Basis of Presentation and Significant Accounting Policies Basis of Presentation and Significant Accounting Policies - Reclassifications (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013
Reclassified Gas Transportation Charges [Line Items]
Reclassified Gas Transportation Charges	$ 8.9	$ 24.2
Affiliated Entity [Member]
Reclassified Gas Transportation Charges [Line Items]
Reclassified Gas Transportation Charges	$ 1.2	$ 3.5