The Interpublic Group of Companies, Inc. (IPG) 10-K 25 Feb 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information Document - USD ($)	12 Months Ended
	Dec. 31, 2018	Feb. 13, 2019	Jun. 30, 2018
DEI [Abstract]
Entity Registrant Name	INTERPUBLIC GROUP OF COMPANIES, INC.
Entity Central Index Key	51,644
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	1,218
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Trading Symbol	IPG
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Common Stock, Shares Outstanding		384,912,527
Entity Public Float			$ 8,998,838,797

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Net revenue	$ 2,413.7	$ 1,895.7	$ 1,948.2	$ 1,774	$ 2,131.1	$ 1,832.5	$ 1,834.6	$ 1,675.3	$ 8,031.6	$ 7,473.5	$ 7,452.3
Billable expenses	442.3	401.8	443.6	395.1	458.7	375.7	351.2	388.5	1,682.8	1,574.1	1,603.9
Total revenue	2,856	2,297.5	2,391.8	2,169.1	2,589.8	2,208.2	2,185.8	2,063.8	9,714.4	9,047.6	9,056.2
OPERATING EXPENSES:
Salaries and related expenses	1,423.7	1,251.4	1,292.9	1,330.3	1,291.3	1,218.8	1,228.9	1,251.7	5,298.3	4,990.7	4,942.2
Office and other direct expenses	381	317	333.3	323.8	334.8	302.9	318.4	312.7	1,355.1	1,268.8	1,274.9
Billable expense	442.3	401.8	443.6	395.1	458.7	375.7	351.2	388.5	1,682.8	1,574.1	1,603.9
Cost of services	2,247	1,970.2	2,069.8	2,049.2	2,084.8	1,897.4	1,898.5	1,952.9	8,336.2	7,833.6	7,821
Selling, General and Administrative Expense	81	21.6	28.8	35.1	49.4	13.6	20.3	35.2	166.5	118.5	138.6
Depreciation and amortization	68.9	44	44	46	32.6	42.2	41.3	41	202.9	157.1	160.2
Total operating expenses	2,396.9	2,035.8	2,142.6	2,130.3	2,166.8	1,953.2	1,960.1	2,029.1	8,705.6	8,109.2	8,119.8
OPERATING INCOME	459.1	261.7	249.2	38.8	423	255	225.7	34.7	1,008.8	938.4	936.4
EXPENSES AND OTHER INCOME:
Interest expense									(123)	(90.8)	(90.6)
Interest income									21.8	19.4	20.1
Other expense, net	(13.6)	(15.3)	(16.3)	(24.4)	(1.7)	(9.9)	(15.4)	0.8	(69.6)	(26.2)	(40.3)
Total (expenses) and other income	(55.2)	(37.6)	(37.7)	(40.3)	(19.5)	(26.8)	(36.4)	(14.9)	(170.8)	(97.6)	(110.8)
Income before income taxes									838	840.8	825.6
Provision for income taxes	62.2	60.7	63.6	12.7	135.1	54.9	81.6	(0.3)	199.2	271.3	196.9
Income of consolidated companies									638.8	569.5	628.7
Equity in net (loss) income of unconsolidated affiliates									(1.1)	0.9	0.3
NET INCOME	$ 342.5	$ 163.5	$ 147.8	$ (16.1)	$ 269.2	$ 172.3	$ 107.6	$ 21.3	637.7	570.4	629
Net income attributable to noncontrolling interests									(18.8)	(16)	(24)
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS									$ 618.9	$ 554.4	$ 605
Earnings per share available to IPG common stockholders:
Earnings per share, Basic	$ 0.85	$ 0.42	$ 0.38	$ (0.04)	$ 0.66	$ 0.44	$ 0.27	$ 0.06	$ 1.61	$ 1.42	$ 1.52
Earnings per share, Diluted	$ 0.84	$ 0.41	$ 0.37	$ (0.04)	$ 0.64	$ 0.43	$ 0.27	$ 0.06	$ 1.59	$ 1.40	$ 1.48
Weighted-average number of common shares outstanding:
Weighted-average number of common shares outstanding, Basic									383.3	389.6	397.9
Weighted-average number of common shares outstanding, Diluted									389	397.3	408

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
NET INCOME	$ 637.7	$ 570.4	$ 629
Foreign Currency Translation:
Foreign currency translation adjustments	(149.6)	133.7	(57.8)
Reclassification adjustments recognized in net income	15.7	1.1	3.7
Foreign currency translation, net of tax	(133.9)	134.8	(54.1)
Available-for-sale securities:
Changes in fair value of available-for-sale securities	0	0	0.5
Recognition of previously unrealized gains in net income	0	(0.7)	(1.3)
Income tax effect	0	0.1	0.1
Available-for-sale securities, net of tax	0	(0.6)	(0.7)
Derivatives instruments:
Recognition of previously unrealized losses included in net income	2.2	2.1	2
Income tax effect	(0.7)	(0.5)	(0.8)
Derivative instruments, net of tax	1.5	1.6	1.2
Defined benefit pension and other postretirement plans:
Net actuarial gains (losses) for the period	12.6	(13.6)	(85.4)
Amortization of unrecognized losses, transition obligation and prior service cost included in net income	7.5	6.9	5.4
Less: settlement and curtailment (gains) losses included in net income	(1)	6.8	0.4
Other	(1)	2.7	(2)
Income tax effect	(1.8)	(0.5)	15.3
Defined benefit pension and other postretirement plans, net of tax	16.3	2.3	(66.3)
Other comprehensive (loss) income, net of tax	(116.1)	138.1	(119.9)
Total comprehensive income	521.6	708.5	509.1
Less: comprehensive income attributable to noncontrolling interests	16	17.5	22.9
Comprehensive Income Attributable to IPG	$ 505.6	$ 691	$ 486.2

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
ASSETS:
Cash and cash equivalents	$ 673.4	$ 790.9
Accounts receivable, net of allowance of $42.5 and $42.7, respectively	5,126.6	4,585
Accounts receivable, billable to clients	1,900.6	1,747.4
Assets held for sale	5.7	5.7
Other current assets	476.6	346.5
Total current assets	8,182.9	7,475.5
Property and equipment, net	790.9	650.4
Deferred income taxes	247	234
Goodwill	4,875.9	3,820.4	$ 3,674.4
Other intangible assets	1,094.7	140.7
Other non-current assets	428.9	383.7
TOTAL ASSETS	15,620.3	12,704.7
LIABILITIES:
Accounts payable	6,698.1	6,420.2
Accrued liabilities	806.9	674.7
Contract liabilities	533.9	484.7
Short-term borrowings	73.7	84.9
Current portion of long-term debt	0.1	2
Liabilities held for sale	11.2	8.8
Total current liabilities	8,123.9	7,675.3
Long-term debt	3,660.2	1,285.6
Deferred compensation	422.7	476.6
Other non-current liabilities	812.8	768.8
TOTAL LIABILITIES	13,019.6	10,206.3
Redeemable noncontrolling interests	167.9	252.1	252.8	$ 251.9
STOCKHOLDERS' EQUITY:
Common Stock, Value, Issued	38.3	38.6
Additional paid-in capital	895.9	955.2
Retained earnings	2,400.1	2,104.5
Accumulated other comprehensive loss, net of tax	(941.1)	(827.8)	(964.4)
Stockholders Equity Subtotal Before Treasury Stock	2,393.2	2,270.5
Less: Treasury stock, at cost: 2017 – 3.0 shares; 2016 – 2.7 shares	0	(59)
Total IPG stockholders' equity	2,393.2	2,211.5
Noncontrolling interests	39.6	34.8
TOTAL STOCKHOLDERS' EQUITY	2,432.8	2,246.3	$ 2,090.4	$ 2,001.8
TOTAL LIABILITIES AND EQUITY	$ 15,620.3	$ 12,704.7

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Millions, $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 42.5	$ 42.7
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	800	800
Common stock, shares issued	383.6	386.2
Common stock, shares outstanding	383.6	383.2
Treasury stock, shares	0	3

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
NET INCOME	$ 637.7	$ 570.4	$ 629
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	202.9	157.1	160.2
Provision for uncollectible receivables	6.5	9.5	16.7
Amortization of restricted stock and other non-cash compensation	82.2	82	85.6
Net amortization of bond discounts and deferred financing costs	6.5	5.8	5.6
Deferred income tax provision	14.1	(9.5)	44.6
Net losses on sales of businesses	61.9	24.1	41.4
Other	1.2	12.7	35.5
Changes in assets and liabilities, net of acquisitions and divestitures, providing (using) cash:
Accounts receivable	(603.8)	37.6	(220.7)
Accounts receivable, billable to clients	(209.5)	(165.5)	(2.2)
Other current assets	(67.2)	50.1	0.5
Accounts payable	428.7	336.4	(147.4)
Accrued liabilities	(24.2)	(241.3)	(61.1)
Contract liabilities	44.9	(12)	20.6
Other non-current assets and liabilities	(16.8)	24.4	(95.5)
Net cash provided by operating activities	565.1	881.8	512.8
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions, net of cash acquired	2,309.8	30.6	52
Capital expenditures	177.1	155.9	200.7
Other investing activities	(4.6)	(9.7)	(11.2)
Net cash used in investing activities	(2,491.5)	(196.2)	(263.9)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from Issuance of Long-term Debt	2,494.2	0	0
Exercise of stock options	15.5	13.1	10.2
Common stock dividends	(322.1)	(280.3)	(238.4)
Repurchases of common stock	(117.1)	(300.1)	(303.3)
Repayments of long-term debt	(104.8)	(324.6)	(1.8)
Acquisition-related payments	(33.7)	(53.7)	(40.8)
Tax payments for employee shares withheld	(29.2)	(38.8)	(23.1)
Net (decrease) increase in short-term borrowings	(17.5)	3	(56.2)
Distributions to noncontrolling interests	(16.9)	(20.4)	(13.7)
Other financing activities	(15.2)	(3.1)	0.7
Net cash provided by (used in) financing activities	1,853.2	(1,004.9)	(666.4)
Effect of foreign exchange rate changes on cash, cash equivalents and restricted cash	(47.3)	16.8	11.6
Net decrease in cash, cash equivalents and restricted cash	(120.5)	(302.5)	(405.9)
Cash, cash equivalents and restricted cash at beginning of period	797.7	1,100.2	1,506.1
Cash, cash equivalents and restricted cash at end of period	$ 677.2	$ 797.7	$ 1,100.2

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	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
Balance at Dec. 31, 2015	$ 2,001.8	$ 40.4	$ 1,404.1	$ 1,437.6	$ (845.6)	$ (71)	$ 1,965.5	$ 36.3
Balance, shares at Dec. 31, 2015		404.4
Cumulative effect of accounting change	39.1			39.1			39.1
NET INCOME	629			605			605	24
Other comprehensive income	(119.9)				(118.8)		(118.8)	(1.1)
Reclassifications related to redeemable noncontrolling interests	(5.8)							(5.8)
Distributions to noncontrolling interests	(13.7)							(13.7)
Change in redemption value of RNCI	(2.1)			(2.1)			(2.1)
Repurchases of common stock	(303.3)					(303.3)	(303.3)
Retirement of treasury stock, shares		(13.7)
Retirement of treasury stock	0	$ (1.4)	(309.6)			311	0
Common stock dividends	(238.4)			(238.4)			(238.4)
Stock-based compensation, shares		3.5
Stock-based compensation, Value	117.1	$ 0.4	116.7				117.1
Exercise of stock options, shares		1.2
Exercise of stock options, Value	10.3	$ 0.1	10.2				10.3
Shares withheld for taxes, shares		(1.1)
Shares withheld for taxes, value	(23.3)	$ (0.1)	(23.2)				(23.3)
Other	(0.4)		1	(1.3)			(0.3)	(0.1)
Balance, shares at Dec. 31, 2016		394.3
Balance at Dec. 31, 2016	2,090.4	$ 39.4	1,199.2	1,839.9	(964.4)	(63.3)	2,050.8	39.6
NET INCOME	570.4			554.4			554.4	16
Other comprehensive income	138.1				136.6		136.6	1.5
Reclassifications related to redeemable noncontrolling interests	0.6		(0.3)				(0.3)	0.9
Distributions to noncontrolling interests	(20.9)							(20.9)
Change in redemption value of RNCI	(7.9)			(7.9)			(7.9)
Repurchases of common stock	(300.1)					(300.1)	(300.1)
Retirement of treasury stock, shares		(13.4)
Retirement of treasury stock	0	$ (1.3)	(303.1)			304.4	0
Common stock dividends	(280.3)			(280.3)			(280.3)
Stock-based compensation, shares		5.7
Stock-based compensation, Value	87	$ 0.6	86.4				87
Exercise of stock options, shares		1.2
Exercise of stock options, Value	13.2	$ 0.1	13.1				13.2
Shares withheld for taxes, shares		(1.6)
Shares withheld for taxes, value	(39)	$ (0.2)	(38.8)				(39)
Other	(5.2)		1.3	(1.6)			(2.9)	(2.3)
Balance, shares at Dec. 31, 2017		386.2
Balance at Dec. 31, 2017	2,246.3	$ 38.6	955.2	2,104.5	(827.8)	(59)	2,211.5	34.8
NET INCOME	637.7			618.9			618.9	18.8
Other comprehensive income	(116.1)				(113.3)		(113.3)	(2.8)
Reclassifications related to redeemable noncontrolling interests	2.4							2.4
Distributions to noncontrolling interests	(16.9)							(16.9)
Change in redemption value of RNCI	42.9		41.8	1.1			42.9
Repurchases of common stock	(117.1)					(117.1)	(117.1)
Retirement of treasury stock, shares		(8.1)
Retirement of treasury stock	0	$ (0.8)	(175.3)			176.1	0
Common stock dividends	(322.1)			(322.1)			(322.1)
Stock-based compensation, shares		4.8
Stock-based compensation, Value	87.5	$ 0.5	87				87.5
Exercise of stock options, shares		1.9
Exercise of stock options, Value	15.7	$ 0.2	15.5				15.7
Shares withheld for taxes, shares		(1.2)
Shares withheld for taxes, value	(29.2)	$ (0.2)	(29)				(29.2)
Other	1.7		0.7	(2.3)			(1.6)	3.3
Balance, shares at Dec. 31, 2018		383.6
Balance at Dec. 31, 2018	$ 2,432.8	$ 38.3	$ 895.9	$ 2,400.1	$ (941.1)	$ 0	$ 2,393.2	$ 39.6

Significant Accounting Policies

Significant Accounting Policies (Notes)	12 Months Ended
	Dec. 31, 2018
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. 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 recorded at cost, less any impairment, adjusted for subsequent observable price changes. 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 As of January 1, 2018, the Company has revised the presentation of its Consolidated Statements of Operations, which disaggregates net revenue and billable expenses within total revenue and separately presents cost of services; selling, general and administrative expenses; and depreciation and amortization within operating expenses. The revised presentation does not impact total revenue, total operating expenses or operating income. Cost of services is comprised of the expenses of our revenue-producing operating segments including salaries and related expenses, office and other direct expenses and billable expenses, as well as an allocation of the centrally managed expenses from Corporate. Office and other direct expenses include rent expense, professional fees, certain expenses incurred by our staff in servicing our clients and other costs directly attributable to client engagements. Selling, general and administrative expenses are primarily the unallocated expenses from Corporate, as disclosed further in Note 14 , excluding depreciation and amortization. Depreciation and amortization of the fixed assets and intangible assets of the Company is disclosed as a separate operating expense. Certain reclassifications and immaterial revisions have been made to prior-period financial statements to conform to the current-period 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 and communications and marketing services, including public relations, meeting and event production, sports and entertainment marketing, corporate and brand identity, and strategic marketing consulting around the world. Most of our client contracts are individually negotiated and, accordingly, the terms of client engagements and the basis on which we earn fees and commissions vary significantly. Our contracts generally provide for termination by either party on relatively short notice, usually 30 to 90 days. Our payment terms vary by client, and the time between invoicing date and due date is typically not significant. We generally have the legally enforceable right to payment for all services provided through the end of the contract or termination date. Effective January 1, 2018, we adopted Accounting Standards Codification Topic 606, Revenue from Contracts with Customers, ("ASC 606") using the full retrospective transition method. Under this method, we revised our consolidated financial statements for the years ended December 31, 2016 and 2017, and applicable interim periods within the year ended December 31, 2017, as if ASC 606 had been effective for those periods. ASC 606 applies to all contracts with customers, except for contracts that are within the scope of other standards. We recognize revenue when we determine our customer obtains control of promised goods or services, in an amount that reflects the consideration which we expect to receive in exchange for those goods or services. To determine revenue recognition, we perform the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue as or when we satisfy the performance obligation. We only apply the five-step model to contracts when it is probable that IPG will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, we assess the goods or services promised within each contract and determine those that are distinct performance obligations. We then assess whether we act as an agent or a principal for each identified performance obligation and include revenue within the transaction price for third-party costs when we determine that we act as principal. We typically do not capitalize costs to obtain a contract as these amounts would generally be recognized over a period of one year or less. Net revenue, primarily consisting of fees, commissions and performance incentives, represents the amount of our gross billings excluding billable expenses charged to a client. Generally, our compensation is based on a negotiated fixed price, rate per hour, a retainer or commission. The majority of our fees are recognized over time as services are performed, utilizing a function of hours incurred and rates per hour, as compared to periodically updated estimates to complete. For certain less-frequent commission-based contracts which contain clauses allowing our clients to terminate the arrangement at any time for no compensation, revenue is recognized at a point in time, typically the date of broadcast or publication. We report revenue net of taxes assessed by governmental authorities that are directly imposed on our revenue-producing transactions. Contractual arrangements with clients may also include performance incentive provisions designed to link a portion of our revenue to our performance relative to mutually agreed-upon qualitative and/or quantitative metrics. Performance incentives are treated as variable consideration which is estimated at contract inception and included in revenue based on the most likely amount earned out of a range of potential outcomes. Our estimates are based on a combination of historical award experience, anticipated performance and our best judgment. These estimates are updated on a periodic basis and are not expected to result in a reversal of a significant amount of the cumulative revenue recognized. The predominant component of billable expenses are third-party vendor costs incurred for performance obligations where we have determined that we are acting as principal. These third-party expenses are generally billed back to our clients. Billable expenses also includes incidental costs incurred in the performance of our services including airfare, mileage, hotel stays, out-of-town meals and telecommunication charges. We record these billable expenses within total revenue with a corresponding offset to operating expenses. In international markets, we may receive rebates or credits from vendors based on transactions entered into on behalf of clients. Rebates and credits are remitted back to our clients in accordance with our contractual requirements or may be retained by us based on the terms of a particular client contract and local law. Amounts owed back to clients are recorded as a liability and amounts retained by us are recorded as revenue when earned. In certain international markets, our media contracts may allow clients to terminate our arrangement at any time for no compensation to the extent that media has not yet run. For those contracts, we do not recognize revenue until the media runs which is the point in time at which we have a legally enforceable right to compensation. Performance Obligations Our client contracts may include various goods and services that are capable of being distinct, are distinct within the context of the contract and are therefore accounted for as separate performance obligations. We allocate revenue to each performance obligation in the contract at inception based on its relative standalone selling price. Our advertising businesses include a wide range of services that involve the creation of an advertising idea, concept, campaign, or marketing strategy in order to promote the client’s brand ("creative services"), and to act as an agent to facilitate the production of advertisements by third-party suppliers ("production services”). Our clients can contract us to perform one or both of these services, as they can derive stand-alone benefit from each. Production services can include formatting creative material for different media and communication mediums including digital, large-scale reproduction such as printing and adaptation services, talent engagement and acquisition, television and radio production, and outdoor billboard production. Our contracts that include both services are typically explicit in the description of which activities constitute the creative advertising services and those that constitute the production services. Both the creative and production services are sold separately, the client can derive utility from each service on its own, we do not provide a significant service of integrating these activities into a bundle, the services do not significantly modify one another, and the services are not highly interrelated or interdependent. As such, we typically identify two performance obligations in the assessment of our advertising contracts. Our media businesses include services to formulate strategic media plans ("media planning services") and to act as an agent to purchase media (e.g. television and radio spots, outdoor advertising, digital banners, etc.) from vendors on their behalf ("media buying services"). Our contracts that include both services are typically explicit in the description of which activities constitute the planning services and those that constitute the buying services. Both the planning and buying services are sold separately, the client can derive utility from each service on its own, we do not provide a significant service of integrating these activities into a bundle, the services do not significantly modify one another, and the services are not highly interrelated or interdependent. As such, we typically identify two performance obligations in the assessment of our media contracts. Our events businesses include creative services related to the conception and planning of custom marketing events as well as activation services which entail the carrying out of the event, including, but not limited to, set-up, design and staffing. Additionally, our public relations businesses include a broad range of services, such as strategic planning, social media strategy and the monitoring and development of communication strategies, among others. While our contracts in these businesses may include some or all of these services, we typically identify only one performance obligation in the assessment of our events and public relations contracts as we provide a significant service of integrating the individual services into a combined service for which the customer has contracted. As part of our adoption of ASC 606, we elected not to disclose information about remaining performance obligations that have original expected durations of one year or less. The majority of our contracts are for periods of one-year or less. For those contracts with a term of more than one year, we had approximately $770.0 of unsatisfied performance obligations as of December 31, 2018 which will be recognized as services are performed over the remaining contractual terms. Principal vs. Agent When a third-party is involved in the delivery of our services to the client, we assess whether or not we are acting as a principal or an agent in the arrangement. The assessment is based on whether we control the specified services at any time before they are transferred to the customer. We have determined that in our events and public relations businesses, we generally act as a principal as our agencies provide a significant service of integrating goods or services provided by third parties into the specified deliverable to our clients. In addition, we have determined that we are responsible for the performance of the third-party suppliers, which are combined with our own services, before transferring those services to the customer. In addition, we have determined that we act as principal when providing creative services and media planning services, as we perform a significant integration service in these transactions. For performance obligations in which we act as principal, we record the gross amount billed to the customer within total revenue and the related incremental direct costs incurred as billable expenses. When a third-party is involved in the production of an advertising campaign and for media buying services, we have determined that we act as the agent and are solely arranging for the third-party to provide services to the customer. Specifically, we do not control the specified services before transferring those services to the customer, we are not primarily responsible for the performance of the third-party services, nor can we redirect those services to fulfill any other contracts. We do not have inventory risk or discretion in establishing pricing in our contracts with customers. For performance obligations for which we act as the agent, we record our revenue as the net amount of our gross billings less amounts remitted to third parties. 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. 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. Accounts Receivable, Billable to Clients Accounts receivable, 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 non-publicly traded investments and all other publicly traded investments are accounted for using the equity method or are recorded at fair value. We regularly review our investments to determine whether a significant event or change in circumstances has occurred that may impact the fair value of each investment, with changes to fair value recorded in earnings. 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 a 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 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 1 st 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 2018 annual impairment testing. Our annual impairment review as of October 1, 2018 did not result in an impairment charge for any of our reporting units. 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 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 sum of the fair values of all our reporting units is also 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 quantitative impairment test is failed and impaired goodwill is written down to its fair value with a charge to expense in the period the impairment is identified. The fair value of each reporting unit for 2018 and 2017 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 asset groups. These asset groups 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 pre-tax gains of $5.6 , $1.9 and $2.1 in for the years ended December 31, 2018 , 2017 and 2016 , respectively. 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. Public Law 115-97, commonly referred to as the Tax Cuts and Jobs Act (the "Tax Act") was signed into law on December 22, 2017. The Tax Act legislated many new tax provisions which have impacted our operations. At December 31, 2017, provisional amounts were recorded as permitted by SEC Staff issued Accounting Bulletin No. 118 (“SAB 118”). We have finalized our calculations of the impact of the Tax Act and have revised our estimates as required by SAB 118. See Note 9 for further information. 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 (“APIC”), 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 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 were exercised. 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 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. 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, 2018 , 2017 and 2016 , 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 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 October 2018 , we retired 8.1 shares of our treasury stock, which resulted in a reduction in common stock of $0.8 , treasury stock of $176.1 and APIC of $175.3 . In October and November 2017 , we retired 13.4 shares of our treasury stock, which resulted in a reduction in common stock of $1.3 , treasury stock of $304.4 and APIC of $303.1 . In October 2016 , we retired 13.7 shares of our treasury stock, which resulted in a reduction in common stock of $1.4 , treasury stock of $311.0 and APIC of $309.6 . There was no effect on total stockholders' equity as a result of these retirements.

Revenue (Notes)

Revenue (Notes)	12 Months Ended
	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer [Text Block]	Note 2 : Revenue Adoption of ASC 606 Effective with the adoption of ASC 606 on January 1, 2018 using the full retrospective transition method, the Company revised its consolidated financial statements for the years ended December 31, 2017 and 2016, and applicable interim periods within the year ended December 31, 2017, as if ASC 606 had been effective for those periods. ASC 606, which accelerates the recognition of revenue primarily as a result of estimating variable consideration, mostly impacts the timing of revenue recognition between quarters, but also can affect, to a lesser extent, the amount of annual revenue recognized. Although ASC 606 results in an increase in the number of performance obligations within certain of our contractual arrangements, the amount or timing of revenue recognized is not materially impacted. ASC 606 also results in an increase in third-party costs being included in revenue and costs, primarily in connection with our events businesses, which has no impact on operating income, net income or cash flows. The increases to retained earnings as of December 31, 2017 and 2016, as well as January 1, 2016, as a result of adopting ASC 606 were not material. The following tables summarize the effects of adopting ASC 606. CONSOLIDATED STATEMENT OF OPERATIONS Year ended December 31, 2017 Year ended December 31, 2016 As Revised 1 ASC 606 Adjustments As Adjusted As Revised 1 ASC 606 Adjustments As Adjusted REVENUE: Net revenue $ 7,508.7 $ (35.2 ) $ 7,473.5 $ 7,456.9 $ (4.6 ) $ 7,452.3 Billable expenses 373.7 1,200.4 1,574.1 389.7 1,214.2 1,603.9 Total revenue 7,882.4 1,165.2 9,047.6 7,846.6 1,209.6 9,056.2 OPERATING EXPENSES: Salaries and related expenses 4,990.7 — 4,990.7 4,942.2 — 4,942.2 Office and other direct expenses 1,268.8 — 1,268.8 1,274.9 — 1,274.9 Billable expenses 373.7 1,200.4 1,574.1 389.7 1,214.2 1,603.9 Cost of services 6,633.2 1,200.4 7,833.6 6,606.8 1,214.2 7,821.0 Selling, general and administrative expenses 118.5 — 118.5 138.6 — 138.6 Depreciation and amortization 157.1 — 157.1 160.2 — 160.2 Total operating expenses 6,908.8 1,200.4 8,109.2 6,905.6 1,214.2 8,119.8 OPERATING INCOME 973.6 (35.2 ) 938.4 941.0 (4.6 ) 936.4 EXPENSES AND OTHER INCOME: Interest expense (90.8 ) — (90.8 ) (90.6 ) — (90.6 ) Interest income 19.4 — 19.4 20.1 — 20.1 Other expense, net (26.2 ) — (26.2 ) (40.3 ) — (40.3 ) Total (expenses) and other income (97.6 ) — (97.6 ) (110.8 ) — (110.8 ) Income before income taxes 876.0 (35.2 ) 840.8 830.2 (4.6 ) 825.6 Provision for income taxes 281.9 (10.6 ) 271.3 198.0 (1.1 ) 196.9 Income of consolidated companies 594.1 (24.6 ) 569.5 632.2 (3.5 ) 628.7 Equity in net income of unconsolidated affiliates 0.9 — 0.9 0.3 — 0.3 NET INCOME 595.0 (24.6 ) 570.4 632.5 (3.5 ) 629.0 Net income attributable to noncontrolling interests (16.0 ) — (16.0 ) (24.0 ) — (24.0 ) NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS $ 579.0 $ (24.6 ) $ 554.4 $ 608.5 $ (3.5 ) $ 605.0 Earnings per share available to IPG common stockholders: Basic $ 1.49 $ (0.07 ) $ 1.42 $ 1.53 $ (0.01 ) $ 1.52 Diluted $ 1.46 $ (0.06 ) $ 1.40 $ 1.49 $ (0.01 ) $ 1.48 Weighted-average number of common shares outstanding: Basic 389.6 — 389.6 397.9 — 397.9 Diluted 397.3 — 397.3 408.0 — 408.0 1 These amounts have been revised for the new presentation as described in Note 1 . CONSOLIDATED BALANCE SHEET December 31, 2017 As Reported ASC 606 Adjustments As Adjusted ASSETS: Cash and cash equivalents $ 790.9 $ — $ 790.9 Accounts receivable, net of allowance of $42.7 4,585.0 — 4,585.0 Expenditures billable to clients 1,747.4 (1,747.4 ) — Accounts receivable, billable to clients — 1,747.4 1,747.4 Assets held for sale 5.7 — 5.7 Other current assets 335.1 11.4 346.5 Total current assets 7,464.1 11.4 7,475.5 Property and equipment, net of accumulated depreciation of $1,036.2 650.4 — 650.4 Deferred income taxes 236.0 (2.0 ) 234.0 Goodwill 3,820.4 — 3,820.4 Other intangible assets 140.7 — 140.7 Other non-current assets 383.6 0.1 383.7 TOTAL ASSETS $ 12,695.2 $ 9.5 $ 12,704.7 LIABILITIES: Accounts payable $ 6,907.8 $ (487.6 ) $ 6,420.2 Accrued liabilities 674.7 — 674.7 Contract liabilities — 484.7 484.7 Short-term borrowings 84.9 — 84.9 Current portion of long-term debt 2.0 — 2.0 Liabilities held for sale 8.8 — 8.8 Total current liabilities 7,678.2 (2.9 ) 7,675.3 Long-term debt 1,285.6 — 1,285.6 Deferred compensation 476.6 — 476.6 Other non-current liabilities 766.9 1.9 768.8 TOTAL LIABILITIES 10,207.3 (1.0 ) 10,206.3 Redeemable noncontrolling interests 252.1 — 252.1 STOCKHOLDERS’ EQUITY: Common stock 38.6 — 38.6 Additional paid-in capital 955.2 — 955.2 Retained earnings 2,093.6 10.9 2,104.5 Accumulated other comprehensive loss, net of tax (827.4 ) (0.4 ) (827.8 ) 2,260.0 10.5 2,270.5 Less: Treasury stock (59.0 ) — (59.0 ) Total IPG stockholders’ equity 2,201.0 10.5 2,211.5 Noncontrolling interests 34.8 — 34.8 TOTAL STOCKHOLDERS’ EQUITY 2,235.8 10.5 2,246.3 TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY $ 12,695.2 $ 9.5 $ 12,704.7 CONSOLIDATED STATEMENT OF CASH FLOWS Year ended December 31, 2017 As Reported ASC 606 Adjustments As Adjusted CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 595.0 $ (24.6 ) $ 570.4 Adjustments to reconcile net income to net cash used in operating activities: Depreciation and amortization 157.1 — 157.1 Provision for uncollectible receivables 9.5 — 9.5 Amortization of restricted stock and other non-cash compensation 82.0 — 82.0 Net amortization of bond discounts and deferred financing costs 5.8 — 5.8 Deferred income tax provision 1.1 (10.6 ) (9.5 ) Net losses on sales of businesses 24.1 — 24.1 Other 12.7 — 12.7 Changes in assets and liabilities, net of acquisitions and divestitures, providing (using) cash: Accounts receivable 37.6 — 37.6 Expenditures billable to clients (165.5 ) 165.5 — Accounts receivable, billable to clients — (165.5 ) (165.5 ) Other current assets 27.4 22.7 50.1 Accounts payable 311.9 24.5 336.4 Accrued liabilities (241.3 ) — (241.3 ) Contract liabilities — (12.0 ) (12.0 ) Other non-current assets and liabilities 24.4 — 24.4 Net cash provided by operating activities 881.8 — 881.8 CASH FLOWS FROM INVESTING ACTIVITIES: Net cash used in investing activities (196.2 ) — (196.2 ) CASH FLOWS FROM FINANCING ACTIVITIES: Net cash used in financing activities (1,004.9 ) — (1,004.9 ) Effect of foreign exchange rate changes on cash, cash equivalents and restricted cash 16.8 — 16.8 Net decrease in cash, cash equivalents and restricted cash (302.5 ) — (302.5 ) Cash, cash equivalents and restricted cash at beginning of period 1,100.2 — 1,100.2 Cash, cash equivalents and restricted cash at end of period $ 797.7 $ — $ 797.7 Year ended December 31, 2016 As Reported ASC 606 Adjustments As Adjusted CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 632.5 $ (3.5 ) $ 629.0 Adjustments to reconcile net income to net cash used in operating activities: Depreciation and amortization 160.2 — 160.2 Provision for uncollectible receivables 16.7 — 16.7 Amortization of restricted stock and other non-cash compensation 85.6 — 85.6 Net amortization of bond discounts and deferred financing costs 5.6 — 5.6 Deferred income tax provision 45.7 (1.1 ) 44.6 Net losses on sales of businesses 41.4 — 41.4 Other 35.5 — 35.5 Changes in assets and liabilities, net of acquisitions and divestitures, providing (using) cash: Accounts receivable (220.7 ) — (220.7 ) Expenditures billable to clients (2.2 ) 2.2 — Accounts receivable, billable to clients — (2.2 ) (2.2 ) Other current assets (4.8 ) 5.3 0.5 Accounts payable (126.1 ) (21.3 ) (147.4 ) Accrued liabilities (61.1 ) — (61.1 ) Contract liabilities — 20.6 20.6 Other non-current assets and liabilities (95.5 ) — (95.5 ) Net cash provided by operating activities 512.8 — 512.8 CASH FLOWS FROM INVESTING ACTIVITIES: Net cash used in investing activities (263.9 ) — (263.9 ) CASH FLOWS FROM FINANCING ACTIVITIES: Net cash used in financing activities (666.4 ) — (666.4 ) Effect of foreign exchange rate changes on cash, cash equivalents and restricted cash 11.6 — 11.6 Net decrease in cash, cash equivalents and restricted cash (405.9 ) — (405.9 ) Cash, cash equivalents and restricted cash at beginning of period 1,506.1 — 1,506.1 Cash, cash equivalents and restricted cash at end of period $ 1,100.2 $ — $ 1,100.2 Retained earnings as of January 1, 2016, December 31, 2016 and 2017 increased by $39.1 , $35.6 , and $10.9 , respectively, as a result of the adoption of ASC 606. Accumulated other comprehensive loss, net of tax, as of December 31, 2016 and 2017 decreased by $1.9 and $0.4 , respectively, as a result of the adoption of the ASC 606. Disaggregation of Revenue The following is a description of the principal activities, by reportable segment, from which we generate revenue. For more detailed information about reportable segments, see Note 14 . Integrated Agency Networks The Integrated Agency Networks ("IAN") segment of IPG principally generates revenue from providing advertising and media services as well as a comprehensive array of global communications and marketing services. Within IAN’s advertising business, we typically identify two performance obligations for creative and production services. Depending on the arrangement, we typically act as the principal for our creative services and as the agent for our production services. Within our media business, we also identify two performance obligations for media planning and media buying services. We typically act as the principal for our media planning services and as the agent for media buying services. Generally, our branding arrangements consist of two performance obligations, and we act as the principal for both performance obligations. Constituency Management Group The Constituency Management Group ("CMG") segment generates revenue from providing events and public relations services as well as sports and entertainment marketing, corporate and brand identity, and strategic marketing consulting. In CMG’s events and public relations arrangements, we typically identify one performance obligation, for which we act as the principal in most arrangements. Generally, our branding arrangements consist of two performance obligations, and we act as the principal for both performance obligations. Corporate and Other Corporate and other includes Acxiom, which was acquired on October 1, 2018 and had total and net revenue of $181.7 for the three months ended December 31, 2018 . Principal Geographic Markets Our agencies are located in over 100 countries, including every significant world market. Our geographic revenue breakdown is listed below. Years ended December 31, Total revenue: 2018 2017 2016 United States $ 5,851.0 $ 5,417.3 $ 5,452.6 International: United Kingdom 881.4 775.7 788.8 Continental Europe 840.2 780.6 764.1 Asia Pacific 1,170.8 1,106.4 1,076.0 Latin America 389.0 386.6 417.2 Other 582.0 581.0 557.5 Total International 3,863.4 3,630.3 3,603.6 Total Consolidated $ 9,714.4 $ 9,047.6 $ 9,056.2 Years ended December 31, Net revenue: 2018 2017 2016 United States $ 4,825.0 $ 4,458.8 $ 4,443.2 International: United Kingdom 711.7 613.1 604.3 Continental Europe 737.5 687.8 682.0 Asia Pacific 896.8 866.9 887.7 Latin America 350.1 350.8 367.8 Other 510.5 496.1 467.3 Total International 3,206.6 3,014.7 3,009.1 Total Consolidated $ 8,031.6 $ 7,473.5 $ 7,452.3 IAN Years ended December 31, Total revenue: 2018 2017 2016 United States $ 4,279.4 $ 4,062.3 $ 4,075.9 International 3,095.0 2,947.3 2,916.9 Total IAN $ 7,374.4 $ 7,009.6 $ 6,992.8 Net revenue: United States $ 3,832.7 $ 3,660.6 $ 3,600.3 International 2,753.1 2,606.1 2,601.1 Total IAN $ 6,585.8 $ 6,266.7 $ 6,201.4 CMG Years ended December 31, Total revenue: 2018 2017 2016 United States $ 1,404.0 $ 1,355.0 $ 1,376.7 International 754.3 683.0 686.7 Total CMG $ 2,158.3 $ 2,038.0 $ 2,063.4 Net revenue: United States $ 824.6 $ 798.2 $ 842.9 International 439.5 408.6 408.0 Total CMG $ 1,264.1 $ 1,206.8 $ 1,250.9 Contract Balances The following table provides information about receivables, contract assets and contract liabilities from contracts with customers. December 31, December 31, Accounts receivable, net of allowance of $42.5 and $42.7, respectively $ 5,126.6 $ 4,585.0 Accounts receivable, billable to clients 1,900.6 1,747.4 Contract assets 67.9 11.5 Contract liabilities (deferred revenue) 533.9 484.7 Contract assets are primarily comprised of contract incentives that are generally satisfied annually under the terms of our contracts and are transferred to accounts receivable when the right to payment becomes unconditional. Contract liabilities relate to advance consideration received from customers under the terms of our contracts primarily related to reimbursements of third-party expenses, whether we act as principal or agent, and to a lesser extent, periodic retainer fees, both of which are generally recognized shortly after billing.

