Equity (Details) (USD $) In Millions, except Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Stockholders' Equity
Beginning balance			$ 56,805	$ 61,485
Beginning balance, shares			3,576,948,356
Net Income Attributable to Merck & Co., Inc.	1,692	342	4,760	1,393
Cash dividends declared on common stock			(3,533)	(3,552)
Mandatory conversion of 6% convertible preferred stock				134
Treasury stock, shares purchased			41,000,000
Treasury stock shares purchased			(1,359)	(1,593)
Share-based compensation plans and other			393	876
Other comprehensive Income			503	(723)
Net income attributable to noncontrolling interests	32	30	89	89
Distributions attributable to noncontrolling interests			(62)	(61)
Ending balance	57,596	58,048	57,596	58,048
Ending balance, shares	3,576,948,356		3,576,948,356
Common Stock [Member]
Stockholders' Equity
Beginning balance			1,788	1,781
Beginning balance, shares			3,576,948,356	3,563,000,000
Mandatory conversion of 6% convertible preferred stock				2
Mandatory conversion of 6% convertible preferred stock, Shares				4,000,000
Share-based compensation plans and other			0	5
Share-based compensation plans and other, shares			0	10,000,000
Ending balance	1,788	1,788	1,788	1,788
Ending balance, shares	3,576,948,356	3,576,948,356	3,576,948,356	3,576,948,356
Other Paid-In Capital [Member]
Stockholders' Equity
Beginning balance			40,701	39,683
Mandatory conversion of 6% convertible preferred stock				132
Share-based compensation plans and other			16	742
Ending balance	40,717	40,557	40,717	40,557
Retained Earnings [Member]
Stockholders' Equity
Beginning balance			37,536	41,405
Net Income Attributable to Merck & Co., Inc.			4,760	1,393
Cash dividends declared on common stock			(3,533)	(3,552)
Ending balance	38,763	39,246	38,763	39,246
Accumulated Other Comprehensive Loss [Member]
Stockholders' Equity
Beginning balance			(3,216)	(2,767)
Other comprehensive Income			503	(723)
Ending balance	(2,713)	(3,490)	(2,713)	(3,490)
Treasury Stock [Member]
Stockholders' Equity
Beginning balance			(22,433)	(21,044)
Beginning balance, shares			495,000,000	454,000,000
Treasury stock, shares purchased				47,000,000
Treasury stock shares purchased			(1,359)	(1,593)
Share-based compensation plans and other			377	129
Share-based compensation plans and other, shares			(11,000,000)	(4,000,000)
Ending balance	(23,415)	(22,508)	(23,415)	(22,508)
Ending balance, shares	525,000,000	497,000,000	525,000,000	497,000,000
Noncontrolling Interests [Member]
Stockholders' Equity
Beginning balance			2,429	2,427
Net income attributable to noncontrolling interests			89	89
Distributions attributable to noncontrolling interests			(62)	(61)
Ending balance	$ 2,456	$ 2,455	$ 2,456	$ 2,455