Retirement and Postretirement Benefits other than Pension Plans (Details) (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, Net Periodic Benefit Cost
Interest cost	$ 1,208	$ 1,309	$ 3,625	$ 3,685
Expected return on plan assets	(1,333)	(1,245)	(4,000)	(3,639)
Amortization of net actuarial loss	619	894	1,857	1,932
Total net periodic pension expense	494	958	1,482	1,978
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost
Service cost	14	17	43	51
Interest cost	257	244	772	731
Amortization of Net Gain	0	(4)	0	(10)
Amortization of curtailment gain	(61)	(61)	(183)	(183)
Total net postretirement benefit expense	$ 210	$ 196	$ 632	$ 589