Quarterly Financial Data (Schedule Of Quarterly Financial Information) (Details) (USD $)	3 Months Ended										12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014		Dec. 31, 2013	Sep. 30, 2013		Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Operating Revenues	$ 366,623,000	$ 440,144,000	$ 756,242,000		$ 550,072,000	$ 338,863,000		$ 440,008,000	$ 597,826,000	$ 452,854,000	$ 2,113,081,000	$ 1,829,551,000	$ 1,626,853,000
Operating Income	102,004,000	127,013,000	180,075,000		160,581,000	96,636,000		127,004,000	162,991,000	131,207,000	569,673,000	517,838,000	448,049,000
Net Income Available for Common Stock	57,431,000	64,520,000	95,210,000	[1]	82,252,000	47,842,000	[2]	58,495,000	85,720,000	67,944,000	299,413,000	260,001,000	220,077,000
Earnings per Common Share, Basic	$ 0.68	$ 0.77	$ 1.14		$ 0.98	$ 0.57		$ 0.70	$ 1.03	$ 0.81	$ 3.57	$ 3.11	$ 2.65
Earnings per Common Share, Diluted	$ 0.68	$ 0.76	$ 1.12		$ 0.97	$ 0.57		$ 0.69	$ 1.02	$ 0.81	$ 3.52	$ 3.08	$ 2.63
Corporate Category [Member]
Death Benefit Gain on Life Insurance Proceeds									3,600,000
Utility [Member]
Net Income Available for Common Stock											64,059,000	65,686,000	58,590,000
Rate proceeding refund provision						$ 4,700,000

[1] Includes $3.6 million of income associated with a death benefit gain on life insurance proceeds recorded in the Corporate category.

[2] Includes a $4.7 million refund provision recorded in the Utility segment related to various issues raised in Distribution Corporation’s rate proceeding in New York.