UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' DEFICIT - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income	MDC Partners Inc. Shareholders' Deficit	Noncontrolling Interest	Series 4 Convertible Preferred Stock [Member] Convertible Preferred Stock
Balance at Dec. 31, 2018	$ (257,590)	$ 90,123		$ 58,579	$ (475,526)	$ 4,720	$ (322,104)	$ 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.	4,177				4,177		4,177
Other comprehensive income	(6,044)					(6,433)	(6,433)	389
Issuance of common and preference shares (in shares)		50,000,000	14,285,714
Issuance of common and convertible preference shares	98,620	$ 62,623		35,997			98,620
Issuance of restricted stock	0
Issuance of restricted stock (in shares)			193,979
Shares acquired and cancelled	(78)			(78)			(78)
Shares acquired and cancelled (in shares)			(53,273)
Stock-based compensation	509			509			509
Changes in redemption value of redeemable noncontrolling interests	2,729			2,729			2,729
Business acquisitions and step-up transactions, net of tax	(97)			(97)			(97)
Changes in ownership interest	(24,826)			(184)			(184)	(24,642)
Business acquisitions and step-up transactions, net of tax							(97)
Balance at Jun. 30, 2019	(182,600)	152,746		97,455	(471,349)	(1,713)	(222,861)	40,261
Balance (in shares) at Jun. 30, 2019									145,000,000
Common stock, balance (in shares) at Jun. 30, 2019			71,947,743
Balance at Mar. 31, 2019	(184,896)	$ 152,117		98,693	(475,639)	(290)	(225,119)	40,223
Balance (in shares) at Mar. 31, 2019									145,000,000
Common stock, balance (in shares) at Mar. 31, 2019			71,890,021
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss attributable to MDC Partners Inc.	4,290				4,290		4,290
Other comprehensive income	(1,385)					(1,423)	(1,423)	38
Issuance of common and preference shares (in shares)		0	0
Issuance of common and convertible preference shares	991	$ 629		362			991
Issuance of restricted stock	0
Issuance of restricted stock (in shares)			76,979
Shares acquired and cancelled	(22)			(22)			(22)
Shares acquired and cancelled (in shares)			(19,257)
Stock-based compensation	1,800			1,800			1,800
Changes in redemption value of redeemable noncontrolling interests	(3,190)			(3,190)			(3,190)
Business acquisitions and step-up transactions, net of tax	(97)			(97)			(97)
Changes in ownership interest	(91)			(91)			(91)	0
Business acquisitions and step-up transactions, net of tax							97
Balance at Jun. 30, 2019	(182,600)	152,746		97,455	(471,349)	(1,713)	(222,861)	40,261
Balance (in shares) at Jun. 30, 2019									145,000,000
Common stock, balance (in shares) at Jun. 30, 2019			71,947,743
Balance at Dec. 31, 2019	(190,575)	152,746		101,469	(480,779)	(4,269)	(230,833)	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.	410				410		410
Other comprehensive income	8,796					8,895	8,895	(99)
Issuance of restricted stock	0
Issuance of restricted stock (in shares)			760,561
Shares acquired and cancelled	(732)			(732)			(732)
Shares acquired and cancelled (in shares)			(327,774)
Stock-based compensation	1,033			1,033			1,033
Changes in redemption value of redeemable noncontrolling interests	(2,630)			(2,630)			(2,630)
Business acquisitions and step-up transactions, net of tax	503			503			(503)
Other	(402)			(403)	1	1	(401)	(1)
Balance at Jun. 30, 2020	(184,603)	152,746		98,234	(480,368)	4,627	(224,761)	40,158
Balance (in shares) at Jun. 30, 2020									145,000,000
Common stock, balance (in shares) at Jun. 30, 2020			72,587,390
Balance at Mar. 31, 2020	(183,943)	152,746		99,587	(479,694)	3,669	(223,692)	39,749
Balance (in shares) at Mar. 31, 2020									145,000,000
Common stock, balance (in shares) at Mar. 31, 2020			72,483,166
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss attributable to MDC Partners Inc.	(593)						(593)
Other comprehensive income	1,367					957	957	410
Issuance of restricted stock	0
Issuance of restricted stock (in shares)			173,334
Shares acquired and cancelled	(95)			(95)			(95)
Shares acquired and cancelled (in shares)			(69,110)
Stock-based compensation	557			557			557
Changes in redemption value of redeemable noncontrolling interests	(1,412)			(1,412)			(1,412)
Business acquisitions and step-up transactions, net of tax							0
Other				(81)	1	(483)	(1)	(484)
Balance at Jun. 30, 2020	$ (184,603)	$ 152,746		$ 98,234	$ (480,368)	$ 4,627	$ (224,761)	$ 40,158
Balance (in shares) at Jun. 30, 2020									145,000,000
Common stock, balance (in shares) at Jun. 30, 2020			72,587,390