Employee Benefit and Deferred Compensation Plans - (Details Textual)	3 Months Ended
	Mar. 31, 2017 USD ($) point shares	Mar. 31, 2016 USD ($) shares
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 | point	70
Minimum eligible age for medicare coverage	65 years
Life insurance coverage face value | $	$ 5,000
Life insurance coverage age (until)	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
Stock options granted (shares) | shares	0	0
Treasury shares reissued (shares) | shares	62,434
Total stock-based compensation expense | $	$ 1,174,000	$ 859,000
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award requisite service period (in years)	1 year