Commodity Derivatives (Details) MWh in Millions, MMBTU in Millions, $ in Millions		Mar. 31, 2022 USD ($) MWh MMBTU	Dec. 31, 2021 USD ($) MMBTU MWh
Gross Notional Amounts of Commodity Forwards, Options and FTRs [Abstract]
Miscellaneous investments		$ 53	$ 52
Cash flow hedge commodity
Derivative [Line Items]
Commodity contracts designated as cash flow hedges		$ 0
Electric commodity
Gross Notional Amounts of Commodity Forwards, Options and FTRs [Abstract]
Derivative, Nonmonetary Notional amount | MWh	[1],[2]	40	57
Natural Gas Commodity
Gross Notional Amounts of Commodity Forwards, Options and FTRs [Abstract]
Derivative, Nonmonetary Notional amount | MMBTU	[1],[2]	86	85

[1] Amounts are not reflective of net positions in the underlying commodities.

[2] Notional amounts for options are included on a gross basis, but are weighted for the probability of exercise.