Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Regulatory charge (credit) resulting from Tax Reform		$ 24,202	$ 20,867	$ (471,096)
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		500,000
Schedule of Equity Method Investments [Line Items]
Prior Period Reclassification Adjustment			11,300	7,200
Proceeds from Equity Method Investment, Distribution		4,908	3,250	8,036
Contributions to unconsolidated affiliates		12,250	0	0
Capitalized Interest Costs, Including Allowance for Funds Used During Construction [Abstract]
Allowance for funds used during construction, borrowed		10,500	29,200	22,300
Allowance for funds used during construction, equity		28,800	87,100	69,700
Inventory Disclosure [Abstract]
Gas in storage, LIFO		$ 0	0
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lessee, Operating Lease, Term of Contract		108 years
Lease Liability		$ 85,339
Right-of-use assets		84,979	0
Operating Expense [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Regulatory charge (credit) resulting from Tax Reform		$ (24,200)	(20,900)	471,100
Nonoperating Income (Expense) [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Regulatory charge (credit) resulting from Tax Reform			$ (2,000)	$ (10,300)
Minimum [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent	21.00%
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lessee, Operating Lease, Term of Contract		1 year
Maximum [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent	35.00%
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lessee, Operating Lease, Term of Contract		15 years
Gathering facilities | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation rates		0.00%	1.35%	1.35%
Gathering facilities | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation rates		1.00%	2.50%	2.50%
Storage facilities | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation rates		1.86%	2.10%	2.10%
Storage facilities | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation rates		2.05%	2.25%	2.25%
Onshore transmission facilities | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation rates		2.50%	2.61%	2.61%
Onshore transmission facilities | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation rates		7.13%	5.00%	5.00%
Offshore transmission facilities | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation rates		1.25%	1.20%	1.20%
Offshore transmission facilities | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation rates		1.25%	1.20%	1.20%
Pine Needle LNG Company LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		35.00%
Cardinal Pipeline Company LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		45.00%
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease Liability					$ 91,300
Right-of-use assets					$ 91,300