The Interpublic Group of Companies, Inc. (IPG) 10-K 23 Feb 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information Document (USD $)	12 Months Ended
	Dec. 31, 2014	Feb. 13, 2015	Jun. 30, 2014
DEI [Abstract]
Entity Registrant Name	INTERPUBLIC GROUP OF COMPANIES, INC.
Entity Central Index Key	51644
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Amendment Flag	FALSE
Trading Symbol	IPG
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Common Stock, Shares Outstanding		412,339,107
Entity Public Float			$8,237,958,432

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
REVENUE	$7,537.10	$7,122.30	$6,956.20
OPERATING EXPENSES:
Salaries and related expenses	4,820.40	4,545.50	4,391.90
Office and general expenses	1,928.10	1,917.90	1,887.20
Restructuring and other reorganization-related charges (reversals), net	0.2	60.6	-1.2
Total operating expenses	6,748.70	6,524	6,277.90
OPERATING INCOME	788.4	598.3	678.3
EXPENSES AND OTHER INCOME:
Interest expense	-84.9	-122.7	-133.5
Interest income	27.4	24.7	29.5
Other (expense) income, net	-10.2	-32.3	100.5
Total (expenses) and other income	-67.7	-130.3	-3.5
Income before income taxes	720.7	468	674.8
Provision for income taxes	216.5	181.2	213.3
Income of consolidated companies	504.2	286.8	461.5
Equity in net income of unconsolidated affiliates	1.2	2.1	3.1
NET INCOME	505.4	288.9	464.6
Net income attributable to noncontrolling interests	-28.3	-21	-17.9
NET INCOME ATTRIBUTABLE TO IPG	477.1	267.9	446.7
Dividends on preferred stock	0	-8.7	-11.6
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS	$477.10	$259.20	$435.10
Earnings per share available to IPG common stockholders:
Basic	$1.14	$0.62	$1.01
Diluted	$1.12	$0.61	$0.94
Weighted-average number of common shares outstanding:
Basic	419.2	421.1	432.5
Diluted	425.4	429.6	481.4
Dividends declared per common share	$0.38	$0.30	$0.24

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
NET INCOME	$505.40	$288.90	$464.60
Other Comprehensive Income
Foreign currency translation adjustments, before tax	-194.3	-116.9	9.7
Less: reclassification adjustments recognized in net income	-0.9	0	0
Foreign currency translation adjustments, income tax effect	0	-0.6	0
Foreign currency translation adjustments, net of tax	-195.2	-117.5	9.7
Available-for-sale securities:
Changes in market value of available-for-sale securities	0.7	0.8	0.4
Less: recognition of previously unrealized (gains) losses included in net income	0	-1.4	0.7
Available-for-sale securities, Income tax effect	-0.3	0.2	-0.5
Available-for-sale securities, Net of tax	0.4	-0.4	0.6
Derivatives instruments:
Changes in fair value of derivative instruments	-0.6	0	-21.9
Less: recognition of previously unrealized losses included in net income	1.9	1.7	0.3
Derivative instruments, Income tax effect	-0.5	-0.7	8.9
Derivative instruments, Net of tax	0.8	1	-12.7
Defined benefit pension and other postretirement plans:
Net actuarial losses for the period	-55.5	-20.6	-67.9
Less: amortization of unrecognized losses, transition obligation and prior service cost included in net income	10	10.8	7.7
Less: settlement and curtailment losses (gains) included in net income	0.5	-0.1	0.7
Other	0.5	1	-3.4
Defined benefit pension and other postretirement plans, Income tax effect	10.4	-1.3	1.9
Defined benefit pension and other postretirement plans, Net of tax	-34.1	-10.2	-61
Other comprehensive loss, net of tax	-228.1	-127.1	-63.4
Total comprehensive income	277.3	161.8	401.2
Less: comprehensive income attributable to noncontrolling interest	25.7	17.1	16.8
Comprehensive Income Attributable to IPG	$251.60	$144.70	$384.40

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
ASSETS:
Cash and cash equivalents	$1,660.60		$1,636.80
Marketable securities	6.6		5.3
Accounts receivable, net of allowance of $59.5 and $64.9	4,376.60		4,565.40
Expenditures billable to clients	1,424.20		1,536.40
Other current assets	342.2		340.1
Total current assets	7,810.20		8,084
Property and equipment, net	548.2		540
Deferred income taxes	192.9		144
Goodwill	3,669.20		3,629
Other non-current assets	526.7		508
TOTAL ASSETS	12,747.20		12,905
LIABILITIES:
Accounts payable	6,558		6,914.20
Accrued liabilities	796		718.4
Short-term borrowings	107.2		179.1
Long-term Debt, Current Maturities	2.1	[1]	353.6	[1]
Total current liabilities	7,463.30		8,165.30
Long-term debt	1,623.50		1,129.80
Deferred compensation	527.9		514.3
Other non-current liabilities	723.9		595.7
TOTAL LIABILITIES	10,338.60		10,405.10
Commitments and contingencies (see Note 14)
Redeemable noncontrolling interests (see Note 4)	257.4		249.1
STOCKHOLDERS' EQUITY:
Common stock, $0.10 par value, shares authorized: 800.0 shares issued: 2014 – 414.6; 2013 – 532.3 shares outstanding: 2014 – 413.8; 2013 – 424.5	41.2		53
Additional paid-in capital	1,547.50		2,975.20
Retained earnings	1,183.30		864.5
Accumulated other comprehensive loss, net of tax	-636.7		-411.2
Stockholders Equity Subtotal Before Treasury Stock	2,135.30		3,481.50
Less: Treasury stock, at cost: 2014 - 0.8 shares; 2013 - 107.8 shares	-19		-1,266.30
Total IPG stockholders' equity	2,116.30		2,215.20
Noncontrolling interests	34.9		35.6
TOTAL STOCKHOLDERS' EQUITY	2,151.20		2,250.80
TOTAL LIABILITIES AND EQUITY	$12,747.20		$12,905
[1]	We included our 6.25% Senior Unsecured Notes due 2014 (the "6.25% Notes") in the current portion of long-debt on our December 31, 2013 Consolidated Balance Sheet because the 6.25% Notes were scheduled to mature on November 15, 2014. We redeemed the 6.25% Notes prior to their scheduled maturity during the second quarter of 2014.

Parenthetical

(Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, except Per Share data, unless otherwise specified
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$59.50	$64.90
Common stock, par value	$0.10	$0.10
Common stock, shares authorized	800	800
Common stock, shares issued	414.6	532.3
Common stock, shares outstanding	413.8	424.5
Treasury stock, shares	0.8	107.8

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$505.40	$288.90	$464.60
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of fixed assets and intangible assets	163	157.4	147.7
Provision for uncollectible receivables	7.4	12.6	16.3
Amortization of restricted stock and other non-cash compensation	54.3	43.1	44.5
Net amortization of bond discounts and deferred financing costs	5.1	8.6	1.8
Non-cash (gain) loss related to early extinguishment of debt	-0.5	15.2	0
Deferred income tax provision	83.5	69.4	103.6
Gain on sale of an investment	0	0	-93.6
Other	13	3.2	12.3
Changes in assets and liabilities, net of acquisitions and dispositions, providing cash
Accounts receivable	-20.1	-157.1	-44.7
Expenditures billable to clients	83.5	-241.5	-73.8
Other current assets	-57.2	-11.3	3.5
Accounts payable	-177.1	417.7	-120.4
Accrued liabilities	39.8	-17.4	-57.8
Other non-current assets and liabilities	-30.6	4.1	-46.8
Net cash provided by operating activities	669.5	592.9	357.2
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	-148.7	-173	-169.2
Acquisitions, including deferred payments, net of cash acquired	-67.8	-61.5	-145.5
Net (purchases) sales and maturities of short-term marketable securities	-0.6	10.8	-1.2
Proceeds from sales of businesses and investments, net of cash sold	14.2	2	107.2
Other investing activities	2.1	-2.8	-1.5
Net cash used in investing activities	-200.8	-224.5	-210.2
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from Issuance of Long-term Debt	499.1	0	1,044.60
Repayments of Long-term Debt	-351.2	-602.4	-401.5
Repurchase of common stock	-275.1	-481.8	-350.5
Common stock dividends	-159	-126	-103.4
Exercise of stock options	20.1	47.4	10.8
Acquisition-related payments	-13.6	-27.6	-37.1
Net (decrease) increase in short term bank borrowings	-63.2	5.4	12.6
Distributions to noncontrolling interests	-17	-14.9	-17
Preferred stock dividends	0	-11.6	-11.6
Excess tax benefit on share-based compensation	16.7	0	15
Other financing activities	-0.7	-0.8	-30.6
Net cash (used in) provided by financing activities	-343.9	-1,212.30	131.3
Effect of foreign exchange rate changes on cash and cash equivalents	-101	-94.1	-6.2
Net increase (decrease) in cash and cash equivalents	23.8	-938	272.1
Cash and cash equivalents at beginning of period	1,636.80	2,574.80	2,302.70
Cash and cash equivalents at end of period	$1,660.60	$1,636.80	$2,574.80

Consolidated_Statements_of_Sto

Consolidated Statements of Stockholders' Equity (USD $)	Total	Preferred Stock	Common Stock	Additional Paid-In Capital	Retained Earnings (Accumulated Deficit)	Accumulated Other Comprehensive Loss, Net of Tax	Treasury Stock	Total IPG Stockholders' Equity	Noncontrolling Interests
In Millions
Balance at Dec. 31, 2011	$2,497.30	$221.50	$48.20	$2,427.50	$405.10	($225.70)	($414.90)	$2,461.70	$35.60
Balance, shares at Dec. 31, 2011			491.4
Net income	464.6				446.7			446.7	17.9
Other comprehensive loss	-63.4					-62.3		-62.3	-1.1
Reclassifications related to redeemable noncontrolling interests	10.9			12				12	-1.1
Noncontrolling interest transactions	-2.2								-2.2
Distributions to noncontrolling interests	-17								-17
Change in redemption value of redeemable noncontrolling interests	2.7				2.7			2.7
Repurchase of common stock	-350.5						-350.5	-350.5
Common stock dividends	-103.4				-103.4			-103.4
Preferred stock dividends	-11.6				-11.6			-11.6
Stock-based compensation, shares			1.6
Stock-based compensation	32		0.7	31.3				32
Exercise of stock options, shares			1.1
Exercise of stock options	10.9		0.1	10.8				10.9
Shares withheld for taxes, shares			-2.1
Shares withheld for taxes	-23.7		-0.2	-23.5				-23.7
Excess tax benefit from stock-based compensation	14.8			14.8				14.8
Other	-4.8			-7.5	-1.2			-8.7	3.9
Balance at Dec. 31, 2012	2,456.60	221.5	48.8	2,465.40	738.3	-288	-765.4	2,420.60	36
Balance, shares at Dec. 31, 2012			492
Net income	288.9				267.9			267.9	21
Other comprehensive loss	-127.1					-123.2		-123.2	-3.9
Reclassifications related to redeemable noncontrolling interests	-4.4			0.2				0.2	-4.6
Noncontrolling interest transactions	1			-0.1				-0.1	1.1
Distributions to noncontrolling interests	-14.9								-14.9
Change in redemption value of redeemable noncontrolling interests	-6.2				-6.2			-6.2
Repurchase of common stock	-481.8						-481.8	-481.8
Common stock dividends	-126				-126			-126
Preferred stock dividends	-8.7				-8.7			-8.7
Conversion of convertible notes to common stock, shares			16.9
Conversion of convertible notes to common stock	200		1.7	198.3				200
Capped call transaction	0			19.1			-19.1	0
Conversion of preferred stock to common stock, shares			17.3
Conversion of preferred stock to common stock	0	-221.5	1.7	219.8				0
Stock-based compensation, shares			2.4
Stock-based compensation	43.6		0.5	43.1				43.6
Exercise of stock options, shares			5.2
Exercise of stock options	47.9		0.5	47.4				47.9
Shares withheld for taxes, shares			-1.5
Shares withheld for taxes	-20.1		-0.2	-19.9				-20.1
Other	2			1.9	-0.8			1.1	0.9
Balance at Dec. 31, 2013	2,250.80	0	53	2,975.20	864.5	-411.2	-1,266.30	2,215.20	35.6
Balance, shares at Dec. 31, 2013			532.3
Net income	505.4				477.1			477.1	28.3
Other comprehensive loss	-228.1					-225.5		-225.5	-2.6
Reclassifications related to redeemable noncontrolling interests	-7.7			-3.5				-3.5	-4.2
Noncontrolling interest transactions	-2.3			2.1				2.1	-4.4
Distributions to noncontrolling interests	-17								-17
Change in redemption value of redeemable noncontrolling interests	1.5				1.5			1.5
Repurchase of common stock	-275.1						-275.1	-275.1
Retirement of treasury stock, shares			-121.9
Retirement of treasury stock	0		-12.2	-1,510.20			1,522.40	0
Common stock dividends	-159				-159			-159
Stock-based compensation, shares			3.4
Stock-based compensation	63.8		0.3	63.5				63.8
Exercise of stock options, shares			1.7
Exercise of stock options	20.3		0.2	20.1				20.3
Shares withheld for taxes, shares			-0.9
Shares withheld for taxes	-15		-0.1	-14.9				-15
Excess tax benefit from stock-based compensation	15.2			15.2				15.2
Other	-1.6				-0.8			-0.8	-0.8
Balance at Dec. 31, 2014	$2,151.20	$0	$41.20	$1,547.50	$1,183.30	($636.70)	($19)	$2,116.30	$34.90
Balance, shares at Dec. 31, 2014			414.6

Summary_of_Significant_Account

Summary of Significant Accounting Policies (Notes)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies
	Business Description
	The Interpublic Group of Companies, Inc. and subsidiaries (the “Company,” “IPG,” “we,” “us” or “our”) is one of the world’s premier global advertising and marketing services companies. Our agencies create customized marketing programs for clients that range in scale from large global marketers to regional and local clients. Comprehensive global services are critical to effectively serve our multinational and local clients in markets throughout the world, as they seek to build brands, increase sales of their products and services and gain market share in an increasingly complex and fragmented media landscape.
	Principles of Consolidation
	The Consolidated Financial Statements include the accounts of the Company and its consolidated subsidiaries, some of which are not wholly owned. Investments in companies over which we do not have control, but have the ability to exercise significant influence, are accounted for using the equity method of accounting. Investments in companies over which we have neither control nor have the ability to exercise significant influence are accounted for under the cost method. All intercompany accounts and transactions have been eliminated in consolidation.
	We have consolidated certain entities meeting the definition of variable interest entities, and the inclusion of these entities does not have a material impact on our Consolidated Financial Statements.
	Reclassifications
	Certain reclassifications have been made to the prior period financial statements to conform to the current-year presentation.
	Use of Estimates
	The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) requires us to make judgments, assumptions and estimates that affect the amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the reporting date and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from these estimates and assumptions.
	Revenue Recognition
	Our revenues are primarily derived from the planning and execution of multi-channel advertising, marketing and communications programs around the world. Our revenues are directly dependent upon the advertising, marketing and corporate communications requirements of our existing clients and our ability to win new clients. Our revenue is typically lowest in the first quarter and highest in the fourth quarter. This reflects the seasonal spending of our clients, incentives earned at year end on various contracts and project work that is typically completed during the fourth quarter.
	Most of our client contracts are individually negotiated and, accordingly, the terms of client engagements and the bases on which we earn commissions and fees vary significantly. As is customary in the industry, our contracts generally provide for termination by either party on relatively short notice, usually 90 days.
	Our client contracts are complex arrangements that may include provisions for incentive compensation and vendor rebates and credits. Our largest clients are multinational entities and, as such, we often provide services to these clients out of multiple offices and across many of our agencies. In arranging for such services, it is possible that we will enter into global, regional and local agreements. Agreements of this nature are reviewed by legal counsel to determine the governing terms to be followed by the offices and agencies involved.
	Revenue for our services is recognized when all of the following criteria are satisfied: (i) persuasive evidence of an arrangement exists; (ii) the price is fixed or determinable; (iii) collectability is reasonably assured; and (iv) services have been performed. Depending on the terms of a client contract, fees for services performed can be recognized in three principal ways: proportional performance (input or output), straight-line (or monthly basis) or completed contract.
	•	Fees are generally recognized as earned based on the proportional performance input method of revenue recognition in situations where our fee is reconcilable to the actual hours incurred to service the client as detailed in a contractual staffing plan, where the fee is earned on a per hour basis or where actual hours incurred are provided to the client on a periodic basis (whether or not the fee is reconcilable), with the amount of revenue recognized in these situations limited to the amount realizable under the client contract. We believe an input-based measure (the ‘hour’) is appropriate in situations where the client arrangement essentially functions as a time and out-of-pocket expense contract and the client receives the benefit of the services provided throughout the contract term.
	•	Fees are recognized on a straight-line or monthly basis when service is provided essentially on a pro-rata basis and the terms of the contract support monthly basis accounting.
	•	Certain fees (such as for major marketing events) are deferred until contract completion if the final act is so significant in relation to the service transaction taken as a whole or if any of the terms of the contract do not otherwise qualify for proportional performance or monthly basis recognition. Fees may also be deferred and recognized upon delivery of a project if the terms of the client contract identify individual discrete projects.
	Depending on the terms of the client contract, revenue is derived from diverse arrangements involving fees for services performed, commissions, performance incentive provisions and combinations of the three. Commissions are generally earned on the date of the broadcast or publication. Contractual arrangements with clients may also include performance incentive provisions designed to link a portion of our revenue to our performance relative to either qualitative or quantitative goals, or both. Performance incentives are recognized as revenue for quantitative targets when the target has been achieved and for qualitative targets when confirmation of the incentive is received from the client.
	The majority of our revenue is recorded as the net amount of our gross billings less pass-through expenses charged to a client. In most cases, the amount that is billed to clients significantly exceeds the amount of revenue that is earned and reflected in our Consolidated Financial Statements because of various pass-through expenses, such as production and media costs. We assess whether our agency or the third-party supplier is the primary obligor, and we evaluate the terms of our client agreements as part of this assessment. In addition, we give appropriate consideration to other key indicators such as latitude in establishing price, discretion in supplier selection and credit risk to the vendor. Because we operate broadly as an advertising agency, based on our primary lines of business and given the industry practice to generally record revenue on a net versus gross basis, we believe that there must be strong evidence in place to overcome the presumption of net revenue accounting. Accordingly, we generally record revenue net of pass-through charges as we believe the key indicators of the business suggest we generally act as an agent on behalf of our clients in our primary lines of business. In those businesses where the key indicators suggest we act as a principal (primarily sales promotion and event, sports and entertainment marketing), we record the gross amount billed to the client as revenue and the related incremental direct costs incurred as office and general expenses. In general, we also report revenue net of taxes assessed by governmental authorities that are directly imposed on our revenue-producing transactions.
	As we provide services as part of our core operations, we generally incur incidental expenses, which, in practice, are commonly referred to as “out-of-pocket” expenses. These expenses often include expenses related to airfare, mileage, hotel stays, out-of-town meals and telecommunication charges. We record the reimbursements received for such incidental expenses as revenue with a corresponding offset to office and general expense.
	We receive credits from our vendors and media outlets for transactions entered into on behalf of our clients that, based on the terms of our contracts and local law, are either remitted to our clients or retained by us. If amounts are to be passed through to clients, they are recorded as liabilities until settlement or, if retained by us, are recorded as revenue when earned.
	Cash and Cash Equivalents
	Cash equivalents are highly liquid investments, which include certificates of deposit, government securities, commercial paper and time deposits with original maturities of three months or less at the time of purchase and are stated at estimated fair value, which approximates cost. Cash is maintained at multiple high-credit-quality financial institutions.
	Short-Term Marketable Securities
	Short-term marketable securities include investment-grade time deposits, commercial paper and government securities with maturities greater than three months but less than twelve months. These securities are classified as available-for-sale and are carried at fair value with net unrealized gains and losses reported as a component of accumulated other comprehensive loss, which is a component of stockholders’ equity. The cost of securities is determined based upon the average cost of the securities sold.
	Allowance for Doubtful Accounts
	The allowance for doubtful accounts is estimated based on the aging of accounts receivable, reviews of client credit reports, industry trends and economic indicators, as well as reviews of recent payment history for specific customers. The estimate is based largely on a formula-driven calculation but is supplemented with economic indicators and knowledge of potential write-offs of specific client accounts.
	Expenditures Billable to Clients
	Expenditures billable to clients are primarily comprised of production and media costs that have been incurred but have not yet been billed to clients, as well as fees that have been earned which have not yet been billed to clients. Unbilled amounts are presented in expenditures billable to clients regardless of whether they relate to our fees or production and media costs. A provision is made for unrecoverable costs as deemed appropriate.
	Accounts Payable
	Accounts payable includes all operating payables, including those related to all media and production costs. These payables are due within one year.
	Investments
	Our investments in publicly traded companies over which we do not exert a significant influence are classified as available-for-sale. These investments are reported at fair value based on quoted market prices with net unrealized gains and losses reported as a component of accumulated other comprehensive loss. Our non-publicly traded investments and all other publicly traded investments, including investments to fund certain deferred compensation and retirement obligations, are accounted for using the equity method or cost method. We do not disclose the fair value for equity method investments or investments held at cost as it is not practical to estimate fair value since there is no readily available market data and it is cost prohibitive to obtain independent valuations. We regularly review our equity and cost method investments to determine whether a significant event or change in circumstances has occurred that may impact the fair value of each investment. In the event a decline in fair value of an investment occurs, we determine if the decline has been other-than-temporary. We consider our investments strategic and long-term in nature, so we determine if the fair value decline is recoverable within a reasonable period. For our investments, we evaluate fair value based on specific information (valuation methodologies, estimates of appraisals, financial statements, etc.) in addition to quoted market price, if available. We consider all known quantitative and qualitative factors in determining if an other-than-temporary decline in value of an investment has occurred.
	Derivatives
	We are exposed to market risk related to interest rates, foreign currency rates and certain balance sheet items. From time to time we enter into derivative instruments for risk management purposes, and not for speculative purposes. All derivative instruments are recorded at fair value on our balance sheet. Changes in fair value are immediately included in earnings if the derivatives are not designated as a hedge instrument or if the derivatives do not qualify as effective hedges. For derivatives designated as hedge instruments, we evaluate for hedge accounting both at inception and throughout the hedge period. If a derivative is designated as a fair value hedge, then changes in the fair value of the derivative are offset against the changes in the fair value of the underlying hedged item. If a derivative is designated as a cash flow hedge, then the effective portion of the changes in the fair value of the derivative is recognized as a component of accumulated other comprehensive income and subsequently reclassified to earnings in our Consolidated Statement of Operations in the same period as the underlying hedged transaction affects earnings.
	Property and Equipment
	Furniture, equipment, leasehold improvements and buildings are stated at cost, net of accumulated depreciation. Furniture and equipment are depreciated generally using the straight-line method over the estimated useful lives of the related assets, which range from 3 to 7 years for furniture and equipment, 10 to 35 years for buildings and the shorter of the useful life or the remaining lease term for leasehold improvements. Land is stated at cost and is not depreciated.
	We capitalize certain internal and external costs incurred to acquire or create internal use software, principally related to our enterprise resource planning (“ERP”) systems. Our ERP systems are stated at cost, net of accumulated amortization and are amortized using the straight-line method over 10 years. All other internal use computer software are stated at cost, net of accumulated amortization and are amortized using the straight-line method over the estimated useful lives of the related assets, which range from 3 to 7 years.
	Goodwill and Other Intangible Assets
	We account for our business combinations using the acquisition accounting method, which requires us to determine the fair value of net assets acquired and the related goodwill and other intangible assets. Determining the fair value of assets acquired and liabilities assumed requires management's judgment and involves the use of significant estimates, including projections of future cash inflows and outflows, discount rates, asset lives and market multiples. Considering the characteristics of advertising, specialized marketing and communication services companies, our acquisitions usually do not have significant amounts of tangible assets, as the principal asset we typically acquire is creative talent. As a result, a substantial portion of the purchase price is allocated to goodwill and other intangible assets.
	We review goodwill and other intangible assets with indefinite lives not subject to amortization as of October 1st each year and whenever events or significant changes in circumstances indicate that the carrying value may not be recoverable. We evaluate the recoverability of goodwill at a reporting unit level. We have 13 reporting units that were subject to the 2014 annual impairment testing. Our annual impairment review as of October 1, 2014 did not result in an impairment charge for any of our reporting units.
	During 2012, we adopted new authoritative guidance for goodwill and indefinite-lived intangible assets, respectively, which permits an entity to first assess qualitative factors to determine whether it is “more likely than not” that the goodwill or indefinite-lived intangible assets are impaired. Qualitative factors to consider may include macroeconomic conditions, industry and market considerations, cost factors that may have a negative effect on earnings, financial performance, and other relevant entity-specific events such as changes in management, key personnel, strategy or clients, as well as pending litigation. If, after assessing the totality of events or circumstances such as those described above, an entity determines that it is "more likely than not" that the goodwill or indefinite-lived intangible asset is impaired, then the entity is required to determine the fair value and perform the quantitative impairment test by comparing the fair value with the carrying value. Otherwise, no additional testing is required.
	For reporting units not included in the qualitative assessment, or for any reporting units identified in the qualitative assessment as "more likely than not" that the fair value is less than its carrying value, the first step of the quantitative impairment test is performed. For our annual impairment test, we compare the respective fair value of our reporting units' equity to the carrying value of their net assets. The first step is a comparison of the fair value of each reporting unit to its carrying value, including goodwill. The sum of the fair values of all our reporting units is reconciled to our current market capitalization plus an estimated control premium. Goodwill allocated to a reporting unit whose fair value is equal to or greater than its carrying value is not impaired, and no further testing is required. Should the carrying amount for a reporting unit exceed its fair value, then the first step of the quantitative impairment test is failed and the magnitude of any goodwill impairment is determined under the second step, which is a comparison of the implied fair value of a reporting unit's goodwill to its carrying value. The implied fair value of goodwill is the excess of the fair value of the reporting unit over its carrying value, excluding goodwill. Impaired goodwill is written down to its implied fair value with a charge to expense in the period the impairment is identified.
	The fair value of a reporting unit for 2014 and 2013 was estimated using a combination of the income approach, which incorporates the use of the discounted cash flow method, and the market approach, which incorporates the use of earnings and revenue multiples based on market data.
	We review intangible assets with definite lives subject to amortization whenever events or circumstances indicate that a carrying amount of an asset may not be recoverable. Recoverability of these assets is determined by comparing the carrying value of these assets to the estimated undiscounted future cash flows expected to be generated by these assets. These assets are impaired when their carrying value exceeds their fair value. Impaired intangible assets with definite lives subject to amortization are written down to their fair value with a charge to expense in the period the impairment is identified. Intangible assets with definite lives are amortized on a straight-line basis with estimated useful lives generally between 7 and 15 years. Events or circumstances that might require impairment testing include the loss of a significant client, the identification of other impaired assets within a reporting unit, loss of key personnel, the disposition of a significant portion of a reporting unit, significant decline in stock price or a significant adverse change in business climate or regulations.
	Foreign Currencies
	The functional currency of our foreign operations is generally their respective local currency. Assets and liabilities are translated at the exchange rates in effect at the balance sheet date, and revenues and expenses are translated at the average exchange rates during the period presented. The resulting translation adjustments are recorded as a component of accumulated other comprehensive loss in the stockholders’ equity section of our Consolidated Balance Sheets. Currency transaction gains or losses primarily arising from transactions in currencies other than the functional currency are included in office and general expenses. Foreign currency transactions resulted in a pre-tax loss of $1.4 in 2014 , a pre-tax loss of $0.6 in 2013 and a pre-tax gain $1.2 in 2012.
	We monitor the currencies of countries in which we operate in order to determine if the country should be considered a highly inflationary environment. A currency is determined to be highly inflationary when there is cumulative inflation of approximately 100% or more over a three-year period. If this occurs the functional currency of that country would be changed to our reporting currency, the U.S. Dollar, and foreign exchange gains or losses would be recognized on all monetary transactions, assets and liabilities in currencies other than the U.S. Dollar until the currency is no longer considered highly inflationary.
	Income Taxes
	The provision for income taxes includes U.S. federal, state, local and foreign taxes. Income taxes are accounted for under the liability method. Deferred tax assets and liabilities are recognized for the estimated future tax consequences of temporary differences between the financial statement carrying amounts and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the year in which the temporary differences are expected to be reversed. We evaluate the realizability of our deferred tax assets and establish a valuation allowance when it is “more likely than not” that all or a portion of the deferred tax assets will not be realized. We evaluate our tax positions using the “more likely than not” recognition threshold and then apply a measurement assessment to those positions that meet the recognition threshold. The factors used in assessing valuation allowances include all available evidence, such as past operating results, estimates of future taxable income and the feasibility of tax planning strategies.We have established tax reserves that we believe to be adequate in relation to the potential for additional assessments in each of the jurisdictions in which we are subject to taxation. We regularly assess the likelihood of additional tax assessments in those jurisdictions and adjust our reserves as additional information or events require.
	Redeemable Noncontrolling Interests
	Many of our acquisitions include provisions under which the noncontrolling equity owners can require us to purchase additional interests in a subsidiary at their discretion. Payments for these redeemable noncontrolling interests may be contingent on projected operating performance and satisfying other conditions specified in the related agreements. These payments are also subject to revision in accordance with the terms of the agreements. We record these redeemable noncontrolling interests in “mezzanine equity” in our Consolidated Balance Sheets. Each reporting period, redeemable noncontrolling interests are reported at their estimated redemption value, but not less than their initial fair value. Any adjustment to the redemption value above initial value prior to exercise will also impact retained earnings or additional paid-in capital, but will not impact net income. Adjustments as a result of currency translation will affect the redeemable noncontrolling interest balance, but do not impact retained earnings or additional paid-in capital.
	Earnings Per Share (“EPS”)
	Basic EPS available to IPG common stockholders equals net income available to IPG common stockholders divided by the weighted-average number of common shares outstanding for the applicable period. Diluted EPS equals net income available to IPG common stockholders adjusted to exclude, if dilutive, preferred stock dividends, interest expense related to potentially dilutive securities calculated using the effective interest rate method and the benefit from the preferred stock repurchased, divided by the weighted-average number of common shares outstanding, plus any additional common shares that would have been outstanding if potentially dilutive shares had been issued.
	Diluted EPS reflect the potential dilution that would occur if certain potentially dilutive securities or debt obligations were exercised or converted into common stock. The potential issuance of common stock is assumed to occur at the beginning of the year (or at the time of issuance of the potentially dilutive instrument, if later) and the incremental shares are included using the treasury stock or “if-converted” method. The proceeds utilized in applying the treasury stock method consist of the amount, if any, to be paid upon exercise and, as it relates to stock-based compensation, the amount of compensation cost attributed to future service not yet recognized and any tax benefits credited to additional paid-in-capital related to the exercise. These proceeds are then assumed to be used to purchase common stock at the average market price of our stock during the period. The incremental shares (difference between the shares assumed to be issued and the shares assumed to be purchased), to the extent they would have been dilutive, are included in the denominator of the diluted EPS calculation.
	We may be required to calculate basic EPS using the two-class method, as a result of our redeemable noncontrolling interests. To the extent that the redemption value increases and exceeds the then-current fair value of a redeemable noncontrolling interest, net income available to IPG common stockholders (used to calculate EPS) could be negatively impacted by that increase, subject to certain limitations. The partial or full recovery of any reductions to net income available to IPG common stockholders (used to calculate EPS) is limited to any cumulative prior-period reductions. For the years ended December 31, 2014, 2013 and 2012, there was no impact to EPS for adjustments related to our redeemable noncontrolling interests.
	Pension and Postretirement Benefits
	We have pension and postretirement benefit plans covering certain domestic and international employees. We use various actuarial methods and assumptions in determining our net pension and postretirement benefit costs and obligations, including the discount rate used to determine the present value of future benefits, expected long-term rate of return on plan assets and healthcare cost trend rates. The overfunded or underfunded status of our pension and postretirement benefit plans is recorded on our Consolidated Balance Sheet.
	Stock-Based Compensation
	Compensation costs related to share-based transactions, including employee stock options, are recognized in the Consolidated Financial Statements based on fair value. Stock-based compensation expense is generally recognized ratably over the requisite service period based on the estimated grant-date fair value, net of estimated forfeitures.
	Treasury Stock
	We account for repurchased common stock under the cost method and include such treasury stock as a component of our Consolidated Statements of Stockholders' Equity. Upon retirement, we reduce common stock for the par value of the shares being retired and the excess of the cost of the shares over par value as a reduction to additional paid-in capital ("APIC"), to the extent there is APIC in the same class of stock, and any remaining amount to retained earnings. These retired shares remain authorized but unissued.
	In November 2014, we retired 121.9 shares of our treasury stock, which resulted in a reduction in common stock of $12.2, treasury stock of $1,522.4 and APIC of $1,510.2. There was no effect on total stockholders' equity as a result of the retirement.

