Retirement and Postretirement Benefits Other than Pension Plans (Details 1) (Other Postretirement Benefit Plans, Defined Benefit [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Other Postretirement Benefit Plans, Defined Benefit [Member]
Net periodic benefit expense components
Service cost	$ 15	$ 15	$ 29	$ 29
Interest cost	253	257	507	515
Amortization of net actuarial loss	176		352
Amortization of prior service credit	(109)		(217)
Amortization of curtailment gain	(22)	(61)	(44)	(122)
Total net postretirement benefit expense	$ 313	$ 211	$ 627	$ 422