0		)	(2.3		)	(5.2		)	(154.1		)
	Amounts reclassified from accumulated other comprehensive income	—			0.3			(1.5		)	—			(1.2		)
	Income tax benefit (expense)	(5.2		)	11.2			1.4			2.1			9.5
	Net current period other comprehensive income attributable to CME Group	(121.8		)	(18.5		)	(2.4		)	(3.1		)	(145.8		)
	Balance at December 31, 2014	$	(22.9	)	$	(31.3	)	$	62.6		$	(2.2	)	$	6.2
	(in millions)	Investment Securities			Defined Benefit Plans			Derivative Investments			Foreign Currency Translation			Total
	Balance at December 31, 2012	$	256.7		$	(32.4	)	$	(16.4	)	$	1.4		$	209.3
	Other comprehensive income before reclassifications and income tax benefit (expense)	(221.0		)	28.4			128.8			(0.8		)	(64.6		)
	Amounts reclassified from accumulated other comprehensive income	(0.7		)	3.2			1.6			—			4.1
	Income tax benefit (expense)	63.9			(12.0		)	(49.0		)	0.3			3.2
	Net current period other comprehensive income attributable to CME Group	(157.8		)	19.6			81.4			(0.5		)	(57.3		)
	Balance at December 31, 2013	$	98.9		$	(12.8	)	$	65		$	0.9		$	152
	(in millions)	Investment Securities			Defined Benefit Plans			Derivative Investments			Foreign Currency Translation			Total
	Balance at December 31, 2011	$	148.4		$	(26.1	)	$	(1.2	)	$	(9.5	)	$	111.6
	Other comprehensive income before reclassifications and income tax benefit (expense)	174.7			(13.0		)	(25.3		)	(1.3		)	135.1
	Ineffectiveness on cash flow hedges	—			—			0.1			—			0.1
	Amounts reclassified from accumulated other comprehensive income (1)	(1.8		)	2.5			1			18.4			20.1
	Income tax benefit (expense)	(64.6		)	4.2			9			(6.2		)	(57.6		)
	Net current period other comprehensive income attributable to CME Group	108.3			(6.3		)	(15.2		)	10.9			97.7
	Balance at December 31, 2012	$	256.7		$	(32.4	)	$	(16.4	)	$	1.4		$	209.3

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Financial instruments measured at fair value on a recurring basis
			December 31, 2014
	(in millions)		Level 1		Level 2		Level 3		Total
	Assets at Fair Value:
	Marketable securities:
	U.S. Treasury securities		$	19.1	$	—	$	—	$	19.1
	Mutual funds		55.1		—		—		55.1
	Equity securities		0.1		—		—		0.1
	Asset-backed security		—		0.4		—		0.4
	Total		74.3		0.4		—		74.7
	Performance bonds and guaranty fund contributions:
	U.S. Treasury securities (1)		16,699.70		—		—		16,699.70
	Equity investments		432.1		—		—		432.1
	Total Assets at Fair Value		$	17,206.10	$	0.4	$	—	$	17,206.50
	Liabilities at Fair Value:
	Interest rate swap contract		$	—	$	2.3	$	—	$	2.3
	Contingent consideration		—		—		17.7		17.7
	Total Liabilities at Fair Value		$	—	$	2.3	$	17.7	$	20
	(1) Performance bonds and guaranty fund contributions on the consolidated balance sheet at December 31, 2014 include cash collateral that has been invested in U.S. Treasury securities.
			December 31, 2013
	(in millions)		Level 1		Level 2		Level 3		Total
	Assets at Fair Value:
	Marketable securities:
	U.S. Treasury securities		$	18.3	$	—	$	—	$	18.3
	Mutual funds		49.6		—		—		49.6
	Equity securities		0.1		—		—		0.1
	Asset-backed securities		—		0.4		—		0.4
	Total		68		0.4		—		68.4
	Equity investments		499.9		—		—		499.9
	Total Assets at Fair Value		$	567.9	$	0.4	$	—	$	568.3
	Liabilities at Fair Value:
	Contingent consideration		$	—	$	—	$	15.7	$	15.7
	Total Liabilities at Fair Value		$	—	$	—	$	15.7	$	15.7
Reconciliation of assets and liabilities valued at fair value on a recurring basis using significant unobservable inputs (level 3)	The following is a reconciliation of level 3 liabilities valued at fair value on a recurring basis during 2014 and 2013. There were no level 3 assets valued at fair value on a recurring basis during 2014 and 2013.
	(in millions)	Contingent Consideration
	Fair value of liability at December 31, 2012	$	12.6
	Contingent obligation arising from acquisition	4.4
	Realized and unrealized gains (losses):
	Included in operating expense	6
	Settlements	(7.3		)
	Fair value of liability at December 31, 2013	15.7
	Realized and unrealized gains (losses):
	Included in operating expense	7.1
	Settlements	(5.1		)
	Fair value of liability at December 31, 2014	$	17.7

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]	Anti-dilutive stock options and stock awards were as follows for the years presented:
	(in thousands)	2014		2013			2012
	Stock options	1,330		1,566			4,851
	Stock awards	124		65			—
	Total	1,454		1,631			4,851
Basic and diluted earnings per share	The following table presents the earnings per share calculation for the years presented:
		2014			2013			2012
	Net Income Attributable to CME Group (in millions)	$	1,127.10		$	976.8		$	896.3
	Weighted Average Common Shares Outstanding (in thousands):
	Basic	334,409			332,678			331,252
	Effect of stock options and stock awards	1,654			1,720			1,067
	Diluted	336,063			334,398			332,319
	Earnings per Common Share Attributable to CME Group:
	Basic	$	3.37		$	2.94		$	2.71
	Diluted	3.35			2.92			2.7

Quarterly_Information_Unaudite1

Quarterly Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Data [Abstract]
Quarterly Information
	(in millions, except per share data)	First			Second			Third			Fourth			Year to Date
		Quarter			Quarter			Quarter			Quarter
	Year Ended December 31, 2014
	Total revenues	$	777.4		$	731.6		$	762.4		$	841.1		$	3,112.50
	Operating income	454.5			412			430.4			471.5			1,768.40
	Non-operating income (expense)	(8.1		)	10.1			(1.3		)	2.3			3
	Income before income taxes	446.4			422.1			429.1			473.8			1,771.40
	Net income attributable to CME Group	266.8			263.8			290			306.5			1,127.10
	Earnings per common share attributable to CME Group:
	Basic	$	0.8		$	0.79		$	0.87		$	0.91		$	3.37
	Diluted	0.79			0.79			0.86			0.91			3.35
	Year Ended December 31, 2013
	Total revenues	$	718.6		$	816.1		$	714.6		$	687		$	2,936.30
	Operating income	405.5			507.8			400.5			323.2			1,637.00
	Non-operating income (expense)	(17.9		)	(0.3		)	(1.6		)	(16.2		)	(36.0		)
	Income before income taxes	387.6			507.5			398.9			307			1,601.00
	Net income attributable to CME Group	235.8			311.2			236.7			193.1			976.8
	Earnings per common share attributable to CME Group:
	Basic	$	0.71		$	0.94		$	0.71		$	0.58		$	2.94
	Diluted	0.71			0.93			0.71			0.58			2.92

