Stock and Other Incentive Plans (Details 1) (Employees Stock Purchase Plan [Member], USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employees Stock Purchase Plan [Member]
Stock Options Outstanding (in shares):
Options outstanding, beginning of year	391,108	433,452	425,196
Granted	275,655	246,717	327,936
Exercised	(51,078)	(69,076)	(59,163)
Forfeited	(63,908)	(49,434)	(78,202)
Expired	(157,875)	(170,551)	(182,315)
Outstanding, end of period	393,902	391,108	433,452
Exercisable, end of year	391,108	433,452	425,196
Weighted-average exercise price of (in dollars per share):
Options outstanding, beginning of year	$ 17.05	$ 16.78	$ 15.80
Options granted during the year	$ 18.11	$ 20.41	$ 15.80
Options exercised during the year	$ 17.76	$ 17.09	$ 16.18
Options forfeited during the year	$ 18.58	$ 17.98	$ 16.74
Options expired during the year	$ 15.80	$ 17.99	$ 18.24
Options outstanding, end of year	$ 19.17	$ 17.05	$ 16.78
Weighted-average fair value of options granted during the year (calculated as of the grant date)	$ 4.35	$ 5.08	$ 4.13
Intrinsic value of options exercised during the year	$ 436,547	$ 375,335	$ 439,645
Intrinsic value of options outstanding (calculated as of December 31)	3,209,456	1,665,331	3,132,506
Intrinsic value of options exercisable (calculated as of December 31)	$ 1,665,331	$ 3,132,506	$ 1,186,297
Exercise prices of options outstanding (calculated as of December 31)	$ 19.17	$ 17.05	$ 16.78
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