Consolidated Statements Of Income And Earnings Reinvested In The Business (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
INCOME
Operating Revenues	$ 596,127	$ 756,242	$ 1,120,036	$ 1,306,314
Operating Expenses
Purchased Gas	190,600	322,772	317,690	490,378
Operation and Maintenance	133,245	137,716	245,827	245,562
Property, Franchise and Other Taxes	24,916	25,704	45,845	46,630
Depreciation, Depletion and Amortization	82,687	89,975	185,433	183,089
Impairment of Oil and Gas Producing Properties	120,348	0	120,348	0
Total Operating Expenses	551,796	576,167	915,143	965,659
Operating Income	44,331	180,075	204,893	340,655
Other Income (Expense):
Interest Income	46	249	1,303	951
Other Income	1,388	5,123	2,571	5,352
Interest Expense on Long-Term Debt	(22,376)	(22,766)	(44,687)	(45,651)
Other Interest Expense	(1,584)	(1,375)	(2,375)	(2,324)
Income Before Income Taxes	21,805	161,306	161,705	298,983
Income Tax Expense	5,136	66,095	60,296	121,520
Net Income Available for Common Stock	16,669	95,211	101,409	177,463
EARNINGS REINVESTED IN THE BUSINESS
Balance at Beginning of Period	1,666,659	1,493,466	1,614,361	1,442,617
Beginning Retained Earnings Unappropriated And Current Period Net Income Loss	1,683,328	1,588,677	1,715,770	1,620,080
Dividends on Common Stock	(32,488)	(31,493)	(64,930)	(62,896)
Balance at March 31	$ 1,650,840	$ 1,557,184	$ 1,650,840	$ 1,557,184
Earnings Per Common Share, Basic:
Net Income Available for Common Stock (in dollars per share)	$ 0.20	$ 1.14	$ 1.20	$ 2.12
Earnings Per Common Share, Diluted:
Net Income Available for Common Stock (in dollars per share)	$ 0.20	$ 1.12	$ 1.19	$ 2.09
Weighted Average Common Shares Outstanding:
Used in Basic Calculation (shares)	84,317,508	83,856,120	84,262,471	83,781,085
Used in Diluted Calculation (shares)	85,133,142	84,837,123	85,175,961	84,787,610
Dividends Per Common Share:
Dividends Declared (in dollars per share)	$ 0.385	$ 0.375	$ 0.770	$ 0.750