Commitments and Contingencies - NPC - Narrative (Details) - NPC $ in Millions	12 Months Ended				36 Months Ended
	Dec. 31, 2021 USD ($) MW	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) MW	Dec. 31, 2017 MW	Dec. 31, 2016 MW
Loss Contingencies [Line Items]
Easement expense | $	$ 4	$ 4	$ 7
536 Megawatts of Renewable Energy
Loss Contingencies [Line Items]
New generation capacity					536
200 Megawatts of Solar Renewable Energy
Loss Contingencies [Line Items]
New generation capacity					200
15 Megawatts of Solar Renewable Energy
Loss Contingencies [Line Items]
New generation capacity					15
35 Megawatts of Renewable Energy
Loss Contingencies [Line Items]
New generation capacity	35
255 Megawatts of Coal Energy
Loss Contingencies [Line Items]
Power plant capacity			255
557 Megawatts of Coal Energy
Loss Contingencies [Line Items]
Power plant capacity				557