CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Operating revenues
Operating revenues	$ 780,168	$ 674,753
Purchased gas cost
Purchased gas cost	311,305	240,326
Gross profit	468,863	434,427
Operating expenses
Operation and maintenance	124,938	119,828
Depreciation and amortization	76,958	70,656
Taxes, other than income	57,049	51,214
Total operating expenses	258,945	241,698
Operating income	209,918	192,729
Miscellaneous income (expense)	(994)	(879)
Interest charges	31,030	29,537
Income (loss) before income taxes	177,894	162,313
Income tax expense (benefit)	63,856	60,767
Income from continuing operations	114,038	101,546
Income from discontinued operations, net of tax	10,994	1,315
Net income (loss)	$ 125,032	$ 102,861
Income (Loss) from Continuing Operations, Per Basic and Diluted Share	$ 1.08	$ 0.99
Income (Loss) from Discontinued Operation, Net of Tax, Per Basic and Diluted Share	0.11	0.01
Basic and diluted net income per share	1.19	1.00
Cash dividends per share	$ 0.45	$ 0.42
Weighted average shares outstanding:
Weighted Average Number of Shares Outstanding, Basic and Diluted	105,284	102,713
Distribution Segment [Member]
Operating revenues
Operating revenues	$ 754,656	$ 649,443
Purchased gas cost
Purchased gas cost	395,346	313,991
Gross profit	359,310	335,452
Operating expenses
Operation and maintenance	92,714	92,189
Depreciation and amortization	61,157	57,614
Taxes, other than income	50,546	45,558
Total operating expenses	204,417	195,361
Operating income	154,893	140,091
Miscellaneous income (expense)	(633)	(477)
Interest charges	21,118	20,390
Income (loss) before income taxes	133,142	119,224
Income tax expense (benefit)	47,778	45,288
Income from continuing operations	85,364	73,936
Income from discontinued operations, net of tax	0	0
Net income (loss)	85,364	73,936
Pipeline and Storage Segment [Member]
Operating revenues
Operating revenues	109,952	98,416
Purchased gas cost
Purchased gas cost	355	(559)
Gross profit	109,597	98,975
Operating expenses
Operation and maintenance	32,268	27,639
Depreciation and amortization	15,801	13,042
Taxes, other than income	6,503	5,656
Total operating expenses	54,572	46,337
Operating income	55,025	52,638
Miscellaneous income (expense)	(361)	(402)
Interest charges	9,912	9,147
Income (loss) before income taxes	44,752	43,089
Income tax expense (benefit)	16,078	15,479
Income from continuing operations	28,674	27,610
Income from discontinued operations, net of tax	0	0
Net income (loss)	28,674	27,610
Natural Gas Marketing Segment [Member]
Operating revenues
Operating revenues	0	0
Purchased gas cost
Purchased gas cost	0	0
Gross profit	0	0
Operating expenses
Operation and maintenance	0	0
Depreciation and amortization	0	0
Taxes, other than income	0	0
Total operating expenses	0	0
Operating income	0	0
Miscellaneous income (expense)	0	0
Interest charges	0	0
Income (loss) before income taxes	0	0
Income tax expense (benefit)	0	0
Income from continuing operations	0	0
Income from discontinued operations, net of tax	10,994	1,315
Net income (loss)	10,994	1,315
Intersegment Elimination [Member]
Operating revenues
Operating revenues	(84,440)	(73,106)
Purchased gas cost
Purchased gas cost	(84,396)	(73,106)
Gross profit	(44)	0
Operating expenses
Operation and maintenance	(44)	0
Depreciation and amortization	0	0
Taxes, other than income	0	0
Total operating expenses	(44)	0
Operating income	0	0
Miscellaneous income (expense)	0	0
Interest charges	0	0
Income (loss) before income taxes	0	0
Income tax expense (benefit)	0	0
Income from continuing operations	0	0
Income from discontinued operations, net of tax	0	0
Net income (loss)	$ 0	$ 0