Postretirement Benefits Other Than Pensions (Details 1) (Other Postretirement Benefit Plans, Defined Benefit [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost
Service cost	$ 46	$ 51	$ 62
Interest cost	1,052	1,045	966
Recognized net actuarial gain (loss)	2		(183)
Amortization of prior service cost	(434)
Amortization of curtailment gain	(244)	(244)	(244)
Net postretirement benefit expense	$ 422	$ 852	$ 601