Derivative Instruments and Hedging Activities Derivative Valuation Activity (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended				3 Months Ended			3 Months Ended					0 Months Ended
	Jun. 30, 2012 Minimum [Member]		Jun. 30, 2012 Maximum [Member]		Jun. 30, 2012 Significant unobservable inputs (Level 3) [Member]		Mar. 31, 2012 Significant unobservable inputs (Level 3) [Member]	Jun. 30, 2012 Significant unobservable inputs (Level 3) [Member] Included in Earnings (or Change in Net Assets) [Member]		Jun. 30, 2012 Significant unobservable inputs (Level 3) [Member] Issuances [Member]		Jun. 30, 2012 Significant unobservable inputs (Level 3) [Member] Equity conversion feature of debt	Jun. 30, 2012 Zero Coupon Senior Unsecured Note [Member] Convertible Debt [Member] Equity conversion feature of debt Molson Coors Central Europe (MCCE) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest Expense, Other													$ 5.6
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases, Sales, Issuances, Settlements										(15.2)	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings					(5.6)	[1]		(5.6)	[1]
Derivative Financial Instruments, Liabilities, Fair Value Disclosure					$ (20.8)		$ 0					$ (20.8)	$ (20.8)
Sensitivitiy of Fair Value Changes, Unobservable Imputs, Implied Volatility Percentage	24.00%	[2]	25.00%	[2]

[1] At issuance, we recorded a liability of €12.1 million or ($15.2 million) related to the Convertible Note's embedded conversion feature. We recognized a $5.6 million unrealized loss, recorded in Interest expense, related to changes in fair value of this conversion feature for the quarter ended June 30, 2012.

[2] (1)Significant increase (decrease) in the unobservable input in isolation would result in a significantly higher (lower) fair value measurement.