Common Stock And Share-Based Compensation (Restricted Stock Units) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common Stock And Share-Based Compensation [Abstract]
Total fair value	$ 36	$ 57	$ 34
Total unrecognized compensation costs	$ 37
Remaining weighted average period, Years	1 year 2 months 19 days
Nonvested at January 1, Number of Restricted Stock Units	1,972,899
Granted, Number of Restricted Stock Units	776,312
Vested, Number of Restricted Stock Units	(770,968)
Forfeited, Number of Restricted Stock Units	(55,233)
Nonvested at December 31, Number of Restricted Stock Units	1,923,010	1,972,899
Nonvested at January 1, Weighted Average Grant-Date Fair Value	$ 47.33
Granted, Weighted Average Grant Date Fair Value	56.68	$ 53.3	$ 43.76
Vested, Weighted Average Grant Date Fair Value	46.79
Forfeited, Weighted Average Grant Date Fair Value	49.65
Nonvested at December 31, Weighted Average Grant-Date Fair Value	$ 51.26	$ 47.33