Subsequent Events (Details)	3 Months Ended
Mar. 31, 2015
Subsequent Event Detail [Abstract]
Subsequent Event, Description	On April 28, 2015, Gill Ranch entered into a second amendment to the loan agreement under which the EBITDA covenant requirement is suspended through maturity of the loan. As part of the second amendment Gill Ranch will increase the debt reserve account by $4.5 million with contributions of $1.5 million by each of May 30, 2015, January 30, 2016, and August 30, 2016. Additionally, Gill Ranch must receive common equity contributions from its parent NWN Gas Storage of at least $2 million by August 31, 2015 and of at least $4 million by August 31, 2016.

Describes the event or transaction that occurred between the balance sheet date and the date the financial statements are issued or available to be issued.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 855

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6842918&loc=SL6314017-165662

Name:	us-gaap_SubsequentEventDescription
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration