Retirement and Postretirement Benefits other than Pension Plans (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost
Interest cost	$ 1,209	$ 1,188	$ 2,417	$ 2,376
Expected return on plan assets	(1,334)	(1,197)	(2,667)	(2,394)
Amortization of net actuarial loss	619	519	1,238	1,038
Total net periodic pension expense	494	510	988	1,020
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost
Service cost	15	17	29	34
Interest cost	257	243	515	487
Amortization of Net Gain	0	(3)	0	(6)
Amortization of curtailment gain	(61)	(61)	(122)	(122)
Total net postretirement benefit expense	$ 211	$ 196	$ 422	$ 393