Merck & Co. (MRK) 10-Q 5 Nov 20 2020 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2020	Oct. 31, 2020
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	1-6571
Entity Registrant Name	Merck & Co., Inc.
Entity Incorporation, State or Country Code	NJ
Entity Tax Identification Number	22-1918501
Entity Address, Address Line One	2000 Galloping Hill Road
Entity Address, City or Town	Kenilworth
Entity Address, State or Province	NJ
Entity Address, Postal Zip Code	07033
City Area Code	(908)
Local Phone Number	740-4000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		2,530,034,437
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Entity Central Index Key	0000310158
Current Fiscal Year End Date	--12-31
Common Stock
Entity Information [Line Items]
Title of 12(b) Security	Common Stock ($0.50 par value)
Trading Symbol	MRK
Security Exchange Name	NYSE
1.125% Notes due 2021
Entity Information [Line Items]
Title of 12(b) Security	1.125% Notes due 2021
Trading Symbol	MRK/21
Security Exchange Name	NYSE
0.500% Notes due 2024
Entity Information [Line Items]
Title of 12(b) Security	0.500% Notes due 2024
Trading Symbol	MRK 24
Security Exchange Name	NYSE
1.875% Notes due 2026
Entity Information [Line Items]
Title of 12(b) Security	1.875% Notes due 2026
Trading Symbol	MRK/26
Security Exchange Name	NYSE
2.500% Notes due 2034
Entity Information [Line Items]
Title of 12(b) Security	2.500% Notes due 2034
Trading Symbol	MRK/34
Security Exchange Name	NYSE
1.375% Notes due 2036
Entity Information [Line Items]
Title of 12(b) Security	1.375% Notes due 2036
Trading Symbol	MRK 36A
Security Exchange Name	NYSE

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENT OF INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Sales	$ 12,551	$ 12,397	$ 35,479	$ 34,972
Costs, Expenses and Other
Cost of sales	3,481	3,990	9,952	10,443
Selling, general and administrative	2,450	2,589	7,383	7,726
Research and development	3,390	3,204	7,721	7,324
Restructuring costs	114	232	269	444
Other (income) expense, net	(312)	35	(630)	362
Total Costs, Expenses and Other	9,123	10,050	24,695	26,299
Income Before Taxes	3,428	2,347	10,784	8,673
Taxes on Income	483	440	1,611	1,259
Net Income	2,945	1,907	9,173	7,414
Less: Net Income (Loss) Attributable to Noncontrolling Interests	4	6	12	(73)
Net Income Attributable to Merck & Co., Inc.	$ 2,941	$ 1,901	$ 9,161	$ 7,487
Basic Earnings per Common Share Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share)	$ 1.16	$ 0.74	$ 3.62	$ 2.91
Earnings per Common Share Assuming Dilution Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share)	$ 1.16	$ 0.74	$ 3.61	$ 2.89

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net Income Attributable to Merck & Co., Inc.	$ 2,941	$ 1,901	$ 9,161	$ 7,487
Other Comprehensive Income (Loss) Net of Taxes:
Net unrealized (loss) gain on derivatives, net of reclassifications	(137)	91	(153)	(9)
Net unrealized (loss) gain on investments, net of reclassifications	0	(17)	(18)	109
Benefit plan net gain and prior service credit, net of amortization	62	15	161	41
Cumulative translation adjustment	85	(117)	(180)	14
Other comprehensive income (loss), net of taxes	10	(28)	(190)	155
Comprehensive Income Attributable to Merck & Co., Inc.	$ 2,951	$ 1,873	$ 8,971	$ 7,642

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEET - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Current Assets
Cash and cash equivalents	$ 7,356	$ 9,676
Short-term investments	0	774
Accounts receivable (net of allowance for doubtful accounts of $89 in 2020 and $86 in 2019)	8,422	6,778
Inventories (excludes inventories of $2,081 in 2020 and $1,480 in 2019 classified in Other assets - see Note 6)	6,128	5,978
Other current assets	4,671	4,277
Total current assets	26,577	27,483
Investments	1,372	1,469
Property, Plant and Equipment, at cost, net of accumulated depreciation of $18,572 in 2020 and $17,686 in 2019	16,919	15,053
Goodwill	20,248	19,425
Other Intangibles, Net	16,677	14,196
Other Assets	8,007	6,771
Total Assets	89,800	84,397
Current Liabilities
Loans payable and current portion of long-term debt	2,420	3,610
Trade accounts payable	3,744	3,738
Accrued and other current liabilities	11,690	12,549
Income taxes payable	984	736
Dividends payable	1,567	1,587
Total current liabilities	20,405	22,220
Long-Term Debt	26,321	22,736
Deferred Income Taxes	1,777	1,470
Other Noncurrent Liabilities	12,027	11,970
Merck & Co., Inc. Stockholders’ Equity
Common stock, $0.50 par value Authorized - 6,500,000,000 shares Issued - 3,577,103,522 shares in 2020 and 2019	1,788	1,788
Other paid-in capital	39,489	39,660
Retained earnings	51,107	46,602
Accumulated other comprehensive loss	(6,383)	(6,193)
Stockholders' equity before deduction for treasury stock	86,001	81,857
Less treasury stock, at cost: 1,047,343,390 shares in 2020 and 1,038,087,496 shares in 2019	56,815	55,950
Total Merck & Co., Inc. stockholders’ equity	29,186	25,907
Noncontrolling Interests	84	94
Total equity	29,270	26,001
Liabilities and Equity	$ 89,800	$ 84,397

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEET (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 89	$ 86
Inventories classified in Other assets	2,081	1,480
Accumulated depreciation	$ 18,572	$ 17,686
Common stock, par value (in dollars per share)	$ 0.50	$ 0.50
Common stock, shares authorized (shares)	6,500,000,000	6,500,000,000
Common stock, shares issued (in shares)	3,577,103,522	3,577,103,522
Treasury Stock, Shares	1,047,343,390	1,038,087,496

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash Flows from Operating Activities
Net income	$ 9,173	$ 7,414
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,721	2,716
Intangible asset impairment charges	35	864
Charge for acquisition of Peloton Therapeutics, Inc.	0	982
Deferred income taxes	47	(386)
Share-based compensation	354	306
Other	(445)	219
Net changes in assets and liabilities	(5,638)	(3,469)
Net Cash Provided by Operating Activities	6,247	8,646
Cash Flows from Investing Activities
Capital expenditures	(3,170)	(2,336)
Purchases of securities and other investments	(78)	(2,380)
Proceeds from sales of securities and other investments	1,894	7,459
Acquisition of ArQule, Inc., net of cash acquired	(2,545)	0
Acquisition of Antelliq Corporation, net of cash acquired	0	(3,620)
Acquisition of Peloton Therapeutics, Inc., net of cash acquired	0	(1,040)
Other acquisitions, net of cash acquired	(907)	(269)
Other	141	320
Net Cash Used in Investing Activities	(4,665)	(1,866)
Cash Flows from Financing Activities
Net change in short-term borrowings	(311)	(3,892)
Payments on debt	(1,954)	0
Proceeds from issuance of debt	4,419	4,958
Purchases of treasury stock	(1,281)	(3,730)
Dividends paid to stockholders	(4,673)	(4,290)
Proceeds from exercise of stock options	68	344
Other	(472)	(240)
Net Cash Used in Financing Activities	(4,204)	(6,850)
Effect of Exchange Rate Changes on Cash, Cash Equivalents and Restricted Cash	89	(26)
Net Decrease in Cash, Cash Equivalents and Restricted Cash	(2,533)	(96)
Cash, Cash Equivalents and Restricted Cash at Beginning of Year (includes restricted cash of $258 at January 1, 2020 included in Other Assets)	9,934	7,967
Cash, Cash Equivalents and Restricted Cash at End of Period (includes restricted cash of $45 at September 30, 2020 included in Other Assets)	$ 7,401	$ 7,871

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Statement of Cash Flows [Abstract]
Restricted cash	$ 45	$ 258

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements of Merck & Co., Inc. (Merck or the Company) have been prepared pursuant to the rules and regulations for reporting on Form 10-Q. Accordingly, certain information and disclosures required by accounting principles generally accepted in the United States (GAAP) for complete consolidated financial statements are not included herein. These interim statements should be read in conjunction with the audited financial statements and notes thereto included in Merck’s Form 10-K filed on February 26, 2020. The results of operations of any interim period are not necessarily indicative of the results of operations for the full year. In the Company’s opinion, all adjustments necessary for a fair statement of these interim statements have been included and are of a normal and recurring nature. Planned Spin-Off of Women’s Health, Biosimilars and Established Brands into New Company In February 2020, Merck announced its intention to spin-off products from its women’s health, biosimilars and established brands businesses into a new, independent, publicly traded company named Organon & Co. (Organon) through a distribution of Organon’s publicly traded stock to Company shareholders. The distribution is expected to qualify as tax-free to the Company and its shareholders for U.S. federal income tax purposes. The established brands included in the transaction consist of dermatology, non-opioid pain management, respiratory, and select cardiovascular products including Zetia (ezetimibe) and Vytorin (ezetimibe and simvastatin), as well as the rest of Merck’s diversified brands franchise. Merck’s existing research pipeline programs will continue to be owned and developed within Merck as planned. Organon will have development capabilities initially focused on late-stage development and life-cycle management and is expected over time to develop research capabilities in selected therapeutic areas. The spin-off is expected to be completed in the second quarter of 2021, subject to market and certain other conditions. Subsequent to the spin-off, the historical results of the women’s health, biosimilars and established brands businesses will be reflected as discontinued operations in the Company’s consolidated financial statements. Recently Adopted Accounting Standards In June 2016, the Financial Accounting Standards Board (FASB) issued new guidance on the accounting for credit losses on financial instruments. The new guidance introduces an expected loss model for estimating credit losses, replacing the incurred loss model. The new guidance also changes the impairment model for available-for-sale debt securities, requiring the use of an allowance to record estimated credit losses (and subsequent recoveries). The Company adopted the new guidance effective January 1, 2020. There was no impact to the Company’s consolidated financial statements upon adoption. In November 2018, the FASB issued new guidance for collaborative arrangements intended to reduce diversity in practice by clarifying whether certain transactions between collaborative arrangement participants should be accounted for under revenue recognition guidance (ASC 606). The Company adopted the new guidance effective January 1, 2020, which resulted in minor changes to the presentation of information related to the Company’s collaborative arrangements. Recently Issued Accounting Standards Not Yet Adopted In December 2019, the FASB issued amended guidance on the accounting and reporting of income taxes. The guidance is intended to simplify the accounting for income taxes by: removing exceptions related to certain intraperiod tax allocations and deferred tax liabilities; clarifying guidance primarily related to evaluating the step-up tax basis for goodwill in a business combination; and reflecting enacted changes in tax laws or rates in the annual effective tax rate. The amended guidance is effective for interim and annual periods in 2021. Early adoption is permitted. The amendments in the new guidance are to be applied on a retrospective basis, on a modified retrospective basis through a cumulative-effect adjustment to retained earnings or prospectively, depending on the amendment. The Company is currently evaluating the impact of adoption on its consolidated financial statements. In January 2020, the FASB issued new guidance intended to clarify certain interactions between accounting standards related to equity securities, equity method investments and certain derivatives. The guidance addresses accounting for the transition into and out of the equity method of accounting and measuring certain purchased options and forward contracts to acquire investments. The new guidance is effective for interim and annual periods in 2021 and is to be applied prospectively. Early adoption is permitted. The Company is currently evaluating the impact of adoption on its consolidated financial statements. In March 2020, the FASB issued optional guidance to ease the potential burden in accounting for (or recognizing the effects of) reference rate reform on financial reporting. The guidance provides optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform. The optional guidance is effective upon issuance and can be applied on a prospective basis at any time between January 1, 2020 through December 31, 2022. The Company is currently evaluating the impact of adoption on its consolidated financial statements.

Acquisitions, Research Collabor

Acquisitions, Research Collaborations and License Agreements	9 Months Ended
	Sep. 30, 2020
Business Combinations [Abstract]
Acquisitions, Research Collaborations and License Agreements	Acquisitions, Research Collaborations and License Agreements The Company continues to pursue acquisitions and the establishment of external alliances such as research collaborations and licensing agreements to complement its internal research capabilities. These arrangements often include upfront payments, as well as expense reimbursements or payments to the third party, and milestone, royalty or profit share arrangements, contingent upon the occurrence of certain future events linked to the success of the asset in development. The Company also reviews its marketed products and pipeline to examine candidates which may provide more value through out-licensing and, as part of its portfolio assessment process, may also divest certain assets. Pro forma financial information for acquired businesses is not presented if the historical financial results of the acquired entity are not significant when compared with the Company’s financial results. In November 2020, Merck and VelosBio, Inc. (VelosBio) announced that the companies had entered into a definitive agreement pursuant to which Merck, through a subsidiary, will acquire all outstanding shares of VelosBio for $2.75 billion, subject to certain customary adjustments. VelosBio is a privately held clinical-stage biopharmaceutical company committed to developing first-in-class cancer therapies targeting receptor tyrosine kinase-like orphan receptor 1 (ROR1). VelosBio’s lead investigational candidate is VLS-101, an antibody-drug conjugate targeting ROR1 that is currently being evaluated in a Phase 1 and a Phase 2 clinical trial for the treatment of patients with hematologic malignancies and solid tumors, respectively. The closing of the transaction, which is subject to approval under the Hart-Scott-Rodino Antitrust Improvements Act and other customary conditions, is expected by the end of 2020. In September 2020, Merck and Seagen Inc. (Seagen, formerly known as Seattle Genetics, Inc.) announced an oncology collaboration to globally develop and commercialize Seagen’s ladiratuzumab vedotin (MK-6440), an investigational antibody-drug conjugate targeting LIV-1, which is currently in Phase 2 clinical trials for breast cancer and other solid tumors. The collaboration will pursue a broad joint development program evaluating ladiratuzumab vedotin as monotherapy and in combination with Keytruda (pembrolizumab) in triple-negative breast cancer, hormone receptor-positive breast cancer and other LIV-1-expressing solid tumors. The companies will equally share profits worldwide. Under the terms of the agreement, Merck made an upfront payment of $600 million and a $1.0 billion equity investment in 5 million shares of Seagen common stock at a price of $200 per share. Merck recorded $622 million in Research and development expenses in the third quarter and first nine months of 2020 related to this transaction reflecting the upfront payment as well as a $22 million mark-to-market loss on the purchase commitment (forward contract) relating to the equity shares (calculated based on the closing price of Seagen common stock on September 30, 2020). The closing of the equity investment occurred in October 2020 and resulted in the recognition of a $6 million reduction to Research and development expenses based on the price of Seagen common stock on the closing date. Seagen is also eligible to receive future contingent milestone payments of up to $2.6 billion, including $850 million in development milestones and $1.75 billion in sales milestones. Concurrent with the above transaction, Seagen granted Merck an exclusive license to commercialize Tukysa (tucatinib), a small molecule tyrosine kinase inhibitor, for the treatment of HER2-positive cancers, in Asia, the Middle East and Latin America and other regions outside of the United States, Canada and Europe. Merck will be responsible for marketing applications seeking approval in its territories, supported by the positive results from the HER2CLIMB clinical trial. Merck will also co-fund a portion of the Tukysa global development plan, which encompasses several ongoing and planned trials across HER2-positive cancers, including breast, colorectal, gastric and other cancers set forth in a global product development plan. Merck will solely fund and conduct country-specific clinical trials necessary to support anticipated regulatory applications in its territories. Under the terms of the agreement, Merck made upfront payments aggregating $210 million, which were recorded as Research and development expenses in the third quarter and first nine months of 2020. Seagen is also eligible to receive future contingent regulatory approval milestones of up to $65 million and will receive tiered royalties ranging from 20% to 33% based on annual sales levels of Tukysa in Merck’s territories. Additionally in September 2020, Merck acquired a biologics manufacturing facility located in Dunboyne, Ireland from Takeda Pharmaceutical Company Limited for €256 million ($302 million). The transaction was accounted for as an acquisition of an asset. Merck recorded property, plant and equipment of $289 million and other net assets of $13 million. There are no future contingent payments associated with the acquisition. In July 2020, Merck acquired the U.S. rights to Sentinel Flavor Tabs and Sentinel Spectrum Chews from Virbac Corporation for $410 million. Sentinel products provide protection against common parasites in dogs. The transaction was accounted for as an acquisition of an asset. Merck recognized intangible assets of $401 million related to currently marketed products and inventory of $9 million at the acquisition date. The estimated fair values of the identifiable intangible assets related to currently marketed products were determined using an income approach. Actual cash flows are likely to be different than those assumed. The intangible assets related to currently marketed products will be amortized over their estimated useful lives of 15 years. There are no future contingent payments associated with the acquisition. Also, in July 2020, Merck and Ridgeback Biotherapeutics LP (Ridgeback Bio), a closely held biotechnology company, closed a collaboration agreement to develop molnupiravir (MK-4482, formerly known as EIDD-2801), an orally available antiviral candidate currently in clinical development for the treatment of patients with COVID-19. Merck gained exclusive worldwide rights to develop and commercialize molnupiravir and related molecules. Under the terms of the agreement, Ridgeback Bio received an upfront payment and also is eligible to receive future contingent payments dependent upon the achievement of certain developmental and regulatory approval milestones, as well as a share of the net profits of molnupiravir and related molecules, if approved. Merck and Ridgeback are committed to ensure that any medicines developed for SARS-CoV-2 (the causative agent of COVID-19) will be accessible and affordable globally. In June 2020, Merck acquired privately held Themis Bioscience GmbH (Themis), a company focused on vaccines and immune-modulation therapies for infectious diseases and cancer for $366 million. Merck may make additional contingent payments of up to $740 million, including up to $80 million for development milestones, up to $260 million for regulatory approval milestones, and up to $400 million for commercial milestones. Themis has a broad pipeline of vaccine candidates and immune-modulatory therapies developed using its innovative measles virus vector platform based on a vector originally developed by scientists at the Institut Pasteur and licensed exclusively to Themis for select viral indications. The acquisition builds upon an ongoing collaboration between the two companies to develop vaccine candidates using the measles virus vector platform and is expected to accelerate the development of the COVID-19 vaccine candidate (V591), which is currently in Phase 1 clinical development. The transaction was accounted for as an acquisition of a business. The Company determined the fair value of the contingent consideration was $97 million at the acquisition date utilizing a probability-weighted estimated cash flow stream using an appropriate discount rate dependent on the nature and timing of the milestone payment. Merck recognized intangible assets for in-process research and development (IPR&D) of $136 million, cash of $59 million, deferred tax assets of $71 million and other net liabilities of $32 million. The excess of the consideration transferred over the fair value of net assets acquired of $229 million was recorded as goodwill that was allocated to the Pharmaceutical segment and is not deductible for tax purposes. The fair values of the identifiable intangible assets related to IPR&D were determined using an income approach. Actual cash flows are likely to be different than those assumed. In connection with the transaction, Merck has entered into a memorandum of understanding that reflects the parties’ commitments to address the COVID-19 pandemic by developing, manufacturing and distributing the vaccine on a global basis and with pricing that makes the vaccine both available around the world and accessible to those who need it. In May 2020, Merck and the International AIDS Vaccine Initiative, Inc. (IAVI), a nonprofit scientific research organization dedicated to addressing urgent, unmet global health challenges, announced a new collaboration to develop V590, an investigational vaccine against SARS-CoV-2 being studied for the prevention of COVID-19. This vaccine candidate will use the recombinant vesicular stomatitis virus (rVSV) technology that is the basis for Merck’s approved Ebola Zaire virus vaccine, Ervebo (Ebola Zaire Vaccine, Live), which was the first rVSV vaccine approved for use in humans. Under the terms of the agreement, Merck made an upfront payment of $6.5 million and may make additional contingent payments of up to $100 million for sales-based milestones, as well as royalty payments. Merck has also signed an agreement with the Biomedical Advanced Research and Development Authority (BARDA), part of the office of the Assistant Secretary for Preparedness and Response within an agency of the United States Department of Health and Human Services, to provide initial funding support for this effort. Under the agreement, IAVI and Merck will work together to advance the development and global clinical evaluation of a SARS-CoV-2 vaccine candidate designed and engineered by IAVI scientists. The vaccine candidate is currently in Phase 1 clinical development. Merck will lead regulatory filings globally. Both organizations will work together to develop the vaccine and make it accessible and affordable globally, if approved. In January 2020, Merck acquired ArQule, Inc. (ArQule), a publicly traded biopharmaceutical company focused on kinase inhibitor discovery and development for the treatment of patients with cancer and other diseases. Total consideration paid of $2.7 billion included $138 million of share-based compensation payments to settle equity awards attributable to precombination service and cash paid for transaction costs on behalf of ArQule. The Company incurred $95 million of transaction costs directly related to the acquisition of ArQule, consisting almost entirely of share-based compensation payments to settle non-vested equity awards attributable to postcombination service. These costs were included in Selling, general and administrative expenses in the first nine months of 2020. ArQule’s lead investigational candidate, MK-1026 (formerly known as ARQ 531), is a novel, oral Bruton’s tyrosine kinase (BTK) inhibitor currently being evaluated for the treatment of B-cell malignancies. The estimated fair value of assets acquired and liabilities assumed from ArQule is as follows: ($ in millions) January 16, 2020 Cash and cash equivalents $ 145 IPR&D MK-1026 (formerly ARQ 531) (1) 2,280 Licensing arrangement for ARQ 087 80 Deferred income tax liabilities (389) Other assets and liabilities, net 34 Total identifiable net assets 2,150 Goodwill (2) 540 Consideration transferred $ 2,690 (1) The estimated fair value of the identifiable intangible asset related to IPR&D was determined using an income approach. The future net cash flows were discounted to present value utilizing a discount rate of 12.5%. Actual cash flows are likely to be different than those assumed. (2) The goodwill was allocated to the Pharmaceutical segment and is not deductible for tax purposes. In July 2019, Merck acquired Peloton Therapeutics, Inc. (Peloton), a clinical-stage biopharmaceutical company focused on the development of novel small molecule therapeutic candidates targeting hypoxia-inducible factor-2α (HIF-2α) for the treatment of patients with cancer and other non-oncology diseases. Peloton’s lead candidate, MK-6482 (formerly known as PT2977), is a novel investigational oral HIF-2α inhibitor in late-stage development for renal cell carcinoma. Merck made an upfront payment of $1.2 billion; additionally, former Peloton shareholders will be eligible to receive $50 million upon U.S. regulatory approval, $50 million upon first commercial sale in the United States, and up to $1.05 billion of sales-based milestones. The transaction was accounted for as an acquisition of an asset. Merck recorded cash of $157 million, deferred tax liabilities of $64 million, and other net liabilities of $6 million at the acquisition date and Research and development expenses of $982 million in the third quarter and first nine months of 2019 related to the transaction. On April 1, 2019, Merck acquired Antelliq Corporation (Antelliq), a leader in digital animal identification, traceability and monitoring solutions. These solutions help veterinarians, farmers and pet owners gather critical data to improve management, health and well-being of livestock and pets. Merck paid $2.3 billion to acquire all outstanding shares of Antelliq and spent $1.3 billion to repay Antelliq’s debt. The transaction was accounted for as an acquisition of a business. The estimated fair value of assets acquired and liabilities assumed from Antelliq is as follows: ($ in millions) April 1, 2019 Cash and cash equivalents $ 31 Accounts receivable 73 Inventories 93 Property, plant and equipment 60 Identifiable intangible assets (useful lives ranging from 18-24 years) (1) 2,689 Deferred income tax liabilities (589) Other assets and liabilities, net (82) Total identifiable net assets 2,275 Goodwill (2) 1,376 Consideration transferred $ 3,651 (1) The estimated fair values of identifiable intangible assets relate primarily to trade names and were determined using an income approach. The future net cash flows were discounted to present value utilizing a discount rate of 11.5%. Actual cash flows are likely to be different than those assumed. (2) The goodwill recognized is largely attributable to anticipated synergies expected to arise after the acquisition and was allocated to the Animal Health segment. The goodwill is not deductible for tax purposes. The Company’s results for the first nine months of 2019 include five months of activity for Antelliq. The Company incurred $47 million of transaction costs directly related to the acquisition of Antelliq, consisting largely of advisory fees, which are reflected in Selling, general and administrative expenses in the first nine months of 2019. Also in April 2019, Merck acquired Immune Design, a late-stage immunotherapy company employing next-generation in vivo approaches to enable the body’s immune system to fight disease, for $301 million in cash. The transaction was accounted for as an acquisition of a business. Merck recognized intangible assets of $156 million, cash of $83 million and other net assets of $42 million. The excess of the consideration transferred over the fair value of net assets acquired of $20

