CME (CME) 10-K 1 Mar 18 2017 FY Annual report Financial data

DEI Statement

DEI Statement - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2017	Feb. 07, 2018	Jun. 30, 2017
Entity Information [Line Items]
Entity Registrant Name	CME GROUP INC.
Entity Central Index Key	1,156,375
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
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			$ 42.2
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		340,382,147

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents		$ 1,903.6	$ 1,868.6
Marketable securities		90.1	83.3
Accounts receivable, net of allowance		359.7	364.4
Other current assets		367.8	171.7
Cash performance bonds and guaranty fund contributions		44,185.3	37,543.5
Total current assets		46,906.5	40,031.5
Property, net of accumulated depreciation and amortization		399.7	425.2
Intangible assets-trading products	[1]	17,175.3	17,175.3
Intangible assets-other, net		2,346.3	2,441.8
Goodwill		7,569	7,569
Other assets		1,394.4	1,726.6
Total Assets		75,791.2	69,369.4
Liabilities and Shareholders' Equity
Accounts payable		31.3	26.2
Other current liabilities		1,456.3	1,376.7
Cash performance bonds and guaranty fund contributions		44,185.3	37,542.7
Total current liabilities		45,672.9	38,945.6
Long-term debt		2,233.1	2,231.2
Deferred Tax Liabilities, Net		4,857.7	7,291
Other liabilities		615.7	560.9
Total Liabilities		53,379.4	49,028.7
Shareholders' Equity:
Preferred stock, $0.01 par value, 10,000 shares authorized, none issued or outstanding		0	0
Additional paid-in capital		17,896.9	17,826.9
Retained earnings		4,497.2	2,524.5
Accumulated other comprehensive income (loss)		14.3	(14.1)
Total Shareholders' Equity		22,411.8	20,340.7
Total Liabilities and Shareholders' Equity		75,791.2	69,369.4
Class A Common Stock (Shares) [Member]
Shareholders' Equity:
Common stock		3.4	3.4
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 Bal

CONSOLIDATED BALANCE SHEETS Balance Sheet Parenthicals - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Allowance for Doubtful Accounts Receivable	$ 2.2	$ 3.5
Restricted Cash and Cash Equivalents, Current	0	30
Restricted Cash and Cash Equivalents, Noncurrent	$ 2.4	$ 61.7
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	339,235,000	338,240,000
Common Stock, Shares, Issued	339,235,000	338,240,000
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 INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Clearing and transaction fees	$ 3,098.6	$ 3,036.4	$ 2,783.9
Market data and information services	391.8	406.5	399.4
Access and communication fees	100.8	91.4	86.1
Other	53.5	60.9	57.4
Total Revenues	3,644.7	3,595.2	3,326.8
Expenses
Compensation and benefits	562.5	541	553.7
Communications	24.3	26.8	27.8
Technology support services	77.3	70.8	64.5
Professional fees and outside services	117.6	144.4	122.8
Amortization of purchased intangibles	95.5	96.1	99.4
Depreciation and amortization	113	129.2	129.2
Occupancy and building operations	80.2	86.7	92.5
Licensing and other fee agreements	146.3	135.8	123.8
Other	116	161.7	124.4
Total Expenses	1,332.7	1,392.5	1,338.1
Operating Income	2,312	2,202.7	1,988.7
Non-Operating Income (Expense)
Investment income	531.7	141.8	30.1
Gains (losses) on derivative investments	0	0	(1.8)
Interest and other borrowing costs	(117)	(123.5)	(117.4)
Equity in net (gains) losses of unconsolidated subsidiaries	129.2	110.2	100
Other income (expense)	(329.6)	(43.6)	(42.8)
Total Non-Operating	214.3	84.9	(31.9)
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	2,526.3	2,287.6	1,956.8
Income tax provision	(1,537.1)	753.5	709.8
Net Income	$ 4,063.4	$ 1,534.1	$ 1,247
Earnings per Common Share Attributable to CME Group:
Basic	$ 12	$ 4.55	$ 3.71
Diluted	$ 11.94	$ 4.53	$ 3.69
Weighted Average Number of Common Shares:
Basic	338,707	337,496	336,224
Diluted	340,226	338,966	337,894

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income	$ 4,063.4	$ 1,534.1	$ 1,247
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax	30.2	170	(78)
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, before Tax	(89.5)	(48.7)	8.5
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	79.4	(45.8)	(2.6)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	20.1	75.5	(72.1)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	0.3	(5.1)	(11.2)
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax	2.9	3.2	2.7
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax	(1.5)	0.7	3.2
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	1.7	(1.2)	(5.3)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	0	0	(4.7)
Derivative, Net Hedge Ineffectiveness Gain (Loss)	0	0	1.8
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, before Tax	(1.2)	(1.2)	(1.2)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax	0.3	0.5	1.1
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	(0.9)	(0.7)	(3)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax	10.4	(8.2)	(10.6)
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	(2.9)	1.3	4
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	7.5	(6.9)	(6.6)
Other Comprehensive Income (Loss), Net of Tax	28.4	66.7	(87)
Comprehensive Income (Loss), Net of Tax	$ 4,091.8	$ 1,600.8	$ 1,160

CONSOLIDATED STATEMENTS OF SHAR

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Millions	Total	Common Stock and Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Class A Common Stock (Shares) [Member]	Class B Common Stock (Shares) [Member]
Stockholders' Equity, beginning at Dec. 31, 2014	$ 20,923.5	$ 17,600	$ 3,317.3	$ 6.2
Beginning Balance (in shares) at Dec. 31, 2014					335,452,000	3,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	1,247
Net income	1,247		1,247
Other Comprehensive Income (Loss), Net of Tax	(87)			(87)
Dividends, Cash	(1,656.7)		(1,656.7)
Adjustments to Additional Paid in Capital, Other	9.3	9.3
Exercise of stock options (in shares)					984,000
Exercise of stock options	64	64
Excess tax benefits from option exercises and restricted stock vesting	3.8	3.8
Stock Issued During Period, Shares, Restricted Stock Award, Gross					456,000
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures	(17.2)	(17.2)
Shares issued to Board of Directors (in shares)					26,000
Stock Issued to Board of Directors, Value, Issued for Services	2.4	2.4
Shares issued under Employee Stock Purchase Plan (in shares)					20,000
Shares issued under Employee Stock Purchase Plan	1.9	1.9
Stock-based compensation	60.8	60.8
Stockholders' Equity, ending at Dec. 31, 2015	20,551.8	17,725	2,907.6	(80.8)
Ending Balance (in shares) at Dec. 31, 2015					336,938,000	3,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,534.1		1,534.1
Other Comprehensive Income (Loss), Net of Tax	66.7			66.7
Dividends, Cash	(1,917.2)		(1,917.2)
Exercise of stock options (in shares)					686,000
Exercise of stock options	51.8	51.8
Excess tax benefits from option exercises and restricted stock vesting	9.5	9.5
Stock Issued During Period, Shares, Restricted Stock Award, Gross					570,000
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures	(26.8)	(26.8)
Shares issued to Board of Directors (in shares)					26,000
Stock Issued to Board of Directors, Value, Issued for Services	2.5	2.5
Shares issued under Employee Stock Purchase Plan (in shares)					20,000
Shares issued under Employee Stock Purchase Plan	2.1	2.1
Stock-based compensation	66.2	66.2
Stockholders' Equity, ending at Dec. 31, 2016	20,340.7	17,830.3	2,524.5	(14.1)
Ending Balance (in shares) at Dec. 31, 2016					338,240,000	3,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	4,063.4		4,063.4
Other Comprehensive Income (Loss), Net of Tax	28.4			28.4
Dividends, Cash	(2,088.5)		(2,088.5)
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 0.8	(1.4)	(2.2)
Exercise of stock options (in shares)	443,911				444,000
Exercise of stock options	$ 36.7	36.7
Stock Issued During Period, Shares, Restricted Stock Award, Gross					511,000
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures	(31.3)	(31.3)
Shares issued to Board of Directors (in shares)					20,000
Stock Issued to Board of Directors, Value, Issued for Services	2.4	2.4
Shares issued under Employee Stock Purchase Plan (in shares)					20,000
Shares issued under Employee Stock Purchase Plan	2.8	2.8
Stock-based compensation	58	58
Stockholders' Equity, ending at Dec. 31, 2017	$ 22,411.8	$ 17,900.3	$ 4,497.2	$ 14.3
Ending Balance (in shares) at Dec. 31, 2017					339,235,000	3,000

CONSOLIDATED STATEMENTS OF SHA7

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY Equity Statement Parentheticals - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity Parentheticals [Abstract]
Common Stock, Dividends, Per Share, Declared	$ 6.14	$ 5.65	$ 4.90

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flows from Operating Activities
Net income	$ 4,063.4	$ 1,534.1	$ 1,247
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation	58	66.2	60.8
Amortization of purchased intangibles	95.5	96.1	99.4
Depreciation and amortization	113	129.2	129.2
Asset Impairment Charges	0	27.1	0
Gain (Loss) on Sale of Securities, Net	(86.5)	(48.4)	8.5
Gain (Loss) on Sale of Investments	(2.3)	0	0
Reclassification from AOCI, Current Period, Tax	87.8	0	0
Gains (Losses) on Extinguishment of Debt	0	0	61.8
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions	(26.8)	(2.3)	(5.1)
Deferred income taxes	(2,445.6)	(83)	63.3
Change in assets and liabilities:
Accounts receivable	6	(8.1)	(17.3)
Other current assets	3.9	3.2	(12.7)
Other assets	(17.8)	5.4	(4)
Accounts payable	5.1	(2.6)	(8.2)
Income tax payable	3.5	60.5	(82.1)
Other current liabilities	(8.9)	(12.4)	(3.9)
Other liabilities	(8.5)	(22.5)	(9.8)
Other	0.6	0.3	5.6
Net Cash Provided by Operating Activities	1,840.4	1,742.8	1,532.5
Cash Flows from Investing Activities
Proceeds from maturities of available-for-sale marketable securities	2.5	41.7	38.3
Purchases of available-for-sale marketable securities	(3)	(45.9)	(35.3)
Purchases of property, net	(81.9)	(91.8)	(114.2)
Investments in business ventures	(5.3)	(9.1)	(16.7)
Proceeds from Divestiture of Businesses	4	8.8	0
Proceeds from Sale of Available-for-sale Securities, Equity	244	150	138.8
Proceeds from Sale and Maturity of Other Investments	19.6	0	0
Settlement of derivative related to debt issuance	0	0	7
Net Cash Provided by (Used in) Investing Activities	179.9	53.7	17.9
Cash Flows from Financing Activities
Proceeds from other borrowings, net of issuance costs	0	0	743.7
Repayment of other borrowings	0	0	(673)
Cash dividends	(1,993.5)	(1,787.2)	(1,343.4)
Sale Leaseback Transaction, Gross Proceeds, Financing Activities	0	130	0
Proceeds from exercise of stock options	36.7	51.8	64
Excess tax benefits related to employee option exercises and restricted stock vesting	0	9.5	7.1
Payments Related to Tax Withholding for Share-based Compensation	(31.3)	(26.8)	(17.2)
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	0	0	(7)
Other	2.8	2.2	1.9
Net Cash Provided by (Used in) Financing Activities	(1,985.3)	(1,620.5)	(1,223.9)
Net change in cash and cash equivalents	35	176	326.5
Cash and cash equivalents, beginning of period	1,868.6	1,692.6	1,366.1
Cash and Cash Equivalents, End of Period	1,903.6	1,868.6	1,692.6
Supplemental Disclosure of Cash Flow Information
Income taxes paid	762.8	706.7	716.6
Interest paid (excluding securities lending program)	84.8	84.8	89.1
dividends declared	$ 1,187.3	$ 1,099.3	$ 977.1

