Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Numerator [Abstract]
Net income	$ 12,232	$ 8,970	$ 24,101	$ 18,274
Basic earnings per share [Abstract]
Weighted average shares (in shares)	15,451	15,308	15,429	15,301
Diluted earnings per share [Abstract]
Effect of dilutive stock options (in shares)	50	24	46	27
Adjusted weighted average shares (in shares)	15,501	15,332	15,475	15,328
Earnings per share [Abstract]
Basic earnings per share (in dollars per share)	$ 0.79	$ 0.59	$ 1.56	$ 1.19
Diluted earnings per share (in dollars per share)	$ 0.79	$ 0.58	$ 1.56	$ 1.19
Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options excluded from diluted calculations (in shares)	89,746	385,022	178,569	385,022

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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