Commitments and Contingencies - Legal Matters (Details) (PacifiCorp [Member], USA Power [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 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 accrual excluding estimated obligations for plaintiff's motions	113
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