Debt_and_Credit_Agreements_Not

Debt and Credit Agreements (Notes)	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Debt Disclosure [Text Block]	Debt and Credit Arrangements
	Long-Term Debt
	A summary of the carrying amounts and fair values of our long-term debt is listed below.
		Effective			December 31,
		Interest Rate			2014								2013
					Book				Fair				Book				Fair
					Value				Value 1				Value				Value
	6.25% Senior Unsecured Notes due 2014	6.29	%		$	0			$	0			$	351.3			$	365.6
	2.25% Senior Notes due 2017 (less unamortized	2.3	%		299.6				301.2				299.4				293
	discount of $0.4)
	4.00% Senior Notes due 2022 (less unamortized	4.13	%		247.7				255.2				247.4				241.6
	discount of $2.3)
	3.75% Senior Notes due 2023 (less unamortized	4.32	%		498.8				499.8				498.6				467.3
	discount of $1.2)
	4.20% Senior Notes due 2024 (less unamortized	4.24	%		499.1				509.8				0				0
	discount of $0.9)
	Other notes payable and capitalized leases				80.4				80.4				86.7				87.8
	Total long-term debt				1,625.60								1,483.40
	Less: current portion 2				2.1								353.6
	Long-term debt, excluding current portion				$	1,623.50							$	1,129.80
	1	See Note 11 for information on the fair value measurement of our long-term debt.
	2	We included our 6.25% Senior Unsecured Notes due 2014 (the "6.25% Notes") in the current portion of long-debt on our December 31, 2013 Consolidated Balance Sheet because the 6.25% Notes were scheduled to mature on November 15, 2014. We redeemed the 6.25% Notes prior to their scheduled maturity during the second quarter of 2014.
	Annual maturities are scheduled as follows based on the book value as of December 31, 2014.
	2015	$	2.1
	2016	2.2
	2017	324.2
	2018	2
	2019	2
	Thereafter	1,293.10
	Total long-term debt	$	1,625.60
	For those debt securities that have a premium or discount at the time of issuance, we amortize the amount through interest expense based on the maturity date or the first date the holders may require us to repurchase the debt securities, if applicable. A premium would result in a decrease in interest expense and a discount would result in an increase in interest expense in future periods. We also have recorded debt issuance costs related to certain financing transactions in other assets in our Consolidated Balance Sheets, which are also amortized through interest expense. As of December 31, 2014 and 2013, we had unamortized debt issuance costs of $16.6 and $15.4, respectively.
	Our debt securities include covenants that, among other things, limit our liens and the liens of certain of our consolidated subsidiaries, but do not require us to maintain any financial ratios or specified levels of net worth or liquidity.
	Debt Transactions
	6.25% Senior Unsecured Notes due 2014
	In May 2014, we redeemed all $350.0 in aggregate principal amount of the 6.25% Notes. Total cash paid to redeem the 6.25% Notes was $371.2, which included accrued and unpaid interest of $10.3. In connection with the redemption of the 6.25% Notes, we recognized a loss on early extinguishment of debt of $10.4 which was primarily due to a redemption premium. The loss on early extinguishment of debt was recorded in other expense, net within our Consolidated Statement of Operations.
	4.20% Senior Notes due 2024
	In April 2014, we issued $500.0 in aggregate principal amount of the 4.20% Senior Notes due 2024 (the "4.20% Notes") at a discount to par. As a result, the 4.20% Notes were reflected on our Consolidated Balance Sheets at a fair value of $499.1 at issuance. The discount of $0.9 and capitalized direct fees, including commissions and offering expenses of $4.4, will be amortized in interest expense through the maturity date of April 15, 2024, using the effective interest method. The net proceeds were $494.7 after deducting discounts, commissions and offering expenses. Interest is payable semi-annually in arrears on April 15th and October 15th of each year, commencing on October 15, 2014. Consistent with our other debt securities, the 4.20% Notes include covenants that, among other things, limit our liens and the liens of certain of our consolidated subsidiaries, but do not require us to maintain any financial ratios or specified levels of net worth or liquidity.
	We used the majority of the net proceeds of the 4.20% Notes toward the redemption of our 6.25% Notes as described above.
	At any time prior to April 15, 2024, at our option, we may redeem all or some of the 4.20% Notes at the greater of 100% of the principal amount or a "make-whole" amount, plus, in either instance, accrued and unpaid interest to the date of redemption. If we experience a change of control event, combined with a specified downgrade in the credit rating, we must offer to repurchase the 4.20% Notes in cash at a price equal to not less than 101% of the aggregate principal amount of the 4.20% Notes, plus accrued and unpaid interest to the date of repurchase.
	10.00% Senior Unsecured Notes due 2017
	In July 2013, we redeemed all $600.0 in aggregate principal amount of the 10.00% Senior Unsecured Notes due 2017 (the "10.00% Notes"). Total cash paid to redeem the 10.00% Notes was $630.0. In connection with the redemption of the 10.00% Notes, we recognized a loss on early extinguishment of debt of $45.2, which included a redemption premium of $30.0, the write-off of the remaining unamortized discount of $7.3 and unamortized debt issuance costs of $7.9. The loss on early extinguishment of debt was recorded in other (expense) income, net within our Consolidated Statement of Operations.
	4.75% Convertible Senior Notes due 2023
	In March 2013, we retired all $200.0 in aggregate principal amount of our 4.75% Convertible Senior Notes due 2023 (the 4.75% Notes"). Of the amount retired, $199.997 in aggregate principal amount of the 4.75% Notes was converted, at the election of the holders, into Interpublic common stock at a conversion rate of 84.3402 shares (actual number) per $1,000 (actual number) principal amount, or approximately 16.9 shares. In connection with the retirement, we exercised our capped call options and elected net share settlement. We received a total of 1.5 settlement shares from the option counterparties as a result of exercising these options.
	Credit Agreements
	We maintain a committed corporate credit facility and uncommitted credit facilities with various banks that permit borrowings at variable interest rates. As of December 31, 2014 and 2013, there were no borrowings under our committed corporate credit facility. However, there were borrowings under some of the uncommitted facilities to manage working capital needs. We have guaranteed the repayment of some of these borrowings made by certain subsidiaries. If we lose access to these credit lines, we would have to provide funding directly to some of our international operations. The weighted-average interest rate on outstanding balances under the uncommitted credit facilities as of December 31, 2014 and 2013 was approximately 4.5%.
	A summary of our credit facilities is presented below.
			December 31,
			2014																2013
			Total				Amount				Letters of				Total				Total		Amount		Letters of		Total
			Facility				Outstanding				Credit				Available				Facility		Outstanding		Credit		Available
	Committed credit agreement		$	1,000.00			$	0			$	16			$	984			$	1,000.00	$	0	$	14.3	$	985.7
	Uncommitted credit agreements		$	740.3			$	107.2			$	3.9			$	629.2			$	700.2	$	179.1	$	4.2	$	516.9
	The Credit Agreement is a revolving facility, expiring in December 2018 (the "Credit Agreement"), under which amounts borrowed by us or any of our subsidiaries designated under the Credit Agreement may be repaid and reborrowed, subject to an aggregate lending limit of $1,000.0 or the equivalent in other currencies. The Company has the ability to increase the commitments under the Credit Agreement from time to time by an additional amount of up to $250.0, provided the Company receives commitments for such increases and satisfies certain other conditions. The aggregate available amount of letters of credit outstanding may decrease or increase, subject to a sublimit on letters of credit of $200.0 or the equivalent in other currencies. Our obligations under the Credit Agreement are unsecured.
	Under the Credit Agreement, we can elect to receive advances bearing interest based on either the base rate or the Eurocurrency rate (each as defined in the Credit Agreement) plus an applicable margin that is determined based on our credit ratings. As of December 31, 2014, the applicable margin is 0.275% for base rate advances and 1.275% for Eurocurrency rate advances. Letter of credit fees accrue on the average daily aggregate amount of letters of credit outstanding, at a rate equal to the applicable margin for Eurocurrency rate advances, and fronting fees accrue on the aggregate amount of letters of credit outstanding at an annual rate of 0.250%. We also pay a facility fee at an annual rate of 0.225% on the aggregate lending commitment under the Credit Agreement.
	We were in compliance with all of our covenants in the Credit Agreement as of December 31, 2014. The financial covenants in the Credit Agreement require that we maintain the following financial covenants listed below as of December 31, 2014 and thereafter.
	Interest coverage ratio (not less than): 1		5.00x
	Leverage ratio (not greater than): 2		3.25x
	1	The interest coverage ratio is defined as EBITDA, as defined in the Credit Agreement, to net interest expense.
	2	The leverage ratio is defined as debt as of the last day of such fiscal quarter to EBITDA, as defined in the Credit Agreement, for the four quarters then ended.
	Cash Pooling
	We aggregate our domestic cash position on a daily basis. Outside the United States we use cash pooling arrangements with banks to help manage our liquidity requirements. In these pooling arrangements, several IPG agencies agree with a single bank that the cash balances of any of the agencies with the bank will be subject to a full right of set-off against amounts the other agencies owe the bank, and the bank provides for overdrafts as long as the net balance for all the agencies does not exceed an agreed-upon level. Typically, each agency pays interest on outstanding overdrafts and receives interest on cash balances. Our Consolidated Balance Sheets reflect cash, net of bank overdrafts, under all of our pooling arrangements, and as of December 31, 2014 and 2013 the amounts netted were $1,590.7 and $1,415.3, respectively.

Acquisitions_Notes

Acquisitions (Notes)	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Acquisitions	Acquisitions
	We continue to evaluate strategic opportunities to expand our industry expertise, strengthen our position in high-growth and key strategic geographical markets and industry sectors, advance technological capabilities and improve operational efficiency through both acquisitions and increased ownership interests in current investments. Our acquisitions typically provide for an initial payment at the time of closing and additional contingent purchase price payments based on the future performance of the acquired entity. We have entered into agreements that may require us to purchase additional equity interests in certain consolidated and unconsolidated subsidiaries. The amounts at which we record these transactions in our financial statements are based on estimates of the future financial performance of the acquired entity, the timing of the exercise of these rights, changes in foreign currency exchange rates and other factors.
	For companies acquired, we estimate the fair values of the assets and liabilities based on 100% of the business for consolidation. The purchase price in excess of the estimated fair value of the tangible net assets acquired is allocated to identifiable intangible assets and then to goodwill. Due to the characteristics of advertising, specialized marketing and communication services companies, our acquisitions typically do not have significant amounts of tangible assets since the principal assets we acquire are client relationships and talent. As a result, a substantial portion of the purchase price is primarily allocated to customer lists, trade names and goodwill.
	For acquisitions we record deferred payment and redeemable noncontrolling interest amounts on our Consolidated Balance Sheets based on their acquisition-date fair value. Deferred payments are recorded on a discounted basis and adjusted quarterly, if necessary, through operating income or net interest expense, depending on the nature of the arrangement, for both changes in estimate and accretion between the acquisition date and the final payment date. See Note 14 for further information on contingent acquisition obligations. Redeemable noncontrolling interests are adjusted quarterly to their estimated redemption value, but not less than their initial fair value. Any adjustments to the redemption value impacts retained earnings or additional paid-in capital, except for foreign currency translation adjustments. The following table presents changes in our redeemable noncontrolling interests.
		Years ended December 31,
		2014			2013			2012
	Balance at beginning of period	$	249.1		$	227.2		$	243.4
	Change in related noncontrolling interest balance	3.2			4.6			1.1
	Changes in redemption value of redeemable noncontrolling interests:
	Additions	18.7			16.2			0
	Redemptions and reclassifications	(7.9		)	(2.3		)	(14.2		)
	Redemption value adjustments	(5.7		)	3.4			(3.1		)
	Balance at end of period	$	257.4		$	249.1		$	227.2
	For all acquisitions, if a portion of the deferred payments and purchases of additional interests after the effective date of purchase are contingent upon employment terms, then that amount is accounted separately from the business combination and recognized as compensation expense over the required earn-out period. Payments deemed as compensation are excluded from the fair value purchase price allocation to tangible net assets and intangible assets acquired.
	During 2014, we completed eight acquisitions, six of which were included in the Integrated Agency Networks ("IAN") operating segment and two of which were included in the Constituency Management Group ("CMG") operating segment. All acquired agencies have been integrated into one of our global networks or existing agencies. The most significant acquisitions included a global full-service digital agency, a digital agency in the United States and a search marketing agency in the Netherlands. During 2014, we recorded approximately $185.0 of goodwill and intangible assets related to our acquisitions.
	During 2013, we completed eleven acquisitions, nine of which were included in the IAN operating segment and two of which were included in the CMG operating segment. All acquired agencies have been integrated into one of our global networks or existing agencies. The most significant acquisitions included a full service digital agency in India, a full service agency in the U.K. and a public relations consultancy in India. During 2013, we recorded approximately $97.0 of goodwill and intangible assets related to these acquisitions.
	During 2012, we completed twelve acquisitions, eight of which were included in the IAN operating segment and four of which were included in the CMG operating segment. All acquired agencies have been integrated into one of our global networks or existing agencies. The most significant acquisitions included a healthcare market research and consulting agency and a search marketing agency in the United Kingdom, and a digital healthcare-marketing specialist and a designer of in-store shopping experiences in the United States. During 2012, we recorded approximately $201.0 of goodwill and intangible assets related to these acquisitions.
	The results of operations of our acquired companies were included in our consolidated results from the closing date of each acquisition. We did not make any payments in stock related to our acquisitions in 2014, 2013 or 2012.
	Details of cash paid for current and prior years' acquisitions are listed below.
		Years ended December 31,
		2014			2013			2012
	Cost of investment: current-year acquisitions	$	97.3		$	67.7		$	156.8
	Cost of investment: prior-year acquisitions	14			28.5			40.6
	Less: net cash acquired	(29.9		)	(7.1		)	(14.8		)
	Total cost of investment	81.4			89.1			182.6
	Operating expense 1	3.4			2			3.2
	Total cash paid for acquisitions 2	$	84.8		$	91.1		$	185.8
	1	Represents cash payments made that were either in excess of the contractual value or contingent upon the future employment of the former owners of acquired companies.
	2	Of the total cash paid, $13.6, $27.6 and $37.1 for the years ended December 31, 2014, 2013 and 2012, respectively, are classified under the financing section of the Consolidated Statements of Cash Flows within acquisition-related payments. These amounts relate to increases in our ownership interests in our consolidated subsidiaries as well as deferred payments for acquisitions. Of the total cash paid, $67.8, $61.5 and $145.5 for the years ended December 31, 2014, 2013 and 2012, respectively, are classified under the investing section of the Consolidated Statements of Cash Flows within acquisitions, net of cash acquired. These amounts relate to initial payments for new transactions.

Supplementary_Data_Notes

Supplementary Data (Notes)	12 Months Ended
	Dec. 31, 2014
Supplementary Data [Abstract]
Supplementary Data	Supplementary Data
	Valuation and Qualifying Accounts – Allowance for Uncollectible Accounts Receivable
		Years ended December 31,
		2014				2013				2012
	Balance at beginning of period	$	64.9			$	59			$	55.4
	Charges to costs and expenses	7.4				12.6				16.3
	Reversals to other accounts1	0.1				0.7				(0.2		)
	Deductions:
	Dispositions	0				0				(0.4		)
	Uncollectible accounts written off	(8.1		)		(7.2		)		(12.6		)
	Foreign currency translation adjustment	(4.8		)		(0.2		)		0.5
	Balance at end of period	$	59.5			$	64.9			$	59
	1	Amounts primarily relate to miscellaneous other amounts and reclassifications.
	Property and Equipment
			December 31,
			2014				2013
	Furniture and equipment		$	640.7			$	661.6
	Leasehold improvements		594				611.4
	Internal use computer software		296.2				269.1
	Land and buildings		87.3				109.6
			1,618.20				1,651.70
	Less: accumulated depreciation		(1,070.0		)		(1,111.7		)
	Total property and equipment, net		548.2				$	540
	The total depreciation and amortization expense for the years ended December 31, 2014, 2013 and 2012 was $132.3, $130.6 and $124.3, respectively.
	Accrued Liabilities
	The following table presents the components of accrued liabilities.
		December 31,
		2014				2013
	Salaries, benefits and related expenses	$	510.6			$	467.2
	Office and related expenses	51.5				56.9
	Acquisition obligations	88.1				12.8
	Interest	18.3				16
	Restructuring and other reorganization-related	5.5				46.7
	Other	122				118.8
	Total accrued liabilities	$	796			$	718.4
	Other (Expense) Income, net
	Results of operations include certain items that are not directly associated with our revenue-producing operations.
		Years ended December 31,
		2014				2013				2012
	Loss on early extinguishment of debt	$	(10.4	)		$	(45.2	)		$	0
	Gains on sales of businesses and investments, net	0.8				1.5				88.2
	Vendor discounts and credit adjustments	3.3				8.6				15.3
	Other (expense) income, net	(3.9		)		2.8				(3.0		)
	Total other (expense) income, net	$	(10.2	)		$	(32.3	)		$	100.5
	Loss on Early Extinguishment of Debt – During 2014, we recorded a charge of $10.4 related to the redemption of our 6.25% Notes. During 2013, we recorded a charge of $45.2 related to the redemption of our 10.00% Notes. See Note 2 to the Consolidated Financial Statements for further information.
	Gains on Sales of Businesses and Investments, net – During 2014, we recognized gains from the sale of a business located in the Continental Europe region within our IAN segment and the sale of investments in our Rabbi Trusts, which were partially offset by a loss from the sale of a business in the domestic market within our IAN segment. During 2013, we recognized gains from the sale of marketable securities in the Asia Pacific region within our IAN segment and the sale of investments in our Rabbi Trusts, which were partially offset by a loss from the sale of a business in the United Kingdom within our IAN segment. During 2012, we recognized gains from the sale of remaining holdings in Facebook and a business in an international market within our CMG segment, which were partially offset by losses from the sale of businesses within our IAN segment, as well as an adjustment relating to a reserve for a change in estimate in connection with a business disposed of in a prior year.
	Vendor Discounts and Credit Adjustments – In connection with the liabilities related to vendor discounts and credits established as part of the restatement we presented in our 2004 Annual Report on Form 10-K, these adjustments reflect the reversal of certain of these liabilities primarily where the statute of limitations has lapsed, or as a result of differences resulting from settlements with clients or vendors.
	Other (Expense) Income, net – During 2014, we recorded an other-than-temporary impairment on an investment in an unconsolidated affiliate in the Asia Pacific region within our IAN segment. During 2013, other income (expense), net primarily included a non-cash gain on re-measurement to fair value of an equity interest in an affiliate, located in the Asia Pacific region within our CMG segment, upon acquiring a controlling interest.
	Share Repurchase Program
	In February 2012, our Board of Directors (the "Board") authorized a share repurchase program to repurchase from time to time up to $300.0, excluding fees, of our common stock (the "2012 Share Repurchase Program"). In November 2012, the Board authorized an increase in the amount available under our 2012 Share Repurchase Program up to $400.0, excluding fees, of our common stock, as a result of the sale of our remaining holdings in Facebook. In February 2013, the Board authorized a new share repurchase program to repurchase from time to time up to $300.0, excluding fees, of our common stock (the "2013 Share Repurchase Program"). In March 2013, the Board authorized an increase in the amount available under our 2013 Share Repurchase Program up to $500.0, excluding fees, of our common stock to be used towards the repurchase of shares resulting from the conversion to common stock of the 4.75% Notes. In February 2014, the Board authorized a new share repurchase program to repurchase from time to time up to $300.0, excluding fees, of our common stock (the "2014 Share Repurchase Program").
	We may effect such repurchases through open market purchases, trading plans established in accordance with SEC rules, derivative transactions or other means. We expect to continue to repurchase our common stock in future periods, although the timing and amount of the repurchases will depend on market conditions and other funding requirements.
	The following table presents our share repurchase activity under our share repurchase programs.
		Years ended December 31,
		2014				2013				2012
	Number of shares repurchased	14.9				31.8				32.7
	Aggregate cost, including fees	$	275.1			$	481.8			$	350.5
	Average price per share, including fees	$	18.41			$	15.17			$	10.72
	We fully utilized the 2012 Share Repurchase Program as of the second quarter of 2013 and the 2013 Share Repurchase Program as of the third quarter of 2014. As of December 31, 2014, $143.6 remained available for repurchase under the 2014 Share Repurchase Program. The 2014 Share Repurchase Program has no expiration date.
	Supplemental Cash Flow Information
		Years ended December 31,
		2014				2013				2012
	Cash paid for interest	$	78.1			$	110.7			$	130.6
	Cash paid for income taxes, net of refunds 1	103.9				111.8				95.7
	1	Refunds of $21.3, $15.0 and $23.5 were received for the years ended December 31, 2014, 2013 and 2012, respectively.

Earnings_Per_Share_Notes

Earnings Per Share (Notes)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share
	The following sets forth basic and diluted earnings per common share available to IPG common stockholders.
		Years ended December 31,
		2014			2013			2012
	Net income available to IPG common stockholders - basic	$	477.1		$	259.2		$	435.1
	Adjustments: Effect of dilutive securities
	Interest on 4.25% Notes 1	0			0			0.3
	Interest on 4.75% Notes 1	0			0.8			4.1
	Dividends on preferred stock	0			0			11.6
	Net income available to IPG common stockholders - diluted	$	477.1		$	260		$	451.1
	Weighted-average number of common shares outstanding - basic	419.2			421.1			432.5
	Add: Effect of dilutive securities
	Restricted stock, stock options and other equity awards	6.2			5.2			7.2
	4.25% Notes 1	0			0			7.9
	4.75% Notes 1	0			3.3			16.9
	Preferred stock outstanding 2	0			0			16.9
	Weighted-average number of common shares outstanding - diluted	425.4			429.6			481.4
	Earnings per share available to IPG common stockholders - basic	$	1.14		$	0.62		$	1.01
	Earnings per share available to IPG common stockholders - diluted	$	1.12		$	0.61		$	0.94
	1	We retired all of our outstanding 4.75% Notes and 4.25% Convertible Senior Notes due 2023 in March 2013 and March 2012, respectively. See Note 2 for further information. For purposes of calculating diluted earnings per share for 2013 and 2012, the potentially dilutive shares are pro-rated based on the period they were outstanding.
	2	We converted all of our 5 1/4% Series B Cumulative Convertible Perpetual Preferred Stock (the "Series B Preferred Stock") into common stock in October 2013. For purposes of calculating diluted earnings per share for 2013, the potentially dilutive shares would have been pro-rated based on the period they were outstanding but were antidilutive.
	The following table presents the potential shares excluded from the diluted earnings per share calculation because the effect of including these potential shares would be antidilutive.
		Years ended December 31,
		2014		2013			2012
	Preferred Stock Outstanding 1	0		13.7			0
	Securities excluded from the diluted earnings per share calculation
	because the exercise price was greater than the average market price:
	Stock options 2	0		0.1			6.6
	1	We converted all of our Series B Preferred Stock into common stock in October 2013. For purposes of calculating diluted earnings per share for 2013, the potentially dilutive shares would have been pro-rated based on the period they were outstanding but were antidilutive.
	2	These options were outstanding at the end of the respective periods. In any period in which the exercise price is less than the average market price, these options have the potential to be dilutive, and application of the treasury stock method would reduce this amount.

Intangible_Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Intangible Assets
	Goodwill
	Goodwill is the excess purchase price remaining from an acquisition after an allocation of purchase price has been made to identifiable assets acquired and liabilities assumed based on estimated fair values. The changes in the carrying value of goodwill for our segments, IAN and CMG, for the years ended December 31, 2014 and 2013 are listed below.
			IAN			CMG			Total 1
	Balance as of December 31, 2012		$	3,074.60		$	506		$	3,580.60
	Current year acquisitions		58.8			16.5			75.3
	Foreign currency and other		(24.1		)	(2.8		)	(26.9		)
	Balance as of December 31, 2013		$	3,109.30		$	519.7		$	3,629.00
	Current year acquisitions		95.2			40.9			136.1
	Foreign currency and other		(83.7		)	(12.2		)	(95.9		)
	Balance as of December 31, 2014		$	3,120.80		$	548.4		$	3,669.20
	1	For all periods presented we have not recorded a goodwill impairment charge.
	See Note 1 for information regarding our annual impairment methodology.
	Other Intangible Assets
	Other intangible assets are comprised of both assets with indefinite lives not subject to amortization and assets with definite lives subject to amortization. Other intangible assets primarily consist of customer lists and trade names, which have definitive lives and are subject to amortization on a straight-line basis with estimated useful lives generally between 7 and 15 years. Amortization expense for other intangible assets for the years ended December 31, 2014, 2013 and 2012 was $29.4, $26.8 and $23.4, respectively. There were no material impairment charges on other intangibles for the years ended December 31, 2014, 2013 and 2012. During 2014 and 2013, we recorded approximately $48.6 and $21.5 of intangible assets related to our acquisitions in the respective year.
	The following table provides a summary of other intangible assets, which are included in other assets on our Consolidated Balance Sheets.
			December 31,
			2014									2013
			Gross Amount			Accumulated			Net Amount			Gross Amount		Accumulated			Net Amount
						Amortization								Amortization
	Customer lists		$	255.8		$	(139.3	)	$	116.5		$	228.1	$	(119.8	)	$	108.3
	Trade names		71			(22.8		)	48.2			64.5		(19.2		)	45.3
	Other		14.1			(3.8		)	10.3			14		(3.8		)	10.2
	Total		$	340.9		$	(165.9	)	$	175		$	306.6	$	(142.8	)	$	163.8
	The estimated annual amortization expense for other intangible assets for the next five years as of December 31, 2014 is listed below.
			2015			2016			2017			2018		2019
	Estimated amortization expense		$	37.2		$	34.7		$	22.7		$	12.8	$	12.1

Notes

(Notes)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes
	The components of income before income taxes are listed below.
		Years ended December 31,
		2014			2013			2012
	Domestic	$	387.7		$	255.3		$	386.9
	Foreign	333			212.7			287.9
	Total	$	720.7		$	468		$	674.8
	The provision for income taxes is listed below.
		Years ended December 31,
		2014			2013			2012
	U.S. federal income taxes (including foreign withholding taxes):
	Current	$	8		$	46.9		$	9.4
	Deferred	130.7			25.2			118.1
		138.7			72.1			127.5
	State and local income taxes:
	Current	9.7			(14.7		)	17.1
	Deferred	23.8			24.7			25.3
		33.5			10			42.4
	Foreign income taxes:
	Current	115.3			79.6			83.2
	Deferred	(71.0		)	19.5			(39.8		)
		44.3			99.1			43.4
	Total	$	216.5		$	181.2		$	213.3
	A reconciliation of the effective income tax rate as reflected in our Consolidated Statements of Operations to the U.S. federal statutory income tax rate is listed below.
		Years ended December 31,
		2014			2013			2012
	U.S. federal statutory income tax rate	35		%	35		%	35		%
	Income tax provision at U.S. federal statutory rate	$	252.3		$	163.8		$	236.2
		21.4			6.5			27.3
	Impact of foreign operations, including withholding taxes	1.7			30.5			8.4
	Change in net valuation allowance 1	(66.0		)	3.2			(57.3		)
	Worthless securities deduction	0			(22.2		)	0
	Increases in unrecognized tax benefits, net	5.2			0			24.1
	Other	1.9			(0.6		)	(25.4		)
	Provision for income taxes	$	216.5		$	181.2		$	213.3
	Effective income tax rate on operations	30		%	38.7		%	31.6		%
	1	Reflects changes in valuation allowance that impacted the effective income tax rate for each year presented.
	In 2014, our effective income tax rate of 30.0% was positively impacted from changes to our valuation allowances of $66.0 million. The primary drivers of the net change were associated with a valuation allowance reversal of $124.8 in one jurisdiction partially offset by the establishment of a valuation allowance of $57.2 in another jurisdiction, both in Continental Europe. In addition, our effective income tax rate was negatively impacted by losses in certain foreign jurisdictions where we receive no tax benefit due to 100% valuation allowances.
	In 2013, our effective income tax rate of 38.7% was positively impacted by the recognition of previously unrecognized tax benefits as a result of the recognition of losses attributable to worthless securities in a consolidated subsidiary and the settlement of the 2002-2006 New York State audit cycle. Our effective income tax rate was negatively impacted primarily by losses in certain foreign jurisdictions where we receive no tax benefit due to 100% valuation allowances.
	In 2012, our effective income tax rate of 31.6% was positively impacted by the reversals of valuation allowances associated with the Asia Pacific and Continental Europe regions, of $26.2 and $21.8, respectively, as well as by a benefit derived from the deduction of foreign tax credits that previously had a full valuation allowance. Our effective income tax rate was negatively impacted by an adjustment of $19.5 associated with the establishment of a previously unrecorded reserve for a tax contingency for the years 2007 through 2010, losses in certain foreign locations where we receive no tax benefit due to 100% valuation allowances and state and local income taxes, net of federal income tax benefit.
	The components of deferred tax assets and liabilities are listed below.
		December 31,
		2014			2013
	Postretirement/post-employment benefits	$	27.4		$	32.5
	Deferred compensation	191.2			187.2
	Pension costs	41.4			31.1
	Basis differences in fixed assets	(38.5		)	(4.1		)
	Rent	45.8			50.7
	Interest	60.9			60.7
	Accruals and reserves	34.8			39.6
	Allowance for doubtful accounts	10.8			10.8
	Basis differences in intangible assets	(412.3		)	(402.2		)
	Investments in equity securities	(2.6		)	48.6
	Tax loss/tax credit carry forwards	404.4			443.6
	Restructuring and other reorganization-related costs	(0.3		)	2.6
	Other	59.2			60.5
	Total deferred tax assets, net	422.2			561.6
	Valuation allowance	(332.2		)	(467.3		)
	Net deferred tax assets	$	90		$	94.3
	We evaluate the realizability of our deferred tax assets on a quarterly basis. The realization of our deferred tax assets is primarily dependent on future earnings. The amount of the deferred tax assets considered realizable could be reduced or increased in the near future if estimates of future taxable income are lower or greater than anticipated. A valuation allowance is established when it is “more likely than not” that all or a portion of deferred tax assets will not be realized. In circumstances where there is negative evidence, establishment of a valuation allowance is considered. The factors used in assessing valuation allowances include all available evidence, such as past operating results, estimates of future taxable income and the feasibility of tax planning strategies. We believe that cumulative losses in the most recent three-year period represent significant negative evidence, and as a result, we determined that certain of our deferred tax assets required the establishment of a valuation allowance. The deferred tax assets for which an allowance was recognized relate primarily to state and foreign tax loss carryforwards.
	The change in the valuation allowance is listed below.
		Years ended December 31,
		2014			2013			2012
	Balance at beginning of period	$	467.3		$	392.9		$	489.9
(Reversed) charged to costs and expenses	(72.8		)	65.2			(49.5		)
(Reversed) charged to gross tax assets and other accounts	(62.3		)	9.2			(47.5		)
Balance at end of period	$	332.2		$	467.3		$	392.9
In 2014, the net decrease was primarily related to a reversal of a valuation allowance for a deferred tax asset of $124.8, where we believe it is now "more likely than not" that the corresponding tax losses will be utilized over an extended period of time, based on implementing an internal financing tax action plan. This was partially offset by the establishment of a valuation allowance of $57.2, where we believe it is no longer "more likely than not" that the corresponding tax losses will be utilized, based on forecasted income not exceeding historical cumulative losses. The amounts charged to gross tax assets and other accounts relate primarily to the effect of foreign currency translation and a reduction to the valuation allowance related to the write-down of a corresponding deferred tax asset.
In 2013, amounts charged to costs and expenses primarily relate to the increase in valuation allowances in the U.S. and Continental Europe regions for existing and additional deferred tax assets. The amounts charged to gross tax assets and other accounts relate primarily to the effect of foreign currency translation.
In 2012, amounts reversed to costs and expenses primarily relate to the net reversal of valuation allowances in the Asia Pacific and Continental Europe regions, based on positive evidence in the form of a sustained pattern of profitability. Amounts reversed to gross tax assets and other accounts relate primarily to the reversal of valuation allowance on foreign tax credits.
As of December 31, 2014, there are $1,263.1 of loss carryforwards. These loss carryforwards are all non-U.S. tax loss carryforwards, of which $1,053.4 have unlimited carryforward periods and $209.7 have expiration periods from 2015 to 2033. As of December 31, 2014, the Company also had $60.3 in deferred tax assets for state net operating loss carryforwards and tax credit carryforwards, which will expire between 2015 and 2034.
As of December 31, 2014 and 2013, we had $2,214.2 and $1,959.8, respectively, of undistributed earnings attributable to foreign subsidiaries. It is our intention to permanently reinvest undistributed earnings of our foreign subsidiaries. We have not provided deferred U.S. income taxes or foreign withholding taxes on temporary differences resulting from earnings for certain foreign subsidiaries which are permanently reinvested outside the U.S. It is not practicable to determine the amount of unrecognized deferred tax liability associated with these temporary differences.
The table below summarizes the activity related to our unrecognized tax benefits.
	December 31,
	2014			2013			2012
Balance at beginning of period	$	219.2		$	194.6		$	161
Increases as a result of tax positions taken during a prior year	29			8.3			28.2
Decreases as a result of tax positions taken during a prior year	(16.3		)	(1.9		)	(6.8		)
Settlements with taxing authorities	(1.1		)	(34.9		)	(0.7		)
Lapse of statutes of limitation	(4.1		)	(10.6		)	(1.1		)
Increases as a result of tax positions taken during the current year	11.3			63.7			14
Balance at end of period	$	238		$	219.2		$	194.6
Included in the total amount of unrecognized tax benefits of $238.0 as of December 31, 2014, is $213.5 of tax benefits that, if recognized, would impact the effective income tax rate. The total amount of accrued interest and penalties as of December 31, 2014 and 2013 is $15.3 and $11.9, respectively, of which a detriment of $5.4 and $2.8 is included in our 2014 and 2013 Consolidated Statements of Operations, respectively. In accordance with our accounting policy, interest and penalties accrued on unrecognized tax benefits are classified as income taxes in our Consolidated Statements of Operations.
In 2013, we settled the 2002-2006 NYS audit cycle. The settlement resulted in a minor cash payment and our effective income tax rate was positively impacted by the recognition of previously unrecognized tax benefits.
We have various tax years under examination by tax authorities in the U.S., in various countries, and in various states, such as New York, in which we have significant business operations. It is not yet known whether these examinations will, in the aggregate, result in our paying additional taxes. We believe our tax reserves are adequate in relation to the potential for additional assessments in each of the jurisdictions in which we are subject to taxation. We regularly assess the likelihood of additional tax assessments in those jurisdictions and, if necessary, adjust our reserves as additional information or events require.
With respect to all tax years open to examination by U.S. federal, various state and local, and non-U.S. tax authorities, we currently anticipate that total unrecognized tax benefits will decrease by an amount between $25.0 and $35.0 in the next twelve months, a portion of which will affect our effective income tax rate, primarily as a result of the settlement of tax examinations and the lapsing of statutes of limitations. This net decrease is related to various items of income and expense, primarily transfer pricing adjustments.
We are effectively settled with respect to U.S. income tax audits for years prior to 2009. With limited exceptions, we are no longer subject to state and local income tax audits for years prior to 2004, or non-U.S. income tax audits for years prior to 2006.