Collaborative Arrangements

Collaborative Arrangements	9 Months Ended
	Sep. 30, 2020
Collaborative Arrangements [Abstract]
Collaborative Arrangements	Collaborative Arrangements Merck has entered into collaborative arrangements that provide the Company with varying rights to develop, produce and market products together with its collaborative partners. Both parties in these arrangements are active participants and exposed to significant risks and rewards dependent on the commercial success of the activities of the collaboration. Merck’s more significant collaborative arrangements are discussed below. AstraZeneca In July 2017, Merck and AstraZeneca PLC (AstraZeneca) entered into a global strategic oncology collaboration to co-develop and co-commercialize AstraZeneca’s Lynparza (olaparib) for multiple cancer types. Lynparza is an oral poly (ADP-ribose) polymerase (PARP) inhibitor currently approved for certain types of advanced ovarian, breast, pancreatic and prostate cancers. The companies are jointly developing and commercializing Lynparza, both as monotherapy and in combination trials with other potential medicines. Independently, Merck and AstraZeneca will develop and commercialize Lynparza in combinations with their respective PD-1 and PD-L1 medicines, Keytruda and Imfinzi. The companies will also jointly develop and commercialize AstraZeneca’s Koselugo (selumetinib), an oral, selective inhibitor of MEK, part of the mitogen-activated protein kinase (MAPK) pathway, currently being developed for multiple indications. In April 2020, Koselugo was approved by the U.S. Food and Drug Administration (FDA) for the treatment of pediatric patients two years of age and older with neurofibromatosis type 1 who have symptomatic, inoperable plexiform neurofibromas. Under the terms of the agreement, AstraZeneca and Merck will share the development and commercialization costs for Lynparza and Koselugo monotherapy and non-PD-L1/PD-1 combination therapy opportunities. Profits from Lynparza and Koselugo product sales generated through monotherapies or combination therapies are shared equally. Merck will fund all development and commercialization costs of Keytruda in combination with Lynparza or Koselugo. AstraZeneca will fund all development and commercialization costs of Imfinzi in combination with Lynparza or Koselugo. AstraZeneca is the principal on Lynparza and Koselugo sales transactions. Merck records its share of Lynparza and Koselugo product sales, net of cost of sales and commercialization costs, as alliance revenue and its share of development costs associated with the collaboration as part of Research and development expenses. Reimbursements received from AstraZeneca for research and development expenses are recognized as reductions to Research and development costs. As part of the agreement, Merck made an upfront payment to AstraZeneca of $1.6 billion in 2017 and made payments of $750 million over a multi-year period for certain license options. In addition, the agreement provides for additional contingent payments from Merck to AstraZeneca related to the successful achievement of sales-based and regulatory milestones. In the second quarter of 2020, Merck determined it was probable that sales of Lynparza in the future would trigger $400 million of sales-based milestone payments from Merck to AstraZeneca. Accordingly, Merck recorded a $400 million liability and a corresponding increase to the intangible asset related to Lynparza. Prior to 2020, Merck accrued sales-based milestone payments aggregating $1.0 billion related to Lynparza, of which $200 million and $250 million was paid to AstraZeneca in 2019 and 2018, respectively, and $250 million was paid in the first nine months of 2020. Potential future sales-based milestone payments of $2.7 billion have not yet been accrued as they are not deemed by the Company to be probable at this time. In the second quarter of 2020, Lynparza received regulatory approvals triggering capitalized milestone payments of $135 million from Merck to AstraZeneca. In 2019 and 2018, Lynparza received regulatory approvals triggering capitalized milestone payments of $60 million and $140 million, respectively, in the aggregate from Merck to AstraZeneca. Potential future regulatory milestone payments of $1.4 billion remain under the agreement. The intangible asset balance related to Lynparza (which includes capitalized sales-based and regulatory milestone payments) was $1.3 billion at September 30, 2020 and is included in Other Intangibles, Net on the Consolidated Balance Sheet. The amount is being amortized over its estimated useful life through 2028 as supported by projected future cash flows, subject to impairment testing. Summarized financial information related to this collaboration is as follows: Three Months Ended Nine Months Ended ($ in millions) 2020 2019 2020 2019 Alliance revenue - Lynparza $ 196 $ 123 $ 519 $ 313 Alliance revenue - Koselugo 3 — 3 — Total alliance revenue $ 199 $ 123 $ 522 $ 313 Cost of sales (1) 41 28 205 120 Selling, general and administrative 40 36 112 96 Research and development 20 44 93 122 ($ in millions) September 30, 2020 December 31, 2019 Receivables from AstraZeneca included in Other current assets $ 197 $ 128 Payables to AstraZeneca included in Accrued and other current liabilities (2) 309 577 Payables to AstraZeneca included in Other Noncurrent Liabilities (2) 400 — (1) Represents amortization of capitalized milestone payments. (2) Includes accrued milestone payments. Eisai In March 2018, Merck and Eisai Co., Ltd. (Eisai) announced a strategic collaboration for the worldwide co-development and co-commercialization of Lenvima (lenvatinib), an orally available tyrosine kinase inhibitor discovered by Eisai. Lenvima is currently approved for the treatment of certain types of thyroid cancer, hepatocellular carcinoma, in combination with everolimus for certain patients with renal cell carcinoma, and in combination with Keytruda for the treatment of certain patients with endometrial carcinoma. Under the agreement, Merck and Eisai will develop and commercialize Lenvima jointly, both as monotherapy and in combination with Keytruda . Eisai records Lenvima product sales globally (Eisai is the principal on Lenvima sales transactions), and Merck and Eisai share profits equally. Merck records its share of Lenvima product sales, net of cost of sales and commercialization costs, as alliance revenue. Expenses incurred during co-development, including for studies evaluating Lenvima as monotherapy, are shared equally by the two companies and reflected in Research and development expenses. Under the agreement, Merck made an upfront payment to Eisai of $750 million and agreed to make payments of up to $650 million for certain option rights through 2021 (of which $325 million was paid in March 2019, $200 million was paid in March 2020 and $125 million is expected to be paid in March 2021). In addition, the agreement provides for additional contingent payments from Merck to Eisai related to the successful achievement of sales-based and regulatory milestones. In the second quarter of 2020, Merck determined it was probable that sales of Lenvima in the future would trigger sales-based milestone payments aggregating $370 million from Merck to Eisai. Accordingly, Merck recorded a $370 million liability and a corresponding increase to the intangible asset related to Lenvima. Prior to 2020, Merck accrued sales-based milestone payments aggregating $950 million. Of these amounts, $50 million was paid to Eisai in 2019 and an additional $500 million was paid in the first nine months of 2020. Potential future sales-based milestone payments of $2.7 billion have not yet been accrued as they are not deemed by the Company to be probable at this time. In 2018, Lenvima received regulatory approvals triggering capitalized milestone payments of $250 million in the aggregate from Merck to Eisai. Potential future regulatory milestone payments of $135 million remain under the agreement. The intangible asset balance related to Lenvima (which includes capitalized sales-based and regulatory milestone payments) was $1.1 billion at September 30, 2020 and is included in Other Intangibles, Net on the Consolidated Balance Sheet. The amount is being amortized over its estimated useful life through 2026 as supported by projected future cash flows, subject to impairment testing. Summarized financial information related to this collaboration is as follows: Three Months Ended Nine Months Ended ($ in millions) 2020 2019 2020 2019 Alliance revenue - Lenvima $ 142 $ 109 $ 421 $ 280 Cost of sales (1) 46 23 215 97 Selling, general and administrative 18 21 48 59 Research and development 48 37 168 146 ($ in millions) September 30, 2020 December 31, 2019 Receivables from Eisai included in Other current assets $ 170 $ 150 Payables to Eisai included in Accrued and other current liabilities (2) 325 700 Payables to Eisai included in Other Noncurrent Liabilities (3) 570 525 (1) Represents amortization of capitalized milestone payments. (2) Includes accrued milestone and future option payments. (3) Includes accrued milestone payments. Bayer AG In 2014, the Company entered into a worldwide clinical development collaboration with Bayer AG (Bayer) to market and develop soluble guanylate cyclase (sGC) modulators including Bayer’s Adempas (riociguat), which is approved to treat pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension. The two companies have implemented a joint development and commercialization strategy. The collaboration also includes clinical development of Bayer’s vericiguat, which is in development for the potential treatment of worsening heart failure. Vericiguat is currently under review by regulatory authorities in the United States, the EU and Japan. Under the agreement, Bayer leads commercialization of Adempas in the Americas, while Merck leads commercialization in the rest of the world. For vericiguat, if approved, Bayer will lead commercialization in the rest of world and Merck will lead in the Americas. Both companies share in development costs and profits on sales and have the right to co-promote in territories where they are not the lead. Merck records sales of Adempas in its marketing territories, as well as alliance revenue, which is Merck’s share of profits from the sale of Adempas in Bayer’s marketing territories. In addition, the agreement provides for contingent payments from Merck to Bayer related to the successful achievement of sales-based milestones. Prior to 2020, Merck accrued $725 million of sales-based milestone payments for this collaboration, of which $350 million was paid to Bayer in 2018. There is an additional $400 million potential future sales-based milestone payment that has not yet been accrued as it is not deemed by the Company to be probable at this time. The intangible asset balance related to this collaboration (which includes the acquired intangible asset balance, as well as capitalized sales-based milestone payments) was $838 million at September 30, 2020 and is included in Other Intangibles, Net on the Consolidated Balance Sheet. The amount is being amortized over its estimated useful life through 2027 as supported by projected future cash flows, subject to impairment testing. Summarized financial information related to this collaboration is as follows: Three Months Ended Nine Months Ended ($ in millions) 2020 2019 2020 2019 Alliance revenue - Adempas $ 83 $ 50 $ 216 $ 144 Net sales of Adempas recorded by Merck 55 57 167 158 Total sales $ 138 $ 107 $ 383 $ 302 Cost of sales (1) 29 28 85 86 Selling, general and administrative 19 12 42 31 Research and development 12 31 53 94 ($ in millions) September 30, 2020 December 31, 2019 Receivables from Bayer included in Other current assets $ 70 $ 49 Payables to Bayer included in Other Noncurrent Liabilities (2) 375 375 (1) Includes amortization of intangible assets. (2) Represents accrued milestone payment.

Restructuring

Restructuring	9 Months Ended
	Sep. 30, 2020
Restructuring and Related Activities [Abstract]
Restructuring	Restructuring In early 2019, Merck approved a new global restructuring program (Restructuring Program) as part of a worldwide initiative focused on further optimizing the Company’s manufacturing and supply network, as well as reducing its global real estate footprint. This program is a continuation of the Company’s plant rationalization, builds on prior restructuring programs and does not include any actions associated with the planned spin-off of Organon. As the Company continues to evaluate its global footprint and overall operating model, it subsequently identified additional actions under the Restructuring Program, and could identify further actions over time. The actions currently contemplated under the Restructuring Program are expected to be substantially completed by the end of 2023, with the cumulative pretax costs to be incurred by the Company to implement the program estimated to be approximately $2.5 billion. The Company estimates that approximately 60% of the cumulative pretax costs will result in cash outlays, primarily related to employee separation expense and facility shut-down costs. Approximately 40% of the cumulative pretax costs will be non-cash, relating primarily to the accelerated depreciation of facilities to be closed or divested. The Company expects to record charges of approximately $800 million in 2020 related to the Restructuring Program. Actions under previous global restructuring programs have been substantially completed. The Company recorded total pretax costs of $186 million and $296 million in the third quarter of 2020 and 2019, respectively, and $504 million and $642 million for the first nine months of 2020 and 2019, respectively, related to restructuring program activities. Since inception of the Restructuring Program through September 30, 2020, Merck has recorded total pretax accumulated costs of approximately $1.4 billion. For segment reporting, restructuring charges are unallocated expenses. The following tables summarize the charges related to restructuring program activities by type of cost: Three Months Ended September 30, 2020 Nine Months Ended September 30, 2020 ($ in millions) Separation Accelerated Other Total Separation Accelerated Other Total Cost of sales $ — $ 33 $ 5 $ 38 $ — $ 89 $ 42 $ 131 Selling, general and administrative — 15 — 15 — 37 — 37 Research and development — 18 1 19 — 66 1 67 Restructuring costs 61 — 53 114 143 — 126 269 $ 61 $ 66 $ 59 $ 186 $ 143 $ 192 $ 169 $ 504 Three Months Ended September 30, 2019 Nine Months Ended September 30, 2019 ($ in millions) Separation Accelerated Other Total Separation Accelerated Other Total Cost of sales $ — $ 41 $ 21 $ 62 $ — $ 139 $ 22 $ 161 Selling, general and administrative — 1 — 1 — 33 — 33 Research and development — (1) 2 1 — 1 3 4 Restructuring costs 205 — 27 232 358 — 86 444 $ 205 $ 41 $ 50 $ 296 $ 358 $ 173 $ 111 $ 642 Separation costs are associated with actual headcount reductions, as well as those headcount reductions which were probable and could be reasonably estimated. Accelerated depreciation costs primarily relate to manufacturing, research and administrative facilities and equipment to be sold or closed as part of the programs. Accelerated depreciation costs represent the difference between the depreciation expense to be recognized over the revised useful life of the asset, based upon the anticipated date the site will be closed or divested or the equipment disposed of, and depreciation expense as determined utilizing the useful life prior to the restructuring actions. All the sites have and will continue to operate up through the respective closure dates and, since future undiscounted cash flows are sufficient to recover the respective book values, Merck is recording accelerated depreciation over the revised useful life of the site assets. Anticipated site closure dates, particularly related to manufacturing locations, have been and may continue to be adjusted to reflect changes resulting from regulatory or other factors. Other activity in 2020 and 2019 includes asset abandonment, facility shut-down and other related costs, as well as pretax gains and losses resulting from the sales of facilities and related assets. Additionally, other activity includes certain employee-related costs associated with pension and other postretirement benefit plans (see Note 12) and share-based compensation. The following table summarizes the charges and spending relating to restructuring program activities for the nine months ended September 30, 2020: ($ in millions) Separation Accelerated Other Total Restructuring reserves January 1, 2020 $ 690 $ — $ 69 $ 759 Expense 143 192 169 504 (Payments) receipts, net (395) — (237) (632) Non-cash activity — (192) 39 (153) Restructuring reserves September 30, 2020 (1) $ 438 $ — $ 40 $ 478

Financial Instruments

Financial Instruments	9 Months Ended
	Sep. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Financial Instruments	Financial Instruments Derivative Instruments and Hedging Activities The Company manages the impact of foreign exchange rate movements and interest rate movements on its earnings, cash flows and fair values of assets and liabilities through operational means and through the use of various financial instruments, including derivative instruments. A significant portion of the Company’s revenues and earnings in foreign affiliates is exposed to changes in foreign exchange rates. The objectives and accounting related to the Company’s foreign currency risk management program, as well as its interest rate risk management activities are discussed below. Foreign Currency Risk Management The Company has established revenue hedging, balance sheet risk management and net investment hedging programs to protect against volatility of future foreign currency cash flows and changes in fair value caused by changes in foreign exchange rates. The objective of the revenue hedging program is to reduce the variability caused by changes in foreign exchange rates that would affect the U.S. dollar value of future cash flows derived from foreign currency denominated sales, primarily the euro, Japanese yen and Chinese renminbi. To achieve this objective, the Company will hedge a portion of its forecasted foreign currency denominated third-party and intercompany distributor entity sales (forecasted sales) that are expected to occur over its planning cycle, typically no more than two years into the future. The Company will layer in hedges over time, increasing the portion of forecasted sales hedged as it gets closer to the expected date of the forecasted sales. The portion of forecasted sales hedged is based on assessments of cost-benefit profiles that consider natural offsetting exposures, revenue and exchange rate volatilities and correlations, and the cost of hedging instruments. The Company manages its anticipated transaction exposure principally with purchased local currency put options, forward contracts and purchased collar options. The fair values of these derivative contracts are recorded as either assets (gain positions) or liabilities (loss positions) in the Condensed Consolidated Balance Sheet. Changes in the fair value of derivative contracts are recorded each period in either current earnings or Other comprehensive income ( OCI ), depending on whether the derivative is designated as part of a hedge transaction and, if so, the type of hedge transaction. For derivatives that are designated as cash flow hedges, the unrealized gains or losses on these contracts are recorded in Accumulated other comprehensive income ( AOCI ) and reclassified into Sales when the hedged anticipated revenue is recognized. For those derivatives which are not designated as cash flow hedges, but serve as economic hedges of forecasted sales, unrealized gains or losses are recorded in Sales each period. The cash flows from both designated and non-designated contracts are reported as operating activities in the Condensed Consolidated Statement of Cash Flows. The Company does not enter into derivatives for trading or speculative purposes. The Company manages operating activities and net asset positions at each local subsidiary in order to mitigate the effects of exchange on monetary assets and liabilities. The Company also uses a balance sheet risk management program to mitigate the exposure of net monetary assets that are denominated in a currency other than a subsidiary’s functional currency from the effects of volatility in foreign exchange. In these instances, Merck principally utilizes forward exchange contracts to offset the effects of exchange on exposures denominated in developed country currencies, primarily the euro and Japanese yen. For exposures in developing country currencies, the Company will enter into forward contracts to partially offset the effects of exchange on exposures when it is deemed economical to do so based on a cost-benefit analysis that considers the magnitude of the exposure, the volatility of the exchange rate and the cost of the hedging instrument. The cash flows from these contracts are reported as operating activities in the Condensed Consolidated Statement of Cash Flows. Monetary assets and liabilities denominated in a currency other than the functional currency of a given subsidiary are remeasured at spot rates in effect on the balance sheet date with the effects of changes in spot rates reported in Other (income) expense, net . The forward contracts are not designated as hedges and are marked to market through Other (income) expense, net . Accordingly, fair value changes in the forward contracts help mitigate the changes in the value of the remeasured assets and liabilities attributable to changes in foreign currency exchange rates, except to the extent of the spot-forward differences. These differences are not significant due to the short-term nature of the contracts, which typically have average maturities at inception of less than one year. The Company also uses forward exchange contracts to hedge a portion of its net investment in foreign operations against movements in exchange rates. The forward contracts are designated as hedges of the net investment in a foreign operation. The unrealized gains or losses on these contracts are recorded in foreign currency translation adjustment within OCI and remain in AOCI until either the sale or complete or substantially complete liquidation of the subsidiary. The Company excludes certain portions of the change in fair value of its derivative instruments from the assessment of hedge effectiveness (excluded components). Changes in fair value of the excluded components are recognized in OCI . The Company recognizes in earnings the initial value of the excluded components on a straight-line basis over the life of the derivative instrument, rather than using the mark-to-market approach. The cash flows from these contracts are reported as investing activities in the Condensed Consolidated Statement of Cash Flows. Foreign exchange risk is also managed through the use of foreign currency debt. The Company’s senior unsecured euro-denominated notes have been designated as, and are effective as, economic hedges of the net investment in a foreign operation. Accordingly, foreign currency transaction gains or losses due to spot rate fluctuations on the euro-denominated debt instruments are included in foreign currency translation adjustment within OCI . The effects of the Company’s net investment hedges on OCI and the Consolidated Statement of Income are shown below: Amount of Pretax (Gain) Loss Recognized in Other Comprehensive Income (1) Amount of Pretax (Gain) Loss Recognized in Other (income) expense, net for Amounts Excluded from Effectiveness Testing Three Months Ended September 30, Nine Months Ended September 30, Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 2020 2019 2020 2019 Net Investment Hedging Relationships Foreign exchange contracts $ 10 $ 1 $ 15 $ 8 $ (4) $ (8) $ (15) $ (23) Euro-denominated notes 162 (150) 182 (152) — — — — (1) No amounts were reclassified from AOCI into income related to the sale of a subsidiary. Interest Rate Risk Management The Company may use interest rate swap contracts on certain investing and borrowing transactions to manage its net exposure to interest rate changes and to reduce its overall cost of borrowing. The Company does not use leveraged swaps and, in general, does not leverage any of its investment activities that would put principal capital at risk. In February 2020, five interest rate swaps with notional amounts of $250 million each matured. These swaps effectively converted the Company’s $1.25 billion, 1.85% fixed-rate notes due 2020 to variable rate debt. At September 30, 2020, the Company was a party to 14 pay-floating, receive-fixed interest rate swap contracts designated as fair value hedges of fixed-rate notes in which the notional amounts match the amount of the hedged fixed-rate notes as detailed in the table below. September 30, 2020 ($ in millions) Par Value of Debt Number of Interest Rate Swaps Held Total Swap Notional Amount 3.875% notes due 2021 $ 1,150 5 $ 1,150 2.40% notes due 2022 1,000 4 1,000 2.35% notes due 2022 1,250 5 1,250 The interest rate swap contracts are designated hedges of the fair value changes in the notes attributable to changes in the benchmark London Interbank Offered Rate (LIBOR) swap rate. The fair value changes in the notes attributable to changes in the LIBOR swap rate are recorded in interest expense along with the offsetting fair value changes in the swap contracts. The cash flows from these contracts are reported as operating activities in the Condensed Consolidated Statement of Cash Flows. The table below presents the location of amounts recorded on the Consolidated Balance Sheet related to cumulative basis adjustments for fair value hedges: Carrying Amount of Hedged Liabilities Cumulative Amount of Fair Value Hedging Adjustment Increase (Decrease) Included in the Carrying Amount ($ in millions) September 30, 2020 December 31, 2019 September 30, 2020 December 31, 2019 Balance Sheet Line Item in which Hedged Item is Included Loans payable and current portion of long-term debt $ 1,155 $ 1,249 $ 5 $ (1) Long-Term Debt 2,309 3,409 62 14 Presented in the table below is the fair value of derivatives on a gross basis segregated between those derivatives that are designated as hedging instruments and those that are not designated as hedging instruments: September 30, 2020 December 31, 2019 Fair Value of Derivative U.S. Dollar Fair Value of Derivative U.S. Dollar ($ in millions) Balance Sheet Caption Asset Liability Asset Liability Derivatives Designated as Hedging Instruments Interest rate swap contracts Other current assets $ 6 $ — $ 1,150 $ — $ — $ — Interest rate swap contracts Other Assets 63 — 2,250 15 — 3,400 Interest rate swap contracts Accrued and other current liabilities — — — — 1 1,250 Foreign exchange contracts Other current assets 30 — 4,120 152 — 6,117 Foreign exchange contracts Other Assets 59 — 1,881 55 — 2,160 Foreign exchange contracts Accrued and other current liabilities — 104 3,096 — 22 1,748 Foreign exchange contracts Other Noncurrent Liabilities — 1 157 — 1 53 $ 158 $ 105 $ 12,654 $ 222 $ 24 $ 14,728 Derivatives Not Designated as Hedging Instruments Foreign exchange contracts Other current assets $ 81 $ — $ 5,455 $ 66 $ — $ 7,245 Foreign exchange contracts Accrued and other current liabilities — 171 8,042 — 73 8,693 Forward contract related to Seagen common stock Accrued and other current liabilities — 22 1,000 — — — $ 81 $ 193 $ 14,497 $ 66 $ 73 $ 15,938 $ 239 $ 298 $ 27,151 $ 288 $ 97 $ 30,666 As noted above, the Company records its derivatives on a gross basis in the Condensed Consolidated Balance Sheet. The Company has master netting agreements with several of its financial institution counterparties (see Concentrations of Credit Risk below). The following table provides information on the Company’s derivative positions subject to these master netting arrangements as if they were presented on a net basis, allowing for the right of offset by counterparty and cash collateral exchanged per the master agreements and related credit support annexes: September 30, 2020 December 31, 2019 ($ in millions) Asset Liability Asset Liability Gross amounts recognized in the condensed consolidated balance sheet $ 239 $ 298 $ 288 $ 97 Gross amounts subject to offset in master netting arrangements not offset in the condensed consolidated balance sheet (140) (140) (84) (84) Cash collateral received — — (34) — Net amounts $ 99 $ 158 $ 170 $ 13 The table below provides information regarding the location and amount of pretax (gains) losses of derivatives designated in fair value or cash flow hedging relationships: Sales Other (income) expense, net (1) Other comprehensive income (loss) Sales Other (income) expense, net (1) Other comprehensive income (loss) Three Months Ended September 30, Three Months Ended September 30, Three Months Ended September 30, Nine Months Ended September 30, Nine Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 2020 2019 2020 2019 2020 2019 2020 2019 Financial Statement Line Items in which Effects of Fair Value or Cash Flow Hedges are Recorded $ 12,551 $ 12,397 $ (312) $ 35 $ 10 $ (28) $ 35,479 $ 34,972 $ (630) $ 362 $ (190) $ 155 (Gain) loss on fair value hedging relationships Interest rate swap contracts Hedged items — — (14) 13 — — — — 54 101 — — Derivatives designated as hedging instruments — — — (6) — — — — (76) (74) — — Impact of cash flow hedging relationships Foreign exchange contracts Amount of (loss) gain recognized in OCI on derivatives — — — — (195) 186 — — — — (126) 183 Increase (decrease) in Sales as a result of AOCI reclassifications (23) 70 — — 23 (70) 65 189 — — (65) (189) Interest rate contracts Amount of gain recognized in Other (income) expense, net on derivatives — — (1) (1) — — — — (3) (3) — — Amount of loss recognized in OCI on derivatives — — — — (1) (1) — — — — (3) (6) (1) Interest expense is a component of Other (income) expense, net. The table below provides information regarding the income statement effects of derivatives not designated as hedging instruments: Amount of Derivative Pretax (Gain) Loss Recognized in Income Three Months Ended Nine Months Ended September 30, ($ in millions) Income Statement Caption 2020 2019 2020 2019 Derivatives Not Designated as Hedging Instruments Foreign exchange contracts (1) Other (income) expense, net $ (7) $ (8) $ (138) $ 112 Foreign exchange contracts (2) Sales 7 (11) 4 (7) Interest rate contracts (3) Other (income) expense, net — — 9 — Forward contract related to Seagen common stock Research and development expenses 22 — 22 — (1) These derivative contracts mitigate changes in the value of remeasured foreign currency denominated monetary assets and liabilities attributable to changes in foreign currency exchange rates. (2) These derivative contracts serve as economic hedges of forecasted transactions. (3) These derivatives serve as economic hedges against rising treasury rates. At September 30, 2020, the Company estimates $155 million of pretax net unrealized losses on derivatives maturing within the next 12 months that hedge foreign currency denominated sales over that same period will be reclassified from AOCI to Sales . The amount ultimately reclassified to Sales may differ as foreign exchange rates change. Realized gains and losses are ultimately determined by actual exchange rates at maturity. Investments in Debt and Equity Securities Information on investments in debt and equity securities is as follows: September 30, 2020 December 31, 2019 Amortized Gross Unrealized Fair Amortized Gross Unrealized Fair ($ in millions) Gains Losses Gains Losses U.S. government and agency securities $ 74 $ — $ — $ 74 $ 266 $ 3 $ — $ 269 Foreign government bonds 2 — — 2 — — — — Commercial paper — — — — 668 — — 668 Corporate notes and bonds — — — — 608 13 — 621 Asset-backed securities — — — — 226 1 — 227 Total debt securities $ 76 $ — $ — $ 76 $ 1,768 $ 17 $ — $ 1,785 Publicly traded equity securities (1) 1,477 838 Total debt and publicly traded equity securities $ 1,553 $ 2,623 (1) Unrealized net (gains) losses recognized in Other (income) expense, net on equity securities still held at September 30, 2020 were $(43) million and $(512) million in the third quarter and first nine months of 2020, respectively. Unrealized net losses (gains) recognized in Other (income) expense, net on equity securities still held at September 30, 2019 were $25 million and $(41) million in the third quarter and first nine months of 2019, respectively. At September 30, 2020 and September 30, 2019, the Company also had $508 million and $393 million, respectively, of equity investments without readily determinable fair values included in Other Assets . The Company recognizes unrealized gains on these equity investments based on favorable observable price changes from transactions involving similar investments of the same investee and recognizes unrealized losses based on unfavorable observable price changes. During the first nine months of 2020, the Company recognized unrealized gains of $21 million and unrealized losses of $3 million in Other (income) expense, net related to these equity investments held at September 30, 2020. During the first nine months of 2019, the Company recognized unrealized gains of $4 million and unrealized losses of $12 million in Other (income) expense, net related to these investments held at September 30, 2019. Cumulative unrealized gains and cumulative unrealized losses based on observable prices changes for investments in equity investments without readily determinable fair values still held at September 30, 2020 were $128 million and $24 million, respectively. Fair Value Measurements Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The Company uses a fair value hierarchy which maximizes the use of observable inputs and minimizes the use of unobservable inputs when measuring fair value. There are three levels of inputs used to measure fair value with Level 1 having the highest priority and Level 3 having the lowest: Level 1 - Quoted prices (unadjusted) in active markets for identical assets or liabilities; Level 2 - Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; Level 3 - Unobservable inputs that are supported by little or no market activity. Level 3 assets or liabilities are those whose values are determined using pricing models, discounted cash flow methodologies, or similar techniques with significant unobservable inputs, as well as assets or liabilities for which the determination of fair value requires significant judgment or estimation. If the inputs used to measure the financial assets and liabilities fall within more than one level described above, the categorization is based on the lowest level input that is significant to the fair value measurement of the instrument. Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis Financial assets and liabilities measured at fair value on a recurring basis are summarized below: Fair Value Measurements Using Fair Value Measurements Using Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total ($ in millions) September 30, 2020 December 31, 2019 Assets Investments Foreign government bonds $ — $ 2 $ — $ 2 $ — $ — $ — $ — Commercial paper — — — — — 668 — 668 Corporate notes and bonds — — — — — 621 — 621 Asset-backed securities (1) — — — — — 227 — 227 U.S. government and agency securities — — — — — 209 — 209 Publicly traded equity securities 1,370 — — 1,370 518 — — 518 1,370 2 — 1,372 518 1,725 — 2,243 Other assets (2) U.S. government and agency securities 74 — — 74 60 — — 60 Publicly traded equity securities 107 — — 107 320 — — 320 181 — — 181 380 — — 380 Derivative assets (3) Forward exchange contracts — 116 — 116 — 169 — 169 Interest rate swaps — 69 — 69 — 15 — 15 Purchased currency options — 54 — 54 — 104 — 104 — 239 — 239 — 288 — 288 Total assets $ 1,551 $ 241 $ — $ 1,792 $ 898 $ 2,013 $ — $ 2,911 Liabilities Other liabilities Contingent consideration $ — $ — $ 829 $ 829 $ — $ — $ 767 $ 767 Derivative liabilities (3) Forward exchange contracts — 275 — 275 — 95 — 95 Forward contract related to Seagen common stock — 22 — 22 — — — — Written currency options — 1 — 1 — 1 — 1 Interest rate swaps — — — — — 1 — 1 — 298 — 298 — 97 — 97 Total liabilities $ — $ 298 $ 829 $ 1,127 $ — $ 97 $ 767 $ 864 (1) Primarily all of the asset-backed securities were highly rated (Standard & Poor’s rating of AAA and Moody’s Investors Service rating of Aaa), secured primarily by auto loan, credit card and student loan receivables, with weighted-average lives of primarily 5 years or less. (2) Investments included in other assets are restricted as to use, including for the payment of benefits under employee benefit plans. (3) The fair value determination of derivatives includes the impact of the credit risk of counterparties to the derivatives and the Company’s own credit risk, the effects of which were not significant. As of September 30, 2020 and December 31, 2019, Cash and cash equivalents included $6.6 billion and $8.9 billion of cash equivalents, respectively (which would be considered Level 2 in the fair value hierarchy). Contingent Consideration Summarized information about the changes in liabilities for contingent consideration associated with business acquisitions is as follows: Nine Months Ended September 30, ($ in millions) 2020 2019 Fair value January 1 $ 767 $ 788 Additions 97 — Changes in estimated fair value (1) 71 52 Payments (106) (85) Fair value September 30 (2)(3) $ 829 $ 755 (1) Recorded in Cost of sales, Research and development expenses, and Other (income) expense, net . Includes cumulative translation adjustments. (2) Balance at September 30, 2020 includes $140 million recorded as a current liability for amounts expected to be paid within the next 12 months. (3) At September 30, 2020 and December 31, 2019, $637 million and $625 million, respectively, of the liabilities relate to the termination of the Sanofi-Pasteur MSD joint venture in 2016. As part of the termination, Merck recorded a liability for contingent future royalty payments of 11.5% on net sales of all Merck products that were previously sold by the joint venture through December 31, 2024. The fair value of this liability is determined utilizing the estimated amount and timing of projected cash flows using a risk-adjusted discount rate of 8% to present value the cash flows. The additions to contingent consideration in 2020 relate to the acquisition of Themis (see Note 2). The payments of contingent consideration in both periods relate to liabilities recorded in connection with the termination of the Sanofi-Pasteur MSD joint venture in 2016. Other Fair Value Measurements Some of the Company’s financial instruments, such as cash and cash equivalents, receivables and payables, are reflected in the balance sheet at carrying value, which approximates fair value due to their short-term nature. The estimated fair value of loans payable and long-term debt (including current portion) at September 30, 2020, was $32.6 billion compared with a carrying value of $28.7 billion and at December 31, 2019, was $28.8 billion compared with a carrying value of $26.3 billion. Fair value was estimated using recent observable market prices and would be considered Level 2 in the fair value hierarchy. Concentrations of Credit Risk On an ongoing basis, the Company monitors concentrations of credit risk associated with corporate and government issuers of securities and financial institutions with which it conducts business. Credit exposure limits are established to limit a concentration with any single issuer or institution. Cash and investments are placed in instruments that meet high credit quality standards as specified in the Company’s investment policy guidelines. The majority of the Company’s accounts receivable arise from product sales in the United States, Europe and China and are primarily due from drug wholesalers and retailers, hospitals, government agencies, managed health care providers and pharmacy benefit managers. The Company monitors the financial performance and creditworthiness of its customers so that it can properly assess and respond to changes in their credit profile. The Company also continues to monitor global economic conditions, including the volatility associated with international sovereign economies, and associated impacts on the financial markets and its business. The Company has accounts receivable factoring agreements with financial institutions in certain countries to sell accounts receivable. The Company factored $2.1 billion and $2.7 billion of accounts receivable in the third quarter of 2020 and the fourth quarter of 2019, respectively, under these factoring arrangements, which reduced outstanding accounts receivable. The cash received from the financial institutions is reported within operating activities in the Consolidated Statement of Cash Flows. In certain of these factoring arrangements, for ease of administration, the Company will collect customer payments related to the factored receivables, which it then remits to the financial institutions. The net cash flows relating to these collections are reported as financing activities in the Consolidated Statement of Cash Flows. The cost of factoring such accounts receivable was de minimis . Derivative financial instruments are executed under International Swaps and Derivatives Association master agreements. The master agreements with several of the Company’s financial institution counterparties also include credit support annexes. These annexes contain provisions that require collateral to be exchanged depending on the value of the derivative assets and liabilities, the Company’s credit rating, and the credit rating of the counterparty. Cash collateral received by the Company from various counterparties was $34 million at December 31, 2019. The obligation to return such collateral is recorded in Accrued and other current liabilities . No cash collateral was advanced by the Company to counterparties as of September 30, 2020 or December 31, 2019.

