Securitized Debt Obligations, Net - Schedule of Information on Securitized Debt Obligations (Detail) $ in Thousands		9 Months Ended		12 Months Ended
		Sep. 30, 2021 USD ($) Loans		Dec. 31, 2020 USD ($) Loans
Financing Provided [Member]
Debt Instrument [Line Items]
Count | Loans		3	[1]	4	[2]
Principal Balance		$ 2,855,625	[1]	$ 2,940,638	[2]
Book Value		$ 2,836,049	[1]	$ 2,922,499	[2]
Financing Provided [Member] | 2021 FL4 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Count | Loans		1
Principal Balance		$ 803,750
Book Value		$ 796,864
Financing Provided [Member] | 2020 FL3 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Count | Loans		1	[3]	1
Principal Balance		$ 808,750	[3]	$ 808,750
Book Value		$ 803,378	[3]	$ 800,993
Financing Provided [Member] | 2020 FL2 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Count | Loans		1	[3]	1
Principal Balance		$ 1,243,125	[3]	$ 1,243,125
Book Value		$ 1,235,807	[3]	$ 1,233,464
Financing Provided [Member] | 2017 FL1 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Count | Loans				1
Principal Balance				$ 483,834
Book Value				$ 483,113
Financing Provided [Member] | Single Asset Securitization [Member]
Debt Instrument [Line Items]
Count | Loans				1
Principal Balance				$ 404,929
Book Value				$ 404,929
Collateral Assets [Member]
Debt Instrument [Line Items]
Count | Loans		80		72
Principal Balance		$ 3,500,000		$ 3,785,528
Book Value		$ 3,500,000		$ 3,785,100
Collateral Assets [Member] | 2021 FL4 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Count | Loans		35
Principal Balance		$ 1,000,000
Book Value		$ 1,000,000
Collateral Assets [Member] | 2020 FL3 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Count | Loans		21		25
Principal Balance		$ 1,000,000		$ 1,000,000
Book Value		$ 1,000,000		$ 1,000,000
Collateral Assets [Member] | 2020 FL2 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Count | Loans		24		31
Principal Balance		$ 1,500,000		$ 1,500,000
Book Value		$ 1,500,000		$ 1,500,000
Collateral Assets [Member] | 2017 FL1 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Count | Loans				15
Principal Balance				$ 666,334
Book Value				$ 666,334
Collateral Assets [Member] | Single Asset Securitization [Member]
Debt Instrument [Line Items]
Count | Loans	[4]			1
Principal Balance	[4]			$ 619,194
Book Value	[4]			$ 618,766
LIBOR [Member] | Financing Provided [Member]
Debt Instrument [Line Items]
Wtd. Avg. Yield/Cost	[5]	1.69%	[1],[3]	1.70%	[2],[6]
LIBOR [Member] | Financing Provided [Member] | 2021 FL4 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Wtd. Avg. Yield/Cost	[3],[5]	1.65%
Term	[7]	2038-05
LIBOR [Member] | Financing Provided [Member] | 2020 FL3 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Wtd. Avg. Yield/Cost	[5]	2.10%	[3]	2.08%	[6]
Term	[7]			2037-11
LIBOR [Member] | Financing Provided [Member] | 2020 FL2 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Wtd. Avg. Yield/Cost	[5]	1.45%	[3]	1.44%	[6]
Term	[7]			2038-02
LIBOR [Member] | Financing Provided [Member] | 2017 FL1 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Wtd. Avg. Yield/Cost	[5],[6]			1.83%
Term	[7]			2035-06
LIBOR [Member] | Financing Provided [Member] | 2020 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Wtd. Avg. Yield/Cost	[5],[6]			1.63%
LIBOR [Member] | Financing Provided [Member] | Single Asset Securitization [Member]
Debt Instrument [Line Items]
Term	[7]			2033-06
LIBOR [Member] | Collateral Assets [Member]
Debt Instrument [Line Items]
Wtd. Avg. Yield/Cost	[5]	3.17%	[3]	3.25%	[6]
LIBOR [Member] | Collateral Assets [Member] | 2021 FL4 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Wtd. Avg. Yield/Cost	[3],[5]	3.41%
Term	[7]	2024-07
LIBOR [Member] | Collateral Assets [Member] | 2020 FL3 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Wtd. Avg. Yield/Cost	[5]	3.02%	[3]	3.09%	[6]
Term	[7]	2024-04		2024-02
LIBOR [Member] | Collateral Assets [Member] | 2020 FL2 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Wtd. Avg. Yield/Cost	[5]	3.10%	[3]	3.17%	[6]
Term	[7]	2024-03		2024-01
LIBOR [Member] | Collateral Assets [Member] | 2017 FL1 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Wtd. Avg. Yield/Cost	[5],[6]			3.39%
Term	[7]			2023-01
LIBOR [Member] | Collateral Assets [Member] | 2020 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Wtd. Avg. Yield/Cost	[4],[5],[6]			3.57%
LIBOR [Member] | Collateral Assets [Member] | Single Asset Securitization [Member]
Debt Instrument [Line Items]
Term	[4],[7]			2023-06
SOFR [Member] | Financing Provided [Member] | 2020 FL3 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Term	[3],[7]	2037-11
SOFR [Member] | Financing Provided [Member] | 2020 FL2 Collateralized Loan Obligation [Member]
Debt Instrument [Line Items]
Term	[3],[7]	2038-02

[1] During the three and nine months ended September 30, 2021, we recorded $10.7 million and $35.2 million, respectively, of interest expense related to our securitized debt obligations.

[2] During the three and nine months ended September 30, 2020, we recorded $9.1 million and $31.8 million, respectively, of interest expense related to our securitized debt obligations.

[3] The weighted-average all-in yield and cost are expressed as a spread over the relevant floating benchmark rates, which include USD LIBOR and SOFR, as applicable to each securitized debt obligation. As of September 30, 2021, the floating benchmark rate for the financing provided on the 2020 FL3 and 2020 FL2 CLOs is the 30-day average compounded SOFR, plus a credit spread adjustment of 0.11%. As of September 30, 2021, the 30-day average compounded SOFR was 0.05% and one-month USD LIBOR was 0.08%.

[4] The collateral assets for the 2017 Single Asset Securitization include the total loan amount, of which we securitized $500.0 million.

[5] In addition to cash coupon, all-in yield includes the amortization of deferred origination and extension fees, loan origination costs, purchase discounts, and accrual of exit fees.

[6] The weighted-average all-in yield and cost are expressed as a spread over USD LIBOR.

[7] Loan term represents weighted-average final maturity, assuming all extension options are exercised by the borrower. Repayments of securitized debt obligations are tied to timing of the related collateral loan asset repayments. The term of these obligations represents the rated final distribution date of the securitizations.