Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Net Income	$ (8,040)	$ (6,685)	$ 30,620	$ 23,998
Average common shares outstanding - basic	27,554	27,363	27,504	27,336
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	0	0	125	63
Average common shares outstanding - diluted	27,554	27,363	27,629	27,399
Earnings per share of common stock - basic	$ (0.29)	$ (0.24)	$ 1.11	$ 0.88
Earnings per share of common stock - diluted	$ (0.29)	$ (0.24)	$ 1.11	$ 0.88
Antidilutive shares excluded from computation of earnings per share amount	159	91	5	19