Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Components of net periodic benefit cost [Abstract]
Contribution made to pension and postretirement plans			$ 0
Pension Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	20	12	34	24
Interest cost	322	365	637	730
Expected return on plan assets	(597)	(474)	(1,095)	(948)
Amortization of net loss (gain)	111	102	258	204
Amortization of prior service credit	0	0	0	0
Net periodic expense (benefit)	(144)	5	(166)	10
Other Postretirement Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	14	8	26	16
Interest cost	27	25	51	51
Expected return on plan assets	(126)	(112)	(249)	(225)
Amortization of net loss (gain)	(10)	(5)	(25)	(10)
Amortization of prior service credit	(65)	(65)	(131)	(131)
Net periodic expense (benefit)	$ (160)	$ (149)	$ (328)	$ (299)