Benefit Plans (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Pension Benefits [Member]
Components of net periodic benefit cost
Service Cost	$ 1,531	$ 1,480	$ 3,062	$ 2,959
Interest Cost	2,860	2,800	5,720	5,600
Expected return on assets	(3,328)	(3,015)	(6,656)	(6,029)
Amortization of unrecognized prior service costs	98	98	196	197
Cumulative net loss	1,780	1,427	3,560	2,854
Net periodic benefit (cost)	2,941	2,790	5,882	5,581
Postretirement Benefit [Member]
Components of net periodic benefit cost
Service Cost	14	15	28	30
Interest Cost	221	240	442	480
Amortization of unrecognized prior service costs	0	0	0	0
Cumulative net loss	28	4	56	8
Net periodic benefit (cost)	$ 263	$ 259	$ 526	$ 518