Components of Net Periodic Pension Benefit Cost (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net pension cost of plans
Service cost	$ 86	$ 117
Interest cost	1,809	1,960
Expected return on plan assets	(1,846)	(1,683)
Amortization of prior service cost	0	1
Recognized actuarial loss	1,672	1,500
Net periodic benefit cost	$ 1,721	$ 1,895