Retirement Plan (Net Periodic Pension Expense) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Defined Benefit Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefit earned during the period	$ 509	$ 1,268	$ 679	$ 2,535
Interest cost on projected benefit obligations	1,061	1,281	2,052	2,562
Expected return on plan assets	(949)	(1,339)	(1,899)	(2,678)
Amortization of prior service cost	50	97	67	195
Amortization of net loss	620	533	1,103	1,066
Estimated effect of curtailment	674	0	899	0
Net periodic pension expense	1,965	1,840	2,901	3,680
Other Post-Retirement Healthcare and Other Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefit earned during the period	475		950
Interest cost on projected benefit obligations	875		1,750
Amortization of prior service cost	(550)		(1,100)
Amortization of net loss	75		150
Net periodic pension expense	$ 875		$ 1,750