Stagwell (STGW) 10-Q 1 Nov 18 2018 Q3 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 31, 2018
Document Information [Line Items]
Entity Registrant Name	MDC PARTNERS INC
Entity Central Index Key	876,883
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Trading Symbol	MDCA
Entity Emerging Growth Company	0
Document Type	10-Q
Entity Small Business	0
Document Fiscal Year Focus	2,018
Document Period End Date	Sep. 30, 2018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Common Class A
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		59,809,581
Common Class B
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		3,755
Convertible Preferred Stock | Series 4 Convertible Preferred Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		95,000

UNAUDITED CONDENSED CONSOLIDATE

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Payments to Acquire Businesses, Net of Cash Acquired			$ 34,303	$ 0
Revenue:
Services	$ 375,830	$ 375,800	1,082,541	1,111,032
Cost of Goods and Services Sold	238,690	249,418	735,110	754,803
Operating expenses:
Office and general expenses	102,380	77,910	270,137	251,313
Depreciation and amortization	11,134	11,252	35,212	32,916
Goodwill and other asset impairment	21,008	0	23,325	0
Costs and Expenses, Total	373,212	338,580	1,063,784	1,039,032
Operating profit	2,618	37,220	18,757	72,000
Other income (expense):
Interest expense and finance charges	(17,063)	(16,258)	(50,005)	(48,309)
Other, net	189	(1,264)	1,222	(986)
Foreign Currency Transaction Gain (Loss), before Tax	3,275	9,913	(9,934)	18,798
Nonoperating Income (Expense), Total	(13,599)	(7,609)	(58,717)	(30,497)
Income (loss) before income taxes and equity in earnings (losses) of non-consolidated affiliates	(10,981)	29,611	(39,960)	41,503
Income tax expense (benefit)	2,986	9,049	(3,367)	17,659
Income (loss) before equity in earnings (losses) of non-consolidated affiliates	(13,967)	20,562	(36,593)	23,844
Equity in earnings of non-consolidated affiliates	300	1,422	358	1,924
Net income (loss)	(13,667)	21,984	(36,235)	25,768
Net income attributable to noncontrolling interests	(2,458)	(3,491)	(5,900)	(6,588)
Net income (loss) attributable to MDC Partners Inc.	(16,125)	18,493	(42,135)	19,180
Net income (loss) attributable to MDC Partners Inc. common shareholders	$ (18,234)	$ 14,137	$ (48,339)	$ 13,033
Income (Loss) from Continuing Operations, Per Basic Share	$ (0.32)	$ 0.25	$ (0.85)	$ 0.24
Weighted Average Number of Common Shares Outstanding:
Stock-based compensation	$ 6,242	$ 6,380	$ 16,882	$ 16,870
Earnings Per Share, Basic		$ 0.25	$ (0.85)	$ 0.24
Income (Loss) from Continuing Operations, Per Diluted Share	$ (0.32)	0.24	(0.85)	0.24
Earnings Per Share, Diluted	$ (0.32)	$ 0.24	$ (0.85)	$ 0.24
Weighted Average Number of Shares Outstanding, Basic	57,498,661	57,566,707	57,117,797	53,915,536
Weighted Average Number of Shares Outstanding, Diluted	57,498,661	57,943,080	57,117,797	54,228,208
Cost of services sold
Weighted Average Number of Common Shares Outstanding:
Stock-based compensation	$ 4,390	$ 5,310	$ 11,784	$ 12,558
Office and general expenses
Weighted Average Number of Common Shares Outstanding:
Stock-based compensation	1,852	1,070	5,098	4,312
Series 4 Convertible Preferred Stock [Domain] | Convertible Preferred Stock
Other income (expense):
Accretion on and net income allocated to convertible preference shares	(2,109)	(4,356)		(6,147)
Series 4 Convertible Preferred Stock [Member] | Convertible Preferred Stock
Other income (expense):
Accretion on and net income allocated to convertible preference shares	$ (2,109)	$ (1,948)	$ (6,204)	$ (4,365)

UNAUDITED CONSOLIDATED STATEMEN

UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Comprehensive income (loss)
Net loss	$ (13,667)	$ 21,984	$ (36,235)	$ 25,768
Other comprehensive income (loss), net of applicable tax:
Foreign currency translation adjustment	1,327	1,912	898	1,294
Other comprehensive income (loss)	(1,327)	(1,912)	(898)	(1,294)
Comprehensive income (loss) for the period	(14,994)	20,072	(37,133)	24,474
Comprehensive income attributable to the noncontrolling interests	(2,931)	(4,695)	(4,367)	(9,063)
Comprehensive income (loss) attributable to MDC Partners Inc.	$ (17,925)	$ 15,377	$ (41,500)	$ 15,411

UNAUDITED CONDENSED CONSOLIDA_2

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 25,056	$ 46,179
Cash held in trusts	3,965	4,632
Accounts receivable, less allowance for doubtful accounts of $3,001 and $2,453	437,024	434,072
Expenditures billable to clients	59,317	31,146
Other current assets	37,867	26,742
Total Current Assets	563,229	542,771
Fixed assets, at cost, less accumulated depreciation of $132,193 and $123,599	90,249	90,306
Investments in non-consolidated affiliates	6,814	6,307
Goodwill	843,180	835,935
Other intangible assets, net	75,115	70,605
Deferred tax assets	122,505	115,325
Other assets	28,632	37,643
Total Assets	1,729,724	1,698,892
Current Liabilities:
Accounts payable	219,757	244,527
Trust liability	3,965	4,632
Accruals and other liabilities	300,664	327,812
Advance billings	182,305	148,133
Current portion of long-term debt	360	313
Current portion of deferred acquisition consideration	37,902	50,213
Total Current Liabilities	744,953	775,630
Long-term debt, less current portion	987,880	882,806
Long-term portion of deferred acquisition consideration	56,827	72,213
Other liabilities	53,912	54,110
Deferred tax liabilities	6,899	6,760
Total Liabilities	1,850,471	1,791,519
Redeemable Noncontrolling Interests	57,193	62,886
Shareholders’ Deficit:
Charges in excess of capital	(311,576)	(314,241)
Accumulated deficit	(383,305)	(340,000)
Total Shareholders' Deficit	(177,940)	(155,513)
Total Liabilities, Redeemable Noncontrolling Interests and Shareholders' Deficit	1,729,724	1,698,892
Common Class A
Shareholders’ Deficit:
Common shares	362,195	352,432
Preferred Stock | Series 4 Convertible Preferred Stock
Shareholders’ Deficit:
Convertible preference shares (liquidation preference $107,556 and $101,352)	90,123	90,220
Total Shareholders' Deficit	90,123	90,220
Accumulated other comprehensive loss
Shareholders’ Deficit:
Accumulated other comprehensive loss	(1,319)	(1,954)
Total Shareholders' Deficit	(1,319)	(1,954)
MDC Partners Inc. Shareholders' Deficit
Shareholders’ Deficit:
MDC Partners Inc. Shareholders' Deficit	(243,882)	(213,543)
Total Shareholders' Deficit	(243,882)	(213,543)
Noncontrolling Interest
Shareholders’ Deficit:
Noncontrolling interests	65,942	58,030
Total Shareholders' Deficit	$ 65,942	$ 58,030

UNAUDITED CONDENSED CONSOLIDA_3

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounts receivable, allowance for doubtful accounts (in dollars)	$ 2,524	$ 2,453
Accumulated depreciation (in dollars)	$ 120,119	$ 123,599

UNAUDITED CONDENSED CONSOLIDA_4

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net loss	$ (36,235)	$ 25,768
Adjustments to reconcile net income (loss) to cash used in operating activities:
Stock-based compensation	16,882	16,870
Depreciation	20,944	18,000
Amortization of intangibles	14,268	14,916
Amortization of deferred finance charges	2,402	2,018
Goodwill and other asset impairment	23,325	0
Adjustment to deferred acquisition consideration	8,522	13,354
Acquisition-related contingent consideration payment	(28,263)	(36,570)
Deferred income taxes (benefits)	(6,690)	8,125
Gain (loss) on sale of assets	(1,408)	1,245
(Earnings) losses of non-consolidated affiliates	(358)	(1,924)
Other non-current assets and liabilities	(956)	(4,388)
Foreign exchange	9,125	(15,113)
Changes in working capital:
Accounts receivable	8,574	(54,723)
Expenditures billable to clients	(28,171)	(9,294)
Prepaid expenses and other current assets	(11,516)	6,400
Accounts payable, accruals and other liabilities	(49,587)	(31,149)
Advance billings	27,413	32,015
Net cash used in operating activities	(31,729)	(14,450)
Cash flows used in investing activities:
Capital expenditures	(15,232)	(28,305)
Deposits	0	(1,461)
Other investments	1,180	(1,530)
Net cash used in investing activities	(48,355)	(19,503)
Cash flows provided by financing activities:
Payment for Contingent Consideration Liability, Financing Activities	32,240	52,556
Repayment of long-term debt	(260)	(310)
Purchase of shares	(776)	(1,239)
Distributions to noncontrolling interests	(10,410)	(5,272)
Payment of dividends	(182)	(284)
Net cash provided by financing activities	59,122	24,887
Effect of exchange rate changes on cash and cash equivalents	(161)	6
Decrease in cash and cash equivalents	(21,123)	(9,060)
Cash and cash equivalents at beginning of period	46,179	27,921
Cash and cash equivalents at end of period	25,056	18,861
Supplemental disclosures:
Cash income taxes paid	4,822	6,909
Cash interest paid	33,011	32,324
Change in cash held in trusts	(667)	(159)
Non-cash transactions:
Capital leases	600	621
Dividends payable	271	453
Payments to Acquire Businesses, Net of Cash Acquired	34,303	0
Proceeds from Sale of Other Assets, Investing Activities	0	11,120
Payments of Distributions to Affiliates	0	673
Wells Fargo Capital Finance, LLC | Revolving Credit Facility
Cash flows provided by financing activities:
Repayments of revolving credit agreement	(1,121,300)	(1,093,508)
Proceeds from revolving credit agreement	1,224,290	1,087,688
Series 4 Convertible Preferred Stock
Cash flows provided by financing activities:
Proceeds from issuance of convertible preference shares	0	95,000
Convertible Preferred Stock
Cash flows provided by financing activities:
Convertible preference shares issuance costs	0	(4,632)
Common Class A [Member] | Common Stock
Non-cash transactions:
Stock Issued During Period, Value, Acquisitions	$ 7,030	$ 28,727

UNAUDITED CONDENSED CONSOLIDA_5

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' DEFICIT - 9 months ended Sep. 30, 2018 - USD ($) $ in Thousands	Total	Convertible Preferred StockSeries 4 Convertible Preferred Stock	Common Stock	Common StockCommon Class A [Member]	Additional Paid-in Capital	Charges in Excess of Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	MDC Partners Inc. Shareholders' Deficit	Noncontrolling Interest	Contingent Consideration, Liability Settlements [Domain]	Contingent Consideration, Liability Settlements [Domain]MDC Partners Inc. Shareholders' Deficit
Stock Issued During Period, Shares, Acquisitions			1,011,561
Balance at Dec. 31, 2017	$ (155,513)	$ 90,220	$ 352,432		$ 0	$ (314,241)	$ (340,000)	$ (1,954)	$ (213,543)	$ 58,030
Balance (in shares) at Dec. 31, 2017		95,000	56,375,131	56,371,376
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss attributable to MDC Partners Inc.	(42,135)								(42,135)
Other comprehensive income (loss)	(898)							635	635	(1,533)
Issuance of Series 4 convertible preference shares in private placement (in shares)		0
Expenses for convertible preference shares (Note 9)	(97)	$ (97)							(97)
Issuance of restricted stock	0		$ 3,509		(3,509)
Issuance of restricted stock (in shares)			237,529
Shares acquired and cancelled	(776)		$ (776)						(776)
Shares acquired and cancelled (in shares)			(108,782)
Stock-based compensation	6,774				6,774				6,774
Changes in redemption value of redeemable noncontrolling interests	(4,409)				(4,409)				(4,409)
Adjustments to Additional Paid in Capital, Changes due to Business Combinations					(3,809)				(3,809)	15,410
Business acquisitions and step-up transactions	19,219
Changes in ownership interest	(5,965)									(5,965)
Cumulative effect of adoption of ASC 606 (Note 14)	(1,170)						(1,170)		(1,170)
Transfer to charges in excess of capital	0				(2,665)	2,665
Balance at Sep. 30, 2018	$ (177,940)	$ 90,123	$ 362,195		$ 0	$ (311,576)	$ (383,305)	$ (1,319)	$ (243,882)	$ 65,942
Balance (in shares) at Sep. 30, 2018		95,000	57,515,439	57,511,684
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Value, Acquisitions				$ 7,030							$ 7,030	$ 7,030

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation and Recent Developments The accompanying consolidated financial statements include the accounts of MDC Partners Inc. (the “Company” or “MDC”), its subsidiaries and variable interest entities for which the Company is the primary beneficiary. References herein to “Partner Firms” generally refer to the Company’s subsidiary agencies. MDC Partners Inc. has prepared the unaudited condensed consolidated interim financial statements included herein in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”) for reporting interim financial information on Form 10-Q. Accordingly, the financial statements have been condensed and do not include certain information and disclosures pursuant to these rules. The preparation of financial statements in conformity with GAAP requires us to make judgments, assumptions and estimates that affect the amounts reported and disclosed. Actual results could differ from these estimates and assumptions. The consolidated results for interim periods are not necessarily indicative of results for the full year and should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 (“2017 Form 10-K”). The accompanying financial statements reflect all adjustments, consisting of normally recurring accruals, which in the opinion of management are necessary for a fair presentation, in all material respects, of the information contained therein. Intercompany balances and transactions have been eliminated in consolidation. Certain reclassifications have been made to the prior year financial information to conform to the current year presentation, such as the reclassification of contingent consideration payments in the statement of cash flows in connection with the adoption of Accounting Standards Update (“ASU”) 2016-15, Statement of Cash Flow. See Note 14 of the Notes to the Unaudited Condensed Consolidated Financial Statements for additional information regarding the new guidance and reclass within the statement of cash flows. On September 12, 2018 the Company announced that Scott Kauffman will step down as the Company’s Chairman and Chief Executive Officer. He will remain in his role as Chairman and CEO until a successor is named. Mr. Kauffman is also expected to continue as a member of the MDC Board of Directors for the remainder of his current term. On September 20, 2018, the Company announced its intention to explore and evaluate potential strategic alternatives, which may result in, among other things, the possible sale of the Company. The Company has not made a decision to pursue any specific strategic alternative, and there is no timetable for completing the strategic review process. This review process is proceeding in parallel with the Company’s search to identify a successor CEO. There can be no assurance that the Company will complete any specific action or transaction.

