Other Comprehensive Income and Accumulated Other Comprehensive Income (Reclassifications out of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total revenues		$ 1,384.3	$ 1,263.1	$ 1,203.3	$ 1,140.4	$ 1,128.8	$ 1,026.5	$ 1,045.0	$ 930.9	$ 4,991.1	$ 4,131.2	$ 3,551.1
Other income and (expense)										2.1	(4.8)	9.4
Interest expense										(77.8)	(98.2)	(98.4)
Income before income taxes										2,178.8	242.2	547.8
Income tax expense										225.5	(164.6)	(104.5)
Net income		$ 889.0	$ 467.6	$ 459.8	$ 587.9	$ (45.0)	$ 330.9	$ (457.4)	$ 249.1	2,404.3	77.6	443.3
Reclassification from accumulated other comprehensive income, net										38.6	9.3	15.4
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from accumulated other comprehensive income, net										38.6	9.4	17.6
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Defined Benefit Pension Items	[1]									0.0	(0.3)	(0.4)
Accumulated Defined Benefit Plans Adjustment, Net Curtailment Attributable to Parent [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Defined Benefit Pension Items	[1]									0.0	(0.6)	(1.8)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from accumulated other comprehensive income, net										0.0	0.6	(0.8)
Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Defined Benefit Pension Items										0.0	(0.9)	(2.2)
Income tax expense										0.0	(0.2)	(0.8)
Reclassification from accumulated other comprehensive income, net										0.0	(0.7)	(1.4)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes										50.1	11.8	27.1
Income tax expense										(11.5)	(2.4)	(9.5)
Net income										38.6	9.4	17.6
Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Contract [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense										13.3	13.6	(1.8)
Net product sales
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total revenues										4,990.0	4,130.1	3,549.5
Net product sales | Reclassification out of Accumulated Other Comprehensive Income [Member] | Foreign Exchange Contract [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total revenues										$ 36.8	$ (1.8)	$ 28.9

[1] This AOCI component is included in the computation of net periodic pension benefit cost see Note 17, Employee Benefit Plans, for additional details.