Restructuring_and_Other_Reorga

Restructuring and Other Reorganization-Related Charges (Reversals), net (Notes)	12 Months Ended
	Dec. 31, 2014
Restructuring [Abstract]
Restructuring and Related Activities Disclosure [Text Block]	Restructuring and Other Reorganization-Related Charges (Reversals), net
	The components of restructuring and other reorganization-related charges (reversals), net are listed below.
		Years ended December 31,
		2014			2013			2012
	Severance and termination costs	$	0.1		$	55.9		$	0
	Lease termination costs	0.1			4.2			(1.1		)
	Other exit costs	0			0.5			(0.1		)
	Total restructuring and other reorganization-related charges (reversals), net	$	0.2		$	60.6		$	(1.2	)
	2013 Restructuring Plan
	In the fourth quarter of 2013, we implemented a cost savings initiative (the "2013 Plan") to better align our cost structure with our revenue, primarily in Continental Europe. In connection with this initiative, we identified and initiated restructuring actions resulting in pre-tax charges in 2013 of $61.2 related to the 2013 Plan, comprised of severance and termination costs of $55.9, lease termination costs of $4.8, and other exit costs of $0.5. In 2014, we recorded an additional $0.1 of net restructuring charges related to the 2013 Plan. All restructuring actions were substantially completed by the end of the first quarter of 2014, with remaining payments expected to be made through 2021.
	A summary of the 2013 Plan restructuring liability activity is listed below.
			31-Dec-13			Net Restructuring Charges			Cash Payments			Foreign Currency Translation Adjustment			31-Dec-14
	Severance and termination costs		$	46.5		$	0.1		$	(41.8	)	$	(0.4	)	$	4.4
	Lease termination costs		3.9			0			(1.2		)	(0.1		)	2.6
	Other exit costs		0.5			0			(0.5		)	0			0
	Total		$	50.9		$	0.1		$	(43.5	)	$	(0.5	)	$	7
	Net restructuring charges related to the 2013 Plan for the year ended December 31, 2014 were comprised of net charges of approximately $0.3 at IAN and net reversals of approximately $0.2 at CMG.
	Prior Restructuring Plans
	The 2007, 2003 and 2001 restructuring plans (the "Prior Restructuring Plans") with current year activity included net charges (reversals) that are adjustments primarily resulting from changes in management’s estimates relating to sublease rental income assumptions. For the years ended December 31, 2014, 2013 and 2012, the Prior Restructuring Plans incurred net restructuring and other reorganization-related charges of $0.1 and net reversals of $0.6 and $1.2, respectively. As of December 31, 2014, the remaining liability for the Prior Restructuring Plans was $1.1.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Loss, net of tax (Notes)	12 Months Ended
	Dec. 31, 2014
Accumulated Other Comprehensive Loss [Abstract]
Comprehensive Income (Loss) Note	Note 9:  Accumulated Other Comprehensive Loss, Net of Tax
	The following table presents the changes in accumulated other comprehensive loss, net of tax by component.
		Foreign Currency Translation Adjustments				Available-for-Sale Securities				Derivative Instruments			Defined Benefit Pension and Other Postretirement Plans			Total
	Balance as of December 31, 2012	$	(130.1	)		$	0.8			$	(12.7	)	$	(146.0	)	$	(288.0	)
	Other comprehensive (loss) income before reclassifications	(113.0		)		0.8				0			(19.7		)	(131.9		)
	Amount reclassified from accumulated other comprehensive loss, net of tax	(0.6		)		(1.2		)		1			9.5			8.7
	Balance as of December 31, 2013	$	(243.7	)		$	0.4			$	(11.7	)	$	(156.2	)	$	(411.2	)
	Other comprehensive (loss) income before reclassifications	(191.7		)		0.7				(0.6		)	(55.0		)	(246.6		)
	Amount reclassified from accumulated other comprehensive loss, net of tax	(0.9		)		(0.3		)		1.4			20.9			21.1
	Balance as of December 31, 2014	$	(436.3	)		$	0.8			$	(10.9	)	$	(190.3	)	$	(636.7	)
	Amounts reclassified from accumulated other comprehensive loss, net of tax for the years ended December 31, 2014, 2013 and 2012 are as follows:
			Years ended December 31,
			2014				2013				2012			Affected Line Item in the Consolidated Statements of Operations
	Foreign currency translation adjustments		$	(0.9	)		$	0			$	0		Other (expense) income, net
	Gains (losses) on available-for-sale securities		0				(1.4		)		0.7			Other (expense) income, net
	Losses on derivative instruments		1.9				1.7				0.3			Interest expense
	Amortization of defined benefit pension and postretirement plans items 1		10.5				10.8				8.4
	Tax effect		9.6				(2.4		)		10.3			Provision for income taxes
	Total amount reclassified from accumulated other comprehensive loss, net of tax		$	21.1			$	8.7			$	19.7
	1	These accumulated other comprehensive loss components are included in the computation of net periodic cost. See Note 12 for further information

Incentive_Compensation_Plans_N

Incentive Compensation Plans (Notes)	12 Months Ended
	Dec. 31, 2014
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Incentive Compensation Plans	Incentive Compensation Plans
	2014 Performance Incentive Plan
	We issue stock-based compensation and cash awards to our employees under a plan established by the Compensation and Leadership Talent Committee of the Board of Directors (the “Compensation Committee”) and approved by our shareholders. In May 2014, our shareholders approved the 2014 Performance Incentive Plan (the “2014 PIP”), replacing the 2009 Performance Incentive Plan (the “2009 PIP”) and previous incentive plans. The number of shares of common stock initially available for grants of all equity awards under the 2014 PIP is 28.8. Pursuant to the terms of the 2014 PIP, the number of shares that may be awarded to any one participant for each type of award is limited to 2.0. The vesting period of awards granted is generally commensurate with the requisite service period. We generally issue new shares to satisfy the exercise of stock options or the distribution of other stock-based awards.
	Additionally, under the 2014 PIP, we have the ability to issue performance cash awards. The performance cash awards are granted to certain employees who otherwise would have been eligible to receive performance-based stock awards. These awards have a service period vesting condition and a performance vesting condition. The amount of the performance cash award received by an employee with a performance vesting condition can range from 0% to 300% of the target amount of the original grant value. Performance cash awards generally vest in three years. A committee of the Board of Directors may grant performance cash awards to any eligible employee; however, no employee can receive more than $10.0 during a performance period.
	The amount of stock-based compensation expense as reflected in salaries and related expenses in our Consolidated Statement of Operations, and the related tax benefit, are listed below.
		Years ended December 31,
		2014				2013				2012
	Stock options	$	2.1			$	3.7			$	5.4
	Stock-settled awards	10				9.8				14.9
	Cash-settled awards	0.6				1.5				3.9
	Performance-based awards	42.2				29.6				24.5
	Employee stock purchase plan	0.6				0.6				0.6
	Other 1	1.2				0.8				1.1
	Stock-based compensation expense	$	56.7			$	46			$	50.4
	Tax benefit	$	20.6			$	17.6			$	19.7
	1	Represents charges recorded for severance expense related to stock-based compensation awards.
	Stock Options
	Stock options are granted with the exercise price equal to the fair market value of our common stock on the grant date. They are generally exercisable between two and four years from the grant date and expire ten years from the grant date (or earlier in the case of certain terminations of employment).
	The following tables are a summary of stock option activity during 2014.
			Options			Weighted-				Weighted-		Aggregate
						Average				Average		Intrinsic
						Exercise Price				Remaining		Value
						(per option)				Contractual Term
										(in years)
	Stock options outstanding as of January 1, 2014		9.4			$10.24
	Exercised		(1.7	)		12.01
	Expired		(0.3	)		14.16
	Stock options outstanding as of December 31, 2014		7.4			9.7				4.1		$	82.1
	Stock options vested and expected to vest as of December 31, 2014		7.4			9.69				4.1		$	82
	Stock options exercisable as of December 31, 2014		6.8			9.44				3.7		$	76.7
			Options			Weighted-				Weighted-		Aggregate
						Average Grant				Average		Intrinsic
						Date Fair Value				Remaining		Value
						(per option)				Contractual Term
										(in years)
	Non-vested as of January 1, 2014		1.5			$	4.21
	Vested		(0.9	)		4.25
	Non-vested as of December 31, 2014		0.6			4.16				7.9		$	3.8
	There were 1.7, 5.2 and 1.2 stock options exercised in 2014, 2013 and 2012, respectively. The total intrinsic value of stock options exercised during 2014, 2013 and 2012 was $10.7, $26.2 and $2.0, respectively. The cash received from the stock options exercised in 2014, 2013 and 2012 was $25.2, $59.5 and $11.7, respectively. As of December 31, 2014, there was $1.2 of total unrecognized compensation expense related to non-vested stock options granted, which is expected to be recognized over a weighted-average period of 0.9 years.
	We use the Black-Scholes option-pricing model to estimate the fair value of options granted, which requires the input of subjective assumptions including the option’s expected term and the price volatility of the underlying stock. Changes in the assumptions can materially affect the estimate of fair value and our results of operations could be materially impacted. There were no stock options granted during the year ended December 31, 2014. The weighted-average grant-date fair value per option during the years ended December 31, 2013 and 2012 was $4.14 and $4.24, respectively.
	The fair value of each option grant has been estimated with the following weighted-average assumptions.
			Years ended December 31,
			2014			2013			2012
	Expected volatility 1		—			40.2	%		43.8	%
	Expected term (years) 2		—			6.9			6.8
	Risk free interest rate 3		—			1.3	%		1.3	%
	Expected dividend yield 4		—			2.4	%		2.1	%
	1	The expected volatility used to estimate the fair value of stock options awarded is based on a blend of: (i) historical volatility of our common stock for periods equal to the expected term of our stock options and (ii) implied volatility of tradable forward put and call options to purchase and sell shares of our common stock.
	2	The estimate of our expected term is based on the average of (i) an assumption that all outstanding options are exercised upon achieving their full vesting date and (ii) an assumption that all outstanding options will be exercised at the midpoint between the current date (i.e., the date awards have ratably vested through) and their full contractual term. In determining the estimate, we considered several factors, including the historical option exercise behavior of our employees and the terms and vesting periods of the options.
	3	The risk free rate is determined using the implied yield currently available for zero-coupon U.S. government issuers with a remaining term equal to the expected term of the options.
	4	The expected dividend yield is calculated based on an annualized dividend of $0.38 per share in 2014, $0.30 per share in 2013 and $0.24 per share in 2012.
	Stock-Based Compensation
	We grant other stock-based compensation awards such as stock-settled awards, cash-settled awards and performance-based awards (settled in cash or shares) to certain key employees. The number of shares or units received by an employee for performance-based awards depends on Company performance against specific performance targets and could range from 0% to 300% of the target amount of shares originally granted. Incentive awards are subject to certain restrictions and vesting requirements as determined by the Compensation Committee. The fair value of the shares on the grant date is amortized over the vesting period, which is generally three years. Upon completion of the vesting period for cash-settled awards, the grantee is entitled to receive a payment in cash based on the fair market value of the corresponding number of shares of common stock. No monetary consideration is paid by a recipient for any incentive award. The fair value of cash-settled awards is adjusted each quarter based on our share price. The holders of stock-settled awards have absolute ownership interest in the underlying shares of common stock prior to vesting, which includes the right to vote and receive dividends. Dividends declared on common stock are accrued during the vesting period and paid when the award vests. The holders of cash-settled and performance-based awards have no ownership interest in the underlying shares of common stock until the awards vest and the shares of common stock are issued.
	Stock-based compensation awards expected to be settled in cash have been classified as liabilities in our Consolidated Balance Sheets as of December 31, 2014 and 2013.
			Years ended December 31,
			2014				2013				2012
	Stock-Settled Awards:
	Awards granted		1.2				1.1				0.9
	Weighted-average grant-date fair value (per award)		$	17.77			$	13.51			$	11.43
	Total fair value of vested awards distributed		$	12.6			$	35.4			$	63.5
	Cash-Settled Awards:
	Awards granted		0.1				0.1				0.1
	Weighted-average grant-date fair value (per award)		$	18.2			$	16.35			$	10.94
	Total fair value of vested awards distributed		$	0.6			$	5.4			$	11.1
Performance-Based Awards:
Awards granted		3.5				1.5				1.8
Weighted-average grant-date fair value (per award)		$	16.56			$	11.97			$	10.61
Total fair value of vested awards distributed		$	15.3			$	0.2			$	11.5
In conjunction with common stock dividends declared in 2014 and 2013, we accrued dividends of $0.8 and $0.7, respectively, on non-vested stock-settled awards and paid $0.5 and $1.5 for stock-settled awards that vested during 2014 and 2013, respectively.
A summary of the activity of our non-vested stock-settled awards, cash-settled awards, and performance-based awards during 2014 is presented below (performance-based awards are shown at 100% of the shares originally granted).
		Stock-Settled Awards								Cash-Settled Awards					Performance-Based Awards
		Awards				Weighted-				Awards			Weighted-		Awards			Weighted-
						Average							Average					Average
						Grant-Date							Grant-Date					Grant-Date
						Fair Value							Fair Value					Fair Value
						(per award)							(per award)					(per award)
Non-vested as of January 1, 2014		1.9				$	12.54			0.1			$	12.03	4.1			$	11.71
Granted		1.2				17.77				0.1			18.2		3.5			16.56
Vested		(0.8		)		12.15				(0.1		)	8.36		(0.9		)	12.24
Forfeited		(0.1		)		12.53				0			0		(0.9		)	12.76
Non-vested as of December 31, 2014		2.2				15.47				0.1			16.99		5.8			14.39
Total unrecognized compensation expense remaining		$	14.3							$	1.4				$	58.1
Weighted-average years expected to be recognized over		1.6								2					2
During 2014, 2013 and 2012, additional performance cash awards with a total target value of $2.9, $35.6 and $33.6, respectively, were awarded under the 2014 PIP and 2009 PIP and will be settled in shares upon vesting, which is three years from the grant date. The total fair value of the vested awards distributed during the years ended December 31, 2014 and 2013 was $19.8 and $17.4, respectively. As of December 31, 2014, there was $13.1 of total unrecognized compensation expense related to these awards, which is expected to be recognized over a remaining weighted-average period of 1.1 years.
In conjunction with our annual grant of long-term incentive compensation awards, we reviewed our estimates and assumptions in 2014, which resulted in an increase to our estimated forfeiture rate, as our review of our actual forfeitures indicated a higher level of forfeitures than previously assumed.
2009 Restricted Cash Plan
In March 2009, the Compensation Committee approved the Interpublic Restricted Cash Plan (the “Cash Plan”). Under the Cash Plan, the Board, the Compensation Committee or the Plan Administrator may grant cash awards to certain employees eligible to receive stock-settled and cash-settled awards. Cash awards, when granted, have a service period vesting condition and generally vest in three years.
Cash Awards
During the years ended December 31, 2014, 2013 and 2012, the Compensation Committee granted cash awards under the Cash Plan with a total target value of $5.8, $4.6 and $2.7, respectively, and we recognized $3.1, $4.0 and $10.9, respectively, in salaries and related expenses in our Consolidated Statements of Operations.
During the years ended December 31, 2014, 2013 and 2012, the Compensation Committee granted performance awards to be settled in cash under the 2014 PIP and 2009 PIP with a total target value of $33.0, $47.4, and $37.4, respectively, and we recognized $27.3, $18.3 and $18.9, respectively, in salaries and related expenses in our Consolidated Statements of Operations.
We amortize the present value of the amount expected to vest for cash awards and performance cash awards over the vesting period using the straight-line method, less an assumed forfeiture rate. Cash awards do not fall within the scope of the authoritative guidance for stock compensation as they are not paid in equity and the value of the award is not correlated with our stock price. Due to the cash nature of the payouts and the vesting period, we account for these awards in accordance with authoritative guidance for deferred compensation arrangements.
Employee Stock Purchase Plans
The Interpublic Group of Companies Employee Stock Purchase Plan (the “ESPP Plan”) became active April 1, 2007. Under the ESPP Plan, eligible employees may purchase our common stock through payroll deductions not exceeding 10% of their eligible compensation or 900 (actual number) shares each offering period. The price an employee pays for a share of common stock under the ESPP Plan is 90% of the lesser of the average market price of a share on the first business day of the offering period or the average market price of a share on the last business day of the offering period of three months. An aggregate of 15.0 shares are reserved for issuance under the ESPP Plan, of which 2.8 shares have been issued through December 31, 2014.

Fair_Value_Measurements_Notes

Fair Value Measurements (Notes)	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Fair Value Disclosures	Fair Value Measurements
	Authoritative guidance for fair value measurements establishes a fair value hierarchy which requires us to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. There are three levels of inputs that may be used to measure fair value:
	Level 1		Unadjusted quoted prices in active markets for identical assets or liabilities. An active market for the asset or liability is a market in which transactions for the asset or liability occur with sufficient frequency and volume to provide pricing information on an ongoing basis.
	Level 2		Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.
	Level 3		Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.
	Financial Instruments that are Measured at Fair Value on a Recurring Basis
	We primarily apply the market approach to determine the fair value of financial instruments that are measured at fair value on a recurring basis. There were no changes to our valuation techniques used to determine the fair value of financial instruments during 2014 as compared to the prior year.
	The following tables present information about our financial instruments measured at fair value on a recurring basis as of December 31, 2014 and 2013, and indicates the fair value hierarchy of the valuation techniques utilized to determine such fair value.
		December 31, 2014														Balance Sheet Classification
		Level 1				Level 2			Level 3				Total
	Assets
	Cash equivalents	$	901.4			$	0		$	0			$	901.4		Cash and cash equivalents
	Short-term marketable securities	6.6				0			0				6.6			Marketable securities
	Long-term investments	0.5				0			0				0.5			Other assets
	Total	$	908.5			$	0		$	0			$	908.5
	As a percentage of total assets	7.1		%		0		%	0		%		7.1		%
	Liabilities
	Mandatorily redeemable noncontrolling interests 1	$	0			$	0		$	32.8			$	32.8
		December 31, 2013														Balance Sheet Classification
		Level 1				Level 2			Level 3				Total
	Assets
	Cash equivalents	$	761.2			$	0		$	0			$	761.2		Cash and cash equivalents
	Short-term marketable securities	5.3				0			0				5.3			Marketable securities
	Long-term investments	1.6				0			0				1.6			Other assets
	Total	$	768.1			$	0		$	0			$	768.1
	As a percentage of total assets	6		%		0		%	0		%		6		%
	Liabilities
	Mandatorily redeemable noncontrolling interests 1	$	0			$	0		$	27			$	27
	1	Relates to unconditional obligations to purchase additional noncontrolling equity shares of consolidated subsidiaries. Fair value measurement of the obligation was based upon the amount payable as if the forward contracts were settled. The amount redeemable within the next twelve months is classified in accrued liabilities; any interests redeemable thereafter are classified in other non-current liabilities.
	The following table presents additional information about financial instruments measured at fair value on a recurring basis and for which we utilize Level 3 inputs to determine fair value.
			Years ended December 31,
	Liabilities		2014				2013
	Mandatorily redeemable noncontrolling interests -		$	27			$	25.3
	Balance at beginning of period
	Level 3 additions		5.6				0.2
	Level 3 reductions		(0.8		)		0
	Realized losses included in net income		1				1.5
	Foreign currency translation		0				0
	Mandatorily redeemable noncontrolling interests -		$	32.8			$	27
	Balance at end of period
	Level 3 reductions primarily consist of cash payments made related to unconditional obligations to purchase additional equity interests in previous acquisitions, which are classified within the financing section of our Consolidated Statements of Cash Flows. Level 3 additions relate to new unconditional obligations to purchase additional equity interests in previous acquisitions for cash in future periods. Realized losses included in net income for mandatorily redeemable noncontrolling interests are reported as a component of interest expense in our Consolidated Statements of Operations.
	Gross unrealized and realized gains and losses for our long-term investments and short-term marketable securities were not material for the years ended December 31, 2014, 2013 and 2012.
	Financial Instruments that are not Measured at Fair Value on a Recurring Basis
	The following table presents information about our financial instruments that are not measured at fair value on a recurring basis as of December 31, 2014, and indicates the fair value hierarchy of the valuation techniques utilized to determine such fair value.
		December 31, 2014
		Level 1				Level 2			Level 3			Total
	Total long-term debt	$	0			$	1,566.00		80.4			$	1,646.40
	Our long-term debt is comprised of senior notes and other notes payable.  The fair value of our senior notes traded over-the-counter is based on quoted prices for such securities, but which fair value can also be derived from inputs that are readily observable. Therefore, these senior notes are classified as Level 2 within the fair value hierarchy.  Our other notes payable are not actively traded and their fair value is not solely derived from readily observable inputs. Thus, the fair value of our other notes payable is determined based on a discounted cash flow model and other proprietary valuation methods, and therefore is classified as Level 3 within the fair value hierarchy.  See Note 2 for further information on our long-term debt.
	Non-financial Instruments that are Measured at Fair Value on a Recurring Basis
	Certain non-financial instruments are measured at fair value on a recurring basis, primarily accrued restructuring charges. Accrued restructuring charges were $8.1 and $52.2 for the years ended December 31, 2014 and 2013, respectively. These charges were valued using our internal estimates based upon a discounted cash flow model and are classified as Level 3 in the fair value hierarchy.
	Non-financial Instruments that are Measured at Fair Value on a Nonrecurring Basis
	Certain non-financial instruments are measured at fair value on a nonrecurring basis, primarily goodwill, intangible assets, and property and equipment. Accordingly, these assets are not measured and adjusted to fair value on an ongoing basis but are subject to periodic evaluations for potential impairment.

