Acquisitions and Divestitures - Statement of Income (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016		Sep. 30, 2017	[2]	Sep. 30, 2016
Revenue
Third parties		$ 53.8				$ 174.9
Related parties		28.1				86.0
Total revenue	$ 94.4	81.9	[1]	$ 265.6		260.9	[1]
Costs and expenses
Operations and maintenance – third parties	25.8	14.1	[1]	64.3		41.7	[1]
Operations and maintenance – related parties	8.4	7.5	[1]	26.6		22.6	[1]
General and administrative – third parties	1.0	2.2	[1]	5.6		6.4	[1]
General and administrative – related parties	8.6	7.4	[1]	25.2		22.3	[1]
Depreciation, amortization and accretion	8.9	9.1	[1]	28.0	[3]	27.1	[1],[4]
Property and other taxes	3.6	2.6	[1]	11.2		10.3	[1]
Total costs and expenses	56.3	42.9	[1]	160.9		130.4	[1]
Operating income	38.1	39.0	[1]	104.7		130.5	[1]
Income from equity investments	41.2	21.4	[1]	117.1		70.2	[1]
Dividend income from cost investments	4.8	4.2	[1]	18.3		11.6	[1]
Investment, dividend and other income	46.1	25.6	[1]	135.5		81.8	[1]
Interest expense, net	9.7	2.8	[1]	22.0		7.8	[1]
Income before income taxes	74.5	61.8	[1]	218.2		204.5	[1]
Income tax expense	0.0	0.0	[1]	0.0		0.0	[1]
Net income	74.5	61.8	[1]	218.2	[3],[5]	204.5	[1],[4]
Less: Net income attributable to Parent	0.0	3.0	[1]	3.0		11.4	[1]
Less: Net income attributable to noncontrolling interests	1.9	2.5	[1]	6.3		17.7	[1]
Net income attributable to the Partnership	$ 72.6	56.3	[1]	$ 208.9		175.4	[1]
Previously Reported
Revenue
Third parties		46.1				149.8
Related parties		21.8				65.9
Total revenue		67.9				215.7
Costs and expenses
Operations and maintenance – third parties		11.4				33.1
Operations and maintenance – related parties		5.3				15.9
General and administrative – third parties		2.2				6.2
General and administrative – related parties		5.7				17.3
Depreciation, amortization and accretion		6.0				17.7
Property and other taxes		1.3				6.4
Total costs and expenses		31.9				96.6
Operating income		36.0				119.1
Income from equity investments		21.4				70.2
Dividend income from cost investments		4.2				11.6
Investment, dividend and other income		25.6				81.8
Interest expense, net		2.8				7.8
Income before income taxes		58.8				193.1
Income tax expense		0.0				0.0
Net income		58.8				193.1
Less: Net income attributable to Parent		0.0				0.0
Less: Net income attributable to noncontrolling interests		2.5				17.7
Net income attributable to the Partnership		56.3				175.4
Adjustment
Revenue
Third parties		7.7				25.1
Related parties		6.3				20.1
Total revenue		14.0				45.2
Costs and expenses
Operations and maintenance – third parties		2.7				8.6
Operations and maintenance – related parties		2.2				6.7
General and administrative – third parties		0.0				0.2
General and administrative – related parties		1.7				5.0
Depreciation, amortization and accretion		3.1				9.4
Property and other taxes		1.3				3.9
Total costs and expenses		11.0				33.8
Operating income		3.0				11.4
Income from equity investments		0.0				0.0
Dividend income from cost investments		0.0				0.0
Investment, dividend and other income		0.0				0.0
Interest expense, net		0.0				0.0
Income before income taxes		3.0				11.4
Income tax expense		0.0				0.0
Net income		3.0				11.4
Less: Net income attributable to Parent		3.0				11.4
Less: Net income attributable to noncontrolling interests		0.0				0.0
Net income attributable to the Partnership		$ 0.0				$ 0.0

[1] Prior period financial information has been retrospectively adjusted for the acquisition of the Shell Delta, Na Kika and Refinery Gas Pipeline Operations.

[2] The financial information for the nine months ended September 30, 2017 reflects adjustments for the acquisition of the Shell Delta, Na Kika and Refinery Gas Pipeline Operations from January 1, 2017 through May 9, 2017.

[3] The financial information for the nine months ended September 30, 2017 reflects adjustments for the acquisition of the Shell Delta,Na Kika and Refinery Gas Pipeline Operations from January 1, 2017 through May 9, 2017.

[4] Prior period financial information has been retrospectively adjusted for the acquisition of the Shell Delta, Na Kika and Refinery Gas Pipeline Operations.

[5] Prior period financial information has been retrospectively adjusted for the acquisition of the Shell Delta, Na Kika and Refinery Gas Pipeline Operations.