Merck & Co. (MRK) 10-K 27 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	MRK
Entity Registrant Name	Merck & Co., Inc.
Entity Central Index Key	310,158
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		2,696,190,502
Entity Public Float			$ 174,700

Consolidated Statement of Incom

Consolidated Statement of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Sales	$ 40,122	$ 39,807	$ 39,498
Costs, Expenses and Other
Materials and production	12,775	13,891	14,934
Marketing and administrative	9,830	9,762	10,313
Research and development	10,208	10,124	6,704
Restructuring costs	776	651	619
Other (income) expense, net	12	720	1,527
Total Costs, Expenses and Other	33,601	35,148	34,097
Income Before Taxes	6,521	4,659	5,401
Taxes on Income	4,103	718	942
Net Income	2,418	3,941	4,459
Less: Net Income Attributable to Noncontrolling Interests	24	21	17
Net Income Attributable to Merck & Co., Inc.	$ 2,394	$ 3,920	$ 4,442
Basic Earnings per Common Share Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share)	$ 0.88	$ 1.42	$ 1.58
Earnings per Common Share Assuming Dilution Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share)	$ 0.87	$ 1.41	$ 1.56

Consolidated Statement of Compr

Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net Income Attributable to Merck & Co., Inc.	$ 2,394	$ 3,920	$ 4,442
Other Comprehensive Income (Loss) Net of Taxes:
Net unrealized loss on derivatives, net of reclassifications	(446)	(66)	(126)
Net unrealized loss on investments, net of reclassifications	(58)	(44)	(70)
Benefit plan net gain (loss) and prior service credit (cost), net of amortization	419	(799)	579
Cumulative translation adjustment	401	(169)	(208)
Other comprehensive income (loss), net of taxes	316	(1,078)	175
Comprehensive Income Attributable to Merck & Co., Inc.	$ 2,710	$ 2,842	$ 4,617

Consolidated Balance Sheet

Consolidated Balance Sheet - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current Assets
Cash and cash equivalents	$ 6,092	$ 6,515
Short-term investments	2,406	7,826
Accounts receivable (net of allowance for doubtful accounts of $210 in 2017 and $195 in 2016)	6,873	7,018
Inventories (excludes inventories of $1,187 in 2017 and $1,117 in 2016 classified in Other assets - see Note 7)	5,096	4,866
Other current assets	4,299	4,389
Total current assets	24,766	30,614
Investments	12,125	11,416
Property, Plant and Equipment (at cost)
Land	365	412
Buildings	11,726	11,439
Machinery, equipment and office furnishings	14,649	14,053
Construction in progress	2,301	1,871
Property, plant and equipment (at cost)	29,041	27,775
Less: accumulated depreciation	16,602	15,749
Property, plant and equipment, net	12,439	12,026
Goodwill	18,284	18,162
Other Intangibles, Net	14,183	17,305
Other Assets	6,075	5,854
Total Assets	87,872	95,377
Current Liabilities
Loans payable and current portion of long-term debt	3,057	568
Trade accounts payable	3,102	2,807
Accrued and other current liabilities	10,427	10,274
Income taxes payable	708	2,239
Dividends payable	1,320	1,316
Total current liabilities	18,614	17,204
Long-Term Debt	21,353	24,274
Deferred Income Taxes	2,219	5,077
Other Noncurrent Liabilities	11,117	8,514
Merck & Co., Inc. Stockholders’ Equity
Common stock, $0.50 par value Authorized - 6,500,000,000 shares Issued - 3,577,103,522 shares in 2017 and 2016	1,788	1,788
Other paid-in capital	39,902	39,939
Retained earnings	41,350	44,133
Accumulated other comprehensive loss	(4,910)	(5,226)
Stockholders' equity before deduction for treasury stock	78,130	80,634
Less treasury stock, at cost: 880,491,914 shares in 2017 and 828,372,200 shares in 2016	43,794	40,546
Total Merck & Co., Inc. stockholders’ equity	34,336	40,088
Noncontrolling Interests	233	220
Total equity	34,569	40,308
Total Liabilities and Equity	$ 87,872	$ 95,377

Consolidated Balance Sheet (Par

Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 210	$ 195
Inventories classified in other assets	$ 1,187	$ 1,117
Common stock, par value (in dollars per share)	$ 0.50	$ 0.50
Common stock, shares authorized (in 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 (in shares)	880,491,914	828,372,200

Consolidated Statement of Equit

Consolidated Statement of Equity - USD ($) $ in Millions	Total	Common Stock	Other Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock	Non- controlling Interests
Beginning Balance at Dec. 31, 2014	$ 48,791	$ 1,788	$ 40,423	$ 46,021	$ (4,323)	$ (35,262)	$ 144
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income Attributable to Merck & Co., Inc.	4,442			4,442
Other comprehensive income (loss), net of taxes	175				175
Cash dividends declared on common stock ($1.89 per share in 2017, $1.85 per share in 2016 and $1.81 per share in 2015)	(5,115)			(5,115)
Treasury stock shares purchased	(4,186)					(4,186)
Changes in noncontrolling ownership interests	(75)		(20)				(55)
Net income attributable to noncontrolling interests	17						17
Distributions attributable to noncontrolling interests	(15)						(15)
Share-based compensation plans and other	733		(181)			914
Ending Balance at Dec. 31, 2015	44,767	1,788	40,222	45,348	(4,148)	(38,534)	91
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income Attributable to Merck & Co., Inc.	3,920			3,920
Other comprehensive income (loss), net of taxes	(1,078)				(1,078)
Cash dividends declared on common stock ($1.89 per share in 2017, $1.85 per share in 2016 and $1.81 per share in 2015)	(5,135)			(5,135)
Treasury stock shares purchased	(3,434)					(3,434)
Changes in noncontrolling ownership interests	124						124
Net income attributable to noncontrolling interests	21						21
Distributions attributable to noncontrolling interests	(16)						(16)
Share-based compensation plans and other	1,139		(283)			1,422
Ending Balance at Dec. 31, 2016	40,308	1,788	39,939	44,133	(5,226)	(40,546)	220
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income Attributable to Merck & Co., Inc.	2,394			2,394
Other comprehensive income (loss), net of taxes	316				316
Cash dividends declared on common stock ($1.89 per share in 2017, $1.85 per share in 2016 and $1.81 per share in 2015)	(5,177)			(5,177)
Treasury stock shares purchased	(4,014)					(4,014)
Changes in noncontrolling ownership interests	7						7
Net income attributable to noncontrolling interests	24						24
Distributions attributable to noncontrolling interests	(18)						(18)
Share-based compensation plans and other	729		(37)			766
Ending Balance at Dec. 31, 2017	$ 34,569	$ 1,788	$ 39,902	$ 41,350	$ (4,910)	$ (43,794)	$ 233

Consolidated Statement of Equi7

Consolidated Statement of Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Common stock, dividends declared (in dollars per share)	$ 1.89	$ 1.85	$ 1.81

Consolidated Statement of Cash

Consolidated Statement of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flows from Operating Activities
Net income	$ 2,418	$ 3,941	$ 4,459
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	4,637	5,441	6,375
Intangible asset impairment charges	646	3,948	162
Provisional charge for one-time transition tax related to the enactment of U.S. tax legislation	5,347	0	0
Charge for future payments related to AstraZeneca collaboration license options	500	0	0
Charge related to the settlement of worldwide Keytruda patent litigation	0	625	0
Foreign currency devaluation related to Venezuela	0	0	876
Net charge related to the settlement of Vioxx shareholder class action litigation	0	0	680
Equity income from affiliates	(42)	(86)	(205)
Dividends and distributions from equity method affiliates	2	16	50
Deferred income taxes	(2,621)	(1,521)	(764)
Share-based compensation	312	300	299
Other	269	313	874
Net changes in assets and liabilities:
Accounts receivable	297	(619)	(480)
Inventories	(145)	206	805
Trade accounts payable	254	278	(37)
Accrued and other current liabilities	(922)	(2,018)	(8)
Income taxes payable	(3,291)	124	(266)
Noncurrent liabilities	(123)	(809)	(277)
Other	(1,091)	237	(5)
Net Cash Provided by Operating Activities	6,447	10,376	12,538
Cash Flows from Investing Activities
Capital expenditures	(1,888)	(1,614)	(1,283)
Purchases of securities and other investments	(10,739)	(15,651)	(16,681)
Proceeds from sales of securities and other investments	15,664	14,353	20,413
Acquisition of Cubist Pharmaceuticals, Inc., net of cash acquired	0	0	(7,598)
Acquisitions of other businesses, net of cash acquired	(396)	(780)	(146)
Dispositions of businesses, net of cash divested	0	0	316
Other	38	482	221
Net Cash Provided by (Used in) Investing Activities	2,679	(3,210)	(4,758)
Cash Flows from Financing Activities
Net change in short-term borrowings	(26)	0	(1,540)
Payments on debt	(1,103)	(2,386)	(2,906)
Proceeds from issuance of debt	0	1,079	7,938
Purchases of treasury stock	(4,014)	(3,434)	(4,186)
Dividends paid to stockholders	(5,167)	(5,124)	(5,117)
Proceeds from exercise of stock options	499	939	485
Other	(195)	(118)	(61)
Net Cash Used in Financing Activities	(10,006)	(9,044)	(5,387)
Effect of Exchange Rate Changes on Cash and Cash Equivalents	457	(131)	(1,310)
Net (Decrease) Increase in Cash and Cash Equivalents	(423)	(2,009)	1,083
Cash and Cash Equivalents at Beginning of Year	6,515	8,524	7,441
Cash and Cash Equivalents at End of Year	$ 6,092	$ 6,515	$ 8,524

Nature of Operations

Nature of Operations	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations	Nature of Operations Merck & Co., Inc. (Merck or the Company) is a global health care company that delivers innovative health solutions through its prescription medicines, vaccines, biologic therapies and animal health products. The Company’s operations are principally managed on a products basis and include four operating segments, which are the Pharmaceutical, Animal Health, Healthcare Services and Alliances segments. The Pharmaceutical segment is the only reportable segment. 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. 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. On December 31, 2016, Merck and Sanofi Pasteur S.A. (Sanofi) terminated their equally-owned joint venture, Sanofi Pasteur MSD (SPMSD), which developed and marketed vaccines in Europe. Beginning in 2017, Merck is recording vaccine sales and incurring costs as a result of operating its vaccines business in the European markets that were previously part of the SPMSD joint venture, which was accounted for as an equity method affiliate. The Company also has an Animal Health segment that discovers, develops, manufactures and markets animal health products, including vaccines, which the Company sells to veterinarians, distributors and animal producers. The Company’s Healthcare Services segment provides services and solutions that focus on engagement, health analytics and clinical services to improve the value of care delivered to patients.

Summary of Accounting Policies

Summary of Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Accounting Policies	Summary of Accounting Policies Principles of Consolidation — The consolidated financial statements include the accounts of the Company and all of its subsidiaries in which a controlling interest is maintained. Intercompany balances and transactions are eliminated. Controlling interest is determined by majority ownership interest and the absence of substantive third-party participating rights or, in the case of variable interest entities, by majority exposure to expected losses, residual returns or both. For those consolidated subsidiaries where Merck ownership is less than 100%, the outside shareholders’ interests are shown as Noncontrolling interests in equity. Investments in affiliates over which the Company has significant influence but not a controlling interest, such as interests in entities owned equally by the Company and a third party that are under shared control, are carried on the equity basis. Acquisitions — In a business combination, the acquisition method of accounting requires that the assets acquired and liabilities assumed be recorded as of the date of the acquisition at their respective fair values with limited exceptions. Assets acquired and liabilities assumed in a business combination that arise from contingencies are generally recognized at fair value. If fair value cannot be determined, the asset or liability is recognized if probable and reasonably estimable; if these criteria are not met, no asset or liability is recognized. 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. Accordingly, the Company may be required to value assets at fair value measures that do not reflect the Company’s intended use of those assets. Any excess of the purchase price (consideration transferred) over the estimated fair values of net assets acquired is recorded as goodwill. Transaction costs and costs to restructure the acquired company are expensed as incurred. The operating results of the acquired business are reflected in the Company’s consolidated financial statements after the date of the acquisition. If the Company determines the assets acquired do not meet the definition of a business under the acquisition method of accounting, the transaction will be accounted for as an acquisition of assets rather than a business combination and, therefore, no goodwill will be recorded. Foreign Currency Translation — The net assets of international subsidiaries where the local currencies have been determined to be the functional currencies are translated into U.S. dollars using current exchange rates. The U.S. dollar effects that arise from translating the net assets of these subsidiaries at changing rates are recorded in the foreign currency translation account, which is included in Accumulated other comprehensive income (loss) ( AOCI ) and reflected as a separate component of equity. For those subsidiaries that operate in highly inflationary economies and for those subsidiaries where the U.S. dollar has been determined to be the functional currency, non-monetary foreign currency assets and liabilities are translated using historical rates, while monetary assets and liabilities are translated at current rates, with the U.S. dollar effects of rate changes included in Other (income) expense, net . Cash Equivalents — Cash equivalents are comprised of certain highly liquid investments with original maturities of less than three months. Inventories — Inventories are valued at the lower of cost or market. The cost of a substantial majority of domestic pharmaceutical and vaccine inventories is determined using the last-in, first-out (LIFO) method for both financial reporting and tax purposes. The cost of all other inventories is determined using the first-in, first-out (FIFO) method. Inventories consist of currently marketed products, as well as certain inventories produced in preparation for product launches that are considered to have a high probability of regulatory approval. In evaluating the recoverability of inventories produced in preparation for product launches, the Company considers the likelihood that revenue will be obtained from the future sale of the related inventory together with the status of the product within the regulatory approval process. Investments — Investments in marketable debt and equity securities classified as available-for-sale are reported at fair value. Fair values of the Company’s investments are determined using quoted market prices in active markets for identical assets or liabilities or 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. Changes in fair value that are considered temporary are reported net of tax in Other Comprehensive Income ( OCI ). For declines in the fair value of equity securities that are considered other-than-temporary, impairment losses are charged to Other (income) expense, net . The Company considers available evidence in evaluating potential impairments of its investments, including the duration and extent to which fair value is less than cost and, for equity securities, the Company’s ability and intent to hold the investments. For debt securities, an other-than-temporary impairment has occurred if the Company does not expect to recover the entire amortized cost basis of the debt security. If the Company does not intend to sell the impaired debt security, and it is not more likely than not it will be required to sell the debt security before the recovery of its amortized cost basis, the amount of the other-than-temporary impairment recognized in earnings, recorded in Other (income) expense, net , is limited to the portion attributed to credit loss. The remaining portion of the other-than-temporary impairment related to other factors is recognized in OCI . Realized gains and losses for both debt and equity securities are included in Other (income) expense, net . Revenue Recognition — Revenues from sales of products are recognized when title and risk of loss passes to the customer, typically upon delivery. Recognition of revenue also requires reasonable assurance of collection of sales proceeds and completion of all performance obligations. Domestically, sales discounts are issued to customers at the point-of-sale, through an intermediary wholesaler (known as chargebacks), or in the form of rebates. Additionally, sales are generally made with a limited right of return under certain conditions. Revenues are recorded net of provisions for sales discounts and returns, which are established at the time of sale. In addition, revenues are recorded net of time value of money discounts if collection of accounts receivable is expected to be in excess of one year. Accruals for chargebacks are reflected as a direct reduction to accounts receivable and accruals for rebates are recorded as current liabilities. The accrued balances relative to the provisions for chargebacks and rebates included in Accounts receivable and Accrued and other current liabilities were $198 million and $2.4 billion , respectively, at December 31, 2017 and $196 million and $2.7 billion , respectively, at December 31, 2016 . The Company recognizes revenue from the sales of vaccines to the Federal government for placement into vaccine stockpiles in accordance with Securities and Exchange Commission (SEC) Interpretation , Commission Guidance Regarding Accounting for Sales of Vaccines and BioTerror Countermeasures to the Federal Government for Placement into the Pediatric Vaccine Stockpile or the Strategic National Stockpile . This interpretation allows companies to recognize revenue for sales of vaccines into U.S. government stockpiles even though these sales might not meet the criteria for revenue recognition under other accounting guidance. Depreciation — Depreciation is provided over the estimated useful lives of the assets, principally using the straight-line method. For tax purposes, accelerated tax methods are used. The estimated useful lives primarily range from 25 to 45 years for Buildings , and from 3 to 15 years for Machinery, equipment and office furnishings . Depreciation expense was $1.5 billion in 2017 , $1.6 billion in 2016 and $1.6 billion in 2015 . Advertising and Promotion Costs — Advertising and promotion costs are expensed as incurred. The Company recorded advertising and promotion expenses of $2.2 billion , $2.1 billion and $2.1 billion in 2017 , 2016 and 2015 , respectively. Software Capitalization — The Company capitalizes certain costs incurred in connection with obtaining or developing internal-use software including external direct costs of material and services, and payroll costs for employees directly involved with the software development. Capitalized software costs are included in Property, plant and equipment and amortized beginning when the software project is substantially complete and the asset is ready for its intended use. Capitalized software costs associated with projects that are being amortized over 6 to 10 years (including the Company’s on-going multi-year implementation of an enterprise-wide resource planning system) were $449 million and $452 million , net of accumulated amortization at December 31, 2017 and 2016 , respectively. All other capitalized software costs are being amortized over periods ranging from 3 to 5 years. Costs incurred during the preliminary project stage and post-implementation stage, as well as maintenance and training costs, are expensed as incurred. Goodwill — Goodwill represents the excess of the consideration transferred over the fair value of net assets of businesses acquired. Goodwill is assigned to reporting units and evaluated for impairment on at least an annual basis, or more frequently if impairment indicators exist, by first assessing qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If the Company concludes it is more likely than not that the fair value of a reporting unit is less than its carrying amount, a quantitative fair value test is performed. Acquired Intangibles — Acquired intangibles include products and product rights, tradenames and patents, which are initially recorded at fair value, assigned an estimated useful life, and are amortized primarily on a straight-line basis over their estimated useful lives ranging from 2 to 20 years (see Note 8). The Company periodically evaluates whether current facts or circumstances indicate that the carrying values of its acquired intangibles may not be recoverable. If such circumstances are determined to exist, an estimate of the undiscounted future cash flows of these assets, or appropriate asset groupings, is compared to the carrying value to determine whether an impairment exists. If the asset is determined to be impaired, the loss is measured based on the difference between the carrying value of the intangible asset and its fair value, which is determined based on the net present value of estimated future cash flows. Acquired In-Process Research and Development — Acquired in-process research and development (IPR&D) that the Company acquires through business combinations represents the fair value assigned to incomplete research projects which, at the time of acquisition, have not reached technological feasibility. The amounts are capitalized and are accounted for as indefinite-lived intangible assets, subject to impairment testing until completion or abandonment of the projects. Upon successful completion of each project, Merck will make a determination as to the then useful life of the intangible asset, generally determined by the period in which the substantial majority of the cash flows are expected to be generated, and begin amortization. The Company tests IPR&D for impairment at least annually, or more frequently if impairment indicators exist, by first assessing qualitative factors to determine whether it is more likely than not that the fair value of the IPR&D intangible asset is less than its carrying amount. If the Company concludes it is more likely than not that the fair value is less than the carrying amount, a quantitative test that compares the fair value of the IPR&D intangible asset with its carrying value is performed. If the fair value is less than the carrying amount, an impairment loss is recognized in operating results. Contingent Consideration — Certain of the Company’s business acquisitions involve the potential for future payment of consideration that is contingent upon the achievement of performance milestones, including product development milestones and royalty payments on future product sales. The fair value of contingent consideration liabilities is determined at the acquisition date using unobservable inputs. These inputs include the estimated amount and timing of projected cash flows, the probability of success (achievement of the contingent event) and the risk-adjusted discount rate used to present value the probability-weighted cash flows. Subsequent to the acquisition date, at each reporting period, the contingent consideration liability is remeasured at current fair value with changes (either expense or income) recorded in earnings. Research and Development — Research and development is expensed as incurred. Nonrefundable advance payments for goods and services that will be used in future research and development activities are expensed when the activity has been performed or when the goods have been received rather than when the payment is made. Research and development expenses include restructuring costs and IPR&D impairment charges in all periods. In addition, research and development expenses include expense or income related to changes in the estimated fair value measurement of liabilities for contingent consideration. 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. Cost reimbursements between the collaborative partners are recognized as incurred and included in Materials and production costs, Marketing and administrative expenses and Research and development expenses based on the underlying nature of the related activities subject to reimbursement. When Merck is the principal on sales transactions with third parties, the Company recognizes sales, materials and production costs and marketing and administrative expenses on a gross basis. The Company records profit sharing amounts received from its collaborative partners as alliance revenue (within Sales ) and profit sharing amounts it pays to its collaborative partners within Materials and production costs. Terms of the collaboration agreements may require the Company to make payments based upon the achievement of certain developmental, regulatory approval or commercial milestones. Upfront and milestone payments payable by Merck to collaborative partners prior to regulatory approval are expensed as incurred and included in Research and development expenses. Payments due to collaborative partners upon or subsequent to regulatory approval are capitalized and amortized over the estimated useful life of the corresponding intangible asset to Materials and production costs provided that future cash flows support the amounts capitalized. Sales-based milestones payable by Merck to collaborative partners are accrued when probable of being achieved and capitalized, subject to cumulative amortization catch-up. The amortization catch-up is calculated either from the time of the first regulatory approval for indications that were unapproved at the time the collaboration was formed, or from time of the formation of the collaboration for approved products. The related intangible asset that is recognized is amortized to Materials and production costs over its remaining useful life, subject to impairment testing. Share-Based Compensation — The Company expenses all share-based payments to employees over the requisite service period based on the grant-date fair value of the awards. Restructuring Costs — The Company records liabilities for costs associated with exit or disposal activities in the period in which the liability is incurred. In accordance with existing benefit arrangements, employee termination costs are accrued when the restructuring actions are probable and estimable. When accruing these costs, the Company will recognize the amount within a range of costs that is the best estimate within the range. When no amount within the range is a better estimate than any other amount, the Company recognizes the minimum amount within the range. Costs for one-time termination benefits in which the employee is required to render service until termination in order to receive the benefits are recognized ratably over the future service period. Contingencies and Legal Defense Costs — The Company records accruals for contingencies and legal defense costs expected to be incurred in connection with a loss contingency when it is probable that a liability has been incurred and the amount can be reasonably estimated. Taxes on Income — Deferred taxes are recognized for the future tax effects of temporary differences between financial and income tax reporting based on enacted tax laws and rates. The Company evaluates tax positions to determine whether the benefits of tax positions are more likely than not of being sustained upon audit based on the technical merits of the tax position. For tax positions that are more likely than not of being sustained upon audit, the Company recognizes the largest amount of the benefit that is greater than 50% likely of being realized upon ultimate settlement in the financial statements. For tax positions that are not more likely than not of being sustained upon audit, the Company does not recognize any portion of the benefit in the financial statements. The Company recognizes interest and penalties associated with uncertain tax positions as a component of Taxes on income in the Consolidated Statement of Income. Use of Estimates — The consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States (GAAP) and, accordingly, include certain amounts that are based on management’s best estimates and judgments. Estimates are used when accounting for amounts recorded in connection with acquisitions, including initial fair value determinations of assets and liabilities, primarily IPR&D, other intangible assets and contingent consideration, as well as subsequent fair value measurements. Additionally, estimates are used in determining such items as provisions for sales discounts and returns, depreciable and amortizable lives, recoverability of inventories, including those produced in preparation for product launches, amounts recorded for contingencies, environmental liabilities and other reserves, pension and other postretirement benefit plan assumptions, share-based compensation assumptions, restructuring costs, impairments of long-lived assets (including intangible assets and goodwill) and investments, and taxes on income. Because of the uncertainty inherent in such estimates, actual results may differ from these estimates. Reclassifications — Certain reclassifications have been made to prior year amounts to conform to the current year presentation. Recently Issued Accounting Standards — In May 2014, the Financial Accounting Standards Board (FASB) issued amended accounting guidance on revenue recognition that will be applied to all contracts with customers. The objective of the new guidance is to improve comparability of revenue recognition practices across entities and to provide more useful information to users of financial statements through improved disclosure requirements. The new standard permits two methods of adoption: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of adopting the guidance being recognized at the date of initial application (modified retrospective method). The new standard will be effective as of January 1, 2018 and will be adopted using the modified retrospective method. The Company anticipates recording a cumulative-effect adjustment upon adoption increasing Retained earnings by $5 million in 2018. The adoption of the new guidance will also result in some additional disclosures. In January 2016, the FASB issued revised guidance for the accounting and reporting of financial instruments. The new guidance requires that equity investments with readily determinable fair values currently classified as available for sale be measured at fair value with changes in fair value recognized in net income. The new guidance also simplifies the impairment testing of equity investments without readily determinable fair values and changes certain disclosure requirements. The new standard will be effective as of January 1, 2018 and will be adopted using a modified retrospective approach. The Company anticipates recording a cumulative-effect adjustment upon adoption increasing Retained earnings by $8 million in 2018. In August 2016, the FASB issued guidance on the classification of certain cash receipts and payments in the statement of cash flows intended to reduce diversity in practice. The new standard is effective as of January 1, 2018 and will be adopted using a retrospective application. The Company does not anticipate any changes to the presentation of its Consolidated Statement of Cash Flows as a result of adopting the new standard. In October 2016, the FASB issued guidance on the accounting for the income tax consequences of intra-entity transfers of assets other than inventory. Under existing guidance, the recognition of current and deferred income taxes for an intra-entity asset transfer is prohibited until the asset has been sold to a third party. The new guidance will require the recognition of the income tax consequences of an intra-entity transfer of an asset (with the exception of inventory) when the intra-entity transfer occurs. The new standard will be effective as of January 1, 2018 and will be adopted using a modified retrospective approach. The Company anticipates recording a cumulative-effect adjustment upon adoption increasing Retained earnings by approximately $60 million in 2018 with a corresponding increase to deferred tax assets, subject to finalization. In November 2016, the FASB issued guidance requiring that amounts generally described as restricted cash and restricted cash equivalents be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The new standard is effective as of January 1, 2018 and will be adopted using a retrospective application. The adoption of the new guidance will not have a material effect on the Company’s Consolidated Statement of Cash Flows. In March 2017, the FASB amended the guidance related to net periodic benefit cost for defined benefit plans that requires entities to (1) disaggregate the current service cost component from the other components of net benefit cost and present it with other employee compensation costs in the income statement within operations if such a subtotal is presented; (2) present the other components of net benefit cost separately in the income statement and outside of income from operations; and (3) only capitalize the service cost component when applicable. Entities must use a retrospective transition method to adopt the requirement for separate presentation in the income statement of service costs and other components and a prospective transition method to adopt the requirement to limit the capitalization of benefit costs to the service cost component. The Company will utilize a practical expedient that permits it to use the amounts disclosed in its pension and other postretirement benefit plan note for the prior comparative periods as the estimation basis for applying the retrospective presentation requirements. The new standard is effective as of January 1, 2018. Net periodic benefit cost (credit) other than service cost was approximately $(510) million and $(530) million for the years ended December 31, 2017 and 2016 , respectively, (see Note 14). Upon adoption, these amounts will be reclassified to Other (income) expense, net from their current classification within Materials and production costs, Marketing and administrative expenses and Research and development costs. In May 2017, the FASB issued guidance clarifying when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new guidance, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. The new standard is effective as of January 1, 2018 and will be applied to future share-based payment award modifications should they occur. In February 2016, the FASB issued new accounting guidance for the accounting and reporting of leases. The new guidance requires that lessees recognize a right-of-use asset and a lease liability recorded on the balance sheet for each of its leases (other than leases that meet the definition of a short-term lease). Leases will be classified as either operating or finance. Operating leases will result in straight-line expense in the income statement (similar to current operating leases) while finance leases will result in more expense being recognized in the earlier years of the lease term (similar to current capital leases). The new guidance will be effective for interim and annual periods beginning in 2019 and will be adopted using a modified retrospective approach which will require application of the new guidance at the beginning of the earliest comparative period presented. Early adoption is permitted. The Company is currently evaluating the impact of adoption on its consolidated financial statements. In August 2017, the FASB issued new guidance on hedge accounting that is intended to more closely align hedge accounting with companies’ risk management strategies, simplify the application of hedge accounting, and increase transparency as to the scope and results of hedging programs. The new guidance makes more financial and nonfinancial hedging strategies eligible for hedge accounting, amends the presentation and disclosure requirements, and changes how companies assess effectiveness. The new guidance is effective for interim and annual periods beginning in 2019 on a modified retrospective basis. Early application is permitted in any interim period. The Company intends to early adopt this guidance as of January 1, 2018 on a modified retrospective basis. The Company anticipates recording a cumulative-effect adjustment upon adoption decreasing Retained earnings by $11 million in 2018.The adoption of the new guidance will result in some additional disclosures. In February 2018, the FASB issued new guidance to address a narrow-scope financial reporting issue that arose as a consequence of the TCJA. Existing guidance requires that deferred tax liabilities and assets be adjusted for a change in tax laws or rates with the effect included in income from continuing operations in the reporting period that includes the enactment date. That guidance is applicable even in situations in which the related income tax effects of items in accumulated other comprehensive income were originally recognized in other comprehensive income (rather than in net income), such as amounts related to benefit plans and hedging activity. As a result, the tax effects of items within accumulated other comprehensive income do not reflect the appropriate tax rate (the difference is referred to as stranded tax effects). The new guidance allows for a reclassification of these amounts to retained earnings thereby eliminating these stranded tax effects. The new guidance is effective for interim and annual periods in 2019. The Company is currently evaluating the impact of adoption on its consolidated financial statements. In June 2016, the FASB issued amended guidance on the accounting for credit losses on financial instruments. The 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 new guidance is effective for interim and annual periods beginning in 2020, with earlier application permitted in 2019. The new guidance is to be applied on a modified retrospective basis through a cumulative-effect adjustment directly to retained earnings in the beginning of the period of adoption. The Company is currently evaluating the impact of adoption on its consolidated financial statements. In January 2017, the FASB issued guidance that provides for the elimination of Step 2 from the goodwill impairment test. Under the new guidance, impairment charges are recognized to the extent the carrying amount of a reporting unit exceeds its fair value with certain limitations. The new guidance is effective for interim and annual periods in 2020. Early adoption is permitted. The Company does not anticipate that the adoption of the new guidance will have a material effect on its consolidated financial statements.

Acquisitions, Divestitures, Res

Acquisitions, Divestitures, Research Collaborations and License Agreements	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisitions, Divestitures, Research Collaborations and License Agreements	Acquisitions, Divestitures, Research Collaborations and License Agreements The Company continues to pursue the acquisition of businesses and 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. Recently Announced Transaction In February 2018, Merck and Viralytics Limited (Viralytics) announced a definitive agreement pursuant to which Merck will acquire Viralytics, an Australian publicly traded company focused on oncolytic immunotherapy treatments for a range of cancers, for AUD 1.75 per share. The proposed acquisition values the total issued shares in Viralytics at approximately AUD 502 million ( $394 million ). Upon completion of the transaction, Merck will gain full rights to Cavatax (CVA21), Viralytics’s investigational oncolytic immunotherapy. The transaction remains subject to a Viralytics’s shareholder vote and customary regulatory approvals. Merck anticipates the transaction will close in the second quarter of 2018. 2017 Transactions In October 2017, Merck acquired Rigontec GmbH (Rigontec). Rigontec is a leader in accessing the retinoic acid-inducible gene I pathway, part of the innate immune system, as a novel and distinct approach in cancer immunotherapy to induce both immediate and long-term anti-tumor immunity. Rigontec’s lead candidate, RGT100, is currently in Phase I development evaluating treatment in patients with various tumors. Under the terms of the agreement, Merck made an upfront cash payment of €119 million ( $140 million ) and may make additional contingent payments of up to €349 million (of which €184 million are related to the achievement of research milestones and regulatory approvals and €165 million are related to the achievement of commercial targets). The transaction was accounted for as an acquisition of an asset and the upfront payment is reflected within Research and development expenses in 2017. In July 2017, Merck and AstraZeneca entered into a global strategic oncology collaboration to co-develop and co-commercialize AstraZeneca’s Lynparza (olaparib) for multiple cancer types (see Note 4). In March 2017, Merck acquired a controlling interest in Vallée S.A. (Vallée), a leading privately held producer of animal health products in Brazil. Vallée has an extensive portfolio of products spanning parasiticides, anti-infectives and vaccines that include products for livestock, horses, and companion animals. Under the terms of the agreement, Merck acquired 93.5% of the shares of Vallée for $358 million . Of the total purchase price, $176 million was placed into escrow pending resolution of certain contingent items. The transaction was accounted for as an acquisition of a business. Merck recognized intangible assets of $291 million related to currently marketed products, net deferred tax liabilities of $93 million , other net assets of $14 million and noncontrolling interest of $25 million . In addition, the Company recorded liabilities of $37 million for contingencies identified at the acquisition date and corresponding indemnification assets of $37 million , representing the amounts to be reimbursed to Merck if and when the contingent liabilities are paid. The excess of the consideration transferred over the fair value of net assets acquired of $171 million was recorded as goodwill. The goodwill was allocated to the Animal Health segment and is not deductible for tax purposes. The estimated fair values of identifiable intangible assets related to currently marketed products were determined using an income approach. The probability-adjusted future net cash flows of each product were discounted to present value utilizing a discount rate of 15.5% . Actual cash flows are likely to be different than those assumed. The intangible assets related to currently marketed products are being amortized over their estimated useful lives of 15 years. In the fourth quarter of 2017, Merck acquired an additional 4.5% interest in Vallée for $18 million , which reduced noncontrolling interest related to Vallée. 2016 Transactions In July 2016, Merck acquired Afferent Pharmaceuticals (Afferent), a privately held pharmaceutical company focused on the development of therapeutic candidates targeting the P2X3 receptor for the treatment of common, poorly-managed, neurogenic conditions. Afferent’s lead investigational candidate, MK-7264 (formerly AF-219), is a selective, non-narcotic, orally-administered P2X3 antagonist being evaluated for the treatment of refractory, chronic cough. Total consideration transferred of $510 million included cash paid for outstanding Afferent shares of $487 million , as well as share-based compensation payments to settle equity awards attributable to precombination service and cash paid for transaction costs on behalf of Afferent. In addition, former Afferent shareholders are eligible to receive a total of up to an additional $750 million contingent upon the attainment of certain clinical development and commercial milestones for multiple indications and candidates, including MK-7264. This transaction was accounted for as an acquisition of a business. The Company determined the fair value of the contingent consideration was $223 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 an intangible asset for IPR&D of $832 million , net deferred tax liabilities of $258 million , and other net assets of $29 million (primarily consisting of cash acquired). The excess of the consideration transferred over the fair value of net assets acquired of $130 million was recorded as goodwill that was allocated to the Pharmaceutical segment and is not deductible for tax purposes. The fair value of the identifiable intangible asset related to IPR&D was determined using an income approach. The asset’s probability-adjusted future net cash flows were discounted to present value using a discount rate of 11.5% . Actual cash flows are likely to be different than those assumed. Also in July 2016, Merck, through its wholly owned subsidiary Healthcare Services & Solutions, LLC, acquired a majority ownership interest in The StayWell Company LLC (StayWell), a portfolio company of Vestar Capital Partners (Vestar). StayWell is a health engagement company that helps its clients engage and educate people to improve health and business results. Under the terms of the transaction, Merck paid $150 million for a majority ownership interest. Additionally, Merck provided StayWell with a $150 million intercompany loan to pay down preexisting third-party debt. Merck has an option to buy, and Vestar has an option to require Merck to buy, some or all of Vestar’s remaining ownership interest at fair value beginning three years from the acquisition date. This transaction was accounted for as an acquisition of a business. Merck recognized intangible assets of $238 million , deferred tax liabilities of $84 million , other net liabilities of $5 million and noncontrolling interest of $124 million . The excess of the consideration transferred over the fair value of net assets acquired of $275 million was recorded as goodwill and is largely attributable to anticipated synergies expected to arise after the acquisition. The goodwill was allocated to the Healthcare Services segment and is not deductible for tax purposes. The intangible assets recognized primarily relate to customer relationships, which are being amortized over a 10 -year useful life, and medical information and solutions content, which are being amortized over a five -year useful life. In June 2016, Merck and Moderna Therapeutics (Moderna) entered into a strategic collaboration and license agreement to develop and commercialize novel messenger RNA (mRNA)-based personalized cancer vaccines. The development program will entail multiple studies in several types of cancer and include the evaluation of mRNA-based personalized cancer vaccines in combination with Merck’s Keytruda . Pursuant to the terms of the agreement, Merck made an upfront cash payment to Moderna of $200 million , which was recorded in Research and development expenses. Following human proof of concept studies, Merck has the right to elect to make an additional payment to Moderna. If Merck exercises this right, the two companies will then equally share costs and profits under a worldwide collaboration for the development of personalized cancer vaccines. Moderna will have the right to elect to co-promote the personalized cancer vaccines in the United States. The agreement entails exclusivity around combinations with Keytruda . Moderna and Merck each have the ability to combine mRNA-based personalized cancer vaccines with other (non-PD-1) agents. In January 2016, Merck acquired IOmet Pharma Ltd (IOmet), a privately held UK-based drug discovery company focused on the development of innovative medicines for the treatment of cancer, with a particular emphasis on the fields of cancer immunotherapy and cancer metabolism. The acquisition provides Merck with IOmet’s preclinical pipeline of IDO (indoleamine-2,3-dioxygenase 1), TDO (tryptophan-2,3-dioxygenase), and dual-acting IDO/TDO inhibitors. The transaction was accounted for as an acquisition of a business. Total purchase consideration in the transaction included a cash payment of $150 million and future additional milestone payments of up to $250 million contingent upon certain clinical and regulatory milestones being achieved. The Company determined the fair value of the contingent consideration was $94 million at the acquisition date utilizing a probability-weighted estimated cash flow stream adjusted for the expected timing of each payment utilizing a discount rate of 10.5% . Merck recognized intangible assets for IPR&D of $155 million and net deferred tax assets of $32 million . The excess of the consideration transferred over the fair value of net assets acquired of $57 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. The assets’ probability-adjusted future net cash flows were discounted to present value also using a discount rate of 10.5% . Actual cash flows are likely to be different than those assumed. In July 2017, Merck made a $100 million payment as a result of the achievement of a clinical development milestone, which was accrued for at estimated fair value at the time of acquisition as noted above. 2015 Transactions In December 2015, the Company divested its remaining ophthalmics portfolio in international markets to Mundipharma Ophthalmology Products Limited. Merck received consideration of approximately $170 million and recognized a gain of $147 million recorded in Other (income) expense, net in 2015. In July 2015, Merck acquired cCAM Biotherapeutics Ltd. (cCAM), a privately held biopharmaceutical company focused on the discovery and development of novel cancer immunotherapies. Total purchase consideration in the transaction included an upfront payment of $96 million in cash and potential future additional payments associated with the attainment of certain clinical development, regulatory and commercial milestones. The transaction was accounted for as an acquisition of a business. Merck recognized an intangible asset for IPR&D of $180 million related to CM-24, a monoclonal antibody, as well as a liability for contingent consideration of $105 million , goodwill of $14 million and other net assets of $7 million . During 2016, as a result of unfavorable efficacy data, the Company determined that it would discontinue development of the pipeline program. Accordingly, the Company recorded an IPR&D impairment charge of $180 million related to CM-24 and reversed the related liability for contingent consideration, which had a fair value of $116 million at the time of program discontinuation. Both the IPR&D impairment charge and the income related to the reduction in the liability for contingent consideration were recorded in Research and development expenses in 2016. Also in July 2015, Merck and Allergan plc (Allergan) entered into an agreement pursuant to which Allergan acquired the exclusive worldwide rights to MK-1602 and MK-8031, Merck’s investigational small molecule oral calcitonin gene-related peptide (CGRP) receptor antagonists, which are being developed for the treatment and prevention of migraine. Under the terms of the agreement, Allergan acquired these rights for upfront payments of $250 million , of which $125 million was paid in August 2015 upon closing of the transaction and the remaining $125 million was paid in April of 2016. The Company recorded a gain of $250 million within Other (income) expense, net in 2015 related to the transaction. Allergan is fully responsible for development of the CGRP programs, as well as manufacturing and commercialization upon approval and launch of the products. Under the agreement, Merck is entitled to receive potential development and commercial milestone payments and royalties at tiered double-digit rates based on commercialization of the programs. During 2016, Merck recognized gains of $100 million within Other (income) expense, net resulting from payments by Allergan for the achievement of research and development milestones. In February 2015, Merck and NGM Biopharmaceuticals, Inc. (NGM), a privately held biotechnology company, entered into a multi-year collaboration to research, discover, develop and commercialize novel biologic therapies across a wide range of therapeutic areas. Under the terms of the agreement, Merck made an upfront payment to NGM of $94 million , which was included in Research and development expenses, and purchased a 15% equity stake in NGM for $106 million . Merck committed up to $250 million to fund all of NGM’s efforts under the initial five -year term of the collaboration, with the potential for additional funding if certain conditions are met. Prior to Merck initiating a Phase 3 study for a licensed program, NGM may elect to either receive milestone and royalty payments or, in certain cases, to co-fund development and participate in a global cost and revenue share arrangement of up to 50% . The agreement also provides NGM with the option to participate in the co-promotion of any co-funded program in the United States. Merck has the option to extend the research agreement for two additional two -year terms. In January 2015, Merck acquired Cubist Pharmaceuticals, Inc. (Cubist), a leader in the development of therapies to treat serious infections caused by a broad range of bacteria. Total consideration transferred of $8.3 billion included cash paid for outstanding Cubist shares of $7.8 billion , as well as share-based compensation payments to settle equity awards attributable to precombination service and cash paid for transaction costs on behalf of Cubist. Share-based compensation payments to settle non-vested equity awards attributable to postcombination service were recognized as transaction expense in 2015. In addition, the Company assumed all of the outstanding convertible debt of Cubist, which had a fair value of approximately $1.9 billion at the acquisition date. Merck redeemed this debt in February 2015. The transaction was accounted for as an acquisition of a business. The estimated fair value of assets acquired and liabilities assumed from Cubist is as follows: Estimated fair value at January 21, 2015 Cash and cash equivalents $ 733 Accounts receivable 123 Inventories 216 Other current assets 55 Property, plant and equipment 151 Identifiable intangible assets: Products and product rights (11 year weighted-average useful life) 6,923 IPR&D 50 Other noncurrent assets 184 Current liabilities (1) (233 ) Deferred income tax liabilities (2,519 ) Long-term debt (1,900 ) Other noncurrent liabilities (1) (122 ) Total identifiable net assets 3,661 Goodwill (2) 4,670 Consideration transferred $ 8,331 (1) Included in current liabilities and other noncurrent liabilities is contingent consideration of $73 million and $50 million , respectively. (2) The goodwill recognized is largely attributable to anticipated synergies expected to arise after the acquisition and was allocated to the Pharmaceutical segment. The goodwill is not deductible for tax purposes. The estimated fair values of identifiable intangible assets related to currently marketed products were determined using an income approach. The Company’s estimates of projected net cash flows considered historical and projected pricing, margins and expense levels; the performance of competing products where applicable; relevant industry and therapeutic area growth drivers and factors; current and expected trends in technology and product life cycles; the extent and timing of potential new product introductions by the Company’s competitors; and the life of each asset’s underlying patent. The net cash flows were probability-adjusted where appropriate to consider the uncertainties associated with the underlying assumptions, as well as the risk profile of the net cash flows utilized in the valuation. The probability-adjusted future net cash flows of each product were then discounted to present value utilizing a discount rate of 8% . Actual cash flows are likely to be different than those assumed. The Company recorded the fair value of incomplete research project surotomycin (MK-4261) which, at the time of acquisition, had not reached technological feasibility and had no alternative future use. During the second quarter of 2015, the Company received unfavorable efficacy data from a clinical trial for surotomycin. The evaluation of this data, combined with an assessment of the commercial opportunity for surotomycin, resulted in the discontinuation of the program and an IPR&D impairment charge (see Note 8). In connection with the Cubist acquisition, liabilities were recorded for potential future consideration that is contingent upon the achievement of future sales-based milestones. The fair value of contingent consideration liabilities was determined at the acquisition date using unobservable inputs. These inputs include the estimated amount and timing of projected cash flows, the probability of success (achievement of the contingent event) and a risk-adjusted discount rate of 8% used to present value the probability-weighted cash flows. Changes in the inputs could result in a different fair value measurement. This transaction closed on January 21, 2015; accordingly, the results of operations of the acquired business have been included in the Company’s results of operations beginning after that date. During 2015, the Company incurred $324 million of transaction costs directly related to the acquisition of Cubist including share-based compensation costs, severance costs, and legal and advisory fees which are reflected in Marketing and administrative expenses. The following unaudited supplemental pro forma data presents consolidated information as if the acquisition of Cubist had been completed on January 1, 2014: Years Ended December 31 2015 Sales $ 39,584 Net income attributable to Merck & Co., Inc. 4,640 Basic earnings per common share attributable to Merck & Co., Inc. common shareholders 1.65 Earnings per common share assuming dilution attributable to Merck & Co., Inc. common shareholders 1.63 The unaudited supplemental pro forma data reflects the historical information of Merck and Cubist adjusted to include additional amortization expense based on the fair value of assets acquired, additional interest expense that would have been incurred on borrowings used to fund the acquisition, transaction costs associated with the acquisition, and the related tax effects of these adjustments. The pro forma data should not be considered indicative of the results that would have occurred if the acquisition had been consummated on January 1, 2014, nor are they indicative of future results. Remicade/Simponi In 1998, a subsidiary of Schering-Plough entered into a licensing agreement with Centocor Ortho Biotech Inc. (Centocor), a Johnson & Johnson (J&J) company, to market Remicade, which is prescribed for the treatment of inflammatory diseases. In 2005, Schering-Plough’s subsidiary exercised an option under its contract with Centocor for license rights to develop and commercialize Simponi , a fully human monoclonal antibody. The Company has marketing rights to both products throughout Europe, Russia and Turkey. Remicade lost market exclusivity in major European markets in February 2015 and the Company no longer has market exclusivity in any of its marketing territories . The Company continues to have market exclusivity for Simponi in all of its marketing territories. All profits derived from Merck’s distribution of the two products in these countries are equally divided between Merck and J&J.

Collaborative Arrangements

Collaborative Arrangements	12 Months Ended
	Dec. 31, 2017
Collaborative Arrangements [Abstract]
Collaborative Arrangement Disclosure	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 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 ovarian and breast cancer. 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 (pembrolizumab) and Imfinzi (durvalumab). The companies will also jointly develop and commercialize AstraZeneca’s selumetinib, an oral, potent, selective inhibitor of MEK, part of the mitogen-activated protein kinase (MAPK) pathway, currently being developed for multiple indications including thyroid cancer. Under the terms of the agreement, AstraZeneca and Merck will share the development and commercialization costs for Lynparza and selumetinib monotherapy and non-PD-L1/PD-1 combination therapy opportunities. Gross profits from Lynparza and selumetinib product sales generated through monotherapies or combination therapies will be shared equally. Merck will fund all development and commercialization costs of Keytruda in combination with Lynparza or selumetinib. AstraZeneca will fund all development and commercialization costs of Imfinzi in combination with Lynparza or selumetinib. AstraZenca is currently the principal on Lynparza sales transactions. Merck is recording its share of product sales of Lynparza, net of costs of sales and commercialization costs, as alliance revenue within the Pharmaceutical segment 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 and is making payments of $750 million over a multi-year period for certain license options ( $250 million was paid in December 2017, $400 million will be paid in 2018 and $100 million will be paid in 2019). The Company recorded an aggregate charge of $2.35 billion in Research and development expenses in 2017 related to the upfront payment and future license options payments. In addition, Merck will pay AstraZeneca up to an additional $6.15 billion contingent upon successful achievement of future regulatory milestones of $2.05 billion and sales-based milestones of $4.1 billion for total aggregate consideration of up to $8.5 billion . During the fourth quarter of 2017, based on the performance of Lynparza since the formation of the collaboration, Merck determined it was probable that annual sales of Lynparza in the future would exceed $250 million , which would trigger a $100 million sales-based milestone payment from Merck to AstraZeneca upon achievement of the sales milestone. Accordingly, in the fourth quarter of 2017, Merck recorded a $100 million liability and a corresponding intangible asset and also recognized $4 million of cumulative amortization expense within Materials and production costs. The remaining intangible asset will be amortized over its remaining estimated useful life of 11 years , subject to impairment testing. The remaining $4.0 billion of potential future sales-based milestone payments have not yet been accrued as they are not deemed by the Company to be probable at this time. Also, in January 2018, Lynparza received approval in the United States for the treatment of certain patients with metastatic breast cancer, triggering a $70 million milestone payment from Merck to AstraZeneca. This milestone payment will be capitalized and amortized over the remaining useful life of Lynparza. Summarized information related to this collaboration is as follows: Year Ended December 31 2017 Alliance revenues (net of commercialization costs) $ 20 Materials and production costs 4 Marketing and administrative expenses 1 Research and development expenses 2,419 Receivables from AstraZeneca 12 Payables to AstraZeneca 643 Expenses do not include all amounts attributed to activities related to the collaboration, rather only the amounts relating to payments between partners. Amounts in materials and production costs include amortization of related intangible assets. 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 equally share costs and profits from the collaboration and implemented a joint development and commercialization strategy. The collaboration also includes clinical development of Bayer’s vericiguat, which is in Phase 3 trials for worsening heart failure, as well as opt-in rights for other early-stage sGC compounds in development by Bayer. Merck in turn made available its early-stage sGC compounds under similar terms. Under the agreement, Bayer leads commercialization of Adempas in the Americas, while Merck leads commercialization in the rest of the world. For vericiguat and other potential opt-in products, Bayer will lead commercialization in the rest of world and Merck will lead in the Americas. For all products and candidates included in the agreement, both companies will share in development costs and profits on sales and will have the right to co-promote in territories where they are not the lead. In 2016, Merck began promoting and distributing Adempas in Europe. Transition from Bayer in other Merck territories, including Japan, continued in 2017. In 2016, the Company determined it was probable that annual sales of Adempas would exceed $500 million triggering a $350 million payment from Merck to Bayer. Accordingly, in 2016, the Company recorded a $350 million liability and a corresponding intangible asset and also recognized $50 million of cumulative amortization expense within Materials and production costs. The remaining intangible asset is being amortized over its then-remaining estimated useful life, subject to impairment testing. In 2017, annual sales of Adempas exceeded $500 million triggering the $350 million milestone payment from Merck to Bayer, which will be paid in the first quarter of 2018. There are $775 million of additional potential future sales-based milestone payments that have not yet been accrued as they are not deemed by the Company to be probable at this time. Summarized information related to this collaboration is as follows: Years Ended December 31 2017 2016 2015 Net product sales recorded by Merck $ 149 $ 88 $ — Merck’s profit share of sales in Bayer's marketing territories 151 81 30 Total sales 300 169 30 Materials and production costs 99 133 67 Marketing and administrative expenses 27 26 3 Research and development expenses 96 45 3 Receivables from Bayer 33 — Payables to Bayer 352 353 Expenses do not include all amounts attributed to activities related to the collaboration, rather only the amounts relating to payments between partners. Amounts in materials and production costs include amortization of related intangible assets.

Restructuring

Restructuring	12 Months Ended
	Dec. 31, 2017
Restructuring and Related Activities [Abstract]
Restructuring	Restructuring The Company incurs substantial costs for restructuring program activities related to Merck’s productivity and cost reduction initiatives, as well as in connection with the integration of certain acquired businesses. In 2010 and 2013, the Company commenced actions under global restructuring programs designed to streamline its cost structure. The actions under these programs include the elimination of positions in sales, administrative and headquarters organizations, as well as the sale or closure of certain manufacturing and research and development sites and the consolidation of office facilities. The Company also continues to reduce its global real estate footprint and improve the efficiency of its manufacturing and supply network. The Company recorded total pretax costs of $927 million in 2017 , $1.1 billion in 2016 and $1.1 billion in 2015 related to restructuring program activities. Since inception of the programs through December 31, 2017 , Merck has recorded total pretax accumulated costs of approximately $13.5 billion and eliminated approximately 43,350 positions comprised of employee separations, as well as the elimination of contractors and vacant positions. The Company estimates that approximately two-thirds of the cumulative pretax costs are cash outlays, primarily related to employee separation expense. Approximately one-third of the cumulative pretax costs are non-cash, relating primarily to the accelerated depreciation of facilities to be closed or divested. While the Company has substantially completed the actions under these programs, approximately $500 million of additional pretax costs are expected to be incurred in 2018 relating to anticipated employee separations and remaining asset-related costs. For segment reporting, restructuring charges are unallocated expenses. The following table summarizes the charges related to restructuring program activities by type of cost: Separation Costs Accelerated Depreciation Other Total Year Ended December 31, 2017 Materials and production $ — $ 52 $ 86 $ 138 Marketing and administrative — 2 — 2 Research and development — 6 5 11 Restructuring costs 552 — 224 776 $ 552 $ 60 $ 315 $ 927 Year Ended December 31, 2016 Materials and production $ — $ 77 $ 104 $ 181 Marketing and administrative — 8 87 95 Research and development — 142 — 142 Restructuring costs 216 — 435 651 $ 216 $ 227 $ 626 $ 1,069 Year Ended December 31, 2015 Materials and production $ — $ 78 $ 283 $ 361 Marketing and administrative — 59 19 78 Research and development — 37 15 52 Restructuring costs 208 — 411 619 $ 208 $ 174 $ 728 $ 1,110 Separation costs are associated with actual headcount reductions, as well as those headcount reductions which were probable and could be reasonably estimated. Positions eliminated under restructuring program activities were approximately 2,450 in 2017 , 2,625 in 2016 and 3,770 in 2015 . 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 of the sites have and will continue to operate up through the respective closure dates and, since future undiscounted cash flows were 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 2017 , 2016 and 2015 includes $267 million , $409 million and $550 million , respectively, of asset abandonment, shut-down and other related costs. Additionally, other activity includes certain employee-related costs associated with pension and other postretirement benefit plans (see Note 14) and share-based compensation. Other activity also reflects net pretax losses resulting from sales of facilities and related assets of $6 million in 2017 , $151 million in 2016 and $117 million in 2015 . The following table summarizes the charges and spending relating to restructuring program activities: Separation Costs Accelerated Depreciation Other Total Restructuring reserves January 1, 2016 $ 592 $ — $ 53 $ 645 Expenses 216 227 626 1,069 (Payments) receipts, net (413 ) — (347 ) (760 ) Non-cash activity — (227 ) (186 ) (413 ) Restructuring reserves December 31, 2016 395 — 146 541 Expenses 552 60 315 927 (Payments) receipts, net (328 ) — (394 ) (722 ) Non-cash activity — (60 ) 61 1 Restructuring reserves December 31, 2017 (1) $ 619 $ — $ 128 $ 747 (1) The remaining cash outlays are expected to be substantially completed by the end of 2020.

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2017
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 volatility 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 and Japanese yen. 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 Consolidated Balance Sheet. Changes in the fair value of derivative contracts are recorded each period in either current earnings or 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 effective portion of the unrealized gains or losses on these contracts is recorded in AOCI and reclassified into Sales when the hedged anticipated revenue is recognized. The hedge relationship is highly effective and hedge ineffectiveness has been de minimis . 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 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 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 may also use forward exchange contracts to hedge 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 Company hedges a portion of the net investment in certain of its foreign operations and measures ineffectiveness based upon changes in spot foreign exchange rates that are recorded in Other (income) expense, net . The effective portion of the unrealized gains or losses on these contracts is recorded in foreign currency translation adjustment within OCI , and remains in AOCI until either the sale or complete or substantially complete liquidation of the subsidiary. The cash flows from these contracts are reported as investing activities in the 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 . Included in the cumulative translation adjustment are pretax losses of $520 million in 2017 , and pretax gains of $193 million in 2016 and $304 million in 2015 from the euro-denominated notes. 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. At December 31, 2017 , the Company was a party to 26 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. 2017 Debt Instrument Par Value of Debt Number of Interest Rate Swaps Held Total Swap Notional Amount 1.30% notes due 2018 $ 1,000 4 $ 1,000 5.00% notes due 2019 1,250 3 550 1.85% notes due 2020 1,250 5 1,250 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 and offset by the fair value changes in the swap contracts. The cash flows from these contracts are reported as operating activities in the Consolidated Statement of Cash Flows. 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 as of December 31: 2017 2016 Fair Value of Derivative U.S. Dollar Notional Fair Value of Derivative U.S. Dollar Notional Balance Sheet Caption Asset Liability Asset Liability Derivatives Designated as Hedging Instruments Interest rate swap contracts Other assets $ 2 $ — $ 550 $ 20 $ — $ 2,700 Interest rate swap contracts Accrued and other current liabilities — 3 1,000 — — — Interest rate swap contracts Other noncurrent liabilities — 52 4,650 — 29 3,500 Foreign exchange contracts Other current assets 51 — 4,216 616 — 6,063 Foreign exchange contracts Other assets 38 — 1,936 129 — 2,075 Foreign exchange contracts Accrued and other current liabilities — 71 2,014 — 1 48 Foreign exchange contracts Other noncurrent liabilities — 1 20 — 1 12 $ 91 $ 127 $ 14,386 $ 765 $ 31 $ 14,398 Derivatives Not Designated as Hedging Instruments Foreign exchange contracts Other current assets $ 39 $ — $ 3,778 $ 230 $ — $ 8,210 Foreign exchange contracts Accrued and other current liabilities — 90 7,431 — 103 2,931 $ 39 $ 90 $ 11,209 $ 230 $ 103 $ 11,141 $ 130 $ 217 $ 25,595 $ 995 $ 134 $ 25,539 As noted above, the Company records its derivatives on a gross basis in the 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 at December 31: 2017 2016 Asset Liability Asset Liability Gross amounts recognized in the consolidated balance sheet $ 130 $ 217 $ 995 $ 134 Gross amount subject to offset in master netting arrangements not offset in the consolidated balance sheet (94 ) (94 ) (131 ) (131 ) Cash collateral (received) posted (3 ) — (529 ) — Net amounts $ 33 $ 123 $ 335 $ 3 The table below provides information on the location and pretax gain or loss amounts for derivatives that are: (i) designated in a fair value hedging relationship, (ii) designated in a foreign currency cash flow hedging relationship, (iii) designated in a foreign currency net investment hedging relationship and (iv) not designated in a hedging relationship: Years Ended December 31 2017 2016 2015 Derivatives designated in a fair value hedging relationship Interest rate swap contracts Amount of loss (gain) recognized in Other (income) expense, net on derivatives (1) $ 43 $ 28 $ (14 ) Amount of (gain) loss recognized in Other (income) expense, net on hedged item (1) (48 ) (29 ) 7 Derivatives designated in foreign currency cash flow hedging relationships Foreign exchange contracts Amount of gain reclassified from AOCI to Sales (138 ) (311 ) (724 ) Amount of loss (gain) recognized in OCI on derivatives 561 (210 ) (526 ) Derivatives designated in foreign currency net investment hedging relationships Foreign exchange contracts Amount of gain recognized in Other (income) expense, net on derivatives (2) — (1 ) (4 ) Amount of loss (gain) recognized in OCI on derivatives — 2 (10 ) Derivatives not designated in a hedging relationship Foreign exchange contracts Amount of loss (gain) recognized in Other (income) expense, net on derivatives (3) 110 132 (461 ) Amount of gain recognized in Sales (3 ) — (1 ) (1) There was $5 million , $1 million and $7 million of ineffectiveness on the hedge during 2017 , 2016 and 2015 , respectively. (2) There was no ineffectiveness on the hedge. Represents the amount excluded from hedge effectiveness testing. (3) 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. At December 31, 2017 , the Company estimates $184 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 at December 31 is as follows: 2017 2016 Fair Value Amortized Cost Gross Unrealized Fair Value Amortized Cost Gross Unrealized Gains Losses Gains Losses Corporate notes and bonds $ 9,806 $ 9,837 $ 9 $ (40 ) $ 10,577 $ 10,601 $ 15 $ (39 ) U.S. government and agency securities 2,042 2,059 — (17 ) 2,232 2,244 1 (13 ) Asset-backed securities 1,542 1,548 1 (7 ) 1,376 1,380 1 (5 ) Foreign government bonds 733 739 — (6 ) 519 521 — (2 ) Mortgage-backed securities 626 634 1 (9 ) 796 801 1 (6 ) Commercial paper 159 159 — — 4,330 4,330 — — Equity securities 275 265 16 (6 ) 349 281 71 (3 ) $ 15,183 $ 15,241 $ 27 $ (85 ) $ 20,179 $ 20,158 $ 89 $ (68 ) Available-for-sale debt securities included in Short-term investments totaled $2.4 billion at December 31, 2017 . Of the remaining debt securities, $11.1 billion mature within five years. At December 31, 2017 and 2016 , there were no debt securities pledged as collateral. 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 at December 31 are summarized below: Fair Value Measurements Using Fair Value Measurements Using Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total 2017 2016 Assets Investments Corporate notes and bonds $ — $ 9,678 $ — $ 9,678 $ — $ 10,389 $ — $ 10,389 U.S. government and agency securities 68 1,767 — 1,835 29 1,890 — 1,919 Asset-backed securities (1) — 1,476 — 1,476 — 1,257 — 1,257 Foreign government bonds — 732 — 732 — 518 — 518 Mortgage-backed securities (1) — 547 — 547 — 628 — 628 Commercial paper — 159 — 159 — 4,330 — 4,330 Equity securities 104 — — 104 201 — — 201 172 14,359 — 14,531 230 19,012 — 19,242 Other assets (2) U.S. government and agency securities — 207 — 207 — 313 — 313 Corporate notes and bonds — 128 — 128 — 188 — 188 Mortgage-backed securities (1) — 79 — 79 — 168 — 168 Asset-backed securities (1) — 66 — 66 — 119 — 119 Foreign government bonds — 1 — 1 — 1 — 1 Equity securities 171 — — 171 148 — — 148 171 481 — 652 148 789 — 937 Derivative assets (3) Purchased currency options — 80 — 80 — 644 — 644 Forward exchange contracts — 48 — 48 — 331 — 331 Interest rate swaps — 2 — 2 — 20 — 20 — 130 — 130 — 995 — 995 Total assets $ 343 $ 14,970 $ — $ 15,313 $ 378 $ 20,796 $ — $ 21,174 Liabilities Other liabilities Contingent consideration $ — $ — $ 935 $ 935 $ — $ — $ 891 $ 891 Derivative liabilities (2) Forward exchange contracts — 162 — 162 — 93 — 93 Interest rate swaps — 55 — 55 — 29 — 29 Written currency options — — — — — 12 — 12 — 217 — 217 — 134 — 134 Total liabilities $ — $ 217 $ 935 $ 1,152 $ — $ 134 $ 891 $ 1,025 (1) Primarily all of the asset-backed securities are 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. Mortgage-backed securities represent AAA-rated securities issued or unconditionally guaranteed as to payment of principal and interest by U.S. government agencies. (2) Investments included in other assets are restricted as to use, primarily 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. There were no transfers between Level 1 and Level 2 during 2017 . As of December 31, 2017 , Cash and cash equivalents of $6.1 billion include $5.2 billion of cash equivalents (which would be considered Level 2 in the fair value hierarchy). Contingent Consideration Summarized information about the changes in liabilities for contingent consideration is as follows: 2017 2016 Fair value January 1 $ 891 $ 590 Changes in estimated fair value (1) 141 (407 ) Additions 3 733 Payments (100 ) (25 ) Fair value December 31 (2) $ 935 $ 891 (1) Recorded in Research and development expenses, Materials and production costs and Other (income) expense, net . Includes cumulative translation adjustments. (2) Includes $315 million recorded as a current liability for amounts expected to be paid within the next 12 months. The changes in the estimated fair value of contingent consideration in 2017 primarily relate to changes in the liabilities recorded in connection with the termination of the SPMSD joint venture and the clinical progression of a program related to the Afferent acquisition. The changes in the estimated fair value of contingent consideration in 2016 were largely attributable to the reversal of liabilities related to programs obtained in connection with the acquisitions of cCAM, OncoEthix and SmartCells (see Note 8). The additions to contingent consideration reflected in the table above in 2016 relate to the termination of the SPMSD joint venture (see Note 9) and the acquisitions of IOmet and Afferent (see Note 3). The payments of contingent consideration in 2017 relate to the achievement of a clinical milestone in connection with the acquisition of IOmet (see Note 3) and in 2016 relate to the first commercial sale of Zerbaxa in the European Union. 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 December 31, 2017 , was $25.6 billion compared with a carrying value of $24.4 billion and at December 31, 2016 , was $25.7 billion compared with a carrying value of $24.8 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 and Europe 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. As of December 31, 2017 , the Company’s total net accounts receivable outstanding for more than one year were approximately $130 million . The Company does not expect to have write-offs or adjustments to accounts receivable which would have a material adverse effect on its financial position, liquidity or results of operations. The Company’s customers with the largest accounts receivable balances are: McKesson Corporation, AmerisourceBergen Corporation, Cardinal Health, Inc. and Zuellig Pharma Ltd. (Asia Pacific), which represented, in aggregate, approximately 40% of total accounts receivable at December 31, 2017 . The Company monitors the creditworthiness of its customers to which it grants credit terms in the normal course of business. Bad debts have been minimal. The Company does not normally require collateral or other security to support credit sales. 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. As of December 31, 2017 and 2016 , the Company had received cash collateral of $3 million and $529 million , respectively, from various counterparties and the obligation to return such collateral is recorded in Accrued and other current liabilities . The Company had not advanced any cash collateral to counterparties as of December 31, 2017 or 2016 .

Inventories

Inventories	12 Months Ended
	Dec. 31, 2017
Inventory Disclosure [Abstract]
Inventories	Inventories Inventories at December 31 consisted of: 2017 2016 Finished goods $ 1,334 $ 1,304 Raw materials and work in process 4,703 4,222 Supplies 201 155 Total (approximates current cost) 6,238 5,681 Increase to LIFO costs 45 302 $ 6,283 $ 5,983 Recognized as: Inventories $ 5,096 $ 4,866 Other assets 1,187 1,117 Inventories valued under the LIFO method comprised approximately $2.2 billion and $2.3 billion of inventories at December 31, 2017 and 2016 , respectively. Amounts recognized as Other assets are comprised almost entirely of raw materials and work in process inventories. At December 31, 2017 and 2016 , these amounts included $1.1 billion and $1.0 billion , respectively, of inventories not expected to be sold within one year. In addition, these amounts included $80 million at both December 31, 2017 and 2016 , of inventories produced in preparation for product launches.

Goodwill and Other Intangibles

Goodwill and Other Intangibles	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangibles	Goodwill and Other Intangibles The following table summarizes goodwill activity by segment: Pharmaceutical All Other Total Balance January 1, 2016 $ 15,862 $ 1,861 $ 17,723 Acquisitions 207 275 482 Impairments — (47 ) (47 ) Other (1) 6 (2 ) 4 Balance December 31, 2016 (2) 16,075 2,087 18,162 Acquisitions — 177 177 Impairments — (38 ) (38 ) Other (1) (9 ) (8 ) (17 ) Balance December 31, 2017 (2) $ 16,066 $ 2,218 $ 18,284 (1) Other includes cumulative translation adjustments on goodwill balances and certain other adjustments. (2) Accumulated goodwill impairment losses at December 31, 2017 and 2016 were $225 million and $187 million , respectively. In 2016, the additions to goodwill in the Pharmaceutical segment resulted primarily from the acquisitions of Afferent and IOmet (see Note 3). The additions to goodwill within other non-reportable segments in 2017 primarily relate to the acquisition of Vallée, which is part of the Animal Health segment (see Note 3), and in 2016 relate to the acquisition of StayWell, which is part of the Healthcare Services segment (see Note 3). The impairments of goodwill within other non-reportable segments in 2017 and 2016 relate to certain businesses within the Healthcare Services segment. Other intangibles at December 31 consisted of: 2017 2016 Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net Products and product rights $ 46,693 $ 34,950 $ 11,743 $ 46,269 $ 31,919 $ 14,350 IPR&D 1,194 — 1,194 1,653 — 1,653 Tradenames 209 97 112 215 89 126 Other 2,035 901 1,134 1,947 771 1,176 $ 50,131 $ 35,948 $ 14,183 $ 50,084 $ 32,779 $ 17,305 Acquired intangibles include products and product rights, tradenames and patents, which are initially recorded at fair value, assigned an estimated useful life, and are amortized primarily on a straight-line basis over their estimated useful lives. Some of the Company’s more significant acquired intangibles related to marketed products (included in product and product rights above) at December 31, 2017 include Zerbaxa , $3.0 billion ; Sivextro , $879 million ; Zetia , $756 million ; Implanon/Nexplanon $529 million ; Dificid , $478 million ; Gardasil/Gardasil 9, $468 million ; Vytorin , $375 million ; Bridion , $320 million ; and Simponi , $226 million . The Company recognized an intangible asset related to Adempas as a result of a collaboration with Bayer (see Note 4) that had a carrying value of $894 million at December 31, 2017 reflected in “Other” in the table above. During 2017 , 2016 and 2015 , the Company recorded impairment charges related to marketed products and other intangibles of $58 million , $347 million and $45 million , respectively, within Material and production costs. During 2017, the Company recorded an intangible asset impairment charge of $47 million related to Intron A , a treatment for certain types of cancers. Sales of Intron A are being adversely affected by the availability of new therapeutic options. In 2017, sales of Intron A in the United States eroded more rapidly than previously anticipated by the Company, which led to changes in the cash flow assumptions for Intron A. These revisions to cash flows indicated that the Intron A intangible asset value was not fully recoverable on an undiscounted cash flows basis. The Company utilized market participant assumptions to determine its best estimate of the fair value of the intangible asset related to Intron A that, when compared with its related carrying value, resulted in the impairment charge noted above. The intangible asset value for Intron A at December 31, 2017 was $13 million . The remaining charges in 2017 relate to the impairment of customer relationship, tradename and developed technology intangibles for certain businesses in the Healthcare Services segment. In 2016, the Company lowered its cash flow projections for Zontivity, a product for the reduction of thrombotic cardiovascular events in patients with a history of myocardial infarction or with peripheral arterial disease, following several business decisions that reduced sales expectations for Zontivity in the United States and Europe. The Company utilized market participant assumptions and considered several different scenarios to determine the fair value of the intangible asset related to Zontivity that, when compared with its related carrying value, resulted in an impairment charge of $252 million . Also during 2016, the Company wrote-off $95 million that had been capitalized in connection with in-licensed products Grastek and Ragwitek , allergy immunotherapy tablets that, for business reasons, the Company returned to the licensor. The charges in 2015 primarily relate to the impairment of customer relationship and tradename intangibles for certain businesses within in the Healthcare Services segment. IPR&D that the Company acquires through business combinations represents the fair value assigned to incomplete research projects which, at the time of acquisition, have not reached technological feasibility. Amounts capitalized as IPR&D are accounted for as indefinite-lived intangible assets, subject to impairment testing until completion or abandonment of the projects. Upon successful completion of each project, the Company will make a separate determination as to the then useful life of the asset and begin amortization. During 2017 , 2016 and 2015 , $14 million , $8 million and $280 million , respectively, of IPR&D was reclassified to products and product rights upon receipt of marketing approval in a major market. In 2017, the Company recorded $483 million of IPR&D impairment charges within Research and development expenses. Of this amount, $240 million resulted from a strategic decision to discontinue the development of the investigational combination regimens MK-3682B (grazoprevir/ruzasvir/uprifosbuvir) and MK-3682C (ruzasvir/uprifosbuvir) for the treatment of chronic hepatitis C virus (HCV) infection. This decision was made based on a review of available Phase 2 efficacy data and in consideration of the evolving marketplace and the growing number of treatment options available for patients with chronic HCV infection, including Zepatier , which is currently marketed by the Company for the treatment of adult patients with chronic HCV infection. As a result of this decision, the Company recorded an IPR&D impairment charge to write-off the remaining intangible asset related to uprifosbuvir. The Company had previously recorded an impairment charge for uprifosbuvir in 2016 as described below. The IPR&D impairment charges in 2017 also include a charge of $226 million to write-off the intangible asset related to verubecestat, an investigational small molecule inhibitor of the beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), resulting from a decision in February 2018 to stop a Phase 3 study evaluating verubecestat in people with prodromal Alzheimer’s disease. The decision to stop the study followed a recommendation by the external Data Monitoring Committee (eDMC), which assessed overall benefit/risk during an interim safety analysis. The eDMC concluded that it was unlikely that positive benefit/risk could be established if the trial continued. During 2016, the Company recorded $3.6 billion of IPR&D impairment charges. Of this amount, $2.9 billion relates to the clinical development program for uprifosbuvir, a nucleotide prodrug that was being evaluated for the treatment of HCV. The Company determined that changes to the product profile, as well as changes to Merck’s expectations for pricing and the market opportunity, taken together constituted a triggering event that required the Company to evaluate the uprifosbuvir intangible asset for impairment. Utilizing market participant assumptions, and considering different scenarios, the Company concluded that its best estimate of the fair value of the intangible asset related to uprifosbuvir was $240 million , resulting in the recognition of the pretax impairment charge noted above. The IPR&D impairment charges in 2016 also include charges of $180 million and $143 million related to the discontinuation of programs obtained in connection with the acquisitions of cCAM and OncoEthix, respectively, resulting from unfavorable efficacy data. An additional $72 million relates to programs obtained in connection with the SmartCells acquisition following a decision to terminate the lead compound due to a lack of efficacy and to pursue a back-up compound which reduced projected future cash flows. The IPR&D impairment charges in 2016 also include $112 million related to an in-licensed program for house dust mite allergies that, for business reasons, was returned to the licensor. The remaining IPR&D impairment charges in 2016 primarily relate to deprioritized pipeline programs that were deemed to have no alternative use during the period, including a $79 million impairment charge for an investigational candidate for contraception. The discontinuation or delay of certain of these clinical development programs resulted in a reduction of the related liabilities for contingent consideration (see Note 6). During 2015, the Company recorded $63 million of IPR&D impairment charges, of which $50 million related to the surotomycin clinical development program. In 2015, the Company received unfavorable efficacy data from a clinical trial for surotomycin. The evaluation of this data, combined with an assessment of the commercial opportunity for surotomycin, resulted in the discontinuation of the program and the IPR&D impairment charge noted above. All of the IPR&D projects that remain in development are subject to the inherent risks and uncertainties in drug development and it is possible that the Company will not be able to successfully develop and complete the IPR&D programs and profitably commercialize the underlying product candidates. The Company may recognize additional non-cash impairment charges in the future related to other marketed products or pipeline programs and such charges could be material. Aggregate amortization expense primarily recorded within Materials and production costs was $3.2 billion in 2017 , $3.8 billion in 2016 and $4.8 billion in 2015 . The estimated aggregate amortization expense for each of the next five years is as follows: 2018 , $2.8 billion ; 2019 , $1.5 billion ; 2020 , $1.2 billion ; 2021 , $1.1 billion ; 2022 , $1.1 billion .

Joint Ventures and Other Equity

Joint Ventures and Other Equity Method Affiliates	12 Months Ended
	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Joint Ventures and Other Equity Method Affiliates	Joint Ventures and Other Equity Method Affiliates Equity income from affiliates reflects the performance of the Company’s joint ventures and other equity method affiliates including SPMSD (until termination on December 31, 2016) and certain investment funds. Equity income from affiliates was $42 million in 2017 , $86 million in 2016 and $205 million in 2015 and is included in Other (income) expense, net (see Note 15). Investments in affiliates accounted for using the equity method totaled $767 million at December 31, 2017 and $715 million at December 31, 2016 . Sanofi Pasteur MSD In 1994, Merck and Pasteur Mérieux Connaught (now Sanofi Pasteur S.A.) established an equally-owned joint venture (SPMSD) to market vaccines in Europe and to collaborate in the development of combination vaccines for distribution in Europe. Joint venture vaccine sales were $1.0 billion for 2016 and $923 million for 2015 . On December 31, 2016, Merck and Sanofi Pasteur (Sanofi) terminated SPMSD and ended their joint vaccines operations in Europe. Under the terms of the termination, Merck acquired Sanofi’s 50% interest in SPMSD in exchange for consideration of $657 million comprised of cash, as well as future royalties of 11.5% on net sales of all Merck products that were previously sold by the joint venture through December 31, 2024, which the Company determined had a fair value of $416 million on the date of termination. The Company accounted for this transaction as a step acquisition, which required that Merck remeasure its ownership interest (previously accounted for as an equity method investment) to fair value at the acquisition date. Merck in turn sold to Sanofi its intellectual property rights held by SPMSD in exchange for consideration of $596 million comprised of cash and future royalties of 11.5% on net sales of all Sanofi products that were previously sold by the joint venture through December 31, 2024, which the Company determined had a fair value of $302 million on the date of termination. Excluded from this arrangement are potential future sales of Vaxelis (a jointly developed investigational pediatric hexavalent combination vaccine that was approved by the European Commission in February 2016). The European marketing rights for Vaxelis were transferred to a separate equally-owned joint venture between Sanofi and Merck. The net impact of the termination of the SPMSD joint venture is as follows: Products and product rights (8 year useful life) $ 936 Accounts receivable 133 Income taxes payable (221 ) Deferred income tax liabilities (147 ) Other, net 47 Net assets acquired 748 Consideration payable to Sanofi, net (392 ) Derecognition of Merck’s previously held equity investment in SPMSD (183 ) Increase in net assets 173 Merck’s share of restructuring costs related to the termination (77 ) Net gain on termination of SPMSD joint venture (1) $ 96 (1) Recorded in Other (income) expense, net . The estimated fair values of identifiable intangible assets related to products and product rights were determined using an income approach through which fair value is estimated based on market participant expectations of each asset’s projected net cash flows. The projected net cash flows were then discounted to present value utilizing a discount rate of 11.5% . Actual cash flows are likely to be different than those assumed. Of the amount recorded for products and product rights, $468 million related to Gardasil/Gardasil 9. The fair value of liabilities for contingent consideration related to Merck’s future royalty payments to Sanofi of $416 million (reflected in the consideration payable to Sanofi, net, in the table above) was determined at the acquisition date using unobservable inputs. These inputs include the estimated amount and timing of projected cash flows and a risk-adjusted discount rate of 8% used to present value the cash flows. Changes in the inputs could result in a different fair value measurement. Based on an existing accounting policy election, Merck did not record the $302 million estimated fair value of contingent future royalties to be received from Sanofi on the sale of Sanofi products, but rather is recognizing such amounts as sales occur and the royalties are earned. The Company incurred $24 million of transaction costs related to the termination of SPMSD included in Marketing and administrative expenses in 2016. Pro forma financial information for this transaction has not been presented as the results are not significant when compared with the Company’s financial results. AstraZeneca LP In 1982, Merck entered into an agreement with Astra AB (Astra) to develop and market Astra products under a royalty-bearing license. In 1993, Merck’s total sales of Astra products reached a level that triggered the first step in the establishment of a joint venture business carried on by Astra Merck Inc. (AMI), in which Merck and Astra each owned a 50% share. This joint venture, formed in 1994, developed and marketed most of Astra’s new prescription medicines in the United States. In 1998, Merck and Astra completed a restructuring of the ownership and operations of the joint venture whereby Merck acquired Astra’s interest in AMI, renamed KBI Inc. (KBI), and contributed KBI’s operating assets to a new U.S. limited partnership, Astra Pharmaceuticals L.P. (the Partnership), in exchange for a 1% limited partner interest. Astra contributed the net assets of its wholly owned subsidiary, Astra USA, Inc., to the Partnership in exchange for a 99% general partner interest. The Partnership, renamed AstraZeneca LP (AZLP) upon Astra’s 1999 merger with Zeneca Group Plc, became the exclusive distributor of the products for which KBI retained rights. Merck earned revenue based on sales of KBI products and earned certain Partnership returns from AZLP. On June 30, 2014, AstraZeneca exercised its option to purchase Merck’s interest in KBI (and redeem Merck’s remaining interest in AZLP). A portion of the exercise price, which is subject to a true-up in 2018 based on actual sales of Nexium and Prilosec from closing in 2014 to June 2018, was deferred and recognized as income as the contingency was eliminated as sales occurred. Once the deferred income amount was fully recognized, in 2016, the Company began recognizing income and a corresponding receivable for amounts that will be due to Merck from AstraZeneca based on the sales performance of Nexium and Prilosec subject to the true-up in June 2018. The Company recognized income of $232 million , $98 million and $182 million in 2017, 2016 and 2015, respectively, in Other (income) expense, net related to these amounts. The receivable from AstraZeneca was $325 million at December 31, 2017.

