The number of units or percentage investment held by the managing member or general partner of the LLC or LP.

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

-Publisher AICPA

-Name Practice Bulletin (PB)

-Number 14

-Paragraph 15

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 272

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

Name:	us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPManagingMemberOrGeneralPartnerOwnershipInterest
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Basis of Presentation (Details Textual) (USD $) In Millions, unless otherwise specified	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012 Operation and maintenance [Member]	Jun. 30, 2012 Operation and maintenance [Member]	Jun. 30, 2012 General and administrative [Member]	Jun. 30, 2012 General and administrative [Member]	Jun. 30, 2012 Taxes Other Than Income [Member]	Jun. 30, 2012 Taxes Other Than Income [Member]
Basis of Presentation [Abstract]
Parent, total ownership percentage	68.00%
Parent, limited partner ownership percentage	66.00%
Parent, general partner ownership percentage	2.00%
Prior Period
Prior Period Reclassification Adjustment		$ 0.7	$ 1.2	$ 0.1	$ 0.4	$ 0.8	$ 1.6