Components of Net Periodic Pension Benefit Cost (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net pension cost of plans
Service cost	$ 86	$ 117	$ 257	$ 350
Interest cost	1,809	1,960	5,428	5,881
Expected return on plan assets	(1,846)	(1,683)	(5,537)	(5,050)
Amortization of prior service cost	0	1	0	3
Recognized actuarial loss	1,672	1,500	5,015	4,500
Net periodic benefit cost	$ 1,721	$ 1,895	$ 5,163	$ 5,684