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Concentrations and Associated Credit Risk (Details)	9 Months Ended			12 Months Ended
	Sep. 30, 2018		Sep. 30, 2017	Dec. 31, 2017
Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	10.00%			10.00%
Accounts Receivable [Member] | Con Edison [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	12.00%			11.00%
Revenues [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	10.00%			10.00%
Revenues [Member] | Con Edison [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	12.00%		16.00%
Revenues [Member] | ComEd [Member]
Concentration Risk [Line Items]
Concentration risk, percentage		[1]	11.00%
[1] less than 10% of consolidated revenue in the period

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- Definition

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.

+ References

No definition available.

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- Definition

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+ References

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