Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Pension Benefits
Components of the net periodic benefit cost
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	1,105	1,163	2,248	2,289
Expected return on plan assets	(1,534)	(1,558)	(3,073)	(3,118)
Recognized net actuarial loss	299	247	749	470
Benefit cost (income)	(130)	(148)	(76)	(359)
Postretirement Benefits
Components of the net periodic benefit cost
Service cost	184	136	376	277
Interest cost	327	325	660	643
Amortization of prior service cost	(136)	(136)	(272)	(272)
Recognized net actuarial loss	313	242	640	451
Benefit cost (income)	$ 688	$ 567	$ 1,404	$ 1,099