Stock-Based Compensation (Stock Options) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock Option Activity, Options [Roll Forward]
Outstanding at beginning of period	103
Exercised	(103)
Outstanding at end of period	0	103
Stock Option Activity, Weighted Average Exercise Price [Roll Forward]
Weighted average exercise price of options outstanding at beginning of period	$ 69
Exercised	69
Weighted average exercise price of options outstanding end of period	$ 0	$ 69
Schedule Of Information Related To Stock Options [Abstract]
Intrinsic value of options exercised	$ 1	$ 5	$ 6
Tax benefit related to options exercised		2	2
Cash received from options exercised	$ 7	$ 17	$ 25