Shareholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Stockholders' Equity [Abstract]
Additional Paid-in Capital	$ 3,271	$ 3,271		$ 3,271	$ 3,806
Common Stock and Additional Paid-in Capital Percentage Change	14.00%	14.00%		14.00%
Common Stock and Additional Paid-in Capital Change	$ 535	$ 535		$ 535
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ 25	$ 25	$ (315)	$ 25	$ (250)	$ (139)
Stock Repurchased During Period, Shares		5,800,000	4,300,000	11,300,000
Shares, Issued	176,900,000	176,900,000		176,900,000
Treasury Stock Acquired, Average Cost Per Share		$ 47.05	$ 54.64	$ 48.50
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 275	$ 275		$ 275
Common Stock, Par or Stated Value Per Share	$ 0.001	$ 0.001		$ 0.001
Stock Repurchased and Retired During Period, Value		$ 275	$ 235	$ 550
Common Stock, Terms of Conversion	1.06
Warrant [Member]
Warrant Exercise Price	$ 34.41	$ 34.41		$ 34.41
Class of Warrant or Right, Outstanding	29,300,000	29,300,000		29,300,000