Benefit Plans (Details) (Postretirement Benefit Cost [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Postretirement Benefit Cost [Member]
Components of net periodic cost:
Service cost	$ 2	$ 2	$ 6	$ 6
Interest cost	9	9	27	27
Amortization of (gain) loss	3		9
Net periodic postretirement benefit cost	$ 14	$ 11	$ 42	$ 33