Other Consolidated Financial Statement Detail (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Accrued Expenses and Other
Current portion of contingent consideration obligations and milestones	$ 580.7		$ 580.7		$ 580.8
Revenue-related reserves for discounts and allowances	724.3		724.3		605.5
Royalties and licensing fees	195.8		195.8		195.8
Collaboration expenses accrual	188.0		188.0		130.9
Employee compensation and benefits	186.6		186.6		282.9
Construction Payable	161.3		161.3		134.0
Accrued TECFIDERA litigation settlement and license charges	0.0		0.0		454.8
Other	591.2		591.2		685.7
Total accrued expenses and other	2,436.9		2,436.9		2,903.5
Other Income (Expense), Net
Interest income	16.9	$ 15.4	33.6	$ 26.6
Interest expense	(63.6)	(65.9)	(127.0)	(129.2)
Gain (loss) on sales of investments, net	(13.4)	(2.7)	(11.0)	(1.1)
Foreign exchange gains (losses), net	(2.3)	0.2	1.7	2.3
Other, net	(5.8)	(5.5)	(3.1)	(9.9)
Other income (expense), net	(68.2)	$ (58.5)	(105.8)	$ (111.3)
Component of accrued expenses and other
Accrued Expenses and Other
Revenue-related reserves for discounts and allowances	$ 533.3		$ 533.3		$ 438.6