XML 127 R103.htm IDEA: XBRL DOCUMENT v3.20.4
Earnings Per Share - Calculations of Earnings Per Share (Details) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Earnings Per Share [Abstract]      
Net income attributable to Merck & Co., Inc. $ 7,067 $ 9,843 $ 6,220
Average common shares outstanding (in shares) 2,530 2,565 2,664
Common shares issuable (in shares) 11 15 15
Average common shares outstanding assuming dilution (in shares) 2,541 2,580 2,679
Basic earnings per common share attributable to Merck & Co., Inc. common shareholders (in dollars per share) $ 2.79 $ 3.84 $ 2.34
Earnings per common share assuming dilution attributable to Merck & Co., Inc. common shareholders (in dollars per share) $ 2.78 $ 3.81 $ 2.32