Loans Payable, Long-Term Debt a

Loans Payable, Long-Term Debt and Other Commitments	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Loans Payable, Long-Term Debt and Other Commitments	Loans Payable, Long-Term Debt and Other Commitments Loans payable at December 31, 2017 included $3.0 billion of notes due in 2018 and $73 million of long-dated notes that are subject to repayment at the option of the holder. Loans payable at December 31, 2016 included $300 million of notes due in 2017 , $267 million of long-dated notes that are subject to repayment at the option of the holders. The weighted-average interest rate of commercial paper borrowings was 0.85% and 0.40% for the years ended December 31, 2017 and 2016 , respectively. Long-term debt at December 31 consisted of: 2017 2016 2.75% notes due 2025 $ 2,488 $ 2,487 3.70% notes due 2045 1,973 1,972 2.80% notes due 2023 1,744 1,743 5.00% notes due 2019 1,260 1,273 4.15% notes due 2043 1,237 1,236 1.85% notes due 2020 1,232 1,238 2.35% notes due 2022 1,220 1,228 1.125% euro-denominated notes due 2021 1,185 1,035 1.875% euro-denominated notes due 2026 1,178 1,028 3.875% notes due 2021 1,140 1,152 2.40% notes due 2022 993 1,003 6.50% notes due 2033 729 806 Floating-rate notes due 2020 699 698 0.50% euro-denominated notes due 2024 591 516 1.375% euro-denominated notes due 2036 587 512 2.50% euro-denominated notes due 2034 585 511 3.60% notes due 2042 489 489 6.55% notes due 2037 415 594 5.75% notes due 2036 338 369 5.95% debentures due 2028 306 355 5.85% notes due 2039 270 415 6.40% debentures due 2028 250 325 6.30% debentures due 2026 135 152 Floating-rate borrowing due 2018 — 999 1.10% notes due 2018 — 999 1.30% notes due 2018 — 985 Other 309 154 $ 21,353 $ 24,274 Other (as presented in the table above) includes $300 million and $147 million at December 31, 2017 and 2016 , respectively, of borrowings at variable rates that resulted in effective interest rates of 1.42% and 0.89% for 2017 and 2016 , respectively. With the exception of the 6.30% debentures due 2026, the notes listed in the table above are redeemable in whole or in part, at Merck’s option at any time, at varying redemption prices. In November 2017, the Company launched tender offers for certain outstanding notes and debentures. The Company paid $810 million in aggregate consideration (applicable purchase price together with accrued interest) to redeem $585 million principal amount of debt that was validly tendered in connection with the tender offers and recognized a loss on extinguishment of debt of $191 million in 2017. Effective as of November 3, 2009, the Company executed a full and unconditional guarantee of the then existing debt of its subsidiary Merck Sharp & Dohme Corp. (MSD) and MSD executed a full and unconditional guarantee of the then existing debt of the Company (excluding commercial paper), including for payments of principal and interest. These guarantees do not extend to debt issued subsequent to that date. Certain of the Company’s borrowings require that Merck comply with financial covenants including a requirement that the Total Debt to Capitalization Ratio (as defined in the applicable agreements) not exceed 60% . At December 31, 2017 , the Company was in compliance with these covenants. The aggregate maturities of long-term debt for each of the next five years are as follows: 2018 , $3.0 billion ; 2019 , $1.3 billion ; 2020 , $1.9 billion ; 2021 , $2.3 billion ; 2022 , $2.2 billion . The Company has a $6.0 billion , five -year credit facility that matures in June 2022. The facility provides backup liquidity for the Company’s commercial paper borrowing facility and is to be used for general corporate purposes. The Company has not drawn funding from this facility. Rental expense under operating leases, net of sublease income, was $327 million in 2017 , $292 million in 2016 and $303 million in 2015 . The minimum aggregate rental commitments under noncancellable leases are as follows: 2018 , $255 million ; 2019 , $175 million ; 2020 , $126 million ; 2021 , $90 million ; 2022 , $68 million and thereafter, $138 million . The Company has no significant capital leases.

Contingencies and Environmental

Contingencies and Environmental Liabilities	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Contingencies and Environmental Liabilities	Contingencies and Environmental Liabilities 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 position, 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 effective August 1, 2004. 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 December 31, 2017 , approximately 4,085 cases are filed and pending against Merck in either federal or state court. In approximately 15 of these actions, plaintiffs allege, among other things, that they have suffered osteonecrosis of the jaw (ONJ), generally subsequent to invasive dental procedures, such as tooth extraction or dental implants and/or delayed healing, in association with the use of Fosamax . In addition, plaintiffs in approximately 4,070 of these actions generally allege that they sustained femur fractures and/or other bone injuries (Femur Fractures) in association with the use of Fosamax . Cases Alleging ONJ and/or Other Jaw Related Injuries In August 2006, the Judicial Panel on Multidistrict Litigation (JPML) ordered that certain Fosamax product liability cases pending in federal courts nationwide should be transferred and consolidated into one multidistrict litigation ( Fosamax ONJ MDL) for coordinated pre-trial proceedings. In December 2013, Merck reached an agreement in principle with the Plaintiffs’ Steering Committee (PSC) in the Fosamax ONJ MDL to resolve pending ONJ cases not on appeal in the Fosamax ONJ MDL and in the state courts for an aggregate amount of $27.7 million . Merck and the PSC subsequently formalized the terms of this agreement in a Master Settlement Agreement (ONJ Master Settlement Agreement) that was executed in April 2014 and included over 1,200 plaintiffs. In July 2014, Merck elected to proceed with the ONJ Master Settlement Agreement at a reduced funding level of $27.3 million since the participation level was approximately 95% . Merck has fully funded the ONJ Master Settlement Agreement and the escrow agent under the agreement has been making settlement payments to qualifying plaintiffs. The ONJ Master Settlement Agreement has no effect on the cases alleging Femur Fractures discussed below. Discovery is currently ongoing in some of the approximately 15 remaining ONJ cases that are pending in various federal and state courts and the Company intends to defend against these lawsuits. Cases Alleging Femur Fractures In March 2011, Merck submitted a Motion to Transfer to the JPML seeking to have all federal cases alleging Femur Fractures consolidated into one multidistrict litigation for coordinated pre-trial proceedings. The Motion to Transfer was granted in May 2011, and all federal cases involving allegations of Femur Fracture 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. The Glynn decision was not appealed by plaintiff. 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). The Femur Fracture MDL court also dismissed without prejudice another approximately 510 cases pending plaintiffs’ appeal of the preemption ruling to the Third Circuit. On March 22, 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. On April 5, 2017, Merck filed a petition seeking a rehearing on the Third Circuit’s March 22, 2017 decision, which was denied on April 24, 2017. Merck filed a petition for a writ of certiorari to the U.S. Supreme Court on August 22, 2017, seeking review of the Third Circuit’s decision. On December 4, 2017, the Supreme Court invited the Solicitor General to file a brief in the case expressing the views of the United States. In addition, in June 2014, the Femur Fracture MDL court granted Merck summary judgment in the Gaynor v. Merck case and found that Merck’s updates in January 2011 to the Fosamax label regarding atypical femur fractures were adequate as a matter of law and that Merck adequately communicated those changes. The plaintiffs in Gaynor did not appeal the Femur Fracture MDL court’s findings with respect to the adequacy of the 2011 label change but did appeal the dismissal of their case based on preemption grounds, and the Third Circuit subsequently reversed that dismissal in its March 22, 2017 decision. In August 2014, Merck filed a motion requesting that the Femur Fracture MDL court enter a further order requiring all plaintiffs in the Femur Fracture MDL who claim that the 2011 Fosamax label is inadequate and the proximate cause of their alleged injuries to show cause why their cases should not be dismissed based on the court’s preemption decision and its ruling in the Gaynor case. In November 2014, the court granted Merck’s motion and entered the requested show cause order. No plaintiffs responded to or appealed the November 2014 show cause order. As of December 31, 2017 , approximately 530 cases were pending in the Femur Fracture MDL following the reinstatement of the cases that had been on appeal to the Third Circuit. The 510 cases dismissed without prejudice that were also pending the final resolution of the aforementioned appeal have not yet been reinstated. As of December 31, 2017 , approximately 2,750 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 30 cases to be reviewed through fact discovery. Two additional groups of 50 cases each to be reviewed through fact discovery were selected in November 2013 and March 2014, respectively. A further group of 25 cases to be reviewed through fact discovery was selected by Merck in July 2015, and Merck has continued to select additional cases to be reviewed through fact discovery during 2016 and 2017. As of December 31, 2017 , approximately 280 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. In March 2014, the court directed that a group of 10 discovery pool cases be reviewed through fact discovery and subsequently scheduled the Galper v. Merck case, which plaintiffs selected, as the first trial. The Galper trial began in February 2015 and the jury returned a verdict in Merck’s favor in April 2015, and plaintiff appealed that verdict to the California appellate court. Oral argument on plaintiff’s appeal in Galper was held in November 2016 and, on April 24, 2017, the California appellate court issued a decision affirming the lower court’s judgment in favor of Merck. The next Femur Fracture trial in California that was scheduled to begin in April 2016 was stayed at plaintiffs’ request and a new trial date has not been set. Additionally, there are five Femur Fracture cases pending in other state courts. Discovery is ongoing in the Femur Fracture MDL and in state courts where Femur Fracture cases are pending and the Company 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 December 31, 2017 , Merck is aware of approximately 1,235 product user claims alleging generally that use of Januvia and/or Janumet caused the development of pancreatic cancer and other injuries. These complaints were filed in several different state and federal courts. Most of the claims were filed in a consolidated multidistrict litigation proceeding in the U.S. District Court for the Southern District of California called “In re Incretin-Based Therapies Products Liability Litigation” (MDL). The MDL includes federal lawsuits alleging pancreatic cancer due to use of the following medicines: Januvia, Janumet , Byetta and Victoza, the latter two of which are products manufactured by other pharmaceutical companies. The majority of claims not filed in the MDL were filed in 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 preemption. Of the approximately 1,235 product user claims, these rulings resulted in the dismissal of approximately 1,100 product user claims. Plaintiffs appealed the MDL and California State Court preemption rulings. On November 28, 2017, the U.S. Court of Appeals for the Ninth Circuit (Ninth Circuit) reversed the trial court’s ruling in the MDL and remanded for further proceedings. The Ninth Circuit did not address the substance of defendants’ preemption argument but instead ruled that the district court made various errors during discovery. Jurisdiction returned to U.S. District Court for the Southern District of California on January 2, 2018. The preemption appeal in the California state court litigation has been fully briefed, but the court has not yet scheduled oral argument. As of December 31, 2017 , seven product users have claims pending against Merck in state courts other than California state court, including four active product user claims pending in Illinois state court. On June 30, 2017, the Illinois trial court denied Merck’s motion for summary judgment on grounds of preemption. Merck sought permission to appeal that order on an interlocutory basis and was granted a stay of proceedings in the trial court. On September 19, 2017, an intermediate appellate court in Illinois denied Merck’s petition for interlocutory review. On October 20, 2017, Merck filed a petition with the Illinois Supreme Court, seeking leave to appeal the appellate court’s denial. The Illinois Supreme Court denied Merck’s petition for certiorari review and, instead, directed the appellate court to answer the certified question. As a result, proceedings in the trial court remain stayed and trials for certain of the product users in Illinois have been delayed. 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. Propecia/Proscar As previously disclosed, Merck is a defendant in product liability lawsuits in the United States involving Propecia and/or Proscar . As of December 31, 2017 , approximately 775 lawsuits have been filed by plaintiffs who allege that they have experienced persistent sexual side effects following cessation of treatment with Propecia and/or Proscar . Approximately 20 of the plaintiffs also allege that Propecia or Proscar has caused or can cause prostate cancer, testicular cancer or male breast cancer. The lawsuits have been filed in various federal courts and in state court in New Jersey. The federal lawsuits have been consolidated for pretrial purposes in a federal multidistrict litigation before Judge Brian Cogan of the Eastern District of New York. The matters pending in state court in New Jersey have been consolidated before Judge Hyland in Middlesex County. In addition, there is one matter pending in state court in California, one matter pending in state court in Ohio, and one matter on appeal in the Massachusetts Supreme Judicial Court. The Company intends to defend against these lawsuits. Governmental Proceedings As previously disclosed, the Company has learned that the Prosecution Office of Milan, Italy is investigating interactions between the Company’s Italian subsidiary, certain employees of the subsidiary and certain Italian health care providers. The Company understands that this is part of a larger investigation involving engagements between various health care companies and those health care providers. The Company is cooperating with the investigation. As previously disclosed, the United Kingdom (UK) Competition and Markets Authority (CMA) issued a Statement of Objections against the Company and MSD Sharp & Dohme Limited (MSD UK) on May 23, 2017. In the Statement of Objections, the CMA alleges that MSD UK abused a dominant position through a discount program for Remicade over the period from March 2015 to February 2016. The Company and MSD UK are contesting the CMA’s allegations. As previously disclosed, the Company has received an investigative subpoena from the California Insurance Commissioner’s Fraud Bureau (Bureau) seeking information from January 1, 2007 to the present related to the pricing and promotion of Cubicin . The Bureau is investigating whether Cubist Pharmaceuticals, Inc., which the Company acquired in 2015, unlawfully induced the presentation of false claims for Cubicin to private insurers under the California Insurance Code False Claims Act. The Company is cooperating with the investigation. As previously disclosed, the Company has received a civil investigative demand from the U.S. Attorney’s Office for the Southern District of New York that requests information relating to the Company’s contracts with, services from and payments to pharmacy benefit managers with respect to Maxalt and Levitra from January 1, 2006 to the present. The Company is cooperating with the investigation. As previously disclosed, the Company has received a subpoena from the Office of Inspector General of the U.S. Department of Health and Human Services on behalf of the U.S. Attorney’s Office for the District of Maryland and the Civil Division of the U.S. Department of Justice that requests information relating to the Company’s marketing of Singulair and Dulera Inhalation Aerosol and certain of its other marketing activities from January 1, 2006 to the present. The Company is cooperating with the investigation. 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 K-DUR Antitrust Litigation In June 1997 and January 1998, Schering-Plough Corporation (Schering-Plough) settled patent litigation with Upsher-Smith, Inc. (Upsher-Smith) and ESI Lederle, Inc. (Lederle), respectively, relating to generic versions of Schering-Plough’s long-acting potassium chloride product supplement used by cardiac patients, for which Lederle and Upsher-Smith had filed abbreviated New DrugApplications (NDA). Putative class and non-class action suits were then filed on behalf of direct and indirect purchasers of K-DUR against Schering-Plough, Upsher-Smith and Lederle and were consolidated in a multidistrict litigation in the U.S. District Court for the District of New Jersey. In February 2016, the court denied the Company’s motion for summary judgment relating to all of the direct purchasers’ claims concerning the settlement with Upsher-Smith and granted the Company’s motion for summary judgment relating to all of the direct purchasers’ claims concerning the settlement with Lederle. As previously disclosed, in February 2017, Merck and Upsher-Smith reached a settlement in principle with the class of direct purchasers and the opt-outs to the class. Merck will contribute approximately $80 million in the aggregate towards the overall settlement. On April 5, 2017, the claims of the opt-outs were dismissed with prejudice pursuant to a written settlement agreement with those parties. On May 15, 2017, Merck and the class executed a settlement agreement, which received preliminary approval from the court on May 23, 2017. On October 5, 2017, the court entered a Final Judgment and Order of Dismissal approving the settlement agreement with the direct purchaser class and dismissing the claims of the class with prejudice. Zetia Antitrust Litigation In May 2010, Schering Corporation (Schering) and MSP Singapore Company LLC (MSP) settled patent litigation with Glenmark Pharmaceuticals Inc., USA, and Glenmark Pharmaceuticals Ltd. (together, Glenmark) relating to a generic version of Zetia , a pharmaceutical product containing ezetimibe used by patients with high cholesterol, for which Glenmark had filed an abbreviated NDA. In January and February 2018, putative class action suits were filed on behalf of direct and indirect purchasers of Zetia against Merck, MSD, Schering-Plough, Schering, MSP, and Glenmark in the U.S. District Courts for the Eastern District of Virginia and the Eastern District of New York. These suits claim violations of federal and state antitrust laws, as well as other state statutory and common law causes of action. These suits seek unspecified damages. Sales Force Litigation As previously disclosed, in May 2013, Ms. Kelli Smith filed a complaint against the Company in the U.S. District Court for the District of New Jersey on behalf of herself and a putative class of female sales representatives and a putative sub-class of female sales representatives with children, claiming (a) discriminatory policies and practices in selection, promotion and advancement, (b) disparate pay, (c) differential treatment, (d) hostile work environment and (e) retaliation under federal and state discrimination laws. Plaintiffs sought and were granted leave to file an amended complaint. In January 2014, plaintiffs filed an amended complaint adding four additional named plaintiffs. In October 2014, the court denied the Company’s motion to dismiss or strike the class claims as premature. In September 2015, plaintiffs filed additional motions, including a motion for conditional certification under the Equal Pay Act; a motion to amend the pleadings seeking to add ERISA and constructive discharge claims and a Company subsidiary as a named defendant; and a motion for equitable relief. Merck filed papers in opposition to the motions. On April 27, 2016, the court granted plaintiff’s motion for conditional certification but denied plaintiffs’ motions to extend the liability period for their Equal Pay Act claims back to June 2009. As a result, the liability period will date back to April 2012, at the earliest. On April 29, 2016, the Magistrate Judge granted plaintiffs’ request to amend the complaint to add the following: (i) a Company subsidiary as a corporate defendant; (ii) an ERISA claim and (iii) an individual constructive discharge claim for one of the named plaintiffs. Approximately 700 individuals have opted-in to this action; the opt-in period has closed. On August 1, 2017, plaintiffs filed their motion for class certification. This motion seeks to certify a Title VII pay discrimination class and also seeks final collective action certification of plaintiffs’ Equal Pay Act claim. The parties are currently engaged in motion practice before the court. Qui Tam Litigation As previously disclosed, on June 21, 2012, the U.S. District Court for the Eastern District of Pennsylvania unsealed a complaint that has been filed against the Company under the federal False Claims Act by two former employees alleging, among other things, that the Company defrauded the U.S. government by falsifying data in connection with a clinical study conducted on the mumps component of the Company’s M-M-R II vaccine. The complaint alleges the fraud took place between 1999 and 2001. The U.S. government had the right to participate in and take over the prosecution of this lawsuit, but notified the court that it declined to exercise that right. The two former employees are pursuing the lawsuit without the involvement of the U.S. government. In addition, as previously disclosed, two putative class action lawsuits on behalf of direct purchasers of the M‑M‑R II vaccine, which charge that the Company misrepresented the efficacy of the M-M-R II vaccine in violation of federal antitrust laws and various state consumer protection laws, are pending in the Eastern District of Pennsylvania. In September 2014, the court denied Merck’s motion to dismiss the False Claims Act suit and granted in part and denied in part its motion to dismiss the then-pending antitrust suit. As a result, both the False Claims Act suit and the antitrust suits have proceeded into discovery. The Company intends to defend against these lawsuits. Merck KGaA Litigation In January 2016, to protect its long-established brand rights in the United States, the Company filed a lawsuit against Merck KGaA, Darmstadt, Germany (KGaA), operating as the EMD Group in the United States, alleging it improperly uses the name “Merck” in the United States. KGaA has filed suit against the Company in France, the UK, Germany, Switzerland, Mexico, and India alleging breach of the parties’ co-existence agreement, unfair competition and/or trademark infringement. In December 2015, the Paris Court of First Instance issued a judgment finding that certain activities by the Company directed towards France did not constitute trademark infringement and unfair competition while other activities were found to infringe. The Company and KGaA appealed the decision, and the appeal was heard in May 2017. In June 2017, the French appeals court held that certain of the activities by the Company directed to France constituted unfair competition or trademark infringement and no further appeal was pursued. In January 2016, the UK High Court issued a judgment finding that the Company had breached the co-existence agreement and infringed KGaA’s trademark rights as a result of certain activities directed towards the UK based on use of the word MERCK on promotional and information activity. As noted in the UK decision, this finding was not based on the Company’s use of the sign MERCK in connection with the sale of products or any material pharmaceutical business transacted in the UK. The Company and KGaA have both appealed this decision, and the appeal was heard in June 2017. In November 2017, the UK Court of Appeals affirmed the decision on the co-existence agreement and remitted for re-hearing issues of trade mark infringement, validity and the relief to which KGaA would be entitled. Patent Litigation From time to time, generic manufacturers of pharmaceutical products file abbreviated 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. Certain products of the Company currently involved in such patent infringement litigation in the United States include Noxafil and NuvaRing . 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. Noxafil — In August 2015, the Company filed a lawsuit against Actavis Laboratories Fl, Inc. (Actavis) in the United States in respect of that company’s application to the FDA seeking pre-patent expiry approval to sell a generic version of Noxafil . In October 2017, the district court held the patent valid and infringed. Actavis has appealed this decision. In March 2016, the Company filed a lawsuit against Roxane Laboratories, Inc. (Roxane) in the United States in respect of that company’s application to the FDA seeking pre-patent expiry approval to sell a generic version of Noxafil . In October 2017, the parties reached a settlement whereby Roxane can launch its generic version upon expiry of the patent, or earlier under certain conditions. In February 2016, the Company filed a lawsuit against Par Sterile Products LLC, Par Pharmaceutical, Inc., Par Pharmaceutical Companies, Inc. and Par Pharmaceutical Holdings, Inc. (collectively, Par) in the United States in respect of that company’s application to the FDA seeking pre-patent expiry approval to sell a generic version of Noxafil injection. In October 2016, the parties reached a settlement whereby Par can launch its generic version in January 2023, or earlier under certain conditions. Nasonex — Nasonex lost market exclusivity in the United States in 2016. Prior to that, in April 2015, the Company filed a patent infringement lawsuit against Apotex Inc. and Apotex Corp. (Apotex) in respect of Apotex’s marketed product that the Company believed was infringing. In January 2018, the Company and Apotex settled this matter with Apotex agreeing to pay the Company $115 million plus certain other consideration. NuvaRing — In December 2013, the Company filed a lawsuit against a subsidiary of Allergan plc in the United States in respect of that company’s application to the FDA seeking pre-patent expiry approval to sell a generic version of NuvaRing . The trial in this matter was held in January 2016. In August 2016, the district court ruled that the patent was invalid and the Company appealed this decision. In October 2017, the appellate court reversed the district court decision and found the patent to be valid. The case was remanded and the district court enjoined the defendant from marketing its generic version of NuvaRing until the patent expires. In September 2015, the Company filed a lawsuit against Teva Pharma in the United States in respect of that company’s application to the FDA seeking pre-patent expiry approval to sell a generic version of NuvaRing . Based on its ruling in the Allergan plc matter, the district court dismissed the Company’s lawsuit in December 2016. Following the appellate reversal in the Allergan plc matter, the defendant has agreed to be enjoined from marketing its generic version of NuvaRing until the patent expires. Anti-PD-1 Antibody Patent Oppositions and Litigation As previously disclosed, Ono Pharmaceutical Co. (Ono) has a European patent (EP 1 537 878) (’878) that broadly claims the use of an anti-PD-1 antibody, such as the Company’s immunotherapy, Keytruda , for the treatment of cancer. Ono has previously licensed its commercial rights to an anti-PD-1 antibody to Bristol-Myers Squibb (BMS) in certain markets. BMS and Ono also own European Patent EP 2 161 336 (’336) that, as granted, broadly claimed anti-PD-1 antibodies that could include Keytruda . As previously disclosed, the Company and BMS and Ono were engaged in worldwide litigation, including in the United States, over the validity and infringement of the ’878 patent, the ’336 patent and their equivalents. In January 2017, the Company announced that it had entered into a settlement and license agreement with BMS and Ono resolving the worldwide patent infringement litigation related to the use of an anti-PD-1 antibody for the treatment of cancer, such as Keytruda . Under the settlement and license agreement, the Company made a one-time payment of $625 million (which was recorded as an expense in the Company’s 2016 financial results) to BMS and will pay royalties on the worldwide sales of Keytruda for a non-exclusive license to market Keytruda in any market in which it is approved. For global net sales of Keytruda , the Company will pay royalties of 6.5% of net sales occurring from January 1, 2017 through and including December 31, 2023; and 2.5% of net sales occurring from January 1, 2024 through and including December 31, 2026. The parties also agreed to dismiss all claims worldwide in the relevant legal proceedings. In October 2015, PDL Biopharma (PDL) filed a lawsuit in the United States against the Company alleging that the manufacture of Keytruda infringed US Patent No. 5,693,761 (’761 patent), which expired in December 2014. This patent claims platform technology used in the creation and manufacture of recombinant antibodies and PDL is seeking damages for pre-expiry infringement of the ’761 patent. In April 2017, the parties reached a settlement pursuant to which, in exchange for a lump sum, PDL dismissed its lawsuit with prejudice and granted the Company a fully paid-up non-exclusive license to the ’761 patent. In July 2016, the Company filed a declaratory judgment action in the United States against Genentech and City of Hope seeking a ruling that US Patent No. 7,923,221 (Cabilly III patent), which claims platform technology used in the creation and manufacture of recombinant antibodies, is invalid and that Keytruda and bezlotoxumab do not infringe the Cabilly III patent. In July 2016, the Company also filed a petition in the USPTO for Inter Partes Review (IPR) of certain claims of US Patent No. 6,331,415 (Cabilly II patent), which claims platform technology

Equity

Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Equity	Equity The Merck certificate of incorporation authorizes 6,500,000,000 shares of common stock and 20,000,000 shares of preferred stock. Capital Stock A summary of common stock and treasury stock transactions (shares in millions) is as follows: 2017 2016 2015 Common Stock Treasury Stock Common Stock Treasury Stock Common Stock Treasury Stock Balance January 1 3,577 828 3,577 796 3,577 739 Purchases of treasury stock — 67 — 60 — 75 Issuances (1) — (15 ) — (28 ) — (18 ) Balance December 31 3,577 880 3,577 828 3,577 796 (1) Issuances primarily reflect activity under share-based compensation plans.

Share-Based Compensation Plans

Share-Based Compensation Plans	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [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. These plans were approved by the Company’s shareholders. At December 31, 2017 , 118 million shares collectively were authorized for future grants under the Company’s share-based compensation plans. These awards are settled primarily with treasury shares. Employee stock options are granted to purchase shares of Company stock at the fair market value at the time of grant. These awards generally vest one-third each year over a three -year period, with a contractual term of 7 - 10 years. RSUs are stock awards that are granted to employees and entitle the holder to shares of common stock as the awards vest. The fair value of the stock option and RSU awards is determined and fixed on the grant date based on the Company’s stock price. PSUs are stock awards where the ultimate number of shares issued will be contingent on the Company’s performance against a pre-set objective or set of objectives. The fair value of each PSU is determined on the date of grant based on the Company’s stock price. For RSUs and PSUs, dividends declared during the vesting period are payable to the employees only upon vesting. Over the PSU performance period, the number of shares of stock that are expected to be issued will be adjusted based on the probability of achievement of a performance target and final compensation expense will be recognized based on the ultimate number of shares issued. RSU and PSU distributions will be in shares of Company stock after the end of the vesting or performance period, subject to the terms applicable to such awards. PSU awards generally vest after three years. Prior to 2018, RSU awards generally vested after three years; beginning with awards granted in 2018, RSU awards will vest one-third each year over a three -year period. Total pretax share-based compensation cost recorded in 2017 , 2016 and 2015 was $312 million , $300 million and $299 million , respectively, with related income tax benefits of $57 million , $92 million and $93 million , respectively. The Company uses the Black-Scholes option pricing model for determining the fair value of option grants. In applying this model, the Company uses both historical data and current market data to estimate the fair value of its options. The Black-Scholes model requires several assumptions including expected dividend yield, risk-free interest rate, volatility, and term of the options. The expected dividend yield is based on historical patterns of dividend payments. The risk-free rate is based on the rate at grant date of zero-coupon U.S. Treasury Notes with a term equal to the expected term of the option. Expected volatility is estimated using a blend of historical and implied volatility. The historical component is based on historical monthly price changes. The implied volatility is obtained from market data on the Company’s traded options. The expected life represents the amount of time that options granted are expected to be outstanding, based on historical and forecasted exercise behavior. The weighted average exercise price of options granted in 2017 , 2016 and 2015 was $63.88 , $54.63 and $59.73 per option, respectively. The weighted average fair value of options granted in 2017 , 2016 and 2015 was $7.04 , $5.89 and $6.46 per option, respectively, and were determined using the following assumptions: Years Ended December 31 2017 2016 2015 Expected dividend yield 3.6 % 3.8 % 4.1 % Risk-free interest rate 2.0 % 1.4 % 1.7 % Expected volatility 17.8 % 19.6 % 19.9 % Expected life (years) 6.1 6.2 6.2 Summarized information relative to stock option plan activity (options in thousands) is as follows: Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value Outstanding January 1, 2017 45,091 $ 44.47 Granted 4,232 63.88 Exercised (11,512 ) 43.38 Forfeited (1,537 ) 51.78 Outstanding December 31, 2017 36,274 $ 46.77 4.89 $ 397 Exercisable December 31, 2017 26,778 $ 42.54 3.64 $ 384 Additional information pertaining to stock option plans is provided in the table below: Years Ended December 31 2017 2016 2015 Total intrinsic value of stock options exercised $ 236 $ 444 $ 332 Fair value of stock options vested 30 28 30 Cash received from the exercise of stock options 499 939 485 A summary of nonvested RSU and PSU activity (shares in thousands) is as follows: RSUs PSUs Number of Shares Weighted Average Grant Date Fair Value Number of Shares Weighted Average Grant Date Fair Value Nonvested January 1, 2017 13,266 $ 57.19 1,744 $ 59.24 Granted 5,014 63.85 1,008 63.62 Vested (3,795 ) 58.13 (833 ) 62.71 Forfeited (876 ) 58.22 (51 ) 60.24 Nonvested December 31, 2017 13,609 $ 59.32 1,868 $ 60.03 At December 31, 2017 , there was $469 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 1.9 years. For segment reporting, share-based compensation costs are unallocated expenses.

Pension and Other Postretiremen

Pension and Other Postretirement Benefit Plans	12 Months Ended
	Dec. 31, 2017
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. In addition, the Company provides medical benefits, principally to its eligible U.S. retirees and their dependents, through its other postretirement benefit plans. The Company uses December 31 as the year-end measurement date for all of its pension plans and other postretirement benefit plans. Net Periodic Benefit Cost The net periodic benefit cost (credit) for pension and other postretirement benefit plans consisted of the following components: Pension Benefits U.S. International Other Postretirement Benefits Years Ended December 31 2017 2016 2015 2017 2016 2015 2017 2016 2015 Service cost $ 312 $ 282 $ 307 $ 252 $ 238 $ 251 $ 57 $ 54 $ 80 Interest cost 454 456 434 172 204 206 81 82 110 Expected return on plan assets (862 ) (831 ) (819 ) (393 ) (382 ) (379 ) (78 ) (107 ) (143 ) Amortization of unrecognized prior service cost (53 ) (55 ) (56 ) (11 ) (11 ) (14 ) (98 ) (106 ) (64 ) Net loss amortization 180 119 214 98 87 118 1 3 5 Termination benefits 44 23 22 4 4 1 8 4 7 Curtailments 3 5 (12 ) (4 ) (1 ) (9 ) (31 ) (18 ) (19 ) Settlements — — 1 5 6 12 — — — Net periodic benefit cost (credit) $ 78 $ (1 ) $ 91 $ 123 $ 145 $ 186 $ (60 ) $ (88 ) $ (24 ) The changes in net periodic benefit cost (credit) year over year for pension plans are largely attributable to changes in the discount rate affecting net loss amortization. The increase in net periodic benefit credit for other postretirement benefit plans in 2017 and 2016 as compared with 2015 is largely attributable to changes in retiree medical benefits approved by the Company in December 2015, partially offset by lower returns on plan assets. In connection with restructuring actions (see Note 5), termination charges were recorded in 2017 , 2016 and 2015 on pension and other postretirement benefit plans related to expanded eligibility for certain employees exiting Merck. Also, in connection with these restructuring activities, 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 table above. Obligations and Funded Status Summarized information about the changes in plan assets and benefit obligations, the funded status and the amounts recorded at December 31 is as follows: Pension Benefits Other Postretirement Benefits U.S. International 2017 2016 2017 2016 2017 2016 Fair value of plan assets January 1 $ 9,766 $ 9,266 $ 7,794 $ 7,204 $ 1,019 $ 1,913 Actual return on plan assets 1,723 941 677 898 161 138 Company contributions, net 58 63 226 424 (4 ) 68 Effects of exchange rate changes — — 843 (546 ) — — Benefits paid (651 ) (504 ) (198 ) (193 ) (62 ) (108 ) Settlements — — (17 ) (21 ) — — Assets no longer restricted to the payment of postretirement benefits (1) — — — — — (992 ) Other — — 14 28 — — Fair value of plan assets December 31 $ 10,896 $ 9,766 $ 9,339 $ 7,794 $ 1,114 $ 1,019 Benefit obligation January 1 $ 10,849 $ 9,723 $ 8,372 $ 7,733 $ 1,922 $ 1,810 Service cost 312 282 252 238 57 54 Interest cost 454 456 172 204 81 82 Actuarial losses (gains) (2) 881 854 (7 ) 938 (87 ) 77 Benefits paid (651 ) (504 ) (198 ) (193 ) (62 ) (108 ) Effects of exchange rate changes — — 916 (576 ) 3 2 Plan amendments — — (22 ) — — — Curtailments 15 15 (3 ) (15 ) — 1 Termination benefits 44 23 4 4 8 4 Settlements — — (17 ) (21 ) — — Other — — 14 60 — — Benefit obligation December 31 $ 11,904 $ 10,849 $ 9,483 $ 8,372 $ 1,922 $ 1,922 Funded status December 31 $ (1,008 ) $ (1,083 ) $ (144 ) $ (578 ) $ (808 ) $ (903 ) Recognized as: Other assets $ — $ — $ 828 $ 451 $ — $ — Accrued and other current liabilities (59 ) (50 ) (17 ) (7 ) (11 ) (11 ) Other noncurrent liabilities (949 ) (1,033 ) (955 ) (1,022 ) (797 ) (892 ) (1) As a result of certain allowable administrative actions that occurred in June 2016, $992 million of plan assets previously restricted for the payment of other postretirement benefits became available to fund certain other health and welfare benefits. (2) Actuarial losses in 2017 and 2016 primarily reflect changes in discount rates. At December 31, 2017 and 2016 , the accumulated benefit obligation was $20.5 billion and $18.4 billion , respectively, for all pension plans, of which $11.5 billion and $10.5 billion , respectively, related to U.S. pension plans. Information related to the funded status of selected pension plans at December 31 is as follows: U.S. International 2017 2016 2017 2016 Pension plans with a projected benefit obligation in excess of plan assets Projected benefit obligation $ 11,904 $ 10,849 $ 3,323 $ 5,486 Fair value of plan assets 10,896 9,766 2,352 4,457 Pension plans with an accumulated benefit obligation in excess of plan assets Accumulated benefit obligation $ 676 $ 9,807 $ 2,120 $ 2,692 Fair value of plan assets — 9,057 1,346 1,898 Plan Assets Entities are required to use 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. The Level 3 assets are those whose values are determined using pricing models, discounted cash flow methodologies, or similar techniques with significant unobservable inputs, as well as instruments for which the determination of fair value requires significant judgment or estimation. At December 31, 2017 and 2016 , $488 million and $435 million , respectively, or approximately 2% of the Company’s pension investments were categorized as Level 3 assets. If the inputs used to measure the financial assets 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. The fair values of the Company’s pension plan assets at December 31 by asset category are as follows: Fair Value Measurements Using Fair Value Measurements Using Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total 2017 2016 U.S. Pension Plans Assets Cash and cash equivalents $ 6 $ — $ — $ 6 $ 2 $ 2 $ — $ 4 Investment funds Developed markets equities 390 — — 390 521 — — 521 Emerging markets equities 138 — — 138 104 — — 104 Equity securities Developed markets 2,743 — — 2,743 2,521 — — 2,521 Fixed income securities Government and agency obligations — 757 — 757 — 475 — 475 Corporate obligations — 900 — 900 — 660 — 660 Mortgage and asset-backed securities — 240 — 240 — 239 — 239 Other investments — — 15 15 — — 18 18 Net assets in fair value hierarchy $ 3,277 $ 1,897 $ 15 $ 5,189 $ 3,148 $ 1,376 $ 18 $ 4,542 Investments measured at NAV (1) 5,707 5,224 Plan assets at fair value $ 10,896 $ 9,766 International Pension Plans Assets Cash and cash equivalents $ 54 $ 19 $ — $ 73 $ 42 $ 11 $ — $ 53 Investment funds Developed markets equities 562 3,326 — 3,888 187 2,846 — 3,033 Emerging markets equities 62 176 — 238 24 148 — 172 Government and agency obligations 249 2,095 — 2,344 123 1,904 — 2,027 Corporate obligations 5 329 — 334 2 282 — 284 Fixed income obligations 7 4 — 11 6 3 — 9 Real estate (2) — 1 2 3 — 3 4 7 Equity securities Developed markets 660 — — 660 565 — — 565 Fixed income securities Government and agency obligations 2 266 — 268 2 235 — 237 Corporate obligations 1 118 — 119 — 92 — 92 Mortgage and asset-backed securities — 55 — 55 — 50 — 50 Other investments Insurance contracts (3) — 67 470 537 — 59 412 471 Other — 6 1 7 1 4 1 6 Net assets in fair value hierarchy $ 1,602 $ 6,462 $ 473 $ 8,537 $ 952 $ 5,637 $ 417 $ 7,006 Investments measured at NAV (1) 802 788 Plan assets at fair value $ 9,339 $ 7,794 (1) Certain investments that were measured at net asset value (NAV) per share or its equivalent as a practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the fair value of plan assets at December 31, 2017 and 2016 . (2) The plans’ Level 3 investments in real estate funds are generally valued by market appraisals of the underlying investments in the funds. (3) The plans’ Level 3 investments in insurance contracts are generally valued using a crediting rate that approximates market returns and invest in underlying securities whose market values are unobservable and determined using pricing models, discounted cash flow methodologies, or similar techniques. The table below provides a summary of the changes in fair value, including transfers in and/or out, of all financial assets measured at fair value using significant unobservable inputs (Level 3) for the Company’s pension plan assets: 2017 2016 Insurance Contracts Real Estate Other Total Insurance Contracts Real Estate Other Total U.S. Pension Plans Balance January 1 $ — $ — $ 18 $ 18 $ — $ — $ 23 $ 23 Actual return on plan assets: Relating to assets still held at December 31 — — (2 ) (2 ) — — (3 ) (3 ) Relating to assets sold during the year — — 4 4 — — 4 4 Purchases and sales, net — — (5 ) (5 ) — — (6 ) (6 ) Balance December 31 $ — $ — $ 15 $ 15 $ — $ — $ 18 $ 18 International Pension Plans Balance January 1 $ 412 $ 4 $ 1 $ 417 $ 393 $ 5 $ 2 $ 400 Actual return on plan assets: Relating to assets still held at December 31 52 — — 52 (9 ) 1 — (8 ) Purchases and sales, net 5 (2 ) — 3 2 (2 ) (1 ) (1 ) Transfers into Level 3 1 — — 1 26 — — 26 Balance December 31 $ 470 $ 2 $ 1 $ 473 $ 412 $ 4 $ 1 $ 417 The fair values of the Company’s other postretirement benefit plan assets at December 31 by asset category are as follows: Fair Value Measurements Using Fair Value Measurements Using Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total 2017 2016 Assets Cash and cash equivalents $ 97 $ — $ — $ 97 $ 125 $ — $ — $ 125 Investment funds Developed markets equities 37 — — 37 48 — — 48 Emerging markets equities 13 — — 13 10 — — 10 Government and agency obligations 1 — — 1 1 — — 1 Equity securities Developed markets 256 — — 256 231 — — 231 Fixed income securities Government and agency obligations — 71 — 71 — 43 — 43 Corporate obligations — 84 — 84 — 60 — 60 Mortgage and asset-backed securities — 23 — 23 — 22 — 22 Net assets in fair value hierarchy $ 404 $ 178 $ — $ 582 $ 415 $ 125 $ — $ 540 Investments measured at NAV (1) 532 479 Plan assets at fair value $ 1,114 $ 1,019 (1) Certain investments that were measured at net asset value (NAV) per share or its equivalent as a practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the fair value of plan assets at December 31, 2017 and 2016 . The Company has established investment guidelines for its U.S. pension and other postretirement plans to create an asset allocation that is expected to deliver a rate of return sufficient to meet the long-term obligation of each plan, given an acceptable level of risk. The target investment portfolio of the Company’s U.S. pension and other postretirement benefit plans is allocated 35% to 55% in U.S. equities, 20% to 35% in international equities, 20% to 35% in fixed-income investments, and up to 5% in cash and other investments. The portfolio’s equity weighting is consistent with the long-term nature of the plans’ benefit obligations. The expected annual standard deviation of returns of the target portfolio, which approximates 13% , reflects both the equity allocation and the diversification benefits among the asset classes in which the portfolio invests. For international pension plans, the targeted investment portfolio varies based on the duration of pension liabilities and local government rules and regulations. Although a significant percentage of plan assets are invested in U.S. equities, concentration risk is mitigated through the use of strategies that are diversified within management guidelines. Expected Contributions Expected contributions during 2018 are approximately $60 million for U.S. pension plans, approximately $150 million for international pension plans and approximately $25 million for other postretirement benefit plans. Expected Benefit Payments Expected benefit payments are as follows: U.S. Pension Benefits International Pension Benefits Other Postretirement Benefits 2018 $ 609 $ 222 $ 96 2019 638 205 101 2020 650 217 104 2021 663 225 109 2022 683 243 113 2023 — 2027 3,760 1,326 623 Expected benefit payments are based on the same assumptions used to measure the benefit obligations and include estimated future employee service. Amounts Recognized in Other Comprehensive Income Net loss amounts reflect experience differentials primarily relating to differences between expected and actual returns on plan assets as well as the effects of changes in actuarial assumptions. Net loss amounts in excess of certain thresholds are amortized into net periodic benefit cost over the average remaining service life of employees. The following amounts were reflected as components of OCI : Pension Plans Other Postretirement Benefit Plans U.S. International Years Ended December 31 2017 2016 2015 2017 2016 2015 2017 2016 2015 Net (loss) gain arising during the period $ (19 ) $ (743 ) $ 73 $ 309 $ (380 ) $ (66 ) $ 170 $ (45 ) $ 209 Prior service (cost) credit arising during the period (13 ) (10 ) (13 ) 22 (2 ) (4 ) (31 ) (19 ) 511 $ (32 ) $ (753 ) $ 60 $ 331 $ (382 ) $ (70 ) $ 139 $ (64 ) $ 720 Net loss amortization included in benefit cost $ 180 $ 119 $ 214 $ 98 $ 87 $ 118 $ 1 $ 3 $ 5 Prior service (credit) cost amortization included in benefit cost (53 ) (55 ) (56 ) (11 ) (11 ) (14 ) (98 ) (106 ) (64 ) $ 127 $ 64 $ 158 $ 87 $ 76 $ 104 $ (97 ) $ (103 ) $ (59 ) The estimated net loss (gain) and prior service cost (credit) amounts that will be amortized from AOCI into net periodic benefit cost during 2018 are $314 million and $(64) million , respectively, for pension plans (of which $230 million and $(51) million , respectively, relates to U.S. pension plans) and $1 million and $(84) million , respectively, for other postretirement benefit plans. Actuarial Assumptions The Company reassesses its benefit plan assumptions on a regular basis. The weighted average assumptions used in determining U.S. pension and other postretirement benefit plan and international pension plan information are as follows: U.S. Pension and Other Postretirement Benefit Plans International Pension Plans December 31 2017 2016 2015 2017 2016 2015 Net periodic benefit cost Discount rate 4.30 % 4.70 % 4.20 % 2.20 % 2.80 % 2.70 % Expected rate of return on plan assets 8.70 % 8.60 % 8.50 % 5.10 % 5.60 % 5.70 % Salary growth rate 4.30 % 4.30 % 4.40 % 2.90 % 2.90 % 2.90 % Benefit obligation Discount rate 3.70 % 4.30 % 4.80 % 2.10 % 2.20 % 2.80 % Salary growth rate 4.30 % 4.30 % 4.30 % 2.90 % 2.90 % 2.90 % For both the pension and other postretirement benefit plans, the discount rate is evaluated on measurement dates and modified to reflect the prevailing market rate of a portfolio of high-quality fixed-income debt instruments that would provide the future cash flows needed to pay the benefits included in the benefit obligation as they come due. The expected rate of return for both the pension and other postretirement benefit plans represents the average rate of return to be earned on plan assets over the period the benefits included in the benefit obligation are to be paid and is determined on a plan basis. The expected rate of return within each plan is developed considering long-term historical returns data, current market conditions, and actual returns on the plan assets. Using this reference information, the long-term return expectations for each asset category and a weighted average expected return for each plan’s target portfolio is developed, according to the allocation among those investment categories. The expected portfolio performance reflects the contribution of active management as appropriate. For 2018 , the expected rate of return for the Company’s U.S. pension and other postretirement benefit plans will range from 7.70% to 8.30% , as compared to a range of 8.00% to 8.75% in 2017 . The decrease is primarily due to a modest shift in asset allocation. The increase in the weighted-average expected return on U.S. pension and other postretirement benefit plan assets from 2015 to 2017 is due to the relative weighting of the referenced plans’ assets. The health care cost trend rate assumptions for other postretirement benefit plans are as follows: December 31 2017 2016 Health care cost trend rate assumed for next year 7.2 % 7.4 % Rate to which the cost trend rate is assumed to decline 4.5 % 4.5 % Year that the trend rate reaches the ultimate trend rate 2032 2032 A one percentage point change in the health care cost trend rate would have had the following effects: One Percentage Point Increase Decrease Effect on total service and interest cost components $ 13 $ (11 ) Effect on benefit obligation 125 (104 ) Savings Plans The Company also maintains defined contribution savings plans in the United States. The Company matches a percentage of each employee’s contributions consistent with the provisions of the plan for which the employee is eligible. Total employer contributions to these plans in 2017 , 2016 and 2015 were $131 million , $126 million and $125 million , respectively.

