New Accounting Pronouncements (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities			$ 818.5	$ 282.4
Net Cash Provided by (Used in) Financing Activities			593.2	(2,338.6)
Income tax benefit (expense)	$ (123.0)	$ (21.2)	(187.6)	(37.9)
Net income (loss) attributable to MCBC	$ 323.3	$ 172.3	$ 524.6	$ 335.0
Basic net income (loss) attributable to Molson Coors Brewing Company per share	$ 1.50	$ 0.80	$ 2.44	$ 1.60
Diluted net income (loss) attributable to Molson Coors Brewing Company per share	$ 1.49	$ 0.80	$ 2.42	$ 1.59
Weighted average shares - diluted (in shares)	216.4	216.0	216.4	210.5
Paid-in capital	$ 6,658.5	$ 6,552.7	$ 6,658.5	$ 6,552.7	$ 6,635.3
Retained earnings	$ 6,467.0	4,654.5	$ 6,467.0	4,654.5	$ 6,119.0
Scenario, Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities				264.4
Net Cash Provided by (Used in) Financing Activities				(2,356.6)
Income tax benefit (expense)				(41.8)
Net income (loss) attributable to MCBC				$ 331.1
Basic net income (loss) attributable to Molson Coors Brewing Company per share				$ 1.58
Diluted net income (loss) attributable to Molson Coors Brewing Company per share				$ 1.58
Weighted average shares - diluted (in shares)				210.2
Paid-in capital		6,556.6		$ 6,556.6
Retained earnings		$ 4,650.6		$ 4,650.6