Variable-Interest Entities - PacifiCorp (Details) - PacifiCorp [Member] - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2014	Dec. 31, 2015
Variable Interest Entity (VIE) or Potential VIE, Information Unavailability [Member]
Schedule of Equity Method Investments [Line Items]
Variable Interest Entity, Measure of Activity, Purchases	$ 20,000,000	$ 38,000,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 0
Variable Interest Entity, Not Primary Beneficiary [Member]
Schedule of Equity Method Investments [Line Items]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage	66.67%
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	$ 165,000,000		$ 190,000,000
Hermiston [Member]
Schedule of Equity Method Investments [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	50.00%
Hermiston [Member] | Variable Interest Entity (VIE) or Potential VIE, Information Unavailability [Member]
Schedule of Equity Method Investments [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	50.00%
Percentage of natural gas for jointly owned utility plant procured by Company	100.00%
Percentage of electricity from jointly owned utility plant received by Company	100.00%
Percentage of electricity acquired from jointly owned utility plant by Company through long-term power purchase agreement	50.00%
Jointly Owned Utility Plant, Joint Owner Share	50.00%
Jim Bridger Unit Nos 1 thru 4 [Member]
Schedule of Equity Method Investments [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	67.00%
Jim Bridger Unit Nos 1 thru 4 [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Schedule of Equity Method Investments [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	66.67%
Jointly Owned Utility Plant, Joint Owner Share	33.33%
Share of coal production purchased by Company	66.67%
Share of coal production purchased by joint venture partner	33.33%