Segment and Related Information (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Total revenues	$ 425,283	$ 347,341	$ 1,477,837	$ 1,372,316	$ 1,198,670
Utilities Operating Expense, Fuel Used			492,011	425,548	306,190
Utility Margin			985,826	946,768	892,480
Operating and maintenance			221,427	208,303	202,991
Administrative and general			113,776	101,873	94,124
Property and other taxes			192,524	173,444	179,517
Depreciation and depletion			195,020	187,467	179,644
Operating Income	83,228	79,990	263,079	275,681	236,204
Interest expense, net			(100,110)	(93,674)	(96,812)
Other income, net			19,434	8,252	4,853
Income tax (expense) benefit			605	(3,419)	10,970
Net Income	66,743	51,336	183,008	186,840	155,215
Total assets	7,317,783	6,780,443	7,317,783	6,780,443	6,389,449
Capital expenditures			515,140	434,328	405,762
Eliminations
Segment Reporting Information [Line Items]
Total revenues			0	0	0
Utilities Operating Expense, Fuel Used			0	0	0
Utility Margin			0	0	0
Operating and maintenance			0	0	0
Administrative and general			0	0	0
Property and other taxes			0	0	0
Depreciation and depletion			0	0	0
Operating Income			0	0	0
Interest expense, net			0	0	0
Other income, net			0	0	0
Income tax (expense) benefit			0	0	0
Net Income			0	0	0
Total assets	0	0	0	0	0
Capital expenditures			0	0	0
Operating Segments | Electric
Segment Reporting Information [Line Items]
Total revenues			1,106,565	1,052,182	940,815
Utilities Operating Expense, Fuel Used			324,434	294,820	236,581
Utility Margin			782,131	757,362	704,234
Operating and maintenance			167,798	156,383	149,220
Administrative and general			82,405	72,641	69,602
Property and other taxes			149,781	134,910	140,621
Depreciation and depletion			162,404	154,626	147,968
Operating Income			219,743	238,802	196,823
Interest expense, net			(74,420)	(82,678)	(85,487)
Other income, net			12,491	3,676	4,867
Income tax (expense) benefit			798	(2,512)	11,282
Net Income			158,612	157,288	127,485
Total assets	5,892,508	5,432,578	5,892,508	5,432,578	5,126,589
Capital expenditures			409,707	354,775	324,369
Operating Segments | Gas Domestic Regulated [Member]
Segment Reporting Information [Line Items]
Total revenues			371,272	320,134	257,855
Utilities Operating Expense, Fuel Used			167,577	130,728	69,609
Utility Margin			203,695	189,406	188,246
Operating and maintenance			53,629	51,920	53,771
Administrative and general			31,002	27,550	26,311
Property and other taxes			42,734	38,526	38,887
Depreciation and depletion			32,616	32,841	31,676
Operating Income			43,714	38,569	37,601
Interest expense, net			(13,030)	(6,083)	(6,341)
Other income, net			6,399	3,046	2,704
Income tax (expense) benefit			(3,108)	(2,640)	(2,426)
Net Income			33,975	32,892	31,538
Total assets	1,418,059	1,342,031	1,418,059	1,342,031	1,251,240
Capital expenditures			105,433	79,553	81,393
Other Segments [Member] | Operating Segments
Segment Reporting Information [Line Items]
Total revenues			0	0	0
Utilities Operating Expense, Fuel Used			0	0	0
Utility Margin			0	0	0
Operating and maintenance			0	0	0
Administrative and general			369	1,682	(1,789)
Property and other taxes			9	8	9
Depreciation and depletion			0	0	0
Operating Income			(378)	(1,690)	1,780
Interest expense, net			(12,660)	(4,913)	(4,984)
Other income, net			544	1,530	(2,718)
Income tax (expense) benefit			2,915	1,733	2,114
Net Income			(9,579)	(3,340)	(3,808)
Total assets	$ 7,216	$ 5,834	7,216	5,834	11,620
Capital expenditures			$ 0	$ 0	$ 0