CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Operating revenues
Total operating revenues	$ 877,782	$ 889,192
Operation and maintenance expense	138,600	129,045
Depreciation and amortization expense	96,065	88,374
Taxes, other than income	64,488	62,773
Operating income	236,464	242,083
Other non-operating expense	(7,723)	(2,557)
Interest charges	27,849	31,509
Income before income taxes	200,892	208,017
Income tax expense (benefit)	43,246	(106,115)
Net income	$ 157,646	$ 314,132
Basic net income per share	$ 1.38	$ 2.89
Diluted net income per share	1.38	2.89
Cash dividends per share	$ 0.525	$ 0.485
Basic weighted average shares outstanding	113,800	108,564
Diluted weighted average shares outstanding	113,832	108,564
Other comprehensive income (loss), net of tax
Net unrealized holding gains (losses) on available-for-sale securities, net of tax of $92, $490, $(246) and $893	$ 0	$ (107)
Cash flow hedges:
Amortization and unrealized gain (loss) on interest rate agreements, net of tax of $2,460, $(10,667), $8,486 and $44,194	(22,258)	(955)
Total other comprehensive income (loss)	(22,258)	(1,062)
Total comprehensive income	135,388	313,070
Operating Segments | Distribution segment
Operating revenues
Total operating revenues	838,835	860,792
Operation and maintenance expense	105,767	103,215
Depreciation and amortization expense	69,709	65,434
Taxes, other than income	56,190	55,107
Operating income	169,437	173,278
Other non-operating expense	(6,477)	(1,922)
Interest charges	18,210	21,368
Income before income taxes	144,750	149,988
Income tax expense (benefit)	30,365	(99,111)
Net income	114,385	249,099
Operating Segments | Pipeline and storage segment
Operating revenues
Total operating revenues	134,470	126,463
Operation and maintenance expense	33,147	26,140
Depreciation and amortization expense	26,356	22,940
Taxes, other than income	8,298	7,666
Operating income	67,027	68,805
Other non-operating expense	(1,246)	(635)
Interest charges	9,639	10,141
Income before income taxes	56,142	58,029
Income tax expense (benefit)	12,881	(7,004)
Net income	43,261	65,033
Intersegment eliminations
Operating revenues
Total operating revenues	(95,523)	(98,063)
Operation and maintenance expense	(314)	(310)
Depreciation and amortization expense	0	0
Taxes, other than income	0	0
Operating income	0	0
Other non-operating expense	0	0
Interest charges	0	0
Income before income taxes	0	0
Income tax expense (benefit)	0	0
Net income	0	0
Natural Gas, US Regulated
Operating revenues
Cost of Revenue	342,165	366,917
Natural Gas, US Regulated | Operating Segments | Distribution segment
Operating revenues
Cost of Revenue	437,732	463,758
Natural Gas, US Regulated | Operating Segments | Pipeline and storage segment
Operating revenues
Cost of Revenue	(358)	912
Natural Gas, US Regulated | Intersegment eliminations
Operating revenues
Cost of Revenue	$ (95,209)	$ (97,753)