Summary of Significant Accounting Policies Significant Accounting Policies - Income Taxes (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Regulatory Assets	$ 1,835		$ 1,884
Regulatory Liabilities	913		893
Investment tax credit	34		38
Deferred income taxes [Member]
Regulatory Liabilities	21		22
Deferred income taxes [Member]
Regulatory Assets	$ 456	[1]	$ 444	[1]

[1] Amounts primarily represent income tax benefits related to certain property-related basis differences and other various items that PacifiCorp is required to pass on to its customers.