Summary of Significant Accounting Policies and Other Matters - Long-Lived and Intangible Assets (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($) MW	Jun. 30, 2020 USD ($)
Finite-Lived Intangible Assets [Line Items]
Net non-utility plant	$ 43,889	$ 44,897
Intangible assets	$ 1,557	$ 1,510
Con Edison Development \| PG&E Project
Finite-Lived Intangible Assets [Line Items]
Aggregate power to be sold (in MW) \| MW	680

Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(14))
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(8))
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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