Employee_Benefits_Notes

Employee Benefits (Notes)	12 Months Ended
	Dec. 31, 2014
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Employee Benefits	Employee Benefits
	Pension and Postretirement Benefit Plans
	We have a defined benefit pension plan (the “Domestic Pension Plan”) that consists of approximately 4,000 participants and has been closed to new participants. We also have numerous funded and unfunded plans outside the U.S. The Interpublic Limited Pension Plan in the U.K. is a defined benefit plan and is our most material foreign pension plan in terms of the benefit obligation and plan assets. Some of our domestic and foreign subsidiaries provide postretirement health benefits and life insurance to eligible employees and, in certain cases, their dependents. The domestic postretirement benefit plan is our most material postretirement benefit plan in terms of the benefit obligation. This plan consists of approximately 2,200 participants, is closed to new participants and is unfunded.
	Differences between the aggregate income statement and balance sheet amounts listed in the tables below and the totals reported in our Consolidated Statements of Operations, Consolidated Statements of Comprehensive Income and Consolidated Balance Sheets relate to non-material foreign pension and postretirement benefit plans.
	Pension and Postretirement Benefit Obligation
	The change in the benefit obligation, the change in plan assets, the funded status and amounts recognized for the domestic pension plan, the significant foreign pension plans and the domestic postretirement benefit plan are listed below.
		Domestic								Foreign							Domestic Postretirement
		Pension Plan								Pension Plans							Benefit Plan
	December 31,	2014				2013				2014			2013				2014				2013
	Benefit Obligation
	Projected benefit obligation as of January 1	$	133.1			$	140.6			$	569.9		$	532.4			$	37.9			$	46.6
	Service cost	0				0				10.3			9.9				0.1				0.1
	Interest cost	6.2				5.5				23.4			21.7				1.7				1.6
	Benefits paid	(10.4		)		(10.4		)		(24.1		)	(23.8		)		(5.6		)		(6.4		)
	Plan participant contributions	0				0				0.6			0.5				1.5				1.7
	Actuarial losses (gains)	18				(2.6		)		55.7			25				4.4				(5.7		)
	Settlements and curtailments	0				0				(4.0		)	(3.1		)		0				0
	Foreign currency effect	0				0				(42.8		)	8.1				0				0
	Other	0				0				0.5			(0.8		)		(0.5		)		0
	Projected benefit obligation as of December 31	$	146.9			$	133.1			$	589.5		$	569.9			$	39.5			$	37.9
	Fair Value of Plan Assets
	Fair value of plan assets as of January 1	$	109.6			$	115.7			$	398.5		$	381.7			$	0			$	0
	Actual return on plan assets	9.6				3.8				44.7			19.5				0				0
	Employer contributions	2.7				0.5				25.7			18.3				4.1				4.7
	Plan participant contributions	0				0				0.6			0.5				1.5				1.7
	Benefits paid	(10.4		)		(10.4		)		(24.1		)	(23.8		)		(5.6		)		(6.4		)
	Settlements	0				0				(4.0		)	(2.7		)		0				0
	Foreign currency effect	0				0				(25.9		)	5				0				0
																					0
	Fair value of plan assets as of December 31	$	111.5			$	109.6			$	415.5		$	398.5			$	0			$	0
	Funded status of the plans at December 31	$	(35.4	)		$	(23.5	)		$	(174.0	)	$	(171.4	)		$	(39.5	)		$	(37.9	)
		Domestic								Foreign							Domestic Postretirement
		Pension Plan								Pension Plans							Benefit Plan
	December 31,	2014				2013				2014			2013				2014				2013
	Amounts recognized in Consolidated Balance Sheets
	Non-current asset	$	0			$	0			$	8.3		$	8			$	0			$	0
	Current liability	0				0				(8.0		)	(7.6		)		(4.0		)		(4.2		)
	Non-current liability	(35.4		)		(23.5		)		(174.3		)	(171.8		)		(35.5		)		(33.7		)
	Net liability recognized	$	(35.4	)		$	(23.5	)		$	(174.0	)	$	(171.4	)		$	(39.5	)		$	(37.9	)
	Accumulated benefit obligation	$	146.9			$	133.1			$	566.2		$	540.9
	Amounts recognized in Accumulated Other Comprehensive Loss, net
	Net actuarial loss (gain)	$	56.1			$	47			$	161		$	141			$	2.9			$	(1.5	)
	Prior service cost (credit)	0				0				1.1			1.5				(0.4		)		(0.1		)
	Transition obligation	0				0				0			0				0				0
	Total amount recognized	$	56.1			$	47			$	162.1		$	142.5			$	2.5			$	(1.6	)
	In 2015, we estimate that we will recognize $8.2 and $4.6 of net actuarial losses from accumulated other comprehensive loss, net into net periodic cost related to our domestic pension plan and significant foreign pension plans, respectively.
		Domestic								Foreign Pension Plans
		Pension Plan
	December 31,	2014				2013				2014			2013
	Pension plans with underfunded or unfunded accumulated benefit obligation
	Aggregate projected benefit obligation	$	146.9			$	133.1			$	577.1		$	553.2
	Aggregate accumulated benefit obligation	146.9				133.1				559.5			528.7
	Aggregate fair value of plan assets	111.5				109.6				395.8			374.7
	Net Periodic Cost
	The components of net periodic benefit cost and key assumptions are listed below.
		Domestic Pension Plan											Foreign Pension Plans											Domestic Postretirement Benefit Plan
	Years ended December 31,	2014				2013				2012			2014				2013				2012			2014			2013			2012
	Service cost	$	0			$	0			$	0		$	10.3			$	9.9			$	10.2		$	0.1		$	0.1		$	0.2
	Interest cost	6.2				5.5				6.3			23.4				21.7				21.9			1.7			1.6			2.3
	Expected return on plan assets	(7.3		)		(7.7		)		(7.7		)	(24.7		)		(19.2		)		(18.2		)	0			0			0
	Settlement and curtailment losses (gains)	0				0				0			0.5				(0.1		)		0.7			0			0			0
	Amortization of:
	Transition obligation	0				0				0			0				0				0			0			0			0.2
	Prior service cost (credit)	0				0				0			0.2				0.2				0.2			(0.2		)	(0.1		)	(0.1		)
Unrecognized actuarial losses	6.6				7.9				6.4			3.4				2.8				1			0			0			0
Net periodic cost	$	5.5			$	5.7			$	5		$	13.1			$	15.3			$	15.8		$	1.6		$	1.6		$	2.6
Assumptions
	Domestic Pension Plan									Foreign Pension Plans								Domestic Postretirement Benefit Plan
Years ended December 31,	2014			2013			2012			2014		2013			2012			2014			2013		2012
Net periodic cost
Discount rate	4.85	%		4	%		5	%		4.29	%	4.32	%		5	%		4.85	%		4	%	5	%
Rate of compensation increase	N/A			N/A			N/A			3.97	%	3.57	%		3.66	%		N/A			N/A		N/A
Expected return on plan assets	7	%		7	%		7.25	%		6.18	%	5.24	%		5.02	%		N/A			N/A		N/A
Benefit obligation
Discount rate	4.15	%		4.85	%		4	%		3.41	%	4.29	%		4.32	%		4	%		4.85	%	4	%
Rate of compensation increase	N/A			N/A			N/A			2.98	%	3.97	%		3.57	%		N/A			N/A		N/A
Health care cost trend rate assumed for next year
Initial rate (weighted-average)																		7	%		7.5	%	8	%
Year ultimate rate is reached																		2019			2019		2019
Ultimate rate																		5	%		5	%	5	%
Discount Rates – At December 31, 2014, 2013 and 2012, we determined our discount rates for our domestic pension plan, foreign pension plans and domestic postretirement benefit plan based on either a bond selection/settlement approach or bond yield curve approach. Using the bond selection/settlement approach, we determine the discount rate by selecting a portfolio of corporate bonds appropriate to provide for the projected benefit payments. Using the bond yield curve approach, we determine the discount rate by matching the plans' cash flows to spot rates developed from a yield curve. Both approaches utilize high quality AA-rated corporate bonds and the plans' projected cash flows to develop a discounted value of the benefit payments, which is then used to develop a single discount rate. In countries where markets for high-quality long-term AA corporate bonds are not well developed, a portfolio of long-term government bonds is used as a basis to develop hypothetical corporate bond yields, which serve as a basis to derive the discount rate.
Expected Return on Assets – Our expected rate of return is determined at the beginning of each year and considers asset class index returns over various market and economic conditions, current and expected market conditions, risk premiums associated with asset classes and long-term inflation rates. We determine both a short-term and long-term view and then select a long-term rate of return assumption that matches the duration of our liabilities.
Fair Value of Pension Plan Assets
The following table presents the fair value of our domestic and foreign pension plan assets as of December 31, 2014 and 2013, and indicates the fair value hierarchy of the valuation techniques utilized to determine such fair value. See Note 11 for a description of the fair value hierarchy.
	December 31, 2014															December 31, 2013
Asset Class	Level 1				Level 2				Level 3			Total				Level 1				Level 2			Level 3			Total
Investment funds	$	18.8			$	372.6			$	40.1		$	431.5			$	22.2			$	359.1		$	25.4		$	406.7
Insurance contracts	0				19.3				0			19.3				0				22			0			22
Limited partnerships	0				0				32.1			32.1				0				0			36.1			36.1
Other	42.4				1.4				0.3			44.1				40.2				2.5			0.6			43.3
Total	$	61.2			$	393.3			$	72.5		$	527			$	62.4			$	383.6		$	62.1		$	508.1
Investment funds include mutual funds, common/collective trusts, hedge funds and other commingled assets that are invested primarily in equity and fixed income securities. Mutual funds, which are publicly traded, are primarily valued using recently reported sales prices. All other investment funds, which are not publicly traded, are valued based on the net asset value of shares held by the plan at year end, which reflects the fair value of the underlying investments. Insurance contracts are valued based on the cash surrender value of the contract. Limited partnerships are invested primarily in equity and fixed income securities. Other investments primarily include cash and cash equivalents, equity securities, derivatives and fixed income securities such as government and investment-grade corporate bonds.
The following table presents additional information about our domestic and foreign pension plan assets for which we utilize Level 3 inputs to determine fair value.
	Year ended December 31, 2014															Year ended December 31, 2013
	Investment				Limited Partnerships				Other			Total				Investment				Limited Partnerships			Other			Total
	Funds															Funds
Balance at beginning of period	$	25.4			$	36.1			$	0.6		$	62.1			$	48.2			$	39.8		$	0.3		$	88.3
Actual return on assets:
Assets sold during the year	0.2				0.2				0			0.4				0.6				0			0			0.6
Assets still held at year end	(0.7		)		(0.3		)		(0.3		)	(1.3		)		1.9				(2.9		)	0.2			(0.8		)
Net purchases, sales and settlements	15.2				(3.9		)		0			11.3				(25.3		)		(0.8		)	0.1			(26.0		)
Balance at end of period	$	40.1			$	32.1			$	0.3		$	72.5			$	25.4			$	36.1		$	0.6		$	62.1
Asset Allocation
The primary investment goal for our plans’ assets is to maximize total asset returns while ensuring the plans’ assets are available to fund the plans’ liabilities as they become due. The plans’ assets in aggregate and at the individual portfolio level are invested so that total portfolio risk exposure and risk-adjusted returns best achieve this objective. The aggregate amount of our own stock held as investment for our domestic and foreign pension funds is considered negligible relative to the total fund assets. As of December 31, 2014, the weighted-average target and actual asset allocations relating to our domestic and foreign pension plans' assets are listed below.
					December 31,
Asset Class		2015 Target Allocation			2014			2013
Equity securities		24	%		22	%		24	%
Fixed income securities		48	%		46	%		43	%
Real estate		6	%		5	%		5	%
Other		22	%		27	%		28	%
Total		100	%		100	%		100	%
Cash Flows
During 2014, we contributed $2.7 and $25.7 of cash to our domestic and foreign pension plans, respectively. For 2015, we expect to contribute approximately $3.0 and $24.0 of cash to our domestic and foreign pension plans, respectively.
The following estimated future benefit payments, which reflect future service, as appropriate, are expected to be paid in the years indicated below.
Years	Domestic				Foreign				Domestic Postretirement
	Pension Plan				Pension Plans				Benefit Plan
2015	$	10.6			$	22.4			$	4.4
2016	10.4				24.2				4.2
2017	10.1				25.6				4.1
2018	9.9				26.1				3.9
2019	9.6				30.7				3.7
2020 - 2024	44.6				148				15.1
The estimated future payments for our domestic postretirement benefit plan is before any estimated federal subsidies expected to be received under the Medicare Prescription Drug, Improvement and Modernization Act of 2003.
The following federal subsidies are expected to be received in the years indicated below.
Years		Domestic Postretirement
		Benefit Plan
2015		$	0.4
2016		0.4
2017		0.4
2018		0.4
2019		0.4
2020 - 2024		2.4
Savings Plans
We sponsor defined contribution plans (the “Savings Plans”) that cover substantially all domestic employees. The Savings Plans permit participants to make contributions on a pre-tax and/or after-tax basis and allow participants to choose among various investment alternatives. We match a portion of participant contributions based upon their years of service. Amounts expensed for the Savings Plans for 2014, 2013 and 2012 were $43.0, $37.7 and $35.6, respectively. Expense includes a discretionary Company contribution of $5.2, $4.9 and $4.8 offset by participant forfeitures of $3.6, $3.3 and $3.0 in 2014, 2013 and 2012, respectively. In addition, we maintain defined contribution plans in various foreign countries and contributed $42.4, $36.9 and $34.0 to these plans in 2014, 2013 and 2012, respectively.
Deferred Compensation and Benefit Arrangements
We have deferred compensation arrangements which (i) permit certain of our key officers and employees to defer a portion of their salary or incentive compensation, or (ii) require us to contribute an amount to the participant’s account. The arrangements typically provide that the participant will receive the amounts deferred plus interest upon attaining certain conditions, such as completing a certain number of years of service or upon retirement or termination. As of December 31, 2014 and 2013, the deferred compensation liability balance was $97.7 and $92.7, respectively. Amounts expensed for deferred compensation arrangements in 2014, 2013 and 2012 were $9.8, $13.4 and $9.8, respectively.
We have deferred benefit arrangements with certain key officers and employees that provide participants with an annual payment, payable when the participant attains a certain age and after the participant’s employment has terminated. The deferred benefit liability was $153.2 and $166.2 as of December 31, 2014 and 2013, respectively. Amounts expensed for deferred benefit arrangements in 2014, 2013 and 2012 were $10.8, $14.0 and $15.0, respectively.
We have purchased life insurance policies on participants’ lives to assist in the funding of the related deferred compensation and deferred benefit liabilities. As of December 31, 2014 and 2013, the cash surrender value of these policies was $165.6 and $162.3, respectively. In addition to the life insurance policies, certain investments are held for the purpose of paying the deferred compensation and deferred benefit liabilities. These investments, along with the life insurance policies, are held in a separate revocable trust for the purpose of paying the deferred compensation and the deferred benefit arrangement liabilities. As of December 31, 2014 and 2013, the value of such investments in the trust was $8.5 and $7.7, respectively. The short-term investments are included in cash and cash equivalents, and the long-term investments and cash surrender value of the policies are included in other assets.
Long-Term Disability Plan
We have a long-term disability plan which provides income replacement benefits to eligible participants who are unable to perform their job duties during the first 24 months of disability. Income replacement benefits are continued thereafter if the participant is unable to perform any job related to his or her education, training or experience. As all income replacement benefits are fully insured, no related obligation is required as of December 31, 2014 and 2013. In addition to income replacement benefits, plan participants may remain covered for certain health and life insurance benefits up to age 65, and accordingly, we have recorded an obligation of $8.0 and $10.5 as of December 31, 2014 and 2013, respectively.

Segment_Information_Notes

Segment Information (Notes)	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Segment Information	Segment Information
	As of December 31, 2014, we have two reportable segments, which are IAN and CMG. IAN is comprised of McCann Worldgroup, Foote, Cone & Belding ("FCB"), Lowe and Partners, IPG Mediabrands, our digital specialist agencies, and our domestic integrated agencies. CMG is comprised of a number of our specialist marketing services offerings. We also report results for the “Corporate and other” group.
	Within IAN, our agencies provide a comprehensive array of global communications and marketing services, each offering a distinctive range of solutions for our clients. Our digital specialist agencies provide unique digital capabilities and service their own client rosters while also serving as key digital partners. In addition, our domestic integrated agencies, including Hill Holliday, Carmichael Lynch, Dailey, Tierney and Mullen, provide a full range of advertising, marketing communications services and/or marketing services and partner with our global operating divisions as needed. IAN’s operating divisions share similar economic characteristics and are similar in other areas, specifically related to the nature of their services, the manner in which the services are provided and the similarity of their respective customers.
	CMG, which includes Weber Shandwick, Cassidy, DeVries, Golin, FutureBrand, Jack Morton, and Octagon Worldwide, provides clients with diversified services, including public relations, meeting and event production, sports and entertainment marketing, corporate and brand identity and strategic marketing consulting. CMG shares some similarities with service lines offered by IAN; however, on an aggregate basis, CMG has a higher proportion of arrangements for which they act as principal, a different distribution model than IAN and different margin structure.
	The profitability measure employed by our chief operating decision maker for allocating resources to operating divisions and assessing operating division performance is operating income, excluding the impact of restructuring and other reorganization-related charges (reversals), net. With the exception of excluding these amounts from reportable segment operating income, all segments follow the same accounting policies as those described in Note 1.
	Certain corporate and other charges are reported as a separate line item within total segment operating income and include corporate office expenses, as well as shared service center expenses and certain other centrally managed expenses that are not fully allocated to operating divisions. Salaries and related expenses include salaries, long-term incentive awards, annual bonuses and other miscellaneous benefits for corporate office employees. Office and general expenses primarily include professional fees related to internal control compliance, financial statement audits and legal, information technology and other consulting services, which are engaged and managed through the corporate office. In addition, office and general expenses includes rental expense and depreciation of leasehold improvements for properties occupied by corporate office employees. A portion of centrally managed expenses are allocated to operating divisions based on a formula that uses the planned revenues of each of the operating units. Amounts allocated also include specific charges for information technology-related projects, which are allocated based on utilization.
	Summarized financial information concerning our reportable segments is shown in the following table.
		Years ended December 31,
		2014			2013			2012
	Revenue:
	IAN	$	6,097.30		$	5,795.60		$	5,728.50
	CMG	1,439.80			1,326.70			1,227.70
	Total	$	7,537.10		$	7,122.30		$	6,956.20
	Segment operating income:
	IAN	$	777.1		$	662.1		$	700.2
	CMG	161			137.6			114.2
	Corporate and other	(149.5		)	(140.8		)	(137.3		)
	Total	788.6			658.9			677.1
	Restructuring and other reorganization-related (charges) reversals, net	(0.2		)	(60.6		)	1.2
	Interest expense	(84.9		)	(122.7		)	(133.5		)
	Interest income	27.4			24.7			29.5
	Other (expense) income, net	(10.2		)	(32.3		)	100.5
	Income before income taxes	$	720.7		$	468		$	674.8
	Depreciation and amortization of fixed assets and intangible assets:
	IAN	$	124.6		$	126		$	119.7
	CMG	18.4			15.6			14.4
	Corporate and other	20			15.8			13.6
	Total	$	163		$	157.4		$	147.7
	Capital expenditures:
	IAN	$	92.1		$	109		$	97.5
	CMG	11.6			18.5			26.7
	Corporate and other	45			45.5			45
	Total	$	148.7		$	173		$	169.2
		December 31,
		2014			2013
	Total assets:
	IAN	$	11,111.20		$	11,425.10
	CMG	1,316.50			1,203.80
	Corporate and other	319.5			276.1
	Total	$	12,747.20		$	12,905.00
	Revenue and long-lived assets, excluding intangible assets, are presented by major geographic area in the following table.
			Revenue								Long-Lived Assets
			Years ended December 31,								December 31,
			2014			2013			2012		2014		2013
	Domestic		$	4,184.00		$	3,972.60		$	3,803.60	$	572.9	$	545.7
	International:
	United Kingdom		688.3			568.3			572		56.7		60.8
	Continental Europe		804.7			800.6			823.1		66.4		79.6
	Asia Pacific		922.5			868.9			838.1		102.2		88.8
	Latin America		470.4			464.5			450.1		69.2		72.3
	Other		467.2			447.4			469.3		32.4		37.1
	Total International		3,353.10			3,149.70			3,152.60		326.9		338.6
	Total Consolidated		$	7,537.10		$	7,122.30		$	6,956.20	$	899.8	$	884.3
	Revenue is primarily attributed to geographic areas based on where the services are performed. Property and equipment are allocated based upon physical location. Other assets and investments are allocated based on the location of the related operations.

Commitments_and_Contingencies_

Commitments and Contingencies (Notes)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies
	Leases
	We lease office premises and equipment. Where leases contain escalation clauses or concessions, such as rent holidays and landlord/tenant incentives or allowances, the impact of such adjustments is recognized on a straight-line basis over the minimum lease period. Certain leases provide for renewal options and require the payment of real estate taxes or other occupancy costs, which are also subject to escalation clauses. Net rent expense is listed in the table below.
		Years ended December 31,
		2014			2013			2012
	Gross rent expense	$	357.7		$	366.1		$	358.5
	Third-party sublease rental income	(6.1		)	(16.1		)	(17.5		)
	Net rent expense	$	351.6		$	350		$	341
	Cash amounts for future minimum lease commitments for office premises and equipment under non-cancelable leases, along with minimum sublease rental income to be received under non-cancelable subleases, are listed in the table below.
	Period	Rent			Sublease Rental			Net Rent
		Obligations			Income
	2015	$	328.4		$	(8.4	)	$	320
	2016	288.9			(2.8		)	286.1
	2017	248.3			(1.1		)	247.2
	2018	222.3			(0.1		)	222.2
	2019	198.9			0			198.9
	Thereafter	845.1			0			845.1
	Total	$	2,131.90		$	(12.4	)	$	2,119.50
	Guarantees
	We have guaranteed certain obligations of our subsidiaries relating principally to operating leases and credit facilities of certain subsidiaries. The amount of parent company guarantees on lease obligations was $580.4 and $588.1 as of December 31, 2014 and 2013, respectively, and the amount of parent company guarantees primarily relating to credit facilities was $329.2 and $279.6 as of December 31, 2014 and 2013, respectively. In the event of non-payment by the applicable subsidiary of the obligations covered by a guarantee, we would be obligated to pay the amounts covered by that guarantee. As of December 31, 2014, there were no material assets pledged as security for such parent company guarantees.
	Contingent Acquisition Obligations
	The following table details the estimated future contingent acquisition obligations payable in cash as of December 31, 2014.
			2015			2016			2017		2018		2019		Thereafter		Total
	Deferred acquisition payments		$	60.3		$	21.3		$	49.1	$	7.9	$	10.8	$	0.9	$	150.3
	Redeemable noncontrolling interests and call options with affiliates 1		35.4			65			37		7.8		10.5		7		162.7
	Total contingent acquisition payments		95.7			86.3			86.1		15.7		21.3		7.9		313
	Less: cash compensation expense included above		1.9			1.6			0.7		0		0		0		4.2
	Total		$	93.8		$	84.7		$	85.4	$	15.7	$	21.3	$	7.9	$	308.8
	1	We have entered into certain acquisitions that contain both redeemable noncontrolling interests and call options with similar terms and conditions. The estimated amounts listed would be paid in the event of exercise at the earliest exercise date. We have certain redeemable noncontrolling interests that are exercisable at the discretion of the noncontrolling equity owners as of December 31, 2014. These estimated payments of $20.5 are included within the total payments expected to be made in 2015, and will continue to be carried forward into 2016 or beyond until exercised or expired. Redeemable noncontrolling interests are included in the table at current exercise price payable in cash, not at applicable redemption value in accordance with the authoritative guidance for classification and measurement of redeemable securities.
	The majority of payments are contingent upon achieving projected operating performance targets and satisfying other conditions specified in the related agreements and are subject to revision in accordance with the terms of the respective agreements. See Note 4 for further information relating to the payment structure of our acquisitions.
	Legal Matters
	We are involved in various legal proceedings, and subject to investigations, inspections, audits, inquiries and similar actions by governmental authorities, arising in the normal course of business.  The types of allegations that arise in connection with such legal proceedings vary in nature, but can include claims related to contract, employment, tax and intellectual property matters. We evaluate all cases each reporting period and record liabilities for losses from legal proceedings when we determine that it is probable that the outcome in a legal proceeding will be unfavorable and the amount, or potential range, of loss can be reasonably estimated. In certain cases, we cannot reasonably estimate the potential loss because, for example, the litigation is in its early stages. While any outcome related to litigation or such governmental proceedings in which we are involved cannot be predicted with certainty, management believes that the outcome of these matters, individually and in the aggregate, will not have a material adverse effect on our financial condition, results of operations or cash flows.

Recent_Accounting_Standards_No

Recent Accounting Standards (Notes)	12 Months Ended
	Dec. 31, 2014
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recent Accounting Standards	Recent Accounting Standards
	Extraordinary and Unusual Items
	In January 2015, the Financial Accounting Standards Board ("FASB") issued amended guidance which eliminates the concept of extraordinary items from generally accepted accounting principles. This amendment is effective beginning January 1, 2016, and may be applied retrospectively or prospectively. Early adoption is permitted. Prior to this amendment, an entity was required to separately classify and present an event or transaction that was determined to be both unusual in nature and infrequent in occurrence as an extraordinary item, net of tax, after income from continuing operations in the income statement. Upon adopting this amended guidance, a material event or transaction that an entity considers to be unusual or infrequent, or both, may still be presented separately but will now be presented on a pre-tax basis within income from continuing operations or disclosed in the notes to the financial statements. We plan to early adopt this guidance for the quarter ending March 31, 2015. The adoption of this amended guidance will not have an impact on our Consolidated Financial Statements.
	Going Concern
	In August 2014, the FASB issued amended guidance which defines management's responsibility to evaluate whether there are conditions or events that raise substantial doubt about the entity’s ability to continue as a going concern and to provide related disclosures. Currently, this evaluation is only an auditor requirement. Specifically, the amendments (1) provide a definition of the term “substantial doubt,” (2) require an evaluation every reporting period, (3) provide principles for considering the mitigating effect of management’s plans, (4) require certain disclosures when substantial doubt is alleviated as a result of the consideration of management’s plans, (5) require an express statement and other disclosures when substantial doubt is not alleviated, and (6) require an assessment for a period of one year after the date that financial statements are issued. This amended guidance will be effective for us beginning January 1, 2016. We do not expect the adoption of this amended guidance to have a significant impact on our Consolidated Financial Statements.
	Share-Based Payments with Performance Targets
	In June 2014, the FASB issued amended guidance which requires that a performance target that affects vesting, and that could be achieved after the requisite service period, be treated as a performance condition. As such, the performance target should not be reflected in estimating the grant date fair value of the award. This amended guidance will be effective for us beginning January 1, 2016 and can be either applied prospectively or retrospectively. We are currently assessing the impact the adoption of the amended guidance will have on our Consolidated Financial Statements.
	Revenue Recognition
	In May 2014, the FASB issued amended guidance on revenue recognition, which will be effective for us beginning January 1, 2017 and can be applied retrospectively or as a cumulative effect adjustment as of the date of adoption. Early adoption is not permitted. The amended guidance requires entities to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. We are currently assessing the impact the adoption of the amended guidance will have on our Consolidated Financial Statements.
	Discontinued Operations
	In April 2014, the FASB issued amended guidance which changes the criteria for reporting a discontinued operation, which will be effective for us beginning January 1, 2015 and applied prospectively. Early adoption is permitted, but only for disposals (or classifications as held for sale) that have not been reported in financial statements previously issued or available for issuance. The amended guidance limits reporting on discontinued operations involving disposals of an entity's components that represent strategic shifts that have (or will have) a major effect on an entity’s operations and financial results. The amended guidance also expands the definition of a discontinued operation to include disposals of equity method investments and a business or nonprofit activity that, on acquisition, meets the criteria to be classified as held for sale. The amended guidance also requires enhanced disclosure requirements related to discontinued operations as well as additional disclosures regarding individually significant disposals that do not qualify for discontinued operations reporting. We early adopted the amended guidance for the quarter ended June 30, 2014. The adoption of this amended guidance did not have a significant impact on our Consolidated Financial Statements.

Results_by_Quarter_Unaudited_N

Results by Quarter (Unaudited) (Notes)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information	Results by Quarter (Unaudited)
		Three Months Ended						Three Months Ended						Three Months Ended						Three Months Ended
		March 31,						June 30,						September 30,						December 31,
		2014			2013			2014			2013			2014			2013			2014			2013
	Revenue	$	1,637.50		$	1,543.00		$	1,851.40		$	1,756.20		$	1,841.10		$	1,700.40		$	2,207.10		$	2,122.70
	Salaries and related expenses	1,188.60			1,132.10			1,170.20			1,120.20			1,195.20			1,093.60			1,266.40			1,199.60
	Office and general expenses	461.1			453.4			484.7			460.9			474.7			465.5			507.6			538.1
	Restructuring and other reorganization-related (reversals) charges, net	(0.5		)	(0.1		)	0.7			0.3			(0.1		)	(0.2		)	0.1			60.6
	Operating (loss) income	(11.7		)	(42.4		)	195.8			174.8			171.3			141.5			433			324.4
	Other income (expense), net 1	1.7			1.8			(11.2		)	4.8			(0.6		)	(46.6		)	(0.1		)	7.7
	Total (expenses) and other income 1	(12.3		)	(28.6		)	(27.2		)	(26.9		)	(13.8		)	(64.5		)	(14.4		)	(10.3		)
	(Benefit of) provision for income taxes 2	(1.7		)	(12.4		)	65.3			62			65			28.4			87.9			103.2
	Net (loss) income	(22.4		)	(58.5		)	103.7			86.1			92.8			49.2			331.3			212.1
	Net (loss) income available to IPG common stockholders 2	$	(20.9	)	$	(59.2	)	$	99.4		$	79.9		$	89.7		$	45.4		$	308.9		$	193.1
	(Loss) earnings per share available to IPG common stockholders:
	Basic	$	(0.05	)	$	(0.14	)	$	0.24		$	0.19		$	0.21		$	0.11		$	0.75		$	0.45
	Diluted	$	(0.05	)	$	(0.14	)	$	0.23		$	0.18		$	0.21		$	0.11		$	0.73		$	0.44
	Dividends declared per common stock	$	0.095		$	0.075		$	0.095		$	0.075		$	0.095		$	0.075		$	0.095		$	0.075
	1	The three months ended June 30, 2014 included a pre-tax loss of $10.4, related to our early extinguishment of debt. The three months ended September 30, 2013 included a pre-tax loss of $45.2, related to our early extinguishment of debt.
	2	The three months ended December 31, 2014 included a tax benefit of $67.6 due to the net reversal of valuation allowances on deferred tax assets in Continental Europe.

Subsequent_Events_Notes

Subsequent Events (Notes)	12 Months Ended
	Dec. 31, 2014
Subsequent Events [Abstract]
Subsequent Events [Text Block]	Subsequent Events
	In February 2015, we announced that our Board had approved a new share repurchase program to repurchase from time to time up to $300.0, excluding fees, of our common stock (the "2015 Share Repurchase Program"). The authorization for repurchases under the 2015 Share Repurchase Program is in addition to any amounts remaining available for repurchase under the 2014 Share Repurchase Program. See Note 5 for further information on the 2014 Share Repurchase Program. We may effect such repurchases under the 2015 Share Repurchase Program through open market purchases, trading plans established in accordance with SEC rules, derivative transactions or other means. The timing and amount of repurchases under the authorization will depend on market conditions and other funding requirements. There is no expiration date associated with the share repurchase programs.
	We also announced in February 2015, that our Board had declared a common stock cash dividend of 0.12 per share, payable on March 16, 2015 to holders of record as of the close of business on March 2, 2015.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies Principles of Consolidation (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Treasury Stock [Text Block]	Treasury Stock
	We account for repurchased common stock under the cost method and include such treasury stock as a component of our Consolidated Statements of Stockholders' Equity. Upon retirement, we reduce common stock for the par value of the shares being retired and the excess of the cost of the shares over par value as a reduction to additional paid-in capital ("APIC"), to the extent there is APIC in the same class of stock, and any remaining amount to retained earnings. These retired shares remain authorized but unissued.
	In November 2014, we retired 121.9 shares of our treasury stock, which resulted in a reduction in common stock of $12.2, treasury stock of $1,522.4 and APIC of $1,510.2. There was no effect on total stockholders' equity as a result of the retirement.
Principles of Consolidation	Principles of Consolidation
	The Consolidated Financial Statements include the accounts of the Company and its consolidated subsidiaries, some of which are not wholly owned. Investments in companies over which we do not have control, but have the ability to exercise significant influence, are accounted for using the equity method of accounting. Investments in companies over which we have neither control nor have the ability to exercise significant influence are accounted for under the cost method. All intercompany accounts and transactions have been eliminated in consolidation.
	We have consolidated certain entities meeting the definition of variable interest entities, and the inclusion of these entities does not have a material impact on our Consolidated Financial Statements.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies Reclassifications (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Reclassifications	Reclassifications
	Certain reclassifications have been made to the prior period financial statements to conform to the current-year presentation.

Summary_of_Significant_Account3

Summary of Significant Accounting Policies Use of Estimates (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates
	The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) requires us to make judgments, assumptions and estimates that affect the amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the reporting date and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from these estimates and assumptions.

Summary_of_Significant_Account4

Summary of Significant Accounting Policies Revenue Recognition (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Revenue Recognition	Revenue Recognition
	Our revenues are primarily derived from the planning and execution of multi-channel advertising, marketing and communications programs around the world. Our revenues are directly dependent upon the advertising, marketing and corporate communications requirements of our existing clients and our ability to win new clients. Our revenue is typically lowest in the first quarter and highest in the fourth quarter. This reflects the seasonal spending of our clients, incentives earned at year end on various contracts and project work that is typically completed during the fourth quarter.
	Most of our client contracts are individually negotiated and, accordingly, the terms of client engagements and the bases on which we earn commissions and fees vary significantly. As is customary in the industry, our contracts generally provide for termination by either party on relatively short notice, usually 90 days.
	Our client contracts are complex arrangements that may include provisions for incentive compensation and vendor rebates and credits. Our largest clients are multinational entities and, as such, we often provide services to these clients out of multiple offices and across many of our agencies. In arranging for such services, it is possible that we will enter into global, regional and local agreements. Agreements of this nature are reviewed by legal counsel to determine the governing terms to be followed by the offices and agencies involved.
	Revenue for our services is recognized when all of the following criteria are satisfied: (i) persuasive evidence of an arrangement exists; (ii) the price is fixed or determinable; (iii) collectability is reasonably assured; and (iv) services have been performed. Depending on the terms of a client contract, fees for services performed can be recognized in three principal ways: proportional performance (input or output), straight-line (or monthly basis) or completed contract.
	•	Fees are generally recognized as earned based on the proportional performance input method of revenue recognition in situations where our fee is reconcilable to the actual hours incurred to service the client as detailed in a contractual staffing plan, where the fee is earned on a per hour basis or where actual hours incurred are provided to the client on a periodic basis (whether or not the fee is reconcilable), with the amount of revenue recognized in these situations limited to the amount realizable under the client contract. We believe an input-based measure (the ‘hour’) is appropriate in situations where the client arrangement essentially functions as a time and out-of-pocket expense contract and the client receives the benefit of the services provided throughout the contract term.
	•	Fees are recognized on a straight-line or monthly basis when service is provided essentially on a pro-rata basis and the terms of the contract support monthly basis accounting.
	•	Certain fees (such as for major marketing events) are deferred until contract completion if the final act is so significant in relation to the service transaction taken as a whole or if any of the terms of the contract do not otherwise qualify for proportional performance or monthly basis recognition. Fees may also be deferred and recognized upon delivery of a project if the terms of the client contract identify individual discrete projects.
	Depending on the terms of the client contract, revenue is derived from diverse arrangements involving fees for services performed, commissions, performance incentive provisions and combinations of the three. Commissions are generally earned on the date of the broadcast or publication. Contractual arrangements with clients may also include performance incentive provisions designed to link a portion of our revenue to our performance relative to either qualitative or quantitative goals, or both. Performance incentives are recognized as revenue for quantitative targets when the target has been achieved and for qualitative targets when confirmation of the incentive is received from the client.
	The majority of our revenue is recorded as the net amount of our gross billings less pass-through expenses charged to a client. In most cases, the amount that is billed to clients significantly exceeds the amount of revenue that is earned and reflected in our Consolidated Financial Statements because of various pass-through expenses, such as production and media costs. We assess whether our agency or the third-party supplier is the primary obligor, and we evaluate the terms of our client agreements as part of this assessment. In addition, we give appropriate consideration to other key indicators such as latitude in establishing price, discretion in supplier selection and credit risk to the vendor. Because we operate broadly as an advertising agency, based on our primary lines of business and given the industry practice to generally record revenue on a net versus gross basis, we believe that there must be strong evidence in place to overcome the presumption of net revenue accounting. Accordingly, we generally record revenue net of pass-through charges as we believe the key indicators of the business suggest we generally act as an agent on behalf of our clients in our primary lines of business. In those businesses where the key indicators suggest we act as a principal (primarily sales promotion and event, sports and entertainment marketing), we record the gross amount billed to the client as revenue and the related incremental direct costs incurred as office and general expenses. In general, we also report revenue net of taxes assessed by governmental authorities that are directly imposed on our revenue-producing transactions.
	As we provide services as part of our core operations, we generally incur incidental expenses, which, in practice, are commonly referred to as “out-of-pocket” expenses. These expenses often include expenses related to airfare, mileage, hotel stays, out-of-town meals and telecommunication charges. We record the reimbursements received for such incidental expenses as revenue with a corresponding offset to office and general expense.
	We receive credits from our vendors and media outlets for transactions entered into on behalf of our clients that, based on the terms of our contracts and local law, are either remitted to our clients or retained by us. If amounts are to be passed through to clients, they are recorded as liabilities until settlement or, if retained by us, are recorded as revenue when earned.

Summary_of_Significant_Account5

Summary of Significant Accounting Policies Cash and Cash Equivalents (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Cash and Cash Equivalents	Cash and Cash Equivalents
	Cash equivalents are highly liquid investments, which include certificates of deposit, government securities, commercial paper and time deposits with original maturities of three months or less at the time of purchase and are stated at estimated fair value, which approximates cost. Cash is maintained at multiple high-credit-quality financial institutions.