Organization and Business

Organization and Business	12 Months Ended
	Dec. 31, 2017
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 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, equity indexes, foreign exchange, energy, agricultural commodities and metals. Trades are executed through CME Group's electronic trading platforms, open outcry and privately negotiated transactions. Through its clearing house, CME Group offers clearing, settlement and guarantees for all products cleared through the exchange. In April 2017, the company announced the wind down of CME Clearing Europe Limited (CMECE) and CME Europe Limited (CME Europe) which was completed by year end. In September 2017, the company also announced we will exit the credit default swaps business by mid-2018.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
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 and include the accounts of the company and its 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 is 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. 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 may be invested in U.S. government securities, U.S. government agency securities and certain foreign government securities acquired through and held by a bank or broker-dealer subsidiary of a bank, a cash account at the Federal Reserve Bank of Chicago, 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. CME may distribute any interest earned on its investments to the clearing firms at its discretion. Because CME has control of the cash collateral and the benefits and risks of ownership accrue to CME, 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 can include reinvestments in U.S. Treasury and U.S. government agency securities with maturity dates of 90 days or less. U.S. Treasury and U.S. government agency securities can be 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 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 which meet the requirements for capitalization are amortized on a straight-line basis over the estimated useful life of the software, generally two to four years. Operating Leases. Most 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. For sale leaseback transactions, the company evaluates the sale and the lease arrangement based on the company's continuing involvement and recognizes the sale leaseback as either a sale leaseback transaction or under the financing method, which requires the asset to remain on the consolidated balance sheets throughout the term of the lease and the proceeds to be recognized as a finance lease obligation. A portion of the lease payments is recognized as a reduction of the finance lease obligation and a portion is recognized as interest expense based on an imputed interest rate. 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 at least quarterly 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 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 for the reporting unit. If the carrying amount exceeds fair value, an impairment loss 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 at least quarterly 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 at least quarterly or 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 and annually challenge the useful lives. 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 accumulated 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 fees for collateral management and fees for trade order routing through agreements from various strategic relationships as well as other services to members and clearing firms. Revenue is recognized as services are provided. Concentration of Revenue. One firm represented 13% and another firm represented 12% of the company's clearing and transaction fees revenue in 2017. One firm represented 13% and another firm represented 11% of the company's clearing and transaction fees revenue in 2016. One firm represented 13% of the company's clearing and transaction fees revenue in 2015. 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 45% of market data and information services revenue in 2017 , 40% in 2016 , and 43% in 2015 . 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. Beginning in 2017, the company recognizes expense for forfeitures of stock grants as they occur. 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. The remaining operations do not meet the thresholds for reporting separate segment information. Newly Adopted and Recently Issued Accounting Pronouncements. In March 2016, the Financial Accounting Standards Board (FASB) issued a standards update that changes certain aspects of accounting for share-based payments to employees. The guidance requires all income tax effects of awards to be recognized in the income statement when the awards vest or are settled. It also allows an employer to repurchase more of an employee’s shares for tax withholding purposes without triggering liability accounting and to make a policy election to account for forfeitures as they occur. The company implemented this standards update as of January 1, 2017 on a prospective basis. Starting in the first quarter of 2017, all income tax effects of awards are recognized in the income statement as part of income tax expense when the awards vest or are settled. For the year-ended 2017, the company recognized a net tax benefit of $13.9 million related to the income tax effects of awards as part of income tax expense. The company also adopted a policy to recognize forfeitures as compensation expense as the forfeitures occur. Previously, the company estimated the number of awards that would be forfeited and recognized the estimate as part of compensation expense. This policy change was adopted on a modified retrospective basis with a cumulative-effect adjustment to additional paid in capital and retained earnings as of January 1, 2017. The excess tax benefits are now reported as an operating activity within the change in income taxes payable instead of a financing activity on the statements of cash flows. Prior periods have not been adjusted for this change. The employee taxes paid by the company when the company withholds shares for tax-withholding purposes when restricted stock awards vest are now classified as a financing activity on the statements of cash flows. Prior periods have been adjusted for this change. In May 2014, the FASB issued a new standard on revenue recognition that replaces numerous, industry-specific requirements and converges U.S. accounting standards with International Financial Reporting Standards. The new standard introduces a framework for recognizing revenue that focuses on the transfer of control rather than risks and rewards. The new standard also requires significant additional disclosures about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments, changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. The application of the new standard becomes effective in the first annual period beginning after December 15, 2017, with early adoption permitted. This guidance may be adopted using one of two transition methods: retrospectively to each prior reporting period presented (full retrospective method) or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial adoption (the modified retrospective approach). The company has completed the contract review and implementation phases and will adopt the standard as of January 1, 2018 using the modified retrospective approach. Management will recognize a $8.7 million reduction to the opening balance of retained earnings as of January 1, 2018 upon adoption of the standard, which it believes to be an immaterial impact to the consolidated financial statements. The adjustment to the opening balance of retained earnings primarily relates to a deferral of a portion of clearing and transaction fees revenue earned and recognized subsequent to the contract trade execution date. The on-going application of the new standard is not expected to have a material impact on the company's financial statements. The adoption of the guidance will also include expanded disclosures within the notes to the consolidated financial statements. In January 2016, the FASB issued a standards update that will change how entities measure certain equity investments. It does not change the guidance for classifying and measuring investments in debt securities and loans. Under the new guidance, entities will have to measure many equity investments at fair value and recognize any changes in fair value in net income, unless the investments qualify for a practicability exception. Entities will no longer be able to recognize unrealized holding gains and losses on equity securities classified today as available for sale in other comprehensive income. The update is effective for reporting periods beginning after December 15, 2017. Early adoption is permitted. The company does not believe that the adoption of this guidance in 2018 will have a material impact on the consolidated financial statements. In February 2016, the FASB issued a standards update that requires lessees to recognize on the balance sheet the assets and liabilities associated with the rights and obligations created by those leases. The guidance for lessors is largely unchanged from current U.S. GAAP. Under the new guidance, a lessee will be required to recognize assets and liabilities for leases with lease terms of more than 12 months. Consistent with current U.S. GAAP, the recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee primarily will depend on its classification as a finance or operating lease. The update is effective for reporting periods beginning after December 15, 2018. Early adoption is permitted. Adoption of the guidance in 2019 will result in the gross-up of our balance sheet to reflect the present value of the lease payments over the lease term and offsetting lease liability at the lease commencement date. Presentation of lease expense and the pattern of expense recognition in the income statement is expected to remain materially consistent with existing lease accounting guidance. In June 2016, the FASB issued guidance that changes how credit losses are measured for most financial assets measured at amortized cost and certain other instruments. The standard requires an entity to estimate its lifetime expected credit loss and record an allowance, that when deducted from the amortized cost basis of the financial asset, presents the net amount expected to be collected on the financial asset. This forward-looking expected loss model generally will result in the earlier recognition of allowances for losses. The standard also amends the impairment model for available for sale debt securities and requires entities to determine whether all or a portion of the unrealized loss on an available for sale debt security is a credit loss. Severity and duration of the unrealized loss are no longer permissible factors in concluding whether a credit loss exists. Entities will recognize improvements to estimated credit losses on available for sale debt securities immediately in earnings rather than as interest income over time. The standard is effective for reporting periods beginning after December 15, 2019. The standard’s provisions must be applied as a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective. Early adoption is permitted for reporting periods beginning in 2019. The company does not believe that the adoption of this guidance in 2020 will have a material impact on the consolidated financial statements. In November 2016, the FASB issued a standards update aimed at promoting consistency in the classification and presentation of changes in restricted cash on the statement of cash flows. Previously, there was diversity in practice as to whether the change in restricted cash was included in the reconciliation of beginning-of-period and end-of-period total cash amounts shown on the statement of cash flows. The amendments require that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, as well as amounts described as restricted cash on the balance sheet. This guidance is effective for fiscal years beginning after December 15, 2017 and interim periods within those fiscal years. Early adoption is permitted. The amendments must be applied using a retrospective transition method to each period presented. The adoption of this guidance in 2018 will not have a material impact on the consolidated financial statements. In March 2017, the FASB issued a standards update that will change certain presentation and disclosure requirements for employers that sponsor defined benefit pension as well as other postretirement benefit plans. Under current accounting rules, defined benefit pension cost and postretirement benefit cost (net benefit cost) comprise several components that reflect different aspects of an employer’s financial arrangements as well as the cost of benefits provided to the employees. Those components are aggregated for reporting in the financial statements within compensation and benefits on the income statement. The amendments in the update require that the service cost component is reported in the same line as other compensation costs, whereas the other components of net benefit cost are required to be presented in the income statement separately from the service cost component. The amendments are effective for reporting periods beginning after December 15, 2017. Early adoption is permitted as of the beginning of an annual period for which financial statements have not been issued. The company will change the presentation of certain components of pension cost upon adoption of this guidance in 2018; however, this change will not have a material impact on the consolidated financial statements. In August 2017, the FASB issued a standards update that amends the existing hedge accounting model to enable entities to better reflect their risk management activities in the financial statements. The amendments expand an entity’s ability to hedge nonfinancial and financial risk components and reduce complexity in fair value hedges of interest rate risk. The guidance eliminates the requirement to separately measure and report hedge ineffectiveness and generally requires the entire change in the fair value of a hedging instrument to be presented in the same income statement line as the hedged item. The guidance also eases certain documentation and assessment requirements and modifies the accounting for components excluded from the assessment of hedge effectiveness. The guidance is effective for fiscal years beginning after December 15, 2018. Early adoption is permitted. The company does not believe that the adoption of this standard will have a material impact on the consolidated financial statements. In December 2017, the staff of the Securities and Exchange Commission (SEC) issued a staff accounting bulletin that addresses situations where the accounting is incomplete for certain income tax effects of the Tax Cuts and Jobs Act (2017 Tax Act) by the time an entity issues its financial statements for 2017. The guidance provides for a measurement period of up to one year after the enactment date to finalize the recording of the related tax impacts. Under existing accounting guidance, entities are required to adjust current and deferred tax liabilities and assets for the effects of changes in tax laws or rates at their date of enactment. However, pursuant to the staff accounting bulletin, if an entity does not have the necessary information available, prepared, or analyzed for certain income tax effects of the 2017 Tax Act at the time an entity's financial statements are issued, an entity may include provisional amounts to reflect its accounting for the change in tax law. The measurement period ends when the company has obtained, prepared and analyzed the information necessary to finalize its accounting, but cannot extend beyond one year. Additional information regarding the adoption of this guidance is contained in note 9. In February 2018, the FASB issued guidance that gives entities the option to reclassify to retained earnings the tax effects related to items in accumulated other comprehensive income (AOCI) that were previously stranded within AOCI as a result of applying the 2017 Tax Act. An entity that elects to reclassify these amounts must reclassify stranded tax effects related to the change in federal tax rate for all items accounted for within AOCI. Entities can also elect to reclassify other stranded tax effects that relate to the 2017 Tax Act but do not directly relate to the change in federal rate. Tax effects that are stranded in AOCI for other reasons may not be reclassified. These amendments should be applied either in the period of adoption as a cumulative adjustment to the opening balance of retained earnings or retrospectively to each period in which the effect of the 2017 Tax Act is recognized. This guidance is effective for entities with fiscal years beginning after December 15, 2018. Early adoption is permitted. The company is in the process of evaluating the impact of this guidance on the consolidated financial statements.

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2017
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: 2017 2016 (in millions) Amortized Cost Fair Value Amortized Cost Fair Value Corporate debt securities (1) $ 20.0 $ 20.8 $ 20.0 $ 20.2 Asset-backed security 0.6 0.3 0.6 0.3 Equity securities — 0.1 0.1 0.1 Total $ 20.6 $ 21.2 $ 20.7 $ 20.6 _______________ (1) The corporate debt securities are maintained for a non-qualified retirement and benefit plan under the COMEX Members' Recognition and Retention Plan (MRRP) (note 10). 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 $0.3 million and $0.3 million , respectively, at December 31, 2017 . The asset-backed security was in an unrealized loss position for more than 12 months at December 31, 2017 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 prior to maturity. The amortized cost and fair value of the corporate debt securities and asset-backed security at December 31, 2017 , by contractual maturity, were as follows: (in millions) Amortized Cost Fair Value Maturity of one year or less $ 1.5 $ 1.5 Maturity between one and five years 7.8 7.8 Maturity between five and ten years 4.2 4.3 Maturity greater than ten years 7.1 7.5 Total $ 20.6 $ 21.1 Trading Securities. The company maintains additional investments in a diverse portfolio of mutual funds related to its non-qualified deferred compensation plans (note 10). The fair value of these securities was $68.9 million and $62.7 million at December 31, 2017 and 2016 , respectively.

Performance Bonds and Guaranty

Performance Bonds and Guaranty Fund Contributions	12 Months Ended
	Dec. 31, 2017
Performance Bonds and Guaranty Fund Contributions [Abstract]
Performance Bonds and Guaranty Fund Contributions	PERFORMANCE BONDS AND GUARANTY FUND CONTRIBUTIONS The clearing house clears and guarantees the settlement of contracts traded in its markets. In its guarantor role, the clearing house has 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 house bears 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 house. The clearing house reduces 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 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. All non-cash deposits are marked-to-market and haircut on a daily basis. Securities deposited by the clearing firms are not reflected in the consolidated financial statements and the clearing house does 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. 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 or letters of credit. The clearing house marks-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 house has 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 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 2017 , the clearing house transferred an average of approximately $2.4 billion a day through the clearing system for settlement from clearing firms whose positions had lost value to clearing firms whose positions had gained value. The clearing house reduces 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, 2017 . At December 31, 2016, performance bond and guaranty fund contribution assets on the consolidated balance sheets included cash as well as U.S. Treasury and U.S. government agency securities with maturity dates of 90 days or less. The U.S. Treasury and U.S. government agency securities were 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. There were no U.S. Treasury and U.S. government agency securities held at December 31, 2017 . The amortized cost and fair value of these securities at December 31, 2016 were as follows: 2016 (in millions) Amortized Fair U.S. Treasury securities $ 5,548.9 $ 5,549.0 U.S. government agency securities 1,228.3 1,228.3 CME has been designated as a systemically important financial market utility by the Financial Stability Oversight Council and maintains a cash account at the Federal Reserve Bank of Chicago. At December 31, 2017 and December 31, 2016, CME maintained $34.2 billion and $6.2 billion , respectively, within the cash account at the Federal Reserve Bank of Chicago. 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 $1.1 billion at December 31, 2017 and $6.8 billion at December 31, 2016 . 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 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, 2017 . 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, 2017 . 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 and credit default swaps 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 . In September 2017, the company announced its plan to exit the credit default business by mid-2018. The disposal of the credit default swap business does not represent a strategic shift that would have a major effect on the company's operations and financial results and therefore will not be classified as discontinued operations. 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 the clearing house. 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, 2017 , guaranty fund contributions available for CME clearing firms were $7.8 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 $2.3 billion multi-currency revolving senior credit facility to provide liquidity for the clearing house in the unlikely event of default. 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. Cash and non-cash deposits held as performance bonds and guaranty fund contributions at fair value at December 31 were as follows: 2017 2016 (in millions) Cash Non-Cash Deposits and IEF Funds Cash Non-Cash Deposits and IEF Funds Performance bonds (1) $ 41,809.5 $ 86,730.4 $ 35,726.5 $ 111,764.2 Guaranty fund contributions 2,281.2 6,102.4 1,702.4 5,246.3 Cross-margin arrangements 93.4 21.5 107.9 351.3 Performance bond collateral for delivery 1.2 — 6.7 — Total $ 44,185.3 $ 92,854.3 $ 37,543.5 $ 117,361.8 _______________ (1) Cash performance bonds include cash collateral reinvested in U.S. Treasury securities and U.S. government agency securities at December 31, 2016. 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 $111.0 million and $131.7 million at December 31, 2017 and 2016 , 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) 2017 2016 Performance bonds $ 2,348.4 $ 2,273.7 Cross-margin arrangements 59.5 — Performance bond collateral for delivery 3,438.5 1,759.8 Total Letters of Credit $ 5,846.4 $ 4,033.5 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 house.

Property

Property	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment, Net [Abstract]
Property	PROPERTY A summary of the property accounts at December 31 is presented below: (in millions) 2017 2016 Estimated Useful Life Land and land improvements $ 7.8 $ 7.8 10 - 20 years (1) Building and building improvements 173.8 179.4 3 - 39 years Leasehold improvements 180.5 180.3 3 - 24 years Furniture, fixtures and equipment 309.9 293.4 2 - 7 years Software and software development costs 404.3 361.5 2 - 4 years Total property 1,076.3 1,022.4 Less accumulated depreciation and amortization (676.6 ) (597.2 ) Property, net $ 399.7 $ 425.2 _______________ (1) Estimated useful life applies only to land improvements.

