Operations and Significant Accounting Policies (Details 2) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of net income per share and net income per share assuming dilution
Income from continuing operations, net of income taxes	$ 8,576	$ 2,200	$ 4,282	$ (1,864)	$ 32,525	$ 1,519	$ 3,542	$ (1,719)	$ 13,194	$ 35,867	$ 9,604
Income from discontinued operations, net of income taxes					577	(75)	74	(8)		568	142
Net income	$ 8,576	$ 2,200	$ 4,282	$ (1,864)	$ 33,102	$ 1,444	$ 3,616	$ (1,727)	$ 13,194	$ 36,435	$ 9,746
Weighted average shares outstanding									8,860	8,829	8,796
Weighted effect of dilutive options and rights									88	75	47
Weighted average shares outstanding assuming dilution									8,948	8,904	8,843
Net income per share:
From continuing operations									$ 1.49	$ 4.06	$ 1.09
From discontinued operations										$ 0.07	$ 0.02
Net income per share									$ 1.49	$ 4.13	$ 1.11
Net income per share assuming dilution [Member]
Net income per share:
From continuing operations									$ 1.47	$ 4.03	$ 1.09
From discontinued operations										$ 0.06	$ 0.01
Net income per share									$ 1.47	$ 4.09	$ 1.10