Summary_of_Significant_Account6

Summary of Significant Accounting Policies Short-Term Marketable Securities (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Short-Term Marketable Securities	Short-Term Marketable Securities
	Short-term marketable securities include investment-grade time deposits, commercial paper and government securities with maturities greater than three months but less than twelve months. These securities are classified as available-for-sale and are carried at fair value with net unrealized gains and losses reported as a component of accumulated other comprehensive loss, which is a component of stockholders’ equity. The cost of securities is determined based upon the average cost of the securities sold.

Summary_of_Significant_Account7

Summary of Significant Accounting Policies Allowance for Doubtful Accounts (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts
	The allowance for doubtful accounts is estimated based on the aging of accounts receivable, reviews of client credit reports, industry trends and economic indicators, as well as reviews of recent payment history for specific customers. The estimate is based largely on a formula-driven calculation but is supplemented with economic indicators and knowledge of potential write-offs of specific client accounts.

Summary_of_Significant_Account8

Summary of Significant Accounting Policies Expenditures Billable to Clients (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Expenditures Billable to Clients	Expenditures Billable to Clients
	Expenditures billable to clients are primarily comprised of production and media costs that have been incurred but have not yet been billed to clients, as well as fees that have been earned which have not yet been billed to clients. Unbilled amounts are presented in expenditures billable to clients regardless of whether they relate to our fees or production and media costs. A provision is made for unrecoverable costs as deemed appropriate.

Summary_of_Significant_Account9

Summary of Significant Accounting Policies Accounts Payable (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Accounts Payable	Accounts Payable
	Accounts payable includes all operating payables, including those related to all media and production costs. These payables are due within one year.

Recovered_Sheet1

Summary of Significant Accounting Policies Investments (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Investments	Investments
	Our investments in publicly traded companies over which we do not exert a significant influence are classified as available-for-sale. These investments are reported at fair value based on quoted market prices with net unrealized gains and losses reported as a component of accumulated other comprehensive loss. Our non-publicly traded investments and all other publicly traded investments, including investments to fund certain deferred compensation and retirement obligations, are accounted for using the equity method or cost method. We do not disclose the fair value for equity method investments or investments held at cost as it is not practical to estimate fair value since there is no readily available market data and it is cost prohibitive to obtain independent valuations. We regularly review our equity and cost method investments to determine whether a significant event or change in circumstances has occurred that may impact the fair value of each investment. In the event a decline in fair value of an investment occurs, we determine if the decline has been other-than-temporary. We consider our investments strategic and long-term in nature, so we determine if the fair value decline is recoverable within a reasonable period. For our investments, we evaluate fair value based on specific information (valuation methodologies, estimates of appraisals, financial statements, etc.) in addition to quoted market price, if available. We consider all known quantitative and qualitative factors in determining if an other-than-temporary decline in value of an investment has occurred.

Recovered_Sheet2

Summary of Significant Accounting Policies Derivatives (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Derivatives	Derivatives
	We are exposed to market risk related to interest rates, foreign currency rates and certain balance sheet items. From time to time we enter into derivative instruments for risk management purposes, and not for speculative purposes. All derivative instruments are recorded at fair value on our balance sheet. Changes in fair value are immediately included in earnings if the derivatives are not designated as a hedge instrument or if the derivatives do not qualify as effective hedges. For derivatives designated as hedge instruments, we evaluate for hedge accounting both at inception and throughout the hedge period. If a derivative is designated as a fair value hedge, then changes in the fair value of the derivative are offset against the changes in the fair value of the underlying hedged item. If a derivative is designated as a cash flow hedge, then the effective portion of the changes in the fair value of the derivative is recognized as a component of accumulated other comprehensive income and subsequently reclassified to earnings in our Consolidated Statement of Operations in the same period as the underlying hedged transaction affects earnings.

Recovered_Sheet3

Summary of Significant Accounting Policies Property and Equipment (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Property and Equipment	Furniture, equipment, leasehold improvements and buildings are stated at cost, net of accumulated depreciation. Furniture and equipment are depreciated generally using the straight-line method over the estimated useful lives of the related assets, which range from 3 to 7 years for furniture and equipment, 10 to 35 years for buildings and the shorter of the useful life or the remaining lease term for leasehold improvements. Land is stated at cost and is not depreciated.
	We capitalize certain internal and external costs incurred to acquire or create internal use software, principally related to our enterprise resource planning (“ERP”) systems. Our ERP systems are stated at cost, net of accumulated amortization and are amortized using the straight-line method over 10 years. All other internal use computer software are stated at cost, net of accumulated amortization and are amortized using the straight-line method over the estimated useful lives of the related assets, which range from 3 to 7 years.

Recovered_Sheet4

Summary of Significant Accounting Policies Goodwill and Other Intangible Assets (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets
	We account for our business combinations using the acquisition accounting method, which requires us to determine the fair value of net assets acquired and the related goodwill and other intangible assets. Determining the fair value of assets acquired and liabilities assumed requires management's judgment and involves the use of significant estimates, including projections of future cash inflows and outflows, discount rates, asset lives and market multiples. Considering the characteristics of advertising, specialized marketing and communication services companies, our acquisitions usually do not have significant amounts of tangible assets, as the principal asset we typically acquire is creative talent. As a result, a substantial portion of the purchase price is allocated to goodwill and other intangible assets.
	We review goodwill and other intangible assets with indefinite lives not subject to amortization as of October 1st each year and whenever events or significant changes in circumstances indicate that the carrying value may not be recoverable. We evaluate the recoverability of goodwill at a reporting unit level. We have 13 reporting units that were subject to the 2014 annual impairment testing. Our annual impairment review as of October 1, 2014 did not result in an impairment charge for any of our reporting units.
	During 2012, we adopted new authoritative guidance for goodwill and indefinite-lived intangible assets, respectively, which permits an entity to first assess qualitative factors to determine whether it is “more likely than not” that the goodwill or indefinite-lived intangible assets are impaired. Qualitative factors to consider may include macroeconomic conditions, industry and market considerations, cost factors that may have a negative effect on earnings, financial performance, and other relevant entity-specific events such as changes in management, key personnel, strategy or clients, as well as pending litigation. If, after assessing the totality of events or circumstances such as those described above, an entity determines that it is "more likely than not" that the goodwill or indefinite-lived intangible asset is impaired, then the entity is required to determine the fair value and perform the quantitative impairment test by comparing the fair value with the carrying value. Otherwise, no additional testing is required.
	For reporting units not included in the qualitative assessment, or for any reporting units identified in the qualitative assessment as "more likely than not" that the fair value is less than its carrying value, the first step of the quantitative impairment test is performed. For our annual impairment test, we compare the respective fair value of our reporting units' equity to the carrying value of their net assets. The first step is a comparison of the fair value of each reporting unit to its carrying value, including goodwill. The sum of the fair values of all our reporting units is reconciled to our current market capitalization plus an estimated control premium. Goodwill allocated to a reporting unit whose fair value is equal to or greater than its carrying value is not impaired, and no further testing is required. Should the carrying amount for a reporting unit exceed its fair value, then the first step of the quantitative impairment test is failed and the magnitude of any goodwill impairment is determined under the second step, which is a comparison of the implied fair value of a reporting unit's goodwill to its carrying value. The implied fair value of goodwill is the excess of the fair value of the reporting unit over its carrying value, excluding goodwill. Impaired goodwill is written down to its implied fair value with a charge to expense in the period the impairment is identified.
	The fair value of a reporting unit for 2014 and 2013 was estimated using a combination of the income approach, which incorporates the use of the discounted cash flow method, and the market approach, which incorporates the use of earnings and revenue multiples based on market data.
	We review intangible assets with definite lives subject to amortization whenever events or circumstances indicate that a carrying amount of an asset may not be recoverable. Recoverability of these assets is determined by comparing the carrying value of these assets to the estimated undiscounted future cash flows expected to be generated by these assets. These assets are impaired when their carrying value exceeds their fair value. Impaired intangible assets with definite lives subject to amortization are written down to their fair value with a charge to expense in the period the impairment is identified. Intangible assets with definite lives are amortized on a straight-line basis with estimated useful lives generally between 7 and 15 years. Events or circumstances that might require impairment testing include the loss of a significant client, the identification of other impaired assets within a reporting unit, loss of key personnel, the disposition of a significant portion of a reporting unit, significant decline in stock price or a significant adverse change in business climate or regulations.

Recovered_Sheet5

Summary of Significant Accounting Policies Foreign Currencies (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Foreign Currencies	Foreign Currencies
	The functional currency of our foreign operations is generally their respective local currency. Assets and liabilities are translated at the exchange rates in effect at the balance sheet date, and revenues and expenses are translated at the average exchange rates during the period presented. The resulting translation adjustments are recorded as a component of accumulated other comprehensive loss in the stockholders’ equity section of our Consolidated Balance Sheets. Currency transaction gains or losses primarily arising from transactions in currencies other than the functional currency are included in office and general expenses. Foreign currency transactions resulted in a pre-tax loss of $1.4 in 2014 , a pre-tax loss of $0.6 in 2013 and a pre-tax gain $1.2 in 2012.
	We monitor the currencies of countries in which we operate in order to determine if the country should be considered a highly inflationary environment. A currency is determined to be highly inflationary when there is cumulative inflation of approximately 100% or more over a three-year period. If this occurs the functional currency of that country would be changed to our reporting currency, the U.S. Dollar, and foreign exchange gains or losses would be recognized on all monetary transactions, assets and liabilities in currencies other than the U.S. Dollar until the currency is no longer considered highly inflationary.

Recovered_Sheet6

Summary of Significant Accounting Policies Income Taxes (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Income Taxes	Income Taxes
	The provision for income taxes includes U.S. federal, state, local and foreign taxes. Income taxes are accounted for under the liability method. Deferred tax assets and liabilities are recognized for the estimated future tax consequences of temporary differences between the financial statement carrying amounts and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the year in which the temporary differences are expected to be reversed. We evaluate the realizability of our deferred tax assets and establish a valuation allowance when it is “more likely than not” that all or a portion of the deferred tax assets will not be realized. We evaluate our tax positions using the “more likely than not” recognition threshold and then apply a measurement assessment to those positions that meet the recognition threshold. The factors used in assessing valuation allowances include all available evidence, such as past operating results, estimates of future taxable income and the feasibility of tax planning strategies.We have established tax reserves that we believe to be adequate in relation to the potential for additional assessments in each of the jurisdictions in which we are subject to taxation. We regularly assess the likelihood of additional tax assessments in those jurisdictions and adjust our reserves as additional information or events require.

Recovered_Sheet7

Summary of Significant Accounting Policies Redeemable Noncontrolling Interests (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Redeemable Noncontrolling Interests	Redeemable Noncontrolling Interests
	Many of our acquisitions include provisions under which the noncontrolling equity owners can require us to purchase additional interests in a subsidiary at their discretion. Payments for these redeemable noncontrolling interests may be contingent on projected operating performance and satisfying other conditions specified in the related agreements. These payments are also subject to revision in accordance with the terms of the agreements. We record these redeemable noncontrolling interests in “mezzanine equity” in our Consolidated Balance Sheets. Each reporting period, redeemable noncontrolling interests are reported at their estimated redemption value, but not less than their initial fair value. Any adjustment to the redemption value above initial value prior to exercise will also impact retained earnings or additional paid-in capital, but will not impact net income. Adjustments as a result of currency translation will affect the redeemable noncontrolling interest balance, but do not impact retained earnings or additional paid-in capital.

Recovered_Sheet8

Summary of Significant Accounting Policies Earnings Per Share (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Earnings Per Share	Earnings Per Share (“EPS”)
	Basic EPS available to IPG common stockholders equals net income available to IPG common stockholders divided by the weighted-average number of common shares outstanding for the applicable period. Diluted EPS equals net income available to IPG common stockholders adjusted to exclude, if dilutive, preferred stock dividends, interest expense related to potentially dilutive securities calculated using the effective interest rate method and the benefit from the preferred stock repurchased, divided by the weighted-average number of common shares outstanding, plus any additional common shares that would have been outstanding if potentially dilutive shares had been issued.
	Diluted EPS reflect the potential dilution that would occur if certain potentially dilutive securities or debt obligations were exercised or converted into common stock. The potential issuance of common stock is assumed to occur at the beginning of the year (or at the time of issuance of the potentially dilutive instrument, if later) and the incremental shares are included using the treasury stock or “if-converted” method. The proceeds utilized in applying the treasury stock method consist of the amount, if any, to be paid upon exercise and, as it relates to stock-based compensation, the amount of compensation cost attributed to future service not yet recognized and any tax benefits credited to additional paid-in-capital related to the exercise. These proceeds are then assumed to be used to purchase common stock at the average market price of our stock during the period. The incremental shares (difference between the shares assumed to be issued and the shares assumed to be purchased), to the extent they would have been dilutive, are included in the denominator of the diluted EPS calculation.
	We may be required to calculate basic EPS using the two-class method, as a result of our redeemable noncontrolling interests. To the extent that the redemption value increases and exceeds the then-current fair value of a redeemable noncontrolling interest, net income available to IPG common stockholders (used to calculate EPS) could be negatively impacted by that increase, subject to certain limitations. The partial or full recovery of any reductions to net income available to IPG common stockholders (used to calculate EPS) is limited to any cumulative prior-period reductions. For the years ended December 31, 2014, 2013 and 2012, there was no impact to EPS for adjustments related to our redeemable noncontrolling interests.

Recovered_Sheet9

Summary of Significant Accounting Policies Pension and Postretirement Benefits (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Pension and Postretirement Benefits	Pension and Postretirement Benefits
	We have pension and postretirement benefit plans covering certain domestic and international employees. We use various actuarial methods and assumptions in determining our net pension and postretirement benefit costs and obligations, including the discount rate used to determine the present value of future benefits, expected long-term rate of return on plan assets and healthcare cost trend rates. The overfunded or underfunded status of our pension and postretirement benefit plans is recorded on our Consolidated Balance Sheet.

Recovered_Sheet10

Summary of Significant Accounting Policies Stock-Based Compensation (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Stock-Based Compensation	Stock-Based Compensation
	Compensation costs related to share-based transactions, including employee stock options, are recognized in the Consolidated Financial Statements based on fair value. Stock-based compensation expense is generally recognized ratably over the requisite service period based on the estimated grant-date fair value, net of estimated forfeitures.

Recovered_Sheet11

Summary of Significant Accounting Policies Treasury Stock (Policies)	12 Months Ended
	Dec. 31, 2014
Treasury Stock [Abstract]
Treasury Stock [Text Block]	Treasury Stock
	We account for repurchased common stock under the cost method and include such treasury stock as a component of our Consolidated Statements of Stockholders' Equity. Upon retirement, we reduce common stock for the par value of the shares being retired and the excess of the cost of the shares over par value as a reduction to additional paid-in capital ("APIC"), to the extent there is APIC in the same class of stock, and any remaining amount to retained earnings. These retired shares remain authorized but unissued.
	In November 2014, we retired 121.9 shares of our treasury stock, which resulted in a reduction in common stock of $12.2, treasury stock of $1,522.4 and APIC of $1,510.2. There was no effect on total stockholders' equity as a result of the retirement.

Debt_and_Credit_Agreements_Tab

Debt and Credit Agreements (Tables)	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments [Table Text Block]	A summary of the carrying amounts and fair values of our long-term debt is listed below.
		Effective			December 31,
		Interest Rate			2014								2013
					Book				Fair				Book				Fair
					Value				Value 1				Value				Value
	6.25% Senior Unsecured Notes due 2014	6.29	%		$	0			$	0			$	351.3			$	365.6
	2.25% Senior Notes due 2017 (less unamortized	2.3	%		299.6				301.2				299.4				293
	discount of $0.4)
	4.00% Senior Notes due 2022 (less unamortized	4.13	%		247.7				255.2				247.4				241.6
	discount of $2.3)
	3.75% Senior Notes due 2023 (less unamortized	4.32	%		498.8				499.8				498.6				467.3
	discount of $1.2)
	4.20% Senior Notes due 2024 (less unamortized	4.24	%		499.1				509.8				0				0
	discount of $0.9)
	Other notes payable and capitalized leases				80.4				80.4				86.7				87.8
	Total long-term debt				1,625.60								1,483.40
	Less: current portion 2				2.1								353.6
	Long-term debt, excluding current portion				$	1,623.50							$	1,129.80
	1	See Note 11 for information on the fair value measurement of our long-term debt.
	2	We included our 6.25% Senior Unsecured Notes due 2014 (the "6.25% Notes") in the current portion of long-debt on our December 31, 2013 Consolidated Balance Sheet because the 6.25% Notes were scheduled to mature on November 15, 2014. We redeemed the 6.25% Notes prior to their scheduled maturity during the second quarter of 2014.
Schedule of Maturities of Long-term Debt [Table Text Block]	Annual maturities are scheduled as follows based on the book value as of December 31, 2014.
	2015	$	2.1
	2016	2.2
	2017	324.2
	2018	2
	2019	2
	Thereafter	1,293.10
	Total long-term debt	$	1,625.60
Schedule of Line of Credit Facilities [Table Text Block]	A summary of our credit facilities is presented below.
			December 31,
			2014																2013
			Total				Amount				Letters of				Total				Total		Amount		Letters of		Total
			Facility				Outstanding				Credit				Available				Facility		Outstanding		Credit		Available
	Committed credit agreement		$	1,000.00			$	0			$	16			$	984			$	1,000.00	$	0	$	14.3	$	985.7
	Uncommitted credit agreements		$	740.3			$	107.2			$	3.9			$	629.2			$	700.2	$	179.1	$	4.2	$	516.9
Schedule of Financial Covenants in Credit Agreement [Table Text Block]	The financial covenants in the Credit Agreement require that we maintain the following financial covenants listed below as of December 31, 2014 and thereafter.
	Interest coverage ratio (not less than): 1		5.00x
	Leverage ratio (not greater than): 2		3.25x
	1	The interest coverage ratio is defined as EBITDA, as defined in the Credit Agreement, to net interest expense.
	2	The leverage ratio is defined as debt as of the last day of such fiscal quarter to EBITDA, as defined in the Credit Agreement, for the four quarters then ended.

Acquisitions_Tables

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Redeemable Noncontrolling Interest	The following table presents changes in our redeemable noncontrolling interests.
		Years ended December 31,
		2014			2013			2012
	Balance at beginning of period	$	249.1		$	227.2		$	243.4
	Change in related noncontrolling interest balance	3.2			4.6			1.1
	Changes in redemption value of redeemable noncontrolling interests:
	Additions	18.7			16.2			0
	Redemptions and reclassifications	(7.9		)	(2.3		)	(14.2		)
	Redemption value adjustments	(5.7		)	3.4			(3.1		)
	Balance at end of period	$	257.4		$	249.1		$	227.2
Cash Paid For Current And Prior Years' Acquisitions	Details of cash paid for current and prior years' acquisitions are listed below.
		Years ended December 31,
		2014			2013			2012
	Cost of investment: current-year acquisitions	$	97.3		$	67.7		$	156.8
	Cost of investment: prior-year acquisitions	14			28.5			40.6
	Less: net cash acquired	(29.9		)	(7.1		)	(14.8		)
	Total cost of investment	81.4			89.1			182.6
	Operating expense 1	3.4			2			3.2
	Total cash paid for acquisitions 2	$	84.8		$	91.1		$	185.8
	1	Represents cash payments made that were either in excess of the contractual value or contingent upon the future employment of the former owners of acquired companies.
	2	Of the total cash paid, $13.6, $27.6 and $37.1 for the years ended December 31, 2014, 2013 and 2012, respectively, are classified under the financing section of the Consolidated Statements of Cash Flows within acquisition-related payments. These amounts relate to increases in our ownership interests in our consolidated subsidiaries as well as deferred payments for acquisitions. Of the total cash paid, $67.8, $61.5 and $145.5 for the years ended December 31, 2014, 2013 and 2012, respectively, are classified under the investing section of the Consolidated Statements of Cash Flows within acquisitions, net of cash acquired. These amounts relate to initial payments for new transactions.

Supplementary_Data_Tables

Supplementary Data (Tables)	12 Months Ended
	Dec. 31, 2014
Supplementary Data [Abstract]
Valuation and Qualifying Accounts - Allowance for Uncollectible Accounts Receivable	Valuation and Qualifying Accounts – Allowance for Uncollectible Accounts Receivable
		Years ended December 31,
		2014				2013				2012
	Balance at beginning of period	$	64.9			$	59			$	55.4
	Charges to costs and expenses	7.4				12.6				16.3
	Reversals to other accounts1	0.1				0.7				(0.2		)
	Deductions:
	Dispositions	0				0				(0.4		)
	Uncollectible accounts written off	(8.1		)		(7.2		)		(12.6		)
	Foreign currency translation adjustment	(4.8		)		(0.2		)		0.5
	Balance at end of period	$	59.5			$	64.9			$	59
	1	Amounts primarily relate to miscellaneous other amounts and reclassifications.
Property and Equipment	Property and Equipment
			December 31,
			2014				2013
	Furniture and equipment		$	640.7			$	661.6
	Leasehold improvements		594				611.4
	Internal use computer software		296.2				269.1
	Land and buildings		87.3				109.6
			1,618.20				1,651.70
	Less: accumulated depreciation		(1,070.0		)		(1,111.7		)
	Total property and equipment, net		548.2				$	540
Accrued Liabilities	Accrued Liabilities
	The following table presents the components of accrued liabilities.
		December 31,
		2014				2013
	Salaries, benefits and related expenses	$	510.6			$	467.2
	Office and related expenses	51.5				56.9
	Acquisition obligations	88.1				12.8
	Interest	18.3				16
	Restructuring and other reorganization-related	5.5				46.7
	Other	122				118.8
	Total accrued liabilities	$	796			$	718.4
Other (Expense) Income, net	Other (Expense) Income, net
	Results of operations include certain items that are not directly associated with our revenue-producing operations.
		Years ended December 31,
		2014				2013				2012
	Loss on early extinguishment of debt	$	(10.4	)		$	(45.2	)		$	0
	Gains on sales of businesses and investments, net	0.8				1.5				88.2
	Vendor discounts and credit adjustments	3.3				8.6				15.3
	Other (expense) income, net	(3.9		)		2.8				(3.0		)
	Total other (expense) income, net	$	(10.2	)		$	(32.3	)		$	100.5
Share Repurchase Program	The following table presents our share repurchase activity under our share repurchase programs.
		Years ended December 31,
		2014				2013				2012
	Number of shares repurchased	14.9				31.8				32.7
	Aggregate cost, including fees	$	275.1			$	481.8			$	350.5
	Average price per share, including fees	$	18.41			$	15.17			$	10.72
Supplemental Cash Flow Information	Supplemental Cash Flow Information
		Years ended December 31,
		2014				2013				2012
	Cash paid for interest	$	78.1			$	110.7			$	130.6
	Cash paid for income taxes, net of refunds 1	103.9				111.8				95.7
	1	Refunds of $21.3, $15.0 and $23.5 were received for the years ended December 31, 2014, 2013 and 2012, respectively.

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Basic and Diluted Earnings Per Common Share Available to IPG Common Stockholders	The following sets forth basic and diluted earnings per common share available to IPG common stockholders.
		Years ended December 31,
		2014			2013			2012
	Net income available to IPG common stockholders - basic	$	477.1		$	259.2		$	435.1
	Adjustments: Effect of dilutive securities
	Interest on 4.25% Notes 1	0			0			0.3
	Interest on 4.75% Notes 1	0			0.8			4.1
	Dividends on preferred stock	0			0			11.6
	Net income available to IPG common stockholders - diluted	$	477.1		$	260		$	451.1
	Weighted-average number of common shares outstanding - basic	419.2			421.1			432.5
	Add: Effect of dilutive securities
	Restricted stock, stock options and other equity awards	6.2			5.2			7.2
	4.25% Notes 1	0			0			7.9
	4.75% Notes 1	0			3.3			16.9
	Preferred stock outstanding 2	0			0			16.9
	Weighted-average number of common shares outstanding - diluted	425.4			429.6			481.4
	Earnings per share available to IPG common stockholders - basic	$	1.14		$	0.62		$	1.01
	Earnings per share available to IPG common stockholders - diluted	$	1.12		$	0.61		$	0.94
	1	We retired all of our outstanding 4.75% Notes and 4.25% Convertible Senior Notes due 2023 in March 2013 and March 2012, respectively. See Note 2 for further information. For purposes of calculating diluted earnings per share for 2013 and 2012, the potentially dilutive shares are pro-rated based on the period they were outstanding.
	2	We converted all of our 5 1/4% Series B Cumulative Convertible Perpetual Preferred Stock (the "Series B Preferred Stock") into common stock in October 2013. For purposes of calculating diluted earnings per share for 2013, the potentially dilutive shares would have been pro-rated based on the period they were outstanding but were antidilutive.
Potential Shares Excluded from Diluted Earnings Per Share Calculation	The following table presents the potential shares excluded from the diluted earnings per share calculation because the effect of including these potential shares would be antidilutive.
		Years ended December 31,
		2014		2013			2012
	Preferred Stock Outstanding 1	0		13.7			0
	Securities excluded from the diluted earnings per share calculation
	because the exercise price was greater than the average market price:
	Stock options 2	0		0.1			6.6
	1	We converted all of our Series B Preferred Stock into common stock in October 2013. For purposes of calculating diluted earnings per share for 2013, the potentially dilutive shares would have been pro-rated based on the period they were outstanding but were antidilutive.
	2	These options were outstanding at the end of the respective periods. In any period in which the exercise price is less than the average market price, these options have the potential to be dilutive, and application of the treasury stock method would reduce this amount.

Intangible_Assets_Tables

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in Carrying Value of Goodwill	The changes in the carrying value of goodwill for our segments, IAN and CMG, for the years ended December 31, 2014 and 2013 are listed below.
			IAN			CMG			Total 1
	Balance as of December 31, 2012		$	3,074.60		$	506		$	3,580.60
	Current year acquisitions		58.8			16.5			75.3
	Foreign currency and other		(24.1		)	(2.8		)	(26.9		)
	Balance as of December 31, 2013		$	3,109.30		$	519.7		$	3,629.00
	Current year acquisitions		95.2			40.9			136.1
	Foreign currency and other		(83.7		)	(12.2		)	(95.9		)
	Balance as of December 31, 2014		$	3,120.80		$	548.4		$	3,669.20
	1	For all periods presented we have not recorded a goodwill impairment charge.
Summary of Other Intangible Assets	The following table provides a summary of other intangible assets, which are included in other assets on our Consolidated Balance Sheets.
			December 31,
			2014									2013
			Gross Amount			Accumulated			Net Amount			Gross Amount		Accumulated			Net Amount
						Amortization								Amortization
	Customer lists		$	255.8		$	(139.3	)	$	116.5		$	228.1	$	(119.8	)	$	108.3
	Trade names		71			(22.8		)	48.2			64.5		(19.2		)	45.3
	Other		14.1			(3.8		)	10.3			14		(3.8		)	10.2
	Total		$	340.9		$	(165.9	)	$	175		$	306.6	$	(142.8	)	$	163.8
Estimated future amortization of other intangible assets	The estimated annual amortization expense for other intangible assets for the next five years as of December 31, 2014 is listed below.
			2015			2016			2017			2018		2019
	Estimated amortization expense		$	37.2		$	34.7		$	22.7		$	12.8	$	12.1

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Schedule of Income before Income Tax, Domestic and Foreign	The components of income before income taxes are listed below.
		Years ended December 31,
		2014			2013			2012
	Domestic	$	387.7		$	255.3		$	386.9
	Foreign	333			212.7			287.9
	Total	$	720.7		$	468		$	674.8
Schedule of Components of Provision for Income Taxes	The provision for income taxes is listed below.
		Years ended December 31,
		2014			2013			2012
	U.S. federal income taxes (including foreign withholding taxes):
	Current	$	8		$	46.9		$	9.4
	Deferred	130.7			25.2			118.1
		138.7			72.1			127.5
	State and local income taxes:
	Current	9.7			(14.7		)	17.1
	Deferred	23.8			24.7			25.3
		33.5			10			42.4
	Foreign income taxes:
	Current	115.3			79.6			83.2
	Deferred	(71.0		)	19.5			(39.8		)
		44.3			99.1			43.4
	Total	$	216.5		$	181.2		$	213.3
Schedule of Effective Income Tax Rate Reconciliation	A reconciliation of the effective income tax rate as reflected in our Consolidated Statements of Operations to the U.S. federal statutory income tax rate is listed below.
		Years ended December 31,
		2014			2013			2012
	U.S. federal statutory income tax rate	35		%	35		%	35		%
	Income tax provision at U.S. federal statutory rate	$	252.3		$	163.8		$	236.2
		21.4			6.5			27.3
	Impact of foreign operations, including withholding taxes	1.7			30.5			8.4
	Change in net valuation allowance 1	(66.0		)	3.2			(57.3		)
	Worthless securities deduction	0			(22.2		)	0
	Increases in unrecognized tax benefits, net	5.2			0			24.1
	Other	1.9			(0.6		)	(25.4		)
	Provision for income taxes	$	216.5		$	181.2		$	213.3
	Effective income tax rate on operations	30		%	38.7		%	31.6		%
	1	Reflects changes in valuation allowance that impacted the effective income tax rate for each year presented.
Schedule of Deferred Tax Assets and Liabilities	The components of deferred tax assets and liabilities are listed below.
		December 31,
		2014			2013
	Postretirement/post-employment benefits	$	27.4		$	32.5
	Deferred compensation	191.2			187.2
	Pension costs	41.4			31.1
	Basis differences in fixed assets	(38.5		)	(4.1		)
	Rent	45.8			50.7
	Interest	60.9			60.7
	Accruals and reserves	34.8			39.6
	Allowance for doubtful accounts	10.8			10.8
	Basis differences in intangible assets	(412.3		)	(402.2		)
	Investments in equity securities	(2.6		)	48.6
	Tax loss/tax credit carry forwards	404.4			443.6
	Restructuring and other reorganization-related costs	(0.3		)	2.6
	Other	59.2			60.5
	Total deferred tax assets, net	422.2			561.6
	Valuation allowance	(332.2		)	(467.3		)
	Net deferred tax assets	$	90		$	94.3
Summary of Valuation Allowance	The change in the valuation allowance is listed below.
		Years ended December 31,
		2014			2013			2012
	Balance at beginning of period	$	467.3		$	392.9		$	489.9
	(Reversed) charged to costs and expenses	(72.8		)	65.2			(49.5		)
	(Reversed) charged to gross tax assets and other accounts	(62.3		)	9.2			(47.5		)
	Balance at end of period	$	332.2		$	467.3		$	392.9
Schedule of Unrecognized Tax Benefits Activity	The table below summarizes the activity related to our unrecognized tax benefits.
		December 31,
		2014			2013			2012
	Balance at beginning of period	$	219.2		$	194.6		$	161
	Increases as a result of tax positions taken during a prior year	29			8.3			28.2
	Decreases as a result of tax positions taken during a prior year	(16.3		)	(1.9		)	(6.8		)
	Settlements with taxing authorities	(1.1		)	(34.9		)	(0.7		)
	Lapse of statutes of limitation	(4.1		)	(10.6		)	(1.1		)
	Increases as a result of tax positions taken during the current year	11.3			63.7			14
	Balance at end of period	$	238		$	219.2		$	194.6

Restructuring_and_Other_Reorga1

Restructuring and Other Reorganization-Related Charges (Reversals), net (Tables)	12 Months Ended
	Dec. 31, 2014
Restructuring and Related Activities [Abstract]
Restructuring Charges (Reversals) by Type	Restructuring and Other Reorganization-Related Charges (Reversals), net
	The components of restructuring and other reorganization-related charges (reversals), net are listed below.
		Years ended December 31,
		2014			2013			2012
	Severance and termination costs	$	0.1		$	55.9		$	0
	Lease termination costs	0.1			4.2			(1.1		)
	Other exit costs	0			0.5			(0.1		)
	Total restructuring and other reorganization-related charges (reversals), net	$	0.2		$	60.6		$	(1.2	)
Restructuring Liability Activity for 2013 Plan	A summary of the 2013 Plan restructuring liability activity is listed below.
			31-Dec-13			Net Restructuring Charges			Cash Payments			Foreign Currency Translation Adjustment			31-Dec-14
	Severance and termination costs		$	46.5		$	0.1		$	(41.8	)	$	(0.4	)	$	4.4
	Lease termination costs		3.9			0			(1.2		)	(0.1		)	2.6
	Other exit costs		0.5			0			(0.5		)	0			0
	Total		$	50.9		$	0.1		$	(43.5	)	$	(0.5	)	$	7

