Share Options And Awards (Summary Of Option Activity) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares under option, outstanding beginning of period (in shares)	934,201	2,366,650	2,897,123
Shares under option, forfeited or expired (in shares)	(4,042)	(460,722)	(435,840)
Shares under option, exercised (in shares)	(101,805)	(971,727)	(94,633)
Shares under option, outstanding end of period (in shares)	828,354	934,201	2,366,650
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted average exercise price, outstanding beginning of period (in dollars per share)	$ 22.85	$ 27.26	$ 28.76
Weighted average exercise price, forfeited or expired (in dollars per share)	43.37	47.42	37.37
Weighted average exercise price, exercised (in dollars per share)	16.11	21.95	26.55
Weighted average exercise price, outstanding end of period (in dollars per share)	$ 23.58	$ 22.85	$ 27.26