Goodwill and Intangible Assets Intangible Assets (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2012 years	Dec. 31, 2011 years
Details of intangible assets, other than goodwill:
Total Gross	$ 5,145,900,000	$ 5,028,700,000
Total Net	4,682,800,000	4,586,000,000
Intangible assets subject to amortization:
Accumulated amortization	(463,100,000)	(442,700,000)
Intangible assets not subject to amortization:
Impairment charge associated with Molson brands intangible asset	0
Goodwill, Impaired, Accumulated Impairment Loss	0
Brands
Intangible assets subject to amortization:
Useful life - minimum (in years)	3	3
Useful life - maximum (in years)	40	40
Gross	326,000,000	316,900,000
Accumulated amortization	(188,400,000)	(179,000,000)
Net	137,600,000	137,900,000
Intangible assets not subject to amortization:
Indefinite-lived intangible assets	3,399,900,000	3,322,400,000
Distribution rights
Intangible assets subject to amortization:
Useful life - minimum (in years)	2	2
Useful life - maximum (in years)	23	23
Gross	350,000,000	342,000,000
Accumulated amortization	(243,200,000)	(234,000,000)
Net	106,800,000	108,000,000
Patents and technology and distribution channels
Intangible assets subject to amortization:
Useful life - minimum (in years)	3	3
Useful life - maximum (in years)	10	10
Gross	35,000,000	34,900,000
Accumulated amortization	(30,600,000)	(28,900,000)
Net	4,400,000	6,000,000
Land use rights and other
Intangible assets subject to amortization:
Useful life - minimum (in years)	2	2
Useful life - maximum (in years)	42	42
Gross	6,500,000	6,500,000
Accumulated amortization	(900,000)	(800,000)
Net	5,600,000	5,700,000
Distribution networks
Intangible assets not subject to amortization:
Indefinite-lived intangible assets	1,012,900,000	990,500,000
Other, intangible
Intangible assets not subject to amortization:
Indefinite-lived intangible assets	$ 15,600,000	$ 15,500,000