Other (Income) Expense, Net

Other (Income) Expense, Net	12 Months Ended
	Dec. 31, 2017
Other Income and Expenses [Abstract]
Other (Income) Expense, Net	Other (Income) Expense, Net Other (income) expense, net, consisted of: Years Ended December 31 2017 2016 2015 Interest income $ (385 ) $ (328 ) $ (289 ) Interest expense 754 693 672 Exchange (gains) losses (11 ) 174 1,277 Equity income from affiliates (42 ) (86 ) (205 ) Other, net (304 ) 267 72 $ 12 $ 720 $ 1,527 The exchange losses in 2015 were related primarily to the Venezuelan Bolívar. During 2015, upon evaluation of evolving economic conditions in Venezuela and volatility in the country, combined with a decline in transactions that were settled at the then official (CENCOEX) rate, the Company determined it was unlikely that all outstanding net monetary assets would be settled at the CENCOEX rate. Accordingly, during 2015, the Company recorded charges of $876 million to devalue its net monetary assets in Venezuela to amounts that represented the Company’s estimate of the U.S. dollar amount that would ultimately be collected and recorded additional exchange losses of $138 million in the aggregate during 2015 reflecting the ongoing effect of translating transactions and net monetary assets consistent with these rates. Since January 2010, Venezuela has been designated hyperinflationary and, as a result, local foreign operations are remeasured in U.S. dollars with the impact recorded in results of operations. The decline in equity income from affiliates in 2017 as compared with 2016 was driven primarily by the termination of the SPMSD joint venture on December 31, 2016, partially offset by higher equity income from certain research investment funds. The decline in equity income from affiliates in 2016 as compared with 2015 was driven primarily by lower equity income from certain research investment funds. Other, net (as presented in the table above) in 2017 includes gains of $291 million on the sale of equity investments, income of $232 million related to AstraZeneca’s option exercise (see Note 9), and a $191 million loss on extinguishment of debt (see Note 10). Other, net in 2016 includes a charge of $625 million to settle worldwide patent litigation related to Keytruda (see Note 11), a gain of $117 million related to the settlement of other patent litigation, gains of $100 million resulting from the receipt of milestone payments for out-licensed migraine clinical development programs (see Note 3) and $98 million of income related to AstraZeneca’s option exercise. Other, net in 2015 includes a $680 million net charge related to the settlement of Vioxx shareholder class action litigation (which was paid in 2016) and an expense of $78 million for a contribution of investments in equity securities to the Merck Foundation, partially offset by a $250 million gain on the sale of certain migraine clinical development programs (see Note 3), a $147 million gain on the divestiture of Merck’s remaining ophthalmics business in international markets (see Note 3), and the recognition of $182 million of income related to AstraZeneca’s option exercise. Interest paid was $723 million in 2017 , $686 million in 2016 and $653 million in 2015 .

Taxes on Income

Taxes on Income	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Taxes on Income	Taxes on Income A reconciliation between the effective tax rate and the U.S. statutory rate is as follows: 2017 2016 2015 Amount Tax Rate Amount Tax Rate Amount Tax Rate U.S. statutory rate applied to income before taxes $ 2,282 35.0 % $ 1,631 35.0 % $ 1,890 35.0 % Differential arising from: Provisional impact of the TCJA 2,625 40.3 — — — — Impact of purchase accounting adjustments, including amortization 713 10.9 623 13.4 797 14.8 Valuation allowances 632 9.7 (5 ) (0.1 ) 39 0.7 Restructuring 142 2.2 145 3.1 167 3.1 State taxes 77 1.2 173 3.7 159 2.9 U.S. health care reform legislation 74 1.1 68 1.4 66 1.2 Foreign currency devaluation related to Venezuela — — — — 321 5.9 Foreign earnings (1,725 ) (26.5 ) (1,646 ) (35.3 ) (2,144 ) (39.7 ) Tax settlements (356 ) (5.5 ) — — (417 ) (7.7 ) Unremitted foreign earnings — — (30 ) (0.6 ) 260 4.8 Other (1) (361 ) (5.5 ) (241 ) (5.2 ) (196 ) (3.6 ) $ 4,103 62.9 % $ 718 15.4 % $ 942 17.4 % (1) Other includes the tax effect of contingency reserves, research credits, losses on foreign subsidiaries and miscellaneous items. The Company’s 2017 effective tax rate reflects a provisional impact of 40.3% for the Tax Cuts and Jobs Act (TCJA), which was enacted on December 22, 2017. Among other provisions, the TCJA reduces the U.S. federal corporate statutory tax rate from 35% to 21% effective January 1, 2018, requires companies to pay a one-time transition tax on undistributed earnings of certain foreign subsidiaries, and creates new taxes on certain foreign sourced earnings. The Company has reflected the impact of the TCJA in its financial statements as described below. However, application of certain provisions of the TCJA remains subject to further interpretation and in these instances the Company has made a reasonable estimate of the effects of the TCJA. The one-time transition tax is based on the Company’s post-1986 undistributed earnings and profits (E&P). For a substantial portion of these undistributed E&P, the Company had not previously provided deferred taxes as these earnings were deemed by Merck to be retained indefinitely by subsidiary companies for reinvestment. The Company recorded a provisional amount for its one-time transition tax liability of $5.3 billion . Merck has not yet finalized its calculation of the total post-1986 undistributed E&P for these foreign subsidiaries. The transition tax is based in part on the amount of undistributed E&P held in cash and other specified assets; therefore, this amount may change when the Company finalizes its calculation of post-1986 undistributed foreign E&P and finalizes the amounts held in cash or other specified assets. This provisional amount was reduced by the reversal of $2.0 billion of deferred taxes that were previously recorded in connection with the merger of Schering-Plough Corporation in 2009 for certain undistributed foreign E&P. The Company anticipates that it will be able to utilize certain foreign tax credits to partially reduce the transition tax payment, resulting in a net transition tax payment of $5.1 billion . As permitted under the TCJA, the Company has elected to pay the one-time transition tax over a period of eight years. The current portion of the transition tax liability of $545 million is included as reduction to prepaid income taxes included in Other Current Assets and the remainder of $4.5 billion is included in Other Noncurrent Liabilities . As a result of the TCJA, the Company has made a determination it is no longer indefinitely reinvested with respect to its undistributed earnings from foreign subsidiaries and has provided a deferred tax liability for withholding tax that would apply. The Company remeasured its deferred tax assets and liabilities at the new federal statutory tax rate of 21%, which resulted in a provisional deferred tax benefit of $779 million . The deferred tax benefit calculation remains subject to certain clarifications, particularly related to executive compensation and benefits. Beginning in 2018, the TCJA includes a tax on “global intangible low-taxed income” (GILTI) as defined in the TCJA. The Company is allowed to make an accounting policy election to account for the tax effects of the GILTI tax either in the income tax provision in future periods as the tax arises, or as a component of deferred taxes on the related investments in foreign subsidiaries. The Company is currently evaluating the GILTI provisions of the TCJA and the implications on its tax provision and has not finalized the accounting policy election; therefore, the Company has not recorded deferred taxes for GILTI as of December 31, 2017. The foreign earnings tax rate differentials in the tax rate reconciliation above primarily reflect the impacts of operations in jurisdictions with different tax rates than the United States, particularly Ireland and Switzerland, as well as Singapore and Puerto Rico which operate under tax incentive grants (which begin to expire in 2022), where the earnings had been indefinitely reinvested, thereby yielding a favorable impact on the effective tax rate as compared with the 35% U.S. statutory rate. The foreign earnings tax rate differentials do not include the impact of intangible asset impairment charges, amortization of purchase accounting adjustments or restructuring costs. These items are presented separately as they each represent a significant, separately disclosed pretax cost or charge, and a substantial portion of each of these items relates to jurisdictions with lower tax rates than the United States. Therefore, the impact of recording these expense items in lower tax rate jurisdictions is an unfavorable impact on the effective tax rate as compared to the 35% U.S. statutory rate. The Company’s 2015 effective tax rate reflects the impact of the Protecting Americans From Tax Hikes Act, which was signed into law on December 18, 2015, extending the research credit permanently and the controlled foreign corporation look-through provisions for five years. Income before taxes consisted of: Years Ended December 31 2017 2016 2015 Domestic $ 3,483 $ 518 $ 2,247 Foreign 3,038 4,141 3,154 $ 6,521 $ 4,659 $ 5,401 Taxes on income consisted of: Years Ended December 31 2017 2016 2015 Current provision Federal $ 5,585 $ 1,166 $ 732 Foreign 1,229 916 844 State (90 ) 157 130 6,724 2,239 1,706 Deferred provision Federal (2,958 ) (1,255 ) (552 ) Foreign 75 (225 ) (163 ) State 262 (41 ) (49 ) (2,621 ) (1,521 ) (764 ) $ 4,103 $ 718 $ 942 Deferred income taxes at December 31 consisted of: 2017 2016 Assets Liabilities Assets Liabilities Intangibles $ 307 $ 2,435 $ 86 $ 3,854 Inventory related 29 499 30 660 Accelerated depreciation 28 642 28 927 Unremitted foreign earnings — 33 — 2,044 Pensions and other postretirement benefits 498 192 727 109 Compensation related 314 — 438 — Unrecognized tax benefits 156 — 383 — Net operating losses and other tax credit carryforwards 654 — 437 — Other 1,088 19 1,248 46 Subtotal 3,074 3,820 3,377 7,640 Valuation allowance (900 ) (268 ) Total deferred taxes $ 2,174 $ 3,820 $ 3,109 $ 7,640 Net deferred income taxes $ 1,646 $ 4,531 Recognized as: Other assets $ 573 $ 546 Deferred income taxes $ 2,219 $ 5,077 The Company has net operating loss (NOL) carryforwards in several jurisdictions. As of December 31, 2017 , $630 million of deferred taxes on NOL carryforwards relate to foreign jurisdictions. Valuation allowances of $900 million have been established on these foreign NOL carryforwards and other foreign deferred tax assets. In addition, the Company has $24 million of deferred tax assets relating to various U.S. tax credit carryforwards and NOL carryforwards, all of which are expected to be fully utilized prior to expiry. Income taxes paid in 2017 , 2016 and 2015 were $4.9 billion , $1.8 billion and $1.8 billion , respectively. Tax benefits relating to stock option exercises were $73 million in 2017 , $147 million in 2016 and $109 million in 2015 . A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows: 2017 2016 2015 Balance January 1 $ 3,494 $ 3,448 $ 3,534 Additions related to current year positions 146 196 198 Additions related to prior year positions 520 75 53 Reductions for tax positions of prior years (1) (1,038 ) (90 ) (59 ) Settlements (1) (1,388 ) (92 ) (184 ) Lapse of statute of limitations (11 ) (43 ) (94 ) Balance December 31 $ 1,723 $ 3,494 $ 3,448 (1) Amounts reflect the settlements with the IRS as discussed below. If the Company were to recognize the unrecognized tax benefits of $1.7 billion at December 31, 2017 , the income tax provision would reflect a favorable net impact of $1.6 billion . The Company is under examination by numerous tax authorities in various jurisdictions globally. The Company believes that it is reasonably possible that the total amount of unrecognized tax benefits as of December 31, 2017 could decrease by up to approximately $165 million in the next 12 months as a result of various audit closures, settlements or the expiration of the statute of limitations. The ultimate finalization of the Company’s examinations with relevant taxing authorities can include formal administrative and legal proceedings, which could have a significant impact on the timing of the reversal of unrecognized tax benefits. The Company believes that its reserves for uncertain tax positions are adequate to cover existing risks or exposures. Expenses for interest and penalties associated with uncertain tax positions amounted to $183 million in 2017 , $134 million in 2016 and $102 million in 2015 . These amounts reflect the beneficial impacts of various tax settlements, including those discussed below. Liabilities for accrued interest and penalties were $341 million and $886 million as of December 31, 2017 and 2016 , respectively. In 2017, the Internal Revenue Service (IRS) concluded its examinations of Merck’s 2006-2011 U.S. federal income tax returns. As a result, the Company was required to make a payment of approximately $2.8 billion . 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 net $234 million tax benefit in 2017. 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, as well as adjustments to reserves for unrecognized tax benefits relating to years which remain open to examination that are affected by this settlement. Although the IRS’s examination of the Company’s 2002-2005 federal tax returns was concluded prior to 2015, one issue relating to a refund claim remained open. During 2015, this issue was resolved and the Company received a refund of approximately $715 million , which exceeded the receivable previously recorded by the Company, resulting in a tax benefit of $410 million . The IRS is currently conducting examinations of the Company’s tax returns for the years 2012 through 2014. In addition, various state and foreign tax examinations are in progress. For most of its other significant tax jurisdictions (both U.S. state and foreign), the Company’s income tax returns are open for examination for the period 2003 through 2017.

Earnings per Share

Earnings per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings per Share	Earnings per Share The calculations of earnings per share (shares in millions) are as follows: Years Ended December 31 2017 2016 2015 Net income attributable to Merck & Co., Inc. $ 2,394 $ 3,920 $ 4,442 Average common shares outstanding 2,730 2,766 2,816 Common shares issuable (1) 18 21 25 Average common shares outstanding assuming dilution 2,748 2,787 2,841 Basic earnings per common share attributable to Merck & Co., Inc. common shareholders $ 0.88 $ 1.42 $ 1.58 Earnings per common share assuming dilution attributable to Merck & Co., Inc. common shareholders $ 0.87 $ 1.41 $ 1.56 (1) Issuable primarily under share-based compensation plans. In 2017 , 2016 and 2015 , 5 million , 13 million and 9 million , respectively, of common shares issuable under share-based compensation plans were excluded from the computation of earnings per common share assuming dilution because the effect would have been antidilutive.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2017
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) Changes in AOCI by component are as follows: Derivatives Investments Employee Benefit Plans Cumulative Translation Adjustment Accumulated Other Comprehensive Income (Loss) Balance January 1, 2015, net of taxes $ 530 $ 111 $ (2,986 ) $ (1,978 ) $ (4,323 ) Other comprehensive income (loss) before reclassification adjustments, pretax 526 (9 ) 710 (158 ) 1,069 Tax (177 ) (13 ) (272 ) (28 ) (490 ) Other comprehensive income (loss) before reclassification adjustments, net of taxes 349 (22 ) 438 (186 ) 579 Reclassification adjustments, pretax (731 ) (1) (73 ) (2) 203 (3) (22 ) (623 ) Tax 256 25 (62 ) — 219 Reclassification adjustments, net of taxes (475 ) (48 ) 141 (22 ) (404 ) Other comprehensive income (loss), net of taxes (126 ) (70 ) 579 (208 ) 175 Balance December 31, 2015, net of taxes 404 41 (2,407 ) (2,186 ) (4,148 ) Other comprehensive income (loss) before reclassification adjustments, pretax 210 (38 ) (1,199 ) (150 ) (1,177 ) Tax (72 ) 16 363 (19 ) 288 Other comprehensive income (loss) before reclassification adjustments, net of taxes 138 (22 ) (836 ) (169 ) (889 ) Reclassification adjustments, pretax (314 ) (1) (31 ) (2) 37 (3) — (308 ) Tax 110 9 — — 119 Reclassification adjustments, net of taxes (204 ) (22 ) 37 — (189 ) Other comprehensive income (loss), net of taxes (66 ) (44 ) (799 ) (169 ) (1,078 ) Balance December 31, 2016, net of taxes 338 (3 ) (3,206 ) (4) (2,355 ) (5,226 ) Other comprehensive income (loss) before reclassification adjustments, pretax (561 ) 212 438 235 324 Tax 207 (35 ) (106 ) 166 232 Other comprehensive income (loss) before reclassification adjustments, net of taxes (354 ) 177 332 401 556 Reclassification adjustments, pretax (141 ) (1) (291 ) (2) 117 (3) — (315 ) Tax 49 56 (30 ) — 75 Reclassification adjustments, net of taxes (92 ) (235 ) 87 — (240 ) Other comprehensive income (loss), net of taxes (446 ) (58 ) 419 401 316 Balance December 31, 2017, net of taxes $ (108 ) $ (61 ) $ (2,787 ) (4) $ (1,954 ) $ (4,910 ) (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 investments 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 14). (4) Includes pension plan net loss of $ 3.5 billion and $3.9 billion at December 31, 2017 and 2016 , respectively, and other postretirement benefit plan net (gain) loss of $(16) million and $115 million at December 31, 2017 and 2016 , respectively, as well as pension plan prior service credit of $326 million and $361 million at December 31, 2017 and 2016 , respectively, and other postretirement benefit plan prior service credit of $383 million and $466 million at December 31, 2017 and 2016 , respectively.

Segment Reporting

Segment Reporting	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting The Company’s operations are principally managed on a products basis and include four operating segments, which are the Pharmaceutical, Animal Health, Healthcare Services and Alliances segments. The Pharmaceutical segment is the only reportable segment. 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. 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. Sales of vaccines in most major European markets were marketed through the Company’s SPMSD joint venture until its termination on December 31, 2016 (see Note 9). The Company also has an Animal Health segment that discovers, develops, manufactures and markets animal health products, including vaccines, which the Company sells to veterinarians, distributors and animal producers. The Company’s Healthcare Services segment provides services and solutions that focus on engagement, health analytics and clinical services to improve the value of care delivered to patients. Sales of the Company’s products were as follows: Years Ended December 31 2017 2016 2015 U.S. Int’l Total U.S. Int’l Total U.S. Int’l Total Primary Care and Women’s Health Cardiovascular Zetia $ 352 $ 992 $ 1,344 $ 1,588 $ 972 $ 2,560 $ 1,612 $ 914 $ 2,526 Vytorin 124 627 751 473 668 1,141 479 771 1,251 Atozet — 225 225 1 146 146 2 34 36 Adempas — 300 300 — 169 169 — 30 30 Diabetes Januvia 2,153 1,584 3,737 2,286 1,622 3,908 2,263 1,601 3,863 Janumet 863 1,296 2,158 984 1,217 2,201 976 1,175 2,151 General Medicine and Women’s Health NuvaRing 564 197 761 576 202 777 515 216 732 Implanon/Nexplanon 496 191 686 420 186 606 367 221 588 Follistim AQ 123 174 298 157 197 355 160 223 383 Hospital and Specialty Hepatitis Zepatier 771 888 1,660 488 67 555 — — — HIV Isentress/Isentress HD 565 639 1,204 721 666 1,387 797 714 1,511 Hospital Acute Care Bridion 239 465 704 77 405 482 — 353 353 Noxafil 309 327 636 284 312 595 212 275 487 Invanz 361 241 602 329 233 561 322 247 569 Cancidas 20 402 422 25 533 558 24 548 573 Cubicin (1) 189 193 382 906 181 1,087 1,030 97 1,127 Primaxin 10 270 280 4 293 297 8 305 313 Immunology Remicade — 837 837 — 1,268 1,268 — 1,794 1,794 Simponi — 819 819 — 766 766 — 690 690 Oncology Keytruda 2,309 1,500 3,809 792 610 1,402 393 173 566 Emend 342 213 556 356 193 549 326 209 535 Temodar 16 256 271 15 268 283 7 306 312 Diversified Brands Respiratory Singulair 40 692 732 40 874 915 39 892 931 Nasonex 54 333 387 184 352 537 449 409 858 Dulera 261 26 287 412 24 436 515 21 536 Other Cozaar/Hyzaar 18 466 484 16 494 511 30 637 667 Arcoxia — 363 363 — 450 450 — 471 471 Fosamax 6 235 241 5 279 284 12 347 359 Vaccines (2) Gardasil/Gardasil 9 1,565 743 2,308 1,780 393 2,173 1,520 388 1,908 ProQuad/M-M-R II/Varivax 1,374 303 1,676 1,362 279 1,640 1,290 214 1,505 Pneumovax 23 581 240 821 447 193 641 378 164 542 RotaTeq 481 204 686 482 169 652 447 163 610 Zostavax 422 246 668 518 168 685 592 157 749 Other pharmaceutical (3) 1,246 3,049 4,295 1,345 3,228 4,574 1,473 3,785 5,256 Total Pharmaceutical segment sales 15,854 19,536 35,390 17,073 18,077 35,151 16,238 18,544 34,782 Other segment sales (4) 1,486 2,785 4,272 1,374 2,489 3,862 1,213 2,454 3,667 Total segment sales 17,340 22,321 39,662 18,447 20,566 39,013 17,451 20,998 38,449 Other (5) 84 377 460 31 763 794 68 981 1,049 $ 17,424 $ 22,698 $ 40,122 $ 18,478 $ 21,329 $ 39,807 $ 17,519 $ 21,979 $ 39,498 U.S. plus international may not equal total due to rounding. (1) Sales of Cubicin in 2015 represent sales subsequent to the Cubist acquisition date. (2) On December 31, 2016, Merck and Sanofi terminated their equally-owned joint venture, SPMSD, which marketed vaccines in most major European markets (see Note 9). Accordingly, vaccine sales in 2017 include sales in the European markets that were previously part of SPMSD. Amounts for 2016 and 2015 do not include sales of vaccines sold through SPMSD, the results of which are reflected in equity income from affiliates included in Other (income) expense, net . Amounts for 2016 and 2015 do, however, include supply sales to SPMSD. (3) Other pharmaceutical primarily reflects sales of other human health pharmaceutical products, including products within the franchises not listed separately. (4) Represents the non-reportable segments of Animal Health, Healthcare Services and Alliances. (5) Other is primarily comprised of miscellaneous corporate revenues, including revenue hedging activities, as well as third-party manufacturing sales. Other in 2017 and 2016 also includes $85 million and $170 million , respectively, related to the sale of the marketing rights to certain products. Consolidated revenues by geographic area where derived are as follows: Years Ended December 31 2017 2016 2015 United States $ 17,424 $ 18,478 $ 17,519 Europe, Middle East and Africa 11,478 10,953 10,677 Asia Pacific 4,337 3,918 3,825 Japan 3,122 2,846 2,673 Latin America 2,339 2,155 2,825 Other 1,422 1,457 1,979 $ 40,122 $ 39,807 $ 39,498 A reconciliation of total segment profits to consolidated Income before taxes is as follows: Years Ended December 31 2017 2016 2015 Segment profits: Pharmaceutical segment $ 22,586 $ 22,180 $ 21,658 Other segments 1,834 1,507 1,573 Total segment profits 24,420 23,687 23,231 Other profits 26 481 810 Unallocated: Interest income 385 328 289 Interest expense (754 ) (693 ) (672 ) Equity income from affiliates 49 (19 ) 135 Depreciation and amortization (1,378 ) (1,585 ) (1,573 ) Research and development (9,355 ) (9,084 ) (5,871 ) Amortization of purchase accounting adjustments (3,056 ) (3,692 ) (4,816 ) Restructuring costs (776 ) (651 ) (619 ) Loss on extinguishment of debt (191 ) — — Gain on sale of certain migraine clinical development programs — 100 250 Charge related to the settlement of worldwide Keytruda patent litigation — (625 ) — Gain on divestiture of certain ophthalmic products — — 147 Foreign currency devaluation related to Venezuela — — (876 ) Net charge related to the settlement of Vioxx shareholder class action litigation — — (680 ) Other unallocated, net (2,849 ) (3,588 ) (4,354 ) $ 6,521 $ 4,659 $ 5,401 Segment profits are comprised of segment sales less standard costs and certain operating expenses directly incurred by the segments. For internal management reporting presented to the chief operating decision maker, Merck does not allocate materials and production costs, other than standard costs, the majority of research and development expenses 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 of contingent consideration, and other miscellaneous income or expense items. Equity income from affiliates and depreciation and amortization included in segment profits is as follows: Pharmaceutical All Other Total Year Ended December 31, 2017 Included in segment profits: Equity income from affiliates $ (7 ) $ — $ (7 ) Depreciation and amortization (125 ) (87 ) (212 ) Year Ended December 31, 2016 Included in segment profits: Equity income from affiliates $ 105 $ — $ 105 Depreciation and amortization (160 ) (23 ) (183 ) Year Ended December 31, 2015 Included in segment profits: Equity income from affiliates $ 70 $ — $ 70 Depreciation and amortization (82 ) (18 ) (100 ) Property, plant and equipment, net by geographic area where located is as follows: December 31 2017 2016 2015 United States $ 8,070 $ 8,114 $ 8,467 Europe, Middle East and Africa 3,151 2,732 2,844 Asia Pacific 782 775 842 Latin America 271 234 182 Japan 158 164 164 Other 7 7 8 $ 12,439 $ 12,026 $ 12,507 The Company does not disaggregate assets on a products and services basis for internal management reporting and, therefore, such information is not presented.

Summary of Accounting Policies

Summary of Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation — The consolidated financial statements include the accounts of the Company and all of its subsidiaries in which a controlling interest is maintained. Intercompany balances and transactions are eliminated. Controlling interest is determined by majority ownership interest and the absence of substantive third-party participating rights or, in the case of variable interest entities, by majority exposure to expected losses, residual returns or both. For those consolidated subsidiaries where Merck ownership is less than 100%, the outside shareholders’ interests are shown as Noncontrolling interests in equity. Investments in affiliates over which the Company has significant influence but not a controlling interest, such as interests in entities owned equally by the Company and a third party that are under shared control, are carried on the equity basis.
Acquisitions	Acquisitions — In a business combination, the acquisition method of accounting requires that the assets acquired and liabilities assumed be recorded as of the date of the acquisition at their respective fair values with limited exceptions. Assets acquired and liabilities assumed in a business combination that arise from contingencies are generally recognized at fair value. If fair value cannot be determined, the asset or liability is recognized if probable and reasonably estimable; if these criteria are not met, no asset or liability is recognized. 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. Accordingly, the Company may be required to value assets at fair value measures that do not reflect the Company’s intended use of those assets. Any excess of the purchase price (consideration transferred) over the estimated fair values of net assets acquired is recorded as goodwill. Transaction costs and costs to restructure the acquired company are expensed as incurred. The operating results of the acquired business are reflected in the Company’s consolidated financial statements after the date of the acquisition. If the Company determines the assets acquired do not meet the definition of a business under the acquisition method of accounting, the transaction will be accounted for as an acquisition of assets rather than a business combination and, therefore, no goodwill will be recorded.
Foreign Currency Translation	Foreign Currency Translation — The net assets of international subsidiaries where the local currencies have been determined to be the functional currencies are translated into U.S. dollars using current exchange rates. The U.S. dollar effects that arise from translating the net assets of these subsidiaries at changing rates are recorded in the foreign currency translation account, which is included in Accumulated other comprehensive income (loss) ( AOCI ) and reflected as a separate component of equity. For those subsidiaries that operate in highly inflationary economies and for those subsidiaries where the U.S. dollar has been determined to be the functional currency, non-monetary foreign currency assets and liabilities are translated using historical rates, while monetary assets and liabilities are translated at current rates, with the U.S. dollar effects of rate changes included in Other (income) expense, net .
Cash Equivalents	Cash Equivalents — Cash equivalents are comprised of certain highly liquid investments with original maturities of less than three months.
Inventories	Inventories — Inventories are valued at the lower of cost or market. The cost of a substantial majority of domestic pharmaceutical and vaccine inventories is determined using the last-in, first-out (LIFO) method for both financial reporting and tax purposes. The cost of all other inventories is determined using the first-in, first-out (FIFO) method. Inventories consist of currently marketed products, as well as certain inventories produced in preparation for product launches that are considered to have a high probability of regulatory approval. In evaluating the recoverability of inventories produced in preparation for product launches, the Company considers the likelihood that revenue will be obtained from the future sale of the related inventory together with the status of the product within the regulatory approval process.
Investments	Investments — Investments in marketable debt and equity securities classified as available-for-sale are reported at fair value. Fair values of the Company’s investments are determined using quoted market prices in active markets for identical assets or liabilities or 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. Changes in fair value that are considered temporary are reported net of tax in Other Comprehensive Income ( OCI ). For declines in the fair value of equity securities that are considered other-than-temporary, impairment losses are charged to Other (income) expense, net . The Company considers available evidence in evaluating potential impairments of its investments, including the duration and extent to which fair value is less than cost and, for equity securities, the Company’s ability and intent to hold the investments. For debt securities, an other-than-temporary impairment has occurred if the Company does not expect to recover the entire amortized cost basis of the debt security. If the Company does not intend to sell the impaired debt security, and it is not more likely than not it will be required to sell the debt security before the recovery of its amortized cost basis, the amount of the other-than-temporary impairment recognized in earnings, recorded in Other (income) expense, net , is limited to the portion attributed to credit loss. The remaining portion of the other-than-temporary impairment related to other factors is recognized in OCI . Realized gains and losses for both debt and equity securities are included in Other (income) expense, net .
Revenue Recognition	Revenue Recognition — Revenues from sales of products are recognized when title and risk of loss passes to the customer, typically upon delivery. Recognition of revenue also requires reasonable assurance of collection of sales proceeds and completion of all performance obligations. Domestically, sales discounts are issued to customers at the point-of-sale, through an intermediary wholesaler (known as chargebacks), or in the form of rebates. Additionally, sales are generally made with a limited right of return under certain conditions. Revenues are recorded net of provisions for sales discounts and returns, which are established at the time of sale. In addition, revenues are recorded net of time value of money discounts if collection of accounts receivable is expected to be in excess of one year. Accruals for chargebacks are reflected as a direct reduction to accounts receivable and accruals for rebates are recorded as current liabilities. The accrued balances relative to the provisions for chargebacks and rebates included in Accounts receivable and Accrued and other current liabilities were $198 million and $2.4 billion , respectively, at December 31, 2017 and $196 million and $2.7 billion , respectively, at December 31, 2016 . The Company recognizes revenue from the sales of vaccines to the Federal government for placement into vaccine stockpiles in accordance with Securities and Exchange Commission (SEC) Interpretation , Commission Guidance Regarding Accounting for Sales of Vaccines and BioTerror Countermeasures to the Federal Government for Placement into the Pediatric Vaccine Stockpile or the Strategic National Stockpile . This interpretation allows companies to recognize revenue for sales of vaccines into U.S. government stockpiles even though these sales might not meet the criteria for revenue recognition under other accounting guidance.
Depreciation	Depreciation — Depreciation is provided over the estimated useful lives of the assets, principally using the straight-line method. For tax purposes, accelerated tax methods are used. The estimated useful lives primarily range from 25 to 45 years for Buildings , and from 3 to 15 years for Machinery, equipment and office furnishings .
Advertising and Promotion Costs	Advertising and Promotion Costs — Advertising and promotion costs are expensed as incurred.
Software Capitalization	Software Capitalization — The Company capitalizes certain costs incurred in connection with obtaining or developing internal-use software including external direct costs of material and services, and payroll costs for employees directly involved with the software development. Capitalized software costs are included in Property, plant and equipment and amortized beginning when the software project is substantially complete and the asset is ready for its intended use. Capitalized software costs associated with projects that are being amortized over 6 to 10 years (including the Company’s on-going multi-year implementation of an enterprise-wide resource planning system) were $449 million and $452 million , net of accumulated amortization at December 31, 2017 and 2016 , respectively. All other capitalized software costs are being amortized over periods ranging from 3 to 5 years. Costs incurred during the preliminary project stage and post-implementation stage, as well as maintenance and training costs, are expensed as incurred.
Goodwill	Goodwill — Goodwill represents the excess of the consideration transferred over the fair value of net assets of businesses acquired. Goodwill is assigned to reporting units and evaluated for impairment on at least an annual basis, or more frequently if impairment indicators exist, by first assessing qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If the Company concludes it is more likely than not that the fair value of a reporting unit is less than its carrying amount, a quantitative fair value test is performed.
Acquired Intangibles	Acquired Intangibles — Acquired intangibles include products and product rights, tradenames and patents, which are initially recorded at fair value, assigned an estimated useful life, and are amortized primarily on a straight-line basis over their estimated useful lives ranging from 2 to 20 years (see Note 8). The Company periodically evaluates whether current facts or circumstances indicate that the carrying values of its acquired intangibles may not be recoverable. If such circumstances are determined to exist, an estimate of the undiscounted future cash flows of these assets, or appropriate asset groupings, is compared to the carrying value to determine whether an impairment exists. If the asset is determined to be impaired, the loss is measured based on the difference between the carrying value of the intangible asset and its fair value, which is determined based on the net present value of estimated future cash flows.
Acquired In-Process Research and Development	Acquired In-Process Research and Development — Acquired in-process research and development (IPR&D) that the Company acquires through business combinations represents the fair value assigned to incomplete research projects which, at the time of acquisition, have not reached technological feasibility. The amounts are capitalized and are accounted for as indefinite-lived intangible assets, subject to impairment testing until completion or abandonment of the projects. Upon successful completion of each project, Merck will make a determination as to the then useful life of the intangible asset, generally determined by the period in which the substantial majority of the cash flows are expected to be generated, and begin amortization. The Company tests IPR&D for impairment at least annually, or more frequently if impairment indicators exist, by first assessing qualitative factors to determine whether it is more likely than not that the fair value of the IPR&D intangible asset is less than its carrying amount. If the Company concludes it is more likely than not that the fair value is less than the carrying amount, a quantitative test that compares the fair value of the IPR&D intangible asset with its carrying value is performed. If the fair value is less than the carrying amount, an impairment loss is recognized in operating results.
Contingent Consideration	Contingent Consideration — Certain of the Company’s business acquisitions involve the potential for future payment of consideration that is contingent upon the achievement of performance milestones, including product development milestones and royalty payments on future product sales. The fair value of contingent consideration liabilities is determined at the acquisition date using unobservable inputs. These inputs include the estimated amount and timing of projected cash flows, the probability of success (achievement of the contingent event) and the risk-adjusted discount rate used to present value the probability-weighted cash flows. Subsequent to the acquisition date, at each reporting period, the contingent consideration liability is remeasured at current fair value with changes (either expense or income) recorded in earnings.
Collaborative Arrangements	Contingent Consideration — Certain of the Company’s business acquisitions involve the potential for future payment of consideration that is contingent upon the achievement of performance milestones, including product development milestones and royalty payments on future product sales. The fair value of contingent consideration liabilities is determined at the acquisition date using unobservable inputs. These inputs include the estimated amount and timing of projected cash flows, the probability of success (achievement of the contingent event) and the risk-adjusted discount rate used to present value the probability-weighted cash flows. Subsequent to the acquisition date, at each reporting period, the contingent consideration liability is remeasured at current fair value with changes (either expense or income) recorded in earnings.
Research and Development	Research and Development — Research and development is expensed as incurred. Nonrefundable advance payments for goods and services that will be used in future research and development activities are expensed when the activity has been performed or when the goods have been received rather than when the payment is made. Research and development expenses include restructuring costs and IPR&D impairment charges in all periods. In addition, research and development expenses include expense or income related to changes in the estimated fair value measurement of liabilities for contingent consideration.
Share-Based Compensation	Share-Based Compensation — The Company expenses all share-based payments to employees over the requisite service period based on the grant-date fair value of the awards.
Restructuring Costs	Restructuring Costs — The Company records liabilities for costs associated with exit or disposal activities in the period in which the liability is incurred. In accordance with existing benefit arrangements, employee termination costs are accrued when the restructuring actions are probable and estimable. When accruing these costs, the Company will recognize the amount within a range of costs that is the best estimate within the range. When no amount within the range is a better estimate than any other amount, the Company recognizes the minimum amount within the range. Costs for one-time termination benefits in which the employee is required to render service until termination in order to receive the benefits are recognized ratably over the future service period.
Contingencies and Legal Defense Costs	Contingencies and Legal Defense Costs — The Company records accruals for contingencies and legal defense costs expected to be incurred in connection with a loss contingency when it is probable that a liability has been incurred and the amount can be reasonably estimated.
Taxes on Income	Taxes on Income — Deferred taxes are recognized for the future tax effects of temporary differences between financial and income tax reporting based on enacted tax laws and rates. The Company evaluates tax positions to determine whether the benefits of tax positions are more likely than not of being sustained upon audit based on the technical merits of the tax position. For tax positions that are more likely than not of being sustained upon audit, the Company recognizes the largest amount of the benefit that is greater than 50% likely of being realized upon ultimate settlement in the financial statements. For tax positions that are not more likely than not of being sustained upon audit, the Company does not recognize any portion of the benefit in the financial statements. The Company recognizes interest and penalties associated with uncertain tax positions as a component of Taxes on income in the Consolidated Statement of Income.
Use of Estimates	Use of Estimates — The consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States (GAAP) and, accordingly, include certain amounts that are based on management’s best estimates and judgments. Estimates are used when accounting for amounts recorded in connection with acquisitions, including initial fair value determinations of assets and liabilities, primarily IPR&D, other intangible assets and contingent consideration, as well as subsequent fair value measurements. Additionally, estimates are used in determining such items as provisions for sales discounts and returns, depreciable and amortizable lives, recoverability of inventories, including those produced in preparation for product launches, amounts recorded for contingencies, environmental liabilities and other reserves, pension and other postretirement benefit plan assumptions, share-based compensation assumptions, restructuring costs, impairments of long-lived assets (including intangible assets and goodwill) and investments, and taxes on income. Because of the uncertainty inherent in such estimates, actual results may differ from these estimates.
Reclassifications	Reclassifications — Certain reclassifications have been made to prior year amounts to conform to the current year presentation.
New Accounting Standards	Recently Issued Accounting Standards — In May 2014, the Financial Accounting Standards Board (FASB) issued amended accounting guidance on revenue recognition that will be applied to all contracts with customers. The objective of the new guidance is to improve comparability of revenue recognition practices across entities and to provide more useful information to users of financial statements through improved disclosure requirements. The new standard permits two methods of adoption: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of adopting the guidance being recognized at the date of initial application (modified retrospective method). The new standard will be effective as of January 1, 2018 and will be adopted using the modified retrospective method. The Company anticipates recording a cumulative-effect adjustment upon adoption increasing Retained earnings by $5 million in 2018. The adoption of the new guidance will also result in some additional disclosures. In January 2016, the FASB issued revised guidance for the accounting and reporting of financial instruments. The new guidance requires that equity investments with readily determinable fair values currently classified as available for sale be measured at fair value with changes in fair value recognized in net income. The new guidance also simplifies the impairment testing of equity investments without readily determinable fair values and changes certain disclosure requirements. The new standard will be effective as of January 1, 2018 and will be adopted using a modified retrospective approach. The Company anticipates recording a cumulative-effect adjustment upon adoption increasing Retained earnings by $8 million in 2018. In August 2016, the FASB issued guidance on the classification of certain cash receipts and payments in the statement of cash flows intended to reduce diversity in practice. The new standard is effective as of January 1, 2018 and will be adopted using a retrospective application. The Company does not anticipate any changes to the presentation of its Consolidated Statement of Cash Flows as a result of adopting the new standard. In October 2016, the FASB issued guidance on the accounting for the income tax consequences of intra-entity transfers of assets other than inventory. Under existing guidance, the recognition of current and deferred income taxes for an intra-entity asset transfer is prohibited until the asset has been sold to a third party. The new guidance will require the recognition of the income tax consequences of an intra-entity transfer of an asset (with the exception of inventory) when the intra-entity transfer occurs. The new standard will be effective as of January 1, 2018 and will be adopted using a modified retrospective approach. The Company anticipates recording a cumulative-effect adjustment upon adoption increasing Retained earnings by approximately $60 million in 2018 with a corresponding increase to deferred tax assets, subject to finalization. In November 2016, the FASB issued guidance requiring that amounts generally described as restricted cash and restricted cash equivalents be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The new standard is effective as of January 1, 2018 and will be adopted using a retrospective application. The adoption of the new guidance will not have a material effect on the Company’s Consolidated Statement of Cash Flows. In March 2017, the FASB amended the guidance related to net periodic benefit cost for defined benefit plans that requires entities to (1) disaggregate the current service cost component from the other components of net benefit cost and present it with other employee compensation costs in the income statement within operations if such a subtotal is presented; (2) present the other components of net benefit cost separately in the income statement and outside of income from operations; and (3) only capitalize the service cost component when applicable. Entities must use a retrospective transition method to adopt the requirement for separate presentation in the income statement of service costs and other components and a prospective transition method to adopt the requirement to limit the capitalization of benefit costs to the service cost component. The Company will utilize a practical expedient that permits it to use the amounts disclosed in its pension and other postretirement benefit plan note for the prior comparative periods as the estimation basis for applying the retrospective presentation requirements. The new standard is effective as of January 1, 2018. Net periodic benefit cost (credit) other than service cost was approximately $(510) million and $(530) million for the years ended December 31, 2017 and 2016 , respectively, (see Note 14). Upon adoption, these amounts will be reclassified to Other (income) expense, net from their current classification within Materials and production costs, Marketing and administrative expenses and Research and development costs. In May 2017, the FASB issued guidance clarifying when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new guidance, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. The new standard is effective as of January 1, 2018 and will be applied to future share-based payment award modifications should they occur. In February 2016, the FASB issued new accounting guidance for the accounting and reporting of leases. The new guidance requires that lessees recognize a right-of-use asset and a lease liability recorded on the balance sheet for each of its leases (other than leases that meet the definition of a short-term lease). Leases will be classified as either operating or finance. Operating leases will result in straight-line expense in the income statement (similar to current operating leases) while finance leases will result in more expense being recognized in the earlier years of the lease term (similar to current capital leases). The new guidance will be effective for interim and annual periods beginning in 2019 and will be adopted using a modified retrospective approach which will require application of the new guidance at the beginning of the earliest comparative period presented. Early adoption is permitted. The Company is currently evaluating the impact of adoption on its consolidated financial statements. In August 2017, the FASB issued new guidance on hedge accounting that is intended to more closely align hedge accounting with companies’ risk management strategies, simplify the application of hedge accounting, and increase transparency as to the scope and results of hedging programs. The new guidance makes more financial and nonfinancial hedging strategies eligible for hedge accounting, amends the presentation and disclosure requirements, and changes how companies assess effectiveness. The new guidance is effective for interim and annual periods beginning in 2019 on a modified retrospective basis. Early application is permitted in any interim period. The Company intends to early adopt this guidance as of January 1, 2018 on a modified retrospective basis. The Company anticipates recording a cumulative-effect adjustment upon adoption decreasing Retained earnings by $11 million in 2018.The adoption of the new guidance will result in some additional disclosures. In February 2018, the FASB issued new guidance to address a narrow-scope financial reporting issue that arose as a consequence of the TCJA. Existing guidance requires that deferred tax liabilities and assets be adjusted for a change in tax laws or rates with the effect included in income from continuing operations in the reporting period that includes the enactment date. That guidance is applicable even in situations in which the related income tax effects of items in accumulated other comprehensive income were originally recognized in other comprehensive income (rather than in net income), such as amounts related to benefit plans and hedging activity. As a result, the tax effects of items within accumulated other comprehensive income do not reflect the appropriate tax rate (the difference is referred to as stranded tax effects). The new guidance allows for a reclassification of these amounts to retained earnings thereby eliminating these stranded tax effects. The new guidance is effective for interim and annual periods in 2019. The Company is currently evaluating the impact of adoption on its consolidated financial statements. In June 2016, the FASB issued amended guidance on the accounting for credit losses on financial instruments. The 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 new guidance is effective for interim and annual periods beginning in 2020, with earlier application permitted in 2019. The new guidance is to be applied on a modified retrospective basis through a cumulative-effect adjustment directly to retained earnings in the beginning of the period of adoption. The Company is currently evaluating the impact of adoption on its consolidated financial statements. In January 2017, the FASB issued guidance that provides for the elimination of Step 2 from the goodwill impairment test. Under the new guidance, impairment charges are recognized to the extent the carrying amount of a reporting unit exceeds its fair value with certain limitations. The new guidance is effective for interim and annual periods in 2020. Early adoption is permitted. The Company does not anticipate that the adoption of the new guidance will have a material effect on its consolidated financial statements.

