Retirement Plans (Details) (Pension Plans, Defined Benefit [Member], USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 605	$ 473	$ 1,818	$ 1,417
Interest cost	725	720	2,178	2,147
Expected return on plan assets	(371)	(332)	(1,111)	(986)
Amortization of prior service cost	811	753	2,434	2,259
Amortization of actuarial loss	336	118	1,008	354
Defined benefit expense	$ 2,106	$ 1,732	$ 6,327	$ 5,191