Rate and Regulatory Matters (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Public Utilities, General Disclosures [Line Items]
Annual cost of service	$ 466.5
General system firm transportation rate, per unit	0.44
General system firm transportation rate, percentage	7.40%
Minimum [Member]
Public Utilities, General Disclosures [Line Items]
Duration of effective period of rates	3 years
Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Duration of effective period of rates	5 years