Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Pension Benefits
Components of the net periodic benefit cost
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	1,124	1,145	3,372	3,434
Expected return on plan assets	(1,536)	(1,559)	(4,609)	(4,677)
Recognized net actuarial loss	374	235	1,123	705
Benefit cost (income)	(38)	(179)	(114)	(538)
Postretirement Benefits
Components of the net periodic benefit cost
Service cost	188	139	564	416
Interest cost	329	321	989	964
Amortization of prior service cost	(135)	(136)	(407)	(407)
Recognized net actuarial loss	320	225	960	676
Benefit cost (income)	$ 702	$ 549	$ 2,106	$ 1,649