CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Convertible Preference Shares Series 4 Convertible Preferred Stock [Member]	Common Stock	Share Capital to Be Issued	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	MDC Partners Inc. Shareholders’ Deficit	Noncontrolling Interests	Contingent Consideration, Liability Settlements [Domain]	Contingent Consideration, Liability Settlements [Domain] Convertible Preference Shares Series 4 Convertible Preferred Stock [Member]	Contingent Consideration, Liability Settlements [Domain] Common Stock	Contingent Consideration, Liability Settlements [Domain] MDC Partners Inc. Shareholders’ Deficit	Aggregate 2017 Dispositions [Domain]	Aggregate 2017 Dispositions [Domain] Noncontrolling Interests
Stockholders' equity, beginning balance at Dec. 31, 2015	$ (496,092)			$ 0	$ (45,419)	$ (536,009)	$ 6,257	$ (575,171)	$ 79,079
Common stock outstanding, beginning balance (in shares) at Dec. 31, 2015			49,990,460.00	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures	$ 12,818				10,458			12,818
Stock Issued During Period, Shares, New Issues	0		691,559
Net income attributable to MDC Partners	$ (45,839)					(45,839)		(45,839)
Other comprehensive income (loss)	(7,687)						(8,081)	(8,081)	394
Stock Appreciation Rights Exercised (in shares)				(100,000)
Stock Authorized During Period, Value, To be Issued				$ (2,360)
Issuance of restricted stock (in shares)			425,915
Stock Issued During Period, Value, Acquisitions	34,219				34,219			34,219
Deferred acquisition consideration settled through issuance of shares	(3,350)				(3,350)			(3,350)
Options Exercised	9,604
Shares issued, acquisitions	10,662				10,662			10,662
Increase (decrease) in noncontrolling interests and redeemable noncontrolling interests from business acquisitions and step-up transactions	(32,747)				(32,747)			(32,747)
Common stock outstanding, ending balance (in shares) at Dec. 31, 2016			52,802,058.000	100,000
Stockholders' equity, ending balance at Dec. 31, 2016	(509,476)			$ 2,360	6,203	(581,848)	(1,824)	(575,109)	65,633
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	8,936				22,776			22,776	(13,840)
Stock Issued During Period, Shares, New Issues			(205,876)
Stock Issued During Period, Shares, Acquisitions			(1,900,000)
Temporary Equity, Accretion to Redemption Value					(9,604)			(9,604)
Stock Issued During Period, Shares, New Issues											95,000,000
Net income attributable to MDC Partners	241,848					241,848		241,848
Other comprehensive income (loss)	2,275						(130)	(130)	2,405
Stock Appreciation Rights Exercised (in shares)				100,000
Stock Authorized During Period, Value, To be Issued	(27,852)			$ 2,360	(30,212)			(27,852)
Issuance of restricted stock (in shares)			380,669
Deferred acquisition consideration settled through issuance of shares	(1,758)				(1,758)			(1,758)
Shares issued, acquisitions					8,028			8,028
Increase (decrease) in noncontrolling interests and redeemable noncontrolling interests from business acquisitions and step-up transactions	(9,650)
Noncontrolling Interest, Increase from Business Combination	1,666				(5,654)			(5,654)	12,614
Changes in noncontrolling interest and redeemable noncontrolling interests from business dispositions	6,960
Common stock outstanding, ending balance (in shares) at Dec. 31, 2017			56,375,131
Stockholders' equity, ending balance at Dec. 31, 2017	(155,513)	$ 90,220			38,191	(340,000)	(1,954)	(213,543)	58,030
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests					2,315			2,315	(11,965)
Increase (Decrease) in Redemption Value of Redeemable Noncontrolling Interests	(1,498)
Stock Issued During Period, Shares, New Issues			3,353,939
Redemption value adjustments										$ 90,220	$ 90,220		$ 90,220
Stock Issued During Period, Shares, Acquisitions			161,535
Temporary Equity, Accretion to Redemption Value	(8,028)				1,498			1,498
Adjustments to Additional Paid in Capital, Other	343				343			343
Noncontrolling Interest, Decrease from Deconsolidation														$ (10,657)	$ (10,657)
Shares, Outstanding		95,000,000
Net income attributable to MDC Partners	(123,733)					(123,733)		(123,733)
Other comprehensive income (loss)	3,713						6,674	6,674	(2,961)
Issuance of restricted stock (in shares)												1,011,561
Stock Issued During Period, Value, Acquisitions					7,030					$ 7,030			$ 7,030
Deferred acquisition consideration settled through issuance of shares	(776)				(776)			(776)
Shares issued, acquisitions	8,165				8,165			8,165
Noncontrolling Interest, Change in Redemption Value	(5,965)								(5,965)
Noncontrolling Interest, Increase from Business Combination	0
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	(1,170)					(1,170)		(1,170)
Common stock outstanding, ending balance (in shares) at Dec. 31, 2018			57,521,323
Stockholders' equity, ending balance at Dec. 31, 2018	(246,967)	$ 90,123			58,579	$ (464,903)	$ 4,720	(311,481)	64,514
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures			243,529
Stock Issued During Period, Value, Convertible Preferred Shares	(97)	$ (97)						(97)
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	25,550				10,140			10,140	$ 15,410
Increase (Decrease) in Redemption Value of Redeemable Noncontrolling Interests	$ (4,171)
Redemption value adjustments			$ 0
Stock Issued During Period, Shares, Acquisitions			(108,898)
Temporary Equity, Accretion to Redemption Value					$ 4,171			$ 4,171
Shares, Outstanding		95,000,000