Stockholders' Equity (Computation of Basic and Diluted Net Income Loss Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stockholders' Equity [Abstract]
Net Income (Loss)	$ 61,427	$ 9,663	$ (54,379)
Weighted Average Common Shares Outstanding-Basic	28,830	28,689	28,571
Effect of Dilutive Securities:
Common Stock Equivalents	417	104
Weighted Average Common Shares Outstanding-Diluted	29,247	28,793	28,571
Net Income per Common Share-Basic	$ 2.13	$ 0.34	$ (1.90)
Net Income per Common Share-Diluted	$ 2.10	$ 0.34	$ (1.90)