Retirement Benefits (Details) (USD $)	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 31, 2013	Sep. 30, 2013 Pension Benefits	Sep. 30, 2012 Pension Benefits	Sep. 30, 2013 Pension Benefits	Sep. 30, 2012 Pension Benefits	Sep. 30, 2013 Pension Benefits	Sep. 30, 2012 Pension Benefits	Sep. 30, 2013 SERP	Sep. 30, 2012 SERP	Sep. 30, 2013 SERP	Sep. 30, 2012 SERP	Sep. 30, 2013 SERP	Sep. 30, 2012 SERP	Sep. 30, 2013 OPEB	Sep. 30, 2012 OPEB	Sep. 30, 2013 OPEB	Sep. 30, 2012 OPEB	Sep. 30, 2013 OPEB	Sep. 30, 2012 OPEB
Net Periodic Pension Benefit Cost:
Service cost		$ 1,863,000	$ 1,439,000	$ 5,590,000	$ 4,696,000	$ 7,156,000	$ 6,094,000	$ 34,000	$ 23,000	$ 101,000	$ 39,000	$ 114,000	$ 62,000	$ 735,000	$ 671,000	$ 2,206,000	$ 1,801,000	$ 2,806,000	$ 2,367,000
Interest cost		2,516,000	2,591,000	7,547,000	7,693,000	10,111,000	10,295,000	78,000	86,000	236,000	197,000	301,000	243,000	957,000	962,000	2,870,000	3,027,000	3,879,000	4,123,000
Expected return on plan assets		(3,107,000)	(3,080,000)	(9,321,000)	(9,232,000)	(12,398,000)	(12,017,000)							(1,088,000)	(1,018,000)	(3,265,000)	(3,101,000)	(4,299,000)	(4,140,000)
Amortization of prior service cost		133,000	133,000	399,000	398,000	531,000	532,000	(2,000)	(2,000)	(6,000)	(6,000)	(8,000)	(8,000)	(253,000)	(253,000)	(758,000)	(758,000)	(1,011,000)	(1,011,000)
Amortization of net actuarial loss		2,611,000	2,052,000	7,834,000	5,952,000	9,818,000	7,325,000	142,000	139,000	426,000	291,000	523,000	334,000	565,000	311,000	1,696,000	1,246,000	2,112,000	1,687,000
Net periodic benefit cost		4,016,000	3,135,000	12,049,000	9,507,000	15,218,000	12,229,000	252,000	246,000	757,000	521,000	930,000	631,000	916,000	673,000	2,749,000	2,215,000	3,487,000	3,026,000
Employer contribution	$ 16,200,000