Pension and Other Postretirement Benefit Plans (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Components of net periodic benefit cost [Abstract]
Defined benefit plans employer contributions toward sponsored pension plans	$ 5,800,000		$ 5,800,000
Anticipated contribution during current fiscal year	8,700,000		8,700,000
Aggregate contribution towards sponsored pension plans	14,500,000		14,500,000
Pension Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost-benefits earned during the period	511,000	385,000	1,028,000	769,000
Interest cost on projected benefit obligation	2,806,000	3,015,000	5,637,000	6,020,000
Expected return on plan assets	(2,957,000)	(3,247,000)	(5,945,000)	(6,482,000)
Amortization of net transition (asset) obligation	0	0	0	0
Amortization of prior service (credit) cost	11,000	11,000	22,000	22,000
Amortization of (gain)/loss	266,000	0	536,000	0
Total benefits cost charged to income	637,000	164,000	1,278,000	329,000
Other Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost-benefits earned during the period	113,000	130,000	228,000	259,000
Interest cost on projected benefit obligation	971,000	1,079,000	1,945,000	2,157,000
Expected return on plan assets	0	0	0	0
Amortization of net transition (asset) obligation	0	0	0	0
Amortization of prior service (credit) cost	0	0	0	0
Amortization of (gain)/loss	(8,000)	0	(16,000)	0
Total benefits cost charged to income	$ 1,076,000	$ 1,209,000	$ 2,157,000	$ 2,416,000