Organization_and_Business_Deta

Organization and Business (Details) (USD $)	6 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2014	Dec. 31, 2012	Apr. 30, 2013	Mar. 18, 2010	Jun. 30, 2012
Business Acquisition [Line Items]
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	$80		$5.80
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage		51.00%
S&P/Dow Jones Indices LLC [Member]
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage				27.00%
Dow Jones [Member]
Business Acquisition [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					10.00%
CME Group net of non-controlling interest [Member]
Business Acquisition [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		24.40%				24.40%

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Narrative) (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Clearing and transaction fees from Firm 1
Concentration Risk, Customer	1	1	2
Concentration of revenue	12.00%	11.00%	12.00%
Clearing and transaction fees from Firm 2
Concentration Risk, Customer		1
Concentration of revenue		10.00%
Market data and information services
Concentration of revenue	44.00%	52.00%	43.00%
Minimum [Member]
Estimated useful live of the assets minimum in years	2 years
Minimum [Member] | Software and software development costs
Estimated useful live of the assets minimum in years	2 years
Maximum [Member]
Estimated useful live of the assets minimum in years	39 years
Maximum [Member] | Software and software development costs
Estimated useful live of the assets minimum in years	4 years

Marketable_Securities_Availabl

Marketable Securities (Available-for-Sale Securities) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Available-for-Sale Securities Amortized Cost	$19.90	$19.10
Available-for-sale Securities	19.6	18.8
US Treasury Securities [Member]
Available-for-Sale Securities Amortized Cost	19.1	18.3
Available-for-sale Securities	19.1	18.3
Asset-backed Securities [Member]
Available-for-Sale Securities Amortized Cost	0.7	0.8
Available-for-sale Securities	0.4	0.4
Equity Securities [Member]
Available-for-Sale Securities Amortized Cost	0.1	0
Available-for-sale Securities	$0.10	$0.10

Marketable_Securities_Amortize

Marketable Securities (Amortized Cost and Fair Value of Marketable Securities) (Details) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Schedule of Held-to-maturity Securities [Line Items]
Maturity of one year or less, Amortized Cost	$19.10
Maturity between one and five years, Amortized Cost	0
Maturity between five and ten years, Amortized Cost	0
Maturity greater than ten years, Amortized Cost	0.7
Total, Amortized Cost	19.8
Maturity of one year or less, Fair Value	19.1
Maturity between one and five years, Fair Value	0
Maturity between five and ten years, Fair Value	0
Maturity greater than ten years, Fair Value	0.4
Total, Fair Value	$19.50

Marketable_Securities_Narrativ

Marketable Securities (Narrative) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Trading securities fair value	$55.10	$49.60
Asset-backed Securities [Member]
Fair value of asset-back securities	0.4
Unrealized losses	($0.30)

Performance_Bonds_and_Guaranty2

Performance Bonds and Guaranty Fund Contributions (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	days
Available-for-Sale Securities Fair Value	$19,900,000	$19,100,000
Average daily clearing settlement	3,000,000,000
Available-for-sale Securities	19,600,000	18,800,000
Total principal in IEF programs	16,400,000,000	19,400,000,000
Management fees earned under the IEF programs	14,900,000	13,900,000	10,600,000
Percentage share of cross-margining collateral	50.00%
Days fully secured	364
Intraday settlements of cash performance bonds	224,200,000	115,600,000
364-day fully secured, committed line of credit
Line of Credit Facility, Maximum Borrowing Capacity	7,000,000,000
Line of Credit, Guaranty Fund Collateral Available	6,600,000,000
Option on increase in line of credit	10,000,000,000
Revolving senior credit facility
Line of Credit Facility, Maximum Borrowing Capacity	1,800,000,000
CME Base Guaranty Fund [Member]
Corporate Contribution	100,000,000
CME IRS Guaranty Fund [Member] [Member]
Corporate Contribution	150,000,000
CME CDS Guaranty Fund [Member] [Member]
Corporate Contribution	50,000,000
Working capital designated for clearance of default in over the counter credit default swap, percent	5.00%
Working capital designated for clearance of default in over the counter interest rate swap	100,000,000
CMECE Commodity Fund [Member]
Corporate Contribution	57,000,000
Guaranty Fund Contributions	10,000,000
Minimum Corporate Contribution	20,000,000
CMECE Interest Rate Swap [Member]
Corporate Contribution	50,500,000
Guaranty Fund Contributions	101,100,000
U.S. Treasury Performance Bond [Member]
Available-for-Sale Securities Fair Value	16,700,000,000
Available-for-sale Securities	$16,700,000,000

Performance_Bonds_and_Guaranty3

Performance Bonds and Guaranty Fund Contributions (Cash and Securities Held as Performance Bonds and Guaranty Fund Contributions at Fair Value) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Performance collateral for delivery	$950.40	$1,005.50
Total	40,566.80	21,355.10
Cash [Member]
Performance bonds	38,729	20,060.10
Guaranty Fund Contributions	1,719.90	1,290.10
Cross-margin arrangements	102.2	3.1
Performance collateral for delivery	15.7	1.8
Total	40,566.80	21,355.10
Non-Cash Deposits and IEF Funds [Member]
Performance bonds	93,972.70	88,152.30
Guaranty Fund Contributions	5,699	4,834.80
Cross-margin arrangements	91.2	76.5
Performance collateral for delivery	2.1	2.6
Total	$99,765	$93,066.20

Performance_Bonds_and_Guaranty4

Performance Bonds and Guaranty Fund Contributions (Performance Bond Deposits and Security Deposits) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Performance Bonds and Guaranty Fund Contributions [Abstract]
Performance bonds	$2,441.90	$3,453.10
Guaranty Fund Letters of Credit	25	25
Cross Margin Letters of Credit	5.5	0
Performance collateral for delivery	950.4	1,005.50
Total Letters of Credit	$3,422.80	$4,483.60

