Number of customers acquired through acquisition

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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The net result for the period of deducting operating expenses from operating revenues.

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- Definition

Amount of acquisition adjustments included in property, plant and equipment (PPE) for utilities.

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- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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Summary of Accounting Policies Acquisitions Additional information (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Business Acquisition [Line Items]
Revenues	$ 92,626	$ 93,400	$ 347,630	$ 356,102
Operating Income (Loss)	14,358	12,879	76,644	65,968
Marlin and Ohl [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred					$ 18,400
Marlin [Member]
Business Acquisition [Line Items]
Revenues	1,059		4,601
Operating Income (Loss)	68		1,491
Ohl [Member]
Business Acquisition [Line Items]
Revenues	149		1,146
Operating Income (Loss)	(35)		177
Public Utilities, Property, Plant and Equipment, Amount of Acquisition Adjustments	200		200
Unregulated Energy [Member]
Business Acquisition [Line Items]
Operating Income (Loss)	$ (3,168)	$ (3,090)	$ 11,316	$ 10,519
Unregulated Energy [Member] \| Marlin [Member]
Business Acquisition [Line Items]
Goodwill, Acquired During Period					4,800
Unregulated Energy [Member] \| Ohl [Member]
Business Acquisition [Line Items]
Goodwill, Acquired During Period					$ 1,500
Number of customers acquired through acquisition					2,500