Commodity Derivatives (Details) MWh in Millions, MMBTU in Millions, $ in Millions		Dec. 31, 2020 USD ($) MMBTU MWh	Dec. 31, 2019 MMBTU MWh
Derivative [Line Items]
Cash Flow Hedges Derivative Instruments at Fair Value, Net | $		$ 0
Electric Commodity
Derivative [Line Items]
Notional Amount | MWh	[1],[2]	17	9
Natural Gas Commodity
Derivative [Line Items]
Notional Amount | MMBTU	[1],[2]	93	32

[1] Not reflective of net positions in the underlying commodities.

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