Other Material Contingencies - Manhattan Steam Main Rupture (Details) - Manhattan Steam Main Rupture - CECONY $ in Millions	1 Months Ended
Jul. 31, 2007 person	Jun. 30, 2017 USD ($) lawsuit
Loss Contingencies [Line Items]
Number of person who died in stream rupture incident \| person	1
Number of pending lawsuits \| lawsuit		45
Estimated accrued liability for suits		$ 18
Insurance receivable for suits		$ 18

Number of pending claims pertaining to a loss contingency.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349

Name:	us-gaap_LossContingencyPendingClaimsNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant