Jointly Owned Utility Facilities - PacifiCorp (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 9,316
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	3,980
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	213
PacifiCorp [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	3,971
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	1,674
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 160
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	$ 1,289
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	566
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 83
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	$ 469
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	154
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 0
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	$ 293
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	94
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 0
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	$ 457
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	198
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 3
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	$ 239
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	128
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 2
PacifiCorp [Member] | Hermiston [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	50.00%	[1]
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 177	[1]
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	71	[1]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 1	[1]
Percentage Of Remaining Output The Entity Has Contracted To Purchase	50.00%
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	$ 325
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	213
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 18
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	$ 76
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	30
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	$ 30
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	18
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 7
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	$ 39
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	24
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	$ 577
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	178
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 46

[1] (1)As discussed in Note 17, PacifiCorp has contracted to purchase the remaining 50% of the output of the Hermiston generating facility.