Property, Plant and Equipment	9 Months Ended
Sep. 30, 2013
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are recorded at historical cost, net of accumulated depreciation. Accumulated depreciation on property, plant and equipment was $1,074.0 million and $941.1 million as of September 30, 2013 and December 31, 2012, respectively. For the three and nine months ended September 30, 2013, we capitalized interest costs related to construction in progress totaling approximately $2.2 million and $5.7 million, respectively, as compared to $6.6 million and $23.4 million, respectively, in the prior year comparative periods. Cambridge Leases In July 2011, we executed leases for two office buildings to be constructed in Cambridge, Massachusetts with a planned occupancy during the second half of 2013. Construction of these facilities began in late 2011. In accordance with accounting guidance applicable to entities involved with the construction of an asset that will be leased when the construction is completed, we are considered the owner of these properties during the construction period. Accordingly, we recorded an asset along with a corresponding financing obligation on our condensed consolidated balance sheet for the amount of total project costs incurred related to the construction in progress for these buildings. In July 2013, the construction of one of the two buildings was completed and we started leasing the facility. Upon completion of the construction of the building, we determined as part of a normal process that we are no longer considered the owner of that building because we do not have any unusual or significant continuing involvement. Consequently, we derecognized the building and its associated financing obligation of approximately $47.7 million from our condensed consolidated balance sheet. The derecognition of the building and its associated financing obligation constitute non-cash investing and financing transactions in the amount of $47.7 million. Upon completion of the second building, we will perform a similar assessment and determine if the remaining asset and corresponding financing obligation should also be derecognized. As of September 30, 2013 and December 31, 2012, the amounts recorded within our condensed consolidated balance sheet as property, plant and equipment and financing obligation totaled approximately $101.3 million and $86.5 million, respectively. As a result of our decision to relocate our corporate headquarters to Cambridge, Massachusetts, we expect to vacate part of our Weston, Massachusetts facility in the fourth quarter of 2013. We expect to incur a charge of approximately $25.0 million in connection with this process. This estimate represents our remaining lease obligation for the vacated portion of our Weston facility, net of sublease income to be received. We will begin to sublease the vacated portion of our Weston facility in the first half of 2014 for the remaining term of our lease agreement. Hillerød, Denmark Facility As of September 2012, our large-scale biologics manufacturing facility in Hillerød, Denmark was ready for its intended use as we began the process of manufacturing clinical products for sale to third parties. As a result, we transferred $465.9 million from construction in progress to various fixed asset accounts. We ceased capitalizing a majority of the interest expense and began recording depreciation on the various assets during the third quarter of 2012. The average estimated useful life for the facility and its assets is 20 years. In July 2013, the facility was approved by the U.S. Food and Drug Administration (FDA) and European Medicines Agency (EMA) for the manufacture of commercial TYSABRI. Research Triangle Park (RTP) Lease In December 2012, we entered into an arrangement with Eisai, Inc. (Eisai) to lease a portion of their facility in RTP to manufacture our and Eisai's oral solid dose products and for Eisai to provide us with vial-filling services for biologic therapies and packaging services for oral solid dose products. The 10 year operating lease agreement, which is cancellable after 5 years, became effective in February 2013 and gives us the option to purchase the facility.

Property, Plant and Equipment

Property, plant and equipment are recorded at historical cost, net of accumulated depreciation. Accumulated depreciation on property, plant and equipment was $1,074.0 million and $941.1 million as of September 30, 2013 and December 31, 2012, respectively.

For the three and nine months ended September 30, 2013, we capitalized interest costs related to construction in progress totaling approximately $2.2 million and $5.7 million, respectively, as compared to $6.6 million and $23.4 million, respectively, in the prior year comparative periods.

Cambridge Leases

In July 2011, we executed leases for two office buildings to be constructed in Cambridge, Massachusetts with a planned occupancy during the second half of 2013. Construction of these facilities began in late 2011. In accordance with accounting guidance applicable to entities involved with the construction of an asset that will be leased when the construction is completed, we are considered the owner of these properties during the construction period. Accordingly, we recorded an asset along with a corresponding financing obligation on our condensed consolidated balance sheet for the amount of total project costs incurred related to the construction in progress for these buildings.

In July 2013, the construction of one of the two buildings was completed and we started leasing the facility. Upon completion of the construction of the building, we determined as part of a normal process that we are no longer considered the owner of that building because we do not have any unusual or significant continuing involvement. Consequently, we derecognized the building and its associated financing obligation of approximately $47.7 million from our condensed consolidated balance sheet. The derecognition of the building and its associated financing obligation constitute non-cash investing and financing transactions in the amount of $47.7 million. Upon completion of the second building, we will perform a similar assessment and determine if the remaining asset and corresponding financing obligation should also be derecognized. As of September 30, 2013 and December 31, 2012, the amounts recorded within our condensed consolidated balance sheet as property, plant and equipment and financing obligation totaled approximately $101.3 million and $86.5 million, respectively.

As a result of our decision to relocate our corporate headquarters to Cambridge, Massachusetts, we expect to vacate part of our Weston, Massachusetts facility in the fourth quarter of 2013. We expect to incur a charge of approximately $25.0 million in connection with this process. This estimate represents our remaining lease obligation for the vacated portion of our Weston facility, net of sublease income to be received. We will begin to sublease the vacated portion of our Weston facility in the first half of 2014 for the remaining term of our lease agreement.

Hillerød, Denmark Facility

As of September 2012, our large-scale biologics manufacturing facility in Hillerød, Denmark was ready for its intended use as we began the process of manufacturing clinical products for sale to third parties. As a result, we transferred $465.9 million from construction in progress to various fixed asset accounts. We ceased capitalizing a majority of the interest expense and began recording depreciation on the various assets during the third quarter of 2012. The average estimated useful life for the facility and its assets is 20 years. In July 2013, the facility was approved by the U.S. Food and Drug Administration (FDA) and European Medicines Agency (EMA) for the manufacture of commercial TYSABRI.

Research Triangle Park (RTP) Lease

In December 2012, we entered into an arrangement with Eisai, Inc. (Eisai) to lease a portion of their facility in RTP to manufacture our and Eisai's oral solid dose products and for Eisai to provide us with vial-filling services for biologic therapies and packaging services for oral solid dose products. The 10 year operating lease agreement, which is cancellable after 5 years, became effective in February 2013 and gives us the option to purchase the facility.