Shareholders' Equity (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Apr. 26, 2018	Dec. 31, 2016
Treasury Stock, Value, Acquired	$ 244	$ 814
The 2016 Repurchase Program [Member]
Stock Repurchase Program, Authorized Amount				$ 4
Treasury Stock, Shares, Acquired		27,100,000
Treasury Stock, Value, Acquired		$ 814
The 2018 Repurchase Program [Member]
Stock Repurchase Program, Authorized Amount			$ 2
Treasury Stock, Shares, Acquired	7,800,000
Treasury Stock, Value, Acquired	$ 244
Common Stock [Member]
Convertible Preferred Stock, Shares Issued upon Conversion	50,000
Series A Convertible Preferred Stock [Member]
Convertible Preferred Stock, Shares Issued upon Conversion	2,300