Document and Entity Information Document	6 Months Ended
	Jun. 30, 2012	Aug. 02, 2012 Class A common stock, voting	Aug. 02, 2012 Class B common stock, non-voting	Aug. 02, 2012 Class A exchangeable shares	Aug. 02, 2012 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	Jun. 30, 2012
Amendment Flag	false
Current Fiscal Year End Date	--12-29
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		2,583,694	156,163,295
Entity Exchangeable Shares Outstanding				2,939,701	19,260,822
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q2