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Loss, net of tax (Tables)	12 Months Ended
	Dec. 31, 2014
Accumulated Other Comprehensive Loss [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table presents the changes in accumulated other comprehensive loss, net of tax by component.
		Foreign Currency Translation Adjustments				Available-for-Sale Securities				Derivative Instruments			Defined Benefit Pension and Other Postretirement Plans			Total
	Balance as of December 31, 2012	$	(130.1	)		$	0.8			$	(12.7	)	$	(146.0	)	$	(288.0	)
	Other comprehensive (loss) income before reclassifications	(113.0		)		0.8				0			(19.7		)	(131.9		)
	Amount reclassified from accumulated other comprehensive loss, net of tax	(0.6		)		(1.2		)		1			9.5			8.7
	Balance as of December 31, 2013	$	(243.7	)		$	0.4			$	(11.7	)	$	(156.2	)	$	(411.2	)
	Other comprehensive (loss) income before reclassifications	(191.7		)		0.7				(0.6		)	(55.0		)	(246.6		)
	Amount reclassified from accumulated other comprehensive loss, net of tax	(0.9		)		(0.3		)		1.4			20.9			21.1
	Balance as of December 31, 2014	$	(436.3	)		$	0.8			$	(10.9	)	$	(190.3	)	$	(636.7	)
Reclassification out of Accumulated Other Comprehensive Income	Amounts reclassified from accumulated other comprehensive loss, net of tax for the years ended December 31, 2014, 2013 and 2012 are as follows:
			Years ended December 31,
			2014				2013				2012			Affected Line Item in the Consolidated Statements of Operations
	Foreign currency translation adjustments		$	(0.9	)		$	0			$	0		Other (expense) income, net
	Gains (losses) on available-for-sale securities		0				(1.4		)		0.7			Other (expense) income, net
	Losses on derivative instruments		1.9				1.7				0.3			Interest expense
	Amortization of defined benefit pension and postretirement plans items 1		10.5				10.8				8.4
	Tax effect		9.6				(2.4		)		10.3			Provision for income taxes
	Total amount reclassified from accumulated other comprehensive loss, net of tax		$	21.1			$	8.7			$	19.7
	1	These accumulated other comprehensive loss components are included in the computation of net periodic cost. See Note 12 for further information

Incentive_Compensation_Plans_T

Incentive Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2014
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Schedule of Stock-based Compensation Expense	The amount of stock-based compensation expense as reflected in salaries and related expenses in our Consolidated Statement of Operations, and the related tax benefit, are listed below.
		Years ended December 31,
		2014				2013				2012
	Stock options	$	2.1			$	3.7			$	5.4
	Stock-settled awards	10				9.8				14.9
	Cash-settled awards	0.6				1.5				3.9
	Performance-based awards	42.2				29.6				24.5
	Employee stock purchase plan	0.6				0.6				0.6
	Other 1	1.2				0.8				1.1
	Stock-based compensation expense	$	56.7			$	46			$	50.4
	Tax benefit	$	20.6			$	17.6			$	19.7
	1	Represents charges recorded for severance expense related to stock-based compensation awards.
Schedule of Stock Options Activity	The following tables are a summary of stock option activity during 2014.
			Options			Weighted-				Weighted-		Aggregate
						Average				Average		Intrinsic
						Exercise Price				Remaining		Value
						(per option)				Contractual Term
										(in years)
	Stock options outstanding as of January 1, 2014		9.4			$10.24
	Exercised		(1.7	)		12.01
	Expired		(0.3	)		14.16
	Stock options outstanding as of December 31, 2014		7.4			9.7				4.1		$	82.1
	Stock options vested and expected to vest as of December 31, 2014		7.4			9.69				4.1		$	82
	Stock options exercisable as of December 31, 2014		6.8			9.44				3.7		$	76.7
			Options			Weighted-				Weighted-		Aggregate
						Average Grant				Average		Intrinsic
						Date Fair Value				Remaining		Value
						(per option)				Contractual Term
										(in years)
	Non-vested as of January 1, 2014		1.5			$	4.21
	Vested		(0.9	)		4.25
	Non-vested as of December 31, 2014		0.6			4.16				7.9		$	3.8
Summary of Stock Options Assumptions	The fair value of each option grant has been estimated with the following weighted-average assumptions.
			Years ended December 31,
			2014			2013			2012
	Expected volatility 1		—			40.2	%		43.8	%
	Expected term (years) 2		—			6.9			6.8
	Risk free interest rate 3		—			1.3	%		1.3	%
	Expected dividend yield 4		—			2.4	%		2.1	%
	1	The expected volatility used to estimate the fair value of stock options awarded is based on a blend of: (i) historical volatility of our common stock for periods equal to the expected term of our stock options and (ii) implied volatility of tradable forward put and call options to purchase and sell shares of our common stock.
	2	The estimate of our expected term is based on the average of (i) an assumption that all outstanding options are exercised upon achieving their full vesting date and (ii) an assumption that all outstanding options will be exercised at the midpoint between the current date (i.e., the date awards have ratably vested through) and their full contractual term. In determining the estimate, we considered several factors, including the historical option exercise behavior of our employees and the terms and vesting periods of the options.
	3	The risk free rate is determined using the implied yield currently available for zero-coupon U.S. government issuers with a remaining term equal to the expected term of the options.
	4	The expected dividend yield is calculated based on an annualized dividend of $0.38 per share in 2014, $0.30 per share in 2013 and $0.24 per share in 2012.
Stock-based Compensation, Grants in Period, Weighted Average Grant Date Fair Value	Stock-based compensation awards expected to be settled in cash have been classified as liabilities in our Consolidated Balance Sheets as of December 31, 2014 and 2013.
			Years ended December 31,
			2014				2013				2012
	Stock-Settled Awards:
	Awards granted		1.2				1.1				0.9
	Weighted-average grant-date fair value (per award)		$	17.77			$	13.51			$	11.43
	Total fair value of vested awards distributed		$	12.6			$	35.4			$	63.5
	Cash-Settled Awards:
	Awards granted		0.1				0.1				0.1
	Weighted-average grant-date fair value (per award)		$	18.2			$	16.35			$	10.94
	Total fair value of vested awards distributed		$	0.6			$	5.4			$	11.1
	Performance-Based Awards:
	Awards granted		3.5				1.5				1.8
	Weighted-average grant-date fair value (per award)		$	16.56			$	11.97			$	10.61
	Total fair value of vested awards distributed		$	15.3			$	0.2			$	11.5
Schedule of Nonvested Stock Activity	A summary of the activity of our non-vested stock-settled awards, cash-settled awards, and performance-based awards during 2014 is presented below (performance-based awards are shown at 100% of the shares originally granted).
			Stock-Settled Awards								Cash-Settled Awards					Performance-Based Awards
			Awards				Weighted-				Awards			Weighted-		Awards			Weighted-
							Average							Average					Average
							Grant-Date							Grant-Date					Grant-Date
							Fair Value							Fair Value					Fair Value
							(per award)							(per award)					(per award)
	Non-vested as of January 1, 2014		1.9				$	12.54			0.1			$	12.03	4.1			$	11.71
	Granted		1.2				17.77				0.1			18.2		3.5			16.56
	Vested		(0.8		)		12.15				(0.1		)	8.36		(0.9		)	12.24
	Forfeited		(0.1		)		12.53				0			0		(0.9		)	12.76
	Non-vested as of December 31, 2014		2.2				15.47				0.1			16.99		5.8			14.39
	Total unrecognized compensation expense remaining		$	14.3							$	1.4				$	58.1
	Weighted-average years expected to be recognized over		1.6								2					2

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Fair Value of Pension Plan Assets	The following table presents the fair value of our domestic and foreign pension plan assets as of December 31, 2014 and 2013, and indicates the fair value hierarchy of the valuation techniques utilized to determine such fair value. See Note 11 for a description of the fair value hierarchy.
		December 31, 2014														December 31, 2013
	Asset Class	Level 1				Level 2			Level 3				Total			Level 1		Level 2		Level 3		Total
	Investment funds	$	18.8			$	372.6		$	40.1			$	431.5		$	22.2	$	359.1	$	25.4	$	406.7
	Insurance contracts	0				19.3			0				19.3			0		22		0		22
	Limited partnerships	0				0			32.1				32.1			0		0		36.1		36.1
	Other	42.4				1.4			0.3				44.1			40.2		2.5		0.6		43.3
	Total	$	61.2			$	393.3		$	72.5			$	527		$	62.4	$	383.6	$	62.1	$	508.1
Assets and liabilities measured at fair value on a recurring basis	The following tables present information about our financial instruments measured at fair value on a recurring basis as of December 31, 2014 and 2013, and indicates the fair value hierarchy of the valuation techniques utilized to determine such fair value.
		December 31, 2014														Balance Sheet Classification
		Level 1				Level 2			Level 3				Total
	Assets
	Cash equivalents	$	901.4			$	0		$	0			$	901.4		Cash and cash equivalents
	Short-term marketable securities	6.6				0			0				6.6			Marketable securities
	Long-term investments	0.5				0			0				0.5			Other assets
	Total	$	908.5			$	0		$	0			$	908.5
	As a percentage of total assets	7.1		%		0		%	0		%		7.1		%
	Liabilities
	Mandatorily redeemable noncontrolling interests 1	$	0			$	0		$	32.8			$	32.8
		December 31, 2013														Balance Sheet Classification
		Level 1				Level 2			Level 3				Total
	Assets
	Cash equivalents	$	761.2			$	0		$	0			$	761.2		Cash and cash equivalents
	Short-term marketable securities	5.3				0			0				5.3			Marketable securities
	Long-term investments	1.6				0			0				1.6			Other assets
	Total	$	768.1			$	0		$	0			$	768.1
	As a percentage of total assets	6		%		0		%	0		%		6		%
	Liabilities
	Mandatorily redeemable noncontrolling interests 1	$	0			$	0		$	27			$	27
	1	Relates to unconditional obligations to purchase additional noncontrolling equity shares of consolidated subsidiaries. Fair value measurement of the obligation was based upon the amount payable as if the forward contracts were settled. The amount redeemable within the next twelve months is classified in accrued liabilities; any interests redeemable thereafter are classified in other non-current liabilities.
Assets and liabilities measured at fair value on recurring basis - level 3 reconciliation	The following table presents additional information about financial instruments measured at fair value on a recurring basis and for which we utilize Level 3 inputs to determine fair value.
			Years ended December 31,
	Liabilities		2014				2013
	Mandatorily redeemable noncontrolling interests -		$	27			$	25.3
	Balance at beginning of period
	Level 3 additions		5.6				0.2
	Level 3 reductions		(0.8		)		0
	Realized losses included in net income		1				1.5
	Foreign currency translation		0				0
	Mandatorily redeemable noncontrolling interests -		$	32.8			$	27
	Balance at end of period
Assets and liabilities measured at fair value on a nonrecurring	The following table presents information about our financial instruments that are not measured at fair value on a recurring basis as of December 31, 2014, and indicates the fair value hierarchy of the valuation techniques utilized to determine such fair value.
		December 31, 2014
		Level 1				Level 2			Level 3			Total
	Total long-term debt	$	0			$	1,566.00		80.4			$	1,646.40

Tables

(Tables)	12 Months Ended
	Dec. 31, 2014
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Schedule of Defined Benefit Plans Disclosures	The change in the benefit obligation, the change in plan assets, the funded status and amounts recognized for the domestic pension plan, the significant foreign pension plans and the domestic postretirement benefit plan are listed below.
		Domestic								Foreign							Domestic Postretirement
		Pension Plan								Pension Plans							Benefit Plan
	December 31,	2014				2013				2014			2013				2014				2013
	Benefit Obligation
	Projected benefit obligation as of January 1	$	133.1			$	140.6			$	569.9		$	532.4			$	37.9			$	46.6
	Service cost	0				0				10.3			9.9				0.1				0.1
	Interest cost	6.2				5.5				23.4			21.7				1.7				1.6
	Benefits paid	(10.4		)		(10.4		)		(24.1		)	(23.8		)		(5.6		)		(6.4		)
	Plan participant contributions	0				0				0.6			0.5				1.5				1.7
	Actuarial losses (gains)	18				(2.6		)		55.7			25				4.4				(5.7		)
	Settlements and curtailments	0				0				(4.0		)	(3.1		)		0				0
	Foreign currency effect	0				0				(42.8		)	8.1				0				0
	Other	0				0				0.5			(0.8		)		(0.5		)		0
	Projected benefit obligation as of December 31	$	146.9			$	133.1			$	589.5		$	569.9			$	39.5			$	37.9
	Fair Value of Plan Assets
	Fair value of plan assets as of January 1	$	109.6			$	115.7			$	398.5		$	381.7			$	0			$	0
	Actual return on plan assets	9.6				3.8				44.7			19.5				0				0
	Employer contributions	2.7				0.5				25.7			18.3				4.1				4.7
	Plan participant contributions	0				0				0.6			0.5				1.5				1.7
	Benefits paid	(10.4		)		(10.4		)		(24.1		)	(23.8		)		(5.6		)		(6.4		)
	Settlements	0				0				(4.0		)	(2.7		)		0				0
	Foreign currency effect	0				0				(25.9		)	5				0				0
																					0
	Fair value of plan assets as of December 31	$	111.5			$	109.6			$	415.5		$	398.5			$	0			$	0
	Funded status of the plans at December 31	$	(35.4	)		$	(23.5	)		$	(174.0	)	$	(171.4	)		$	(39.5	)		$	(37.9	)
		Domestic								Foreign							Domestic Postretirement
		Pension Plan								Pension Plans							Benefit Plan
	December 31,	2014				2013				2014			2013				2014				2013
	Amounts recognized in Consolidated Balance Sheets
	Non-current asset	$	0			$	0			$	8.3		$	8			$	0			$	0
	Current liability	0				0				(8.0		)	(7.6		)		(4.0		)		(4.2		)
	Non-current liability	(35.4		)		(23.5		)		(174.3		)	(171.8		)		(35.5		)		(33.7		)
	Net liability recognized	$	(35.4	)		$	(23.5	)		$	(174.0	)	$	(171.4	)		$	(39.5	)		$	(37.9	)
	Accumulated benefit obligation	$	146.9			$	133.1			$	566.2		$	540.9
	Amounts recognized in Accumulated Other Comprehensive Loss, net
	Net actuarial loss (gain)	$	56.1			$	47			$	161		$	141			$	2.9			$	(1.5	)
	Prior service cost (credit)	0				0				1.1			1.5				(0.4		)		(0.1		)
	Transition obligation	0				0				0			0				0				0
	Total amount recognized	$	56.1			$	47			$	162.1		$	142.5			$	2.5			$	(1.6	)
	In 2015, we estimate that we will recognize $8.2 and $4.6 of net actuarial losses from accumulated other comprehensive loss, net into net periodic cost related to our domestic pension plan and significant foreign pension plans, respectively.
		Domestic								Foreign Pension Plans
		Pension Plan
	December 31,	2014				2013				2014			2013
	Pension plans with underfunded or unfunded accumulated benefit obligation
	Aggregate projected benefit obligation	$	146.9			$	133.1			$	577.1		$	553.2
	Aggregate accumulated benefit obligation	146.9				133.1				559.5			528.7
	Aggregate fair value of plan assets	111.5				109.6				395.8			374.7
Schedule of Net Benefit Costs	The components of net periodic benefit cost and key assumptions are listed below.
		Domestic Pension Plan											Foreign Pension Plans											Domestic Postretirement Benefit Plan
	Years ended December 31,	2014				2013				2012			2014				2013				2012			2014			2013			2012
	Service cost	$	0			$	0			$	0		$	10.3			$	9.9			$	10.2		$	0.1		$	0.1		$	0.2
	Interest cost	6.2				5.5				6.3			23.4				21.7				21.9			1.7			1.6			2.3
	Expected return on plan assets	(7.3		)		(7.7		)		(7.7		)	(24.7		)		(19.2		)		(18.2		)	0			0			0
	Settlement and curtailment losses (gains)	0				0				0			0.5				(0.1		)		0.7			0			0			0
	Amortization of:
	Transition obligation	0				0				0			0				0				0			0			0			0.2
	Prior service cost (credit)	0				0				0			0.2				0.2				0.2			(0.2		)	(0.1		)	(0.1		)
	Unrecognized actuarial losses	6.6				7.9				6.4			3.4				2.8				1			0			0			0
	Net periodic cost	$	5.5			$	5.7			$	5		$	13.1			$	15.3			$	15.8		$	1.6		$	1.6		$	2.6
	Assumptions
		Domestic Pension Plan									Foreign Pension Plans								Domestic Postretirement Benefit Plan
	Years ended December 31,	2014			2013			2012			2014		2013			2012			2014			2013		2012
	Net periodic cost
	Discount rate	4.85	%		4	%		5	%		4.29	%	4.32	%		5	%		4.85	%		4	%	5	%
	Rate of compensation increase	N/A			N/A			N/A			3.97	%	3.57	%		3.66	%		N/A			N/A		N/A
	Expected return on plan assets	7	%		7	%		7.25	%		6.18	%	5.24	%		5.02	%		N/A			N/A		N/A
	Benefit obligation
	Discount rate	4.15	%		4.85	%		4	%		3.41	%	4.29	%		4.32	%		4	%		4.85	%	4	%
	Rate of compensation increase	N/A			N/A			N/A			2.98	%	3.97	%		3.57	%		N/A			N/A		N/A
	Health care cost trend rate assumed for next year
	Initial rate (weighted-average)																		7	%		7.5	%	8	%
	Year ultimate rate is reached																		2019			2019		2019
	Ultimate rate																		5	%		5	%	5	%
Fair Value of Pension Plan Assets	The following table presents the fair value of our domestic and foreign pension plan assets as of December 31, 2014 and 2013, and indicates the fair value hierarchy of the valuation techniques utilized to determine such fair value. See Note 11 for a description of the fair value hierarchy.
		December 31, 2014															December 31, 2013
	Asset Class	Level 1				Level 2				Level 3			Total				Level 1				Level 2			Level 3			Total
	Investment funds	$	18.8			$	372.6			$	40.1		$	431.5			$	22.2			$	359.1		$	25.4		$	406.7
	Insurance contracts	0				19.3				0			19.3				0				22			0			22
	Limited partnerships	0				0				32.1			32.1				0				0			36.1			36.1
	Other	42.4				1.4				0.3			44.1				40.2				2.5			0.6			43.3
	Total	$	61.2			$	393.3			$	72.5		$	527			$	62.4			$	383.6		$	62.1		$	508.1
Schedule of Effect of Significant Unobservable Inputs, Changes in Plan Assets	The following table presents additional information about our domestic and foreign pension plan assets for which we utilize Level 3 inputs to determine fair value.
		Year ended December 31, 2014															Year ended December 31, 2013
		Investment				Limited Partnerships				Other			Total				Investment				Limited Partnerships			Other			Total
		Funds															Funds
	Balance at beginning of period	$	25.4			$	36.1			$	0.6		$	62.1			$	48.2			$	39.8		$	0.3		$	88.3
	Actual return on assets:
	Assets sold during the year	0.2				0.2				0			0.4				0.6				0			0			0.6
	Assets still held at year end	(0.7		)		(0.3		)		(0.3		)	(1.3		)		1.9				(2.9		)	0.2			(0.8		)
	Net purchases, sales and settlements	15.2				(3.9		)		0			11.3				(25.3		)		(0.8		)	0.1			(26.0		)
	Balance at end of period	$	40.1			$	32.1			$	0.3		$	72.5			$	25.4			$	36.1		$	0.6		$	62.1
Schedule of Allocation of Plan Assets	As of December 31, 2014, the weighted-average target and actual asset allocations relating to our domestic and foreign pension plans' assets are listed below.
						December 31,
	Asset Class		2015 Target Allocation			2014			2013
	Equity securities		24	%		22	%		24	%
	Fixed income securities		48	%		46	%		43	%
	Real estate		6	%		5	%		5	%
	Other		22	%		27	%		28	%
	Total		100	%		100	%		100	%
Schedule of Estimated Future Benefit Payments	The following estimated future benefit payments, which reflect future service, as appropriate, are expected to be paid in the years indicated below.
	Years	Domestic				Foreign				Domestic Postretirement
		Pension Plan				Pension Plans				Benefit Plan
	2015	$	10.6			$	22.4			$	4.4
	2016	10.4				24.2				4.2
	2017	10.1				25.6				4.1
	2018	9.9				26.1				3.9
	2019	9.6				30.7				3.7
	2020 - 2024	44.6				148				15.1
Schedule of Federal Subsidies	The following federal subsidies are expected to be received in the years indicated below.
	Years		Domestic Postretirement
			Benefit Plan
	2015		$	0.4
	2016		0.4
	2017		0.4
	2018		0.4
	2019		0.4
	2020 - 2024		2.4

Segment_Information_Tables

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Summarized financial information concerning our reportable segments is shown in the following table.
		Years ended December 31,
		2014			2013			2012
	Revenue:
	IAN	$	6,097.30		$	5,795.60		$	5,728.50
	CMG	1,439.80			1,326.70			1,227.70
	Total	$	7,537.10		$	7,122.30		$	6,956.20
	Segment operating income:
	IAN	$	777.1		$	662.1		$	700.2
	CMG	161			137.6			114.2
	Corporate and other	(149.5		)	(140.8		)	(137.3		)
	Total	788.6			658.9			677.1
	Restructuring and other reorganization-related (charges) reversals, net	(0.2		)	(60.6		)	1.2
	Interest expense	(84.9		)	(122.7		)	(133.5		)
	Interest income	27.4			24.7			29.5
	Other (expense) income, net	(10.2		)	(32.3		)	100.5
	Income before income taxes	$	720.7		$	468		$	674.8
	Depreciation and amortization of fixed assets and intangible assets:
	IAN	$	124.6		$	126		$	119.7
	CMG	18.4			15.6			14.4
	Corporate and other	20			15.8			13.6
	Total	$	163		$	157.4		$	147.7
	Capital expenditures:
	IAN	$	92.1		$	109		$	97.5
	CMG	11.6			18.5			26.7
	Corporate and other	45			45.5			45
	Total	$	148.7		$	173		$	169.2
		December 31,
		2014			2013
	Total assets:
	IAN	$	11,111.20		$	11,425.10
	CMG	1,316.50			1,203.80
	Corporate and other	319.5			276.1
	Total	$	12,747.20		$	12,905.00
Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas	Revenue and long-lived assets, excluding intangible assets, are presented by major geographic area in the following table.
			Revenue								Long-Lived Assets
			Years ended December 31,								December 31,
			2014			2013			2012		2014		2013
	Domestic		$	4,184.00		$	3,972.60		$	3,803.60	$	572.9	$	545.7
	International:
	United Kingdom		688.3			568.3			572		56.7		60.8
	Continental Europe		804.7			800.6			823.1		66.4		79.6
	Asia Pacific		922.5			868.9			838.1		102.2		88.8
	Latin America		470.4			464.5			450.1		69.2		72.3
	Other		467.2			447.4			469.3		32.4		37.1
	Total International		3,353.10			3,149.70			3,152.60		326.9		338.6
	Total Consolidated		$	7,537.10		$	7,122.30		$	6,956.20	$	899.8	$	884.3

Commitments_and_Contingencies_1

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Schedule of Net Rent Expense	Net rent expense is listed in the table below.
		Years ended December 31,
		2014			2013			2012
	Gross rent expense	$	357.7		$	366.1		$	358.5
	Third-party sublease rental income	(6.1		)	(16.1		)	(17.5		)
	Net rent expense	$	351.6		$	350		$	341
Schedule of Future Minimum Lease Commitments	Cash amounts for future minimum lease commitments for office premises and equipment under non-cancelable leases, along with minimum sublease rental income to be received under non-cancelable subleases, are listed in the table below.
	Period	Rent			Sublease Rental			Net Rent
		Obligations			Income
	2015	$	328.4		$	(8.4	)	$	320
	2016	288.9			(2.8		)	286.1
	2017	248.3			(1.1		)	247.2
	2018	222.3			(0.1		)	222.2
	2019	198.9			0			198.9
	Thereafter	845.1			0			845.1
	Total	$	2,131.90		$	(12.4	)	$	2,119.50
Schedule of Contingent Acquisition Obligations	The following table details the estimated future contingent acquisition obligations payable in cash as of December 31, 2014.
			2015			2016			2017		2018		2019		Thereafter		Total
	Deferred acquisition payments		$	60.3		$	21.3		$	49.1	$	7.9	$	10.8	$	0.9	$	150.3
	Redeemable noncontrolling interests and call options with affiliates 1		35.4			65			37		7.8		10.5		7		162.7
	Total contingent acquisition payments		95.7			86.3			86.1		15.7		21.3		7.9		313
	Less: cash compensation expense included above		1.9			1.6			0.7		0		0		0		4.2
	Total		$	93.8		$	84.7		$	85.4	$	15.7	$	21.3	$	7.9	$	308.8
	1	We have entered into certain acquisitions that contain both redeemable noncontrolling interests and call options with similar terms and conditions. The estimated amounts listed would be paid in the event of exercise at the earliest exercise date. We have certain redeemable noncontrolling interests that are exercisable at the discretion of the noncontrolling equity owners as of December 31, 2014. These estimated payments of $20.5 are included within the total payments expected to be made in 2015, and will continue to be carried forward into 2016 or beyond until exercised or expired. Redeemable noncontrolling interests are included in the table at current exercise price payable in cash, not at applicable redemption value in accordance with the authoritative guidance for classification and measurement of redeemable securities.

Results_by_Quarter_Unaudited_T

Results by Quarter (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	Results by Quarter (Unaudited)																									[1]
		Three Months Ended						Three Months Ended						Three Months Ended						Three Months Ended
		March 31,						June 30,						September 30,						December 31,
		2014			2013			2014			2013			2014			2013			2014			2013
	Revenue	$	1,637.50		$	1,543.00		$	1,851.40		$	1,756.20		$	1,841.10		$	1,700.40		$	2,207.10		$	2,122.70
	Salaries and related expenses	1,188.60			1,132.10			1,170.20			1,120.20			1,195.20			1,093.60			1,266.40			1,199.60
	Office and general expenses	461.1			453.4			484.7			460.9			474.7			465.5			507.6			538.1
	Restructuring and other reorganization-related (reversals) charges, net	(0.5		)	(0.1		)	0.7			0.3			(0.1		)	(0.2		)	0.1			60.6
	Operating (loss) income	(11.7		)	(42.4		)	195.8			174.8			171.3			141.5			433			324.4
	Other income (expense), net 1	1.7			1.8			(11.2		)	4.8			(0.6		)	(46.6		)	(0.1		)	7.7
	Total (expenses) and other income 1	(12.3		)	(28.6		)	(27.2		)	(26.9		)	(13.8		)	(64.5		)	(14.4		)	(10.3		)
	(Benefit of) provision for income taxes 2	(1.7		)	(12.4		)	65.3			62			65			28.4			87.9			103.2
	Net (loss) income	(22.4		)	(58.5		)	103.7			86.1			92.8			49.2			331.3			212.1
	Net (loss) income available to IPG common stockholders 2	$	(20.9	)	$	(59.2	)	$	99.4		$	79.9		$	89.7		$	45.4		$	308.9		$	193.1
	(Loss) earnings per share available to IPG common stockholders:
	Basic	$	(0.05	)	$	(0.14	)	$	0.24		$	0.19		$	0.21		$	0.11		$	0.75		$	0.45
	Diluted	$	(0.05	)	$	(0.14	)	$	0.23		$	0.18		$	0.21		$	0.11		$	0.73		$	0.44
	Dividends declared per common stock	$	0.095		$	0.075		$	0.095		$	0.075		$	0.095		$	0.075		$	0.095		$	0.075
	1	The three months ended June 30, 2014 included a pre-tax loss of $10.4, related to our early extinguishment of debt. The three months ended September 30, 2013 included a pre-tax loss of $45.2, related to our early extinguishment of debt.
	2	The three months ended December 31, 2014 included a tax benefit of $67.6 due to the net reversal of valuation allowances on deferred tax assets in Continental Europe.
[1]	The three months ended June 30, 2014 included a pre-tax loss of $10.4, related to our early extinguishment of debt. The three months ended September 30, 2013 included a pre-tax loss of $45.2, related to our early extinguishment of debt.

Recovered_Sheet12

Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2011
Capitalized Internal Use Software, Useful Life	10
Leasehold improvements, useful life	the shorter of the useful life or the remaining lease term
Number of Reporting Units for Purposes of Annual Goodwill Impairment Test	13
Foreign currency transaction pre-tax loss	$1.40	$0.60	$1.20
Minimum
Property, Plant and Equipment, Useful Life	3 years
Buildings, useful life	10 years
Internal Use Software, Useful Life	3
Finite-Lived Intangible Asset, Useful Life	7 years
Maximum
Property, Plant and Equipment, Useful Life	7 years
Buildings, useful life	35 years
Internal Use Software, Useful Life	7
Finite-Lived Intangible Asset, Useful Life	15 years

Debt_and_Credit_Agreements_Lon

Debt and Credit Agreements Long term debt (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Debt Instrument [Line Items]
Long-term Debt, Gross	$1,625.60		$1,483.40
Long-term Debt, Current Maturities	2.1	[1]	353.6	[1]
Long-term Debt, Excluding Current Maturities	1,623.50		1,129.80
6.25% Notes
Debt Instrument [Line Items]
Long-term Debt, Gross	0		351.3
Debt Instrument, Unamortized Discount	0
Debt Instrument, Face Amount	350
Debt Instrument, Maturity Date	15-Nov-14
Interest Rate, Stated Percentage	6.25%
Debt Instrument, Fair Value Disclosure	0	[2]	365.6
Debt Instrument, Interest Rate, Effective Percentage			6.29%
2.25% Notes
Debt Instrument [Line Items]
Long-term Debt, Gross	299.6		299.4
Debt Instrument, Unamortized Discount	0.4
Debt Instrument, Maturity Date	15-Nov-17
Interest Rate, Stated Percentage	2.25%
Debt Instrument, Fair Value Disclosure	301.2	[2]	293
Debt Instrument, Interest Rate, Effective Percentage	2.30%
4.00% Notes
Debt Instrument [Line Items]
Long-term Debt, Gross	247.7		247.4
Debt Instrument, Unamortized Discount	2.3
Debt Instrument, Maturity Date	15-Mar-22
Interest Rate, Stated Percentage	4.00%
Debt Instrument, Fair Value Disclosure	255.2	[2]	241.6
Debt Instrument, Interest Rate, Effective Percentage	4.13%
3.75% Notes
Debt Instrument [Line Items]
Long-term Debt, Gross	498.8		498.6
Debt Instrument, Unamortized Discount	1.2
Debt Instrument, Maturity Date	15-Feb-23
Interest Rate, Stated Percentage	3.75%
Debt Instrument, Fair Value Disclosure	499.8	[2]	467.3
Debt Instrument, Interest Rate, Effective Percentage	4.32%
4.25% Convertible Senior Notes
Debt Instrument [Line Items]
Interest Rate, Stated Percentage			4.25%
4.20% Notes
Debt Instrument [Line Items]
Long-term Debt, Gross	499.1		0
Debt Instrument, Unamortized Discount	0.9
Debt Instrument, Face Amount	500
Debt Instrument, Maturity Date	15-Apr-24
Interest Rate, Stated Percentage	4.20%
Debt Instrument, Fair Value Disclosure	509.8	[2]	0
Debt Instrument, Interest Rate, Effective Percentage	4.24%
Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	80.4		86.7
Debt Instrument, Fair Value Disclosure	$80.40	[2]	$87.80
[1]	We included our 6.25% Senior Unsecured Notes due 2014 (the "6.25% Notes") in the current portion of long-debt on our December 31, 2013 Consolidated Balance Sheet because the 6.25% Notes were scheduled to mature on November 15, 2014. We redeemed the 6.25% Notes prior to their scheduled maturity during the second quarter of 2014.
[2]	See Note 11 for information on the fair value measurement of our long-term debt.

