New Accounting Pronouncements (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities	$ (118.3)	$ (88.3)
Net Cash Provided by (Used in) Financing Activities	(80.3)	(2,458.5)
Income tax benefit (expense)	(64.6)	(16.7)
Net income (loss) attributable to MCBC	$ 201.3	$ 162.7
Basic net income (loss) attributable to Molson Coors Brewing Company per share	$ 0.94	$ 0.80
Diluted net income (loss) attributable to Molson Coors Brewing Company per share	$ 0.93	$ 0.80
Weighted average shares - diluted (in shares)	216.5	205.1
Paid-in capital	$ 6,629.9	$ 6,546.1	$ 6,635.3
Retained earnings	$ 6,232.0	4,570.4	$ 6,119.0
Scenario, Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities		(93.4)
Net Cash Provided by (Used in) Financing Activities		(2,463.6)
Income tax benefit (expense)		20.6
Net income (loss) attributable to MCBC		$ 158.8
Basic net income (loss) attributable to Molson Coors Brewing Company per share		$ 0.78
Diluted net income (loss) attributable to Molson Coors Brewing Company per share		$ 0.78
Weighted average shares - diluted (in shares)		204.8
Paid-in capital		$ 6,550.0
Retained earnings		$ 4,566.5