Property_Details

Property (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Proceeds from sale of building property	$7.90	$192.40	$148.60
Gain (Loss) on Disposition of Property Plant Equipment	0	-27.1	0
Property, gross	1,249.90	1,191.80
Less accumulated depreciation and amortization	-741	-678.4
Property, net	508.9	513.4
NYMEX [Member]
Property, Plant and Equipment [Line Items]
Proceeds from sale of building property		200
Gain (Loss) on Disposition of Property Plant Equipment		27.1
Land and land improvements
Property, Plant and Equipment [Line Items]
Property, gross	17.7	20.1
Building and building improvements
Property, Plant and Equipment [Line Items]
Property, gross	273.5	280
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, gross	219.1	218.6
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Property, gross	360.1	352.1
Software and software development costs
Property, Plant and Equipment [Line Items]
Property, gross	$379.50	$321
Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	2 years
Minimum [Member] | Land and land improvements
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	10 years
Minimum [Member] | Building and building improvements
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	3 years
Minimum [Member] | Leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	3 years
Minimum [Member] | Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	2 years
Minimum [Member] | Software and software development costs
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	2 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	39 years
Maximum [Member] | Land and land improvements
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	20 years
Maximum [Member] | Building and building improvements
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	39 years
Maximum [Member] | Leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	24 years
Maximum [Member] | Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	7 years
Maximum [Member] | Software and software development costs
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	4 years

Intangible_Assets_and_Goodwill2

Intangible Assets and Goodwill (Narrative) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Amortization of purchased intangibles	$100.60	$103	$116.20
Intangible assets-other, net	2,637.40	2,741.20
Lease Agreements [Member] | NYMEX [Member]
Net book value		$13.80

Intangible_Assets_and_Goodwill3

Intangible Assets and Goodwill (Components of Intangible Assets) (Details) (USD $)	Dec. 31, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Indefinite-lived Intangible Assets	$2,637.40		$2,741.20
Other Indefinite-lived Intangible Assets	17,175.30	[1]	17,175.30	[1]
Trade Names [Member]
Indefinite-lived Intangible Assets	450		450
Clearing Firm, Market Data, and Other Customer Relationships [Member]
Cost	2,838.80		2,838.80
Accumulated amortization	-658.8		-563.2
Net book value	2,180		2,275.60
Technology-Related Intellectual Property [Member]
Cost	29.4		33.8
Accumulated amortization	-23.5		-19.8
Net book value	5.9		14
Other - Finite [Member]
Cost	2.4		2.4
Accumulated amortization	-0.9		-0.8
Net book value	1.5		1.6
Finite-Lived Intangible Assets [Member]
Cost	2,870.60		2,875
Accumulated amortization	-683.2		-583.8
Net book value	$2,187.40		$2,291.20
[1]	(1)Trading products represent futures and options products acquired in our business combinations with CBOT Holdings, Inc., NYMEX Holdings, Inc. and The Board of Trade of Kansas City, Missouri, Inc. Clearing and transaction fees are generated through the trading of these products. These trading products, most of which have traded for decades, require authorization from the CFTC. Product authorizations from the CFTC have no term limits.

Intangible_Assets_and_Goodwill4

Intangible Assets and Goodwill Intangible Assets and Goodwill (Useful Lives of Intangible Assets) (Details)	12 Months Ended
	Dec. 31, 2014
Minimum [Member] | Clearing Firm, Market Data, and Other Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Useful life, minimum	5 years
Minimum [Member] | Technology-Related Intellectual Property [Member]
Finite-Lived Intangible Assets [Line Items]
Useful life, minimum	4 years
Minimum [Member] | Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Useful life, minimum	3 years
Maximum [Member] | Clearing Firm, Market Data, and Other Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Useful life, minimum	30 years
Maximum [Member] | Technology-Related Intellectual Property [Member]
Finite-Lived Intangible Assets [Line Items]
Useful life, minimum	5 years
Maximum [Member] | Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Useful life, minimum	24 years 6 months

Intangible_Assets_and_Goodwill5

Intangible Assets and Goodwill (Future Estimated Amortization Expense) (Details) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Goodwill and Intangible Assets Disclosure [Abstract]
2015	$99.50
2016	96.1
2017	95.5
2018	94.7
2019	94.7
Thereafter	$1,706.90

Intangible_Assets_and_Goodwill6

Intangible Assets and Goodwill (Goodwill Activity) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Total Goodwill, beginning balance	$7,569	$7,566.90
Business Combinations	0	0
Goodwill, Written off Related to Sale of Business Unit	0	0
Other Activity	0	2.1
Total Goodwill, ending balance	7,569	7,569
CBOT holdings [Member]
Total Goodwill, beginning balance	5,035.70	5,035.70
Business Combinations	0	0
Goodwill, Written off Related to Sale of Business Unit	0	0
Other Activity	0	0
Total Goodwill, ending balance	5,035.70	5,035.70
NYMEX holdings [Member]
Total Goodwill, beginning balance	2,462.20	2,462.20
Business Combinations	0	0
Goodwill, Written off Related to Sale of Business Unit	0	0
Other Activity	0	0
Total Goodwill, ending balance	2,462.20	2,462.20
Other Affiliates [Member]
Total Goodwill, beginning balance	71.1	69
Business Combinations	0	0
Goodwill, Written off Related to Sale of Business Unit	0	0
Other Activity	0	2.1
Total Goodwill, ending balance	$71.10	$71.10

LongTerm_Investments_Details

Long-Term Investments (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Fair value of investment		$499.90
BM&F [Member]
Equity Method Investment, Ownership Percentage	5.00%
Fair value of investment	410.8	473.1
Cost-basis value of investment	405.7	356.9
Bolsa Mexicana De Valores, S A B De C V [Member]
Equity Method Investment, Ownership Percentage	2.00%
Fair value of investment	21.2	26.8
Cost-basis value of investment	17.3
Bursa Malaysia Derivatives Berhad [Member]
Equity Method Investment, Ownership Percentage	25.00%
Fair value of investment	27.6
DME Holdings [Member]
Equity Method Investment, Ownership Percentage	50.00%
Fair value of investment	7.6
S&P/DJI [Member]
Equity Method Investment, Ownership Percentage	27.00%
Fair value of investment	$962.20

Debt_Narrative_Details

Debt (Narrative) (Details) (USD $)	1 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Feb. 28, 2010	Dec. 31, 2014
Forward starting interest rate swap agreement fixed rate	4.73%
Seven Hundred Fifty Million Fixed Rate Notes Due March Two Thousand Twenty Two, Interest Equal To Four Point Three Zero Percent [Member]
Debt Instrument, Interest Rate, Stated Percentage			3.00%
Forward starting interest rate swap agreement fixed rate		3.32%
Debt instrument, face amount			$750

Debt_Schedule_of_ShortTerm_and

Debt (Schedule of Short-Term and Long-Term Debt) (Details) (USD $)	1 Months Ended	12 Months Ended		1 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2014		Feb. 28, 2010	Dec. 31, 2013
Short-term Debt
Short-term debt		$0			$749.90
Long-term Debt
Long-term debt		2,107.90			2,107.20
Forward starting interest rate swap agreement fixed rate	4.73%
$750.0 Million Fixed Rate Notes Due February 2014, Interest Equal To 5.75% [Member]
Short-term Debt
Short-term debt		0	[1]		749.9	[1]
Long-term Debt
Debt instrument, face amount		750
Debt Instrument, maturity date		1-Feb-14
Debt Instrument, Interest Rate, Stated Percentage		5.75%
$612.5 Million Fixed Rate Notes Due March 2018, Interest Equal To 4.40% [Member]
Long-term Debt
Long-term debt		611			610.5
Forward starting interest rate swap agreement fixed rate				4.46%
Debt instrument, face amount		612.5
Debt Instrument, maturity date		1-Mar-18
Debt Instrument, Interest Rate, Stated Percentage		4.40%
Seven Hundred Fifty Million Fixed Rate Notes Due March Two Thousand Twenty Two, Interest Equal To Three Point Zero Percent [Member] [Member]
Long-term Debt
Long-term debt		748.2	[2]		748	[2]
Debt Instrument, maturity date		1-Sep-22
Seven Hundred Fifty Million Fixed Rate Notes Due March Two Thousand Forty Three, Interest Equal To Five Point Three Percent [Member]
Long-term Debt
Long-term debt		748.7	[2]		748.7	[2]
Debt instrument, face amount		750
Debt Instrument, maturity date		1-Sep-43
Debt Instrument, Interest Rate, Stated Percentage		5.30%
Seven Hundred Fifty Million Fixed Rate Notes Due March Two Thousand Twenty Two, Interest Equal To Four Point Three Zero Percent [Member]
Long-term Debt
Forward starting interest rate swap agreement fixed rate				3.32%
Debt instrument, face amount		$750
Debt Instrument, Interest Rate, Stated Percentage		3.00%
[1]	In February 2010, the company entered into a forward-starting interest rate swap agreement that modified the interest obligation associated with these notes so that the interest payable on the notes effectively became fixed at a rate of 4.46%.
[2]	In August 2012, the company entered into a forward-starting interest rate swap agreement that modified the interest obligation associated with these notes so that the interest payable on the notes effectively became fixed at a rate of 3.32%.

Debt_LongTerm_Debt_Maturities_

Debt (Long-Term Debt Maturities at Par Value) (Details) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Debt Disclosure [Abstract]
2015	$0
2016	0
2017	0
2018	612.5
2019	0
Thereafter	$1,500

Debt_Fair_Value_of_Fixed_Rate_

Debt (Fair Value of Fixed Rate Notes by Maturity Date) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014
$750.0 Million Fixed Rate Notes Due February 2014, Interest Equal To 5.75% [Member]
Debt instrument, face amount	$750
Debt Instrument, maturity date	1-Feb-14
$612.5 Million Fixed Rate Notes Due March 2018, Interest Equal To 4.40% [Member]
Debt instrument, fair value	650.5
Debt instrument, face amount	612.5
Debt Instrument, maturity date	1-Mar-18
Seven Hundred Fifty Million Fixed Rate Notes Due March Two Thousand Twenty Two, Interest Equal To Three Point Zero Percent [Member] [Member]
Debt instrument, fair value	763
Debt Instrument, maturity date	1-Sep-22
Seven Hundred Fifty Million Fixed Rate Notes Due March Two Thousand Twenty Two, Interest Equal To Four Point Three Zero Percent [Member]
Debt instrument, face amount	750
Seven Hundred Fifty Million Fixed Rate Notes Due March Two Thousand Forty Three, Interest Equal To Five Point Three Percent [Member]
Debt instrument, fair value	913.4
Debt instrument, face amount	$750
Debt Instrument, maturity date	1-Sep-43

Derivative_Instruments_Narrati

Derivative Instruments (Narrative) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2012	Dec. 31, 2013
In Millions, unless otherwise specified
ExpectedReclassificationAdjustment	$1.40
Derivative, Notional Amount	500	1,500
Other Liabilities [Member]
Fair value of the interest rate derivative instruments	($2.30)		$0

Derivative_Instruments_Effect_

Derivative Instruments (Effect of Derivative Instruments on the Statements of Income and Shareholders' Equity) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	($2.30)	$128.80	($25.30)
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, before Tax	-1.5	1.6	1.1
Derivative, Net Hedge Ineffectiveness Gain (Loss)	$0	$0	($0.10)

Derivative_Instruments_Fair_Va

Derivative Instruments Fair Value of Derivatives by Balance Sheet Location (Details) (Other Liabilities [Member], USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Interest Rate Cash Flow Hedge Derivative at Fair Value, Net	$2.30	$0

Income_Taxes_Income_Tax_Provis

Income Taxes (Income Tax Provision) (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Income before income taxes: Domestic									$1,783.70	$1,599.20	$1,703.50
Income before income taxes: Foreign									-12.3	1.8	-10.1
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	473.8	429.1	422.1	446.4	307	398.9	507.5	387.6	1,771.40	1,601	1,693.40
Current income tax provision: Federal									526.4	491.9	585.2
Current income tax provision: State									36.5	128.8	117.6
Current income tax provision: Foreign									2.7	8.2	1.7
Current income tax provision: Total									565.6	628.9	704.5
Deferred income tax provision: Federal									47.1	-157.6	50.3
Deferred income tax provision: State									32.4	153.4	37
Deferred income tax provision: Foreign									-0.6	-1.8	-5.1
Deferred income tax provision: Total									78.9	-6	82.2
Total Income Tax Provision									$644.50	$622.90	$786.70

Income_Taxes_Federal_Income_Ta

Income Taxes (Federal Income Tax Rate) (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Statutory U.S. federal tax rate	35.00%	35.00%	35.00%
State taxes, net of federal benefit	1.60%	4.80%	4.80%
Effective Income Tax Rate Reconciliation, Deductions, Qualified Production Activities	-1.40%	-7.70%	0.00%
Increase (decrease) in domestic valuation allowance	0.10%	0.60%	0.00%
Impact of revised state apportionment estimates	1.10%	6.60%	1.00%
Effective Income Tax Rate Reconciliation, Disposition of Business	0.00%	0.00%	6.30%
Other, net	0.00%	-0.40%	-0.60%
Effective Tax Rate	36.40%	38.90%	46.50%

Income_Taxes_Deferred_Tax_Asse

Income Taxes (Deferred Tax Assets (Liabilities) ) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Subtotal	$258.30	$232
Valuation allowance	-99.2	-47.5
Total non-current deferred tax assets	159.1	184.5
Total non-current deferred tax liabilities	-7,461.80	-7,434.20
Net Non-Current Deferred Tax Liabilities	-7,302.70	-7,249.70
current [Member]
Stock-based compensation	19.2	19.1
Unrealized loss on securities	3	3
Accrued expenses and other	2.2	30.2
Noncurrent [Member]
Domestic unrealized loss on investment in BM&FBOVESPA	101.7	59.7
Deferred Tax Assets, Unrealized Currency Losses	19.7	18.8
Deferred tax asset Domestic Losses	7.3	8.5
Stock-based compensation	30.7	49.3
Deferred compensation	38.1	23.8
Deferred Tax Assets, Property, Plant and Equipment	44.3	35.2
Unrealized loss on securities	16.5	22.9
Accrued expenses and other	0	13.8
Purchase intangible assets	-7,448.20	-7,434.20
Deferred Tax Liabilities, Other	13.6	0
Domestic Tax Authority [Member]
Valuation allowance	($99.20)	($47.50)

