Summary of Significant Accounting Policies Revenue Recognition (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Summary of Significant Accounting Policies [Abstract]
Gas Balancing Asset (Liability)	$ 7.9us-gaap_GasImbalanceAssetLiability	$ 10.7us-gaap_GasImbalanceAssetLiability

The value of gas balancing asset or liability as of the end of the period.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 10

-Section S99

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=27015464&loc=d3e512571-122862

Name:	us-gaap_GasImbalanceAssetLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant