Pension Benefits - Schedule of Assumptions (Details)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CECONY
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	3.80%	3.80%	4.25%
Rate of compensation increase	3.80%	4.25%	4.25%
O&R
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	3.20%	3.20%	4.00%
Rate of compensation increase	3.20%	4.00%	4.00%
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount rate, benefit obligations	2.55%	3.35%	4.25%
Interest crediting rate for cash balance plan	3.00%	3.30%	4.00%
Discount rate, net periodic benefit cost	3.35%	4.25%	3.70%
Interest crediting rate for cash balance plan	3.30%	4.00%	4.10%
Expected return on plan assets	7.00%	7.00%	7.50%

Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

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- Definition

Weighted average rate increase of compensation, used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

+ References

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Weighted-average interest crediting rate used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, cash balance and other defined benefit plans with promised interest crediting rate.

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Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan.

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Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(3)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2919-114920

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- Definition

Weighted average rate of compensation increase used to determine net periodic benefit cost of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

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- Definition

Weighted-average interest crediting rate used to determine net periodic benefit cost of defined benefit plan. Plan includes, but is not limited to, cash balance and other defined benefit plans with promised interest crediting rate.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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