Intangible Assets and Goodwill

Intangible Assets and Goodwill	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets and Goodwill	INTANGIBLE ASSETS AND GOODWILL Intangible assets consisted of the following at December 31: 2017 2016 (in millions) Assigned Value Accumulated Amortization Net Book Value Assigned Value Accumulated Amortization Net Book Value Amortizable Intangible Assets: Clearing firm, market data and other customer relationships $ 2,838.8 $ (943.7 ) $ 1,895.1 $ 2,838.8 $ (849.2 ) $ 1,989.6 Technology-related intellectual property 29.4 (29.4 ) — 29.4 (28.6 ) 0.8 Other 2.4 (1.2 ) 1.2 2.4 (1.0 ) 1.4 Total Amortizable Intangible Assets $ 2,870.6 $ (974.3 ) 1,896.3 $ 2,870.6 $ (878.8 ) 1,991.8 Indefinite-Lived Intangible Assets: Trade names 450.0 450.0 Total Intangible Assets—Other, Net $ 2,346.3 $ 2,441.8 Trading products (1) $ 17,175.3 $ 17,175.3 _______________ (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. The originally assigned useful lives for the amortizable intangible assets as of December 31, 2017 are as follows: Clearing firm, market data and other customer relationships 5 - 30 years Technology-related intellectual property 5 years Other 3 - 24.5 years Total amortization expense for intangible assets was $95.5 million , $96.1 million and $99.4 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. As of December 31, 2017 , the future estimated amortization expense related to amortizable intangible assets is expected to be as follows: (in millions) 2018 $ 94.7 2019 94.7 2020 94.7 2021 94.7 2022 94.7 Thereafter 1,422.8 There were no changes within goodwill during the years ended December 31, 2017 and 2016 .

Long-term Investments

Long-term Investments	12 Months Ended
	Dec. 31, 2017
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. In 2017, the company sold its remaining 43.4 million shares of BM&FBOVESPA S.A. (BM&FBOVESPA) and recognized a gain of $86.5 million , net of transaction costs, within investment income on the consolidated statements of income based on the average cost method. In conjunction with the final sale of shares, the company reclassified income tax expense of $87.8 million from accumulated other comprehensive income to the income tax provision. The company accounted for its investment in BM&FBOVESPA as an available-for-sale security. The fair value and cost basis of the investment were $218.7 million and $157.0 million , respectively, at December 31, 2016 . Bolsa Mexicana de Valores, S.A.B de C.V. In 2017, the company sold its approximate 2% interest in Bolsa Mexicana de Valores, S.A.B. de C.V. (Bolsa Mexicana), a financial exchange operator in Mexico, and recognized a gain of $2.3 million , net of transaction costs, within investment income on the consolidated statements of income. The company accounted for its investment in Bolsa Mexicana stock as an available-for-sale security. The fair value and cost basis of the investment in Bolsa Mexicana at December 31, 2016 was $15.4 million and $17.3 million , respectively. 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 $27.1 million at December 31, 2017 . 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 $16.9 million at December 31, 2017 . The company and DME Holdings maintain an agreement for Dubai Mercantile Exchange 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/Dow Jones Indices LLC (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 $955.0 million at December 31, 2017. The company has long-term exclusive licensing agreements with S&P/DJI to list products based on the Standard & Poor's Indices and Dow Jones Indices.

Debt

Debt	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt	DEBT Long-term debt outstanding consisted of the following at December 31: (in millions) 2017 2016 $750.0 million fixed rate notes due September 2022, stated rate of 3.00% (1) $ 746.0 $ 745.2 $750.0 million fixed rate notes due March 2025, stated rate of 3.00% (2) 744.9 744.2 $750.0 million fixed rate notes due September 2043, stated rate of 5.30% (3) 742.2 741.8 Total long-term debt $ 2,233.1 $ 2,231.2 _______________ (1) 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% . (2) In December 2014, 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 3.11% . (3) 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 4.73% . Long-term debt maturities, at par value, were as follows as of December 31, 2017 : (in millions) Par Value 2018 $ — 2019 — 2020 — 2021 — 2022 750.0 Thereafter 1,500.0

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES The company is subject to regulation under a wide variety of U.S., federal, state and foreign tax laws and regulations. Income before income taxes and the income tax provision consisted of the following for the years ended December 31: (in millions) 2017 2016 2015 Income before income taxes: Domestic $ 2,464.2 $ 2,221.8 $ 1,927.3 Foreign 62.1 65.8 29.5 Total $ 2,526.3 $ 2,287.6 $ 1,956.8 Income tax provision: Current: Federal $ 783.7 $ 684.4 $ 554.5 State 85.7 118.6 81.0 Foreign 39.1 33.5 11.0 Total 908.5 836.5 646.5 Deferred: Federal (2,576.3 ) (95.4 ) 75.6 State 130.8 10.0 (12.0 ) Foreign (0.1 ) 2.4 (0.3 ) Total (2,445.6 ) (83.0 ) 63.3 Total Income Tax Provision (Benefit) $ (1,537.1 ) $ 753.5 $ 709.8 On December 22, 2017, the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act (the 2017 Tax Act). The 2017 Tax Act establishes new tax laws that will affect 2018 and after, including a reduction in the U.S. federal corporate income tax rate from 35% to 21% . The 2017 Tax Act makes broad and complex changes to the U.S. tax code including, but not limited to, the repeal of the IRC Section 199 domestic production activities deduction in 2018 and accelerated depreciation that allows for full expensing of qualified property beginning in the fourth quarter of 2017. On December 22, 2017, the SEC staff issued a staff accounting bulletin that provides guidance on accounting for the tax effects of the 2017 Tax Act. The guidance provides a measurement period that should not extend beyond one year from the 2017 Tax Act enactment date for companies to complete the accounting for income taxes related to changes associated with the 2017 Tax Act. According to the staff accounting bulletin, entities must recognize the impact in the financial statements for the activities that they have completed the work to understand the impact as a result of the tax reform law. For those activities which have not completed, the company would include provisional amounts if a reasonable estimate is available. As a result of the reduction of the federal corporate income tax rate, the company has revalued its net deferred tax liability, excluding after tax credits, as of December 31, 2017. Based on this revaluation and other impacts of the 2017 Tax Act, the company has recognized a net tax benefit of $2.6 billion , which was recorded as a reduction to income tax expense for the year ended December 31, 2017. The company has recognized provisional adjustments but management has not completed its accounting for income tax effects for certain elements of the 2017 Tax Act, principally due to the accelerated depreciation that will allow for full expensing of qualified property. Reconciliation of the statutory U.S. federal income tax rate to the effective tax rate is as follows: 2017 2016 2015 Statutory U.S. federal tax rate 35.0 % 35.0 % 35.0 % State taxes, net of federal benefit 2.1 3.7 3.0 Domestic production activities deduction (1.0 ) (1.3 ) (1.3 ) Increase (decrease) in domestic valuation allowance (0.1 ) (4.7 ) 0.1 Impact of revised state and local apportionment estimates 3.1 0.5 (0.7 ) Reclassification of accumulated other comprehensive income 3.5 — — Impact of 2017 Tax Act (101.6 ) — — Other, net (1.8 ) (0.3 ) 0.2 Effective Tax Expense (Benefit) Rate (60.8 )% 32.9 % 36.3 % In 2017, the effective rate was lower than the statutory tax rate due to the remeasurement of the deferred tax liabilities as a result of the 2017 Tax Act. This decrease was partially offset by an increase in the state apportionment impact of the Illinois income tax rate change on deferred tax liabilities as well as the reclassification of income tax expense from accumulated other comprehensive income related to the disposal of BM&FBOVESPA shares. In 2016, the effective rate was lower than the statutory tax rate largely due to the release of the valuation allowances related to the sale of BM&FBOVESPA shares. The decrease was partially offset by an increase in state tax expense and the state apportionment impact on deferred tax liabilities. In 2015, the effective rate was higher than the statutory tax rate primarily due to the impact of state and local income taxes. The effective rate was primarily reduced by the Section 199 Domestic Productions Activities Deduction (Section 199 deduction) and the impact of state and local apportionment factors in deferred tax expense. The Section 199 deduction is related to certain activities performed by the company's electronic platform. At December 31, deferred income tax assets (liabilities) consisted of the following: (in millions) 2017 2016 Deferred Income Tax Assets: Net operating losses $ 13.0 $ 18.8 Property 5.5 31.4 Accrued expenses, compensation and other 37.2 119.0 Subtotal 55.7 169.2 Valuation allowance (11.2 ) (14.9 ) Total deferred income tax assets 44.5 154.3 Deferred Income Tax Liabilities: Purchased intangible assets (4,902.2 ) (7,445.3 ) Total deferred income tax liabilities (4,902.2 ) (7,445.3 ) Net Deferred Income Tax Liabilities $ (4,857.7 ) $ (7,291.0 ) 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, 2017 and 2016, the company had domestic and foreign income tax loss carry forwards of $73.3 million and $96.8 million , respectively. These amounts primarily related to losses from the acquisition of Swapstream Limited and its affiliates, the acquisition of Pivot, Inc., losses incurred in the operation of various foreign entities and capital losses from the sales of securities. At December 31, 2016, the company also had a net built-in, unrealized capital gain of $19.3 million . At December 31, 2017 and 2016, 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 and other deferred income tax assets created from the start-up of various foreign operations will be fully realized. As a result, valuation allowances of $11.2 million and $14.9 million were recorded at December 31, 2017 and 2016, respectively. The following is a summary of the company’s unrecognized tax benefits: (in millions) 2017 2016 2015 Gross unrecognized tax benefits $ 308.8 $ 252.1 $ 206.9 Unrecognized tax benefits, net of tax impacts in other jurisdictions 276.0 216.1 179.6 Unrecognized interest and penalties related to uncertain tax positions 34.0 32.7 19.5 Interest and penalties recognized in the consolidated statements of income 1.3 13.2 8.6 The company does not believe it is reasonably possible that within the next twelve months, unrecognized 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) 2017 2016 2015 Balance at January 1 $ 252.1 $ 206.9 $ 187.6 Additions based on tax positions related to the current year 41.8 29.6 20.4 Additions for tax positions of prior years 47.7 18.5 2.7 Reductions for tax positions of prior years (8.7 ) (2.8 ) (3.8 ) Reductions resulting from the lapse of statutes of limitations (2.1 ) (0.1 ) — Settlements with taxing authorities (22.0 ) — — Balance at December 31 $ 308.8 $ 252.1 $ 206.9 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, 2017 , 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, 2017
Retirement Benefits, Description [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 pay-based credit added 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) 2017 2016 Balance at January 1 $ 239.9 $ 217.3 Service cost 18.7 16.7 Interest cost 10.8 10.3 Actuarial (gain) loss 15.1 5.3 Benefits paid (10.6 ) (9.7 ) Balance at December 31 $ 273.9 $ 239.9 The aggregate accumulated benefit obligation was $245.4 million and $211.4 million at December 31, 2017 and 2016 , respectively. The following is a summary of the change in fair value of plan assets: (in millions) 2017 2016 2015 Balance at January 1 $ 238.8 $ 217.5 $ 225.1 Actual return on plan assets 29.8 16.0 (7.2 ) Employer contributions 90.0 15.0 22.6 Benefits paid (10.6 ) (9.7 ) (23.0 ) Balance at December 31 $ 348.0 $ 238.8 $ 217.5 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) 2017 2016 Level 2: Money market funds $ 95.8 $ 31.5 Mutual funds: Fixed income 109.7 68.6 U.S. equity 83.6 63.9 Foreign equity 58.9 64.5 Commodity — 10.3 Total $ 348.0 $ 238.8 At December 31, 2017 , the fair value of pension plan assets exceeded the projected benefit obligation by $74.1 million and the excess was recorded as a non-current pension asset in other assets. At December 31, 2016 , the projected benefit obligation exceeded the fair value of pension plan asset by $1.1 million and the excess was recorded as a non-current pension liability in other liabilities. 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. In 2017, the company contributed $90.0 million to the plan, which resulted in plan assets exceeding the projected benefit obligation by $74.1 million . Year-end 2017 assumptions have been used to project the assets and liabilities from December 31, 2017 to December 31, 2018 . The result of this projection is that estimated liabilities would not exceed the fair value of the plan assets at December 31, 2018 . Accordingly, the company anticipates based on this projection that no additional contribution in 2018 will be necessary for it to meet its funding goal. However, the amount of the actual contribution is contingent on various factors, including the actual rate of return on the plan assets during 2018 and the December 31, 2018 discount rate. 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) 2017 2016 2015 Components of Net Pension Expense: Service cost $ 18.7 $ 16.7 $ 18.4 Interest cost 10.8 10.3 9.8 Expected return on plan assets (15.1 ) (15.7 ) (16.3 ) Recognized net actuarial loss 2.9 3.2 2.7 Net Pension Expense $ 17.3 $ 14.5 $ 14.6 Assumptions Used to Determine End-of-Year Benefit Obligation: Discount rate 3.70 % 4.30 % 4.60 % 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 4.30 % 4.60 % 4.20 % Rate of compensation increase 5.00 5.00 5.00 Expected return on plan assets 6.50 7.50 7.50 Interest crediting rate 4.00 4.00 4.00 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: 2017 2016 Fixed income 31.6 % 28.8 % Money market funds 27.5 13.2 U.S. equity 24.0 26.7 Foreign equity 16.9 27.0 Commodity — 4.3 The range of target allocation percentages for 2018 is as follows: Minimum Maximum U.S. large-cap equity 20.0 % 80.0 % U.S. mid-cap equity 10.0 25.0 U.S. small-cap equity 10.0 20.0 Foreign developed equity — 40.0 Foreign small-cap equity — 10.0 Emerging markets equity — 10.0 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 or Moody's. The pre-tax balance and activity of actuarial losses for the pension plan, which are included in other comprehensive income (loss), for 2017 are as follows: (in millions) Actuarial Loss Balance at January 1 $ 62.8 Unrecognized net loss 0.3 Recognized as a component of net pension expense (2.9 ) Balance at December 31 $ 60.2 The company expects to amortize $2.9 million of actuarial loss and prior service costs from accumulated other comprehensive income (loss) into net periodic benefit costs in 2018 . At December 31, 2017 , anticipated benefit payments from the plan in future years are as follows: (in millions) 2018 $ 16.6 2019 18.3 2020 18.6 2021 20.0 2022 20.3 2023-2027 112.4 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 $11.8 million , $11.3 million and $11.7 million in 2017 , 2016 and 2015 , 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 $68.9 million and $62.7 million at December 31, 2017 and 2016 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 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. 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. There were no contributions to the plan in 2017. Total contributions to the plan were $3.0 million in 2016 and $2.0 million in 2015. At December 31, 2017 and 2016 , the obligation for the MRRP totaled $18.6 million and $19.4 million , respectively. Assets with a fair value of $21.6 million and $22.0 million have been allocated to this plan at December 31, 2017 and 2016 , 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, 2017
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 March 2016, the company sold its datacenter and leased back a portion of the property. The sale leaseback transaction was recognized under the financing method and not as a sale leaseback arrangement. The operating lease, which has an initial lease term ending in March 2031, contains two consecutive renewal options for five years. • 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 terminates on March 24, 2026, with an option to terminate without penalty in January 2021. • The company maintains an operating lease for its headquarters at 20 South Wacker Drive in Chicago. In January 2018, the company signed a lease extension. The new lease expires in 2032 and contains two consecutive renewal options for five years each. • In August 2006, the company entered into an operating lease for additional office space in Chicago. The initial lease term ends on November 30, 2023. The lease contains two 5 -year renewal options beginning in 2023. At December 31, 2017 , future minimum payments under non-cancellable operating leases were payable as follows (in millions): Year 2018 $ 64.3 2019 63.8 2020 61.6 2021 56.8 2022 56.5 Thereafter 435.2 Total $ 738.2 Total rental expense, including equipment rental, was $41.7 million in 2017 , $47.9 million in 2016 and $54.8 million in 2015 . 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, 2017 , future minimum payments due under purchase obligations were payable as follows (in millions): Year 2018 $ 23.8 2019 12.7 2020 11.0 2021 8.8 2022 6.5 Thereafter 5.4 Total $ 68.2

Contingencies

Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Contingencies	CONTINGENCIES Legal and Regulatory Matters. In 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 in 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 2003, the U.S. Futures Exchange, L.L.C. (Eurex U.S.) and U.S. Exchange Holdings, Inc. filed suit in federal court alleging that CBOT and CME violated the antitrust laws and tortuously interfered with the business relationship and contract between Eurex U.S. and The Clearing Corporation. While the complaint requests treble damages, 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 losses in the unlikely event it were found to be liable at trial in the matter. A trial date is set for June 4, 2018. 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 or aggregate basis will not have a material impact on its consolidated financial position or results of operations. No accrual was required for legal and regulatory matters that were probable and estimable as of December 31, 2017 and 2016. 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, 2017
Guarantees [Abstract]
Guarantees	GUARANTEES Mutual Offset Agreement. CME and Singapore Exchange Limited (SGX) have a mutual offset agreement with a current term through October 2018. 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, 2017 , CME was contingently liable to SGX on irrevocable letters of credit totaling $285.0 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, 2017 . 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, 2017 .