Debt and Credit Agreements (Not

Debt and Credit Agreements (Notes)	12 Months Ended
	Dec. 31, 2018
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 Interest Rate December 31, 2018 2017 Book Value Fair Value 1 Book Value Fair 1 3.50% Senior Notes due 2020 (less unamortized discount and issuance costs of $0.8 and $2.6, respectively) 3.89 % $ 496.6 $ 499.9 $ — $ — 3.75% Senior Notes due 2021 (less unamortized discount and issuance costs of $0.3 and $2.9, respectively) 3.98 % 496.8 503.2 — — 4.00% Senior Notes due 2022 (less unamortized discount and issuance costs of $1.0 and $0.8, respectively) 4.13 % 248.2 250.3 247.6 259.0 3.75% Senior Notes due 2023 (less unamortized discount and issuance costs of $0.6 and $1.7, respectively) 4.32 % 497.7 491.4 497.1 513.2 4.20% Senior Notes due 2024 (less unamortized discount and issuance costs of $0.5 and $2.2, respectively) 4.24 % 497.3 492.6 496.7 524.2 4.65% Senior Notes due 2028 (less unamortized discount and issuance costs of $1.7 and $4.3, respectively) 4.78 % 494.0 494.1 — — 5.40% Senior Notes due 2048 (less unamortized discount and issuance costs of $2.8 and $5.5, respectively) 5.48 % 491.7 474.1 — — Term Loan due 2021 - LIBOR plus 1.25% 400.0 400.0 — Other notes payable and capitalized leases 38.0 38.0 46.2 46.2 Total long-term debt 3,660.3 1,287.6 Less: current portion 0.1 2.0 Long-term debt, excluding current portion $ 3,660.2 $ 1,285.6 1 See Note 12 for information on the fair value measurement of our long-term debt. Annual maturities are scheduled as follows based on the book value as of December 31, 2018 . 2019 $ 0.1 2020 496.9 2021 896.8 2022 248.2 2023 497.7 Thereafter 1,520.6 Total long-term debt $ 3,660.3 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. Additionally, we have debt issuance costs related to certain financing transactions which are also amortized through interest expense. As of December 31, 2018 and 2017 , we had total unamortized debt issuance costs of $26.0 and $13.0 , 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 See Note 6 for further information regarding the Company's acquisition of Acxiom (the "Acxiom Acquisition") on October 1, 2018 (the "Closing Date"). Senior Notes On September 21, 2018, in order to fund the Acxiom Acquisition and related fees and expenses, we issued a total of $2,000.0 in aggregate principal amount of unsecured senior notes (in four separate series of $500.0 each, together, the "Senior Notes"). Upon issuance, the Senior Notes were reflected on our Consolidated Balance Sheets net of discount of $5.8 and net of the capitalized debt issuance costs, including commissions and offering expenses of $16.1 , both of which will be amortized in interest expense through the respective maturity dates of each series of Senior Notes using the effective interest method. Interest is payable semi-annually in arrears on April 1st and October 1st of each year, commencing on April 1, 2019. The issuance was comprised of the following four series of notes: Senior Notes Par Value Discount at Issuance Net Price at Issuance Issuance Cost Net Proceeds 3.50% Senior Notes due 2020 $ 500.0 $ 1.0 $ 499.0 $ 2.9 $ 496.1 3.75% Senior Notes due 2021 500.0 0.3 499.7 3.2 496.5 4.65% Senior Notes due 2028 500.0 1.7 498.3 4.4 493.9 5.40% Senior Notes due 2048 500.0 2.8 497.2 5.6 491.6 Total $ 2,000.0 $ 5.8 $ 1,994.2 $ 16.1 $ 1,978.1 Consistent with our other debt securities, the newly issued Senior 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 may redeem each series of the Senior Notes at any time in whole or from time to time in part in accordance with the provisions of the indenture, including the applicable supplemental indenture, under which such series of Senior Notes was issued. If the Acxiom Acquisition had been terminated or had not closed on or prior to June 30, 2019, we would have been required to redeem the Senior Notes due 2020, 2021 and 2028 at a redemption price equal to 101% of the principal amount thereof, plus accrued and unpaid interest. Additionally, upon the occurrence of a change of control repurchase event with respect to the Senior Notes, each holder of the Senior Notes has the right to require the Company to purchase that holder’s Senior Notes at a price equal to 101% of the principal amount thereof, plus accrued and unpaid interest, unless the Company has exercised its option to redeem all the Senior Notes. Term Loan Agreement On October 1, 2018, in order to fund the Acxiom Acquisition and related fees and expenses, we borrowed $500.0 through debt financing arrangements with third-party lenders under a three-year term loan agreement (the "Term Loan Agreement"), $100.0 of which we paid down on December 3, 2018. Consistent with our other debt securities, the Term Loan Agreement includes covenants that, among other things, limit our liens and the liens of certain of our consolidated subsidiaries. In addition, it requires us to maintain the same financial maintenance covenants as discussed below. Loans under the Term Loan bear interest at a variable rate based on, at the Company’s option, either the base rate or the Eurodollar rate (each as defined in the Term Loan Agreement) plus an applicable margin that is determined based on our credit ratings. As of December 31, 2018, the applicable margin was 0.25% for base rate loans and 1.25% for Eurodollar rate loans. Credit Agreements We maintain a committed corporate credit facility, originally dated as of July 18, 2008, which has been amended and restated from time to time (the "Credit Agreement"). We use our Credit Agreement to increase our financial flexibility, to provide letters of credit primarily to support obligations of our subsidiaries and to support our commercial paper program. The Credit Agreement is a revolving facility, expiring in October 2022 , 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 $1,500.0 , 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 $50.0 , or the equivalent in other currencies. Our obligations under the Credit Agreement are unsecured. As of December 31, 2018 and 2017 , there were no borrowings under the Credit Agreement; however, we had $8.5 and $8.4 of letters of credit under the Credit Agreement, which reduced our total availability to $1,491.5 and $1,491.6 , respectively. On July 27, 2018, we entered into Amendment No. 1 to our Credit Agreement (the "Amendment"). The Amendment increased the maximum leverage ratio covenant to (i) 4.00 to 1.00 for the first, second and third fiscal quarters ending after the Acxiom Closing Date, (ii) 3.75 to 1.00 for the fourth, fifth, sixth and seventh full fiscal quarters ending after the Acxiom Closing Date and (iii) 3.50 to 1.00 for the eighth full fiscal quarter ending after the Acxiom Closing Date and thereafter. 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, 2018 , the applicable margin was 0.10% for base rate advances and 1.10% 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 0.25% . We also pay a facility fee at an annual rate that is determined based on our credit ratings, which as of December 31, 2018 , was 0.15% on the aggregate lending commitment under the Credit Agreement. In addition to other and customary covenants, the Credit Agreement and the Term Loan each require that we maintain the financial covenants listed below as of the end of each fiscal quarter for the period of four fiscal quarters then ended. We were in compliance with all of our covenants in the Credit Agreement and the Term Loan as of December 31, 2018 . Interest coverage ratio (not less than): 1 5.00x Leverage ratio (not greater than): 2 4.00x 1 The interest coverage ratio is defined as EBITDA, as defined in the Credit Agreement and Term Loan Agreement, to net interest expense for the four quarters then ended. 2 The leverage ratio is defined as debt as of the last day of such fiscal quarter to EBITDA, as defined in the Amended Credit Agreement and Term Loan Agreement, for the four quarters then ended. We also have uncommitted lines of credit with various banks that permit borrowings at variable interest rates and that are primarily used to fund 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 operations. As of December 31, 2018 and 2017 , the Company had uncommitted lines of credit in an aggregate amount of $1,173.1 and $926.2 , under which we had outstanding borrowings of $73.7 and $84.9 classified as short-term borrowings on our Consolidated Balance Sheets, respectively. The average amounts outstanding during 2018 and 2017 were $96.4 and $223.8 , respectively, with weighted-average interest rates of approximately 4.5% and 2.9% , respectively. Commercial Paper The Company is authorized to issue unsecured commercial paper up to a maximum aggregate amount outstanding at any time of $1,500.0 . Borrowings under the commercial paper program are supported by the Credit Agreement described above. Proceeds of the commercial paper are used for working capital and general corporate purposes, including the repayment of maturing indebtedness and other short-term liquidity needs. The maturities of the commercial paper vary but may not exceed 397 days from the date of issue. As of December 31, 2018 , there was no commercial paper outstanding. The average amount outstanding under the program was $648.7 in 2018, with a weighted-average interest rate of 2.4% and a weighted-average maturity of twenty-two days. 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 other agencies owe the bank, and the bank provides for overdrafts as long as the net balance for all 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, 2018 and 2017 the amounts netted were $2,065.8 and $1,412.0 , respectively.

Earnings Per Share (Notes)

Earnings Per Share (Notes)	12 Months Ended
	Dec. 31, 2018
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, 2018 2017 2016 Net income available to IPG common stockholders $ 618.9 $ 554.4 $ 605.0 Weighted-average number of common shares outstanding - basic 383.3 389.6 397.9 Dilutive effect of stock options and restricted shares 5.7 7.7 10.1 Weighted-average number of common shares outstanding - diluted 389.0 397.3 408.0 Earnings per share available to IPG common stockholders: Basic $ 1.61 $ 1.42 $ 1.52 Diluted $ 1.59 $ 1.40 $ 1.48

Acquisitions (Notes)

Acquisitions (Notes)	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Business Combination Disclosure [Text Block]	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. During 2018 , we completed five acquisitions, one of which was included in the IAN reportable segment, three of which were included in the CMG reportable segment, and Acxiom which is included in the "Corporate and other" group. See Note 6 for discussion of our acquisition of Acxiom. These acquisitions include a full-service digital agency based in Brazil, an entertainment marketing and brand licensing agency in the fashion and lifestyle sector based in the U.K., a content-focused social creative agency based in the U.K., a data and technology company based in the U.S., and a content production firm based in Israel. During 2018 , we recorded approximately $2,131.0 of goodwill and other intangible assets related to our acquisitions. During 2017 , we completed ten acquisitions, eight of which were included in the IAN reportable segment, and two of which were included in the CMG reportable segment. The most significant acquisitions included a product and service design consultancy based in the U.S., an integrated healthcare marketing communications agency based in the U.S., a content creation and digital agency with offices in the U.S. and the U.K., a mobile consultancy and application development agency based in the U.K., a full-service public relations and digital agency based in China, a search engine optimization and digital content marketing agency based in the U.K., and a mobile focused digital agency based in the U.K. During 2017 , we recorded approximately $62.0 of goodwill and other intangible assets related to our acquisitions. During 2016 , we completed ten acquisitions, three of which were included in the IAN reportable segment, and seven of which was included in the CMG reportable segment. The most significant acquisitions included a full-service digital agency in the U.K., a group of creative marketing agencies based in Russia, and a media planning and buying agency with significant digital capabilities in Canada. During 2016 , we recorded approximately $149.0 of goodwill and other intangible assets related to our 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 2018 , 2017 or 2016 . Details of cash paid for current and prior years' acquisitions are listed below. Years ended December 31, 2018 2017 2016 Cost of investment: current-year acquisitions 1 $ 2,323.4 $ 36.8 $ 65.7 Cost of investment: prior-year acquisitions 33.9 54.6 40.7 Less: net cash acquired (13.8 ) (7.1 ) (13.6 ) Total cost of investment 2,343.5 84.3 92.8 Operating payments 2 19.4 47.1 19.1 Total cash paid for acquisitions 3 $ 2,362.9 $ 131.4 $ 111.9 1 The cost of investment: current-year acquisitions line significantly increased in the year ended December 31, 2018, primarily as a result of payments related to the acquisition of Acxiom. See Note 6 for further information on the Acxiom Acquisition. 2 Represents cash payments for amounts that have been recognized in operating expenses since the date of acquisition either relating to adjustments to estimates in excess of the initial value of contingent payments recorded or were contingent upon the future employment of the former owners of the acquired companies. Amounts are reflected in the operating section of the Consolidated Statements of Cash Flows. 3 Of the total cash paid for acquisitions, $2,309.8 , $30.6 and $52.0 for the years ended December 31, 2018 , 2017 and 2016 , respectively, are classified under the investing section of the Consolidated Statements of Cash Flows as acquisitions, net of cash acquired. These amounts relate to initial payments for new transactions. Of the total cash paid for acquisitions, $33.7 , $53.7 and $40.8 for the years ended December 31, 2018 , 2017 and 2016 , respectively, are classified under the financing section of the Consolidated Statements of Cash Flows as acquisition-related payments. These amounts relate to deferred payments and increases in our ownership interest for prior acquisitions. 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 15 for further information on contingent acquisition obligations. Redeemable noncontrolling interests are adjusted quarterly, if necessary, to their estimated redemption value, but not less than their initial fair value. Any adjustments to the redemption value impact 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, 2018 2017 2016 Balance at beginning of period $ 252.1 $ 252.8 $ 251.9 Change in related noncontrolling interests balance (10.7 ) (2.8 ) 4.9 Changes in redemption value of redeemable noncontrolling interests: Additions — 7.7 6.8 Redemptions and other (33.7 ) (18.5 ) (14.8 ) Redemption value adjustments (39.8 ) 12.9 4.0 Balance at end of period $ 167.9 $ 252.1 $ 252.8 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 for 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.

Acxiom Acquisition (Notes)

Acxiom Acquisition (Notes)	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Business Combination Disclosure [Text Block]	Acxiom Acquisition On October 1, 2018, pursuant to the terms of the Membership Interest Purchase Agreement dated as of July 2, 2018, the Company completed the acquisition of Acxiom Holdings, Inc.’s Marketing Solutions business ("Acxiom") through the acquisition of 100% of the equity interests of Acxiom for $2,327.9 , subject to customary closing adjustments. The purpose of the acquisition is to combine the Company's media, creative, marketing services and analytics capabilities, global scale and consumer insights, with Acxiom's expertise in identity, data, integrations and data stewardship. The Company funded the acquisition of Acxiom from a term loan agreement with third-party lenders for $500.0 and unsecured senior notes issued for a total of $2,000.0 in aggregate principal amount. See Note 3 for further information regarding the Company's debt. The following table summarizes the preliminary fair values of the assets acquired and liabilities assumed at the closing date: October 1, 2018 Cash and cash equivalents $ 13.3 Accounts receivable 112.9 Accounts receivable, billable to clients 8.3 Other current assets 28.2 Property and equipment, net 159.7 Deferred income taxes (0.6 ) Goodwill 1,110.8 Intangible assets, net 995.0 Other non-current assets 8.3 Accounts payable (37.1 ) Accrued liabilities (46.9 ) Contract liabilities (23.2 ) Other non-current liabilities (0.8 ) Net assets acquired $ 2,327.9 The preliminary fair values of the identifiable intangible assets acquired at the closing date are as follows: Fair Value Weighted Average Amortization Period (Years) Customer lists $ 600.0 15.0 Know-how and technology 235.0 9.0 Trade names 160.0 15.0 to indefinite Total intangible assets 995.0 The preliminary fair value of the customer lists was determined by applying the multi-period excess earnings method, a variation of the income approach. The preliminary fair values of the know-how and technology and the trade names were determined using the relief from royalty method of the income approach. Goodwill generated by the Acxiom Acquisition, the majority of which is tax deductible, primarily relates to intangible assets that do not qualify for separate recognition, including assembled workforce and synergies. The purchase accounting process has not been completed primarily because the valuation of acquired assets has not been finalized. We expect to complete the purchase accounting as soon as practicable but no later than one year from the acquisition date. We do not believe there will be material adjustments. The operating results of Acxiom for the period from October 1, 2018 to December 31, 2018, including net revenue of $181.7 and net income available to IPG common stockholders of $20.4 , are included in our Consolidated Statements of Operations for the year ended December 31, 2018. The Company incurred a total of $35.0 in "Selling, general and administrative expenses," $3.7 in "Interest expense," $0.4 in "Interest income" and $10.3 in "Other expense, net," for transaction-related costs in connection with the acquisition. The following table presents the combined results of the Company and Acxiom for the years ended December 31, 2018 and 2017 on an unaudited pro forma basis, as if the acquisition had occurred on January 1, 2017. The unaudited pro forma financial information is presented for informational purposes only and is not indicative of the results of operations that would have been achieved if that acquisition had taken place at the beginning of January 1, 2017. It also does not reflect changes in cost structure or operations resulting from restructuring activities, changes in the business, or future events that may occur after the completion of the acquisition. The pro forma combined results of operations shown below include after-tax nonrecurring transaction-related charges of $27.6 in 2017, and the business combination accounting effects resulting from the acquisition. (unaudited) December 31, 2018 2017 Pro forma revenues $ 10,230.4 $ 9,736.1 Pro forma net income 642.2 519.2

Supplementary Data (Notes)

Supplementary Data (Notes)	12 Months Ended
	Dec. 31, 2018
Supplementary Data [Abstract]
Supplementary Data	Supplementary Data Valuation and Qualifying Accounts – Allowance for Uncollectible Accounts Receivable Years ended December 31, 2018 2017 2016 Balance at beginning of period $ 42.7 $ 55.7 $ 54.2 Charges to costs and expenses 6.5 9.5 16.7 Adjustments: Acquisitions/(dispositions) 2.2 (1.0 ) (2.5 ) Uncollectible accounts written off (7.1 ) (25.5 ) (9.4 ) Foreign currency translation adjustments (1.8 ) 4.0 (3.3 ) Balance at end of period $ 42.5 $ 42.7 $ 55.7 Property and Equipment December 31, 2018 2017 Furniture and equipment $ 681.7 $ 634.8 Leasehold improvements 629.0 641.5 Internal-use computer software 368.5 331.3 Land and buildings 146.6 79.0 Gross property and equipment 1,825.8 1,686.6 Less: accumulated depreciation (1,034.9 ) (1,036.2 ) Total property and equipment, net $ 790.9 $ 650.4 Total depreciation and amortization expense for property and equipment for the years ended December 31, 2018 , 2017 and 2016 was $165.3 , $136.0 and $138.3 , respectively. Accrued Liabilities The following table presents the components of accrued liabilities. December 31, 2018 2017 Salaries, benefits and related expenses $ 494.9 $ 441.7 Acquisition obligations 65.7 42.0 Office and related expenses 52.2 53.2 Interest 43.6 16.4 Other 150.5 121.4 Total accrued liabilities $ 806.9 $ 674.7 Other Expense, Net Results of operations include certain items that are not directly associated with our revenue-producing operations. Years ended December 31, 2018 2017 2016 Net losses on sales of businesses $ (61.9 ) $ (24.1 ) $ (41.4 ) Other (7.7 ) (2.1 ) 1.1 Total other expense, net $ (69.6 ) $ (26.2 ) $ (40.3 ) Net losses on sales of businesses – During 2018 , the amounts recognized were related to sales of businesses and the classification of certain assets and liabilities, consisting primarily of cash, as held for sale within our IAN and CMG reportable segments. The businesses held for sale as of year end primarily represent unprofitable, non-strategic agencies which are expected to be sold within the next twelve months. During 2017, the amounts recognized were related to sales of businesses and the classification of certain assets and liabilities, consisting primarily of cash, accounts receivable and accounts payable, as held for sale within our IAN reportable segment. During 2016, the amounts recognized were related to sales of businesses and the classification of certain assets and liabilities, consisting primarily of accounts receivable and accounts payable, as held for sale within both our IAN and CMG reportable segments. Other – During 2018 , the amounts recognized were primarily a result of transaction-related costs from the Acxiom Acquisition. Share Repurchase Program In February 2018, our Board of Directors (the "Board") authorized a new share repurchase program to repurchase from time to time up to $300.0 , excluding fees, of our common stock, which was in addition to the remaining amount available to be repurchased from the $300.0 authorization made by the Board in February 2017. We may effect such repurchases through open market purchases, trading plans established in accordance with SEC rules, derivative transactions or other means. The timing and amount of repurchases in future periods 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, 2018 2017 2016 Number of shares repurchased 5.1 13.7 13.3 Aggregate cost, including fees $ 117.1 $ 300.1 $ 303.3 Average price per share, including fees $ 23.03 $ 21.97 $ 22.76 On July 2, 2018, in connection with the announcement of the Acxiom acquisition, we announced that share repurchases will be suspended for a period of time in order to reduce the increased debt levels incurred in conjunction with the acquisition. As of December 31, 2018 , $338.4 remained available for repurchase under the share repurchase programs, which has no expiration date. Supplemental Cash Flow Information Years ended December 31, 2018 2017 2016 Cash paid for interest $ 88.7 $ 82.3 $ 78.8 Cash paid for income taxes, net of refunds 1 207.9 228.4 244.1 1 Refunds of $24.3 , $31.9 and $26.6 were received for the years ended December 31, 2018 , 2017 and 2016 , respectively.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets (Notes)	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets [Abstract]
Goodwill and Intangible Assets Disclosure [Text Block]	Goodwill and Other 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, CMG and Corporate & other, for the years ended December 31, 2018 and 2017 are listed below. IAN CMG Corporate & other 1 Total 2 Balance as of December 31, 2016 $ 3,043.8 $ 630.6 $ — $ 3,674.4 Acquisitions 39.6 15.5 — 55.1 Foreign currency and other 78.4 12.5 — 90.9 Balance as of December 31, 2017 $ 3,161.8 $ 658.6 $ — $ 3,820.4 Acquisitions 1.2 20.0 1,110.8 1,132.0 Foreign currency and other (63.3 ) (12.0 ) (1.2 ) (76.5 ) Balance as of December 31, 2018 $ 3,099.7 $ 666.6 $ 1,109.6 $ 4,875.9 1 During 2018, the increase in goodwill is primarily due to the acquisition of Acxiom. See Note 6 for further information on the Acxiom Acquisition. 2 For all periods presented, no goodwill impairment charge has been recorded. See Note 1 for information regarding our annual impairment methodology. Other Intangible Assets Other intangible assets primarily consist of customer lists and know-how and technology, which have definite lives and are subject to amortization on a straight-line basis with estimated useful lives generally between 7 and 15 years, as well as trade names which have both indefinite and definite lives which are subject to amortization on a straight-line basis with estimated useful lives of 15 years. Amortization expense for other intangible assets for the years ended December 31, 2018 , 2017 and 2016 was $37.6 , $21.1 and $21.9 , respectively. There were no material impairment charges on other intangibles for the years ended December 31, 2018 , 2017 and 2016 . During 2018 and 2017 , we recorded approximately $999.0 and $7.0 of other intangible assets related to our acquisitions in the respective year. The increase in 2018 is primarily due to the acquisition of Acxiom. The following table provides a summary of other intangible assets, which are included in our Consolidated Balance Sheets. December 31, 2018 2017 Gross Amount Accumulated Amortization Net Amount Gross Amount Accumulated Amortization Net Amount Customer lists $ 857.2 $ (190.9 ) $ 666.3 $ 267.3 $ (172.2 ) $ 95.1 Know-how and technology 235.0 (6.5 ) 228.5 — — — Trade names 226.2 (36.8 ) 189.4 68.8 (33.8 ) 35.0 Other 14.4 (3.8 ) 10.6 14.4 (3.8 ) 10.6 Total $ 1,332.8 $ (238.0 ) $ 1,094.8 $ 350.5 $ (209.8 ) $ 140.7 The estimated annual amortization expense for other intangible assets for the next five years as of December 31, 2018 is listed below. 2019 2020 2021 2022 2023 Estimated amortization expense $ 87.8 $ 87.3 $ 85.6 $ 82.3 $ 78.2

Income Taxes (Notes)

