Shareholders' Equity (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Jul. 17, 2019	Apr. 26, 2018	Dec. 31, 2016
Treasury Stock, Value, Acquired	$ 308	$ 151	$ 244	$ 384	$ 674	$ 814
The 2016 Repurchase Program [Member]
Stock Repurchase Program, Authorized Amount											$ 4,000
The 2018 Repurchase Program [Member]
Stock Repurchase Program, Authorized Amount										$ 2,000
Treasury Stock, Shares, Acquired	10,800,000						23,400,000
Treasury Stock, Value, Acquired	$ 308						$ 703
The 2016 and 2018 Repurchase Program [Member]
Treasury Stock, Shares, Acquired				11,800,000				63,400,000
Treasury Stock, Value, Acquired				$ 384				$ 1,900
2019 Repurchase Authorization [Member]
Stock Repurchase Program, Authorized Amount									$ 5,000
Common Stock [Member]
Convertible Preferred Stock, Shares Issued upon Conversion	50,000						50,000
Series A Convertible Preferred Stock [Member]
Convertible Preferred Stock, Shares Issued upon Conversion	2,300						2,300