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Accounts Receivable (Details Textual) | 3 Months Ended |  | 3 Months Ended |  |
--- | --- | --- | --- | --- | ---
Mar. 31, 2015 USD ($) | Mar. 31, 2014 USD ($) | Dec. 31, 2014 USD ($) | Jun. 30, 2014 Italy USD ($) | Dec. 31, 2011 Italy | Mar. 31, 2015 Italy EUR (€) | Dec. 31, 2014 Italy EUR (€)
Accounts Receivable (Textual) [Abstract] |  |  |  |  |  |  |
Payment terms of accounts receivable arising from product sales | 30 to 90 days |  |  |  |  |  |
Minimum term for accounts receivable | 30 days |  |  |  |  |  |
Maximum term for accounts receivable | 90 days |  |  |  |  |  |
Net accounts receivable balances overdue more than one year | $ 11,400,000 biib_AccountsReceivableOutstandingForGreaterThanOneYear |  | $ 11,100,000 biib_AccountsReceivableOutstandingForGreaterThanOneYear |  |  |  |
Reimbursement limit stated in the resolution |  |  |  |  | 24 months |  |
Product, net | 2,172,322,000 us-gaap_SalesRevenueGoodsNet | 1,742,765,000 us-gaap_SalesRevenueGoodsNet |  | 53,500,000 us-gaap_SalesRevenueGoodsNet / us-gaap_StatementGeographicalAxis = country_IT |  |  |
Proposed settlement |  |  |  |  |  |  | 35,600,000 us-gaap_LossContingencyEstimateOfPossibleLoss / us-gaap_StatementGeographicalAxis = country_IT
Amount reserved for this matter |  |  |  |  |  | € 75,000,000 us-gaap_DeferredCreditsAndOtherLiabilitiesCurrent / us-gaap_StatementGeographicalAxis = country_IT |

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