Business Segment Data - Schedule of Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2025	Sep. 30, 2024
Segment Reporting Information [Line Items]
Operating revenues	$ 315,036			$ 289,694			$ 1,341,055	$ 1,222,440
Purchased natural gas sold	58,514			53,377			471,728	406,569
Electric fuel and purchased power	41,098			32,576			119,737	108,991
Operation and maintenance	101,762			101,211			325,696	308,780
Depreciation and amortization	52,046			49,835			155,160	149,292
Taxes, other than income	21,776			17,849			85,699	77,731
Other income	7,298			8,970			22,240	31,242
Interest expense	26,417			27,337			78,684	80,349
Income tax expense (benefit)	2,371			876			11,597	11,390
Income (loss) from continuing operations	18,350			15,603			114,994	110,580
Discontinued operations, net of tax	(39)			49,012			(938)	115,370
Net income (loss)	18,311	$ 13,780	$ 81,965	64,615	$ 60,436	$ 100,898	114,056	225,950
Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	319,535			293,660			1,389,191	1,265,850
Operating Segments | Electric
Segment Reporting Information [Line Items]
Operating revenues	117,662			108,468			327,808	315,385
Purchased natural gas sold	0			0			0	0
Electric fuel and purchased power	41,098			32,576			119,737	108,991
Operation and maintenance	25,957			23,359			84,186	69,989
Depreciation and amortization	17,479			16,848			52,055	49,685
Taxes, other than income	4,713			3,606			14,176	13,222
Other income	2,027			1,403			5,745	5,449
Interest expense	7,639			7,646			23,140	22,367
Income tax expense (benefit)	1,339			1,544			(6,646)	(1,109)
Income (loss) from continuing operations	21,464			24,292			46,905	57,689
Discontinued operations, net of tax	0			0			0	0
Net income (loss)	21,464			24,292			46,905	57,689
Operating Segments | Natural gas distribution
Segment Reporting Information [Line Items]
Operating revenues	144,215			133,590			890,257	794,519
Purchased natural gas sold	58,514			53,377			471,728	406,569
Electric fuel and purchased power	0			0			0	0
Operation and maintenance	56,531			54,785			180,471	169,034
Depreciation and amortization	26,558			25,055			79,151	76,081
Taxes, other than income	13,375			11,180			60,938	55,130
Other income	3,850			5,985			12,246	19,506
Interest expense	14,686			15,901			43,307	46,925
Income tax expense (benefit)	(7,612)			(7,130)			519	(253)
Income (loss) from continuing operations	(18,213)			(17,481)			19,089	17,581
Discontinued operations, net of tax	0			0			0	0
Net income (loss)	(18,213)			(17,481)			19,089	17,581
Operating Segments | Pipeline
Segment Reporting Information [Line Items]
Operating revenues	53,159			47,635			122,990	112,518
Purchased natural gas sold	0			0			0	0
Electric fuel and purchased power	0			0			0	0
Operation and maintenance	21,016			18,969			62,608	56,461
Depreciation and amortization	8,009			7,369			23,954	21,806
Taxes, other than income	3,688			3,006			10,585	9,108
Other income	880			1,117			2,804	4,616
Interest expense	2,447			2,564			8,703	7,466
Income tax expense (benefit)	4,782			4,688			14,246	14,493
Income (loss) from continuing operations	16,758			15,184			49,385	47,501
Discontinued operations, net of tax	0			0			0	0
Net income (loss)	16,758			15,184			49,385	47,501
Operating Segments | Other
Segment Reporting Information [Line Items]
Operating revenues	0			1			0	18
Purchased natural gas sold	0			0			0	0
Electric fuel and purchased power	0			0			0	0
Operation and maintenance	(1,742)			4,098			(1,569)	13,296
Depreciation and amortization	0			563			0	1,720
Taxes, other than income	0			57			0	271
Other income	541			465			1,445	1,671
Interest expense	1,645			1,226			3,534	3,591
Income tax expense (benefit)	3,862			1,774			3,478	(1,741)
Income (loss) from continuing operations	(1,659)			(6,392)			(385)	(12,191)
Discontinued operations, net of tax	(39)			49,012			(938)	115,370
Net income (loss)	(1,698)			42,620			(1,323)	103,179
Intersegment eliminations
Segment Reporting Information [Line Items]
Operating revenues	(4,681)			(3,988)			(48,676)	(43,492)
Purchased natural gas sold	(4,226)			(3,888)			(47,300)	(42,958)
Operation and maintenance	(455)			(100)			(1,376)	(534)
Other income	(1,687)			(4,031)			(3,947)	(12,945)
Interest expense	(1,687)			(4,031)			(3,947)	(12,945)
Intersegment eliminations | Electric
Segment Reporting Information [Line Items]
Operating revenues	(138)			(12)			(457)	(71)
Purchased natural gas sold	0			0			0	0
Operation and maintenance	(138)			(12)			(457)	(71)
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)			(31)			(278)	(108)
Purchased natural gas sold	(4,226)			(3,888)			(47,300)	(42,958)
Operation and maintenance	(92)			(31)			(278)	(108)
Other income	0			0			0	0
Interest expense	0			0			0	0
Intersegment eliminations | Pipeline
Segment Reporting Information [Line Items]
Operating revenues	(4,269)			(3,924)			(47,401)	(43,249)
Purchased natural gas sold	0			0			0	0
Operation and maintenance	(43)			(36)			(101)	(291)
Other income	(122)			(237)			(334)	(692)
Interest expense	(1,687)			(1,097)			(3,947)	(3,949)
Intersegment eliminations | Other
Segment Reporting Information [Line Items]
Operating revenues	(182)			(21)			(540)	(64)
Purchased natural gas sold	0			0			0	0
Operation and maintenance	(182)			(21)			(540)	(64)
Other income	(1,565)			(3,794)			(3,613)	(12,253)
Interest expense	$ 0			$ (2,934)			$ 0	$ (8,996)