Derivative Accounting - Outstanding Gross Notional Amounts Outstanding (Details) - Commodity Contracts MWh in Thousands	12 Months Ended
Dec. 31, 2020 MWh Bcf	Dec. 31, 2019 MWh Bcf
Outstanding gross notional amount of derivatives
Power (in MWh) \| MWh	368	193
Gas (in bcf) \| Bcf	205	257

Nominal energy measure used to calculate payments on a derivative instrument.

No definition available.

Name:	us-gaap_DerivativeNonmonetaryNotionalAmountEnergyMeasure
Namespace Prefix:	us-gaap_
Data Type:	num:energyItemType
Balance Type:	na
Period Type:	duration