Capital Stock and Stock-Based Compensation Plans - Summary of Stock Option Activity (Details) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares shares
Summary of stock option plan activity [Roll Forward]
Options - beginning balance (in shares) | shares	39,710
Granted (in shares) | shares	5,364
Exercised (in shares) | shares	(8,205)
Forfeited or expired (in shares) | shares	(684)
Options - ending balance (in shares) | shares	36,185
Options exercisable (in shares) | shares	25,142
Additional disclosures pertaining to stock options [Abstract]
Weighted average exercise price of options - beginning of period (in dollars per share) | $ / shares	$ 67
Weighted average exercise price of options - shares granted (in dollars per share) | $ / shares	72
Weighted average exercise price of options - shares exercised (in dollars per share) | $ / shares	61
Weighted average exercise price of options - shares forfeited or expired (in dollars per share) | $ / shares	70
Weighted average exercise price of options - end of period (in dollars per share) | $ / shares	69
Weighted average exercise price of options exercisable - end of period (in dollars per share) | $ / shares	$ 69
Weighted average remaining contractual life, options outstanding (in years)	4 years
Weighted average remaining contractual life, options exercisable (in years)	3 years
Value of unexercised in-the-money options, options outstanding | $	$ 63
Value of unexercised in-the-money options, options exercisable | $	$ 60