Acquisitions, Divestitures, R29

Acquisitions, Divestitures, Research Collaborations and License Agreements (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Schedule of Fair Value of Assets Acquired and Liabilities Assumed	The estimated fair value of assets acquired and liabilities assumed from Cubist is as follows: Estimated fair value at January 21, 2015 Cash and cash equivalents $ 733 Accounts receivable 123 Inventories 216 Other current assets 55 Property, plant and equipment 151 Identifiable intangible assets: Products and product rights (11 year weighted-average useful life) 6,923 IPR&D 50 Other noncurrent assets 184 Current liabilities (1) (233 ) Deferred income tax liabilities (2,519 ) Long-term debt (1,900 ) Other noncurrent liabilities (1) (122 ) Total identifiable net assets 3,661 Goodwill (2) 4,670 Consideration transferred $ 8,331 (1) Included in current liabilities and other noncurrent liabilities is contingent consideration of $73 million and $50 million , respectively. (2) The goodwill recognized is largely attributable to anticipated synergies expected to arise after the acquisition and was allocated to the Pharmaceutical segment. The goodwill is not deductible for tax purposes. The net impact of the termination of the SPMSD joint venture is as follows: Products and product rights (8 year useful life) $ 936 Accounts receivable 133 Income taxes payable (221 ) Deferred income tax liabilities (147 ) Other, net 47 Net assets acquired 748 Consideration payable to Sanofi, net (392 ) Derecognition of Merck’s previously held equity investment in SPMSD (183 ) Increase in net assets 173 Merck’s share of restructuring costs related to the termination (77 ) Net gain on termination of SPMSD joint venture (1) $ 96 (1) Recorded in Other (income) expense, net .
Unaudited Supplemental Pro Forma Data	The following unaudited supplemental pro forma data presents consolidated information as if the acquisition of Cubist had been completed on January 1, 2014: Years Ended December 31 2015 Sales $ 39,584 Net income attributable to Merck & Co., Inc. 4,640 Basic earnings per common share attributable to Merck & Co., Inc. common shareholders 1.65 Earnings per common share assuming dilution attributable to Merck & Co., Inc. common shareholders 1.63

Collaborative Arrangements (Tab

Collaborative Arrangements (Tables)	12 Months Ended
	Dec. 31, 2017
Collaborative Arrangements [Abstract]
Schedule of Collaborative Arrangements and Non-collaborative Arrangement Transactions	Summarized information related to this collaboration is as follows: Year Ended December 31 2017 Alliance revenues (net of commercialization costs) $ 20 Materials and production costs 4 Marketing and administrative expenses 1 Research and development expenses 2,419 Receivables from AstraZeneca 12 Payables to AstraZeneca 643 Expenses do not include all amounts attributed to activities related to the collaboration, rather only the amounts relating to payments between partners. Amounts in materials and production costs include amortization of related intangible assets. Summarized information related to this collaboration is as follows: Years Ended December 31 2017 2016 2015 Net product sales recorded by Merck $ 149 $ 88 $ — Merck’s profit share of sales in Bayer's marketing territories 151 81 30 Total sales 300 169 30 Materials and production costs 99 133 67 Marketing and administrative expenses 27 26 3 Research and development expenses 96 45 3 Receivables from Bayer 33 — Payables to Bayer 352 353

Restructuring (Tables)

Restructuring (Tables)	12 Months Ended
	Dec. 31, 2017
Restructuring and Related Activities [Abstract]
Charges Related to Restructuring Program Activities by Type of Cost	The following table summarizes the charges related to restructuring program activities by type of cost: Separation Costs Accelerated Depreciation Other Total Year Ended December 31, 2017 Materials and production $ — $ 52 $ 86 $ 138 Marketing and administrative — 2 — 2 Research and development — 6 5 11 Restructuring costs 552 — 224 776 $ 552 $ 60 $ 315 $ 927 Year Ended December 31, 2016 Materials and production $ — $ 77 $ 104 $ 181 Marketing and administrative — 8 87 95 Research and development — 142 — 142 Restructuring costs 216 — 435 651 $ 216 $ 227 $ 626 $ 1,069 Year Ended December 31, 2015 Materials and production $ — $ 78 $ 283 $ 361 Marketing and administrative — 59 19 78 Research and development — 37 15 52 Restructuring costs 208 — 411 619 $ 208 $ 174 $ 728 $ 1,110
Charges and Spending Relating to Restructuring Activities by Program	The following table summarizes the charges and spending relating to restructuring program activities: Separation Costs Accelerated Depreciation Other Total Restructuring reserves January 1, 2016 $ 592 $ — $ 53 $ 645 Expenses 216 227 626 1,069 (Payments) receipts, net (413 ) — (347 ) (760 ) Non-cash activity — (227 ) (186 ) (413 ) Restructuring reserves December 31, 2016 395 — 146 541 Expenses 552 60 315 927 (Payments) receipts, net (328 ) — (394 ) (722 ) Non-cash activity — (60 ) 61 1 Restructuring reserves December 31, 2017 (1) $ 619 $ — $ 128 $ 747 (1) The remaining cash outlays are expected to be substantially completed by the end of 2020.

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of Interest Rate Derivatives	At December 31, 2017 , the Company was a party to 26 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. 2017 Debt Instrument Par Value of Debt Number of Interest Rate Swaps Held Total Swap Notional Amount 1.30% notes due 2018 $ 1,000 4 $ 1,000 5.00% notes due 2019 1,250 3 550 1.85% notes due 2020 1,250 5 1,250 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
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 as of December 31: 2017 2016 Fair Value of Derivative U.S. Dollar Notional Fair Value of Derivative U.S. Dollar Notional Balance Sheet Caption Asset Liability Asset Liability Derivatives Designated as Hedging Instruments Interest rate swap contracts Other assets $ 2 $ — $ 550 $ 20 $ — $ 2,700 Interest rate swap contracts Accrued and other current liabilities — 3 1,000 — — — Interest rate swap contracts Other noncurrent liabilities — 52 4,650 — 29 3,500 Foreign exchange contracts Other current assets 51 — 4,216 616 — 6,063 Foreign exchange contracts Other assets 38 — 1,936 129 — 2,075 Foreign exchange contracts Accrued and other current liabilities — 71 2,014 — 1 48 Foreign exchange contracts Other noncurrent liabilities — 1 20 — 1 12 $ 91 $ 127 $ 14,386 $ 765 $ 31 $ 14,398 Derivatives Not Designated as Hedging Instruments Foreign exchange contracts Other current assets $ 39 $ — $ 3,778 $ 230 $ — $ 8,210 Foreign exchange contracts Accrued and other current liabilities — 90 7,431 — 103 2,931 $ 39 $ 90 $ 11,209 $ 230 $ 103 $ 11,141 $ 130 $ 217 $ 25,595 $ 995 $ 134 $ 25,539
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 at December 31: 2017 2016 Asset Liability Asset Liability Gross amounts recognized in the consolidated balance sheet $ 130 $ 217 $ 995 $ 134 Gross amount subject to offset in master netting arrangements not offset in the consolidated balance sheet (94 ) (94 ) (131 ) (131 ) Cash collateral (received) posted (3 ) — (529 ) — Net amounts $ 33 $ 123 $ 335 $ 3
Location and Pretax Gain or Loss Amounts for Derivatives	The table below provides information on the location and pretax gain or loss amounts for derivatives that are: (i) designated in a fair value hedging relationship, (ii) designated in a foreign currency cash flow hedging relationship, (iii) designated in a foreign currency net investment hedging relationship and (iv) not designated in a hedging relationship: Years Ended December 31 2017 2016 2015 Derivatives designated in a fair value hedging relationship Interest rate swap contracts Amount of loss (gain) recognized in Other (income) expense, net on derivatives (1) $ 43 $ 28 $ (14 ) Amount of (gain) loss recognized in Other (income) expense, net on hedged item (1) (48 ) (29 ) 7 Derivatives designated in foreign currency cash flow hedging relationships Foreign exchange contracts Amount of gain reclassified from AOCI to Sales (138 ) (311 ) (724 ) Amount of loss (gain) recognized in OCI on derivatives 561 (210 ) (526 ) Derivatives designated in foreign currency net investment hedging relationships Foreign exchange contracts Amount of gain recognized in Other (income) expense, net on derivatives (2) — (1 ) (4 ) Amount of loss (gain) recognized in OCI on derivatives — 2 (10 ) Derivatives not designated in a hedging relationship Foreign exchange contracts Amount of loss (gain) recognized in Other (income) expense, net on derivatives (3) 110 132 (461 ) Amount of gain recognized in Sales (3 ) — (1 ) (1) There was $5 million , $1 million and $7 million of ineffectiveness on the hedge during 2017 , 2016 and 2015 , respectively. (2) There was no ineffectiveness on the hedge. Represents the amount excluded from hedge effectiveness testing. (3) 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.
Information on Available-for-Sale Investments	Information on investments in debt and equity securities at December 31 is as follows: 2017 2016 Fair Value Amortized Cost Gross Unrealized Fair Value Amortized Cost Gross Unrealized Gains Losses Gains Losses Corporate notes and bonds $ 9,806 $ 9,837 $ 9 $ (40 ) $ 10,577 $ 10,601 $ 15 $ (39 ) U.S. government and agency securities 2,042 2,059 — (17 ) 2,232 2,244 1 (13 ) Asset-backed securities 1,542 1,548 1 (7 ) 1,376 1,380 1 (5 ) Foreign government bonds 733 739 — (6 ) 519 521 — (2 ) Mortgage-backed securities 626 634 1 (9 ) 796 801 1 (6 ) Commercial paper 159 159 — — 4,330 4,330 — — Equity securities 275 265 16 (6 ) 349 281 71 (3 ) $ 15,183 $ 15,241 $ 27 $ (85 ) $ 20,179 $ 20,158 $ 89 $ (68 )
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis	Financial assets and liabilities measured at fair value on a recurring basis at December 31 are summarized below: Fair Value Measurements Using Fair Value Measurements Using Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total 2017 2016 Assets Investments Corporate notes and bonds $ — $ 9,678 $ — $ 9,678 $ — $ 10,389 $ — $ 10,389 U.S. government and agency securities 68 1,767 — 1,835 29 1,890 — 1,919 Asset-backed securities (1) — 1,476 — 1,476 — 1,257 — 1,257 Foreign government bonds — 732 — 732 — 518 — 518 Mortgage-backed securities (1) — 547 — 547 — 628 — 628 Commercial paper — 159 — 159 — 4,330 — 4,330 Equity securities 104 — — 104 201 — — 201 172 14,359 — 14,531 230 19,012 — 19,242 Other assets (2) U.S. government and agency securities — 207 — 207 — 313 — 313 Corporate notes and bonds — 128 — 128 — 188 — 188 Mortgage-backed securities (1) — 79 — 79 — 168 — 168 Asset-backed securities (1) — 66 — 66 — 119 — 119 Foreign government bonds — 1 — 1 — 1 — 1 Equity securities 171 — — 171 148 — — 148 171 481 — 652 148 789 — 937 Derivative assets (3) Purchased currency options — 80 — 80 — 644 — 644 Forward exchange contracts — 48 — 48 — 331 — 331 Interest rate swaps — 2 — 2 — 20 — 20 — 130 — 130 — 995 — 995 Total assets $ 343 $ 14,970 $ — $ 15,313 $ 378 $ 20,796 $ — $ 21,174 Liabilities Other liabilities Contingent consideration $ — $ — $ 935 $ 935 $ — $ — $ 891 $ 891 Derivative liabilities (2) Forward exchange contracts — 162 — 162 — 93 — 93 Interest rate swaps — 55 — 55 — 29 — 29 Written currency options — — — — — 12 — 12 — 217 — 217 — 134 — 134 Total liabilities $ — $ 217 $ 935 $ 1,152 $ — $ 134 $ 891 $ 1,025 (1) Primarily all of the asset-backed securities are 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. Mortgage-backed securities represent AAA-rated securities issued or unconditionally guaranteed as to payment of principal and interest by U.S. government agencies. (2) Investments included in other assets are restricted as to use, primarily 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.
Summarized Information about the Changes in Liabilities for Contingent Consideration	Summarized information about the changes in liabilities for contingent consideration is as follows: 2017 2016 Fair value January 1 $ 891 $ 590 Changes in estimated fair value (1) 141 (407 ) Additions 3 733 Payments (100 ) (25 ) Fair value December 31 (2) $ 935 $ 891 (1) Recorded in Research and development expenses, Materials and production costs and Other (income) expense, net . Includes cumulative translation adjustments. (2) Includes $315 million recorded as a current liability for amounts expected to be paid within the next 12 months.

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2017
Inventory Disclosure [Abstract]
Inventories	Inventories at December 31 consisted of: 2017 2016 Finished goods $ 1,334 $ 1,304 Raw materials and work in process 4,703 4,222 Supplies 201 155 Total (approximates current cost) 6,238 5,681 Increase to LIFO costs 45 302 $ 6,283 $ 5,983 Recognized as: Inventories $ 5,096 $ 4,866 Other assets 1,187 1,117

Goodwill and Other Intangibles

Goodwill and Other Intangibles (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill Activity by Segment	The following table summarizes goodwill activity by segment: Pharmaceutical All Other Total Balance January 1, 2016 $ 15,862 $ 1,861 $ 17,723 Acquisitions 207 275 482 Impairments — (47 ) (47 ) Other (1) 6 (2 ) 4 Balance December 31, 2016 (2) 16,075 2,087 18,162 Acquisitions — 177 177 Impairments — (38 ) (38 ) Other (1) (9 ) (8 ) (17 ) Balance December 31, 2017 (2) $ 16,066 $ 2,218 $ 18,284 (1) Other includes cumulative translation adjustments on goodwill balances and certain other adjustments. (2) Accumulated goodwill impairment losses at December 31, 2017 and 2016 were $225 million and $187 million , respectively.
Other Intangibles	Other intangibles at December 31 consisted of: 2017 2016 Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net Products and product rights $ 46,693 $ 34,950 $ 11,743 $ 46,269 $ 31,919 $ 14,350 IPR&D 1,194 — 1,194 1,653 — 1,653 Tradenames 209 97 112 215 89 126 Other 2,035 901 1,134 1,947 771 1,176 $ 50,131 $ 35,948 $ 14,183 $ 50,084 $ 32,779 $ 17,305

Joint Ventures and Other Equi35

Joint Ventures and Other Equity Method Affiliates (Tables)	12 Months Ended
	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Fair Value of Assets Acquired and Liabilities Assumed	The estimated fair value of assets acquired and liabilities assumed from Cubist is as follows: Estimated fair value at January 21, 2015 Cash and cash equivalents $ 733 Accounts receivable 123 Inventories 216 Other current assets 55 Property, plant and equipment 151 Identifiable intangible assets: Products and product rights (11 year weighted-average useful life) 6,923 IPR&D 50 Other noncurrent assets 184 Current liabilities (1) (233 ) Deferred income tax liabilities (2,519 ) Long-term debt (1,900 ) Other noncurrent liabilities (1) (122 ) Total identifiable net assets 3,661 Goodwill (2) 4,670 Consideration transferred $ 8,331 (1) Included in current liabilities and other noncurrent liabilities is contingent consideration of $73 million and $50 million , respectively. (2) The goodwill recognized is largely attributable to anticipated synergies expected to arise after the acquisition and was allocated to the Pharmaceutical segment. The goodwill is not deductible for tax purposes. The net impact of the termination of the SPMSD joint venture is as follows: Products and product rights (8 year useful life) $ 936 Accounts receivable 133 Income taxes payable (221 ) Deferred income tax liabilities (147 ) Other, net 47 Net assets acquired 748 Consideration payable to Sanofi, net (392 ) Derecognition of Merck’s previously held equity investment in SPMSD (183 ) Increase in net assets 173 Merck’s share of restructuring costs related to the termination (77 ) Net gain on termination of SPMSD joint venture (1) $ 96 (1) Recorded in Other (income) expense, net .

Loans Payable, Long-Term Debt36

Loans Payable, Long-Term Debt and Other Commitments (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	Long-term debt at December 31 consisted of: 2017 2016 2.75% notes due 2025 $ 2,488 $ 2,487 3.70% notes due 2045 1,973 1,972 2.80% notes due 2023 1,744 1,743 5.00% notes due 2019 1,260 1,273 4.15% notes due 2043 1,237 1,236 1.85% notes due 2020 1,232 1,238 2.35% notes due 2022 1,220 1,228 1.125% euro-denominated notes due 2021 1,185 1,035 1.875% euro-denominated notes due 2026 1,178 1,028 3.875% notes due 2021 1,140 1,152 2.40% notes due 2022 993 1,003 6.50% notes due 2033 729 806 Floating-rate notes due 2020 699 698 0.50% euro-denominated notes due 2024 591 516 1.375% euro-denominated notes due 2036 587 512 2.50% euro-denominated notes due 2034 585 511 3.60% notes due 2042 489 489 6.55% notes due 2037 415 594 5.75% notes due 2036 338 369 5.95% debentures due 2028 306 355 5.85% notes due 2039 270 415 6.40% debentures due 2028 250 325 6.30% debentures due 2026 135 152 Floating-rate borrowing due 2018 — 999 1.10% notes due 2018 — 999 1.30% notes due 2018 — 985 Other 309 154 $ 21,353 $ 24,274

Equity (Tables)

Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Summary of Common Stock and Treasury Stock Transactions	A summary of common stock and treasury stock transactions (shares in millions) is as follows: 2017 2016 2015 Common Stock Treasury Stock Common Stock Treasury Stock Common Stock Treasury Stock Balance January 1 3,577 828 3,577 796 3,577 739 Purchases of treasury stock — 67 — 60 — 75 Issuances (1) — (15 ) — (28 ) — (18 ) Balance December 31 3,577 880 3,577 828 3,577 796 (1) Issuances primarily reflect activity under share-based compensation plans.

Share-Based Compensation Plans

Share-Based Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Assumptions Used to Determine Weighted-Average Fair Value of Options Granted	The weighted average fair value of options granted in 2017 , 2016 and 2015 was $7.04 , $5.89 and $6.46 per option, respectively, and were determined using the following assumptions: Years Ended December 31 2017 2016 2015 Expected dividend yield 3.6 % 3.8 % 4.1 % Risk-free interest rate 2.0 % 1.4 % 1.7 % Expected volatility 17.8 % 19.6 % 19.9 % Expected life (years) 6.1 6.2 6.2
Summarized Information Relative to Stock Option Plan Activity	Summarized information relative to stock option plan activity (options in thousands) is as follows: Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value Outstanding January 1, 2017 45,091 $ 44.47 Granted 4,232 63.88 Exercised (11,512 ) 43.38 Forfeited (1,537 ) 51.78 Outstanding December 31, 2017 36,274 $ 46.77 4.89 $ 397 Exercisable December 31, 2017 26,778 $ 42.54 3.64 $ 384
Additional Information Pertaining to Stock Option Plans	Additional information pertaining to stock option plans is provided in the table below: Years Ended December 31 2017 2016 2015 Total intrinsic value of stock options exercised $ 236 $ 444 $ 332 Fair value of stock options vested 30 28 30 Cash received from the exercise of stock options 499 939 485
Summary of Nonvested RSU and PSU Activity	A summary of nonvested RSU and PSU activity (shares in thousands) is as follows: RSUs PSUs Number of Shares Weighted Average Grant Date Fair Value Number of Shares Weighted Average Grant Date Fair Value Nonvested January 1, 2017 13,266 $ 57.19 1,744 $ 59.24 Granted 5,014 63.85 1,008 63.62 Vested (3,795 ) 58.13 (833 ) 62.71 Forfeited (876 ) 58.22 (51 ) 60.24 Nonvested December 31, 2017 13,609 $ 59.32 1,868 $ 60.03

Pension and Other Postretirem39

Pension and Other Postretirement Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Components of Net Periodic Benefit Cost	The net periodic benefit cost (credit) for pension and other postretirement benefit plans consisted of the following components: Pension Benefits U.S. International Other Postretirement Benefits Years Ended December 31 2017 2016 2015 2017 2016 2015 2017 2016 2015 Service cost $ 312 $ 282 $ 307 $ 252 $ 238 $ 251 $ 57 $ 54 $ 80 Interest cost 454 456 434 172 204 206 81 82 110 Expected return on plan assets (862 ) (831 ) (819 ) (393 ) (382 ) (379 ) (78 ) (107 ) (143 ) Amortization of unrecognized prior service cost (53 ) (55 ) (56 ) (11 ) (11 ) (14 ) (98 ) (106 ) (64 ) Net loss amortization 180 119 214 98 87 118 1 3 5 Termination benefits 44 23 22 4 4 1 8 4 7 Curtailments 3 5 (12 ) (4 ) (1 ) (9 ) (31 ) (18 ) (19 ) Settlements — — 1 5 6 12 — — — Net periodic benefit cost (credit) $ 78 $ (1 ) $ 91 $ 123 $ 145 $ 186 $ (60 ) $ (88 ) $ (24 )
Obligation and Funded Status	Summarized information about the changes in plan assets and benefit obligations, the funded status and the amounts recorded at December 31 is as follows: Pension Benefits Other Postretirement Benefits U.S. International 2017 2016 2017 2016 2017 2016 Fair value of plan assets January 1 $ 9,766 $ 9,266 $ 7,794 $ 7,204 $ 1,019 $ 1,913 Actual return on plan assets 1,723 941 677 898 161 138 Company contributions, net 58 63 226 424 (4 ) 68 Effects of exchange rate changes — — 843 (546 ) — — Benefits paid (651 ) (504 ) (198 ) (193 ) (62 ) (108 ) Settlements — — (17 ) (21 ) — — Assets no longer restricted to the payment of postretirement benefits (1) — — — — — (992 ) Other — — 14 28 — — Fair value of plan assets December 31 $ 10,896 $ 9,766 $ 9,339 $ 7,794 $ 1,114 $ 1,019 Benefit obligation January 1 $ 10,849 $ 9,723 $ 8,372 $ 7,733 $ 1,922 $ 1,810 Service cost 312 282 252 238 57 54 Interest cost 454 456 172 204 81 82 Actuarial losses (gains) (2) 881 854 (7 ) 938 (87 ) 77 Benefits paid (651 ) (504 ) (198 ) (193 ) (62 ) (108 ) Effects of exchange rate changes — — 916 (576 ) 3 2 Plan amendments — — (22 ) — — — Curtailments 15 15 (3 ) (15 ) — 1 Termination benefits 44 23 4 4 8 4 Settlements — — (17 ) (21 ) — — Other — — 14 60 — — Benefit obligation December 31 $ 11,904 $ 10,849 $ 9,483 $ 8,372 $ 1,922 $ 1,922 Funded status December 31 $ (1,008 ) $ (1,083 ) $ (144 ) $ (578 ) $ (808 ) $ (903 ) Recognized as: Other assets $ — $ — $ 828 $ 451 $ — $ — Accrued and other current liabilities (59 ) (50 ) (17 ) (7 ) (11 ) (11 ) Other noncurrent liabilities (949 ) (1,033 ) (955 ) (1,022 ) (797 ) (892 ) (1) As a result of certain allowable administrative actions that occurred in June 2016, $992 million of plan assets previously restricted for the payment of other postretirement benefits became available to fund certain other health and welfare benefits. (2) Actuarial losses in 2017 and 2016 primarily reflect changes in discount rates.
Schedule of Accumulated and Projected Benefit Obligations in Excess of Fair Value of Plan Assets [Table Text Block]	Information related to the funded status of selected pension plans at December 31 is as follows: U.S. International 2017 2016 2017 2016 Pension plans with a projected benefit obligation in excess of plan assets Projected benefit obligation $ 11,904 $ 10,849 $ 3,323 $ 5,486 Fair value of plan assets 10,896 9,766 2,352 4,457 Pension plans with an accumulated benefit obligation in excess of plan assets Accumulated benefit obligation $ 676 $ 9,807 $ 2,120 $ 2,692 Fair value of plan assets — 9,057 1,346 1,898
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Summary of Changes in Fair Value of Company's Level 3 Pension Plan Assets	The table below provides a summary of the changes in fair value, including transfers in and/or out, of all financial assets measured at fair value using significant unobservable inputs (Level 3) for the Company’s pension plan assets: 2017 2016 Insurance Contracts Real Estate Other Total Insurance Contracts Real Estate Other Total U.S. Pension Plans Balance January 1 $ — $ — $ 18 $ 18 $ — $ — $ 23 $ 23 Actual return on plan assets: Relating to assets still held at December 31 — — (2 ) (2 ) — — (3 ) (3 ) Relating to assets sold during the year — — 4 4 — — 4 4 Purchases and sales, net — — (5 ) (5 ) — — (6 ) (6 ) Balance December 31 $ — $ — $ 15 $ 15 $ — $ — $ 18 $ 18 International Pension Plans Balance January 1 $ 412 $ 4 $ 1 $ 417 $ 393 $ 5 $ 2 $ 400 Actual return on plan assets: Relating to assets still held at December 31 52 — — 52 (9 ) 1 — (8 ) Purchases and sales, net 5 (2 ) — 3 2 (2 ) (1 ) (1 ) Transfers into Level 3 1 — — 1 26 — — 26 Balance December 31 $ 470 $ 2 $ 1 $ 473 $ 412 $ 4 $ 1 $ 417
Summary of Expected Benefit Payments	Expected benefit payments are as follows: U.S. Pension Benefits International Pension Benefits Other Postretirement Benefits 2018 $ 609 $ 222 $ 96 2019 638 205 101 2020 650 217 104 2021 663 225 109 2022 683 243 113 2023 — 2027 3,760 1,326 623
Components of Other Comprehensive Income	The following amounts were reflected as components of OCI : Pension Plans Other Postretirement Benefit Plans U.S. International Years Ended December 31 2017 2016 2015 2017 2016 2015 2017 2016 2015 Net (loss) gain arising during the period $ (19 ) $ (743 ) $ 73 $ 309 $ (380 ) $ (66 ) $ 170 $ (45 ) $ 209 Prior service (cost) credit arising during the period (13 ) (10 ) (13 ) 22 (2 ) (4 ) (31 ) (19 ) 511 $ (32 ) $ (753 ) $ 60 $ 331 $ (382 ) $ (70 ) $ 139 $ (64 ) $ 720 Net loss amortization included in benefit cost $ 180 $ 119 $ 214 $ 98 $ 87 $ 118 $ 1 $ 3 $ 5 Prior service (credit) cost amortization included in benefit cost (53 ) (55 ) (56 ) (11 ) (11 ) (14 ) (98 ) (106 ) (64 ) $ 127 $ 64 $ 158 $ 87 $ 76 $ 104 $ (97 ) $ (103 ) $ (59 )
Summary of Weighted Average Assumptions Used in Determining Pension Plan and U.S. Pension and Other Postretirement Benefit Plan Information	The Company reassesses its benefit plan assumptions on a regular basis. The weighted average assumptions used in determining U.S. pension and other postretirement benefit plan and international pension plan information are as follows: U.S. Pension and Other Postretirement Benefit Plans International Pension Plans December 31 2017 2016 2015 2017 2016 2015 Net periodic benefit cost Discount rate 4.30 % 4.70 % 4.20 % 2.20 % 2.80 % 2.70 % Expected rate of return on plan assets 8.70 % 8.60 % 8.50 % 5.10 % 5.60 % 5.70 % Salary growth rate 4.30 % 4.30 % 4.40 % 2.90 % 2.90 % 2.90 % Benefit obligation Discount rate 3.70 % 4.30 % 4.80 % 2.10 % 2.20 % 2.80 % Salary growth rate 4.30 % 4.30 % 4.30 % 2.90 % 2.90 % 2.90 %
Summary of Health Care Cost Trend Rate Assumptions for Other Postretirement Benefit Plans	The health care cost trend rate assumptions for other postretirement benefit plans are as follows: December 31 2017 2016 Health care cost trend rate assumed for next year 7.2 % 7.4 % Rate to which the cost trend rate is assumed to decline 4.5 % 4.5 % Year that the trend rate reaches the ultimate trend rate 2032 2032
One Percentage Point Change in Health Care Cost Trend Rate	A one percentage point change in the health care cost trend rate would have had the following effects: One Percentage Point Increase Decrease Effect on total service and interest cost components $ 13 $ (11 ) Effect on benefit obligation 125 (104 )
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Schedule of Allocation of Plan Assets [Table Text Block]	The fair values of the Company’s pension plan assets at December 31 by asset category are as follows: Fair Value Measurements Using Fair Value Measurements Using Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total 2017 2016 U.S. Pension Plans Assets Cash and cash equivalents $ 6 $ — $ — $ 6 $ 2 $ 2 $ — $ 4 Investment funds Developed markets equities 390 — — 390 521 — — 521 Emerging markets equities 138 — — 138 104 — — 104 Equity securities Developed markets 2,743 — — 2,743 2,521 — — 2,521 Fixed income securities Government and agency obligations — 757 — 757 — 475 — 475 Corporate obligations — 900 — 900 — 660 — 660 Mortgage and asset-backed securities — 240 — 240 — 239 — 239 Other investments — — 15 15 — — 18 18 Net assets in fair value hierarchy $ 3,277 $ 1,897 $ 15 $ 5,189 $ 3,148 $ 1,376 $ 18 $ 4,542 Investments measured at NAV (1) 5,707 5,224 Plan assets at fair value $ 10,896 $ 9,766 International Pension Plans Assets Cash and cash equivalents $ 54 $ 19 $ — $ 73 $ 42 $ 11 $ — $ 53 Investment funds Developed markets equities 562 3,326 — 3,888 187 2,846 — 3,033 Emerging markets equities 62 176 — 238 24 148 — 172 Government and agency obligations 249 2,095 — 2,344 123 1,904 — 2,027 Corporate obligations 5 329 — 334 2 282 — 284 Fixed income obligations 7 4 — 11 6 3 — 9 Real estate (2) — 1 2 3 — 3 4 7 Equity securities Developed markets 660 — — 660 565 — — 565 Fixed income securities Government and agency obligations 2 266 — 268 2 235 — 237 Corporate obligations 1 118 — 119 — 92 — 92 Mortgage and asset-backed securities — 55 — 55 — 50 — 50 Other investments Insurance contracts (3) — 67 470 537 — 59 412 471 Other — 6 1 7 1 4 1 6 Net assets in fair value hierarchy $ 1,602 $ 6,462 $ 473 $ 8,537 $ 952 $ 5,637 $ 417 $ 7,006 Investments measured at NAV (1) 802 788 Plan assets at fair value $ 9,339 $ 7,794 (1) Certain investments that were measured at net asset value (NAV) per share or its equivalent as a practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the fair value of plan assets at December 31, 2017 and 2016 . (2) The plans’ Level 3 investments in real estate funds are generally valued by market appraisals of the underlying investments in the funds. (3) The plans’ Level 3 investments in insurance contracts are generally valued using a crediting rate that approximates market returns and invest in underlying securities whose market values are unobservable and determined using pricing models, discounted cash flow methodologies, or similar techniques.
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Schedule of Allocation of Plan Assets [Table Text Block]	The fair values of the Company’s other postretirement benefit plan assets at December 31 by asset category are as follows: Fair Value Measurements Using Fair Value Measurements Using Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Quoted Prices In Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total 2017 2016 Assets Cash and cash equivalents $ 97 $ — $ — $ 97 $ 125 $ — $ — $ 125 Investment funds Developed markets equities 37 — — 37 48 — — 48 Emerging markets equities 13 — — 13 10 — — 10 Government and agency obligations 1 — — 1 1 — — 1 Equity securities Developed markets 256 — — 256 231 — — 231 Fixed income securities Government and agency obligations — 71 — 71 — 43 — 43 Corporate obligations — 84 — 84 — 60 — 60 Mortgage and asset-backed securities — 23 — 23 — 22 — 22 Net assets in fair value hierarchy $ 404 $ 178 $ — $ 582 $ 415 $ 125 $ — $ 540 Investments measured at NAV (1) 532 479 Plan assets at fair value $ 1,114 $ 1,019 (1) Certain investments that were measured at net asset value (NAV) per share or its equivalent as a practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the fair value of plan assets at December 31, 2017 and 2016 .

Other (Income) Expense, Net (Ta

Other (Income) Expense, Net (Tables)	12 Months Ended
	Dec. 31, 2017
Other Income and Expenses [Abstract]
Other (Income) Expense, Net	Other (income) expense, net, consisted of: Years Ended December 31 2017 2016 2015 Interest income $ (385 ) $ (328 ) $ (289 ) Interest expense 754 693 672 Exchange (gains) losses (11 ) 174 1,277 Equity income from affiliates (42 ) (86 ) (205 ) Other, net (304 ) 267 72 $ 12 $ 720 $ 1,527

Taxes on Income (Tables)

Taxes on Income (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Reconciliation Between Effective Tax Rate and U.S. Statutory Rate	A reconciliation between the effective tax rate and the U.S. statutory rate is as follows: 2017 2016 2015 Amount Tax Rate Amount Tax Rate Amount Tax Rate U.S. statutory rate applied to income before taxes $ 2,282 35.0 % $ 1,631 35.0 % $ 1,890 35.0 % Differential arising from: Provisional impact of the TCJA 2,625 40.3 — — — — Impact of purchase accounting adjustments, including amortization 713 10.9 623 13.4 797 14.8 Valuation allowances 632 9.7 (5 ) (0.1 ) 39 0.7 Restructuring 142 2.2 145 3.1 167 3.1 State taxes 77 1.2 173 3.7 159 2.9 U.S. health care reform legislation 74 1.1 68 1.4 66 1.2 Foreign currency devaluation related to Venezuela — — — — 321 5.9 Foreign earnings (1,725 ) (26.5 ) (1,646 ) (35.3 ) (2,144 ) (39.7 ) Tax settlements (356 ) (5.5 ) — — (417 ) (7.7 ) Unremitted foreign earnings — — (30 ) (0.6 ) 260 4.8 Other (1) (361 ) (5.5 ) (241 ) (5.2 ) (196 ) (3.6 ) $ 4,103 62.9 % $ 718 15.4 % $ 942 17.4 % (1) Other includes the tax effect of contingency reserves, research credits, losses on foreign subsidiaries and miscellaneous items.
Income Before Taxes	Income before taxes consisted of: Years Ended December 31 2017 2016 2015 Domestic $ 3,483 $ 518 $ 2,247 Foreign 3,038 4,141 3,154 $ 6,521 $ 4,659 $ 5,401
Taxes on Income	Taxes on income consisted of: Years Ended December 31 2017 2016 2015 Current provision Federal $ 5,585 $ 1,166 $ 732 Foreign 1,229 916 844 State (90 ) 157 130 6,724 2,239 1,706 Deferred provision Federal (2,958 ) (1,255 ) (552 ) Foreign 75 (225 ) (163 ) State 262 (41 ) (49 ) (2,621 ) (1,521 ) (764 ) $ 4,103 $ 718 $ 942
Deferred Income Taxes	Deferred income taxes at December 31 consisted of: 2017 2016 Assets Liabilities Assets Liabilities Intangibles $ 307 $ 2,435 $ 86 $ 3,854 Inventory related 29 499 30 660 Accelerated depreciation 28 642 28 927 Unremitted foreign earnings — 33 — 2,044 Pensions and other postretirement benefits 498 192 727 109 Compensation related 314 — 438 — Unrecognized tax benefits 156 — 383 — Net operating losses and other tax credit carryforwards 654 — 437 — Other 1,088 19 1,248 46 Subtotal 3,074 3,820 3,377 7,640 Valuation allowance (900 ) (268 ) Total deferred taxes $ 2,174 $ 3,820 $ 3,109 $ 7,640 Net deferred income taxes $ 1,646 $ 4,531 Recognized as: Other assets $ 573 $ 546 Deferred income taxes $ 2,219 $ 5,077
Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows: 2017 2016 2015 Balance January 1 $ 3,494 $ 3,448 $ 3,534 Additions related to current year positions 146 196 198 Additions related to prior year positions 520 75 53 Reductions for tax positions of prior years (1) (1,038 ) (90 ) (59 ) Settlements (1) (1,388 ) (92 ) (184 ) Lapse of statute of limitations (11 ) (43 ) (94 ) Balance December 31 $ 1,723 $ 3,494 $ 3,448 (1) Amounts reflect the settlements with the IRS as discussed below.

