Earnings Per Share and Capital Structure Computation of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Net income available to common shareholders	$ 12,695	$ 7,308	$ 3,407	$ 26,313
Weighted average common shares outstanding - Basic	38,114	39,213	38,329	39,268
Dilutive effect of stock-based awards	244	280	262	248
Weighted average common shares outstanding - Diluted	38,358	39,493	38,591	39,516
Earnings per common share - Basic	$ 0.33	$ 0.19	$ 0.09	$ 0.67
Earnings per common share - Diluted	$ 0.33	$ 0.19	$ 0.09	$ 0.67