Operations and Significant Accounting Policies (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, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net income	$ 6,708	$ 7,337	$ 2,884	$ (2,265)	$ 7,852	$ 8,873	$ 7,461	$ 6,312	$ 14,664	$ 30,498	$ 32,192
Basic-weighted average shares outstanding									27,804	27,653	27,401
Effect of dilutive potential securities									160	205	368
Diluted-weighted average shares outstanding									27,964	27,858	27,769
Basic EPS (in dollars per share)	$ 0.24	$ 0.26	$ 0.10	$ (0.08)	$ 0.28	$ 0.32	$ 0.27	$ 0.23	$ 0.53	$ 1.10	$ 1.17
Diluted EPS (in dollars per share)	$ 0.24	$ 0.26	$ 0.10	$ (0.08)	$ 0.28	$ 0.32	$ 0.27	$ 0.23	$ 0.52	$ 1.09	$ 1.16
Shares excluded from computation of earnings per share									1,400	500	0