Goodwill and Intangible Assets - Schedule of Finite-Lived Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 41,580	$ 41,580
Accumulated amortization of intangible assets	(17,633)	(14,976)
Amortized intangible assets, Net	23,947	26,604
Railcar Leases
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	3,249	3,249
Accumulated amortization of intangible assets	(3,249)	(3,249)
Amortized intangible assets, Net	0	0
Trade names and trademarks
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	6,267	6,267
Accumulated amortization of intangible assets	(5,037)	(4,951)
Amortized intangible assets, Net	1,230	1,316
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	32,064	32,064
Accumulated amortization of intangible assets	(9,347)	(6,776)
Amortized intangible assets, Net	$ 22,717	$ 25,288