Income Taxes (Notes)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Tax Disclosure [Text Block]	Income Taxes The components of income before income taxes are listed below. Years ended December 31, 2018 2017 2016 Domestic $ 474.0 $ 514.8 $ 502.1 Foreign 364.0 326.0 323.5 Total $ 838.0 $ 840.8 $ 825.6 The provision for income taxes is listed below. Years ended December 31, 2018 2017 2016 U.S. federal income taxes (including foreign withholding taxes): Current $ 38.1 $ 154.1 $ 54.3 Deferred 29.9 (37.6 ) 35.7 68.0 116.5 90.0 State and local income taxes: Current 25.1 18.8 8.2 Deferred 3.4 19.7 (1.6 ) 28.5 38.5 6.6 Foreign income taxes: Current 121.9 107.9 89.8 Deferred (19.2 ) 8.4 10.5 102.7 116.3 100.3 Total $ 199.2 $ 271.3 $ 196.9 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, 2018 2017 2016 U.S. federal statutory income tax rate 21.0 % 35.0 % 35.0 % Income tax provision at U.S. federal statutory rate $ 176.0 $ 294.3 $ 289.0 State and local income taxes, net of U.S. federal income tax benefit 23.8 23.5 4.3 Impact of foreign operations, including withholding taxes 50.7 (6.7 ) (23.9 ) U.S. tax incentives (17.5 ) (1.3 ) (1.3 ) Change in net valuation allowance 1 (16.9 ) 1.4 (13.4 ) Divestitures 11.7 1.1 9.7 U.S. federal tax credits (48.1 ) (0.4 ) (44.6 ) Stock compensation (6.8 ) (15.3 ) (9.0 ) Increase/(decrease) in unrecognized tax benefits 8.4 7.0 (21.8 ) Net impact of the Tax Act 13.4 (36.0 ) 0.0 Statutory tax rate changes 0.0 0.0 11.4 Other 4.5 3.7 (3.5 ) Provision for income taxes $ 199.2 $ 271.3 $ 196.9 Effective income tax rate on operations 23.8 % 32.3 % 23.8 % 1 Reflects changes in valuation allowances that impacted the effective income tax rate for each year presented. In 2018 , our effective income tax rate of 23.8% was positively impacted by U.S. tax incentives, foreign tax credits from a distribution of unremitted earnings, the net reversal of valuation allowance in Continental Europe and research and development credits. The effective income tax rate was negatively impacted by losses in certain foreign jurisdictions where we receive no tax benefit due to 100% valuation allowances, non-deductible losses on sales of businesses and assets held for sale, by tax expense associated with the change to our assertion regarding the permanent reinvestment of undistributed earnings attributable to certain foreign subsidiaries, and by tax expense related to the true-up of our December 31, 2017 tax reform estimates as permitted by SEC Staff issued Accounting Bulletin No. 118 (“SAB 118”). Public Law 115-97, commonly referred to as the Tax Cuts and Jobs Act (the "Tax Act") was signed into law on December 22, 2017. The Tax Act legislated many new tax provisions which have impacted our operations. At December 31, 2017, provisional amounts were recorded as permitted by SAB 118. We have finalized our calculations of the impact of the Tax Act and have revised our estimates as required by SAB 118. This resulted in a tax expense of $13.4 , primarily attributable to our estimate of the tax imposed on the deemed repatriation of unremitted foreign earnings. The Tax Act imposed a new tax on certain foreign earnings generated in 2018 and forward. These global intangible low-taxed income ("GILTI") tax rules are complex. U.S. GAAP allows us to choose an accounting policy which treats the U.S. tax under GILTI provisions as either a current expense, as incurred, or as a component of the Company’s measurement of deferred taxes. The Company has elected to account for the GILTI tax as a current expense. In 2017 , our effective income tax rate of 32.3% was positively impacted by a net benefit of $36.0 as a result of the Tax Act as well as excess tax benefits on employee share-based payments, partially offset by losses in certain foreign jurisdictions where we receive no tax benefit due to 100% valuation allowances. In 2016 , our effective income tax rate of 23.8% was positively impacted by a benefit of $44.6 related to refunds to be claimed on future amended U.S. federal returns for tax years 2014 and 2015 primarily related to foreign tax credits and, to a lesser extent, research and development credits based on the conclusion of multi-year studies; the settlement of 2011 and 2012 income tax audits, which included the recognition of certain previously unrecognized tax benefits of $23.4 ; the reversal of valuation allowances of $12.2 as a consequence of the disposition of certain businesses in Continental Europe; excess tax benefits on employee share-based payments; and various changes in state income tax laws as well as the recognition of previously unrecognized state tax benefits as a result of a lapse in statute of limitations. The positive impacts to our tax rates were partially offset by the revaluation of deferred tax assets as a result of a statutory tax rate change in Continental Europe, losses in certain foreign jurisdictions where we receive no tax benefit due to 100% valuation allowances and by losses on sales of businesses for which we did not receive a full tax benefit. The components of deferred tax assets and liabilities are listed below. December 31, 2018 2017 Postretirement/post-employment benefits $ 17.9 $ 19.5 Deferred compensation 99.8 91.7 Pension costs 22.2 27.6 Basis differences in fixed assets (71.7 ) (52.0 ) Rent 27.3 27.5 Interest 48.8 45.8 Accruals and reserves 21.0 18.4 Allowance for doubtful accounts 7.4 10.2 Basis differences in intangible assets (302.7 ) (281.3 ) Investments in equity securities 1.2 (3.3 ) Tax loss/tax credit carry forwards 345.6 357.9 Prepaid expenses (6.3 ) (1.7 ) Deferred revenue (26.8 ) (41.3 ) Unremitted foreign earnings (9.5 ) 0.0 Other 38.2 43.7 Total deferred tax assets, net 212.4 262.7 Valuation allowance (211.0 ) (243.0 ) Net deferred tax assets $ 1.4 $ 19.7 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, 2018 2017 2016 Balance at beginning of period $ 243.0 $ 255.6 $ 275.1 Reversed to costs and expenses (28.0 ) (4.6 ) (15.4 ) Charged (reversed) to gross tax assets and other accounts 1 5.1 (27.3 ) 9.5 Foreign currency translation (9.1 ) 19.3 (13.6 ) Balance at end of period $ 211.0 $ 243.0 $ 255.6 1 Primarily represents changes to the valuation allowance related to the change of a corresponding deferred tax asset. In 2018, 2017, and 2016, amounts reversed to costs and expenses primarily related to decreases in valuation allowances in Continental Europe for existing deferred tax assets. As of December 31, 2018 , there were $1,149.4 of loss carryforwards. These loss carryforwards were all non-U.S. tax loss carryforwards, of which $994.1 have unlimited carryforward periods and $155.3 have expiration periods from 2019 to 2038 . As of December 31, 2018 , the Company also had $26.8 in deferred tax assets for state net operating loss carryforwards and tax credit carryforwards, which will expire between 2019 and 2038 . As of December 31, 2018 , we had $1,079.1 of undistributed earnings attributable to foreign subsidiaries. The Company has historically asserted that its unremitted foreign earnings are permanently reinvested, and therefore has not recorded any deferred taxes on such amounts. During the third quarter ended September 30, 2018, as a result of our increased debt and associated servicing commitments in connection with the Acxiom Acquisition that was consummated on October 1, 2018, the Company re-evaluated its global cash needs and as a result determined that approximately $435.0 of undistributed foreign earnings from certain international entities are no longer subject to the permanent reinvestment assertion. We recorded a tax expense of $10.8 representing our estimate of the tax costs associated with this change to our assertion. We have not changed our permanent reinvestment assertion with respect to any other international entities as we intend to use the related historical earnings and profits to fund international operations and investments. The table below summarizes the activity related to our unrecognized tax benefits. Years ended December 31, 2018 2017 2016 Balance at beginning of period $ 271.9 $ 246.7 $ 226.9 Increases as a result of tax positions taken during a prior year 65.9 6.3 65.0 Decreases as a result of tax positions taken during a prior year (10.8 ) (8.1 ) (47.5 ) Settlements with taxing authorities (6.5 ) (0.8 ) (4.6 ) Lapse of statutes of limitation (1.7 ) (3.3 ) (11.8 ) Increases as a result of tax positions taken during the current year 16.6 31.1 18.7 Balance at end of period $ 335.4 $ 271.9 $ 246.7 Included in the total amount of unrecognized tax benefits of $335.4 as of December 31, 2018 , is $313.5 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, 2018 and 2017 is $42.4 and $27.9 , respectively, of which a detriment of $14.5 and $7.0 is included in our 2018 and 2017 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. 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 $15.0 and $25.0 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. federal income tax audits through 2012, with the exception of 2009. With limited exceptions, we are no longer subject to state and local income tax audits for years prior to 2007 or non-U.S. income tax audits for years prior to 2009.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss, Net of Tax (Notes)	12 Months Ended
	Dec. 31, 2018
Accumulated Other Comprehensive Loss [Abstract]
Comprehensive Income (Loss) Note	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, 2016 $ (718.6 ) $ 0.6 $ (8.4 ) $ (238.0 ) $ (964.4 ) Other comprehensive income (loss) before reclassifications 132.2 0.0 0.0 (9.7 ) 122.5 Amount reclassified from accumulated other comprehensive loss, net of tax 1.1 (0.6 ) 1.6 12.0 14.1 Balance as of December 31, 2017 $ (585.3 ) $ 0.0 $ (6.8 ) $ (235.7 ) $ (827.8 ) Other comprehensive (loss) income before reclassifications (146.8 ) 0.0 0.0 11.4 (135.4 ) Amount reclassified from accumulated other comprehensive loss, net of tax 15.7 0.0 1.5 4.9 22.1 Balance as of December 31, 2018 $ (716.4 ) $ 0.0 $ (5.3 ) $ (219.4 ) $ (941.1 ) Amounts reclassified from accumulated other comprehensive loss, net of tax, for the years ended December 31, 2018 , 2017 and 2016 are as follows: Years ended December 31, Affected Line Item in the Consolidated Statements of Operations 2018 2017 2016 Foreign currency translation adjustments 1 $ 15.7 $ 1.1 $ 3.7 Other expense, net Gains on available-for-sale securities 0.0 (0.7 ) (1.3 ) Other expense, net Losses on derivative instruments 2.2 2.1 2.0 Interest expense Amortization of defined benefit pension and postretirement plans items 6.5 13.7 5.8 Other expense, net Tax effect (2.3 ) (2.1 ) (2.1 ) Provision for income taxes Total amount reclassified from accumulated other comprehensive loss, net of tax $ 22.1 $ 14.1 $ 8.1 1 These foreign currency translation adjustments are primarily a result of the sales of businesses.

Incentive Compensation Plans (N

Incentive Compensation Plans (Notes)	12 Months Ended
	Dec. 31, 2018
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 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. 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, except for Executive Officers of IPG, with a range of 0% to 200%. Performance cash awards generally vest in three years. The Compensation Committee may grant performance cash awards to any eligible employee; however, no employee can receive more than $10.0 during a performance period. The amounts of stock-based compensation expense as reflected in salaries and related expenses in our Consolidated Statements of Operations, and the related tax benefit, are listed below. Years ended December 31, 2018 2017 2016 Stock options $ 0.0 $ 0.0 $ 0.2 Stock-settled awards 24.7 20.5 16.0 Cash-settled awards 0.6 1.0 0.9 Performance-based awards 57.5 61.5 69.4 Employee stock purchase plan 0.9 1.0 0.7 Other 1 0.9 0.5 0.8 Stock-based compensation expense $ 84.6 $ 84.5 $ 88.0 Tax benefit $ 20.4 $ 30.4 $ 32.1 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. 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. They are generally first exercisable between two and four years from the grant date and expire ten years after the grant date (or earlier in the case of certain terminations of employment). There were no stock options granted during the years ended December 31, 2018 , 2017 and 2016 . As of December 31, 2018 , all stock options granted were fully vested and exercisable. The following table summarizes our stock option activity during 2018 . Options Weighted- Average Exercise Price (per option) Weighted- Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Stock options outstanding as of January 1, 2018 3.7 $ 9.44 Exercised (1.9 ) $ 8.30 Stock options outstanding as of December 31, 2018 1.8 $ 10.66 2.8 $ 17.6 There were 1.9 , 1.1 and 1.2 stock options exercised in 2018 , 2017 and 2016 , respectively. The total intrinsic value of stock options exercised during 2018 , 2017 and 2016 was $27.9 , $15.1 and $15.2 , respectively. The cash received from the stock options exercised in 2018 , 2017 and 2016 was $29.0 , $20.0 and $18.2 , which include taxes withheld of $13.3 , $6.8 , and $7.8 , respectively. 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, except for Executive Officers of IPG, with a range of 0% to 200%. 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 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, 2018 and 2017 . Years ended December 31, 2018 2017 2016 Stock-Settled Awards: Awards granted 2.1 0.8 1.1 Weighted-average grant-date fair value (per award) $ 23.60 $ 24.18 $ 21.87 Total fair value of vested awards distributed $ 24.2 $ 22.6 $ 17.5 Cash-Settled Awards: Awards granted 0.1 0.0 0.1 Weighted-average grant-date fair value (per award) $ 23.62 $ 23.33 $ 22.54 Total fair value of vested awards distributed $ 0.8 $ 0.9 $ 0.7 Performance-Based Awards: Awards granted 2.9 4.8 3.3 Weighted-average grant-date fair value (per award) $ 21.13 $ 20.06 $ 19.58 Total fair value of vested awards distributed $ 87.2 $ 112.4 $ 27.9 In conjunction with common stock dividends declared in 2018 and 2017 , we accrued dividends of $2.4 and $1.5 , respectively, on non-vested stock-settled awards and paid dividends of $1.5 and $1.2 for stock-settled awards that vested during 2018 and 2017 , respectively. A summary of the activity of our non-vested stock-settled awards, cash-settled awards and performance-based awards during 2018 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- Average Grant-Date Fair Value (per award) Awards Weighted- Average Grant-Date Fair Value (per award) Awards Weighted- Average Grant-Date Fair Value (per award) Non-vested as of January 1, 2018 2.1 $ 22.78 0.1 $ 22.52 8.3 $ 21.05 Granted 2.1 23.60 0.1 23.62 2.9 21.13 Vested (1.0 ) 22.18 (0.1 ) 21.54 (3.6 ) 21.02 Forfeited (0.1 ) 23.67 0.0 23.17 (0.6 ) 21.06 Non-vested as of December 31, 2018 3.1 $ 23.51 0.1 $ 23.47 7.0 $ 21.10 Total unrecognized compensation expense remaining $ 39.4 $ 1.0 $ 54.7 Weighted-average years expected to be recognized over 1.6 1.3 1.7 In conjunction with our annual grant of long-term incentive compensation awards, we reviewed our estimates and assumptions in 2018 , which resulted in a forfeiture rate consistent with prior years. 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, 2018 , 2017 and 2016 , the Compensation Committee granted cash awards under the Cash Plan with a total target value of $20.9 , $2.8 and $5.2 , respectively. For those same years, we recognized $7.0 , $2.5 and $3.1 , respectively, in salaries and related expenses in our Consolidated Statements of Operations. During the years ended December 31, 2018 , 2017 and 2016 , the Compensation Committee granted performance awards to be settled in cash under the 2014 PIP with a total target value of $39.9 , $38.4 , and $37.4 , respectively. For those same years, we recognized $37.6 , $35.3 and $39.8 , 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 In May 2016, our shareholders approved The Interpublic Group of Companies Employee Stock Purchase Plan (2016) (the “ESPP”), replacing the prior employee stock purchase plan under which, prior to its expiration on December 31, 2015, 3.0 shares were issued. Under the ESPP, 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, consistent with the prior employee stock purchase plan. The price an employee pays for a share of common stock under the ESPP 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 10.0 shares are reserved for issuance under the ESPP, of which 0.8 shares have been issued since the inception of the ESPP through December 31, 2018 .

Fair Value Measurements (Notes)

Fair Value Measurements (Notes)	12 Months Ended
	Dec. 31, 2018
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 2018 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, 2018 and 2017 , and indicates the fair value hierarchy of the valuation techniques utilized to determine such fair value. December 31, 2018 Balance Sheet Classification Level 1 Level 2 Level 3 Total Assets Cash equivalents $ 132.1 $ 0.0 $ 0.0 $ 132.1 Cash and cash equivalents Liabilities Contingent acquisition obligations 1 $ 0.0 $ 0.0 $ 148.4 $ 148.4 December 31, 2017 Balance Sheet Classification Level 1 Level 2 Level 3 Total Assets Cash equivalents $ 201.6 $ 0.0 $ 0.0 $ 201.6 Cash and cash equivalents Liabilities Contingent acquisition obligations 1 $ 0.0 $ 0.0 $ 147.0 $ 147.0 1 Contingent acquisition obligations includes deferred acquisition payments and unconditional obligations to purchase additional noncontrolling equity shares of consolidated subsidiaries. Fair value measurement of the obligations is based upon actual and projected operating performance targets as specified in the related agreements. The increase in this balance of $1.4 from December 31, 2017 to December 31, 2018 is primarily due to acquisitions and exercised put options of $61.8 , partially offset by payments of $54.0 . The amounts payable within the next twelve months are classified in accrued liabilities; any amounts payable thereafter are classified in other non-current liabilities. 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, 2018 , and indicates the fair value hierarchy of the valuation techniques utilized to determine such fair value. December 31, 2018 Level 1 Level 2 Level 3 Total Total long-term debt $ 0.0 $ 3,605.6 $ 38.0 $ 3,643.6 Our long-term debt is comprised of senior notes, a term loan and other notes payable. The fair value of our senior notes, which are traded over-the-counter, is based on quoted prices in markets that are not active. Therefore, these senior notes are classified as Level 2 within the fair value hierarchy. Our term loan is a fixed price commitment that cannot be traded on the open market, and therefore is 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. 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 3 for further information on our long-term debt. 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, 2018
Retirement Benefits [Abstract]
Employee Benefits	Employee Benefits Pension and Postretirement Benefit Plans We have a defined benefit pension plan covering certain U.S. employees (the “Domestic Pension Plan”) that consists of approximately 3,300 participants and is 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. (the "U.K. Pension Plan") is a defined benefit plan and is our most material foreign pension plan in terms of the benefit obligation and plan assets. The domestic postretirement benefit plan is our most material postretirement benefit plan in terms of the benefit obligation. This plan consists of approximately 1,600 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 Pension Plan Foreign Pension Plans Domestic Postretirement Benefit Plan 2018 2017 2018 2017 2018 2017 Benefit Obligation Projected benefit obligation as of January 1 $ 125.4 $ 126.6 $ 582.3 $ 530.6 $ 31.8 $ 32.3 Service cost 0.0 0.0 5.4 4.9 0.0 0.0 Interest cost 4.5 5.1 13.1 13.5 1.1 1.3 Benefits paid (9.5 ) (11.4 ) (27.4 ) (19.0 ) (5.9 ) (5.9 ) Plan participant contributions 0.0 0.0 0.1 0.2 1.8 1.6 Actuarial (gains) losses (5.0 ) 5.1 (47.6 ) 20.3 (1.1 ) 2.5 Settlements and curtailments 0.0 0.0 (5.8 ) (19.8 ) 0.0 0.0 Foreign currency effect 0.0 0.0 (26.4 ) 50.4 0.0 0.0 Other 0.0 0.0 2.3 1.2 0.0 0.0 Projected benefit obligation as of December 31 $ 115.4 $ 125.4 $ 496.0 $ 582.3 $ 27.7 $ 31.8 Fair Value of Plan Assets Fair value of plan assets as of January 1 $ 98.8 $ 95.2 $ 404.2 $ 365.9 $ 0.0 $ 0.0 Actual return on plan assets (8.1 ) 12.4 (8.0 ) 25.1 0.0 0.0 Employer contributions 8.6 2.6 19.1 17.5 4.1 4.3 Plan participant contributions 0.0 0.0 0.1 0.2 1.8 1.6 Benefits paid (9.5 ) (11.4 ) (27.4 ) (19.0 ) (5.9 ) (5.9 ) Settlements 0.0 0.0 (4.6 ) (19.1 ) 0.0 0.0 Foreign currency effect 0.0 0.0 (21.1 ) 33.2 0.0 0.0 Other 0.0 0.0 1.6 0.4 0.0 0.0 0.0 Fair value of plan assets as of December 31 $ 89.8 $ 98.8 $ 363.9 $ 404.2 $ 0.0 $ 0.0 Funded status of the plans at December 31 $ (25.6 ) $ (26.6 ) $ (132.1 ) $ (178.1 ) $ (27.7 ) $ (31.8 ) Domestic Pension Plan Foreign Pension Plans Domestic Postretirement Benefit Plan December 31, 2018 2017 2018 2017 2018 2017 Amounts recognized in Consolidated Balance Sheets Non-current asset $ 0.0 $ 0.0 $ 8.6 $ 9.0 $ 0.0 $ 0.0 Current liability 0.0 0.0 (6.2 ) (6.5 ) (2.9 ) (3.1 ) Non-current liability (25.6 ) (26.6 ) (134.5 ) (180.6 ) (24.8 ) (28.7 ) Net liability recognized $ (25.6 ) $ (26.6 ) $ (132.1 ) $ (178.1 ) $ (27.7 ) $ (31.8 ) Accumulated benefit obligation $ 115.4 $ 125.4 $ 493.2 $ 577.9 Amounts recognized in Accumulated Other Comprehensive Loss, net Net actuarial loss $ 60.4 $ 52.2 $ 165.6 $ 201.6 $ 3.1 $ 4.2 Prior service cost (credit) 0.0 0.0 1.2 1.1 (0.3 ) (0.4 ) Total amount recognized $ 60.4 $ 52.2 $ 166.8 $ 202.7 $ 2.8 $ 3.8 Actuarial gains of $5.0 for the Domestic Pension Plan are attributed to an increase in the discount rate from 3.70% as of December 31, 2017 to 4.35% as of December 31, 2018 , partially offset by changes in demographic experience. Actuarial gains of $47.6 for the foreign pension plans are attributed to an increase in the weighted-average discount rate from 2.36% as of December 31, 2017 to 2.61% as of December 31, 2018 and changes in demographic experience. Domestic Pension Plan Foreign Pension Plans December 31, 2018 2017 2018 2017 Pension plans with an accumulated benefit obligation and projected benefit obligation in excess of plan assets Aggregate projected benefit obligation $ 115.4 $ 125.4 $ 491.2 $ 576.6 Aggregate accumulated benefit obligation 115.4 125.4 489.9 575.2 Aggregate fair value of plan assets 89.8 98.8 350.5 389.5 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, 2018 2017 2016 2018 2017 2016 2018 2017 2016 Service cost $ 0.0 $ 0.0 $ 0.0 $ 5.4 $ 4.9 $ 6.7 $ 0.0 $ 0.0 $ 0.0 Interest cost 4.5 5.1 5.9 13.1 13.5 15.1 1.1 1.3 1.5 Expected return on plan assets (6.6 ) (6.2 ) (6.6 ) (18.8 ) (17.7 ) (18.7 ) 0.0 0.0 0.0 Settlement and curtailment (gains) losses 0.0 0.0 0.0 (1.0 ) 6.8 0.4 0.0 0.0 0.0 Amortization of: Prior service cost (credit) 0.0 0.0 0.0 0.1 0.1 0.1 (0.2 ) (0.2 ) (0.2 ) Net actuarial losses 1.6 1.5 1.3 5.9 5.5 4.2 0.1 0.0 0.0 Net periodic cost $ (0.5 ) $ 0.4 $ 0.6 $ 4.7 $ 13.1 $ 7.8 $ 1.0 $ 1.1 $ 1.3 Assumptions Domestic Pension Plan Foreign Pension Plans Domestic Postretirement Benefit Plan Years ended December 31, 2018 2017 2016 2018 2017 2016 2018 2017 2016 Net periodic cost Discount rate 3.70 % 4.20 % 4.80 % 2.36 % 2.52 % 3.61 % 3.65 % 4.05 % 4.65 % Rate of compensation increase N/A N/A N/A 2.37 % 2.36 % 3.18 % N/A N/A N/A Expected return on plan assets 7.00 % 7.00 % 7.00 % 4.70 % 4.66 % 5.38 % N/A N/A N/A Interest crediting rates 5.10 % 5.10 % 5.10 % 1.31 % 1.29 % 1.35 % N/A N/A N/A Benefit obligation Discount rate 4.35 % 3.70 % 4.20 % 2.61 % 2.36 % 2.52 % 4.30 % 3.65 % 4.05 % Rate of compensation increase N/A N/A N/A 2.58 % 2.37 % 2.36 % N/A N/A N/A Interest crediting rates 5.10 % 5.10 % 5.10 % 1.44 % 1.31 % 1.29 % N/A N/A N/A Health care cost trend rate assumed for next year Initial rate (weighted-average) 6.25 % 6.50 % 6.75 % Year ultimate rate is reached 2024 2024 2024 Ultimate rate 5.00 % 5.00 % 5.00 % Discount Rates – At December 31, 2018 , 2017 and 2016 , 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, 2018 and 2017 , and indicates the fair value hierarchy of the valuation techniques utilized to determine such fair value. See Note 12 for a description of the fair value hierarchy. December 31, 2018 December 31, 2017 Plan assets subject to fair value hierarchy Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Registered investment companies $ 13.0 $ 0.0 $ 0.0 $ 13.0 $ 14.7 $ 0.0 $ 0.0 $ 14.7 Limited partnerships 0.0 0.0 25.6 25.6 0.0 0.0 29.5 29.5 Fixed income securities 23.1 0.0 0.0 23.1 23.4 0.0 0.0 23.4 Insurance contracts 0.0 5.8 0.0 5.8 0.0 7.9 0.0 7.9 Other 20.0 0.0 0.0 20.0 27.7 0.0 0.0 27.7 Total plan assets, subject to leveling $ 56.1 $ 5.8 $ 25.6 $ 87.5 $ 65.8 $ 7.9 $ 29.5 $ 103.2 Plan assets measured at net asset value Other investments measured at net asset value 1 366.2 399.8 Total plan assets $ 453.7 $ 503.0 1 Certain investments that are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient have not been classified in the fair value hierarchy but are included to reconcile to the amounts presented in the fair value of plan assets table above. Registered investment companies, which are publicly traded, are primarily valued using recently reported sales prices. Limited partnerships are invested primarily in equity and fixed income securities. Fixed income securities include government and investment-grade corporate bonds. Insurance contracts are valued based on the cash surrender value of the contract. Other investments primarily include cash and cash equivalents, equity securities and derivatives. Other investments measured at net asset value include common/collective trusts, hedge funds and other commingled assets that are invested primarily in equity and fixed income securities. These investments are not publicly traded and 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. The following table presents additional information about our significant foreign pension plan assets for which we utilize Level 3 inputs to determine fair value. Years ended December 31, Plan assets subject to fair value hierarchy, level 3 2018 2017 Balance at beginning of period $ 29.5 $ 28.0 Actual return on plan assets (3.9 ) 1.5 Balance at end of period $ 25.6 $ 29.5 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, 2018 , the weighted-average target and actual asset allocations relating to our domestic and foreign pension plans' assets are listed below. December 31, Asset Class 2019 Target Allocation 2018 2017 Alternative investments 1 26 % 26 % 27 % Equity securities 23 % 22 % 23 % Fixed income securities 21 % 21 % 21 % Liability driven investments 2 16 % 16 % 14 % Real estate 6 % 6 % 6 % Other 8 % 9 % 9 % Total 100 % 100 % 100 % 1 Alternative investments have the flexibility to dynamically invest across a broad range of asset classes including bonds, equity, cash, property and commodities. 2 Liability driven investment strategies use government bonds as well as derivative instruments to hedge a portion of the impact of interest rates and inflation movements on the long-term liabilities. Cash Flows During 2018 , we contributed $8.6 and $19.1 of cash to our domestic and foreign pension plans, respectively. For 2019 , we expect to contribute approximately $2.5 and $17.0 of cash to our domestic and foreign pension plans, respectively. The estimated future benefit payments expected to be paid are presented below. Years Domestic Pension Plan Foreign Pension Plans Domestic Postretirement Benefit Plan 2019 $ 14.5 $ 21.7 $ 3.0 2020 8.8 18.7 2.8 2021 8.0 19.8 2.6 2022 8.3 20.9 2.4 2023 7.8 21.8 2.2 2024 - 2028 36.7 117.2 9.8 The estimated future payments for our domestic postretirement benefit plan are net of any estimated U.S. federal subsidies expected to be received under the Medicare Prescription Drug, Improvement and Modernization Act of 2003, which total no more than $0.3 in any individual year. 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 2018 , 2017 and 2016 were $52.6 , $47.2 and $47.0 , respectively. Expenses include a discretionary Company contribution of $6.7 , $3.6 and $6.1 offset by participant forfeitures of $5.8 , $4.6 and $4.4 in 2018 , 2017 and 2016 , respectively. In addition, we maintain defined contribution plans in various foreign countries and contributed $51.3 , $47.4 and $44.5 to these plans in 2018 , 2017 and 2016 , respectively. Deferred Compensation and Benefit Arrangements We have deferred compensation and benefit 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. These arrangements may provide participants with the amounts deferred plus interest upon attaining certain conditions, such as completing a certain number of years of service, attaining a certain age or upon retirement or termination. As of December 31, 2018 and 2017, the deferred compensation and deferred benefit liability balance was $196.2 and $213.2 , respectively. Amounts expensed for deferred compensation and benefit arrangements in 2018, 2017 and 2016 were $10.0 , $18.5 and $18.5 , 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, 2018 and 2017, the cash surrender value of these policies was $177.3 and $177.4 , respectively. 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 or 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, 2018 and 2017 . In addition to income replacement benefits, plan participants may remain covered for certain health and life insurance benefits up to normal retirement age, and accordingly, we have recorded an obligation of $5.9 and $8.4 as of December 31, 2018 and 2017 , respectively.

