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]
Pension plan contribution	$ 10,000,000
Pension and Supplemental Executive Retirement Plans [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost	2,952,000	2,441,000	5,669,000	4,831,000
Interest Cost	3,845,000	4,135,000	7,644,000	8,241,000
Expected Return on Assets	(5,034,000)	(4,590,000)	(10,072,000)	(9,106,000)
Recognized net actuarial loss	1,557,000	1,437,000	3,073,000	2,915,000
Amortization of prior service cost	127,000	172,000	252,000	333,000
Net periodic benefit cost	3,447,000	3,595,000	6,566,000	7,214,000
Other Postretirement Benefits [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost	212,000	304,000	406,000	613,000
Interest Cost	156,000	280,000	309,000	571,000
Expected Return on Assets	(920,000)	(791,000)	(1,840,000)	(1,581,000)
Recognized net actuarial loss	0	189,000	0	400,000
Amortization of prior service cost	(1,662,000)	(1,555,000)	(3,324,000)	(3,109,000)
Net periodic benefit cost	$ (2,214,000)	$ (1,573,000)	$ (4,449,000)	$ (3,106,000)