Summary of Significant Accounting Policies - Activity in the Allowance for Credit Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 67	$ 43
Acquired balance from Direct Energy	112	0
Provision for credit losses	698	108	$ 95
Write-offs	(224)	(101)
Recoveries collected	30	17
Ending balance	683	$ 67	$ 43
Increase in provision for credit losses due to impacts of Winter Storm Uri on bilateral finance hedging risk	403
Increase to provision due to counterparty credit risk	126
Increase to provision due to shortfall payments	$ 67