Acquisitions Divestitures (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Transactions		4
Accrued Revenue		$ 20,846	$ 22,640
Proceeds from the sale of discontinued operations		22,871
Depreciation and amortization		477	582	$ 213
Property, plant and equipment	[1]		1,036
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment		(336,876)	(294,089)
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment, Noncurrent			1,242
Disposal Group, Including Discontinued Operation, Revenue	[2]	161,289	258,713	184,519
Disposal Group, Including Discontinued Operation, Costs of Goods Sold	[2]	157,646	252,111	182,307
Disposal Group, Including Discontinued Operation, Operating Expense		5,222	6,825	4,522
Disposal Group, Including Discontinued Operation, Operating Income (Loss)		(1,579)	(223)	(2,310)
Disposal Group, Including Discontinued Operation, Interest Expense		315	297	253
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax		(1,894)	(520)	(2,563)
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax		7,344	0	0
Discontinued Operation, Tax Effect of Discontinued Operation		1,439	238	361
Gain Loss From Discontinued Operations			(282)	(2,202)
Disposal Group, Including Discontinued Operation, Assets, Current		134,826	191,537
Disposal Group, Including Discontinued Operation, Other Assets	[1]		6,626
Disposal Group, Including Discontinued Operation, Assets			60,343
Disposal Group, Including Discontinued Operation, Liabilities	[3]		48,672
Deferred Income Tax Expense (Benefit)	[4]	23,901	20,650	12,085
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		4,011
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Business Combination, Working Capital		8,000
Capital Expenditure, Discontinued Operations			115	11,766
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment			(206)
Disposal Group, Including Discontinued Operation, Assets, Current	[5]		52,681
Deferred Income Tax Expense (Benefit)		(125)	1,088	(1,515)
Settlement Gain		(2,161)	5,002	4,911
Net Assets			11,671
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		$ 19,800	31,500	$ 16,600
Accounts Receivable, before Allowance for Credit Loss, Current			31,100
Derivative Asset			13,100
Accrued Revenue			4,900
Prepaid Expense			3,200
Accounts Payable			31,100
Derivative Liability			13,300
Other Liabilities			$ 2,700

[1] These balances have been combined within the consolidated balance sheets to arrive at noncurrent assets held for sale.

[2] ) Included in operating revenues and cost of sales for the years ended December 31, 2019, 2018 and 2017, is $19.8 million, $31.5 million and $16.6 million respectively, 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.

[3] ⁽³⁾ At December 31, 2018, current liabilities were primarily comprised of $31.1 million of accounts payable, $13.3 million of derivative liabilities at fair value and $2.7 million of other accrued liabilities.

[4] ⁽¹⁾ Includes $4.7 million, $3.5 million, and $0.9 million of deferred state income taxes for the years 2019, 2018 and 2017, respectively.

[5] At December 31, 2018, current assets were primarily comprised of $31.1 million of accounts receivable, $13.1 million of derivative assets at fair value, $4.9 million of accrued revenue and $3.2 million of storage gas prepayments