Variable Interest Entities - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021
Clean Energy Businesses
Variable Interest Entity [Line Items]
Equity method investments	$ 7		$ 7		$ 11
Variable Interest Entity, Primary Beneficiary | Tax Equity Projects
Variable Interest Entity [Line Items]
Income (loss) before tax	14		(20)
Net income (loss)	(11)		27
Variable Interest Entity, Primary Beneficiary | Tax Equity Investors | Tax Equity Construction Projects
Variable Interest Entity [Line Items]
Income (loss) before tax	(74)		(127)
Net income (loss)	$ 56		96
Variable Interest Entity, Primary Beneficiary | Tax Equity Investors | Tax Equity Projects
Variable Interest Entity [Line Items]
Income (loss) before tax		$ 9	6	$ 29
Net income (loss)		(7)	$ (8)	(38)
Variable Interest Entity, Primary Beneficiary | Con Edison Development | Tax Equity Projects
Variable Interest Entity [Line Items]
Income (loss) before tax		(7)		(2)
Net income (loss)		$ 5		$ 3
Percentage of variable interests (less than)			100.00%