Employee Benefit Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Employees' Stock Ownership Plan
Compensation expense	$ 100,000	$ 100,000	$ 100,000
Shares released to participant accounts in each year	20,000	20,000	20,000
Number of allocated shares acquired prior to December 31, 1992	594,504	642,128
Associated fair values of allocated shares acquired prior to December 31, 1992	2,800,000	3,200,000
Shares
Allocated shares	212,146	210,876
Unallocated shares		20,000
Total (in shares)	212,146	230,876
Fair Value
Allocated shares, Fair Value	986,000	1,054,000
Unallocated shares, Fair Value		100,000
Total, Fair Value	986,000	1,154,000
Profit Sharing Plan
Vesting period	5 years
Expenses related to employee benefit plans
Employee benefits	3,024,000	2,985,000	2,859,000
Interest on employee stock ownership plan debt	5,000	11,000	18,000
Total employer contributions	3,029,000	2,996,000	2,877,000
Deferred compensation plans for deferral of performance bonuses
Deferred compensation expense	200,000	200,000	300,000
Deferred compensation liability	$ 4,500,000	$ 4,300,000	$ 4,300,000