Shareholders' Equity - (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 05, 2018
Class of Stock [Line Items]
Authorized capital stock, common stock (shares)	500,000,000
Common stock, par value (in dollars per share)	$ 1
Authorized capital stock, preferred stock (shares)	50,000,000
Preferred stock, par value (in dollars per share)	$ 1
Common stock, issued (shares)	481,880,634	481,880,634
Common stock, outstanding (shares)	286,477,836	289,610,336
Preferred stock, outstanding (shares)	0	0
Share repurchased, additional amount authorized (shares)				10,000,000
Stock repurchased (shares)	4,100,000	1,100,000	10,100,000
Shares repurchased	$ 602	$ 184	$ 1,806
Shares remaining under a prior authorization	12,300,000
Percent of total shares outstanding authorized for repurchase	4.30%
Dividends declared per share	$ 4.40	$ 4.08	$ 3.72
Dividends paid	$ (1,240)	$ (1,152)	$ (1,075)
Restricted Stock
Class of Stock [Line Items]
Unvested restricted stock (shares)	488,435