Supplemental Guarantor Information Income statement (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Condensed financial statements
Sales	$ 3,625.1	$ 3,552.9	$ 10,313.6	$ 10,259.8
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Excise taxes	(690.9)	(669.7)	(1,962.7)	(1,836.6)
Net Sales	2,934.2	2,883.2	8,350.9	8,423.2
Cost of Goods Sold	(1,714.0)	(1,589.1)	(4,988.8)	(4,716.9)
Gross profit	1,220.2	1,294.1	3,362.1	3,706.3
Marketing, general and administrative expenses	(713.9)	(783.8)	(2,139.7)	(2,271.5)
Special items, net	(36.6)	(4.1)	267.7	(27.3)
Operating income (loss)	469.7	506.2	1,490.1	1,407.5
Interest income (expense), net	(67.4)	(72.6)	(227.3)	(258.4)
Other pension and postretirement benefits (costs), net	7.6	9.6	27.5	32.3
Other pension and postretirement benefits (costs), net		9.6	27.5	32.3
Other income (expense), net	0.2	(2.7)	0.2	0.2
Income tax benefit (expense)	(64.5)	(147.4)	(231.6)	(338.5)
Net Income (loss)	345.6	293.1	1,058.9	843.1
Net (income) loss attributable to noncontrolling interests	(7.3)	(6.1)	(18.4)	(17.7)
Net income (loss) attributable to Molson Coors Brewing Company	338.3	287.0	1,040.5	825.4
Comprehensive income (loss) attributable to Molson Coors Brewing Company	367.3	468.9	904.1	1,326.3
Parent Company [Member]
Condensed financial statements
Sales	2.1	7.6	7.0	22.9
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Excise taxes	0.0	0.0	0.0	0.0
Net Sales	2.1	7.6	7.0	22.9
Cost of Goods Sold	(0.5)	(0.5)	(1.5)	(1.5)
Gross profit	1.6	7.1	5.5	21.4
Marketing, general and administrative expenses	(57.4)	(67.6)	(188.5)	(203.5)
Special items, net	(0.1)	0.0	(0.5)	(0.8)
Equity income (loss) in subsidiaries	434.7	390.5	1,332.1	1,177.1
Operating income (loss)	378.8	330.0	1,148.6	994.2
Interest income (expense), net	(78.5)	(72.6)	(244.9)	(228.1)
Other pension and postretirement benefits (costs), net	(0.1)	0.0	(0.1)	0.0
Other income (expense), net	0.0	0.3	0.1	(7.9)
Income (loss) before income taxes	300.2	257.7	903.7	758.2
Income tax benefit (expense)	38.1	29.3	136.8	67.2
Net Income (loss)	338.3	287.0	1,040.5	825.4
Net (income) loss attributable to noncontrolling interests	0.0	0.0	0.0	0.0
Net income (loss) attributable to Molson Coors Brewing Company	338.3	287.0	1,040.5	825.4
Comprehensive income (loss) attributable to Molson Coors Brewing Company	367.3	468.9	904.1	1,326.3
Subsidiary Guarantors [Member]
Condensed financial statements
Sales	2,714.4	2,696.1	7,823.7	8,026.8
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Excise taxes	(391.2)	(388.2)	(1,099.0)	(1,125.4)
Net Sales	2,323.2	2,307.9	6,724.7	6,901.4
Cost of Goods Sold	(1,356.2)	(1,248.9)	(3,982.9)	(3,810.7)
Gross profit	967.0	1,059.0	2,741.8	3,090.7
Marketing, general and administrative expenses	(496.6)	(560.1)	(1,473.9)	(1,617.0)
Special items, net	(34.2)	(6.0)	279.5	(23.3)
Equity income (loss) in subsidiaries	18.9	(72.7)	(60.7)	(276.6)
Operating income (loss)	455.1	420.2	1,486.7	1,173.8
Interest income (expense), net	90.9	81.7	257.7	200.9
Other pension and postretirement benefits (costs), net	(0.5)	(1.9)	2.5	(1.9)
Other income (expense), net	(9.4)	43.9	(49.7)	155.5
Income (loss) before income taxes	536.1	543.9	1,697.2	1,528.3
Income tax benefit (expense)	(101.5)	(153.2)	(364.7)	(351.0)
Net Income (loss)	434.6	390.7	1,332.5	1,177.3
Net (income) loss attributable to noncontrolling interests	0.0	0.0	0.0	0.0
Net income (loss) attributable to Molson Coors Brewing Company	434.6	390.7	1,332.5	1,177.3
Comprehensive income (loss) attributable to Molson Coors Brewing Company	435.9	577.2	1,148.4	1,725.4
