Business Segment Data - Schedule of Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2025	Mar. 31, 2025	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2025	Jun. 30, 2024
Segment Reporting Information [Line Items]
Operating revenues	$ 351,186		$ 344,471		$ 1,026,019	$ 932,746
Purchased natural gas sold	96,057		94,591		413,214	353,192
Electric fuel and purchased power	34,891		36,692		78,639	76,415
External operation and maintenance	112,887		99,955		223,934	207,570
Depreciation and amortization	51,853		49,690		103,114	99,456
Taxes, other than income	25,166		23,969		63,923	59,883
Other income	9,945		10,363		14,942	22,273
Interest expense	25,445		26,500		52,267	53,012
Income tax expense (benefit)	655		3,195		9,226	10,514
Income (loss) from continuing operations	14,177		20,242		96,644	94,977
Discontinued operations, net of tax	(397)		40,194		(899)	66,357
Net income (loss)	13,780	$ 81,965	60,436	$ 100,898	95,745	161,334
Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	361,215		353,587		1,069,656	972,190
Operating Segments | Electric
Segment Reporting Information [Line Items]
Operating revenues	97,886		99,173		210,147	206,916
Purchased natural gas sold	0		0		0	0
Electric fuel and purchased power	34,891		36,692		78,639	76,415
External operation and maintenance	29,823		23,100		58,230	46,631
Depreciation and amortization	17,393		16,220		34,576	32,836
Taxes, other than income	4,648		4,530		9,463	9,616
Other income	2,726		2,065		3,718	4,047
Interest expense	7,614		7,226		15,501	14,722
Income tax expense (benefit)	(4,254)		(2,057)		(7,985)	(2,652)
Income (loss) from continuing operations	10,497		15,527		25,441	33,396
Discontinued operations, net of tax	0		0		0	0
Net income (loss)	10,497		15,527		25,441	33,396
Operating Segments | Natural gas distribution
Segment Reporting Information [Line Items]
Operating revenues	206,794		201,445		746,041	660,930
Purchased natural gas sold	96,057		94,591		413,214	353,192
Electric fuel and purchased power	0		0		0	0
External operation and maintenance	60,456		54,919		123,939	114,249
Depreciation and amortization	26,471		25,548		52,593	51,026
Taxes, other than income	16,935		16,358		47,563	43,950
Other income	5,095		5,350		8,396	13,521
Interest expense	13,745		15,364		28,621	31,024
Income tax expense (benefit)	(4,170)		(3,803)		8,131	6,876
Income (loss) from continuing operations	(7,356)		(5,007)		37,302	35,063
Discontinued operations, net of tax	0		0		0	0
Net income (loss)	(7,356)		(5,007)		37,302	35,063
Operating Segments | Pipeline
Segment Reporting Information [Line Items]
Operating revenues	46,507		43,851		69,831	64,883
Purchased natural gas sold	0		0		0	0
Electric fuel and purchased power	0		0		0	0
External operation and maintenance	22,352		19,079		41,592	37,494
Depreciation and amortization	7,989		7,318		15,945	14,436
Taxes, other than income	3,583		3,007		6,897	6,102
Other income	1,616		2,729		1,923	3,498
Interest expense	3,135		2,708		6,256	4,901
Income tax expense (benefit)	4,337		5,295		9,464	9,805
Income (loss) from continuing operations	15,417		17,259		32,627	32,317
Discontinued operations, net of tax	0		0		0	0
Net income (loss)	15,417		17,259		32,627	32,317
Operating Segments | Other
Segment Reporting Information [Line Items]
Operating revenues	(1)		2		0	17
Purchased natural gas sold	0		0		0	0
Electric fuel and purchased power	0		0		0	0
External operation and maintenance	256		2,857		173	9,196
Depreciation and amortization	0		604		0	1,158
Taxes, other than income	0		74		0	215
Other income	508		219		905	1,207
Interest expense	951		1,202		1,889	2,365
Income tax expense (benefit)	4,742		3,760		(384)	(3,515)
Income (loss) from continuing operations	(4,381)		(7,537)		1,274	(5,799)
Discontinued operations, net of tax	(397)		40,194		(899)	66,357
Net income (loss)	(4,778)		32,657		375	60,558
Intersegment eliminations
Segment Reporting Information [Line Items]
Operating revenues	(10,208)		(9,138)		(43,995)	(39,503)
Purchased natural gas sold	(9,751)		(8,825)		(43,074)	(39,071)
External operation and maintenance	(457)		(313)		(921)	(432)
Other income	(1,151)		(4,403)		(2,260)	(8,914)
Interest expense	(1,151)		(4,403)		(2,260)	(8,914)
Intersegment eliminations | Electric
Segment Reporting Information [Line Items]
Operating revenues	(140)		(48)		(318)	(60)
Purchased natural gas sold	0		0		0	0
External operation and maintenance	(140)		(48)		(318)	(59)
Other income	0		0		0	0
Interest expense	0		0		0	0
Intersegment eliminations | Natural gas distribution
Segment Reporting Information [Line Items]
Operating revenues	(92)		(35)		(187)	(76)
Purchased natural gas sold	(9,751)		(8,825)		(43,074)	(39,071)
External operation and maintenance	(92)		(35)		(187)	(76)
Other income	0		0		0	0
Interest expense	0		0		0	0
Intersegment eliminations | Pipeline
Segment Reporting Information [Line Items]
Operating revenues	(9,796)		(9,035)		(43,132)	(39,325)
Purchased natural gas sold	0		0		0	0
External operation and maintenance	(45)		(210)		(58)	(254)
Other income	(90)		(332)		(213)	(455)
Interest expense	(1,151)		(1,071)		(2,260)	(2,852)
Intersegment eliminations | Other
Segment Reporting Information [Line Items]
Operating revenues	(180)		(20)		(358)	(42)
Purchased natural gas sold	0		0		0	0
External operation and maintenance	(180)		(20)		(358)	(43)
Other income	(1,061)		(4,071)		(2,047)	(8,459)
Interest expense	$ 0		$ (3,332)		$ 0	$ (6,062)