Components of Net Periodic Pension Benefit Cost (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
Net pension cost of plans
Service cost	$ 86	$ 117	$ 171	$ 233
Interest cost	1,809	1,960	3,618	3,920
Expected return on plan assets	(1,846)	(1,683)	(3,691)	(3,366)
Amortization of prior service cost	0	1	0	2
Recognized actuarial loss	1,672	1,500	3,344	3,000
Net periodic benefit cost	$ 1,721	$ 1,895	$ 3,442	$ 3,789