Subsidiary Non Guarantors [Member]
Condensed financial statements
Sales	1,030.9	991.8	2,853.2	2,615.0
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Excise taxes	(299.7)	(281.5)	(863.7)	(711.2)
Net Sales	731.2	710.3	1,989.5	1,903.8
Cost of Goods Sold	(479.2)	(470.7)	(1,364.7)	(1,275.8)
Gross profit	252.0	239.6	624.8	628.0
Marketing, general and administrative expenses	(160.3)	(167.7)	(487.3)	(484.8)
Special items, net	(2.3)	1.9	(11.3)	(3.2)
Equity income (loss) in subsidiaries	62.6	71.8	124.8	153.8
Operating income (loss)	152.0	145.6	251.0	293.8
Interest income (expense), net	(79.8)	(81.7)	(240.1)	(231.2)
Other pension and postretirement benefits (costs), net	8.2	11.5	25.1	34.2
Other income (expense), net	9.6	(46.9)	49.8	(147.4)
Income (loss) before income taxes	90.0	28.5	85.8	(50.6)
Income tax benefit (expense)	(1.1)	(23.5)	(3.7)	(54.7)
Net Income (loss)	88.9	5.0	82.1	(105.3)
Net (income) loss attributable to noncontrolling interests	(7.3)	(6.1)	(18.4)	(17.7)
Net income (loss) attributable to Molson Coors Brewing Company	81.6	(1.1)	63.7	(123.0)
Comprehensive income (loss) attributable to Molson Coors Brewing Company	51.0	77.2	(43.3)	160.0
Consolidated [Member]
Condensed financial statements
Sales	3,625.1	3,552.9	10,313.6	10,259.8
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Excise taxes	(690.9)	(669.7)	(1,962.7)	(1,836.6)
Net Sales	2,934.2	2,883.2	8,350.9	8,423.2
Cost of Goods Sold	(1,714.0)	(1,589.1)	(4,988.8)	(4,716.9)
Gross profit	1,220.2	1,294.1	3,362.1	3,706.3
Marketing, general and administrative expenses	(713.9)	(783.8)	(2,139.7)	(2,271.5)
Special items, net	(36.6)	(4.1)	267.7	(27.3)
Equity income (loss) in subsidiaries	0.0	0.0	0.0	0.0
Operating income (loss)	469.7	506.2	1,490.1	1,407.5
Interest income (expense), net	(67.4)	(72.6)	(227.3)	(258.4)
Other pension and postretirement benefits (costs), net	7.6	9.6	27.5	32.3
Other income (expense), net	0.2	(2.7)	0.2	0.2
Income (loss) before income taxes	410.1	440.5	1,290.5	1,181.6
Income tax benefit (expense)	(64.5)	(147.4)	(231.6)	(338.5)
Net Income (loss)	345.6	293.1	1,058.9	843.1
Net (income) loss attributable to noncontrolling interests	(7.3)	(6.1)	(18.4)	(17.7)
Net income (loss) attributable to Molson Coors Brewing Company	338.3	287.0	1,040.5	825.4
Comprehensive income (loss) attributable to Molson Coors Brewing Company	367.3	468.9	904.1	1,326.3
Consolidation, Eliminations [Member]
Condensed financial statements
Sales	(122.3)	(142.6)	(370.3)	(404.9)
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Excise taxes	0.0	0.0	0.0	0.0
Net Sales	(122.3)	(142.6)	(370.3)	(404.9)
Cost of Goods Sold	121.9	131.0	360.3	371.1
Gross profit	(0.4)	(11.6)	(10.0)	(33.8)
Marketing, general and administrative expenses	0.4	11.6	10.0	33.8
Special items, net	0.0	0.0	0.0	0.0
Equity income (loss) in subsidiaries	(516.2)	(389.6)	(1,396.2)	(1,054.3)
Operating income (loss)	(516.2)	(389.6)	(1,396.2)	(1,054.3)
Interest income (expense), net	0.0	0.0	0.0	0.0
Other pension and postretirement benefits (costs), net	0.0	0.0	0.0	0.0
Other income (expense), net	0.0	0.0	0.0	0.0
Income (loss) before income taxes	(516.2)	(389.6)	(1,396.2)	(1,054.3)
Income tax benefit (expense)	0.0	0.0	0.0	0.0
Net Income (loss)	(516.2)	(389.6)	(1,396.2)	(1,054.3)
Net (income) loss attributable to noncontrolling interests	0.0	0.0	0.0	0.0
Net income (loss) attributable to Molson Coors Brewing Company	(516.2)	(389.6)	(1,396.2)	(1,054.3)
Comprehensive income (loss) attributable to Molson Coors Brewing Company	$ (486.9)	$ (654.4)	$ (1,105.1)	$ (1,885.4)