Consolidated Statements Of Income And Earnings Reinvested In The Business (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
INCOME
Operating Revenues	$ 348,368	$ 335,617	$ 1,292,944	$ 1,159,943
Operating Expenses:
Purchased Gas	46,135	23,477	264,349	147,168
Property, Franchise and Other Taxes	21,447	20,261	64,368	61,923
Depreciation, Depletion and Amortization	55,617	58,802	168,812	193,300
Impairment of Oil and Gas Producing Properties	0	82,658	0	915,552
Total Operating Expenses	225,014	290,456	827,494	1,657,706
Operating Income (Loss)	123,354	45,161	465,450	(497,763)
Other Income (Expense):
Interest Income	853	564	2,844	2,640
Other Income	1,370	1,519	4,728	7,173
Interest Expense on Long-Term Debt	(29,225)	(28,897)	(87,241)	(88,263)
Other Interest Expense	(846)	(1,321)	(2,680)	(3,938)
Income (Loss) Before Income Taxes	95,506	17,026	383,101	(580,151)
Income Tax Expense (Benefit)	35,792	8,740	145,195	(251,641)
Net Income (Loss) Available for Common Stock	59,714	8,286	237,906	(328,510)
EARNINGS REINVESTED IN THE BUSINESS
Balance at Beginning of Period	817,348	699,399	676,361	1,103,200
Beginning Retained Earnings Unappropriated And Current Period Net Income Loss	877,062	707,685	914,267	774,690
Dividends on Common Stock	(35,469)	(34,404)	(104,590)	(101,409)
Cumulative Effect of Adoption of Authoritative Guidance for Stock-Based Compensation	0	0	31,916	0
Balance at June 30	$ 841,593	$ 673,281	$ 841,593	$ 673,281
Earnings Per Common Share, Basic:
Net Income (Loss) Available for Common Stock (in dollars per share)	$ 0.70	$ 0.10	$ 2.79	$ (3.87)
Earnings Per Common Share, Diluted:
Net Income (Loss) Available for Common Stock (in dollars per share)	$ 0.69	$ 0.10	$ 2.77	$ (3.87)
Weighted Average Common Shares Outstanding:
Used in Basic Calculation (shares)	85,422,313	84,917,664	85,315,154	84,791,447
Used in Diluted Calculation (shares)	86,064,464	85,470,216	85,950,742	84,791,447
Dividends Per Common Share:
Dividends Declared (in dollars per share)	$ 0.415	$ 0.405	$ 1.225	$ 1.195
Utility and Energy Marketing [Member]
INCOME
Operating Revenues	$ 146,360	$ 123,976	$ 663,029	$ 540,981
Operating Expenses:
Operation and Maintenance	44,467	46,616	158,796	151,474
Exploration and Production and Other [Member]
INCOME
Operating Revenues	151,925	158,578	473,617	456,032
Operating Expenses:
Operation and Maintenance	34,098	35,427	102,153	123,965
Pipeline and Storage and Gathering [Member]
INCOME
Operating Revenues	50,083	53,063	156,298	162,930
Operating Expenses:
Operation and Maintenance	$ 23,250	$ 23,215	$ 69,016	$ 64,324