Acquisitions and Dispositions (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Transfers to (from) the noncontrolling interest:
Noncontrolling interest, ownership percentage by Parent (percent)	100.00%
Net loss attributable to MDC Partners Inc.	$ (29,416)	$ (10,566)
Increase (decrease) in noncontrolling interests and redeemable noncontrolling interests from business acquisitions and step-up transactions	(1,166)	0
Change from net loss attributable to MDC Partners Inc. and transfers to noncontrolling interests	(30,582)	(10,566)
MDC Partners Inc. Shareholders' Deficit
Transfers to (from) the noncontrolling interest:
Net loss attributable to MDC Partners Inc.	(29,416)
Increase (decrease) in noncontrolling interests and redeemable noncontrolling interests from business acquisitions and step-up transactions	$ (1,166)	$ 0