New Accounting Pronouncements (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								6 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2016	Sep. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
New Accounting Pronouncement, Early Adoption [Line Items]
Paid-in capital	$ 6,635.3		$ 6,552.7	$ 6,546.1	$ 4,000.4				$ 6,552.7		$ 6,635.3	$ 4,000.4
Income tax benefit (expense)				16.7					37.9		(1,050.7)	(51.8)	$ (69.0)
Net cash provided by (used in) operating activities				(88.3)					282.4	$ 479.0	1,126.9	715.9	1,287.9
Other current assets	210.7				122.7						210.7	122.7
Other assets	382.5				256.7						382.5	256.7
Current portion of long-term debt and short-term borrowings	684.8				28.7						684.8	28.7
Long-term debt	11,387.7				2,908.7						11,387.7	2,908.7
Net Cash Provided by (Used in) Financing Activities				2,458.5					2,338.6	(327.6)	11,317.9	(531.5)	(817.3)
Net income (loss) attributable to Molson Coors Brewing Company	$ 1,438.4	$ 202.5	$ 172.3	$ 162.7	$ 32.8	$ 16.6	$ 229.0	$ 81.1	$ 335.0		$ 1,975.9	$ 359.5	$ 514.0
Basic net income (loss) attributable to Molson Coors Brewing Company per share	$ 6.70	$ 0.94	$ 0.80	$ 0.80	$ 0.18	$ 0.09	$ 1.23	$ 0.44	$ 1.60		$ 9.32	$ 1.94	$ 2.78
Earnings Per Share, Diluted	$ 6.65	$ 0.94	$ 0.80	$ 0.80	$ 0.18	$ 0.09	$ 1.23	$ 0.43	$ 1.59		$ 9.26	$ 1.93	$ 2.76
Weighted-average shares for diluted EPS				205.1					210.5		213.4	186.4	186.1
Retained earnings	$ 6,119.0		$ 4,654.5	$ 4,570.4	$ 4,496.0				$ 4,654.5		$ 6,119.0	$ 4,496.0
Scenario, Previously Reported [Member]
New Accounting Pronouncement, Early Adoption [Line Items]
Paid-in capital			6,556.6	6,550.0					6,556.6
Income tax benefit (expense)				20.6					41.8
Net cash provided by (used in) operating activities				(93.4)					264.4	461.5		696.4	$ 1,272.6
Net Cash Provided by (Used in) Financing Activities				2,463.6					2,356.6	$ (310.1)		(512.0)	(802.0)
Net income (loss) attributable to Molson Coors Brewing Company				$ 158.8					$ 331.1
Basic net income (loss) attributable to Molson Coors Brewing Company per share				$ 0.78					$ 1.58
Earnings Per Share, Diluted				$ 0.78					$ 1.58
Weighted-average shares for diluted EPS				204.8					210.2
Retained earnings			$ 4,650.6	$ 4,566.5					$ 4,650.6
Restatement Adjustment [Member]
New Accounting Pronouncement, Early Adoption [Line Items]
Net cash provided by (used in) operating activities												715.9	1,287.9
Net Cash Provided by (Used in) Financing Activities												$ (531.5)	$ (817.3)
New Accounting Pronouncement, Early Adoption, Effect [Member]
New Accounting Pronouncement, Early Adoption [Line Items]
Income tax benefit (expense)											(8.8)
Net cash provided by (used in) operating activities											$ 26.2