Acquisitions and Divestitures Acquisitions and Divestitures (Details)		3 Months Ended
		Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Revenue	[1]	$ 0	$ 77,022,000
Disposal Group, Including Discontinued Operation, Costs of Goods Sold	[1]	(9,000)	75,162,000
Disposal Group, Including Discontinued Operation, Operating Expense		116,000	1,991,000
Disposal Group, Including Discontinued Operation, Operating Income (Loss)		(107,000)	(131,000)
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax		5,400,000
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax		(131,000)	(201,000)
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, Net of Tax		(96,000)	(150,000)
Disposal Group, Including Discontinued Operation, Interest Expense		(24,000)	(70,000)
Discontinued Operation, Tax Effect of Gain (Loss) from Disposal of Discontinued Operation		(35,000)	(51,000)
Revenues		152,710,000	160,464,000
Operating Income (Loss)		$ 42,113,000	44,124,000
Number of Transactions		4
Proceeds from Divestiture of Businesses		$ 22,900,000
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax		7,300,000
Regulated Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating Income (Loss)		27,888,000	29,741,000
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			9,900,000
Discontinued Operations, Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain Loss From Discontinued Operations		(96,000)	(150,000)
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Settlement Gain		584,000
Business Combination, Working Capital		8,000,000.0
Unregulated Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating Income (Loss)		$ 13,841,000	$ 15,258,000
Boulden [Member] | Unregulated Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of customers acquired through acquisition		5,200
Business Combination, Consideration Transferred		$ 24,600,000
Business Combination, Working Capital		200,000
Business Combination, Contingent Consideration, Liability		600,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment		8,300,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles		5,100,000
Goodwill, Acquired During Period		11,200,000
Revenues		2,800,000
Operating Income (Loss)		$ 1,400,000
Elkton Gas [Member] | Regulated Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of customers acquired through acquisition		7,000

[1] ⁽¹⁾ Included in operating revenues and cost of sales for the three months ended March 31, 2019, is $9.9 million representing amounts which had been previously eliminated in consolidation related to intercompany activity that will continue with the buyers after the disposition of the assets of PESCO.