Stock-Based Compensation (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013 plan	Sep. 30, 2012	Sep. 30, 2013 plan	Sep. 30, 2012	Dec. 31, 2010	Dec. 31, 2005
Stock-Based Compensation
Number of stock-based compensation plans	1		1
Number of shares reserved under the plan						735,000
Number of additional shares authorized under the plan					700,000
Number of shares available for future awards	505,012		505,012
Stock-based compensation
Stock-based compensation expense before income taxes	$ 488,000	$ 378,000	$ 1,473,000	$ 1,118,000
Deferred tax benefit	(171,000)	(132,000)	(516,000)	(391,000)
Reduction of net income	317,000	246,000	957,000	727,000
Additional expected stock-based compensation expense			470,000
Unrecognized stock-based compensation expense	3,607,000		3,607,000
Period of recognition of stock-based compensation expense			5 years
Amount received from exercise of options			$ 1,260,000	$ 562,000
Options and stock appreciation rights (SARs)
Stock-based compensation
Award vesting limit per year (as a percent)			20.00%
Period after grant date after which the award expires			10 years
Assumptions used in SAR/Option valuations
Dividend yield (as a percent)			2.80%	2.52%
Expected volatility (as a percent)			22.54%	22.04%
Risk free interest rate (as a percent)			1.26%	1.44%
Forfeitures (as a percent)			6.40%	4.20%
Expected life of awards			6 years 7 months 6 days	7 years 7 months 6 days
Restricted stock | Minimum
Stock-based compensation
Award vesting period			3 years
Restricted stock | Maximum
Stock-based compensation
Award vesting period			5 years
Restricted stock units (RSUs) | Executive Officer
Stock-based compensation
Award vesting period			3 years