Summary of Significant Accounting Policies Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income (Loss) Attributable to Parent	$ 10,168	$ 650
Weighted Average Number of Shares Outstanding, Basic	18,826	18,628
Weighted Average Number of Shares Outstanding, Diluted	19,321	19,219
Earnings Per Share, Basic	$ 0.54	$ 0.03
Earnings Per Share, Diluted	$ 0.53	$ 0.03
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	149	160
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	346	431