Employee Benefit Plans (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Components of net periodic benefit cost [Abstract]
Employer contribution to 401 (k) defined contribution plan	$ 56,000	$ 52,000
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
Number of restricted stock available for grant (in shares)	70,783
Restricted stock activity [Roll Forward]
Outstanding, beginning of period	8,646	9,921
Granted	0	0
Forfeited	(55)	0
Vested	(1,322)	(3,641)
Outstanding, end of period	7,269	6,280
Weighted average market price [Roll Forward]
Outstanding, beginning of period	$ 35.51	$ 29.37
Granted	$ 0	$ 0
Forfeited	$ 37.10	$ 0
Vested	$ 37.35	$ 25.06
Outstanding, end of period	$ 35.16	$ 28.15
Directors [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Deferred interest expense	4,000	4,000
Pension Plan [Member]
Components of net periodic benefit cost [Abstract]
Service cost	101,000	113,000
Interest cost	106,000	139,000
Expected return on plan assets	(174,000)	(206,000)
Net amortization and deferral	42,000	16,000
Net periodic benefit cost	75,000	62,000
Expected employer contribution to pension plan	500,000
Supplemental Executive Retirement Plans [Member]
Components of net periodic benefit cost [Abstract]
Obligation included in other liabilities	937,000		901,000
Cost recognized	36,000	23,000
Deferred Compensation Plan [Member]
Components of net periodic benefit cost [Abstract]
Obligation included in other liabilities	$ 967,000		$ 1,001,000