CONDENSED CONSOLIDATED STATEMENT OF INCOME - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Sales	$ 10,816	$ 10,037
Costs, Expenses and Other
Cost of sales	3,052	3,184
Selling, general and administrative	2,425	2,508
Research and development	1,931	3,196
Restructuring costs	153	95
Other (income) expense, net	188	(291)
Total Costs, Expenses and Other	7,749	8,692
Income Before Taxes	3,067	1,345
Taxes on Income	205	604
Net Income	2,862	741
Less: Net (Loss) Income Attributable to Noncontrolling Interests	(53)	5
Net Income Attributable to Merck & Co., Inc.	$ 2,915	$ 736
Basic Earnings per Common Share Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share)	$ 1.13	$ 0.27
Earnings per Common Share Assuming Dilution Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share)	$ 1.12	$ 0.27

Total of cost of sales, operating expenses and nonoperating income or expense.

No definition available.

Name:	mrk_CostsExpensesAndOther
Namespace Prefix:	mrk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2(a),(d))
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227