Segment Information (Details 1) $ in Thousands	3 Months Ended					9 Months Ended				12 Months Ended
	Sep. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2020 reporting_segment	Sep. 30, 2020 reportable_segment	Sep. 30, 2019 USD ($)	Dec. 31, 2019 operating_segment
Segment Reporting Information [Line Items]
Number of reportable segments							2	3
Number of operating segments | operating_segment										4
Revenues	$ 283,423	$ 1,415,803	$ 342,907	$ 1,475,088	$ 1,513,779	$ 870,843			$ 1,033,828
Segment operating income (loss)	28,889		29,421			58,316			68,544
EBITDA	54,058		49,205			129,787			117,117
Interest expense and finance charges	(15,266)		(16,110)			(46,819)			(49,284)
Foreign exchange gain (loss)	2,159		(3,973)			(7,256)			4,401
Other, net	505		(431)			22,723			(4,559)
Income (loss) before income taxes and equity in earnings of non-consolidated affiliates	16,287	20,867	8,907	(88,669)	86,022	26,964			19,102
Income tax expense	1,452	10,316	3,457	29,615	(168,358)	7,029			6,292
Income before equity in earnings of non-consolidated affiliates	14,835		5,450			19,935			12,810
Equity in earnings (losses) of non-consolidated affiliates	(31)		63			(829)			352
Net income	14,804		5,513			19,106			13,162
Net income attributable to the noncontrolling interest	(10,728)	(16,156)	(7,265)			(14,620)			(10,737)
Net income (loss) attributable to MDC Partners Inc.	4,076		(1,752)			4,486			2,425
Depreciation and amortization	(9,332)		(9,368)			(27,437)			(28,869)
Asset Impairment Charges	(159)	(8,599)	(1,944)	(87,204)	(5,471)	(19,159)			(1,944)
Depreciation, Depletion and Amortization, Nonproduction	9,332		9,368						28,869
Depreciation						27,437			28,869
Stock-based compensation	(6,459)		(6,026)			(10,568)			(12,632)
Capital expenditures	24,187		5,863			27,877			13,786
Change in contingent purchase price obligation	(2,803)		(1,943)			(515)			3,627
Proceeds from (Payments to) Noncontrolling Interests	(208)		202			(1,273)			171
Other Operating Income	(6,208)		(705)			(12,519)			(8,926)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	360	$ (17,557)	(5,058)	$ (138,362)	$ 204,832	(6,042)			(6,506)
Capital expenditures incurred but not yet paid						(16,403)
Global Integrated Agencies, Group A
Segment Reporting Information [Line Items]
Revenues	87,064		99,299			260,420			276,286
EBITDA	21,009		23,974			54,516			43,128
Depreciation and amortization	(1,601)		(2,132)			(4,908)			(6,420)
Stock-based compensation	(4,024)		(4,330)			(5,880)			(8,564)
Capital expenditures	269		1,083			835			5,120
Global Integrated Agencies, Group B
Segment Reporting Information [Line Items]
Revenues	112,159		129,057			323,264			395,622
EBITDA	29,598		21,989			63,121			65,117
Depreciation and amortization	(4,813)		(3,872)			(13,726)			(11,964)
Stock-based compensation	(742)		(740)			(2,388)			(3,231)
Capital expenditures	694		4,108			899			6,287
Media Services
Segment Reporting Information [Line Items]
Revenues	33,572		36,235			103,181			118,923
EBITDA	3,031		1,354			5,710			2,388
Depreciation and amortization	(786)		(1,004)			(2,401)			(3,332)
Stock-based compensation	(131)		(16)			(122)			(22)
Capital expenditures	72		116			269			460
All Other
Segment Reporting Information [Line Items]
Revenues	50,628		78,316			183,978			242,997
EBITDA	7,146		9,221			23,936			26,962
Depreciation and amortization	(1,933)		(2,168)			(5,735)			(6,523)
Stock-based compensation	(141)		(107)			(339)			(363)
Capital expenditures	79		545			536			1,889
Corporate, Non-Segment
Segment Reporting Information [Line Items]
EBITDA	(6,726)		(7,333)			(17,496)			(20,478)
Depreciation and amortization	(199)		(192)			(667)			(630)
Stock-based compensation	(1,421)		(833)			(1,839)			(452)
Capital expenditures	$ 23,073		$ 11			$ 25,338			$ 30