Management Compensation Plans (Schedule of Summary of Changes in Stock Options Outstanding) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2016		Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
As of beginning of period, number of options	249
Granted, number of options	0
Exercised, number of options	(195)
Forfeited, number of options	0
Expired, number of options	0
As of end of period, number of options	54	[1]	249
As of beginning of period, weighted average exercise price	$ 35.19
Granted, weighted average exercise price	0.00
Exercised, weighted average exercise price	33.08
Forfeited, weighted average exercise price	0.00
Expired, weighted average exercise price	0.00
As of end of period, weighted average exercise price	$ 42.77	[1]	$ 35.19
As of beginning of period, weighted average remaining contractual term	2 years	[1]	2 years 5 months
As of end of period, weighted average remaining contractual term	2 years	[1]	2 years 5 months
As of beginning of period, aggregate intrinsic value	$ 9
As of end of period, aggregate intrinsic value	$ 2	[1]	$ 9

[1] All stock options outstanding as of December 31, 2016 were vested and exercisable.