Segment Information (Tables)

12 Months Ended

Dec. 31, 2011

Segment Information [Abstract]

Revenue by product

	For the Years Ended December 31,
	2011						2010						2009
(In millions)	United States		Rest of World		Total		United States		Rest of World		Total		United States		Rest of World		Total
AVONEX	$	1,628.3	$	1,058.3	$	2,686.6	$	1,491.6	$	1,026.8	$	2,518.4	$	1,406.2	$	916.7	$	2,322.9
TYSABRI		326.5		753.0		1,079.5		252.8		647.4		900.2		231.8		544.2		776.0
Other		—		70.0		70.0		—		51.5		51.5		—		54.0		54.0
Total product revenues	$	1,954.8	$	1,881.3	$	3,836.1	$	1,744.4	$	1,725.7	$	3,470.1	$	1,638.0	$	1,514.9	$	3,152.9

Geographic information

December 31, 2011 (In millions)	U.S.		Europe(1)		Germany		Asia		Other		Total
Product revenues from external customers	$	1,954.8	$	1,163.3	$	377.5	$	88.7	$	251.8	$	3,836.1
Revenues from unconsolidated joint business	$	878.8	$	29.9	$	—	$	30.7	$	57.2	$	996.6
Other revenues from external customers	$	187.0	$	28.3	$	0.6	$	—	$	—	$	215.9
Long-lived assets	$	1,012.5	$	816.6	$	1.6	$	5.3	$	2.4	$	1,838.4
December 31, 2010 (In millions)	U.S.		Europe(1)		Germany		Asia		Other		Total
Product revenues from external customers	$	1,744.4	$	1,090.7	$	362.4	$	69.0	$	203.6	$	3,470.1
Revenues from unconsolidated joint business	$	906.3	$	95.3	$	—	$	26.0	$	49.6	$	1,077.2
Other revenues from external customers	$	136.0	$	32.6	$	0.5	$	—	$	—	$	169.1
Long-lived assets	$	1,100.3	$	717.4	$	1.5	$	5.4	$	1.6	$	1,826.2
December 31, 2009 (In millions)	U.S.		Europe(1)		Germany		Asia		Other		Total
Product revenues from external customers	$	1,638.0	$	913.7	$	374.8	$	47.9	$	178.5	$	3,152.9
Revenues from unconsolidated joint business	$	839.2	$	190.2	$	—	$	24.1	$	41.4	$	1,094.9
Other revenues from external customers	$	102.8	$	26.2	$	0.5	$	—	$	—	$	129.5
Long-lived assets	$	1,092.7	$	705.6	$	1.4	$	3.6	$	2.1	$	1,805.4

(1) Represents amounts related to Europe less those attributable to Germany.