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	Common Class A [Member] Common Stock	Series 4 Convertible Preferred Stock [Member] Convertible Preferred Stock
Balance at Dec. 31, 2017	$ (155,513)			$ 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.	3,406							3,406
Shares acquired and cancelled	(39)			(39)				(39)
Balance at Mar. 31, 2018	(153,336)	$ 90,123		45,824	(367,180)	481		(230,752)	77,416
Balance (in shares) at Mar. 31, 2018		95,000,000
Common stock, balance (in shares) at Mar. 31, 2018			57,454,028
Adjustments to Additional Paid in Capital, Changes due to Business Combinations				(97)				(97)
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								57,517,568
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
Other comprehensive income (loss)	(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
Changes in ownership interest									(24,642)
Balance at Jun. 30, 2019	$ (171,977)	$ 152,746		$ 97,455	$ (460,726)	$ (1,713)		$ (212,238)	$ 40,261
Balance (in shares) at Jun. 30, 2019		145,000,000								71,943,994	145,000
Common stock, balance (in shares) at Jun. 30, 2019			71,947,743