Acquisitions, Narrative (Details) bbl / d in Thousands, bbl in Thousands, $ in Millions			6 Months Ended
	Nov. 01, 2017 USD ($) bbl / d shares	Jan. 18, 2017 USD ($) bbl / d property bbl	Jun. 30, 2018
Red River Crude System [Member] | Pipelines and Related Assets [Member]
Business Acquisition [Line Items]
Date of asset acquisition			Jan. 18, 2017
Undivided ownership interest acquired (percent)		40.00%
Number of properties | property		2
Storage capacity (barrels) | bbl		150
Cash consideration		$ 71.8
Throughput capacity (barrels per day) | bbl / d		150
Red River Crude System [Member] | Pipelines and Related Assets [Member] | Joint Ownership Agreement (JOA) and Operating and Administrative Services Agreement with Plains [Member]
Business Acquisition [Line Items]
Duration of agreement		5 years
Duration of renewal option		5 years
Red River Crude System [Member] | Pipelines and Related Assets [Member] | Plains All American Pipeline L.P.’s (Plains) [Member] | Joint Ownership Agreement (JOA) and Operating and Administrative Services Agreement with Plains [Member]
Business Acquisition [Line Items]
Undivided ownership interest acquired (percent)		60.00%
Parkway Pipeline [Member] | Revolver [Member]
Business Acquisition [Line Items]
Proceeds from debt borrowings	$ 118.0
Parkway Pipeline [Member] | Majority Shareholder [Member]
Business Acquisition [Line Items]
Cash consideration	$ 82.0
Parkway Pipeline [Member] | Pipelines and Related Assets [Member] | Majority Shareholder [Member]
Business Acquisition [Line Items]
Date of asset acquisition			Nov. 01, 2017
Throughput capacity (barrels per day) | bbl / d	110
Consideration transferred for acquisition of assets	$ 200.0
Port Arthur Terminal [Member] | Revolver [Member]
Business Acquisition [Line Items]
Proceeds from debt borrowings	262.0
Port Arthur Terminal [Member] | Majority Shareholder [Member]
Business Acquisition [Line Items]
Cash consideration	262.0
Aggregate value of units issued to Valero Energy Corporation in connection with acquisition	$ 46.0
Port Arthur Terminal [Member] | Majority Shareholder [Member] | Limited Partner [Member] | Common Unitholder Valero [Member]
Business Acquisition [Line Items]
Units issued in connection with acquisition (units) | shares	1,081,315
Port Arthur Terminal [Member] | Majority Shareholder [Member] | General Partner Valero [Member]
Business Acquisition [Line Items]
Units issued in connection with acquisition (units) | shares	22,068
Port Arthur Terminal [Member] | Pipelines and Related Assets [Member] | Majority Shareholder [Member]
Business Acquisition [Line Items]
Date of asset acquisition			Nov. 01, 2017
Consideration transferred for acquisition of assets	$ 308.0