Equity - At-the-Market Program (Details) - USD ($)				3 Months Ended		6 Months Ended
	Jun. 09, 2016	Mar. 29, 2016	Mar. 02, 2016	Jun. 30, 2017	Mar. 31, 2016	Jun. 30, 2017		Jun. 30, 2016	[2]
Class of Stock [Line Items]
Issuance of common units, maximum (in units)			$ 300,000,000
Consideration for units issued in connection with private placement						$ 100,000	[1]	$ 9,800,000
Aggregate percentage of general partner interest						2.00%
Shell Treasury Center West Inc | Five Year Revolver
Class of Stock [Line Items]
Debt instrument term		5 years			5 years	5 years
Shell Treasury Center West Inc | 364 Day Revolver
Class of Stock [Line Items]
Debt instrument term		364 days			364 days	364 days
Common Units | General Public
Class of Stock [Line Items]
Units issued in connection with private placement (in units)				94,925	750,000
Net proceeds from public offerings				$ 2,900,000	$ 25,400,000
Gross proceed issuance of private placement offering				$ 3,000,000	$ 25,500,000
Common units per share (in units per share)	$ 33.25	$ 31.75		$ 31.51	$ 34.00	$ 31.51
Placement fees	$ 100,000	$ 200,000		$ 100,000	$ 100,000
General Partner
Class of Stock [Line Items]
Units issued in connection with private placement (in units)				1,938	15,307
Consideration for units issued in connection with private placement	$ 1,100,000	$ 8,200,000		$ 100,000	$ 500,000
Aggregate percentage of general partner interest	2.00%	2.00%		2.00%	2.00%	2.00%

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

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