Revenue

Revenue	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Effective January 1, 2018, the Company adopted Financial Accounting Standards Board (the “FASB”) ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”). ASC 606 was applied using the modified retrospective method, with the cumulative effect of the initial adoption being recognized as an adjustment to opening retained earnings at January 1, 2018. As a result, comparative prior periods have not been adjusted and continue to be reported under FASB ASC Topic 605, Revenue Recognition (“ASC 605”). See Note 14 of the Notes to the Unaudited Condensed Consolidated Financial Statements included herein for additional details surrounding the Company’s adoption of ASC 606. The Company’s policy surrounding revenue under ASC 605 is described in Note 2 of Item 8 of the Company’s 2017 Form 10-K. The policies described herein refer to those in effect as of January 1, 2018. The Company’s revenue recognition policies are established in accordance with the Revenue Recognition topics of ASC 606, and accordingly, revenue is recognized when control of the promised goods or services is transferred to our clients, in an amount that reflects the consideration we expect to be entitled to in exchange for those goods or services. The primary source of the Company’s revenue is from agency arrangements in the form of fees for services performed, commissions, and from performance incentives or bonuses, depending on the terms of the client contract. In all circumstances, revenue is only recognized when collection is reasonably assured. Certain of the Company’s contractual arrangements have more than one performance obligation. For such arrangements, revenue is allocated to each performance obligation based on its relative stand-alone selling price. Stand-alone selling prices are determined based on the prices charged to clients or using expected cost plus margin. Revenue is recognized net of sales and other taxes due to be collected and remitted to governmental authorities. The Company’s contracts typically provide for termination by either party within 30 to 90 days. Although payment terms vary by client, they are typically within 30 to 60 days. In addition, the Company generally has the right to payment for all services provided through the end of the contract or termination date. Although certain of our performance obligations are recognized at a point in time, we typically satisfy our performance obligations over time, as services are performed. Point in time recognition primarily relates to certain commission-based contracts, which are recognized upon the placement of advertisements in various media when the Company has no further performance obligation. Fees for services are typically recognized using input methods that correspond with efforts incurred to date in relation to total estimated efforts to complete the contract. Within each contract, we identify whether the Company is principal or agent at the performance obligation level. In arrangements where the Company has substantive control over the service before transferring it to the client and is primarily responsible for integrating the services into the final deliverables, we act as principal. In these arrangements, revenue is recorded at the gross amount billed. Accordingly, for these contracts the Company has included reimbursed expenses in revenue. In other arrangements where a third-party supplier, rather than the Company is primarily responsible for the integration of services into the final deliverables for our client, then we generally act as agent and record revenue equal to the net amount retained, when the fee or commission is earned. We have determined that we primarily act as agent for production and media buying services. A small portion of the Company’s contractual arrangements with clients include performance incentive provisions, which allow the Company to earn additional revenues as a result of its performance relative to both quantitative and qualitative goals. Incentive compensation is primarily estimated using the most likely amount method and is included in revenue up to the amount that is not expected to result in a reversal of a significant amount of cumulative revenue recognized. We recognize revenue related to performance incentives as we satisfy the performance obligation to which the performance incentives are related. Disaggregated Revenue Data The Company provides a broad range of services to a large base of clients across the full spectrum of industry verticals on a global basis. The primary source of revenue is from agency arrangements in the form of fees for services performed, commissions, and from performance incentives or bonuses. Certain clients may engage with the Company in various geographic locations, across multiple disciplines, and through multiple Partner Firms. Representation of a client rarely means that MDC handles marketing communications for all brands or product lines of the client in every geographical location. The Company’s Partner firms often cooperate with one another through referrals and the sharing of both services and expertise, which enables MDC to service clients’ varied marketing needs by crafting custom integrated solutions. Additionally, the Company maintains separate, independent operating companies to enable it to effectively manage potential conflicts of interest by representing competing clients across the MDC network. The following table presents revenue disaggregated by client industry vertical for the three and nine months ended September 30, 2018 and 2017 , and the impact of adoption of ASC 606: Three Months Ended September 30, 2018 2017 Industry Reportable Segment As reported Adjustment to exclude impact of Adoption of ASC 606 Adjusted Food & Beverage All $ 80,919 $ (1,212 ) $ 79,707 $ 80,247 Retail All 40,421 (4,457 ) 35,964 43,202 Consumer Products All 40,124 1,136 41,260 43,825 Communications All 46,779 8,337 55,116 46,649 Automotive All 21,282 734 22,016 30,547 Technology All 26,005 171 26,176 25,748 Healthcare All 33,751 84 33,835 31,181 Financials All 30,378 283 30,661 26,631 Transportation and Travel/Lodging All 19,357 1,333 20,690 14,412 Other All 36,814 1,763 38,577 33,358 $ 375,830 $ 8,172 $ 384,002 $ 375,800 Nine Months Ended September 30, 2018 2017 Industry Reportable Segment As reported Adjustment to exclude impact of Adoption of ASC 606 Adjusted Food & Beverage All $ 234,203 $ 4,171 $ 238,374 $ 225,873 Retail All 116,832 (2,685 ) 114,147 134,993 Consumer Products All 118,097 362 118,459 119,554 Communications All 128,232 20,519 148,751 150,703 Automotive All 67,070 6,809 73,879 96,832 Technology All 71,085 (139 ) 70,946 72,620 Healthcare All 101,753 603 102,356 92,380 Financials All 83,079 1,194 84,273 73,777 Transportation and Travel/Lodging All 53,021 2,109 55,130 42,187 Other All 109,169 6,233 115,402 102,113 $ 1,082,541 $ 39,176 $ 1,121,717 $ 1,111,032 MDC has historically largely focused where the Company was founded in North America, the largest market for its services in the world. In recent years the Company has expanded its global footprint to support clients looking for help to grow their businesses in new markets. Today, MDC’s Partner Firms are located in the United States, Canada, and an additional thirteen countries around the world. In the past, some clients have responded to weakening economic conditions with reductions to their marketing budgets, which included discretionary components that are easier to reduce in the short term than other operating expenses. The following table presents revenue disaggregated by geography: Three Months Ended September 30, 2018 2017 Geographic Location Reportable Segment As reported Adjustment to exclude impact of Adoption of ASC 606 Adjusted United States All $ 296,544 $ 1,899 $ 298,443 $ 289,701 Canada All 32,132 286 32,418 31,418 Other All 47,154 5,987 53,141 54,681 $ 375,830 $ 8,172 $ 384,002 $ 375,800 Nine Months Ended September 30, 2018 2017 Geographic Location Reportable Segment As reported Adjustment to exclude impact of Adoption of ASC 606 Adjusted United States All $ 848,336 $ 16,940 $ 865,276 $ 868,847 Canada All 91,597 (2,352 ) 89,245 88,471 Other All 142,608 24,588 167,196 153,714 $ 1,082,541 $ 39,176 $ 1,121,717 $ 1,111,032 See Note 12 of the Notes to the Unaudited Condensed Consolidated Financial Statements for information related to the nature of the services offered by the Company’s reportable segments. Contract assets and liabilities Contract assets consist of fees and reimbursable outside vendor costs incurred on behalf of clients when providing advertising, marketing and corporate communications services that have not yet been invoiced to clients. Unbilled service fees were $92,900 and $54,177 at September 30, 2018 and December 31, 2017 , respectively, and are included as a component of accounts receivable on the unaudited condensed consolidated balance sheets. Outside vendor costs incurred on behalf of clients which have yet to be invoiced were $59,317 and $31,146 at September 30, 2018 and December 31, 2017 , respectively, and are included on the unaudited condensed consolidated balance sheets as expenditures billable to clients. Such amounts are invoiced to clients at various times over the course of the production process. Contract liabilities consist of fees billed to clients in excess of fees recognized as revenue and are classified as advance billings on the Company’s unaudited condensed consolidated balance sheets. Advance billings at September 30, 2018 and December 31, 2017 were $182,305 and $148,133 , respectively. The increase in the advance billings balance of $34,172 for the nine months ended September 30, 2018 is primarily driven by cash payments received or due in advance of satisfying our performance obligations, offset by $85,665 of revenues recognized that were included in the advance billings balances as of December 31, 2017 and reductions due to the incurrence of third-party costs. Changes in the contract asset and liability balances during the nine months ended September 30, 2018 and December 31, 2017 were not materially impacted by write offs, impairment losses or any other factors. Practical expedients In adopting ASC 606, the Company applied the practical expedient to not disclose information about remaining performance obligations that have original expected durations of one year or less. Amounts related to those performance obligations with expected durations of more than one year are immaterial.

Loss Per Common Share

Loss Per Common Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Loss Per Common Share	Loss) Per Common Share The following table sets forth the computation of basic and diluted income (loss) per common share: Three Months Ended Nine Months Ended 2018 2017 2018 2017 Numerator Net income (loss) attributable to MDC Partners Inc. $ (16,125 ) $ 18,493 $ (42,135 ) $ 19,180 Accretion on convertible preference shares (2,109 ) (1,948 ) (6,204 ) (4,365 ) Net income allocated to convertible preference shares — (2,408 ) — (1,782 ) Numerator for basic income (loss) per common share - Net income (loss) attributable to MDC Partners Inc. common shareholders (18,234 ) 14,137 (48,339 ) 13,033 Adjustment to net income allocated to convertible preference shares — 13 — 9 Numerator for diluted income (loss) per common share- Net income (loss) attributable to MDC Partners Inc. common shareholders $ (18,234 ) $ 14,150 $ (48,339 ) $ 13,042 Denominator Denominator for basic income (loss) per common share - weighted average common shares 57,498,661 57,566,707 57,117,797 53,915,536 Impact of stock options and non-vested stock under employee stock incentive plans — 376,373 — 312,672 Denominator for diluted income (loss) per common share - adjusted weighted shares and assumed conversions 57,498,661 57,943,080 57,117,797 54,228,208 Basic income (loss) per common share $ (0.32 ) $ 0.25 $ (0.85 ) $ 0.24 Diluted income (loss) per common share $ (0.32 ) $ 0.24 $ (0.85 ) $ 0.24 Anti-dilutive stock awards 1,524,218 - 1,524,218 - Restricted stock and restricted stock unit awards of 1,015,637 and 1,443,921 for the three and nine months ended September 30, 2018 and 2017 , respectively, which are contingent upon the Company meeting a cumulative three year earnings target (2018, 2019 and 2020) and contingent upon continued employment, are excluded from the computation of diluted income per common share as the contingency was not satisfied at September 30, 2018 or 2017 . In addition, there were 95,000 shares of Preference Shares outstanding which were convertible into 10,755,602 and 9,936,514 Class A common shares at September 30, 2018 and 2017 , respectively. These Preference Shares were anti-dilutive for each period presented in the table above and are therefore excluded from the diluted income (loss) per common share calculation.

