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Fair Value Measurements (Details Textual) (USD $) In Millions, unless otherwise specified | 12 Months Ended |  |  | 12 Months Ended |  | 12 Months Ended |  |  | 12 Months Ended |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2013 Other Liabilities Non Current | Dec. 31, 2012 Other Liabilities Non Current | Dec. 31, 2013 Stromedix, Inc. | Dec. 31, 2012 Stromedix, Inc. | Mar. 08, 2012 Stromedix, Inc. | Dec. 31, 2013 Biogen Dompe SRL and Biogen Dompe Switzerland GmbH | Dec. 31, 2011 Biogen Dompe SRL and Biogen Dompe Switzerland GmbH | Dec. 31, 2012 Biogen Dompe SRL and Biogen Dompe Switzerland GmbH | Sep. 06, 2011 Biogen Dompe SRL and Biogen Dompe Switzerland GmbH | Dec. 31, 2013 Biogen Idec International Neuroscience GmbH | Dec. 31, 2012 Biogen Idec International Neuroscience GmbH | Dec. 31, 2010 Biogen Idec International Neuroscience GmbH | Dec. 31, 2013 6.0% Senior Notes due 2013 | Dec. 31, 2013 6.875% Senior Notes due 2018
Business Acquisition, Contingent Consideration [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Venture capital investments as percentage of our assets | approximately 0.2% of total assets | approximately 0.2% of total assets |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of venture capital investments to assets | 0.20% | 0.20% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate on senior notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6.00% | 6.875%
Contingent consideration obligations |  |  | $ 251.9 | $ 271.5 | $ 140.7 | $ 135.3 |  | $ 31.6 |  | $ 29.8 |  | $ 108.6 | $ 128.8 |  |  |
Additions | 0 | 122.2 |  |  |  | 122.2 |  |  | 38.8 |  |  |  |  | 81.2 |  |
Maximum contingent consideration in the form of development and approval milestones |  |  |  |  |  |  | 487.5 | 38.5 |  |  | 42.5 | 375.0 |  |  |  |
Discount rate used for net cash outflow projections for fair value measurement |  |  |  |  | 3.76% | 4.40% |  | 1.50% |  |  |  | 3.80% |  |  |  |
Milestone payments made during period |  |  |  |  |  |  |  | 4.0 |  |  |  | 12.5 | 2.5 |  |  |
Total purchase price allocated to IPR&D |  |  |  |  |  |  | $ 219.2 |  |  |  |  |  |  |  |  |
Fair value measurements, changes in valuation techniques | 0 | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |

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- Definition Percentage of venture capital investments to assets. + References No definition available. + Details
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