Income_Taxes_Summary_Of_Unreco

Income Taxes (Summary Of Unrecognized Tax Benefits) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Gross unrecognized tax benefits	$187.60	$231.60	$37.70	$36.80
Unrecognized tax benefits, net of tax impacts in other jurisdictions	160.8	183.3	24.5
Interest and penalties related to uncertain tax positions	11	42.5	20.1
Interest and penalties recognized in the consolidated statements of income	($12.50)	$22.40	$3

Income_Taxes_Reconciliation_Of

Income Taxes (Reconciliation Of Unrecognized Tax Benefits) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Balance as of January 1	$231.60	$37.70	$36.80
Additions based on tax positions related to the current year	30.5	26.1	5.3
Additions for tax positions of prior years	24.9	168.4	3.2
Reductions for tax positions of prior years	-51.8	-0.4	-2
Reductions resulting from the lapse of statutes of limitations	0	-0.2	-2.2
Settlements with taxing authorities	-47.6	0	-3.4
Balance as of December 31	$187.60	$231.60	$37.70

Income_Taxes_Income_Taxes_Narr

Income Taxes Income Taxes (Narrative) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Operating Loss Carryforwards	$118.90	$117.30
unrealized capital tax loss	317.7	223.4
Deferred Tax Assets, Valuation Allowance, Noncurrent	99.2	47.5
Long-term deferred tax asset	258.3	232
Domestic Tax Authority [Member]
Deferred Tax Assets, Valuation Allowance, Noncurrent	$99.20	$47.50

Employee_Benefit_Plans_Narrati

Employee Benefit Plans (Narrative) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Amortization of actuarial loss from accumulated other comprehensive income (loss) into net periodic benefit costs	$2.60
Trading securities fair value	55.1	49.6
Pension Plans [Member]
Age for participation eligibility in benefit plan	21
Years of service for vesting eligibility	3 years
Accumulated benefit obligation	195.6	154.8
Excess of pension plan assets over the projected benefit obligation	1.4	17.9
Defined Benefit Plan Funding Goal Percentage	100.00%
Estimated liabilities exceeding the fair value of the plan assets	21.8
Estimated contribution to meet projected excess of pension plan liabilities of pension plan assets	21.8
Percentage of employees base salary matched by employer, maximum	3.00%
Defined Contribution Plan, Cost Recognized	11.2	9.9	8.9
NYMEX Members' Retirement Plan and Benefits [Member]
Minimum annual contribution NYMEX Members' Retirement Plan and Benefits	0.8
Total contribution	0.8
Total obligation	21.2	20.3
Fair value of assets	$20	$19.20
Pension Plans [Member]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Cash Balance Interest Crediting Rate	4.00%	4.00%	4.00%

Employee_Benefit_Plans_Summary

Employee Benefit Plans (Summary of the change in projected benefit obligation) (Details) (Pension Plans [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Plans [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Balance at January 1	$175.70	$181.60
Service cost	17.1	18	16
Interest cost	9.6	7.9	7.9
Actuarial (gain) loss	30.1	-23.4
Benefits paid	-8.8	-8.4	-9.6
Balance at December 31	$223.70	$175.70	$181.60

Employee_Benefit_Plans_Change_

Employee Benefit Plans (Change in Plan Assets) (Details) (Pension Plans [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Plans [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance at January 1	$193.60	$183.90	$149.10
Actual return on plan assets	14.3	18.1	16.4
Employer contributions	26	0	28
Benefits paid	-8.8	-8.4	-9.6
Balance at December 31	$225.10	$193.60	$183.90

Employee_Benefit_Plans_Fair_Va

Employee Benefit Plans (Fair Value of Plan Assets) (Details) (Pension Plans [Member], USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Millions, unless otherwise specified
Defined Benefit Plan, Fair Value of Plan Assets	$225.10	$193.60	$183.90	$149.10
Fair Value, Inputs, level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	225.1	193.6
Fair Value, Inputs, level 2 [Member] | Money Market Funds [Member]
Defined Benefit Plan, Fair Value of Plan Assets	27.2	4.4
Fair Value, Inputs, level 2 [Member] | US Equity [Member]
Defined Benefit Plan, Fair Value of Plan Assets	67.2	60.7
Fair Value, Inputs, level 2 [Member] | Foreign Equity [Member]
Defined Benefit Plan, Fair Value of Plan Assets	63.4	59.6
Fair Value, Inputs, level 2 [Member] | Fixed Income [Member]
Defined Benefit Plan, Fair Value of Plan Assets	57.6	59.7
Fair Value, Inputs, level 2 [Member] | Commodity [Member]
Defined Benefit Plan, Fair Value of Plan Assets	$9.70	$9.20

Employee_Benefit_Plans_Compone

Employee Benefit Plans (Components of Net Pension Expense) (Details) (Pension Plans [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Plans [Member]
Components of Net Pension Expense:
Service cost	$17.10	$18	$16
Interest cost	9.6	7.9	7.9
Expected return on plan assets	-14	-13.3	-11
Recognized net actuarial loss	0.6	3.1	2.5
Net Pension Expense	$13.30	$15.70	$15.40
Assumptions Used to Determine End-of-Year Benefit Obligation:
Discount rate	4.20%	5.10%	4.10%
Rate of compensation increase	5.00%	5.00%	5.00%
Cash balance interest crediting rate	4.00%	4.00%	4.00%
Assumptions Used to Determine Net Pension Expense:
Discount rate	5.10%	4.10%	5.00%
Rate of compensation increase	5.00%	5.00%	5.00%
Expected return on plan assets	7.50%	7.50%	7.75%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Cash Balance Interest Crediting Rate	4.00%	4.00%	4.00%

Employee_Benefit_Plans_Asset_A

Employee Benefit Plans (Asset Allocation for the Plan) (Details) (Pension Plans [Member])	Dec. 31, 2014	Dec. 31, 2013
Fixed Income [Member]
Actual allocation of plan assets, Fixed income	29.80%	31.40%
US Equity [Member]
Actual allocation of plan assets, Fixed income	28.20%	30.80%
Foreign Equity [Member]
Actual allocation of plan assets, Fixed income	25.60%	30.80%
Commodity [Member]
Actual allocation of plan assets, Fixed income	12.10%	2.30%
Money Market Funds [Member]
Actual allocation of plan assets, Fixed income	4.30%	4.70%