Inventories

Inventories	9 Months Ended
	Sep. 30, 2020
Inventory Disclosure [Abstract]
Inventories	Inventories Inventories consisted of: ($ in millions) September 30, 2020 December 31, 2019 Finished goods $ 2,038 $ 1,772 Raw materials and work in process 6,073 5,650 Supplies 197 207 Total (approximates current cost) 8,308 7,629 Decrease to LIFO cost (99) (171) $ 8,209 $ 7,458 Recognized as: Inventories $ 6,128 $ 5,978 Other assets 2,081 1,480 Amounts recognized as Other Assets are comprised almost entirely of raw materials and work in process inventories. At September 30, 2020 and December 31, 2019, these amounts included $1.8 billion and $1.3 billion, respectively, of inventories not expected to be sold within one year. In addition, these amounts included $288 million and $168 million at September 30, 2020 and December 31, 2019, respectively, of inventories produced in preparation for product launches.

Other Intangibles

Other Intangibles	9 Months Ended
	Sep. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Other Intangibles	7. Other Intangibles During the third quarter and first nine months of 2019, the Company recorded $612 million and $693 million, respectively, of intangible asset impairment charges related to marketed products within Cost of sales . During the third quarter of 2019, the Company recorded an impairment charge of $612 million related to Sivextro (tedizolid phosphate), a product for the treatment of acute bacterial skin and skin structure infections caused by susceptible isolates of certain Gram-positive microorganisms. As part of a reorganization and reprioritization of its internal sales force, the Company made the decision to cease promotion of Sivextro in the U.S. market by the end of 2019. This decision resulted in reduced cash flow projections for Sivextro , which indicated that the Sivextro 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 Sivextro that, when compared with its related carrying value, resulted in the impairment charge noted above.

Long-Term Debt

Long-Term Debt	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Long-Term Debt	Long-Term DebtIn June 2020, the Company issued $4.5 billion principal amount of senior unsecured notes consisting of $1.0 billion of 0.75% notes due 2026, $1.25 billion of 1.45% notes due 2030, $1.0 billion of 2.35% notes due 2040 and $1.25 billion of 2.45% notes due 2050. Merck used the net proceeds from the offering for general corporate purposes, including without limitation the repayment of outstanding commercial paper borrowings and other indebtedness with upcoming maturities.

Contingencies

Contingencies	9 Months Ended
	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Contingencies The Company is involved in various claims and legal proceedings of a nature considered normal to its business, including product liability, intellectual property, and commercial litigation, as well as certain additional matters including governmental and environmental matters. In the opinion of the Company, it is unlikely that the resolution of these matters will be material to the Company’s financial condition, results of operations or cash flows. Given the nature of the litigation discussed below and the complexities involved in these matters, the Company is unable to reasonably estimate a possible loss or range of possible loss for such matters until the Company knows, among other factors, (i) what claims, if any, will survive dispositive motion practice, (ii) the extent of the claims, including the size of any potential class, particularly when damages are not specified or are indeterminate, (iii) how the discovery process will affect the litigation, (iv) the settlement posture of the other parties to the litigation and (v) any other factors that may have a material effect on the litigation. The Company records accruals for contingencies when it is probable that a liability has been incurred and the amount can be reasonably estimated. These accruals are adjusted periodically as assessments change or additional information becomes available. For product liability claims, a portion of the overall accrual is actuarially determined and considers such factors as past experience, number of claims reported and estimates of claims incurred but not yet reported. Individually significant contingent losses are accrued when probable and reasonably estimable. Legal defense costs expected to be incurred in connection with a loss contingency are accrued when probable and reasonably estimable. The Company’s decision to obtain insurance coverage is dependent on market conditions, including cost and availability, existing at the time such decisions are made. The Company has evaluated its risks and has determined that the cost of obtaining product liability insurance outweighs the likely benefits of the coverage that is available and, as such, has no insurance for most product liabilities. Product Liability Litigation Fosamax As previously disclosed, Merck is a defendant in product liability lawsuits in the United States involving Fosamax ( Fosamax Litigation). As of September 30, 2020, approximately 3,590 cases are pending against Merck in either federal or state court. Plaintiffs in the vast majority of these cases generally allege that they sustained femur fractures and/or other bone injuries (Femur Fractures) in association with the use of Fosamax . All federal cases involving allegations of Femur Fractures have been or will be transferred to a multidistrict litigation in the District of New Jersey (Femur Fracture MDL). In the only bellwether case tried to date in the Femur Fracture MDL, Glynn v. Merck , the jury returned a verdict in Merck’s favor. In addition, in June 2013, the Femur Fracture MDL court granted Merck’s motion for judgment as a matter of law in the Glynn case and held that the plaintiff’s failure to warn claim was preempted by federal law. In August 2013, the Femur Fracture MDL court entered an order requiring plaintiffs in the Femur Fracture MDL to show cause why those cases asserting claims for a femur fracture injury that took place prior to September 14, 2010, should not be dismissed based on the court’s preemption decision in the Glynn case. Pursuant to the show cause order, in March 2014, the Femur Fracture MDL court dismissed with prejudice approximately 650 cases on preemption grounds. Plaintiffs in approximately 515 of those cases appealed that decision to the U.S. Court of Appeals for the Third Circuit (Third Circuit). In March 2017, the Third Circuit issued a decision reversing the Femur Fracture MDL court’s preemption ruling and remanding the appealed cases back to the Femur Fracture MDL court. In May 2019, the U.S. Supreme Court decided that the Third Circuit had incorrectly concluded that the issue of preemption should be resolved by a jury, and accordingly vacated the judgment of the Third Circuit and remanded the proceedings back to the Third Circuit to address the issue in a manner consistent with the Supreme Court’s opinion. In November 2019, the Third Circuit remanded the cases back to the District Court in order to allow that court to determine in the first instance whether the plaintiffs’ state law claims are preempted by federal law under the standards described by the Supreme Court in its opinion. Briefing on the issue is closed, and the parties await the decision of the District Court. Accordingly, as of September 30, 2020, approximately 970 cases were actively pending in the Femur Fracture MDL. As of September 30, 2020, approximately 2,340 cases alleging Femur Fractures have been filed in New Jersey state court and are pending before Judge James Hyland in Middlesex County. The parties selected an initial group of cases to be reviewed through fact discovery, and Merck has continued to select additional cases to be reviewed. As of September 30, 2020, approximately 275 cases alleging Femur Fractures have been filed and are pending in California state court. All of the Femur Fracture cases filed in California state court have been coordinated before a single judge in Orange County, California. Additionally, there are four Femur Fracture cases pending in other state courts. Discovery is presently stayed in the Femur Fracture MDL and in the state court in California. Merck intends to defend against these lawsuits. Januvia/Janumet As previously disclosed, Merck is a defendant in product liability lawsuits in the United States involving Januvia and/or Janumet . As of September 30, 2020, Merck is aware of approximately 1,465 product users alleging that Januvia and/or Janumet caused the development of pancreatic cancer and other injuries. Most claims have been filed in multidistrict litigation before the U.S. District Court for the Southern District of California (MDL). Outside of the MDL, the majority of claims have been filed in coordinated proceedings before the Superior Court of California, County of Los Angeles (California State Court). In November 2015, the MDL and California State Court–in separate opinions–granted summary judgment to defendants on grounds of federal preemption. Plaintiffs appealed in both forums. In November 2017, the U.S. Court of Appeals for the Ninth Circuit vacated the judgment and remanded for further discovery. In November 2018, the California state appellate court reversed and remanded on similar grounds. In March 2019, the parties in the MDL and the California coordinated proceedings agreed to coordinate and adopt a schedule for completing discovery on general causation and preemption issues and for renewing summary judgment and Daubert motions. Under the stipulated case management schedule, the hearings for Daubert and summary judgment motions took place on October 20, 2020. As of September 30, 2020, six product users have claims pending against Merck in state courts other than California, including Illinois. In June 2017, the Illinois trial court denied Merck’s motion for summary judgment based on federal preemption. Merck appealed, and the Illinois appellate court affirmed in December 2018. Merck filed a petition for leave to appeal to the Illinois Supreme Court in February 2019. In April 2019, the Illinois Supreme Court stayed consideration of the pending petition to appeal until the U.S. Supreme Court issued its opinion in Merck Sharp & Dohme Corp. v. Albrecht (relating to the Fosamax matter discussed above). Merck filed the opinion in Albrecht with the Illinois Supreme Court in June 2019. The petition for leave to appeal was decided in September 2019, in which the Illinois Supreme Court directed the intermediate appellate court to reconsider its earlier ruling. The Illinois Appellate Court issued a favorable decision concluding, consistent with Albrecht , that preemption presents a legal question to be resolved by the court. In addition to the claims noted above, the Company has agreed to toll the statute of limitations for approximately 50 additional claims. The Company intends to continue defending against these lawsuits. Vioxx As previously disclosed, Merck is a defendant in a lawsuit brought by the Attorney General of Utah alleging that Merck misrepresented the safety of Vioxx . The lawsuit is pending in Utah state court. Utah seeks damages and penalties under the Utah False Claims Act. A bench trial in this matter has been rescheduled for April 6, 2021. Governmental Proceedings As previously disclosed, the Company’s subsidiaries in China have received and may continue to receive inquiries regarding their operations from various Chinese governmental agencies. Some of these inquiries may be related to matters involving other multinational pharmaceutical companies, as well as Chinese entities doing business with such companies. The Company’s policy is to cooperate with these authorities and to provide responses as appropriate. As previously disclosed, from time to time, the Company receives inquiries and is the subject of preliminary investigation activities from competition and other governmental authorities in markets outside the United States. These authorities may include regulators, administrative authorities, and law enforcement and other similar officials, and these preliminary investigation activities may include site visits, formal or informal requests or demands for documents or materials, inquiries or interviews and similar matters. Certain of these preliminary inquiries or activities may lead to the commencement of formal proceedings. Should those proceedings be determined adversely to the Company, monetary fines and/or remedial undertakings may be required. Commercial and Other Litigation Zetia Antitrust Litigation As previously disclosed, Merck, MSD, Schering Corporation and MSP Singapore Company LLC (collectively, the Merck Defendants) are defendants in putative class action and opt-out lawsuits filed in 2018 on behalf of direct and indirect purchasers of Zetia alleging violations of federal and state antitrust laws, as well as other state statutory and common law causes of action. The cases have been consolidated for pretrial purposes in a federal multidistrict litigation before Judge Rebecca Beach Smith in the Eastern District of Virginia. In December 2018, the court denied the Merck Defendants’ motions to dismiss or stay the direct purchaser putative class actions pending bilateral arbitration. In August 2019, the district court adopted in full the report and recommendation of the magistrate judge with respect to the Merck Defendants’ motions to dismiss on non-arbitration issues, thereby granting in part and denying in part Merck Defendants’ motions to dismiss. In addition, in June 2019, the representatives of the putative direct purchaser class filed an amended complaint, and in August 2019, retailer opt-out plaintiffs filed an amended complaint. The Merck Defendants moved to dismiss the new allegations in both complaints. In October 2019, the magistrate judge issued a report and recommendation recommending that the district judge grant the motions in their entirety. In December 2019, the district court adopted this report and recommendation in part. The district court granted the Merck Defendants’ motion to dismiss to the extent the motion sought dismissal of claims for overcharges paid by entities that purchased generic ezetimibe from Par Pharmaceutical, Inc. (Par Pharmaceutical) and dismissed any claims for such overcharges. In November 2019, the direct purchaser plaintiffs and the indirect purchaser plaintiffs filed motions for class certification. On June 18, 2020, the magistrate judge issued a report and recommendation recommending that the district judge grant in part the direct purchasers’ motion for class certification and certify a class of 35 direct purchasers. On August 21, 2020, the district court adopted the report and recommendation in full, and on November 2, 2020, the U.S. Court of Appeals for the Fourth Circuit granted defendants’ motion for permission to appeal the district court’s order. Also, on August 14, 2020, the magistrate judge recommended that the court grant the motion for class certification filed by the putative indirect purchaser class. The Merck Defendants objected to this report and recommendation and are awaiting a decision from the district court. On August 10, 2020, the Merck Defendants filed a motion for summary judgment and other motions, and plaintiffs filed a motion for partial summary judgment, and other motions. Those motions are now fully briefed, and the court will likely hold a hearing on the competing motions. Trial in this matter has been adjourned. Patent Litigation From time to time, generic manufacturers of pharmaceutical products file abbreviated New Drug Applications (NDAs) with the FDA seeking to market generic forms of the Company’s products prior to the expiration of relevant patents owned by the Company. To protect its patent rights, the Company may file patent infringement lawsuits against such generic companies. Similar lawsuits defending the Company’s patent rights may exist in other countries. The Company intends to vigorously defend its patents, which it believes are valid, against infringement by companies attempting to market products prior to the expiration of such patents. As with any litigation, there can be no assurance of the outcomes, which, if adverse, could result in significantly shortened periods of exclusivity for these products and, with respect to products acquired through acquisitions, potentially significant intangible asset impairment charges. Bridion — Between January and March 2020, the Company received multiple Paragraph IV Certification Letters under the Hatch-Waxman Act notifying the Company that generic drug companies have filed applications to the FDA seeking pre-patent expiry approval to sell generic versions of Bridion (sugammadex) Injection. In March and April 2020, the Company filed patent infringement lawsuits in the U.S. District Courts for the District of New Jersey and the Northern District of West Virginia against those generic companies. These lawsuits, which assert one or more patents covering sugammadex and methods of using sugammadex, automatically stay FDA approval of the generic applications until June 2023 or until adverse court decisions, if any, whichever may occur earlier. Mylan Pharmaceuticals Inc., Mylan API US LLC, and Mylan Inc. (Mylan) have filed motions to dismiss in the District of New Jersey for lack of venue and failure to state a claim against certain defendants, and in the Northern District of West Virginia for failure to state a claim against certain defendants. The New Jersey motion has not yet been decided, and the West Virginia action is stayed pending resolution of the New Jersey motion. All New Jersey actions against all defendants have been consolidated. Januvia, Janumet, Janumet XR — In February 2019, Par Pharmaceutical filed suit against the Company in the U.S. District Court for the District of New Jersey, seeking a declaratory judgment of invalidity of a patent owned by the Company covering certain salt and polymorphic forms of sitagliptin that expires in 2026. In response, the Company filed a patent infringement lawsuit in the U.S. District Court for the District of Delaware against Par Pharmaceutical and additional companies that also indicated an intent to market generic versions of Januvia , Janumet , and Janumet XR following expiration of key patent protection in 2022, but prior to the expiration of the later-granted patent owned by the Company covering certain salt and polymorphic forms of sitagliptin that expires in 2026 (2026 salt/polymorph patent), and a later granted patent owned by the Company covering the Janumet formulation which expires in 2028. Par Pharmaceutical dismissed its case in the U.S. District Court for the District of New Jersey against the Company and will litigate the action in the U.S. District Court for the District of Delaware. The Company filed a patent infringement lawsuit against Mylan in the Northern District of West Virginia. The Judicial Panel of Multidistrict Litigation entered an order transferring the Company’s lawsuit against Mylan to the U.S. District Court for the District of Delaware for coordinated and consolidated pretrial proceedings with the other cases pending in that district. The U.S. District Court for the District of Delaware has scheduled the lawsuits for a single three-day trial on invalidity issues in October 2021. The Court will schedule separate one-day trials on infringement issues if necessary. In the Company’s case against Mylan, the U.S. District Court for the Northern District of West Virginia has conditionally scheduled a three-day trial in December 2021 on all issues. In February 2020, the Company amended its complaint against one defendant, Teva Pharmaceuticals USA, Inc., to add patent infringement claims related to a patent that expires in 2025 and covers certain processes for manufacturing sitagliptin. In July 2020, the Company amended its complaints against two defendants, Teva Pharmaceuticals USA, Inc. and Watson Laboratories, Inc., to add patent infringement claims related to a patent that also expires in 2026 and covers certain amorphous forms of sitagliptin. The Company has settled with five generic companies such that these generic companies can bring their products to the market in November 2026 or earlier under certain circumstances. In October 2019, Mylan filed a petition for Inter Partes Review (IPR) at the United States Patent and Trademark Office (USPTO) seeking invalidity of some, but not all, of the claims of the 2026 salt/polymorph patent. The USPTO instituted IPR proceedings in May 2020, finding a reasonable likelihood that the challenged claims are not valid. A trial is scheduled for February 2021 and a final decision is expected in May 2021. After institution, three additional IPR petitions were filed by Teva Pharmaceuticals USA, Inc., Dr. Reddy’s Laboratories, Inc., and Sun Pharmaceutical Industries Ltd., as well as related entities, which requested joinder with Mylan’s IPR proceedings. If the challenges are successful, the unchallenged claims of the 2026 salt/polymorph patent will remain valid, subject to the court proceedings described above. In Germany, two generic companies have sought the revocation of the Supplementary Protection Certificate (SPC) for Janumet . If the generic companies are successful, Janumet could lose market exclusivity in Germany as early as July 2022. Challenges to the Janumet SPC have also occurred in Portugal and Finland, and could occur in other European countries. Other Litigation There are various other pending legal proceedings involving the Company, principally product liability and intellectual property lawsuits. While it is not feasible to predict the outcome of such proceedings, in the opinion of the Company, either the likelihood of loss is remote or any reasonably possible loss associated with the resolution of such proceedings is not expected to be material to the Company’s financial condition, results of operations or cash flows either individually or in the aggregate. Legal Defense Reserves Legal defense costs expected to be incurred in connection with a loss contingency are accrued when probable and reasonably estimable. Some of the significant factors considered in the review of these legal defense reserves are as follows: the actual costs incurred by the Company; the development of the Company’s legal defense strategy and structure in light of the scope of its litigation; the number of cases being brought against the Company; the costs and outcomes of completed trials and the most current information regarding anticipated timing, progression, and related costs of pre-trial activities and trials in the associated litigation. The amount of legal defense reserves as of September 30, 2020 and December 31, 2019 of approximately $255 million and $240 million, respectively, represents the Company’s best estimate of the minimum amount of defense costs to be incurred in connection with its outstanding litigation; however, events such as additional trials and other events that could arise in the course of its litigation could affect the ultimate amount of legal defense costs to be incurred by the Company. The Company will continue to monitor its legal defense costs and review the adequacy of the associated reserves and may determine to increase the reserves at any time in the future if, based upon the factors set forth, it believes it would be appropriate to do so.

