Leases - Schedule of Capital Leases (Details) - Common - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Property Subject to or Available for Operating Lease [Line Items]
Utility Plant	$ 2	$ 3
CECONY
Property Subject to or Available for Operating Lease [Line Items]
Utility Plant	$ 1	$ 2

Amount before accumulated depreciation of leased physical assets used in the normal conduct of business to produce goods and services.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=84164758&loc=d3e45014-112735

Name:	us-gaap_CapitalLeasedAssetsGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant