Employee Benefit Plans Summary of Pension Plan and Postretirement Plan Net Periodic Benefit Cost (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Pension Plan [Member]
Define Benefit Plan Disclosure [Line Items]
Service cost	$ 51	[1]	$ 39	[1]
Interest cost	772		806
Expected return on plan assets	(800)		(808)
Net amortization and deferral	596		420
Net periodic benefit cost	619		457
Postretirement Plan [Member]
Define Benefit Plan Disclosure [Line Items]
Service cost	57		53
Interest cost	81		87
Expected return on plan assets	0		(1)
Net accretion and deferral	(91)		(91)
Net periodic benefit cost	$ 47		$ 48

[1] The net periodic benefit cost for the Corporation’s Pension Plan, as determined by consulting actuaries, consisted of the following components: Three months ended March 31 2013 2012 (in thousands)Service cost (1)$51 $39Interest cost772 806Expected return on plan assets(800) (808)Net amortization and deferral596 420Net periodic benefit cost$619 $457 (1)The Pension Plan service cost recorded for the three months ended March 31, 2013 and 2012, respectively, was related to administrative costs associated with the plan and was not due to the accrual of additional participant benefits.