Acquisitions and Dispositions

Acquisitions and Dispositions	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Acquisitions and Dispositions	Acquisitions and Dispositions 2018 Acquisitions On September 7, 2018, a subsidiary of the Company purchased 100% interests of OneChocolate Communications Limited and OneChocolate Communications LLC, PR (“OneChocolate”) a digital marketing consultancy headquartered in London, UK, for an aggregate purchase price of $3,231 (subject to a working capital adjustment) and additional deferred acquisition payments estimated to be a nominal amount. OneChocolate’s results are reflected in the Allison & Partners operating segment which is included in the Specialist Communications reportable segment which had an immaterial impact on our results. On July 1, 2018, the Company acquired the remaining 14.87% and 3% of membership interests of Doner Partners, LLC and Source Marketing LLC respectively for an aggregate purchase price of $7,618 , comprised of a closing cash payment of $3,279 and additional payments to be made on or before April 2020. As a result of the transaction, the Company reduced noncontrolling interest by $11,946 and redeemable noncontrolling interest by $933 . On April 2, 2018, the Company purchased 51% of the membership interests of Instrument LLC (“Instrument”), a digital creative agency based in Portland, Oregon, for an aggregate estimated purchase price of $35,591 . The acquisition is expected to facilitate the Company’s growth and help to build its portfolio of modern, innovative and digital-first agencies. The purchase price consisted of a cash payment of $28,561 and the issuance of 1,011,561 shares of the Company’s Class A subordinate voting stock with an acquisition date fair value of $7,030 . The Company issued these shares in a transaction exempt from the registration requirements of the Securities Act of 1933, as amended, pursuant to Section 4(a)(2) of the Securities Act. The preliminary purchase price allocation for Instrument resulted in tangible assets of $10,304 , identifiable intangibles of $23,130 , consisting primarily of customer lists and a trade name, and goodwill of $29,514 . In addition, the Company has recorded $27,357 as the fair value of noncontrolling interests, which was derived from the Company’s purchase price less a discount related to the noncontrolling parties’ lack of control. The identified assets have a weighted average useful life of approximately six years and will be amortized in a manner represented by the pattern in which the economic benefits of such assets are expected to be realized. The goodwill is tax deductible. Instruments’ results are included in the All Other category from a segment reporting perspective. The Company has a controlling financial interest in Instrument through its majority voting interest, and as such, has aggregated the acquired Partner Firm’s financial data into the Company’s consolidated financial statements. The operating results of Instrument in the current and prior year are not material. Effective January 1, 2018, the Company acquired the remaining 24.5% ownership interest of Allison & Partners LLC for an aggregate purchase price of $10,023 , comprised of a closing cash payment of $300 and additional deferred acquisition payments with an estimated present value at the acquisition date of $9,723 . The deferred payments are based on the future financial results of the underlying business from 2017 to 2020 with final payments due in 2021. As a result of the transaction, the Company reduced redeemable noncontrolling interests by $8,857 . The difference between the purchase price and the noncontrolling interest of $1,166 was recorded in additional paid-in capital. 2017 Acquisitions In 2017, the Company entered into various non-material transactions in connection with certain of its majority-owned entities. As a result of the foregoing, the Company made total cash closing payments of $3,352 , increased fixed deferred consideration liability by $7,208 , reduced redeemable noncontrolling interests by $269 , reduced noncontrolling interests by $11,947 , and increased additional paid-in capital by $2,652 . In addition, a stock-based compensation charge of $997 has been recognized representing the consideration paid in excess of the fair value of the interest acquired. 2017 Dispositions In 2017, the Company sold all of its ownership interests in three subsidiaries resulting in recognition of a net loss on sale of business of $1,424 . The net assets reflected in the calculation of the net loss on sale was inclusive of goodwill of $17,593 . Goodwill was allocated to subsidiaries based on relative fair value of the sold subsidiaries compared to the fair value of the respective reporting units. Additionally, the Company recorded a reduction in noncontrolling interests of $10,657 . The Company expenses acquisition related costs as incurred. For the three and nine months ended September 30, 2018 and 2017 , $232 and $943 , respectively, and $216 and $693 respectively, of acquisition related costs were charged to operations.

Accounts Payable, Accruals and

Accounts Payable, Accruals and Other Liabilities	9 Months Ended
	Sep. 30, 2018
Accrued and Other Liabilities [Abstract]
Accounts Payable, Accruals and Other Liabilities	When acquiring less than 100% ownership of an entity, the Company may enter into agreements that give the Company an option to purchase, or require the Company to purchase, the incremental ownership interests under certain circumstances. Where the option to purchase the incremental ownership is within the Company’s control, the amounts are recorded as noncontrolling interests in the equity section of the Company’s balance sheet. Where the incremental purchase may be required of the Company, the amounts are recorded as redeemable noncontrolling interests in mezzanine equity at their estimated acquisition date redemption value and adjusted at each reporting period for changes to their estimated redemption value through additional paid-in capital (but not less than their initial redemption value), except for foreign currency translation adjustments. On occasion, the Company may initiate a renegotiation to acquire an incremental ownership interest and the amount of consideration paid may differ materially from the balance sheet amounts. Noncontrolling Interests Changes in amounts due to noncontrolling interest holders included in accrued and other liabilities for the year ended December 31, 2017 and nine months ended September 30, 2018 were as follows: Noncontrolling Balance, December 31, 2016 $ 4,154 Income attributable to noncontrolling interests 15,375 Distributions made (8,865 ) Other (1) 366 Balance, December 31, 2017 $ 11,030 Income attributable to noncontrolling interests 5,900 Distributions made (10,410 ) Other (1) 196 Balance, September 30, 2018 $ 6,716 (1) Other consists primarily of business acquisitions, sale of a business, step-up transactions, and cumulative translation adjustments. Changes in the Company’s ownership interests in our less than 100% owned subsidiaries during the three and nine months ended September 30, 2018 and 2017 were as follows: Three Months Ended September 30, 2018 Nine Months Ended September 30, 2018 2018 2017 2018 2017 Net income (loss) attributable to MDC Partners Inc. $ (16,125 ) $ 18,493 $ (42,135 ) $ 19,180 Transfers from the noncontrolling interest: Increase (Decrease) in MDC Partners Inc. paid-in capital for purchase of equity interests in excess of Redeemable Noncontrolling Interests and Noncontrolling Interests 4,975 (337 ) 3,809 2,315 Net transfers from noncontrolling interests $ 4,975 $ (337 ) $ 3,809 $ 2,315 Change from net income (loss) attributable to MDC Partners Inc. and transfers to noncontrolling interests $ (11,150 ) $ 18,156 $ (38,326 ) $ 21,495 Redeemable Noncontrolling Interests The following table presents changes in redeemable noncontrolling interests: Nine Months Ended September 30, 2018 Year Ended December 31, 2017 Beginning Balance $ 62,886 $ 60,180 Redemptions (9,791 ) (910 ) Granted — 1,666 Changes in redemption value 4,409 1,498 Currency translation adjustments (311 ) 452 Ending Balance $ 57,193 $ 62,886 The noncontrolling shareholders’ ability to exercise any such option right is subject to the satisfaction of certain conditions, including conditions requiring notice in advance of exercise and specific employment termination conditions. In addition, these rights cannot be exercised prior to specified staggered exercise dates. The exercise of these rights at their earliest contractual date would result in obligations of the Company to fund the related amounts during 2018 to 2023 . It is not determinable, at this time, if or when the owners of these rights will exercise all or a portion of these rights. The amount payable by the Company to purchase the noncontrolling shareholders’ incremental ownership interests if exercised is dependent on various valuation formulas and on future events, such as the average earnings of the relevant subsidiary through the date of exercise, the growth rate of the earnings of the relevant subsidiary during that period and, in some cases, the currency exchange rate at the date of payment. The ultimate amount payable relating to these transactions will vary because it is dependent on the future results of operations of the subject businesses and the timing of when these rights are exercised. The redeemable noncontrolling interest of $57,193 as of September 30, 2018 , consists of $14,320 assuming that the subsidiaries perform over the relevant future periods at their discounted cash flows earnings level and such rights are exercised, $38,540 upon termination of such owner’s employment with the applicable subsidiary or death and $4,333 representing the initial redemption value (required floor) recorded for certain acquisitions in excess of the amount the Company would have to pay should the Company acquire the remaining ownership interests for such subsidiaries. These adjustments will not impact the calculation of earnings (loss) per share if the redemption values are less than the estimated fair values. For the nine months ended September 30, 2018 and 2017 , there was no related impact on the Company’s loss per share calculation.

Debt

Debt	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Debt	Debt The Company’s indebtedness was comprised as follows: September 30, December 31, 2017 Revolving credit agreement $ 102,990 $ — 6.50% Notes due 2024 900,000 900,000 Debt issuance costs (15,350 ) (17,587 ) 987,640 882,413 Obligations under capital leases 600 706 988,240 883,119 Less: Current portion of long-term debt 360 313 $ 987,880 $ 882,806 6.50% Notes On March 23, 2016 , MDC entered into an indenture (the “Indenture”) among MDC, its existing and future restricted subsidiaries that guarantee, are co-borrowers under, or grant liens to secure, the Credit Agreement, as guarantors (the “Guarantors”) and The Bank of New York Mellon, as trustee, relating to the issuance by MDC of $900,000 aggregate principal amount of the senior unsecured notes due 2024 (the “6.50% Notes”) . The 6.50% Notes were sold in a private placement in reliance on exceptions from registration under the Securities Act of 1933. The 6.50% Notes bear interest, payable semiannually in arrears on May 1 and November 1, at a rate of 6.50% per annum. The 6.50% Notes mature on May 1, 2024 , unless earlier redeemed or repurchased. MDC may, at its option, redeem the 6.50% Notes in whole at any time or in part from time to time, on and after May 1, 2019 , at varying prices based on the timing of the redemption. If MDC experiences certain kinds of changes of control (as defined in the Indenture), holders of the 6.50% Notes may require MDC to repurchase any 6.50% Notes held by them at a price equal to 101% of the principal amount of the 6.50% Notes plus accrued and unpaid interest. In addition, if MDC sells assets under certain circumstances, it must apply the proceeds from such sale and offer to repurchase the 6.50% Notes at a price equal to 100% of the principal amount plus accrued and unpaid interest. The Indenture includes covenants that are subject to a number of important limitations and exceptions. The 6.50% Notes are also subject to customary events of default, including a cross-payment default and cross-acceleration provision. The Company was in compliance with all covenants at September 30, 2018 . Revolving Credit Agreement MDC, Maxxcom Inc. (a subsidiary of MDC) and each of their subsidiaries party thereto entered into an amended and restated, $325,000 senior secured revolving credit agreement due May 3, 2021 (the “Credit Agreement”) with Wells Fargo Capital Finance, LLC, as agent, and the lenders from time to time party thereto. Advances under the Credit Agreement are to be used for working capital and general corporate purposes, in each case pursuant to the terms of the Credit Agreement. Capitalized terms used in this section and not otherwise defined have the meanings set forth in the Credit Agreement. Advances under the Credit Agreement bear interest as follows: (a)(i) LIBOR Rate Loans bear interest at the LIBOR Rate and (ii) Base Rate Loans bear interest at the Base Rate, plus (b) an applicable margin. The initial applicable margin for borrowing is 1.50% in the case of Base Rate Loans and 1.75% in the case of LIBOR Rate Loans. In addition to paying interest on outstanding principal under the Credit Agreement, MDC is required to pay an unused revolver fee to lenders under the Credit Agreement in respect of unused commitments thereunder. The Credit Agreement, which includes financial and non-financial covenants, is guaranteed by substantially all of MDC’s present and future subsidiaries, other than immaterial subsidiaries and subject to customary exceptions. The Company is currently in compliance with all of the terms and conditions of its Credit Agreement, and management believes, based on its current financial projections, that the Company will be in compliance with the covenants over the next twelve months. At September 30, 2018 , the Company had issued $5,248 of undrawn outstanding letters of credit. The foregoing descriptions of the Indenture and the Credit Agreement do not purport to be complete and are qualified in their entirety by reference to the full text of the agreements.

Share Capital

Share Capital	9 Months Ended
	Sep. 30, 2018
Share Capital [Abstract]
Share Capital	Share Capital The Company’s issued and outstanding share capital is as follows: Series 4 Convertible Preference Shares A total of 95,000 , non-voting convertible preference shares, all of which were issued and outstanding as of September 30, 2018 and December 31, 2017 . See Note 9 of the Notes to the Unaudited Condensed Consolidated Financial Statements included herein for further information. Class A Common Shares (“Class A Shares”) An unlimited number of subordinate voting shares, carrying one vote each, entitled to dividends equal to or greater than Class B Shares, convertible at the option of the holder into one Class B Share for each Class A Share after the occurrence of certain events related to an offer to purchase all Class B shares. There were 57,511,684 and 56,371,376 Class A Shares issued and outstanding as of September 30, 2018 and December 31, 2017 , respectively. On June 6, 2018, the Company’s shareholders approved additional authorized Class A Shares of 1,250,000 to be added to the Company’s 2016 Stock Incentive Plan, for a total of 2,750,000 authorized Class A Shares under the 2016 Stock Incentive Plan. Class B Common Shares (“Class B Shares”) An unlimited number of voting shares, carrying 20 votes each, convertible at any time at the option of the holder into one Class A share for each Class B share. There were 3,755 Class B Shares issued and outstanding as of September 30, 2018 and December 31, 2017 .

