Capital Stock (Cash Dividend Activity) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Dividends, Cash [Abstract]
Declaration Date	Oct. 27, 2020	Jul. 28, 2020	Apr. 28, 2020	Jan. 28, 2020	Oct. 22, 2019	Jul. 23, 2019	Apr. 23, 2019	Jan. 29, 2019
Record Date	Dec. 07, 2020	Sep. 10, 2020	Jun. 10, 2020	Mar. 16, 2020	Dec. 05, 2019	Sep. 10, 2019	Jun. 10, 2019	Mar. 18, 2019
Payment Date	Dec. 22, 2020	Sep. 25, 2020	Jun. 25, 2020	Mar. 27, 2020	Dec. 20, 2019	Sep. 25, 2019	Jun. 25, 2019	Mar. 29, 2019
Cash Dividend per Share	$ 0.95	$ 0.95	$ 0.95	$ 0.95	$ 0.80	$ 0.80	$ 0.80	$ 0.80
Total	$ 234	$ 238	$ 242	$ 240	$ 202	$ 204	$ 206	$ 206	$ 954	$ 818	$ 776