CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Utility revenues:
Utility revenues, exclusive of alternative revenue programs	$ 306,398	$ 276,351	$ 1,019,756	$ 944,146
Alternative revenue programs	(10,499)	(3,972)	(13,069)	(4,023)
Total utility revenues	295,899	272,379	1,006,687	940,123
Non-utility revenues	108	267	445	1,345
Total operating revenues	296,007	272,646	1,007,132	941,468
Utility operating expenses:
Resource costs	102,133	78,785	327,390	276,297
Other operating expenses	85,625	85,551	267,233	266,251
Depreciation and amortization	57,722	53,953	169,009	169,282
Taxes other than income taxes	25,440	24,016	82,223	79,736
Non-utility operating expenses:
Other operating expenses	843	1,697	3,186	3,716
Depreciation and amortization	30	146	230	569
Total operating expenses	271,793	244,148	849,271	795,851
Income from operations	24,214	28,498	157,861	145,617
Interest expense	26,547	25,812	78,982	77,784
Interest expense to affiliated trusts	102	128	317	606
Capitalized interest	(1,102)	(1,009)	(3,033)	(2,979)
Other income-net	(10,267)	(2,168)	(23,992)	(2,019)
Income before income taxes	8,934	5,735	105,587	72,225
Income tax expense (benefit)	(5,432)	859	9,130	1,472
Net income	$ 14,366	$ 4,876	$ 96,457	$ 70,753
Weighted-average common shares outstanding (thousands), basic	70,054	68,194	69,582	67,638
Weighted-average common shares outstanding (thousands), diluted	70,129	68,337	69,722	67,769
Earnings per common share:
Basic	$ 0.21	$ 0.07	$ 1.39	$ 1.05
Diluted	$ 0.20	$ 0.07	$ 1.38	$ 1.04