Equity

Equity	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Equity	Equity Three Months Ended September 30, Common Stock Other Retained Accumulated Treasury Stock Non- Total ($ and shares in millions except per share amounts) Shares Par Value Shares Cost Balance at July 1, 2019 3,577 $ 1,788 $ 39,484 $ 45,295 $ (5,362) 1,010 $ (53,570) $ 102 $ 27,737 Net income attributable to Merck & Co., Inc. — — — 1,901 — — — — 1,901 Other comprehensive loss, net of taxes — — — — (28) — — — (28) Cash dividends declared on common stock ($0.55 per share) — — — (1,392) — — — — (1,392) Treasury stock shares purchased — — — — — 17 (1,405) — (1,405) Share-based compensation plans and other — — 77 — — (1) 50 — 127 Net income attributable to noncontrolling interests — — — — — — — 6 6 Distributions attributable to noncontrolling interests — — — — — — — (21) (21) Balance at September 30, 2019 3,577 $ 1,788 $ 39,561 $ 45,804 $ (5,390) 1,026 $ (54,925) $ 87 $ 26,925 Balance at July 1, 2020 3,577 $ 1,788 $ 39,373 $ 49,724 $ (6,393) 1,048 $ (56,850) $ 102 $ 27,744 Net income attributable to Merck & Co., Inc. — — — 2,941 — — — — 2,941 Other comprehensive income, net of taxes — — — — 10 — — — 10 Cash dividends declared on common stock ($0.61 per share) — — — (1,558) — — — — (1,558) Share-based compensation plans and other — — 116 — — (1) 35 — 151 Net income attributable to noncontrolling interests — — — — — — — 4 4 Distributions attributable to noncontrolling interests — — — — — — — (22) (22) Balance at September 30, 2020 3,577 $ 1,788 $ 39,489 $ 51,107 $ (6,383) 1,047 $ (56,815) $ 84 $ 29,270 Nine Months Ended September 30, Common Stock Other Retained Accumulated Treasury Stock Non- Total ($ and shares in millions except per share amounts) Shares Par Value Shares Cost Balance at January 1, 2019 3,577 $ 1,788 $ 38,808 $ 42,579 $ (5,545) 985 $ (50,929) $ 181 $ 26,882 Net income attributable to Merck & Co., Inc. — — — 7,487 — — — — 7,487 Other comprehensive income, net of taxes — — — — 155 — — — 155 Cash dividends declared on common stock ($1.65 per share) — — — (4,262) — — — — (4,262) Treasury stock shares purchased — — 1,000 — — 54 (4,730) — (3,730) Share-based compensation plans and other — — (247) — — (13) 734 — 487 Net loss attributable to noncontrolling interests — — — — — — — (73) (73) Distributions attributable to noncontrolling interests — — — — — — — (21) (21) Balance at September 30, 2019 3,577 1,788 39,561 45,804 (5,390) 1,026 (54,925) 87 26,925 Balance at January 1, 2020 3,577 $ 1,788 $ 39,660 $ 46,602 $ (6,193) 1,038 $ (55,950) $ 94 $ 26,001 Net income attributable to Merck & Co., Inc. — — — 9,161 — — — — 9,161 Other comprehensive loss, net of taxes — — — — (190) — — — (190) Cash dividends declared on common stock ($1.83 per share) — — — (4,656) — — — — (4,656) Treasury stock shares purchased — — — — — 16 (1,281) — (1,281) Share-based compensation plans and other — — (171) — — (7) 416 — 245 Net income attributable to noncontrolling interests — — — — — — — 12 12 Distributions attributable to noncontrolling interests — — — — — — — (22) (22) Balance at September 30, 2020 3,577 $ 1,788 $ 39,489 $ 51,107 $ (6,383) 1,047 $ (56,815) $ 84 $ 29,270

Share-Based Compensation Plans

Share-Based Compensation Plans	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Share-Based Compensation Plans	Share-Based Compensation Plans The Company has share-based compensation plans under which the Company grants restricted stock units (RSUs) and performance share units (PSUs) to certain management level employees. In addition, employees and non-employee directors may be granted options to purchase shares of Company common stock at the fair market value at the time of grant. The following table provides the amounts of share-based compensation cost recorded in the Condensed Consolidated Statement of Income: Three Months Ended Nine Months Ended ($ in millions) 2020 2019 2020 2019 Pretax share-based compensation expense $ 126 $ 101 $ 354 $ 306 Income tax benefit (17) (14) (48) (42) Total share-based compensation expense, net of taxes $ 109 $ 87 $ 306 $ 264 During the first nine months of 2020, the Company granted 7 million RSUs with a weighted-average grant date fair value of $77.83 per RSU and during the first nine months of 2019 granted 5 million RSUs with a weighted-average grant date fair value of $80.03 per RSU. During the first nine months of 2020, the Company granted 773 thousand PSUs with a weighted-average grant date fair value of $75.22 per PSU and during the first nine months of 2019 granted 609 thousand PSUs with a weighted-average grant date fair value of $90.50 per PSU. During the first nine months of 2020, the Company granted 4 million stock options with a weighted-average exercise price of $77.67 per option and during the first nine months of 2019 granted 3 million stock options with a weighted-average exercise price of $80.05 per option. The weighted-average fair value of options granted during the first nine months of 2020 and 2019 was $9.93 and $10.63 per option, respectively, and was determined using the following assumptions: Nine Months Ended 2020 2019 Expected dividend yield 3.1 % 3.2 % Risk-free interest rate 0.4 % 2.4 % Expected volatility 22.1 % 18.7 % Expected life (years) 5.8 5.9 At September 30, 2020, there was $800 million of total pretax unrecognized compensation expense related to nonvested stock options, RSU and PSU awards which will be recognized over a weighted-average period of 2.1 years. For segment reporting, share-based compensation costs are unallocated expenses.

Pension and Other Postretiremen

Pension and Other Postretirement Benefit Plans	9 Months Ended
	Sep. 30, 2020
Retirement Benefits [Abstract]
Pension and Other Postretirement Benefit Plans	Pension and Other Postretirement Benefit Plans The Company has defined benefit pension plans covering eligible employees in the United States and in certain of its international subsidiaries. The net periodic benefit cost of such plans consisted of the following components: Three Months Ended Nine Months Ended 2020 2019 2020 2019 ($ in millions) U.S. International U.S. International U.S. International U.S. International Service cost $ 96 $ 77 $ 76 $ 58 $ 270 $ 225 $ 221 $ 178 Interest cost 107 35 115 44 323 103 343 133 Expected return on plan assets (193) (104) (202) (106) (581) (310) (613) (320) Amortization of unrecognized prior service credit (12) (3) (12) (3) (37) (9) (37) (9) Net loss amortization 75 32 43 16 228 94 113 47 Termination benefits 1 1 3 — 5 2 7 1 Curtailments 1 — 5 — 4 (1) 6 — Settlements 2 — — — 11 2 — — $ 77 $ 38 $ 28 $ 9 $ 223 $ 106 $ 40 $ 30 The Company anticipates that in 2020 it will contribute approximately $200 million and $375 million to its U.S. and international pension plans, respectively, of which $184 million and $123 million, respectively, was contributed in the first nine months of the year. The Company provides medical benefits, principally to its eligible U.S. retirees and similar benefits to their dependents, through its other postretirement benefit plans. The net credit of such plans consisted of the following components: Three Months Ended Nine Months Ended ($ in millions) 2020 2019 2020 2019 Service cost $ 13 $ 12 $ 39 $ 36 Interest cost 14 17 43 52 Expected return on plan assets (19) (18) (56) (54) Amortization of unrecognized prior service credit (18) (20) (54) (59) Net gain amortization (5) (3) (13) (7) Termination benefits — 1 — 1 Curtailments — (3) (1) (4) $ (15) $ (14) $ (42) $ (35) In connection with restructuring actions (see Note 4), termination charges were recorded on pension plans related to expanded eligibility for certain employees exiting Merck. Also, in connection with these restructuring actions, curtailments were recorded on pension and other postretirement benefit plans and settlements were recorded on certain U.S. and international pension plans as reflected in the tables above. The components of net periodic benefit cost (credit) other than the service cost component are included in Other (income) expense, net (see Note 13), with the exception of certain amounts for termination benefits, curtailments and settlements, which are recorded in Restructuring costs if the event giving rise to the termination benefits, curtailment or settlement is related to restructuring actions as noted above.

Other (Income) Expense, Net

Other (Income) Expense, Net	9 Months Ended
	Sep. 30, 2020
Other Income and Expenses [Abstract]
Other (Income) Expense, Net	Other (Income) Expense, Net Other (income) expense, net, consisted of: Three Months Ended Nine Months Ended ($ in millions) 2020 2019 2020 2019 Interest income $ (9) $ (61) $ (48) $ (225) Interest expense 203 231 624 674 Exchange losses 10 38 89 166 Income from investments in equity securities, net (1) (360) (16) (964) (50) Net periodic defined benefit plan (credit) cost other than service cost (88) (128) (259) (409) Other, net (68) (29) (72) 206 $ (312) $ 35 $ (630) $ 362 (1) Includes net realized and unrealized gains and losses from investments in equity securities either owned directly or through ownership interests in investment funds. Unrealized gains and losses from investments that are directly owned are determined at the end of the reporting period, while ownership interests in investment funds are accounted for on a one quarter lag. The decline in interest income in the third quarter and first nine months of 2020 reflects lower investments and lower interest rates. The lower exchange losses in the first nine months of 2020 reflect losses on forward exchange contracts in 2019 related to the acquisition of Antelliq. The increase in income from investments in equity securities, net, in both the third quarter and first nine months of 2020 was driven primarily by the recognition of unrealized gains on certain investments, most of which relate to Moderna, Inc. Other, net (as reflected in the table above) in the first nine months of 2019 includes $162 million of goodwill impairment charges related to certain businesses in the Healthcare Services segment. Interest paid for the nine months ended September 30, 2020 and 2019 was $605 million and $629 million, respectively.

Taxes on Income

Taxes on Income	9 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Taxes on Income	Taxes on Income The effective income tax rates of 14.1% and 18.7% for the third quarter of 2020 and 2019, respectively, and 14.9% and 14.5% for the first nine months of 2020 and 2019, respectively, reflect the impacts of acquisition and divestiture-related costs and restructuring costs, partially offset by the beneficial impact of foreign earnings. The effective income tax rates in the third quarter and first nine months of 2019 also reflect the unfavorable impact of a charge for the acquisition of Peloton for which no tax benefit was recognized and the favorable impact of product mix on the estimated 2019 full-year tax rate. In addition, the effective income tax rate for the first nine months of 2019 reflects the favorable impact of a $360 million net tax benefit related to the settlement of certain federal income tax matters. In the first quarter of 2019, the Internal Revenue Service (IRS) concluded its examinations of Merck’s 2012-2014 U.S. federal income tax returns. As a result, the Company was required to make a payment of $107 million. The Company’s reserves for unrecognized tax benefits for the years under examination exceeded the adjustments relating to this examination period and therefore the Company recorded a $360 million net tax benefit in the first nine months of 2019. This net benefit reflects reductions in reserves for unrecognized tax benefits for tax positions relating to the years that were under examination, partially offset by additional reserves for tax positions not previously reserved for.

Earnings Per Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share The calculations of earnings per share are as follows: Three Months Ended Nine Months Ended ($ and shares in millions except per share amounts) 2020 2019 2020 2019 Net income attributable to Merck & Co., Inc. $ 2,941 $ 1,901 $ 9,161 $ 7,487 Average common shares outstanding 2,529 2,558 2,530 2,572 Common shares issuable (1) 9 14 11 15 Average common shares outstanding assuming dilution 2,538 2,572 2,541 2,587 Basic earnings per common share attributable to Merck & Co., Inc. common shareholders $ 1.16 $ 0.74 $ 3.62 $ 2.91 Earnings per common share assuming dilution attributable to Merck & Co., Inc. common shareholders $ 1.16 $ 0.74 $ 3.61 $ 2.89 (1) Issuable primarily under share-based compensation plans.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) Changes in AOCI by component are as follows: Three Months Ended September 30, ($ in millions) Derivatives Investments Employee Cumulative Accumulated Other Balance July 1, 2019, net of taxes $ 66 $ 48 $ (3,530) $ (1,946) $ (5,362) Other comprehensive income (loss) before reclassification adjustments, pretax 186 8 (4) (84) 106 Tax (39) — — (33) (72) Other comprehensive income (loss) before reclassification adjustments, net of taxes 147 8 (4) (117) 34 Reclassification adjustments, pretax (71) (1) (25) (2) 21 (3) — (75) Tax 15 — (2) — 13 Reclassification adjustments, net of taxes (56) (25) 19 — (62) Other comprehensive income (loss), net of taxes 91 (17) 15 (117) (28) Balance September 30, 2019, net of taxes $ 157 $ 31 $ (3,515) $ (2,063) $ (5,390) Balance July 1, 2020, net of taxes $ 15 $ — $ (4,162) $ (2,246) $ (6,393) Other comprehensive income (loss) before reclassification adjustments, pretax (195) — 2 50 (143) Tax 41 — 1 35 77 Other comprehensive income (loss) before reclassification adjustments, net of taxes (154) — 3 85 (66) Reclassification adjustments, pretax 22 (1) — 72 (3) — 94 Tax (5) — (13) — (18) Reclassification adjustments, net of taxes 17 — 59 — 76 Other comprehensive income (loss), net of taxes (137) — 62 85 10 Balance September 30, 2020, net of taxes $ (122) $ — $ (4,100) $ (2,161) $ (6,383) Nine Months Ended September 30, ($ in millions) Derivatives Investments Employee Cumulative Accumulated Other Balance January 1, 2019, net of taxes $ 166 $ (78) $ (3,556) $ (2,077) $ (5,545) Other comprehensive income (loss) before reclassification adjustments, pretax 183 139 (5) 47 364 Tax (38) — 6 (33) (65) Other comprehensive income (loss) before reclassification adjustments, net of taxes 145 139 1 14 299 Reclassification adjustments, pretax (195) (1) (30) (2) 49 (3) — (176) Tax 41 — (9) — 32 Reclassification adjustments, net of taxes (154) (30) 40 — (144) Other comprehensive income (loss), net of taxes (9) 109 41 14 155 Balance September 30, 2019, net of taxes $ 157 $ 31 $ (3,515) $ (2,063) $ (5,390) Balance January 1, 2020, net of taxes $ 31 $ 18 $ (4,261) $ (1,981) $ (6,193) Other comprehensive income (loss) before reclassification adjustments, pretax (126) 3 (19) (220) (362) Tax 27 — 12 40 79 Other comprehensive income (loss) before reclassification adjustments, net of taxes (99) 3 (7) (180) (283) Reclassification adjustments, pretax (68) (1) (21) (2) 210 (3) — 121 Tax 14 — (42) — (28) Reclassification adjustments, net of taxes (54) (21) 168 — 93 Other comprehensive income (loss), net of taxes (153) (18) 161 (180) (190) Balance September 30, 2020, net of taxes $ (122) $ — $ (4,100) $ (2,161) $ (6,383) (1) Relates to foreign currency cash flow hedges that were reclassified from AOCI to Sales . (2) Represents net realized (gains) losses on the sales of available-for-sale debt securities that were reclassified from AOCI to Other (income) expense, net . (3) Includes net amortization of prior service cost and actuarial gains and losses included in net periodic benefit cost (see Note 12).

Segment Reporting

Segment Reporting	9 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting The Company’s operations are principally managed on a products basis and include three operating segments, which are the Pharmaceutical, Animal Health and Healthcare Services segments. The Pharmaceutical and Animal Health segments are the only reportable segments. The Pharmaceutical segment includes human health pharmaceutical and vaccine products. Human health pharmaceutical products consist of therapeutic and preventive agents, generally sold by prescription, for the treatment of human disorders. The Company sells these human health pharmaceutical products primarily to drug wholesalers and retailers, hospitals, government agencies and managed health care providers such as health maintenance organizations, pharmacy benefit managers and other institutions. Human health vaccine products consist of preventive pediatric, adolescent and adult vaccines, primarily administered at physician offices. The Company sells these human health vaccines primarily to physicians, wholesalers, physician distributors and government entities. A large component of pediatric and adolescent vaccine sales are made to the U.S. Centers for Disease Control and Prevention Vaccines for Children program, which is funded by the U.S. government. Additionally, the Company sells vaccines to the Federal government for placement into vaccine stockpiles. The Animal Health segment discovers, develops, manufactures and markets a wide range of veterinary pharmaceutical and vaccine products, as well as health management solutions and services, for the prevention, treatment and control of disease in all major livestock and companion animal species. The Company also offers an extensive suite of digitally connected identification, traceability and monitoring products. The Company sells its products to veterinarians, distributors and animal producers. The Healthcare Services segment provided services and solutions that focus on engagement, health analytics and clinical services to improve the value of care delivered to patients. The Company has been in the process of divesting the businesses in the Healthcare Services segment. The remaining businesses were divested during the first quarter of 2020. Sales of the Company’s products were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 ($ in millions) U.S. Int’l Total U.S. Int’l Total U.S. Int’l Total U.S. Int’l Total Pharmaceutical: Oncology Keytruda $ 2,157 $ 1,559 $ 3,715 $ 1,743 $ 1,327 $ 3,070 $ 6,106 $ 4,281 $ 10,387 $ 4,525 $ 3,448 $ 7,973 Alliance revenue - Lynparza (1) 107 89 196 71 53 123 297 223 519 186 126 313 Alliance revenue - Lenvima (1) 82 60 142 65 44 109 270 152 421 169 112 280 Emend 8 31 39 42 56 98 18 96 115 173 163 336 Vaccines Gardasil/Gardasil 9 579 608 1,187 761 558 1,320 1,209 1,732 2,941 1,579 1,464 3,044 ProQuad/M-M-R II /Varivax 437 139 576 482 141 623 1,033 356 1,390 1,325 469 1,794 Pneumovax 23 276 99 375 179 58 237 478 270 748 428 164 592 RotaTeq 114 96 210 102 78 180 355 246 601 360 203 564 Vaqta 32 19 51 36 26 62 79 60 139 103 65 167 Hospital Acute Care Bridion 162 157 320 133 151 284 412 431 843 381 437 817 Noxafil 13 66 79 77 100 177 27 220 247 268 291 560 Prevymis 32 46 77 22 23 45 87 113 200 60 55 115 Primaxin 1 73 74 2 75 77 2 187 189 2 204 207 Invanz 1 50 51 (1) 58 57 7 152 159 30 176 206 Cancidas 1 49 50 — 62 62 2 147 148 5 187 191 Cubicin 11 28 39 14 38 52 36 80 116 78 129 207 Zerbaxa 20 23 43 20 15 35 57 54 112 45 43 88 Immunology Simponi — 209 209 — 203 203 — 615 615 — 625 625 Remicade — 82 82 — 101 101 — 242 242 — 322 322 Neuroscience Belsomra 18 63 81 23 57 80 67 177 244 68 155 223 Virology Isentress/Isentress HD 92 113 205 102 149 250 243 403 646 304 449 752 Zepatier 6 22 28 24 59 83 38 83 122 96 208 304 Cardiovascular Zetia (1) 103 103 5 142 147 (4) 389 384 11 432 443 Vytorin 3 44 47 5 52 57 9 130 139 11 219 231 Atozet — 111 111 — 97 97 — 348 348 — 283 283 Alliance revenue - Adempas (2) 78 5 83 48 2 50 200 16 216 137 7 144 Adempas — 55 55 — 57 57 — 167 167 — 158 158 Diabetes Januvia 342 479 821 367 440 807 1,110 1,339 2,449 1,223 1,317 2,539 Janumet 105 400 506 129 375 503 361 1,138 1,499 462 1,105 1,567 Women’s Health Implanon/Nexplanon 137 52 189 136 62 199 374 142 515 421 160 581 NuvaRing 24 34 58 202 39 241 85 98 184 593 107 700 Diversified Brands Singulair 4 78 82 11 140 152 14 324 338 24 479 503 Cozaar/Hyzaar 5 86 91 6 110 116 17 275 292 16 313 329 Arcoxia — 68 68 — 72 72 — 204 204 — 221 221 Nasonex — 41 41 4 55 58 9 152 161 2 224 226 Follistim AQ 20 31 50 27 35 62 60 76 136 80 102 182 Other pharmaceutical (3) 352 834 1,186 343 804 1,149 1,144 2,334 3,478 1,037 2,394 3,431 Total Pharmaceutical segment sales 5,218 6,102 11,320 5,180 5,914 11,095 14,202 17,452 31,654 14,202 17,016 31,218 Animal Health: Livestock 164 594 758 144 582 726 448 1,697 2,145 406 1,601 2,007 Companion Animals 234 228 462 193 203 396 676 714 1,390 560 704 1,264 Total Animal Health segment sales 398 822 1,220 337 785 1,122 1,124 2,411 3,535 966 2,305 3,271 Other segment sales (4) — — — 46 — 46 23 — 23 133 1 133 Total segment sales 5,616 6,924 12,540 5,563 6,699 12,263 15,349 19,863 35,212 15,301 19,322 34,622 Other (5) 9 2 11 10 125 134 47 221 267 19 330 350 $ 5,625 $ 6,926 $ 12,551 $ 5,573 $ 6,824 $ 12,397 $ 15,396 $ 20,084 $ 35,479 $ 15,320 $ 19,652 $ 34,972 U.S. plus international may not equal total due to rounding. (1) Alliance revenue represents Merck’s share of profits, which are product sales net of cost of sales and commercialization costs (see Note 3). (2) Alliance revenue represents Merck’s share of profits from sales in Bayer’s marketing territories, which are product sales net of cost of sales and commercialization costs (see Note 3). (3) Other pharmaceutical primarily reflects sales of other human health pharmaceutical products, including products within the franchises not listed separately. (4) Represents sales for the Healthcare Services segment. All the businesses in the Healthcare Services segment were divested as of March 31, 2020. (5) Other is primarily comprised of miscellaneous corporate revenues, including revenue hedging activities, as well as third-party manufacturing sales. Product sales are recorded net of the provision for discounts, including chargebacks, which are customer discounts that occur when a contracted customer purchases through an intermediary wholesale purchaser, and rebates that are owed based upon definitive contractual agreements or legal requirements with private sector and public sector (Medicaid and Medicare Part D) benefit providers, after the final dispensing of the product by a pharmacy to a benefit plan participant. These discounts, in the aggregate, reduced U.S. sales by $3.4 billion and $3.0 billion for the three months ended September 30, 2020 and 2019, respectively, and $9.6 billion and $8.6 billion for the nine months ended September 30, 2020 and 2019, respectively. Consolidated sales by geographic area where derived are as follows: Three Months Ended Nine Months Ended ($ in millions) 2020 2019 2020 2019 United States $ 5,625 $ 5,573 $ 15,396 $ 15,320 Europe, Middle East and Africa 3,454 3,189 10,059 9,452 China 1,016 914 2,715 2,423 Japan 828 919 2,506 2,639 Asia Pacific (other than China and Japan) 735 756 2,129 2,217 Latin America 604 671 1,670 1,889 Other 289 375 1,004 1,032 $ 12,551 $ 12,397 $ 35,479 $ 34,972 A reconciliation of segment profits to Income before taxes is as follows: Three Months Ended Nine Months Ended ($ in millions) 2020 2019 2020 2019 Segment profits: Pharmaceutical segment $ 7,974 $ 7,747 $ 22,010 $ 21,437 Animal Health segment 451 423 1,336 1,243 Other segment (1) (2) 1 (2) Total segment profits 8,424 8,168 23,347 22,678 Other profits (12) 101 188 226 Unallocated: Interest income 9 61 48 225 Interest expense (203) (231) (624) (674) Depreciation and amortization (395) (382) (1,173) (1,169) Research and development (3,272) (3,110) (7,364) (7,045) Amortization of purchase accounting adjustments (285) (329) (879) (1,105) Restructuring costs (114) (232) (269) (444) Other unallocated, net (724) (1,699) (2,490) (4,019) $ 3,428 $ 2,347 $ 10,784 $ 8,673 Pharmaceutical segment profits are comprised of segment sales less standard costs, as well as selling, general and administrative expenses directly incurred by the segment. Animal Health segment profits are comprised of segment sales, less all cost of sales, as well as selling, general and administrative expenses and research and development costs directly incurred by the segment. For internal management reporting presented to the chief operating decision maker, Merck does not allocate the remaining cost of sales not included in segment profits as described above, research and development expenses incurred in Merck Research Laboratories, the Company’s research and development division that focuses on human health-related activities, or general and administrative expenses, nor the cost of financing these activities. Separate divisions maintain responsibility for monitoring and managing these costs, including depreciation related to fixed assets utilized by these divisions and, therefore, they are not included in segment profits. In addition, costs related to restructuring activities, as well as the amortization of purchase accounting adjustments are not allocated to segments. Other profits are primarily comprised of miscellaneous corporate profits, as well as operating profits related to third-party manufacturing sales. Other unallocated, net, includes expenses from corporate and manufacturing cost centers, goodwill and other intangible asset impairment charges, gains or losses on sales of businesses, expense or income related to changes in the estimated fair value measurement of liabilities for contingent consideration, and other miscellaneous income or expense items.