Convertible Preference Shares (

Convertible Preference Shares (Notes)	9 Months Ended
	Sep. 30, 2018
Convertible Preference Shares [Abstract]
Convertible Preference Shares	Convertible Preference Shares On March 7, 2017 (the “Issue Date”), the Company issued 95,000 newly created Preference Shares to affiliates of The Goldman Sachs Group, Inc. (collectively, the “Purchaser”) pursuant to a $95,000 private placement. The Company received proceeds of approximately $90,123 , net of fees and estimated expenses, which were primarily used to pay down existing debt under the Company’s credit facility and for general corporate purposes. In connection with the closing of the transaction, effective March 7, 2017 , the Company increased the size of its Board of Directors (the “Board”) to seven members and appointed one nominee designated by the Purchaser. Except as required by law, the Preference Shares do not have voting rights, and are not redeemable at the option of the Purchaser. The holders of the Preference Shares have the right to convert their Preference Shares in whole at any time and from time to time, and in part at any time and from time to time after the ninetieth day following the original issuance date of the Preference Shares, into a number of Class A Shares equal to the then-applicable liquidation preference divided by the applicable conversion price at such time (the “Conversion Price”). The initial liquidation per share preference of each Preference Share is $1,000 . The initial Conversion Price will be $10.00 per Preference Share, subject to customary adjustments for share splits and combinations, dividends, recapitalizations and other matters, including weighted average anti-dilution protection for certain issuances of equity or equity-linked securities. The Preference Shares’ liquidation preference accretes at 8.0% per annum, compounded quarterly until the five-year anniversary of the Issue Date. During the nine months ended September 30, 2018 , the Preference Shares accreted at a monthly rate of approximately $7.40 per Preference Share, for total accretion of $6,204 , bringing the aggregate liquidation preference to $107,556 as of September 30, 2018 . The accretion is considered in the calculation of net income (loss) attributable to MDC Partners Inc. common shareholders. See Note 3 of the Notes to the Unaudited Condensed Consolidated Financial Statements included herein for further information. Holders of the Preference Shares are entitled to dividends in an amount equal to any dividends that would otherwise have been payable on the Class A Shares issued upon conversion of the Preference Shares. The Preference Shares are convertible at the Company’s option (i) on and after the two-year anniversary of the Issue Date, if the closing trading price of the Class A Shares over a specified period prior to conversion is at least 125% of the Conversion Price or (ii) after the fifth anniversary of the Issue Date, if the closing trading price of the Class A Shares over a specified period prior to conversion is at least equal to the Conversion Price. Following certain change in control transactions of the Company in which holders of Preference Shares are not entitled to receive cash or qualifying listed securities with a value at least equal to the liquidation preference plus accrued and unpaid dividends, (i) holders will be entitled to cash dividends on the liquidation preference at an increasing rate (beginning at 7% ), and (ii) the Company will have a right to redeem the Preference Shares for cash at the greater of their liquidation preference plus accrued and unpaid dividends or their as-converted value.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements A fair value measurement assumes a transaction to sell an asset or transfer a liability occurs in the principal market for the asset or liability or, in the absence of a principal market, the most advantageous market for the asset or liability. In determining fair value, the Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible as well as considers counterparty credit risk in its assessment of fair value. The hierarchy for observable and unobservable inputs used to measure fair value into three broad levels are described below: • Level 1 - Quoted prices (unadjusted) in active markets that are accessible at the measurement date for assets or liabilities. The fair value hierarchy gives the highest priority to Level 1 inputs. • Level 2 - Observable prices that are based on inputs not quoted on active markets, but corroborated by market data. • Level 3 - Unobservable inputs are used when little or no market data is available. The fair value hierarchy gives the lowest priority to Level 3 inputs. Financial Liabilities that are not Measured at Fair Value on a Recurring Basis The following table presents certain information for our financial liability that is not measured at fair value on a recurring basis at September 30, 2018 and December 31, 2017 : September 30, 2018 December 31, 2017 Carrying Fair Value Carrying Fair Value Liabilities: 6.50% Senior Notes due 2024 $ 900,000 $ 798,750 $ 900,000 $ 904,500 Our long-term debt includes fixed rate debt. The fair value of this instrument is based on quoted market prices. Financial Liabilities Measured at Fair Value on a Recurring Basis Contingent deferred acquisition consideration are recorded at the acquisition date fair value and adjusted at each reporting period. The estimated liability is determined in accordance with various contractual valuation formulas that may be dependent on future events, such as the growth rate of the earnings of the relevant subsidiary during the contractual period and, in some cases, the currency exchange rate as of the date of payment (Level 3). See Note 5 of the Notes to the Unaudited Condensed Consolidated Financial Statements for additional information regarding contingent deferred acquisition consideration. At September 30, 2018 and December 31, 2017 , the carrying amount of the Company’s financial instruments, including cash and cash equivalents, accounts receivable and accounts payable, approximated fair value because of their short-term maturity. The Company does not disclose the fair value for equity method investments or investments held at cost as it is not practical to estimate fair value since there is no readily available market data. Non-financial Assets and Liabilities that are Measured at Fair Value on a Nonrecurring Basis Certain non-financial assets 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. During the third quarter of 2018, the Company performed an interim goodwill impairment evaluation resulting in an impairment of goodwill. See Note 11 of the Notes to the Unaudited Condensed Consolidated Financial Statements for information related to the measurement of the fair value of goodwill and the impairment.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment Information	Segment Information The Company determines an operating segment if a component (i) engages in business activities from which it earns revenues and incurs expenses, (ii) has discrete financial information, and is (iii) regularly reviewed by the Chief Operating Decision Maker (“CODM”) to make decisions regarding resource allocation for the segment and assess its performance. Once operating segments are identified, the Company performs an analysis to determine if aggregation of operating segments is applicable. This determination is based upon a quantitative analysis of the expected and historic average long-term profitability for each operating segment, together with a qualitative assessment to determine if operating segments have similar operating characteristics. Due to changes in the Company’s internal management and reporting structure during 2018, reportable segment results for the 2017 periods presented have been recast to reflect the reclassification of certain businesses between segments. The changes were as follows: • Source Marketing, previously within the All Other category, was included within the Doner operating segment, which is aggregated into the Global Integrated Agencies reportable segment • Yamamoto, previously within the All Other category, was operationally merged with Civilian and is now included within the Domestic Creative Agencies reportable segment • Bruce Mau Design, Hello Design and Northstar Research Partners, previously within the All Other category, and Varick Media Management, previously within the Media Services reportable segment, were included into a newly-formed operating segment, Yes & Company, which is aggregated within the Media Services reportable segment In the third quarter of 2018, Forsman & Bodenfors and kbs+, both within the Global Integrated Agencies reportable segment, merged under the Forsman & Bodenfors name. The four reportable segments that result from applying the aggregation criteria are as follows: “Global Integrated Agencies”; “Domestic Creative Agencies”; “Specialist Communications”; and “Media Services.” In addition, the Company combines and discloses those operating segments that do not meet the aggregation criteria as “All Other.” The Company also reports corporate expenses, as further detailed below, as “Corporate.” All segments follow the same basis of presentation and accounting policies as those described throughout the Notes to the Unaudited Condensed Consolidated Financial Statements included herein, and Note 2 of the Company’s Form 10-K for the year ended December 31, 2017. • The Global Integrated Agencies reportable segment is comprised of the Company’s five global, integrated operating segments (72andSunny, Anomaly, Crispin Porter + Bogusky, Doner and Forsman & Bodenfors) serving multinational clients around the world. These operating segments share similar characteristics related to (i) the nature of their services; (ii) the type of global clients and the methods used to provide services; and (iii) the extent to which they may be impacted by global economic and geopolitical risks. In addition, these operating segments compete with each other for new business and from time to time have business move between them. The Company believes the historic and expected average long-term profitability is similar among the operating segments aggregated in the Global Integrated Agencies reportable segment. The operating segments within the Global Integrated Agencies reportable segment provides a range of different services for its clients, including strategy, creative and production for advertising campaigns across a variety of platforms (print, digital, social media, television broadcast). • The Domestic Creative Agencies reportable segment is comprised of five operating segments that are national advertising agencies (Colle + McVoy, Laird + Partners, Mono Advertising, Union and Yamamoto) leveraging creative capabilities at their core. These operating segments share similar characteristics related to (i) the nature of their services; (ii) the type of domestic client accounts and the methods used to provide services; and (iii) the extent to which they may be impacted by domestic economic and policy factors within North America. In addition, these operating segments compete with each other for new business and from time to time have business move between them. The Company believes the historic and expected average long- term profitability is similar among the operating segments aggregated in the Domestic Creative Agencies reportable segment. The operating segments within the Domestic Creative Agencies reportable segment provide similar services as the Global Integrated Agencies. • The Specialist Communications reportable segment is comprised of five operating segments that are each communications agencies (Allison & Partners, HL Group Partners, Hunter PR, KWT Global (formerly Kwittken), and Veritas) with core service offerings in public relations and related communications services. These operating segments share similar characteristics related to (i) the nature of their services; (ii) the type of client accounts and the methods used to provide services; (iii) the extent to which they may be impacted by domestic economic and policy factors within North America; and (iv) the regulatory environment regarding public relations and social media. In addition, these operating segments compete with each other for new business and from time to time have business move between them. The Company believes the historic and expected average long-term profitability is similar among the operating segments aggregated in the Specialist Communications reportable segment. The operating segments within the Specialist Communications reportable segment provide public relations and communications services including strategy, editorial, crisis support or issues management, media training, influencer engagement, and events management. • The Media Services reportable segment is comprised of two operating segments (MDC Media Partners and Yes & Company). These operating segments perform media buying and planning as their core competency across a range of platforms (out-of-home, paid search, social media, lead generation, programmatic, television broadcast). • All Other consists of the Company’s remaining operating segments that provide a range of diverse marketing communication services, but generally do not have similar services offerings or financial characteristics as those aggregated in the reportable segments. The All Other category includes 6Degrees Communications, Concentric Partners, Gale Partners, Kenna, Kingsdale, Instrument, Redscout, Relevent, Team, Vitro, and Y Media Labs. The nature of the specialist services provided by these operating segments vary among each other and from those operating segments aggregated into the reportable segments. This results in these operating segments having current and long-term performance expectations inconsistent with those operating segments aggregated in the reportable segments.The operating segments within All Other provide a range of diverse marketing communication services, including application and website design and development, data and analytics, experiential marketing, customer research management, creative services, and branding. • Corporate consists of corporate office expenses incurred in connection with the strategic resources provided to the operating segments, as well as certain other centrally managed expenses that are not fully allocated to the operating segments. These office and general expenses include (i) salaries and related expenses for corporate office employees, including employees dedicated to supporting the operating segments, (ii) occupancy expenses relating to properties occupied by all corporate office employees, (iii) other office and general expenses including professional fees for the financial statement audits and other public company costs, and (iv) certain other professional fees managed by the corporate office. Additional expenses managed by the corporate office that are directly related to the operating segments are allocated to the appropriate reportable segment and the All Other category. Three Months Ended Nine Months Ended 2018 2017 2018 2017 Revenue: Global Integrated Agencies $ 177,398 $ 196,974 $ 510,360 $ 585,290 Domestic Creative Agencies 24,798 28,096 75,503 77,325 Specialist Communications 42,636 40,670 129,724 125,470 Media Services 35,022 38,315 104,460 122,207 All Other 95,976 71,745 262,494 200,740 Total $ 375,830 $ 375,800 $ 1,082,541 $ 1,111,032 Operating profit (loss): Global Integrated Agencies* $ 2,633 $ 20,069 $ 6,099 $ 33,240 Domestic Creative Agencies 5,532 6,627 14,451 15,411 Specialist Communications 4,677 4,775 14,471 13,423 Media Services 1,387 2,555 407 9,169 All Other 6,413 13,920 28,565 29,740 Corporate (18,024 ) (10,726 ) (45,236 ) (28,983 ) Total $ 2,618 $ 37,220 $ 18,757 $ 72,000 Other income (expense): Interest expense and finance charges, net (17,063 ) (16,258 ) (50,005 ) (48,309 ) Foreign exchange transaction gain (loss) 3,275 9,913 (9,934 ) 18,798 Other, net 189 (1,264 ) 1,222 (986 ) Income (loss) before income taxes and equity in earnings (losses) of non-consolidated affiliates (10,981 ) 29,611 (39,960 ) 41,503 Income tax expense (benefit) 2,986 9,049 (3,367 ) 17,659 Income (loss) before equity in earnings (losses) of non-consolidated affiliates (13,967 ) 20,562 (36,593 ) 23,844 Equity in earnings of non-consolidated affiliates 300 1,422 358 1,924 Net income (loss) (13,667 ) 21,984 (36,235 ) 25,768 Net income attributable to the noncontrolling interest (2,458 ) (3,491 ) (5,900 ) (6,588 ) Net income (loss) attributable to MDC Partners Inc. $ (16,125 ) $ 18,493 $ (42,135 ) $ 19,180 * A goodwill and other asset impairment charge of $21,008 was recognized within the Global Integrated Agencies reportable segment in the three and nine months ended of 2018. See Note 11 of the Notes to the Unaudited Condensed Consolidated Financial Statements for information related to the impairment. Three Months Ended Nine Months Ended 2018 2017 2018 2017 Depreciation and amortization: Global Integrated Agencies $ 5,154 $ 6,365 $ 18,499 $ 17,913 Domestic Creative Agencies 396 375 1,185 1,172 Specialist Communications 1,134 1,220 3,163 3,657 Media Services 781 1,011 2,315 3,232 All Other 3,470 2,026 9,467 6,078 Corporate 199 255 583 864 Total $ 11,134 $ 11,252 $ 35,212 $ 32,916 Stock-based compensation: Global Integrated Agencies $ 3,360 $ 3,840 $ 8,492 $ 9,912 Domestic Creative Agencies 175 187 945 534 Specialist Communications 43 659 542 2,264 Media Services 112 161 282 495 All Other 932 1,056 2,532 2,066 Corporate 1,620 477 4,089 1,599 Total $ 6,242 $ 6,380 $ 16,882 $ 16,870 Capital expenditures: Global Integrated Agencies $ 2,418 $ 1,950 $ 7,875 $ 17,645 Domestic Creative Agencies 371 367 860 980 Specialist Communications 743 206 3,207 673 Media Services 428 2,308 845 4,107 All Other 1,551 2,317 2,380 4,896 Corporate 32 1 65 4 Total $ 5,543 $ 7,149 $ 15,232 $ 28,305 The Company’s CODM does not use segment assets to allocate resources or to assess performance of the segments and therefore, total segment assets have not been disclosed. See Note 2 of the Notes to the Unaudited Condensed Consolidated Financial Statements included herein for a summary of the Company’s revenue by geographic region for three and nine months ended September 30, 2018 and 2017 .

