Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2015 USD ($) employee	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Parent, total ownership percentage	60.00%
Parent, limited partner ownership percentage	58.00%
Parent, general partner ownership percentage	2.00%
Entity number of employees | employee	0
Revenue Recognition [Abstract]
Reserve for rate refund, Current	$ 0
Reserve for rate refund, Noncurrent	0
Public Utility, Property, Plant and Equipment [Line Items]
Regulatory debits	2,550,000	$ 1,487,000	$ 921,000
Regulatory assets	40,853,000	49,923,000
Capitalized Interest Costs, Including Allowance for Funds Used During Construction [Abstract]
Allowance for funds used during construction, debt	500,000	200,000	500,000
Allowance for funds used during construction, equity	1,099,000	391,000	945,000
Interest Payments [Abstract]
Cash payments for interest, net of interest capitalized	45,300,000	44,500,000	44,600,000
Levelized depreciation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Regulatory debits	2,600,000	1,500,000	$ 900,000
Regulatory assets	26,493,000	29,775,000
Asset retirement obligation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Regulatory assets	70,900,000	63,700,000
Negative salvage [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Regulatory assets	$ (69,300,000)	$ (60,200,000)
Storage Facilities [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciaton rates	1.60%	1.60%	1.60%
Storage Facilities [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciaton rates	2.76%	2.76%	2.76%
Transmission Facilities [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciaton rates	2.80%	2.80%	2.80%
Transmission Facilities [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciaton rates	6.97%	6.97%	6.97%