Basis of Presentation (Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of PresentationThe accompanying unaudited condensed consolidated financial statements of Merck & Co., Inc. (Merck or the Company) have been prepared pursuant to the rules and regulations for reporting on Form 10-Q. Accordingly, certain information and disclosures required by accounting principles generally accepted in the United States (GAAP) for complete consolidated financial statements are not included herein. These interim statements should be read in conjunction with the audited financial statements and notes thereto included in Merck’s Form 10-K filed on February 26, 2020.The results of operations of any interim period are not necessarily indicative of the results of operations for the full year. In the Company’s opinion, all adjustments necessary for a fair statement of these interim statements have been included and are of a normal and recurring nature.
Recently Adopted and Issued Accounting Standards	Recently Adopted Accounting Standards In June 2016, the Financial Accounting Standards Board (FASB) issued new guidance on the accounting for credit losses on financial instruments. The new guidance introduces an expected loss model for estimating credit losses, replacing the incurred loss model. The new guidance also changes the impairment model for available-for-sale debt securities, requiring the use of an allowance to record estimated credit losses (and subsequent recoveries). The Company adopted the new guidance effective January 1, 2020. There was no impact to the Company’s consolidated financial statements upon adoption. In November 2018, the FASB issued new guidance for collaborative arrangements intended to reduce diversity in practice by clarifying whether certain transactions between collaborative arrangement participants should be accounted for under revenue recognition guidance (ASC 606). The Company adopted the new guidance effective January 1, 2020, which resulted in minor changes to the presentation of information related to the Company’s collaborative arrangements. Recently Issued Accounting Standards Not Yet Adopted In December 2019, the FASB issued amended guidance on the accounting and reporting of income taxes. The guidance is intended to simplify the accounting for income taxes by: removing exceptions related to certain intraperiod tax allocations and deferred tax liabilities; clarifying guidance primarily related to evaluating the step-up tax basis for goodwill in a business combination; and reflecting enacted changes in tax laws or rates in the annual effective tax rate. The amended guidance is effective for interim and annual periods in 2021. Early adoption is permitted. The amendments in the new guidance are to be applied on a retrospective basis, on a modified retrospective basis through a cumulative-effect adjustment to retained earnings or prospectively, depending on the amendment. The Company is currently evaluating the impact of adoption on its consolidated financial statements. In January 2020, the FASB issued new guidance intended to clarify certain interactions between accounting standards related to equity securities, equity method investments and certain derivatives. The guidance addresses accounting for the transition into and out of the equity method of accounting and measuring certain purchased options and forward contracts to acquire investments. The new guidance is effective for interim and annual periods in 2021 and is to be applied prospectively. Early adoption is permitted. The Company is currently evaluating the impact of adoption on its consolidated financial statements. In March 2020, the FASB issued optional guidance to ease the potential burden in accounting for (or recognizing the effects of) reference rate reform on financial reporting. The guidance provides optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform. The optional guidance is effective upon issuance and can be applied on a prospective basis at any time between January 1, 2020 through December 31, 2022. The Company is currently evaluating the impact of adoption on its consolidated financial statements.
Legal Costs, Policy	Legal defense costs expected to be incurred in connection with a loss contingency are accrued when probable and reasonably estimable.

Acquisitions, Research Collab_2

Acquisitions, Research Collaborations and License Agreements (Tables)	9 Months Ended
	Sep. 30, 2020
Business Combinations [Abstract]
Fair Value of Assets Acquired and Liabilities Assumed	The estimated fair value of assets acquired and liabilities assumed from ArQule is as follows: ($ in millions) January 16, 2020 Cash and cash equivalents $ 145 IPR&D MK-1026 (formerly ARQ 531) (1) 2,280 Licensing arrangement for ARQ 087 80 Deferred income tax liabilities (389) Other assets and liabilities, net 34 Total identifiable net assets 2,150 Goodwill (2) 540 Consideration transferred $ 2,690 (1) The estimated fair value of the identifiable intangible asset related to IPR&D was determined using an income approach. The future net cash flows were discounted to present value utilizing a discount rate of 12.5%. Actual cash flows are likely to be different than those assumed. (2) The goodwill was allocated to the Pharmaceutical segment and is not deductible for tax purposes. The estimated fair value of assets acquired and liabilities assumed from Antelliq is as follows: ($ in millions) April 1, 2019 Cash and cash equivalents $ 31 Accounts receivable 73 Inventories 93 Property, plant and equipment 60 Identifiable intangible assets (useful lives ranging from 18-24 years) (1) 2,689 Deferred income tax liabilities (589) Other assets and liabilities, net (82) Total identifiable net assets 2,275 Goodwill (2) 1,376 Consideration transferred $ 3,651 (1) The estimated fair values of identifiable intangible assets relate primarily to trade names and were determined using an income approach. The future net cash flows were discounted to present value utilizing a discount rate of 11.5%. Actual cash flows are likely to be different than those assumed. (2) The goodwill recognized is largely attributable to anticipated synergies expected to arise after the acquisition and was allocated to the Animal Health segment. The goodwill is not deductible for tax purposes.

Collaborative Arrangements (Tab

Collaborative Arrangements (Tables)	9 Months Ended
	Sep. 30, 2020
Collaborative Arrangements [Abstract]
Collaboration Arrangements	Summarized financial information related to this collaboration is as follows: Three Months Ended Nine Months Ended ($ in millions) 2020 2019 2020 2019 Alliance revenue - Lynparza $ 196 $ 123 $ 519 $ 313 Alliance revenue - Koselugo 3 — 3 — Total alliance revenue $ 199 $ 123 $ 522 $ 313 Cost of sales (1) 41 28 205 120 Selling, general and administrative 40 36 112 96 Research and development 20 44 93 122 ($ in millions) September 30, 2020 December 31, 2019 Receivables from AstraZeneca included in Other current assets $ 197 $ 128 Payables to AstraZeneca included in Accrued and other current liabilities (2) 309 577 Payables to AstraZeneca included in Other Noncurrent Liabilities (2) 400 — (1) Represents amortization of capitalized milestone payments. (2) Includes accrued milestone payments. Summarized financial information related to this collaboration is as follows: Three Months Ended Nine Months Ended ($ in millions) 2020 2019 2020 2019 Alliance revenue - Lenvima $ 142 $ 109 $ 421 $ 280 Cost of sales (1) 46 23 215 97 Selling, general and administrative 18 21 48 59 Research and development 48 37 168 146 ($ in millions) September 30, 2020 December 31, 2019 Receivables from Eisai included in Other current assets $ 170 $ 150 Payables to Eisai included in Accrued and other current liabilities (2) 325 700 Payables to Eisai included in Other Noncurrent Liabilities (3) 570 525 (1) Represents amortization of capitalized milestone payments. (2) Includes accrued milestone and future option payments. (3) Includes accrued milestone payments. Summarized financial information related to this collaboration is as follows: Three Months Ended Nine Months Ended ($ in millions) 2020 2019 2020 2019 Alliance revenue - Adempas $ 83 $ 50 $ 216 $ 144 Net sales of Adempas recorded by Merck 55 57 167 158 Total sales $ 138 $ 107 $ 383 $ 302 Cost of sales (1) 29 28 85 86 Selling, general and administrative 19 12 42 31 Research and development 12 31 53 94 ($ in millions) September 30, 2020 December 31, 2019 Receivables from Bayer included in Other current assets $ 70 $ 49 Payables to Bayer included in Other Noncurrent Liabilities (2) 375 375 (1) Includes amortization of intangible assets. (2) Represents accrued milestone payment.

Restructuring (Tables)

Restructuring (Tables)	9 Months Ended
	Sep. 30, 2020
Restructuring and Related Activities [Abstract]
Charges Related to Restructuring Program Activities by Type of Cost	The following tables summarize the charges related to restructuring program activities by type of cost: Three Months Ended September 30, 2020 Nine Months Ended September 30, 2020 ($ in millions) Separation Accelerated Other Total Separation Accelerated Other Total Cost of sales $ — $ 33 $ 5 $ 38 $ — $ 89 $ 42 $ 131 Selling, general and administrative — 15 — 15 — 37 — 37 Research and development — 18 1 19 — 66 1 67 Restructuring costs 61 — 53 114 143 — 126 269 $ 61 $ 66 $ 59 $ 186 $ 143 $ 192 $ 169 $ 504 Three Months Ended September 30, 2019 Nine Months Ended September 30, 2019 ($ in millions) Separation Accelerated Other Total Separation Accelerated Other Total Cost of sales $ — $ 41 $ 21 $ 62 $ — $ 139 $ 22 $ 161 Selling, general and administrative — 1 — 1 — 33 — 33 Research and development — (1) 2 1 — 1 3 4 Restructuring costs 205 — 27 232 358 — 86 444 $ 205 $ 41 $ 50 $ 296 $ 358 $ 173 $ 111 $ 642
Charges and Spending Relating to Restructuring Activities by Program	The following table summarizes the charges and spending relating to restructuring program activities for the nine months ended September 30, 2020: ($ in millions) Separation Accelerated Other Total Restructuring reserves January 1, 2020 $ 690 $ — $ 69 $ 759 Expense 143 192 169 504 (Payments) receipts, net (395) — (237) (632) Non-cash activity — (192) 39 (153) Restructuring reserves September 30, 2020 (1) $ 438 $ — $ 40 $ 478

Financial Instruments (Tables)

Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Effect of Net Investment Hedges on OCI and the Consolidated Statement of Income	The effects of the Company’s net investment hedges on OCI and the Consolidated Statement of Income are shown below: Amount of Pretax (Gain) Loss Recognized in Other Comprehensive Income (1) Amount of Pretax (Gain) Loss Recognized in Other (income) expense, net for Amounts Excluded from Effectiveness Testing Three Months Ended September 30, Nine Months Ended September 30, Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 2020 2019 2020 2019 Net Investment Hedging Relationships Foreign exchange contracts $ 10 $ 1 $ 15 $ 8 $ (4) $ (8) $ (15) $ (23) Euro-denominated notes 162 (150) 182 (152) — — — — (1) No amounts were reclassified from AOCI into income related to the sale of a subsidiary.
Summary of Interest Rate Swaps Held	At September 30, 2020, the Company was a party to 14 pay-floating, receive-fixed interest rate swap contracts designated as fair value hedges of fixed-rate notes in which the notional amounts match the amount of the hedged fixed-rate notes as detailed in the table below. September 30, 2020 ($ in millions) Par Value of Debt Number of Interest Rate Swaps Held Total Swap Notional Amount 3.875% notes due 2021 $ 1,150 5 $ 1,150 2.40% notes due 2022 1,000 4 1,000 2.35% notes due 2022 1,250 5 1,250
Amounts Recorded on Balance Sheet Related to Fair Value Hedges	The table below presents the location of amounts recorded on the Consolidated Balance Sheet related to cumulative basis adjustments for fair value hedges: Carrying Amount of Hedged Liabilities Cumulative Amount of Fair Value Hedging Adjustment Increase (Decrease) Included in the Carrying Amount ($ in millions) September 30, 2020 December 31, 2019 September 30, 2020 December 31, 2019 Balance Sheet Line Item in which Hedged Item is Included Loans payable and current portion of long-term debt $ 1,155 $ 1,249 $ 5 $ (1) Long-Term Debt 2,309 3,409 62 14
Fair Value of Derivatives on a Gross Basis Segregated between those Derivatives that are Designated as Hedging Instruments and those that are Not Designated as Hedging Instruments	Presented in the table below is the fair value of derivatives on a gross basis segregated between those derivatives that are designated as hedging instruments and those that are not designated as hedging instruments: September 30, 2020 December 31, 2019 Fair Value of Derivative U.S. Dollar Fair Value of Derivative U.S. Dollar ($ in millions) Balance Sheet Caption Asset Liability Asset Liability Derivatives Designated as Hedging Instruments Interest rate swap contracts Other current assets $ 6 $ — $ 1,150 $ — $ — $ — Interest rate swap contracts Other Assets 63 — 2,250 15 — 3,400 Interest rate swap contracts Accrued and other current liabilities — — — — 1 1,250 Foreign exchange contracts Other current assets 30 — 4,120 152 — 6,117 Foreign exchange contracts Other Assets 59 — 1,881 55 — 2,160 Foreign exchange contracts Accrued and other current liabilities — 104 3,096 — 22 1,748 Foreign exchange contracts Other Noncurrent Liabilities — 1 157 — 1 53 $ 158 $ 105 $ 12,654 $ 222 $ 24 $ 14,728 Derivatives Not Designated as Hedging Instruments Foreign exchange contracts Other current assets $ 81 $ — $ 5,455 $ 66 $ — $ 7,245 Foreign exchange contracts Accrued and other current liabilities — 171 8,042 — 73 8,693 Forward contract related to Seagen common stock Accrued and other current liabilities — 22 1,000 — — — $ 81 $ 193 $ 14,497 $ 66 $ 73 $ 15,938 $ 239 $ 298 $ 27,151 $ 288 $ 97 $ 30,666
Information on Derivative Positions Subject to Master Netting Arrangements as if they were Presented on a Net Basis	The following table provides information on the Company’s derivative positions subject to these master netting arrangements as if they were presented on a net basis, allowing for the right of offset by counterparty and cash collateral exchanged per the master agreements and related credit support annexes: September 30, 2020 December 31, 2019 ($ in millions) Asset Liability Asset Liability Gross amounts recognized in the condensed consolidated balance sheet $ 239 $ 298 $ 288 $ 97 Gross amounts subject to offset in master netting arrangements not offset in the condensed consolidated balance sheet (140) (140) (84) (84) Cash collateral received — — (34) — Net amounts $ 99 $ 158 $ 170 $ 13
Location and Amount of Pretax (Gains) Losses of Derivatives	The table below provides information regarding the location and amount of pretax (gains) losses of derivatives designated in fair value or cash flow hedging relationships: Sales Other (income) expense, net (1) Other comprehensive income (loss) Sales Other (income) expense, net (1) Other comprehensive income (loss) Three Months Ended September 30, Three Months Ended September 30, Three Months Ended September 30, Nine Months Ended September 30, Nine Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 2020 2019 2020 2019 2020 2019 2020 2019 Financial Statement Line Items in which Effects of Fair Value or Cash Flow Hedges are Recorded $ 12,551 $ 12,397 $ (312) $ 35 $ 10 $ (28) $ 35,479 $ 34,972 $ (630) $ 362 $ (190) $ 155 (Gain) loss on fair value hedging relationships Interest rate swap contracts Hedged items — — (14) 13 — — — — 54 101 — — Derivatives designated as hedging instruments — — — (6) — — — — (76) (74) — — Impact of cash flow hedging relationships Foreign exchange contracts Amount of (loss) gain recognized in OCI on derivatives — — — — (195) 186 — — — — (126) 183 Increase (decrease) in Sales as a result of AOCI reclassifications (23) 70 — — 23 (70) 65 189 — — (65) (189) Interest rate contracts Amount of gain recognized in Other (income) expense, net on derivatives — — (1) (1) — — — — (3) (3) — — Amount of loss recognized in OCI on derivatives — — — — (1) (1) — — — — (3) (6) (1) Interest expense is a component of Other (income) expense, net.
Income Statement Effects of Derivatives Not Designated as Hedging Instruments	The table below provides information regarding the income statement effects of derivatives not designated as hedging instruments: Amount of Derivative Pretax (Gain) Loss Recognized in Income Three Months Ended Nine Months Ended September 30, ($ in millions) Income Statement Caption 2020 2019 2020 2019 Derivatives Not Designated as Hedging Instruments Foreign exchange contracts (1) Other (income) expense, net $ (7) $ (8) $ (138) $ 112 Foreign exchange contracts (2) Sales 7 (11) 4 (7) Interest rate contracts (3) Other (income) expense, net — — 9 — Forward contract related to Seagen common stock Research and development expenses 22 — 22 — (1) These derivative contracts mitigate changes in the value of remeasured foreign currency denominated monetary assets and liabilities attributable to changes in foreign currency exchange rates. (2) These derivative contracts serve as economic hedges of forecasted transactions. (3) These derivatives serve as economic hedges against rising treasury rates.
Information on Investments in Debt and Equity Securities	Information on investments in debt and equity securities is as follows: September 30, 2020 December 31, 2019 Amortized Gross Unrealized Fair Amortized Gross Unrealized Fair ($ in millions) Gains Losses Gains Losses U.S. government and agency securities $ 74 $ — $ — $ 74 $ 266 $ 3 $ — $ 269 Foreign government bonds 2 — — 2 — — — — Commercial paper — — — — 668 — — 668 Corporate notes and bonds — — — — 608 13 — 621 Asset-backed securities — — — — 226 1 — 227 Total debt securities $ 76 $ — $ — $ 76 $ 1,768 $ 17 $ — $ 1,785 Publicly traded equity securities (1) 1,477 838 Total debt and publicly traded equity securities $ 1,553 $ 2,623 (1) Unrealized net (gains) losses recognized in Other (income) expense, net on equity securities still held at September 30, 2020 were $(43) million and $(512) million in the third quarter and first nine months of 2020, respectively. Unrealized net losses (gains) recognized in Other (income) expense, net on equity securities still held at September 30, 2019 were $25 million and $(41) million in the third quarter and first nine months of 2019, respectively.
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis	Financial assets and liabilities measured at fair value on a recurring basis are summarized below: Fair Value Measurements Using Fair Value Measurements Using Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total ($ in millions) September 30, 2020 December 31, 2019 Assets Investments Foreign government bonds $ — $ 2 $ — $ 2 $ — $ — $ — $ — Commercial paper — — — — — 668 — 668 Corporate notes and bonds — — — — — 621 — 621 Asset-backed securities (1) — — — — — 227 — 227 U.S. government and agency securities — — — — — 209 — 209 Publicly traded equity securities 1,370 — — 1,370 518 — — 518 1,370 2 — 1,372 518 1,725 — 2,243 Other assets (2) U.S. government and agency securities 74 — — 74 60 — — 60 Publicly traded equity securities 107 — — 107 320 — — 320 181 — — 181 380 — — 380 Derivative assets (3) Forward exchange contracts — 116 — 116 — 169 — 169 Interest rate swaps — 69 — 69 — 15 — 15 Purchased currency options — 54 — 54 — 104 — 104 — 239 — 239 — 288 — 288 Total assets $ 1,551 $ 241 $ — $ 1,792 $ 898 $ 2,013 $ — $ 2,911 Liabilities Other liabilities Contingent consideration $ — $ — $ 829 $ 829 $ — $ — $ 767 $ 767 Derivative liabilities (3) Forward exchange contracts — 275 — 275 — 95 — 95 Forward contract related to Seagen common stock — 22 — 22 — — — — Written currency options — 1 — 1 — 1 — 1 Interest rate swaps — — — — — 1 — 1 — 298 — 298 — 97 — 97 Total liabilities $ — $ 298 $ 829 $ 1,127 $ — $ 97 $ 767 $ 864 (1) Primarily all of the asset-backed securities were highly rated (Standard & Poor’s rating of AAA and Moody’s Investors Service rating of Aaa), secured primarily by auto loan, credit card and student loan receivables, with weighted-average lives of primarily 5 years or less. (2) Investments included in other assets are restricted as to use, including for the payment of benefits under employee benefit plans. (3) The fair value determination of derivatives includes the impact of the credit risk of counterparties to the derivatives and the Company’s own credit risk, the effects of which were not significant.
Information About the Changes in Liabilities for Contingent Consideration	Summarized information about the changes in liabilities for contingent consideration associated with business acquisitions is as follows: Nine Months Ended September 30, ($ in millions) 2020 2019 Fair value January 1 $ 767 $ 788 Additions 97 — Changes in estimated fair value (1) 71 52 Payments (106) (85) Fair value September 30 (2)(3) $ 829 $ 755 (1) Recorded in Cost of sales, Research and development expenses, and Other (income) expense, net . Includes cumulative translation adjustments. (2) Balance at September 30, 2020 includes $140 million recorded as a current liability for amounts expected to be paid within the next 12 months. (3) At September 30, 2020 and December 31, 2019, $637 million and $625 million, respectively, of the liabilities relate to the termination of the Sanofi-Pasteur MSD joint venture in 2016. As part of the termination, Merck recorded a liability for contingent future royalty payments of 11.5% on net sales of all Merck products that were previously sold by the joint venture through December 31, 2024. The fair value of this liability is determined utilizing the estimated amount and timing of projected cash flows using a risk-adjusted discount rate of 8% to present value the cash flows.

Inventories (Tables)

Inventories (Tables)	9 Months Ended
	Sep. 30, 2020
Inventory Disclosure [Abstract]
Schedule of Inventories	Inventories consisted of: ($ in millions) September 30, 2020 December 31, 2019 Finished goods $ 2,038 $ 1,772 Raw materials and work in process 6,073 5,650 Supplies 197 207 Total (approximates current cost) 8,308 7,629 Decrease to LIFO cost (99) (171) $ 8,209 $ 7,458 Recognized as: Inventories $ 6,128 $ 5,978 Other assets 2,081 1,480

Equity (Tables)

Equity (Tables)	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Equity	Three Months Ended September 30, Common Stock Other Retained Accumulated Treasury Stock Non- Total ($ and shares in millions except per share amounts) Shares Par Value Shares Cost Balance at July 1, 2019 3,577 $ 1,788 $ 39,484 $ 45,295 $ (5,362) 1,010 $ (53,570) $ 102 $ 27,737 Net income attributable to Merck & Co., Inc. — — — 1,901 — — — — 1,901 Other comprehensive loss, net of taxes — — — — (28) — — — (28) Cash dividends declared on common stock ($0.55 per share) — — — (1,392) — — — — (1,392) Treasury stock shares purchased — — — — — 17 (1,405) — (1,405) Share-based compensation plans and other — — 77 — — (1) 50 — 127 Net income attributable to noncontrolling interests — — — — — — — 6 6 Distributions attributable to noncontrolling interests — — — — — — — (21) (21) Balance at September 30, 2019 3,577 $ 1,788 $ 39,561 $ 45,804 $ (5,390) 1,026 $ (54,925) $ 87 $ 26,925 Balance at July 1, 2020 3,577 $ 1,788 $ 39,373 $ 49,724 $ (6,393) 1,048 $ (56,850) $ 102 $ 27,744 Net income attributable to Merck & Co., Inc. — — — 2,941 — — — — 2,941 Other comprehensive income, net of taxes — — — — 10 — — — 10 Cash dividends declared on common stock ($0.61 per share) — — — (1,558) — — — — (1,558) Share-based compensation plans and other — — 116 — — (1) 35 — 151 Net income attributable to noncontrolling interests — — — — — — — 4 4 Distributions attributable to noncontrolling interests — — — — — — — (22) (22) Balance at September 30, 2020 3,577 $ 1,788 $ 39,489 $ 51,107 $ (6,383) 1,047 $ (56,815) $ 84 $ 29,270 Nine Months Ended September 30, Common Stock Other Retained Accumulated Treasury Stock Non- Total ($ and shares in millions except per share amounts) Shares Par Value Shares Cost Balance at January 1, 2019 3,577 $ 1,788 $ 38,808 $ 42,579 $ (5,545) 985 $ (50,929) $ 181 $ 26,882 Net income attributable to Merck & Co., Inc. — — — 7,487 — — — — 7,487 Other comprehensive income, net of taxes — — — — 155 — — — 155 Cash dividends declared on common stock ($1.65 per share) — — — (4,262) — — — — (4,262) Treasury stock shares purchased — — 1,000 — — 54 (4,730) — (3,730) Share-based compensation plans and other — — (247) — — (13) 734 — 487 Net loss attributable to noncontrolling interests — — — — — — — (73) (73) Distributions attributable to noncontrolling interests — — — — — — — (21) (21) Balance at September 30, 2019 3,577 1,788 39,561 45,804 (5,390) 1,026 (54,925) 87 26,925 Balance at January 1, 2020 3,577 $ 1,788 $ 39,660 $ 46,602 $ (6,193) 1,038 $ (55,950) $ 94 $ 26,001 Net income attributable to Merck & Co., Inc. — — — 9,161 — — — — 9,161 Other comprehensive loss, net of taxes — — — — (190) — — — (190) Cash dividends declared on common stock ($1.83 per share) — — — (4,656) — — — — (4,656) Treasury stock shares purchased — — — — — 16 (1,281) — (1,281) Share-based compensation plans and other — — (171) — — (7) 416 — 245 Net income attributable to noncontrolling interests — — — — — — — 12 12 Distributions attributable to noncontrolling interests — — — — — — — (22) (22) Balance at September 30, 2020 3,577 $ 1,788 $ 39,489 $ 51,107 $ (6,383) 1,047 $ (56,815) $ 84 $ 29,270

Share-Based Compensation Plans

Share-Based Compensation Plans (Tables)	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Amounts of Share-Based Compensation Cost Recorded in Consolidated Statement of Income	The following table provides the amounts of share-based compensation cost recorded in the Condensed Consolidated Statement of Income: Three Months Ended Nine Months Ended ($ in millions) 2020 2019 2020 2019 Pretax share-based compensation expense $ 126 $ 101 $ 354 $ 306 Income tax benefit (17) (14) (48) (42) Total share-based compensation expense, net of taxes $ 109 $ 87 $ 306 $ 264
Assumptions Used to Determine Weighted-Average Fair Value of Options Granted	During the first nine months of 2020, the Company granted 4 million stock options with a weighted-average exercise price of $77.67 per option and during the first nine months of 2019 granted 3 million stock options with a weighted-average exercise price of $80.05 per option. The weighted-average fair value of options granted during the first nine months of 2020 and 2019 was $9.93 and $10.63 per option, respectively, and was determined using the following assumptions: Nine Months Ended 2020 2019 Expected dividend yield 3.1 % 3.2 % Risk-free interest rate 0.4 % 2.4 % Expected volatility 22.1 % 18.7 % Expected life (years) 5.8 5.9

Pension and Other Postretirem_2

Pension and Other Postretirement Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2020
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Components of net cost of defined benefit plans	The Company has defined benefit pension plans covering eligible employees in the United States and in certain of its international subsidiaries. The net periodic benefit cost of such plans consisted of the following components: Three Months Ended Nine Months Ended 2020 2019 2020 2019 ($ in millions) U.S. International U.S. International U.S. International U.S. International Service cost $ 96 $ 77 $ 76 $ 58 $ 270 $ 225 $ 221 $ 178 Interest cost 107 35 115 44 323 103 343 133 Expected return on plan assets (193) (104) (202) (106) (581) (310) (613) (320) Amortization of unrecognized prior service credit (12) (3) (12) (3) (37) (9) (37) (9) Net loss amortization 75 32 43 16 228 94 113 47 Termination benefits 1 1 3 — 5 2 7 1 Curtailments 1 — 5 — 4 (1) 6 — Settlements 2 — — — 11 2 — — $ 77 $ 38 $ 28 $ 9 $ 223 $ 106 $ 40 $ 30
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Components of net cost of defined benefit plans	The Company provides medical benefits, principally to its eligible U.S. retirees and similar benefits to their dependents, through its other postretirement benefit plans. The net credit of such plans consisted of the following components: Three Months Ended Nine Months Ended ($ in millions) 2020 2019 2020 2019 Service cost $ 13 $ 12 $ 39 $ 36 Interest cost 14 17 43 52 Expected return on plan assets (19) (18) (56) (54) Amortization of unrecognized prior service credit (18) (20) (54) (59) Net gain amortization (5) (3) (13) (7) Termination benefits — 1 — 1 Curtailments — (3) (1) (4) $ (15) $ (14) $ (42) $ (35)

Other (Income) Expense, Net (Ta

Other (Income) Expense, Net (Tables)	9 Months Ended
	Sep. 30, 2020
Other Income and Expenses [Abstract]
Other (Income) Expense, Net	Other (income) expense, net, consisted of: Three Months Ended Nine Months Ended ($ in millions) 2020 2019 2020 2019 Interest income $ (9) $ (61) $ (48) $ (225) Interest expense 203 231 624 674 Exchange losses 10 38 89 166 Income from investments in equity securities, net (1) (360) (16) (964) (50) Net periodic defined benefit plan (credit) cost other than service cost (88) (128) (259) (409) Other, net (68) (29) (72) 206 $ (312) $ 35 $ (630) $ 362

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Calculations of Earnings Per Share	The calculations of earnings per share are as follows: Three Months Ended Nine Months Ended ($ and shares in millions except per share amounts) 2020 2019 2020 2019 Net income attributable to Merck & Co., Inc. $ 2,941 $ 1,901 $ 9,161 $ 7,487 Average common shares outstanding 2,529 2,558 2,530 2,572 Common shares issuable (1) 9 14 11 15 Average common shares outstanding assuming dilution 2,538 2,572 2,541 2,587 Basic earnings per common share attributable to Merck & Co., Inc. common shareholders $ 1.16 $ 0.74 $ 3.62 $ 2.91 Earnings per common share assuming dilution attributable to Merck & Co., Inc. common shareholders $ 1.16 $ 0.74 $ 3.61 $ 2.89 (1) Issuable primarily under share-based compensation plans.