Commitments, Contingencies and

Commitments, Contingencies and Guarantees	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments, Contingencies and Guarantees	Commitments, Contingencies, and Guarantees Legal Proceedings. The Company’s operating entities are involved in legal proceedings of various types. While any litigation contains an element of uncertainty, the Company has no reason to believe that the outcome of such proceedings or claims will have a material adverse effect on the financial condition or results of operations of the Company. Dismissal of Class Action Litigation in Canada. On August 7, 2015, Roberto Paniccia issued a Statement of Claim in the Ontario Superior Court of Justice in the City of Brantford, Ontario seeking to certify a class action suit naming the following as defendants: MDC, former CEO Miles S. Nadal, former CAO Michael C. Sabatino, CFO David Doft and BDO U.S.A. LLP. The Plaintiff alleged violations of section 138.1 of the Ontario Securities Act (and equivalent legislation in other Canadian provinces and territories) as well as common law misrepresentation based on allegedly materially false and misleading statements in the Company’s public statements, as well as omitting to disclose material facts with respect to the SEC investigation. On June 4, 2018, the Court dismissed (with costs) the putative class members’ motion for leave to proceed with the Plaintiff’s claims for misrepresentations of material facts pursuant to the Ontario Securities Act. Following the Court’s decision, on June 18, 2018, the Plaintiff, MDC and each of the other defendants consented to the dismissal of the action with prejudice (and without costs). In July 2018, the Court entered a final order approving the dismissal of this claim. Antitrust Subpoena. In 2016, one of the Company’s subsidiary agencies received a subpoena from the U.S. Department of Justice Antitrust Division (the “DOJ”) concerning the DOJ’s ongoing investigation of production bidding practices in the advertising industry. The Company and its subsidiary are fully cooperating with this confidential investigation. Specifically, the Company and its subsidiary are providing information and engaging in discussions with the DOJ, including preliminary discussions regarding the feasibility of a potential settlement with the DOJ. However, there can be no assurance as to the timing of any settlement or that a settlement will be reached on any particular terms or at all. Moreover, the DOJ may determine to expand the scope of its investigation or initiate a proceeding to bring charges against our subsidiary or one or more members of the subsidiary agency’s former management. The DOJ may also seek to impose monetary sanctions. Deferred Acquisition Consideration and Options to Purchase. See Note 5 and 8 of the Notes to the Unaudited Condensed Consolidated Financial Statements for information regarding potential payments associated with deferred acquisition consideration and the acquisition of noncontrolling shareholders’ ownership interest in subsidiaries. Natural Disasters. Certain of the Company’s operations are located in regions of the United States which typically are subject to hurricanes. During the nine months ended September 30, 2018 and 2017 , these operations did not incur any material costs related to damages resulting from hurricanes. Guarantees . Generally, the Company has indemnified the purchasers of certain assets in the event that a third party asserts a claim against the purchaser that relates to a liability retained by the Company. These types of indemnification guarantees typically extend for a number of years. Historically, the Company has not made any significant indemnification payments under such agreements and no amount has been accrued in the accompanying consolidated financial statements with respect to these indemnification guarantees. The Company continues to monitor the conditions that are subject to guarantees and indemnifications to identify whether it is probable that a loss has occurred and would recognize any such losses under any guarantees or indemnifications in the period when those losses are probable and estimable. Commitments. At September 30, 2018 , the Company had $5,248 of undrawn letters of credit. In addition, the Company has commitments to fund investments in an aggregate amount of $60 .

New Accounting Pronouncements

New Accounting Pronouncements	9 Months Ended
	Sep. 30, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New Accounting Pronouncements	New Accounting Pronouncements Adopted In The Current Reporting Period Effective January 1, 2018, the Company adopted FASB ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”). ASC 606 was applied using the modified retrospective method, with the cumulative effect of the initial adoption being recognized as an adjustment to opening retained earnings at January 1, 2018. As a result, comparative prior periods have not been adjusted and continue to be reported under FASB ASC Topic 605, Revenue Recognition (“ASC 605”). The following represents changes to the Company’s policies resulting from the adoption of ASC 606: i. Under the guidance in effect through December 31, 2017, performance incentives were recognized in revenue when specific quantitative goals were achieved, or when the Company’s performance against qualitative goals was determined by the client. Under ASC 606, the Company now estimates the amount of the incentive that will be earned at the inception of the contract and recognizes such incentive over the term of the contract. This results in an acceleration of revenue recognition for certain contract incentives compared to ASC 605. ii. Under the guidance in effect through December 31, 2017, non-refundable retainer fees were generally recognized on a straight-line basis over the term of the specific customer arrangement. Under ASC 606, an input method is typically used to measure progress and recognize revenue for these types of arrangements. This resulted in both the deferral and acceleration of revenue recognition in certain instances. iii. In certain client arrangements, the Company records revenue as a principal and includes within revenue certain third-party-pass-through and out-of-pocket costs, which are billed to clients in connection with the services provided. In other arrangements, the Company acts as an agent and records revenue equal to the net amount retained. The adoption of ASC 606 resulted in certain arrangements previously being accounted for as principal, now being accounted for as agent. As a result of these changes, the Company recorded a cumulative effect adjustment to increase opening accumulated deficit at January 1, 2018 by $1,170 . The following table summarizes the impact of adoption of ASC 606 on the unaudited condensed consolidated statement of operations during the three and nine months ended September 30, 2018 : Three Months Ended September 30, 2018 As Reported Adjustments Adjusted to Exclude Adoption of ASC 606 Revenue - Services $ 375,830 $ 8,172 $ 384,002 Costs of services sold $ 238,690 $ 14,122 $ 252,812 Operating profit (loss) $ 2,618 $ (5,950 ) $ (3,332 ) Net loss attributable to MDC Partners, Inc. common shareholders $ (18,234 ) $ (4,700 ) $ (22,934 ) Loss per common share - basic and diluted $ (0.32 ) $ (0.08 ) $ (0.40 ) Nine Months Ended September 30, 2018 As Reported Adjustments Adjusted to Exclude Adoption of ASC 606 Revenue - Services $ 1,082,541 $ 39,176 $ 1,121,717 Costs of services sold $ 735,110 $ 48,083 $ 783,193 Operating profit (loss) $ 18,757 $ (8,907 ) $ 9,850 Net loss attributable to MDC Partners, Inc. common shareholders $ (48,339 ) $ (6,085 ) $ (54,424 ) Loss per common share - basic and diluted $ (0.85 ) $ (0.10 ) $ (0.95 ) The impact on the balance sheets and shareholders’ deficit as of and for the nine months ended September 30, 2018 was immaterial. There was no effect on other comprehensive income (loss) and the statement of cash flows for the three and nine months ended September 30, 2018 and 2017. In May 2017, the FASB issued Accounting Standards Update (“ASU”) 2017-09, Compensation - Stock Compensation: Scope of Modification Accounting, which provides guidance concerning which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in ASC 718. This guidance is effective for annual and interim periods beginning after December 15, 2017. Amendments in this ASU are applied prospectively to any award modified on or after the adoption date. The Company adopted this guidance on January 1, 2018. The impact on the Company’s consolidated statement of financial position and results of operations was not material. In March 2017, the FASB issued ASU 2017-07, Compensation - Retirement Benefits, which requires the presentation of the service cost component of the net periodic pension and postretirement benefits costs in the same line item in the statement of operations as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of the net periodic pension and postretirement benefits costs are required to be presented as non-operating expenses in the statement of operations. This guidance is effective for annual periods beginning after December 15, 2017. The Company adopted this guidance on January 1, 2018. The impact on the Company’s consolidated statement of financial position and results of operations was not material. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows. This new guidance is intended to reduce diversity in practice regarding the classification of certain transactions in the statement of cash flows. This guidance is effective January 1, 2018 and requires a retrospective transition method. Prior to the Company’s adoption on January 1, 2018, all cash outflows for contingent consideration were classified as a financing activity. Effective January 1, 2018, the Company is now required to classify any cash payments made soon after the acquisition date of a business to settle a contingent consideration liability as cash outflows for investing activities. Cash payments which are not made soon after the acquisition date of a business to settle a contingent consideration liability are separated and classified as cash outflows for financing activities up to the amount of the contingent consideration liability recognized at the acquisition date and as cash outflows from operating activities for any excess. As a result, $36,570 of an acquisition-related contingent consideration payment of $89,126 , which was in excess of the liability initially recognized at the acquisition date, has been classified as a cash outflow within net cash provided by operating activities in the accompanying consolidated statement of cash flows for the nine months ended September 30, 2017 . There was no impact on the Company’s consolidated statement of financial position and results of operations. In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall: Recognition and Measurement of Financial Assets and Liabilities , which will require equity investments, except equity method investments, to be measured at fair value and any changes in fair value will be recognized in results of operations. This guidance is effective for annual and interim periods beginning after December 15, 2017. Additionally, this guidance provides for the recognition of the cumulative effect of retrospective application of the new standard in the period of initial application. The Company adopted this guidance on January 1, 2018. The impact on the Company’s consolidated statement of financial position and results of operations was not material. In January 2018, the FASB released guidance on the accounting for tax on the global intangible low-taxed income (“GILTI”) provisions of the Tax Cuts and Jobs Act (the “Act”). The GILTI provisions impose a tax on foreign income in excess of a deemed return on tangible assets of foreign corporations. The guidance indicates that either accounting for deferred taxes related to GILTI inclusions or treating any taxes on GILTI inclusions as period cost are both acceptable methods subject to an accounting policy election. During the quarter ended September 30, 2018 the Company has made a policy election to record tax effects of GILTI as an expense in the period incurred. Standard to be Adopted in Future Reporting Periods In February 2016, the FASB issued ASU 2016-02, Leases. The new guidance will require lessees to recognize a right-to-use asset and lease liability for most of its leases with a term of more than twelve months, including those classified as operating leases. The new guidance also requires additional quantitative and qualitative disclosures. This guidance will be effective for annual periods beginning after December 15, 2018, with early adoption permitted. In July 2018, the FASB issued ASU 2018-11 to provide an optional transition method allowing entities to apply the new lease standard at the adoption date with a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption (modified retrospective approach) as opposed to restating prior period financial statements. The Company plans to adopt the standard on its effective date of January 1, 2019 using the modified adoption method. The Company is in the process of reviewing its lease contracts, updating its accounting policies, and implementing a new system as well as processes and internal controls to support the Company’s financial reporting and disclosure under the new standard. The Company is not yet able to assess the full impact of the application of the new guidance; however, it expects that the recognition of a right-to-use asset and lease liability for operating leases will have a significant impact on its balance sheet.

Significant Accounting Policies

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
New Accounting Pronouncements	Adopted In The Current Reporting Period Effective January 1, 2018, the Company adopted FASB ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”). ASC 606 was applied using the modified retrospective method, with the cumulative effect of the initial adoption being recognized as an adjustment to opening retained earnings at January 1, 2018. As a result, comparative prior periods have not been adjusted and continue to be reported under FASB ASC Topic 605, Revenue Recognition (“ASC 605”). The following represents changes to the Company’s policies resulting from the adoption of ASC 606: i. Under the guidance in effect through December 31, 2017, performance incentives were recognized in revenue when specific quantitative goals were achieved, or when the Company’s performance against qualitative goals was determined by the client. Under ASC 606, the Company now estimates the amount of the incentive that will be earned at the inception of the contract and recognizes such incentive over the term of the contract. This results in an acceleration of revenue recognition for certain contract incentives compared to ASC 605. ii. Under the guidance in effect through December 31, 2017, non-refundable retainer fees were generally recognized on a straight-line basis over the term of the specific customer arrangement. Under ASC 606, an input method is typically used to measure progress and recognize revenue for these types of arrangements. This resulted in both the deferral and acceleration of revenue recognition in certain instances. iii. In certain client arrangements, the Company records revenue as a principal and includes within revenue certain third-party-pass-through and out-of-pocket costs, which are billed to clients in connection with the services provided. In other arrangements, the Company acts as an agent and records revenue equal to the net amount retained. The adoption of ASC 606 resulted in certain arrangements previously being accounted for as principal, now being accounted for as agent. As a result of these changes, the Company recorded a cumulative effect adjustment to increase opening accumulated deficit at January 1, 2018 by $1,170 . The following table summarizes the impact of adoption of ASC 606 on the unaudited condensed consolidated statement of operations during the three and nine months ended September 30, 2018 : Three Months Ended September 30, 2018 As Reported Adjustments Adjusted to Exclude Adoption of ASC 606 Revenue - Services $ 375,830 $ 8,172 $ 384,002 Costs of services sold $ 238,690 $ 14,122 $ 252,812 Operating profit (loss) $ 2,618 $ (5,950 ) $ (3,332 ) Net loss attributable to MDC Partners, Inc. common shareholders $ (18,234 ) $ (4,700 ) $ (22,934 ) Loss per common share - basic and diluted $ (0.32 ) $ (0.08 ) $ (0.40 ) Nine Months Ended September 30, 2018 As Reported Adjustments Adjusted to Exclude Adoption of ASC 606 Revenue - Services $ 1,082,541 $ 39,176 $ 1,121,717 Costs of services sold $ 735,110 $ 48,083 $ 783,193 Operating profit (loss) $ 18,757 $ (8,907 ) $ 9,850 Net loss attributable to MDC Partners, Inc. common shareholders $ (48,339 ) $ (6,085 ) $ (54,424 ) Loss per common share - basic and diluted $ (0.85 ) $ (0.10 ) $ (0.95 ) The impact on the balance sheets and shareholders’ deficit as of and for the nine months ended September 30, 2018 was immaterial. There was no effect on other comprehensive income (loss) and the statement of cash flows for the three and nine months ended September 30, 2018 and 2017. In May 2017, the FASB issued Accounting Standards Update (“ASU”) 2017-09, Compensation - Stock Compensation: Scope of Modification Accounting, which provides guidance concerning which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in ASC 718. This guidance is effective for annual and interim periods beginning after December 15, 2017. Amendments in this ASU are applied prospectively to any award modified on or after the adoption date. The Company adopted this guidance on January 1, 2018. The impact on the Company’s consolidated statement of financial position and results of operations was not material. In March 2017, the FASB issued ASU 2017-07, Compensation - Retirement Benefits, which requires the presentation of the service cost component of the net periodic pension and postretirement benefits costs in the same line item in the statement of operations as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of the net periodic pension and postretirement benefits costs are required to be presented as non-operating expenses in the statement of operations. This guidance is effective for annual periods beginning after December 15, 2017. The Company adopted this guidance on January 1, 2018. The impact on the Company’s consolidated statement of financial position and results of operations was not material. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows. This new guidance is intended to reduce diversity in practice regarding the classification of certain transactions in the statement of cash flows. This guidance is effective January 1, 2018 and requires a retrospective transition method. Prior to the Company’s adoption on January 1, 2018, all cash outflows for contingent consideration were classified as a financing activity. Effective January 1, 2018, the Company is now required to classify any cash payments made soon after the acquisition date of a business to settle a contingent consideration liability as cash outflows for investing activities. Cash payments which are not made soon after the acquisition date of a business to settle a contingent consideration liability are separated and classified as cash outflows for financing activities up to the amount of the contingent consideration liability recognized at the acquisition date and as cash outflows from operating activities for any excess. As a result, $36,570 of an acquisition-related contingent consideration payment of $89,126 , which was in excess of the liability initially recognized at the acquisition date, has been classified as a cash outflow within net cash provided by operating activities in the accompanying consolidated statement of cash flows for the nine months ended September 30, 2017 . There was no impact on the Company’s consolidated statement of financial position and results of operations. In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall: Recognition and Measurement of Financial Assets and Liabilities , which will require equity investments, except equity method investments, to be measured at fair value and any changes in fair value will be recognized in results of operations. This guidance is effective for annual and interim periods beginning after December 15, 2017. Additionally, this guidance provides for the recognition of the cumulative effect of retrospective application of the new standard in the period of initial application. The Company adopted this guidance on January 1, 2018. The impact on the Company’s consolidated statement of financial position and results of operations was not material. In January 2018, the FASB released guidance on the accounting for tax on the global intangible low-taxed income (“GILTI”) provisions of the Tax Cuts and Jobs Act (the “Act”). The GILTI provisions impose a tax on foreign income in excess of a deemed return on tangible assets of foreign corporations. The guidance indicates that either accounting for deferred taxes related to GILTI inclusions or treating any taxes on GILTI inclusions as period cost are both acceptable methods subject to an accounting policy election. During the quarter ended September 30, 2018 the Company has made a policy election to record tax effects of GILTI as an expense in the period incurred. Standard to be Adopted in Future Reporting Periods

