Pension and Other Post-Retirement Benefit Plans (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Pension Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	9,272,000	9,290,000	18,544,000	18,581,000
Expected return on plan assets	(9,970,000)	(9,757,000)	(19,940,000)	(19,514,000)
Amortization of prior service cost	0	0	0	0
Amortization of net loss	2,670,000	675,000	5,340,000	1,350,000
Net periodic benefit cost	1,972,000	208,000	3,944,000	417,000
Employer contributions	2,800,000		3,600,000
Estimated future employer contributions in current fiscal year	21,400,000		21,400,000
Post-Retirement Healthcare Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	67,000	62,000	134,000	124,000
Interest cost	95,000	97,000	190,000	194,000
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	(1,388,000)	(1,388,000)	(2,776,000)	(2,776,000)
Amortization of net loss	108,000	132,000	216,000	264,000
Net periodic benefit cost	$ (1,118,000)	$ (1,097,000)	$ (2,236,000)	$ (2,194,000)