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, 2015	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
As of beginning of period, number of options	343
Granted, number of options	0
Exercised, number of options	(94)
Forfeited, number of options	0
Expired, number of options	0
As of end of period, number of options	249	343
Options exercisable at end of year, number of options	239
As of beginning of period, weighted average exercise price	$ 33.72
Granted, weighted average exercise price	0.00
Exercised, weighted average exercise price	29.82
Forfeited, weighted average exercise price	0.00
Expired, weighted average exercise price	0.00
As of end of period, weighted average exercise price	35.19	$ 33.72
Options exercisable at end of year, weighted average exercise price	$ 34.74
As of beginning of period, weighted average remaining contractual term	2 years 5 months	3 years 2 months
As of end of period, weighted average remaining contractual term	2 years 5 months	3 years 2 months
Options exercisable at end of year, weighted average remaining contractual term	2 years 4 months
As of beginning of period, aggregate intrinsic value	$ 7
As of end of period, aggregate intrinsic value	9	$ 7
Options exercisable at end of year, aggregate intrinsic value	$ 9