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 30, 2018
By Location
Disaggregation of Revenue [Line Items]
Disaggregation of Revenue	The following table presents revenue disaggregated by geography: Three Months Ended September 30, 2018 2017 Geographic Location Reportable Segment As reported Adjustment to exclude impact of Adoption of ASC 606 Adjusted United States All $ 296,544 $ 1,899 $ 298,443 $ 289,701 Canada All 32,132 286 32,418 31,418 Other All 47,154 5,987 53,141 54,681 $ 375,830 $ 8,172 $ 384,002 $ 375,800 Nine Months Ended September 30, 2018 2017 Geographic Location Reportable Segment As reported Adjustment to exclude impact of Adoption of ASC 606 Adjusted United States All $ 848,336 $ 16,940 $ 865,276 $ 868,847 Canada All 91,597 (2,352 ) 89,245 88,471 Other All 142,608 24,588 167,196 153,714 $ 1,082,541 $ 39,176 $ 1,121,717 $ 1,111,032
Industry Vertical
Disaggregation of Revenue [Line Items]
Disaggregation of Revenue	The following table presents revenue disaggregated by client industry vertical for the three and nine months ended September 30, 2018 and 2017 , and the impact of adoption of ASC 606: Three Months Ended September 30, 2018 2017 Industry Reportable Segment As reported Adjustment to exclude impact of Adoption of ASC 606 Adjusted Food & Beverage All $ 80,919 $ (1,212 ) $ 79,707 $ 80,247 Retail All 40,421 (4,457 ) 35,964 43,202 Consumer Products All 40,124 1,136 41,260 43,825 Communications All 46,779 8,337 55,116 46,649 Automotive All 21,282 734 22,016 30,547 Technology All 26,005 171 26,176 25,748 Healthcare All 33,751 84 33,835 31,181 Financials All 30,378 283 30,661 26,631 Transportation and Travel/Lodging All 19,357 1,333 20,690 14,412 Other All 36,814 1,763 38,577 33,358 $ 375,830 $ 8,172 $ 384,002 $ 375,800 Nine Months Ended September 30, 2018 2017 Industry Reportable Segment As reported Adjustment to exclude impact of Adoption of ASC 606 Adjusted Food & Beverage All $ 234,203 $ 4,171 $ 238,374 $ 225,873 Retail All 116,832 (2,685 ) 114,147 134,993 Consumer Products All 118,097 362 118,459 119,554 Communications All 128,232 20,519 148,751 150,703 Automotive All 67,070 6,809 73,879 96,832 Technology All 71,085 (139 ) 70,946 72,620 Healthcare All 101,753 603 102,356 92,380 Financials All 83,079 1,194 84,273 73,777 Transportation and Travel/Lodging All 53,021 2,109 55,130 42,187 Other All 109,169 6,233 115,402 102,113 $ 1,082,541 $ 39,176 $ 1,121,717 $ 1,111,032

Loss Per Common Share (Tables)

Loss Per Common Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Schedule of Calculation of Numerator and Denominator in Earnings Per Share	The following table sets forth the computation of basic and diluted income (loss) per common share: Three Months Ended Nine Months Ended 2018 2017 2018 2017 Numerator Net income (loss) attributable to MDC Partners Inc. $ (16,125 ) $ 18,493 $ (42,135 ) $ 19,180 Accretion on convertible preference shares (2,109 ) (1,948 ) (6,204 ) (4,365 ) Net income allocated to convertible preference shares — (2,408 ) — (1,782 ) Numerator for basic income (loss) per common share - Net income (loss) attributable to MDC Partners Inc. common shareholders (18,234 ) 14,137 (48,339 ) 13,033 Adjustment to net income allocated to convertible preference shares — 13 — 9 Numerator for diluted income (loss) per common share- Net income (loss) attributable to MDC Partners Inc. common shareholders $ (18,234 ) $ 14,150 $ (48,339 ) $ 13,042 Denominator Denominator for basic income (loss) per common share - weighted average common shares 57,498,661 57,566,707 57,117,797 53,915,536 Impact of stock options and non-vested stock under employee stock incentive plans — 376,373 — 312,672 Denominator for diluted income (loss) per common share - adjusted weighted shares and assumed conversions 57,498,661 57,943,080 57,117,797 54,228,208 Basic income (loss) per common share $ (0.32 ) $ 0.25 $ (0.85 ) $ 0.24 Diluted income (loss) per common share $ (0.32 ) $ 0.24 $ (0.85 ) $ 0.24

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Schedule of Debt	The Company’s indebtedness was comprised as follows: September 30, December 31, 2017 Revolving credit agreement $ 102,990 $ — 6.50% Notes due 2024 900,000 900,000 Debt issuance costs (15,350 ) (17,587 ) 987,640 882,413 Obligations under capital leases 600 706 988,240 883,119 Less: Current portion of long-term debt 360 313 $ 987,880 $ 882,806

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value of Financial Liability Measured on a Non-recurring Basis	The following table presents certain information for our financial liability that is not measured at fair value on a recurring basis at September 30, 2018 and December 31, 2017 : September 30, 2018 December 31, 2017 Carrying Fair Value Carrying Fair Value Liabilities: 6.50% Senior Notes due 2024 $ 900,000 $ 798,750 $ 900,000 $ 904,500

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2018
Redeemable Noncontrolling Interest [Line Items]
Schedule of Segment Reporting Information, by Segment	Three Months Ended Nine Months Ended 2018 2017 2018 2017 Revenue: Global Integrated Agencies $ 177,398 $ 196,974 $ 510,360 $ 585,290 Domestic Creative Agencies 24,798 28,096 75,503 77,325 Specialist Communications 42,636 40,670 129,724 125,470 Media Services 35,022 38,315 104,460 122,207 All Other 95,976 71,745 262,494 200,740 Total $ 375,830 $ 375,800 $ 1,082,541 $ 1,111,032 Operating profit (loss): Global Integrated Agencies* $ 2,633 $ 20,069 $ 6,099 $ 33,240 Domestic Creative Agencies 5,532 6,627 14,451 15,411 Specialist Communications 4,677 4,775 14,471 13,423 Media Services 1,387 2,555 407 9,169 All Other 6,413 13,920 28,565 29,740 Corporate (18,024 ) (10,726 ) (45,236 ) (28,983 ) Total $ 2,618 $ 37,220 $ 18,757 $ 72,000 Other income (expense): Interest expense and finance charges, net (17,063 ) (16,258 ) (50,005 ) (48,309 ) Foreign exchange transaction gain (loss) 3,275 9,913 (9,934 ) 18,798 Other, net 189 (1,264 ) 1,222 (986 ) Income (loss) before income taxes and equity in earnings (losses) of non-consolidated affiliates (10,981 ) 29,611 (39,960 ) 41,503 Income tax expense (benefit) 2,986 9,049 (3,367 ) 17,659 Income (loss) before equity in earnings (losses) of non-consolidated affiliates (13,967 ) 20,562 (36,593 ) 23,844 Equity in earnings of non-consolidated affiliates 300 1,422 358 1,924 Net income (loss) (13,667 ) 21,984 (36,235 ) 25,768 Net income attributable to the noncontrolling interest (2,458 ) (3,491 ) (5,900 ) (6,588 ) Net income (loss) attributable to MDC Partners Inc. $ (16,125 ) $ 18,493 $ (42,135 ) $ 19,180 * A goodwill and other asset impairment charge of $21,008 was recognized within the Global Integrated Agencies reportable segment in the three and nine months ended of 2018. See Note 11 of the Notes to the Unaudited Condensed Consolidated Financial Statements for information related to the impairment. Three Months Ended Nine Months Ended 2018 2017 2018 2017 Depreciation and amortization: Global Integrated Agencies $ 5,154 $ 6,365 $ 18,499 $ 17,913 Domestic Creative Agencies 396 375 1,185 1,172 Specialist Communications 1,134 1,220 3,163 3,657 Media Services 781 1,011 2,315 3,232 All Other 3,470 2,026 9,467 6,078 Corporate 199 255 583 864 Total $ 11,134 $ 11,252 $ 35,212 $ 32,916 Stock-based compensation: Global Integrated Agencies $ 3,360 $ 3,840 $ 8,492 $ 9,912 Domestic Creative Agencies 175 187 945 534 Specialist Communications 43 659 542 2,264 Media Services 112 161 282 495 All Other 932 1,056 2,532 2,066 Corporate 1,620 477 4,089 1,599 Total $ 6,242 $ 6,380 $ 16,882 $ 16,870 Capital expenditures: Global Integrated Agencies $ 2,418 $ 1,950 $ 7,875 $ 17,645 Domestic Creative Agencies 371 367 860 980 Specialist Communications 743 206 3,207 673 Media Services 428 2,308 845 4,107 All Other 1,551 2,317 2,380 4,896 Corporate 32 1 65 4 Total $ 5,543 $ 7,149 $ 15,232 $ 28,305

New Accounting Pronouncements (

New Accounting Pronouncements (Tables)	9 Months Ended
	Sep. 30, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Schedule of Adoption of ASC 606	Nine Months Ended September 30, 2018 As Reported Adjustments Adjusted to Exclude Adoption of ASC 606 Revenue - Services $ 1,082,541 $ 39,176 $ 1,121,717 Costs of services sold $ 735,110 $ 48,083 $ 783,193 Operating profit (loss) $ 18,757 $ (8,907 ) $ 9,850 Net loss attributable to MDC Partners, Inc. common shareholders $ (48,339 ) $ (6,085 ) $ (54,424 ) Loss per common share - basic and diluted $ (0.85 ) $ (0.10 ) $ (0.95 ) The following table summarizes the impact of adoption of ASC 606 on the unaudited condensed consolidated statement of operations during the three and nine months ended September 30, 2018 : Three Months Ended September 30, 2018 As Reported Adjustments Adjusted to Exclude Adoption of ASC 606 Revenue - Services $ 375,830 $ 8,172 $ 384,002 Costs of services sold $ 238,690 $ 14,122 $ 252,812 Operating profit (loss) $ 2,618 $ (5,950 ) $ (3,332 ) Net loss attributable to MDC Partners, Inc. common shareholders $ (18,234 ) $ (4,700 ) $ (22,934 ) Loss per common share - basic and diluted $ (0.32 ) $ (0.08 ) $ (0.40 )

Significant Accounting Polici_2

Significant Accounting Policies (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Significant Accounting Policies [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	$ (10,981,000)	$ 29,611,000	$ (39,960,000)	$ 41,503,000
Tax Cuts and Jobs Act of 2017, Change in Tax Rate, Deferred Tax Asset, Income Tax Expense (Benefit)					$ (26,674,000)
Goodwill	843,180,000		$ 843,180,000		835,935,000
Effective Income Tax Rate Reconciliation, Percent			8.40%	42.50%
Income Tax Expense (Benefit), Change				$ 21,026,000
Unrecognized Tax Benefits	1,198,000		$ 1,198,000		1,556,000
Redeemable noncontrolling interest, redemptions, value			(9,791,000)		(910,000)
Beginning Balance			62,886,000	$ 60,180,000	60,180,000
Granted			0		1,666,000
Redeemable noncontrolling interest, changes in redemption value			4,409,000		1,498,000
Currency translation adjustments			(311,000)		452,000
Ending Balance	$ 57,193,000		$ 57,193,000		$ 62,886,000
Foreign Tax Authority [Member]
Significant Accounting Policies [Line Items]
Effective Income Tax Rate Reconciliation, Percent			26.30%
Minimum [Member]
Significant Accounting Policies [Line Items]
Unrecognized Tax Benefits, Decrease Resulting from Current Period Tax Positions			$ 400,000
Maximum [Member]
Significant Accounting Policies [Line Items]
Unrecognized Tax Benefits, Decrease Resulting from Current Period Tax Positions			$ 500,000