Capital Stock

Capital Stock	12 Months Ended
	Dec. 31, 2017
Capital Stock [abstract]
Capital Stock	CAPITAL STOCK Shares Outstanding. The following table presents information regarding capital stock: December 31, (in thousands) 2017 2016 Class A common stock authorized 1,000,000 1,000,000 Class A common stock issued and outstanding 339,235 338,240 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 open outcry trading, 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, 1/6 th 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 20 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 24.0 million shares have been granted and are outstanding or have been exercised under this plan at December 31, 2017 (note 15). 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 366,000 shares have been awarded through December 31, 2017 . 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 260,000 shares have been purchased through December 31, 2017 (note 15).

Stock-Based Payments

Stock-Based Payments	12 Months Ended
	Dec. 31, 2017
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 24.0 million shares have been granted and are outstanding or have been exercised under the plan as of December 31, 2017 . 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) 2017 2016 2015 Compensation expense $ 58.3 $ 66.4 $ 61.0 Income tax benefit recognized 42.6 38.6 32.4 At December 31, 2017 , there was $106.6 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 2.2 years. Stock options have not been granted since 2012. The following table summarizes stock option activity for 2017 . Aggregate intrinsic value is in millions. Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Life (in years) Aggregate Intrinsic Value Outstanding at December 31, 2016 1,021,537 $ 69 2.9 $ 47.4 Exercised (443,911 ) 83 Cancelled (4,650 ) 74 Outstanding at December 31, 2017 572,976 58 2.7 50.3 Exercisable at December 31, 2017 572,976 58 2.7 50.3 The total intrinsic value of options exercised during 2017 , 2016 and 2015 was $20.4 million , $19.9 million and $29.5 million , respectively. In 2017 , the company granted 440,076 shares of restricted Class A common stock and 7,568 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 $58.7 million , which is recognized as compensation expense on an accelerated basis over the vesting period. Dividends are accrued on restricted Class A common stock and restricted stock units and are paid once the restricted stock vests. In 2017 , the company also granted 203,298 performance shares. The fair value related to these grants was $25.3 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 2017 : Number of Shares Weighted Average Grant Date Fair Value Outstanding at December 31, 2016 1,820,578 $ 98 Granted 650,942 129 Vested (510,590 ) 87 Cancelled (401,699 ) 95 Outstanding at December 31, 2017 1,559,231 116 The total fair value of restricted stock, restricted stock units, and performance shares that vested during 2017 , 2016 and 2015 was $66.0 million , $59.8 million and $43.3 million , respectively. Under the ESPP, 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 2017 , 2016 and 2015 , a total of 19,936 , 19,858 and 19,756 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 $0.3 million for the purchase discount was recognized in 2017 , and $0.2 million was recognized in both 2016 and 2015 . 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, 19,736 shares, 26,439 shares and 25,853 shares of Class A common stock were issued to non-executive directors during 2017 , 2016 and 2015 , respectively. These shares are not subject to any vesting restrictions. Expense of $2.5 million , $2.4 million and $2.5 million related to these stock-based payments was recognized for the years ended December 31, 2017 , 2016 and 2015 , respectively.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Comprehensive Income (Loss) Note [Text Block]	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) The following tables present changes in the accumulated balances for each component of other comprehensive income (loss), including current period other comprehensive income and reclassifications out of accumulated other comprehensive income (loss): (in millions) Investment Securities Defined Benefit Plans Derivative Investments Foreign Currency Translation Total Balance at December 31, 2016 $ (19.5 ) $ (37.8 ) $ 58.9 $ (15.7 ) $ (14.1 ) Other comprehensive income before reclassifications and income tax benefit (expense) 30.2 0.3 — 10.4 40.9 Amounts reclassified from accumulated other comprehensive income (89.5 ) 2.9 (1.2 ) — (87.8 ) Income tax benefit (expense) 79.4 (1.5 ) 0.3 (2.9 ) 75.3 Net current period other comprehensive income 20.1 1.7 (0.9 ) 7.5 28.4 Balance at December 31, 2017 $ 0.6 $ (36.1 ) $ 58.0 $ (8.2 ) $ 14.3 (in millions) Investment Securities Defined Benefit Plans Derivative Investments Foreign Currency Translation Total Balance at December 31, 2015 $ (95.0 ) $ (36.6 ) $ 59.6 $ (8.8 ) $ (80.8 ) Other comprehensive income before reclassifications and income tax benefit (expense) 170.0 (5.1 ) — (8.2 ) 156.7 Amounts reclassified from accumulated other comprehensive income (48.7 ) 3.2 (1.2 ) — (46.7 ) Income tax benefit (expense) (45.8 ) 0.7 0.5 1.3 (43.3 ) Net current period other comprehensive income 75.5 (1.2 ) (0.7 ) (6.9 ) 66.7 Balance at December 31, 2016 $ (19.5 ) $ (37.8 ) $ 58.9 $ (15.7 ) $ (14.1 ) (in millions) Investment Securities Defined Benefit Plans Derivative Investments Foreign Currency Translation Total Balance at December 31, 2014 $ (22.9 ) $ (31.3 ) $ 62.6 $ (2.2 ) $ 6.2 Other comprehensive income before reclassifications and income tax benefit (expense) (78.0 ) (11.2 ) (4.7 ) (10.6 ) (104.5 ) Amounts reclassified from accumulated other comprehensive income 8.5 2.7 0.6 — 11.8 Income tax benefit (expense) (2.6 ) 3.2 1.1 4.0 5.7 Net current period other comprehensive income (72.1 ) (5.3 ) (3.0 ) (6.6 ) (87.0 ) Balance at December 31, 2015 $ (95.0 ) $ (36.6 ) $ 59.6 $ (8.8 ) $ (80.8 )

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
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, U.S. government agency securities, investments in publicly traded mutual funds, equity securities and corporate debt securities 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 included in level 2 generally consist of asset-backed securities. 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. Financial assets and liabilities recorded at fair value in the consolidated balance sheets as of December 31, 2017 and 2016 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, 2017 (in millions) Level 1 Level 2 Level 3 Total Assets at Fair Value: Marketable securities: Corporate debt securities $ 20.8 $ — $ — $ 20.8 Mutual funds 68.9 — — 68.9 Equity securities 0.1 — — 0.1 Asset-backed securities — 0.3 — 0.3 Total Marketable Securities 89.8 0.3 — 90.1 Total Assets at Fair Value $ 89.8 $ 0.3 $ — $ 90.1 December 31, 2016 (in millions) Level 1 Level 2 Level 3 Total Assets at Fair Value: Marketable securities: Corporate debt securities $ 20.2 $ — $ — $ 20.2 Mutual funds 62.7 — — 62.7 Equity securities 0.1 — — 0.1 Asset-backed securities — 0.3 — 0.3 Total Marketable Securities 83.0 0.3 — 83.3 Performance bonds and guaranty fund contributions (1) : U.S. Treasury securities 5,549.0 — — 5,549.0 U.S. government agencies securities 1,228.3 — — 1,228.3 Equity investments 234.1 — — 234.1 Total Assets at Fair Value $ 7,094.4 $ 0.3 $ — $ 7,094.7 _______________ (1) Performance bonds and guaranty fund contributions on the consolidated balance sheet at December 31, 2016 include cash collateral that has been invested in U.S. Treasury securities and U.S. government agencies securities. There were no transfers of assets between level 1, level 2 and level 3 during 2017 and 2016 . There were no level 3 assets or liabilities valued at fair value on a recurring basis during 2017 and 2016 . The following is a reconciliation of level 3 liabilities valued at fair value on a recurring basis during 2017 and 2016 . (in millions) Contingent Consideration Fair Value of Liability at December 31, 2015 $ 0.3 Realized and unrealized gains (losses): Included in other expense (0.3 ) Fair Value of Liability at December 31, 2016 — Realized and unrealized gains (losses): Included in other expense — Fair Value of Liability at December 31, 2017 $ — In the first quarter of 2016, the company sold a datacenter and leased back a portion of the property. Under generally accepted accounting principles, the transaction has been recognized under the financing method instead of recognized as a sale leaseback arrangement. As a result, the property and equipment legally sold will continue to be recognized on the consolidated balance sheets and was written down to a fair value of $130.0 million at March 31, 2016. During 2016, the company also recorded impairment charges totaling $5.5 million on one of its strategic investments. The fair value of the investment was estimated to be zero at September 30, 2016. Both assessments were based on qualitative indications of impairment and a quantitative analysis of undiscounted cash flows. The fair values of the datacenter and strategic investment are considered level 3 and nonrecurring. There were no other level 3 assets or liabilities valued at fair value on a nonrecurring basis during 2017 and 2016. The following presents the estimated fair values of long-term debt notes, which are carried at amortized cost on the consolidated balance sheets. The fair values, which are classified as level 2 under the fair value hierarchy, were estimated using quoted market prices. At December 31, 2017 , the fair values were as follows: (in millions) Fair Value $750.0 million fixed rate notes due September 2022, stated rate of 3.00% $ 764.9 $750.0 million fixed rate notes due March 2025, stated rate of 3.00% 758.2 $750.0 million fixed rates notes due September 2043, stated rate of 5.30% 960.0

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share	EARNINGS PER SHARE Basic earnings per share is computed by dividing net income 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) 2017 2016 2015 Stock options — 171 420 Stock awards 104 138 115 Total 104 309 535 The following table presents the earnings per share calculation for the years presented: 2017 2016 2015 Net Income (in millions) $ 4,063.4 $ 1,534.1 $ 1,247.0 Weighted Average Common Shares Outstanding (in thousands): Basic 338,707 337,496 336,224 Effect of stock options and stock awards 1,519 1,470 1,670 Diluted 340,226 338,966 337,894 Earnings per Common Share: Basic $ 12.00 $ 4.55 $ 3.71 Diluted 11.94 4.53 3.69

Quarterly Information (Unaudite

Quarterly Information (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Data [Abstract]
Quarterly Information	QUARTERLY INFORMATION (UNAUDITED) (in millions, except per share data) First Quarter Second Quarter Third Quarter Fourth Quarter Year to Date Year Ended December 31, 2017 Total revenues $ 929.3 $ 924.6 $ 890.8 $ 900.0 $ 3,644.7 Operating income 601.2 605.6 567.9 537.3 2,312.0 Non-operating income (expense) 105.8 31.7 39.4 37.4 214.3 Income before income taxes 707.0 637.3 607.3 574.7 2,526.3 Net income 399.8 415.8 308.6 2,939.2 4,063.4 Earnings per common share: Basic $ 1.18 $ 1.23 $ 0.91 $ 8.67 $ 12.00 Diluted 1.18 1.22 0.91 8.63 11.94 Year Ended December 31, 2016 Total revenues $ 934.2 $ 906.4 $ 841.7 $ 912.9 $ 3,595.2 Operating income 573.9 563.3 525.3 540.2 2,202.7 Non-operating income (expense) 4.6 2.8 23.5 54.0 84.9 Income before income taxes 578.5 566.1 548.8 594.2 2,287.6 Net income 367.8 320.1 472.8 373.4 1,534.1 Earnings per common share: Basic $ 1.09 $ 0.95 $ 1.40 $ 1.10 $ 4.55 Diluted 1.09 0.95 1.39 1.10 4.53

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
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 II_Valuation and Quali

Schedule II—Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2017
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, 2017 , 2016 and 2015 (dollars in millions) Balance at beginning of year Charged (credited) to costs and expenses Other (1) Balance at end of year Year Ended December 31, 2017 Allowance for doubtful accounts $ 3.5 $ 0.6 $ (1.9 ) $ 2.2 Allowance for deferred tax assets 14.9 (3.7 ) — 11.2 Year Ended December 31, 2016 Allowance for doubtful accounts $ 1.9 $ 2.4 $ (0.8 ) $ 3.5 Allowance for deferred tax assets 122.3 (107.4 ) — 14.9 Year Ended December 31, 2015 Allowance for doubtful accounts $ 1.2 $ 1.1 $ (0.4 ) $ 1.9 Allowance for deferred tax assets 99.2 (2.4 ) 25.5 122.3 _______________ (1) Includes write-offs of doubtful accounts and additions to allowance for deferred tax assets through accumulated other comprehensive income (loss). All other schedules have been omitted because the information required to be set forth in those schedules is not applicable or is shown in the consolidated financial statements or notes thereto.

