Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 5,486	$ 7,035	$ 6,348
Other comprehensive income (loss), pretax	111	(202)	(14)
Tax	(13)	29	8
Other comprehensive income (loss), net of taxes	98	(173)	(6)
Net transfer of benefit plans to Merck affiliates	11	465
Ending balance	(1,508)	5,486	7,035
Accumulated Other Comprehensive (Loss) Income
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(622)	(914)	(908)
Ending balance	(513)	(622)	(914)
Employee Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(32)	(354)	(294)
Other comprehensive income (loss), pretax	21	(172)	(68)
Tax	(13)	29	8
Other comprehensive income (loss), net of taxes	8	(143)	(60)
Net transfer of benefit plans to Merck affiliates	11	465
Ending balance	(13)	(32)	(354)
Cumulative Translation Adjustment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(590)	(560)	(614)
Other comprehensive income (loss), pretax	90	(30)	54
Other comprehensive income (loss), net of taxes	90	(30)	54
Ending balance	$ (500)	$ (590)	$ (560)