Risk Management and Hedging Activities - PacifiCorp - Derivative Contract Volumes (Details) - PacifiCorp [Member] - Commodity derivative [Member] gal in Millions, MWh in Millions, Dth in Millions	Sep. 30, 2018 gal Dth MWh	Dec. 31, 2017 gal Dth MWh
Electricity sales
Notional Amounts of Outstanding Derivative Positions [Line Items]
Derivative, nonmonetary notional amount | MWh	7	9
Natural gas purchases
Notional Amounts of Outstanding Derivative Positions [Line Items]
Derivative, nonmonetary notional amount | Dth	115	113
Fuel oil purchases
Notional Amounts of Outstanding Derivative Positions [Line Items]
Derivative, nonmonetary notional amount | gal	2	0