Consolidated Statements Of Income And Earnings Reinvested In The Business (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
INCOME
Operating Revenues	$ 449,132	$ 596,127	$ 824,327	$ 1,120,036
Operating Expenses:
Purchased Gas	81,623	190,600	123,691	317,690
Property, Franchise and Other Taxes	21,305	24,916	41,662	45,845
Depreciation, Depletion and Amortization	63,947	82,687	134,498	185,433
Impairment of Oil and Gas Producing Properties	397,443	120,348	832,894	120,348
Total Operating Expenses	686,132	551,796	1,367,251	915,143
Operating Income (Loss)	(237,000)	44,331	(542,924)	204,893
Other Income (Expense):
Interest Income	278	46	2,077	1,303
Other Income	3,236	1,388	5,654	2,571
Interest Expense on Long-Term Debt	(28,994)	(22,376)	(59,366)	(44,687)
Other Interest Expense	(1,237)	(1,584)	(2,617)	(2,375)
Income (Loss) Before Income Taxes	(263,717)	21,805	(597,176)	161,705
Income Tax Expense (Benefit)	(116,030)	5,136	(260,380)	60,296
Net Income (Loss) Available for Common Stock	(147,687)	16,669	(336,796)	101,409
EARNINGS REINVESTED IN THE BUSINESS
Balance at Beginning of Period	880,619	1,666,659	1,103,200	1,614,361
Beginning Retained Earnings Unappropriated And Current Period Net Income Loss	732,932	1,683,328	766,404	1,715,770
Dividends on Common Stock	(33,533)	(32,488)	(67,005)	(64,930)
Balance at March 31	$ 699,399	$ 1,650,840	$ 699,399	$ 1,650,840
Earnings Per Common Share, Basic:
Net Income (Loss) Available for Common Stock (in dollars per share)	$ (1.74)	$ 0.20	$ (3.97)	$ 1.20
Earnings Per Common Share, Diluted:
Net Income (Loss) Available for Common Stock (in dollars per share)	$ (1.74)	$ 0.20	$ (3.97)	$ 1.19
Weighted Average Common Shares Outstanding:
Used in Basic Calculation (shares)	84,806,982	84,317,508	84,728,680	84,262,471
Used in Diluted Calculation (shares)	84,806,982	85,133,142	84,728,680	85,175,961
Dividends Per Common Share:
Dividends Declared (in dollars per share)	$ 0.395	$ 0.385	$ 0.790	$ 0.770
Utility and Energy Marketing [Member]
INCOME
Operating Revenues	$ 248,173	$ 374,141	$ 417,005	$ 640,380
Operating Expenses:
Operation and Maintenance	57,309	62,764	104,858	112,461
Exploration and Production and Other [Member]
INCOME
Operating Revenues	144,570	166,139	297,454	371,917
Operating Expenses:
Operation and Maintenance	42,964	50,906	88,539	94,401
Pipeline and Storage and Gathering [Member]
INCOME
Operating Revenues	56,389	55,847	109,868	107,739
Operating Expenses:
Operation and Maintenance	$ 21,541	$ 19,575	$ 41,109	$ 38,965