Consolidated Statements Of Income And Earnings Reinvested In The Business (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
INCOME
Operating Revenues	$ 357,200	$ 342,912	$ 1,399,991	$ 1,303,473
Operating Expenses:
Property, Franchise and Other Taxes	21,506	20,595	68,046	64,245
Depreciation, Depletion and Amortization	71,072	60,817	200,990	177,802
Total Operating Expenses	244,373	228,909	972,122	868,412
Operating Income	112,827	114,003	427,869	435,061
Other Income (Expense):
Other Income (Deductions)	(1,456)	(3,612)	(16,977)	(20,205)
Interest Expense on Long-Term Debt	(25,303)	(27,177)	(76,016)	(82,412)
Other Interest Expense	(1,202)	(1,006)	(4,061)	(2,742)
Income Before Income Taxes	84,866	82,208	330,815	329,702
Income Tax Expense (Benefit)	21,113	19,183	73,806	(23,825)
Net Income Available for Common Stock	63,753	63,025	257,009	353,527
EARNINGS REINVESTED IN THE BUSINESS
Balance at Beginning of Period	1,236,657	1,070,939	1,098,900	851,669
Beginning Retained Earnings Unappropriated And Current Period Net Income	1,300,410	1,133,964	1,355,909	1,205,196
Dividends on Common Stock	(37,543)	(36,526)	(110,885)	(107,758)
Balance at June 30	$ 1,262,867	$ 1,097,438	$ 1,262,867	$ 1,097,438
Earnings Per Common Share, Basic:
Net Income Available for Common Stock (in dollars per share)	$ 0.74	$ 0.73	$ 2.98	$ 4.12
Earnings Per Common Share, Diluted:
Net Income Available for Common Stock (in dollars per share)	$ 0.73	$ 0.73	$ 2.96	$ 4.09
Weighted Average Common Shares Outstanding:
Used in Basic Calculation (shares)	86,306,434	85,930,289	86,208,766	85,789,279
Used in Diluted Calculation (shares)	86,839,841	86,501,194	86,765,781	86,370,900
Dividends Per Common Share:
Dividends Declared (in dollars per share)	$ 0.435	$ 0.425	$ 1.285	$ 1.255
Purchased Gas [Member]
Operating Expenses:
Purchased Gas	$ 47,839	$ 52,211	$ 381,537	$ 322,854
Utility and Energy Marketing [Member]
INCOME
Operating Revenues	151,312	154,088	781,059	719,234
Operating Expenses:
Operation and Maintenance	39,607	39,560	132,082	130,348
Exploration and Production and Other [Member]
INCOME
Operating Revenues	159,864	137,492	470,267	425,811
Operating Expenses:
Operation and Maintenance	35,674	30,682	108,610	104,891
Pipeline and Storage and Gathering [Member]
INCOME
Operating Revenues	46,024	51,332	148,665	158,428
Operating Expenses:
Operation and Maintenance	28,675	25,044	80,857	68,272
Guidance for Recognition and Measurement of Financial Assets and Liabilities [Member]
EARNINGS REINVESTED IN THE BUSINESS
Cumulative Effect of Adoption of Authoritative Guidance	0	0	7,437	0
Guidance for Reclassification of Stranded Tax Effects [Member]
EARNINGS REINVESTED IN THE BUSINESS
Cumulative Effect of Adoption of Authoritative Guidance	$ 0	$ 0	$ 10,406	$ 0