Share-Based Compensation (Summary Of Stock Option Activity) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Balance, Number of shares	3,804,095	5,630,502	5,874,590
Balance, Weighted average exercise price	$ 27.30	$ 31.60	$ 35.54
Granted, Number of shares	789,651	740,300	947,758
Granted, Weighted average exercise price	$ 21.25	$ 29.01	$ 28.67
Exercised, Number of shares	1,055,532	1,165,287	489,905
Exercised, Weighted average exercise price	$ 23.75	$ 25.11	$ 21.60
Expired, Number of shares	(56,297)	(1,322,067)	(618,207)
Expired, Weighted average exercise price	$ 61.60	$ 48.44	$ 73.28
Forfeited, Number of shares	(44,007)	(79,353)	(83,734)
Forfeited, Weighted average exercise price	$ 27.66	$ 28.09	$ 25.72
Balance, Number of shares	3,437,910	3,804,095	5,630,502
Balance, Weighted average exercise price	$ 26.44	$ 27.30	$ 31.60
Outstanding stock options exercisable, Number of shares	1,892,136	2,187,259	3,804,873
Outstanding stock options exercisable, Weighted average exercise price	$ 27.60	$ 26.35	$ 33.86