Debt_and_Credit_Agreements_Nar

Debt and Credit Agreements Narrative (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense	$16.60	$15.40
Proceeds from Issuance of Long-term Debt	499.1	0	1,044.60
Long-term Debt, Gross	1,625.60	1,483.40
4.20% Notes
Debt Instrument [Line Items]
Proceeds from Issuance of Long-term Debt	494.7
Repurchase Price Percentage Due to Change of Control	101.00%
Debt Issuance Cost	0.9
Fees and Commissions	4.4
Interest Rate, Stated Percentage	4.20%
Long-term Debt, Gross	499.1	0
Debt Instrument, Face Amount	500
6.25% Notes
Debt Instrument [Line Items]
Interest Rate, Stated Percentage	6.25%
Long-term Debt, Gross	0	351.3
Debt Instrument, Face Amount	350
3.75% Notes
Debt Instrument [Line Items]
Interest Rate, Stated Percentage	3.75%
Long-term Debt, Gross	498.8	498.6
10.00% Notes
Debt Instrument [Line Items]
Interest Rate, Stated Percentage		10.00%
Debt Instrument, Face Amount		$600
Uncommitted credit facility
Debt Instrument [Line Items]
Line of Credit Facility Weighted Average Interest Rate	4.50%	4.50%

Debt_and_Credit_Agreements_Ext

Debt and Credit Agreements Extinguishment of Debt (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Extinguishment of Debt [Line Items]
Gains (Losses) on Extinguishment of Debt	$10.40	$45.20	$0
6.25% Notes
Extinguishment of Debt [Line Items]
Early Repayment of Senior Debt	371.2
Debt Instrument, Face Amount	350
Accrued Interest, Paid	10.3
Gains (Losses) on Extinguishment of Debt	10.4
10.00% Notes
Extinguishment of Debt [Line Items]
Write off of Debt Issuance Cost		7.9
Early Repayment of Senior Debt		630
Debt Instrument, Face Amount		600
Gains (Losses) on Extinguishment of Debt		45.2
Redemption Premium		30
Write off of Unamortized Discount		$7.30

Debt_and_Credit_Agreements_Con

Debt and Credit Agreements Convertible Notes (Details) (4.75% Convertible Notes, USD $)	12 Months Ended
Share data in Millions, unless otherwise specified	Dec. 31, 2013	Mar. 31, 2013
4.75% Convertible Notes
Debt Conversion [Line Items]
Interest Rate, Stated Percentage	4.75%
Debt Instrument, Face Amount	$200,000,000
Debt Conversion Rate	84.3402
Principal Amount Converted into Stock		$200.00
Conversion of Stock, Shares Issued	16.9
Net Share Settlement	1.5

Debt_and_Credit_Agreements_Ann

Debt and Credit Agreements Annual Maturities (Details) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Debt Disclosure [Abstract]
Long-term Debt, Maturities, Repayments of Principal in Year Two	$2.20
Long-term Debt, Maturities, Repayments of Principal in Year Three	324.2
Long-term Debt, Maturities, Repayments of Principal in Year Four	2
Long-term Debt, Maturities, Repayments of Principal in Year Five	2
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	2.1	[1]
Long-term Debt, Maturities, Repayments of Principal after Year Five	$1,293.10
[1]	The interest coverage ratio is defined as EBITDA, as defined in the Credit Agreement, to net interest expense

Debt_and_Credit_Agreements_Cre

Debt and Credit Agreements Credit Facility (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Line of Credit Facility [Line Items]
Line of Credit Facility Commitment Increase	$250
Line of Credit Facility Limits on Letters of Credit	200
Margin for base rate advances	0.28%
Margin for Eurocurrency rate advances	1.28%
Annual rate for fronting fees accrued on letters of credit	0.25%
Line of Credit Facility, Commitment Fee Percentage	0.23%
Leverage ratio maximum	3.25x	[1]
Interest coverage ratio minimum	5.00x	[2]
Cash debt pooling arrangements, amount netted	1,590.70		1,415.30
Committed credit facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	984		985.7
Line of Credit Facility, Maximum Borrowing Capacity	1,000		1,000
Long-term Line of Credit	0		0
Letters of Credit Outstanding, Amount	16		14.3
Uncommitted credit facility
Line of Credit Facility [Line Items]
Line of Credit Facility Weighted Average Interest Rate	4.50%		4.50%
Line of Credit Facility, Remaining Borrowing Capacity	629.2		516.9
Line of Credit Facility, Maximum Borrowing Capacity	740.3		700.2
Long-term Line of Credit	107.2		179.1
Letters of Credit Outstanding, Amount	$3.90		$4.20
[1]	The leverage ratio is defined as debt as of the last day of such fiscal quarter to EBITDA, as defined in the Credit Agreement, for the four quarters then ended.
[2]	The interest coverage ratio is defined as EBITDA, as defined in the Credit Agreement, to net interest expense

Acquisitions_Narrative_Details

Acquisitions Narrative (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	$185	$97	$201
Number of Businesses Acquired	8	11	12
IAN
Number of Businesses Acquired	6	9	8
CMG
Number of Businesses Acquired	2	2	4

Redeemable_Noncontrolling_Inte

Redeemable Noncontrolling Interests (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Redeemable Noncontrolling Interests
Balance at beginning of period	$249.10	$227.20	$243.40
Change in related noncontrolling interest balance	3.2	4.6	1.1
Changes in redemption value of redeemable noncontrolling interests:
Additions	18.7	16.2	0
Redemptions and reclassifications	-7.9	-2.3	-14.2
Redemption value adjustments	-5.7	3.4	-3.1
Balance at end of period	$257.40	$249.10	$227.20

Acquisitions_Cash_Paid_for_Acq

Acquisitions Cash Paid for Acquisitions (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Business Acquisition [Line Items]
Acquisition related payments	$13.60		$27.60		$37.10
Payments to Acquire Businesses, Net of Cash Acquired	67.8		61.5		145.5
Cash Acquired from Acquisition	-29.9		-7.1		-14.8
PaymentsToAcquireBusinessesGrossLessOperatingExpense s	84.8		91.1		185.8
Business Combination, Separately Recognized Transactions, Expenses and Losses Recognized	3.4	[1]	2	[1]	3.2	[1]
Payments to Acquire Businesses, Gross	81.4	[2]	89.1	[2]	182.6	[2]
Current Year Acquisition [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	97.3		67.7		156.8
Prior Year Acquisition [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$14		$28.50		$40.60
[1]	Of the total cash paid, $13.6, $27.6 and $37.1 for the years ended December 31, 2014, 2013 and 2012, respectively, are classified under the financing section of the Consolidated Statements of Cash Flows within acquisition-related payments. These amounts relate to increases in our ownership interests in our consolidated subsidiaries as well as deferred payments for acquisitions. Of the total cash paid, $67.8, $61.5 and $145.5 for the years ended December 31, 2014, 2013 and 2012, respectively, are classified under the investing section of the Consolidated Statements of Cash Flows within acquisitions, net of cash acquired. These amounts relate to initial payments for new transactions.
[2]	Represents cash payments made that were either in excess of the contractual value or contingent upon the future employment of the former owners of acquired companies

Valuation_and_Qualifying_Accou

Valuation and Qualifying Accounts - Allowance for Uncollectible Accounts Receivable (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	$64.90		$59		$55.40
Charges to costs and expenses	7.4		12.6		16.3
Reversals to other accounts	0.1	[1]	0.7	[1]	-0.2	[1]
Deductions:
Dispositions	0		0		-0.4
Uncollectible accounts written off	-8.1		-7.2		-12.6
Foreign currency translation adjustment	-4.8		-0.2		0.5
Balance at end of period	$59.50		$64.90		$59
[1]	Amounts primarily relate to miscellaneous other amounts and reclassifications.

Supplementary_Data_Property_an

Supplementary Data Property and Equipment (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Depreciation, Depletion and Amortization	$132.30	$130.60	$124.30
Furniture and equipment	640.7	661.6
Leasehold improvements	594	611.4
Internal use computer software	296.2	269.1
Land and buildings	87.3	109.6
Property and Equipment	1,618.20	1,651.70
Less: accumulated depreciation	1,070	1,111.70
Total property and equipment, net	$548.20	$540

Accrued_Liabilities_Details

Accrued Liabilities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Accrued Liabilities [Abstract]
Salaries, benefits and related expenses	$510.60	$467.20
Office and related expenses	51.5	56.9
Acquisition obligations	88.1	12.8
Interest	18.3	16
Restructuring and other reorganization-related	5.5	46.7
Other	122	118.8
Total accrued liabilities	$796	$718.40

Other_Expense_Income_Net_Detai

Other (Expense) Income, Net (Details) (USD $)	3 Months Ended										12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014		Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013		Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Loss on early extinguishment of debt											($10.40)	($45.20)	$0
Gains on sales of businesses and investments											0.8	-1.5	88.2
Vendor discounts and credit adjustments											3.3	8.6	15.3
Other (expense) income, net											-3.9	-2.8	-3
Total other (expense) income, net	0.1	0.6	11.2	[1]	-1.7	-7.7	46.6	[1]	-4.8	-1.8	-10.2	-32.3	100.5
6.25% Notes
Loss on early extinguishment of debt											-10.4
Debt Instrument, Interest Rate, Stated Percentage	-6.25%										-6.25%
10.00% Notes
Loss on early extinguishment of debt												($45.20)
Debt Instrument, Interest Rate, Stated Percentage						-10.00%						-10.00%
[1]	The three months ended June 30, 2014 included a pre-tax loss of $10.4, related to our early extinguishment of debt. The three months ended September 30, 2013 included a pre-tax loss of $45.2, related to our early extinguishment of debt.

Share_Repurchase_Program_Detai

Share Repurchase Program (Details) (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Number of shares repurchased	14.9	31.8	32.7
Aggregated cost, including fees	$275.10	$481.80	$350.50
Average price per share, including fees	$18.41	$15.17	$10.72
2014 Share Repurchase Program
Share repurchase program, initial authorized amount	300
Remaining available for repurchase	143.6
2013 Share Repurchase Program
Share repurchase program, initial authorized amount		300
Share repurchase program, increased authorized amount		500
2012 Share Repurchase Program
Share repurchase program, initial authorized amount			300
Share repurchase program, increased authorized amount			$400

Supplemental_Cash_Flow_Informa

Supplemental Cash Flow Information (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Supplemental Cash Flow Information [Abstract]
Cash paid for interest	$78.10		$110.70		$130.60
Cash paid for income taxes, net of refunds	103.9	[1]	111.8	[1]	95.7	[1]
Proceeds from Income Tax Refunds	$21.30		$15		$23.50
[1]	Refunds of $21.3, $15.0 and $23.5 were received for the years ended December 31, 2014, 2013 and 2012, respectively.

Earnings_Per_Share_Basic_and_D

Earnings Per Share Basic and Diluted (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Net income available to IPG common stockholders - basic	$308.90	$89.70	$99.40	($20.90)	$193.10	$45.40	$79.90	($59.20)	$477.10		$259.20		$435.10
Dividends on preferred stock									0		0		11.6
Net income available to IPG common stockholders - diluted									477.1		260		451.1
Weighted-average number of common shares outstanding - basic									419.2		421.1		432.5
Restricted stock, stock options and other equity awards									6.2		5.2		7.2
Preferred stock outstanding 2									0	[1]	0		16.9
Weighted-average number of common shares outstanding - diluted									425.4		429.6		481.4
Earnings per share available to IPG common stockholders - basic	$0.75	$0.21	$0.24	($0.05)	$0.45	$0.11	$0.19	($0.14)	$1.14		$0.62		$1.01
Earnings per share available to IPG common stockholders - diluted	$0.73	$0.21	$0.23	($0.05)	$0.44	$0.11	$0.18	($0.14)	$1.12		$0.61		$0.94
4.75% Convertible Notes
Interest on convertible debt									0	[2]	0.8	[2]	4.1
Convertible debt securities									0	[2]	3.3	[2]	16.9
4.25% Convertible Notes
Interest on convertible debt									$0	[2]	$0	[2]	$0.30
Convertible debt securities									0	[2]	0	[2]	7.9
[1]	We converted all of our 5 1/4% Series B Cumulative Convertible Perpetual Preferred Stock (the "Series B Preferred Stock") into common stock in October 2013. For purposes of calculating diluted earnings per share for 2013, the potentially dilutive shares would have been pro-rated based on the period they were outstanding but were antidilutive.
[2]	We retired all of our outstanding 4.75% Notes and 4.25% Convertible Senior Notes due 2023 in March 2013 and March 2012, respectively. See Note 2 for further information. For purposes of calculating diluted earnings per share for 2013 and 2012, the potentially dilutive shares are pro-rated based on the period they were outstanding.

Antidilutive_Shares_Details

Antidilutive Shares (Details)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Preferred Stock Outstanding
Antidilutive Securities
Securities Excluded from Computation of Earnings Per Share, Amount	0	[1]	13.7		0
Stock options
Antidilutive Securities
Stock options 2	0	[2]	0.1	[2]	6.6	[2]
[1]	1We converted all of our Series B Preferred Stock into common stock in October 2013. For purposes of calculating diluted earnings per share for 2013, the potentially dilutive shares would have been pro-rated based on the period they were outstanding but were antidilutive.
[2]	These options were outstanding at the end of the respective periods. In any period in which the exercise price is less than the average market price, these options have the potential to be dilutive, and application of the treasury stock method would reduce this amount.

Goodwill_Details

Goodwill (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Goodwill
Goodwill	$3,669.20		$3,629		$3,580.60	[1]
Current year acquisitions	136.1	[1]	75.3	[1]
Foreign currency and other	-95.9	[1]	-26.9	[1]
IAN
Goodwill
Goodwill	3,120.80	[1]	3,109.30	[1]	3,074.60	[1]
Current year acquisitions	95.2	[1]	58.8	[1]
Foreign currency and other	-83.7	[1]	-24.1	[1]
CMG
Goodwill
Goodwill	548.4	[1]	519.7	[1]	506	[1]
Current year acquisitions	40.9	[1]	16.5	[1]
Foreign currency and other	($12.20)	[1]	($2.80)	[1]
[1]	For all periods presented we have not recorded a goodwill impairment charge.

Other_Intangible_Assets_Detail

Other Intangible Assets (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Future Amortization Expense 2015	$37.20
Future Amortization Expense 2016	34.7
Future Amortization Expense 2017	22.7
Future Amortization Expense 2018	12.8
Future Amortization Expense 2019	12.1
Finite-Lived Intangible Assets [Line Items]
Amortization Expense of Intangible Assets	29.4	26.8	23.4
Acquired Finite-Lived Intangible Assets related to Acquisitions	48.6	21.5
Gross Amount	340.9	306.6
Accumulated Amortization	-165.9	-142.8
Net Amount	175	163.8
Customer Lists
Finite-Lived Intangible Assets [Line Items]
Gross Amount	255.8	228.1
Accumulated Amortization	-139.3	-119.8
Net Amount	116.5	108.3
Trade Names
Finite-Lived Intangible Assets [Line Items]
Gross Amount	71	64.5
Accumulated Amortization	-22.8	-19.2
Net Amount	48.2	45.3
Other Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Gross Amount	14.1	14
Accumulated Amortization	-3.8	-3.8
Net Amount	$10.30	$10.20
Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	7 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	15 years

Components_of_Income_Before_In

Components of Income Before Income Taxes (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Income before income taxes, Domestic	$387.70	$255.30	$386.90
Income before income taxes, Foreign	333	212.7	287.9
Income before income taxes	$720.70	$468	$674.80

Provision_for_Income_Taxes_Det

Provision for Income Taxes (Details) (USD $)	3 Months Ended									12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
U.S. federal income taxes (including foreign withholding taxes):
Current federal income taxes										$8	$46.90	$9.40
Deferred federal income taxes										130.7	25.2	118.1
Total federal income taxes										138.7	72.1	127.5
State and local income taxes:
Current state and local income taxes										9.7	-14.7	17.1
Deferred state and local income taxes										23.8	24.7	25.3
Total state and local income taxes										33.5	10	42.4
Foreign income taxes:
Current foreign income taxes										115.3	79.6	83.2
Deferred foreign income taxes										-71	19.5	-39.8
Total foreign income taxes										44.3	99.1	43.4
Total provision for income taxes	$87.90	[1]	$65	$65.30	($1.70)	$103.20	$28.40	$62	($12.40)	$216.50	$181.20	$213.30
[1]	The three months ended December 31, 2014 included a tax benefit of $67.6 due to the net reversal of valuation allowances on deferred tax assets in Continental Europe.

Reconciliation_of_Effective_In

Reconciliation of Effective Income Tax Rate (Details) (USD $)	3 Months Ended									12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Valuation Allowance [Line Items]
U.S. federal statutory income tax rate										35.00%		35.00%		35.00%
Income tax provision at U.S. federal statutory rate										$252.30		$163.80		$236.20
State and local income taxes, net of federal income tax benefit										21.4		6.5		27.3
Impact of foreign operations, including withholding taxes										1.7		30.5		8.4
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount										-66	[1]	3.2	[1]	-57.3	[1]
Worthless securities deduction										0		-22.2		0
Increases in unrecognized tax benefits, net										5.2		0		24.1
Other										1.9		-0.6		-25.4
Total provision for income taxes	87.9	[2]	65	65.3	-1.7	103.2	28.4	62	-12.4	216.5		181.2		213.3
Effective income tax rate on operations										30.00%		38.70%		31.60%
One hundred percent valuation allowance										100.00%		100.00%		100.00%
Asia Pacific
Valuation Allowance [Line Items]
Reversal of valuation allowance														26.2
Continental Europe
Valuation Allowance [Line Items]
Reversal of valuation allowance										124.8				21.8
Valuation allowance established										57.2
Tax Contingency for the years 2007 - 2010 [Member]
Valuation Allowance [Line Items]
Valuation Allowances and Reserves, Charged to Cost and Expense														$19.50
[1]	Reflects changes in valuation allowance that impacted the effective income tax rate for each year presented.
[2]	The three months ended December 31, 2014 included a tax benefit of $67.6 due to the net reversal of valuation allowances on deferred tax assets in Continental Europe.

Components_of_Deferred_Tax_Ass

Components of Deferred Tax Assets (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Millions, unless otherwise specified
Deferred Tax Assets, Net [Abstract]
Postretirement/post-employment benefits	$27.40	$32.50
Deferred compensation	191.2	187.2
Pension costs	41.4	31.1
Basis differences in fixed assets	-38.5	-4.1
Rent	45.8	50.7
Interest	60.9	60.7
Accruals and reserves	34.8	39.6
Allowance for doubtful accounts	10.8	10.8
Basis differences in intangible assets	-412.3	-402.2
Investments in equity securities	-2.6	48.6
Tax loss/tax credit carry forwards	404.4	443.6
Restructuring and other reorganization-related costs	-0.3	2.6
Other	59.2	60.5
Total Deferred Tax Assets, Net	422.2	561.6
Valuation allowance	-332.2	-467.3	-392.9	-489.9
Net Deferred Tax Assets	$90	$94.30

Income_Taxes_Change_in_Valuati

Income Taxes Change in Valuation Allowances (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Summary of Valuation Allowances
Deferred Tax Assets, Valuation Allowance	$332.20	$467.30	$392.90	$489.90
(Reversed) charged to costs and expenses	-72.8	65.2	-49.5
(Reversed) charged to gross tax assets and other accounts	-62.3	9.2	-47.5
Operating Loss Carryforwards	1,263.10
Deferred Tax Liabilities, Undistributed Foreign Earnings	2,214.20	1,959.80
Foreign Tax Authority
Summary of Valuation Allowances
Income Tax Examination, Year under Examination	2006
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration	1,053.40
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	209.7
Domestic Tax Authority
Summary of Valuation Allowances
Income Tax Examination, Year under Examination	2009
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration	$60.30
Minimum | Foreign Tax Authority
Summary of Valuation Allowances
Operating Loss Carryforwards, Expiration Date	1-Jan-15
Minimum | Domestic Tax Authority
Summary of Valuation Allowances
Income Tax Examination, Year under Examination		2002
Operating Loss Carryforwards, Expiration Date	1-Jan-15
Maximum | Foreign Tax Authority
Summary of Valuation Allowances
Operating Loss Carryforwards, Expiration Date	1-Jan-33
Maximum | Domestic Tax Authority
Summary of Valuation Allowances
Income Tax Examination, Year under Examination		2006
Operating Loss Carryforwards, Expiration Date	1-Jan-34

Unrecognized_Tax_Benefits_Deta

Unrecognized Tax Benefits (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued [Abstract]
Balance at beginning of period	$219.20	$194.60	$161
Increases as a result of tax positions taken during a prior year	29	8.3	28.2
Decreases as a result of tax positions taken during a prior year	-16.3	-1.9	-6.8
Settlements with taxing authorities	-1.1	-34.9	-0.7
Lapse of statutes of limitation	-4.1	-10.6	-1.1
Increases as a result of tax positions taken during the current year	11.3	63.7	14
Balance at end of period	238	219.2	194.6
Income Tax Contingency [Line Items]
Unrecognized tax benefits that would impact effective tax rate	213.5
Income tax penalties and interest accrued	15.3	11.9
Income tax penalties and interest expense	-5.4	-2.8
Estimated unrecognized tax benefit decrease, lower bound	25
Estimated unrecognized tax benefit decrease, upper bound	$35
Foreign Tax Authority
Income Tax Contingency [Line Items]
Income Tax Examination, Year under Examination	2006
Domestic Tax Authority [Member]
Income Tax Contingency [Line Items]
Income Tax Examination, Year under Examination	2009
State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Income Tax Examination, Year under Examination	2004
Minimum [Member] | Domestic Tax Authority [Member]
Income Tax Contingency [Line Items]
Income Tax Examination, Year under Examination		2002
Maximum [Member] | Domestic Tax Authority [Member]
Income Tax Contingency [Line Items]
Income Tax Examination, Year under Examination		2006

Restructuring_and_Other_Reorga2

Restructuring and Other Reorganization-Related Charges (Reversals), net (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restructuring Cost and Reserve [Line Items]
Restructuring and other reorganization-related charges (reversals), net	$0.10	($0.10)	$0.70	($0.50)	$60.60	($0.20)	$0.30	($0.10)	$0.20	$60.60	($1.20)
Severance and termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other reorganization-related charges (reversals), net									0.1	55.9	0
Payments for Restructuring									41.8
Restructuring Reserve, Translation Adjustment									-0.4
Restructuring Reserve	4.4				46.5				4.4	46.5
Lease termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other reorganization-related charges (reversals), net									0.1	4.2	-1.1
Payments for Restructuring									1.2
Restructuring Reserve, Translation Adjustment									-0.1
Restructuring Reserve	2.6				3.9				2.6	3.9
Other exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other reorganization-related charges (reversals), net									0	0.5	-0.1
Payments for Restructuring									0.5
Restructuring Reserve, Translation Adjustment									0
Restructuring Reserve	0				0.5				0	0.5
IAN
Restructuring Cost and Reserve [Line Items]
Restructuring and other reorganization-related charges (reversals), net										0.3
CMG
Restructuring Cost and Reserve [Line Items]
Restructuring and other reorganization-related charges (reversals), net										-0.2
2013 Restructuring Plan [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and other reorganization-related charges (reversals), net									0.1	61.2
Payments for Restructuring									43.5
Restructuring Reserve, Translation Adjustment									-0.5
Restructuring Reserve	7				50.9				7	50.9
2013 Restructuring Plan [Domain] | Severance and termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other reorganization-related charges (reversals), net										55.9
2013 Restructuring Plan [Domain] | Lease termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other reorganization-related charges (reversals), net									0	4.8
2013 Restructuring Plan [Domain] | Other exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other reorganization-related charges (reversals), net										0.5
Prior Restructuring Plan [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and other reorganization-related charges (reversals), net									0.1	-0.6	-1.2
Restructuring Reserve	$1.10								$1.10

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Loss, net of tax Changes in AOCI (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Changes in market value of available-for-sale securities	$0.70	$0.80	$0.40
Changes in fair value of derivative instruments	-0.6	0	-21.9
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent	-246.6	-131.9
Total Reclassification from AOCI	21.1	8.7	19.7
Accumulated Other Comprehensive Income (Loss), Net of Tax	-636.7	-411.2	-288
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Foreign Currency Transaction and Translation Gain (Loss), before Reclassification and Tax	-191.7	-113
Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax	-0.9	-0.6
Foreign Currency Translation Adjustment, Net of Tax	-436.3	-243.7	-130.1
Available-for-sale Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Changes in market value of available-for-sale securities	0.7	0.8
Available-for-sale Securities Adjustment, Net of Tax	0.8	0.4	0.8
Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	-0.3	-1.2
Derivative Instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Changes in fair value of derivative instruments	-0.6	0
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	1.4	1
Cumulative Changes in Net Gain (Loss) from Hedges, Effect Net of Tax	-10.9	-11.7	-12.7
Defined Benefit and Postretirement Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pension and Other Postretirement Benefit Plans, Adjustment, before Reclassification Adjustments and Tax	-55	-19.7
Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Net of Tax	20.9	9.5
Pension and Other Postretirement Benefit Plans, Net of Tax	$190.30	($156.20)	($146)

Accumulated_Other_Comprehensiv3

Accumulated Other Comprehensive Loss, net of tax Reclassifications from AOCI, net of tax (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other Comprehensive Income (Loss), Tax	$9.60		($2.40)		$10.30
Total Reclassification from AOCI	21.1		8.7		19.7
Foreign Currency Translation Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	-0.9		0		0
Available-for-sale Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	0		1.4		-0.7
Derivative Instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	1.9		1.7		0.3
Defined Benefit and Postretirement Plans
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	$10.50	[1]	$10.80	[1]	$8.40	[1]
[1]	1These accumulated other comprehensive loss components are included in the computation of net periodic cost. See Note 12 for further information

Plan_Information_Details

Plan Information (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014
Incentive Compensation Plan Initiation Year	2014
Number of shares initially available for grant	28.8
Maximum shares participants are eligible to receive	2
Cash Award performance vesting condition	range from 0% to 300% of the target amount
Maximum Cash Award Per Employee	$10
Number of years stock options expire from grant date	10 years
Fair Value of shares on grant date is amortized over vesting period, years	3 years
Minimum
Stock options exercisable period	2 years
Maximum
Stock options exercisable period	4 years

Stock_Based_Compensation_Expen

Stock Based Compensation Expense (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Stock-based Payment Award
Stock-based compensation expense	$56.70		$46		$50.40
Tax benefit	20.6		17.6		19.7
Employee Stock Option
Stock-based Payment Award
Stock-based compensation expense	2.1		3.7		5.4
Stock-settled awards
Stock-based Payment Award
Stock-based compensation expense	10		9.8		14.9
Cash-settled awards
Stock-based Payment Award
Stock-based compensation expense	0.6		1.5		3.9
Performance-based awards
Stock-based Payment Award
Stock-based compensation expense	42.2		29.6		24.5
Employee stock purchase plan
Stock-based Payment Award
Stock-based compensation expense	0.6		0.6		0.6
Other
Stock-based Payment Award
Stock-based compensation expense	$1.20	[1]	$0.80	[1]	$1.10	[1]
[1]	Represents charges recorded for severance expense related to stock-based compensation awards.

Incentive_Compensation_Plans_S

Incentive Compensation Plans Stock Option Activity (Details) (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock-based Payment Award
Intrinsic value of stock options exercised	$10.70	$26.20	$2
Proceeds from Stock Options Exercised including Taxes Withheld	25.2	59.5	11.7
Total unrecognized compensation expense remaining	1.2
Weighted-average years expected to be recognized over	0 years 11 months
Weighted average grant date fair value per option		$4.14	$4.24
Employee Stock Option
Stock-based Payment Award
Stock options outstanding as of January 1, 2014	9.4
Stock options outstanding as of Jan 1, 2014, Weighted-average exercise price	$10.24
Exercised	-1.7	-5.2	-1.2
Exercised, Weighted-average exercise price	$12.01
Cancelled/expired	-0.3
Cancelled/expired, Weighted-average exercise price	$14.16
Stock options outstanding as of December 31, 2014	7.4	9.4
Stock options outstanding as of Dec 31, 2014, Weighted-average exercise price	$9.70	$10.24
Options outstanding, Weighted Average Remaining Contractual Term	4 years 1 month
Stock options outstanding, Aggregate intrinsic value	82.1
Stock options vested and expected to vest, Outstanding	7.4
Stock options vested and expected to vest, Weighted-average exercise price	$9.69
Options Vested and Expected. Weighted Average Remaining Contractual Term	4 years 1 month
Stock options vested and expected to vest, Aggregate intrinsic value	82
Stock options exercisable, Number	6.8
Stock options exercisable, Weighted-average exercise price	$9.44
Options exercisable, Weighted-average remaining contractual term	3 years 8 months
Stock options exercisable, Aggregate intrinsic value	76.7
Employee Stock Option Non vested [Member]
Stock-based Payment Award
Stock options outstanding as of January 1, 2014	1.5
Stock options outstanding as of Jan 1, 2014, Weighted-average exercise price	$4.21
Stock options outstanding as of December 31, 2014	0.6
Stock options outstanding as of Dec 31, 2014, Weighted-average exercise price	$4.16
Options outstanding, Weighted Average Remaining Contractual Term	7 years 11 months
Stock options outstanding, Aggregate intrinsic value	3.8
Vested	-0.9
Vested, Weighted-average grant date fair value	$4.25
Performance based cash awards settled in shares
Stock-based Payment Award
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value	19.8	17.4
Total unrecognized compensation expense remaining	$13.10
Weighted-average years expected to be recognized over	1 year 1 month

Stock_Option_Valuation_Assumpt

Stock Option Valuation Assumptions (Details) (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected volatility	0.00%	[1]	40.20%	[1]	43.80%	[1]
Expected term of share-based compensation awards	0 years	[2]
Expected term (years)			6 years 11 months	[2]	6 years 9 months	[2]
Risk free interest rate	0.00%	[3]	1.30%	[3]	1.30%	[3]
Expected dividend yield	0.00%	[4]	2.40%	[4]	2.10%	[4]
Annualized dividend per share used in calculation of expected dividend yield	$0.38		$0.30		$0.24
[1]	The expected volatility used to estimate the fair value of stock options awarded is based on a blend of: (i) historical volatility of our common stock for periods equal to the expected term of our stock options and (ii) implied volatility of tradable forward put and call options to purchase and sell shares of our common stock.
[2]	The estimate of our expected term is based on the average of (i) an assumption that all outstanding options are exercised upon achieving their full vesting date and (ii) an assumption that all outstanding options will be exercised at the midpoint between the current date (i.e., the date awards have ratably vested through) and their full contractual term. In determining the estimate, we considered several factors, including the historical option exercise behavior of our employees and the terms and vesting periods of the options.
[3]	The risk free rate is determined using the implied yield currently available for zero-coupon U.S. government issuers with a remaining term equal to the expected term of the options.
[4]	The expected dividend yield is calculated based on an annualized dividend of $0.38 per share in 2014, $0.30 per share in 2013 and $0.24 per share in 2012.

