Accounting Policies and Basis of Presentation - Narrative (Details) $ in Thousands	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($) rail_car
Accounting Policies [Abstract]
Debt instrument, fair value disclosure	$ 45,045	$ 24,838
Long-term debt	$ 45,120	$ 24,554
Property Subject to Operating Lease
Property Subject to or Available for Operating Lease [Line Items]
Property subject to operating leases, number of rail cars \| rail_car		223

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- Definition

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
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-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
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-Section S99
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The number of units (items of property) under operating lease arrangements.

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