Other Material Contingencies Other Material Contingencies - Energy Transactions (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Guarantor Obligations [Line Items]
Guarantee obligations maximum exposure	$ 2,329	$ 2,370
Financial and Performance Guarantee for Commodity Transactions During Period in which Con Edison Solutions Provides Transition Services
Guarantor Obligations [Line Items]
Guarantee obligations maximum exposure	$ 21

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=82913245&loc=d3e12069-110248

Name:	us-gaap_GuaranteeObligationsMaximumExposure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant