Commitments and Contingencies - Legal Matters (Details) - PacifiCorp [Member] - USA Power [Member] $ in Millions	3 Months Ended
Mar. 31, 2016 USD ($)
Loss Contingencies [Line Items]
Loss contingency, damages and attorney fees awarded, value	$ 115
Loss contingency accrual, at carrying value	122
Damages from Breach of Contract, Awarded By Jury [Member]
Loss Contingencies [Line Items]
Loss contingency, damages awarded by jury, value	$ 18

Amount of loss contingency liability.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant