Stockholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Nov. 05, 2019	Nov. 07, 2017
Stockholders' Equity [Line Items]
Amount authorized for stock repurchase program									$ 3,200	$ 2,200
Repurchased shares of treasury stock			386,463	390,904
Treasury stock activity	$ 20		$ 70	$ 84
Dividends declared per share	$ 1.14	$ 1.03	$ 2.28	$ 2.06
Dividends paid			$ 92	$ 84
Accumulated other comprehensive income (loss)	$ (1,501)	$ (1,376)	(1,501)	(1,376)	$ (1,523)	$ (1,547)	$ (1,394)	$ (1,409)
Benefit Plans
Stockholders' Equity [Line Items]
Accumulated other comprehensive income (loss)	(1,502)	(1,373)	(1,502)	(1,373)	(1,524)	(1,546)	(1,390)	(1,407)
Other
Stockholders' Equity [Line Items]
Accumulated other comprehensive income (loss)	$ 1	$ (3)	$ 1	$ (3)	$ 1	$ (1)	$ (4)	$ (2)