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Adjustment to Net Income, Allocated to Convertible Shares

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Amount of income (loss) from continuing operations attributable to the parent, and includes adjustments resulting from the assumption that dilutive convertible securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions.

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Net Income Allocated to Convertible Shares

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount after tax of income (loss) from continuing operations attributable to the parent.

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The amount of net income (loss) from continuing operations per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) derived from continuing operations during the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Loss Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2018	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Class of Stock [Line Items]
Net loss attributable to MDC Partners Inc.	$ (1,752)	$ (16,125)	$ (16,125)	$ (42,135)	$ 2,425	$ (42,135)
Numerator
Accretion on and net income allocated to convertible preference shares		2,109
Net loss attributable to MDC Partners Inc. common shareholders	$ (5,058)	$ (18,234)			$ (6,506)	$ (48,339)
Denominator
Denominator for basic income (loss) per common share - weighted average common shares	72,044,480	57,498,661			68,154,306	57,117,797
Weighted Average Number Diluted Shares Outstanding Adjustment	0	0			0	0
Denominator for diluted income (loss) per common share - adjusted weighted shares and assumed conversions	72,044,480	57,498,661			68,154,306	57,117,797
Income (loss) from continuing operations attributable to MDC Partners Inc. common shareholders (usd per share)	$ (0.07)	$ (0.32)			$ (0.10)	$ (0.85)
Income (loss) from continuing operations attributable to MDC Partners Inc. common shareholders (usd per share)	$ (0.07)	$ (0.32)			$ (0.10)	$ (0.85)
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	3,714,595,000
Adjustment to Net Income, Allocated to Convertible Shares	$ 0	$ 0			$ 0	$ 0
Income (Loss) from Continuing Operations Attributable to Parent, Diluted	(5,058)	(18,234)			(6,506)	(48,339)
MDC Partners Inc. Shareholders' Deficit
Class of Stock [Line Items]
Net loss attributable to MDC Partners Inc.			$ (16,125)	$ (42,135)
Series 4 Convertible Preferred Stock \| Convertible Preferred Stock
Numerator
Accretion on and net income allocated to convertible preference shares	3,306	2,109			8,931	$ 6,204
Net Income Allocated to Convertible Shares	0	$ 0			$ 0
Denominator
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		1,524,218,000			3,714,595,000	1,524,218,000
Series 4 Convertible Preferred Stock [Domain] \| Convertible Preferred Stock
Numerator
Accretion on and net income allocated to convertible preference shares	$ 3,306					$ 6,204
Net Income Allocated to Convertible Shares						$ 0