Other Consolidated Financial Statement Detail (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Accrued Expenses and Other
Current portion of contingent consideration obligations and milestones	$ 611.5		$ 611.5		$ 580.8
Revenue-related reserves for discounts and allowances	664.6		664.6		605.5
Employee compensation and benefits	241.9		241.9		282.9
Collaboration expenses accrual	180.1		180.1		130.9
Royalties and licensing fees	190.8		190.8		195.8
Construction Payable	157.6		157.6		134.0
Accrued TECFIDERA litigation settlement and license charges	0.0		0.0		454.8
Other	606.1		606.1		685.7
Total accrued expenses and other	2,455.2		2,455.2		2,903.5
Other Income (Expense), Net
Interest income	20.6	$ 16.4	54.2	$ 43.0
Interest expense	(61.8)	(66.0)	(188.8)	(195.2)
Gain (loss) on sales of investments, net	(4.0)	0.8	(15.0)	(0.3)
Foreign exchange gains (losses), net	6.7	(4.9)	8.4	(2.6)
Other, net	(5.1)	(4.4)	(8.2)	(14.3)
Other income (expense), net	(43.6)	$ (58.1)	(149.4)	$ (169.4)
Component of accrued expenses and other
Accrued Expenses and Other
Revenue-related reserves for discounts and allowances	$ 467.2		$ 467.2		$ 438.6