Significant Accounting Polici_3

Significant Accounting Policies (Details Textual) - USD ($)	May 01, 2024	May 03, 2016	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Significant Accounting Policies [Line Items]
Redeemable noncontrolling interest, changes in redemption value						$ 4,409,000		$ 1,498,000
Redeemable Noncontrolling Interest Currency Adjustments						(311,000)		452,000
Asset Impairment Charges			$ 21,008,000	$ 0		23,325,000	$ 0
Redeemable Noncontrolling Interest, Equity, Fair Value			57,193,000			57,193,000		62,886,000	$ 60,180,000
Net cash provided by (used in) operating activities						(31,729,000)	(14,450,000)
Payment for contingent consideration							89,126,000
Goodwill			843,180,000			843,180,000		835,935,000
Acquisition related costs			232,000	216,000		943,000	$ 693,000
Assets			1,729,724,000			1,729,724,000		1,698,892,000
Liabilities			1,850,471,000			$ 1,850,471,000		1,791,519,000
Effective tax rate (percent)						8.40%	42.50%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent						26.50%
Provisional tax expense								(26,674,000)
Deferred Tax Assets, Net			1,198,000			$ 1,198,000		1,556,000
Income Tax Expense (Benefit)			2,986,000	9,049,000		(3,367,000)	$ 17,659,000
Income Tax Expense (Benefit), Change							21,026,000
Redeemable noncontrolling interest, redemptions, value						(9,791,000)		(910,000)
Noncontrolling Interest, Increase from Business Combination						0		1,666,000
Common Class A
Significant Accounting Policies [Line Items]
Restricted stock grant date fair value								$ 3,353,939
Aggregate 2017 Step-up Transaction
Significant Accounting Policies [Line Items]
Noncontrolling Interest, Increase from Business Combination					$ 2,652,000
Minimum
Significant Accounting Policies [Line Items]
Unrecognized Tax Benefits, Decrease Resulting from Current Period Tax Positions						400,000
Maximum
Significant Accounting Policies [Line Items]
Unrecognized Tax Benefits, Decrease Resulting from Current Period Tax Positions						500,000
Wells Fargo Capital Finance, LLC
Significant Accounting Policies [Line Items]
Debt instrument, maturity date		May 3, 2021
Contingent Payment
Significant Accounting Policies [Line Items]
Change in contingent purchase price obligation			$ 11,003,000	$ (2,462,000)		$ 8,522,000	$ 12,152,000
Forecast | 6.50% Notes due 2024 | Wells Fargo Capital Finance, LLC
Significant Accounting Policies [Line Items]
Debt instrument, maturity date	May 1, 2024
Preferred Stock | Series 4 Convertible Preferred Stock
Significant Accounting Policies [Line Items]
Shares outstanding (shares)			95,000			95,000		95,000
Accounting Standards Update 2016-15
Significant Accounting Policies [Line Items]
Net cash provided by (used in) operating activities						$ (36,570,000)
Canada
Significant Accounting Policies [Line Items]
Effective tax rate (percent)						26.30%
Vesting over period [Member]
Significant Accounting Policies [Line Items]
Redeemable Noncontrolling Interest, Equity, Fair Value			$ 14,320			$ 14,320
Acquisition Value in excess of Redemption Value [Member]
Significant Accounting Policies [Line Items]
Redeemable Noncontrolling Interest, Equity, Fair Value			4,333			4,333
Termination, disability, or death [Member]
Significant Accounting Policies [Line Items]
Redeemable Noncontrolling Interest, Equity, Fair Value			38,540			38,540
Unidentified Reporting Unit [Member]
Significant Accounting Policies [Line Items]
Goodwill			$ 130,000,000			$ 130,000,000

Revenue - Disaggregation of Rev

Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Services	$ 375,830	$ 375,800	$ 1,082,541	$ 1,111,032
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Services	8,172		39,176
Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Services	384,002		1,121,717
United States
Disaggregation of Revenue [Line Items]
Services	296,544	289,701	848,336	868,847
United States | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Services	1,899		16,940
United States | Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Services	298,443		865,276
Canada
Disaggregation of Revenue [Line Items]
Services	32,132	31,418	91,597	88,471
Canada | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Services	286		(2,352)
Canada | Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Services	32,418		89,245
Other
Disaggregation of Revenue [Line Items]
Services	47,154	54,681	142,608	153,714
Other | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Services	5,987		24,588
Other | Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Services	53,141		167,196
Food & Beverage
Disaggregation of Revenue [Line Items]
Services	80,919	80,247	234,203	225,873
Food & Beverage | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Services	(1,212)		4,171
Food & Beverage | Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Services	79,707		238,374
Retail
Disaggregation of Revenue [Line Items]
Services	40,421	43,202	116,832	134,993
Retail | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Services	(4,457)		(2,685)
Retail | Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Services	35,964		114,147
Consumer Products
Disaggregation of Revenue [Line Items]
Services	40,124	43,825	118,097	119,554
Consumer Products | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Services	1,136		362
Consumer Products | Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Services	41,260		118,459
Communications
Disaggregation of Revenue [Line Items]
Services	46,779	46,649	128,232	150,703
Communications | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Services	8,337		20,519
Communications | Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Services	55,116		148,751
Automotive
Disaggregation of Revenue [Line Items]
Services	21,282	30,547	67,070	96,832
Automotive | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Services	734		6,809
Automotive | Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Services	22,016		73,879
Technology
Disaggregation of Revenue [Line Items]
Services	26,005	25,748	71,085	72,620
Technology | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Services	171		(139)
Technology | Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Services	26,176		70,946
Healthcare
Disaggregation of Revenue [Line Items]
Services	33,751	31,181	101,753	92,380
Healthcare | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Services	84		603
Healthcare | Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Services	33,835		102,356
Financials
Disaggregation of Revenue [Line Items]
Services	30,378	26,631	83,079	73,777
Financials | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Services	283		1,194
Financials | Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Services	30,661		84,273
Transportation and Travel/Lodging
Disaggregation of Revenue [Line Items]
Services	19,357	14,412	53,021	42,187
Transportation and Travel/Lodging | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Services	1,333		2,109
Transportation and Travel/Lodging | Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Services	20,690		55,130
Other
Disaggregation of Revenue [Line Items]
Services	36,814	$ 33,358	109,169	$ 102,113
Other | Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Services	1,763		6,233
Other | Calculated under Revenue Guidance in Effect before Topic 606
Disaggregation of Revenue [Line Items]
Services	$ 38,577		$ 115,402

Revenue - Contract Assets and L

Revenue - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Unbilled service fees	$ 92,900	$ 54,177
Unbilled outside vendor costs, billable to clients	59,317	31,146
Advance billings	182,305	$ 148,133
Increase in advance billings	34,172
Revenue recognized	$ 85,665

Loss Per Common Share (Details)

Loss Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Class of Stock [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,524,218	0	1,524,218	0
Net loss attributable to MDC Partners Inc.	$ (16,125)	$ 18,493	$ (42,135)	$ 19,180
Numerator
Numerator for basic income (loss) per common share - Net income (loss) attributable to MDC Partners Inc. common shareholders	(18,234)	14,137	(48,339)	13,033
Adjustment to Net Income, Allocated to Convertible Shares	0	13	0	9
Numerator for diluted income (loss) per common share- Net income (loss) attributable to MDC Partners Inc. common shareholders	$ (18,234)	$ 14,150	$ (48,339)	$ 13,042
Denominator
Denominator for basic income (loss) per common share - weighted average common shares	57,498,661	57,566,707	57,117,797	53,915,536
Weighted Average Number Diluted Shares Outstanding Adjustment	0	376,373	0	312,672
Denominator for diluted income (loss) per common share - adjusted weighted shares and assumed conversions	57,498,661	57,943,080	57,117,797	54,228,208
Income (loss) from continuing operations attributable to MDC Partners Inc. common shareholders (usd per share)	$ (0.32)	$ 0.25	$ (0.85)	$ 0.24
Income (loss) from continuing operations attributable to MDC Partners Inc. common shareholders (usd per share)	$ (0.32)	$ 0.24	$ (0.85)	$ 0.24
Series 4 Convertible Preferred Stock | Convertible Preferred Stock
Numerator
Accretion on and net income allocated to convertible preference shares	$ (2,109)	$ (1,948)	$ (6,204)	$ (4,365)
Net income allocated to convertible preference shares	0	(2,408)	$ 0
Series 4 Convertible Preferred Stock [Domain] | Convertible Preferred Stock
Numerator
Accretion on and net income allocated to convertible preference shares	$ (2,109)	$ (4,356)		(6,147)
Net income allocated to convertible preference shares				$ (1,782)

Loss Per Common Share (Details

Loss Per Common Share (Details Textual) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (shares)	1,524,218	0	1,524,218	0
Contingent Restricted Stock Units (RSUs)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (shares)	1,015,637			1,443,921
Series 4 Convertible Preferred Stock | Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares outstanding (shares)	95,000		95,000		95,000
Convertible preferred stock, shares issued upon conversion (shares)	10,755,602	9,936,514	10,755,602	9,936,514

Acquisitions and Dispositions (

Acquisitions and Dispositions (Details Textual) - USD ($)	Sep. 07, 2018	Jul. 01, 2018	Apr. 02, 2018	Jan. 01, 2018	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Redeemable Noncontrolling Interest, Equity, Fair Value					$ 57,193,000			$ 57,193,000		$ 62,886,000	$ 60,180,000
Noncontrolling interest, ownership percentage by Parent (percent)					100.00%			100.00%
Adjustments to deferred acquisition consideration included in share-based compensation					$ 3,076,000	$ 3,160,000		$ 7,758,000	$ 7,080,000
Goodwill					843,180,000			843,180,000		835,935,000
Deferred acquisition consideration					94,729,000			94,729,000		122,426,000
Business acquisitions and step-up transactions								19,219,000
Noncontrolling Interest, Increase from Business Combination								0		1,666,000
Stock-based compensation					6,242,000	6,380,000		16,882,000	16,870,000
Net loss attributable to MDC Partners Inc.					(16,125,000)	18,493,000		(42,135,000)	19,180,000
Change from net loss attributable to MDC Partners Inc. and transfers to noncontrolling interests					(11,150,000)	18,156,000		(38,326,000)	21,495,000
Changes in redemption value								(5,965,000)
Business Combination, Acquisition Related Costs					232,000	216,000		943,000	693,000
Aggregate 2018 Step-up Transaction [Member] [Member]
Business Acquisition [Line Items]
Closing cash payment			$ 3,279,000
Allison & Partners LLC
Business Acquisition [Line Items]
Remaining ownership interest acquired (percent)				24.50%
Aggregate purchase price				$ 10,023,000
Closing cash payment				300,000
Deferred acquisition consideration				9,723,000
Business acquisitions and step-up transactions				(8,857,000)
Noncontrolling Interest, Increase from Business Combination				$ 1,166,000
Aggregate 2017 Step-up Transaction
Business Acquisition [Line Items]
Closing cash payment							$ 3,352,000
Deferred acquisition consideration							7,208,000
Business acquisitions and step-up transactions							(11,947,000)
Noncontrolling Interest, Increase from Business Combination							2,652,000
Stock-based compensation							997,000
Reduction in noncontrolling interests							$ 269,000
Aggregate 2017 Dispositions [Member]
Business Acquisition [Line Items]
Loss on disposition of business										1,424,000
Goodwill, Written off Related to Sale of Business Unit										17,593
Noncontrolling Interest, Decrease from Deconsolidation										$ 10,657
Parent [Member]
Business Acquisition [Line Items]
Net loss attributable to MDC Partners Inc.								$ (42,135,000)
Common Stock [Member]
Business Acquisition [Line Items]
Stock Issued During Period, Shares, Acquisitions								1,011,561
Noncontrolling Interest
Business Acquisition [Line Items]
Changes in redemption value								$ (5,965,000)
OneChocolate [Domain]
Business Acquisition [Line Items]
Remaining ownership interest acquired (percent)	100.00%
Aggregate purchase price	$ 3,231,000
Doner [Domain]
Business Acquisition [Line Items]
Remaining ownership interest acquired (percent)		14.90%
Source [Domain]
Business Acquisition [Line Items]
Remaining ownership interest acquired (percent)		3.00%
Doner and Source [Domain]
Business Acquisition [Line Items]
Aggregate purchase price		$ 7,618,000
Business acquisitions and step-up transactions		(11,946,000)
Reduction in noncontrolling interests		$ 933,000
Instrument [Domain]
Business Acquisition [Line Items]
Remaining ownership interest acquired (percent)			51.00%
Business Combination, Consideration Transferred, Other			$ 10,304,000
Finite-lived Intangible Assets Acquired			23,130,000
Goodwill			29,514,000
Aggregate purchase price			35,591,000
Closing cash payment			28,561,000
Noncontrolling Interest, Increase from Business Combination			$ 27,357,000
Common Class A [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Stock Issued During Period, Value, Acquisitions								7,030,000	28,727,000
Common Class A [Member] | Instrument [Domain] | Common Stock [Member]
Business Acquisition [Line Items]
Stock Issued During Period, Shares, Acquisitions			1,011,561
Stock Issued During Period, Value, Acquisitions			$ 7,030,000
Contingent Payment [Member]
Business Acquisition [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability					$ 11,003,000	$ (2,462,000)		$ 8,522,000	$ 12,152,000

