Summary of Significant Accounting Policies (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2012 Employees	Dec. 31, 2011	Dec. 31, 2010
Summary of Significant Accounting Policies [Abstract]
Parent, total ownership percentage	70.00%
Parent, limited partner ownership percentage	68.00%
Parent, general partner ownership percentage	2.00%
Entity Number of Employees	0
Prior Period
Prior Period Reclassification Adjustment		$ 3,500,000	$ 3,100,000
Rate Refund Liabilities	0
Public Utility, Property, Plant and Equipment [Line Items]
Regulatory credits	494,000	1,023,000	1,662,000
Nonoperating Income (Expense) [Abstract]
PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedInterest	700,000	700,000	900,000
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	1,600,000	1,400,000	1,900,000
PublicUtilitiesAllowanceForFundsUsedDuringConstructionRate	9.00%	9.00%	10.00%
SupplementalCashFlowInformationAbstract
Cash Payments for Interest	44,600,000	44,600,000	44,600,000
Levelized Depreciation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Regulatory Assets Disclosure	34,000,000	33,500,000
Asset Retirement Obligation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Regulatory Assets Disclosure	51,900,000	45,900,000
Negative Salvage [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Regulatory Assets Disclosure	$ (42,400,000)	$ (37,900,000)
Storage Facilities [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation Rates Used For Major Regulated Gas Plant Facilities	1.60%	1.60%	1.60%
Storage Facilities [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation Rates Used For Major Regulated Gas Plant Facilities	2.76%	2.76%	2.76%
Transmission Facilities [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation Rates Used For Major Regulated Gas Plant Facilities	2.80%	2.80%	2.80%
Transmission Facilities [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation Rates Used For Major Regulated Gas Plant Facilities	6.82%	6.82%	6.82%