Pension and Other Postretirement Benefit Plans (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Components of net periodic benefit cost [Abstract]
Defined benefit plans employer contributions toward sponsored pension plans	$ 4,300,000		$ 4,300,000
Anticipated contribution during current fiscal year	6,900,000		6,900,000
Aggregate contribution towards sponsored pension plans	11,200,000		11,200,000
Pension Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost-benefits earned during the period	281,000	511,000	567,000	1,028,000
Interest cost on projected benefit obligation	2,583,000	2,806,000	5,207,000	5,637,000
Expected return on plan assets	(2,936,000)	(2,957,000)	(5,924,000)	(5,945,000)
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	649,000	266,000	1,312,000	536,000
Total benefits cost charged to income	588,000	637,000	1,184,000	1,278,000
Other Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost-benefits earned during the period	139,000	113,000	281,000	228,000
Interest cost on projected benefit obligation	883,000	971,000	1,773,000	1,945,000
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	24,000	(8,000)	50,000	(16,000)
Total benefits cost charged to income	$ 1,046,000	$ 1,076,000	$ 2,104,000	$ 2,157,000