Quarterly Financial Information (Unaudited) Prior Period Adjustment - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Paid-in capital	$ 6,688.5				$ 6,635.3				$ 6,688.5	$ 6,635.3
Net cash provided by (used in) operating activities									1,866.3	1,126.9	$ 715.9
Income tax benefit (expense)									(53.2)	1,055.2	61.5
Net income (loss) attributable to Molson Coors Brewing Company	$ 588.8	$ 287.0	$ 329.9	$ 208.5	$ 1,439.3	$ 207.7	$ 177.9	$ 168.1	$ 1,414.2	$ 1,993.0	$ 395.2
Basic net income (loss) attributable to Molson Coors Brewing Company per share	$ 2.73	$ 1.33	$ 1.53	$ 0.97	$ 6.70	$ 0.97	$ 0.83	$ 0.83	$ 6.57	$ 9.40	$ 2.13
Earnings Per Share, Diluted	$ 2.72	$ 1.33	$ 1.52	$ 0.96	$ 6.65	$ 0.96	$ 0.82	$ 0.82	$ 6.53	$ 9.34	$ 2.12
Weighted-average shares for diluted EPS									216.5	213.4	186.4
Net Cash Provided by (Used in) Financing Activities									$ (1,496.4)	$ 11,317.9	$ (531.5)
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Income tax benefit (expense)	$ (392.4)	$ 145.3	$ 123.0	$ 64.6	$ 993.2	$ 19.6	$ 21.2	$ 16.7	59.5	(1,050.7)	(51.8)
Net income (loss) attributable to Molson Coors Brewing Company	$ 580.4	$ 280.0	$ 323.3	$ 201.3	$ 1,438.4	$ 202.5	$ 172.3	$ 162.7	$ 1,385.0	$ 1,975.9	$ 359.5
Basic net income (loss) attributable to Molson Coors Brewing Company per share	$ 2.69	$ 1.30	$ 1.50	$ 0.94	$ 6.70	$ 0.94	$ 0.80	$ 0.80	$ 6.43	$ 9.32	$ 1.94
Earnings Per Share, Diluted	$ 2.68	$ 1.29	$ 1.49	$ 0.93	$ 6.65	$ 0.94	$ 0.80	$ 0.80	$ 6.40	$ 9.26	$ 1.93