Stock and Other Incentive Plans (Details 1) - Employees Stock Purchase Plan [Member] - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock Options Outstanding (in shares):
Options outstanding, beginning of year	393,902	391,108	433,452
Granted	197,640	275,655	246,717
Exercised	(44,462)	(51,078)	(69,076)
Forfeited	(47,176)	(63,908)	(49,434)
Expired	(158,946)	(157,875)	(170,551)
Outstanding, end of period	340,958	393,902	391,108
Exercisable, end of period	340,958	393,902	391,108
Weighted-average exercise price of (in dollars per share):
Options outstanding, beginning of year	$ 19.17	$ 17.05	$ 16.78
Options granted during the year	23.22	18.11	20.41
Options exercised during the year	19.41	17.76	17.09
Options forfeited during the year	19.90	18.58	17.98
Options expired during the year	20.41	15.80	17.99
Options outstanding, end of year	20.70	19.17	17.05
Weighted-average fair value of options granted during the year (calculated as of the grant date)	$ 5.39	$ 4.35	$ 5.08
Intrinsic value of options exercised during the year	$ 380,615	$ 436,547	$ 375,335
Intrinsic value of options outstanding (calculated as of December 31)	2,597,238	3,209,456	1,665,331
Intrinsic value of options exercisable (calculated as of December 31)	$ 2,597,238	$ 3,209,456	$ 1,665,331
Exercise prices of options outstanding (calculated as of December 31)	$ 20.70	$ 19.17	$ 17.05
Weighted-average contractual life of outstanding options (calculated as of December 31, in years)	9 months 18 days	9 months 18 days	9 months 18 days