Consolidated Statement of Income - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Sales	$ 42,294	$ 40,122	$ 39,807
Costs, Expenses and Other
Cost of sales	13,509	12,912	14,030
Selling, general and administrative	10,102	10,074	10,017
Research and development	9,752	10,339	10,261
Restructuring costs	632	776	651
Other (income) expense, net	(402)	(500)	189
Total Costs, Expenses and Other	33,593	33,601	35,148
Income Before Taxes	8,701	6,521	4,659
Taxes on Income	2,508	4,103	718
Net Income	6,193	2,418	3,941
Less: Net (Loss) Income Attributable to Noncontrolling Interests	(27)	24	21
Net Income Attributable to Merck & Co., Inc.	$ 6,220	$ 2,394	$ 3,920
Basic Earnings per Common Share Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share)	$ 2.34	$ 0.88	$ 1.42
Earnings per Common Share Assuming Dilution Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share)	$ 2.32	$ 0.87	$ 1.41

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