Benefit Plans (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Components of Net Periodic Benefit Cost [Abstract]
Estimate of future pension plan contributions	$ 10,000,000
Pension and Supplemental Executive Retirement Plans [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost	2,717,000	2,390,000
Interest Cost	3,799,000	4,106,000
Expected Return on Assets	(5,038,000)	(4,516,000)
Recognized net actuarial loss	1,516,000	1,478,000
Amortization of prior service cost	125,000	161,000
Net periodic benefit cost	3,119,000	3,619,000
Other Postretirement Benefits [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost	194,000	309,000
Interest Cost	154,000	292,000
Expected Return on Assets	(920,000)	(790,000)
Recognized net actuarial loss	0	210,000
Amortization of prior service cost	(1,663,000)	(1,554,000)
Net periodic benefit cost	$ (2,235,000)	$ (1,533,000)