Employee Benefit Plans (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Components of net periodic benefit cost [Abstract]
Employer contribution to 401 (k) defined contribution plan	$ 93,000	$ 88,000	$ 155,000	$ 146,000
Directors [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Deferred interest expense	5,000	6,000	12,000	11,000
Pension Plan [Member]
Components of net periodic benefit cost [Abstract]
Service cost	78,000	63,000	132,000	153,000
Interest cost	90,000	111,000	153,000	207,000
Expected return on plan assets	(172,000)	(215,000)	(290,000)	(393,000)
Net amortization and deferral	45,000	(43,000)	76,000	25,000
Net periodic cost (benefit)	41,000	(84,000)	71,000	(8,000)
Employer contribution to pension plan			400,000
Supplemental Executive Retirement Plans [Member]
Components of net periodic benefit cost [Abstract]
Obligation included in other liabilities	1,269,000		1,269,000		$ 1,198,000
Cost recognized	36,000	$ 38,000	71,000	$ 76,000
Deferred Compensation Plan [Member]
Components of net periodic benefit cost [Abstract]
Obligation included in other liabilities	$ 945,000		$ 945,000		$ 969,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)	100,000		100,000
Number of shares available for grant (in shares)	60,662		60,662
Restricted stock activity [Roll Forward]
Outstanding, beginning of period (in shares)	6,998	6,240	6,971	7,172
Granted (in shares)	3,340	3,206	3,496	3,598
Forfeited (in shares)	0	0	0	0
Vested (in shares)	(3,320)	(2,259)	(3,449)	(3,583)
Outstanding, end of period (in shares)	7,018	7,187	7,018	7,187
Weighted average market price [Roll Forward]
Outstanding, beginning of period (in dollars per share)	$ 48.61	$ 43.55	$ 48.55	$ 42.02
Granted (in dollars per share)	49.87	53.10	50.02	52.82
Forfeited (in dollars per share)	0	0	0	0
Vested (in dollars per share)	45.62	42.06	45.80	40.30
Outstanding, end of period (in dollars per share)	$ 50.63	$ 48.28	$ 50.63	$ 48.28
Share-based compensation expense	$ 43,000	$ 37,000	$ 85,000	$ 73,000
Compensation cost related to nonvested awards that has not yet been recognized	$ 355,000		$ 355,000
Compensation cost related to nonvested awards, period to be recognized			2 years 9 months 29 days