CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (DEFICIT) - USD ($)	Total	Common Class B [Member]	Common Class A	Common Stock	Common Stock Common Class B [Member]	Common Stock Common Class A	Share Capital to Be Issued	Additional Paid-in Capital	Charges in Excess of Capital	Retained Earnings [Member]	Stock Subscription Receivable	Accumulated Other Comprehensive Loss	MDC Partners Inc. Shareholders’ Deficit	Preferred Stock [Member] Series 4 Convertible Preferred Stock [Domain]	Noncontrolling Interests	AOCI Including Portion Attributable to Noncontrolling Interest [Member]	Forsman & Bodenfors AB [Domain] Common Stock Common Class A	Contingent Consideration Classified as Equity [Member] MDC Partners Inc. Shareholders’ Deficit	Contingent Consideration, Liability Settlements [Domain]	Contingent Consideration, Liability Settlements [Domain] MDC Partners Inc. Shareholders’ Deficit
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures	$ 0					$ 6,069,000		$ (6,069,000)
Noncontrolling Interest, Increase from Business Combination	(51,488,000)							42,780,000					$ 42,780,000		$ 8,708,000
Stockholders' equity, beginning balance at Dec. 31, 2014								0	$ (209,668,000)		$ 0	$ (7,752,000)	(452,157,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss attributable to MDC Partners	(35,454,000)												(35,454,000)
Other comprehensive income (loss)	9,141,000											14,009,000	14,009,000		(4,868,000)
Shares acquired and canceled	(2,388,000)					$ (2,388,000)							(2,388,000)
Shares acquired and cancelled (in shares)						(96,777)
Options Exercised	224,000					$ 343,000		(119,000)					224,000
Options Exercised (in shares)						37,500
Stock-based compensation	8,437,000							8,437,000					8,437,000
Dividends paid and to be paid	(42,253,000)							(42,253,000)					(42,253,000)
Transfer to charges in excess of capital	0							105,593,000	(105,593,000)
Common stock outstanding, ending balance (in shares) at Dec. 31, 2015					49,990,460	49,990,460	0
Stockholders' equity, ending balance at Dec. 31, 2015	$ (496,092,000)				$ 269,842,000	$ 269,842,000	$ 0	0	(315,261,000)	$ (536,009,000)	0	6,257,000	(575,171,000)		79,079,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures						365,873
Stock Issued During Period, Shares, New Issues	0
Stock Issued During Period, Value, New Issues						$ 0
Stock Issued During Period, Value, Acquisitions																	$ 0
Temporary Equity, Accretion to Redemption Value	$ (22,809,000)							22,809,000					22,809,000
Noncontrolling Interest, Increase from Business Combination	(8,936,000)							(22,776,000)					(22,776,000)		13,840,000
Net loss attributable to MDC Partners	(45,839,000)												(45,839,000)
Other comprehensive income (loss)	(7,687,000)											(8,081,000)	(8,081,000)		394,000
Issuance of restricted stock (in shares)						425,915
Stock Issued During Period, Value, Restricted Stock and Stock Options, Net of Forfeitures	0					$ 6,615,000		(6,615,000)					0
Shares acquired and canceled	(3,350,000)					$ (3,350,000)							(3,350,000)
Shares acquired and cancelled (in shares)						(205,876)
Stock-based compensation	10,662,000							10,662,000					10,662,000
Dividends paid and to be paid	(32,747,000)							(32,747,000)					(32,747,000)
Transfer to charges in excess of capital	0							(3,680,000)	3,680,000
Common stock outstanding, ending balance (in shares) at Dec. 31, 2016		3,755	52,798,303			52,802,058	100,000
Stockholders' equity, ending balance at Dec. 31, 2016	$ (509,476,000)					$ 317,784,000	$ 2,360,000	0	(311,581,000)	(581,848,000)	0	$ (1,824,000)	(575,109,000)	$ 0	65,633,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Shares, New Issues	0					691,559
Stock Issued During Period, Value, New Issues						$ 10,458,000													$ 12,818,000	$ 12,818,000
Stock Issued During Period, Shares, Acquisitions						1,900,000
Stock Issued During Period, Value, Acquisitions	$ 34,219,000																34,219,000	$ 34,219,000
Temporary Equity, Accretion to Redemption Value	$ (9,604,000)							(9,604,000)					(9,604,000)
Common Stock, Shares, To be Issued	100,000
Common Stock, Value, To be Issued	$ 2,360,000
Shares, Outstanding														0
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures	0			$ 7,679,000				(7,679,000)					0
Noncontrolling Interest, Increase from Business Combination	(6,960,000)							5,654,000					5,654,000		(12,614,000)
Noncontrolling Interest, Decrease from Deconsolidation	(10,657,000)
Net loss attributable to MDC Partners	241,848,000												241,848,000
Other comprehensive income (loss)	2,275,000												(130,000)		2,405,000	$ (130,000)
Stock Appreciation Rights Exercised (in shares)							(100,000)
Stock Authorized During Period, Value, To be Issued							$ (2,360,000)
Shares acquired and canceled	(1,758,000)			$ (1,758,000)									(1,758,000)
Shares acquired and cancelled (in shares)				(161,535)
Stock-based compensation	8,028,000							8,028,000					8,028,000
Transfer to charges in excess of capital								2,660,000	(2,660,000)
Common stock outstanding, ending balance (in shares) at Dec. 31, 2017		3,755	58,432,677
Stockholders' equity, ending balance at Dec. 31, 2017	$ (155,513,000)			$ 352,432,000				0	$ (314,241,000)	$ (340,000,000)	$ 0		$ (213,543,000)	$ 90,220,000	58,030,000	$ (1,954,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Shares, Convertible Preferred Shares	90,220,000												90,220,000	95,000,000
Stock Issued During Period, Value, Convertible Preferred Shares														$ 90,220,000
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures				380,669
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	$ 9,650,000							(2,315,000)					$ (2,315,000)		$ 11,965,000
Stock Issued During Period, Shares, New Issues				3,353,939		3,353,939
Stock Issued During Period, Value, New Issues	27,852,000			$ 28,727,000		$ 28,727		1,485,000					27,852,000
Stock Issued During Period, Value, Acquisitions																	$ 0
Temporary Equity, Accretion to Redemption Value	(1,498,000)							1,498,000					1,498,000
Adjustments to Additional Paid in Capital, Other	$ 343,000							$ 343,000					$ 343,000
Common Stock, Shares, To be Issued	100,000						0
Common Stock, Value, To be Issued	$ 0						$ 0
Shares, Outstanding				56,375,131										95,000,000