Loss Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Sep. 30, 2018	Mar. 31, 2018
Class of Stock [Line Items]
Net loss attributable to MDC Partners Inc.	$ (113)		$ (29,416)
Numerator
Accretion on convertible preference shares	$ (2,383)		(2,027)
Net loss attributable to MDC Partners Inc. common shareholders		$ (2,496)	$ (31,443)
Denominator
Denominator for basic income (loss) per common share - weighted average common shares	60,258,102	60,258,102	56,415,042
Denominator for diluted income (loss) per common share - adjusted weighted shares and assumed conversions	60,258,102	60,258,102	56,415,042
Income (loss) from continuing operations attributable to MDC Partners Inc. common shareholders (usd per share)	$ (0.04)		$ (0.56)
Income (loss) from continuing operations attributable to MDC Partners Inc. common shareholders (usd per share)	$ (0.04)		$ (0.56)
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,633,464		1,560,856
MDC Partners Inc. Shareholders' Deficit
Class of Stock [Line Items]
Net loss attributable to MDC Partners Inc.			$ (29,416)
Series 4 Convertible Preferred Stock | Convertible Preferred Stock
Numerator
Accretion on convertible preference shares			$ (2,027)