Employee Benefit Plans Summary of Pension Plan and Postretirement Plan Net Periodic Benefit Cost (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Pension Plan [Member]
Define Benefit Plan Disclosure [Line Items]
Service cost	$ 39	[1]	$ 15	[1]	$ 117	[1]	$ 45	[1]
Interest cost	806		853		2,418		2,559
Expected return on plan assets	(808)		(837)		(2,424)		(2,511)
Net amortization and deferral	420		72		1,260		216
Net periodic benefit cost	457		103		1,371		309
Postretirement Plan [Member]
Define Benefit Plan Disclosure [Line Items]
Service cost	53		50		159		151
Interest cost	87		107		261		321
Expected return on plan assets	(1)		(1)		(3)		(3)
Net accretion and deferral	(91)		(91)		(273)		(273)
Net periodic benefit cost	$ 48		$ 65		$ 144		$ 196

[1] The net periodic benefit cost for the Corporation’s Pension Plan, as determined by consulting actuaries, consisted of the following components for the three and nine months ended September 30: Three months ended September 30 Nine months ended September 30 2012 2011 2012 2011 (in thousands)Service cost (1)$39 $15 $117 $45Interest cost806 853 2,418 2,559Expected return on plan assets(808) (837) (2,424) (2,511)Net amortization and deferral420 72 1,260 216Net periodic benefit cost$457 $103 $1,371 $309 (1)The Pension Plan service cost recorded for the three and nine months ended September 30, 2012 and 2011, respectively, was related to administrative costs associated with the plan and was not due to the accrual of additional participant benefits.