Intangible Assets and Goodwill (Tables)

9 Months Ended

Sep. 30, 2013

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible assets

		As of September 30, 2013							As of December 31, 2012
(In millions)	Estimated Life	Cost		Accumulated Amortization			Net		Cost		Accumulated Amortization			Net
Out-licensed patents	13-23 years	$	578.0	$	(443.3	)	$	134.7	$	578.0	$	(421.0	)	$	157.0
AVONEX Core developed  technology	15-23 years	3,005.3		(2,107.0		)	898.3		3,005.3		(1,965.7		)	1,039.6
In-process research and development	Up to 15 years upon commercialization	327.4		—			327.4		330.1		—			330.1
Trademarks and  tradenames	Indefinite	64.0		—			64.0		64.0		—			64.0
Acquired and in-licensed rights  and patents	6-17 years	3,236.1		(80.3		)	3,155.8		53.7		(12.9		)	40.8
Total intangible assets		$	7,210.8	$	(2,630.6	)	$	4,580.2	$	4,031.1	$	(2,399.6	)	$	1,631.5

Estimated future amortization for acquired intangible assets

(In millions)	As of September 30, 2013
2013 (remaining three months)	$	113.2
2014	418.9
2015	337.4
2016	323.4
2017	328.1
2018	330.7
Total	$	1,851.7

Summary of roll forward of the changes in goodwill

(In millions)	As of September 30, 2013			As of December 31, 2012
Goodwill, beginning of period	$	1,201.3		$	1,146.3
Goodwill acquired during the period	13.5			48.2
Other	(4.1		)	6.8
Goodwill, end of period	$	1,210.7		$	1,201.3