Acquisitions and Divestitures - Impact to Historical Consolidated Statements of Income Table (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015		Sep. 30, 2016	Sep. 30, 2015
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other	$ 481,645	$ 432,515	[1]	$ 1,293,450	$ 1,335,514	[1]
Net income (loss)	$ 169,175	185,583	[1]	$ 452,711	165,855	[1]
Springfield Pipeline LLC [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other		47,431			145,482
Net income (loss)		19,848			61,864
Springfield Pipeline LLC [Member] | Eliminations [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other		(17)			(50)
Net income (loss)		0			0
WGP Historical [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues and other		385,101			1,190,082
Net income (loss)		$ 165,735			$ 103,991

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