Acquisitions and Divestitures (Details) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2020 USD ($)		Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) Customer		Sep. 30, 2019 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Depreciation and Amortization						$ 437
Deferred Income Tax Expense (Benefit)				$ 22,184		8,789
Number of Disposal Transactions	4			4
Proceeds from Divestiture of Businesses				$ 23,100
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax				5,400
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax, Incremental				200		0
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, Net of Tax	$ (19)		$ (630)	165		(1,388)
Gain from a settlement				(130)		(130)
Revenues	101,419		92,626	351,160		347,630
Operating Income (Loss)	17,406		14,357	77,518		76,645
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax	7,300			7,500
Discontinued Operations, Held-for-sale or Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Revenue	3	[1]	34,271	26	[1]	152,573
Disposal Group, Including Discontinued Operation, Costs of Goods Sold	(40)	[1]	33,763	(39)	[1]	149,464
Disposal Group, Including Discontinued Operation, Operating Expense	75		1,360	272		4,819
Disposal Group, Including Discontinued Operation, Operating Income (Loss)	(32)		(852)	(207)		(1,710)
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax	(26)		(926)	(230)		(1,952)
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax, Incremental				200		0
Disposal Group, Including Discontinued Operation, Interest Expense	6		(74)	(23)		(242)
Discontinued Operation, Tax Effect of Gain (Loss) from Disposal of Discontinued Operation	(7)		(296)	(195)		(564)
Regulated Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating Income (Loss)	20,482		17,540	66,376		65,310
PESCO [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Intra-Entity Amounts, Discontinued Operation after Disposal, Revenue	4,300			19,100
Discontinued Operations, Disposed of by Sale [Member] | Discontinued Operations, Held-for-sale or Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain Loss From Discontinued Operations	(19)		(630)	165		(1,388)
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Deferred Income Tax Expense (Benefit)						513
Gain from a settlement						(623)
Business Combination, Working Capital	8,000			8,000
Unregulated Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating Income (Loss)	(3,092)		$ (3,169)	11,050		$ 11,317
Elkton Gas [Member] | Regulated Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	15,900			15,900
Revenues				600
Operating Income (Loss)				$ 100
Number of customers acquired through acquisition				7,000
Business Combination, Consideration Transferred				$ 15,600
Business Combination, Working Capital	600			600
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables	600			600
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	2,600			2,600
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net	4,300			4,300
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Regulatory Liabilities				2,600
Boulden [Member] | Unregulated Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	8,300			8,300
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	5,100			5,100
Goodwill, Acquired During Period				11,200
Revenues	400			4,100
Operating Income (Loss)	(200)			$ 1,200
Number of customers acquired through acquisition | Customer				5,200
Business Combination, Consideration Transferred				$ 24,600
Business Combination, Working Capital	200			200
Business Combination, Contingent Consideration, Liability	$ 600			600
Western Natural Gas [Member] | Unregulated Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Business Combination, Consideration Transferred				$ 6,700

[1] (1) Included in operating revenues and cost of sales for the three and nine months ended September 30, 2019, is $4.3 million and $19.1 million, respectively, representing amounts which had been previously eliminated in consolidation related to intercompany activity that continued with the buyers after the disposition of the assets of PESCO.