Acquisitions and Dispositions_2

Acquisitions and Dispositions (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Apr. 02, 2018
Business Combination, Acquisition Related Costs	$ 232	$ 216	$ 943	$ 693
Transfers to (from) the noncontrolling interest:
Noncontrolling interest, ownership percentage by Parent (percent)	100.00%		100.00%
Net loss attributable to MDC Partners Inc.	$ (16,125)	18,493	$ (42,135)	19,180
Business acquisitions and step-up transactions			19,219
Change from net loss attributable to MDC Partners Inc. and transfers to noncontrolling interests	(11,150)	18,156	(38,326)	21,495
MDC Partners Inc. Shareholders' Deficit
Transfers to (from) the noncontrolling interest:
Net loss attributable to MDC Partners Inc.			(42,135)
Adjustments to Additional Paid in Capital, Changes due to Business Combinations	$ 4,975	$ (337)	$ 3,809	$ 2,315
Instrument [Domain]
Business Acquisition, Percentage of Voting Interests Acquired					51.00%

Accruals and Other Liabilities

Accruals and Other Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Accrued and Other Liabilities [Abstract]
Beginning balance			$ 11,030	$ 4,154	$ 4,154
Income attributable to noncontrolling interests	$ 2,458	$ 3,491	5,900	6,588	15,375
Distributions made			(10,410)	$ (5,272)	(8,865)
Other			196		366
Ending balance	$ 6,716		$ 6,716		$ 11,030

Accruals and Other Liabilitie_2

Accruals and Other Liabilities (Details Textual) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Accrued and Other Liabilities [Abstract]
Accrued media	$ 173,222	$ 207,482
Amounts due to noncontrolling interest holders for their share of profits	6,716	11,030	$ 4,154
Outstanding checks	$ 54,320	$ 41,989

Debt (Details)

Debt (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Debt [Line Items]
Revolving credit agreement	$ 102,990,000	$ 0
Debt issuance costs	(15,350,000)	(17,587,000)
Debt, Long-term and Short-term, Combined Amount, Total	987,640,000	882,413,000
Obligations under capital leases	600,000	706,000
Debt and Capital Lease Obligations	988,240,000	883,119,000
Less current portion:	360,000	313,000
Long-term Debt, Excluding Current Maturities, Total	987,880,000	882,806,000
6.50% Notes due 2024
Debt [Line Items]
Senior Notes	$ 900,000,000	$ 900,000,000

Debt (Details Textual)

Debt (Details Textual) - USD ($)	May 01, 2024	May 03, 2016	Mar. 23, 2016	Jun. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
Debt [Line Items]
Amount outstanding under the line of credit					$ 102,990,000	$ 0
Amount of letters of credit outstanding					5,248,000
Wells Fargo Capital Finance, LLC
Debt [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity					$ 325,000
Debt instrument, maturity date		May 3, 2021
Wells Fargo Capital Finance, LLC | Base Rate
Debt [Line Items]
Interest rate, stated percentage		1.75%
Wells Fargo Capital Finance, LLC | Non-Prime Rate and Prime Rate on European Advances
Debt [Line Items]
Interest rate, stated percentage		1.50%
Senior Notes | 6.50% Notes due 2024
Debt [Line Items]
Aggregate principal amount			$ 900,000
Interest rate, stated percentage			6.50%	6.50%	6.50%
Debt instrument, maturity date			May 1, 2024
Debt instrument, redemption date, one				May 1, 2019
Percentage of redemption price, redemption date, latest for redemption at face amount (percent)					100.00%
Percentage of redemption price, change in ownership control (percent)					101.00%
Forecast | Wells Fargo Capital Finance, LLC | 6.50% Notes due 2024
Debt [Line Items]
Debt instrument, maturity date	May 1, 2024

Share Capital (Details Textual)

Share Capital (Details Textual)	Sep. 30, 2018voteshares	Dec. 31, 2017shares	Jun. 01, 2016shares
Preferred Stock | Series 4 Convertible Preferred Stock
Share Capital [Line Items]
Shares outstanding (shares)	95,000	95,000
Common Stock
Share Capital [Line Items]
Shares outstanding (shares)	57,515,439	56,375,131
Common Stock | Common Class A
Share Capital [Line Items]
Shares outstanding (shares)	57,511,684	56,371,376
Common stock, voting rights, number of votes per share | vote	1
Common Stock | Common Class B
Share Capital [Line Items]
Shares outstanding (shares)	3,755	3,755
Common stock, voting rights, number of votes per share | vote	20
Employee Stock Option [Member] | Stock Incentive Plan 2016 [Member]
Share Capital [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized			2,750,000
Additional Authorized on June 2018 [Member] | Employee Stock Option [Member] | Stock Incentive Plan 2016 [Member]
Share Capital [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized			1,250,000

Convertible Preference Shares_2

Convertible Preference Shares (Details) - USD ($) $ / shares in Units, $ in Thousands	Mar. 07, 2017	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Preferred Units [Line Items]
Preferred Stock, Value, Issued					$ (97)
Series 4 Convertible Preferred Stock
Preferred Units [Line Items]
Proceeds from issuance of convertible preference shares					$ 0	$ 95,000
Convertible Preferred Stock | Series 4 Convertible Preferred Stock
Preferred Units [Line Items]
Stock issued during period, convertible preferred (shares)	95,000				0
Proceeds from issuance of convertible preference shares	$ 95,000
Preferred Stock, Value, Issued	$ 90,123				$ (97)
Preferred Stock, Liquidation Preference Per Share	$ 1,000
Preferred Stock, Conversion Price, Preference Per Share	$ 10
Preferred Stock, Accretion Percentage, Preference	8.00%
Preferred Stock, Accretion Rate, Preference Per Share			$ 7.11		$ 7.40
Accretion on convertible preferred shares		$ 2,109		$ 1,948	$ 6,204	$ 4,365
Preferred Stock, Liquidation Preference, Value		$ 107,556			$ 107,556
Preferred Stock, Conversion Basis, Common Stock Class A Closing Trade Price					125.00%
Preferred Stock, Liquidation Preference Percentage Rate, Change of Control of the Company					7.00%

Fair Value Measurements (Detail

Fair Value Measurements (Details) - 6.50% Notes due 2024 - Fair Value, Inputs, Level 1 - Senior Notes - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Liabilities:
Long term debt, Carrying Amount	$ 900,000	$ 900,000
Long term debt, Fair Value	$ 798,750	$ 904,500

Fair Value Measurements (Deta_2

Fair Value Measurements (Details 1) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Business Combination, Contingent Consideration, Liability	$ 94,729,000	$ 122,426,000
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance of contingent payments	119,086,000	224,754,000
Payments	54,947,000	110,234,000
Additions	12,816,000	0
Redemption value adjustments	16,276,000	3,273,000
Foreign translation adjustment	(22,000)	1,293,000
Ending balance of contingent payments	93,209,000	119,086,000
Fixed payments [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Business Combination, Contingent Consideration, Liability	$ 1,520,000	3,340,000
Common Class A [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Restricted stock grant date fair value		$ 3,353,939

Fair Value Measurements (Deta_3

Fair Value Measurements (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred acquisition consideration	$ 122,426,000	$ 94,729,000
Fixed payments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred acquisition consideration	3,340,000	$ 1,520,000
Common Class A
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Acquisition related consideration settled through issuance of shares	3,353,939
Common Stock | Common Class A
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Acquisition related consideration settled through issuance of shares	$ 28,727

Other Income (Loss) (Details)

Other Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Other Income and Expenses [Abstract]
Foreign currency transaction gain	$ 3,275	$ 9,913	$ (9,934)	$ 18,798
Other, net	$ 189	$ (1,264)	$ 1,222	$ (986)

Segment Information (Details 1)

Segment Information (Details 1) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)reportable_segment	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Segment Reporting Information [Line Items]
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent			26.50%
Depreciation, Depletion, Amortization and Impairment, Nonproduction	$ 11,134	$ 11,252	$ 35,212	$ 32,916
Share-based Compensation	6,242	6,380	16,882	16,870
Payments to Acquire Property, Plant, and Equipment	5,543	7,149	$ 15,232	28,305
Number of reportable segments | reportable_segment			4
Revenue	375,830	375,800	$ 1,082,541	1,111,032
Segment operating income (loss)	2,618	37,220	18,757	72,000
Interest and Debt Expense	(17,063)	(16,258)	(50,005)	(48,309)
Foreign Currency Transaction Gain (Loss), before Tax	3,275	9,913	(9,934)	18,798
Other income (expense):
Other, net	189	(1,264)	1,222	(986)
Income (loss) before income taxes and equity in earnings (losses) of non-consolidated affiliates	(10,981)	29,611	(39,960)	41,503
Income tax expense (benefit)	2,986	9,049	(3,367)	17,659
Income (loss) before equity in earnings (losses) of non-consolidated affiliates	(13,967)	20,562	(36,593)	23,844
Equity in earnings of non-consolidated affiliates	300	1,422	358	1,924
Net income (loss)	(13,667)	21,984	(36,235)	25,768
Net income attributable to the noncontrolling interest	(2,458)	(3,491)	(5,900)	(6,588)	$ (15,375)
Net income (loss) attributable to MDC Partners Inc.	(16,125)	18,493	(42,135)	19,180
Global Integrated Agencies
Segment Reporting Information [Line Items]
Depreciation, Depletion, Amortization and Impairment, Nonproduction	5,154	6,365	18,499	17,913
Share-based Compensation	3,360	3,840	8,492	9,912
Payments to Acquire Property, Plant, and Equipment	2,418	1,950	7,875	17,645
Revenue	177,398	196,974	510,360	585,290
Segment operating income (loss)	2,633	20,069	6,099	33,240
Domestic Creative Agencies
Segment Reporting Information [Line Items]
Depreciation, Depletion, Amortization and Impairment, Nonproduction	396	375	1,185	1,172
Share-based Compensation	175	187	945	534
Payments to Acquire Property, Plant, and Equipment	371	367	860	980
Revenue	24,798	28,096	75,503	77,325
Segment operating income (loss)	5,532	6,627	14,451	15,411
Specialized Communications
Segment Reporting Information [Line Items]
Depreciation, Depletion, Amortization and Impairment, Nonproduction	1,134	1,220	3,163	3,657
Share-based Compensation	43	659	542	2,264
Payments to Acquire Property, Plant, and Equipment	743	206	3,207	673
Revenue	42,636	40,670	129,724	125,470
Segment operating income (loss)	4,677	4,775	14,471	13,423
Media Services
Segment Reporting Information [Line Items]
Depreciation, Depletion, Amortization and Impairment, Nonproduction	781	1,011	2,315	3,232
Share-based Compensation	112	161	282	495
Payments to Acquire Property, Plant, and Equipment	428	2,308	845	4,107
Revenue	35,022	38,315	104,460	122,207
Segment operating income (loss)	1,387	2,555	407	9,169
All Other
Segment Reporting Information [Line Items]
Depreciation, Depletion, Amortization and Impairment, Nonproduction	3,470	2,026	9,467	6,078
Share-based Compensation	932	1,056	2,532	2,066
Payments to Acquire Property, Plant, and Equipment	1,551	2,317	2,380	4,896
Revenue	95,976	71,745	262,494	200,740
Segment operating income (loss)	6,413	13,920	28,565	29,740
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Depreciation, Depletion, Amortization and Impairment, Nonproduction	199	255	583	864
Share-based Compensation	1,620	477	4,089	1,599
Payments to Acquire Property, Plant, and Equipment	32	1	65	4
Segment operating income (loss)	$ (18,024)	$ (10,726)	$ (45,236)	$ (28,983)

Commitments, Contingencies an_2

Commitments, Contingencies and Guarantees (Details Textual) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Commitments [Line Items]
Redeemable Noncontrolling Interests	$ 57,193	$ 62,886	$ 60,180
Investment commitments	60
Amount of letters of credit outstanding	$ 5,248

New Accounting Pronouncements_2

New Accounting Pronouncements (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by (used in) operating activities	$ (31,729)	$ (14,450)
Payment for contingent consideration		$ 89,126
Accounting Standards Update 2016-15
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by (used in) operating activities	$ (36,570)

New Accounting Pronouncements -

New Accounting Pronouncements - Adoption of ASC 606 (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Services	$ 375,830	$ 375,800	$ 1,082,541	$ 1,111,032
Cost of services sold	238,690	249,418	735,110	754,803
Operating profit (loss)	2,618	37,220	18,757	72,000
Net loss attributable to MDC Partners, Inc. common shareholders	$ (18,234)	$ 14,137	$ (48,339)	$ 13,033
Loss per common share - basic and diluted (in USD per share)	$ (0.32)		$ (0.85)
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Services	$ 384,002		$ 1,121,717
Cost of services sold	252,812		783,193
Operating profit (loss)	(3,332)		9,850
Net loss attributable to MDC Partners, Inc. common shareholders	$ (22,934)		$ (54,424)
Loss per common share - basic and diluted (in USD per share)	$ (0.40)		$ (0.95)
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Services	$ 8,172		$ 39,176
Cost of services sold	14,122		48,083
Operating profit (loss)	(5,950)		(8,907)
Net loss attributable to MDC Partners, Inc. common shareholders	$ (4,700)		$ (6,085)
Loss per common share - basic and diluted (in USD per share)	$ (0.08)		$ (0.10)