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
	Mar. 31, 2012	Mar. 31, 2011
Other Postretirement Benefit Plans, Defined Benefit [Member]
Net periodic benefit expense components
Service cost	$ 14	$ 14
Interest cost	254	258
Amortization of net actuarial loss	176
Amortization of prior service credit	(108)
Amortization of curtailment gain	(22)	(61)
Total net postretirement benefit expense	$ 314	$ 211