Common Stock And Share-Based Compensation (Restricted Stock Units) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Common Stock And Share-Based Compensation [Abstract]
Total fair value	$ 57	$ 34	$ 30
Total unrecognized compensation costs	$ 45
Remaining weighted average period, Years	1 year 5 months 23 days
Nonvested at January 1, Number of Restricted Stock Units	2,538,357
Granted, Number of Restricted Stock Units	820,834
Vested, Number of Restricted Stock Units	(1,304,150)
Forfeited, Number of Restricted Stock Units	(82,142)
Nonvested at December 31, Number of Restricted Stock Units	1,972,899	2,538,357
Nonvested at January 1, Weighted Average Grant-Date Fair Value	$ 43.39
Granted, Weighted Average Grant Date Fair Value	53.30	$ 43.76	$ 42.92
Vested, Weighted Average Grant Date Fair Value	43.51
Forfeited, Weighted Average Grant Date Fair Value	45.63
Nonvested at December 31, Weighted Average Grant-Date Fair Value	$ 47.33	$ 43.39