Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating revenues:
Operating revenues:	$ 976,293	$ 937,925
Operating expenses:
Operation and maintenance:	600,856	558,542
Purchased natural gas sold	181,967	192,948
Depreciation, depletion and amortization	52,729	51,325
Taxes, other than income	48,854	47,438
Electric fuel and purchased power	22,511	21,886
Total operating expenses	906,917	872,139
Operating income	69,376	65,786
Other income	582	2,343
Interest expense	20,447	20,303
Income before income taxes	49,511	47,826
Income taxes	7,551	12,188
Income from continuing operations	41,960	35,638
Income from discontinued operations, net of tax (Note 9)	477	1,687	[1]
Net income	42,437	37,325
Dividends declared on preferred stocks	0	171
Earnings on common stock	$ 42,437	$ 37,154
Earnings per common share - basic:
Earnings before discontinued operations	$ 0.22	$ 0.18
Discontinued operations, net of tax	0	0.01
Earnings per common share - basic	0.22	0.19
Earnings per common share - diluted:
Earnings before discontinued operations	0.22	0.18
Discontinued operations, net of tax	0	0.01
Earnings per common share - diluted	0.22	0.19
Dividends declared per common share	$ 0.1975	$ 0.1925
Weighted average common shares outstanding - basic	195,304	195,304
Weighted average common shares outstanding - diluted	195,982	196,023
Regulated operations [Member]
Operating revenues:
Operating revenues:	$ 424,459	$ 433,614
Operating expenses:
Operation and maintenance:	86,112	79,548
Nonregulated operations [Member]
Operating revenues:
Operating revenues:	551,834	504,311
Operating expenses:
Operation and maintenance:	$ 514,744	$ 478,994

[1] Includes an elimination for the presentation of income tax adjustments between continuing and discontinued operations.