Special items Summary Special Items (Details) £ in Millions, $ in Millions		3 Months Ended					6 Months Ended			12 Months Ended
	Apr. 30, 2015 GBP (£)	Jun. 30, 2015 GBP (£)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	[1]	Jun. 30, 2015 GBP (£)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Dec. 31, 2014 GBP (£)
Restructuring Cost and Reserve [Line Items]
Special items			$ 33.7	$ 2.7				$ 42.3	$ (49.8)
Intangible asset write-off			5.9	10.4				13.7	21.0
Heineken [Member]
Restructuring Cost and Reserve [Line Items]
Proceeds from early contract termination | £	£ 8.0	£ 13.0								£ 5.0
Modelo [Member]
Restructuring Cost and Reserve [Line Items]
Termination fee (income) expense			0.0	0.0	$ (63.2)			0.0	(63.2)
Canada [Member]
Restructuring Cost and Reserve [Line Items]
Assets Disposed of by Method Other than Sale, in Period of Disposition, Gain (Loss) on Disposition			8.2
Canada [Member] | Licensing Agreements [Member]
Restructuring Cost and Reserve [Line Items]
Intangible asset write-off			0.0	0.0				0.0	4.9
Canada [Member] | Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Special items			0.0	0.1				0.0	5.4
Canada [Member] | Asset Abandonment [Member]
Restructuring Cost and Reserve [Line Items]
Special items			8.2	0.0				8.2	0.0
Europe [Member]
Restructuring Cost and Reserve [Line Items]
Termination fee (income) expense			10.0	0.0				10.0	0.0
Accelerated depreciation expense			8.0					19.8
Assets Disposed of by Method Other than Sale, in Period of Disposition, Gain (Loss) on Disposition			1.3
Loss on contract termination			29.4				£ 19.0	29.4
Europe [Member] | Heineken [Member]
Restructuring Cost and Reserve [Line Items]
Termination fee (income) expense			(19.4)					(19.4)
Europe [Member] | Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Special items			0.2	0.5				(1.0)	1.0
Europe [Member] | Asset Abandonment [Member]
Restructuring Cost and Reserve [Line Items]
Special items			9.3	0.0				21.1	0.0
Europe [Member] | Flood loss [Member]
Restructuring Cost and Reserve [Line Items]
Unusual or Infrequent Item, Net of Insurance Proceeds			(0.4)	1.8				(2.4)	1.8
Restructuring, Settlement and Impairment Provisions - Gain			0.4					2.4
MCI [Member] | Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Special items			3.2	0.0				3.2	0.0
MCI [Member] | China Impairment [Member]
Restructuring Cost and Reserve [Line Items]
Special items			3.2	0.0				3.2	0.0
Corporate [Member] | Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Special items			$ 0.0	$ 0.3				$ 0.0	$ 0.3

[1] During the second quarter of 2015, we announced our decision to substantially restructure our business in China and consequently, recognized employee-related and asset write-off charges.