Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues:
Product, net	$ 8,203,404us-gaap_SalesRevenueGoodsNet	$ 5,542,331us-gaap_SalesRevenueGoodsNet	$ 4,166,074us-gaap_SalesRevenueGoodsNet
Unconsolidated joint business	1,195,389biib_UnconsolidatedJointBusiness	1,126,017biib_UnconsolidatedJointBusiness	1,137,923biib_UnconsolidatedJointBusiness
Other	304,531us-gaap_OtherSalesRevenueNet	263,851us-gaap_OtherSalesRevenueNet	212,464us-gaap_OtherSalesRevenueNet
Total revenues	9,703,324us-gaap_Revenues	6,932,199us-gaap_Revenues	5,516,461us-gaap_Revenues
Cost and expenses:
Cost of sales, excluding amortization of acquired intangible assets	1,171,036us-gaap_CostOfGoodsSold	857,726us-gaap_CostOfGoodsSold	545,494us-gaap_CostOfGoodsSold
Research and development	1,893,422	1,444,053	1,334,919
Selling, general and administrative	2,232,342	1,712,051	1,277,465
Amortization of acquired intangible assets	489,761us-gaap_AmortizationOfIntangibleAssets	342,948us-gaap_AmortizationOfIntangibleAssets	202,204us-gaap_AmortizationOfIntangibleAssets
Collaboration profit sharing	0biib_CollaborationProfitSharing	85,357biib_CollaborationProfitSharing	317,895biib_CollaborationProfitSharing
(Gain) loss on fair value remeasurement of contingent consideration	(38,893)	(547)	27,202
Restructuring charges	0us-gaap_RestructuringCharges	0us-gaap_RestructuringCharges	2,225us-gaap_RestructuringCharges
Total cost and expenses	5,747,668us-gaap_CostsAndExpenses	4,441,588us-gaap_CostsAndExpenses	3,707,404us-gaap_CostsAndExpenses
Gain on sale of rights	16,758biib_GainOnSaleOfRights	24,898biib_GainOnSaleOfRights	46,792biib_GainOnSaleOfRights
Income from operations	3,972,414us-gaap_OperatingIncomeLoss	2,515,509us-gaap_OperatingIncomeLoss	1,855,849us-gaap_OperatingIncomeLoss
Other income (expense), net	(25,781)us-gaap_OtherNonoperatingIncomeExpense	(34,930)us-gaap_OtherNonoperatingIncomeExpense	(744)us-gaap_OtherNonoperatingIncomeExpense
Income before income tax expense and equity in loss of investee, net of tax	3,946,633	2,480,579	1,855,105
Income tax expense	989,942us-gaap_IncomeTaxExpenseBenefit	601,014us-gaap_IncomeTaxExpenseBenefit	470,554us-gaap_IncomeTaxExpenseBenefit
Equity in loss of investee, net of tax	15,126	17,224	4,518
Net income	2,941,565us-gaap_ProfitLoss	1,862,341us-gaap_ProfitLoss	1,380,033us-gaap_ProfitLoss
Net income attributable to noncontrolling interests, net of tax	6,781	0	0
Net income attributable to Biogen Idec Inc.	$ 2,934,784us-gaap_NetIncomeLoss	$ 1,862,341us-gaap_NetIncomeLoss	$ 1,380,033us-gaap_NetIncomeLoss
Net income per share:
Basic earnings per share attributable to Biogen Idec Inc.	$ 12.42us-gaap_EarningsPerShareBasic	$ 7.86us-gaap_EarningsPerShareBasic	$ 5.80us-gaap_EarningsPerShareBasic
Diluted earnings per share attributable to Biogen Idec Inc.	$ 12.37us-gaap_EarningsPerShareDiluted	$ 7.81us-gaap_EarningsPerShareDiluted	$ 5.76us-gaap_EarningsPerShareDiluted
Weighted-average shares used in calculating:
Basic earnings per share attributable to Biogen Idec Inc.	236,359	236,919	237,938
Diluted earnings per share attributable to Biogen Idec Inc.	237,176	238,308	239,740

Payments are made to Elan for their share of rest of world net operating profits to effect an equal sharing of collaboration operating profit. These payments include the reimbursement of our portion of third-party royalties that Elan pays on behalf of the collaboration, relating to sales outside of the U.S. These amounts are reflected in the collaboration profit sharing line in our consolidated statement of income. As sales of TYSABRI outside the U.S. increase, our collaboration profit sharing expense will increase.

No definition available.