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Document and Entity Information Document	9 Months Ended
Document and Entity Information Document	Sep. 24, 2011	Oct. 28, 2011 Class A common stock, voting	Oct. 28, 2011 Class B common stock, non-voting	Oct. 28, 2011 Class A exchangeable shares	Oct. 28, 2011 Class B exchangeable shares
Document Information [Line Items]
Entity Registrant Name	MOLSON COORS BREWING CO
Entity Central Index Key	0000024545
Document Type	10-Q
Document Period End Date	Sep. 24, 2011
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		2,583,694	156,283,195
Class A exchangeable shares				2,939,707	19,260,989
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	Q3