Income (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Net loss attributable to MDC Partners Inc.	$ (593)	$ 4,290	$ 410	$ 4,177
Numerator
Net income (loss) attributable to MDC Partners Inc. common shareholders	$ (4,102)	$ 775	$ (6,539)	$ (1,448)	$ (17,557)	$ (138,362)	$ 204,832
Denominator
Denominator for basic income (loss) per common share - weighted average common shares	72,528,455	71,915,832	72,463,058	66,118,749	69,132,100	57,218,994	55,255,797
Impact of stock options and non-vested stock under employee stock incentive plans (in shares)	0	108,857	0	0
Denominator for diluted income (loss) per common share - adjusted weighted shares and assumed conversions	72,528,455	72,024,689	72,463,058	66,118,749	69,132,100	57,218,994	55,481,786
Earnings per share, basic	$ (0.06)	$ 0.01	$ (0.09)	$ (0.02)	$ (250)	$ (2,420)	$ 3,710
Earnings per share, diluted	$ (0.06)	$ 0.01	$ (0.09)	$ (0.02)	$ (250)	$ (2,420)	$ 3,700
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2,912,436,000
MDC Partners Inc. Shareholders' Deficit
Class of Stock [Line Items]
Net loss attributable to MDC Partners Inc.	$ (593)	$ 4,290	$ 410	$ 4,177
Series 4 Convertible Preferred Stock | Convertible Preferred Stock
Numerator
Accretion on and net income allocated to convertible preference shares	3,509	3,242	6,949	5,625
Net income allocated to convertible preference shares	$ 0	$ (273)	$ 0	$ 0
Denominator
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		2,662,666,000