Commitments and Contingencies - Legal Matters (Details) (PacifiCorp [Member], USA Power [Member], USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Loss Contingencies [Line Items]
Loss contingency, damages sought, legal fees as a percentage of damages	40.00%
Loss contingency, damages awarded, value	$ 113
Loss contingency, damages and attorney fees awarded, value	115
Loss contingency accrual, at carrying value	116
Damages from Breach of Contract, Awarded By Jury [Member]
Loss Contingencies [Line Items]
Loss contingency, damages awarded by jury, value	18
Damages from Unjust Enrichment, Awarded By Jury [Member]
Loss Contingencies [Line Items]
Loss contingency, damages awarded by jury, value	$ 113