Acquisitions and Divestitures - Impact to Historical Consolidated Statements of Income Table (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015		Jun. 30, 2016	Jun. 30, 2015
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other	$ 428,664	$ 465,993	[1]	$ 811,805	$ 902,999	[1]
Net income (loss)	$ 165,777	134,367	[1]	$ 283,536	(19,728)	[1]
Springfield Pipeline LLC [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other		49,438			98,051
Net income (loss)		18,719			42,016
Springfield Pipeline LLC [Member] | Eliminations [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other		(17)			(33)
Net income (loss)		0			0
WGP Historical [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other		416,572			804,981
Net income (loss)		$ 115,648			$ (61,744)

[1] Financial information has been recast to include the financial position and results attributable to the Springfield interest. See Note 1 and Note 2.