Employee Benefit Plans (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Components of net periodic benefit cost [Abstract]
Employer contribution to 401 (k) defined contribution plan	$ 88,000	$ 92,000	$ 146,000	$ 147,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized under restricted stock plan (in shares)	100,000		100,000
Number of restricted stock available for grant (in shares)	64,158		64,158
Restricted stock activity [Roll Forward]
Outstanding, beginning of period (in shares)	6,240	7,269	7,172	8,646
Granted (in shares)	3,206	3,027	3,598	3,027
Forfeited (in shares)	0	0	0	(55)
Vested (in shares)	(2,259)	(2,830)	(3,583)	(4,152)
Outstanding, end of period (in shares)	7,187	7,466	7,187	7,466
Weighted average market price [Roll Forward]
Outstanding, beginning of period (in dollars per share)	$ 43.55	$ 35.16	$ 42.02	$ 35.51
Granted (in dollars per share)	$ 53.10	$ 48.21	$ 52.82	$ 48.21
Forfeited (in dollars per share)	$ 0	$ 0	$ 0	$ 37.10
Vested (in dollars per share)	$ 42.06	$ 31.35	$ 40.30	$ 33.26
Outstanding, end of period (in dollars per share)	$ 48.28	$ 41.89	$ 48.28	$ 41.89
Share-based compensation expense	37,000	39,000	73,000	77,000
Directors [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Deferred interest expense	6,000	3,000	11,000	7,000
Pension Plan [Member]
Components of net periodic benefit cost [Abstract]
Service cost	63,000	76,000	153,000	177,000
Interest cost	111,000	79,000	207,000	185,000
Expected return on plan assets	(215,000)	(169,000)	(393,000)	(343,000)
Net amortization and deferral	(43,000)	86,000	25,000	128,000
Net periodic benefit expense (income)	(84,000)	72,000	(8,000)	147,000
Employer contribution to pension plan			300,000
Supplemental Executive Retirement Plans [Member]
Components of net periodic benefit cost [Abstract]
Obligation included in other liabilities	1,122,000		1,122,000		1,046,000
Cost recognized	38,000	36,000	76,000	72,000
Deferred Compensation Plan [Member]
Components of net periodic benefit cost [Abstract]
Obligation included in other liabilities	$ 956,000		$ 956,000		$ 981,000