Common Stock And Stock Options (Summary Of Stock Option Activity) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Common Stock And Stock Options [Abstract]
Number of Shares, Outstanding	1,385	1,324	1,313
Number of Shares, Options forfeited or cancelled	(15)	(70)
Number of Shares, Options granted	303	192	170
Number of Shares, Options exercised	(220)	(61)	(159)
Number of Shares, Outstanding	1,453	1,385	1,324
Weighted-average Exercise Price, Outstanding	$ 6.54	$ 6.36	$ 5.86
Weighted-average Exercise Price, Options forfeited or cancelled	12.42	5.75
Weighted-average Exercise Price, Options granted	7.28	7.11	7.14
Weighted-average Exercise Price, Options exercised	10.67	5.22	3.12
Weighted-average Exercise Price, Outstanding	$ 5.95	$ 6.54	$ 6.36
Aggregate Intrinsic Value, Outstanding	$ 19,000
Number of Shares, Exercisable	970	1,025
Weighted-average Exercise Price, Exercisable	$ 5.42	$ 6.45
Aggregate Intrinsic Value, Exercisable	$ 13,958	$ 1,615
Number of Shares, Available for future grant	251