Fair Value of Financial Instruments - Derivative Fair Value Measurements (Details) $ in Millions	Sep. 30, 2022 USD ($) $ / MWh	Dec. 31, 2021 USD ($) $ / MWh
Liabilities
Commodity contracts	$ 9,643	$ 4,799
Level 3
Liabilities
Commodity contracts	331	164
Commodity contracts
Assets
Derivative assets	14,822	7,139
Liabilities
Commodity contracts	9,643	4,798
Commodity contracts | Level 3
Assets
Derivative assets	1,013	457
Liabilities
Commodity contracts	331	164
Commodity contracts | Level 3 | Natural Gas Contracts
Assets
Derivative assets	90	16
Liabilities
Commodity contracts	$ 46	$ 1
Commodity contracts | Level 3 | Natural Gas Contracts | Low
Fair Value Inputs / Range
Forward Market Price (per MWh) | $ / MWh	3	3
Commodity contracts | Level 3 | Natural Gas Contracts | High
Fair Value Inputs / Range
Forward Market Price (per MWh) | $ / MWh	35	40
Commodity contracts | Level 3 | Natural Gas Contracts | Weighted Average
Fair Value Inputs / Range
Forward Market Price (per MWh) | $ / MWh	11	15
Commodity contracts | Level 3 | Power Contracts
Assets
Derivative assets	$ 842	$ 392
Liabilities
Commodity contracts	$ 221	$ 121
Commodity contracts | Level 3 | Power Contracts | Low
Fair Value Inputs / Range
Forward Market Price (per MWh) | $ / MWh	20	3
Commodity contracts | Level 3 | Power Contracts | High
Fair Value Inputs / Range
Forward Market Price (per MWh) | $ / MWh	263	212
Commodity contracts | Level 3 | Power Contracts | Weighted Average
Fair Value Inputs / Range
Forward Market Price (per MWh) | $ / MWh	55	35
Commodity contracts | Level 3 | FTRs
Assets
Derivative assets	$ 81	$ 49
Liabilities
Commodity contracts	$ 64	$ 42
Commodity contracts | Level 3 | FTRs | Low
Fair Value Inputs / Range
Auction Prices (per MWh) | $ / MWh	(67)	(122)
Commodity contracts | Level 3 | FTRs | High
Fair Value Inputs / Range
Auction Prices (per MWh) | $ / MWh	46	43
Commodity contracts | Level 3 | FTRs | Weighted Average
Fair Value Inputs / Range
Auction Prices (per MWh) | $ / MWh	1	0