Employee_Benefit_Plans_Target_

Employee Benefit Plans (Target Allocation Percentages) (Details) (Pension Plans [Member])	12 Months Ended
	Dec. 31, 2014
US Equity [Member]
Minimum	23.50%
Maximum	35.00%
Foreign Equity [Member]
Minimum	23.50%
Maximum	35.00%
Fixed Income [Member]
Minimum	33.00%
Maximum	45.00%
Commodity [Member]
Minimum	2.00%
Maximum	8.00%

Employee_Benefit_Plans_Accumul

Employee Benefit Plans (Accumulated Other Comprehensive Income (Loss), of the Prior Service Costs and Actuarial Losses) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax	($30)	$28.40	($13)
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax	0.3	3.2	2.5
Pension Plans [Member]
Prior Service Cost Beginning Balance	0.1
Defined Benefit Plan, Amortization of Net Prior Service Cost (Credit)	0
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0
Prior Service Cost Ending Balance	0.1
Actuarial Loss Beginning Balance	51.6
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax	29.7
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax	-0.6
Actuarial Loss Ending Balance	$22.50

Employee_Benefit_Plans_Anticip

Employee Benefit Plans (Anticipated Benefit Payments from the Plan in Future Years) (Details) (Pension Plans [Member], USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Pension Plans [Member]
2015	$13.80
2016	14.8
2017	15.7
2018	17.3
2019	18.4
2020-2024	$108.50

Commitments_Narrative_Details

Commitments (Narrative) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating leases, rent expense	$51	$28.60	$25.30
NYMEX [Member]
Operating leases number of renewal options	2
Operating leases renewal option, period (in years)	5 years
Chicago CBOT Building [Member] [Member]
Operating leases number of renewal options	4
Operating leases renewal option, period (in years)	5 years
Chicago [Member]
Operating leases number of renewal options	2
Additional Office Space Chicago [Member]
Operating leases number of renewal options	2
Operating leases renewal option, period (in years)	5 years
First Lease Renewal Option [Member]
Operating leases renewal option, period (in years)	7 years
Second Lease Renewal Option [Member]
Operating leases renewal option, period (in years)	10 years

Commitments_NonCancelable_Oper

Commitments (Non-Cancelable Operating Leases and Contractual Obligations) (Details) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Operating Leases, Future Minimum Payments Due [Abstract]
2015	$59.10
2016	47.8
2017	42.4
2018	42
2019	41.6
Thereafter	221.7
Total	454.6
Unrecorded Unconditional Purchase Obligation [Abstract]
2015	14.6
2016	9.8
2017	9.2
2018	8.3
2019	1.2
Thereafter	2.3
Total	$45.40

Contingencies_Details

Contingencies (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Accrued liability related to all outstanding legal matters	$4.30	$11.30

Guarantees_Details

Guarantees (Details) (USD $)	12 Months Ended
	Dec. 31, 2014
Guarantor Obligations [Line Items]
PaymentPerParticipant	$25,000
Contingent liability to SGX, amount of irrevocable letters of credit	410
PaymentPerCooperative	100,000
FutureLosses	100,000,000
Family Farmer and Ranchers Protection Fund [Member]
Guarantor Obligations [Line Items]
Payments under Guarantee	2,000,000
Guarantor Obligations, Maximum Exposure, Undiscounted	$98,000,000

Redeemable_NonControlling_Inte2

Redeemable Non-Controlling Interest (Details) (USD $)	6 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 18, 2010	Jun. 30, 2012	Apr. 30, 2013
Noncontrolling Interest [Line Items]
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	$80			$5.80
Adjustments to Additional Paid in Capital, Deferred Tax Liabilities	165.6
Gain on Purchase of NonControlling Interest	2.3
Temporary Equity, Carrying Amount, Period Increase (Decrease)			-82.3	0
Changes in Redeemable Non-controlling Interest [Roll Forward]
Balance at January 1	80.8	0	80.8	70.3
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest		-0.2	1.3	10.5
Comprehensive Income (Loss), Net of Tax, Attributable to Redeemable Non-controlling Interest			1.5	10.5
Balance at December 31			$0	$80.80
Dow Jones [Member]
Noncontrolling Interest [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					10.00%
CME Group net of non-controlling interest [Member]
Noncontrolling Interest [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		24.40%				24.40%
S&P/Dow Jones Indices LLC [Member]
Noncontrolling Interest [Line Items]
Equity Method Investment, Ownership Percentage							27.00%

Capital_Stock_Narrative_Detail

Capital Stock (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Number of directors	24
Class A Common Stock (Shares) [Member]
Common Stock, Par or Stated Value Per Share	$0.01	$0.01
Class B Common Stock (Shares)
Common Stock, Par or Stated Value Per Share	$0.01	$0.01
Common stock, voting rights	1
Class B Common Stock, Class B1 [Member]
Common stock, voting rights	6
Number of directors	3
Class B Common Stock, Class B2 [Member]
Common stock, voting rights	2
Number of directors	2
Class B Common Stock, Class B3 [Member]
Common stock, voting rights	1
Number of directors	1
Class B Common Stock, Class B4 [Member]
Common stock, voting rights	6-Jan
Class B common stock, Class B1, B2, B3 [Member]
Number of directors	6
CME Group Omnibus Stock Plan [Member]
Shares granted, outstanding and exercised	23,100,000
Number of shares reserved for awards under the plan	40,200,000
CBOT Holdings Long-Term Equity Plan [Member]
Number of shares reserved for awards under the plan	2,300,000
Shares authorized for future awards, frozen awards	1,600,000
NYMEX Holdings Omnibus Long-Term Incentive Plan [Member]
Number of shares reserved for awards under the plan	5,000,000
Shares authorized for future awards, frozen awards	3,500,000
Director Stock Plan; Class A Shares [Member]
Number of shares reserved for awards under the plan	625,000
Class A shares awarded under Director Stock Plan	294,000
Employee Stock Purchase Plan; Class A Shares [Member]
Number of shares reserved for awards under the plan	500,000
Market value of the shares an Employee Stock Purchase Plan	90.00%
Class A shares Purchased under Employee Stock Purchase Plan	201,000

Capital_Stock_Capital_stock_De

Capital Stock (Capital stock) (Details)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Class A Common Stock
Common Stock, Shares Authorized	1,000,000,000	1,000,000,000
Common Stock, Shares, Outstanding	335,452,000	333,852,000	331,832,000	330,653,000
Class B Common Stock, Class B1 [Member]
Common Stock, Shares, Outstanding	600	600
Class B Common Stock, Class B2 [Member]
Common Stock, Shares, Outstanding	800	800
Class B Common Stock, Class B3 [Member]
Common Stock, Shares, Outstanding	1,300	1,300
Class B Common Stock, Class B4 [Member]
Common Stock, Shares, Outstanding	400	400

