Other (Income) Expense, Net - Narrative (Details) $ in Millions	3 Months Ended			12 Months Ended			18 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($) VEF / $	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2015 USD ($)	Feb. 28, 2013 VEF / $	Jan. 31, 2013 VEF / $
Component of Other Income / Expense of Nonoperating [Line Items]
Foreign currency devaluation related to Venezuela				$ 876	$ 0	$ 140
Net charge related to the settlement of Vioxx shareholder class action litigation				680	0	0
Noncash Contribution Expense				78
Recognition of Deferred Income				182	140		$ 322
Gain on divestiture of Merck Consumer Care				0	11,209	0
Gain on disposition of interest in equity method investment				0	741	0
Loss on extinguishment of debt				0	628	0
Goodwill, Impairment Loss				47	93
Interest paid				653	852	922
Supera
Component of Other Income / Expense of Nonoperating [Line Items]
Goodwill, Impairment Loss					93
CGRP receptor antagonists
Component of Other Income / Expense of Nonoperating [Line Items]
Gain (loss) on sale of clinical development program				250
Consumer Care
Component of Other Income / Expense of Nonoperating [Line Items]
Gain on divestiture of Merck Consumer Care					11,200
ophthalmic products
Component of Other Income / Expense of Nonoperating [Line Items]
Gain (Loss) on Disposition of Business				$ 147	480
Sirna Therapeutics Inc.
Component of Other Income / Expense of Nonoperating [Line Items]
Gain on disposition of subsidiary					$ 204
Venezuela
Component of Other Income / Expense of Nonoperating [Line Items]
Foreign Currency Exchange Rate, Translation | VEF / $			6.30					6.30	4.30
Foreign currency devaluation related to Venezuela	$ 161	$ 138	$ 715			$ 140