v2.4.0.6

Accounts Receivable (Tables) | 9 Months Ended
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Sep. 30, 2012
Receivables [Abstract] |
Net accounts receivable balances from product sales in selected European countries |
| As of September 30, 2012
(In millions) | Current Balance Included within Accounts Receivable, net |  | Non-Current Balance Included within Investments and Other Assets |  | Total
Spain | $ | 73.5 |  |  | $ | — |  |  | $ | 73.5 |
Italy | $ | 94.6 |  |  | $ | 13.8 |  |  | $ | 108.4 |
Portugal | $ | 19.6 |  |  | $ | 7.2 |  |  | $ | 26.8 |
Greece | $ | 2.4 |  |  | $ | — |  |  | $ | 2.4 |
| As of December 31, 2011
(In millions) | Current Balance Included within Accounts Receivable, net |  | Non-Current Balance Included within Investments and Other Assets |  | Total
Spain | $ | 68.5 |  |  | $ | 65.5 |  |  | $ | 134.0 |
Italy | $ | 19.4 |  |  | $ | 48.7 |  |  | $ | 68.1 |
Portugal | $ | 20.6 |  |  | $ | 12.3 |  |  | $ | 32.9 |
Greece | $ | 4.0 |  |  | $ | — |  |  | $ | 4.0 |

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- Definition Tabular disclosure of the accounts receivable from product sales in various foreign countries. + References No definition available. + Details
Name: | biib_ScheduleOfAccountsReceivableFromProductSalesInForeignCountriesTableTextBlock
Namespace Prefix: | biib_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_ReceivablesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration