Common Shares And Stock-Based Awards Plans (Summary Of Stock-Based Awards) (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested shares outstanding, shares or units, beginning balance	525	467	412
Granted, shares or units	314	392	228
Vested, shares or units	(206)	(209)	(161)
Forfeited, shares or units	(40)	(125)	(12)
Non-vested shares outstanding, shares or units, ending balance	593	525	467
Non-vested outstanding, weighted-average grant date fair value, beginning balance	$ 22.57	$ 21.59	$ 20.33
Granted, weighted-average grant date fair value	31.56	22.71	23.06
Vested, weighted-average grant date fair value	21.84	21.07	20.51
Forfeited, weighted-average grant date fair value	24.21	21.85	21.03
Non-vested outstanding, weighted-average grant date fair value, ending balance	$ 27.47	$ 22.57	$ 21.59
Performance-Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested shares outstanding, shares or units, beginning balance	227	306	274
Granted, shares or units	172	184	85
Forfeited, shares or units	(53)	(263)	(53)
Non-vested shares outstanding, shares or units, ending balance	346	227	306
Non-vested outstanding, weighted-average grant date fair value, beginning balance	$ 21.43	$ 19.77	$ 18.56
Granted, weighted-average grant date fair value	31.6	21.63	22.93
Forfeited, weighted-average grant date fair value	18.81	19.64	18.57
Non-vested outstanding, weighted-average grant date fair value, ending balance	$ 26.88	$ 21.43	$ 19.77