Summary of Significant Accoun30

Summary of Significant Accounting Policies (Policy)	12 Months Ended
	Dec. 31, 2017
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 and include the accounts of the company and its 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 is 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. 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 may be invested in U.S. government securities, U.S. government agency securities and certain foreign government securities acquired through and held by a bank or broker-dealer subsidiary of a bank, a cash account at the Federal Reserve Bank of Chicago, 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. CME may distribute any interest earned on its investments to the clearing firms at its discretion. Because CME has control of the cash collateral and the benefits and risks of ownership accrue to CME, 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 can include reinvestments in U.S. Treasury and U.S. government agency securities with maturity dates of 90 days or less. U.S. Treasury and U.S. government agency securities can be 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 which meet the requirements for capitalization are amortized on a straight-line basis over the estimated useful life of the software, generally two to four years.
Operating Leases	Operating Leases. Most 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. For sale leaseback transactions, the company evaluates the sale and the lease arrangement based on the company's continuing involvement and recognizes the sale leaseback as either a sale leaseback transaction or under the financing method, which requires the asset to remain on the consolidated balance sheets throughout the term of the lease and the proceeds to be recognized as a finance lease obligation. A portion of the lease payments is recognized as a reduction of the finance lease obligation and a portion is recognized as interest expense based on an imputed interest rate.
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 at least quarterly 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 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 for the reporting unit. If the carrying amount exceeds fair value, an impairment loss 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 at least quarterly 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 at least quarterly or 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 and annually challenge the useful lives.
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 accumulated 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 fees for collateral management and fees for trade order routing through agreements from various strategic relationships as well as other services to members and clearing firms. Revenue is recognized as services are provided. Concentration of Revenue. One firm represented 13% and another firm represented 12% of the company's clearing and transaction fees revenue in 2017. One firm represented 13% and another firm represented 11% of the company's clearing and transaction fees revenue in 2016. One firm represented 13% of the company's clearing and transaction fees revenue in 2015. 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 45% of market data and information services revenue in 2017 , 40% in 2016 , and 43% in 2015 . 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. Beginning in 2017, the company recognizes expense for forfeitures of stock grants as they occur.
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. The remaining operations do not meet the thresholds for reporting separate segment information.

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2017
Marketable Securities [Abstract]
Available-for-sale securities	The amortized cost and fair value of these securities at December 31 were as follows: 2017 2016 (in millions) Amortized Cost Fair Value Amortized Cost Fair Value Corporate debt securities (1) $ 20.0 $ 20.8 $ 20.0 $ 20.2 Asset-backed security 0.6 0.3 0.6 0.3 Equity securities — 0.1 0.1 0.1 Total $ 20.6 $ 21.2 $ 20.7 $ 20.6
Amortized cost and fair value of marketable securities by contractual maturity	The amortized cost and fair value of the corporate debt securities and asset-backed security at December 31, 2017 , by contractual maturity, were as follows: (in millions) Amortized Cost Fair Value Maturity of one year or less $ 1.5 $ 1.5 Maturity between one and five years 7.8 7.8 Maturity between five and ten years 4.2 4.3 Maturity greater than ten years 7.1 7.5 Total $ 20.6 $ 21.1

Performance Bonds and Guarant32

Performance Bonds and Guaranty Fund Contributions (Tables)	12 Months Ended
	Dec. 31, 2017
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 were as follows: 2017 2016 (in millions) Cash Non-Cash Deposits and IEF Funds Cash Non-Cash Deposits and IEF Funds Performance bonds (1) $ 41,809.5 $ 86,730.4 $ 35,726.5 $ 111,764.2 Guaranty fund contributions 2,281.2 6,102.4 1,702.4 5,246.3 Cross-margin arrangements 93.4 21.5 107.9 351.3 Performance bond collateral for delivery 1.2 — 6.7 — Total $ 44,185.3 $ 92,854.3 $ 37,543.5 $ 117,361.8 _______________ (1) Cash performance bonds include cash collateral reinvested in U.S. Treasury securities and U.S. government agency securities at December 31, 2016.
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) 2017 2016 Performance bonds $ 2,348.4 $ 2,273.7 Cross-margin arrangements 59.5 — Performance bond collateral for delivery 3,438.5 1,759.8 Total Letters of Credit $ 5,846.4 $ 4,033.5

Performance Bonds and Guarant33

Performance Bonds and Guaranty Fund Contributions Reinvested Collateral (Tables)	12 Months Ended
	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Performance Bond Reinvestment [Table Text Block]	The amortized cost and fair value of these securities at December 31, 2016 were as follows: 2016 (in millions) Amortized Fair U.S. Treasury securities $ 5,548.9 $ 5,549.0 U.S. government agency securities 1,228.3 1,228.3

Property (Tables)

Property (Tables)	12 Months Ended
	Dec. 31, 2017
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) 2017 2016 Estimated Useful Life Land and land improvements $ 7.8 $ 7.8 10 - 20 years (1) Building and building improvements 173.8 179.4 3 - 39 years Leasehold improvements 180.5 180.3 3 - 24 years Furniture, fixtures and equipment 309.9 293.4 2 - 7 years Software and software development costs 404.3 361.5 2 - 4 years Total property 1,076.3 1,022.4 Less accumulated depreciation and amortization (676.6 ) (597.2 ) Property, net $ 399.7 $ 425.2 _______________ (1) Estimated useful life applies only to land improvements.

Intangible Assets and Goodwill

Intangible Assets and Goodwill (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Components of intangible assets	Intangible assets consisted of the following at December 31: 2017 2016 (in millions) Assigned Value Accumulated Amortization Net Book Value Assigned Value Accumulated Amortization Net Book Value Amortizable Intangible Assets: Clearing firm, market data and other customer relationships $ 2,838.8 $ (943.7 ) $ 1,895.1 $ 2,838.8 $ (849.2 ) $ 1,989.6 Technology-related intellectual property 29.4 (29.4 ) — 29.4 (28.6 ) 0.8 Other 2.4 (1.2 ) 1.2 2.4 (1.0 ) 1.4 Total Amortizable Intangible Assets $ 2,870.6 $ (974.3 ) 1,896.3 $ 2,870.6 $ (878.8 ) 1,991.8 Indefinite-Lived Intangible Assets: Trade names 450.0 450.0 Total Intangible Assets—Other, Net $ 2,346.3 $ 2,441.8 Trading products (1) $ 17,175.3 $ 17,175.3 _______________ (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, 2017 are as follows: Clearing firm, market data and other customer relationships 5 - 30 years Technology-related intellectual property 5 years Other 3 - 24.5 years
Future estimated amortization expense	As of December 31, 2017 , the future estimated amortization expense related to amortizable intangible assets is expected to be as follows: (in millions) 2018 $ 94.7 2019 94.7 2020 94.7 2021 94.7 2022 94.7 Thereafter 1,422.8

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Long-term Debt	Long-term debt outstanding consisted of the following at December 31: (in millions) 2017 2016 $750.0 million fixed rate notes due September 2022, stated rate of 3.00% (1) $ 746.0 $ 745.2 $750.0 million fixed rate notes due March 2025, stated rate of 3.00% (2) 744.9 744.2 $750.0 million fixed rate notes due September 2043, stated rate of 5.30% (3) 742.2 741.8 Total long-term debt $ 2,233.1 $ 2,231.2 _______________ (1) 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% . (2) In December 2014, 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 3.11% . (3) 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 4.73%
Long-term debt maturities at par value	Long-term debt maturities, at par value, were as follows as of December 31, 2017 : (in millions) Par Value 2018 $ — 2019 — 2020 — 2021 — 2022 750.0 Thereafter 1,500.0

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
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: (in millions) 2017 2016 2015 Income before income taxes: Domestic $ 2,464.2 $ 2,221.8 $ 1,927.3 Foreign 62.1 65.8 29.5 Total $ 2,526.3 $ 2,287.6 $ 1,956.8 Income tax provision: Current: Federal $ 783.7 $ 684.4 $ 554.5 State 85.7 118.6 81.0 Foreign 39.1 33.5 11.0 Total 908.5 836.5 646.5 Deferred: Federal (2,576.3 ) (95.4 ) 75.6 State 130.8 10.0 (12.0 ) Foreign (0.1 ) 2.4 (0.3 ) Total (2,445.6 ) (83.0 ) 63.3 Total Income Tax Provision (Benefit) $ (1,537.1 ) $ 753.5 $ 709.8
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: 2017 2016 2015 Statutory U.S. federal tax rate 35.0 % 35.0 % 35.0 % State taxes, net of federal benefit 2.1 3.7 3.0 Domestic production activities deduction (1.0 ) (1.3 ) (1.3 ) Increase (decrease) in domestic valuation allowance (0.1 ) (4.7 ) 0.1 Impact of revised state and local apportionment estimates 3.1 0.5 (0.7 ) Reclassification of accumulated other comprehensive income 3.5 — — Impact of 2017 Tax Act (101.6 ) — — Other, net (1.8 ) (0.3 ) 0.2 Effective Tax Expense (Benefit) Rate (60.8 )% 32.9 % 36.3 %
Deferred tax assets (liabilities)	At December 31, deferred income tax assets (liabilities) consisted of the following: (in millions) 2017 2016 Deferred Income Tax Assets: Net operating losses $ 13.0 $ 18.8 Property 5.5 31.4 Accrued expenses, compensation and other 37.2 119.0 Subtotal 55.7 169.2 Valuation allowance (11.2 ) (14.9 ) Total deferred income tax assets 44.5 154.3 Deferred Income Tax Liabilities: Purchased intangible assets (4,902.2 ) (7,445.3 ) Total deferred income tax liabilities (4,902.2 ) (7,445.3 ) Net Deferred Income Tax Liabilities $ (4,857.7 ) $ (7,291.0 )
Unrecognized tax benefits	The following is a summary of the company’s unrecognized tax benefits: (in millions) 2017 2016 2015 Gross unrecognized tax benefits $ 308.8 $ 252.1 $ 206.9 Unrecognized tax benefits, net of tax impacts in other jurisdictions 276.0 216.1 179.6 Unrecognized interest and penalties related to uncertain tax positions 34.0 32.7 19.5 Interest and penalties recognized in the consolidated statements of income 1.3 13.2 8.6
Reconciliation of unrecognized tax benefits	A reconciliation of the beginning and ending amounts of unrecognized tax benefits is as follows: (in millions) 2017 2016 2015 Balance at January 1 $ 252.1 $ 206.9 $ 187.6 Additions based on tax positions related to the current year 41.8 29.6 20.4 Additions for tax positions of prior years 47.7 18.5 2.7 Reductions for tax positions of prior years (8.7 ) (2.8 ) (3.8 ) Reductions resulting from the lapse of statutes of limitations (2.1 ) (0.1 ) — Settlements with taxing authorities (22.0 ) — — Balance at December 31 $ 308.8 $ 252.1 $ 206.9

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Retirement Benefits, Description [Abstract]
Summary of the change in projected benefit obligation	The following is a summary of the change in projected benefit obligation: (in millions) 2017 2016 Balance at January 1 $ 239.9 $ 217.3 Service cost 18.7 16.7 Interest cost 10.8 10.3 Actuarial (gain) loss 15.1 5.3 Benefits paid (10.6 ) (9.7 ) Balance at December 31 $ 273.9 $ 239.9
Change in plan assets	The following is a summary of the change in fair value of plan assets: (in millions) 2017 2016 2015 Balance at January 1 $ 238.8 $ 217.5 $ 225.1 Actual return on plan assets 29.8 16.0 (7.2 ) Employer contributions 90.0 15.0 22.6 Benefits paid (10.6 ) (9.7 ) (23.0 ) Balance at December 31 $ 348.0 $ 238.8 $ 217.5
Fair value of plan assets	The fair value of each major category of plan assets as of December 31 is indicated below. (in millions) 2017 2016 Level 2: Money market funds $ 95.8 $ 31.5 Mutual funds: Fixed income 109.7 68.6 U.S. equity 83.6 63.9 Foreign equity 58.9 64.5 Commodity — 10.3 Total $ 348.0 $ 238.8
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) 2017 2016 2015 Components of Net Pension Expense: Service cost $ 18.7 $ 16.7 $ 18.4 Interest cost 10.8 10.3 9.8 Expected return on plan assets (15.1 ) (15.7 ) (16.3 ) Recognized net actuarial loss 2.9 3.2 2.7 Net Pension Expense $ 17.3 $ 14.5 $ 14.6 Assumptions Used to Determine End-of-Year Benefit Obligation: Discount rate 3.70 % 4.30 % 4.60 % 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 4.30 % 4.60 % 4.20 % Rate of compensation increase 5.00 5.00 5.00 Expected return on plan assets 6.50 7.50 7.50 Interest crediting rate 4.00 4.00 4.00
Asset allocation for the plan	The asset allocation for the plan, by asset category, at December 31 was as follows: 2017 2016 Fixed income 31.6 % 28.8 % Money market funds 27.5 13.2 U.S. equity 24.0 26.7 Foreign equity 16.9 27.0 Commodity — 4.3 The range of target allocation percentages for 2018 is as follows: Minimum Maximum U.S. large-cap equity 20.0 % 80.0 % U.S. mid-cap equity 10.0 25.0 U.S. small-cap equity 10.0 20.0 Foreign developed equity — 40.0 Foreign small-cap equity — 10.0 Emerging markets equity — 10.0
Prior service costs and actuarial losses included in accumulated other comprehensive income (loss)	The pre-tax balance and activity of actuarial losses for the pension plan, which are included in other comprehensive income (loss), for 2017 are as follows: (in millions) Actuarial Loss Balance at January 1 $ 62.8 Unrecognized net loss 0.3 Recognized as a component of net pension expense (2.9 ) Balance at December 31 $ 60.2
Anticipated benefit payments from the plan in future years	At December 31, 2017 , anticipated benefit payments from the plan in future years are as follows: (in millions) 2018 $ 16.6 2019 18.3 2020 18.6 2021 20.0 2022 20.3 2023-2027 112.4

Commitments (Tables)

Commitments (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Schedule of future minimum payments under non-cancelable operating leases	At December 31, 2017 , future minimum payments under non-cancellable operating leases were payable as follows (in millions): Year 2018 $ 64.3 2019 63.8 2020 61.6 2021 56.8 2022 56.5 Thereafter 435.2 Total $ 738.2
Schedule of other commitments	At December 31, 2017 , future minimum payments due under purchase obligations were payable as follows (in millions): Year 2018 $ 23.8 2019 12.7 2020 11.0 2021 8.8 2022 6.5 Thereafter 5.4 Total $ 68.2

Capital Stock (Tables)

Capital Stock (Tables)	12 Months Ended
	Dec. 31, 2017
Capital Stock [abstract]
Capital stock	The following table presents information regarding capital stock: December 31, (in thousands) 2017 2016 Class A common stock authorized 1,000,000 1,000,000 Class A common stock issued and outstanding 339,235 338,240 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

Stock-Based Payments (Tables)

