Retirement Plans (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 Plan Disclosure [Line Items]
Service cost	$ 635	$ 606	$ 1,271	$ 1,213
Interest cost	675	727	1,352	1,453
Expected return on plan assets	(358)	(370)	(717)	(740)
Amortization of prior service cost	493	811	986	1,623
Amortization of actuarial loss	188	336	377	672
Defined benefit expense	$ 1,633	$ 2,110	$ 3,269	$ 4,221