Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating revenues:
Operating revenues:	$ 1,280,787	$ 1,272,548	$ 3,321,678	$ 3,278,112
Operating expenses:
Operation and maintenance:	996,591	973,966	2,419,531	2,354,456
Purchased natural gas sold	32,123	33,319	270,319	283,936
Depreciation, depletion and amortization	55,016	52,155	161,298	155,138
Taxes, other than income	38,647	38,882	128,257	127,273
Electric fuel and purchased power	18,406	18,906	58,901	57,544
Total operating expenses	1,140,783	1,117,228	3,038,306	2,978,347
Operating income	140,004	155,320	283,372	299,765
Other income	2,683	2,068	4,864	6,212
Interest expense	20,955	20,909	62,202	61,978
Income before income taxes	121,732	136,479	226,034	243,999
Income taxes	14,363	46,930	32,629	74,406
Income from continuing operations	107,369	89,549	193,405	169,593
Income (loss) from discontinued operations, net of tax (Note 10)	(118)	(2,198)	85	(3,702)
Net income	107,251	87,351	193,490	165,891
Loss on redemption of preferred stocks	0	0	0	600
Dividends declared on preferred stocks	0	0	0	171
Earnings on common stock	$ 107,251	$ 87,351	$ 193,490	$ 165,120
Earnings per common share - basic:
Earnings before discontinued operations	$ 0.55	$ 0.46	$ 0.99	$ 0.86
Discontinued operations, net of tax	0	(0.01)	0	(0.01)
Earnings per common share - basic	0.55	0.45	0.99	0.85
Earnings per common share - diluted:
Earnings before discontinued operations	0.55	0.46	0.99	0.86
Discontinued operations, net of tax	0	(0.01)	0	(0.02)
Earnings per common share - diluted	0.55	0.45	0.99	0.84
Dividends declared per common share	$ 0.1975	$ 0.1925	$ 0.5925	$ 0.5775
Weighted average common shares outstanding - basic	196,018	195,304	195,618	195,304
Weighted average common shares outstanding - diluted	196,265	195,783	196,104	195,922
Regulated operation
Operating revenues:
Operating revenues:	$ 200,617	$ 206,936	$ 851,761	$ 866,035
Operating expenses:
Operation and maintenance:	82,920	80,204	252,961	237,881
Nonregulated operation
Operating revenues:
Operating revenues:	1,080,170	1,065,612	2,469,917	2,412,077
Operating expenses:
Operation and maintenance:	$ 913,671	$ 893,762	$ 2,166,570	$ 2,116,575