Segment Information (Notes)

Segment Information (Notes)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Segment Information	Segment Information As of December 31, 2018 , we have two reportable segments: IAN and CMG. IAN is comprised of McCann Worldgroup, Foote, Cone & Belding ("FCB"), MullenLowe Group, 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 range of solutions for our clients. Our digital specialist agencies provide digital capabilities and serve as key digital partners. In addition, our domestic integrated agencies, including Hill Holliday, Carmichael Lynch and Tierney, 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, 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. The profitability measure employed by our chief operating decision maker for allocating resources to operating divisions and assessing operating division performance is operating income (loss). All segments follow the same accounting policies as those described in Note 1 . Corporate and other is primarily comprised of selling, general and administrative expenses as well as three months of results from Acxiom in 2018. Selling, general and administrative expenses includes corporate office expenses as well as shared service center and certain other centrally managed expenses that are not fully allocated to operating divisions; salaries, long-term incentives, annual bonuses and other miscellaneous benefits for corporate office employees; professional fees related to internal control compliance, financial statement audits and legal, information technology and other consulting services that are engaged and managed through the corporate office; and rental expense for properties occupied by corporate office employees. A portion of centrally managed expenses is 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 tables. Years ended December 31, 2018 2017 2016 Total Revenue: IAN $ 7,374.4 $ 7,009.6 $ 6,992.8 CMG 2,158.3 2,038.0 2,063.4 Corporate and other 1 181.7 — — Total $ 9,714.4 $ 9,047.6 $ 9,056.2 Net revenue: IAN $ 6,585.8 $ 6,266.7 $ 6,201.4 CMG 1,264.1 1,206.8 1,250.9 Corporate and other 1 181.7 — — Total $ 8,031.6 $ 7,473.5 $ 7,452.3 Segment operating income (loss): IAN $ 982.8 $ 875.1 $ 894.3 CMG 175.0 189.9 189.3 Corporate and other (149.0 ) (126.6 ) (147.2 ) Total 1,008.8 938.4 936.4 Interest expense (123.0 ) (90.8 ) (90.6 ) Interest income 21.8 19.4 20.1 Other expense, net (69.6 ) (26.2 ) (40.3 ) Income before income taxes $ 838.0 $ 840.8 $ 825.6 Depreciation and amortization IAN $ 142.8 $ 125.5 $ 129.2 CMG 24.3 23.5 22.4 Corporate and other 35.8 8.1 8.6 Total $ 202.9 $ 157.1 $ 160.2 Capital expenditures: IAN $ 128.5 $ 112.0 $ 149.2 CMG 13.0 17.7 16.6 Corporate and other 35.6 26.2 34.9 Total $ 177.1 $ 155.9 $ 200.7 December 31, 2018 2017 Total assets: IAN $ 11,446.2 $ 10,978.0 CMG 1,516.7 1,427.4 Corporate and other 2 2,657.4 299.3 Total $ 15,620.3 $ 12,704.7 1 Revenue is from Acxiom which was acquired on October 1, 2018. See Note 6 for further detail on the acquisition. 2 Includes $2,421.7 of assets held at Acxiom. See Note 6 for further detail on the acquisition. Net revenue and long-lived assets, excluding intangible assets, are presented by major geographic area in the following table. Net Revenue Long-Lived Assets Years ended December 31, December 31, 2018 2017 2016 2018 2017 Domestic $ 4,825.0 $ 4,458.8 $ 4,443.2 $ 892.9 $ 694.5 International: United Kingdom 711.7 613.1 604.3 57.9 56.2 Continental Europe 737.5 687.8 682.0 57.9 73.6 Asia Pacific 896.8 866.9 887.7 121.7 115.5 Latin America 350.1 350.8 367.8 43.6 48.2 Other 510.5 496.1 467.3 45.7 46.1 Total International 3,206.6 3,014.7 3,009.1 326.8 339.6 Total Consolidated $ 8,031.6 $ 7,473.5 $ 7,452.3 $ 1,219.7 $ 1,034.1 Net 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, 2018
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, 2018 2017 2016 Gross rent expense $ 375.9 $ 371.0 $ 366.1 Third-party sublease rental income (5.3 ) (4.6 ) (4.1 ) Net rent expense $ 370.6 $ 366.4 $ 362.0 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 Obligations Sublease Rental Income Net Rent 2019 $ 352.0 $ (7.7 ) $ 344.3 2020 324.3 (5.2 ) 319.1 2021 282.3 (2.2 ) 280.1 2022 242.5 (1.3 ) 241.2 2023 184.0 (0.6 ) 183.4 Thereafter 714.6 (0.5 ) 714.1 Total $ 2,099.7 $ (17.5 ) $ 2,082.2 Guarantees We have guaranteed certain obligations of our subsidiaries relating principally to operating leases and uncommitted lines of credit of certain subsidiaries. As of December 31, 2018 and 2017, the amount of parent company guarantees on lease obligations was $824.5 and $829.2 , respectively, the amount of parent company guarantees primarily relating to uncommitted lines of credit was $349.1 and $308.8 , respectively, and the amount of parent company guarantees related to daylight overdrafts, primarily utilized to manage intra-day overdrafts due to timing of transactions under cash pooling arrangements without resulting in incremental borrowings, was $207.8 and $182.2 , 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, 2018 , 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, 2018 . 2019 2020 2021 2022 2023 Thereafter Total Deferred acquisition payments $ 65.7 $ 20.0 $ 23.6 $ 4.7 $ 10.2 $ 2.7 $ 126.9 Redeemable noncontrolling interests and call options with affiliates 1 30.1 30.6 42.9 5.7 3.5 2.5 115.3 Total contingent acquisition payments $ 95.8 $ 50.6 $ 66.5 $ 10.4 $ 13.7 $ 5.2 $ 242.2 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, 2018 . These estimated payments of $24.9 are included within the total payments expected to be made in 2019 , and will continue to be carried forward into 2020 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 these 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 5 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. As previously disclosed, on April 10, 2015, a federal judge in Brazil authorized the search of the records of an agency's offices in São Paulo and Brasilia, in connection with an ongoing investigation by Brazilian authorities involving payments potentially connected to local government contracts. The Company had previously investigated the matter and taken a number of remedial and disciplinary actions. The Company has been in the process of concluding a settlement related to these matters with government agencies, and that settlement was fully executed in April 2018. The Company has previously provided for such settlement in its Consolidated Financial Statements. In December 2016, one of the Company's standalone domestic agencies was contacted by the Department of Justice Antitrust Division (the "DOJ") for documents regarding video production practices. By letter dated November 5, 2018, the DOJ confirmed that the foregoing investigation has been closed, and all documents produced by the Company and its subsidiary were returned to the Company. The DOJ did not bring any charges against the Company or its subsidiary.

Recent Accounting Standards (No

Recent Accounting Standards (Notes)	12 Months Ended
	Dec. 31, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recent Accounting Standards	Recent Accounting Standards Accounting pronouncements not listed below were assessed and determined to be not applicable or are expected to have minimal impact on our Consolidated Financial Statements. Revenue Recognition See Notes 1 and 2 for further discussion on the adoption of ASC 606. Employee Benefits In August 2018, the Financial Accounting Standards Board (the "FASB") issued amended guidance that modifies the disclosure requirements for employers that sponsor defined benefit pension or other postretirement plans by removing disclosures that are no longer considered cost beneficial, clarifying requirements for certain disclosures, and adding disclosure requirements identified as relevant. The amended guidance is effective December 31, 2020, with early adoption permitted. We early adopted this amended guidance prospectively as of the quarter ended December 31, 2018. The adoption of this amended guidance did not have a significant impact on our Consolidated Financial Statements. Derivatives and Hedging In August 2017, the FASB issued amended guidance on hedge accounting which expands an entity’s ability to hedge non-financial and financial risk components and aligns the recognition and presentation of the effects of the hedging instrument and the hedged item in the financial statements. The new guidance also eliminates the requirement to separately measure and report hedge ineffectiveness. This amended guidance is effective beginning January 1, 2019, with early adoption permitted. We early adopted this amended guidance prospectively as of the quarter ended December 31, 2018, and applied the adoption as of January 1, 2018, as required. The adoption of this amended guidance did not have a significant impact on our Consolidated Financial Statements. Financial Instrument Credit Losses In June 2016, the FASB issued amended guidance on the accounting for credit losses on certain types of financial instruments, including trade receivables. The new model uses a forward-looking expected loss method, as opposed to the incurred loss method in current U.S. GAAP, which will generally result in earlier recognition of allowances for losses. This amended guidance is effective beginning January 1, 2020, with early adoption permitted as early as January 1, 2019. We are currently assessing the impact the adoption of the amended guidance will have on our Consolidated Financial Statements. Leases In February 2016, the FASB issued amended guidance on lease accounting which requires an entity to recognize a right-of-use asset and a corresponding lease liability on its balance sheet for virtually all of its leases with a term of more than 12 months, including those classified as operating leases. Both the asset and liability will initially be measured at the present value of the future minimum lease payments, with the asset being subject to adjustments such as initial direct costs. Consistent with current U.S. GAAP, the presentation of expenses and cash flows will depend primarily on the classification of the lease as either a finance or an operating lease. The new standard also requires additional quantitative and qualitative disclosures regarding the amount, timing and uncertainty of cash flows arising from leases in order to provide additional information about the nature of an organization’s leasing activities. This amended guidance, which is effective beginning January 1, 2019, requires modified retrospective application, and allows for the application of the new guidance at the adoption date. We have made significant progress in implementing the system upgrades required to adopt the leasing standard, and are currently in the process of establishing appropriate controls and procedures surrounding the new guidance. As an accounting policy, we have elected not to apply the recognition requirements to short-term leases, not to separate non-lease components from lease components, and have elected the package of practical expedients as it relates to reassessment of existing leases as granted by the FASB. We do not expect the adoption of this amended guidance to have a significant impact on our Consolidated Statements of Operations, but will result in an estimated right-of-use asset and lease liability between $1,300.0 to $1,600.0 each on our Consolidated Balance Sheet effective January 1, 2019. Fair Value Measurements In January 2016, the FASB issued amended guidance that updates the fair value presentation requirements for certain financial instruments. Equity investments with readily determinable fair values, other than those accounted for using the equity method of accounting, will be measured at fair value with changes recorded through current earnings rather than other comprehensive income. This amended guidance was effective January 1, 2018. The adoption of this amended guidance did not have a significant impact on our Consolidated Financial Statements.

Results by Quarter (Unaudited)

Results by Quarter (Unaudited) (Notes)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information	Results by Quarter (Unaudited) Three Months Ended March 31, Three Months Ended June 30, Three Months Ended September 30, Three Months Ended December 31, 2018 2017 2018 2017 2018 2017 2018 2017 Revenue: Net revenue 1,2 $ 1,774.0 $ 1,675.3 $ 1,948.2 $ 1,834.6 $ 1,895.7 $ 1,832.5 $ 2,413.7 $ 2,131.1 Billable expenses 1,2 395.1 388.5 443.6 351.2 401.8 375.7 442.3 458.7 Total Revenue 1,2 2,169.1 2,063.8 2,391.8 2,185.8 2,297.5 2,208.2 2,856.0 2,589.8 Operating Expenses: Salaries and related expenses 2 1,330.3 1,251.7 1,292.9 1,228.9 1,251.4 1,218.8 1,423.7 1,291.3 Office and other direct 2 expenses 323.8 312.7 333.3 318.4 317.0 302.9 381.0 334.8 Billable expenses 1,2 395.1 388.5 443.6 351.2 401.8 375.7 442.3 458.7 Cost of services 2 2,049.2 1,952.9 2,069.8 1,898.5 1,970.2 1,897.4 2,247.0 2,084.8 Selling, general and administrative expenses 2 35.1 35.2 28.8 20.3 21.6 13.6 81.0 49.4 Depreciation and amortization 2 46.0 41.0 44.0 41.3 44.0 42.2 68.9 32.6 Total operating expenses 1,2 2,130.3 2,029.1 2,142.6 1,960.1 2,035.8 1,953.2 2,396.9 2,166.8 Operating income 1 38.8 34.7 249.2 225.7 261.7 255.0 459.1 423.0 Other (expense) income, net 3 (24.4 ) 0.8 (16.3 ) (15.4 ) (15.3 ) (9.9 ) (13.6 ) (1.7 ) Total (expenses) and other income (40.3 ) (14.9 ) (37.7 ) (36.4 ) (37.6 ) (26.8 ) (55.2 ) (19.5 ) Provision for (benefit of) income taxes 1,4 12.7 (0.3 ) 63.6 81.6 60.7 54.9 62.2 135.1 Net (loss) income 1 (16.1 ) 21.3 147.8 107.6 163.5 172.3 342.5 269.2 Net (loss) income available to IPG common stockholders 1 $ (14.1 ) $ 24.7 $ 145.8 $ 107.7 $ 161.0 $ 169.7 $ 326.2 $ 252.3 (Loss) earnings per share available to IPG common stockholders: Basic 1 $ (0.04 ) $ 0.06 $ 0.38 $ 0.27 $ 0.42 $ 0.44 $ 0.85 $ 0.66 Diluted 1 $ (0.04 ) $ 0.06 $ 0.37 $ 0.27 $ 0.41 $ 0.43 $ 0.84 $ 0.64 Dividends declared per common share $ 0.21 $ 0.18 $ 0.21 $ 0.18 $ 0.21 $ 0.18 $ 0.21 $ 0.18 1 Effective January 1, 2018, the Company adopted Accounting Standards Codification Topic 606, Revenue from Contracts with Customers, ("ASC 606") using the full retrospective transition method and revised its Consolidated financial statements for the years ended December 31, 2017. See Note 1 and 2 for further detail on the ASC 606 adoption. 2 The Company has revised the presentation of its Consolidated Statements of Operations, which disaggregates net revenue and billable expenses within total revenue and separately presents cost of services; selling, general and administrative expenses; and depreciation and amortization within operating expenses. The revised presentation does not impact total revenue, total operating expenses or operating income. 3 The three months ended March 31, June 30, September 30 and December 31, 2018 included pre-tax net losses of $24.4 , $19.8 , $5.8 , and $11.9 , respectively, on sales of businesses. The three months ended June 30 and September 30, 2017 included pre-tax net losses of $13.1 and $8.7 , respectively, on sales of businesses. 4 The three months ended December 31, 2018 included a tax benefit of $23.4 related to various discrete tax items. The three months ended September 30, 2017 included a tax benefit of $31.2 related to foreign tax credits from distributions of unremitted earnings, which was reversed during the three months ended December 31, 2017 as a result of the enactment of the Tax Cuts and Jobs Act. The three months ended December 31, 2017 included a net tax benefit of $36.0 as a result of the enactment of the Tax Cuts and Jobs Act.

Subsequent Events (Notes)

Subsequent Events (Notes)	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events [Text Block]	Subsequent Events We announced on February 13, 2019 that our Board had declared a common stock cash dividend of $0.235 per share, payable on March 15, 2019 to holders of record as of the close of business on March 1, 2019.

Significant Accounting Polici_2

Significant Accounting Policies Principles of Consolidation (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
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 recorded at cost, less any impairment, adjusted for subsequent observable price changes. 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.

Significant Accounting Polici_3

Significant Accounting Policies Reclassifications (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Reclassifications	Reclassifications As of January 1, 2018, the Company has revised the presentation of its Consolidated Statements of Operations, which disaggregates net revenue and billable expenses within total revenue and separately presents cost of services; selling, general and administrative expenses; and depreciation and amortization within operating expenses. The revised presentation does not impact total revenue, total operating expenses or operating income. Cost of services is comprised of the expenses of our revenue-producing operating segments including salaries and related expenses, office and other direct expenses and billable expenses, as well as an allocation of the centrally managed expenses from Corporate. Office and other direct expenses include rent expense, professional fees, certain expenses incurred by our staff in servicing our clients and other costs directly attributable to client engagements. Selling, general and administrative expenses are primarily the unallocated expenses from Corporate, as disclosed further in Note 14 , excluding depreciation and amortization. Depreciation and amortization of the fixed assets and intangible assets of the Company is disclosed as a separate operating expense. Certain reclassifications and immaterial revisions have been made to prior-period financial statements to conform to the current-period presentation.

Significant Accounting Polici_4

Significant Accounting Policies Use of Estimates (Policies)	12 Months Ended
	Dec. 31, 2018
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.

Significant Accounting Polici_5

Significant Accounting Policies Revenue Recognition (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Revenue Recognition	Revenue Recognition Our revenues are primarily derived from the planning and execution of multi-channel advertising and communications and marketing services, including public relations, meeting and event production, sports and entertainment marketing, corporate and brand identity, and strategic marketing consulting around the world. Most of our client contracts are individually negotiated and, accordingly, the terms of client engagements and the basis on which we earn fees and commissions vary significantly. Our contracts generally provide for termination by either party on relatively short notice, usually 30 to 90 days. Our payment terms vary by client, and the time between invoicing date and due date is typically not significant. We generally have the legally enforceable right to payment for all services provided through the end of the contract or termination date. Effective January 1, 2018, we adopted Accounting Standards Codification Topic 606, Revenue from Contracts with Customers, ("ASC 606") using the full retrospective transition method. Under this method, we revised our consolidated financial statements for the years ended December 31, 2016 and 2017, and applicable interim periods within the year ended December 31, 2017, as if ASC 606 had been effective for those periods. ASC 606 applies to all contracts with customers, except for contracts that are within the scope of other standards. We recognize revenue when we determine our customer obtains control of promised goods or services, in an amount that reflects the consideration which we expect to receive in exchange for those goods or services. To determine revenue recognition, we perform the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue as or when we satisfy the performance obligation. We only apply the five-step model to contracts when it is probable that IPG will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, we assess the goods or services promised within each contract and determine those that are distinct performance obligations. We then assess whether we act as an agent or a principal for each identified performance obligation and include revenue within the transaction price for third-party costs when we determine that we act as principal. We typically do not capitalize costs to obtain a contract as these amounts would generally be recognized over a period of one year or less. Net revenue, primarily consisting of fees, commissions and performance incentives, represents the amount of our gross billings excluding billable expenses charged to a client. Generally, our compensation is based on a negotiated fixed price, rate per hour, a retainer or commission. The majority of our fees are recognized over time as services are performed, utilizing a function of hours incurred and rates per hour, as compared to periodically updated estimates to complete. For certain less-frequent commission-based contracts which contain clauses allowing our clients to terminate the arrangement at any time for no compensation, revenue is recognized at a point in time, typically the date of broadcast or publication. We report revenue net of taxes assessed by governmental authorities that are directly imposed on our revenue-producing transactions. Contractual arrangements with clients may also include performance incentive provisions designed to link a portion of our revenue to our performance relative to mutually agreed-upon qualitative and/or quantitative metrics. Performance incentives are treated as variable consideration which is estimated at contract inception and included in revenue based on the most likely amount earned out of a range of potential outcomes. Our estimates are based on a combination of historical award experience, anticipated performance and our best judgment. These estimates are updated on a periodic basis and are not expected to result in a reversal of a significant amount of the cumulative revenue recognized. The predominant component of billable expenses are third-party vendor costs incurred for performance obligations where we have determined that we are acting as principal. These third-party expenses are generally billed back to our clients. Billable expenses also includes incidental costs incurred in the performance of our services including airfare, mileage, hotel stays, out-of-town meals and telecommunication charges. We record these billable expenses within total revenue with a corresponding offset to operating expenses. In international markets, we may receive rebates or credits from vendors based on transactions entered into on behalf of clients. Rebates and credits are remitted back to our clients in accordance with our contractual requirements or may be retained by us based on the terms of a particular client contract and local law. Amounts owed back to clients are recorded as a liability and amounts retained by us are recorded as revenue when earned. In certain international markets, our media contracts may allow clients to terminate our arrangement at any time for no compensation to the extent that media has not yet run. For those contracts, we do not recognize revenue until the media runs which is the point in time at which we have a legally enforceable right to compensation. Performance Obligations Our client contracts may include various goods and services that are capable of being distinct, are distinct within the context of the contract and are therefore accounted for as separate performance obligations. We allocate revenue to each performance obligation in the contract at inception based on its relative standalone selling price. Our advertising businesses include a wide range of services that involve the creation of an advertising idea, concept, campaign, or marketing strategy in order to promote the client’s brand ("creative services"), and to act as an agent to facilitate the production of advertisements by third-party suppliers ("production services”). Our clients can contract us to perform one or both of these services, as they can derive stand-alone benefit from each. Production services can include formatting creative material for different media and communication mediums including digital, large-scale reproduction such as printing and adaptation services, talent engagement and acquisition, television and radio production, and outdoor billboard production. Our contracts that include both services are typically explicit in the description of which activities constitute the creative advertising services and those that constitute the production services. Both the creative and production services are sold separately, the client can derive utility from each service on its own, we do not provide a significant service of integrating these activities into a bundle, the services do not significantly modify one another, and the services are not highly interrelated or interdependent. As such, we typically identify two performance obligations in the assessment of our advertising contracts. Our media businesses include services to formulate strategic media plans ("media planning services") and to act as an agent to purchase media (e.g. television and radio spots, outdoor advertising, digital banners, etc.) from vendors on their behalf ("media buying services"). Our contracts that include both services are typically explicit in the description of which activities constitute the planning services and those that constitute the buying services. Both the planning and buying services are sold separately, the client can derive utility from each service on its own, we do not provide a significant service of integrating these activities into a bundle, the services do not significantly modify one another, and the services are not highly interrelated or interdependent. As such, we typically identify two performance obligations in the assessment of our media contracts. Our events businesses include creative services related to the conception and planning of custom marketing events as well as activation services which entail the carrying out of the event, including, but not limited to, set-up, design and staffing. Additionally, our public relations businesses include a broad range of services, such as strategic planning, social media strategy and the monitoring and development of communication strategies, among others. While our contracts in these businesses may include some or all of these services, we typically identify only one performance obligation in the assessment of our events and public relations contracts as we provide a significant service of integrating the individual services into a combined service for which the customer has contracted. As part of our adoption of ASC 606, we elected not to disclose information about remaining performance obligations that have original expected durations of one year or less. The majority of our contracts are for periods of one-year or less. For those contracts with a term of more than one year, we had approximately $770.0 of unsatisfied performance obligations as of December 31, 2018 which will be recognized as services are performed over the remaining contractual terms. Principal vs. Agent When a third-party is involved in the delivery of our services to the client, we assess whether or not we are acting as a principal or an agent in the arrangement. The assessment is based on whether we control the specified services at any time before they are transferred to the customer. We have determined that in our events and public relations businesses, we generally act as a principal as our agencies provide a significant service of integrating goods or services provided by third parties into the specified deliverable to our clients. In addition, we have determined that we are responsible for the performance of the third-party suppliers, which are combined with our own services, before transferring those services to the customer. In addition, we have determined that we act as principal when providing creative services and media planning services, as we perform a significant integration service in these transactions. For performance obligations in which we act as principal, we record the gross amount billed to the customer within total revenue and the related incremental direct costs incurred as billable expenses. When a third-party is involved in the production of an advertising campaign and for media buying services, we have determined that we act as the agent and are solely arranging for the third-party to provide services to the customer. Specifically, we do not control the specified services before transferring those services to the customer, we are not primarily responsible for the performance of the third-party services, nor can we redirect those services to fulfill any other contracts. We do not have inventory risk or discretion in establishing pricing in our contracts with customers. For performance obligations for which we act as the agent, we record our revenue as the net amount of our gross billings less amounts remitted to third parties.

Significant Accounting Polici_6

Significant Accounting Policies Cash and Cash Equivalents (Policies)	12 Months Ended
	Dec. 31, 2018
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.

Significant Accounting Polici_7

Significant Accounting Policies Allowance for Doubtful Accounts (Policies)	12 Months Ended
	Dec. 31, 2018
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.

Significant Accounting Polici_8

Significant Accounting Policies Acounts Receivable, Billable to Clients (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Accounts Receivable, Billable to Clients	Accounts Receivable, Billable to Clients Accounts receivable, 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.

Significant Accounting Polici_9

Significant Accounting Policies Accounts Payable (Policies)	12 Months Ended
	Dec. 31, 2018
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.

Significant Accounting Polic_10

Significant Accounting Policies Investments (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Investments	Investments Our non-publicly traded investments and all other publicly traded investments are accounted for using the equity method or are recorded at fair value. We regularly review our investments to determine whether a significant event or change in circumstances has occurred that may impact the fair value of each investment, with changes to fair value recorded in earnings. 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 a decline in value of an investment has occurred.

Significant Accounting Polic_11

Significant Accounting Policies Derivatives (Policies)	12 Months Ended
	Dec. 31, 2018
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 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.

Significant Accounting Polic_12

Significant Accounting Policies Property and Equipment (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Property and Equipment	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.

Significant Accounting Polic_13

Significant Accounting Policies Goodwill and Other Intangible Assets (Policies)	12 Months Ended
	Dec. 31, 2018
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 1 st 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 2018 annual impairment testing. Our annual impairment review as of October 1, 2018 did not result in an impairment charge for any of our reporting units. 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 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 sum of the fair values of all our reporting units is also 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 quantitative impairment test is failed and impaired goodwill is written down to its fair value with a charge to expense in the period the impairment is identified. The fair value of each reporting unit for 2018 and 2017 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 asset groups. These asset groups 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.

Significant Accounting Polic_14

Significant Accounting Policies Foreign Currencies (Policies)	12 Months Ended
	Dec. 31, 2018
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 pre-tax gains of $5.6 , $1.9 and $2.1 in for the years ended December 31, 2018 , 2017 and 2016 , respectively. 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.

Significant Accounting Polic_15

Significant Accounting Policies Income Taxes (Policies)	12 Months Ended
	Dec. 31, 2018
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. Public Law 115-97, commonly referred to as the Tax Cuts and Jobs Act (the "Tax Act") was signed into law on December 22, 2017. The Tax Act legislated many new tax provisions which have impacted our operations. At December 31, 2017, provisional amounts were recorded as permitted by SEC Staff issued Accounting Bulletin No. 118 (“SAB 118”). We have finalized our calculations of the impact of the Tax Act and have revised our estimates as required by SAB 118. See Note 9 for further information.

Significant Accounting Polic_16

Significant Accounting Policies Redeemable Noncontrolling Interests (Policies)	12 Months Ended
	Dec. 31, 2018
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 (“APIC”), 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.

Significant Accounting Polic_17

Significant Accounting Policies Earnings Per Share (Policies)	12 Months Ended
	Dec. 31, 2018
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 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 were exercised. 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 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. 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, 2018 , 2017 and 2016 , there was no impact to EPS for adjustments related to our redeemable noncontrolling interests.

Significant Accounting Polic_18

Significant Accounting Policies Pension and Postretirement Benefits (Policies)	12 Months Ended
	Dec. 31, 2018
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.

Significant Accounting Polic_19

Significant Accounting Policies Stock-Based Compensation (Policies)	12 Months Ended
	Dec. 31, 2018
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.

Significant Accounting Polic_20

Significant Accounting Policies Treasury Stock (Policies)	12 Months Ended
	Dec. 31, 2018
Treasury Stock, Shares [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 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 October 2018 , we retired 8.1 shares of our treasury stock, which resulted in a reduction in common stock of $0.8 , treasury stock of $176.1 and APIC of $175.3 . In October and November 2017 , we retired 13.4 shares of our treasury stock, which resulted in a reduction in common stock of $1.3 , treasury stock of $304.4 and APIC of $303.1 . In October 2016 , we retired 13.7 shares of our treasury stock, which resulted in a reduction in common stock of $1.4 , treasury stock of $311.0 and APIC of $309.6 . There was no effect on total stockholders' equity as a result of these retirements.

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Condensed Income Statement [Table Text Block]	CONSOLIDATED STATEMENT OF OPERATIONS Year ended December 31, 2017 Year ended December 31, 2016 As Revised 1 ASC 606 Adjustments As Adjusted As Revised 1 ASC 606 Adjustments As Adjusted REVENUE: Net revenue $ 7,508.7 $ (35.2 ) $ 7,473.5 $ 7,456.9 $ (4.6 ) $ 7,452.3 Billable expenses 373.7 1,200.4 1,574.1 389.7 1,214.2 1,603.9 Total revenue 7,882.4 1,165.2 9,047.6 7,846.6 1,209.6 9,056.2 OPERATING EXPENSES: Salaries and related expenses 4,990.7 — 4,990.7 4,942.2 — 4,942.2 Office and other direct expenses 1,268.8 — 1,268.8 1,274.9 — 1,274.9 Billable expenses 373.7 1,200.4 1,574.1 389.7 1,214.2 1,603.9 Cost of services 6,633.2 1,200.4 7,833.6 6,606.8 1,214.2 7,821.0 Selling, general and administrative expenses 118.5 — 118.5 138.6 — 138.6 Depreciation and amortization 157.1 — 157.1 160.2 — 160.2 Total operating expenses 6,908.8 1,200.4 8,109.2 6,905.6 1,214.2 8,119.8 OPERATING INCOME 973.6 (35.2 ) 938.4 941.0 (4.6 ) 936.4 EXPENSES AND OTHER INCOME: Interest expense (90.8 ) — (90.8 ) (90.6 ) — (90.6 ) Interest income 19.4 — 19.4 20.1 — 20.1 Other expense, net (26.2 ) — (26.2 ) (40.3 ) — (40.3 ) Total (expenses) and other income (97.6 ) — (97.6 ) (110.8 ) — (110.8 ) Income before income taxes 876.0 (35.2 ) 840.8 830.2 (4.6 ) 825.6 Provision for income taxes 281.9 (10.6 ) 271.3 198.0 (1.1 ) 196.9 Income of consolidated companies 594.1 (24.6 ) 569.5 632.2 (3.5 ) 628.7 Equity in net income of unconsolidated affiliates 0.9 — 0.9 0.3 — 0.3 NET INCOME 595.0 (24.6 ) 570.4 632.5 (3.5 ) 629.0 Net income attributable to noncontrolling interests (16.0 ) — (16.0 ) (24.0 ) — (24.0 ) NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS $ 579.0 $ (24.6 ) $ 554.4 $ 608.5 $ (3.5 ) $ 605.0 Earnings per share available to IPG common stockholders: Basic $ 1.49 $ (0.07 ) $ 1.42 $ 1.53 $ (0.01 ) $ 1.52 Diluted $ 1.46 $ (0.06 ) $ 1.40 $ 1.49 $ (0.01 ) $ 1.48 Weighted-average number of common shares outstanding: Basic 389.6 — 389.6 397.9 — 397.9 Diluted 397.3 — 397.3 408.0 — 408.0 1 These amounts have been revised for the new presentation as described in Note 1 .
Condensed Cash Flow Statement [Table Text Block]	CONSOLIDATED STATEMENT OF CASH FLOWS Year ended December 31, 2017 As Reported ASC 606 Adjustments As Adjusted CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 595.0 $ (24.6 ) $ 570.4 Adjustments to reconcile net income to net cash used in operating activities: Depreciation and amortization 157.1 — 157.1 Provision for uncollectible receivables 9.5 — 9.5 Amortization of restricted stock and other non-cash compensation 82.0 — 82.0 Net amortization of bond discounts and deferred financing costs 5.8 — 5.8 Deferred income tax provision 1.1 (10.6 ) (9.5 ) Net losses on sales of businesses 24.1 — 24.1 Other 12.7 — 12.7 Changes in assets and liabilities, net of acquisitions and divestitures, providing (using) cash: Accounts receivable 37.6 — 37.6 Expenditures billable to clients (165.5 ) 165.5 — Accounts receivable, billable to clients — (165.5 ) (165.5 ) Other current assets 27.4 22.7 50.1 Accounts payable 311.9 24.5 336.4 Accrued liabilities (241.3 ) — (241.3 ) Contract liabilities — (12.0 ) (12.0 ) Other non-current assets and liabilities 24.4 — 24.4 Net cash provided by operating activities 881.8 — 881.8 CASH FLOWS FROM INVESTING ACTIVITIES: Net cash used in investing activities (196.2 ) — (196.2 ) CASH FLOWS FROM FINANCING ACTIVITIES: Net cash used in financing activities (1,004.9 ) — (1,004.9 ) Effect of foreign exchange rate changes on cash, cash equivalents and restricted cash 16.8 — 16.8 Net decrease in cash, cash equivalents and restricted cash (302.5 ) — (302.5 ) Cash, cash equivalents and restricted cash at beginning of period 1,100.2 — 1,100.2 Cash, cash equivalents and restricted cash at end of period $ 797.7 $ — $ 797.7 Year ended December 31, 2016 As Reported ASC 606 Adjustments As Adjusted CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 632.5 $ (3.5 ) $ 629.0 Adjustments to reconcile net income to net cash used in operating activities: Depreciation and amortization 160.2 — 160.2 Provision for uncollectible receivables 16.7 — 16.7 Amortization of restricted stock and other non-cash compensation 85.6 — 85.6 Net amortization of bond discounts and deferred financing costs 5.6 — 5.6 Deferred income tax provision 45.7 (1.1 ) 44.6 Net losses on sales of businesses 41.4 — 41.4 Other 35.5 — 35.5 Changes in assets and liabilities, net of acquisitions and divestitures, providing (using) cash: Accounts receivable (220.7 ) — (220.7 ) Expenditures billable to clients (2.2 ) 2.2 — Accounts receivable, billable to clients — (2.2 ) (2.2 ) Other current assets (4.8 ) 5.3 0.5 Accounts payable (126.1 ) (21.3 ) (147.4 ) Accrued liabilities (61.1 ) — (61.1 ) Contract liabilities — 20.6 20.6 Other non-current assets and liabilities (95.5 ) — (95.5 ) Net cash provided by operating activities 512.8 — 512.8 CASH FLOWS FROM INVESTING ACTIVITIES: Net cash used in investing activities (263.9 ) — (263.9 ) CASH FLOWS FROM FINANCING ACTIVITIES: Net cash used in financing activities (666.4 ) — (666.4 ) Effect of foreign exchange rate changes on cash, cash equivalents and restricted cash 11.6 — 11.6 Net decrease in cash, cash equivalents and restricted cash (405.9 ) — (405.9 ) Cash, cash equivalents and restricted cash at beginning of period 1,506.1 — 1,506.1 Cash, cash equivalents and restricted cash at end of period $ 1,100.2 $ — $ 1,100.2
Condensed Balance Sheet [Table Text Block]	CONSOLIDATED BALANCE SHEET December 31, 2017 As Reported ASC 606 Adjustments As Adjusted ASSETS: Cash and cash equivalents $ 790.9 $ — $ 790.9 Accounts receivable, net of allowance of $42.7 4,585.0 — 4,585.0 Expenditures billable to clients 1,747.4 (1,747.4 ) — Accounts receivable, billable to clients — 1,747.4 1,747.4 Assets held for sale 5.7 — 5.7 Other current assets 335.1 11.4 346.5 Total current assets 7,464.1 11.4 7,475.5 Property and equipment, net of accumulated depreciation of $1,036.2 650.4 — 650.4 Deferred income taxes 236.0 (2.0 ) 234.0 Goodwill 3,820.4 — 3,820.4 Other intangible assets 140.7 — 140.7 Other non-current assets 383.6 0.1 383.7 TOTAL ASSETS $ 12,695.2 $ 9.5 $ 12,704.7 LIABILITIES: Accounts payable $ 6,907.8 $ (487.6 ) $ 6,420.2 Accrued liabilities 674.7 — 674.7 Contract liabilities — 484.7 484.7 Short-term borrowings 84.9 — 84.9 Current portion of long-term debt 2.0 — 2.0 Liabilities held for sale 8.8 — 8.8 Total current liabilities 7,678.2 (2.9 ) 7,675.3 Long-term debt 1,285.6 — 1,285.6 Deferred compensation 476.6 — 476.6 Other non-current liabilities 766.9 1.9 768.8 TOTAL LIABILITIES 10,207.3 (1.0 ) 10,206.3 Redeemable noncontrolling interests 252.1 — 252.1 STOCKHOLDERS’ EQUITY: Common stock 38.6 — 38.6 Additional paid-in capital 955.2 — 955.2 Retained earnings 2,093.6 10.9 2,104.5 Accumulated other comprehensive loss, net of tax (827.4 ) (0.4 ) (827.8 ) 2,260.0 10.5 2,270.5 Less: Treasury stock (59.0 ) — (59.0 ) Total IPG stockholders’ equity 2,201.0 10.5 2,211.5 Noncontrolling interests 34.8 — 34.8 TOTAL STOCKHOLDERS’ EQUITY 2,235.8 10.5 2,246.3 TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY $ 12,695.2 $ 9.5 $ 12,704.7
Revenue from External Customers by Geographic Areas [Table Text Block]	Years ended December 31, Total revenue: 2018 2017 2016 United States $ 5,851.0 $ 5,417.3 $ 5,452.6 International: United Kingdom 881.4 775.7 788.8 Continental Europe 840.2 780.6 764.1 Asia Pacific 1,170.8 1,106.4 1,076.0 Latin America 389.0 386.6 417.2 Other 582.0 581.0 557.5 Total International 3,863.4 3,630.3 3,603.6 Total Consolidated $ 9,714.4 $ 9,047.6 $ 9,056.2 Years ended December 31, Net revenue: 2018 2017 2016 United States $ 4,825.0 $ 4,458.8 $ 4,443.2 International: United Kingdom 711.7 613.1 604.3 Continental Europe 737.5 687.8 682.0 Asia Pacific 896.8 866.9 887.7 Latin America 350.1 350.8 367.8 Other 510.5 496.1 467.3 Total International 3,206.6 3,014.7 3,009.1 Total Consolidated $ 8,031.6 $ 7,473.5 $ 7,452.3 IAN Years ended December 31, Total revenue: 2018 2017 2016 United States $ 4,279.4 $ 4,062.3 $ 4,075.9 International 3,095.0 2,947.3 2,916.9 Total IAN $ 7,374.4 $ 7,009.6 $ 6,992.8 Net revenue: United States $ 3,832.7 $ 3,660.6 $ 3,600.3 International 2,753.1 2,606.1 2,601.1 Total IAN $ 6,585.8 $ 6,266.7 $ 6,201.4 CMG Years ended December 31, Total revenue: 2018 2017 2016 United States $ 1,404.0 $ 1,355.0 $ 1,376.7 International 754.3 683.0 686.7 Total CMG $ 2,158.3 $ 2,038.0 $ 2,063.4 Net revenue: United States $ 824.6 $ 798.2 $ 842.9 International 439.5 408.6 408.0 Total CMG $ 1,264.1 $ 1,206.8 $ 1,250.9
Contract with Customer, Asset and Liability [Table Text Block]	Contract Balances The following table provides information about receivables, contract assets and contract liabilities from contracts with customers. December 31, December 31, Accounts receivable, net of allowance of $42.5 and $42.7, respectively $ 5,126.6 $ 4,585.0 Accounts receivable, billable to clients 1,900.6 1,747.4 Contract assets 67.9 11.5 Contract liabilities (deferred revenue) 533.9 484.7