Other Comprehensive Income (L_2

Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Changes in AOCI by Component	Changes in AOCI by component are as follows: Three Months Ended September 30, ($ in millions) Derivatives Investments Employee Cumulative Accumulated Other Balance July 1, 2019, net of taxes $ 66 $ 48 $ (3,530) $ (1,946) $ (5,362) Other comprehensive income (loss) before reclassification adjustments, pretax 186 8 (4) (84) 106 Tax (39) — — (33) (72) Other comprehensive income (loss) before reclassification adjustments, net of taxes 147 8 (4) (117) 34 Reclassification adjustments, pretax (71) (1) (25) (2) 21 (3) — (75) Tax 15 — (2) — 13 Reclassification adjustments, net of taxes (56) (25) 19 — (62) Other comprehensive income (loss), net of taxes 91 (17) 15 (117) (28) Balance September 30, 2019, net of taxes $ 157 $ 31 $ (3,515) $ (2,063) $ (5,390) Balance July 1, 2020, net of taxes $ 15 $ — $ (4,162) $ (2,246) $ (6,393) Other comprehensive income (loss) before reclassification adjustments, pretax (195) — 2 50 (143) Tax 41 — 1 35 77 Other comprehensive income (loss) before reclassification adjustments, net of taxes (154) — 3 85 (66) Reclassification adjustments, pretax 22 (1) — 72 (3) — 94 Tax (5) — (13) — (18) Reclassification adjustments, net of taxes 17 — 59 — 76 Other comprehensive income (loss), net of taxes (137) — 62 85 10 Balance September 30, 2020, net of taxes $ (122) $ — $ (4,100) $ (2,161) $ (6,383) Nine Months Ended September 30, ($ in millions) Derivatives Investments Employee Cumulative Accumulated Other Balance January 1, 2019, net of taxes $ 166 $ (78) $ (3,556) $ (2,077) $ (5,545) Other comprehensive income (loss) before reclassification adjustments, pretax 183 139 (5) 47 364 Tax (38) — 6 (33) (65) Other comprehensive income (loss) before reclassification adjustments, net of taxes 145 139 1 14 299 Reclassification adjustments, pretax (195) (1) (30) (2) 49 (3) — (176) Tax 41 — (9) — 32 Reclassification adjustments, net of taxes (154) (30) 40 — (144) Other comprehensive income (loss), net of taxes (9) 109 41 14 155 Balance September 30, 2019, net of taxes $ 157 $ 31 $ (3,515) $ (2,063) $ (5,390) Balance January 1, 2020, net of taxes $ 31 $ 18 $ (4,261) $ (1,981) $ (6,193) Other comprehensive income (loss) before reclassification adjustments, pretax (126) 3 (19) (220) (362) Tax 27 — 12 40 79 Other comprehensive income (loss) before reclassification adjustments, net of taxes (99) 3 (7) (180) (283) Reclassification adjustments, pretax (68) (1) (21) (2) 210 (3) — 121 Tax 14 — (42) — (28) Reclassification adjustments, net of taxes (54) (21) 168 — 93 Other comprehensive income (loss), net of taxes (153) (18) 161 (180) (190) Balance September 30, 2020, net of taxes $ (122) $ — $ (4,100) $ (2,161) $ (6,383) (1) Relates to foreign currency cash flow hedges that were reclassified from AOCI to Sales . (2) Represents net realized (gains) losses on the sales of available-for-sale debt securities that were reclassified from AOCI to Other (income) expense, net . (3) Includes net amortization of prior service cost and actuarial gains and losses included in net periodic benefit cost (see Note 12).

Segment Reporting (Tables)

Segment Reporting (Tables)	9 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
Sales of Company's products	Sales of the Company’s products were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 ($ in millions) U.S. Int’l Total U.S. Int’l Total U.S. Int’l Total U.S. Int’l Total Pharmaceutical: Oncology Keytruda $ 2,157 $ 1,559 $ 3,715 $ 1,743 $ 1,327 $ 3,070 $ 6,106 $ 4,281 $ 10,387 $ 4,525 $ 3,448 $ 7,973 Alliance revenue - Lynparza (1) 107 89 196 71 53 123 297 223 519 186 126 313 Alliance revenue - Lenvima (1) 82 60 142 65 44 109 270 152 421 169 112 280 Emend 8 31 39 42 56 98 18 96 115 173 163 336 Vaccines Gardasil/Gardasil 9 579 608 1,187 761 558 1,320 1,209 1,732 2,941 1,579 1,464 3,044 ProQuad/M-M-R II /Varivax 437 139 576 482 141 623 1,033 356 1,390 1,325 469 1,794 Pneumovax 23 276 99 375 179 58 237 478 270 748 428 164 592 RotaTeq 114 96 210 102 78 180 355 246 601 360 203 564 Vaqta 32 19 51 36 26 62 79 60 139 103 65 167 Hospital Acute Care Bridion 162 157 320 133 151 284 412 431 843 381 437 817 Noxafil 13 66 79 77 100 177 27 220 247 268 291 560 Prevymis 32 46 77 22 23 45 87 113 200 60 55 115 Primaxin 1 73 74 2 75 77 2 187 189 2 204 207 Invanz 1 50 51 (1) 58 57 7 152 159 30 176 206 Cancidas 1 49 50 — 62 62 2 147 148 5 187 191 Cubicin 11 28 39 14 38 52 36 80 116 78 129 207 Zerbaxa 20 23 43 20 15 35 57 54 112 45 43 88 Immunology Simponi — 209 209 — 203 203 — 615 615 — 625 625 Remicade — 82 82 — 101 101 — 242 242 — 322 322 Neuroscience Belsomra 18 63 81 23 57 80 67 177 244 68 155 223 Virology Isentress/Isentress HD 92 113 205 102 149 250 243 403 646 304 449 752 Zepatier 6 22 28 24 59 83 38 83 122 96 208 304 Cardiovascular Zetia (1) 103 103 5 142 147 (4) 389 384 11 432 443 Vytorin 3 44 47 5 52 57 9 130 139 11 219 231 Atozet — 111 111 — 97 97 — 348 348 — 283 283 Alliance revenue - Adempas (2) 78 5 83 48 2 50 200 16 216 137 7 144 Adempas — 55 55 — 57 57 — 167 167 — 158 158 Diabetes Januvia 342 479 821 367 440 807 1,110 1,339 2,449 1,223 1,317 2,539 Janumet 105 400 506 129 375 503 361 1,138 1,499 462 1,105 1,567 Women’s Health Implanon/Nexplanon 137 52 189 136 62 199 374 142 515 421 160 581 NuvaRing 24 34 58 202 39 241 85 98 184 593 107 700 Diversified Brands Singulair 4 78 82 11 140 152 14 324 338 24 479 503 Cozaar/Hyzaar 5 86 91 6 110 116 17 275 292 16 313 329 Arcoxia — 68 68 — 72 72 — 204 204 — 221 221 Nasonex — 41 41 4 55 58 9 152 161 2 224 226 Follistim AQ 20 31 50 27 35 62 60 76 136 80 102 182 Other pharmaceutical (3) 352 834 1,186 343 804 1,149 1,144 2,334 3,478 1,037 2,394 3,431 Total Pharmaceutical segment sales 5,218 6,102 11,320 5,180 5,914 11,095 14,202 17,452 31,654 14,202 17,016 31,218 Animal Health: Livestock 164 594 758 144 582 726 448 1,697 2,145 406 1,601 2,007 Companion Animals 234 228 462 193 203 396 676 714 1,390 560 704 1,264 Total Animal Health segment sales 398 822 1,220 337 785 1,122 1,124 2,411 3,535 966 2,305 3,271 Other segment sales (4) — — — 46 — 46 23 — 23 133 1 133 Total segment sales 5,616 6,924 12,540 5,563 6,699 12,263 15,349 19,863 35,212 15,301 19,322 34,622 Other (5) 9 2 11 10 125 134 47 221 267 19 330 350 $ 5,625 $ 6,926 $ 12,551 $ 5,573 $ 6,824 $ 12,397 $ 15,396 $ 20,084 $ 35,479 $ 15,320 $ 19,652 $ 34,972 U.S. plus international may not equal total due to rounding. (1) Alliance revenue represents Merck’s share of profits, which are product sales net of cost of sales and commercialization costs (see Note 3). (2) Alliance revenue represents Merck’s share of profits from sales in Bayer’s marketing territories, which are product sales net of cost of sales and commercialization costs (see Note 3). (3) Other pharmaceutical primarily reflects sales of other human health pharmaceutical products, including products within the franchises not listed separately. (4) Represents sales for the Healthcare Services segment. All the businesses in the Healthcare Services segment were divested as of March 31, 2020.
Consolidated revenues by geographic area	Consolidated sales by geographic area where derived are as follows: Three Months Ended Nine Months Ended ($ in millions) 2020 2019 2020 2019 United States $ 5,625 $ 5,573 $ 15,396 $ 15,320 Europe, Middle East and Africa 3,454 3,189 10,059 9,452 China 1,016 914 2,715 2,423 Japan 828 919 2,506 2,639 Asia Pacific (other than China and Japan) 735 756 2,129 2,217 Latin America 604 671 1,670 1,889 Other 289 375 1,004 1,032 $ 12,551 $ 12,397 $ 35,479 $ 34,972
Reconciliation of segment profits to income before taxes	A reconciliation of segment profits to Income before taxes is as follows: Three Months Ended Nine Months Ended ($ in millions) 2020 2019 2020 2019 Segment profits: Pharmaceutical segment $ 7,974 $ 7,747 $ 22,010 $ 21,437 Animal Health segment 451 423 1,336 1,243 Other segment (1) (2) 1 (2) Total segment profits 8,424 8,168 23,347 22,678 Other profits (12) 101 188 226 Unallocated: Interest income 9 61 48 225 Interest expense (203) (231) (624) (674) Depreciation and amortization (395) (382) (1,173) (1,169) Research and development (3,272) (3,110) (7,364) (7,045) Amortization of purchase accounting adjustments (285) (329) (879) (1,105) Restructuring costs (114) (232) (269) (444) Other unallocated, net (724) (1,699) (2,490) (4,019) $ 3,428 $ 2,347 $ 10,784 $ 8,673

Acquisitions, Research Collab_3

Acquisitions, Research Collaborations and License Agreements - Acquisitions (Details) $ / shares in Units, shares in Thousands, € in Millions, $ in Millions	Jan. 16, 2020USD ($)	Apr. 01, 2019USD ($)	Nov. 30, 2020USD ($)	Oct. 31, 2020USD ($)	Sep. 30, 2020USD ($)$ / sharesshares	Sep. 30, 2020EUR (€)	Jul. 31, 2020USD ($)	Jun. 30, 2020USD ($)	May 31, 2020USD ($)	Jul. 31, 2019USD ($)	Apr. 30, 2019USD ($)	Sep. 30, 2020USD ($)$ / sharesshares	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)$ / sharesshares	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent consideration					$ 829							$ 829	$ 755	$ 829	$ 755	$ 767	$ 788
Goodwill					20,248							20,248		20,248		19,425
Research and development												3,390	3,204	7,721	7,324
Inventories					6,128							6,128		6,128		$ 5,978
Payments to Acquire Productive Assets														3,170	2,336
Forward Contracts | Research and development
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Amount of Derivative Pretax (Gain) Loss Recognized in Income												(22)	$ 0	(22)	$ 0
Forward Contracts | Research and development | Subsequent Event
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Amount of Derivative Pretax (Gain) Loss Recognized in Income				$ 6
Sentinel
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Payment to acquire business							$ 410
Dunboyne
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Other assets and liabilities, net					13							13		13
Payments to Acquire Productive Assets					302	€ 256
Property, plant and equipment					289							$ 289		$ 289
Themis
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Payment to acquire business								$ 366
Contingent consideration, maximum								740
Contingent consideration								97
IPR&D								136
Cash and cash equivalents								59
Goodwill								229
Deferred tax assets								71
Other assets and liabilities, net								(32)
ArQule
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Payment to acquire business	$ 2,700
IPR&D	2,280
Share-based compensation payments attributable to precombination service	138
Transaction costs	95
Cash and cash equivalents	145
Goodwill	540
Other assets and liabilities, net	34
Deferred income tax liabilities	389
Intangible assets	$ 80
Peloton
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Payment to acquire business										$ 1,200
Cash and cash equivalents										157
Other assets and liabilities, net										6
Research and development										982
Deferred income tax liabilities										64
Antelliq
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Payment to acquire business		$ 2,300
Transaction costs		47
Cash and cash equivalents		31
Goodwill		1,376
Debt assumed and paid		1,300
Other assets and liabilities, net		(82)
Deferred income tax liabilities		589
Inventories		93
Intangible assets		2,689
Property, plant and equipment		$ 60
Immune Design
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Payment to acquire business											$ 301
IPR&D											156
Cash and cash equivalents											83
Other net assets											42
Goodwill											$ 20
VelosBio [Member] | Forecast
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Payment to acquire business			$ 2,750
Development Milestones | Themis
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent consideration, maximum								80
Sales-Based Milestones | Themis
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent consideration, maximum								400
Sales-Based Milestones | Peloton
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent consideration, maximum										1,050
Regulatory Milestones | Themis
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent consideration, maximum								$ 260
Regulatory Milestones | Peloton
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent consideration, maximum										50
Commercial Milestone | Peloton
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent consideration, maximum										$ 50
Seagen
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Upfront and milestone payments					$ 600
Share price (in dollars per share) | $ / shares					$ 200							$ 200		$ 200
Contingent milestone payments collaborative arrangement					$ 2,600
Payments to Acquire Investments					1,000
Research and development					$ 622
Forward contract, shares | shares					5,000							5,000		5,000
Seagen | Tukysa
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Upfront and milestone payments					$ 210
Seagen | Tukysa | Minimum
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Royalty Rate, Percentage					20.00%	20.00%
Seagen | Tukysa | Maximum
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Royalty Rate, Percentage					33.00%	33.00%
Seagen | Sales-Based Milestones
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent milestone payments collaborative arrangement					$ 1,750
Seagen | Regulatory Milestones
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent milestone payments collaborative arrangement					850
Seagen | Regulatory Milestones | Tukysa
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent milestone payments collaborative arrangement					$ 65
IAVI
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Upfront and milestone payments									$ 6.5
Contingent milestone payments collaborative arrangement									$ 100
Technology Rights | Sentinel
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Acquired rights							401
Inventories							$ 9

Acquisitions, Research Collab_4

Acquisitions, Research Collaborations and License Agreements - Fair Value of Assets Acquired and Liabilities Assumed (Details) $ in Millions	Apr. 01, 2019USD ($)	Jul. 31, 2020	Sep. 30, 2020USD ($)	Jan. 16, 2020USD ($)	Dec. 31, 2019USD ($)
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Goodwill			$ 20,248		$ 19,425
Sentinel | Technology Rights
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Weighted average useful life of acquired finite-lived intangible assets		15 years
Antelliq | Technology Rights | Minimum
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Weighted average useful life of acquired finite-lived intangible assets	18 years
Antelliq | Technology Rights | Maximum
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Weighted average useful life of acquired finite-lived intangible assets	24 years
ArQule
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Cash and cash equivalents				$ 145
IPR&D				2,280
Intangible assets				80
Deferred income tax liabilities				(389)
Other assets and liabilities, net				34
Total identifiable net assets				2,150
Goodwill				540
Consideration transferred				$ 2,690
Antelliq
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Cash and cash equivalents	$ 31
Accounts receivable	73
Inventories	93
Property, plant and equipment	60
Intangible assets	2,689
Deferred income tax liabilities	(589)
Other assets and liabilities, net	(82)
Total identifiable net assets	2,275
Goodwill	1,376
Consideration transferred	$ 3,651
Measurement Input, Discount Rate | ArQule
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Present value discount rate				0.125
Measurement Input, Discount Rate | Antelliq
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Present value discount rate	0.115

Collaborative Arrangements - Na

Collaborative Arrangements - Narrative (Details) - USD ($) $ in Millions

1 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

21 Months Ended

29 Months Ended

37 Months Ended

Mar. 31, 2021

Mar. 31, 2020

Mar. 31, 2019

Mar. 31, 2018

Jul. 31, 2017

Sep. 30, 2020

Jun. 30, 2020

Sep. 30, 2019

Sep. 30, 2020

Sep. 30, 2019

Dec. 31, 2019

Dec. 31, 2018

Dec. 31, 2019

Dec. 31, 2019

Mar. 31, 2021

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Research and development

$ 3,390

$ 3,204

$ 7,721

$ 7,324

Other liabilities, noncurrent

12,027

12,027

$ 11,970

$ 11,970

$ 11,970

Lynparza | Other Assets

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Finite-lived intangible assets

1,300

1,300

Lenvima | Other Assets

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Finite-lived intangible assets

1,100

1,100

Adempas | Other intangible assets

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Finite-lived intangible assets

$ 838

838

AstraZeneca

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Upfront and milestone payments

$ 1,600

License option payment related to collaborative arrangement

$ 750

AstraZeneca | Sales-Based Milestones

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Contingent milestone payments collaborative arrangement

2,700

AstraZeneca | Sales-Based Milestones | Lynparza

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Probable contingent payments collaborative arrangement

$ 400

$ 1,000

Liabilities

400

Milestone payments made to collaborative partner

250

200

$ 250

AstraZeneca | Regulatory Milestones | Lynparza

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Milestone payments made to collaborative partner

135

60

140

Contingent milestone payments collaborative arrangement

1,400

Eisai

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Upfront and milestone payments

$ 750

License option payment related to collaborative arrangement

$ 200

$ 325

Eisai | Forecast

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

License option payment related to collaborative arrangement

$ 125

$ 650

Eisai | Sales-Based Milestones

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Contingent milestone payments collaborative arrangement

2,700

Eisai | Sales-Based Milestones | Lenvima

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Probable contingent payments collaborative arrangement

370

$ 950

Liabilities

$ 370

Milestone payments made to collaborative partner

500

50

Eisai | Regulatory Milestones

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Contingent milestone payments collaborative arrangement

135

Eisai | Regulatory Milestones | Lenvima

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Milestone payments made to collaborative partner

250

Bayer AG | Sales-Based Milestones

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Probable contingent payments collaborative arrangement

$ 725

Milestone payments made to collaborative partner

$ 350

Contingent milestone payments collaborative arrangement

$ 400

Collaborative Arrangements - Sc

Collaborative Arrangements - Schedule of Transactions (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Sales	$ 12,551	$ 12,397	$ 35,479	$ 34,972
Cost of sales	3,481	3,990	9,952	10,443
Selling, general and administrative	2,450	2,589	7,383	7,726
Research and development	3,390	3,204	7,721	7,324
Payables, current	20,405		20,405		$ 22,220
Other current assets | AstraZeneca | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Receivables	197		197		128
Other current assets | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Receivables	170		170		150
Other current assets | Bayer AG | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Receivables	70		70		49
Accounts payable and accrued liabilities | AstraZeneca | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Payables, current	309		309		577
Payables, Noncurrent	400		400		0
Accounts payable and accrued liabilities | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Payables, current	325		325		700
Other Noncurrent Liabilities | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Payables, Noncurrent	570		570		525
Other Noncurrent Liabilities | Bayer AG | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Payables, Noncurrent	375		375		$ 375
Revenue | AstraZeneca | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Alliance revenue - profit sharing	199	123	522	313
Revenue | AstraZeneca | Collaborative Arrangement | Alliance revenue - Lynparza (1)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Alliance revenue - profit sharing	196	123	519	313
Revenue | AstraZeneca | Collaborative Arrangement | Alliance revenue - Koselugo
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Alliance revenue - profit sharing	3	0	3	0
Revenue | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Alliance revenue - profit sharing	142	109	421	280
Revenue | Bayer AG | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Alliance revenue - profit sharing	83	50	216	144
Collaborative Arrangement, Sales, Net	55	57	167	158
Sales	138	107	383	302
Cost of sales | AstraZeneca | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cost of sales	41	28	205	120
Cost of sales | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cost of sales	46	23	215	97
Cost of sales | Bayer AG | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cost of sales	29	28	85	86
Selling, general and administrative | AstraZeneca | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Selling, general and administrative	40	36	112	96
Selling, general and administrative | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Selling, general and administrative	18	21	48	59
Selling, general and administrative | Bayer AG | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Selling, general and administrative	19	12	42	31
Research and development | AstraZeneca | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development	20	44	93	122
Research and development | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development	48	37	168	146
Research and development | Bayer AG | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development	$ 12	$ 31	$ 53	$ 94

Restructuring - Narrative (Deta

Restructuring - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020
Restructuring Cost and Reserve [Line Items]
Cumulative costs since program inception	$ 1,400		$ 1,400
Estimate of cumulative pre tax costs that will result in cash outlays			60.00%
Estimate of cumulative pre tax costs that will be noncash			40.00%
Expected restructuring and related cost	2,500		$ 2,500
Total pretax restructuring costs	$ 186	$ 296	$ 504	$ 642
Forecast
Restructuring Cost and Reserve [Line Items]
Expected restructuring and related cost					$ 800

Restructuring - Charges Activit

Restructuring - Charges Activities by Type of Cost (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	$ 186	$ 296	$ 504	$ 642
Separation Costs
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	61	205	143	358
Accelerated Depreciation
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	66	41	192	173
Other
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	59	50	169	111
Cost of sales
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	38	62	131	161
Cost of sales | Separation Costs
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	0	0	0	0
Cost of sales | Accelerated Depreciation
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	33	41	89	139
Cost of sales | Other
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	5	21	42	22
Selling, general and administrative
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	15	1	37	33
Selling, general and administrative | Separation Costs
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	0	0	0	0
Selling, general and administrative | Accelerated Depreciation
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	15	1	37	33
Selling, general and administrative | Other
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	0	0	0	0
Research and development
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	19	1	67	4
Research and development | Separation Costs
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	0	0	0	0
Research and development | Accelerated Depreciation
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	18	(1)	66	1
Research and development | Other
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	1	2	1	3
Restructuring costs
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	114	232	269	444
Restructuring costs | Separation Costs
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	61	205	143	358
Restructuring costs | Accelerated Depreciation
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	0	0	0	0
Restructuring costs | Other
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	$ 53	$ 27	$ 126	$ 86

Restructuring - Activities by P

Restructuring - Activities by Program (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance			$ 759
Expense	$ 186	$ 296	504	$ 642
(Payments) receipts, net			(632)
Non-cash activity			(153)
Restructuring reserve, ending balance	478		478
Separation Costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance			690
Expense	61	205	143	358
(Payments) receipts, net			(395)
Non-cash activity			0
Restructuring reserve, ending balance	438		438
Accelerated Depreciation
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance			0
Expense	66	41	192	173
(Payments) receipts, net			0
Non-cash activity			(192)
Restructuring reserve, ending balance	0		0
Other
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance			69
Expense	59	$ 50	169	$ 111
(Payments) receipts, net			(237)
Non-cash activity			39
Restructuring reserve, ending balance	$ 40		$ 40

Financial Instruments - Narrati

Financial Instruments - Narrative (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2020USD ($)interest_rate_swap	Dec. 31, 2019USD ($)	Sep. 30, 2020USD ($)interest_rate_swap	Sep. 30, 2019USD ($)	Jun. 30, 2020USD ($)	Feb. 29, 2020USD ($)interest_rate_swap
Derivative [Line Items]
Pretax net unrealized losses on derivatives maturing within next 12 months estimated to be reclassified from AOCI to sales			$ 155,000,000
Equity investments without readily determinable fair values	$ 508,000,000		508,000,000	$ 393,000,000
Unrealized gains recognized on investments in equity securities without readily determinable fair value			21,000,000	4,000,000
Unrealized losses recognized on investments in equity securities without readily determinable fair values			3,000,000	12,000,000
Cumulative unrealized gains on investments	128,000,000		128,000,000
Cumulative unrealized losses on investments	24,000,000		24,000,000
Payments of contingent consideration			106,000,000	$ 85,000,000
Fair value of loans payable and long-term debt, including current portion	32,600,000,000	$ 28,800,000,000	32,600,000,000
Debt, carrying amount	28,700,000,000	26,300,000,000	28,700,000,000
Accounts Receivable, Sale	2,100,000,000	2,700,000,000
Cash collateral received from counterparties	0	34,000,000	0
Cash collateral advanced to counterparties	0	0	0
Total swap notional amount	27,151,000,000	30,666,000,000	27,151,000,000
Face amount of debt					$ 4,500,000,000
Level 2
Derivative [Line Items]
Cash equivalents	6,600,000,000	8,900,000,000	6,600,000,000
Derivatives Designated as Hedging Instruments
Derivative [Line Items]
Total swap notional amount	12,654,000,000	14,728,000,000	$ 12,654,000,000
Derivatives Designated as Hedging Instruments | Maximum
Derivative [Line Items]
Maximum average period of maturities of contracts in years (less than)			2 years
Derivatives Not Designated as Hedging Instruments
Derivative [Line Items]
Total swap notional amount	$ 14,497,000,000	$ 15,938,000,000	$ 14,497,000,000
Derivatives Not Designated as Hedging Instruments | Maximum
Derivative [Line Items]
Maximum average period of maturities of contracts in years (less than)			1 year
1.85% Notes Due 2020
Derivative [Line Items]
Face amount of debt						$ 1,250,000,000
Stated interest rate (as percent)						1.85%
Interest rate swap contracts
Derivative [Line Items]
Number of interest rate swaps held (in interest rate swaps) | interest_rate_swap	14		14			5
Total swap notional amount						$ 250,000,000

