Capital Stock (Summary Of Stock Option Activity) (Details) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Number of Shares
Outstanding at beginning of period, Number of Shares | shares	4.3
Granted, Number of Shares | shares	0.9
Exercised, Number of Shares | shares	(1.3)
Forfeited or expired, Number of Shares | shares	(0.2)
Outstanding at end of period, Number of Shares | shares	3.7
Exercisable at end of period, Number of Shares | shares	2.4
Weighted-Average Option Price per Share
Outstanding at beginning of period, Weighted-Average Option Price per Share | $ / shares	$ 124.31
Granted, Weighted-Average Option Price per Share | $ / shares	232.79
Exercised, Weighted-Average Option Price per Share | $ / shares	112.72
Forfeited or expired, Weighted-Average Option Price per Share | $ / shares	189.52
Outstanding at end of period, Weighted-Average Option Price per Share | $ / shares	149.65
Exercisable at end of period, Weighted-Average Option Price per Share | $ / shares	$ 125.88
Outstanding at end of period, Weighted-Average Remaining Contractual Life	6 years 1 month 23 days
Exercisable at end of period, Weighted-Average Remaining Contractual Life	5 years
Outstanding at end of period, Aggregate Intrinsic Value | $	$ 416
Exercisable at end of period, Aggregate Intrinsic Value | $	$ 331