Debt and Credit Agreements Sche

Debt and Credit Agreements Schedule of Long-term Debt Instruments (Tables)	12 Months Ended
	Dec. 31, 2018
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 Interest Rate December 31, 2018 2017 Book Value Fair Value 1 Book Value Fair 1 3.50% Senior Notes due 2020 (less unamortized discount and issuance costs of $0.8 and $2.6, respectively) 3.89 % $ 496.6 $ 499.9 $ — $ — 3.75% Senior Notes due 2021 (less unamortized discount and issuance costs of $0.3 and $2.9, respectively) 3.98 % 496.8 503.2 — — 4.00% Senior Notes due 2022 (less unamortized discount and issuance costs of $1.0 and $0.8, respectively) 4.13 % 248.2 250.3 247.6 259.0 3.75% Senior Notes due 2023 (less unamortized discount and issuance costs of $0.6 and $1.7, respectively) 4.32 % 497.7 491.4 497.1 513.2 4.20% Senior Notes due 2024 (less unamortized discount and issuance costs of $0.5 and $2.2, respectively) 4.24 % 497.3 492.6 496.7 524.2 4.65% Senior Notes due 2028 (less unamortized discount and issuance costs of $1.7 and $4.3, respectively) 4.78 % 494.0 494.1 — — 5.40% Senior Notes due 2048 (less unamortized discount and issuance costs of $2.8 and $5.5, respectively) 5.48 % 491.7 474.1 — — Term Loan due 2021 - LIBOR plus 1.25% 400.0 400.0 — Other notes payable and capitalized leases 38.0 38.0 46.2 46.2 Total long-term debt 3,660.3 1,287.6 Less: current portion 0.1 2.0 Long-term debt, excluding current portion $ 3,660.2 $ 1,285.6 1 See Note 12 for information on the fair value measurement of our long-term debt.

Debt and Credit Agreements Sc_2

Debt and Credit Agreements Schedule of Maturities of Long-term Debt (Tables)	12 Months Ended
	Dec. 31, 2018
Long-term Debt, Fiscal Year Maturity [Abstract]
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, 2018 . 2019 $ 0.1 2020 496.9 2021 896.8 2022 248.2 2023 497.7 Thereafter 1,520.6 Total long-term debt $ 3,660.3

Debt and Credit Agreements Summ

Debt and Credit Agreements Summary of New Debt Issuance (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Summary of New Debt Issuance [Table Text Block]	The issuance was comprised of the following four series of notes: Senior Notes Par Value Discount at Issuance Net Price at Issuance Issuance Cost Net Proceeds 3.50% Senior Notes due 2020 $ 500.0 $ 1.0 $ 499.0 $ 2.9 $ 496.1 3.75% Senior Notes due 2021 500.0 0.3 499.7 3.2 496.5 4.65% Senior Notes due 2028 500.0 1.7 498.3 4.4 493.9 5.40% Senior Notes due 2048 500.0 2.8 497.2 5.6 491.6 Total $ 2,000.0 $ 5.8 $ 1,994.2 $ 16.1 $ 1,978.1

Debt and Credit Agreements Sc_3

Debt and Credit Agreements Schedule of Financial Covenants in Credit Agreement (Tables)	12 Months Ended
	Dec. 31, 2018
Schedule of Line of Credit Facility [Abstract]
Schedule of Financial Covenants in Credit Agreement [Table Text Block]	Interest coverage ratio (not less than): 1 5.00x Leverage ratio (not greater than): 2 4.00x 1 The interest coverage ratio is defined as EBITDA, as defined in the Credit Agreement and Term Loan Agreement, to net interest expense for the four quarters then ended. 2 The leverage ratio is defined as debt as of the last day of such fiscal quarter to EBITDA, as defined in the Amended Credit Agreement and Term Loan Agreement, for the four quarters then ended.

Earnings Per Share Basic and Di

Earnings Per Share Basic and Diluted Earnings Per Common Share Available to IPG Common Stockholders (Tables)	12 Months Ended
	Dec. 31, 2018
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, 2018 2017 2016 Net income available to IPG common stockholders $ 618.9 $ 554.4 $ 605.0 Weighted-average number of common shares outstanding - basic 383.3 389.6 397.9 Dilutive effect of stock options and restricted shares 5.7 7.7 10.1 Weighted-average number of common shares outstanding - diluted 389.0 397.3 408.0 Earnings per share available to IPG common stockholders: Basic $ 1.61 $ 1.42 $ 1.52 Diluted $ 1.59 $ 1.40 $ 1.48

Acquisitions Cash Paid for Curr

Acquisitions Cash Paid for Current and Prior Years' Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Cash Paid For Current And Prior Years' Acquisitions [Table Text Block]	Details of cash paid for current and prior years' acquisitions are listed below. Years ended December 31, 2018 2017 2016 Cost of investment: current-year acquisitions 1 $ 2,323.4 $ 36.8 $ 65.7 Cost of investment: prior-year acquisitions 33.9 54.6 40.7 Less: net cash acquired (13.8 ) (7.1 ) (13.6 ) Total cost of investment 2,343.5 84.3 92.8 Operating payments 2 19.4 47.1 19.1 Total cash paid for acquisitions 3 $ 2,362.9 $ 131.4 $ 111.9 1 The cost of investment: current-year acquisitions line significantly increased in the year ended December 31, 2018, primarily as a result of payments related to the acquisition of Acxiom. See Note 6 for further information on the Acxiom Acquisition. 2 Represents cash payments for amounts that have been recognized in operating expenses since the date of acquisition either relating to adjustments to estimates in excess of the initial value of contingent payments recorded or were contingent upon the future employment of the former owners of the acquired companies. Amounts are reflected in the operating section of the Consolidated Statements of Cash Flows. 3 Of the total cash paid for acquisitions, $2,309.8 , $30.6 and $52.0 for the years ended December 31, 2018 , 2017 and 2016 , respectively, are classified under the investing section of the Consolidated Statements of Cash Flows as acquisitions, net of cash acquired. These amounts relate to initial payments for new transactions. Of the total cash paid for acquisitions, $33.7 , $53.7 and $40.8 for the years ended December 31, 2018 , 2017 and 2016 , respectively, are classified under the financing section of the Consolidated Statements of Cash Flows as acquisition-related payments. These amounts relate to deferred payments and increases in our ownership interest for prior acquisitions.

Acquisitions Redeemable Noncont

Acquisitions Redeemable Noncontrolling Interest (Tables)	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Redeemable Noncontrolling Interest	The following table presents changes in our redeemable noncontrolling interests. Years ended December 31, 2018 2017 2016 Balance at beginning of period $ 252.1 $ 252.8 $ 251.9 Change in related noncontrolling interests balance (10.7 ) (2.8 ) 4.9 Changes in redemption value of redeemable noncontrolling interests: Additions — 7.7 6.8 Redemptions and other (33.7 ) (18.5 ) (14.8 ) Redemption value adjustments (39.8 ) 12.9 4.0 Balance at end of period $ 167.9 $ 252.1 $ 252.8 .

Acxiom Acquisition (Tables)

Acxiom Acquisition (Tables)	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Preliminary fair values of the assets acquired and liabilities assumed Table	October 1, 2018 Cash and cash equivalents $ 13.3 Accounts receivable 112.9 Accounts receivable, billable to clients 8.3 Other current assets 28.2 Property and equipment, net 159.7 Deferred income taxes (0.6 ) Goodwill 1,110.8 Intangible assets, net 995.0 Other non-current assets 8.3 Accounts payable (37.1 ) Accrued liabilities (46.9 ) Contract liabilities (23.2 ) Other non-current liabilities (0.8 ) Net assets acquired $ 2,327.9
Preliminary fair values of the identifiable intangible assets acquired at the closing date Table	Fair Value Weighted Average Amortization Period (Years) Customer lists $ 600.0 15.0 Know-how and technology 235.0 9.0 Trade names 160.0 15.0 to indefinite Total intangible assets 995.0
Acxiom pro forma Table	(unaudited) December 31, 2018 2017 Pro forma revenues $ 10,230.4 $ 9,736.1 Pro forma net income 642.2 519.2

Supplementary Data Valuation an

Supplementary Data Valuation and Qualifying Accounts - Allowance for Uncollectible Accounts (Tables)	12 Months Ended
	Dec. 31, 2018
Valuation and Qualifying Accounts - Allowance for Uncollectible Accounts [Abstract]
Valuation and Qualifying Accounts - Allowance for Uncollectible Accounts Receivable	Valuation and Qualifying Accounts – Allowance for Uncollectible Accounts Receivable Years ended December 31, 2018 2017 2016 Balance at beginning of period $ 42.7 $ 55.7 $ 54.2 Charges to costs and expenses 6.5 9.5 16.7 Adjustments: Acquisitions/(dispositions) 2.2 (1.0 ) (2.5 ) Uncollectible accounts written off (7.1 ) (25.5 ) (9.4 ) Foreign currency translation adjustments (1.8 ) 4.0 (3.3 ) Balance at end of period $ 42.5 $ 42.7 $ 55.7

Supplementary Data Property and

Supplementary Data Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property and Equipment [Abstract]
Property, Plant and Equipment [Table Text Block]	Property and Equipment December 31, 2018 2017 Furniture and equipment $ 681.7 $ 634.8 Leasehold improvements 629.0 641.5 Internal-use computer software 368.5 331.3 Land and buildings 146.6 79.0 Gross property and equipment 1,825.8 1,686.6 Less: accumulated depreciation (1,034.9 ) (1,036.2 ) Total property and equipment, net $ 790.9 $ 650.4

Supplementary Data Accrued Liab

Supplementary Data Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2018
Accrued Liabilities [Abstract]
Schedule of Accrued Liabilities [Table Text Block]	Accrued Liabilities The following table presents the components of accrued liabilities. December 31, 2018 2017 Salaries, benefits and related expenses $ 494.9 $ 441.7 Acquisition obligations 65.7 42.0 Office and related expenses 52.2 53.2 Interest 43.6 16.4 Other 150.5 121.4 Total accrued liabilities $ 806.9 $ 674.7

Supplementary Data Other Expens

Supplementary Data Other Expense, Net (Tables)	12 Months Ended
	Dec. 31, 2018
Other Nonoperating Income (Expense) [Abstract]
Schedule of Other Nonoperating Income (Expense) [Table Text Block]	Other Expense, Net Results of operations include certain items that are not directly associated with our revenue-producing operations. Years ended December 31, 2018 2017 2016 Net losses on sales of businesses $ (61.9 ) $ (24.1 ) $ (41.4 ) Other (7.7 ) (2.1 ) 1.1 Total other expense, net $ (69.6 ) $ (26.2 ) $ (40.3 )

Supplementary Data Share Repurc

Supplementary Data Share Repurchase Program (Tables)	12 Months Ended
	Dec. 31, 2018
Share Repurchase Program [Abstract]
Share Repurchase Program [Table Text Block]	The following table presents our share repurchase activity under our share repurchase programs. Years ended December 31, 2018 2017 2016 Number of shares repurchased 5.1 13.7 13.3 Aggregate cost, including fees $ 117.1 $ 300.1 $ 303.3 Average price per share, including fees $ 23.03 $ 21.97 $ 22.76

Supplementary Data Supplemental

Supplementary Data Supplemental Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2018
Supplemental Cash Flow Information [Abstract]
Schedule of Cash Flow, Supplemental Disclosures [Table Text Block]	Supplemental Cash Flow Information Years ended December 31, 2018 2017 2016 Cash paid for interest $ 88.7 $ 82.3 $ 78.8 Cash paid for income taxes, net of refunds 1 207.9 228.4 244.1 1 Refunds of $24.3 , $31.9 and $26.6 were received for the years ended December 31, 2018 , 2017 and 2016 , respectively.

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets Changes in Carrying Value of Goodwill (Tables)	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in Carrying Value of Goodwill	The changes in the carrying value of goodwill for our segments, IAN, CMG and Corporate & other, for the years ended December 31, 2018 and 2017 are listed below. IAN CMG Corporate & other 1 Total 2 Balance as of December 31, 2016 $ 3,043.8 $ 630.6 $ — $ 3,674.4 Acquisitions 39.6 15.5 — 55.1 Foreign currency and other 78.4 12.5 — 90.9 Balance as of December 31, 2017 $ 3,161.8 $ 658.6 $ — $ 3,820.4 Acquisitions 1.2 20.0 1,110.8 1,132.0 Foreign currency and other (63.3 ) (12.0 ) (1.2 ) (76.5 ) Balance as of December 31, 2018 $ 3,099.7 $ 666.6 $ 1,109.6 $ 4,875.9

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets Summary of Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2018
Summary of Other Intangible Assets [Abstract]
Schedule of Finite-Lived Intangible Assets [Table Text Block]	The following table provides a summary of other intangible assets, which are included in our Consolidated Balance Sheets. December 31, 2018 2017 Gross Amount Accumulated Amortization Net Amount Gross Amount Accumulated Amortization Net Amount Customer lists $ 857.2 $ (190.9 ) $ 666.3 $ 267.3 $ (172.2 ) $ 95.1 Know-how and technology 235.0 (6.5 ) 228.5 — — — Trade names 226.2 (36.8 ) 189.4 68.8 (33.8 ) 35.0 Other 14.4 (3.8 ) 10.6 14.4 (3.8 ) 10.6 Total $ 1,332.8 $ (238.0 ) $ 1,094.8 $ 350.5 $ (209.8 ) $ 140.7

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets Estimated future amortization of other intangible assets (Tables)	12 Months Ended
	Dec. 31, 2018
Summary of Other Intangible Assets [Abstract]
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]	The estimated annual amortization expense for other intangible assets for the next five years as of December 31, 2018 is listed below. 2019 2020 2021 2022 2023 Estimated amortization expense $ 87.8 $ 87.3 $ 85.6 $ 82.3 $ 78.2

Income Taxes Schedule of Income

Income Taxes Schedule of Income before Income Tax, Domestic and Foreign (Tables)	12 Months Ended
	Dec. 31, 2018
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, 2018 2017 2016 Domestic $ 474.0 $ 514.8 $ 502.1 Foreign 364.0 326.0 323.5 Total $ 838.0 $ 840.8 $ 825.6

Income Taxes Schedule of Compon

Income Taxes Schedule of Components of Provision for Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	The provision for income taxes is listed below. Years ended December 31, 2018 2017 2016 U.S. federal income taxes (including foreign withholding taxes): Current $ 38.1 $ 154.1 $ 54.3 Deferred 29.9 (37.6 ) 35.7 68.0 116.5 90.0 State and local income taxes: Current 25.1 18.8 8.2 Deferred 3.4 19.7 (1.6 ) 28.5 38.5 6.6 Foreign income taxes: Current 121.9 107.9 89.8 Deferred (19.2 ) 8.4 10.5 102.7 116.3 100.3 Total $ 199.2 $ 271.3 $ 196.9

Income Taxes Schedule of Effect

Income Taxes Schedule of Effective Income Tax Rate Reconciliation (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	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, 2018 2017 2016 U.S. federal statutory income tax rate 21.0 % 35.0 % 35.0 % Income tax provision at U.S. federal statutory rate $ 176.0 $ 294.3 $ 289.0 State and local income taxes, net of U.S. federal income tax benefit 23.8 23.5 4.3 Impact of foreign operations, including withholding taxes 50.7 (6.7 ) (23.9 ) U.S. tax incentives (17.5 ) (1.3 ) (1.3 ) Change in net valuation allowance 1 (16.9 ) 1.4 (13.4 ) Divestitures 11.7 1.1 9.7 U.S. federal tax credits (48.1 ) (0.4 ) (44.6 ) Stock compensation (6.8 ) (15.3 ) (9.0 ) Increase/(decrease) in unrecognized tax benefits 8.4 7.0 (21.8 ) Net impact of the Tax Act 13.4 (36.0 ) 0.0 Statutory tax rate changes 0.0 0.0 11.4 Other 4.5 3.7 (3.5 ) Provision for income taxes $ 199.2 $ 271.3 $ 196.9 Effective income tax rate on operations 23.8 % 32.3 % 23.8 % 1 Reflects changes in valuation allowances that impacted the effective income tax rate for each year presented.

Income Taxes Schedule of Deferr

Income Taxes Schedule of Deferred Tax Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]	The components of deferred tax assets and liabilities are listed below. December 31, 2018 2017 Postretirement/post-employment benefits $ 17.9 $ 19.5 Deferred compensation 99.8 91.7 Pension costs 22.2 27.6 Basis differences in fixed assets (71.7 ) (52.0 ) Rent 27.3 27.5 Interest 48.8 45.8 Accruals and reserves 21.0 18.4 Allowance for doubtful accounts 7.4 10.2 Basis differences in intangible assets (302.7 ) (281.3 ) Investments in equity securities 1.2 (3.3 ) Tax loss/tax credit carry forwards 345.6 357.9 Prepaid expenses (6.3 ) (1.7 ) Deferred revenue (26.8 ) (41.3 ) Unremitted foreign earnings (9.5 ) 0.0 Other 38.2 43.7 Total deferred tax assets, net 212.4 262.7 Valuation allowance (211.0 ) (243.0 ) Net deferred tax assets $ 1.4 $ 19.7

Income Taxes Summary of Valuati

Income Taxes Summary of Valuation Allowance (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Summary of Valuation Allowance [Table Text Block]	The change in the valuation allowance is listed below. Years ended December 31, 2018 2017 2016 Balance at beginning of period $ 243.0 $ 255.6 $ 275.1 Reversed to costs and expenses (28.0 ) (4.6 ) (15.4 ) Charged (reversed) to gross tax assets and other accounts 1 5.1 (27.3 ) 9.5 Foreign currency translation (9.1 ) 19.3 (13.6 ) Balance at end of period $ 211.0 $ 243.0 $ 255.6

Income Taxes Schedule of Unreco

Income Taxes Schedule of Unrecognized Tax Benefits Activity (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Schedule of Unrecognized Tax Benefits Activity [Table Text Block]	The table below summarizes the activity related to our unrecognized tax benefits. Years ended December 31, 2018 2017 2016 Balance at beginning of period $ 271.9 $ 246.7 $ 226.9 Increases as a result of tax positions taken during a prior year 65.9 6.3 65.0 Decreases as a result of tax positions taken during a prior year (10.8 ) (8.1 ) (47.5 ) Settlements with taxing authorities (6.5 ) (0.8 ) (4.6 ) Lapse of statutes of limitation (1.7 ) (3.3 ) (11.8 ) Increases as a result of tax positions taken during the current year 16.6 31.1 18.7 Balance at end of period $ 335.4 $ 271.9 $ 246.7

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss, Net of Tax Schedule of Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2018
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, 2016 $ (718.6 ) $ 0.6 $ (8.4 ) $ (238.0 ) $ (964.4 ) Other comprehensive income (loss) before reclassifications 132.2 0.0 0.0 (9.7 ) 122.5 Amount reclassified from accumulated other comprehensive loss, net of tax 1.1 (0.6 ) 1.6 12.0 14.1 Balance as of December 31, 2017 $ (585.3 ) $ 0.0 $ (6.8 ) $ (235.7 ) $ (827.8 ) Other comprehensive (loss) income before reclassifications (146.8 ) 0.0 0.0 11.4 (135.4 ) Amount reclassified from accumulated other comprehensive loss, net of tax 15.7 0.0 1.5 4.9 22.1 Balance as of December 31, 2018 $ (716.4 ) $ 0.0 $ (5.3 ) $ (219.4 ) $ (941.1 )

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Loss, Net of Tax Reclassification out of Accumulated Other Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2018
Accumulated Other Comprehensive Loss [Abstract]
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	Amounts reclassified from accumulated other comprehensive loss, net of tax, for the years ended December 31, 2018 , 2017 and 2016 are as follows: Years ended December 31, Affected Line Item in the Consolidated Statements of Operations 2018 2017 2016 Foreign currency translation adjustments 1 $ 15.7 $ 1.1 $ 3.7 Other expense, net Gains on available-for-sale securities 0.0 (0.7 ) (1.3 ) Other expense, net Losses on derivative instruments 2.2 2.1 2.0 Interest expense Amortization of defined benefit pension and postretirement plans items 6.5 13.7 5.8 Other expense, net Tax effect (2.3 ) (2.1 ) (2.1 ) Provision for income taxes Total amount reclassified from accumulated other comprehensive loss, net of tax $ 22.1 $ 14.1 $ 8.1 1 These foreign currency translation adjustments are primarily a result of the sales of businesses.

Incentive Compensation Plans Sc

Incentive Compensation Plans Schedule of Stock-based Compensation Expense (Tables)	12 Months Ended
	Dec. 31, 2018
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Schedule of Stock-based Compensation Expense	The amounts of stock-based compensation expense as reflected in salaries and related expenses in our Consolidated Statements of Operations, and the related tax benefit, are listed below. Years ended December 31, 2018 2017 2016 Stock options $ 0.0 $ 0.0 $ 0.2 Stock-settled awards 24.7 20.5 16.0 Cash-settled awards 0.6 1.0 0.9 Performance-based awards 57.5 61.5 69.4 Employee stock purchase plan 0.9 1.0 0.7 Other 1 0.9 0.5 0.8 Stock-based compensation expense $ 84.6 $ 84.5 $ 88.0 Tax benefit $ 20.4 $ 30.4 $ 32.1 1 Represents charges recorded for severance expense related to stock-based compensation awards.

Incentive Compensation Plans _2

Incentive Compensation Plans Schedule of Stock Options Activity (Tables)	12 Months Ended
	Dec. 31, 2018
Summary of Stock Options Assumptions [Abstract]
Share-based Compensation, Stock Options, Activity [Table Text Block]	The following table summarizes our stock option activity during 2018 . Options Weighted- Average Exercise Price (per option) Weighted- Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Stock options outstanding as of January 1, 2018 3.7 $ 9.44 Exercised (1.9 ) $ 8.30 Stock options outstanding as of December 31, 2018 1.8 $ 10.66 2.8 $ 17.6

Incentive Compensation Plans St

Incentive Compensation Plans Stock-based Compensation, Grants in Period Weighted Average (Tables)	12 Months Ended
	Dec. 31, 2018
Summary of Stock Options Assumptions [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value [Table Text Block]	Stock-based compensation awards expected to be settled in cash have been classified as liabilities in our Consolidated Balance Sheets as of December 31, 2018 and 2017 . Years ended December 31, 2018 2017 2016 Stock-Settled Awards: Awards granted 2.1 0.8 1.1 Weighted-average grant-date fair value (per award) $ 23.60 $ 24.18 $ 21.87 Total fair value of vested awards distributed $ 24.2 $ 22.6 $ 17.5 Cash-Settled Awards: Awards granted 0.1 0.0 0.1 Weighted-average grant-date fair value (per award) $ 23.62 $ 23.33 $ 22.54 Total fair value of vested awards distributed $ 0.8 $ 0.9 $ 0.7 Performance-Based Awards: Awards granted 2.9 4.8 3.3 Weighted-average grant-date fair value (per award) $ 21.13 $ 20.06 $ 19.58 Total fair value of vested awards distributed $ 87.2 $ 112.4 $ 27.9

Incentive Compensation Plans _3

Incentive Compensation Plans Schedule of Nonvested Stock Activity (Tables)	12 Months Ended
	Dec. 31, 2018
Summary of Stock Options Assumptions [Abstract]
Schedule of Nonvested Share Activity [Table Text Block]	A summary of the activity of our non-vested stock-settled awards, cash-settled awards and performance-based awards during 2018 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- Average Grant-Date Fair Value (per award) Awards Weighted- Average Grant-Date Fair Value (per award) Awards Weighted- Average Grant-Date Fair Value (per award) Non-vested as of January 1, 2018 2.1 $ 22.78 0.1 $ 22.52 8.3 $ 21.05 Granted 2.1 23.60 0.1 23.62 2.9 21.13 Vested (1.0 ) 22.18 (0.1 ) 21.54 (3.6 ) 21.02 Forfeited (0.1 ) 23.67 0.0 23.17 (0.6 ) 21.06 Non-vested as of December 31, 2018 3.1 $ 23.51 0.1 $ 23.47 7.0 $ 21.10 Total unrecognized compensation expense remaining $ 39.4 $ 1.0 $ 54.7 Weighted-average years expected to be recognized over 1.6 1.3 1.7

Fair Value Measurements Fair Va

Fair Value Measurements Fair Value of Assets and Liabilities Measured on a Recurring Basis (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]	The following tables present information about our financial instruments measured at fair value on a recurring basis as of December 31, 2018 and 2017 , and indicates the fair value hierarchy of the valuation techniques utilized to determine such fair value. December 31, 2018 Balance Sheet Classification Level 1 Level 2 Level 3 Total Assets Cash equivalents $ 132.1 $ 0.0 $ 0.0 $ 132.1 Cash and cash equivalents Liabilities Contingent acquisition obligations 1 $ 0.0 $ 0.0 $ 148.4 $ 148.4 December 31, 2017 Balance Sheet Classification Level 1 Level 2 Level 3 Total Assets Cash equivalents $ 201.6 $ 0.0 $ 0.0 $ 201.6 Cash and cash equivalents Liabilities Contingent acquisition obligations 1 $ 0.0 $ 0.0 $ 147.0 $ 147.0 1 Contingent acquisition obligations includes deferred acquisition payments and unconditional obligations to purchase additional noncontrolling equity shares of consolidated subsidiaries. Fair value measurement of the obligations is based upon actual and projected operating performance targets as specified in the related agreements. The increase in this balance of $1.4 from December 31, 2017 to December 31, 2018 is primarily due to acquisitions and exercised put options of $61.8 , partially offset by payments of $54.0 . The amounts payable within the next twelve months are classified in accrued liabilities; any amounts payable thereafter are classified in other non-current liabilities.

