Noncontrolling and Redeemable Noncontrolling Interests - Changes in Noncontrolling Interests (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Noncontrolling Interest [Line Items]
Net loss attributable to MDC Partners Inc.	$ 4,076	$ (1,752)	$ 4,486	$ 2,425
Increase (decrease) in MDC Partners Inc. paid-in capital for purchase of redeemable noncontrolling interests and noncontrolling interests	2,129		1,626
Change from net income (loss) attributable to MDC Partners Inc. and transfers to noncontrolling interests	(6,205)	2,400	(6,112)	(1,680)
MDC Partners Inc. Shareholders' Deficit
Noncontrolling Interest [Line Items]
Net loss attributable to MDC Partners Inc.	4,076	(1,752)	4,486	2,425
Increase (decrease) in MDC Partners Inc. paid-in capital for purchase of redeemable noncontrolling interests and noncontrolling interests	$ 2,129	$ (648)	$ (1,626)	$ 745

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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