CONDENSED CONSOLIDATED STATEMENT OF INCOME - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Sales	$ 10,794	$ 10,325	$ 31,296	$ 29,689
Costs, Expenses and Other
Materials and production	3,619	3,307	10,220	9,472
Marketing and administrative	2,443	2,459	7,459	7,432
Research and development	2,068	4,413	7,538	8,024
Restructuring costs	171	153	494	470
Other (income) expense, net	(172)	(207)	(512)	(351)
Total Costs, Expenses and Other	8,129	10,125	25,199	25,047
Income Before Taxes	2,665	200	6,097	4,642
Taxes on Income	707	251	1,682	1,186
Net Income (Loss)	1,958	(51)	4,415	3,456
Less: Net Income Attributable to Noncontrolling Interests	8	5	22	16
Net Income (Loss) Attributable to Merck & Co., Inc.	$ 1,950	$ (56)	$ 4,393	$ 3,440
Basic Earnings (Loss) per Common Share Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share)	$ 0.73	$ (0.02)	$ 1.64	$ 1.26
Earnings (Loss) per Common Share Assuming Dilution Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share)	$ 0.73	$ (0.02)	$ 1.63	$ 1.25

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