Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share [Abstract]
Net income	$ 2,197	$ 1,071	$ 30,683	$ 38,955
Average common shares outstanding - basic	27,343	27,139	27,322	27,116
Additional shares for stock based compensation plans	45	43	56	42
Average common shares outstanding - diluted	27,388	27,182	27,378	27,158
Earnings per share of common stock - basic	$ 0.08	$ 0.04	$ 1.12	$ 1.44
Earnings per share of common stock - diluted	$ 0.08	$ 0.04	$ 1.12	$ 1.43
Earnings Per Share, Diluted, Other Disclosures [Abstract]
Antidilutive Shares Excluded from Net Income Per Diluted Common Share Calculation	35	39	27	28