Earnings Per Share (Calculation of Basic and Diluted EPS) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Share [Abstract]
Net Income	$ 8,575	$ 10,056	$ 24,704	$ 24,637
Average Common Shares:
Basic (weighted-average outstanding shares)	11,903	11,857	11,887	11,845
Dilutive potential common shares from stock options, shares	153	90	160	119
Diluted (weighted-average outstanding shares)	12,056	11,947	12,047	11,964
Basic earnings per share (in dollars per share)	$ 0.72	$ 0.85	$ 2.08	$ 2.08
Diluted earnings per share (in dollars per share)	$ 0.71	$ 0.84	$ 2.05	$ 2.06