Other Intangibles	9 Months Ended
Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Other Intangibles	Other Intangibles In connection with acquisitions, the Company measures the fair value of research and development pipeline programs and marketed products and capitalizes these amounts. See Note 3 for information on intangible assets acquired as a result of business acquisitions in the first nine months of 2018 and 2017. During the third quarter and first nine months of 2017, the Company recorded $245 million and $253 million, respectively, of IPR&D impairment charges within Research and development expenses. In the third quarter of 2017, Merck made a strategic decision to discontinue the development of the investigational combination regimens MK-3682B (grazoprevir/ruzasvir/uprifosbuvir) and MK-3682C (ruzasvir/uprifosbuvir) for the treatment of chronic hepatitis C virus (HCV) infection. This decision was made based on a review of available Phase 2 efficacy data and in consideration of the evolving marketplace and the growing number of treatment options available for patients with chronic HCV infection, including Zepatier, which is marketed by the Company for the treatment of adult patients with chronic HCV infection. As a result of this decision, the Company recorded an IPR&D impairment charge of $240 million in the third quarter and first nine months of 2017 to write-off the remaining intangible asset related to uprifosbuvir. Also, during the first nine months of 2017, the Company recorded an intangible asset impairment charge of $47 million within Materials and production costs related to Intron A, a treatment for certain types of cancers. Sales of Intron A were being adversely affected by the availability of new therapeutic options. Sales of Intron A in the United States eroded more rapidly than previously anticipated by the Company, which led to changes in the cash flow assumptions for Intron A. These revisions to cash flows indicated that the Intron A intangible asset value was not fully recoverable on an undiscounted cash flows basis. The Company utilized market participant assumptions to determine its best estimate of the fair value of the intangible asset related to Intron A that, when compared with its related carrying value, resulted in the impairment charge noted above.

Other Intangibles

In connection with acquisitions, the Company measures the fair value of research and development pipeline programs and marketed products and capitalizes these amounts. See Note 3 for information on intangible assets acquired as a result of business acquisitions in the first nine months of 2018 and 2017.

During the third quarter and first nine months of 2017, the Company recorded $245 million and $253 million, respectively, of IPR&D impairment charges within Research and development expenses. In the third quarter of 2017, Merck made a strategic decision to discontinue the development of the investigational combination regimens MK-3682B (grazoprevir/ruzasvir/uprifosbuvir) and MK-3682C (ruzasvir/uprifosbuvir) for the treatment of chronic hepatitis C virus (HCV) infection. This decision was made based on a review of available Phase 2 efficacy data and in consideration of the evolving marketplace and the growing number of treatment options available for patients with chronic HCV infection, including Zepatier, which is marketed by the Company for the treatment of adult patients with chronic HCV infection. As a result of this decision, the Company recorded an IPR&D impairment charge of $240 million in the third quarter and first nine months of 2017 to write-off the remaining intangible asset related to uprifosbuvir.

Also, during the first nine months of 2017, the Company recorded an intangible asset impairment charge of $47 million within Materials and production costs related to Intron A, a treatment for certain types of cancers. Sales of Intron A were being adversely affected by the availability of new therapeutic options. Sales of Intron A in the United States eroded more rapidly than previously anticipated by the Company, which led to changes in the cash flow assumptions for Intron A. These revisions to cash flows indicated that the Intron A intangible asset value was not fully recoverable on an undiscounted cash flows basis. The Company utilized market participant assumptions to determine its best estimate of the fair value of the intangible asset related to Intron A that, when compared with its related carrying value, resulted in the impairment charge noted above.