Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net Income Attributable to Merck & Co., Inc.	$ 4,442	$ 11,920	$ 4,404
Other Comprehensive Income (Loss) Net of Taxes:
Net unrealized (loss) gain on derivatives, net of reclassifications	(126)	398	229
Net unrealized (loss) gain on investments, net of reclassifications	(70)	57	(19)
Benefit plan net gain (loss) and prior service credit (cost), net of amortization	579	(2,077)	2,758
Cumulative translation adjustment	(208)	(504)	(483)
Other comprehensive income (loss), net of taxes	175	(2,126)	2,485
Comprehensive Income Attributable to Merck & Co., Inc.	$ 4,617	$ 9,794	$ 6,889