Acquisition and Investments MCBC proportional share in MillerCoors (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Oct. 10, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Oct. 11, 2016
Schedule of Equity Method Investments [Line Items]
MillerCoors owners' equity		$ 13,226.1	$ 11,418.7
Equity income in MillerCoors		$ 0.0	$ 500.9	$ 516.3
Millercoors [Member]
Schedule of Equity Method Investments [Line Items]
MillerCoors owners' equity	$ 7,822.3
Net income attributable to MillerCoors	$ 1,157.2			$ 1,217.8
MCBC economic Interest (as a percent)	42.00%		42.00%	42.00%	100.00%
MCBC proportionate share in MillerCoors' equity	$ 3,285.4
Difference between MCBC contributed cost basis and proportionate share of the underlying equity in net assets of MillerCoors	(653.7)
Accounting policy elections	35.0
Investment in MillerCoors	2,666.7
MCBC proportionate share of MillerCoors net income	486.0			$ 511.5
Amortization of the difference between MCBC contributed cost basis and proportionate share of the underlying equity in net assets of MillerCoors	3.3			4.6
Share-based compensation adjustment	(0.7)			0.2
Equity Method Investment, Adjustment, Import Tax Benefit	12.3			0.0
Equity income in MillerCoors	$ 500.9			$ 516.3