Variable Interest Entities - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Clean Energy Businesses
Variable Interest Entity [Line Items]
Equity method investments	$ 11		$ 11
Variable Interest Entity, Primary Beneficiary | Tax Equity Projects
Variable Interest Entity [Line Items]
Income (loss) before tax	10		(10)
Net income (loss)	(7)		$ 13
Variable Interest Entity, Primary Beneficiary | Con Edison Development | Tax Equity Projects
Variable Interest Entity [Line Items]
Income (loss) before tax		$ (4)		$ (8)
Net income (loss)		3		10
Percentage of variable interests (less than)			100.00%
Variable Interest Entity, Primary Beneficiary | Tax Equity Investors | Tax Equity Construction Projects
Variable Interest Entity [Line Items]
Income (loss) before tax	(53)
Net income (loss)	40
Variable Interest Entity, Primary Beneficiary | Tax Equity Investors | Tax Equity Projects
Variable Interest Entity [Line Items]
Income (loss) before tax	6	12	$ 6	22
Net income (loss)	$ (5)	$ (9)	$ (8)	$ (29)