UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' DEFICIT - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit	AOCI Attributable to Parent [Member]	Accumulated Other Comprehensive Income (Loss)	MDC Partners Inc. Shareholders' Deficit	Noncontrolling Interest
Balance at Dec. 31, 2017	$ (155,513)	$ 90,220		$ 38,191	$ (340,000)	$ (1,954)		$ (213,543)	$ 58,030
Balance (in shares) at Dec. 31, 2017		95,000
Common stock, balance (in shares) at Dec. 31, 2017			56,375,131
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss attributable to MDC Partners Inc.	(29,416)							(29,416)
Temporary Equity, Accretion to Redemption Value				(375)				(375)
Other comprehensive income (loss)	2,278						$ 3,379	3,379	(1,101)
Expenses for convertible preference shares	(97)	$ (97)						(97)
Issuance of restricted stock (in shares)			109,444
Shares acquired and cancelled	(455)			(455)				(455)
Shares acquired and cancelled (in shares)			(48,508)
Stock-based compensation	2,217			2,217				2,217
Changes in redemption value of redeemable noncontrolling interests	(375)
Business acquisitions and step-up transactions, net of tax	(1,166)			(1,166)				(1,166)
Changes in ownership interest	(5,965)								(5,965)
Cumulative effect of adoption of ASC 606	(1,170)				(1,170)			(1,170)
Balance at Mar. 31, 2018	(189,662)	$ 90,123		38,412	(370,586)	1,425		(240,626)	50,964
Balance (in shares) at Mar. 31, 2018		95,000
Common stock, balance (in shares) at Mar. 31, 2018			56,436,067
Balance at Dec. 31, 2018	(246,967)	$ 90,123		58,579	(464,903)	4,720		(311,481)	64,514
Balance (in shares) at Dec. 31, 2018		95,000
Common stock, balance (in shares) at Dec. 31, 2018			57,521,323
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss attributable to MDC Partners Inc.	(113)
Other comprehensive income (loss)	(4,659)						$ (5,010)	(5,010)	351
Issuance of common and preference shares (in shares)		50,000	14,285,714
Issuance of common and convertible preference shares	97,629	$ 61,994		35,635				97,629
Issuance of restricted stock	0
Issuance of restricted stock (in shares)			117,000
Shares acquired and cancelled	(56)			(56)				(56)
Shares acquired and cancelled (in shares)			(34,016)
Stock-based compensation	(1,291)			(1,291)				(1,291)
Changes in redemption value of redeemable noncontrolling interests	5,919			5,919				5,919
Changes in ownership interest	(24,735)								(24,642)
Transfer to charges in excess of capital and other	0			0				0
Balance at Mar. 31, 2019	$ (174,273)	$ 152,117		$ 98,693	$ (465,016)	$ (290)		$ (214,496)	$ 40,223
Balance (in shares) at Mar. 31, 2019		145,000
Common stock, balance (in shares) at Mar. 31, 2019			71,890,021