Summary of Significant Accounting Policies Earnings 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, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income (Loss) Attributable to Parent	$ 8,171	$ 6,940	$ (9,427)	$ 14,920
Weighted Average Number of Shares Outstanding, Basic	18,781	18,577	18,720	18,528
Weighted Average Number of Shares Outstanding, Diluted	19,016	18,850	18,720	18,801
Earnings Per Share, Basic	$ 0.44	$ 0.37	$ (0.50)	$ 0.81
Earnings Per Share, Diluted	$ 0.43	$ 0.37	$ (0.50)	$ 0.79
Performance Shares [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	48	71	0	71
Restricted Stock Units (RSUs) [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	187	202	0	202