Employee Benefit Plans Summary of Pension Plan and Postretirement Plan Net Periodic Benefit Cost (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Pension Plan [Member]
Define Benefit Plan Disclosure [Line Items]
Service cost	$ 51	[1]	$ 39	[1]	$ 102	[1]	$ 78	[1]
Interest cost	772		806		1,544		1,612
Expected return on plan assets	(800)		(808)		(1,600)		(1,616)
Net amortization and deferral	596		420		1,192		840
Net periodic benefit cost	619		457		1,238		914
Postretirement Plan [Member]
Define Benefit Plan Disclosure [Line Items]
Service cost	57		53		114		106
Interest cost	81		87		162		174
Expected return on plan assets	0		(1)		0		(2)
Net accretion and deferral	(91)		(91)		(182)		(182)
Net periodic benefit cost	$ 47		$ 48		$ 94		$ 96

[1] The Pension Plan service cost recorded for the three and six months ended June 30, 2013 and 2012, respectively, was related to administrative costs associated with the plan and was not due to the accrual of additional participant benefits.