Long-Term Debt - Summary of the Company's Long-Term Debt (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term debt	$ 595,765	$ 571,496
Unamortized debt issuance costs	(7,437)	(4,950)
Net long-term debt	588,328	566,546
Unused amount of revolving credit facilities (subject to borrowing base)	375,128	244,884
Senior Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term debt	383,180	452,050
Unamortized debt issuance costs	(1,814)	(2,162)
Net long-term debt	381,366	449,888
Amortizing Loan [Member]
Debt Instrument [Line Items]
Long-term debt	32,893	53,380
Unamortized debt issuance costs	(344)	(547)
Net long-term debt	32,549	52,833
Revolving Warehouse Credit Facility [Member]
Debt Instrument [Line Items]
Long-term debt	29,692	66,066
Unamortized debt issuance costs	(1,925)	(2,241)
Net long-term debt	27,767	$ 63,825
RMIT 2018-1 securitization [Member]
Debt Instrument [Line Items]
Long-term debt	150,000
Unamortized debt issuance costs	(3,354)
Net long-term debt	$ 146,646

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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