Debt - Summary of the Company's Debt (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Debt	$ 978,803	$ 768,909
Unamortized debt issuance costs	(10,110)	(6,661)
Net long-term debt	968,693	762,248
Unused amount of revolving credit facilities (subject to borrowing base)	721,632	438,082
Senior Revolving Credit Facility
Debt Instrument [Line Items]
Debt	130,985	286,113
Unamortized debt issuance costs	(1,003)	(1,687)
Net long-term debt	129,982	284,426
RMR II revolving warehouse credit facility
Debt Instrument [Line Items]
Debt	23,060	42,061
Unamortized debt issuance costs	(1,547)	(1,486)
Net long-term debt	21,513	40,575
RMR IV revolving warehouse credit facility
Debt Instrument [Line Items]
Debt	23,613
Unamortized debt issuance costs	(588)
Net long-term debt	23,025
RMR V revolving warehouse credit facility
Debt Instrument [Line Items]
Debt	41,651
Unamortized debt issuance costs	(571)
Net long-term debt	41,080
RMIT 2018-2 securitization
Debt Instrument [Line Items]
Debt		130,349
Net long-term debt		130,349
RMIT 2019-1 securitization
Debt Instrument [Line Items]
Debt	130,172	130,172
Unamortized debt issuance costs	(643)	(1,216)
Net long-term debt	129,529	128,956
RMIT 2020-1 securitization
Debt Instrument [Line Items]
Debt	180,214	180,214
Unamortized debt issuance costs	(1,648)	(2,272)
Net long-term debt	178,566	$ 177,942
RMIT 2021-1 securitization
Debt Instrument [Line Items]
Debt	248,916
Unamortized debt issuance costs	(2,041)
Net long-term debt	246,875
RMIT 2021-2 securitization
Debt Instrument [Line Items]
Debt	200,192
Unamortized debt issuance costs	(2,069)
Net long-term debt	$ 198,123

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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Amount of unamortized debt discount (premium) and debt issuance costs.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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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.

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