Employee 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
Pension Benefits
Components of the net periodic benefit cost
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	1,048	1,105	2,114	2,248
Expected return on plan assets	(1,747)	(1,534)	(3,503)	(3,073)
Recognized net actuarial loss	373	299	765	749
Benefit cost (income)	(326)	(130)	(624)	(76)
Postretirement Benefits
Components of the net periodic benefit cost
Service cost	197	184	421	376
Interest cost	338	327	683	660
Amortization of prior service cost	(136)	(136)	(272)	(272)
Recognized net actuarial loss	377	313	737	640
Benefit cost (income)	$ 776	$ 688	$ 1,569	$ 1,404