General (Details)	3 Months Ended
Mar. 31, 2018 subsidiary registrant
Accounting Policies [Abstract]
Number of registrants \| registrant	2
Number of regulated utility subsidiaries	2
Clean Energy Businesses
Investment [Line Items]
Number of subsidiaries	3

Line items represent reporting 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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 12
-Sentence Column A

Name:	invest_InvestmentLineItems
Namespace Prefix:	invest_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration