CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating revenues	$ 492,995	$ 485,738	$ 2,346,223	$ 2,458,165
Purchased gas cost	26,072	31,326	640,823	845,167
Operation and maintenance expense	149,460	164,545	449,529	452,572
Depreciation and amortization expense	107,104	97,700	318,082	290,537
Taxes, other than income	71,324	69,965	214,535	213,546
Operating income	139,035	122,202	723,254	656,343
Other non-operating income	7,235	1,645	9,133	(1,846)
Interest charges	19,580	19,592	68,980	74,390
Income before income taxes	126,690	104,255	663,407	580,107
Income tax expense	8,899	23,789	127,297	127,107
Net income	$ 117,791	$ 80,466	$ 536,110	$ 453,000
Basic net income per share (USD per share)	$ 0.96	$ 0.68	$ 4.38	$ 3.89
Diluted net income per share (USD per share)	0.96	0.68	4.37	3.88
Cash dividends per share (USD per share)	$ 0.575	$ 0.525	$ 1.725	$ 1.575
Basic weighted average shares outstanding (in shares)	123,026	118,075	122,352	116,485
Diluted weighted average shares outstanding (in shares)	123,032	118,430	122,463	116,673
Other comprehensive income (loss), net of tax
Net unrealized holding gains on available-for-sale securities, net of tax	$ 364	$ 94	$ 200	$ 191
Cash flow hedges:
Amortization and unrealized gain (loss) on interest rate agreements, net of tax	(4,450)	1,053	(2,344)	(23,997)
Total other comprehensive income (loss)	(4,086)	1,147	(2,144)	(23,806)
Total comprehensive income	113,705	81,613	533,966	429,194
Distribution segment
Operating revenues	434,650	444,287	2,194,786	2,339,660
Pipeline and storage segment
Operating revenues	58,345	41,451	151,437	118,505
Operating Segments | Distribution segment
Operating revenues	435,308	444,944	2,196,817	2,341,668
Purchased gas cost	126,093	139,518	942,586	1,147,598
Operation and maintenance expense	107,537	123,998	337,740	347,386
Depreciation and amortization expense	77,187	70,611	229,526	210,224
Taxes, other than income	61,980	62,134	190,636	189,377
Operating income	62,511	48,683	496,329	447,083
Other non-operating income	5,167	3,005	1,930	1,791
Interest charges	7,969	10,597	35,128	44,703
Income before income taxes	59,709	41,091	463,131	404,171
Income tax expense	810	8,693	87,411	85,195
Net income	58,899	32,398	375,720	318,976
Operating Segments | Pipeline and storage segment
Operating revenues	158,008	149,198	452,421	419,318
Purchased gas cost	(11)	(96)	290	(544)
Operation and maintenance expense	42,234	40,855	112,751	106,120
Depreciation and amortization expense	29,917	27,089	88,556	80,313
Taxes, other than income	9,344	7,831	23,899	24,169
Operating income	76,524	73,519	226,925	209,260
Other non-operating income	2,068	(1,360)	7,203	(3,637)
Interest charges	11,611	8,995	33,852	29,687
Income before income taxes	66,981	63,164	200,276	175,936
Income tax expense	8,089	15,096	39,886	41,912
Net income	58,892	48,068	160,390	134,024
Intersegment eliminations
Operating revenues	(100,321)	(108,404)	(303,015)	(302,821)
Purchased gas cost	(100,010)	(108,096)	(302,053)	(301,887)
Operation and maintenance expense	(311)	(308)	(962)	(934)
Depreciation and amortization expense	0	0	0	0
Taxes, other than income	0	0	0	0
Operating income	0	0	0	0
Other non-operating income	0	0	0	0
Interest charges	0	0	0	0
Income before income taxes	0	0	0	0
Income tax expense	0	0	0	0
Net income	0	0	0	0
Intersegment eliminations | Distribution segment
Operating revenues	658	657	2,031	2,008
Intersegment eliminations | Pipeline and storage segment
Operating revenues	99,663	107,747	300,984	300,813
Purchased gas cost
Purchased gas cost	26,072	31,326	640,823	845,167
Purchased gas cost | Operating Segments | Distribution segment
Purchased gas cost	126,093	139,518	942,586	1,147,598
Purchased gas cost | Operating Segments | Pipeline and storage segment
Purchased gas cost	(11)	(96)	290	(544)
Purchased gas cost | Intersegment eliminations
Purchased gas cost	$ (100,010)	$ (108,096)	$ (302,053)	$ (301,887)