CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Operating revenues
Operating revenues	$ 1,258,765	$ 1,243,858
Purchased gas cost
Purchased gas cost	835,480	854,901
Gross profit	423,285	388,957
Operating expenses
Operation and maintenance	118,582	115,757
Depreciation and amortization	67,593	60,469
Taxes, other than income	49,385	42,011
Total operating expenses	235,560	218,237
Operating income	187,725	170,720
Miscellaneous income (expense)	(1,707)	(2,132)
Interest charges	29,764	32,115
Income (loss) before income taxes	156,254	136,473
Income tax expense (benefit)	58,659	49,457
Net income (loss)	97,595	87,016
Basic net income (loss) per share	$ 0.96	$ 0.95
Diluted net income (loss) per share	$ 0.96	$ 0.95
Cash dividends per share	$ 0.39	$ 0.37
Weighted average shares outstanding:
Basic weighted average shares outstanding	101,581	91,841
Diluted weighted average shares outstanding	101,581	91,843
Regulated Distribution Segment [Member]
Operating revenues
Operating revenues	846,772	843,865
Purchased gas cost
Purchased gas cost	522,960	544,694
Gross profit	323,812	299,171
Operating expenses
Operation and maintenance	86,985	89,663
Depreciation and amortization	55,086	49,551
Taxes, other than income	43,644	37,084
Total operating expenses	185,715	176,298
Operating income	138,097	122,873
Miscellaneous income (expense)	(1,329)	(471)
Interest charges	21,640	23,325
Income (loss) before income taxes	115,128	99,077
Income tax expense (benefit)	43,741	36,320
Net income (loss)	71,387	62,757
Regulated Pipeline Segment [Member]
Operating revenues
Operating revenues	83,567	71,341
Purchased gas cost
Purchased gas cost	0	0
Gross profit	83,567	71,341
Operating expenses
Operation and maintenance	24,615	17,300
Depreciation and amortization	11,382	9,786
Taxes, other than income	4,865	4,663
Total operating expenses	40,862	31,749
Operating income	42,705	39,592
Miscellaneous income (expense)	(252)	(1,181)
Interest charges	8,324	8,957
Income (loss) before income taxes	34,129	29,454
Income tax expense (benefit)	12,094	10,008
Net income (loss)	22,035	19,446
Nonregulated Segment [Member]
Operating revenues
Operating revenues	462,288	436,431
Purchased gas cost
Purchased gas cost	446,249	417,865
Gross profit	16,039	18,566
Operating expenses
Operation and maintenance	7,115	8,915
Depreciation and amortization	1,125	1,132
Taxes, other than income	876	264
Total operating expenses	9,116	10,311
Operating income	6,923	8,255
Miscellaneous income (expense)	300	324
Interest charges	226	637
Income (loss) before income taxes	6,997	7,942
Income tax expense (benefit)	2,824	3,129
Net income (loss)	4,173	4,813
Intersegment Elimination [Member]
Operating revenues
Operating revenues	(133,862)	(107,779)
Purchased gas cost
Purchased gas cost	(133,729)	(107,658)
Gross profit	(133)	(121)
Operating expenses
Operation and maintenance	(133)	(121)
Depreciation and amortization	0	0
Taxes, other than income	0	0
Total operating expenses	(133)	(121)
Operating income	0	0
Miscellaneous income (expense)	(426)	(804)
Interest charges	(426)	(804)
Income (loss) before income taxes	0	0
Income tax expense (benefit)	0	0
Net income (loss)	$ 0	$ 0