Noncontrolling and Redeemable Noncontrolling Interests - Changes in Noncontrolling Interests (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2018	Mar. 31, 2018	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Noncontrolling Interest [Line Items]
Net loss attributable to MDC Partners Inc.	$ (1,752)		$ (16,125)	$ (16,125)	$ (42,135)	$ 2,425	$ (42,135)
Decrease in MDC Partners Inc. paid-in capital for purchase of equity interests in excess of redeemable noncontrolling interests and noncontrolling interests	648
Change from net income (loss) attributable to MDC Partners Inc. and transfers to noncontrolling interests	2,400		11,150			(1,680)	38,326
MDC Partners Inc. Shareholders' Deficit
Noncontrolling Interest [Line Items]
Net loss attributable to MDC Partners Inc.				$ (16,125)	$ (42,135)
Decrease in MDC Partners Inc. paid-in capital for purchase of equity interests in excess of redeemable noncontrolling interests and noncontrolling interests	$ (648)	$ 648	$ (4,975)			$ 745	$ (3,809)