Contingencies and Environmental Liabilities (Details Textuals)	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		1 Months Ended		9 Months Ended					3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended			3 Months Ended	9 Months Ended						9 Months Ended						12 Months Ended
	Sep. 30, 2011 USD ($) Plaintiff Derivative LegalMatter Defendant	Sep. 30, 2010 USD ($)	Sep. 30, 2011 USD ($) Year Plaintiff Segment LegalMatter Derivative Defendant	Sep. 30, 2010 USD ($)	Sep. 30, 2011 Remicade [Member] USD ($)	Sep. 30, 2010 Remicade [Member] USD ($)	Sep. 30, 2011 Remicade [Member] USD ($)	Sep. 30, 2010 Remicade [Member] USD ($)	Sep. 30, 2011 Vytorin [Member] USD ($)	Sep. 30, 2010 Vytorin [Member] USD ($)	Sep. 30, 2011 Vytorin [Member] USD ($)	Sep. 30, 2010 Vytorin [Member] USD ($)	Sep. 30, 2011 Fosamax [Member] USD ($) PlaintiffGroup LegalMatter	Sep. 30, 2010 Fosamax [Member] USD ($)	Sep. 30, 2011 Fosamax [Member] USD ($) PlaintiffGroup LegalMatter	Sep. 30, 2010 Fosamax [Member] USD ($)	Oct. 31, 2010 Fosamax [Member] ONJ Litigation [Member] USD ($)	Jun. 30, 2010 Fosamax [Member] ONJ Litigation [Member] USD ($)	Sep. 30, 2011 Fosamax [Member] ONJ Litigation [Member] LegalMatter	Sep. 30, 2011 Fosamax [Member] ONJ Litigation [Member] New Jersey [Member] LegalMatter	Sep. 30, 2011 Fosamax [Member] Other Bone Injuries [Member] LegalMatter	Sep. 30, 2011 Fosamax [Member] Other Bone Injuries [Member] New Jersey [Member] LegalMatter	Sep. 30, 2011 Fosamax [Member] Cases with a fact discovery deadline of July 31, 2012 [Member] LegalMatter	Sep. 30, 2011 NuvaRing [Member] USD ($) LegalMatter	Sep. 30, 2010 NuvaRing [Member] USD ($)	Sep. 30, 2011 NuvaRing [Member] USD ($) LegalMatter	Sep. 30, 2010 NuvaRing [Member] USD ($)	Sep. 30, 2011 NuvaRing [Member] New Jersey [Member] LegalMatter	Sep. 30, 2011 Propecia [Member] USD ($) LegalMatter	Sep. 30, 2010 Propecia [Member] USD ($)	Sep. 30, 2011 Propecia [Member] USD ($) LegalMatter	Sep. 30, 2010 Propecia [Member] USD ($)	Jun. 30, 2011 DOJ and EPA Matters [Member] USD ($)	Sep. 30, 2011 DOJ and EPA Matters [Member] USD ($)	Sep. 30, 2010 Department of Justice [Member] USD ($)	Sep. 30, 2011 AWP Litigation and Investigation [Member] USD ($)	Sep. 30, 2011 Vytorin shareholder lawsuits [Member] USD ($)	Sep. 30, 2011 Vytorin ERISA lawsuits [Member] USD ($)	Sep. 30, 2011 Vioxx Litigation [Member] USD ($)	Sep. 30, 2011 Vioxx Litigation [Member] USD ($)	Dec. 31, 2010 Vioxx Litigation [Member] USD ($)	Sep. 30, 2011 Vioxx Product Liability [Member] PlaintiffGroup	Sep. 30, 2011 U.S. Vioxx Product Liability Lawsuits currently scheduled for trial in 2011 [Member] LegalMatter	Sep. 30, 2011 Vioxx litigation, unresolved post-trial appeal: Ernst v. Merck [Member] LegalMatter	Sep. 30, 2011 Other Vioxx Lawsuits [Member] LegalMatter	Sep. 30, 2011 Vioxx Securities Lawsuits [Member] USD ($)	Sep. 30, 2011 Vioxx ERISA Lawsuits [Member] USD ($)	Aug. 16, 2011 Vioxx ERISA Lawsuits [Member] USD ($)	Sep. 30, 2011 Fosamax bellwether trials [Member] LegalMatter	Sep. 30, 2011 Lawsuits filed by state Attorney Generals [Member] LegalMatter	Sep. 30, 2011 ABP Lawsuits defendants can file motion to dismiss [Member] LegalMatter	Dec. 31, 2010 International Lawsuits [Member] AUD
Loss Contingencies [Line Items]
Number of plaintiff groups													2,420		2,420
Number of lawsuits in federal court																			940							775
Number of lawsuits in New Jersey state court																				210		645						120
Plaintiff groups not eligible for Settlement Program claims remain pending																																										75
Number of plaintiffs																															100
Loss contingency, pending claims number	1		1										2,000		2,000				1,160		840		40	900		900			60		60											25	0	1	30				2	12	1
Upper limit of directors and officers insurance coverage																																					$ 250,000,000	$ 265,000,000								$ 175,000,000	$ 275,000,000
Litigation losses		950,000,000	500,000,000	950,000,000																															950,000,000																	330,465
Amount of Vioxx legal defense costs reserve																																							64,000,000	64,000,000	76,000,000
Charge recorded for future legal defense costs																																							30,000,000	49,000,000
Initial group of cases to complete fact discovery																			25
Number of cases pending in other state courts																					30					4
Trial pool cases which are the subject of fact discovery																										20
Additional trial pool cases selected																										8
Sales	12,022,000,000	11,125,000,000	35,753,000,000	33,893,000,000	561,000,000	661,000,000	2,156,000,000	2,004,000,000	469,000,000	485,000,000	1,407,000,000	1,452,000,000	215,000,000	220,000,000	644,000,000	692,000,000								159,000,000	134,000,000	455,000,000	414,000,000		112,000,000	109,000,000	330,000,000	322,000,000
Verdict amount in favor of the plaintiff																		8,000,000																		13,800,000
Reduced verdict amount																	1,500,000
Aggregate amount spent in legal defense costs worldwide related to Vioxx Litigation																																							24,000,000	61,000,000
Civil penalties sought against Merck by DOJ and EPA																																	2,000,000
Agreed upon civil penalty for environmental matters																																		1,500,000
Parties agreement to Merck for the legal Settlement																																																$ 49,500,000
Contingencies and Environmental Liabilities (Textuals) [Abstract]
Number of plaintiffs filed amended complaint	2,200		2,200
Number of other defendants in environmental matters	12		12
Number of other defendants in phase 1 trial	3		3