Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Decrease (increase) in current assets:
Receivables – related party	$ 1,375	$ 1,450
Receivables	576	(216)
Prepaid expenses and other	37	366
Increase (decrease) in current liabilities:
Accounts payable	(2,763)	738
Accounts payable – related party	3,696	(655)
Accrued liabilities	(122)	(118)
Accrued liabilities – related party	(715)	(3,171)
Accrued interest payable	4,108	(304)
Accrued interest payable – related party	(84)	739
Taxes other than income taxes payable	(7)	437
Changes in current assets and current liabilities	6,101	(734)
Cash Flows Related to Interest and Income Taxes Paid
Interest paid	21,641	16,044
Income taxes paid	918	695
Other Noncash Activities
Decrease in accounts payable related to capital expenditures	(1,718)	(1,721)
Capital Projects [Member] | Majority Shareholder [Member]
Other Noncash Activities
Noncash capital contributions from Valero for capital projects	$ 22,317	$ 19,276