Contract Termination (Details) - SPS $ in Millions	9 Months Ended
Sep. 30, 2021 USD ($) MW
Loss Contingencies [Line Items]
Megawatts, Lubbock Power and Light contract \| MW	170
Lubbock Power and Light Contract Length	25 years
Settlement Agreement Payment, Lubbock Power and Light Contract \| $	$ 78

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