The amount for notes payable (written promise to pay), payable to related parties, which are due after one year (or one business cycle).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(k)(1))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.23)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_NotesPayableRelatedPartiesNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Debt and Notes Payable - Related Party, Notes Payable - Related Party (Details) - USD ($) $ in Thousands	Mar. 29, 2018	Jun. 30, 2018	Dec. 31, 2017
Subordinated Credit Agreement (Textual)
Notes payable – related party		$ 285,000	$ 370,000
Subordinated Debt [Member] \| Majority Shareholder [Member]
Subordinated Credit Agreement (Textual)
Repayments under loan agreement	$ 85,000
Notes payable – related party		$ 285,000	$ 370,000
Subordinated Credit Agreements With Valero [Member] \| Subordinated Debt [Member] \| Majority Shareholder [Member]
Subordinated Credit Agreement (Textual)
Subordinated credit agreements, rate at period end (percent)		3.48246%	2.86069%