Earnings per Share (Tables)

Earnings per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Calculations of Earnings Per Share	The calculations of earnings per share (shares in millions) are as follows: Years Ended December 31 2017 2016 2015 Net income attributable to Merck & Co., Inc. $ 2,394 $ 3,920 $ 4,442 Average common shares outstanding 2,730 2,766 2,816 Common shares issuable (1) 18 21 25 Average common shares outstanding assuming dilution 2,748 2,787 2,841 Basic earnings per common share attributable to Merck & Co., Inc. common shareholders $ 0.88 $ 1.42 $ 1.58 Earnings per common share assuming dilution attributable to Merck & Co., Inc. common shareholders $ 0.87 $ 1.41 $ 1.56 (1) Issuable primarily under share-based compensation plans.

Other Comprehensive Income (L43

Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2017
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Changes in AOCI by Component	Changes in AOCI by component are as follows: Derivatives Investments Employee Benefit Plans Cumulative Translation Adjustment Accumulated Other Comprehensive Income (Loss) Balance January 1, 2015, net of taxes $ 530 $ 111 $ (2,986 ) $ (1,978 ) $ (4,323 ) Other comprehensive income (loss) before reclassification adjustments, pretax 526 (9 ) 710 (158 ) 1,069 Tax (177 ) (13 ) (272 ) (28 ) (490 ) Other comprehensive income (loss) before reclassification adjustments, net of taxes 349 (22 ) 438 (186 ) 579 Reclassification adjustments, pretax (731 ) (1) (73 ) (2) 203 (3) (22 ) (623 ) Tax 256 25 (62 ) — 219 Reclassification adjustments, net of taxes (475 ) (48 ) 141 (22 ) (404 ) Other comprehensive income (loss), net of taxes (126 ) (70 ) 579 (208 ) 175 Balance December 31, 2015, net of taxes 404 41 (2,407 ) (2,186 ) (4,148 ) Other comprehensive income (loss) before reclassification adjustments, pretax 210 (38 ) (1,199 ) (150 ) (1,177 ) Tax (72 ) 16 363 (19 ) 288 Other comprehensive income (loss) before reclassification adjustments, net of taxes 138 (22 ) (836 ) (169 ) (889 ) Reclassification adjustments, pretax (314 ) (1) (31 ) (2) 37 (3) — (308 ) Tax 110 9 — — 119 Reclassification adjustments, net of taxes (204 ) (22 ) 37 — (189 ) Other comprehensive income (loss), net of taxes (66 ) (44 ) (799 ) (169 ) (1,078 ) Balance December 31, 2016, net of taxes 338 (3 ) (3,206 ) (4) (2,355 ) (5,226 ) Other comprehensive income (loss) before reclassification adjustments, pretax (561 ) 212 438 235 324 Tax 207 (35 ) (106 ) 166 232 Other comprehensive income (loss) before reclassification adjustments, net of taxes (354 ) 177 332 401 556 Reclassification adjustments, pretax (141 ) (1) (291 ) (2) 117 (3) — (315 ) Tax 49 56 (30 ) — 75 Reclassification adjustments, net of taxes (92 ) (235 ) 87 — (240 ) Other comprehensive income (loss), net of taxes (446 ) (58 ) 419 401 316 Balance December 31, 2017, net of taxes $ (108 ) $ (61 ) $ (2,787 ) (4) $ (1,954 ) $ (4,910 ) (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 investments 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 14). (4) Includes pension plan net loss of $ 3.5 billion and $3.9 billion at December 31, 2017 and 2016 , respectively, and other postretirement benefit plan net (gain) loss of $(16) million and $115 million at December 31, 2017 and 2016 , respectively, as well as pension plan prior service credit of $326 million and $361 million at December 31, 2017 and 2016 , respectively, and other postretirement benefit plan prior service credit of $383 million and $466 million at December 31, 2017 and 2016 , respectively.

Segment Reporting (Tables)

Segment Reporting (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Sales of Company's Products	Sales of the Company’s products were as follows: Years Ended December 31 2017 2016 2015 U.S. Int’l Total U.S. Int’l Total U.S. Int’l Total Primary Care and Women’s Health Cardiovascular Zetia $ 352 $ 992 $ 1,344 $ 1,588 $ 972 $ 2,560 $ 1,612 $ 914 $ 2,526 Vytorin 124 627 751 473 668 1,141 479 771 1,251 Atozet — 225 225 1 146 146 2 34 36 Adempas — 300 300 — 169 169 — 30 30 Diabetes Januvia 2,153 1,584 3,737 2,286 1,622 3,908 2,263 1,601 3,863 Janumet 863 1,296 2,158 984 1,217 2,201 976 1,175 2,151 General Medicine and Women’s Health NuvaRing 564 197 761 576 202 777 515 216 732 Implanon/Nexplanon 496 191 686 420 186 606 367 221 588 Follistim AQ 123 174 298 157 197 355 160 223 383 Hospital and Specialty Hepatitis Zepatier 771 888 1,660 488 67 555 — — — HIV Isentress/Isentress HD 565 639 1,204 721 666 1,387 797 714 1,511 Hospital Acute Care Bridion 239 465 704 77 405 482 — 353 353 Noxafil 309 327 636 284 312 595 212 275 487 Invanz 361 241 602 329 233 561 322 247 569 Cancidas 20 402 422 25 533 558 24 548 573 Cubicin (1) 189 193 382 906 181 1,087 1,030 97 1,127 Primaxin 10 270 280 4 293 297 8 305 313 Immunology Remicade — 837 837 — 1,268 1,268 — 1,794 1,794 Simponi — 819 819 — 766 766 — 690 690 Oncology Keytruda 2,309 1,500 3,809 792 610 1,402 393 173 566 Emend 342 213 556 356 193 549 326 209 535 Temodar 16 256 271 15 268 283 7 306 312 Diversified Brands Respiratory Singulair 40 692 732 40 874 915 39 892 931 Nasonex 54 333 387 184 352 537 449 409 858 Dulera 261 26 287 412 24 436 515 21 536 Other Cozaar/Hyzaar 18 466 484 16 494 511 30 637 667 Arcoxia — 363 363 — 450 450 — 471 471 Fosamax 6 235 241 5 279 284 12 347 359 Vaccines (2) Gardasil/Gardasil 9 1,565 743 2,308 1,780 393 2,173 1,520 388 1,908 ProQuad/M-M-R II/Varivax 1,374 303 1,676 1,362 279 1,640 1,290 214 1,505 Pneumovax 23 581 240 821 447 193 641 378 164 542 RotaTeq 481 204 686 482 169 652 447 163 610 Zostavax 422 246 668 518 168 685 592 157 749 Other pharmaceutical (3) 1,246 3,049 4,295 1,345 3,228 4,574 1,473 3,785 5,256 Total Pharmaceutical segment sales 15,854 19,536 35,390 17,073 18,077 35,151 16,238 18,544 34,782 Other segment sales (4) 1,486 2,785 4,272 1,374 2,489 3,862 1,213 2,454 3,667 Total segment sales 17,340 22,321 39,662 18,447 20,566 39,013 17,451 20,998 38,449 Other (5) 84 377 460 31 763 794 68 981 1,049 $ 17,424 $ 22,698 $ 40,122 $ 18,478 $ 21,329 $ 39,807 $ 17,519 $ 21,979 $ 39,498 U.S. plus international may not equal total due to rounding. (1) Sales of Cubicin in 2015 represent sales subsequent to the Cubist acquisition date. (2) On December 31, 2016, Merck and Sanofi terminated their equally-owned joint venture, SPMSD, which marketed vaccines in most major European markets (see Note 9). Accordingly, vaccine sales in 2017 include sales in the European markets that were previously part of SPMSD. Amounts for 2016 and 2015 do not include sales of vaccines sold through SPMSD, the results of which are reflected in equity income from affiliates included in Other (income) expense, net . Amounts for 2016 and 2015 do, however, include supply sales to SPMSD. (3) Other pharmaceutical primarily reflects sales of other human health pharmaceutical products, including products within the franchises not listed separately. (4) Represents the non-reportable segments of Animal Health, Healthcare Services and Alliances. (5) Other is primarily comprised of miscellaneous corporate revenues, including revenue hedging activities, as well as third-party manufacturing sales. Other in 2017 and 2016 also includes $85 million and $170 million , respectively, related to the sale of the marketing rights to certain products.
Consolidated Revenues by Geographic Area	Consolidated revenues by geographic area where derived are as follows: Years Ended December 31 2017 2016 2015 United States $ 17,424 $ 18,478 $ 17,519 Europe, Middle East and Africa 11,478 10,953 10,677 Asia Pacific 4,337 3,918 3,825 Japan 3,122 2,846 2,673 Latin America 2,339 2,155 2,825 Other 1,422 1,457 1,979 $ 40,122 $ 39,807 $ 39,498
Reconciliation of Segment Profits to Income Before Taxes	A reconciliation of total segment profits to consolidated Income before taxes is as follows: Years Ended December 31 2017 2016 2015 Segment profits: Pharmaceutical segment $ 22,586 $ 22,180 $ 21,658 Other segments 1,834 1,507 1,573 Total segment profits 24,420 23,687 23,231 Other profits 26 481 810 Unallocated: Interest income 385 328 289 Interest expense (754 ) (693 ) (672 ) Equity income from affiliates 49 (19 ) 135 Depreciation and amortization (1,378 ) (1,585 ) (1,573 ) Research and development (9,355 ) (9,084 ) (5,871 ) Amortization of purchase accounting adjustments (3,056 ) (3,692 ) (4,816 ) Restructuring costs (776 ) (651 ) (619 ) Loss on extinguishment of debt (191 ) — — Gain on sale of certain migraine clinical development programs — 100 250 Charge related to the settlement of worldwide Keytruda patent litigation — (625 ) — Gain on divestiture of certain ophthalmic products — — 147 Foreign currency devaluation related to Venezuela — — (876 ) Net charge related to the settlement of Vioxx shareholder class action litigation — — (680 ) Other unallocated, net (2,849 ) (3,588 ) (4,354 ) $ 6,521 $ 4,659 $ 5,401
Equity Income from Affiliates and Depreciation and Amortization Included in Segment Profits	Equity income from affiliates and depreciation and amortization included in segment profits is as follows: Pharmaceutical All Other Total Year Ended December 31, 2017 Included in segment profits: Equity income from affiliates $ (7 ) $ — $ (7 ) Depreciation and amortization (125 ) (87 ) (212 ) Year Ended December 31, 2016 Included in segment profits: Equity income from affiliates $ 105 $ — $ 105 Depreciation and amortization (160 ) (23 ) (183 ) Year Ended December 31, 2015 Included in segment profits: Equity income from affiliates $ 70 $ — $ 70 Depreciation and amortization (82 ) (18 ) (100 )
Property, Plant and Equipment, Net by Geographic Area	Property, plant and equipment, net by geographic area where located is as follows: December 31 2017 2016 2015 United States $ 8,070 $ 8,114 $ 8,467 Europe, Middle East and Africa 3,151 2,732 2,844 Asia Pacific 782 775 842 Latin America 271 234 182 Japan 158 164 164 Other 7 7 8 $ 12,439 $ 12,026 $ 12,507

Nature of Operations (Details)

Nature of Operations (Details)	12 Months Ended
	Dec. 31, 2017segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments	4

Summary of Accounting Policie46

Summary of Accounting Policies - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Accrual for chargebacks reflected as direct reduction to Accounts receivable	$ 198	$ 196
Accrual for rebates included in Accrued and other current liabilities	2,400	2,700
Depreciation expense	1,500	1,600	$ 1,600
Advertising expenses	2,200	2,100	$ 2,100
Accounting Standards Update 2016-01 | Forecast
Summary Of Significant Accounting Policies [Line Items]
Increase in Retained earnings				$ 8
Accounting Standards Update 2016-16 | Forecast
Summary Of Significant Accounting Policies [Line Items]
Increase in Retained earnings				60
Accounting Standards Update 2017-07
Summary Of Significant Accounting Policies [Line Items]
Net periodic benefit cost (credit)	(510)	(530)
Accounting Standards Update 2017-12 | Forecast
Summary Of Significant Accounting Policies [Line Items]
Increase in Retained earnings				11
Enterprise wide resource planning system
Summary Of Significant Accounting Policies [Line Items]
Unamortized capitalized software costs	$ 449	$ 452
Minimum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of intangible assets	2 years
Minimum | Enterprise wide resource planning system
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of intangible assets	6 years
Minimum | Capitalized Software
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of intangible assets	3 years
Minimum | Building
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of property, plant and equipment	25 years
Minimum | Machinery and Equipment
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of property, plant and equipment	3 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of intangible assets	20 years
Maximum | Enterprise wide resource planning system
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of intangible assets	10 years
Maximum | Capitalized Software
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of intangible assets	5 years
Maximum | Building
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of property, plant and equipment	45 years
Maximum | Machinery and Equipment
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of property, plant and equipment	15 years
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09 | Forecast
Summary Of Significant Accounting Policies [Line Items]
Increase in Retained earnings				$ 5

Acquisitions, Divestitures, R47

Acquisitions, Divestitures, Research Collaborations and License Agreements - Acqusitions Narrative (Detail) AUD / shares in Units, € in Millions, AUD in Millions	Dec. 31, 2016USD ($)	Jan. 21, 2015USD ($)	Oct. 31, 2017USD ($)	Oct. 31, 2017EUR (€)	Jul. 31, 2017USD ($)	Mar. 31, 2017USD ($)	Jul. 31, 2016USD ($)	Jun. 30, 2016USD ($)	Jan. 31, 2016USD ($)	Jul. 31, 2015USD ($)	Feb. 28, 2015USD ($)renewal	Dec. 31, 2017USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Feb. 28, 2018AUDAUD / shares	Feb. 28, 2018USD ($)
Acquisitions Divestitures Research Collaborations And License Agreements Transactions [Line Items]
Contingent consideration	$ 891,000,000											$ 935,000,000	$ 935,000,000	$ 891,000,000	$ 590,000,000
Goodwill	$ 18,162,000,000											18,284,000,000	18,284,000,000	18,162,000,000	17,723,000,000
Discount rate (as percent)	11.50%
In-process research and development impairment charges													483,000,000	3,600,000,000	63,000,000
Changes in fair value													(141,000,000)	407,000,000
Agreement term											2 years
Payments to acquire business, net of cash acquired													396,000,000	780,000,000	146,000,000
Liability	$ 8,514,000,000											$ 11,117,000,000	11,117,000,000	8,514,000,000
Amortization expense for intangible assets													3,200,000,000	3,800,000,000	4,800,000,000
Payments of contingent consideration													100,000,000	25,000,000
monoclonal antibody (cCAM)
Acquisitions Divestitures Research Collaborations And License Agreements Transactions [Line Items]
In-process research and development impairment charges														180,000,000
Changes in fair value														116,000,000
uprifosbuvir
Acquisitions Divestitures Research Collaborations And License Agreements Transactions [Line Items]
In-process research and development impairment charges													$ 240,000,000	$ 2,900,000,000
Rigontec
Acquisitions Divestitures Research Collaborations And License Agreements Transactions [Line Items]
Cash paid for acquisition of business			$ 140,000,000	€ 119
Potential future milestone payments, maximum | €				349
Potential future milestone payment, research milestones and regulatory approvals | €				184
Potential future milestone payment, commercial targets | €				€ 165
Afferent Pharmaceuticals
Acquisitions Divestitures Research Collaborations And License Agreements Transactions [Line Items]
Consideration transferred in business combination							$ 510,000,000
Cash paid for acquisition of business							487,000,000
Potential future milestone payments, maximum							750,000,000
Contingent consideration							223,000,000
In-process research and development (IPR&D)							832,000,000
Other net assets							29,000,000
Goodwill							$ 130,000,000
Discount rate (as percent)							11.50%
Deferred tax liabilities							$ 258,000,000
StayWell Company
Acquisitions Divestitures Research Collaborations And License Agreements Transactions [Line Items]
Cash paid for acquisition of business							150,000,000
Goodwill							275,000,000
Fair value of debt assumed in business combination							$ 150,000,000
Period before option becomes exercisable							3 years
Identifiable intangible assets							$ 238,000,000
Deferred tax liabilities							84,000,000
Other net liabilities							5,000,000
Noncontrolling interest							$ 124,000,000
Estimated useful life of intangible assets, acquired							10 years
Estimated useful life of intangible assets							5 years
Vallee SA
Acquisitions Divestitures Research Collaborations And License Agreements Transactions [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired						93.50%						4.50%	4.50%
Cash paid for acquisition of business						$ 358,000,000
Escrow Deposit						176,000,000
Other net assets						14,000,000
Goodwill						$ 171,000,000
Discount rate (as percent)						15.50%
Identifiable intangible assets						$ 291,000,000
Deferred tax liabilities						93,000,000
Noncontrolling interest						$ 25,000,000
Estimated useful life of intangible assets, acquired						15 years
Payments to Acquire Additional Interest in Subsidiaries												$ 18,000,000
Contingent liabilities						$ 37,000,000
Indemnification assets						$ 37,000,000
Moderna Therapeutics
Acquisitions Divestitures Research Collaborations And License Agreements Transactions [Line Items]
Upfront and milestone payments								$ 200,000,000
IOmet Pharma Ltd
Acquisitions Divestitures Research Collaborations And License Agreements Transactions [Line Items]
Cash paid for acquisition of business									$ 150,000,000
Potential future milestone payments, maximum									250,000,000
Contingent consideration									94,000,000
In-process research and development (IPR&D)									155,000,000
Goodwill									$ 57,000,000
Discount rate (as percent)									10.50%
Deferred tax assets									$ 32,000,000
Payments of contingent consideration					$ 100,000,000
cCAM Biotherapeutics
Acquisitions Divestitures Research Collaborations And License Agreements Transactions [Line Items]
Cash paid for acquisition of business										$ 96,000,000
Contingent consideration										105,000,000
In-process research and development (IPR&D)										180,000,000
Goodwill										14,000,000
Other net noncurrent assets										$ 7,000,000
NGM Biopharmaceuticals
Acquisitions Divestitures Research Collaborations And License Agreements Transactions [Line Items]
Upfront and milestone payments											$ 94,000,000
Cost Method Investment, ownership percentage											15.00%
Payments to acquire cost method investment											$ 106,000,000
Purchase commitment, maximum amount (up to)											$ 250,000,000
Agreement term											5 years
Revenue and cost allocation percentage (as percent) (up to)											50.00%
Number of extensions for research agreement | renewal											2
Cubist Pharmaceuticals Inc
Acquisitions Divestitures Research Collaborations And License Agreements Transactions [Line Items]
Consideration transferred in business combination		$ 8,300,000,000
Cash paid for acquisition of business		7,800,000,000
In-process research and development (IPR&D)		50,000,000
Other net assets		55,000,000
Goodwill		$ 4,670,000,000
Discount rate (as percent)		8.00%
Fair value of debt assumed in business combination		$ 1,900,000,000
Identifiable intangible assets		6,923,000,000
Deferred tax liabilities		2,519,000,000
Other net liabilities		$ 122,000,000
Estimated useful life of intangible assets, acquired		11 years
Transaction costs															$ 324,000,000
Other net noncurrent assets		$ 184,000,000
Cubist Pharmaceuticals Inc | Other noncurrent liabilities
Acquisitions Divestitures Research Collaborations And License Agreements Transactions [Line Items]
Contingent consideration		$ 50,000,000
Subsequent Event | Viralytics Limited [Member]
Acquisitions Divestitures Research Collaborations And License Agreements Transactions [Line Items]
Business acquisition, share price (in dollars per share) | AUD / shares																AUD 1.75
Future Payment That Will Be Made To Acquire Business																AUD 502	$ 394,000,000

Acquisitions, Divestitures, R48

Acquisitions, Divestitures, Research Collaborations and License Agreements - Divestitures Narrative (Detail) - USD ($)	1 Months Ended			12 Months Ended
	Apr. 30, 2016	Aug. 31, 2015	Feb. 28, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 31, 2015
Acquisitions Divestitures Research Collaborations and License Agreements Transactions [Line Items]
Agreement term			2 years
Proceeds from sale of intangible assets				$ 85,000,000	$ 170,000,000
ophthalmic products
Acquisitions Divestitures Research Collaborations and License Agreements Transactions [Line Items]
Proceeds from divestiture of business						$ 170,000,000
Gain on disposition of business						147,000,000
CGRP receptor antagonists
Acquisitions Divestitures Research Collaborations and License Agreements Transactions [Line Items]
Total Consideration Received For Sale Of Asset							$ 250,000,000
Proceeds from collaborators	$ 125,000,000	$ 125,000,000
Gain (loss) on sale of clinical development programs					$ 100,000,000	$ 250,000,000

Acquisitions, Divestitures, R49

Acquisitions, Divestitures, Research Collaborations and License Agreements - Schedule of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions	Jan. 21, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Acquisitions Divestitures Research Collaborations And License Agreements Transactions [Line Items]
Goodwill		$ 18,284	$ 18,162	$ 17,723
Contingent consideration		$ 935	$ 891	$ 590
Cubist Pharmaceuticals Inc
Acquisitions Divestitures Research Collaborations And License Agreements Transactions [Line Items]
Cash and cash equivalents	$ 733
Accounts receivable	123
Inventories	216
Other current assets	55
Property, plant and equipment	151
Products and product rights (11 year weighted-average useful life)	6,923
IPR&D	50
Other noncurrent assets	184
Current liabilities	(233)
Deferred income tax liabilities	(2,519)
Long-term debt	(1,900)
Other noncurrent liabilities	(122)
Total identifiable net assets	3,661
Goodwill	4,670
Consideration transferred	$ 8,331
Finite-lived intangible assets, useful life	11 years
Cubist Pharmaceuticals Inc | Other current liabilities
Acquisitions Divestitures Research Collaborations And License Agreements Transactions [Line Items]
Contingent consideration	$ 73
Cubist Pharmaceuticals Inc | Other noncurrent liabilities
Acquisitions Divestitures Research Collaborations And License Agreements Transactions [Line Items]
Contingent consideration	$ 50

Acquisitions, Divestitures, R50

Acquisitions, Divestitures, Research Collaborations and License Agreements - Pro Forma Financial Information (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)$ / shares
Business Combinations [Abstract]
Sales | $	$ 39,584
Net income attributable to Merck & Co., Inc. | $	$ 4,640
Basic earnings per common share attributable to Merck & Co., Inc. common shareholders (in dollars per share) | $ / shares	$ 1.65
Earnings per common share assuming dilution attributable to Merck & Co. Inc. common shareholders (in dollars per share) | $ / shares	$ 1.63

Collaborative Arrangements - Na

Collaborative Arrangements - Narrative (Details) - USD ($) $ in Millions	1 Months Ended			12 Months Ended
	Jan. 31, 2018	Dec. 31, 2017	Jul. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development						$ 10,208	$ 10,124	$ 6,704
Sales						40,122	39,807	39,498
Accrued and other current liabilities		$ 10,427				10,427	10,274
Other Noncurrent Liabilities		11,117				11,117	8,514
Amortization expense for intangible assets						3,200	3,800	$ 4,800
AstraZeneca
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront and milestone payments			$ 1,600
Payments to Acquire Intangible Assets		250	750
Research and development						2,350
Contingent Payments Collaborative Arrangement			6,150
Total Consideration Collaborative Arrangement			8,500
AstraZeneca | Future Regulatory Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contingent Payments Collaborative Arrangement			2,050
AstraZeneca | Future Sales-Based Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contingent Payments Collaborative Arrangement			$ 4,100			4,000
AstraZeneca | Forecast
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Payments to Acquire Intangible Assets				$ 100	$ 400
AstraZeneca | Lynparza
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accrued and other current liabilities		$ 100				100
Amortization expense for intangible assets						$ 4
Finite-Lived Intangible Assets, Remaining Amortization Period						11 years
AstraZeneca | Lynparza | Forecast
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contingent Payments Collaborative Arrangement					100
Sales					$ 250
AstraZeneca | Subsequent Event
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contingent Payments Collaborative Arrangement	$ 70
Bayer AG | Future Sales-Based Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contingent Payments Collaborative Arrangement						$ 775
Bayer AG | Adempas
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contingent Payments Collaborative Arrangement							350
Sales						$ 500	500
Other Noncurrent Liabilities							350
Amortization expense for intangible assets							$ 50

Collaborative Arrangements - Sc

Collaborative Arrangements - Schedule of Collaborative Arrangement Transactions (Details) - Collaborative Arrangement - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
AstraZeneca
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Receivables from counterparty	$ 12
Payables to counterparty	643
AstraZeneca | Total Sales
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total Sales	20
AstraZeneca | Materials and production costs
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Expenses	4
AstraZeneca | Marketing and administrative expenses
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Expenses	1
AstraZeneca | Research and development expenses
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Expenses	2,419
Bayer AG
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Receivables from counterparty	33	$ 0
Payables to counterparty	352	353
Bayer AG | Total Sales
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Product sales, net	149	88	$ 0
Profit sharing	151	81	30
Total Sales	300	169	30
Bayer AG | Materials and production costs
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Expenses	99	133	67
Bayer AG | Marketing and administrative expenses
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Expenses	27	26	3
Bayer AG | Research and development expenses
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Expenses	$ 96	$ 45	$ 3

Restructuring - Narrative (Deta

Restructuring - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)position	Dec. 31, 2016USD ($)position	Dec. 31, 2015USD ($)position
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 927	$ 1,069	$ 1,110
Cumulative restructuring costs incurred to date since program inception	$ 13,500
Number of positions elimination since inception of program | position	43,350
Expected remaining costs related to restructuring program activities	$ 500
Percentage estimate of cumulative pretax costs that will result in cash outlays (primarily from employee separation expense) (as percent)	66.67%
Percentage estimate of cumulative pretax costs that will be non-cash (primarily from accelerated depreciation of facilities) (as percent)	33.33%
Number of positions eliminated | position	2,450	2,625	3,770
Asset abandonment, shut-down and other related costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 267	$ 409	$ 550
Facility Closing
Restructuring Cost and Reserve [Line Items]
Pretax losses resulting from sales of facilities and related assets	$ 6	$ 151	$ 117

Restructuring - Charges Related

Restructuring - Charges Related to Restructuring Program Activities by Type of Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 927	$ 1,069	$ 1,110
Materials and production
Restructuring Cost and Reserve [Line Items]
Restructuring costs	138	181	361
Marketing and administrative
Restructuring Cost and Reserve [Line Items]
Restructuring costs	2	95	78
Research and development
Restructuring Cost and Reserve [Line Items]
Restructuring costs	11	142	52
Restructuring costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs	776	651	619
Separation Costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs	552	216	208
Separation Costs | Materials and production
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0	0	0
Separation Costs | Marketing and administrative
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0	0	0
Separation Costs | Research and development
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0	0	0
Separation Costs | Restructuring costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs	552	216	208
Accelerated Depreciation
Restructuring Cost and Reserve [Line Items]
Restructuring costs	60	227	174
Accelerated Depreciation | Materials and production
Restructuring Cost and Reserve [Line Items]
Restructuring costs	52	77	78
Accelerated Depreciation | Marketing and administrative
Restructuring Cost and Reserve [Line Items]
Restructuring costs	2	8	59
Accelerated Depreciation | Research and development
Restructuring Cost and Reserve [Line Items]
Restructuring costs	6	142	37
Accelerated Depreciation | Restructuring costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0	0	0
Other
Restructuring Cost and Reserve [Line Items]
Restructuring costs	315	626	728
Other | Materials and production
Restructuring Cost and Reserve [Line Items]
Restructuring costs	86	104	283
Other | Marketing and administrative
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0	87	19
Other | Research and development
Restructuring Cost and Reserve [Line Items]
Restructuring costs	5	0	15
Other | Restructuring costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 224	$ 435	$ 411

Restructuring - Charges and Spe

Restructuring - Charges and Spending Relating to Restructuring Activities by Program (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	$ 541	$ 645
Expenses	927	1,069	$ 1,110
(Payments) receipts, net	(722)	(760)
Non-cash activity	1	(413)
Restructuring reserve, ending balance	747	541	645
Separation Costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	395	592
Expenses	552	216	208
(Payments) receipts, net	(328)	(413)
Non-cash activity	0	0
Restructuring reserve, ending balance	619	395	592
Accelerated Depreciation
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	0	0
Expenses	60	227	174
(Payments) receipts, net	0	0
Non-cash activity	(60)	(227)
Restructuring reserve, ending balance	0	0	0
Other
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	146	53
Expenses	315	626	728
(Payments) receipts, net	(394)	(347)
Non-cash activity	61	(186)
Restructuring reserve, ending balance	$ 128	$ 146	$ 53

Financial Instruments - Narrati

Financial Instruments - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)interest_rate_swap	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Derivative [Line Items]
Pretax gains (losses) from euro-denominated notes included in cumulative translation adjustments	$ (520)	$ 193	$ 304
Number of interest rate swaps held | interest_rate_swap	26
Notional amount of derivative	$ 25,595	25,539
Pre tax net unrealized gain (loss) on derivatives maturing within next 12 months estimated to be reclassified from AOCI to sales	(184)
Available-for-sale debt securities included in Short-term investments	2,400
Available-for-sale debt securities maturing after one year through five years	11,100
Cash and cash equivalents	6,092	6,515	$ 8,524	$ 7,441
Fair value of loans payable and long-term debt, including current portion	25,600	25,700
Carrying value of Loans payable and long-term debt, including current portion	24,400	24,800
Total accounts receivable outstanding in excess of one year	$ 130
Percentage of accounts receivable represented by customers with largest balances (as percent)	40.00%
Cash collateral received from counterparties	$ 3	529
Significant Other Observable Inputs (Level 2)
Derivative [Line Items]
Cash and cash equivalents	6,100
Cash equivalents	5,200
Derivatives Designated as Hedging Instruments
Derivative [Line Items]
Notional amount of derivative	$ 14,386	14,398
Derivatives Designated as Hedging Instruments | Maximum
Derivative [Line Items]
Maximum planning cycle of third-party sales hedges (no more than)	2 years
Derivatives Not Designated as Hedging Instruments
Derivative [Line Items]
Notional amount of derivative	$ 11,209	$ 11,141
Derivatives Not Designated as Hedging Instruments | Maximum
Derivative [Line Items]
Maximum planning cycle of third-party sales hedges (no more than)	1 year

Financial Instruments - Informa

Financial Instruments - Information About Interest Rate Swaps (Details)	Dec. 31, 2017USD ($)interest_rate_swap	Dec. 31, 2016USD ($)
Derivative [Line Items]
Number of Interest Rate Swaps Held | interest_rate_swap	26
U.S. Dollar Notional	$ 25,595,000,000	$ 25,539,000,000
1.30% notes due 2018 | Interest Rate Swap
Derivative [Line Items]
Par Value of Debt	$ 1,000,000,000
Number of Interest Rate Swaps Held | interest_rate_swap	4
U.S. Dollar Notional	$ 1,000,000,000
Fixed-rate notes, stated interest rate (as percent)	1.30%
5.00% notes due 2019 | Interest Rate Swap
Derivative [Line Items]
Par Value of Debt	$ 1,250,000,000
Number of Interest Rate Swaps Held | interest_rate_swap	3
U.S. Dollar Notional	$ 550,000,000
Fixed-rate notes, stated interest rate (as percent)	5.00%
1.85% notes due 2020 | Interest Rate Swap
Derivative [Line Items]
Par Value of Debt	$ 1,250,000,000
Number of Interest Rate Swaps Held | interest_rate_swap	5
U.S. Dollar Notional	$ 1,250,000,000
Fixed-rate notes, stated interest rate (as percent)	1.85%
3.875% notes due 2021 | Interest Rate Swap
Derivative [Line Items]
Par Value of Debt	$ 1,150,000,000
Number of Interest Rate Swaps Held | interest_rate_swap	5
U.S. Dollar Notional	$ 1,150,000,000
Fixed-rate notes, stated interest rate (as percent)	3.875%
2.40% notes due 2022 | Interest Rate Swap
Derivative [Line Items]
Par Value of Debt	$ 1,000,000,000
Number of Interest Rate Swaps Held | interest_rate_swap	4
U.S. Dollar Notional	$ 1,000,000,000
Fixed-rate notes, stated interest rate (as percent)	2.40%
2.35% notes due 2022 | Interest Rate Swap
Derivative [Line Items]
Par Value of Debt	$ 1,250,000,000
Number of Interest Rate Swaps Held | interest_rate_swap	5
U.S. Dollar Notional	$ 1,250,000,000
Fixed-rate notes, stated interest rate (as percent)	2.35%

Financial Instruments - Fair Va

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	Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	$ 130	$ 995
Fair Value of Derivative, Liability	217	134
U.S. Dollar Notional	25,595	25,539
Derivatives Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	91	765
Fair Value of Derivative, Liability	127	31
U.S. Dollar Notional	14,386	14,398
Derivatives Not Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	39	230
Fair Value of Derivative, Liability	90	103
U.S. Dollar Notional	11,209	11,141
Interest rate swap contracts | Derivatives Designated as Hedging Instruments | Other assets
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	2	20
U.S. Dollar Notional	550	2,700
Interest rate swap contracts | Derivatives Designated as Hedging Instruments | Accrued and other current liabilities
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Liability	3	0
U.S. Dollar Notional	1,000	0
Interest rate swap contracts | Derivatives Designated as Hedging Instruments | Other noncurrent liabilities
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Liability	52	29
U.S. Dollar Notional	4,650	3,500
Foreign exchange contracts | Derivatives Designated as Hedging Instruments | Other assets
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	38	129
Fair Value of Derivative, Liability
U.S. Dollar Notional	1,936	2,075
Foreign exchange contracts | Derivatives Designated as Hedging Instruments | Other current assets
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	51	616
U.S. Dollar Notional	4,216	6,063
Foreign exchange contracts | Derivatives Designated as Hedging Instruments | Accrued and other current liabilities
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Liability	71	1
U.S. Dollar Notional	2,014	48
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	20	12
Foreign exchange contracts | Derivatives Not Designated as Hedging Instruments | Other current assets
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	39	230
U.S. Dollar Notional	3,778	8,210
Foreign exchange contracts | Derivatives Not Designated as Hedging Instruments | Accrued and other current liabilities
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Liability	90	103
U.S. Dollar Notional	$ 7,431	$ 2,931

Financial Instruments - Infor59

Financial Instruments - Information on Derivative Positions Subject to Master Netting Arrangements as if they were Presented on a Net Basis (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gross amounts recognized in the consolidated balance sheet, Asset	$ 130	$ 995
Gross amount subject to offset in master netting arrangements not offset in the consolidated balance sheet, Asset	(94)	(131)
Cash collateral (received) posted, Asset	(3)	(529)
Net amounts, Asset	33	335
Gross amounts recognized in the consolidated balance sheet, Liability	217	134
Gross amount subject to offset in master netting arrangements not offset in the consolidated balance sheet, Liability	(94)	(131)
Cash collateral (received) posted, Liability	0	0
Net amounts, Liability	$ 123	$ 3

Financial Instruments - Locatio

Financial Instruments - Location and Pretax Gain or Loss Amounts for Derivatives (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Ineffectiveness on the hedged item	$ 5	$ 1	$ 7
Derivatives not designated in a hedging relationship | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of (gain) loss recognized in Other (income) expense, net on derivatives	110	132	(461)
Amount of gain recognized in Sales	(3)	0	(1)
Derivatives designated in a fair value hedging relationship | Interest rate swap contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of (gain) loss recognized in Other (income) expense, net on derivatives	43	28	(14)
Amount of loss (gain) recognized in Other (income) expense, net on hedged item	(48)	(29)	7
Derivatives designated in foreign currency cash flow hedging relationships | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain reclassified from AOCI to Sales	(138)	(311)	(724)
Amount of loss (gain) recognized in OCI on derivatives	561	(210)	(526)
Derivatives designated in foreign currency net investment hedging relationships | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain recognized in Other (income) expense, net on derivatives	0	(1)	(4)
Amount of loss (gain) recognized in OCI on derivatives	$ 0	$ 2	$ (10)

Financial Instruments - Infor61

Financial Instruments - Information on Available-for-sale Investments (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 15,183	$ 20,179
Amortized Cost	15,241	20,158
Gross Unrealized Gains	27	89
Gross Unrealized Losses	(85)	(68)
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Fair Value	159	4,330
Amortized Cost	159	4,330
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Corporate notes and bonds
Schedule of Available-for-sale Securities [Line Items]
Fair Value	9,806	10,577
Amortized Cost	9,837	10,601
Gross Unrealized Gains	9	15
Gross Unrealized Losses	(40)	(39)
U.S. government and agency securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	2,042	2,232
Amortized Cost	2,059	2,244
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(17)	(13)
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,542	1,376
Amortized Cost	1,548	1,380
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(7)	(5)
Foreign government bonds
Schedule of Available-for-sale Securities [Line Items]
Fair Value	733	519
Amortized Cost	739	521
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(6)	(2)
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	626	796
Amortized Cost	634	801
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(9)	(6)
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	275	349
Amortized Cost	265	281
Gross Unrealized Gains	16	71
Gross Unrealized Losses	$ (6)	$ (3)