Financial Instruments - Effect

Financial Instruments - Effect of Net Investment Hedges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Pretax (Gain) Loss Recognized in Other Comprehensive Income	$ 10	$ 1	$ 15	$ 8
Foreign exchange contracts | Other (income) expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Pretax (Gain) Loss Recognized in Other (income) expense, net for Amounts Excluded from Effectiveness Testing	(4)	(8)	(15)	(23)
Euro-denominated notes
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Pretax (Gain) Loss Recognized in Other Comprehensive Income	162	(150)	182	(152)
Euro-denominated notes | Other (income) expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Pretax (Gain) Loss Recognized in Other (income) expense, net for Amounts Excluded from Effectiveness Testing	$ 0	$ 0	$ 0	$ 0

Financial Instruments - Summary

Financial Instruments - Summary of Interest Rate Swaps Held (Details)	Sep. 30, 2020USD ($)interest_rate_swap	Jun. 30, 2020USD ($)	Feb. 29, 2020USD ($)interest_rate_swap	Dec. 31, 2019USD ($)
Derivative [Line Items]
Par Value of Debt		$ 4,500,000,000
Total swap notional amount	$ 27,151,000,000			$ 30,666,000,000
Interest rate swap contracts
Derivative [Line Items]
Number of Interest Rate Swaps Held (in interest rate swaps) | interest_rate_swap	14		5
Total swap notional amount			$ 250,000,000
3.875% notes due 2021 | Interest rate swap contracts
Derivative [Line Items]
Stated interest rate (as percent)	3.875%
Par Value of Debt	$ 1,150,000,000
Number of Interest Rate Swaps Held (in interest rate swaps) | interest_rate_swap	5
Total swap notional amount	$ 1,150,000,000
2.40% notes due 2022 | Interest rate swap contracts
Derivative [Line Items]
Stated interest rate (as percent)	2.40%
Par Value of Debt	$ 1,000,000,000
Number of Interest Rate Swaps Held (in interest rate swaps) | interest_rate_swap	4
Total swap notional amount	$ 1,000,000,000
2.35% notes due 2022 | Interest rate swap contracts
Derivative [Line Items]
Stated interest rate (as percent)	2.35%
Par Value of Debt	$ 1,250,000,000
Number of Interest Rate Swaps Held (in interest rate swaps) | interest_rate_swap	5
Total swap notional amount	$ 1,250,000,000

Financial Instruments - Fair Va

Financial Instruments - Fair Value Hedges (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Loans payable and current portion of long-term debt
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying Amount of Hedged Liabilities	$ 1,155	$ 1,249
Cumulative Amount of Fair Value Hedging Adjustment Increase (Decrease) Included in the Carrying Amount	5	(1)
Long-Term Debt
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying Amount of Hedged Liabilities	2,309	3,409
Cumulative Amount of Fair Value Hedging Adjustment Increase (Decrease) Included in the Carrying Amount	$ 62	$ 14

Financial Instruments - Fair _2

Financial Instruments - Fair Value of Derivatives Segregated between those Derivatives that are Designated as Hedging Instruments and those that are Not Designated as Hedging Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	$ 239	$ 288
Fair Value of Derivative, Liability	298	97
U.S Dollar Notional Amount	27,151	30,666
Derivatives Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	158	222
Fair Value of Derivative, Liability	105	24
U.S Dollar Notional Amount	12,654	14,728
Derivatives Not Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	81	66
Fair Value of Derivative, Liability	193	73
U.S Dollar Notional Amount	14,497	15,938
Interest rate swap contracts | Derivatives Designated as Hedging Instruments | Other current assets
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	6	0
U.S Dollar Notional Amount	1,150	0
Interest rate swap contracts | Derivatives Designated as Hedging Instruments | Other Assets
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	63	15
U.S Dollar Notional Amount	2,250	3,400
Interest rate swap contracts | Derivatives Designated as Hedging Instruments | Accrued and other current liabilities
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Liability	0	1
U.S Dollar Notional Amount	0	1,250
Foreign exchange contracts | Derivatives Designated as Hedging Instruments | Other current assets
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	30	152
U.S Dollar Notional Amount	4,120	6,117
Foreign exchange contracts | Derivatives Designated as Hedging Instruments | Other Assets
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	59	55
U.S Dollar Notional Amount	1,881	2,160
Foreign exchange contracts | Derivatives Designated as Hedging Instruments | Accrued and other current liabilities
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Liability	104	22
U.S Dollar Notional Amount	3,096	1,748
Foreign exchange contracts | Derivatives Designated as Hedging Instruments | Other Noncurrent Liabilities
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Liability	1	1
U.S Dollar Notional Amount	157	53
Foreign exchange contracts | Derivatives Not Designated as Hedging Instruments | Other current assets
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	81	66
U.S Dollar Notional Amount	5,455	7,245
Foreign exchange contracts | Derivatives Not Designated as Hedging Instruments | Accrued and other current liabilities
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Liability	171	73
U.S Dollar Notional Amount	8,042	8,693
Forward Contracts | Derivatives Not Designated as Hedging Instruments | Accrued and other current liabilities
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Liability	22	0
U.S Dollar Notional Amount	$ 1,000	$ 0

Financial Instruments - Informa

Financial Instruments - Information on Derivative Positions Subject to Master Netting Arrangements as if they were Presented on a Net Basis (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gross amounts recognized in the consolidated balance sheet, asset	$ 239,000,000	$ 288,000,000
Gross amount subject to offset in master netting arrangements not offset in the condensed balance sheet, asset	(140,000,000)	(84,000,000)
Cash collateral received, asset	0	(34,000,000)
Net amounts, asset	99,000,000	170,000,000
Gross amounts recognized in the consolidated balance sheet, liability	298,000,000	97,000,000
Gross amount subject to offset in master netting arrangements not offset in the condensed balance sheet, liability	(140,000,000)	(84,000,000)
Cash collateral received, liability	0	0
Net amounts, liability	$ 158,000,000	$ 13,000,000

Financial Instruments - Locatio

Financial Instruments - Location and Amount of Pretax (Gains) Losses of Derivatives (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Sales	$ 12,551	$ 12,397	$ 35,479	$ 34,972
Other (income) expense, net	(312)	35	(630)	362
Other comprehensive income (loss)	10	(28)	(190)	155
Interest rate swap contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of (loss) gain recognized in OCI on derivatives	(1)	(1)	(3)	(6)
Interest rate swap contracts | Other (income) expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Hedged items	(14)	13	54	101
Derivatives designated as hedging instruments	0	(6)	(76)	(74)
Amount of gain recognized in Other (income) expense, net on derivatives	(1)	(1)	(3)	(3)
Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of (loss) gain recognized in OCI on derivatives	(195)	186	(126)	183
Increase (decrease) in Sales as a result of AOCI reclassifications	23	(70)	(65)	(189)
Foreign exchange contracts | Reclassification out of Accumulated Other Comprehensive Income | Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest
Derivative Instruments, Gain (Loss) [Line Items]
Sales	$ (23)	$ 70	$ 65	$ 189

Financial Instruments - Income

Financial Instruments - Income Statement Effects on Derivatives Not Designated as Hedging Instruments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Foreign currency | Other (income) expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Pretax (Gain) Loss Recognized in Income	$ (7)	$ (8)	$ (138)	$ 112
Forecasted transactions | Sales
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Pretax (Gain) Loss Recognized in Income	7	(11)	4	(7)
Treasury lock | Other (income) expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Pretax (Gain) Loss Recognized in Income	0	0	9	0
Forward Contracts | Research and development
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Pretax (Gain) Loss Recognized in Income	$ 22	$ 0	$ 22	$ 0

Financial Instruments - Infor_2

Financial Instruments - Information on Available-for-sale Investments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Debt securities, amortized cost	$ 76		$ 76		$ 1,768
Debt securities, unrealized gains	0		0		17
Debt securities, unrealized losses	0		0		0
Debt securities, fair value	76		76		1,785
Publicly traded equity securities, fair value	1,477		1,477		838
Total debt and publicly traded equity securities, fair value	1,553		1,553		2,623
Unrealized net losses (gains)	(43)	$ 25	(512)	$ (41)
U.S. government and agency securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, amortized cost	74		74		266
Debt securities, unrealized gains	0		0		3
Debt securities, unrealized losses	0		0		0
Debt securities, fair value	74		74		269
Foreign government bonds
Debt Securities, Available-for-sale [Line Items]
Debt securities, amortized cost	2		2		0
Debt securities, unrealized gains	0		0		0
Debt securities, unrealized losses	0		0		0
Debt securities, fair value	2		2		0
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Debt securities, amortized cost	0		0		668
Debt securities, unrealized gains	0		0		0
Debt securities, unrealized losses	0		0		0
Debt securities, fair value	0		0		668
Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Debt securities, amortized cost	0		0		608
Debt securities, unrealized gains	0		0		13
Debt securities, unrealized losses	0		0		0
Debt securities, fair value	0		0		621
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, amortized cost	0		0		226
Debt securities, unrealized gains	0		0		1
Debt securities, unrealized losses	0		0		0
Debt securities, fair value	$ 0		$ 0		$ 227

Financial Instruments - Financi

Financial Instruments - Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Assets
Investments	$ 76	$ 1,785
Publicly traded equity securities	1,477	838
Derivative assets	239	288
Liabilities
Contingent consideration	829	767	$ 755	$ 788
Derivative liabilities	298	97
Foreign government bonds
Assets
Investments	2	0
Corporate notes and bonds
Assets
Investments	0	621
Commercial paper
Assets
Investments	0	668
Asset-backed securities
Assets
Investments	$ 0	227
Liabilities
Primary weighted average life of collateral	5 years
U.S. government and agency securities
Assets
Investments	$ 74	269
Fair Value, Measurements, Recurring
Assets
Investments	1,372	2,243
Other assets	181	380
Derivative assets	239	288
Total assets	1,792	2,911
Liabilities
Contingent consideration	829	767
Derivative liabilities	298	97
Total liabilities	1,127	864
Fair Value, Measurements, Recurring | Foreign exchange contracts
Assets
Derivative assets	116	169
Liabilities
Derivative liabilities	275	95
Fair Value, Measurements, Recurring | Interest rate swap contracts
Assets
Derivative assets	69	15
Fair Value, Measurements, Recurring | Currency options
Assets
Derivative assets	54	104
Liabilities
Derivative liabilities	1	1
Fair Value, Measurements, Recurring | Interest rate swap contracts
Liabilities
Derivative liabilities	0	1
Fair Value, Measurements, Recurring | Forward Contracts
Liabilities
Derivative liabilities	22	0
Fair Value, Measurements, Recurring | Level 1
Assets
Investments	1,370	518
Other assets	181	380
Derivative assets	0	0
Total assets	1,551	898
Liabilities
Contingent consideration	0	0
Derivative liabilities	0	0
Total liabilities	0	0
Fair Value, Measurements, Recurring | Level 1 | Foreign exchange contracts
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 1 | Interest rate swap contracts
Assets
Derivative assets	0	0
Fair Value, Measurements, Recurring | Level 1 | Currency options
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 1 | Interest rate swap contracts
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 1 | Forward Contracts
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 2
Assets
Investments	2	1,725
Other assets	0	0
Derivative assets	239	288
Total assets	241	2,013
Liabilities
Contingent consideration	0	0
Derivative liabilities	298	97
Total liabilities	298	97
Fair Value, Measurements, Recurring | Level 2 | Foreign exchange contracts
Assets
Derivative assets	116	169
Liabilities
Derivative liabilities	275	95
Fair Value, Measurements, Recurring | Level 2 | Interest rate swap contracts
Assets
Derivative assets	69	15
Fair Value, Measurements, Recurring | Level 2 | Currency options
Assets
Derivative assets	54	104
Liabilities
Derivative liabilities	1	1
Fair Value, Measurements, Recurring | Level 2 | Interest rate swap contracts
Liabilities
Derivative liabilities	0	1
Fair Value, Measurements, Recurring | Level 2 | Forward Contracts
Liabilities
Derivative liabilities	22	0
Fair Value, Measurements, Recurring | Level 3
Assets
Investments	0	0
Other assets	0	0
Derivative assets	0	0
Total assets	0	0
Liabilities
Contingent consideration	829	767
Derivative liabilities	0	0
Total liabilities	829	767
Fair Value, Measurements, Recurring | Level 3 | Foreign exchange contracts
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 3 | Interest rate swap contracts
Assets
Derivative assets	0	0
Fair Value, Measurements, Recurring | Level 3 | Currency options
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 3 | Interest rate swap contracts
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 3 | Forward Contracts
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Foreign government bonds
Assets
Investments	2	0
Fair Value, Measurements, Recurring | Foreign government bonds | Level 1
Assets
Investments	0	0
Fair Value, Measurements, Recurring | Foreign government bonds | Level 2
Assets
Investments	2	0
Fair Value, Measurements, Recurring | Foreign government bonds | Level 3
Assets
Investments	0	0
Fair Value, Measurements, Recurring | Corporate notes and bonds
Assets
Investments	0	621
Fair Value, Measurements, Recurring | Corporate notes and bonds | Level 1
Assets
Investments	0	0
Fair Value, Measurements, Recurring | Corporate notes and bonds | Level 2
Assets
Investments	0	621
Fair Value, Measurements, Recurring | Corporate notes and bonds | Level 3
Assets
Investments	0	0
Fair Value, Measurements, Recurring | Commercial paper
Assets
Investments	0	668
Fair Value, Measurements, Recurring | Commercial paper | Level 1
Assets
Investments	0	0
Fair Value, Measurements, Recurring | Commercial paper | Level 2
Assets
Investments	0	668
Fair Value, Measurements, Recurring | Commercial paper | Level 3
Assets
Investments	0	0
Fair Value, Measurements, Recurring | Asset-backed securities
Assets
Investments	0	227
Fair Value, Measurements, Recurring | Asset-backed securities | Level 1
Assets
Investments	0	0
Fair Value, Measurements, Recurring | Asset-backed securities | Level 2
Assets
Investments	0	227
Fair Value, Measurements, Recurring | Asset-backed securities | Level 3
Assets
Investments	0	0
Fair Value, Measurements, Recurring | U.S. government and agency securities
Assets
Investments	0	209
Other assets	74	60
Fair Value, Measurements, Recurring | U.S. government and agency securities | Level 1
Assets
Investments	0	0
Other assets	74	60
Fair Value, Measurements, Recurring | U.S. government and agency securities | Level 2
Assets
Investments	0	209
Other assets	0	0
Fair Value, Measurements, Recurring | U.S. government and agency securities | Level 3
Assets
Investments	0	0
Other assets	0	0
Fair Value, Measurements, Recurring | Publicly traded equity securities
Assets
Publicly traded equity securities	1,370	518
Other assets	107	320
Fair Value, Measurements, Recurring | Publicly traded equity securities | Level 1
Assets
Publicly traded equity securities	1,370	518
Other assets	107	320
Fair Value, Measurements, Recurring | Publicly traded equity securities | Level 2
Assets
Publicly traded equity securities	0	0
Other assets	0	0
Fair Value, Measurements, Recurring | Publicly traded equity securities | Level 3
Assets
Publicly traded equity securities	0	0
Other assets	$ 0	$ 0

Financial Instruments - Infor_3

Financial Instruments - Information About Changes in Liabilities for Contingent Consideration (Details) $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	$ 767	$ 788
Additions	97	0
Changes in estimated fair value	71	52
Payments	(106)	(85)
Fair value, ending balance	829	755
Current liability			$ 140
Contingent consideration	829	$ 755	829
Sanofi Pasteur
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	625
Fair value, ending balance	637
Contingent consideration	$ 625		$ 637
Contingent consideration, measurement input, discount rate (as percent)			0.115
Measurement Input, Discount Rate | Sanofi Pasteur
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration, measurement input, discount rate (as percent)			0.08

Inventories - Inventories (Deta

Inventories - Inventories (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
Finished goods	$ 2,038	$ 1,772
Raw materials and work in process	6,073	5,650
Supplies	197	207
Total (approximates current cost)	8,308	7,629
Decrease to LIFO cost	(99)	(171)
Total current and noncurrent inventories	8,209	7,458
Recognized as:
Inventories	6,128	5,978
Other assets	$ 2,081	$ 1,480

Inventories - Narrative (Detail

Inventories - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Inventory [Line Items]
Inventories classified in Other assets	$ 2,081	$ 1,480
Inventories Not Expected to be Sold Within One Year
Inventory [Line Items]
Inventories classified in Other assets	1,800	1,300
Inventories Produced in Preparation for Product Launches
Inventory [Line Items]
Inventories classified in Other assets	$ 288	$ 168

Other Intangibles (Details)

Other Intangibles (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Finite-Lived Intangible Assets [Line Items]
Intangible asset impairment charges	$ 612	$ 693
Sivextro [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset impairment charges	$ 612

Long-Term Debt - Narrative (Det

Long-Term Debt - Narrative (Details)	Jun. 30, 2020USD ($)
Debt Instrument [Line Items]
Face amount of debt	$ 4,500,000,000
0.75% notes due 2026
Debt Instrument [Line Items]
Face amount of debt	$ 1,000,000,000
Stated interest rate (as percent)	0.75%
1.45% notes due 2030
Debt Instrument [Line Items]
Face amount of debt	$ 1,250,000,000
Stated interest rate (as percent)	1.45%
2.35% notes due 2040
Debt Instrument [Line Items]
Face amount of debt	$ 1,000,000,000
Stated interest rate (as percent)	2.35%
2.45% notes due 2050
Debt Instrument [Line Items]
Face amount of debt	$ 1,250,000,000
Stated interest rate (as percent)	2.45%

Contingencies - Narrative (Deta

Contingencies - Narrative (Details) $ in Millions	1 Months Ended	9 Months Ended
	Mar. 31, 2014Case	Sep. 30, 2020USD ($)CaseClaim	Dec. 31, 2019USD ($)
Legal Defense Costs
Loss Contingencies [Line Items]
Legal defense costs reserve | $		$ 255	$ 240
Zetia antitrust litigation [Member]
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters) | Claim		35
Patents [Member]
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters)		3
Loss Contingency, Claims Settled, Number		5
Fosamax
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters)		3,590
Fosamax | Femur Fracture Litigation | Federal
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters)		970
Loss contingency, claims dismissed, number (in legal matters)	650
Loss contingency, claims on appeal, number (in legal matters)	515
Fosamax | Femur Fracture Litigation | New Jersey state court
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters)		2,340
Fosamax | Femur Fracture Litigation | California state court
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters)		275
Fosamax | Femur Fracture Litigation | Other state courts
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters)		4
Januvia
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters) | Claim		1,465
Januvia | Other state courts
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters) | Claim		6
Januvia | Cases Company Agreed To Toll Statute Of Limitations
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters) | Claim		50

Equity - Rollforward Reconcilia

Equity - Rollforward Reconciliations (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, beginning balance (in shares)			3,577,103,522
Equity, beginning balance	$ 27,744	$ 27,737	$ 26,001	$ 26,882
Net income attributable to Merck & Co., Inc.	2,941	1,901	9,161	7,487
Other comprehensive income (loss), net of taxes	10	(28)	(190)	155
Cash dividends declared on common stock	(1,558)	(1,392)	(4,656)	(4,262)
Treasury stock shares purchased		(1,405)	(1,281)	(3,730)
Share-based compensation plans and other	151	127	245	487
Net income (loss) attributable to noncontrolling interests	4	6	12	(73)
Distributions attributable to noncontrolling interests	$ (22)	(21)	$ (22)	(21)
Shares, ending balance (in shares)	3,577,103,522		3,577,103,522
Equity, ending balance	$ 29,270	$ 26,925	$ 29,270	$ 26,925
Cash dividends declared on common stock (in dollars per share)	$ 0.61	$ 0.55	$ 1.83	$ 1.65
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, beginning balance (in shares)	3,577,000,000	3,577,000,000	3,577,000,000	3,577,000,000
Equity, beginning balance	$ 1,788	$ 1,788	$ 1,788	$ 1,788
Shares, ending balance (in shares)	3,577,000,000	3,577,000,000	3,577,000,000	3,577,000,000
Equity, ending balance	$ 1,788	$ 1,788	$ 1,788	$ 1,788
Other Paid-In Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity, beginning balance	39,373	39,484	39,660	38,808
Treasury stock shares purchased				1,000
Share-based compensation plans and other	116	77	(171)	(247)
Equity, ending balance	39,489	39,561	39,489	39,561
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity, beginning balance	49,724	45,295	46,602	42,579
Net income attributable to Merck & Co., Inc.	2,941	1,901	9,161	7,487
Cash dividends declared on common stock	(1,558)	(1,392)	(4,656)	(4,262)
Equity, ending balance	51,107	45,804	51,107	45,804
Accumulated Other Comprehensive Loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity, beginning balance	(6,393)	(5,362)	(6,193)	(5,545)
Other comprehensive income (loss), net of taxes	10	(28)	(190)	155
Equity, ending balance	$ (6,383)	$ (5,390)	$ (6,383)	$ (5,390)
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, beginning balance (in shares)	1,048,000,000	1,010,000,000	1,038,000,000	985,000,000
Equity, beginning balance	$ (56,850)	$ (53,570)	$ (55,950)	$ (50,929)
Treasury stock shares purchased (in shares)		17,000,000	16,000,000	54,000,000
Treasury stock shares purchased		$ (1,405)	$ (1,281)	$ (4,730)
Share-based compensation plans and other (in shares)	(1,000,000)	(1,000,000)	(7,000,000)	(13,000,000)
Share-based compensation plans and other	$ 35	$ 50	$ 416	$ 734
Shares, ending balance (in shares)	1,047,000,000	1,026,000,000	1,047,000,000	1,026,000,000
Equity, ending balance	$ (56,815)	$ (54,925)	$ (56,815)	$ (54,925)
Non- controlling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity, beginning balance	102	102	94	181
Net income (loss) attributable to noncontrolling interests	4	6	12	(73)
Distributions attributable to noncontrolling interests	(22)	(21)	(22)	(21)
Equity, ending balance	$ 84	$ 87	$ 84	$ 87

Share-Based Compensation Plan_2

Share-Based Compensation Plans - Expense Allocations (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
Pretax share-based compensation expense	$ 126	$ 101	$ 354	$ 306
Income tax benefit	(17)	(14)	(48)	(42)
Total share-based compensation expense, net of taxes	$ 109	$ 87	$ 306	$ 264

Share-Based Compensation Plan_3

Share-Based Compensation Plans - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	4,000,000	3,000,000
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 77.67	$ 80.05
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 9.93	$ 10.63
Total pretax unrecognized compensation expense related to nonvested stock options, RSU and PSU awards	$ 800
Weighted average period in years of recognition for nonvested stock options, RSU and PSU awards	2 years 1 month 6 days
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	7,000,000	5,000,000
Weighted-average fair value per share granted (in dollars per share)	$ 77.83	$ 80.03
Performance Share Units (PSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	773,000	609,000
Weighted-average fair value per share granted (in dollars per share)	$ 75.22	$ 90.50

Share-Based Compensation Plan_4

Share-Based Compensation Plans - Assumptions Used for Options Granted (Details)	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
Expected dividend yield	3.10%	3.20%
Risk-free interest rate	0.40%	2.40%
Expected volatility	22.10%	18.70%
Expected life (years)	5 years 9 months 18 days	5 years 10 months 24 days

Pension and Other Postretirem_3

Pension and Other Postretirement Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 13	$ 12	$ 39	$ 36
Interest cost	14	17	43	52
Expected return on plan assets	(19)	(18)	(56)	(54)
Amortization of unrecognized prior service credit	(18)	(20)	(54)	(59)
Net loss amortization	(5)	(3)	(13)	(7)
Termination benefits	0	1	0	1
Curtailments	0	(3)	(1)	(4)
Net periodic benefit cost	(15)	(14)	(42)	(35)
U.S. | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	96	76	270	221
Interest cost	107	115	323	343
Expected return on plan assets	(193)	(202)	(581)	(613)
Amortization of unrecognized prior service credit	(12)	(12)	(37)	(37)
Net loss amortization	75	43	228	113
Termination benefits	1	3	5	7
Curtailments	1	5	4	6
Settlements	2	0	11	0
Net periodic benefit cost	77	28	223	40
International | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	77	58	225	178
Interest cost	35	44	103	133
Expected return on plan assets	(104)	(106)	(310)	(320)
Amortization of unrecognized prior service credit	(3)	(3)	(9)	(9)
Net loss amortization	32	16	94	47
Termination benefits	1	0	2	1
Curtailments	0	0	(1)	0
Settlements	0	0	2	0
Net periodic benefit cost	$ 38	$ 9	$ 106	$ 30

Pension and Other Postretirem_4

Pension and Other Postretirement Benefit Plans Pension and Other Postretirement Benefit Plans (Narrative) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)
International
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions, current fiscal year	$ 375
Contributions by employer	123
U.S.
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions, current fiscal year	200
Contributions by employer	$ 184

