Jointly Owned Utility Facilities Jointly Owned Utility Facilities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Jointly Owned Utility Plant Interests [Line Items]
Facility in Service	$ 3,250
Accumulated Depreciation and Amortization	1,267
Construction Work-in-Progress	62
Jim Bridger Nos. 1-4 [Member]
Jointly Owned Utility Plant Interests [Line Items]
PacifiCorp Share	67.00%
Facility in Service	1,087
Accumulated Depreciation and Amortization	505
Construction Work-in-Progress	33
Hunter No. 1 [Member]
Jointly Owned Utility Plant Interests [Line Items]
PacifiCorp Share	94.00%
Facility in Service	391
Accumulated Depreciation and Amortization	143
Construction Work-in-Progress	19
Hunter No. 2 [Member]
Jointly Owned Utility Plant Interests [Line Items]
PacifiCorp Share	60.00%
Facility in Service	301
Accumulated Depreciation and Amortization	81
Construction Work-in-Progress	0
Wyodak [Member]
Jointly Owned Utility Plant Interests [Line Items]
PacifiCorp Share	80.00%
Facility in Service	450
Accumulated Depreciation and Amortization	158
Construction Work-in-Progress	2
Colstrip Nos. 3 and 4 [Member]
Jointly Owned Utility Plant Interests [Line Items]
PacifiCorp Share	10.00%
Facility in Service	223
Accumulated Depreciation and Amortization	119
Construction Work-in-Progress	1
Hermiston [Member]
Jointly Owned Utility Plant Interests [Line Items]
PacifiCorp Share	50.00%	[1]
Facility in Service	172	[1]
Accumulated Depreciation and Amortization	56	[1]
Construction Work-in-Progress	1	[1]
Percentage of remaining output the company has contracted to purchase	50.00%
Craig Nos. 1 and 2 [Member]
Jointly Owned Utility Plant Interests [Line Items]
PacifiCorp Share	19.00%
Facility in Service	177
Accumulated Depreciation and Amortization	92
Construction Work-in-Progress	4
Hayden No. 1 [Member]
Jointly Owned Utility Plant Interests [Line Items]
PacifiCorp Share	25.00%
Facility in Service	55
Accumulated Depreciation and Amortization	24
Construction Work-in-Progress	1
Hayden No. 2 [Member]
Jointly Owned Utility Plant Interests [Line Items]
PacifiCorp Share	13.00%
Facility in Service	32
Accumulated Depreciation and Amortization	16
Construction Work-in-Progress	0
Foote Creek [Member]
Jointly Owned Utility Plant Interests [Line Items]
PacifiCorp Share	79.00%
Facility in Service	37
Accumulated Depreciation and Amortization	20
Construction Work-in-Progress	0
Transmission and distribution facilities [Member]
Jointly Owned Utility Plant Interests [Line Items]
PacifiCorp Share	Various
Facility in Service	325
Accumulated Depreciation and Amortization	53
Construction Work-in-Progress	$ 1

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