Fair Value Measurements Assets

Fair Value Measurements Assets and Liabilities Measured at Fair Value on a Nonrecurring (Tables)	12 Months Ended
	Dec. 31, 2018
Assets and Liabilities Measured at Fair Value on Recurring Basis [Abstract]
Fair Value Measurements, Nonrecurring [Table Text Block]	The following table presents information about our financial instruments that are not measured at fair value on a recurring basis as of December 31, 2018 , and indicates the fair value hierarchy of the valuation techniques utilized to determine such fair value. December 31, 2018 Level 1 Level 2 Level 3 Total Total long-term debt $ 0.0 $ 3,605.6 $ 38.0 $ 3,643.6

Schedule of Defined Benefit Pla

Schedule of Defined Benefit Plans Disclosures (Tables)	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [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 Pension Plan Foreign Pension Plans Domestic Postretirement Benefit Plan 2018 2017 2018 2017 2018 2017 Benefit Obligation Projected benefit obligation as of January 1 $ 125.4 $ 126.6 $ 582.3 $ 530.6 $ 31.8 $ 32.3 Service cost 0.0 0.0 5.4 4.9 0.0 0.0 Interest cost 4.5 5.1 13.1 13.5 1.1 1.3 Benefits paid (9.5 ) (11.4 ) (27.4 ) (19.0 ) (5.9 ) (5.9 ) Plan participant contributions 0.0 0.0 0.1 0.2 1.8 1.6 Actuarial (gains) losses (5.0 ) 5.1 (47.6 ) 20.3 (1.1 ) 2.5 Settlements and curtailments 0.0 0.0 (5.8 ) (19.8 ) 0.0 0.0 Foreign currency effect 0.0 0.0 (26.4 ) 50.4 0.0 0.0 Other 0.0 0.0 2.3 1.2 0.0 0.0 Projected benefit obligation as of December 31 $ 115.4 $ 125.4 $ 496.0 $ 582.3 $ 27.7 $ 31.8 Fair Value of Plan Assets Fair value of plan assets as of January 1 $ 98.8 $ 95.2 $ 404.2 $ 365.9 $ 0.0 $ 0.0 Actual return on plan assets (8.1 ) 12.4 (8.0 ) 25.1 0.0 0.0 Employer contributions 8.6 2.6 19.1 17.5 4.1 4.3 Plan participant contributions 0.0 0.0 0.1 0.2 1.8 1.6 Benefits paid (9.5 ) (11.4 ) (27.4 ) (19.0 ) (5.9 ) (5.9 ) Settlements 0.0 0.0 (4.6 ) (19.1 ) 0.0 0.0 Foreign currency effect 0.0 0.0 (21.1 ) 33.2 0.0 0.0 Other 0.0 0.0 1.6 0.4 0.0 0.0 0.0 Fair value of plan assets as of December 31 $ 89.8 $ 98.8 $ 363.9 $ 404.2 $ 0.0 $ 0.0 Funded status of the plans at December 31 $ (25.6 ) $ (26.6 ) $ (132.1 ) $ (178.1 ) $ (27.7 ) $ (31.8 ) Domestic Pension Plan Foreign Pension Plans Domestic Postretirement Benefit Plan December 31, 2018 2017 2018 2017 2018 2017 Amounts recognized in Consolidated Balance Sheets Non-current asset $ 0.0 $ 0.0 $ 8.6 $ 9.0 $ 0.0 $ 0.0 Current liability 0.0 0.0 (6.2 ) (6.5 ) (2.9 ) (3.1 ) Non-current liability (25.6 ) (26.6 ) (134.5 ) (180.6 ) (24.8 ) (28.7 ) Net liability recognized $ (25.6 ) $ (26.6 ) $ (132.1 ) $ (178.1 ) $ (27.7 ) $ (31.8 ) Accumulated benefit obligation $ 115.4 $ 125.4 $ 493.2 $ 577.9 Amounts recognized in Accumulated Other Comprehensive Loss, net Net actuarial loss $ 60.4 $ 52.2 $ 165.6 $ 201.6 $ 3.1 $ 4.2 Prior service cost (credit) 0.0 0.0 1.2 1.1 (0.3 ) (0.4 ) Total amount recognized $ 60.4 $ 52.2 $ 166.8 $ 202.7 $ 2.8 $ 3.8 Actuarial gains of $5.0 for the Domestic Pension Plan are attributed to an increase in the discount rate from 3.70% as of December 31, 2017 to 4.35% as of December 31, 2018 , partially offset by changes in demographic experience. Actuarial gains of $47.6 for the foreign pension plans are attributed to an increase in the weighted-average discount rate from 2.36% as of December 31, 2017 to 2.61% as of December 31, 2018 and changes in demographic experience. Domestic Pension Plan Foreign Pension Plans December 31, 2018 2017 2018 2017 Pension plans with an accumulated benefit obligation and projected benefit obligation in excess of plan assets Aggregate projected benefit obligation $ 115.4 $ 125.4 $ 491.2 $ 576.6 Aggregate accumulated benefit obligation 115.4 125.4 489.9 575.2 Aggregate fair value of plan assets 89.8 98.8 350.5 389.5

Employee Benefits Schedule of N

Employee Benefits Schedule of Net Benefit Costs (Tables)	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Schedule of Net Benefit Costs [Table Text Block]	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, 2018 2017 2016 2018 2017 2016 2018 2017 2016 Service cost $ 0.0 $ 0.0 $ 0.0 $ 5.4 $ 4.9 $ 6.7 $ 0.0 $ 0.0 $ 0.0 Interest cost 4.5 5.1 5.9 13.1 13.5 15.1 1.1 1.3 1.5 Expected return on plan assets (6.6 ) (6.2 ) (6.6 ) (18.8 ) (17.7 ) (18.7 ) 0.0 0.0 0.0 Settlement and curtailment (gains) losses 0.0 0.0 0.0 (1.0 ) 6.8 0.4 0.0 0.0 0.0 Amortization of: Prior service cost (credit) 0.0 0.0 0.0 0.1 0.1 0.1 (0.2 ) (0.2 ) (0.2 ) Net actuarial losses 1.6 1.5 1.3 5.9 5.5 4.2 0.1 0.0 0.0 Net periodic cost $ (0.5 ) $ 0.4 $ 0.6 $ 4.7 $ 13.1 $ 7.8 $ 1.0 $ 1.1 $ 1.3 Assumptions Domestic Pension Plan Foreign Pension Plans Domestic Postretirement Benefit Plan Years ended December 31, 2018 2017 2016 2018 2017 2016 2018 2017 2016 Net periodic cost Discount rate 3.70 % 4.20 % 4.80 % 2.36 % 2.52 % 3.61 % 3.65 % 4.05 % 4.65 % Rate of compensation increase N/A N/A N/A 2.37 % 2.36 % 3.18 % N/A N/A N/A Expected return on plan assets 7.00 % 7.00 % 7.00 % 4.70 % 4.66 % 5.38 % N/A N/A N/A Interest crediting rates 5.10 % 5.10 % 5.10 % 1.31 % 1.29 % 1.35 % N/A N/A N/A Benefit obligation Discount rate 4.35 % 3.70 % 4.20 % 2.61 % 2.36 % 2.52 % 4.30 % 3.65 % 4.05 % Rate of compensation increase N/A N/A N/A 2.58 % 2.37 % 2.36 % N/A N/A N/A Interest crediting rates 5.10 % 5.10 % 5.10 % 1.44 % 1.31 % 1.29 % N/A N/A N/A Health care cost trend rate assumed for next year Initial rate (weighted-average) 6.25 % 6.50 % 6.75 % Year ultimate rate is reached 2024 2024 2024 Ultimate rate 5.00 % 5.00 % 5.00 %

Employee Benefits Fair Value of

Employee Benefits Fair Value of Pension Plan Assets (Tables)	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Fair Value of Pension Plan Assets [Table Text Block]	The following table presents the fair value of our domestic and foreign pension plan assets as of December 31, 2018 and 2017 , and indicates the fair value hierarchy of the valuation techniques utilized to determine such fair value. See Note 12 for a description of the fair value hierarchy. December 31, 2018 December 31, 2017 Plan assets subject to fair value hierarchy Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Registered investment companies $ 13.0 $ 0.0 $ 0.0 $ 13.0 $ 14.7 $ 0.0 $ 0.0 $ 14.7 Limited partnerships 0.0 0.0 25.6 25.6 0.0 0.0 29.5 29.5 Fixed income securities 23.1 0.0 0.0 23.1 23.4 0.0 0.0 23.4 Insurance contracts 0.0 5.8 0.0 5.8 0.0 7.9 0.0 7.9 Other 20.0 0.0 0.0 20.0 27.7 0.0 0.0 27.7 Total plan assets, subject to leveling $ 56.1 $ 5.8 $ 25.6 $ 87.5 $ 65.8 $ 7.9 $ 29.5 $ 103.2 Plan assets measured at net asset value Other investments measured at net asset value 1 366.2 399.8 Total plan assets $ 453.7 $ 503.0 1 Certain investments that are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient have not been classified in the fair value hierarchy but are included to reconcile to the amounts presented in the fair value of plan assets table above.

Employee Benefits Schedule of E

Employee Benefits Schedule of Effect of Significant Unobservable Inputs, Changes in Plan Assets (Tables)	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Schedule of Effect of Significant Unobservable Inputs, Changes in Plan Assets [Table Text Block]	The following table presents additional information about our significant foreign pension plan assets for which we utilize Level 3 inputs to determine fair value. Years ended December 31, Plan assets subject to fair value hierarchy, level 3 2018 2017 Balance at beginning of period $ 29.5 $ 28.0 Actual return on plan assets (3.9 ) 1.5 Balance at end of period $ 25.6 $ 29.5

Employee Benefits Schedule of A

Employee Benefits Schedule of Allocation of Plan Assets (Tables)	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Schedule of Allocation of Plan Assets [Table Text Block]	As of December 31, 2018 , the weighted-average target and actual asset allocations relating to our domestic and foreign pension plans' assets are listed below. December 31, Asset Class 2019 Target Allocation 2018 2017 Alternative investments 1 26 % 26 % 27 % Equity securities 23 % 22 % 23 % Fixed income securities 21 % 21 % 21 % Liability driven investments 2 16 % 16 % 14 % Real estate 6 % 6 % 6 % Other 8 % 9 % 9 % Total 100 % 100 % 100 % 1 Alternative investments have the flexibility to dynamically invest across a broad range of asset classes including bonds, equity, cash, property and commodities. 2 Liability driven investment strategies use government bonds as well as derivative instruments to hedge a portion of the impact of interest rates and inflation movements on the long-term liabilities.

Employee Benefits Schedule of_2

Employee Benefits Schedule of Estimated Future Benefit Payments (Tables)	12 Months Ended
	Dec. 31, 2018
Retirement Benefits [Abstract]
Schedule of Expected Benefit Payments [Table Text Block]	The estimated future benefit payments expected to be paid are presented below. Years Domestic Pension Plan Foreign Pension Plans Domestic Postretirement Benefit Plan 2019 $ 14.5 $ 21.7 $ 3.0 2020 8.8 18.7 2.8 2021 8.0 19.8 2.6 2022 8.3 20.9 2.4 2023 7.8 21.8 2.2 2024 - 2028 36.7 117.2 9.8

Segment Information Schedule of

Segment Information Schedule of Segment Reporting Information, by Segment (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Summarized financial information concerning our reportable segments is shown in the following tables. Years ended December 31, 2018 2017 2016 Total Revenue: IAN $ 7,374.4 $ 7,009.6 $ 6,992.8 CMG 2,158.3 2,038.0 2,063.4 Corporate and other 1 181.7 — — Total $ 9,714.4 $ 9,047.6 $ 9,056.2 Net revenue: IAN $ 6,585.8 $ 6,266.7 $ 6,201.4 CMG 1,264.1 1,206.8 1,250.9 Corporate and other 1 181.7 — — Total $ 8,031.6 $ 7,473.5 $ 7,452.3 Segment operating income (loss): IAN $ 982.8 $ 875.1 $ 894.3 CMG 175.0 189.9 189.3 Corporate and other (149.0 ) (126.6 ) (147.2 ) Total 1,008.8 938.4 936.4 Interest expense (123.0 ) (90.8 ) (90.6 ) Interest income 21.8 19.4 20.1 Other expense, net (69.6 ) (26.2 ) (40.3 ) Income before income taxes $ 838.0 $ 840.8 $ 825.6 Depreciation and amortization IAN $ 142.8 $ 125.5 $ 129.2 CMG 24.3 23.5 22.4 Corporate and other 35.8 8.1 8.6 Total $ 202.9 $ 157.1 $ 160.2 Capital expenditures: IAN $ 128.5 $ 112.0 $ 149.2 CMG 13.0 17.7 16.6 Corporate and other 35.6 26.2 34.9 Total $ 177.1 $ 155.9 $ 200.7 December 31, 2018 2017 Total assets: IAN $ 11,446.2 $ 10,978.0 CMG 1,516.7 1,427.4 Corporate and other 2 2,657.4 299.3 Total $ 15,620.3 $ 12,704.7

Segment Information Schedule _2

Segment Information Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block]	evenue and long-lived assets, excluding intangible assets, are presented by major geographic area in the following table. Net Revenue Long-Lived Assets Years ended December 31, December 31, 2018 2017 2016 2018 2017 Domestic $ 4,825.0 $ 4,458.8 $ 4,443.2 $ 892.9 $ 694.5 International: United Kingdom 711.7 613.1 604.3 57.9 56.2 Continental Europe 737.5 687.8 682.0 57.9 73.6 Asia Pacific 896.8 866.9 887.7 121.7 115.5 Latin America 350.1 350.8 367.8 43.6 48.2 Other 510.5 496.1 467.3 45.7 46.1 Total International 3,206.6 3,014.7 3,009.1 326.8 339.6 Total Consolidated $ 8,031.6 $ 7,473.5 $ 7,452.3 $ 1,219.7 $ 1,034.1

Commitments and Contingencies S

Commitments and Contingencies Schedule of Net Rent Expense (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of Net Rent Expense	Net rent expense is listed in the table below. Years ended December 31, 2018 2017 2016 Gross rent expense $ 375.9 $ 371.0 $ 366.1 Third-party sublease rental income (5.3 ) (4.6 ) (4.1 ) Net rent expense $ 370.6 $ 366.4 $ 362.0

Commitments and Contingencies_2

Commitments and Contingencies Schedule of Future Minimum Lease Commitments (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	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 Obligations Sublease Rental Income Net Rent 2019 $ 352.0 $ (7.7 ) $ 344.3 2020 324.3 (5.2 ) 319.1 2021 282.3 (2.2 ) 280.1 2022 242.5 (1.3 ) 241.2 2023 184.0 (0.6 ) 183.4 Thereafter 714.6 (0.5 ) 714.1 Total $ 2,099.7 $ (17.5 ) $ 2,082.2

Commitments and Contingencies_3

Commitments and Contingencies Schedule of Contingent Acquisition Obligations (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of Business Acquisitions by Acquisition, Contingent Consideration [Table Text Block]	The following table details the estimated future contingent acquisition obligations payable in cash as of December 31, 2018 . 2019 2020 2021 2022 2023 Thereafter Total Deferred acquisition payments $ 65.7 $ 20.0 $ 23.6 $ 4.7 $ 10.2 $ 2.7 $ 126.9 Redeemable noncontrolling interests and call options with affiliates 1 30.1 30.6 42.9 5.7 3.5 2.5 115.3 Total contingent acquisition payments $ 95.8 $ 50.6 $ 66.5 $ 10.4 $ 13.7 $ 5.2 $ 242.2 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, 2018 . These estimated payments of $24.9 are included within the total payments expected to be made in 2019 , and will continue to be carried forward into 2020 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_2

Results by Quarter (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	Results by Quarter (Unaudited) Three Months Ended March 31, Three Months Ended June 30, Three Months Ended September 30, Three Months Ended December 31, 2018 2017 2018 2017 2018 2017 2018 2017 Revenue: Net revenue 1,2 $ 1,774.0 $ 1,675.3 $ 1,948.2 $ 1,834.6 $ 1,895.7 $ 1,832.5 $ 2,413.7 $ 2,131.1 Billable expenses 1,2 395.1 388.5 443.6 351.2 401.8 375.7 442.3 458.7 Total Revenue 1,2 2,169.1 2,063.8 2,391.8 2,185.8 2,297.5 2,208.2 2,856.0 2,589.8 Operating Expenses: Salaries and related expenses 2 1,330.3 1,251.7 1,292.9 1,228.9 1,251.4 1,218.8 1,423.7 1,291.3 Office and other direct 2 expenses 323.8 312.7 333.3 318.4 317.0 302.9 381.0 334.8 Billable expenses 1,2 395.1 388.5 443.6 351.2 401.8 375.7 442.3 458.7 Cost of services 2 2,049.2 1,952.9 2,069.8 1,898.5 1,970.2 1,897.4 2,247.0 2,084.8 Selling, general and administrative expenses 2 35.1 35.2 28.8 20.3 21.6 13.6 81.0 49.4 Depreciation and amortization 2 46.0 41.0 44.0 41.3 44.0 42.2 68.9 32.6 Total operating expenses 1,2 2,130.3 2,029.1 2,142.6 1,960.1 2,035.8 1,953.2 2,396.9 2,166.8 Operating income 1 38.8 34.7 249.2 225.7 261.7 255.0 459.1 423.0 Other (expense) income, net 3 (24.4 ) 0.8 (16.3 ) (15.4 ) (15.3 ) (9.9 ) (13.6 ) (1.7 ) Total (expenses) and other income (40.3 ) (14.9 ) (37.7 ) (36.4 ) (37.6 ) (26.8 ) (55.2 ) (19.5 ) Provision for (benefit of) income taxes 1,4 12.7 (0.3 ) 63.6 81.6 60.7 54.9 62.2 135.1 Net (loss) income 1 (16.1 ) 21.3 147.8 107.6 163.5 172.3 342.5 269.2 Net (loss) income available to IPG common stockholders 1 $ (14.1 ) $ 24.7 $ 145.8 $ 107.7 $ 161.0 $ 169.7 $ 326.2 $ 252.3 (Loss) earnings per share available to IPG common stockholders: Basic 1 $ (0.04 ) $ 0.06 $ 0.38 $ 0.27 $ 0.42 $ 0.44 $ 0.85 $ 0.66 Diluted 1 $ (0.04 ) $ 0.06 $ 0.37 $ 0.27 $ 0.41 $ 0.43 $ 0.84 $ 0.64 Dividends declared per common share $ 0.21 $ 0.18 $ 0.21 $ 0.18 $ 0.21 $ 0.18 $ 0.21 $ 0.18 1 Effective January 1, 2018, the Company adopted Accounting Standards Codification Topic 606, Revenue from Contracts with Customers, ("ASC 606") using the full retrospective transition method and revised its Consolidated financial statements for the years ended December 31, 2017. See Note 1 and 2 for further detail on the ASC 606 adoption. 2 The Company has revised the presentation of its Consolidated Statements of Operations, which disaggregates net revenue and billable expenses within total revenue and separately presents cost of services; selling, general and administrative expenses; and depreciation and amortization within operating expenses. The revised presentation does not impact total revenue, total operating expenses or operating income. 3 The three months ended March 31, June 30, September 30 and December 31, 2018 included pre-tax net losses of $24.4 , $19.8 , $5.8 , and $11.9 , respectively, on sales of businesses. The three months ended June 30 and September 30, 2017 included pre-tax net losses of $13.1 and $8.7 , respectively, on sales of businesses. 4 The three months ended December 31, 2018 included a tax benefit of $23.4 related to various discrete tax items. The three months ended September 30, 2017 included a tax benefit of $31.2 related to foreign tax credits from distributions of unremitted earnings, which was reversed during the three months ended December 31, 2017 as a result of the enactment of the Tax Cuts and Jobs Act. The three months ended December 31, 2017 included a net tax benefit of $36.0 as a result of the enactment of the Tax Cuts and Jobs Act.

Summary of Significant Accounti

Summary of Significant Accounting Policies (Details) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)shares	Dec. 31, 2017USD ($)shares	Dec. 31, 2016USD ($)shares
Revenue, remaining performance obligation, amount	$ 770
Retirement of treasury stock, amount	$ 0	$ 0	$ 0
ERP Systems, 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 Gain (Loss)	$ 5.6	$ 1.9	$ 2.1
Minimum
Furniture and Equipment, Useful Life	3 years
Buildings, Useful Life	10 years
Other Internal Use Software, Useful Life	3
Identifiable Intangible Assets, Useful Life	7 years
Maximum
Furniture and Equipment, Useful Life	7 years
Buildings, Useful Life	35 years
Other Internal Use Software, Useful Life	7
Identifiable Intangible Assets, Useful Life	15 years
Common Stock [Member]
Retirement of treasury stock, shares | shares	(8.1)	(13.4)	(13.7)
Retirement of treasury stock, amount	$ (0.8)	$ (1.3)	$ (1.4)
Treasury Stock [Member]
Retirement of treasury stock, amount	176.1	304.4	311
Additional Paid-in Capital [Member]
Retirement of treasury stock, amount	$ (175.3)	$ (303.1)	$ (309.6)

Revenue Income Statement (Detai

Revenue Income Statement (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenue	$ 2,413.7	$ 1,895.7	$ 1,948.2	$ 1,774	$ 2,131.1	$ 1,832.5	$ 1,834.6	$ 1,675.3	$ 8,031.6	$ 7,473.5	$ 7,452.3
Billable expenses	442.3	401.8	443.6	395.1	458.7	375.7	351.2	388.5	1,682.8	1,574.1	1,603.9
Total revenue	2,856	2,297.5	2,391.8	2,169.1	2,589.8	2,208.2	2,185.8	2,063.8	9,714.4	9,047.6	9,056.2
OPERATING EXPENSES:
Salaries and related expenses	1,423.7	1,251.4	1,292.9	1,330.3	1,291.3	1,218.8	1,228.9	1,251.7	5,298.3	4,990.7	4,942.2
Office and other direct expenses	381	317	333.3	323.8	334.8	302.9	318.4	312.7	1,355.1	1,268.8	1,274.9
Billable expense	442.3	401.8	443.6	395.1	458.7	375.7	351.2	388.5	1,682.8	1,574.1	1,603.9
Cost of services	2,247	1,970.2	2,069.8	2,049.2	2,084.8	1,897.4	1,898.5	1,952.9	8,336.2	7,833.6	7,821
Selling, General and Administrative Expense	81	21.6	28.8	35.1	49.4	13.6	20.3	35.2	166.5	118.5	138.6
Depreciation and amortization	68.9	44	44	46	32.6	42.2	41.3	41	202.9	157.1	160.2
Total operating expenses	2,396.9	2,035.8	2,142.6	2,130.3	2,166.8	1,953.2	1,960.1	2,029.1	8,705.6	8,109.2	8,119.8
Operating Income (Loss)	459.1	261.7	249.2	38.8	423	255	225.7	34.7	1,008.8	938.4	936.4
EXPENSES AND OTHER INCOME:
Interest Expense									(123)	(90.8)	(90.6)
Interest income									21.8	19.4	20.1
Other expense, net	(13.6)	(15.3)	(16.3)	(24.4)	(1.7)	(9.9)	(15.4)	0.8	(69.6)	(26.2)	(40.3)
Total (expenses) and other income	(55.2)	(37.6)	(37.7)	(40.3)	(19.5)	(26.8)	(36.4)	(14.9)	(170.8)	(97.6)	(110.8)
Income before income taxes									838	840.8	825.6
Provision for income taxes	62.2	60.7	63.6	12.7	135.1	54.9	81.6	(0.3)	199.2	271.3	196.9
Income of consolidated companies									638.8	569.5	628.7
Equity in net (loss) income of unconsolidated affiliates									(1.1)	0.9	0.3
NET INCOME	$ 342.5	$ 163.5	$ 147.8	$ (16.1)	$ 269.2	$ 172.3	$ 107.6	$ 21.3	637.7	570.4	629
Net income attributable to noncontrolling interests									(18.8)	(16)	(24)
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS									$ 618.9	$ 554.4	$ 605
Earnings per share, Basic	$ 0.85	$ 0.42	$ 0.38	$ (0.04)	$ 0.66	$ 0.44	$ 0.27	$ 0.06	$ 1.61	$ 1.42	$ 1.52
Earnings per share, Diluted	$ 0.84	$ 0.41	$ 0.37	$ (0.04)	$ 0.64	$ 0.43	$ 0.27	$ 0.06	$ 1.59	$ 1.40	$ 1.48
Weighted-average number of common shares outstanding, Basic									383.3	389.6	397.9
Weighted-average number of common shares outstanding, Diluted									389	397.3	408
As Previously Reported [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenue										$ 7,508.7	$ 7,456.9
Billable expenses										373.7	389.7
Total revenue										7,882.4	7,846.6
OPERATING EXPENSES:
Salaries and related expenses										4,990.7	4,942.2
Office and other direct expenses										1,268.8	1,274.9
Billable expense										373.7	389.7
Cost of services										6,633.2	6,606.8
Selling, General and Administrative Expense										118.5	138.6
Depreciation and amortization										157.1	160.2
Total operating expenses										6,908.8	6,905.6
Operating Income (Loss)										973.6	941
EXPENSES AND OTHER INCOME:
Interest Expense										(90.8)	(90.6)
Interest income										19.4	20.1
Other expense, net										(26.2)	(40.3)
Total (expenses) and other income										(97.6)	(110.8)
Income before income taxes										876	830.2
Provision for income taxes										281.9	198
Income of consolidated companies										594.1	632.2
Equity in net (loss) income of unconsolidated affiliates										0.9	0.3
NET INCOME										595	632.5
Net income attributable to noncontrolling interests										(16)	(24)
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS										$ 579	$ 608.5
Earnings per share, Basic										$ 1.49	$ 1.53
Earnings per share, Diluted										$ 1.46	$ 1.49
Weighted-average number of common shares outstanding, Basic										389.6	397.9
Weighted-average number of common shares outstanding, Diluted										397.3	408
ASC 606 Adjustments [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenue										$ (35.2)	$ (4.6)
Billable expenses										1,200.4	1,214.2
Total revenue										1,165.2	1,209.6
OPERATING EXPENSES:
Salaries and related expenses										0	0
Office and other direct expenses										0	0
Billable expense										1,200.4	1,214.2
Cost of services										1,200.4	1,214.2
Selling, General and Administrative Expense										0	0
Depreciation and amortization										0	0
Total operating expenses										1,200.4	1,214.2
Operating Income (Loss)										(35.2)	(4.6)
EXPENSES AND OTHER INCOME:
Interest Expense										0	0
Interest income										0	0
Other expense, net										0	0
Total (expenses) and other income										0	0
Income before income taxes										(35.2)	(4.6)
Provision for income taxes										(10.6)	(1.1)
Income of consolidated companies										(24.6)	(3.5)
Equity in net (loss) income of unconsolidated affiliates										0	0
NET INCOME										(24.6)	(3.5)
Net income attributable to noncontrolling interests										0	0
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS										$ (24.6)	$ (3.5)
Earnings per share, Basic										$ (0.07)	$ (0.01)
Earnings per share, Diluted										$ (0.06)	$ (0.01)
Weighted-average number of common shares outstanding, Basic										0	0
Weighted-average number of common shares outstanding, Diluted										0	0

Revenue Balance Sheet (Details)

Revenue Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cash and cash equivalents	$ 673.4	$ 790.9
Accounts receivable, net of allowance	5,126.6	4,585
Expenditures billable to clients		0
Accounts receivable, billable to clients	1,900.6	1,747.4
Assets held for sale	5.7	5.7
Other current assets	476.6	346.5
Assets, Current	8,182.9	7,475.5
Deferred income taxes	247	234
Property, Plant and Equipment, Net	790.9	650.4
Goodwill	4,875.9	3,820.4	$ 3,674.4
Other intangible assets	1,094.7	140.7
Other non-current assets	428.9	383.7
Assets	15,620.3	12,704.7
Accounts Payable, Current	6,698.1	6,420.2
Accrued Liabilities, Current	806.9	674.7
Contract liabilities	533.9	484.7
Short-term borrowings	73.7	84.9
Current portion of long-term debt	0.1	2
Liabilities held for sale	11.2	8.8
Liabilities, Current	8,123.9	7,675.3
Long-term debt	3,660.2	1,285.6
Deferred compensation	422.7	476.6
Other non-current liabilities	812.8	768.8
Liabilities	13,019.6	10,206.3
Redeemable noncontrolling interests	167.9	252.1	252.8	$ 251.9
STOCKHOLDERS' EQUITY:
Common Stock, Value, Issued	38.3	38.6
Additional Paid in Capital	895.9	955.2
Retained Earnings (Accumulated Deficit)	2,400.1	2,104.5
Accumulated other comprehensive loss, net of tax	(941.1)	(827.8)	(964.4)
Stockholders' Equity before Treasury Stock	2,393.2	2,270.5
Treasury Stock, Value	0	59
Stockholders' Equity Attributable to Parent	2,393.2	2,211.5
Stockholders' Equity Attributable to Noncontrolling Interest	39.6	34.8
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	2,432.8	2,246.3	2,090.4	$ 2,001.8
Liabilities and Equity	$ 15,620.3	12,704.7
As Previously Reported [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cash and cash equivalents		790.9
Accounts receivable, net of allowance		4,585
Expenditures billable to clients		1,747.4
Accounts receivable, billable to clients		0
Assets held for sale		5.7
Other current assets		335.1
Assets, Current		7,464.1
Deferred income taxes		236
Property, Plant and Equipment, Net		650.4
Goodwill		3,820.4
Other non-current assets		383.6
Assets		12,695.2
Accounts Payable, Current		6,907.8
Accrued Liabilities, Current		674.7
Contract liabilities		0
Short-term borrowings		84.9
Current portion of long-term debt		2
Liabilities held for sale		8.8
Liabilities, Current		7,678.2
Long-term debt		1,285.6
Deferred compensation		476.6
Other non-current liabilities		766.9
Liabilities		10,207.3
Redeemable noncontrolling interests		252.1
STOCKHOLDERS' EQUITY:
Common Stock, Value, Issued		38.6
Additional Paid in Capital		955.2
Retained Earnings (Accumulated Deficit)		2,093.6
Accumulated other comprehensive loss, net of tax		(827.4)
Stockholders' Equity before Treasury Stock		2,260
Treasury Stock, Value		59
Stockholders' Equity Attributable to Parent		2,201
Stockholders' Equity Attributable to Noncontrolling Interest		34.8
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		2,235.8
Liabilities and Equity		12,695.2
ASC 606 Adjustments [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cash and cash equivalents		0
Accounts receivable, net of allowance		0
Expenditures billable to clients		(1,747.4)
Accounts receivable, billable to clients		1,747.4
Assets held for sale		0
Other current assets		11.4
Assets, Current		11.4
Deferred income taxes		(2)
Property, Plant and Equipment, Net		0
Goodwill		0
Other intangible assets		0
Other non-current assets		0.1
Assets		9.5
Accounts Payable, Current		(487.6)
Accrued Liabilities, Current		0
Contract liabilities		484.7
Short-term borrowings		0
Current portion of long-term debt		0
Liabilities held for sale		0
Liabilities, Current		(2.9)
Long-term debt		0
Deferred compensation		0
Other non-current liabilities		1.9
Liabilities		(1)
Redeemable noncontrolling interests		0
STOCKHOLDERS' EQUITY:
Common Stock, Value, Issued		0
Additional Paid in Capital		0
Retained Earnings (Accumulated Deficit)		10.9	35.6
Accumulated other comprehensive loss, net of tax		(0.4)	$ (1.9)
Stockholders' Equity before Treasury Stock		10.5
Treasury Stock, Value		0
Stockholders' Equity Attributable to Parent		10.5
Stockholders' Equity Attributable to Noncontrolling Interest		0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		10.5
Liabilities and Equity		$ 9.5

Revenue Statement of Cash Flows

Revenue Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
NET INCOME	$ 342.5	$ 163.5	$ 147.8	$ (16.1)	$ 269.2	$ 172.3	$ 107.6	$ 21.3	$ 637.7	$ 570.4	$ 629
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization									202.9	157.1	160.2
Provision for uncollectible receivables									6.5	9.5	16.7
Amortization of restricted stock and other non-cash compensation									82.2	82	85.6
Net amortization of bond discounts and deferred financing costs									6.5	5.8	5.6
Deferred income tax provision									14.1	(9.5)	44.6
Net losses on sales of businesses									61.9	24.1	41.4
Other									1.2	12.7	35.5
Net Cash Provided by (Used in) Investing Activities [Abstract]
Accounts receivable									(603.8)	37.6	(220.7)
Expenditures billable to clients										0	0
Accounts receivable, billable to clients									(209.5)	(165.5)	(2.2)
Other current assets									(67.2)	50.1	0.5
Accounts payable									428.7	336.4	(147.4)
Accrued liabilities									(24.2)	(241.3)	(61.1)
Contract liabilities									44.9	(12)	20.6
Other non-current assets and liabilities									(16.8)	24.4	(95.5)
Net cash provided by operating activities									565.1	881.8	512.8
Net cash used in investing activities									(2,491.5)	(196.2)	(263.9)
Net cash provided by (used in) financing activities									1,853.2	(1,004.9)	(666.4)
Effect of foreign exchange rate changes on cash, cash equivalents and restricted cash									(47.3)	16.8	11.6
Net decrease in cash, cash equivalents and restricted cash									(120.5)	(302.5)	(405.9)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 677.2				797.7				$ 677.2	797.7	1,100.2	$ 1,506.1
As Previously Reported [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
NET INCOME										595	632.5
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization										157.1	160.2
Provision for uncollectible receivables										9.5	16.7
Amortization of restricted stock and other non-cash compensation										82	85.6
Net amortization of bond discounts and deferred financing costs										5.8	5.6
Deferred income tax provision										1.1	45.7
Net losses on sales of businesses										24.1	41.4
Other										12.7	35.5
Net Cash Provided by (Used in) Investing Activities [Abstract]
Accounts receivable										37.6	(220.7)
Expenditures billable to clients										(165.5)	(2.2)
Accounts receivable, billable to clients										0	0
Other current assets										27.4	(4.8)
Accounts payable										311.9	(126.1)
Accrued liabilities										(241.3)	(61.1)
Contract liabilities										0	0
Other non-current assets and liabilities										24.4	(95.5)
Net cash provided by operating activities										881.8	512.8
Net cash used in investing activities										(196.2)	(263.9)
Net cash provided by (used in) financing activities										(1,004.9)	(666.4)
Effect of foreign exchange rate changes on cash, cash equivalents and restricted cash										16.8	11.6
Net decrease in cash, cash equivalents and restricted cash										(302.5)	(405.9)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents					797.7					797.7	1,100.2	1,506.1
ASC 606 Adjustments [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
NET INCOME										(24.6)	(3.5)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization										0	0
Provision for uncollectible receivables										0	0
Amortization of restricted stock and other non-cash compensation										0	0
Net amortization of bond discounts and deferred financing costs										0	0
Deferred income tax provision										(10.6)	(1.1)
Net losses on sales of businesses										0	0
Other										0	0
Net Cash Provided by (Used in) Investing Activities [Abstract]
Accounts receivable										0	0
Expenditures billable to clients										165.5	2.2
Accounts receivable, billable to clients										(165.5)	(2.2)
Other current assets										22.7	5.3
Accounts payable										24.5	(21.3)
Accrued liabilities										0	0
Contract liabilities										(12)	20.6
Other non-current assets and liabilities										0	0
Net cash provided by operating activities										0	0
Net cash used in investing activities										0	0
Net cash provided by (used in) financing activities										0	0
Effect of foreign exchange rate changes on cash, cash equivalents and restricted cash										0	0
Net decrease in cash, cash equivalents and restricted cash										0	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents					$ 0					$ 0	$ 0	$ 0

Revenue Major Geographical Area

Revenue Major Geographical Area (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Total revenue	$ 2,856	$ 2,297.5	$ 2,391.8	$ 2,169.1	$ 2,589.8	$ 2,208.2	$ 2,185.8	$ 2,063.8	$ 9,714.4	$ 9,047.6	$ 9,056.2
Net revenue	$ 2,413.7	$ 1,895.7	$ 1,948.2	$ 1,774	$ 2,131.1	$ 1,832.5	$ 1,834.6	$ 1,675.3	8,031.6	7,473.5	7,452.3
United States
Total revenue									5,851	5,417.3	5,452.6
Net revenue									4,825	4,458.8	4,443.2
Total International
Total revenue									3,863.4	3,630.3	3,603.6
Net revenue									3,206.6	3,014.7	3,009.1
United Kingdom
Total revenue									881.4	775.7	788.8
Net revenue									711.7	613.1	604.3
Continental Europe
Total revenue									840.2	780.6	764.1
Net revenue									737.5	687.8	682
Asia Pacific
Total revenue									1,170.8	1,106.4	1,076
Net revenue									896.8	866.9	887.7
Latin America
Total revenue									389	386.6	417.2
Net revenue									350.1	350.8	367.8
Other
Total revenue									582	581	557.5
Net revenue									510.5	496.1	467.3
CMG
Total revenue									2,158.3	2,038	2,063.4
Net revenue									1,264.1	1,206.8	1,250.9
CMG | United States
Total revenue									1,404	1,355	1,376.7
Net revenue									824.6	798.2	842.9
CMG | Total International
Total revenue									754.3	683	686.7
Net revenue									439.5	408.6	408
IAN
Total revenue									7,374.4	7,009.6	6,992.8
Net revenue									6,585.8	6,266.7	6,201.4
IAN | United States
Total revenue									4,279.4	4,062.3	4,075.9
Net revenue									3,832.7	3,660.6	3,600.3
IAN | Total International
Total revenue									3,095	2,947.3	2,916.9
Net revenue									$ 2,753.1	$ 2,606.1	$ 2,601.1

Revenue Contract Balances (Deta

Revenue Contract Balances (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Accounts receivable, net of allowance of $42.5 and $42.7, respectively	$ 5,126.6	$ 4,585
Accounts receivable, billable to clients	1,900.6	1,747.4
Contract with Customer, Asset, Net	67.9	11.5
Contract liabilities	$ 533.9	$ 484.7

Debt and Credit Agreements Long

Debt and Credit Agreements Long-Term Debt (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term debt, gross		$ 3,660.3	$ 1,287.6
Long-term debt, current maturities		0.1	2
Long-term debt, excluding current maturities		3,660.2	1,285.6
Deb instrument, unamortized debt issuance costs		26	13
Long-term debt, fair value		3,643.6
3.50% Notes Due 2020 (less unamortized discount and issuance costs of $0.9 and $2.9, respectively)
Debt Instrument [Line Items]
Senior Notes		500
Long-term debt, gross		496.6	0
Debt instrument, unamortized discount		0.8
Deb instrument, unamortized debt issuance costs		2.6
Long-term debt, fair value		$ 499.9	0
Debt instrument, maturity date		Oct. 1, 2020
Interest rate, stated percentage		3.50%
Debt instrument, interest rate, effective percentage		3.89%
3.75% Notes Due 2021 (less unamortized discount and issuance costs of $0.3 and $3.2, respectively)
Debt Instrument [Line Items]
Senior Notes		$ 500
Long-term debt, gross		496.8	0
Debt instrument, unamortized discount		0.3
Deb instrument, unamortized debt issuance costs		2.9
Long-term debt, fair value		$ 503.2	0
Debt instrument, maturity date		Oct. 1, 2021
Interest rate, stated percentage		3.75%
Debt instrument, interest rate, effective percentage		3.98%
4.00% Notes Due 2022 (less unamortized discount and issuance costs of $1.1 and $0.9, respectively)
Debt Instrument [Line Items]
Senior Notes		$ 250
Long-term debt, gross		248.2	247.6
Debt instrument, unamortized discount		1
Deb instrument, unamortized debt issuance costs		0.8
Long-term debt, fair value	[1]	$ 250.3	259
Debt instrument, maturity date		Mar. 15, 2022
Interest rate, stated percentage		4.00%
Debt instrument, interest rate, effective percentage		4.13%
3.75% Notes Due 2023 (less unamortized discount and issuance costs of $0.7 and $1.8, respectively)
Debt Instrument [Line Items]
Senior Notes		$ 500
Long-term debt, gross		497.7	497.1
Debt instrument, unamortized discount		0.6
Deb instrument, unamortized debt issuance costs		1.7
Long-term debt, fair value	[1]	$ 491.4	513.2
Debt instrument, maturity date		Feb. 15, 2023
Interest rate, stated percentage		3.75%
Debt instrument, interest rate, effective percentage		4.32%
4.20% Notes Due 2024 (less unamortized discount and issuance costs of $0.6 and $2.3, respectively)
Debt Instrument [Line Items]
Senior Notes		$ 500
Long-term debt, gross		497.3	496.7
Debt instrument, unamortized discount		0.5
Deb instrument, unamortized debt issuance costs		2.2
Long-term debt, fair value	[1]	$ 492.6	524.2
Debt instrument, maturity date		Apr. 15, 2024
Interest rate, stated percentage		4.20%
Debt instrument, interest rate, effective percentage		4.24%
4.65% Notes Due 2028 (less unamortized discount and issuance costs of $1.7 and $4.4, respectively)
Debt Instrument [Line Items]
Senior Notes		$ 500
Long-term debt, gross		494	0
Debt instrument, unamortized discount		1.7
Deb instrument, unamortized debt issuance costs		4.3
Long-term debt, fair value		$ 494.1	0
Debt instrument, maturity date		Oct. 1, 2028
Interest rate, stated percentage		4.65%
Debt instrument, interest rate, effective percentage		4.78%
5.40% Notes Due 2048 (less unamortized discount and issuance costs of $2.8 and $5.6, respectively)
Debt Instrument [Line Items]
Senior Notes		$ 500
Long-term debt, gross		491.7	0
Debt instrument, unamortized discount		2.8
Deb instrument, unamortized debt issuance costs		5.5
Long-term debt, fair value		$ 474.1	0
Debt instrument, maturity date		Oct. 1, 2048
Interest rate, stated percentage		5.40%
Debt instrument, interest rate, effective percentage		5.48%
Term Loan Due 2021 (LIBOR plus 1.25%)
Debt Instrument [Line Items]
Long-term debt, gross		$ 400
Loans Payable, Fair Value Disclosure		400
Other notes payable and capitalized leases
Debt Instrument [Line Items]
Long-term debt, gross		38	46.2
Long-term debt, fair value	[1]	$ 38	$ 46.2
[1]	See Note 12 for information on the fair value measurement of our long-term debt.

Debt and Credit Agreements Debt

Debt and Credit Agreements Debt Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Sep. 21, 2018
Schedule of New Debt Issuance [Line Items]
Debt Instrument, Redemption Price, Percentage	101.00%
Debt Instrument Change of Control Repurchase Event Price Percentage	101.00%
Term Loan		$ 500
3.50% Notes Due 2020
Schedule of New Debt Issuance [Line Items]
Debt Instrument, Face Amount	$ 500
Debt Issuance Face Amount			$ 500
Unamortized Discount at Issuance			1
Senior Notes Net of Discount			499
Debt Issuance Cost at Issuance			2.9
Senior Notes			496.1
3.75% Notes Due 2021
Schedule of New Debt Issuance [Line Items]
Debt Instrument, Face Amount	500
Debt Issuance Face Amount			500
Unamortized Discount at Issuance			0.3
Senior Notes Net of Discount			499.7
Debt Issuance Cost at Issuance			3.2
Senior Notes			496.5
4.65% Notes Due 2028
Schedule of New Debt Issuance [Line Items]
Debt Instrument, Face Amount	500
Debt Issuance Face Amount			500
Unamortized Discount at Issuance			1.7
Senior Notes Net of Discount			498.3
Debt Issuance Cost at Issuance			4.4
Senior Notes			493.9
5.40% Notes Due 2048
Schedule of New Debt Issuance [Line Items]
Debt Instrument, Face Amount	$ 500
Debt Issuance Face Amount			500
Unamortized Discount at Issuance			2.8
Senior Notes Net of Discount			497.2
Debt Issuance Cost at Issuance			5.6
Senior Notes			491.6
Aggregate Senior Notes Issued [Domain]
Schedule of New Debt Issuance [Line Items]
Debt Issuance Face Amount			2,000
Unamortized Discount at Issuance			5.8
Senior Notes Net of Discount			1,994.2
Debt Issuance Cost at Issuance			16.1
Senior Notes			$ 1,978.1

Debt and Credit Agreements Annu

Debt and Credit Agreements Annual Maturities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
Long-term debt, maturities, repayments of principal in next twelve months	$ 0.1
Long-term debt, maturities, repayments of principal in year two	496.9
Long-term debt, maturities,repayments of principal in year three	896.8
Long-term debt, maturities, repayments of principal in year four	248.2
Long-term debt, maturities, repayments of principal in year five	497.7
Long-term debt, maturities, repayments of principal after year five	1,520.6
Total long-term debt	$ 3,660.3	$ 1,287.6

Debt and Credit Agreements Cred

Debt and Credit Agreements Credit Agreements (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Line of Credit Facility [Line Items]
Margin for base rate advances			0.10%
Margin for Eurocurrency rate advances			1.10%
Annual rate for fronting fees accrued on letters of credit			0.25%
Annual facility fee			0.15%
Interest coverage ratio minimum	[1]		5.00x
Leverage ratio maximum	[2]		4.00x
Quarters 1-3 Maximum Leverage Ratio Covenant		4.00 to 1.00
Quarters 4-7 Maximum Leverage Ratio Covenant		3.75 to 1.00
Quarters 8-Thereafter Maximum Leverage Ratio Covenant		3.50 to 1.00
Committed credit facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			$ 1,500
Line of credit facility, available capacity increase amount			250
Limits on letters of credit			50
Line of credit facility, amount outstanding			0
Letters of credit, amount outstanding			8.5	$ 8.4
Line of credit facility, remaining borrowing capacity			1,491.5	1,491.6
Uncommitted credit facility
Line of Credit Facility [Line Items]
Line of credit facility, amount outstanding			73.7	84.9
Line of credit facility, current borrowing capacity			1,173.1	926.2
Line of credit facility, average outstanding amount			$ 96.4	$ 223.8
Line of credit facility, weighted average interest rate, over time			4.50%	2.90%
[1]	The interest coverage ratio is defined as EBITDA, as defined in the Credit Agreement and Term Loan Agreement, to net interest expense for the four quarters then ended.
[2]	The leverage ratio is defined as debt as of the last day of such fiscal quarter to EBITDA, as defined in the Amended Credit Agreement and Term Loan Agreement, for the four quarters then ended.

Debt and Credit Agreements Comm

Debt and Credit Agreements Commercial Paper (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Debt Disclosure [Abstract]
Commercial paper, current borrowing capacity	$ 1,500
Commercial paper, amount outstanding	0
Commercial paper, average outstanding amount	$ 648.7
Commercial paper, weighted average interest rate, over time	2.40%
Commercial paper, weighted-average maturity days outstanding, over time	22

Debt and Credit Agreements Cash

Debt and Credit Agreements Cash Pooling (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
Cash debt pooling arrangements, amount netted	$ 2,065.8	$ 1,412

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS									$ 618.9	$ 554.4	$ 605
Weighted-average number of common shares outstanding, Basic									383.3	389.6	397.9
Restricted stock, stock options and other equity awards									5.7	7.7	10.1
Weighted-average number of common shares outstanding, Diluted									389	397.3	408
Basic	$ 0.85	$ 0.42	$ 0.38	$ (0.04)	$ 0.66	$ 0.44	$ 0.27	$ 0.06	$ 1.61	$ 1.42	$ 1.52
Diluted	$ 0.84	$ 0.41	$ 0.37	$ (0.04)	$ 0.64	$ 0.43	$ 0.27	$ 0.06	$ 1.59	$ 1.40	$ 1.48

Acquisitions Narrative (Details

Acquisitions Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Goodwill and intangible assets related to acquisitions	$ 2,131	$ 62	$ 149
Number of businesses acquired	5	10	10
IAN
Number of businesses acquired	1	8	3
CMG
Number of businesses acquired	3	2	7

Acquisitions Cash Paid for Acqu

Acquisitions Cash Paid for Acquisitions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Paid for Acquisitions [Abstract]
Cost of investment: current-year acquisitions 1	$ 2,323.4	$ 36.8	$ 65.7
Cost of investment: prior-year acquisitions	33.9	54.6	40.7
Less: net cash acquired	(13.8)	(7.1)	(13.6)
Total cost of investment	2,343.5	84.3	92.8
Operating payments	19.4	47.1	19.1
Total cash paid for acquisitions	2,362.9	131.4	111.9
Acquisitions, net of cash acquired	2,309.8	30.6	52
Payments for previous acquisition, financing cash flows	$ 33.7	$ 53.7	$ 40.8

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interests (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Redeemable Noncontrolling Interests
Balance at beginning of period	$ 252.1	$ 252.8	$ 251.9
Change in related noncontrolling interest balance	(10.7)	(2.8)	4.9
Changes in redemption value of redeemable noncontrolling interests:
Additions	0	7.7	6.8
Redemptions and other	(33.7)	(18.5)	(14.8)
Redemption value adjustments	(39.8)	12.9	4
Balance at end of period	$ 167.9	$ 252.1	$ 252.8

Acxiom Acquisition Preliminary

Acxiom Acquisition Preliminary fair values of the assets acquired and liabilities assumed (Details) - Acxiom - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Oct. 01, 2018
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents		$ 13.3
Accounts receivable, net of allowance		112.9
Accounts receivable, billable to clients		8.3
Other current assets		28.2
Property, Plant and Equipment, Other, Net		159.7
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		(0.6)
Goodwill		1,110.8
Intangible Assets, Net (excluding Goodwill)		995
Other non-current assets		8.3
Accounts Payable		(37.1)
Accrued Liabilities		(46.9)
Contract liabilities		23.2
Other non-current liabilities		0.8
Net Asset Acquired		2,327.9
Identifiable Intangible Assets		995
Customer Lists with useful life of 15 years
Identifiable Intangible Assets, Useful Life	15 years
Identifiable Intangible Assets		600
Know-how technology with useful life with 9 years
Identifiable Intangible Assets, Useful Life	9 years
Identifiable Intangible Assets		235
Trade Names with useful life 15 years to indefinite
Identifiable Intangible Assets		$ 160

Acxiom Acquisition Operating Re

Acxiom Acquisition Operating Results (Three Months in 2018) (Details) - Acxiom $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Net revenue	$ 181.7
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS	$ 20.4

Acxiom Acquisition Transaction

Acxiom Acquisition Transaction Related (Details) - Acxiom $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Term Loan	$ 500
Debt Issuance Face Amount	2,000
Selling, General and Administrative Expense	35
Interest Expense	3.7
Interest Income	0.4
Other expense, net	$ 10.3

Acxiom Acquisition Pro Forma (D

Acxiom Acquisition Pro Forma (Details) - Acxiom - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition, Pro Forma Revenue	$ 10,230.4	$ 9,736.1
Business Acquisition, Pro Forma Net Income (Loss)	$ 642.2	$ 519.2
After-tax nonrecurring transaction-related charges		27.6

Valuation and Qualifying Accoun

Valuation and Qualifying Accounts - Allowance for Uncollectible Accounts Receivable (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	$ 42.7	$ 55.7	$ 54.2
Charges to costs and expenses	6.5	9.5	16.7
Adjustments:
Acquisitions/(dispositions)	2.2	(1)	(2.5)
Uncollectible accounts written off	(7.1)	(25.5)	(9.4)
Foreign currency translation adjustment	(1.8)	4	(3.3)
Balance at end of period	$ 42.5	$ 42.7	$ 55.7

Supplementary Data Property a_2

Supplementary Data Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property and Equipment [Abstract]
Depreciation	$ 165.3	$ 136	$ 138.3
Property, Plant and Equipment [Line Items]
Furniture and equipment	681.7	634.8
Leasehold improvements	629	641.5
Internal-use computer software	368.5	331.3
Land and buildings	146.6	79
Total property and equipment, gross	1,825.8	1,686.6
Less: accumulated depreciation	(1,034.9)	(1,036.2)
Total property and equipment, net	$ 790.9	$ 650.4

Accrued Liabilities (Details)

Accrued Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Accrued Liabilities [Abstract]
Salaries, benefits and related expenses	$ 494.9	$ 441.7
Office and related expenses	52.2	53.2
Acquisition obligations	65.7	42
Interest	43.6	16.4
Other	150.5	121.4
Total accrued liabilities	$ 806.9	$ 674.7

Other Expense, Net (Details)

Other Expense, Net (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Nonoperating Income (Expense) [Abstract]
Net losses on sales of businesses									$ (61.9)	$ (24.1)	$ (41.4)
Other									(7.7)	(2.1)	1.1
Total other expense, net	$ (13.6)	$ (15.3)	$ (16.3)	$ (24.4)	$ (1.7)	$ (9.9)	$ (15.4)	$ 0.8	$ (69.6)	$ (26.2)	$ (40.3)

Share Repurchase Program (Detai

Share Repurchase Program (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of shares repurchased	5.1	13.7	13.3
Aggregate cost, including fees	$ 117.1	$ 300.1	$ 303.3
Average price per share, including fees	$ 23.03	$ 21.97	$ 22.76
2017 Share Repurchase Program
Share repurchase program, initial authorized amount	$ 300
Stock repurchase program, remaining authorized repurchase amount	$ 338.4

Supplemental Cash Flow Informat

Supplemental Cash Flow Information (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Cash Flow Information [Abstract]
Cash paid for interest		$ 88.7	$ 82.3	$ 78.8
Cash paid for income taxes, net of refunds	[1]	207.9	228.4	244.1
Tax refunds		$ 24.3	$ 31.9	$ 26.6
[1]	Refunds of $24.3, $31.9 and $26.6 were received for the years ended December 31, 2018, 2017 and 2016, respectively.

Goodwill (Details)

Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill
Goodwill	$ 4,875.9	$ 3,820.4	$ 3,674.4
Current year acquisitions	1,132	55.1
Foreign currency and other	(76.5)	90.9
IAN
Goodwill
Goodwill	3,099.7	3,161.8	3,043.8
Current year acquisitions	1.2	39.6
Foreign currency and other	(63.3)	78.4
CMG
Goodwill
Goodwill	666.6	658.6	630.6
Current year acquisitions	20	15.5
Foreign currency and other	(12)	12.5
Corporate and Other
Goodwill
Goodwill	1,109.6	0	$ 0
Current year acquisitions	1,110.8	0
Foreign currency and other	$ (1.2)	$ 0

Other Intangible Assets (Detail

Other Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Future amortization expense 2018	$ 87.8
Future amortization expense 2019	87.3
Future amortization expense 2020	85.6
Future amortization expense 2021	82.3
Future amortization expense 2022	78.2
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets	37.6	$ 21.1	$ 21.9
Acquired finite-lived intangible assets related to acquisitions	999	7
Gross Amount	1,332.8	350.5
Accumulated Amortization	(238)	(209.8)
Net Amount	1,094.8	140.7
Customer lists
Finite-Lived Intangible Assets [Line Items]
Gross Amount	857.2	267.3
Accumulated Amortization	(190.9)	(172.2)
Net Amount	666.3	95.1
know-how technology
Finite-Lived Intangible Assets [Line Items]
Gross Amount	235	0
Accumulated Amortization	(6.5)	0
Net Amount	228.5	0
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Amount	226.2	68.8
Accumulated Amortization	(36.8)	(33.8)
Net Amount	189.4	35
Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Gross Amount	14.4	14.4
Accumulated Amortization	(3.8)	(3.8)
Net Amount	$ 10.6	$ 10.6
Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, useful life	7 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, useful life	15 years

Components of Income Before Inc

Components of Income Before Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income before income taxes, Domestic	$ 474	$ 514.8	$ 502.1
Income before income taxes, Foreign	364	326	323.5
Income before income taxes	$ 838	$ 840.8	$ 825.6

Provision for Income Taxes (Det

Provision for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
U.S. federal income taxes (including foreign withholding taxes):
Current federal income taxes									$ 38.1	$ 154.1	$ 54.3
Deferred federal income taxes									29.9	(37.6)	35.7
Total federal income taxes									68	116.5	90
State and local income taxes:
Current state and local income taxes									25.1	18.8	8.2
Deferred state and local income taxes									3.4	19.7	(1.6)
Total state and local income taxes									28.5	38.5	6.6
Foreign income taxes:
Current foreign income taxes									121.9	107.9	89.8
Deferred foreign income taxes									(19.2)	8.4	10.5
Total foreign income taxes									102.7	116.3	100.3
Provision for income taxes	$ 62.2	$ 60.7	$ 63.6	$ 12.7	$ 135.1	$ 54.9	$ 81.6	$ (0.3)	$ 199.2	$ 271.3	$ 196.9

Reconciliation of Effective Inc

Reconciliation of Effective Income Tax Rate (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. federal statutory income tax rate										21.00%	35.00%	35.00%
Income tax provision at U.S. federal statutory rate										$ 176	$ 294.3	$ 289
State and local income taxes, net of federal income tax benefit										23.8	23.5	4.3
Impact of foreign operations, including withholding taxes										50.7	(6.7)	(23.9)
U.S. tax incentives										(17.5)	(1.3)	(1.3)
Change in net valuation allowance	[1]									(16.9)	1.4	(13.4)
Divestitures										11.7	1.1	9.7
U.S. federal tax credits										(48.1)	(0.4)	(44.6)
Stock compensation										(6.8)	(15.3)	(9)
Change in unrecognized tax benefits										8.4	7	(21.8)
Net impact of the Tax Act										13.4	(36)	0
Statutory tax rate changes										0	0	11.4
Other										4.5	3.7	(3.5)
Provision for income taxes		$ 62.2	$ 60.7	$ 63.6	$ 12.7	$ 135.1	$ 54.9	$ 81.6	$ (0.3)	$ 199.2	$ 271.3	$ 196.9
Effective income tax rate on operations										23.80%	32.30%	23.80%
[1]	Reflects changes in valuation allowances that impacted the effective income tax rate for each year presented.

Income Taxes Primary Impact on

Income Taxes Primary Impact on Provision for Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Previously unrecognized tax benefits		$ 23.4
Reversal of valuation allowance	$ 12.2

Components of Deferred Tax Asse

Components of Deferred Tax Assets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Tax Assets, Net [Abstract]
Postretirement/post-employment benefits	$ 17.9	$ 19.5
Deferred compensation	99.8	91.7
Pension costs	22.2	27.6
Basis differences in fixed assets	(71.7)	(52)
Rent	27.3	27.5
Interest	48.8	45.8
Accruals and reserves	21	18.4
Allowance for doubtful accounts	7.4	10.2
Basis differences in intangible assets	(302.7)	(281.3)
Investments in equity securities	1.2	(3.3)
Tax loss/tax credit carry forwards	345.6	357.9
Prepaid expenses	(6.3)	(1.7)
Deferred revenue	(26.8)	(41.3)
Unremitted foreign earnings	(9.5)	0
Other	38.2	43.7
Total deferred tax assets, net	212.4	262.7
Valuation allowance	(211)	(243)	$ (255.6)	$ (275.1)
Net deferred tax assets	$ 1.4	$ 19.7

Income Taxes Change in Valuatio

Income Taxes Change in Valuation Allowances (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Summary of Valuation Allowances
Beginning balance		$ 243	$ 255.6	$ 275.1
Reversed to costs and expenses		(28)	(4.6)	(15.4)
Charged (reversed) to gross tax assets and other accounts 1	[1]	5.1	(27.3)	9.5
Foreign currency translation		(9.1)	19.3	(13.6)
Ending balance		211	$ 243	$ 255.6
Deferred Tax Assets, Operating Loss Carryforwards, Components [Abstract]
Operating Loss Carryforwards		1,149.4
Undistributed Earnings of Foreign Subsidiaries		1,079.1
Foreign Tax Authority
Deferred Tax Assets, Operating Loss Carryforwards, Components [Abstract]
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration		994.1
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration		155.3
State and Local Jurisdiction
Deferred Tax Assets, Operating Loss Carryforwards, Components [Abstract]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration		$ 26.8
Minimum | Foreign Tax Authority
Deferred Tax Assets, Operating Loss Carryforwards, Components [Abstract]
Operating Loss Carryforwards, Expiration Date		Jan. 1, 2019
Minimum | State and Local Jurisdiction
Deferred Tax Assets, Operating Loss Carryforwards, Components [Abstract]
Operating Loss Carryforwards, Expiration Date		Jan. 1, 2019
Maximum | Foreign Tax Authority
Deferred Tax Assets, Operating Loss Carryforwards, Components [Abstract]
Operating Loss Carryforwards, Expiration Date		Jan. 1, 2038
Maximum | State and Local Jurisdiction
Deferred Tax Assets, Operating Loss Carryforwards, Components [Abstract]
Operating Loss Carryforwards, Expiration Date		Jan. 1, 2038
[1]	Primarily represents changes to the valuation allowance related to the change of a corresponding deferred tax asset.

Unrecognized Tax Benefits (Deta

Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued [Abstract]
Balance at beginning of period	$ 271.9	$ 246.7	$ 226.9
Increases as a result of tax positions taken during a prior year	65.9	6.3	65
Decreases as a result of tax positions taken during a prior year	(10.8)	(8.1)	(47.5)
Settlements with taxing authorities	(6.5)	(0.8)	(4.6)
Lapse of statutes of limitation	(1.7)	(3.3)	(11.8)
Increases as a result of tax positions taken during the current year	16.6	31.1	18.7
Balance at end of period	335.4	271.9	$ 246.7
Income Tax Contingency [Line Items]
Unrecognized tax benefits that would impact effective tax rate	313.5
Income tax penalties and interest accrued	42.4	27.9
Income tax penalties and interest expense	14.5	$ 7
Minimum [Member]
Income Tax Contingency [Line Items]
Anticipated decrease in unrecognized tax benefits	15
Maximum [Member]
Income Tax Contingency [Line Items]
Anticipated decrease in unrecognized tax benefits	$ 25
Foreign Tax Authority | Minimum [Member]
Income Tax Contingency [Line Items]
Operating Loss Carryforwards, Expiration Date	Jan. 1, 2019
Foreign Tax Authority | Maximum [Member]
Income Tax Contingency [Line Items]
Operating Loss Carryforwards, Expiration Date	Jan. 1, 2038

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Loss, Net of Tax Changes in AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Available-for-sale securities, before reclassifications	$ 0	$ 0	$ 0.5
Total other comprehensive income, before reclassifications	(135.4)	122.5
Total reclassification from AOCI	22.1	14.1	8.1
Accumulated other comprehensive loss, net of tax	(941.1)	(827.8)	(964.4)
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Foreign currency translation adjustment, before reclassifications	(146.8)	132.2
Foreign currency translation adjustment, amount reclassified from AOCI, net of tax	15.7	1.1
Foreign currency translation adjustment, net of tax	(716.4)	(585.3)	(718.6)
Available-for-sale Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Available-for-sale securities, before reclassifications	0	0
Available-for-sale securities, amount reclassified from AOCI, net of tax	0	(0.6)
Available-for-sale securities adjustment, net of tax	0	0	0.6
Derivative Instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Derivative instruments, before reclassifications	0	0
Derivative instruments, amount reclassified from AOCI, net of tax	1.5	1.6
Derivative Instruments, net of tax	(5.3)	(6.8)	(8.4)
Defined Benefit and Postretirement Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Defined Benefit and Postretirement Plans, before reclassifications	11.4	(9.7)
Defined benefit and Postretirement Plans, amount reclassified from AOCI, net of tax	4.9	12
Pension and Other Postretirement Benefit Plans, net of tax	$ (219.4)	$ (235.7)	$ (238)

Accumulated Other Comprehensi_5

Accumulated Other Comprehensive Loss, Net of Tax Reclassifications from AOCI, net of tax (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total income tax effect		$ (2.3)	$ (2.1)	$ (2.1)
Total reclassified from AOCI, net of tax		22.1	14.1	8.1
Foreign Currency Translation Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI, before tax	[1]	15.7	1.1	3.7
Available-for-sale Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI, before tax		0	(0.7)	(1.3)
Derivative Instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI, before tax		2.2	2.1	2
Defined Benefit and Postretirement Plans
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI, before tax		$ 6.5	$ 13.7	$ 5.8
[1]	These foreign currency translation adjustments are primarily a result of the sales of businesses.