Other (Income) Expense, Net (De

Other (Income) Expense, Net (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Component of Other Income / Expense of Nonoperating [Line Items]
Interest income	$ (9)	$ (61)	$ (48)	$ (225)
Interest expense	203	231	624	674
Exchange losses	10	38	89	166
Income from investments in equity securities, net (1)	(360)	(16)	(964)	(50)
Net periodic defined benefit plan (credit) cost other than service cost	(88)	(128)	(259)	(409)
Other, net	(68)	(29)	(72)	206
Other (income) expense, net	$ (312)	$ 35	$ (630)	$ 362

Other (Income) Expense, Net Oth

Other (Income) Expense, Net Other (Income) Expense, Net - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Component of Other Income / Expense of Nonoperating [Line Items]
Interest paid	$ 605	$ 629
Healthcare Services Segment
Component of Other Income / Expense of Nonoperating [Line Items]
Goodwill, Impairment Loss		$ 162

Taxes on Income (Details)

Taxes on Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Tax Examination [Line Items]
Effective income tax rate (as percent)	14.10%	18.70%	14.90%	14.50%
Internal Revenue Service (IRS) | Domestic Tax Authority
Income Tax Examination [Line Items]
Tax benefit recognized related to settlement				$ 360
Income taxes paid				$ 107

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net income attributable to Merck & Co., Inc.	$ 2,941	$ 1,901	$ 9,161	$ 7,487
Average common shares outstanding	2,529	2,558	2,530	2,572
Common shares issuable (1)	9	14	11	15
Average common shares outstanding assuming dilution	2,538	2,572	2,541	2,587
Basic earnings per common share attributable to Merck & Co., Inc. common shareholders	$ 1.16	$ 0.74	$ 3.62	$ 2.91
Earnings per common share assuming dilution attributable to Merck & Co., Inc. common shareholders	$ 1.16	$ 0.74	$ 3.61	$ 2.89
Common shares issuable under share-based compensation plans excluded from diluted earnings per common share because the effect would have been antidilutive (in shares)	5	3	5	2

Other Comprehensive Income (L_3

Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	$ 27,744	$ 27,737	$ 26,001	$ 26,882
Other comprehensive income (loss) before reclassification adjustments, pretax	(143)	106	(362)	364
Tax	77	(72)	79	(65)
Other comprehensive income (loss) before reclassification adjustments, net of taxes	(66)	34	(283)	299
Reclassification adjustments, pretax	94	(75)	121	(176)
Tax	(18)	13	(28)	32
Reclassification adjustments, net of taxes	76	(62)	93	(144)
Other comprehensive income (loss), net of taxes	10	(28)	(190)	155
Equity, ending balance	29,270	26,925	29,270	26,925
Derivatives
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	15	66	31	166
Other comprehensive income (loss) before reclassification adjustments, pretax	(195)	186	(126)	183
Tax	41	(39)	27	(38)
Other comprehensive income (loss) before reclassification adjustments, net of taxes	(154)	147	(99)	145
Reclassification adjustments, pretax	22	(71)	(68)	(195)
Tax	(5)	15	14	41
Reclassification adjustments, net of taxes	17	(56)	(54)	(154)
Other comprehensive income (loss), net of taxes	(137)	91	(153)	(9)
Equity, ending balance	(122)	157	(122)	157
Investments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	0	48	18	(78)
Other comprehensive income (loss) before reclassification adjustments, pretax	0	8	3	139
Tax	0	0	0	0
Other comprehensive income (loss) before reclassification adjustments, net of taxes	0	8	3	139
Reclassification adjustments, pretax	0	(25)	(21)	(30)
Tax	0	0	0	0
Reclassification adjustments, net of taxes	0	(25)	(21)	(30)
Other comprehensive income (loss), net of taxes	0	(17)	(18)	109
Equity, ending balance	0	31	0	31
Employee Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	(4,162)	(3,530)	(4,261)	(3,556)
Other comprehensive income (loss) before reclassification adjustments, pretax	2	(4)	(19)	(5)
Tax	1	0	12	6
Other comprehensive income (loss) before reclassification adjustments, net of taxes	3	(4)	(7)	1
Reclassification adjustments, pretax	72	21	210	49
Tax	(13)	(2)	(42)	(9)
Reclassification adjustments, net of taxes	59	19	168	40
Other comprehensive income (loss), net of taxes	62	15	161	41
Equity, ending balance	(4,100)	(3,515)	(4,100)	(3,515)
Cumulative Translation Adjustment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	(2,246)	(1,946)	(1,981)	(2,077)
Other comprehensive income (loss) before reclassification adjustments, pretax	50	(84)	(220)	47
Tax	35	(33)	40	(33)
Other comprehensive income (loss) before reclassification adjustments, net of taxes	85	(117)	(180)	14
Reclassification adjustments, pretax	0	0	0	0
Tax	0	0	0	0
Reclassification adjustments, net of taxes	0	0	0	0
Other comprehensive income (loss), net of taxes	85	(117)	(180)	14
Equity, ending balance	(2,161)	(2,063)	(2,161)	(2,063)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	(6,393)	(5,362)	(6,193)	(5,545)
Equity, ending balance	$ (6,383)	$ (5,390)	$ (6,383)	$ (5,390)

Segment Reporting - Narrative (

Segment Reporting - Narrative (Details) $ in Billions	3 Months Ended		9 Months Ended
	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)segment	Sep. 30, 2019USD ($)
Segment Reporting [Abstract]
Number of operating segments | segment			3
Sales discounts | $	$ 3.4	$ 3	$ 9.6	$ 8.6

Segment Reporting - Sales of Co

Segment Reporting - Sales of Company's Products (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Sales	$ 12,551	$ 12,397	$ 35,479	$ 34,972
Operating Segments
Segment Reporting Information [Line Items]
Sales	12,540	12,263	35,212	34,622
Other
Segment Reporting Information [Line Items]
Sales	11	134	267	350
United States
Segment Reporting Information [Line Items]
Sales	5,625	5,573	15,396	15,320
United States | Operating Segments
Segment Reporting Information [Line Items]
Sales	5,616	5,563	15,349	15,301
United States | Other
Segment Reporting Information [Line Items]
Sales	9	10	47	19
International
Segment Reporting Information [Line Items]
Sales	6,926	6,824	20,084	19,652
International | Operating Segments
Segment Reporting Information [Line Items]
Sales	6,924	6,699	19,863	19,322
International | Other
Segment Reporting Information [Line Items]
Sales	2	125	221	330
Total Pharmaceutical segment sales | Operating Segments
Segment Reporting Information [Line Items]
Sales	11,320	11,095	31,654	31,218
Total Pharmaceutical segment sales | Operating Segments | Keytruda
Segment Reporting Information [Line Items]
Sales	3,715	3,070	10,387	7,973
Total Pharmaceutical segment sales | Operating Segments | Alliance revenue - Lynparza (1)
Segment Reporting Information [Line Items]
Sales	196	123	519	313
Total Pharmaceutical segment sales | Operating Segments | Alliance revenue - Lenvima (1)
Segment Reporting Information [Line Items]
Sales	142	109	421	280
Total Pharmaceutical segment sales | Operating Segments | Emend
Segment Reporting Information [Line Items]
Sales	39	98	115	336
Total Pharmaceutical segment sales | Operating Segments | Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	1,187	1,320	2,941	3,044
Total Pharmaceutical segment sales | Operating Segments | ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	576	623	1,390	1,794
Total Pharmaceutical segment sales | Operating Segments | Pneumovax 23
Segment Reporting Information [Line Items]
Sales	375	237	748	592
Total Pharmaceutical segment sales | Operating Segments | RotaTeq
Segment Reporting Information [Line Items]
Sales	210	180	601	564
Total Pharmaceutical segment sales | Operating Segments | Vaqta
Segment Reporting Information [Line Items]
Sales	51	62	139	167
Total Pharmaceutical segment sales | Operating Segments | Bridion
Segment Reporting Information [Line Items]
Sales	320	284	843	817
Total Pharmaceutical segment sales | Operating Segments | Noxafil
Segment Reporting Information [Line Items]
Sales	79	177	247	560
Total Pharmaceutical segment sales | Operating Segments | Prevymis
Segment Reporting Information [Line Items]
Sales	77	45	200	115
Total Pharmaceutical segment sales | Operating Segments | Primaxin
Segment Reporting Information [Line Items]
Sales	74	77	189	207
Total Pharmaceutical segment sales | Operating Segments | Invanz
Segment Reporting Information [Line Items]
Sales	51	57	159	206
Total Pharmaceutical segment sales | Operating Segments | Cancidas
Segment Reporting Information [Line Items]
Sales	50	62	148	191
Total Pharmaceutical segment sales | Operating Segments | Cubicin
Segment Reporting Information [Line Items]
Sales	39	52	116	207
Total Pharmaceutical segment sales | Operating Segments | Zerbaxa
Segment Reporting Information [Line Items]
Sales	43	35	112	88
Total Pharmaceutical segment sales | Operating Segments | Simponi
Segment Reporting Information [Line Items]
Sales	209	203	615	625
Total Pharmaceutical segment sales | Operating Segments | Remicade
Segment Reporting Information [Line Items]
Sales	82	101	242	322
Total Pharmaceutical segment sales | Operating Segments | Belsomra
Segment Reporting Information [Line Items]
Sales	81	80	244	223
Total Pharmaceutical segment sales | Operating Segments | Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	205	250	646	752
Total Pharmaceutical segment sales | Operating Segments | Zepatier
Segment Reporting Information [Line Items]
Sales	28	83	122	304
Total Pharmaceutical segment sales | Operating Segments | Zetia
Segment Reporting Information [Line Items]
Sales	103	147	384	443
Total Pharmaceutical segment sales | Operating Segments | Vytorin
Segment Reporting Information [Line Items]
Sales	47	57	139	231
Total Pharmaceutical segment sales | Operating Segments | Atozet
Segment Reporting Information [Line Items]
Sales	111	97	348	283
Total Pharmaceutical segment sales | Operating Segments | Alliance revenue - Adempas (2)
Segment Reporting Information [Line Items]
Sales	83	50	216	144
Total Pharmaceutical segment sales | Operating Segments | Adempas
Segment Reporting Information [Line Items]
Sales	55	57	167	158
Total Pharmaceutical segment sales | Operating Segments | Januvia
Segment Reporting Information [Line Items]
Sales	821	807	2,449	2,539
Total Pharmaceutical segment sales | Operating Segments | Janumet
Segment Reporting Information [Line Items]
Sales	506	503	1,499	1,567
Total Pharmaceutical segment sales | Operating Segments | Implanon/Nexplanon
Segment Reporting Information [Line Items]
Sales	189	199	515	581
Total Pharmaceutical segment sales | Operating Segments | NuvaRing
Segment Reporting Information [Line Items]
Sales	58	241	184	700
Total Pharmaceutical segment sales | Operating Segments | Singulair
Segment Reporting Information [Line Items]
Sales	82	152	338	503
Total Pharmaceutical segment sales | Operating Segments | Cozaar/Hyzaar
Segment Reporting Information [Line Items]
Sales	91	116	292	329
Total Pharmaceutical segment sales | Operating Segments | Arcoxia
Segment Reporting Information [Line Items]
Sales	68	72	204	221
Total Pharmaceutical segment sales | Operating Segments | Nasonex
Segment Reporting Information [Line Items]
Sales	41	58	161	226
Total Pharmaceutical segment sales | Operating Segments | Follistim AQ
Segment Reporting Information [Line Items]
Sales	50	62	136	182
Total Pharmaceutical segment sales | Operating Segments | Other pharmaceutical (3)
Segment Reporting Information [Line Items]
Sales	1,186	1,149	3,478	3,431
Total Pharmaceutical segment sales | United States | Operating Segments
Segment Reporting Information [Line Items]
Sales	5,218	5,180	14,202	14,202
Total Pharmaceutical segment sales | United States | Operating Segments | Keytruda
Segment Reporting Information [Line Items]
Sales	2,157	1,743	6,106	4,525
Total Pharmaceutical segment sales | United States | Operating Segments | Alliance revenue - Lynparza (1)
Segment Reporting Information [Line Items]
Sales	107	71	297	186
Total Pharmaceutical segment sales | United States | Operating Segments | Alliance revenue - Lenvima (1)
Segment Reporting Information [Line Items]
Sales	82	65	270	169
Total Pharmaceutical segment sales | United States | Operating Segments | Emend
Segment Reporting Information [Line Items]
Sales	8	42	18	173
Total Pharmaceutical segment sales | United States | Operating Segments | Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	579	761	1,209	1,579
Total Pharmaceutical segment sales | United States | Operating Segments | ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	437	482	1,033	1,325
Total Pharmaceutical segment sales | United States | Operating Segments | Pneumovax 23
Segment Reporting Information [Line Items]
Sales	276	179	478	428
Total Pharmaceutical segment sales | United States | Operating Segments | RotaTeq
Segment Reporting Information [Line Items]
Sales	114	102	355	360
Total Pharmaceutical segment sales | United States | Operating Segments | Vaqta
Segment Reporting Information [Line Items]
Sales	32	36	79	103
Total Pharmaceutical segment sales | United States | Operating Segments | Bridion
Segment Reporting Information [Line Items]
Sales	162	133	412	381
Total Pharmaceutical segment sales | United States | Operating Segments | Noxafil
Segment Reporting Information [Line Items]
Sales	13	77	27	268
Total Pharmaceutical segment sales | United States | Operating Segments | Prevymis
Segment Reporting Information [Line Items]
Sales	32	22	87	60
Total Pharmaceutical segment sales | United States | Operating Segments | Primaxin
Segment Reporting Information [Line Items]
Sales	1	2	2	2
Total Pharmaceutical segment sales | United States | Operating Segments | Invanz
Segment Reporting Information [Line Items]
Sales	1	(1)	7	30
Total Pharmaceutical segment sales | United States | Operating Segments | Cancidas
Segment Reporting Information [Line Items]
Sales	1	0	2	5
Total Pharmaceutical segment sales | United States | Operating Segments | Cubicin
Segment Reporting Information [Line Items]
Sales	11	14	36	78
Total Pharmaceutical segment sales | United States | Operating Segments | Zerbaxa
Segment Reporting Information [Line Items]
Sales	20	20	57	45
Total Pharmaceutical segment sales | United States | Operating Segments | Simponi
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Total Pharmaceutical segment sales | United States | Operating Segments | Remicade
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Total Pharmaceutical segment sales | United States | Operating Segments | Belsomra
Segment Reporting Information [Line Items]
Sales	18	23	67	68
Total Pharmaceutical segment sales | United States | Operating Segments | Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	92	102	243	304
Total Pharmaceutical segment sales | United States | Operating Segments | Zepatier
Segment Reporting Information [Line Items]
Sales	6	24	38	96
Total Pharmaceutical segment sales | United States | Operating Segments | Zetia
Segment Reporting Information [Line Items]
Sales	(1)	5	(4)	11
Total Pharmaceutical segment sales | United States | Operating Segments | Vytorin
Segment Reporting Information [Line Items]
Sales	3	5	9	11
Total Pharmaceutical segment sales | United States | Operating Segments | Atozet
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Total Pharmaceutical segment sales | United States | Operating Segments | Alliance revenue - Adempas (2)
Segment Reporting Information [Line Items]
Sales	78	48	200	137
Total Pharmaceutical segment sales | United States | Operating Segments | Adempas
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Total Pharmaceutical segment sales | United States | Operating Segments | Januvia
Segment Reporting Information [Line Items]
Sales	342	367	1,110	1,223
Total Pharmaceutical segment sales | United States | Operating Segments | Janumet
Segment Reporting Information [Line Items]
Sales	105	129	361	462
Total Pharmaceutical segment sales | United States | Operating Segments | Implanon/Nexplanon
Segment Reporting Information [Line Items]
Sales	137	136	374	421
Total Pharmaceutical segment sales | United States | Operating Segments | NuvaRing
Segment Reporting Information [Line Items]
Sales	24	202	85	593
Total Pharmaceutical segment sales | United States | Operating Segments | Singulair
Segment Reporting Information [Line Items]
Sales	4	11	14	24
Total Pharmaceutical segment sales | United States | Operating Segments | Cozaar/Hyzaar
Segment Reporting Information [Line Items]
Sales	5	6	17	16
Total Pharmaceutical segment sales | United States | Operating Segments | Arcoxia
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Total Pharmaceutical segment sales | United States | Operating Segments | Nasonex
Segment Reporting Information [Line Items]
Sales	0	4	9	2
Total Pharmaceutical segment sales | United States | Operating Segments | Follistim AQ
Segment Reporting Information [Line Items]
Sales	20	27	60	80
Total Pharmaceutical segment sales | United States | Operating Segments | Other pharmaceutical (3)
Segment Reporting Information [Line Items]
Sales	352	343	1,144	1,037
Total Pharmaceutical segment sales | International | Operating Segments
Segment Reporting Information [Line Items]
Sales	6,102	5,914	17,452	17,016
Total Pharmaceutical segment sales | International | Operating Segments | Keytruda
Segment Reporting Information [Line Items]
Sales	1,559	1,327	4,281	3,448
Total Pharmaceutical segment sales | International | Operating Segments | Alliance revenue - Lynparza (1)
Segment Reporting Information [Line Items]
Sales	89	53	223	126
Total Pharmaceutical segment sales | International | Operating Segments | Alliance revenue - Lenvima (1)
Segment Reporting Information [Line Items]
Sales	60	44	152	112
Total Pharmaceutical segment sales | International | Operating Segments | Emend
Segment Reporting Information [Line Items]
Sales	31	56	96	163
Total Pharmaceutical segment sales | International | Operating Segments | Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	608	558	1,732	1,464
Total Pharmaceutical segment sales | International | Operating Segments | ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	139	141	356	469
Total Pharmaceutical segment sales | International | Operating Segments | Pneumovax 23
Segment Reporting Information [Line Items]
Sales	99	58	270	164
Total Pharmaceutical segment sales | International | Operating Segments | RotaTeq
Segment Reporting Information [Line Items]
Sales	96	78	246	203
Total Pharmaceutical segment sales | International | Operating Segments | Vaqta
Segment Reporting Information [Line Items]
Sales	19	26	60	65
Total Pharmaceutical segment sales | International | Operating Segments | Bridion
Segment Reporting Information [Line Items]
Sales	157	151	431	437
Total Pharmaceutical segment sales | International | Operating Segments | Noxafil
Segment Reporting Information [Line Items]
Sales	66	100	220	291
Total Pharmaceutical segment sales | International | Operating Segments | Prevymis
Segment Reporting Information [Line Items]
Sales	46	23	113	55
Total Pharmaceutical segment sales | International | Operating Segments | Primaxin
Segment Reporting Information [Line Items]
Sales	73	75	187	204
Total Pharmaceutical segment sales | International | Operating Segments | Invanz
Segment Reporting Information [Line Items]
Sales	50	58	152	176
Total Pharmaceutical segment sales | International | Operating Segments | Cancidas
Segment Reporting Information [Line Items]
Sales	49	62	147	187
Total Pharmaceutical segment sales | International | Operating Segments | Cubicin
Segment Reporting Information [Line Items]
Sales	28	38	80	129
Total Pharmaceutical segment sales | International | Operating Segments | Zerbaxa
Segment Reporting Information [Line Items]
Sales	23	15	54	43
Total Pharmaceutical segment sales | International | Operating Segments | Simponi
Segment Reporting Information [Line Items]
Sales	209	203	615	625
Total Pharmaceutical segment sales | International | Operating Segments | Remicade
Segment Reporting Information [Line Items]
Sales	82	101	242	322
Total Pharmaceutical segment sales | International | Operating Segments | Belsomra
Segment Reporting Information [Line Items]
Sales	63	57	177	155
Total Pharmaceutical segment sales | International | Operating Segments | Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	113	149	403	449
Total Pharmaceutical segment sales | International | Operating Segments | Zepatier
Segment Reporting Information [Line Items]
Sales	22	59	83	208
Total Pharmaceutical segment sales | International | Operating Segments | Zetia
Segment Reporting Information [Line Items]
Sales	103	142	389	432
Total Pharmaceutical segment sales | International | Operating Segments | Vytorin
Segment Reporting Information [Line Items]
Sales	44	52	130	219
Total Pharmaceutical segment sales | International | Operating Segments | Atozet
Segment Reporting Information [Line Items]
Sales	111	97	348	283
Total Pharmaceutical segment sales | International | Operating Segments | Alliance revenue - Adempas (2)
Segment Reporting Information [Line Items]
Sales	5	2	16	7
Total Pharmaceutical segment sales | International | Operating Segments | Adempas
Segment Reporting Information [Line Items]
Sales	55	57	167	158
Total Pharmaceutical segment sales | International | Operating Segments | Januvia
Segment Reporting Information [Line Items]
Sales	479	440	1,339	1,317
Total Pharmaceutical segment sales | International | Operating Segments | Janumet
Segment Reporting Information [Line Items]
Sales	400	375	1,138	1,105
Total Pharmaceutical segment sales | International | Operating Segments | Implanon/Nexplanon
Segment Reporting Information [Line Items]
Sales	52	62	142	160
Total Pharmaceutical segment sales | International | Operating Segments | NuvaRing
Segment Reporting Information [Line Items]
Sales	34	39	98	107
Total Pharmaceutical segment sales | International | Operating Segments | Singulair
Segment Reporting Information [Line Items]
Sales	78	140	324	479
Total Pharmaceutical segment sales | International | Operating Segments | Cozaar/Hyzaar
Segment Reporting Information [Line Items]
Sales	86	110	275	313
Total Pharmaceutical segment sales | International | Operating Segments | Arcoxia
Segment Reporting Information [Line Items]
Sales	68	72	204	221
Total Pharmaceutical segment sales | International | Operating Segments | Nasonex
Segment Reporting Information [Line Items]
Sales	41	55	152	224
Total Pharmaceutical segment sales | International | Operating Segments | Follistim AQ
Segment Reporting Information [Line Items]
Sales	31	35	76	102
Total Pharmaceutical segment sales | International | Operating Segments | Other pharmaceutical (3)
Segment Reporting Information [Line Items]
Sales	834	804	2,334	2,394
Total Animal Health segment sales | Operating Segments
Segment Reporting Information [Line Items]
Sales	1,220	1,122	3,535	3,271
Total Animal Health segment sales | Operating Segments | Livestock
Segment Reporting Information [Line Items]
Sales	758	726	2,145	2,007
Total Animal Health segment sales | Operating Segments | Companion Animals
Segment Reporting Information [Line Items]
Sales	462	396	1,390	1,264
Total Animal Health segment sales | United States | Operating Segments
Segment Reporting Information [Line Items]
Sales	398	337	1,124	966
Total Animal Health segment sales | United States | Operating Segments | Livestock
Segment Reporting Information [Line Items]
Sales	164	144	448	406
Total Animal Health segment sales | United States | Operating Segments | Companion Animals
Segment Reporting Information [Line Items]
Sales	234	193	676	560
Total Animal Health segment sales | International | Operating Segments
Segment Reporting Information [Line Items]
Sales	822	785	2,411	2,305
Total Animal Health segment sales | International | Operating Segments | Livestock
Segment Reporting Information [Line Items]
Sales	594	582	1,697	1,601
Total Animal Health segment sales | International | Operating Segments | Companion Animals
Segment Reporting Information [Line Items]
Sales	228	203	714	704
Other segment sales (4) | Operating Segments
Segment Reporting Information [Line Items]
Sales	0	46	23	133
Other segment sales (4) | United States | Operating Segments
Segment Reporting Information [Line Items]
Sales	0	46	23	133
Other segment sales (4) | International | Operating Segments
Segment Reporting Information [Line Items]
Sales	$ 0	$ 0	$ 0	$ 1

Segment Reporting - Revenues by

Segment Reporting - Revenues by Geographic Area (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue from External Customer [Line Items]
Sales	$ 12,551	$ 12,397	$ 35,479	$ 34,972
United States
Revenue from External Customer [Line Items]
Sales	5,625	5,573	15,396	15,320
Europe, Middle East and Africa
Revenue from External Customer [Line Items]
Sales	3,454	3,189	10,059	9,452
China
Revenue from External Customer [Line Items]
Sales	1,016	914	2,715	2,423
Japan
Revenue from External Customer [Line Items]
Sales	828	919	2,506	2,639
Asia Pacific (other than China and Japan)
Revenue from External Customer [Line Items]
Sales	735	756	2,129	2,217
Latin America
Revenue from External Customer [Line Items]
Sales	604	671	1,670	1,889
Other
Revenue from External Customer [Line Items]
Sales	$ 289	$ 375	$ 1,004	$ 1,032

Segment Reporting - Profits to

Segment Reporting - Profits to Income Before Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Profits	$ 3,428	$ 2,347	$ 10,784	$ 8,673
Interest income	9	61	48	225
Interest expense	(203)	(231)	(624)	(674)
Depreciation and amortization			(2,721)	(2,716)
Research and development	(3,390)	(3,204)	(7,721)	(7,324)
Restructuring costs	(114)	(232)	(269)	(444)
Total segment profits
Segment Reporting Information [Line Items]
Profits	8,424	8,168	23,347	22,678
Total segment profits | Pharmaceutical segment
Segment Reporting Information [Line Items]
Profits	7,974	7,747	22,010	21,437
Total segment profits | Animal Health segment
Segment Reporting Information [Line Items]
Profits	451	423	1,336	1,243
Total segment profits | Other segment
Segment Reporting Information [Line Items]
Profits	(1)	(2)	1	(2)
Other profits
Segment Reporting Information [Line Items]
Profits	(12)	101	188	226
Unallocated
Segment Reporting Information [Line Items]
Interest income	9	61	48	225
Interest expense	(203)	(231)	(624)	(674)
Depreciation and amortization	(395)	(382)	(1,173)	(1,169)
Research and development	(3,272)	(3,110)	(7,364)	(7,045)
Amortization of purchase accounting adjustments	(285)	(329)	(879)	(1,105)
Restructuring costs	(114)	(232)	(269)	(444)
Other unallocated, net	$ (724)	$ (1,699)	$ (2,490)	$ (4,019)