Sharebased_Compensation_Awards

Share-based Compensation Awards (Details) (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock-settled awards
Stock-based Payment Award
Stock based awards expected to be settled in cash	1.2	1.1	0.9
Weighted-average grant-date fair value (per award)	$17.77	$13.51	$11.43
Total fair value of vested awards distributed	$12.60	$35.40	$63.50
Accrued dividends on non-vested stock-settled awards	0.8	0.7
Dividends paid for stock-settled awards	0.5	1.5
Cash-settled awards
Stock-based Payment Award
Stock based awards expected to be settled in cash	0.1	0.1	0.1
Weighted-average grant-date fair value (per award)	$18.20	$16.35	$10.94
Total fair value of vested awards distributed	0.6	5.4	11.1
Performance-based awards
Stock-based Payment Award
Stock based awards expected to be settled in cash	3.5	1.5	1.8
Weighted-average grant-date fair value (per award)	$16.56	$11.97	$10.61
Total fair value of vested awards distributed	15.3	0.2	11.5
Performance based cash awards settled in shares
Stock-based Payment Award
Total fair value of vested awards distributed	$19.80	$17.40

Nonvested_Award_Activity_Detai

Non-vested Award Activity (Details) (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock-based Payment Award
Total unrecognized compensation expense remaining	$1.20
Weighted-average years expected to be recognized over	0 years 11 months
Stock-settled awards
Stock-based Payment Award
Non-vested as of January 1, 2014	1.9
Nonvested as of January 1, 2014, Weighted-average grant date fair value	$12.54
Granted	1.2
Granted, Weighted-average grant-date fair value	$17.77	$13.51	$11.43
Vested	-0.8
Vested, Weighted-average grant date fair value	$12.15
Forfeited	-0.1
Forfeited, Weighted-average grant date fair value	$12.53
Non-vested as of December 31, 2014	2.2	1.9
Nonvested as of December 31, 2014, Weighted-average grant date fair value	$15.47	$12.54
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value	12.6	35.4	63.5
Total unrecognized compensation expense remaining	14.3
Weighted-average years expected to be recognized over	1 year 7 months
Cash-settled awards
Stock-based Payment Award
Non-vested as of January 1, 2014	0.1
Nonvested as of January 1, 2014, Weighted-average grant date fair value	$12.03
Granted	0.1
Granted, Weighted-average grant-date fair value	$18.20	$16.35	$10.94
Vested	-0.1
Vested, Weighted-average grant date fair value	$8.36
Forfeited	0
Forfeited, Weighted-average grant date fair value	$0
Non-vested as of December 31, 2014	0.1	0.1
Nonvested as of December 31, 2014, Weighted-average grant date fair value	$16.99	$12.03
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value	0.6	5.4	11.1
Total unrecognized compensation expense remaining	1.4
Weighted-average years expected to be recognized over	2 years 0 months
Performance-based awards
Stock-based Payment Award
Non-vested as of January 1, 2014	4.1
Nonvested as of January 1, 2014, Weighted-average grant date fair value	$11.71
Granted	3.5
Granted, Weighted-average grant-date fair value	$16.56	$11.97	$10.61
Vested	-0.9
Vested, Weighted-average grant date fair value	$12.24
Forfeited	-0.9
Forfeited, Weighted-average grant date fair value	$12.76
Non-vested as of December 31, 2014	5.8	4.1
Nonvested as of December 31, 2014, Weighted-average grant date fair value	$14.39	$11.71
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value	15.3	0.2	11.5
Total unrecognized compensation expense remaining	58.1
Weighted-average years expected to be recognized over	2 years 0 months
Performance based cash awards settled in shares
Stock-based Payment Award
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value	19.8	17.4
Cash awards granted during the period target value	2.9	35.6	33.6
Total unrecognized compensation expense remaining	13.1
Weighted-average years expected to be recognized over	1 year 1 month
Cash Awards Total Target Value
Stock-based Payment Award
Cash awards granted during the period target value	5.8	4.6	2.7
Recognized in salaries and related expense	3.1	4	10.9
Performance based cash awards
Stock-based Payment Award
Cash awards granted during the period target value	33	47.4	37.4
Recognized in salaries and related expense	$27.30	$18.30	$18.90

Incentive_Compensation_Plans_E

Incentive Compensation Plans Employee Stock Purchase Plans (Details)	12 Months Ended
	Dec. 31, 2014
Employee Stock Purchase Plan description	90% of the lesser of the average market price of a share on the first business day of the offering period or the average market price of a share on the last business day of the offering period of three months
Number of shares initially available for grant	28,800,000
Stock Issued During Period, Shares, Employee Stock Purchase Plans	2,800,000
Employee stock purchase plan
Maximum Employee Subscription Rate	10.00%
Maximum Number of Shares Per Employee	900
Number of shares initially available for grant	15,000,000

Fair_Value_on_a_Recurring_Basi

Fair Value on a Recurring Basis (Details) (USD $)	Dec. 31, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Cash equivalents	$901.40		$761.20
Short-term marketable securities	6.6		5.3
Long-term investments	0.5		1.6
Fair value of total assets, recurring	908.5		768.1
Fair value of assets measured on a recurring basis, percentage of total assets	7.10%		6.00%
Mandatorily redeemable noncontrolling interests	0	[1]	0	[1]
Level 2
Fair value assets and liabilities measured on recurring and nonrecurring basis
Cash equivalents	0		0
Short-term marketable securities	0		0
Long-term investments	0		0
Fair value of total assets, recurring	0		0
Fair value of assets measured on a recurring basis, percentage of total assets	0.00%		0.00%
Mandatorily redeemable noncontrolling interests	0	[1]	0	[1]
Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Restructuring Reserve	8.1		52.2
Cash equivalents	0		0
Short-term marketable securities	0		0
Long-term investments	0		0
Fair value of total assets, recurring	0		0
Fair value of assets measured on a recurring basis, percentage of total assets	0.00%		0.00%
Mandatorily redeemable noncontrolling interests	32.8	[1]	27	[1]
Fair Value, Total
Fair value assets and liabilities measured on recurring and nonrecurring basis
Cash equivalents	901.4		761.2
Short-term marketable securities	6.6		5.3
Long-term investments	0.5		1.6
Fair value of total assets, recurring	908.5		768.1
Fair value of assets measured on a recurring basis, percentage of total assets	7.10%		6.00%
Mandatorily redeemable noncontrolling interests	$32.80	[1]	$27	[1]
[1]	Relates to unconditional obligations to purchase additional noncontrolling equity shares of consolidated subsidiaries. Fair value measurement of the obligation was based upon the amount payable as if the forward contracts were settled. The amount redeemable within the next twelve months is classified in accrued liabilities; any interests redeemable thereafter are classified in other non-current liabilities.

Fair_Value_Unobservable_Inputs

Fair Value Unobservable Inputs (Details) (Mandatorily redeemable noncontrolling interests, USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Mandatorily redeemable noncontrolling interests
Fair value assets and liabilities measured on recurring basis unobservable input reconciliation
Balance at beginning of period, mandatorily redeemable noncontrolling interests	$27	$25.30
Level 3 additions	5.6	0.2
Level 3 reductions	-0.8	0
Realized losses included in net income	1	1.5
Foreign currency translation	0	0
Balance at end of period, mandatorily redeemable noncontrolling interests	$32.80	$27

Fair_Value_on_a_Nonrecurring_B

Fair Value on a Nonrecurring Basis (Details) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value	$0
Level 2
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value	1,566
Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value	80.4
Fair Value, Total
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value	$1,646.40

Employee_Benefits_Details

Employee Benefits (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
General Discussion of Pension and Other Postretirement Benefits [Abstract]
Number of Participants Domestic Pension Plan	4,000
Number of Participants Postretirement Benefit Plan	2,200
Deferred Compensation Arrangements [Abstract]
Deferred Compensation Liability	$97.70	$92.70
Deferred Compensation Expense	9.8	13.4	9.8
Deferred Benefit Liability	153.2	166.2
Deferred Benefit Expense	10.8	14	15
Cash Surrender Value of Life Insurance	165.6	162.3
Deferred Compensation Plan Assets	8.5	7.7
Supplemental Unemployment Benefits [Abstract]
Duration of disability benefits	24 months
Health and Life Insurance Benefit Obligation	8	10.5
Income Replacement Benefit Obligation	$0

Pension_and_Postretirement_Ben

Pension and Postretirement Benefit Obligation (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets (Period End)	$527	$508.10
Domestic Pension Plan
Benefit Obligation [Roll Forward]
Benefit Obligation (Period Start)	133.1	140.6
Service cost	0	0	0
Interest cost	6.2	5.5	6.3
Benefits paid	-10.4	-10.4
Plan participant contributions	0	0
Actuarial losses (gains)	18	-2.6
Settlements and curtailments	0	0
Foreign currency effect	0	0
Other	0	0
Benefit Obligation (Period End)	146.9	133.1	140.6
Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets (Period Start)	109.6	115.7
Actual return on plan assets	9.6	3.8
Employer contributions	2.7	0.5
Plan participant contributions	0	0
Benefits paid	-10.4	-10.4
Settlements	0	0
Foreign currency effect	0	0
Fair Value of Plan Assets (Period End)	111.5	109.6	115.7
Defined Benefit Plan, Funded Status of Plan	-35.4	-23.5
Amounts Recognized in Consolidated Balance Sheets
Non-current asset	0	0
Current liability	0	0
Non-current liability	-35.4	-23.5
Net liability recognized	-35.4	-23.5
Accumulated benefit obligation	146.9	133.1
Amounts recognized in Accumulated Other Comprehensive Loss, net
Net actuarial loss (gain)	56.1	47
Prior service cost (credit)	0	0
Transition obligation	0	0
Total amount recognized	56.1	47
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Loss in Next Fiscal Year	8.2
Pension plans with underfunded or unfunded accumulated benefit obligation
Aggregate projected benefit obligation	146.9	133.1
Aggregate accumulated benefit obligation	146.9	133.1
Aggregate fair value of plan assets	111.5	109.6
Foreign Pension Plans
Benefit Obligation [Roll Forward]
Benefit Obligation (Period Start)	569.9	532.4
Service cost	10.3	9.9	10.2
Interest cost	23.4	21.7	21.9
Benefits paid	-24.1	-23.8
Plan participant contributions	0.6	0.5
Actuarial losses (gains)	55.7	25
Settlements and curtailments	-4	-3.1
Foreign currency effect	-42.8	8.1
Other	0.5	-0.8
Benefit Obligation (Period End)	589.5	569.9	532.4
Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets (Period Start)	398.5	381.7
Actual return on plan assets	44.7	19.5
Employer contributions	25.7	18.3
Plan participant contributions	0.6	0.5
Benefits paid	-24.1	-23.8
Settlements	-4	-2.7
Foreign currency effect	-25.9	5
Fair Value of Plan Assets (Period End)	415.5	398.5	381.7
Defined Benefit Plan, Funded Status of Plan	-174	-171.4
Amounts Recognized in Consolidated Balance Sheets
Non-current asset	8.3	8
Current liability	-8	-7.6
Non-current liability	-174.3	-171.8
Net liability recognized	-174	-171.4
Accumulated benefit obligation	566.2	540.9
Amounts recognized in Accumulated Other Comprehensive Loss, net
Net actuarial loss (gain)	161	141
Prior service cost (credit)	1.1	1.5
Transition obligation	0	0
Total amount recognized	162.1	142.5
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Loss in Next Fiscal Year	4.6
Pension plans with underfunded or unfunded accumulated benefit obligation
Aggregate projected benefit obligation	577.1	553.2
Aggregate accumulated benefit obligation	559.5	528.7
Aggregate fair value of plan assets	395.8	374.7
Domestic Postretirement Benefit Plan
Benefit Obligation [Roll Forward]
Benefit Obligation (Period Start)	37.9	46.6
Service cost	0.1	0.1	0.2
Interest cost	1.7	1.6	2.3
Benefits paid	-5.6	-6.4
Plan participant contributions	1.5	1.7
Actuarial losses (gains)	4.4	-5.7
Settlements and curtailments	0	0
Foreign currency effect	0	0
Other	-0.5	0
Benefit Obligation (Period End)	39.5	37.9	46.6
Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets (Period Start)	0	0
Actual return on plan assets	0	0
Employer contributions	4.1	4.7
Plan participant contributions	1.5	1.7
Benefits paid	-5.6	-6.4
Settlements	0	0
Foreign currency effect	0	0
Fair Value of Plan Assets (Period End)	0	0	0
Defined Benefit Plan, Funded Status of Plan	-39.5	-37.9
Amounts Recognized in Consolidated Balance Sheets
Non-current asset	0	0
Current liability	-4	-4.2
Non-current liability	-35.5	-33.7
Net liability recognized	-39.5	-37.9
Amounts recognized in Accumulated Other Comprehensive Loss, net
Net actuarial loss (gain)	2.9	-1.5
Prior service cost (credit)	-0.4	-0.1
Transition obligation	0	0
Total amount recognized	$2.50	($1.60)

Net_Periodic_Cost_Details

Net Periodic Cost (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Domestic Pension Plan
Defined Benefit Plan, Net Periodic Benefit Cost
Service cost	$0	$0	$0
Interest cost	6.2	5.5	6.3
Expected return on plan assets	-7.3	-7.7	-7.7
Settlement and curtailment losses (gains)	0	0	0
Amortization of:
Transition obligation	0	0	0
Prior service cost (credit)	0	0	0
Unrecognized actuarial losses	6.6	7.9	6.4
Defined Benefit Plan, Net Periodic Benefit Cost	5.5	5.7	5
Net Periodic Benefit, Discount Rate	4.85%	4.00%	5.00%
Expected Long-term Return on Assets	7.00%	7.00%	7.25%
Benefit Obligation, Discount Rate	4.15%	4.85%	4.00%
Foreign Pension Plans
Defined Benefit Plan, Net Periodic Benefit Cost
Service cost	10.3	9.9	10.2
Interest cost	23.4	21.7	21.9
Expected return on plan assets	-24.7	-19.2	-18.2
Settlement and curtailment losses (gains)	0.5	-0.1	0.7
Amortization of:
Transition obligation	0	0	0
Prior service cost (credit)	0.2	0.2	0.2
Unrecognized actuarial losses	3.4	2.8	1
Defined Benefit Plan, Net Periodic Benefit Cost	13.1	15.3	15.8
Net Periodic Benefit, Discount Rate	4.29%	4.32%	5.00%
Net Periodic Benefit, Rate of Compensation Increase	3.97%	3.57%	3.66%
Expected Long-term Return on Assets	6.18%	5.24%	5.02%
Benefit Obligation, Discount Rate	3.41%	4.29%	4.32%
Benefit Obligation, Rate of Compensation Increase	2.98%	3.97%	3.57%
Domestic Postretirement Benefit Plan
Defined Benefit Plan, Net Periodic Benefit Cost
Service cost	0.1	0.1	0.2
Interest cost	1.7	1.6	2.3
Expected return on plan assets	0	0	0
Settlement and curtailment losses (gains)	0	0	0
Amortization of:
Transition obligation	0	0	0.2
Prior service cost (credit)	-0.2	-0.1	-0.1
Unrecognized actuarial losses	0	0	0
Defined Benefit Plan, Net Periodic Benefit Cost	$1.60	$1.60	$2.60
Net Periodic Benefit, Discount Rate	4.85%	4.00%	5.00%
Benefit Obligation, Discount Rate	4.00%	4.85%	4.00%
Health Care Cost Trend Rate Assumed for Next Year	7.00%	7.50%	8.00%
Year Ultimate Trend Rate is Reached	2019	2019	2019
Ultimate Health Care Cost Trend Rate	5.00%	5.00%	5.00%

Fair_Value_of_Pension_Plan_Ass

Fair Value of Pension Plan Assets (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	$527	$508.10
Balance at beginning of period	62.1	88.3
Actual return on plan assets:
Assets sold during the year	0.4	0.6
Assets still held at year end	-1.3	-0.8
Net purchases, sales and settlements	11.3	-26
Balance at end of period	72.5	62.1
Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	61.2	62.4
Level 2
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	393.3	383.6
Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	72.5	62.1
Investment funds
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	431.5	406.7
Balance at beginning of period	25.4	48.2
Actual return on plan assets:
Assets sold during the year	0.2	0.6
Assets still held at year end	-0.7	1.9
Net purchases, sales and settlements	15.2	-25.3
Balance at end of period	40.1	25.4
Investment funds | Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	18.8	22.2
Investment funds | Level 2
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	372.6	359.1
Investment funds | Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	40.1	25.4
Insurance contracts
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	19.3	22
Insurance contracts | Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	0	0
Insurance contracts | Level 2
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	19.3	22
Insurance contracts | Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	0	0
Limited partnerships
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	32.1	36.1
Balance at beginning of period	36.1	39.8
Actual return on plan assets:
Assets sold during the year	0.2	0
Assets still held at year end	-0.3	-2.9
Net purchases, sales and settlements	-3.9	-0.8
Balance at end of period	32.1	36.1
Limited partnerships | Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	0	0
Limited partnerships | Level 2
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	0	0
Limited partnerships | Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	32.1	36.1
Other plan assets
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	44.1	43.3
Balance at beginning of period	0.6	0.3
Actual return on plan assets:
Assets sold during the year	0	0
Assets still held at year end	-0.3	0.2
Net purchases, sales and settlements	0	0.1
Balance at end of period	0.3	0.6
Other plan assets | Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	42.4	40.2
Other plan assets | Level 2
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	1.4	2.5
Other plan assets | Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	$0.30	$0.60

Employee_Benefits_Allocation_o

Employee Benefits Allocation of Plan Assets (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Allocation of Plan Assets
Defined Benefit Plan, Target Plan Asset Allocations	100.00%
Defined Benefit Plan, Actual Plan Asset Allocations	100.00%	100.00%
Equity securities
Allocation of Plan Assets
Defined Benefit Plan, Target Plan Asset Allocations	24.00%
Defined Benefit Plan, Actual Plan Asset Allocations	22.00%	24.00%
Fixed income securities
Allocation of Plan Assets
Defined Benefit Plan, Target Plan Asset Allocations	48.00%
Defined Benefit Plan, Actual Plan Asset Allocations	46.00%	43.00%
Real estate
Allocation of Plan Assets
Defined Benefit Plan, Target Plan Asset Allocations	6.00%
Defined Benefit Plan, Actual Plan Asset Allocations	5.00%	5.00%
Other plan assets
Allocation of Plan Assets
Defined Benefit Plan, Target Plan Asset Allocations	22.00%
Defined Benefit Plan, Actual Plan Asset Allocations	27.00%	28.00%

Pension_Cash_Flows_Details

Pension Cash Flows (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Domestic Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Employer contributions	$2.70	$0.50
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	3
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity
Expected Future Benefit Payments in 2015	10.6
Expected Future Benefit Payments in 2016	10.4
Expected Future Benefit Payments in 2017	10.1
Expected Future Benefit Payments in 2018	9.9
Expected Future Benefit Payments in 2019	9.6
Expected Future Benefit Payments in 2020-2024	44.6
Foreign Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Employer contributions	25.7	18.3
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	24
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity
Expected Future Benefit Payments in 2015	22.4
Expected Future Benefit Payments in 2016	24.2
Expected Future Benefit Payments in 2017	25.6
Expected Future Benefit Payments in 2018	26.1
Expected Future Benefit Payments in 2019	30.7
Expected Future Benefit Payments in 2020-2024	148
Domestic Postretirement Benefit Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Employer contributions	4.1	4.7
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity
Expected Future Benefit Payments in 2015	4.4
Expected Future Benefit Payments in 2016	4.2
Expected Future Benefit Payments in 2017	4.1
Expected Future Benefit Payments in 2018	3.9
Expected Future Benefit Payments in 2019	3.7
Expected Future Benefit Payments in 2020-2024	15.1
Disclosure of Expected Federal Subsidy Receipts
Prescription Drug Subsidy Receipts in 2015	0.4
Prescription Drug Subsidy Receipts in 2016	0.4
Prescription Drug Subsidy Receipts in 2017	0.4
Prescription Drug Subsidy Receipts in 2018	0.4
Prescription Drug Subsidy Receipts in 2019	0.4
Prescription Drug Subsidy Receipts in 2020-2024	$2.40

Savings_Plans_Details

Savings Plans (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Domestic Tax Authority
Defined Benefit Plans and Other Postretirement Benefit Plans
Cost Recognized	$43	$37.70	$35.60
Discretionary Company Contribution
Defined Benefit Plans and Other Postretirement Benefit Plans
Cost Recognized	5.2	4.9	4.8
Defined Contribution Plans Participant Forfeitures
Defined Benefit Plans and Other Postretirement Benefit Plans
Cost Recognized	-3.6	-3.3	-3
Foreign Tax Authority
Defined Benefit Plans and Other Postretirement Benefit Plans
Cost Recognized	$42.40	$36.90	$34

Operations_Details

Operations (Details) (USD $)	3 Months Ended										12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014		Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013		Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segments:
Revenue	$2,207.10	$1,841.10	$1,851.40		$1,637.50	$2,122.70	$1,700.40		$1,756.20	$1,543	$7,537.10	$7,122.30	$6,956.20
Segment operating income											788.6	658.9	677.1
Restructuring and other reorganization-related (charges) reversals, net	-0.1	0.1	-0.7		0.5	-60.6	0.2		-0.3	0.1	-0.2	-60.6	1.2
Interest expense											84.9	122.7	133.5
Interest income											27.4	24.7	29.5
Other (expense) income, net	-0.1	-0.6	-11.2	[1]	1.7	7.7	-46.6	[1]	4.8	1.8	10.2	32.3	-100.5
Income before income taxes											720.7	468	674.8
Depreciation and amortization of fixed assets and intangible assets											163	157.4	147.7
Capital expenditures											148.7	173	169.2
Assets	12,747.20					12,905					12,747.20	12,905
IAN
Segments:
Revenue											6,097.30	5,795.60	5,728.50
Segment operating income											777.1	662.1	700.2
Restructuring and other reorganization-related (charges) reversals, net												-0.3
Depreciation and amortization of fixed assets and intangible assets											124.6	126	119.7
Capital expenditures											-92.1	-109	-97.5
Assets	11,111.20					11,425.10					11,111.20	11,425.10
CMG
Segments:
Revenue											1,439.80	1,326.70	1,227.70
Segment operating income											161	137.6	114.2
Restructuring and other reorganization-related (charges) reversals, net												0.2
Depreciation and amortization of fixed assets and intangible assets											18.4	15.6	14.4
Capital expenditures											-11.6	-18.5	-26.7
Assets	1,316.50					1,203.80					1,316.50	1,203.80
Corporate and Other
Segments:
Segment operating income											-149.5	-140.8	-137.3
Depreciation and amortization of fixed assets and intangible assets											20	15.8	13.6
Capital expenditures											-45	-45.5	-45
Assets	$319.50					$276.10					$319.50	$276.10
[1]	The three months ended June 30, 2014 included a pre-tax loss of $10.4, related to our early extinguishment of debt. The three months ended September 30, 2013 included a pre-tax loss of $45.2, related to our early extinguishment of debt.

Segment_Information_Major_Geog

Segment Information Major Geographic Area (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues and Long-Lived Assets
Long-Lived Assets	$899.80				$884.30				$899.80	$884.30
Revenue	2,207.10	1,841.10	1,851.40	1,637.50	2,122.70	1,700.40	1,756.20	1,543	7,537.10	7,122.30	6,956.20
Domestic
Revenues and Long-Lived Assets
Long-Lived Assets	572.9				545.7				572.9	545.7
Revenue									4,184	3,972.60	3,803.60
Total international
Revenues and Long-Lived Assets
Long-Lived Assets	326.9				338.6				326.9	338.6
Revenue									3,353.10	3,149.70	3,152.60
United Kingdom
Revenues and Long-Lived Assets
Long-Lived Assets	56.7				60.8				56.7	60.8
Revenue									688.3	568.3	572
Continental Europe
Revenues and Long-Lived Assets
Long-Lived Assets	66.4				79.6				66.4	79.6
Revenue									804.7	800.6	823.1
Asia Pacific
Revenues and Long-Lived Assets
Long-Lived Assets	102.2				88.8				102.2	88.8
Revenue									922.5	868.9	838.1
Latin America
Revenues and Long-Lived Assets
Long-Lived Assets	69.2				72.3				69.2	72.3
Revenue									470.4	464.5	450.1
Other
Revenues and Long-Lived Assets
Long-Lived Assets	32.4				37.1				32.4	37.1
Revenue									$467.20	$447.40	$469.30

Commitments_and_Contingencies_2

Commitments and Contingencies Net Rent Expense (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]
Gross rent expense	$357.70	$366.10	$358.50
Third-party sublease rental income	-6.1	-16.1	-17.5
Net rent expense	$351.60	$350	$341

Future_minimum_lease_payments_

Future minimum lease payments (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating Leases, Rent Expense	$357.70	$366.10	$358.50
Rent Obligations, due 2015	328.4
Rent Obligations, due 2016	288.9
Rent Obligations, due 2017	248.3
Rent Obligations, due 2018	222.3
Rent Obligations, due 2019	198.9
Rent Obligations, due thereafter	845.1
Total Rent Obligations	2,131.90
Sublease Rental Income, due 2015	-8.4
Sublease Rental Income, due 2016	-2.8
Sublease Rental Income, due 2017	-1.1
Sublease Rental Income, due 2018	-0.1
Sublease Rental Income, due 2019	0
Sublease Rental Income, due thereafter	0
Total Sublease Rental Income	-12.4
Net Rent, due 2015	320
Net Rent, due 2016	286.1
Net Rent, due 2017	247.2
Net Rent, due 2018	222.2
Net Rent, due 2019	198.9
Net Rent, due thereafter	845.1
Total Net Rent	2,119.50
Operating Leases, Rent Expense, Sublease Rentals	6.1	16.1	17.5
Operating Leases, Rent Expense, Net	$351.60	$350	$341

Guarantees_Details

Guarantees (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Commitments and Contingencies Disclosure [Abstract]
Parent company guarantees on lease obligations	$580.40	$588.10
Parent company guarantees relating to credit facilities	329.2	279.6
Assets pledged as security for parent company guarantees	$0

Contingent_Acquisition_Obligat

Contingent Acquisition Obligations (Details) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Deferred acquisition payments
Business Acquisition, Contingent Consideration [Line Items]
Recorded Unconditional Purchase Obligation Due in Next Twelve Months	$60.30
Recorded Unconditional Purchase Obligation Due in Second Year	21.3
Recorded Unconditional Purchase Obligation Due in Third Year	49.1
Recorded Unconditional Purchase Obligation Due in Fourth Year	7.9
Recorded Unconditional Purchase Obligation Due in Fifth Year	10.8
Recorded Unconditional Purchase Obligation Due after Fifth Year	0.9
Recorded Unconditional Purchase Obligation	150.3
Redeemable noncontrolling interests and call options with affiliates
Business Acquisition, Contingent Consideration [Line Items]
Recorded Unconditional Purchase Obligation Due in Next Twelve Months	35.4
Recorded Unconditional Purchase Obligation Due in Second Year	65
Recorded Unconditional Purchase Obligation Due in Third Year	37
Recorded Unconditional Purchase Obligation Due in Fourth Year	7.8
Recorded Unconditional Purchase Obligation Due in Fifth Year	10.5
Recorded Unconditional Purchase Obligation Due after Fifth Year	7
Recorded Unconditional Purchase Obligation	162.7	[1]
Redeemable at noncontrolling equity owners discretion
Business Acquisition, Contingent Consideration [Line Items]
Recorded Unconditional Purchase Obligation Due in Next Twelve Months	20.5
Total contingent acquisition payments
Business Acquisition, Contingent Consideration [Line Items]
Recorded Unconditional Purchase Obligation Due in Next Twelve Months	95.7
Recorded Unconditional Purchase Obligation Due in Second Year	86.3
Recorded Unconditional Purchase Obligation Due in Third Year	86.1
Recorded Unconditional Purchase Obligation Due in Fourth Year	15.7
Recorded Unconditional Purchase Obligation Due in Fifth Year	21.3
Recorded Unconditional Purchase Obligation Due after Fifth Year	7.9
Recorded Unconditional Purchase Obligation	313
Cash compensation expense included in contingent acquisitions
Business Acquisition, Contingent Consideration [Line Items]
Recorded Unconditional Purchase Obligation Due in Next Twelve Months	1.9
Recorded Unconditional Purchase Obligation Due in Second Year	1.6
Recorded Unconditional Purchase Obligation Due in Third Year	0.7
Recorded Unconditional Purchase Obligation Due in Fourth Year	0
Recorded Unconditional Purchase Obligation Due in Fifth Year	0
Recorded Unconditional Purchase Obligation Due after Fifth Year	0
Recorded Unconditional Purchase Obligation	4.2
Total contingent acquisition payments excluding compensation expense
Business Acquisition, Contingent Consideration [Line Items]
Recorded Unconditional Purchase Obligation Due in Next Twelve Months	93.8
Recorded Unconditional Purchase Obligation Due in Second Year	84.7
Recorded Unconditional Purchase Obligation Due in Third Year	85.4
Recorded Unconditional Purchase Obligation Due in Fourth Year	15.7
Recorded Unconditional Purchase Obligation Due in Fifth Year	21.3
Recorded Unconditional Purchase Obligation Due after Fifth Year	7.9
Recorded Unconditional Purchase Obligation	$308.80
[1]	We have entered into certain acquisitions that contain both redeemable noncontrolling interests and call options with similar terms and conditions. The estimated amounts listed would be paid in the event of exercise at the earliest exercise date. We have certain redeemable noncontrolling interests that are exercisable at the discretion of the noncontrolling equity owners as of December 31, 2014. These estimated payments of $20.5 are included within the total payments expected to be made in 2015, and will continue to be carried forward into 2016 or beyond until exercised or expired. Redeemable noncontrolling interests are included in the table at current exercise price payable in cash, not at applicable redemption value in accordance with the authoritative guidance for classification and measurement of redeemable securities.

Results_by_Quarter_Unaudited_D

Results by Quarter (Unaudited) (Details) (USD $)	3 Months Ended											12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014		Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013		Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Revenue	$2,207.10		$1,841.10	$1,851.40		$1,637.50	$2,122.70	$1,700.40		$1,756.20	$1,543	$7,537.10	$7,122.30	$6,956.20
Salaries and related expenses	1,266.40		1,195.20	1,170.20		1,188.60	1,199.60	1,093.60		1,120.20	1,132.10	4,820.40	4,545.50	4,391.90
Office and general expenses	507.6		474.7	484.7		461.1	538.1	465.5		460.9	453.4	1,928.10	1,917.90	1,887.20
Restructuring and other reorganization-related charges (reversals), net	0.1		-0.1	0.7		-0.5	60.6	-0.2		0.3	-0.1	0.2	60.6	-1.2
Operating (loss) income	433		171.3	195.8		-11.7	324.4	141.5		174.8	-42.4	-788.4	-598.3	-678.3
Other income (expense), net 1	-0.1		-0.6	-11.2	[1]	1.7	7.7	-46.6	[1]	4.8	1.8	10.2	32.3	-100.5
Total (expenses) and other income	-14.4		-13.8	-27.2	[1]	-12.3	-10.3	-64.5	[1]	-26.9	-28.6	67.7	130.3	3.5
(Benefit of) provision for income taxes	87.9	[2]	65	65.3		-1.7	103.2	28.4		62	-12.4	216.5	181.2	213.3
Net (loss) income	-331.3		-92.8	-103.7		22.4	-212.1	-49.2		-86.1	58.5	-505.4	-288.9	-464.6
Net (loss) income available to IPG common stockholders	308.9		89.7	99.4		-20.9	193.1	45.4		79.9	-59.2	477.1	259.2	435.1
Quarterly Information Tables [Line Items]
Gains (Losses) on Extinguishment of Debt												10.4	45.2	0
Dividends declared per common share	$0.10		$0.10	$0.10		$0.10	$0.08	$0.08		$0.08	$0.08	$0.38	$0.30	$0.24
Basic	$0.75		$0.21	$0.24		($0.05)	$0.45	$0.11		$0.19	($0.14)	$1.14	$0.62	$1.01
Diluted	$0.73		$0.21	$0.23		($0.05)	$0.44	$0.11		$0.18	($0.14)	$1.12	$0.61	$0.94
6.25% Notes
Quarterly Information Tables [Line Items]
Gains (Losses) on Extinguishment of Debt												$10.40
[1]	The three months ended June 30, 2014 included a pre-tax loss of $10.4, related to our early extinguishment of debt. The three months ended September 30, 2013 included a pre-tax loss of $45.2, related to our early extinguishment of debt.
[2]	The three months ended December 31, 2014 included a tax benefit of $67.6 due to the net reversal of valuation allowances on deferred tax assets in Continental Europe.

Subsequent_Events_Details

Subsequent Events (Details) (USD $)	0 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 16, 2015	Mar. 02, 2015	Feb. 13, 2015
2015 Share Repurchase Program
Subsequent Event [Line Items]
Share repurchase program, initial authorized amount			$300
Dividends [Domain]
Subsequent Event [Line Items]
Dividends Payable, Amount Per Share			$0.12
Dividend Paid
Subsequent Event [Line Items]
Dividends Payable, Date to be Paid	16-Mar-15
Dividend Declared
Subsequent Event [Line Items]
Dividends Payable, Date of Record		2-Mar-15