Segment Reporting (Revenue by Product) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenue from External Customer [Line Items]
Product sales	$ 3,591.8	$ 2,322.1	$ 7,004.1	$ 3,949.4
Royalties and Other revenues	154.0	107.0	314.0	189.0
Total revenues	3,745.8	2,429.1	7,318.1	4,138.4
Hematology
Revenue from External Customer [Line Items]
Product sales	964.6	349.6	1,835.5	349.6
HEMOPHILIA
Revenue from External Customer [Line Items]
Product sales	743.9	275.6	1,394.3	275.6
INHIBITOR THERAPIES
Revenue from External Customer [Line Items]
Product sales	220.7	74.0	441.2	74.0
Genetic Diseases
Revenue from External Customer [Line Items]
Product sales	704.9	687.8	1,401.1	1,301.1
CINRYZE
Revenue from External Customer [Line Items]
Product sales	175.9	173.0	401.8	337.2
ELAPRASE
Revenue from External Customer [Line Items]
Product sales	161.0	154.0	301.6	277.6
FIRAZYR
Revenue from External Customer [Line Items]
Product sales	137.4	136.7	265.9	265.0
REPLAGAL
Revenue from External Customer [Line Items]
Product sales	122.1	118.4	231.8	221.6
VPRIV
Revenue from External Customer [Line Items]
Product sales	87.9	88.0	167.7	171.6
KALBITOR
Revenue from External Customer [Line Items]
Product sales	20.6	17.7	32.3	28.1
Immunology
Revenue from External Customer [Line Items]
Product sales	682.7	189.5	1,358.9	189.5
IMMUNOGLOBULIN THERAPIES
Revenue from External Customer [Line Items]
Product sales	510.5	138.2	1,008.8	138.2
BIO THERAPEUTICS
Revenue from External Customer [Line Items]
Product sales	172.2	51.3	350.1	51.3
Neuroscience
Revenue from External Customer [Line Items]
Product sales	635.4	655.2	1,288.7	1,285.3
VYVANSE
Revenue from External Customer [Line Items]
Product sales	518.2	517.7	1,081.9	1,026.9
ADDERALL XR
Revenue from External Customer [Line Items]
Product sales	71.4	101.8	136.3	200.6
MYDAYIS
Revenue from External Customer [Line Items]
Product sales	15.7	0.0	15.7	0.0
Other Neuroscience
Revenue from External Customer [Line Items]
Product sales	30.1	35.7	54.8	57.8
Internal Medicine
Revenue from External Customer [Line Items]
Product sales	484.3	419.7	903.1	803.6
LIALDA/MEZAVANT
Revenue from External Customer [Line Items]
Product sales	207.8	193.7	382.9	361.7
PENTASA
Revenue from External Customer [Line Items]
Product sales	83.3	72.9	152.4	136.9
GATTEX/REVESTIVE
Revenue from External Customer [Line Items]
Product sales	75.3	44.5	144.3	96.2
NATPARA
Revenue from External Customer [Line Items]
Product sales	34.5	19.9	64.2	35.5
Other Internal Medicine
Revenue from External Customer [Line Items]
Product sales	83.4	88.7	159.3	173.3
Oncology
Revenue from External Customer [Line Items]
Product sales	62.5	20.3	120.8	20.3
Ophthalmology
Revenue from External Customer [Line Items]
Product sales	57.4	0.0	96.0	0.0
SENSIPAR royalties
Revenue from External Customer [Line Items]
Royalties and Other revenues	46.4	35.6	85.3	73.5
ADDERALL XR royalties
Revenue from External Customer [Line Items]
Royalties and Other revenues	13.4	5.2	25.9	11.0
FOSRENOL royalties
Revenue from External Customer [Line Items]
Royalties and Other revenues	12.1	11.4	20.7	20.6
3TC and ZEFFIX royalties
Revenue from External Customer [Line Items]
Royalties and Other revenues	8.2	12.1	22.7	27.1
Other royalties and revenues
Revenue from External Customer [Line Items]
Royalties and Other revenues	$ 73.9	$ 42.7	$ 159.4	$ 56.8