Environmental Matters - Accrued Liability (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Site Contingency [Line Items]
Regulatory assets	$ 3,975	$ 4,333
Asbestos Suits
Site Contingency [Line Items]
Accrued liability	8	8
Regulatory assets	8	8
Workers’ Compensation
Site Contingency [Line Items]
Accrued liability	80	84
Regulatory assets	6	10
CECONY
Site Contingency [Line Items]
Regulatory assets	3,595	3,925
CECONY \| Asbestos Suits
Site Contingency [Line Items]
Accrued liability	7	7
Regulatory assets	7	7
CECONY \| Workers’ Compensation
Site Contingency [Line Items]
Accrued liability	76	80
Regulatory assets	$ 6	$ 10

Total costs accrued as of the balance sheet date for environmental loss contingencies.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 25
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859

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