v2.4.0.6

Earnings per Share | 9 Months Ended
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Sep. 30, 2012
Earnings Per Share [Abstract] |
Earnings per Share | Earnings per Share Basic and diluted earnings per share are calculated as follows:
| For the Three Months Ended September 30, |  | For the Nine Months Ended September 30,
(In millions) | 2012 |  | 2011 |  | 2012 |  | 2011
Numerator: |  |  |  |  |  |  |
Net income attributable to Biogen Idec Inc. | $ | 398.4 |  |  | $ | 351.8 |  |  | $ | 1,087.9 |  |  | $ | 934.2 |
Adjustment for net income allocable to preferred stock | — |  |  | — |  |  | — |  |  | (0.6 | )
Net income used in calculating basic and diluted earnings per share | $ | 398.4 |  |  | $ | 351.8 |  |  | $ | 1,087.9 |  |  | $ | 933.6 |
Denominator: |  |  |  |  |  |  |
Weighted average number of common shares outstanding | 236.5 |  |  | 242.9 |  |  | 238.3 |  |  | 242.3 |
Effect of dilutive securities: |  |  |  |  |  |  |
Stock options and employee stock purchase plan | 0.4 |  |  | 0.7 |  |  | 0.5 |  |  | 1.1 |
Time-vested restricted stock units | 0.9 |  |  | 1.6 |  |  | 1.0 |  |  | 1.5 |
Market stock units | 0.3 |  |  | 0.2 |  |  | 0.3 |  |  | 0.2 |
Dilutive potential common shares | 1.6 |  |  | 2.5 |  |  | 1.8 |  |  | 2.8 |
Shares used in calculating diluted earnings per share | 238.1 |  |  | 245.4 |  |  | 240.1 |  |  | 245.1 |
Amounts excluded from the calculation of net income per diluted share because their effects were anti-dilutive were insignificant.

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- Definition The entire disclosure for earnings per share. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=7655603&loc=d3e1252-109256 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 55 -Paragraph 52 -URI http://asc.fasb.org/extlink&oid=16381557&loc=d3e4984-109258 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=7655603&loc=d3e1278-109256 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 128 -Paragraph 40 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.21) -URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688 + Details
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