Special items Summary Special Items (Details) (USD $)	3 Months Ended				9 Months Ended				12 Months Ended
	Sep. 29, 2012		Sep. 24, 2011		Sep. 29, 2012 Employees		Sep. 24, 2011		Dec. 26, 2009
Restructuring Cost and Reserve [Line Items]
Total special items	$ 35,900,000		$ 100,000		$ 58,600,000		$ 11,100,000
Reduction in number of employees due to restructuring					189
Non-income-related Tax Reserves									10,400,000
Gain (Loss) Related to Restructuring Reserve Low End of Range	0
Gain (Loss) Related to Restructuring Reserve High End of Range	22,300,000
Canada [Member] | Restructuring, exit and other related costs associated with the Edmonton and Montreal breweries
Restructuring Cost and Reserve [Line Items]
Total special items	2,500,000	[1]	0	[1]	4,100,000	[1]	600,000	[1]
Canada [Member] | Special termination benefits
Restructuring Cost and Reserve [Line Items]
Total special items	300,000	[2]	700,000	[2]	2,200,000	[2]	4,700,000	[2]
Canada [Member] | Flood insurance reimbursement
Restructuring Cost and Reserve [Line Items]
Total special items	900,000	[3]	(400,000)	[3]	(1,400,000)	[3]	(300,000)	[3]
Canada [Member] | BRI loan guarantee adjustment
Restructuring Cost and Reserve [Line Items]
Total special items	0	[4]	0	[4]	0	[4]	(2,000,000)	[4]
Canada [Member] | Fixed asset adjustment
Restructuring Cost and Reserve [Line Items]
Total special items	0	[5]	0	[5]	0	[5]	7,600,000	[5]
Central Europe | Restructuring, exit and other related costs associated with the Edmonton and Montreal breweries
Restructuring Cost and Reserve [Line Items]
Total special items	100,000	[1]	0	[1]	100,000	[1]	0	[1]
U.K. [Member] | Restructuring charge
Restructuring Cost and Reserve [Line Items]
Total special items	2,400,000	[1]	(500,000)	[1]	8,700,000	[1]	2,200,000	[1]
U.K. [Member] | Asset abandonment
Restructuring Cost and Reserve [Line Items]
Total special items	0	[6]	0	[6]	7,200,000	[6]	0	[6]
U.K. [Member] | Release of non-income-related tax reserve
Restructuring Cost and Reserve [Line Items]
Total special items	0	[7]	0	[7]	(3,500,000)	[7]	(2,500,000)	[7]
U.K. [Member] | Costs associated with strategic initiatives
Restructuring Cost and Reserve [Line Items]
Total special items	0		100,000		0		100,000
Corporate | Restructuring charge
Restructuring Cost and Reserve [Line Items]
Total special items	0	[1]	0	[1]	1,100,000	[1]	0	[1]
MCI | Restructuring, exit and other related costs associated with the Edmonton and Montreal breweries
Restructuring Cost and Reserve [Line Items]
Total special items	1,200,000	[1]	0	[1]	1,200,000	[1]	0	[1]
MCI | China impairment
Restructuring Cost and Reserve [Line Items]
Total special items	28,500,000	[8]	0	[8]	38,900,000	[8]	0	[8]
MCI | Costs associated with outsourcing and other strategic initiatives
Restructuring Cost and Reserve [Line Items]
Total special items	0		200,000		0		700,000
MC Si Hai
Restructuring Cost and Reserve [Line Items]
Asset impairment charges	27,600,000
Legal costs	$ 900,000

[1] During 2012, we initiated restructuring programs in each of our segments focused on labor savings across all functions. As a result, we have reduced headcount by 189 employees during the first three quarters of 2012 and we expect further headcount reduction during the fourth quarter, although we are unable to estimate future costs at this time.

[2] During the third quarter and first three quarters of 2012 and 2011, we recognized charges related to special termination benefits as eligible employees elected early retirement offered as a result of the ratification of Collective Bargaining Agreements with MCC's brewery groups in 2011 and 2012.

[3] In the third quarter of 2012, we incurred expenses in excess of insurance proceeds related to flood damage at our Toronto offices. In the first three quarters of 2012 and third quarter and first three quarters of 2011, we received insurance proceeds in excess of expenses incurred related to these damages.

[4] During the first three quarters of 2011, we recognized a gain resulting from a reduction of our guarantee of BRI debt obligations.

[5] During the first three quarters of 2011, we recognized a loss related to the correction of an immaterial error in prior periods to reduce Properties in the Canada segment, resulting from the performance of a fixed asset count. The impact of the error and the related correction in 2011 is not material to any prior annual or interim financial statements and is not material to the fiscal year results for 2011.

[6] During the second quarter of 2012, we recognized an asset abandonment charge related to the discontinuation of the Home Draft packaging in the U.K. This packaging was not meeting expectations driven by a lack of demand in the U.K. market and as a result, we recognized a loss related to the write-off of the Home Draft packaging line, tooling equipment and packaging materials inventory.

[7] During 2009, we established a non-income-related tax reserve of $10.4 million that was recorded as a Special item. Our estimates indicated a range of possible loss relative to this reserve of zero to $22.3 million, inclusive of potential penalties and interest. The amounts recorded in 2012 and 2011 represent a release of a portion of this reserve as a result of a change in estimate.

[8] In the second quarter of 2012, we recognized impairment charges related to goodwill and definite-lived intangible assets in our MC Si'hai joint venture in China. See related detail in Note 12 "Goodwill and Intangible Assets." In the third quarter of 2012, we deconsolidated our MC Si'hai joint venture in China and recognized an impairment loss of $27.6 million upon deconsolidation and $0.9 million of related costs. See related detail in Note 5, "Investments."