Basis of Presentation (Details) $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
	May 16, 2018 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Schedule of Equity Method Investments [Line Items]
Distribution from unconsolidated affiliates				$ 931	$ 4,848
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest				74.00%
Regulatory credit resulting from Tax Reform (Note 1)		$ (20,867)	$ 0	$ (20,867)	0
WPZ Merger Public Unit Exchange [Member]
Schedule of Equity Method Investments [Line Items]
Termination Fee	$ 410,000
WPZ Merger Public Unit Exchange [Member] | Merger Closed Prior To Third Quarter 2018 Dividend Record Date [Member]
Schedule of Equity Method Investments [Line Items]
Conversion Ratio	1.494
WPZ Merger Public Unit Exchange [Member] | Merger Closed After Third Quarter 2018 Dividend Record Date [Member]
Schedule of Equity Method Investments [Line Items]
Conversion Ratio	1.513
Operating Expense [Member]
Schedule of Equity Method Investments [Line Items]
Regulatory charge resulting from Tax Reform						$ 471,100
Regulatory credit resulting from Tax Reform (Note 1)				$ (20,867)
Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Description of Principal Activities				.20
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent						21.00%
Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Description of Principal Activities				.50
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent						35.00%
Cardinal Pipeline Company, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage		45.00%		45.00%		45.00%
Pine Needle LNG Company, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage		35.00%		35.00%		35.00%
Accounting Standards Update 2016-15 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities					$ 2,100