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)