Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net income (loss) from continuing operations	$ (11,144)	$ (7,887)	$ 30,528	$ 37,585
Average common shares outstanding - basic (in shares)	28,815	28,678	28,787	28,653
Additional shares for stock-based compensation plans (in shares)	0	0	59	81
Average common shares outstanding - diluted (in shares)	28,815	28,678	28,846	28,734
Income (Loss) from Continuing Operations, Per Basic Share	$ (0.39)	$ (0.28)	$ 1.06	$ 1.32
Income (Loss) from Continuing Operations, Per Diluted Share	$ (0.39)	$ (0.28)	$ 1.06	$ 1.31
Antidilutive shares (in shares)	73	96	4	15