Plan Information (Details)

Plan Information (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Deferred Compensation Liability, Current and Noncurrent	$ 196.2	$ 213.2
Incentive compensation plan initiation year	2,014
Number of shares initially available for grant	28.8
Maximum shares participants are eligible to receive	2
Maximum cash award per employee	$ 10
Number of years stock options expire from grant date	10 years
Vesting period in which the fair value of shares on grant date is amortized over, years	3 years
Minimum [Member]
Stock options exercisable period	2 years
Maximum [Member]
Stock options exercisable period	4 years

Stock Based Compensation Expens

Stock Based Compensation Expense (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock-based Payment Award
Stock-based compensation expense		$ 84.6	$ 84.5	$ 88
Tax benefit		20.4	30.4	32.1
Employee Stock Option
Stock-based Payment Award
Stock-based compensation expense		0	0	0.2
Stock-settled awards
Stock-based Payment Award
Stock-based compensation expense		24.7	20.5	16
Cash-settled awards
Stock-based Payment Award
Stock-based compensation expense		0.6	1	0.9
Performance-based awards
Stock-based Payment Award
Stock-based compensation expense		57.5	61.5	69.4
Employee stock purchase plan
Stock-based Payment Award
Stock-based compensation expense		0.9	1	0.7
Other
Stock-based Payment Award
Stock-based compensation expense	[1]	$ 0.9	$ 0.5	$ 0.8
[1]	Represents charges recorded for severance expense related to stock-based compensation awards.

Incentive Compensation Plans _4

Incentive Compensation Plans Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock-based Payment Award
Intrinsic value of stock options exercised	$ 27.9	$ 15.1	$ 15.2
Proceeds from stock options exercised including taxes withheld	29	20	18.2
Tax withheld on stock options received	$ 13.3	$ 6.8	$ 7.8
Employee Stock Option
Stock-based Payment Award
Stock options outstanding as of January 1, 2018	3.7
Stock options outstanding as of Jan 1, 2018, Weighted-average exercise price	$ 9.44
Exercised	(1.9)	(1.1)	(1.2)
Exercised, weighted-average exercise price	$ 8.30
Stock options outstanding as of December 31, 2018	1.8	3.7
Stock options outstanding as of Dec 31, 2018, Weighted-average exercise price	$ 10.66	$ 9.44
Options outstanding, weighted average remaining contractual term	2 years 9 months
Stock options outstanding, aggregate intrinsic value	$ 17.6

Share-based Compensation Awards

Share-based Compensation Awards (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock-settled awards
Stock-based Payment Award
Awards granted	2.1	0.8	1.1
Weighted-average grant-date fair value (per award)	$ 23.60	$ 24.18	$ 21.87
Total fair value of vested awards distributed	$ 24.2	$ 22.6	$ 17.5
Accrued dividends on non-vested stock-settled awards	2.4	1.5
Dividends paid for stock-settled awards	$ 1.5	$ 1.2
Cash-settled awards
Stock-based Payment Award
Awards granted	0.1	0	0.1
Weighted-average grant-date fair value (per award)	$ 23.62	$ 23.33	$ 22.54
Total fair value of vested awards distributed	$ 0.8	$ 0.9	$ 0.7
Performance-based awards
Stock-based Payment Award
Awards granted	2.9	4.8	3.3
Weighted-average grant-date fair value (per award)	$ 21.13	$ 20.06	$ 19.58
Total fair value of vested awards distributed	$ 87.2	$ 112.4	$ 27.9

Non-vested Award Activity (Deta

Non-vested Award Activity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock-settled awards
Stock-based Payment Award
Non-vested as of January 1, 2018	2.1
Nonvested as of January 1, 2018, weighted-average grant date fair value	$ 22.78
Granted	2.1
Granted, Weighted-average grant-date fair value	$ 23.60	$ 24.18	$ 21.87
Vested	(1)
Vested, Weighted-average grant date fair value	$ 22.18
Forfeited	(0.1)
Forfeited, Weighted-average grant date fair value	$ 23.67
Non-vested as of December 31, 2018	3.1	2.1
Nonvested as of December 31, 2018, weighted-average grant date fair value	$ 23.51	$ 22.78
Total unrecognized compensation expense remaining	$ 39.4
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, 2018	0.1
Nonvested as of January 1, 2018, weighted-average grant date fair value	$ 22.52
Granted	0.1
Granted, Weighted-average grant-date fair value	$ 23.62	$ 23.33	$ 22.54
Vested	(0.1)
Vested, Weighted-average grant date fair value	$ 21.54
Forfeited	0
Forfeited, Weighted-average grant date fair value	$ 23.17
Non-vested as of December 31, 2018	0.1	0.1
Nonvested as of December 31, 2018, weighted-average grant date fair value	$ 23.47	$ 22.52
Total unrecognized compensation expense remaining	$ 1
Weighted-average years expected to be recognized over	1 year 3 months
Cash awards granted during the period target value	$ 20.9	$ 2.8	$ 5.2
Incentive compensation expense, non share-based	$ 7	$ 2.5	$ 3.1
Performance-based awards
Stock-based Payment Award
Non-vested as of January 1, 2018	8.3
Nonvested as of January 1, 2018, weighted-average grant date fair value	$ 21.05
Granted	2.9
Granted, Weighted-average grant-date fair value	$ 21.13	$ 20.06	$ 19.58
Vested	(3.6)
Vested, Weighted-average grant date fair value	$ 21.02
Forfeited	(0.6)
Forfeited, Weighted-average grant date fair value	$ 21.06
Non-vested as of December 31, 2018	7	8.3
Nonvested as of December 31, 2018, weighted-average grant date fair value	$ 21.10	$ 21.05
Total unrecognized compensation expense remaining	$ 54.7
Weighted-average years expected to be recognized over	1 year 8 months
Cash awards granted during the period target value	$ 39.9	$ 38.4	$ 37.4
Incentive compensation expense, non share-based	$ 37.6	$ 35.3	$ 39.8

Incentive Compensation Plans Em

Incentive Compensation Plans Employee Stock Purchase Plans (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2016
Employee Stock Ownership Plan (ESOP), Shares in ESOP [Abstract]
Maximum employee subscription rate	10.00%
Maximum number of shares per employee	900
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
Employee Stock Purchase Plan, stock issued, shares	800,000	3,000,000
Employee Stock Purchase Plan, stock reserved for issuance, shares	10,000,000

Fair Value on a Recurring Basis

Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Fair value assets and liabilities measured on recurring basis
Cash equivalents		$ 132.1	$ 201.6
Contingent acquisition obligations	[1]	148.4	147
Contingent acquisition obligation, total change		1.4
Contingent acquisition obligation, payments		(54)
Contingent acquisition obligation, additions		61.8
Level 1
Fair value assets and liabilities measured on recurring basis
Cash equivalents		132.1	201.6
Contingent acquisition obligations	[1]	0	0
Level 2
Fair value assets and liabilities measured on recurring basis
Cash equivalents		0	0
Contingent acquisition obligations	[1]	0	0
Level 3
Fair value assets and liabilities measured on recurring basis
Cash equivalents		0	0
Contingent acquisition obligations	[1]	$ 148.4	$ 147
[1]	Contingent acquisition obligations includes deferred acquisition payments and unconditional obligations to purchase additional noncontrolling equity shares of consolidated subsidiaries. Fair value measurement of the obligations is based upon actual and projected operating performance targets as specified in the related agreements. The increase in this balance of $1.4 from December 31, 2017 to December 31, 2018 is primarily due to acquisitions and exercised put options of $61.8, partially offset by payments of $54.0. The amounts payable within the next twelve months are classified in accrued liabilities; any amounts payable thereafter are classified in other non-current liabilities.

Fair Value on a Nonrecurring Ba

Fair Value on a Nonrecurring Basis (Details) $ in Millions	Dec. 31, 2018USD ($)
Fair value assets and liabilities measured on nonrecurring basis
Long-term debt, fair value	$ 3,643.6
Level 1
Fair value assets and liabilities measured on nonrecurring basis
Long-term debt, fair value	0
Level 2
Fair value assets and liabilities measured on nonrecurring basis
Long-term debt, fair value	3,605.6
Level 3
Fair value assets and liabilities measured on nonrecurring basis
Long-term debt, fair value	$ 38

Employee Benefits (Details)

Employee Benefits (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Retirement Benefits, Description [Abstract]
Number of participants domestic pension plan	3,300
Number of participants postretirement benefit plan	1,600
Deferred Compensation Arrangements [Abstract]
Deferred compensation and benefit liability balance	$ 196.2	$ 213.2
Deferred compensation and benefit arrangement expense	10	18.5	$ 18.5
Cash Surrender Value of Life Insurance	177.3	177.4
Long-Term Disability Plan [Abstract]
Long-term disability plan obligation	5.9	$ 8.4
Long term disability plan, income replacement benefit obligation	$ 0

Pension and Postretirement Bene

Pension and Postretirement Benefit Obligation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets (Period Start)	$ 503
Fair Value of Plan Assets (Period End)	453.7	$ 503
Domestic Plan [Member]
Benefit Obligation [Roll Forward]
Benefit obligation (period start)	125.4	126.6
Service cost	0	0	$ 0
Interest cost	4.5	5.1	5.9
Benefits Paid	(9.5)	(11.4)
Plan participant contributions	0	0
Actuarial losses (gains)	(5)	5.1
Settlements and curtailments	0	0
Foreign currency effect	0	0
Other	0	0
Benefit Obligation (Period End)	115.4	125.4	126.6
Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets (Period Start)	98.8	95.2
Actual return on plan assets	(8.1)	12.4
Employer contributions	8.6	2.6
Plan participant contributions	0	0
Benefits paid	(9.5)	(11.4)
Settlements	0	0
Foreign currency effect	0	0
Other	0	0
Fair Value of Plan Assets (Period End)	89.8	98.8	95.2
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(25.6)	(26.6)
Amounts Recognized in Consolidated Balance Sheets
Non-current asset	0	0
Current liability	0	0
Non-current liability	(25.6)	(26.6)
Net liability recognized	(25.6)	(26.6)
Accumulated benefit obligation	115.4	125.4
Amounts recognized in Accumulated Other Comprehensive Loss, net
Net actuarial loss	60.4	52.2
Prior service cost (credit)	0	0
Total amount recognized	60.4	52.2
Pension plans with underfunded or unfunded accumulated benefit obligation
Aggregate projected benefit obligation	115.4	125.4
Aggregate accumulated benefit obligation	115.4	125.4
Aggregate fair value of plan assets	89.8	98.8
Foreign Plan [Member]
Benefit Obligation [Roll Forward]
Benefit obligation (period start)	582.3	530.6
Service cost	5.4	4.9	6.7
Interest cost	13.1	13.5	15.1
Benefits Paid	(27.4)	(19)
Plan participant contributions	0.1	0.2
Actuarial losses (gains)	(47.6)	20.3
Settlements and curtailments	(5.8)	(19.8)
Foreign currency effect	(26.4)	50.4
Other	2.3	1.2
Benefit Obligation (Period End)	496	582.3	530.6
Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets (Period Start)	404.2	365.9
Actual return on plan assets	(8)	25.1
Employer contributions	19.1	17.5
Plan participant contributions	0.1	0.2
Benefits paid	(27.4)	(19)
Settlements	(4.6)	(19.1)
Foreign currency effect	(21.1)	33.2
Other	1.6	0.4
Fair Value of Plan Assets (Period End)	363.9	404.2	365.9
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(132.1)	(178.1)
Amounts Recognized in Consolidated Balance Sheets
Non-current asset	8.6	9
Current liability	(6.2)	(6.5)
Non-current liability	(134.5)	(180.6)
Net liability recognized	(132.1)	(178.1)
Accumulated benefit obligation	493.2	577.9
Amounts recognized in Accumulated Other Comprehensive Loss, net
Net actuarial loss	165.6	201.6
Prior service cost (credit)	1.2	1.1
Total amount recognized	166.8	202.7
Pension plans with underfunded or unfunded accumulated benefit obligation
Aggregate projected benefit obligation	491.2	576.6
Aggregate accumulated benefit obligation	489.9	575.2
Aggregate fair value of plan assets	350.5	389.5
Other Postretirement Benefits Plan [Member]
Benefit Obligation [Roll Forward]
Benefit obligation (period start)	31.8	32.3
Service cost	0	0	0
Interest cost	1.1	1.3	1.5
Benefits Paid	(5.9)	(5.9)
Plan participant contributions	1.8	1.6
Actuarial losses (gains)	(1.1)	2.5
Settlements and curtailments	0	0
Foreign currency effect	0	0
Other	0	0
Benefit Obligation (Period End)	27.7	31.8	32.3
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	4.3
Plan participant contributions	1.8	1.6
Benefits paid	(5.9)	(5.9)
Settlements	0	0
Foreign currency effect	0	0
Other	0	0
Fair Value of Plan Assets (Period End)	0	0	$ 0
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(27.7)	(31.8)
Amounts Recognized in Consolidated Balance Sheets
Non-current asset	0	0
Current liability	(2.9)	(3.1)
Non-current liability	(24.8)	(28.7)
Net liability recognized	(27.7)	(31.8)
Amounts recognized in Accumulated Other Comprehensive Loss, net
Net actuarial loss	3.1	4.2
Prior service cost (credit)	(0.3)	(0.4)
Total amount recognized	$ 2.8	$ 3.8

Net Periodic Cost (Details)

Net Periodic Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Domestic Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost
Service cost	$ 0	$ 0	$ 0
Interest cost	4.5	5.1	5.9
Expected return on plan assets	(6.6)	(6.2)	(6.6)
Settlement and curtailment (gains) losses	0	0	0
Amortization of:
Prior service cost (credit)	0	0	0
Net actuarial losses	1.6	1.5	1.3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ (0.5)	$ 0.4	$ 0.6
Discount rate	3.70%	4.20%	4.80%
Expected return on plan assets	7.00%	7.00%	7.00%
Interest crediting rate	5.10%	5.10%	5.10%
Discount rate	4.35%	3.70%	4.20%
Interest crediting rate	5.10%	5.10%	5.10%
Foreign Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost
Service cost	$ 5.4	$ 4.9	$ 6.7
Interest cost	13.1	13.5	15.1
Expected return on plan assets	(18.8)	(17.7)	(18.7)
Settlement and curtailment (gains) losses	(1)	6.8	0.4
Amortization of:
Prior service cost (credit)	0.1	0.1	0.1
Net actuarial losses	5.9	5.5	4.2
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 4.7	$ 13.1	$ 7.8
Discount rate	2.36%	2.52%	3.61%
Rate of compensation increase	2.37%	2.36%	3.18%
Expected return on plan assets	4.70%	4.66%	5.38%
Interest crediting rate	1.31%	1.29%	1.35%
Discount rate	2.61%	2.36%	2.52%
Rate of compensation increase	2.58%	2.37%	2.36%
Interest crediting rate	1.44%	1.31%	1.29%
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost
Service cost	$ 0	$ 0	$ 0
Interest cost	1.1	1.3	1.5
Expected return on plan assets	0	0	0
Settlement and curtailment (gains) losses	0	0	0
Amortization of:
Prior service cost (credit)	(0.2)	(0.2)	(0.2)
Net actuarial losses	0.1	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 1	$ 1.1	$ 1.3
Discount rate	3.65%	4.05%	4.65%
Discount rate	4.30%	3.65%	4.05%
Health care cost trend rate assumed for next year	6.25%	6.50%	6.75%
Year ultimate rate is reached	2,024	2,024	2,024
Ultimate rate	5.00%	5.00%	5.00%

Fair Value of Pension Plan Asse

Fair Value of Pension Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	$ 453.7	$ 503
Investment funds
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	13	14.7
Limited partnerships
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	25.6	29.5
Fixed income securities
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	23.1	23.4
Insurance contracts
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	5.8	7.9
Other plan assets
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	20	27.7
Total plan assets subject to leveling
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	87.5	103.2
Investments measured at net asset value
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	366.2	399.8
Level 1 | Investment funds
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	13	14.7
Level 1 | Limited partnerships
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	0	0
Level 1 | Fixed income securities
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	23.1	23.4
Level 1 | Insurance contracts
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	0	0
Level 1 | Other plan assets
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	20	27.7
Level 1 | Total plan assets subject to leveling
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	56.1	65.8
Level 2 | Investment funds
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	0	0
Level 2 | Limited partnerships
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	0	0
Level 2 | Fixed income securities
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	0	0
Level 2 | Insurance contracts
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	5.8	7.9
Level 2 | Other plan assets
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	0	0
Level 2 | Total plan assets subject to leveling
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	5.8	7.9
Level 3 | Investment funds
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	0	0
Level 3 | Limited partnerships
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	25.6	29.5
Balance at beginning of period	29.5	28
Actual return on plan assets	(3.9)	1.5
Balance at end of period	25.6	29.5
Level 3 | Fixed income securities
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	0	0
Level 3 | Insurance contracts
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	0	0
Level 3 | Other plan assets
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	0	0
Level 3 | Total plan assets subject to leveling
Fair value assets and liabilities measured on recurring basis
Defined Benefit Plan, Plan Assets, Amount	$ 25.6	$ 29.5

Employee Benefits Allocation of

Employee Benefits Allocation of Plan Assets (Details)	Dec. 31, 2018	Dec. 31, 2017
Allocation of Plan Assets
Defined benefit plan, plan assets, target allocation, percentage	100.00%
Defined benefit plan, actual plan asset allocations	100.00%	100.00%
Alternative Investments
Allocation of Plan Assets
Defined benefit plan, plan assets, target allocation, percentage	26.00%
Defined benefit plan, actual plan asset allocations	26.00%	27.00%
Equity securities
Allocation of Plan Assets
Defined benefit plan, plan assets, target allocation, percentage	23.00%
Defined benefit plan, actual plan asset allocations	22.00%	23.00%
Fixed income securities
Allocation of Plan Assets
Defined benefit plan, plan assets, target allocation, percentage	21.00%
Defined benefit plan, actual plan asset allocations	21.00%	21.00%
Liability driven investments
Allocation of Plan Assets
Defined benefit plan, plan assets, target allocation, percentage	16.00%
Defined benefit plan, actual plan asset allocations	16.00%	14.00%
Real estate
Allocation of Plan Assets
Defined benefit plan, plan assets, target allocation, percentage	6.00%
Defined benefit plan, actual plan asset allocations	6.00%	6.00%
Other plan assets
Allocation of Plan Assets
Defined benefit plan, plan assets, target allocation, percentage	8.00%
Defined benefit plan, actual plan asset allocations	9.00%	9.00%

Pension Cash Flows (Details)

Pension Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans
Estimated U.S. federal subsidies expected to be received under the Medicare Prescription Drug, Improvement and Modernization Act of 2003, no more than	$ 0.3
Domestic Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Employer contributions	8.6	$ 2.6
Defined benefit plan, estimated future employer contributions in next fiscal year	2.5
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity
Expected future benefit payments in 2019	14.5
Expected future benefit payments in 2020	8.8
Expected future benefit payments in 2021	8
Expected future benefit payments in 2022	8.3
Expected future benefit payments in 2023	7.8
Expected future benefit payments in 2024-2025	36.7
Foreign Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Employer contributions	19.1	17.5
Defined benefit plan, estimated future employer contributions in next fiscal year	17
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity
Expected future benefit payments in 2019	21.7
Expected future benefit payments in 2020	18.7
Expected future benefit payments in 2021	19.8
Expected future benefit payments in 2022	20.9
Expected future benefit payments in 2023	21.8
Expected future benefit payments in 2024-2025	117.2
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Employer contributions	4.1	$ 4.3
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity
Expected future benefit payments in 2019	3
Expected future benefit payments in 2020	2.8
Expected future benefit payments in 2021	2.6
Expected future benefit payments in 2022	2.4
Expected future benefit payments in 2023	2.2
Expected future benefit payments in 2024-2025	$ 9.8

Savings Plans (Details)

Savings Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Domestic Tax Authority
Defined Benefit Plans and Other Postretirement Benefit Plans
Cost Recognized	$ 52.6	$ 47.2	$ 47
Discretionary Company Contribution
Defined Benefit Plans and Other Postretirement Benefit Plans
Cost Recognized	6.7	3.6	6.1
Defined Contribution Plans Participant Forfeitures
Defined Benefit Plans and Other Postretirement Benefit Plans
Cost Recognized	5.8	4.6	4.4
Foreign Tax Authority
Defined Benefit Plans and Other Postretirement Benefit Plans
Cost Recognized	$ 51.3	$ 47.4	$ 44.5

Segment Operations (Details)

Segment Operations (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segments:
Total revenue	$ 2,856	$ 2,297.5	$ 2,391.8	$ 2,169.1	$ 2,589.8	$ 2,208.2	$ 2,185.8	$ 2,063.8	$ 9,714.4	$ 9,047.6	$ 9,056.2
Net revenue	2,413.7	1,895.7	1,948.2	1,774	2,131.1	1,832.5	1,834.6	1,675.3	8,031.6	7,473.5	7,452.3
Operating Income (Loss)	459.1	261.7	249.2	38.8	423	255	225.7	34.7	1,008.8	938.4	936.4
Interest expense									(123)	(90.8)	(90.6)
Interest income									21.8	19.4	20.1
Other expense, net	(13.6)	(15.3)	(16.3)	(24.4)	(1.7)	(9.9)	(15.4)	0.8	(69.6)	(26.2)	(40.3)
Income before income taxes									838	840.8	825.6
Depreciation and amortization	68.9	$ 44	$ 44	$ 46	32.6	$ 42.2	$ 41.3	$ 41	202.9	157.1	160.2
Capital expenditures									177.1	155.9	200.7
Assets	15,620.3				12,704.7				15,620.3	12,704.7
IAN
Segments:
Total revenue									7,374.4	7,009.6	6,992.8
Net revenue									6,585.8	6,266.7	6,201.4
Operating Income (Loss)									982.8	875.1	894.3
Depreciation and amortization									142.8	125.5	129.2
Capital expenditures									128.5	112	149.2
Assets	11,446.2				10,978				11,446.2	10,978
CMG
Segments:
Total revenue									2,158.3	2,038	2,063.4
Net revenue									1,264.1	1,206.8	1,250.9
Operating Income (Loss)									175	189.9	189.3
Depreciation and amortization									24.3	23.5	22.4
Capital expenditures									13	17.7	16.6
Assets	1,516.7				1,427.4				1,516.7	1,427.4
Corporate and Other
Segments:
Total revenue									181.7	0	0
Net revenue									181.7	0	0
Operating Income (Loss)									(149)	(126.6)	(147.2)
Depreciation and amortization									35.8	8.1	8.6
Capital expenditures									35.6	26.2	$ 34.9
Assets	$ 2,657.4				$ 299.3				$ 2,657.4	$ 299.3

Segment Information Major Geogr

Segment Information Major Geographic Area (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues and Long-Lived Assets
Long-Lived Assets	$ 1,219.7				$ 1,034.1				$ 1,219.7	$ 1,034.1
Net revenue	2,413.7	$ 1,895.7	$ 1,948.2	$ 1,774	2,131.1	$ 1,832.5	$ 1,834.6	$ 1,675.3	8,031.6	7,473.5	$ 7,452.3
Domestic
Revenues and Long-Lived Assets
Long-Lived Assets	892.9				694.5				892.9	694.5
Total International
Revenues and Long-Lived Assets
Long-Lived Assets	326.8				339.6				326.8	339.6
Net revenue									3,206.6	3,014.7	3,009.1
United Kingdom
Revenues and Long-Lived Assets
Long-Lived Assets	57.9				56.2				57.9	56.2
Net revenue									711.7	613.1	604.3
Continental Europe
Revenues and Long-Lived Assets
Long-Lived Assets	57.9				73.6				57.9	73.6
Net revenue									737.5	687.8	682
Asia Pacific
Revenues and Long-Lived Assets
Long-Lived Assets	121.7				115.5				121.7	115.5
Net revenue									896.8	866.9	887.7
Latin America
Revenues and Long-Lived Assets
Long-Lived Assets	43.6				48.2				43.6	48.2
Net revenue									350.1	350.8	367.8
Other
Revenues and Long-Lived Assets
Long-Lived Assets	$ 45.7				$ 46.1				45.7	46.1
Net revenue									$ 510.5	$ 496.1	$ 467.3

Commitments and Contingencies N

Commitments and Contingencies Net Rent Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Gross rent expense	$ 375.9	$ 371	$ 366.1
Third-party sublease rental income	(5.3)	(4.6)	(4.1)
Net rent expense	$ 370.6	$ 366.4	$ 362

Future Minimum Lease Payments (

Future Minimum Lease Payments (Details) $ in Millions	Dec. 31, 2018USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Rent Obligations, due 2018	$ 352
Rent Obligations, due 2019	324.3
Rent Obligations, due 2020	282.3
Rent Obligations, due 2021	242.5
Rent Obligations, due 2022	184
Rent Obligations, due thereafter	714.6
Total Rent Obligations	2,099.7
Sublease Rental Income, due 2018	(7.7)
Sublease Rental Income, due 2019	(5.2)
Sublease Rental Income, due 2020	(2.2)
Sublease Rental Income, due 2021	(1.3)
Sublease Rental Income, due 2022	(0.6)
Sublease Rental Income, due thereafter	(0.5)
Total Sublease Rental Income	(17.5)
Net Rent, due 2018	344.3
Net Rent, due 2019	319.1
Net Rent, due 2020	280.1
Net Rent, due 2021	241.2
Net Rent, due 2022	183.4
Net Rent, due thereafter	714.1
Total Net Rent	$ 2,082.2

Guarantees (Details)

Guarantees (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Parent company guarantees on lease obligations	$ 824.5	$ 829.2
Parent company guarantees relating to credit facilities	349.1	308.8
Cash pooling guarantees	207.8	$ 182.2
Assets pledged as security for parent company guarantees	$ 0

Contingent Acquisition Obligati

Contingent Acquisition Obligations (Details) $ in Millions	Dec. 31, 2018USD ($)
Deferred acquisition payments
Business Acquisition, Contingent Consideration [Line Items]
Future contingent acquisition obligation due in 2018	$ 65.7
Future contingent acquisition obligation due in 2019	20
Future contingent acquisition obligation due in 2020	23.6
Future contingent acquisition obligation due in 2021	4.7
Future contingent acquisition obligation due in 2022	10.2
Future contingent acquisition obligation due thereafter	2.7
Future contingent acquisition obligation due, total	126.9
Redeemable noncontrolling interests and call options with affiliates
Business Acquisition, Contingent Consideration [Line Items]
Future contingent acquisition obligation due in 2018	30.1	[1]
Future contingent acquisition obligation due in 2019	30.6	[1]
Future contingent acquisition obligation due in 2020	42.9	[1]
Future contingent acquisition obligation due in 2021	5.7	[1]
Future contingent acquisition obligation due in 2022	3.5	[1]
Future contingent acquisition obligation due thereafter	2.5	[1]
Future contingent acquisition obligation due, total	115.3	[1]
Redeemable at noncontrolling equity owners discretion
Business Acquisition, Contingent Consideration [Line Items]
Future contingent acquisition obligation due in 2018	24.9
Total contingent acquisition payments
Business Acquisition, Contingent Consideration [Line Items]
Future contingent acquisition obligation due in 2018	95.8
Future contingent acquisition obligation due in 2019	50.6
Future contingent acquisition obligation due in 2020	66.5
Future contingent acquisition obligation due in 2021	10.4
Future contingent acquisition obligation due in 2022	13.7
Future contingent acquisition obligation due thereafter	5.2
Future contingent acquisition obligation due, total	$ 242.2
[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, 2018. These estimated payments of $24.9 are included within the total payments expected to be made in 2019, and will continue to be carried forward into 2020 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.

Recent Accounting Standards Rec

Recent Accounting Standards Recent Accounting Standards (Details) $ in Billions	Dec. 31, 2018USD ($)
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Minimum Estimate of Right of Use Asset and Liability for Operating Leases	$ 1.3
Maximum Estimate of Right of Use Asset and Liability for Operating Leases	$ 1.6

Results by Quarter (Unaudited_3

Results by Quarter (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Net revenue	$ 2,413.7	$ 1,895.7	$ 1,948.2	$ 1,774	$ 2,131.1	$ 1,832.5	$ 1,834.6	$ 1,675.3	$ 8,031.6	$ 7,473.5	$ 7,452.3
Billable expenses	442.3	401.8	443.6	395.1	458.7	375.7	351.2	388.5	1,682.8	1,574.1	1,603.9
Total revenue	2,856	2,297.5	2,391.8	2,169.1	2,589.8	2,208.2	2,185.8	2,063.8	9,714.4	9,047.6	9,056.2
Salaries and related expenses	1,423.7	1,251.4	1,292.9	1,330.3	1,291.3	1,218.8	1,228.9	1,251.7	5,298.3	4,990.7	4,942.2
Office and other direct expenses	381	317	333.3	323.8	334.8	302.9	318.4	312.7	1,355.1	1,268.8	1,274.9
Billable expense	442.3	401.8	443.6	395.1	458.7	375.7	351.2	388.5	1,682.8	1,574.1	1,603.9
Cost of services	2,247	1,970.2	2,069.8	2,049.2	2,084.8	1,897.4	1,898.5	1,952.9	8,336.2	7,833.6	7,821
Selling, General and Administrative Expense	81	21.6	28.8	35.1	49.4	13.6	20.3	35.2	166.5	118.5	138.6
Depreciation and amortization	68.9	44	44	46	32.6	42.2	41.3	41	202.9	157.1	160.2
Total operating expenses	2,396.9	2,035.8	2,142.6	2,130.3	2,166.8	1,953.2	1,960.1	2,029.1	8,705.6	8,109.2	8,119.8
Operating Income (Loss)	459.1	261.7	249.2	38.8	423	255	225.7	34.7	1,008.8	938.4	936.4
Other expense, net	(13.6)	(15.3)	(16.3)	(24.4)	(1.7)	(9.9)	(15.4)	0.8	(69.6)	(26.2)	(40.3)
Total (expenses) and other income	(55.2)	(37.6)	(37.7)	(40.3)	(19.5)	(26.8)	(36.4)	(14.9)	(170.8)	(97.6)	(110.8)
Provision for income taxes	62.2	60.7	63.6	12.7	135.1	54.9	81.6	(0.3)	199.2	271.3	196.9
NET INCOME	342.5	163.5	147.8	(16.1)	269.2	172.3	107.6	21.3	$ 637.7	$ 570.4	$ 629
Net income available to IPG common stockholders	$ 326.2	$ 161	$ 145.8	$ (14.1)	$ 252.3	$ 169.7	$ 107.7	$ 24.7
Earnings per share, Basic	$ 0.85	$ 0.42	$ 0.38	$ (0.04)	$ 0.66	$ 0.44	$ 0.27	$ 0.06	$ 1.61	$ 1.42	$ 1.52
Earnings per share, Diluted	0.84	0.41	0.37	(0.04)	0.64	0.43	0.27	0.06	$ 1.59	$ 1.40	$ 1.48
Dividends declared per common share	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.18	$ 0.18	$ 0.18	$ 0.18

Subsequent Events (Details)

Subsequent Events (Details)	Feb. 13, 2019$ / shares
Subsequent Event [Member]
Subsequent Event [Line Items]
Dividends payable, amount per share	$ 0.235