Retirement Benefits (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Pension Benefits
Net Periodic Pension Benefit Cost:
Service cost	$ 1,439,000	$ 1,399,000	$ 4,696,000	$ 4,197,000	$ 6,094,000	$ 5,418,000
Interest cost	2,591,000	2,601,000	7,693,000	7,804,000	10,295,000	10,333,000
Expected return on plan assets	(3,080,000)	(2,785,000)	(9,232,000)	(8,354,000)	(12,017,000)	(10,816,000)
Amortization of prior service cost	133,000	133,000	398,000	398,000	532,000	532,000
Amortization of net actuarial loss	2,052,000	1,374,000	5,952,000	4,121,000	7,325,000	5,120,000
Net periodic benefit cost	3,135,000	2,722,000	9,507,000	8,166,000	12,229,000	10,587,000
Employer contribution			11,100,000
SERP
Net Periodic Pension Benefit Cost:
Service cost	23,000	23,000	39,000	70,000	62,000	87,000
Interest cost	86,000	46,000	197,000	137,000	243,000	176,000
Amortization of prior service cost	(2,000)	(2,000)	(6,000)	(6,000)	(8,000)	(8,000)
Amortization of net actuarial loss	139,000	43,000	291,000	128,000	334,000	152,000
Net periodic benefit cost	246,000	110,000	521,000	329,000	631,000	407,000
OPEB
Net Periodic Pension Benefit Cost:
Service cost	671,000	566,000	1,801,000	1,699,000	2,367,000	2,234,000
Interest cost	962,000	1,096,000	3,027,000	3,287,000	4,123,000	4,370,000
Expected return on plan assets	(1,018,000)	(1,039,000)	(3,101,000)	(3,118,000)	(4,140,000)	(4,079,000)
Amortization of prior service cost	(253,000)	(253,000)	(758,000)	(758,000)	(1,011,000)	(1,011,000)
Amortization of net actuarial loss	311,000	441,000	1,246,000	1,322,000	1,687,000	1,696,000
Net periodic benefit cost	$ 673,000	$ 811,000	$ 2,215,000	$ 2,432,000	$ 3,026,000	$ 3,210,000