Earnings per Share (Computation of Basic and Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Net Income	$ 4,424	$ 6,366	$ 6,331	$ 5,662	$ 4,178	$ 6,255	$ 6,412	$ 6,583	$ 22,783		$ 23,428		$ 26,177
Dividends and undistributed earnings allocated to participating securities									(64)	[1]	(60)	[1]	(42)	[1]
Net income available to common shareholders									$ 22,719		$ 23,368		$ 26,135
Weighted-average common shares outstanding for basic EPS									7,634,455		7,646,861		7,672,126
Dilutive effect of stock-based awards									18,815	[2]	14,412	[2]	7,769	[2]
Weighted-average common and potential common shares for diluted EPS									7,653,270		7,661,273		7,679,895
Basic EPS	$ 0.58	$ 0.83	$ 0.83	$ 0.74	$ 0.55	$ 0.82	$ 0.83	$ 0.86	$ 2.98		$ 3.06		$ 3.41
Diluted EPS	$ 0.58	$ 0.83	$ 0.82	$ 0.74	$ 0.55	$ 0.82	$ 0.83	$ 0.86	$ 2.97		$ 3.05		$ 3.40
Shares that were not considered in computation of potential common shares for purposes of diluted EPS									15,250		49,500		102,000

[1] Represents dividends paid and undistributed earnings allocated to nonvested stock-based awards that contain non-forfeitable rights to dividends.

[2] Represents the effect of the assumed exercise of stock options, vesting of restricted shares, vesting of restricted stock units, and vesting of LTIP awards that have met the performance criteria, utilizing the treasury stock method.