Employee Benefit and Deferred Compensation Plans - (Details Textual) (USD $)	3 Months Ended
	Mar. 31, 2015 Point	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Retiring age limit, minimum	55 years
Retiring age limit, maximum	65 years
Eligible employee years of service (in years)	15 years
Number of points for eligibility	70
Minimum Eligible Age for Medicare Coverage	65 years
Life Insurance Coverage Face Value	$ 5
Life Insurance Coverage Age Maximum	70 years
Life Insurance Coverage at Retiree Expense after Age	70 years
Option expiration period (in years)	10 years
Award vesting period (in years)	3 years
Option exercisable period (in years)	3 years
Treasury shares reissued (shares)	59,792
Total stock-based compensation expense	$ 864,000	$ 871,000
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period	1 year