Stock-Based Payments (Tables)	12 Months Ended
	Dec. 31, 2017
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) 2017 2016 2015 Compensation expense $ 58.3 $ 66.4 $ 61.0 Income tax benefit recognized 42.6 38.6 32.4
Share-based Compensation, Stock Options, Activity [Table Text Block]	The following table summarizes stock option activity for 2017 . Aggregate intrinsic value is in millions. Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Life (in years) Aggregate Intrinsic Value Outstanding at December 31, 2016 1,021,537 $ 69 2.9 $ 47.4 Exercised (443,911 ) 83 Cancelled (4,650 ) 74 Outstanding at December 31, 2017 572,976 58 2.7 50.3 Exercisable at December 31, 2017 572,976 58 2.7 50.3
Schedule of Nonvested Share Activity [Table Text Block]	The following table summarizes restricted stock, restricted stock units, and performance shares activity for 2017 : Number of Shares Weighted Average Grant Date Fair Value Outstanding at December 31, 2016 1,820,578 $ 98 Granted 650,942 129 Vested (510,590 ) 87 Cancelled (401,699 ) 95 Outstanding at December 31, 2017 1,559,231 116

Accumulated Other Comprehensi42

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2017
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, 2016 $ (19.5 ) $ (37.8 ) $ 58.9 $ (15.7 ) $ (14.1 ) Other comprehensive income before reclassifications and income tax benefit (expense) 30.2 0.3 — 10.4 40.9 Amounts reclassified from accumulated other comprehensive income (89.5 ) 2.9 (1.2 ) — (87.8 ) Income tax benefit (expense) 79.4 (1.5 ) 0.3 (2.9 ) 75.3 Net current period other comprehensive income 20.1 1.7 (0.9 ) 7.5 28.4 Balance at December 31, 2017 $ 0.6 $ (36.1 ) $ 58.0 $ (8.2 ) $ 14.3 (in millions) Investment Securities Defined Benefit Plans Derivative Investments Foreign Currency Translation Total Balance at December 31, 2015 $ (95.0 ) $ (36.6 ) $ 59.6 $ (8.8 ) $ (80.8 ) Other comprehensive income before reclassifications and income tax benefit (expense) 170.0 (5.1 ) — (8.2 ) 156.7 Amounts reclassified from accumulated other comprehensive income (48.7 ) 3.2 (1.2 ) — (46.7 ) Income tax benefit (expense) (45.8 ) 0.7 0.5 1.3 (43.3 ) Net current period other comprehensive income 75.5 (1.2 ) (0.7 ) (6.9 ) 66.7 Balance at December 31, 2016 $ (19.5 ) $ (37.8 ) $ 58.9 $ (15.7 ) $ (14.1 ) (in millions) Investment Securities Defined Benefit Plans Derivative Investments Foreign Currency Translation Total Balance at December 31, 2014 $ (22.9 ) $ (31.3 ) $ 62.6 $ (2.2 ) $ 6.2 Other comprehensive income before reclassifications and income tax benefit (expense) (78.0 ) (11.2 ) (4.7 ) (10.6 ) (104.5 ) Amounts reclassified from accumulated other comprehensive income 8.5 2.7 0.6 — 11.8 Income tax benefit (expense) (2.6 ) 3.2 1.1 4.0 5.7 Net current period other comprehensive income (72.1 ) (5.3 ) (3.0 ) (6.6 ) (87.0 ) Balance at December 31, 2015 $ (95.0 ) $ (36.6 ) $ 59.6 $ (8.8 ) $ (80.8 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Fair value of Debt Instruments [Table Text Block]	At December 31, 2017 , the fair values were as follows: (in millions) Fair Value $750.0 million fixed rate notes due September 2022, stated rate of 3.00% $ 764.9 $750.0 million fixed rate notes due March 2025, stated rate of 3.00% 758.2 $750.0 million fixed rates notes due September 2043, stated rate of 5.30% 960.0
Financial instruments measured at fair value on a recurring basis	December 31, 2017 (in millions) Level 1 Level 2 Level 3 Total Assets at Fair Value: Marketable securities: Corporate debt securities $ 20.8 $ — $ — $ 20.8 Mutual funds 68.9 — — 68.9 Equity securities 0.1 — — 0.1 Asset-backed securities — 0.3 — 0.3 Total Marketable Securities 89.8 0.3 — 90.1 Total Assets at Fair Value $ 89.8 $ 0.3 $ — $ 90.1 December 31, 2016 (in millions) Level 1 Level 2 Level 3 Total Assets at Fair Value: Marketable securities: Corporate debt securities $ 20.2 $ — $ — $ 20.2 Mutual funds 62.7 — — 62.7 Equity securities 0.1 — — 0.1 Asset-backed securities — 0.3 — 0.3 Total Marketable Securities 83.0 0.3 — 83.3 Performance bonds and guaranty fund contributions (1) : U.S. Treasury securities 5,549.0 — — 5,549.0 U.S. government agencies securities 1,228.3 — — 1,228.3 Equity investments 234.1 — — 234.1 Total Assets at Fair Value $ 7,094.4 $ 0.3 $ — $ 7,094.7 _______________ (1) Performance bonds and guaranty fund contributions on the consolidated balance sheet at December 31, 2016 include cash collateral that has been invested in U.S. Treasury securities and U.S. government agencies securities.
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 2017 and 2016 . (in millions) Contingent Consideration Fair Value of Liability at December 31, 2015 $ 0.3 Realized and unrealized gains (losses): Included in other expense (0.3 ) Fair Value of Liability at December 31, 2016 — Realized and unrealized gains (losses): Included in other expense — Fair Value of Liability at December 31, 2017 $ —

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
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) 2017 2016 2015 Stock options — 171 420 Stock awards 104 138 115 Total 104 309 535
Basic and diluted earnings per share	The following table presents the earnings per share calculation for the years presented: 2017 2016 2015 Net Income (in millions) $ 4,063.4 $ 1,534.1 $ 1,247.0 Weighted Average Common Shares Outstanding (in thousands): Basic 338,707 337,496 336,224 Effect of stock options and stock awards 1,519 1,470 1,670 Diluted 340,226 338,966 337,894 Earnings per Common Share: Basic $ 12.00 $ 4.55 $ 3.71 Diluted 11.94 4.53 3.69

Quarterly Information (Unaudi45

Quarterly Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Data [Abstract]
Quarterly Information	(in millions, except per share data) First Quarter Second Quarter Third Quarter Fourth Quarter Year to Date Year Ended December 31, 2017 Total revenues $ 929.3 $ 924.6 $ 890.8 $ 900.0 $ 3,644.7 Operating income 601.2 605.6 567.9 537.3 2,312.0 Non-operating income (expense) 105.8 31.7 39.4 37.4 214.3 Income before income taxes 707.0 637.3 607.3 574.7 2,526.3 Net income 399.8 415.8 308.6 2,939.2 4,063.4 Earnings per common share: Basic $ 1.18 $ 1.23 $ 0.91 $ 8.67 $ 12.00 Diluted 1.18 1.22 0.91 8.63 11.94 Year Ended December 31, 2016 Total revenues $ 934.2 $ 906.4 $ 841.7 $ 912.9 $ 3,595.2 Operating income 573.9 563.3 525.3 540.2 2,202.7 Non-operating income (expense) 4.6 2.8 23.5 54.0 84.9 Income before income taxes 578.5 566.1 548.8 594.2 2,287.6 Net income 367.8 320.1 472.8 373.4 1,534.1 Earnings per common share: Basic $ 1.09 $ 0.95 $ 1.40 $ 1.10 $ 4.55 Diluted 1.09 0.95 1.39 1.10 4.53

Summary of Significant Accoun46

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Excess Tax Benefit from Share-based Compensation, Operating Activities	$ 13.9
Cumulative Effect on Retained Earnings, before Tax	$ 8.7
Clearing and transaction fees from Firm 1
Concentration of revenue	13.00%	13.00%	13.00%
Clearing and transaction fees from Firm 2
Concentration of revenue	12.00%	11.00%
Market data and information services
Concentration of revenue	45.00%	40.00%	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 ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities, Amortized Cost Basis	$ 20.6	$ 20.7
Available-for-sale Securities	21.2	20.6
Corporate Debt Securities [Member]
Available-for-sale Securities, Amortized Cost Basis	20	20
Available-for-sale Securities	20.8	20.2
Asset-backed Securities [Member]
Available-for-sale Securities, Amortized Cost Basis	0.6	0.6
Available-for-sale Securities	0.3	0.3
Equity Securities [Member]
Available-for-sale Securities, Amortized Cost Basis	0	0.1
Available-for-sale Securities	$ 0.1	$ 0.1

Marketable Securities (Amortize

Marketable Securities (Amortized Cost and Fair Value of Marketable Securities) (Details) $ in Millions	Dec. 31, 2017USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Maturity of one year or less, Amortized Cost	$ 1.5
Maturity between one and five years, Amortized Cost	7.8
Maturity between five and ten years, Amortized Cost	4.2
Maturity greater than ten years, Amortized Cost	7.1
Total, Amortized Cost	20.6
Maturity of one year or less, Fair Value	1.5
Maturity between one and five years, Fair Value	7.8
Maturity between five and ten years, Fair Value	4.3
Maturity greater than ten years, Fair Value	7.5
Total, Fair Value	$ 21.1

Marketable Securities (Narrativ

Marketable Securities (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities	$ 21.2	$ 20.6
Trading securities fair value	68.9	$ 62.7
Asset-backed Securities [Member]
Available-for-sale Securities	0.3
Unrealized losses	$ 0.3

Performance Bonds and Guarant50

Performance Bonds and Guaranty Fund Contributions (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)days	Dec. 31, 2016USD ($)
Federal Reserve Reinvestment	$ 34,200	$ 6,200
Available-for-sale Securities, Amortized Cost Basis	20.6	20.7
Average daily clearing settlement	2,400
Available-for-sale Securities	21.2	20.6
Total principal in IEF programs	$ 1,100	6,800
Percentage share of cross-margining collateral	50.00%
Days fully secured | days	364
Intraday settlements of cash performance bonds	$ 111	131.7
364-day fully secured, committed line of credit
Line of Credit Facility, Maximum Borrowing Capacity	7,000
Line of Credit, Guaranty Fund Collateral Available	7,800
Option on increase in line of credit	10,000
Revolving senior credit facility
Line of Credit Facility, Maximum Borrowing Capacity	2,300
CME Base Guaranty Fund [Member]
Corporate Contribution	100
CME IRS Guaranty Fund [Member] [Member]
Corporate Contribution	150
CME CDS Guaranty Fund [Member] [Member]
Corporate Contribution	$ 50
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
U.S. Treasury Performance Bond [Member]
Available-for-sale Securities, Amortized Cost Basis		5,548.9
Available-for-sale Securities		5,549
U.S. Government Agency Security Performance Bond [Member]
Available-for-sale Securities, Amortized Cost Basis		1,228.3
Available-for-sale Securities		$ 1,228.3

Performance Bonds and Guarant51

Performance Bonds and Guaranty Fund Contributions (Cash and Securities Held as Performance Bonds and Guaranty Fund Contributions at Fair Value) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Cross-margin arrangements	$ 59.5	$ 0
Performance collateral for delivery	3,438.5	1,759.8
Total	44,185.3	37,543.5
Cash [Member]
Performance bonds	41,809.5	35,726.5
Guaranty Fund Contributions	2,281.2	1,702.4
Cross-margin arrangements	93.4	107.9
Performance collateral for delivery	1.2	6.7
Total	44,185.3	37,543.5
Non-Cash Deposits and IEF Funds [Member]
Performance bonds	86,730.4	111,764.2
Guaranty Fund Contributions	6,102.4	5,246.3
Cross-margin arrangements	21.5	351.3
Performance collateral for delivery	0	0
Total	$ 92,854.3	$ 117,361.8

Performance Bonds and Guarant52

Performance Bonds and Guaranty Fund Contributions (Performance Bond Deposits and Security Deposits) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Performance Bonds and Guaranty Fund Contributions [Abstract]
Performance bonds	$ 2,348.4	$ 2,273.7
Cross-margin arrangements	59.5	0
Performance collateral for delivery	3,438.5	1,759.8
Letters of Credit	$ 5,846.4	$ 4,033.5

Performance Bonds and Guarant53

Performance Bonds and Guaranty Fund Contributions Performance Bond Reinvestment (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 20.6	$ 20.7
Available-for-sale Securities	$ 21.2	20.6
U.S. Government Agency Security Performance Bond [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis		1,228.3
Available-for-sale Securities		1,228.3
U.S. Treasury Performance Bond [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis		5,548.9
Available-for-sale Securities		$ 5,549

Property (Details)

Property (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, gross	$ 1,076.3	$ 1,022.4
Less accumulated depreciation and amortization	(676.6)	(597.2)
Property, net	399.7	425.2
Software and software development costs
Property, Plant and Equipment [Line Items]
Property, gross	404.3	361.5
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Property, gross	309.9	293.4
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, gross	180.5	180.3
Building and building improvements
Property, Plant and Equipment [Line Items]
Property, gross	173.8	179.4
Land and land improvements
Property, Plant and Equipment [Line Items]
Property, gross	$ 7.8	$ 7.8
Minimum [Member]
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
Minimum [Member] | Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	2 years
Minimum [Member] | Leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	3 years
Minimum [Member] | Building and building improvements
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	3 years
Minimum [Member] | Land and land improvements
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	10 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	39 years
Maximum [Member] | Software and software development costs
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	4 years
Maximum [Member] | Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	7 years
Maximum [Member] | Leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated useful life, minimum	24 years
Maximum [Member] | Building and building improvements
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

Intangible Assets and Goodwil55

Intangible Assets and Goodwill (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amortization of purchased intangibles	$ 95.5	$ 96.1	$ 99.4
Intangible assets-other, net	$ 2,346.3	$ 2,441.8

Intangible Assets and Goodwil56

Intangible Assets and Goodwill (Components of Intangible Assets) (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Indefinite-lived Intangible Assets		$ 2,346.3	$ 2,441.8
Other Indefinite-lived Intangible Assets	[1]	17,175.3	17,175.3
Trade Names [Member]
Indefinite-lived Intangible Assets		450	450
Clearing Firm, Market Data, and Other Customer Relationships [Member]
Cost		2,838.8	2,838.8
Accumulated amortization		(943.7)	(849.2)
Net book value		1,895.1	1,989.6
Technology-Related Intellectual Property [Member]
Cost		29.4	29.4
Accumulated amortization		(29.4)	(28.6)
Net book value		0	0.8
Other - Finite [Member]
Cost		2.4	2.4
Accumulated amortization		(1.2)	(1)
Net book value		1.2	1.4
Finite-Lived Intangible Assets [Member]
Cost		2,870.6	2,870.6
Accumulated amortization		(974.3)	(878.8)
Net book value		$ 1,896.3	$ 1,991.8
[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 Goodwil57

