Share-Based Payments - Schedule of Share-based Compensation, Stock Options, Activity (Detail) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) $ / shares shares
Shares (Thousands)
Outstanding, beginning of period, shares | shares	88,600	[1]
Granted, shares | shares	1,755	[1]
Exercised, shares | shares	(18,492)	[1]
Forfeited, shares | shares	(160)	[1]
Expired, shares | shares	(326)	[1]
Spin-off adjustment, shares | shares	4,024	[2]
Outstanding, end of period, shares | shares	75,402
Vested and expected to vest, end of period, shares | shares	75,226	[3]
Exercisable, end of period, shares | shares	71,732
Weighted-Average Exercise Price Per Share
Outstanding, beginning of period, weighted-average exercise price per share (in dollars per share) | $ / shares	$ 28.39	[1]
Granted, weighted-average exercise price per share (in dollars per share) | $ / shares	34.10	[1]
Exercised, weighted-average exercise price per share (in dollars per share) | $ / shares	23.05	[1]
Forfeited, weighted-average exercise price per share (in dollars per share) | $ / shares	35.49	[1]
Expired, weighted-average exercise price per share (in dollars per share) | $ / shares	24.91	[1]
Spin-off adjustment, weighted-average exercise price per share (in dollars per share) | $ / shares	28.08	[2]
Outstanding, end of period, weighted-average exercise price per share (in dollars per share) | $ / shares	28.31
Vested and expected to vest, end of period, weighted-average exercise price per share (in dollars per share) | $ / shares	28.30	[3]
Exercisable, end of period, weighted-average exercise price per share (in dollars per share) | $ / shares	$ 27.97
Outstanding, end of period, weighted-average remaining contractual term	3 years 1 month 6 days
Vested and expected to vest, end of period, weighted-average remaining contractual term	3 years	[3]
Exercisable, end of period, weighted-average remaining contractual term	2 years 9 months 18 days
Outstanding, end of period, aggregate intrinsic value | $	$ 645	[4]
Vested and expected to vest, end of period, aggregate intrinsic value | $	645	[3],[4]
Exercisable, end of period, aggregate intrinsic value | $	$ 635	[4]

[1] Activity prior to the Upjohn Business spin-off has not been adjusted.

[2] In connection with the Upjohn business spin-off discussed above, the number of shares of common stock subject to each outstanding stock option was increased and the exercise price was decreased. These adjustments did not result in additional compensation cost.

[3] The number of options expected to vest takes into account an estimate of expected forfeitures.

[4] Market price of our underlying common stock less exercise price.