Acquisitions and Divestiture - 2016 Acquisitions (Details) - USD ($)											3 Months Ended			12 Months Ended
		Sep. 15, 2017	Dec. 27, 2016	Oct. 03, 2016	Aug. 09, 2016	Jun. 09, 2016	May 23, 2016	Mar. 29, 2016	Nov. 17, 2015	May 18, 2015	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015		Dec. 01, 2017
Business Acquisition [Line Items]
Net proceeds from public offerings	[1]													$ 277,900,000	$ 818,100,000		$ 296,800,000
Units issued in connection with public offering (in units)														5,275,510	25,229,591
Consideration for units issued in connection with private placement														$ 5,800,000	$ 9,800,000	[2]	6,100,000	[2]
Aggregate percentage of interest														2.00%
Contribution in excess of book value														$ 1,034,500,000	$ 896,300,000	[2]	$ 1,002,100,000	[2]
Explorer
Business Acquisition [Line Items]
Voting interest acquired					2.62%														10.00%
Mars
Business Acquisition [Line Items]
Voting interest acquired				20.00%															22.90%
October 2016 Acquisitions
Business Acquisition [Line Items]
Consideration transferred				$ 350,000,000
Consideration, cash on hand				50,000,000
Consideration, funded with borrowings				300,000,000
Contingent consideration receivable (up to)				$ 10,000,000.0
December 2016 Acquisition
Business Acquisition [Line Items]
Consideration transferred			$ 42,000,000
Odyssey Pipeline L.L.C.
Business Acquisition [Line Items]
Voting interest acquired																			22.00%
August 2016 Acquisition
Business Acquisition [Line Items]
Consideration transferred					$ 26,200,000
Consideration, cash on hand					26,300,000
Transaction costs					$ 100,000
Zydeco
Business Acquisition [Line Items]
Voting interest acquired							30.00%
Bengal
Business Acquisition [Line Items]
Voting interest acquired							1.00%
Colonial
Business Acquisition [Line Items]
Voting interest acquired							3.00%
May 2016 Acquisition
Business Acquisition [Line Items]
Consideration transferred							$ 700,000,000
Consideration, cash on hand							50,400,000
Consideration for units issued in connection with private placement							7,100,000
Contribution in excess of book value of net assets acquired							606,300,000
Contribution in excess of book value							599,200,000
Explorer
Business Acquisition [Line Items]
Noncontrolling interest, ownership percentage by Parent					35.97%									25.97%
Proteus
Business Acquisition [Line Items]
Noncontrolling interest, ownership percentage by Parent														0.00%
Proteus | December 2016 Acquisition
Business Acquisition [Line Items]
Voting interest acquired			10.00%
Endymion
Business Acquisition [Line Items]
Noncontrolling interest, ownership percentage by Parent														0.00%
Endymion | December 2016 Acquisition
Business Acquisition [Line Items]
Voting interest acquired			10.00%
Cleopatra
Business Acquisition [Line Items]
Noncontrolling interest, ownership percentage by Parent														0.00%
Cleopatra | December 2016 Acquisition
Business Acquisition [Line Items]
Voting interest acquired			1.00%
Odyssey Pipeline L.L.C.
Business Acquisition [Line Items]
Noncontrolling interest, ownership percentage by Parent														0.00%
Odyssey Pipeline L.L.C. | Odyssey Pipeline L.L.C.
Business Acquisition [Line Items]
Voting interest acquired				49.00%
Affiliated Entity | Five Year Revolver | Shell Treasury Center West Inc
Business Acquisition [Line Items]
Debt instrument term														5 years
Common Units
Business Acquisition [Line Items]
Units issued in connection with public offering (in units)									9,200,000
Consideration for units issued in connection with private placement										$ 6,100,000
Placement fees										$ 2,600,000	$ 400,000
Common Units | May 2016 Acquisition
Business Acquisition [Line Items]
Net proceeds from public offerings							$ 345,800,000
Units issued in connection with public offering (in units)							10,500,000
General Partner
Business Acquisition [Line Items]
Units issued in connection with public offering (in units)		105,510				32,143		258,163	187,755					105,510	504,591
Consideration for units issued in connection with private placement						$ 1,100,000		$ 8,200,000			$ 2,900,000	$ 100,000	$ 500,000
General Partner | May 2016 Acquisition
Business Acquisition [Line Items]
Units issued in connection with public offering (in units)							214,285
Shell Pipeline Company L P | Common Units
Business Acquisition [Line Items]
Units issued in connection with public offering (in units)														0	0
Shell Pipeline Company L P | General Partner
Business Acquisition [Line Items]
Net proceeds from public offerings														$ 0
Aggregate percentage of interest														2.00%
Shell Pipeline Company L P | General Partner | May 2016 Acquisition
Business Acquisition [Line Items]
Aggregate percentage of interest														2.00%
General Public | Common Units
Business Acquisition [Line Items]
Net proceeds from public offerings		$ 135,100,000				51,800,000		$ 395,100,000
Units issued in connection with public offering (in units)		5,170,000					1,575,000	12,650,000						5,170,000	24,725,000
Placement fees						$ 100,000	$ 400,000	$ 200,000				$ 100,000	$ 100,000

[1] The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.

[2] The financial information presented has been retrospectively adjusted for acquisitions of businesses under common control.