Intangible Assets and Goodwill Intangible Assets and Goodwill (Useful Lives of Intangible Assets) (Details)	12 Months Ended
	Dec. 31, 2017
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	5 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 Goodwil58

Intangible Assets and Goodwill (Future Estimated Amortization Expense) (Details) $ in Millions	Dec. 31, 2017USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2,018	$ 94.7
2,019	94.7
2,020	94.7
2,021	94.7
2,022	94.7
Thereafter	$ 1,422.8

Long-Term Investments (Details)

Long-Term Investments (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Gain (Loss) on Sale of Other Investments	$ 2.3	$ 0	$ 0
Gain (Loss) on Sale of Securities, Net	$ 86.5	48.4	$ (8.5)
BM&F [Member]
Investment Shares Sold	43.4
Gain (Loss) on Sale of Securities, Net	$ (86.5)
Fair value of investment		218.7
Cost-basis value of investment		157
Bolsa Mexicana De Valores, S A B De C V [Member]
investment ownership	2.00%
Gain (Loss) on Sale of Other Investments	$ (2.3)
Fair value of investment		15.4
Cost-basis value of investment		$ 17.3
Bursa Malaysia Derivatives Berhad [Member]
Equity Method Investment, Ownership Percentage	25.00%
Equity Method Investments	$ 27.1
DME Holdings [Member]
Equity Method Investment, Ownership Percentage	50.00%
Equity Method Investments	$ 16.9
S&P/DJI [Member]
Equity Method Investment, Ownership Percentage	27.00%
Equity Method Investments	$ 955

Debt (Schedule of Short-Term an

Debt (Schedule of Short-Term and Long-Term Debt) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Long-term Debt
Long-term debt		$ 2,233.1	$ 2,231.2
Seven Hundred Fifty Million Fixed Rate Notes Due September Two Thousand Twenty Two, Interest Equal To Four Point Three Zero Percent [Member]
Long-term Debt
Long-term debt	[1]	746	745.2
Debt instrument, face amount		$ 750
Debt Instrument, maturity date		Sep. 1, 2022
Debt Instrument, Interest Rate, Stated Percentage		3.00%
Debt Instrument, Interest Rate During Period		3.32%
Seven Hundred Fifty Million Fixed Rate Notes Due March Two Thousand Twenty Five, Interest Equal To Three Point Zero Percent [Member] [Member]
Long-term Debt
Long-term debt	[1]	$ 744.9	744.2
Debt instrument, face amount		$ 750
Debt Instrument, maturity date		Mar. 1, 2025
Debt Instrument, Interest Rate, Stated Percentage		3.00%
Debt Instrument, Interest Rate During Period		3.11%
Seven Hundred Fifty Million Fixed Rate Notes Due September Two Thousand Forty Three, Interest Equal To Five Point Three Percent [Member]
Long-term Debt
Long-term debt	[1]	$ 742.2	$ 741.8
Debt instrument, face amount		$ 750
Debt Instrument, maturity date		Sep. 1, 2043
Debt Instrument, Interest Rate, Stated Percentage		5.30%
Debt Instrument, Interest Rate During Period		4.73%
[1]	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 (Long-Term Debt Maturities

Debt (Long-Term Debt Maturities at Par Value) (Details) $ in Millions	Dec. 31, 2017USD ($)
Debt Disclosure [Abstract]
2,018	$ 0
2,019	0
2,020	0
2,021	0
2,022	750
Thereafter	$ 1,500

Income Taxes (Income Tax Provis

Income Taxes (Income Tax Provision) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income before income taxes: Domestic									$ 2,464.2	$ 2,221.8	$ 1,927.3
Income before income taxes: Foreign									62.1	65.8	29.5
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	$ 574.7	$ 607.3	$ 637.3	$ 707	$ 594.2	$ 548.8	$ 566.1	$ 578.5	2,526.3	2,287.6	1,956.8
Current income tax provision: Federal									783.7	684.4	554.5
Current income tax provision: State									85.7	118.6	81
Current income tax provision: Foreign									39.1	33.5	11
Current income tax provision: Total									908.5	836.5	646.5
Deferred income tax provision: Federal									(2,576.3)	(95.4)	75.6
Deferred income tax provision: State									130.8	10	(12)
Deferred income tax provision: Foreign									(0.1)	2.4	(0.3)
Deferred income tax provision: Total									(2,445.6)	(83)	63.3
Total Income Tax Provision									$ (1,537.1)	$ 753.5	$ 709.8

Income Taxes (Federal Income Ta

Income Taxes (Federal Income Tax Rate) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Statutory U.S. federal tax rate	35.00%	35.00%	35.00%
State taxes, net of federal benefit	2.10%	3.70%	3.00%
Effective Income Tax Rate Reconciliation, Deduction, Other, Percent	(1.00%)	(1.30%)	(1.30%)
Increase (decrease) in domestic valuation allowance	(0.10%)	(4.70%)	0.10%
Impact of revised state apportionment estimates	3.10%	0.50%	(0.70%)
effective tax rate reconciliation reclassification of comprehensive income	3.50%	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent	(101.60%)	0.00%	0.00%
Other, net	(1.80%)	(0.30%)	0.20%
Effective Tax Rate	(60.80%)	32.90%	36.30%

Income Taxes (Deferred Tax Asse

Income Taxes (Deferred Tax Assets (Liabilities) ) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets, Operating Loss Carryforwards	$ 13	$ 18.8
Deferred Tax Assets, Property, Plant and Equipment	5.5	31.4
Deferred Tax Assets, Other	37.2	119
Subtotal	55.7	169.2
Valuation allowance	(11.2)	(14.9)
Total deferred tax assets	44.5	154.3
Purchase intangible assets	(4,902.2)	(7,445.3)
Deferred Tax Liabilities, Gross	(4,902.2)	(7,445.3)
Deferred Tax Liabilities, Net	$ (4,857.7)	$ (7,291)

Income Taxes (Summary Of Unreco

Income Taxes (Summary Of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Gross unrecognized tax benefits	$ 308.8	$ 252.1	$ 206.9	$ 187.6
Unrecognized tax benefits, net of tax impacts in other jurisdictions	276	216.1	179.6
Interest and penalties related to uncertain tax positions	34	32.7	19.5
Interest and penalties recognized in the consolidated statements of income	$ 1.3	$ 13.2	$ 8.6

Income Taxes (Reconciliation Of

Income Taxes (Reconciliation Of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Balance as of January 1	$ 252.1	$ 206.9	$ 187.6
Additions based on tax positions related to the current year	41.8	29.6	20.4
Additions for tax positions of prior years	47.7	18.5	2.7
Reductions for tax positions of prior years	(8.7)	(2.8)	(3.8)
Reductions resulting from the lapse of statutes of limitations	(2.1)	(0.1)	0
Settlements with taxing authorities	(22)	0	0
Balance as of December 31	$ 308.8	$ 252.1	$ 206.9

Income Taxes Income Taxes (Narr

Income Taxes Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statutory U.S. federal tax rate	35.00%	35.00%	35.00%
Future Federal Statutory Rate	21.00%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	$ 2,600
Operating Loss Carryforwards	73.3	$ 96.8
Unrealized capital tax gain (loss)		19.3
Deferred Tax Assets, Valuation Allowance, Noncurrent	11.2	14.9
Long-term deferred tax asset	$ 55.7	$ 169.2

Employee Benefit Plans (Narrati

Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amortization of actuarial loss from accumulated other comprehensive income (loss) into net periodic benefit costs	$ 2.9
Defined Contribution Plan, Cost	11.8	$ 11.3	$ 11.7
Trading securities fair value	$ 68.9	$ 62.7
Pension Plans [Member]
Age for participation eligibility in benefit plan	21
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Cash Balance Interest Crediting Rate	4.00%	4.00%	4.00%
Years of service for vesting eligibility	3 years
Accumulated benefit obligation	$ 245.4	$ 211.4
Excess of pension plan assets over the projected benefit obligation	$ 74.1	1.1
Defined Benefit Plan Funding Goal Percentage	100.00%
Percentage of employees base salary matched by employer, maximum	3.00%
Other Postretirement Benefits Plan [Member]
Total contribution	$ 0	3	$ 2
Total obligation	18.6	19.4
Fair value of assets	$ 21.6	$ 22

Employee Benefit Plans (Summary

Employee Benefit Plans (Summary of the change in projected benefit obligation) (Details) - Pension Plans [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Balance at January 1	$ 239.9	$ 217.3
Service cost	18.7	16.7	$ 18.4
Interest cost	10.8	10.3	9.8
Actuarial (gain) loss	15.1	5.3
Balance at December 31	273.9	239.9	$ 217.3
Defined Benefit Plan, Benefit Obligation, Benefits Paid	$ 10.6	$ 9.7

Employee Benefit Plans (Change

Employee Benefit Plans (Change in Plan Assets) (Details) - Pension Plans [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance at January 1	$ 238.8	$ 217.5	$ 225.1
Actual return on plan assets	29.8	16	(7.2)
Employer contributions	90	15	22.6
Defined Benefit Plan, Plan Assets, Benefits Paid	(10.6)	(9.7)	(23)
Balance at December 31	$ 348	$ 238.8	$ 217.5

Employee Benefit Plans (Fair Va

Employee Benefit Plans (Fair Value of Plan Assets) (Details) - Pension Plans [Member] - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan, Fair Value of Plan Assets	$ 348	$ 238.8	$ 217.5	$ 225.1
Fair Value, Inputs, level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	348	238.8
Fair Value, Inputs, level 2 [Member] | Money Market Funds [Member]
Defined Benefit Plan, Fair Value of Plan Assets	95.8	31.5
Fair Value, Inputs, level 2 [Member] | Fixed Income Securities [Member]
Defined Benefit Plan, Fair Value of Plan Assets	109.7	68.6
Fair Value, Inputs, level 2 [Member] | US Equity [Member]
Defined Benefit Plan, Fair Value of Plan Assets	83.6	63.9
Fair Value, Inputs, level 2 [Member] | Foreign equity [Member]
Defined Benefit Plan, Fair Value of Plan Assets	58.9	64.5
Fair Value, Inputs, level 2 [Member] | Commodity [Member]
Defined Benefit Plan, Fair Value of Plan Assets	$ 0	$ 10.3

Employee Benefit Plans (Compone

Employee Benefit Plans (Components of Net Pension Expense) (Details) - Pension Plans [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components of Net Pension Expense:
Service cost	$ 18.7	$ 16.7	$ 18.4
Interest cost	10.8	10.3	9.8
Expected return on plan assets	(15.1)	(15.7)	(16.3)
Recognized net actuarial loss	2.9	3.2	2.7
Net Pension Expense	$ 17.3	$ 14.5	$ 14.6
Assumptions Used to Determine End-of-Year Benefit Obligation:
Discount rate	3.70%	4.30%	4.60%
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	4.30%	4.60%	4.20%
Rate of compensation increase	5.00%	5.00%	5.00%
Expected return on plan assets	6.50%	7.50%	7.50%
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, 2017	Dec. 31, 2016
Fixed Income [Member]
Actual allocation of plan assets, Fixed income	31.60%	28.80%
Mutual Funds [Member]
Actual allocation of plan assets, Fixed income	27.50%	13.20%
US Equity [Member]
Actual allocation of plan assets, Fixed income	24.00%	26.70%
Foreign equity [Member]
Actual allocation of plan assets, Fixed income	16.90%	27.00%
Commodity [Member]
Actual allocation of plan assets, Fixed income	0.00%	4.30%

Employee Benefit Plans (Target

Employee Benefit Plans (Target Allocation Percentages) (Details)	12 Months Ended
	Dec. 31, 2017
Minimum [Member] | Foreign small cap equity [Member]
Defined Benefit Plan, Target Allocation Percentage	0
Minimum [Member] | Pension Plans [Member] | US large-cap equity [Member]
Defined Benefit Plan, Target Allocation Percentage	0.2
Minimum [Member] | Pension Plans [Member] | U.S. mid-cap equity [Member]
Defined Benefit Plan, Target Allocation Percentage	0.1
Minimum [Member] | Pension Plans [Member] | Foreign developed equity [Member]
Defined Benefit Plan, Target Allocation Percentage	0
Minimum [Member] | Pension Plans [Member] | U.S small-cap equity [Member]
Defined Benefit Plan, Target Allocation Percentage	0.1
Minimum [Member] | Pension Plans [Member] | Emerging markets equity [Member]
Defined Benefit Plan, Target Allocation Percentage	0
Maximum [Member] | Foreign small cap equity [Member]
Defined Benefit Plan, Target Allocation Percentage	0.1
Maximum [Member] | Pension Plans [Member] | US large-cap equity [Member]
Defined Benefit Plan, Target Allocation Percentage	0.8
Maximum [Member] | Pension Plans [Member] | U.S. mid-cap equity [Member]
Defined Benefit Plan, Target Allocation Percentage	0.25
Maximum [Member] | Pension Plans [Member] | Foreign developed equity [Member]
Defined Benefit Plan, Target Allocation Percentage	0.4
Maximum [Member] | Pension Plans [Member] | U.S small-cap equity [Member]
Defined Benefit Plan, Target Allocation Percentage	0.2
Maximum [Member] | Pension Plans [Member] | Emerging markets equity [Member]
Defined Benefit Plan, Target Allocation Percentage	0.1

Employee Benefit Plans (Accumul

Employee Benefit Plans (Accumulated Other Comprehensive Income (Loss), of the Prior Service Costs and Actuarial Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Actuarial Losses [Roll Forward]
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	$ 0.3	$ (5.1)	$ (11.2)
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax	2.9	3.2	$ 2.7
Pension Plans [Member]
Actuarial Losses [Roll Forward]
Actuarial Loss Beginning Balance	62.8
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	0.3
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax	(2.9)
Actuarial Loss Ending Balance	$ 60.2	$ 62.8

Employee Benefit Plans (Anticip

Employee Benefit Plans (Anticipated Benefit Payments from the Plan in Future Years) (Details) - Pension Plans [Member] $ in Millions	Dec. 31, 2017USD ($)
2,018	$ 16.6
2,019	18.3
2,020	18.6
2,021	20
2,022	20.3
2023-2027	$ 112.4

