Intangible Assets and Goodwill	12 Months Ended
Intangible Assets and Goodwill	Dec. 31, 2012
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets and Goodwill	Intangible Assets and Goodwill Intangible Assets As of December 31, 2012 and 2011, the Company's intangible assets consisted of indefinite-lived in-process research and development assets of (i) $250.6 million related to its HCV nucleotide analogue program, which includes the HCV nucleotide analogue VX-135 and included the HCV nucleotide analogue ALS-2158 and (ii) $412.9 million related to VX-222. The Company collaborates with Alios on research and development activities related to the HCV nucleotide program and acquired VX-222 when it acquired ViroChem Pharma Inc. ("ViroChem") in March 2009. Each of these research and development assets relate to drug candidates that are being developed for the treatment of HCV infection. The Company tests its intangible assets for impairment on an annual basis as of October 1, and more frequently if indicators are present or changes in circumstance suggest that impairment may exist. Events that could result in an impairment, or trigger an interim impairment assessment, include the receipt of additional clinical or nonclinical data regarding the Company's drug candidate or a potentially competitive drug candidate, changes in the clinical development program for a drug candidate or new information regarding potential sales for the drug. The field of HCV infection treatment is highly competitive and characterized by rapid technological advances, and several of the Company's competitors are conducting Phase 3 clinical trials evaluating their drug candidates for the treatment of genotype 1 HCV infection, including clinical trials evaluating all-oral combinations and combinations that include pegylated-interferon and ribavirin. There can be no assurance that the Company will be able to successfully develop VX-135 or VX-222. If the fair value of VX-135 or VX-222 becomes impaired as the result of unfavorable safety or efficacy data from any ongoing or future clinical trial or because of any other information regarding the prospects of successfully developing or commercializing VX-135 or VX-222, the Company would incur significant charges in the period in which the impairment occurs. Alios Collaboration In June 2011, the Company recorded $250.6 million of intangible assets on its consolidated balance sheet based on the Company's estimate of the fair value of Alios' HCV nucleotide analogue program, including the intellectual property related to ALS-2200 and ALS-2158. In the third quarter of 2012, after the Company discontinued the development of ALS-2158, the Company evaluated the Alios HCV nucleotide analogue program for impairment. The Company determined that there was no impairment to the program in the third quarter of 2012 because of the advancement of ALS-2200 (now formulated as VX-135). No impairment has been found with respect to the HCV nucleotide analogue program since the effective date of the Alios Agreement. ViroChem Acquisition As of December 31, 2010, the intangible assets acquired from ViroChem that were reflected on the Company's consolidated balance sheet related to two drug candidates, VX-222 and VX-759. VX-222 and VX-759 had estimated fair values on the acquisition date and December 31, 2010 of $412.9 million and $105.8 million, respectively. In the third quarter of 2011, the Company determined that the fair value of VX-759 had become impaired and that its fair value was zero. As a result, the Company recorded an impairment charge in 2011 of $105.8 million that was reflected as an intangible asset impairment charge on the Company's consolidated statement of operations. In connection with this impairment charge, the Company recorded a benefit from income taxes of $32.7 million. The Company has tested the fair value of VX-222 on an annual basis since the acquisition date and no impairment has been identified. As of October 1, 2012, the Company estimated the fair value that would be attributed to VX-222 by a market participant based on probability weighted present-value models involving updated assumptions and estimates regarding the status of the VX-222 development program, the potential future cash flows from sales of VX-222 and an appropriate discount rate. When the Company updated its assumptions, it considered among other factors, the following: (i) the Company continues to evaluate VX-222 in Phase 2 clinical trials and believes that a treatment regimen containing VX-222 in combination with other direct-acting antivirals such as VX-135 can be developed for patients with genotype 1 HCV infection, (ii) the Company's competitors initiated several Phase 2 and Phase 3 clinical trials during the second half of 2012 that include treatment arms with non-nucleoside HCV polymerase inhibitors in combination with other direct-acting antivirals that could potentially be competitive in the market for the treatment of HCV infection and (iii) the Company believes that in the future several competitive treatment regimens will be available to treat patients with genotype 1 HCV infection. Using these updated assumptions, the Company determined that as of October 1, 2012, a market participant would assign a fair value to VX-222 exceeding the value reflected on the consolidated balance sheet. Accordingly, the Company determined that the value of VX-222 was not impaired as of October 1, 2012. There were no indicators of impairment as of December 31, 2012. A deferred tax liability related to ViroChem of $127.6 million recorded as of December 31, 2012 and 2011 primarily relates to the tax effect of future amortization or impairments associated with VX-222, which are not deductible for tax purposes. Goodwill As of December 31, 2012 and 2011, goodwill of $31.0 million was recorded on the Company's consolidated balance sheets. There was no change to goodwill during the year ended December 31, 2012.

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

+ References+ Details