Revenue Reserves (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Analysis of the amount of, and change in, reserves
Beginning balance	$ 605.5	$ 662.7	$ 483.8
Current provisions relating to sales in current year	2,917.3	2,668.0	2,229.4
Adjustments relating to prior years	6.0	(16.7)	(32.3)
Payments/returns relating to sales in current year	(2,232.8)	(2,099.5)	(1,666.6)
Payments/returns relating to sales in prior years	(534.4)	(609.0)	(351.6)
Ending balance	761.6	605.5	662.7
Discounts
Analysis of the amount of, and change in, reserves
Beginning balance	71.6	56.1	47.6
Current provisions relating to sales in current year	583.0	592.6	459.7
Adjustments relating to prior years	(0.1)	(1.4)	(1.3)
Payments/returns relating to sales in current year	(475.8)	(522.5)	(405.9)
Payments/returns relating to sales in prior years	(69.1)	(53.2)	(44.0)
Ending balance	109.6	71.6	56.1
Contractual Adjustments
Analysis of the amount of, and change in, reserves
Beginning balance	482.7	548.7	387.1
Current provisions relating to sales in current year	2,307.4	2,044.5	1,732.1
Adjustments relating to prior years	15.0	1.5	(16.3)
Payments/returns relating to sales in current year	(1,756.9)	(1,576.0)	(1,258.1)
Payments/returns relating to sales in prior years	(442.2)	(536.0)	(296.1)
Ending balance	606.0	482.7	548.7
Returns
Analysis of the amount of, and change in, reserves
Beginning balance	51.2	57.9	49.1
Current provisions relating to sales in current year	26.9	30.9	37.6
Adjustments relating to prior years	(8.9)	(16.8)	(14.7)
Payments/returns relating to sales in current year	(0.1)	(1.0)	(2.6)
Payments/returns relating to sales in prior years	(23.1)	(19.8)	(11.5)
Ending balance	$ 46.0	$ 51.2	$ 57.9