Risk Management and Hedging Activities - PacifiCorp - Derivative Contract Volumes (Details) - PacifiCorp [Member] - Commodity derivative [Member] gal in Millions, MWh in Millions, Dth in Millions	Mar. 31, 2018 gal Dth MWh	Dec. 31, 2017 gal Dth MWh
Electricity purchases (in megawatt hours) [Member]
Notional Amounts of Outstanding Derivative Positions [Line Items]
Derivative, nonmonetary notional amount | MWh	(6)	(9)
Natural gas purchases (in decatherms) [Member]
Notional Amounts of Outstanding Derivative Positions [Line Items]
Derivative, nonmonetary notional amount | Dth	(115)	(113)
Fuel purchases (in gallons) [Member]
Notional Amounts of Outstanding Derivative Positions [Line Items]
Derivative, nonmonetary notional amount | gal	(7)	0