Financial Instruments - Financi

Financial Instruments - Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets
Investments	$ 15,183	$ 20,179
Derivative assets	130	995
Liabilities
Contingent consideration	935	891	$ 590
Derivative liabilities	217	134
Commercial paper
Assets
Investments	159	4,330
Corporate notes and bonds
Assets
Investments	9,806	10,577
U.S. government and agency securities
Assets
Investments	2,042	2,232
Asset-backed securities
Assets
Investments	$ 1,542	1,376
Liabilities
Primary weighted-average lives of investment collateral (or less)	5 years
Mortgage-backed securities
Assets
Investments	$ 626	796
Foreign government bonds
Assets
Investments	733	519
Equity securities
Assets
Investments	275	349
Fair Value, Measurements, Recurring
Assets
Investments	14,531	19,242
Other assets	652	937
Derivative assets	130	995
Total assets	15,313	21,174
Liabilities
Contingent consideration	935	891
Derivative liabilities	217	134
Total liabilities	1,152	1,025
Fair Value, Measurements, Recurring | Purchased currency options
Assets
Derivative assets	80	644
Liabilities
Derivative liabilities	0	12
Fair Value, Measurements, Recurring | Foreign exchange contracts
Assets
Derivative assets	48	331
Liabilities
Derivative liabilities	162	93
Fair Value, Measurements, Recurring | Interest rate swap contracts
Assets
Derivative assets	2	20
Liabilities
Derivative liabilities	55	29
Fair Value, Measurements, Recurring | Commercial paper
Assets
Investments	159	4,330
Fair Value, Measurements, Recurring | Corporate notes and bonds
Assets
Investments	9,678	10,389
Other assets	128	188
Fair Value, Measurements, Recurring | U.S. government and agency securities
Assets
Investments	1,835	1,919
Other assets	207	313
Fair Value, Measurements, Recurring | Asset-backed securities
Assets
Investments	1,476	1,257
Other assets	66	119
Fair Value, Measurements, Recurring | Mortgage-backed securities
Assets
Investments	547	628
Other assets	79	168
Fair Value, Measurements, Recurring | Foreign government bonds
Assets
Investments	732	518
Other assets	1	1
Fair Value, Measurements, Recurring | Equity securities
Assets
Investments	104	201
Other assets	171	148
Fair Value, Measurements, Recurring | Quoted Prices In Active Markets for Identical Assets (Level 1)
Assets
Investments	172	230
Other assets	171	148
Derivative assets	0	0
Total assets	343	378
Liabilities
Contingent consideration	0	0
Derivative liabilities	0	0
Total liabilities	0	0
Fair Value, Measurements, Recurring | Quoted Prices In Active Markets for Identical Assets (Level 1) | Purchased currency options
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Quoted Prices In Active Markets for Identical Assets (Level 1) | Foreign exchange contracts
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Quoted Prices In Active Markets for Identical Assets (Level 1) | Interest rate swap contracts
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Quoted Prices In Active Markets for Identical Assets (Level 1) | Commercial paper
Assets
Investments	0	0
Fair Value, Measurements, Recurring | Quoted Prices In Active Markets for Identical Assets (Level 1) | Corporate notes and bonds
Assets
Investments	0	0
Other assets	0	0
Fair Value, Measurements, Recurring | Quoted Prices In Active Markets for Identical Assets (Level 1) | U.S. government and agency securities
Assets
Investments	68	29
Other assets	0	0
Fair Value, Measurements, Recurring | Quoted Prices In Active Markets for Identical Assets (Level 1) | Asset-backed securities
Assets
Investments	0	0
Other assets	0	0
Fair Value, Measurements, Recurring | Quoted Prices In Active Markets for Identical Assets (Level 1) | Mortgage-backed securities
Assets
Investments	0	0
Other assets	0	0
Fair Value, Measurements, Recurring | Quoted Prices In Active Markets for Identical Assets (Level 1) | Foreign government bonds
Assets
Investments	0	0
Other assets	0	0
Fair Value, Measurements, Recurring | Quoted Prices In Active Markets for Identical Assets (Level 1) | Equity securities
Assets
Investments	104	201
Other assets	171	148
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Assets
Investments	14,359	19,012
Other assets	481	789
Derivative assets	130	995
Total assets	14,970	20,796
Liabilities
Contingent consideration	0	0
Derivative liabilities	217	134
Total liabilities	217	134
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Purchased currency options
Assets
Derivative assets	80	644
Liabilities
Derivative liabilities	0	12
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Foreign exchange contracts
Assets
Derivative assets	48	331
Liabilities
Derivative liabilities	162	93
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Interest rate swap contracts
Assets
Derivative assets	2	20
Liabilities
Derivative liabilities	55	29
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Commercial paper
Assets
Investments	159	4,330
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Corporate notes and bonds
Assets
Investments	9,678	10,389
Other assets	128	188
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. government and agency securities
Assets
Investments	1,767	1,890
Other assets	207	313
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Asset-backed securities
Assets
Investments	1,476	1,257
Other assets	66	119
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Mortgage-backed securities
Assets
Investments	547	628
Other assets	79	168
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Foreign government bonds
Assets
Investments	732	518
Other assets	1	1
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Equity securities
Assets
Investments	0	0
Other assets	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Assets
Investments	0	0
Other assets	0	0
Derivative assets	0	0
Total assets	0	0
Liabilities
Contingent consideration	935	891
Derivative liabilities	0	0
Total liabilities	935	891
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Purchased currency options
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Foreign exchange contracts
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Interest rate swap contracts
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Commercial paper
Assets
Investments	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Corporate notes and bonds
Assets
Investments	0	0
Other assets	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | U.S. government and agency securities
Assets
Investments	0	0
Other assets	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Asset-backed securities
Assets
Investments	0	0
Other assets	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Mortgage-backed securities
Assets
Investments	0	0
Other assets	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Foreign government bonds
Assets
Investments	0	0
Other assets	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Equity securities
Assets
Investments	0	0
Other assets	$ 0	$ 0

Financial Instruments - Summari

Financial Instruments - Summarized Information About Changes in Liabilities for Contingent Consideration (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Contingent consideration, liability, current	$ 315
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration	891	$ 590
Changes in fair value	141	(407)
Additions	3	733
Payments	(100)	(25)
Contingent consideration	$ 935	$ 891

Inventories - Narrative (Detail

Inventories - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Inventory [Line Items]
LIFO Inventory Amount	$ 2,200	$ 2,300
Inventories classified in other assets	1,187	1,117
Inventory Not Expected to be Sold Within One Year
Inventory [Line Items]
Inventories classified in other assets	1,100	1,000
Inventories Produced in Preparation for Product Launches
Inventory [Line Items]
Inventories classified in other assets	$ 80	$ 80

Inventories - Inventories (Deta

Inventories - Inventories (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Finished goods	$ 1,334	$ 1,304
Raw materials and work in process	4,703	4,222
Supplies	201	155
Total (approximates current cost)	6,238	5,681
Increase to LIFO costs	45	302
Total current and noncurrent inventories	6,283	5,983
Recognized as:
Inventories	5,096	4,866
Other assets	$ 1,187	$ 1,117

Goodwill and Other Intangible66

Goodwill and Other Intangibles - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangible Assets Excluding Goodwill [Line Items]
Other intangibles, net	$ 14,183	$ 17,305
Other intangibles, net	50,131	50,084
Accumulated Amortization	35,948	32,779
Intangible asset impairment charge related to marketed product	58	347	$ 45
IPR&D reclassified to products and product rights upon receipt of marketing approval	14	8	280
IPR&D impairment charges	483	3,600	63
Amortization expense for intangible assets	3,200	3,800	4,800
Estimated Future Amortization Expense, 2018	2,800
Estimated Future Amortization Expense, 2019	1,500
Estimated Future Amortization Expense, 2020	1,200
Estimated Future Amortization Expense, 2021	1,100
Estimated Future Amortization Expense, 2022	1,100
Zerbaxa
Intangible Assets Excluding Goodwill [Line Items]
Other intangibles, net	3,000
Sivextro
Intangible Assets Excluding Goodwill [Line Items]
Other intangibles, net	879
Zetia
Intangible Assets Excluding Goodwill [Line Items]
Other intangibles, net	756
Implanon/Nexplanon
Intangible Assets Excluding Goodwill [Line Items]
Other intangibles, net	529
Dificid
Intangible Assets Excluding Goodwill [Line Items]
Other intangibles, net	478
Gardasil/Gardasil 9
Intangible Assets Excluding Goodwill [Line Items]
Other intangibles, net	468	468
Vytorin
Intangible Assets Excluding Goodwill [Line Items]
Other intangibles, net	375
Bridion
Intangible Assets Excluding Goodwill [Line Items]
Other intangibles, net	320
Simponi
Intangible Assets Excluding Goodwill [Line Items]
Other intangibles, net	226
Adempas
Intangible Assets Excluding Goodwill [Line Items]
Other intangibles, net	894
Intron A
Intangible Assets Excluding Goodwill [Line Items]
Other intangibles, net	13
Intangible asset impairment charge related to marketed product	47
Zontivity
Intangible Assets Excluding Goodwill [Line Items]
Intangible asset impairment charge related to marketed product		252
Grastek/Ragwitek
Intangible Assets Excluding Goodwill [Line Items]
Intangible asset impairment charge related to marketed product		95
uprifosbuvir
Intangible Assets Excluding Goodwill [Line Items]
Other intangibles, net		240
IPR&D impairment charges	240	2,900
verubecestat [Member]
Intangible Assets Excluding Goodwill [Line Items]
IPR&D impairment charges	$ 226
monoclonal antibody (cCAM)
Intangible Assets Excluding Goodwill [Line Items]
IPR&D impairment charges		180
BET inhibitor (OncoEthix)
Intangible Assets Excluding Goodwill [Line Items]
IPR&D impairment charges		143
diabetes treatment
Intangible Assets Excluding Goodwill [Line Items]
IPR&D impairment charges		72
House Dust Mite
Intangible Assets Excluding Goodwill [Line Items]
IPR&D impairment charges		112
Next Generation Ring
Intangible Assets Excluding Goodwill [Line Items]
IPR&D impairment charges		$ 79
surotomycin
Intangible Assets Excluding Goodwill [Line Items]
IPR&D impairment charges			$ 50

Goodwill and Other Intangible67

Goodwill and Other Intangibles - Goodwill Activity by Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Goodwill, Beginning Balance	$ 18,162	$ 17,723
Acquisitions	177	482
Impairments	(38)	(47)
Other	(17)	4
Goodwill, Ending Balance	18,284	18,162
Accumulated goodwill impairment losses	225	187
Pharmaceutical
Goodwill [Roll Forward]
Goodwill, Beginning Balance	16,075	15,862
Acquisitions	0	207
Impairments	0	0
Other	(9)	6
Goodwill, Ending Balance	16,066	16,075
All Other
Goodwill [Roll Forward]
Goodwill, Beginning Balance	2,087	1,861
Acquisitions	177	275
Impairments	(38)	(47)
Other	(8)	(2)
Goodwill, Ending Balance	$ 2,218	$ 2,087

Goodwill and Other Intangible68

Goodwill and Other Intangibles - Other Intangibles (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Intangible Assets Excluding Goodwill [Line Items]
Gross Carrying Amount	$ 50,131	$ 50,084
Accumulated Amortization	35,948	32,779
Net	14,183	17,305
IPR&D
Intangible Assets Excluding Goodwill [Line Items]
Gross Carrying Amount	1,194	1,653
Net	1,194	1,653
Products and product rights
Intangible Assets Excluding Goodwill [Line Items]
Gross Carrying Amount	46,693	46,269
Accumulated Amortization	34,950	31,919
Net	11,743	14,350
Tradenames
Intangible Assets Excluding Goodwill [Line Items]
Gross Carrying Amount	209	215
Accumulated Amortization	97	89
Net	112	126
Other
Intangible Assets Excluding Goodwill [Line Items]
Gross Carrying Amount	2,035	1,947
Accumulated Amortization	901	771
Net	$ 1,134	$ 1,176

Joint Ventures and Other Equi69

Joint Ventures and Other Equity Method Affiliates - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 1998	Dec. 31, 1993
Equity Income from Affiliates [Line Items]
Equity income from affiliates		$ (42)	$ (86)	$ (205)
Investments in affiliates accounted for using the equity method	$ 715	767	715
Contingent consideration	$ 891	935	891	590
Proceeds from sale of intangible assets		85	170
Discount rate (as percent)	11.50%
Other intangibles, net	$ 17,305	14,183	17,305
Gardasil/Gardasil 9
Equity Income from Affiliates [Line Items]
Other intangibles, net	468	468	468
Step Acquisition and Termination of SPMSD
Equity Income from Affiliates [Line Items]
Investments in affiliates accounted for using the equity method	$ 183		$ 183
Equity interest acquired (as percent)	50.00%		50.00%
Consideration transferred in business combination	$ 657
Royalty rate (as percent)	11.50%
Contingent consideration	$ 416		$ 416
Proceeds from sale of intangible assets	596
Fair value of future royalties	$ 302		302
Discount rate (as percent)	8.00%
Transaction costs	$ 24
AstraZeneca LP
Equity Income from Affiliates [Line Items]
Ownership percentage (as percent)						50.00%
Limited partner interest in AZLP (as percent)					1.00%
General partner interest in AZLP (as percent)					99.00%
Other Noncash Income		232	98	182
Other Receivables		$ 325
Sanofi Pasteur MSD
Equity Income from Affiliates [Line Items]
Equity Method Investment, Summarized Financial Information, Revenue			$ 1,000	$ 923

Joint Ventures and Other Equi70

Joint Ventures and Other Equity Method Affiliates Joint Ventures and Other Equity Method Affiliates - Termination of SPMSD (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill	$ 18,162	$ 18,284	$ 17,723
Investments in affiliates accounted for using the equity method	$ (715)	$ (767)
Step Acquisition and Termination of SPMSD
Business Acquisition [Line Items]
Estimated useful life of intangible assets	8 years
Products and product rights	$ 936
Accounts receivable	133
Current liabilities	(221)
Deferred income tax liabilities	(147)
Other current assets	47
Total identifiable net assets	748
Consideration payable to Sanofi, net	(392)
Investments in affiliates accounted for using the equity method	(183)
Increase in net assets	173
Merck's share of restructuring costs	(77)
Net loss on termination of SPMSD joint venture	$ 96

Loans Payable, Long-Term Debt71

Loans Payable, Long-Term Debt and Other Commitments - Narrative (Details) - USD ($)	1 Months Ended	12 Months Ended
	Nov. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Long-term debt, current maturities		$ 3,000,000,000	$ 300,000,000
Loans payable and current portion of long-term debt		3,057,000,000	568,000,000
Long-term debt		21,353,000,000	24,274,000,000
Payment for Debt Extinguishment or Debt Prepayment Cost	$ 810,000,000
Repurchased face amount	$ 585,000,000
Loss on extinguishment of debt		$ (191,000,000)
Maximum total debt to capitalization ratio allowable by financial covenants under certain borrowings (not to exceed) (as percent)		60.00%
Long-term debt, maturities, repayments of principal in 2018		$ 3,000,000,000
Long-term debt, maturities, repayments of principal in 2019		1,300,000,000
Long-term debt, maturities, repayments of principal in 2020		1,900,000,000
Long-term debt, maturities, repayments of principal in 2021		2,300,000,000
Long-term debt, maturities, repayments of principal in 2022		2,200,000,000
Available borrowing capacity under credit facility		$ 6,000,000,000
Term of debt		5 years
Rental expense under operating leases net of sublease income		$ 327,000,000	292,000,000	$ 303,000,000
Minimum aggregate rental commitments under noncancellable leases in 2018		255,000,000
Minimum aggregate rental commitments under noncancellable leases in 2019		175,000,000
Minimum aggregate rental commitments under noncancellable leases in 2020		126,000,000
Minimum aggregate rental commitments under noncancellable leases in 2021		90,000,000
Minimum aggregate rental commitments under noncancellable leases in 2022		68,000,000
Minimum aggregate rental commitments under noncancellable leases thereafter		138,000,000
Other Variable Rate Debt
Debt Instrument [Line Items]
Long-term debt		$ 300,000,000	$ 147,000,000
Effective interest rate (as percent)		1.42%	0.89%
6.30% debentures due 2026
Debt Instrument [Line Items]
Long-term debt		$ 135,000,000	$ 152,000,000
Stated interest rate (as percent)		6.30%
Notes Subject To Repayment At Option Of Holder
Debt Instrument [Line Items]
Loans payable and current portion of long-term debt		$ 73,000,000	$ 267,000,000
Commercial paper
Debt Instrument [Line Items]
Weighted-average interest rate of commercial paper (as percent)		0.85%	0.40%

Loans Payable, Long-Term Debt72

Loans Payable, Long-Term Debt and Other Commitments - Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term debt	$ 21,353	$ 24,274
2.75% notes due 2025
Debt Instrument [Line Items]
Long-term debt	$ 2,488	2,487
Stated interest rate (as percent)	2.75%
3.70% notes due 2045
Debt Instrument [Line Items]
Long-term debt	$ 1,973	1,972
Stated interest rate (as percent)	3.70%
2.80% notes due 2023
Debt Instrument [Line Items]
Long-term debt	$ 1,744	1,743
Stated interest rate (as percent)	2.80%
5.00% notes due 2019
Debt Instrument [Line Items]
Long-term debt	$ 1,260	1,273
Stated interest rate (as percent)	5.00%
4.15% notes due 2043
Debt Instrument [Line Items]
Long-term debt	$ 1,237	1,236
Stated interest rate (as percent)	4.15%
1.85% notes due 2020
Debt Instrument [Line Items]
Long-term debt	$ 1,232	1,238
Stated interest rate (as percent)	1.85%
2.35% notes due 2022
Debt Instrument [Line Items]
Long-term debt	$ 1,220	1,228
Stated interest rate (as percent)	2.35%
1.125% euro-denominated notes due 2021
Debt Instrument [Line Items]
Long-term debt	$ 1,185	1,035
Stated interest rate (as percent)	1.125%
1.875% euro-denominated notes due 2026
Debt Instrument [Line Items]
Long-term debt	$ 1,178	1,028
Stated interest rate (as percent)	1.875%
3.875% notes due 2021
Debt Instrument [Line Items]
Long-term debt	$ 1,140	1,152
Stated interest rate (as percent)	3.875%
2.40% notes due 2022
Debt Instrument [Line Items]
Long-term debt	$ 993	1,003
Stated interest rate (as percent)	2.40%
6.50% notes due 2033
Debt Instrument [Line Items]
Long-term debt	$ 729	806
Stated interest rate (as percent)	6.50%
Floating-rate notes due 2020
Debt Instrument [Line Items]
Long-term debt	$ 699	698
0.50% euro-denominated notes due 2024
Debt Instrument [Line Items]
Long-term debt	$ 591	516
Stated interest rate (as percent)	0.50%
1.375% euro-denominated notes due 2036
Debt Instrument [Line Items]
Long-term debt	$ 587	512
Stated interest rate (as percent)	1.375%
2.50% euro-denominated notes due 2034
Debt Instrument [Line Items]
Long-term debt	$ 585	511
Stated interest rate (as percent)	2.50%
3.60% notes due 2042
Debt Instrument [Line Items]
Long-term debt	$ 489	489
Stated interest rate (as percent)	3.60%
6.55% notes due 2037
Debt Instrument [Line Items]
Long-term debt	$ 415	594
Stated interest rate (as percent)	6.55%
5.75% notes due 2036
Debt Instrument [Line Items]
Long-term debt	$ 338	369
Stated interest rate (as percent)	5.75%
5.95% debentures due 2028
Debt Instrument [Line Items]
Long-term debt	$ 306	355
Stated interest rate (as percent)	5.95%
5.85% notes due 2039
Debt Instrument [Line Items]
Long-term debt	$ 270	415
Stated interest rate (as percent)	5.85%
6.40% debentures due 2028
Debt Instrument [Line Items]
Long-term debt	$ 250	325
Stated interest rate (as percent)	6.40%
6.30% debentures due 2026
Debt Instrument [Line Items]
Long-term debt	$ 135	152
Stated interest rate (as percent)	6.30%
Floating-rate borrowing due 2018
Debt Instrument [Line Items]
Long-term debt	$ 0	999
1.10% notes due 2018
Debt Instrument [Line Items]
Long-term debt	$ 0	999
Stated interest rate (as percent)	1.10%
1.30% notes due 2018
Debt Instrument [Line Items]
Long-term debt	$ 0	985
Stated interest rate (as percent)	1.30%
Other
Debt Instrument [Line Items]
Long-term debt	$ 309	$ 154

Contingencies and Environment73

Contingencies and Environmental Liabilities - Fosamax Product Liability Litigation - Narrative (Details) - Fosamax $ in Millions	1 Months Ended				12 Months Ended
	Jun. 30, 2015legalmatter	Jul. 31, 2014USD ($)	Mar. 31, 2014legalmatter	Dec. 31, 2013USD ($)legalmatter	Dec. 31, 2017legalmatter	Jul. 31, 2015legalmatter	Nov. 30, 2013legalmatter
Loss Contingencies [Line Items]
Loss contingency, pending claims number					4,085
New Jersey
Loss Contingencies [Line Items]
Loss contingency, pending claims number					2,750
Initial number of cases selected for review					30
Subsequent number of cases selected for review			50			25	50
California State Court
Loss Contingencies [Line Items]
Loss contingency, pending claims number					280
Initial number of cases selected for review			10
Femur Fracture Litigation
Loss Contingencies [Line Items]
Loss contingency, pending claims number					4,070
Femur Fracture Litigation | Other State Court
Loss Contingencies [Line Items]
Loss contingency, pending claims number					5
ONJ Litigation
Loss Contingencies [Line Items]
Loss contingency, pending claims number					15
Litigation Settlement, Amount Awarded to Other Party | $		$ 27.3		$ 27.7
Number of plaintiffs				1,200
Percentage of participation in litigation settlement (as percent)		95.00%
Federal
Loss Contingencies [Line Items]
Loss contingency, pending claims number					530
Loss contingency, claims dismissed number	510		650		510
Loss contingency, claims on appeal, number					515

Contingencies and Environment74

Contingencies and Environmental Liabilities - Januvia/Janumet Litigation - Narrative (Details) - Januvia - legalmatter	Nov. 30, 2015	Dec. 31, 2017
Loss Contingencies [Line Items]
Loss contingency, pending claims number		1,235
Loss contingency, claims dismissed number	1,100
Cases Company Agreed ToToll Statute Of Limitations
Loss Contingencies [Line Items]
Loss contingency, pending claims number		50
Other State Court
Loss Contingencies [Line Items]
Loss contingency, pending claims number		7
ILLINOIS | Other State Court
Loss Contingencies [Line Items]
Loss contingency, pending claims number		4

Contingencies and Environment75

Contingencies and Environmental Liabilities - Propecia/Proscar Litigation - Narrative (Details)	12 Months Ended
	Dec. 31, 2017legalmatterPlaintiff
Propecia
Loss Contingencies [Line Items]
Loss contingency, pending claims number	775
Propecia | Cases alleging cancer
Loss Contingencies [Line Items]
Number of plaintiff groups | Plaintiff	20
Propecia/Proscar | Other State Court | California
Loss Contingencies [Line Items]
Loss contingency, pending claims number	1
Propecia/Proscar | Other State Court | Ohio
Loss Contingencies [Line Items]
Loss contingency, pending claims number	1
Propecia/Proscar | Other State Court | MASSACHUSETTS
Loss Contingencies [Line Items]
Loss contingency, pending claims number	1

Contingencies and Environment76

Contingencies and Environmental Liabilities - Commercial and Other Litigation- Narrative (Details) $ in Millions	Apr. 29, 2016legalmatter	Feb. 28, 2017USD ($)	Jan. 31, 2014legalmatter	Dec. 31, 2017USD ($)legalmatter	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Loss Contingencies [Line Items]
Litigation settlement | $		$ (80)		$ 0	$ (625)	$ 0
Commercial Litigation
Loss Contingencies [Line Items]
Additional claims filed	1		4
Loss contingency, pending claims number				700
Number of plaintiffs				2
Loss contingency, claims on appeal, number				2

Contingencies and Environment77

Contingencies and Environmental Liabilities Contingencies and Environmental Liabilities - Patent Litigation - Narrative (Details) $ in Millions	1 Months Ended				12 Months Ended			36 Months Ended	84 Months Ended
	Jan. 31, 2018USD ($)	Feb. 28, 2017USD ($)	Dec. 31, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2017USD ($)patent	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2026	Dec. 31, 2023
Loss Contingencies [Line Items]
Litigation settlement		$ (80)			$ 0	$ (625)	$ 0
Number of Patents Involved in Legal Dispute | patent					2
Percentage of settlement to be paid to third-party (as percent)					20.00%
Litigation Settlement, Amount Awarded from Other Party			$ 2,540	$ 200
Forecast
Loss Contingencies [Line Items]
Royalty rate (as percent)								2.50%	6.50%
Patent litigation
Loss Contingencies [Line Items]
Litigation settlement						$ 117
Subsequent Event
Loss Contingencies [Line Items]
Litigation settlement	$ 115

Contingencies and Environment78

Contingencies and Environmental Liabilities - Legal Defense Reserves - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Legal Defense Costs
Loss Contingencies [Line Items]
Legal defense costs reserve	$ 160	$ 185

Contingencies and Environment79

Contingencies and Environmental Liabilities - Environmental Litigation and Matters - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Site Contingency [Line Items]
Accrued liabilities for environmental matters	$ 82,000	$ 83,000
Term for paying off environmental liabilities	15 years
Aggregate possible expenditure on environmental matters in excess of amounts accrued	$ 63,000
Oss Netherlands
Site Contingency [Line Items]
Environmental remediation expense	$ 235

Equity - Narrative (Details)

Equity - Narrative (Details) - shares	Dec. 31, 2017	Dec. 31, 2016
Equity [Abstract]
Common stock, shares authorized	6,500,000,000	6,500,000,000
Preferred stock, shares authorized	20,000,000

Equity - Shareholders' Equity (

Equity - Shareholders' Equity (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in Common Stock and Treasury Stock [Roll Forward]
Balance January 1 (in shares)	3,577,103,522
Balance December 31 (in shares)	3,577,103,522	3,577,103,522
Common Stock
Movement in Common Stock and Treasury Stock [Roll Forward]
Balance January 1 (in shares)	3,577,000,000	3,577,000,000	3,577,000,000
Purchases of treasury stock (in shares)	0	0	0
Issuances (in shares)	0	0	0
Balance December 31 (in shares)	3,577,000,000	3,577,000,000	3,577,000,000
Treasury Stock
Movement in Common Stock and Treasury Stock [Roll Forward]
Balance January 1 (in shares)	828,000,000	796,000,000	739,000,000
Purchases of treasury stock (in shares)	67,000,000	60,000,000	75,000,000
Issuances (in shares)	(15,000,000)	(28,000,000)	(18,000,000)
Balance December 31 (in shares)	880,000,000	828,000,000	796,000,000

Share-Based Compensation Plan82

Share-Based Compensation Plans - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Shares collectively authorized for future grants under share-based compensation plans (in shares)	118,000,000
Quantity of stock options that vest per year (as percent)	33.33%
Period over which share-based payment awards vest	3 years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pretax share-based compensation cost	$ 312	$ 300	$ 299
Income tax benefits related to share-based compensation	$ 57	$ 92	$ 93
Weighted average exercise price of options granted (in dollars per share)	$ 63.88	$ 54.63	$ 59.73
Weighted average fair value of options granted (in dollars per share)	$ 7.04	$ 5.89	$ 6.46
Total pre tax unrecognized compensation expense related to nonvested stock options, RSU and PSU awards	$ 469
Weighted average period in years of recognition for nonvested stock options, RSU and PSU awards	1 year 10 months 25 days
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual term of options	7 years
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual term of options	10 years

Share-Based Compensation Plan83

Share-Based Compensation Plans - Assumptions Used to Determine Weighted-Average Fair Value of Options Granted (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Expected dividend yield	3.60%	3.80%	4.10%
Risk-free interest rate	2.00%	1.40%	1.70%
Expected volatility	17.80%	19.60%	19.90%
Expected life (years)	6 years 1 month 6 days	6 years 2 months 12 days	6 years 2 months 12 days

Share-Based Compensation Plan84

Share-Based Compensation Plans - Summary of Information Relative to Stock Option Plan Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of Options, Outstanding, January 1 (in shares)	45,091
Number of Options, Granted (in shares)	4,232
Number of Options, Exercised (in shares)	(11,512)
Number of Options, Forfeited (in shares)	(1,537)
Number of Options, Outstanding, December 31 (in shares)	36,274	45,091
Number of Options, Exercisable (in shares)	26,778
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted Average Exercise Price, Options Outstanding, January 1 (in dollars per share)	$ 44.47
Weighted Average Exercise Price, Granted (in dollars per share)	63.88	$ 54.63	$ 59.73
Weighted Average Exercise Price, Exercised (in dollars per share)	43.38
Weighted Average Exercise Price, Forfeited (in dollars per share)	51.78
Weighted Average Exercise Price, Options Outstanding, December 31 (in dollars per share)	46.77	$ 44.47
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 42.54
Weighted Average Remaining Contractual Term, Outstanding	4 years 10 months 21 days
Weighted Average Remaining Contractual Term, Exercisable	3 years 7 months 21 days
Aggregate Intrinsic Value, Outstanding	$ 397
Aggregate Intrinsic Value, Exercisable	$ 384

Share-Based Compensation Plan85

Share-Based Compensation Plans - Additional Information Pertaining to Stock Option Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Total intrinsic value of stock options exercised	$ 236	$ 444	$ 332
Fair value of stock options vested	30	28	30
Cash received from the exercise of stock options	$ 499	$ 939	$ 485

Share-Based Compensation Plan86

Share-Based Compensation Plans - Summary of Nonvested RSU and PSU Activity (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2017$ / sharesshares
RSUs
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of Shares, Nonvested January 1 | shares	13,266
Number of Shares, Granted | shares	5,014
Number of Shares, Vested | shares	(3,795)
Number of Shares, Forfeited | shares	(876)
Number of Shares, Nonvested December 31 | shares	13,609
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted Average Grant Date Fair Value, Nonvested January 1 (in dollars per share) | $ / shares	$ 57.19
Weighted Average Grant Date Fair Value, Granted (in dollars per share) | $ / shares	63.85
Weighted Average Grant Date Fair Value, Vested (in dollars per share) | $ / shares	58.13
Weighted Average Grant Date Fair Value, Forfeited (in dollars per share) | $ / shares	58.22
Weighted Average Grant Date Fair Value, Nonvested December 31 (in dollars per share) | $ / shares	$ 59.32
PSUs
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of Shares, Nonvested January 1 | shares	1,744
Number of Shares, Granted | shares	1,008
Number of Shares, Vested | shares	(833)
Number of Shares, Forfeited | shares	(51)
Number of Shares, Nonvested December 31 | shares	1,868
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted Average Grant Date Fair Value, Nonvested January 1 (in dollars per share) | $ / shares	$ 59.24
Weighted Average Grant Date Fair Value, Granted (in dollars per share) | $ / shares	63.62
Weighted Average Grant Date Fair Value, Vested (in dollars per share) | $ / shares	62.71
Weighted Average Grant Date Fair Value, Forfeited (in dollars per share) | $ / shares	60.24
Weighted Average Grant Date Fair Value, Nonvested December 31 (in dollars per share) | $ / shares	$ 60.03

Pension and Other Postretirem87

Pension and Other Postretirement Benefit Plans - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation		$ 20,500	$ 18,400
Percentage of Company's pension investments categorized as Level 3 assets (as percent)		2.00%	2.00%
Employer contributions to defined contribution savings plans		$ 131	$ 126	$ 125
United States
Defined Benefit Plan Disclosure [Line Items]
Expected annual standard deviation in returns of the target portfolio which reflects both the equity allocation and the diversification benefits among the asset classes in which the portfolio invests (as percent)		13.00%
United States | Minimum
Defined Benefit Plan Disclosure [Line Items]
Expected rate of return on plan assets (as percent)		8.00%
United States | Maximum
Defined Benefit Plan Disclosure [Line Items]
Expected rate of return on plan assets (as percent)		8.75%
Forecast | United States | Minimum
Defined Benefit Plan Disclosure [Line Items]
Expected rate of return on plan assets (as percent)	7.70%
Forecast | United States | Maximum
Defined Benefit Plan Disclosure [Line Items]
Expected rate of return on plan assets (as percent)	8.30%
U.S. Equity Securities | United States | Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		35.00%
U.S. Equity Securities | United States | Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		55.00%
International Securities | United States | Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		20.00%
International Securities | United States | Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		35.00%
Fixed Income Investments | United States | Minimum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		20.00%
Fixed Income Investments | United States | Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		35.00%
Cash And Other Investments | United States | Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		5.00%
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Assets no longer restricted to the payment of postretirement benefits		$ 0	992
Fair value of plan assets		1,114	1,019	1,913
Expected contributions to the pension plans and other postretirement benefit plans during next fiscal year		25
Estimated net loss (gain) amounts that will be amortized from AOCI into net pension and postretirement benefit cost during next fiscal year		1
Estimated prior service cost (credit) amounts that will be amortized from AOCI into net pension and postretirement benefit cost during next fiscal year		(84)
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Estimated net loss (gain) amounts that will be amortized from AOCI into net pension and postretirement benefit cost during next fiscal year		314
Estimated prior service cost (credit) amounts that will be amortized from AOCI into net pension and postretirement benefit cost during next fiscal year		(64)
Pension Plan | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		488	435
International | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Assets no longer restricted to the payment of postretirement benefits		0	0
Fair value of plan assets		9,339	$ 7,794	$ 7,204
Expected contributions to the pension plans and other postretirement benefit plans during next fiscal year		$ 150
Expected rate of return on plan assets (as percent)		5.10%	5.60%	5.70%
United States
Defined Benefit Plan Disclosure [Line Items]
Expected rate of return on plan assets (as percent)		8.70%	8.60%	8.50%
United States | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Assets no longer restricted to the payment of postretirement benefits		$ 0	$ 0
Accumulated benefit obligation		11,500	10,500
Fair value of plan assets		10,896	$ 9,766	$ 9,266
Expected contributions to the pension plans and other postretirement benefit plans during next fiscal year		60
Estimated net loss (gain) amounts that will be amortized from AOCI into net pension and postretirement benefit cost during next fiscal year		230
Estimated prior service cost (credit) amounts that will be amortized from AOCI into net pension and postretirement benefit cost during next fiscal year		$ (51)

Pension and Other Postretirem88

Pension and Other Postretirement Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 57	$ 54	$ 80
Interest cost	81	82	110
Expected return on plan assets	(78)	(107)	(143)
Amortization of unrecognized prior service cost	(98)	(106)	(64)
Net loss amortization	1	3	5
Termination benefits	8	4	7
Curtailments	(31)	(18)	(19)
Settlements	0	0	0
Net periodic benefit cost (credit)	(60)	(88)	(24)
United States | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	312	282	307
Interest cost	454	456	434
Expected return on plan assets	(862)	(831)	(819)
Amortization of unrecognized prior service cost	(53)	(55)	(56)
Net loss amortization	180	119	214
Termination benefits	44	23	22
Curtailments	3	5	(12)
Settlements	0	0	1
Net periodic benefit cost (credit)	78	(1)	91
International | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	252	238	251
Interest cost	172	204	206
Expected return on plan assets	(393)	(382)	(379)
Amortization of unrecognized prior service cost	(11)	(11)	(14)
Net loss amortization	98	87	118
Termination benefits	4	4	1
Curtailments	(4)	(1)	(9)
Settlements	5	6	12
Net periodic benefit cost (credit)	$ 123	$ 145	$ 186

Pension and Other Postretirem89

Pension and Other Postretirement Benefit Plans - Obligation and Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Postretirement Benefits
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets January 1	$ 1,019	$ 1,913
Actual return on plan assets	161	138
Company contributions, net	(4)	68
Effects of exchange rate changes	0	0
Benefits paid	(62)	(108)
Settlements	0	0
Assets no longer restricted to the payment of postretirement benefits	0	(992)
Other	0	0
Fair value of plan assets December 31	1,114	1,019	$ 1,913
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation January 1	1,922	1,810
Service cost	57	54	80
Interest cost	81	82	110
Actuarial losses (gains)	(87)	77
Benefits paid	(62)	(108)
Effects of exchange rate changes	3	2
Plan amendments	0	0
Curtailments	0	1
Termination benefits	8	4	7
Settlements	0	0
Other	0	0
Benefit obligation December 31	1,922	1,922	1,810
Funded status December 31	(808)	(903)
Recognized as:
Other assets	0	0
Accrued and other current liabilities	(11)	(11)
Other noncurrent liabilities	(797)	(892)
United States | Pension Plan
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets January 1	9,766	9,266
Actual return on plan assets	1,723	941
Company contributions, net	58	63
Effects of exchange rate changes	0	0
Benefits paid	(651)	(504)
Settlements	0	0
Assets no longer restricted to the payment of postretirement benefits	0	0
Other	0	0
Fair value of plan assets December 31	10,896	9,766	9,266
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation January 1	10,849	9,723
Service cost	312	282	307
Interest cost	454	456	434
Actuarial losses (gains)	881	854
Benefits paid	(651)	(504)
Effects of exchange rate changes	0	0
Plan amendments	0	0
Curtailments	15	15
Termination benefits	44	23	22
Settlements	0	0
Other	0	0
Benefit obligation December 31	11,904	10,849	9,723
Funded status December 31	(1,008)	(1,083)
Recognized as:
Other assets	0	0
Accrued and other current liabilities	(59)	(50)
Other noncurrent liabilities	(949)	(1,033)
International | Pension Plan
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets January 1	7,794	7,204
Actual return on plan assets	677	898
Company contributions, net	226	424
Effects of exchange rate changes	843	(546)
Benefits paid	(198)	(193)
Settlements	(17)	(21)
Assets no longer restricted to the payment of postretirement benefits	0	0
Other	14	28
Fair value of plan assets December 31	9,339	7,794	7,204
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation January 1	8,372	7,733
Service cost	252	238	251
Interest cost	172	204	206
Actuarial losses (gains)	(7)	938
Benefits paid	(198)	(193)
Effects of exchange rate changes	916	(576)
Plan amendments	(22)	0
Curtailments	(3)	(15)
Termination benefits	4	4	1
Settlements	(17)	(21)
Other	14	60
Benefit obligation December 31	9,483	8,372	$ 7,733
Funded status December 31	(144)	(578)
Recognized as:
Other assets	828	451
Accrued and other current liabilities	(17)	(7)
Other noncurrent liabilities	$ (955)	$ (1,022)

Pension and Other Postretirem90

Pension and Other Postretirement Benefit Plans - Accumulated and Projected Benefit Obligation in Excess of Plan Assets (Details) - Pension Plan - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
United States
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Projected benefit obligation	$ 11,904	$ 10,849
Fair value of plan assets	10,896	9,766
Accumulated benefit obligation	676	9,807
Fair value of plan assets	0	9,057
International
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Projected benefit obligation	3,323	5,486
Fair value of plan assets	2,352	4,457
Accumulated benefit obligation	2,120	2,692
Fair value of plan assets	$ 1,346	$ 1,898

Pension and Other Postretirem91

Pension and Other Postretirement Benefit Plans - Fair Values of Pension Plan Assets (Details) - Pension Plan - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 488	$ 435
United States
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10,896	9,766	$ 9,266
Fair Value of Plan Assets Excluding Net Asset Value Investments	5,189	4,542
Investments measured at NAV practical expedient	5,707	5,224
United States | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6	4
United States | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	390	521
United States | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	138	104
United States | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,743	2,521
United States | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	757	475
United States | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	900	660
United States | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	240	239
United States | Other, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15	18
United States | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets Excluding Net Asset Value Investments	3,277	3,148
United States | Quoted Prices In Active Markets for Identical Assets (Level 1) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6	2
United States | Quoted Prices In Active Markets for Identical Assets (Level 1) | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	390	521
United States | Quoted Prices In Active Markets for Identical Assets (Level 1) | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	138	104
United States | Quoted Prices In Active Markets for Identical Assets (Level 1) | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,743	2,521
United States | Quoted Prices In Active Markets for Identical Assets (Level 1) | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Quoted Prices In Active Markets for Identical Assets (Level 1) | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Quoted Prices In Active Markets for Identical Assets (Level 1) | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Quoted Prices In Active Markets for Identical Assets (Level 1) | Other, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets Excluding Net Asset Value Investments	1,897	1,376
United States | Significant Other Observable Inputs (Level 2) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	2
United States | Significant Other Observable Inputs (Level 2) | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Significant Other Observable Inputs (Level 2) | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Significant Other Observable Inputs (Level 2) | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Significant Other Observable Inputs (Level 2) | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	757	475
United States | Significant Other Observable Inputs (Level 2) | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	900	660
United States | Significant Other Observable Inputs (Level 2) | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	240	239
United States | Significant Other Observable Inputs (Level 2) | Other, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets Excluding Net Asset Value Investments	15	18	23
United States | Significant Unobservable Inputs (Level 3) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Significant Unobservable Inputs (Level 3) | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Significant Unobservable Inputs (Level 3) | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Significant Unobservable Inputs (Level 3) | Real estate, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets Excluding Net Asset Value Investments	0	0	0
United States | Significant Unobservable Inputs (Level 3) | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Significant Unobservable Inputs (Level 3) | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Significant Unobservable Inputs (Level 3) | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Significant Unobservable Inputs (Level 3) | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Significant Unobservable Inputs (Level 3) | Insurance contracts, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets Excluding Net Asset Value Investments	0	0	0
United States | Significant Unobservable Inputs (Level 3) | Other, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15	18
Fair Value of Plan Assets Excluding Net Asset Value Investments	15	18	23
International
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9,339	7,794	7,204
Fair Value of Plan Assets Excluding Net Asset Value Investments	8,537	7,006
Investments measured at NAV practical expedient	802	788
International | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	73	53
International | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,888	3,033
International | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	238	172
International | Government and agency obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,344	2,027
International | Corporate obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	334	284
International | Fixed income obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11	9
International | Real estate, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	7
International | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	660	565
International | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	268	237
International | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	119	92
International | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	55	50
International | Insurance contracts, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	537	471
International | Other, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7	6
International | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets Excluding Net Asset Value Investments	1,602	952
International | Quoted Prices In Active Markets for Identical Assets (Level 1) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	54	42
International | Quoted Prices In Active Markets for Identical Assets (Level 1) | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	562	187
International | Quoted Prices In Active Markets for Identical Assets (Level 1) | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	62	24
International | Quoted Prices In Active Markets for Identical Assets (Level 1) | Government and agency obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	249	123
International | Quoted Prices In Active Markets for Identical Assets (Level 1) | Corporate obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	2
International | Quoted Prices In Active Markets for Identical Assets (Level 1) | Fixed income obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7	6
International | Quoted Prices In Active Markets for Identical Assets (Level 1) | Real estate, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Quoted Prices In Active Markets for Identical Assets (Level 1) | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	660	565
International | Quoted Prices In Active Markets for Identical Assets (Level 1) | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	2
International | Quoted Prices In Active Markets for Identical Assets (Level 1) | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	0
International | Quoted Prices In Active Markets for Identical Assets (Level 1) | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Quoted Prices In Active Markets for Identical Assets (Level 1) | Insurance contracts, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Quoted Prices In Active Markets for Identical Assets (Level 1) | Other, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1
International | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets Excluding Net Asset Value Investments	6,462	5,637
International | Significant Other Observable Inputs (Level 2) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	19	11
International | Significant Other Observable Inputs (Level 2) | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,326	2,846
International | Significant Other Observable Inputs (Level 2) | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	176	148
International | Significant Other Observable Inputs (Level 2) | Government and agency obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,095	1,904
International | Significant Other Observable Inputs (Level 2) | Corporate obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	329	282
International | Significant Other Observable Inputs (Level 2) | Fixed income obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4	3
International | Significant Other Observable Inputs (Level 2) | Real estate, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	3
International | Significant Other Observable Inputs (Level 2) | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Significant Other Observable Inputs (Level 2) | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	266	235
International | Significant Other Observable Inputs (Level 2) | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	118	92
International | Significant Other Observable Inputs (Level 2) | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	55	50
International | Significant Other Observable Inputs (Level 2) | Insurance contracts, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	67	59
International | Significant Other Observable Inputs (Level 2) | Other, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6	4
International | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets Excluding Net Asset Value Investments	473	417	400
International | Significant Unobservable Inputs (Level 3) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Significant Unobservable Inputs (Level 3) | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Significant Unobservable Inputs (Level 3) | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Significant Unobservable Inputs (Level 3) | Government and agency obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Significant Unobservable Inputs (Level 3) | Corporate obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Significant Unobservable Inputs (Level 3) | Fixed income obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Significant Unobservable Inputs (Level 3) | Real estate, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	4
Fair Value of Plan Assets Excluding Net Asset Value Investments	2	4	5
International | Significant Unobservable Inputs (Level 3) | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Significant Unobservable Inputs (Level 3) | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Significant Unobservable Inputs (Level 3) | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Significant Unobservable Inputs (Level 3) | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International | Significant Unobservable Inputs (Level 3) | Insurance contracts, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	470	412
Fair Value of Plan Assets Excluding Net Asset Value Investments	470	412	393
International | Significant Unobservable Inputs (Level 3) | Other, Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	1
Fair Value of Plan Assets Excluding Net Asset Value Investments	$ 1	$ 1	$ 2

Pension and Other Postretirem92

Pension and Other Postretirement Benefit Plans - Summary of Changes in Fair Value of Company's Level 3 Pension Plan Assets (Details) - Pension Plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
United States
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance January 1	$ 4,542
Actual return on plan assets:
Balance December 31	5,189	$ 4,542
United States | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance January 1	18	23
Actual return on plan assets:
Relating to assets still held at December 31	(2)	(3)
Relating to assets sold during the year	4	4
Purchases and sales, net	(5)	(6)
Balance December 31	15	18
United States | Significant Unobservable Inputs (Level 3) | Insurance Contracts
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance January 1	0	0
Actual return on plan assets:
Relating to assets still held at December 31	0	0
Relating to assets sold during the year	0	0
Purchases and sales, net	0	0
Balance December 31	0	0
United States | Significant Unobservable Inputs (Level 3) | Real Estate
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance January 1	0	0
Actual return on plan assets:
Relating to assets still held at December 31	0	0
Relating to assets sold during the year	0	0
Purchases and sales, net	0	0
Balance December 31	0	0
United States | Significant Unobservable Inputs (Level 3) | Other
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance January 1	18	23
Actual return on plan assets:
Relating to assets still held at December 31	(2)	(3)
Relating to assets sold during the year	4	4
Purchases and sales, net	(5)	(6)
Balance December 31	15	18
International
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance January 1	7,006
Actual return on plan assets:
Balance December 31	8,537	7,006
International | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance January 1	417	400
Actual return on plan assets:
Relating to assets still held at December 31	52	(8)
Purchases and sales, net	3	(1)
Transfers into Level 3	1	26
Balance December 31	473	417
International | Significant Unobservable Inputs (Level 3) | Insurance Contracts
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance January 1	412	393
Actual return on plan assets:
Relating to assets still held at December 31	52	(9)
Purchases and sales, net	5	2
Transfers into Level 3	1	26
Balance December 31	470	412
International | Significant Unobservable Inputs (Level 3) | Real Estate
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance January 1	4	5
Actual return on plan assets:
Relating to assets still held at December 31	0	1
Purchases and sales, net	(2)	(2)
Transfers into Level 3	0	0
Balance December 31	2	4
International | Significant Unobservable Inputs (Level 3) | Other
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance January 1	1	2
Actual return on plan assets:
Relating to assets still held at December 31	0	0
Purchases and sales, net	0	(1)
Transfers into Level 3	0	0
Balance December 31	$ 1	$ 1

Pension and Other Postretirem93

Pension and Other Postretirement Benefit Plans - Fair Values of Other Postretirement Benefit Plan Assets (Details) - Other Postretirement Benefits - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Net assets in fair value hierarchy	$ 582	$ 540
Investments measured at NAV practical expedient	532	479
Plan assets at fair value	1,114	1,019	$ 1,913
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	97	125
Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	37	48
Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	13	10
Government and agency obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1	1
Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	256	231
Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	71	43
Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	84	60
Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	23	22
Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Net assets in fair value hierarchy	404	415
Quoted Prices In Active Markets for Identical Assets (Level 1) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	97	125
Quoted Prices In Active Markets for Identical Assets (Level 1) | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	37	48
Quoted Prices In Active Markets for Identical Assets (Level 1) | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	13	10
Quoted Prices In Active Markets for Identical Assets (Level 1) | Government and agency obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1	1
Quoted Prices In Active Markets for Identical Assets (Level 1) | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	256	231
Quoted Prices In Active Markets for Identical Assets (Level 1) | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Quoted Prices In Active Markets for Identical Assets (Level 1) | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Quoted Prices In Active Markets for Identical Assets (Level 1) | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Net assets in fair value hierarchy	178	125
Significant Other Observable Inputs (Level 2) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Significant Other Observable Inputs (Level 2) | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Significant Other Observable Inputs (Level 2) | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Significant Other Observable Inputs (Level 2) | Government and agency obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Significant Other Observable Inputs (Level 2) | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Significant Other Observable Inputs (Level 2) | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	71	43
Significant Other Observable Inputs (Level 2) | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	84	60
Significant Other Observable Inputs (Level 2) | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	23	22
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Net assets in fair value hierarchy	0	0
Significant Unobservable Inputs (Level 3) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Significant Unobservable Inputs (Level 3) | Developed markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Significant Unobservable Inputs (Level 3) | Emerging markets equities, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Significant Unobservable Inputs (Level 3) | Government and agency obligations, Investment funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Significant Unobservable Inputs (Level 3) | Developed markets, Equity securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Significant Unobservable Inputs (Level 3) | Government and agency obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Significant Unobservable Inputs (Level 3) | Corporate obligations, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	0	0
Significant Unobservable Inputs (Level 3) | Mortgage and asset backed-securities, Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	$ 0	$ 0

Pension and Other Postretirem94

Pension and Other Postretirement Benefit Plans - Summary of Expected Benefit Payments (Details) $ in Millions	Dec. 31, 2017USD ($)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
2,018	$ 96
2,019	101
2,020	104
2,021	109
2,022	113
2023 — 2027	623
United States | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
2,018	609
2,019	638
2,020	650
2,021	663
2,022	683
2023 — 2027	3,760
International | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
2,018	222
2,019	205
2,020	217
2,021	225
2,022	243
2023 — 2027	$ 1,326

Pension and Other Postretirem95

Pension and Other Postretirement Benefit Plans - Components of Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net loss amortization included in benefit cost	$ 170	$ (45)	$ 209
Prior service (cost) credit arising during the period	(31)	(19)	511
Total	139	(64)	720
Net loss amortization included in benefit cost	1	3	5
Prior service (credit) cost amortization included in benefit cost	(98)	(106)	(64)
Total	(97)	(103)	(59)
United States | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Net loss amortization included in benefit cost	(19)	(743)	73
Prior service (cost) credit arising during the period	(13)	(10)	(13)
Total	(32)	(753)	60
Net loss amortization included in benefit cost	180	119	214
Prior service (credit) cost amortization included in benefit cost	(53)	(55)	(56)
Total	127	64	158
International | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Net loss amortization included in benefit cost	309	(380)	(66)
Prior service (cost) credit arising during the period	22	(2)	(4)
Total	331	(382)	(70)
Net loss amortization included in benefit cost	98	87	118
Prior service (credit) cost amortization included in benefit cost	(11)	(11)	(14)
Total	$ 87	$ 76	$ 104

Pension and Other Postretirem96

Pension and Other Postretirement Benefit Plans - Summary of Weighted Average Assumptions Used in Determining Pension Plan and U.S. Pension and Other Postretirement Benefit Plan Information (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
United States
Net periodic benefit cost
Discount rate	4.30%	4.70%	4.20%
Expected rate of return on plan assets	8.70%	8.60%	8.50%
Salary growth rate	4.30%	4.30%	4.40%
Benefit obligation
Discount rate	3.70%	4.30%	4.80%
Salary growth rate	4.30%	4.30%	4.30%
International | Pension Plan
Net periodic benefit cost
Discount rate	2.20%	2.80%	2.70%
Expected rate of return on plan assets	5.10%	5.60%	5.70%
Salary growth rate	2.90%	2.90%	2.90%
Benefit obligation
Discount rate	2.10%	2.20%	2.80%
Salary growth rate	2.90%	2.90%	2.90%

Pension and Other Postretirem97

Pension and Other Postretirement Benefit Plans - Summary of Health Care Cost Trend Rate Assumptions for Other Postretirement Benefit Plans (Details) - Other Postretirement Benefits	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for next year	7.20%	7.40%
Rate to which the cost trend rate is assumed to decline	4.50%	4.50%

Pension and Other Postretirem98

Pension and Other Postretirement Benefit Plans - One Percentage Point Change in Health Care Cost Trend Rate (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Retirement Benefits [Abstract]
Effect on total service and interest cost components, Increase	$ 13
Effect on benefit obligation, Increase	125
Effect on total service and interest cost components, Decrease	(11)
Effect on benefit obligation, Decrease	$ (104)

Other (Income) Expense, Net - N

Other (Income) Expense, Net - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	Feb. 28, 2017	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Component of Other Income / Expense of Nonoperating [Line Items]
Foreign exchange losses related to Venezuela				$ 0	$ 0	$ 876
Loss on extinguishment of debt				191
Marketable Securities, Realized Gain (Loss)				291
Litigation settlement	$ (80)			0	(625)	0
Net charge related to the settlement of Vioxx shareholder class action litigation				0	0	680
Contribution expense						78
Interest paid				723	686	653
AstraZeneca LP
Component of Other Income / Expense of Nonoperating [Line Items]
Other income				$ 232	98	182
CGRP receptor antagonists
Component of Other Income / Expense of Nonoperating [Line Items]
Gain (loss) on sale of clinical development programs					100	250
ophthalmic products
Component of Other Income / Expense of Nonoperating [Line Items]
Gain on disposition of business						147
Patent litigation
Component of Other Income / Expense of Nonoperating [Line Items]
Litigation settlement					$ 117
Vioxx Securities Lawsuits | Vioxx
Component of Other Income / Expense of Nonoperating [Line Items]
Net charge related to the settlement of Vioxx shareholder class action litigation						$ 680
Venezuela
Component of Other Income / Expense of Nonoperating [Line Items]
Foreign exchange losses related to Venezuela		$ 138	$ 876

Other (Income) Expense, Net (De

Other (Income) Expense, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Income and Expenses [Abstract]
Interest income	$ (385)	$ (328)	$ (289)
Interest expense	754	693	672
Exchange (gains) losses	(11)	174	1,277
Equity income from affiliates	(42)	(86)	(205)
Other, net	(304)	267	72
Other (income) expense, net	$ 12	$ 720	$ 1,527

Taxes on Income - Narrative (De

Taxes on Income - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax [Line Items]
Provisional charge for one-time transition tax related to Tax Cuts and Jobs Act of 2017	$ 5,347	$ 0	$ 0
Provisional liability for one-time transition tax related to Tax Cuts and Job Act of 2017	5,100
Deferred Tax Liabilities, Undistributed Foreign Earnings	33	$ 2,044
Provisional current liability for one-time transition tax related to Tax Cuts and Jobs Act of 2017	545
Provisional noncurrent liability for one-time transition tax related to Tax Cuts and Jobs Act of 2017	$ 4,500
U.S. statutory rate applied to income before taxes (as percent)	35.00%	35.00%	35.00%
Remeasurement of deferred taxes related to Tax Cuts and Jobs Act of 2017 provisional benefit	$ 779
Deferred tax assets on NOL carryforwards relating to foreign jurisdictions	630
Deferred tax assets relating to various U.S. tax credit carryforwards and NOL carryforwards	24
Income taxes paid	4,900	$ 1,800	$ 1,800
Tax benefits relating to stock option exercises	73	147	109
Unrecognized tax benefits	1,723	3,494	3,448	$ 3,534
Favorable net impact to income tax provision if unrecognized tax benefits were recognized	1,600
Reasonably possible amount that liability for unrecognized tax benefits could decline up to in next 12 months (up to)	165
Interest and penalties associated with uncertain tax positions, expense (benefit)	183	134	102
Liabilities for accrued interest and penalties	341	886
Unrecognized tax benefits from adjustments related to examination	1,388	92	184
Proceeds from refunds			715
Income tax expense (benefit)	(4,103)	$ (718)	(942)
Foreign Jurisdiction
Income Tax [Line Items]
Valuation allowance on foreign NOL carryforwards	900
Internal Revenue Service (IRS)
Income Tax [Line Items]
Income tax expense (benefit)			$ 410
Internal Revenue Service (IRS)
Income Tax [Line Items]
Income taxes paid	2,800
Unrecognized tax benefits from adjustments related to examination	234
2017 Tax Cuts and Jobs Act (TCJA) [Member]
Income Tax [Line Items]
Deferred Tax Liabilities, Undistributed Foreign Earnings	$ 2,000

Taxes on Income - Reconciliatio

Taxes on Income - Reconciliation Between Effective Tax Rate and US Statutory Rate (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amount
U.S. statutory rate applied to income before taxes	$ 2,282	$ 1,631	$ 1,890
Differential arising from:
Provisional impact of the TCJA	2,625	0	0
Impact of purchase accounting adjustments, including amortization	713	623	797
Valuation allowances	632	(5)	39
Restructuring	142	145	167
State taxes	77	173	159
U.S. health care reform legislation	74	68	66
Foreign currency devaluation related to Venezuela	0	0	321
Foreign earnings	(1,725)	(1,646)	(2,144)
Tax settlements	(356)	0	(417)
Unremitted foreign earnings	0	(30)	260
Other	(361)	(241)	(196)
Taxes on income	$ 4,103	$ 718	$ 942
Tax Rate
U.S. statutory rate applied to income before taxes	35.00%	35.00%	35.00%
Differential arising from:
Provisional impact of the TCJA	40.30%	0.00%	0.00%
Impact of purchase accounting adjustments, including amortization	10.90%	13.40%	14.80%
Valuation allowances	9.70%	(0.10%)	0.70%
Restructuring	2.20%	3.10%	3.10%
State taxes	1.20%	3.70%	2.90%
U.S. health care reform legislation	1.10%	1.40%	1.20%
Foreign currency devaluation related to Venezuela	0.00%	0.00%	5.90%
Foreign earnings	(26.50%)	(35.30%)	(39.70%)
Tax settlements	(5.50%)	0.00%	(7.70%)
Unremitted foreign earnings	0.00%	(0.60%)	4.80%
Other	(5.50%)	(5.20%)	(3.60%)
Total, Tax Rate	62.90%	15.40%	17.40%

Taxes on Income - Income Before

Taxes on Income - Income Before Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Domestic	$ 3,483	$ 518	$ 2,247
Foreign	3,038	4,141	3,154
Income Before Taxes	$ 6,521	$ 4,659	$ 5,401

Taxes on Income - Taxes on Inco

Taxes on Income - Taxes on Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current provision
Federal	$ 5,585	$ 1,166	$ 732
Foreign	1,229	916	844
State	(90)	157	130
Total current provision	6,724	2,239	1,706
Deferred provision
Federal	(2,958)	(1,255)	(552)
Foreign	75	(225)	(163)
State	262	(41)	(49)
Total deferred provision	(2,621)	(1,521)	(764)
Taxes on income	$ 4,103	$ 718	$ 942

Taxes on Income - Deferred Inco

Taxes on Income - Deferred Income Taxes (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Income Tax [Line Items]
Intangibles, Assets	$ 307	$ 86
Inventory related, Assets	29	30
Accelerated depreciation, Assets	28	28
Pensions and other postretirement benefits, Assets	498	727
Compensation related, Assets	314	438
Unrecognized tax benefits, Assets	156	383
Net operating losses and other tax credit carryforwards, Assets	654	437
Other, Assets	1,088	1,248
Subtotal, Assets	3,074	3,377
Valuation allowance, Assets	(900)	(268)
Deferred Tax Assets	2,174	3,109
Intangibles, Liabilities	2,435	3,854
Inventory related, Liabilities	499	660
Accelerated depreciation, Liabilities	642	927
Unremitted foreign earnings, Liabilities	33	2,044
Pensions and other postretirement benefits, Liabilities	192	109
Other, Liabilities	19	46
Subtotal, Liabilities	3,820	7,640
Deferred income taxes, Liabilities	1,646	4,531
Deferred income taxes	2,219	5,077
Other assets
Income Tax [Line Items]
Deferred Tax Assets	$ 573	$ 546

Taxes on Income - Unrecognized

Taxes on Income - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Balance January 1	$ 3,494	$ 3,448	$ 3,534
Additions related to current year positions	146	196	198
Additions related to prior year positions	520	75	53
Reductions for tax positions of prior years	(1,038)	(90)	(59)
Settlements	(1,388)	(92)	(184)
Lapse of statute of limitations	(11)	(43)	(94)
Balance December 31	$ 1,723	$ 3,494	$ 3,448

Earnings Per Share - Narrative

Earnings Per Share - Narrative (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Common shares issuable under share-based compensation plans excluded from diluted earnings per common share because the effect would have been antidilutive	5	13	9

Earnings Per Share - Calculatio

Earnings Per Share - Calculations of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net Income Attributable to Merck & Co., Inc.	$ 2,394	$ 3,920	$ 4,442
Average common shares outstanding, in shares	2,730	2,766	2,816
Common shares issuable, in shares	18	21	25
Average common shares outstanding assuming dilution, in shares	2,748	2,787	2,841
Basic earnings per common share attributable to Merck & Co., Inc. common shareholders, in dollars per share	$ 0.88	$ 1.42	$ 1.58
Earnings per common share assuming dilution attributable to Merck & Co., Inc. common shareholders, in dollars per share	$ 0.87	$ 1.41	$ 1.56

Other Comprehensive Income (109

Other Comprehensive Income (Loss) - Changes in AOCI by Component (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ 40,308	$ 44,767	$ 48,791
Accumulated Other Comprehensive Income (Loss), ending balance	(4,910)	(5,226)
Ending Balance	34,569	40,308	44,767
Derivatives
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	338	404	530
Other comprehensive income (loss) before reclassification adjustments, pretax	(561)	210	526
Tax	207	(72)	(177)
Other comprehensive income (loss) before reclassification adjustments, net of taxes	(354)	138	349
Reclassification adjustments, pretax	(141)	(314)	(731)
Tax	49	110	256
Reclassification adjustments, net of taxes	(92)	(204)	(475)
Other comprehensive income (loss), net of taxes	(446)	(66)	(126)
Ending Balance	(108)	338	404
Investments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(3)	41	111
Other comprehensive income (loss) before reclassification adjustments, pretax	212	(38)	(9)
Tax	(35)	16	(13)
Other comprehensive income (loss) before reclassification adjustments, net of taxes	177	(22)	(22)
Reclassification adjustments, pretax	(291)	(31)	(73)
Tax	56	9	25
Reclassification adjustments, net of taxes	(235)	(22)	(48)
Other comprehensive income (loss), net of taxes	(58)	(44)	(70)
Ending Balance	(61)	(3)	41
Employee Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(3,206)	(2,407)	(2,986)
Other comprehensive income (loss) before reclassification adjustments, pretax	438	(1,199)	710
Tax	(106)	363	(272)
Other comprehensive income (loss) before reclassification adjustments, net of taxes	332	(836)	438
Reclassification adjustments, pretax	117	37	203
Tax	(30)	0	(62)
Reclassification adjustments, net of taxes	87	37	141
Other comprehensive income (loss), net of taxes	419	(799)	579
Ending Balance	(2,787)	(3,206)	(2,407)
Pension Plan Net Loss
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Pension and other postretirement benefit plans, net loss and prior service credit included in AOCI	3,500	3,900
Other Postretirement Benefit Plan Net Loss
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Pension and other postretirement benefit plans, net loss and prior service credit included in AOCI	(16)	115
Pension Plan Prior Service Credit
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Pension and other postretirement benefit plans, net loss and prior service credit included in AOCI	326	361
Other Postretirement Benefit Plan Prior Service Credit
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Pension and other postretirement benefit plans, net loss and prior service credit included in AOCI	383	466
Cumulative Translation Adjustment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(2,355)	(2,186)	(1,978)
Other comprehensive income (loss) before reclassification adjustments, pretax	235	(150)	(158)
Tax	166	(19)	(28)
Other comprehensive income (loss) before reclassification adjustments, net of taxes	401	(169)	(186)
Reclassification adjustments, pretax	0	0	(22)
Tax	0	0	0
Reclassification adjustments, net of taxes	0	0	(22)
Other comprehensive income (loss), net of taxes	401	(169)	(208)
Ending Balance	(1,954)	(2,355)	(2,186)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(5,226)	(4,148)	(4,323)
Other comprehensive income (loss) before reclassification adjustments, pretax	324	(1,177)	1,069
Tax	232	288	(490)
Other comprehensive income (loss) before reclassification adjustments, net of taxes	556	(889)	579
Reclassification adjustments, pretax	(315)	(308)	(623)
Tax	75	119	219
Reclassification adjustments, net of taxes	(240)	(189)	(404)
Other comprehensive income (loss), net of taxes	316	(1,078)	175
Ending Balance	$ (4,910)	$ (5,226)	$ (4,148)

Segment Reporting - Narrative (

Segment Reporting - Narrative (Details)	12 Months Ended
	Dec. 31, 2017segment
Segment Reporting [Abstract]
Number of operating segments	4

Segment Reporting - Sales of Co

Segment Reporting - Sales of Company's Products (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Sales	$ 40,122	$ 39,807	$ 39,498
Proceeds from sale of intangible assets	85	170
Operating Segments
Segment Reporting Information [Line Items]
Sales	39,662	39,013	38,449
Operating Segments | Pharmaceutical segment
Segment Reporting Information [Line Items]
Sales	35,390	35,151	34,782
Operating Segments | Pharmaceutical segment | Zetia
Segment Reporting Information [Line Items]
Sales	1,344	2,560	2,526
Operating Segments | Pharmaceutical segment | Vytorin
Segment Reporting Information [Line Items]
Sales	751	1,141	1,251
Operating Segments | Pharmaceutical segment | Atozet
Segment Reporting Information [Line Items]
Sales	225	146	36
Operating Segments | Pharmaceutical segment | Adempas
Segment Reporting Information [Line Items]
Sales	300	169	30
Operating Segments | Pharmaceutical segment | Januvia
Segment Reporting Information [Line Items]
Sales	3,737	3,908	3,863
Operating Segments | Pharmaceutical segment | Janumet
Segment Reporting Information [Line Items]
Sales	2,158	2,201	2,151
Operating Segments | Pharmaceutical segment | NuvaRing
Segment Reporting Information [Line Items]
Sales	761	777	732
Operating Segments | Pharmaceutical segment | Implanon/Nexplanon
Segment Reporting Information [Line Items]
Sales	686	606	588
Operating Segments | Pharmaceutical segment | Follistim AQ
Segment Reporting Information [Line Items]
Sales	298	355	383
Operating Segments | Pharmaceutical segment | Zepatier
Segment Reporting Information [Line Items]
Sales	1,660	555	0
Operating Segments | Pharmaceutical segment | Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	1,204	1,387	1,511
Operating Segments | Pharmaceutical segment | Bridion
Segment Reporting Information [Line Items]
Sales	704	482	353
Operating Segments | Pharmaceutical segment | Noxafil
Segment Reporting Information [Line Items]
Sales	636	595	487
Operating Segments | Pharmaceutical segment | Invanz
Segment Reporting Information [Line Items]
Sales	602	561	569
Operating Segments | Pharmaceutical segment | Cancidas
Segment Reporting Information [Line Items]
Sales	422	558	573
Operating Segments | Pharmaceutical segment | Cubicin
Segment Reporting Information [Line Items]
Sales	382	1,087	1,127
Operating Segments | Pharmaceutical segment | Primaxin
Segment Reporting Information [Line Items]
Sales	280	297	313
Operating Segments | Pharmaceutical segment | Remicade
Segment Reporting Information [Line Items]
Sales	837	1,268	1,794
Operating Segments | Pharmaceutical segment | Simponi
Segment Reporting Information [Line Items]
Sales	819	766	690
Operating Segments | Pharmaceutical segment | Keytruda
Segment Reporting Information [Line Items]
Sales	3,809	1,402	566
Operating Segments | Pharmaceutical segment | Emend
Segment Reporting Information [Line Items]
Sales	556	549	535
Operating Segments | Pharmaceutical segment | Temodar
Segment Reporting Information [Line Items]
Sales	271	283	312
Operating Segments | Pharmaceutical segment | Singulair
Segment Reporting Information [Line Items]
Sales	732	915	931
Operating Segments | Pharmaceutical segment | Nasonex
Segment Reporting Information [Line Items]
Sales	387	537	858
Operating Segments | Pharmaceutical segment | Dulera
Segment Reporting Information [Line Items]
Sales	287	436	536
Operating Segments | Pharmaceutical segment | Cozaar/Hyzaar
Segment Reporting Information [Line Items]
Sales	484	511	667
Operating Segments | Pharmaceutical segment | Arcoxia
Segment Reporting Information [Line Items]
Sales	363	450	471
Operating Segments | Pharmaceutical segment | Fosamax
Segment Reporting Information [Line Items]
Sales	241	284	359
Operating Segments | Pharmaceutical segment | Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	2,308	2,173	1,908
Operating Segments | Pharmaceutical segment | ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	1,676	1,640	1,505
Operating Segments | Pharmaceutical segment | Pneumovax 23
Segment Reporting Information [Line Items]
Sales	821	641	542
Operating Segments | Pharmaceutical segment | RotaTeq
Segment Reporting Information [Line Items]
Sales	686	652	610
Operating Segments | Pharmaceutical segment | Zostavax
Segment Reporting Information [Line Items]
Sales	668	685	749
Operating Segments | Pharmaceutical segment | Other pharmaceutical
Segment Reporting Information [Line Items]
Sales	4,295	4,574	5,256
Operating Segments | Other segments
Segment Reporting Information [Line Items]
Sales	4,272	3,862	3,667
Other
Segment Reporting Information [Line Items]
Sales	460	794	1,049
United States
Segment Reporting Information [Line Items]
Sales	17,424	18,478	17,519
United States | Operating Segments
Segment Reporting Information [Line Items]
Sales	17,340	18,447	17,451
United States | Operating Segments | Pharmaceutical segment
Segment Reporting Information [Line Items]
Sales	15,854	17,073	16,238
United States | Operating Segments | Pharmaceutical segment | Zetia
Segment Reporting Information [Line Items]
Sales	352	1,588	1,612
United States | Operating Segments | Pharmaceutical segment | Vytorin
Segment Reporting Information [Line Items]
Sales	124	473	479
United States | Operating Segments | Pharmaceutical segment | Atozet
Segment Reporting Information [Line Items]
Sales	0	1	2
United States | Operating Segments | Pharmaceutical segment | Adempas
Segment Reporting Information [Line Items]
Sales	0	0	0
United States | Operating Segments | Pharmaceutical segment | Januvia
Segment Reporting Information [Line Items]
Sales	2,153	2,286	2,263
United States | Operating Segments | Pharmaceutical segment | Janumet
Segment Reporting Information [Line Items]
Sales	863	984	976
United States | Operating Segments | Pharmaceutical segment | NuvaRing
Segment Reporting Information [Line Items]
Sales	564	576	515
United States | Operating Segments | Pharmaceutical segment | Implanon/Nexplanon
Segment Reporting Information [Line Items]
Sales	496	420	367
United States | Operating Segments | Pharmaceutical segment | Follistim AQ
Segment Reporting Information [Line Items]
Sales	123	157	160
United States | Operating Segments | Pharmaceutical segment | Zepatier
Segment Reporting Information [Line Items]
Sales	771	488	0
United States | Operating Segments | Pharmaceutical segment | Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	565	721	797
United States | Operating Segments | Pharmaceutical segment | Bridion
Segment Reporting Information [Line Items]
Sales	239	77	0
United States | Operating Segments | Pharmaceutical segment | Noxafil
Segment Reporting Information [Line Items]
Sales	309	284	212
United States | Operating Segments | Pharmaceutical segment | Invanz
Segment Reporting Information [Line Items]
Sales	361	329	322
United States | Operating Segments | Pharmaceutical segment | Cancidas
Segment Reporting Information [Line Items]
Sales	20	25	24
United States | Operating Segments | Pharmaceutical segment | Cubicin
Segment Reporting Information [Line Items]
Sales	189	906	1,030
United States | Operating Segments | Pharmaceutical segment | Primaxin
Segment Reporting Information [Line Items]
Sales	10	4	8
United States | Operating Segments | Pharmaceutical segment | Remicade
Segment Reporting Information [Line Items]
Sales	0	0	0
United States | Operating Segments | Pharmaceutical segment | Simponi
Segment Reporting Information [Line Items]
Sales	0	0	0
United States | Operating Segments | Pharmaceutical segment | Keytruda
Segment Reporting Information [Line Items]
Sales	2,309	792	393
United States | Operating Segments | Pharmaceutical segment | Emend
Segment Reporting Information [Line Items]
Sales	342	356	326
United States | Operating Segments | Pharmaceutical segment | Temodar
Segment Reporting Information [Line Items]
Sales	16	15	7
United States | Operating Segments | Pharmaceutical segment | Singulair
Segment Reporting Information [Line Items]
Sales	40	40	39
United States | Operating Segments | Pharmaceutical segment | Nasonex
Segment Reporting Information [Line Items]
Sales	54	184	449
United States | Operating Segments | Pharmaceutical segment | Dulera
Segment Reporting Information [Line Items]
Sales	261	412	515
United States | Operating Segments | Pharmaceutical segment | Cozaar/Hyzaar
Segment Reporting Information [Line Items]
Sales	18	16	30
United States | Operating Segments | Pharmaceutical segment | Arcoxia
Segment Reporting Information [Line Items]
Sales	0	0	0
United States | Operating Segments | Pharmaceutical segment | Fosamax
Segment Reporting Information [Line Items]
Sales	6	5	12
United States | Operating Segments | Pharmaceutical segment | Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	1,565	1,780	1,520
United States | Operating Segments | Pharmaceutical segment | ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	1,374	1,362	1,290
United States | Operating Segments | Pharmaceutical segment | Pneumovax 23
Segment Reporting Information [Line Items]
Sales	581	447	378
United States | Operating Segments | Pharmaceutical segment | RotaTeq
Segment Reporting Information [Line Items]
Sales	481	482	447
United States | Operating Segments | Pharmaceutical segment | Zostavax
Segment Reporting Information [Line Items]
Sales	422	518	592
United States | Operating Segments | Pharmaceutical segment | Other pharmaceutical
Segment Reporting Information [Line Items]
Sales	1,246	1,345	1,473
United States | Operating Segments | Other segments
Segment Reporting Information [Line Items]
Sales	1,486	1,374	1,213
United States | Other
Segment Reporting Information [Line Items]
Sales	84	31	68
Int’l
Segment Reporting Information [Line Items]
Sales	22,698	21,329	21,979
Int’l | Operating Segments
Segment Reporting Information [Line Items]
Sales	22,321	20,566	20,998
Int’l | Operating Segments | Pharmaceutical segment
Segment Reporting Information [Line Items]
Sales	19,536	18,077	18,544
Int’l | Operating Segments | Pharmaceutical segment | Zetia
Segment Reporting Information [Line Items]
Sales	992	972	914
Int’l | Operating Segments | Pharmaceutical segment | Vytorin
Segment Reporting Information [Line Items]
Sales	627	668	771
Int’l | Operating Segments | Pharmaceutical segment | Atozet
Segment Reporting Information [Line Items]
Sales	225	146	34
Int’l | Operating Segments | Pharmaceutical segment | Adempas
Segment Reporting Information [Line Items]
Sales	300	169	30
Int’l | Operating Segments | Pharmaceutical segment | Januvia
Segment Reporting Information [Line Items]
Sales	1,584	1,622	1,601
Int’l | Operating Segments | Pharmaceutical segment | Janumet
Segment Reporting Information [Line Items]
Sales	1,296	1,217	1,175
Int’l | Operating Segments | Pharmaceutical segment | NuvaRing
Segment Reporting Information [Line Items]
Sales	197	202	216
Int’l | Operating Segments | Pharmaceutical segment | Implanon/Nexplanon
Segment Reporting Information [Line Items]
Sales	191	186	221
Int’l | Operating Segments | Pharmaceutical segment | Follistim AQ
Segment Reporting Information [Line Items]
Sales	174	197	223
Int’l | Operating Segments | Pharmaceutical segment | Zepatier
Segment Reporting Information [Line Items]
Sales	888	67	0
Int’l | Operating Segments | Pharmaceutical segment | Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	639	666	714
Int’l | Operating Segments | Pharmaceutical segment | Bridion
Segment Reporting Information [Line Items]
Sales	465	405	353
Int’l | Operating Segments | Pharmaceutical segment | Noxafil
Segment Reporting Information [Line Items]
Sales	327	312	275
Int’l | Operating Segments | Pharmaceutical segment | Invanz
Segment Reporting Information [Line Items]
Sales	241	233	247
Int’l | Operating Segments | Pharmaceutical segment | Cancidas
Segment Reporting Information [Line Items]
Sales	402	533	548
Int’l | Operating Segments | Pharmaceutical segment | Cubicin
Segment Reporting Information [Line Items]
Sales	193	181	97
Int’l | Operating Segments | Pharmaceutical segment | Primaxin
Segment Reporting Information [Line Items]
Sales	270	293	305
Int’l | Operating Segments | Pharmaceutical segment | Remicade
Segment Reporting Information [Line Items]
Sales	837	1,268	1,794
Int’l | Operating Segments | Pharmaceutical segment | Simponi
Segment Reporting Information [Line Items]
Sales	819	766	690
Int’l | Operating Segments | Pharmaceutical segment | Keytruda
Segment Reporting Information [Line Items]
Sales	1,500	610	173
Int’l | Operating Segments | Pharmaceutical segment | Emend
Segment Reporting Information [Line Items]
Sales	213	193	209
Int’l | Operating Segments | Pharmaceutical segment | Temodar
Segment Reporting Information [Line Items]
Sales	256	268	306
Int’l | Operating Segments | Pharmaceutical segment | Singulair
Segment Reporting Information [Line Items]
Sales	692	874	892
Int’l | Operating Segments | Pharmaceutical segment | Nasonex
Segment Reporting Information [Line Items]
Sales	333	352	409
Int’l | Operating Segments | Pharmaceutical segment | Dulera
Segment Reporting Information [Line Items]
Sales	26	24	21
Int’l | Operating Segments | Pharmaceutical segment | Cozaar/Hyzaar
Segment Reporting Information [Line Items]
Sales	466	494	637
Int’l | Operating Segments | Pharmaceutical segment | Arcoxia
Segment Reporting Information [Line Items]
Sales	363	450	471
Int’l | Operating Segments | Pharmaceutical segment | Fosamax
Segment Reporting Information [Line Items]
Sales	235	279	347
Int’l | Operating Segments | Pharmaceutical segment | Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	743	393	388
Int’l | Operating Segments | Pharmaceutical segment | ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	303	279	214
Int’l | Operating Segments | Pharmaceutical segment | Pneumovax 23
Segment Reporting Information [Line Items]
Sales	240	193	164
Int’l | Operating Segments | Pharmaceutical segment | RotaTeq
Segment Reporting Information [Line Items]
Sales	204	169	163
Int’l | Operating Segments | Pharmaceutical segment | Zostavax
Segment Reporting Information [Line Items]
Sales	246	168	157
Int’l | Operating Segments | Pharmaceutical segment | Other pharmaceutical
Segment Reporting Information [Line Items]
Sales	3,049	3,228	3,785
Int’l | Operating Segments | Other segments
Segment Reporting Information [Line Items]
Sales	2,785	2,489	2,454
Int’l | Other
Segment Reporting Information [Line Items]
Sales	$ 377	$ 763	$ 981

Segment Reporting - Consolidate

Segment Reporting - Consolidated Revenues by Geographic Area (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales	$ 40,122	$ 39,807	$ 39,498
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales	17,424	18,478	17,519
Europe, Middle East and Africa
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales	11,478	10,953	10,677
Asia Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales	4,337	3,918	3,825
Japan
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales	3,122	2,846	2,673
Latin America
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales	2,339	2,155	2,825
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales	$ 1,422	$ 1,457	$ 1,979

Segment Reporting - Reconciliat

Segment Reporting - Reconciliation of Segment Profits to Income Before Taxes (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Feb. 28, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Interest income		$ 385	$ 328	$ 289
Interest expense		(754)	(693)	(672)
Equity income from affiliates		42	86	205
Depreciation and amortization		(4,637)	(5,441)	(6,375)
Research and development		(10,208)	(10,124)	(6,704)
Restructuring costs		(776)	(651)	(619)
Loss on extinguishment of debt		(191)
Charge related to the settlement of worldwide Keytruda patent litigation	$ (80)	0	(625)	0
Foreign currency devaluation related to Venezuela		0	0	(876)
Net charge related to the settlement of Vioxx shareholder class action litigation		0	0	680
Income Before Taxes		6,521	4,659	5,401
Total segment profits
Segment Reporting Information [Line Items]
Equity income from affiliates		(7)	105	70
Depreciation and amortization		(212)	(183)	(100)
Income Before Taxes		24,420	23,687	23,231
Total segment profits | Pharmaceutical segment
Segment Reporting Information [Line Items]
Equity income from affiliates		(7)	105	70
Depreciation and amortization		(125)	(160)	(82)
Income Before Taxes		22,586	22,180	21,658
Total segment profits | Other segments
Segment Reporting Information [Line Items]
Equity income from affiliates		0	0	0
Depreciation and amortization		(87)	(23)	(18)
Income Before Taxes		1,834	1,507	1,573
Other profits
Segment Reporting Information [Line Items]
Income Before Taxes		26	481	810
Unallocated
Segment Reporting Information [Line Items]
Interest income		385	328	289
Interest expense		(754)	(693)	(672)
Equity income from affiliates		49	(19)	135
Depreciation and amortization		(1,378)	(1,585)	(1,573)
Research and development		(9,355)	(9,084)	(5,871)
Amortization of purchase accounting adjustments		(3,056)	(3,692)	(4,816)
Restructuring costs		(776)	(651)	(619)
Loss on extinguishment of debt		(191)	0	0
Gain on sale of certain migraine clinical development programs		0	100	250
Charge related to the settlement of worldwide Keytruda patent litigation		0	(625)	0
Gain on divestiture of certain ophthalmic products		0	0	147
Foreign currency devaluation related to Venezuela		0	0	(876)
Net charge related to the settlement of Vioxx shareholder class action litigation		0	0	(680)
Other unallocated, net		$ (2,849)	$ (3,588)	$ (4,354)

Segment Reporting - Schedule of

Segment Reporting - Schedule of Equity Income from Affiliates and Depreciation and Amortization Included in Segment Profits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Equity income from affiliates	$ 42	$ 86	$ 205
Depreciation and amortization	(4,637)	(5,441)	(6,375)
Operating Segments
Segment Reporting Information [Line Items]
Equity income from affiliates	(7)	105	70
Depreciation and amortization	(212)	(183)	(100)
Operating Segments | Pharmaceutical
Segment Reporting Information [Line Items]
Equity income from affiliates	(7)	105	70
Depreciation and amortization	(125)	(160)	(82)
Operating Segments | All Other
Segment Reporting Information [Line Items]
Equity income from affiliates	0	0	0
Depreciation and amortization	$ (87)	$ (23)	$ (18)

Segment Reporting - Property, P

Segment Reporting - Property, Plant and Equipment, Net by Geographic Area (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	$ 12,439	$ 12,026	$ 12,507
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	8,070	8,114	8,467
Europe, Middle East and Africa
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	3,151	2,732	2,844
Asia Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	782	775	842
Latin America
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	271	234	182
Japan
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	158	164	164
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	$ 7	$ 7	$ 8