Operations and Significant Accounting Policies (Earnings Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 30, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Earnings Per Share [Abstract]
Net income	$ (25,134)	$ 8,211	$ 8,680	$ 8,995	$ 6,963	$ 8,758	$ 7,306	$ 7,319	$ 752	$ 30,346	$ 12,137
Basic-weighted average shares outstanding									28,246,000	28,715,000	29,074,000
Effect of dilutive potential securities									387,000	196,000	68,000
Diluted-weighted average shares outstanding									28,633,000	28,911,000	29,142,000
Basic EPS (per share)	$ (0.90)	$ 0.29	$ 0.31	$ 0.32	$ 0.25	$ 0.31	$ 0.25	$ 0.25	$ 0.03	$ 1.06	$ 0.42
Diluted EPS (per share)	$ (0.90)	$ 0.29	$ 0.30	$ 0.31	$ 0.24	$ 0.31	$ 0.25	$ 0.25	$ 0.03	$ 1.05	$ 0.42
Shares excluded from computation of earnings per share									700,000	1,500,000	2,200,000