Summary of Significant Accounting Policies Significant Accounting Policies - Income Taxes (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Regulatory assets	$ 1,705		$ 1,384
Regulatory liabilities	944		934
Investment tax credits	27		32
Deferred income taxes [Member]
Regulatory liabilities	13		21
Deferred income taxes [Member]
Regulatory assets	$ 446	[1]	$ 461	[1]

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