Capital Stock (Cash Dividend Activity) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Dividends, Cash [Abstract]
Declaration Date	Oct. 22, 2019	Jul. 23, 2019	Apr. 23, 2019	Jan. 29, 2019	Oct. 30, 2018	Jul. 24, 2018	Apr. 24, 2018	Jan. 30, 2018
Record Date	Dec. 05, 2019	Sep. 10, 2019	Jun. 10, 2019	Mar. 18, 2019	Dec. 05, 2018	Sep. 10, 2018	Jun. 08, 2018	Mar. 09, 2018
Payment Date	Dec. 20, 2019	Sep. 25, 2019	Jun. 25, 2019	Mar. 29, 2019	Dec. 21, 2018	Sep. 25, 2018	Jun. 25, 2018	Mar. 23, 2018
Cash Dividend per Share	$ 0.80	$ 0.80	$ 0.80	$ 0.80	$ 0.75	$ 0.75	$ 0.75	$ 0.75
Total	$ 202	$ 204	$ 206	$ 206	$ 193	$ 195	$ 196	$ 192	$ 818	$ 776	$ 705