StockBased_Payments_Narrative_

Stock-Based Payments (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2008
Vesting percentage after one year	25.00%			20.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$114,500,000
Employee service share-based compensation, unrecognized compensation costs on nonvested awards, Weighted Average Period of Recognition, years	2 years 1 month
Share-based compensation arrangement by share-based payment award, options, grants in period, weighted average grant date fair value			$13
Share-based compensation arrangement by share-based payment award, options, exercises in period, total intrinsic value	29,500,000	35,300,000	19,000,000
Granted performance shares	948,740
Restricted Class A common stock, fair value	40,500,000	31,900,000	20,900,000
Total expense for stock payments	55,000,000	54,400,000	61,400,000
Share-based compensation arrangement by share-based payment award, discount from market price	90.00%
Class A common stock issued to participating employees	23,678	18,632	27,768
Director Stock Plan; Class A Shares [Member]
Total expense for stock payments	2,100,000	2,100,000	2,200,000
Annual award of class A common stock value	100,000
Annual stipend allowance in shares of stock	60,000
Annual stipend allowance in shares of stock (in shares)	33,735	27,168	40,260
Employee Stock Purchase Plan; Class A Shares [Member]
Total expense for stock payments	200,000	100,000	100,000
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate		4.20%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	2 years
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate		40.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate		0.80%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term		5 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate		4.50%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate		41.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate		1.50%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term		6 years 2 months
Performance Shares [Member]
Granted performance shares	211,785
Restricted Class A common stock, fair value	18,800,000
Restricted Stock Units (RSUs) [Member]
Stock options, granted, shares	5,796
Class A Common Stock (Shares) [Member]
Stock options, granted, shares	731,159
Restricted Class A common stock, fair value	$58,600,000

StockBased_Payments_Compensati

Stock-Based Payments (Compensation Expense And Income Tax Benefit Recognized) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation [Abstract]
Compensation expense	$55	$54.40	$61.40
Income tax benefit recognized	$19.50	$20	$22.50

StockBased_Payments_Stock_Opti

Stock-Based Payments (Stock Option Activity) (Details) (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding in Shares [Roll Forward]
Number of shares outstanding at December 31 (shares)	4,191,594
Number of shares exercised	-1,030,952
Number of shares cancelled	-149,375
Number of shares outstanding at December 31 (shares)	3,011,267	4,191,594
Number of shares exercisable at December 31 (shares)	2,761,127
Weighted average exercise price exercised	$52
Weighted average exercise price cancelled	$76
Weighted average exercise price outstanding	$72	$67
Weighted average exercise price exercisable	$74
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Remaining Contractual Term	3 years 6 months
Weighted average remaining contractual life outstanding	3 years 8 months	4 years 11 months
Aggregate intrinsic value outstanding	$60.10	$70.40
Aggregate intrinsic value exercisable	$51.50

StockBased_Payments_Restricted

Stock-Based Payments (Restricted Stock Activity) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding in Shares [Roll Forward]
Number of shares outstanding at December 31 (shares)	2,085,251	2,098,308
Number of shares granted	948,740
Number of shares vested	-511,575
Number of shares cancelled	-424,108
Weighted average grant date fair value granted	$82
Weighted average grant date fair value vested	$60
Weighted average grant date fair value cancelled	$64
Weighted average grant date fair value outstanding	$72		$63

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Income) (Details) (USD $)	3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stockholders' Equity Attributable to Parent		$20,923.50	$21,154.80
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax		-116.6	-221	174.7
Balance at beginning of period		152
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax		-5.2	-0.8	-1.3
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax		0.3	3.2	2.5
Derivative, Net Hedge Ineffectiveness Gain (Loss)		0	0	0.1
Balance at end of period		6.2	152
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax		-2.3	128.8	-25.3
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, before Tax		0	-0.7	-1.8
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, before Tax		-1.5	1.6	1.1
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment Realized upon Sale or Liquidation, before Tax	18.4	0	0	18.4
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax		-5.2	63.9	-64.6
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax		11.2	-12	4.2
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax		2.1	0.3	-6.2
Other Comprehensive Income (Loss), Net of Tax		-145.8	-57.3	97.8
Accumulated Defined Benefit Plans Adjustment [Member]
Stockholders' Equity Attributable to Parent		-31.3	-12.8	-32.4	-26.1
Net actuarial gain (loss)		-30	28.4	-13
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax		0.3	3.2	2.5
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax		11.2	-12	4.2
Other Comprehensive Income (Loss), Net of Tax		-18.5	19.6	-6.3
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Stockholders' Equity Attributable to Parent		-22.9	98.9	256.7	148.4
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax		-116.6	-221	174.7
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, before Tax		0	-0.7	-1.8
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax		-5.2	63.9	-64.6
Other Comprehensive Income (Loss), Net of Tax		-121.8	-157.8	108.3
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Stockholders' Equity Attributable to Parent		62.6	65	-16.4	-1.2
Derivative, Net Hedge Ineffectiveness Gain (Loss)				0.1
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax		-2.3	128.8	-25.3
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, before Tax		-1.5	1.6	1
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax		1.4	-49	9
Other Comprehensive Income (Loss), Net of Tax		-2.4	81.4	-15.2
Foreign Currency Gain (Loss) [Member]
Stockholders' Equity Attributable to Parent		-2.2	0.9	1.4	-9.5
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax		-5.2	-0.8	-1.3
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment Realized upon Sale or Liquidation, before Tax		0	0	18.4
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax		2.1	0.3	-6.2
Other Comprehensive Income (Loss), Net of Tax		-3.1	-0.5	10.9
Accumulated Other Comprehensive Income (Loss) [Member]
Stockholders' Equity Attributable to Parent		6.2	152	209.3	111.6
Comprehensive Income Reclassification Adjustments				0.1
Comprehensive Income Before Reclassification Adjustments		-154.1	-64.6	135.1
Comprehensive Income Reclassification Adjustments		-1.2	4.1	20.1
Other Comprehensive Income (Loss), Net of Tax		9.5	3.2	-57.6
Other Comprehensive Income (Loss), Net of Tax		($145.80)	($57.30)	$97.70

Fair_Value_Measurements_Narrat

Fair Value Measurements (Narrative) (Details)	12 Months Ended
	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate	20.00%
Valulation Model Probability Low Range	0.00%
fair value inputs probability of payout	100.00%

