Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Oct. 18, 2019	Dec. 31, 2018	Dec. 31, 2017
Document Information [Line Items]
Entity Registrant Name	MDC PARTNERS INC
Entity Central Index Key	0000876883
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Current Reporting Status	Yes
Document Type	10-Q
Entity Small Business	false
Document Fiscal Year Focus	2019
Document Period End Date	Sep. 30, 2019
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		145,000,000
Common Stock [Member] | Common Class A
Document Information [Line Items]
Shares outstanding (shares)		72,142,668	57,517,568
Common Stock [Member] | Common Class B
Document Information [Line Items]
Shares outstanding (shares)		3,749	3,755	3,755