Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
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%
Purchase Price Allocation
Purchase price allocation, gross		$ 1,500,000
Purchase price allocation, property, plant and equipment, estimated useful lIfe		40 years
Purchase price allocation, depreciation		$ 35,000
Purchase price allocation, remaining allocation		600,000
Schedule of Equity Method Investments [Line Items]
Equity method investment, distributions		8,600	$ 7,600	$ 9,100
Equity method investment, return of capital		2,767	2,015	2,333
Capitalized Interest Costs, Including Allowance for Funds Used During Construction [Abstract]
Allowance for funds used during construction, borrowed		12,500	14,600	6,300
Allowance for funds used during construction, equity		56,468	48,435	$ 18,701
Inventory Disclosure [Abstract]
Gas in storage, LIFO		0	0
Excess of replacement cost over LIFO cost		$ 0	$ 0
Subsequent Event [Member] | Financial Repositioning [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Parent, limited partner ownership percentage	74.00%
Parent, general partner ownership percentage	2.00%
Gathering facilities | Minimum
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation rates		1.35%	1.35%	1.35%
Gathering facilities | Maximum
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation rates		2.50%	2.50%	2.50%
Storage facilities | Minimum
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation rates		2.10%	2.10%	2.10%
Storage facilities | Maximum
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation rates		2.25%	2.25%	2.25%
Onshore transmission facilities | Minimum
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation rates		2.61%	2.61%	2.61%
Onshore transmission facilities | Maximum
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation rates		5.00%	5.00%	5.00%
Offshore transmission facilities | Minimum
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation rates		1.20%	1.20%	1.20%
Offshore transmission facilities | Maximum
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation rates		1.20%	1.20%	1.20%
Cardinal Pipeline Company, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		45.00%	45.00%
Pine Needle LNG Company, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		35.00%	35.00%