Basis of Presentation (Details) - USD ($) $ in Thousands, shares in Millions		3 Months Ended		9 Months Ended		12 Months Ended
	Aug. 10, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Distribution from unconsolidated affiliates				$ 1,751	$ 6,261
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Regulatory credit resulting from Tax Reform (Note 1)		$ 0	$ 0	$ (20,867)	0
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%
Operating Expense [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Regulatory charge resulting from Tax Reform						$ 471,100
Regulatory credit resulting from Tax Reform (Note 1)				$ (20,867)
WPZ Merger Public Unit Exchange [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Limited Partners' Capital Account, Units Outstanding	256
Stock Issued During Period, Shares, New Issues	382
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					$ 2,700