Earnings (Loss) Per Share (Schedule of Earnings (Loss) Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Earnings (loss) of basic earnings (loss) per common share	$ 3,705	$ (24,022)	$ 28,693	$ (137,307)
Income of effect of dilutive stock options, restricted stock, and stock appreciation rights (SARs)	0	0	0	0
Earnings (loss) of diluted loss per common share	$ 3,705	$ (24,022)	$ 28,693	$ (137,307)
Weighted shares of basic earnings (loss) per common share	51,386	50,081	51,019	50,012
Weighted shares of effect of dilutive stock options, restricted stock, and stock appreciation rights (SARs)	586	0	550	0
Weighted shares of diluted earnings (loss) per common share	51,972	50,081	51,569	50,012
Per-Share amount of basic earnings (loss) per common share	$ 0.07	$ (0.48)	$ 0.56	$ (2.75)
Per-Share amount of effect of dilutive stock options, restricted stock, and stock appreciation rights (SARs)	0.00	0.00	0.00	0.00
Per-Share amount of diluted earnings (loss) per common share	$ 0.07	$ (0.48)	$ 0.56	$ (2.75)