Commitments (Narrative) (Detail

Commitments (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)RenewalOptionsyears	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Lessee, Operating Lease, Renewal Term	5 years
Operating leases, rent expense | $	$ 41.7	$ 47.9	$ 54.8
Datacenter [Member]
Operating leases number of renewal options | years	2
Lessee, Operating Lease, Renewal Term	5 years
NYMEX [Member]
Operating leases number of renewal options | years	2
Lessee, Operating Lease, Renewal Term	5 years
Chicago CBOT Building [Member] [Member]
Operating leases number of renewal options	4
Lessee, Operating Lease, Renewal Term	5 years
Chicago [Member]
Operating leases number of renewal options	2
Additional Office Space Chicago [Member]
Operating leases number of renewal options	2
Lessee, Operating Lease, Renewal Term	5 years

Commitments (Non-Cancelable Ope

Commitments (Non-Cancelable Operating Leases and Contractual Obligations) (Details) $ in Millions	Dec. 31, 2017USD ($)
Operating Leases, Future Minimum Payments Due [Abstract]
2,018	$ 64.3
2,019	63.8
2,020	61.6
2,021	56.8
2,022	56.5
Thereafter	435.2
Total	738.2
Unrecorded Unconditional Purchase Obligation [Abstract]
2,018	23.8
2,019	12.7
2,020	11
2,021	8.8
2,022	6.5
Thereafter	5.4
Total	$ 68.2

Guarantees (Details)

Guarantees (Details)	12 Months Ended
	Dec. 31, 2017USD ($)
Guarantor Obligations [Line Items]
PaymentPerParticipant	$ 25,000
Contingent liability to SGX, amount of irrevocable letters of credit	285,000,000
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

Capital Stock (Narrative) (Deta

Capital Stock (Narrative) (Details)	12 Months Ended
	Dec. 31, 2017directors$ / sharesshares	Dec. 31, 2016$ / shares
Number of directors	20
Class A Common Stock (Shares) [Member]
Common Stock, Par or Stated Value Per Share | $ / shares	$ 0.01	$ 0.01
Class B Common Stock (Shares)
Common Stock, Par or Stated Value Per Share | $ / shares	$ 0.01	$ 0.01
Common stock, voting rights	1
Class B Common Stock, Class B1 [Member]
Common stock, voting rights	6
Number of directors | directors	3
Class B Common Stock, Class B2 [Member]
Common stock, voting rights	2
Number of directors | directors	2
Class B Common Stock, Class B3 [Member]
Common stock, voting rights	1
Number of directors | directors	1
Class B Common Stock, Class B4 [Member]
Common stock, voting rights	1/6
Class B common stock, Class B1, B2, B3 [Member]
Number of directors | directors	6
CME Group Omnibus Stock Plan [Member]
Shares granted, outstanding and exercised	24,000,000
Number of shares reserved for awards under the plan	40,200,000
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	366,000
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	260,000

Capital Stock (Capital stock) (

Capital Stock (Capital stock) (Details) - shares	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Class A Common Stock
Common Stock, Shares Authorized	1,000,000,000	1,000,000,000
Common Stock, Shares, Outstanding	339,235,000	338,240,000	336,938,000	335,452,000
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

Stock-Based Payments (Narrative

Stock-Based Payments (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Vesting percentage after one year	25.00%
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	$ 106,600,000
Employee service share-based compensation, unrecognized compensation costs on nonvested awards, Weighted Average Period of Recognition, years	2 years 2 months
Share-based compensation arrangement by share-based payment award, options, exercises in period, total intrinsic value	$ 20,400,000	$ 19,900,000	$ 29,500,000
Granted performance shares	650,942
Restricted Class A common stock, fair value	$ 66,000,000	59,800,000	43,300,000
Total expense for stock payments	$ 58,300,000	$ 66,400,000	$ 61,000,000
Share-based compensation arrangement by share-based payment award, discount from market price	90.00%
Class A common stock issued to participating employees	19,936	19,858	19,756
Director Stock Plan; Class A Shares [Member]
Total expense for stock payments	$ 2,500,000	$ 2,400,000	$ 2,500,000
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)	19,736	26,439	25,853
Employee Stock Purchase Plan; Class A Shares [Member]
Total expense for stock payments	$ 300,000
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	2 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
Performance Shares [Member]
Granted performance shares	203,298
Restricted Class A common stock, fair value	$ 25,300,000
Restricted Stock Units (RSUs) [Member]
Stock options, granted, shares	7,568
Class A Common Stock (Shares) [Member]
Stock options, granted, shares	440,076
Restricted Class A common stock, fair value	$ 58,700,000
CME Group Omnibus Stock Plan [Member]
Share-based compensation arrangement by share-based payment award, number of shares reserved	40,200,000
Share-based compensation arrangement by share-based payment award, number of shares authorized	24,000,000

Stock-Based Payments (Compensat

Stock-Based Payments (Compensation Expense And Income Tax Benefit Recognized) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 58.3	$ 66.4	$ 61
Income tax benefit recognized	$ 42.6	$ 38.6	$ 32.4

Stock-Based Payments (Stock Opt

Stock-Based Payments (Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding in Shares [Roll Forward]
Number of shares outstanding at December 31 (shares)	1,021,537
Number of shares exercised	(443,911)
Number of shares cancelled	(4,650)
Number of shares outstanding at December 31 (shares)	572,976	1,021,537
Number of shares exercisable at December 31 (shares)	572,976
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Weighted average exercise price outstanding, beginning	$ 69
Weighted average exercise price exercised	83
Weighted average exercise price cancelled	74
Weighted average exercise price outstanding, ending	58	$ 69
Weighted average exercise price exercisable	$ 58
Weighted average remaining contractual life outstanding	2 years 8 months	2 years 11 months
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Remaining Contractual Term	2 years 8 months
Aggregate intrinsic value outstanding, beginning	$ 47.4
Aggregate intrinsic value outstanding, ending	50.3	$ 47.4
Aggregate intrinsic value exercisable	$ 50.3

Stock-Based Payments (Restricte

Stock-Based Payments (Restricted Stock Activity) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of shares outstanding at December 31 (shares)	1,820,578
Number of shares granted	650,942
Number of shares vested	(510,590)
Number of shares cancelled	(401,699)
Number of shares outstanding at December 31 (shares)	1,559,231
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Weighted average grant date fair value outstanding	$ 116	$ 98
Weighted average grant date fair value granted	129
Weighted average grant date fair value vested	87
Weighted average grant date fair value cancelled	$ 95

Accumulated Other Comprehensi86

Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, beginning	$ 20,340.7	$ 20,551.8	$ 20,923.5
Other Comprehensive Income (Loss), Net of Tax	28.4	66.7	(87)
Stockholders' Equity, ending	22,411.8	20,340.7	20,551.8
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, beginning	(14.1)	(80.8)	6.2
Other Comprehensive Income (Loss), Net of Tax	28.4	66.7	(87)
Stockholders' Equity, ending	14.3	(14.1)	(80.8)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, beginning	(14.1)	(80.8)	6.2
Comprehensive Income Before Reclassification Adjustments	40.9	156.7	(104.5)
Comprehensive Income Reclassification Adjustments	(87.8)	(46.7)	11.8
Other Comprehensive Income (Loss), Net of Tax	75.3	(43.3)	5.7
Other Comprehensive Income (Loss), Net of Tax	28.4	66.7	(87)
Stockholders' Equity, ending	14.3	(14.1)	(80.8)
Foreign Currency Gain (Loss) [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, beginning	(15.7)	(8.8)	(2.2)
Comprehensive Income Before Reclassification Adjustments	10.4	(8.2)	(10.6)
Comprehensive Income Reclassification Adjustments	0	0	0
Other Comprehensive Income (Loss), Net of Tax	(2.9)	1.3	4
Other Comprehensive Income (Loss), Net of Tax	7.5	(6.9)	(6.6)
Stockholders' Equity, ending	(8.2)	(15.7)	(8.8)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, beginning	58.9	59.6	62.6
Comprehensive Income Before Reclassification Adjustments	0	0	(4.7)
Comprehensive Income Reclassification Adjustments	(1.2)	(1.2)	0.6
Other Comprehensive Income (Loss), Net of Tax	0.3	0.5	1.1
Other Comprehensive Income (Loss), Net of Tax	(0.9)	(0.7)	(3)
Stockholders' Equity, ending	58	58.9	59.6
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, beginning	(37.8)	(36.6)	(31.3)
Comprehensive Income Before Reclassification Adjustments	0.3	(5.1)	(11.2)
Comprehensive Income Reclassification Adjustments	2.9	3.2	2.7
Other Comprehensive Income (Loss), Net of Tax	(1.5)	0.7	3.2
Other Comprehensive Income (Loss), Net of Tax	1.7	(1.2)	(5.3)
Stockholders' Equity, ending	(36.1)	(37.8)	(36.6)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, beginning	(19.5)	(95)	(22.9)
Comprehensive Income Before Reclassification Adjustments	30.2	170	(78)
Comprehensive Income Reclassification Adjustments	(89.5)	(48.7)	8.5
Other Comprehensive Income (Loss), Net of Tax	79.4	(45.8)	(2.6)
Other Comprehensive Income (Loss), Net of Tax	20.1	75.5	(72.1)
Stockholders' Equity, ending	$ 0.6	$ (19.5)	$ (95)

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details)	12 Months Ended
	Dec. 31, 2016USD ($)
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Property, Plant, and Equipment, Fair Value Disclosure	$ 130,000,000
Cost Method Investments, Fair Value Disclosure	0
Cost-method Investments, Other than Temporary Impairment	$ 5,500,000

Fair Value Measurements (Financ

Fair Value Measurements (Financial Instruments Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	$ 21.2	$ 20.6
Trading Securities at Fair Value	68.9	62.7
Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0.3
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Securities at Fair Value	90.1	83.3
Investment Owned, at Fair Value		234.1
Total Assets at Fair Value	90.1	7,094.7
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	20.8	20.2
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	68.9	62.7
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	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	0.3	0.3
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	89.8	83
Investment Owned, at Fair Value		234.1
Total Assets at Fair Value	89.8	7,094.4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 1 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	20.8	20.2
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	68.9	62.7
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	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	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	0.3	0.3
Investment Owned, at Fair Value		0
Total Assets at Fair Value	0.3	0.3
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 2 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0	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	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	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	0.3	0.3
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	0
Investment Owned, at Fair Value		0
Total Assets at Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, level 3 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0	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	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	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	0
U.S. Treasury Performance Bond [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		5,549
U.S. Government Agency Performance Bond [Member] [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		1,228.3
U.S. Government Agency Performance Bond [Member] [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		1,228.3
U.S. Government Agency Performance Bond [Member] [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. Government Agency Performance Bond [Member] [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
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		5,549
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		5,549
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 ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	$ 0	$ 0	$ (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]
Business Combination, Contingent Consideration Liability, Beginning	0	0.3
Included in operating expense	0	(0.3)
Business Combination, Contingent Consideration Liability, Ending	$ 0	$ 0	$ 0.3

Fair Value Measurements (Debt I

Fair Value Measurements (Debt Instruments) (Details) $ in Millions	Dec. 31, 2017USD ($)
$750.0 million fixed rate notes due September 2022, stated rate of 3.00%
Debt Instrument, Fair Value Disclosure	$ 764.9
Seven Hundred Fifty Million Fixed Rate Notes Due March Two Thousand Twenty Five, Interest Equal To Three Point Zero Percent [Member] [Member]
Debt Instrument, Fair Value Disclosure	758.2
Seven Hundred Fifty Million Fixed Rate Notes Due September Two Thousand Forty Three, Interest Equal To Five Point Three Percent [Member]
Debt Instrument, Fair Value Disclosure	$ 960

Earnings Per Share (Basic and D

Earnings Per Share (Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income attributable to CME Group	$ 2,939.2	$ 308.6	$ 415.8	$ 399.8	$ 373.4	$ 472.8	$ 320.1	$ 367.8	$ 4,063.4	$ 1,534.1
Net income									$ 4,063.4	$ 1,534.1	$ 1,247
Basic									338,707	337,496	336,224
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements									1,519	1,470	1,670
Diluted									340,226	338,966	337,894
Earnings per common share, basic	$ 8.67	$ 0.91	$ 1.23	$ 1.18	$ 1.10	$ 1.40	$ 0.95	$ 1.09	$ 12	$ 4.55	$ 3.71
Earnings per common share, diluted	$ 8.63	$ 0.91	$ 1.22	$ 1.18	$ 1.10	$ 1.39	$ 0.95	$ 1.09	$ 11.94	$ 4.53	$ 3.69
Outstanding anti-dilutive options									104	309	535
Stock Options [Member]
Outstanding anti-dilutive options									0	171	420
Restricted Stock [Member]
Outstanding anti-dilutive options									104	138	115
Retained Earnings [Member]
Net income									$ 4,063.4	$ 1,534.1	$ 1,247

Quarterly Information (Unaudi92

Quarterly Information (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Total Revenues	$ 900	$ 890.8	$ 924.6	$ 929.3	$ 912.9	$ 841.7	$ 906.4	$ 934.2	$ 3,644.7	$ 3,595.2	$ 3,326.8
Operating Income	537.3	567.9	605.6	601.2	540.2	525.3	563.3	573.9	2,312	2,202.7	1,988.7
Non-operating income (expense)	37.4	39.4	31.7	105.8	54	23.5	2.8	4.6	214.3	84.9	(31.9)
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	574.7	607.3	637.3	707	594.2	548.8	566.1	578.5	2,526.3	2,287.6	$ 1,956.8
Net income attributable to CME Group	$ 2,939.2	$ 308.6	$ 415.8	$ 399.8	$ 373.4	$ 472.8	$ 320.1	$ 367.8	$ 4,063.4	$ 1,534.1
Earnings per Common Share Attributable to CME Group:
Basic	$ 8.67	$ 0.91	$ 1.23	$ 1.18	$ 1.10	$ 1.40	$ 0.95	$ 1.09	$ 12	$ 4.55	$ 3.71
Diluted	$ 8.63	$ 0.91	$ 1.22	$ 1.18	$ 1.10	$ 1.39	$ 0.95	$ 1.09	$ 11.94	$ 4.53	$ 3.69
Weighted Average Number of Common Shares:
Basic									338,707	337,496	336,224
Diluted									340,226	338,966	337,894

Schedule II_Valuation and Qua93

Schedule II—Valuation and Qualifying Accounts Schedule II—Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	$ 3.5	$ 1.9	$ 1.2
Charged (credited) to costs and expenses	0.6	2.4	1.1
Other	(1.9)	(0.8)	(0.4)
Balance at end of year	2.2	3.5	1.9
Allowance for deferred tax assets
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	14.9	122.3	99.2
Charged (credited) to costs and expenses	(3.7)	(107.4)	(2.4)
Other	0	0	25.5
Balance at end of year	$ 11.2	$ 14.9	$ 122.3