Jointly Owned Utility Facilities - PacifiCorp (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 9,651
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	4,353
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	183
PacifiCorp [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	4,425
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	1,872
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 96
PacifiCorp [Member] | Jim Bridger Unit Nos 1 thru 4 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	67.00%
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 1,442
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	616
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 12
PacifiCorp [Member] | Hunter Unit No 1 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	94.00%
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 474
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	172
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 7
PacifiCorp [Member] | Hunter No. 2 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	60.00%
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 297
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	106
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 1
PacifiCorp [Member] | Wyodak [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	80.00%
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 469
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	216
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 1
PacifiCorp [Member] | Colstrip Unit Nos 3 and 4 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	10.00%
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 247
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	131
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 4
PacifiCorp [Member] | Hermiston [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	50.00%
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 180
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	81
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 1
PacifiCorp [Member] | Craig Units Nos 1 and 2 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	19.00%
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 365
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	231
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 3
PacifiCorp [Member] | Hayden Unit No 1 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	25.00%
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 74
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	34
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 0
PacifiCorp [Member] | Hayden No. 2 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	13.00%
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 43
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	21
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 0
PacifiCorp [Member] | Foote Creek [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	79.00%
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 40
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	26
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 0
PacifiCorp [Member] | Transmission and distribution facilities
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Percentage Share	Various
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 794
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	238
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 67