Postretirement Benefits Other Than Pensions (Details 2) (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]
Weighted-average assumptions used to determine the benefit obligation
Discount rate	4.21%	5.29%	5.77%
Measurement date	2011-12-31	2010-12-31	2009-12-31
Weighted average assumptions used in determining net periodic pension expense
Discount rate	5.29%	5.77%	6.10%
Measurement date	2011-12-31	2010-12-31	2009-12-31
Expected future benefit payments
2012	$ 1,055
2013	1,125
2014	1,196
2015	1,218
2016	1,261
2017 - 2021	$ 6,611