Summary of Significant Accounting Policies and Other Matters - Reconciliation of Cash, Temporary Investments and Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Line Items]
Cash and temporary cash investments	$ 992	$ 1,272
Restricted cash	154	164
Total cash, temporary cash investments and restricted cash	1,146	1,436	$ 1,217	$ 1,006
Cash Collateral Held For Project Finance Agreements | Clean Energy Businesses
Cash and Cash Equivalents [Line Items]
Restricted cash	154	164
CECONY
Cash and Cash Equivalents [Line Items]
Cash and temporary cash investments	920	1,067
Restricted cash	0	0
Total cash, temporary cash investments and restricted cash	$ 920	$ 1,067	$ 933	$ 818