Capital Stock (Summary of Cash Dividend Activity) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Capital [Abstract]
Declaration date	Jul. 28, 2020	Apr. 28, 2020	Jan. 28, 2020	Jul. 23, 2019	Apr. 23, 2019	Jan. 29, 2019
Record date	Sep. 10, 2020	Jun. 10, 2020	Mar. 16, 2020	Sep. 10, 2019	Jun. 10, 2019	Mar. 18, 2019
Payment date	Sep. 25, 2020	Jun. 25, 2020	Mar. 27, 2020	Sep. 25, 2019	Jun. 25, 2019	Mar. 29, 2019
Cash dividends per share	$ 0.95	$ 0.95	$ 0.95	$ 0.80	$ 0.80	$ 0.80
Total payment	$ 238	$ 242	$ 240	$ 204	$ 206	$ 206	$ 720	$ 616