Intangible Assets and Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Feb. 12, 2015	Dec. 31, 2014
Intangible assets
Total intangible assets, gross	$ 7,661,300		$ 7,661,300			$ 7,207,100
Accumulated Amortization	(3,366,500)		(3,366,500)			(3,178,600)
Intangible assets, net	4,294,791		4,294,791			4,028,507
Intangible Assets and Goodwill (Textual) [Abstract]
Amortization of acquired intangible assets	92,004	$ 116,826	187,907	$ 260,084
Accumulated impairment losses related to goodwill	0		0
Expected future amortization expense, 2015 (remaining six months)	185,500		185,500
Expected future amortization expense, 2016	312,500		312,500
Expected future amortization expense, 2017	285,800		285,800
Expected future amortization expense, 2018	281,600		281,600
Expected future amortization expense, 2019	270,600		270,600
Expected future amortization expense, 2020	263,800		263,800
Total	1,599,800		1,599,800
Out-licensed patents
Intangible assets
Cost	543,300		543,300			543,300
Accumulated Amortization	(493,900)		(493,900)			(481,700)
Net	49,400		$ 49,400			61,600
Impairment of out-licensed patent		$ 34,700
Out-licensed patents | Minimum
Intangible assets
Estimated life, (in years)			13 years
Out-licensed patents | Maximum
Intangible assets
Estimated life, (in years)			23 years
Developed technology
Intangible assets
Cost	3,005,300		$ 3,005,300			3,005,300
Accumulated Amortization	(2,492,100)		(2,492,100)			(2,396,800)
Net	513,200		$ 513,200			608,500
Developed technology | Minimum
Intangible assets
Estimated life, (in years)			15 years
Developed technology | Maximum
Intangible assets
Estimated life, (in years)			23 years
Developed technology | AVONEX
Intangible assets
Net	504,300		$ 504,300
Acquired and in-licensed rights and patents
Intangible assets
Cost	3,296,700		3,296,700			3,280,400
Accumulated Amortization	(380,500)		(380,500)			(300,100)
Net	2,916,200		$ 2,916,200			2,980,300
Acquired and in-licensed rights and patents | Minimum
Intangible assets
Estimated life, (in years)			3 years
Acquired and in-licensed rights and patents | Maximum
Intangible assets
Estimated life, (in years)			17 years
In-process research and development
Intangible assets
Indefinite lived intangible assets useful life
Cost and Net	752,000		$ 752,000			314,100
Accumulated Amortization	0		$ 0			0
Trademarks and trade names
Intangible assets
Indefinite lived intangible assets useful life
Cost and Net	64,000		$ 64,000			64,000
Accumulated Amortization	0		0			$ 0
Convergence Pharmaceuticals
Intangible assets
In-process research and development and other intangible assets					$ 424,600
TYSABRI product | Acquired and in-licensed rights and patents
Intangible assets
Net	$ 2,851,900		$ 2,851,900