Employee Benefits (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Employee Stock Ownership Plan and Trust (ESOP) [Member]
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Shares contributed to ESOP (in shares)	182,000
Shares released from trust (in shares)	182,500
Total balance of share in the ESOP (in shares)	430
Pension benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 45,000	$ 33,000
Interest cost	59,000	47,000
Amortization of prior service cost	7,000	28,000
Actuarial net loss	174,000	65,000
Net periodic benefit cost (credit)	285,000	173,000
Postretirement benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1,000	1,000
Interest cost	9,000	25,000
Amortization of prior service cost	(1,087,000)	(1,224,000)
Actuarial net loss	611,000	648,000
Net periodic benefit cost (credit)	(466,000)	(550,000)
Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract]
Contributions by employer on behalf of employees	300,000
Estimated future employer contributions in current fiscal year	1,900,000
Supplemental Executive Retirement Plan [Member]
Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract]
Employer discretionary contribution amount	$ 500,000