Fair_Value_Measurements_Financ

Fair Value Measurements (Financial Instruments Measured at Fair Value on a Recurring Basis) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	$19.60	$18.80
Trading Securities at Fair Value	55.1	49.6
Marketable Securities at Fair Value		68.4
Investment Owned, at Fair Value		499.9
Business Combination, Contingent Consideration, Liability		15.7
Total liabilities at fair value		15.7
US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		18.3
Total Assets at Fair Value		568.3
Mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities at Fair Value		49.6
Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0.4
Domestic Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0.1
Fair Value, Inputs, level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities at Fair Value		68
Investment Owned, at Fair Value		499.9
Business Combination, Contingent Consideration, Liability		0
Total liabilities at fair value		0
Fair Value, Inputs, level 1 [Member] | US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		18.3
Total Assets at Fair Value		567.9
Fair Value, Inputs, level 1 [Member] | Mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities at Fair Value		49.6
Fair Value, Inputs, level 1 [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0
Fair Value, Inputs, level 1 [Member] | Domestic Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0.1
Fair Value, Inputs, level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities at Fair Value		0.4
Investment Owned, at Fair Value		0
Business Combination, Contingent Consideration, Liability		0
Total liabilities at fair value		0
Fair Value, Inputs, level 2 [Member] | US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0
Total Assets at Fair Value		0.4
Fair Value, Inputs, level 2 [Member] | Mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities at Fair Value		0
Fair Value, Inputs, level 2 [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0.4
Fair Value, Inputs, level 2 [Member] | Domestic Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0
Fair Value, Inputs, level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities at Fair Value		0
Investment Owned, at Fair Value		0
Business Combination, Contingent Consideration, Liability		15.7
Total liabilities at fair value		15.7
Fair Value, Inputs, level 3 [Member] | US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0
Total Assets at Fair Value		0
Fair Value, Inputs, level 3 [Member] | Mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities at Fair Value		0
Fair Value, Inputs, level 3 [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0
Fair Value, Inputs, level 3 [Member] | Domestic Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities at Fair Value	74.7
Investment Owned, at Fair Value	432.1
Total Assets at Fair Value	17,206.50
Derivative Liability, Fair Value, Gross Liability	2.3
Business Combination, Contingent Consideration, Liability	17.7
Total liabilities at fair value	20
Fair Value, Measurements, Recurring [Member] | US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	19.1
Fair Value, Measurements, Recurring [Member] | Mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities at Fair Value	55.1
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0.1
Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0.4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities at Fair Value	74.3
Investment Owned, at Fair Value	432.1
Total Assets at Fair Value	17,206.10
Derivative Liability, Fair Value, Gross Liability	0
Business Combination, Contingent Consideration, Liability	0
Total liabilities at fair value	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 1 [Member] | US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	19.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 1 [Member] | Mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities at Fair Value	55.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 1 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 1 [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities at Fair Value	0.4
Investment Owned, at Fair Value	0
Total Assets at Fair Value	0.4
Derivative Liability, Fair Value, Gross Liability	2.3
Business Combination, Contingent Consideration, Liability	0
Total liabilities at fair value	2.3
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 2 [Member] | US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 2 [Member] | Mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities at Fair Value	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 2 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 2 [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0.4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities at Fair Value	0
Investment Owned, at Fair Value	0
Total Assets at Fair Value	0
Derivative Liability, Fair Value, Gross Liability	0
Business Combination, Contingent Consideration, Liability	17.7	15.7	12.6
Total liabilities at fair value	17.7
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 3 [Member] | US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 3 [Member] | Mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities at Fair Value	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 3 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 3 [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0
U.S. Treasury Performance Bond [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	16,700
U.S. Treasury Performance Bond [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	16,699.70
U.S. Treasury Performance Bond [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	16,699.70
U.S. Treasury Performance Bond [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0
U.S. Treasury Performance Bond [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	$0

Fair_Value_Measurements_Reconc

Fair Value Measurements (Reconciliation Using Significant Unobservable Inputs) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent Consideration Settlement	($7.30)
Business Combination, Contingent Consideration, Liability		15.7
Fair Value, Inputs, level 3 [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Business Combination, Contingent Consideration, Liability		15.7
Fair Value, Measurements, Recurring [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Business Combination, Contingent Consideration, Liability	17.7
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 3 [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent obligation arising from acquisition		4.4
Included in operating expense	7.1	6
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	-5.1
Business Combination, Contingent Consideration, Liability	$17.70	$15.70	$12.60

Earnings_Per_Share_Basic_and_D

Earnings Per Share (Basic and Diluted Earnings Per Share) (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, except Share data in Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net income attributable to CME Group	$306.50	$290	$263.80	$266.80	$193.10	$236.70	$311.20	$235.80	$1,127.10	$976.80	$896.30
Basic									334,409	332,678	331,252
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements									1,654	1,720	1,067
Diluted									336,063	334,398	332,319
Earnings per common share, basic	$0.91	$0.87	$0.79	$0.80	$0.58	$0.71	$0.94	$0.71	$3.37	$2.94	$2.71
Earnings per common share, diluted	$0.91	$0.86	$0.79	$0.79	$0.58	$0.71	$0.93	$0.71	$3.35	$2.92	$2.70
Outstanding anti-dilutive options									1,454	1,631	4,851
Stock Options [Member]
Outstanding anti-dilutive options									1,330	1,566	4,851
Restricted Stock [Member]
Outstanding anti-dilutive options									124	65	0

Quarterly_Information_Unaudite2

Quarterly Information (Unaudited) (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, except Share data in Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Data [Abstract]
Total Revenues	$841.10	$762.40	$731.60	$777.40	$687	$714.60	$816.10	$718.60	$3,112.50	$2,936.30	$2,914.60
Operating Income	471.5	430.4	412	454.5	323.2	400.5	507.8	405.5	1,768.40	1,637	1,692
Non-operating income (expense)	2.3	-1.3	10.1	-8.1	-16.2	-1.6	-0.3	-17.9	3	-36	1.4
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	473.8	429.1	422.1	446.4	307	398.9	507.5	387.6	1,771.40	1,601	1,693.40
Net income attributable to CME Group	$306.50	$290	$263.80	$266.80	$193.10	$236.70	$311.20	$235.80	$1,127.10	$976.80	$896.30
Earnings per Common Share Attributable to CME Group:
Basic	$0.91	$0.87	$0.79	$0.80	$0.58	$0.71	$0.94	$0.71	$3.37	$2.94	$2.71
Diluted	$0.91	$0.86	$0.79	$0.79	$0.58	$0.71	$0.93	$0.71	$3.35	$2.92	$2.70
Weighted Average Number of Common Shares:
Basic									334,409	332,678	331,252
Diluted									336,063	334,398	332,319

Schedule_IIValuation_and_Quali1

Schedule IIbValuation and Qualifying Accounts Schedule IIbValuation and Qualifying Accounts (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for doubtful accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	$1.20	$0.80	$1.30
Charged against goodwill	0	0	0
Charged (credited) to costs and expenses	0.1	0.8	1
Other	-0.1	-0.4	-1.5
Balance at end of year	1.2	1.2	0.8
Allowance for deferred tax assets
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	47.5	24.8	43.2
Charged against goodwill	0	0	0.5
Charged (credited) to costs and expenses	0	4.6	-3
Other	51.7	18.1	-15.9
Balance at end of year	$99.20	$47.50	$24.80