Benefit Plans (Details) (USD $)	3 Months Ended			9 Months Ended		3 Months Ended		9 Months Ended
	Jun. 30, 2013	Sep. 30, 2013 Pension and Supplemental Executive Retirement Plans [Member]	Sep. 30, 2012 Pension and Supplemental Executive Retirement Plans [Member]	Sep. 30, 2013 Pension and Supplemental Executive Retirement Plans [Member]	Sep. 30, 2012 Pension and Supplemental Executive Retirement Plans [Member]	Sep. 30, 2013 Other Postretirement Benefits [Member]	Sep. 30, 2012 Other Postretirement Benefits [Member]	Sep. 30, 2013 Other Postretirement Benefits [Member]	Sep. 30, 2012 Other Postretirement Benefits [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost		$ 2,835,000	$ 2,416,000	$ 8,504,000	$ 7,247,000	$ 202,000	$ 307,000	$ 609,000	$ 920,000
Interest Cost		3,823,000	4,120,000	11,467,000	12,361,000	155,000	286,000	464,000	857,000
Expected Return on Assets		(5,035,000)	(4,553,000)	(15,108,000)	(13,659,000)	(919,000)	(791,000)	(2,759,000)	(2,372,000)
Recognized net actuarial loss		1,536,000	1,457,000	4,609,000	4,372,000	0	199,000	0	599,000
Amortization of prior service cost		125,000	166,000	377,000	499,000	(1,663,000)	(1,554,000)	(4,987,000)	(4,663,000)
Net periodic benefit cost		3,284,000	3,606,000	9,849,000	10,820,000	(2,225,000)	(1,553,000)	(6,673,000)	(4,659,000)
Pension plan contribution	$ 10,000,000