Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues:
Product, net	$ 5,542,331	$ 4,166,074	$ 3,836,117
Unconsolidated joint business	1,126,017	1,137,923	996,597
Other	263,851	212,464	215,920
Total revenues	6,932,199	5,516,461	5,048,634
Cost and expenses:
Cost of sales, excluding amortization of acquired intangible assets	857,726	545,494	466,780
Research and development	1,444,053	1,334,919	1,219,602
Selling, general and administrative	1,712,051	1,277,465	1,056,133
Amortization of acquired intangible assets	342,948	202,204	208,566
Collaboration profit sharing	85,357	317,895	317,771
(Gain) loss on fair value remeasurement of contingent consideration	(547)	27,202	36,065
Restructuring charges	0	2,225	19,026
Total cost and expenses	4,441,588	3,707,404	3,323,943
Gain on sale of rights	24,898	46,792	0
Income from operations	2,515,509	1,855,849	1,724,691
Other income (expense), net	(34,930)	(744)	(13,477)
Income before income tax expense and equity in loss of investee, net of tax	2,480,579	1,855,105	1,711,214
Income tax expense	601,014	470,554	444,528
Equity in loss of investee, net of tax	17,224	4,518	0
Net income	1,862,341	1,380,033	1,266,686
Net income attributable to noncontrolling interests, net of tax	0	0	32,258
Net income attributable to Biogen Idec Inc.	$ 1,862,341	$ 1,380,033	$ 1,234,428
Net income per share:
Basic earnings per share attributable to Biogen Idec Inc.	$ 7.86	$ 5.80	$ 5.09
Diluted earnings per share attributable to Biogen Idec Inc.	$ 7.81	$ 5.76	$ 5.04
Weighted-average shares used in calculating:
Basic earnings per share attributable to Biogen Idec Inc.	236,919	237,938	242,395
Diluted earnings per share attributable to Biogen Idec Inc.	238,308	239,740	245,033