Variable Interest Entities - Additional Information (Details) - Variable Interest Entity, Primary Beneficiary - Tax Equity Projects - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Variable Interest Entity [Line Items]
Income (loss) before tax	$ 3
Net income (loss)	$ 2
Con Edison Development
Variable Interest Entity [Line Items]
Percentage of variable interests (less than)	100.00%
Income (loss) before tax		$ (14)
Net income (loss)		(10)
Tax Equity Investors
Variable Interest Entity [Line Items]
Income (loss) before tax	$ 2	17
Net income (loss)	$ 1	$ 13