Risk Management and Hedging Activities - PacifiCorp - Derivative Contract Volumes (Details) - Commodity derivative [Member] gal in Millions, MWh in Millions, Dth in Millions	Sep. 30, 2017 MWh gal Dth	Dec. 31, 2016 MWh gal Dth
Electricity purchases (in megawatt hours) [Member]
Notional Amounts of Outstanding Derivative Positions [Line Items]
Derivative, nonmonetary notional amount | MWh	(9)	(5)
Natural gas purchases (in decatherms) [Member]
Notional Amounts of Outstanding Derivative Positions [Line Items]
Derivative, nonmonetary notional amount | Dth	(339)	(271)
Fuel purchases (in gallons) [Member]
Notional Amounts of Outstanding Derivative Positions [Line Items]
Derivative, nonmonetary notional amount | gal	(2)	(11)
PacifiCorp [Member] | Electricity purchases (in megawatt hours) [Member]
Notional Amounts of Outstanding Derivative Positions [Line Items]
Derivative, nonmonetary notional amount | MWh	(3)	(3)
PacifiCorp [Member] | Natural gas purchases (in decatherms) [Member]
Notional Amounts of Outstanding Derivative Positions [Line Items]
Derivative, nonmonetary notional amount | Dth	(97)	(84)
PacifiCorp [Member] | Fuel purchases (in gallons) [Member]
Notional Amounts of Outstanding Derivative Positions [Line Items]
Derivative, nonmonetary notional amount | gal	(2)	(11)