Earnings Per Share Computation of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net income (loss) available to common shareholders	$ 11,649	$ (9,885)	$ 19,917	$ 10,089	$ 8,986	$ 12,640	$ (14,346)	$ 5,398	$ 31,770	$ 12,678	$ (23,670)
Weighted average common shares outstanding - Basic									38,207	38,224	39,184
Dilutive effect of stock-based awards									436	282	0
Weighted average common shares outstanding - Diluted									38,643	38,506	39,184
Earnings (loss) per common share - Basic(1)	$ 0.30	$ (0.26)	$ 0.52	$ 0.27	$ 0.23	$ 0.33	$ (0.37)	$ 0.14	$ 0.83	$ 0.33	$ (0.60)
Earnings (loss) per common share - Diluted	$ 0.30	$ (0.26)	$ 0.52	$ 0.26	$ 0.23	$ 0.33	$ (0.37)	$ 0.14	$ 0.82	$ 0.33	$ (0.60)