Energy Purchase Contracts (PUD Contracts Expenses) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014
PUD Contracts Expenses [Abstract]
Long-term Contract for Purchase of Electric Power, Amount of Long-term Debt or Lease Obligation Outstanding	$ 59.4

Under long-term contracts with public utility districts, cooperatives or other organizations, a utility company receives a portion of the output of a production plant constructed and financed by the district or cooperative. The utility has only a nominal or no investment at all in the plant but pays a proportionate part of the plant's costs, including debt service.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 10.D)

-URI http://asc.fasb.org/extlink&oid=6499423&loc=d3e659339-123030

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 10

-Section D

Name:	us-gaap_LongTermContractForPurchaseOfElectricPowerAmountOfLongTermDebtOrLeaseObligationOutstanding
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration