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]	MDC Partners Inc. Shareholders' Deficit	Noncontrolling Interest	Series 4 Convertible Preferred Stock [Member] Convertible Preferred Stock
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									95,000,000
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)				(113)		(113)
Other comprehensive income (loss)	(4,659)					(5,010)	(5,010)	351
Issuance of common and preference shares (in shares)		50,000,000	14,285,714
Issuance of common and convertible preference shares	97,629	$ 61,994		35,635			97,629
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)			(93)			(93)	(24,642)
Business acquisitions and step-up transactions, net of tax	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									145,000,000
Common stock, balance (in shares) at Mar. 31, 2019			71,890,021
Balance at Dec. 31, 2019	(179,389)	152,746		101,469	(469,593)	(4,269)	(219,647)	40,258
Balance (in shares) at Dec. 31, 2019									145,000,000
Common stock, balance (in shares) at Dec. 31, 2019			72,154,603
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss attributable to MDC Partners Inc.	1,003						1,003
Other comprehensive income (loss)	7,429					7,938	7,938	(509)
Issuance of restricted stock	0
Issuance of restricted stock (in shares)			587,227
Shares acquired and cancelled	(637)			(637)			(637)
Shares acquired and cancelled (in shares)			(258,664)
Stock-based compensation	476			476			476
Changes in redemption value of redeemable noncontrolling interests	(1,218)			(1,218)			(1,218)
Business acquisitions and step-up transactions, net of tax	(503)			(503)			(503)
Other	82			0	82	0	82	0
Balance at Mar. 31, 2020	$ (172,757)	$ 152,746		$ 99,587	$ (468,508)	$ 3,669	$ (212,506)	$ 39,749
Balance (in shares) at Mar. 31, 2020									145,000,000
Common stock, balance (in shares) at Mar. 31, 2020			72,483,166